US20060147707A1

US20060147707A1 - Compacted, chopped fiber glass strands

Info

Publication number: US20060147707A1
Application number: US11/029,115
Authority: US
Inventors: Jian Meng; Raphael Kollah; Paul Westbrook; Ramasubraman Narayanan
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-30
Filing date: 2004-12-30
Publication date: 2006-07-06
Also published as: WO2006073831A1; TW200630307A

Abstract

Embodiments of the present invention relate to compacted chopped strands. In one embodiment, a compacted chopped strand comprises a plurality of fiber glass filaments and a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: a film-former, a coupling agent, and at least one alkylene oxide polymer, the alkylene oxide polymer comprising at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. The compacted chopped strand, in some embodiments, has a cross-sectional area that is greater than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, the compacted chopped strand comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand.

Description

FIELD OF THE INVENTION

The present invention relates generally to compacted chopped fiber strands and in particular to compacted chopped fiber glass strands.

BACKGROUND OF THE INVENTION

Chopped fiber glass strands are often used as reinforcements in thermoplastic and thermoset applications. Chopped fiber glass strands are typically manufactured by either direct or indirect processing operations. Direct processing operations, such as “direct chop” operations, involve feeding a generally continuous, fiber glass strand directly from a fiber forming assembly into a chopping assembly where the strand is chopped. Indirect processing operations, such as “remote chop” operations, involve winding a generally continuous fiber strand onto a tube to form a package and subsequently feeding the generally continuous strand from the package into a chopping assembly. Packages of generally continuous fiber strands can also undergo additional processing steps, such as roving wherein multiple packages are combined into one package, prior to being chopped.
In direct-chop operations, a plurality of generally continuous, individual glass filaments are drawn from a fiber forming apparatus, such as a heated metal bushing or spinneret, and bundled together by a gathering device to form a generally continuous fiber strand. Before bundling the filaments together, a sizing composition or binder is applied to at least a portion of the surface of the individual filaments to protect them from abrasion. Such compositions are well known to those skilled in the art and are disclosed in K. Loewenstein, The Manufacturing Technology of Glass Fibers, (3rd. Ed. 1993) at pages 237-289, which are hereby incorporated by reference. After bundling, the generally continuous fiber strand is chopped to form a plurality of discrete, chopped strands. These wet chopped strands are then typically processed through a drying oven to at least partially dry the size on the surfaces thereof.
Transferring the wet, chopped strands to a drying oven can be done by collecting the chopped strands in a container or tote immediately after chopping and transporting the totes to a drying oven. This process can be undesirable, however, due to the labor and handling associated with moving the totes.
An alternative method of transporting wet, chopped strands to a drying oven involves the use of a conveyance system, such as a conveyor belt. In this method, immediately after chopping, the wet strands are deposited directly onto a conveyor belt which transports them to a drying oven.
Several patents have been directed toward improving chopped strand manufacture operations and the quality of the product produced therefrom. Such patents typically utilize a combination of moisture, sizing composition, movement of the chopped strands, or combinations thereof to agglomerate the chopped strands.
U.S. Pat. No. 4,840,755 discloses the use of a spheroidizing or rolling apparatus to form chopped strands having a rod-like shape. Chopped strands formed by a cutting device are dropped onto a spheroidizing plate and subjected to a rolling action by a vibrating plate. The rolling action causes rounding and compacting of the strands into rod-like shapes. After rolling, the strands are transferred to a drying station, either directly through an opening in the rolling apparatus or indirectly by means of a transfer device.
U.S. Pat. No. 5,578,535 and U.S. Pat. No. 5,693,378 disclose hydrating glass fibers after chopping to achieve a water content on the glass fibers of from about 11 weight percent to about 20 weight percent. The hydrated glass fibers are mixed to form pellets. These patents disclose mixing the hydrated glass fibers in a plastic bag or in a modified disk pelletizer. According to the patents, pellets produced by the process described in these patents are about 20 to 30 percent denser than an individual glass strand, are about five to fifteen times larger in diameter than an individual glass strand, and are the same length as the input chopped strands.
U.S. Pat. No. 5,868,982 and U.S. Pat. No. 5,945,134 also disclose systems and methods for making pellets from chopped fiber glass strands. Continuous fiber glass strands are chopped into lengths from about one-eighth inch to one and one-fourth inch. The moisture content of the chopped strand segments is adjusted as they enter a pelletizer or inside the pelletizer. The moisture content of the chopped strand segments in the pelletizer is from about 12 percent to about 16 percent, preferably from about 13 percent to about 14 percent. The hydrating fluid preferably includes a binder or second sizing composition. The pelletizer disclosed is a rotary drum. The '134 patent discloses that the drum may also include interior baffles. After the formation of pellets in the pelletizer, the pellets are fed into a densifier, where the pellets are further compacted and densified. The densifier is a zig-zag tube rotationally driven about a longitudinal axis. According to the patents, the pellets formed by the process can be made that are from about 13% to about 60% denser than the corresponding unpelletized glass strand segments, and from about 10 times to about 65 times larger in diameter.
The above patents are generally directed to providing fiber glass strands or pellets having particular sizes. For example, the '982 and '134 patents appear to focus on producing large diameter pellets, such as pellets that are from about 10 times to about 65 times larger in diameter than the diameters of the corresponding unpelletized glass strand segments.
It would be desirable to have a system and method for producing compacted chopped fiber glass strands with desirable properties, which can include, for example, a desirable size and shape, uniform size distribution, good dispersion in a resin, good flowability, good compatibility with the resin to be reinforced, and/or other properties.

SUMMARY

The present invention relates generally to compacted chopped fiber glass strands. Embodiments of compacted chopped strands of the present invention can possess a number of properties which can be desirable in particular applications including, without limitation, desirable sizes and shapes, uniform size distributions, good dispersion in resins, good flowability, good compatibility with the resins to be reinforced, and/or other properties and various combinations thereof.
In some embodiments, a compacted chopped strand of the present invention comprises a plurality of fiber glass filaments and a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: a film-former, a coupling agent, and at least one alkylene oxide polymer, the alkylene oxide polymer comprising at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. In some embodiments, the compacted chopped strand has a cross-sectional area that is larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments the compacted chopped strands can have a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments the compacted chopped strands can have a cross-sectional area that is greater than about 1.0 and up to about three times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, the compacted chopped strand comprises a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, the compacted chopped strand comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand.
In some embodiments, the present invention relates to a compacted chopped strand comprising: a plurality of fiber glass filaments and a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: at least one film-former in an amount up to about 90 weight percent on a total solids basis, at least one coupling agent in an amount up to about 50 weight percent on a total solids basis, and up to about five weight percent polyalkylene oxide on a total solids basis. In some embodiments, the polyalkylene oxide can comprise polyethylene oxide.
These and other embodiments of the present invention are described in greater detail in the detailed description of the invention which follows.

BRIEF SUMMARY OF THE FIGURES

FIG. 1 is a cross-sectional view of an example of a chopped strand prior to agglomerating.
FIG. 2 is a cross-sectional view of an embodiment of a compacted chopped strand of the present invention.
FIG. 3 is an apparatus that can be used to calculate the flow index of compacted chopped strands.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification are approximations that can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g. 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10. Additionally, any reference referred to as being “incorporated herein” is to be understood as being incorporated in its entirety.
It is further noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless expressly and unequivocally limited to one referent.
Further, when the phrase “up to” is used in connection with an amount of a component, material, or composition in the claims, it is to be understood that the component, material, or composition is present in at least a detectable amount (e.g., its presence can be determined) and may be present up to and including the specified amount.
The present invention relates generally to compacted chopped fiber strands. The present invention will be discussed generally in connection with compacted chopped fiber glass strands. However, one of ordinary skill in the art will understand that some embodiments of the present invention can be adapted for use in the production of non-glass, compacted chopped fiber strands.
Persons of ordinary skill in the art will recognize that the present invention can be implemented in the production, assembly, and application of a number of glass fibers. Non-limiting examples of glass fibers suitable for use in the present invention can include those prepared from fiberizable glass compositions such as “E-glass”, “A-glass”, “C-glass”, “S-glass”, “ECR-glass” (corrosion resistant glass), and fluorine and/or boron-free derivatives thereof. Typical formulations of glass fibers are disclosed in K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibres, (3d Ed. 1993). The present invention is particularly useful in the production, assembly, and application of glass fibers prepared from E-glass compositions.
Some embodiments of the present invention are adapted to produce consistent, uniform, round chopped strands that disperse well in a resin system. Examples of factors that can affect the quality and properties of compacted chopped strands are the formulation of the sizing composition used on the fiber glass strands and the amount of sizing composition applied to the fiber glass strands. As used herein, the term “sizing composition” refers to a coating composition applied to fiber glass filaments immediately after forming, and the term may be used interchangeably with the terms “binder composition,” “binder,” “sizing,” and “size.” Sizing compositions are typically used to at least partially coat continuous fiber glass filaments to provide protection to the fiber glass and can also be used to provide compatibility between the fiber glass and a matrix polymer or resin to be reinforced.
Sizing compositions can provide protection through subsequent processing steps, such as those where the fibers pass by contact points as in the winding of the fibers and strands onto a forming package, drying the aqueous-based or solvent-based sizing composition to remove the water or solvent, twisting from one package to a bobbin, beaming to place the yarn onto very large packages ordinarily used as the warp in a fabric, chopping in a wet or dry condition, roving into larger bundles or groups of strands, unwinding for use as a reinforcement, weaving, and other production and downstream processes.
In addition, sizing compositions can play a dual role when placed on fibers that reinforce polymeric matrices in the production of fiber-reinforced plastics or in the reinforcement of other materials. In the reinforcement of polymeric matrices, the sizing composition provides protection and also can provide compatibility between the fiber and the matrix polymer or resin. For example, glass fibers in various forms (e.g., woven and nonwoven fabrics, mats, rovings, chopped strands, etc.) have been used with resins, such as thermosetting and thermoplastic resins, for impregnation by, encapsulation by, and/or reinforcement of the resin. In such applications, it is often desirable to maximize the compatibility between the surface and the polymeric resin while also improving the ease of processability and manufacturability.
The sizing compositions described herein generally relate to aqueous sizing compositions. In non-limiting embodiments, the sizing compositions can be used on fiber glass for forming compacted chopped strands of fiber glass. Non-limiting embodiments of the present invention relate to compacted chopped strands at least partially coated with the sizing compositions.
Non-limiting embodiments of compacted chopped fiber glass strands of the present invention can have several desirable properties. For example, embodiments of compacted chopped strands can be at least partially coated with a sizing composition that results in compacted chopped strands having desirable bulk densities, improved flow, and shapes, as well as other properties. The desired level of a particular property may depend on the application or end use, although for chopped strands (compacted or not), many end users prefer chopped strands having similar properties.
In addition to the components of the sizing composition, the amount of moisture provided to the fiber glass strands can also effect the properties of compacted chopped strands. As noted above, the sizing composition provides moisture to fiber glass strands. Moisture can also be applied to fiber glass strands in other ways and at other locations using techniques known to those of ordinary skill in the art.
As embodiments of the present invention relate to compacted chopped strands, the production of such products includes severing fiber glass strands into a plurality of chopped fiber glass strands. Fiber glass strands are typically severed after the strands have been at least partially coated with a sizing composition. Fiber glass strands can be severed in any number of ways using techniques known to those of skill in the art.
After severing, the chopped strands can be agglomerated to form compacted chopped strands. The chopped strands can be agglomerated in any number of ways using techniques known to those of skill in the art as set forth below. For example, and without limitation, the chopped strands can be agglomerated by tumbling, mixing, shaking, rolling, vibrating, or otherwise moving the chopped strands amongst other chopped strands and loose filaments. As used herein, the term “chopped strands” refers to chopped strands prior to agglomerating. The use of the terms “agglomerated” and “agglomerating” should be understood to comprise the agglomerating of a plurality of chopped strands into a compacted chopped strand, the agglomerating of a chopped strand with a plurality of loose filaments into a compacted chopped strand, the agglomerating of a plurality of chopped strands and a plurality of loose filaments into a compacted chopped strand, the agglomerating of a chopped strand with a partial chopped strand (i.e., a segment or portion of a chopped strand comprising less filaments than the strand prior to chopping) into a compacted chopped strand, the agglomerating of a plurality of chopped strands, a plurality of partial chopped strands and/or a plurality of loose filaments into a compacted chopped strand, and/or various other combinations comprising the agglomerating of at least one chopped strand, at least one partial chopped strand, and/or at least one loose filament.
The agglomeration of chopped strands is believed to have a number of effects on the chopped strands. For example, agglomerating chopped fiber glass strands can result in improved flow of the chopped fiber glass strands. Agglomerating can result in the bulk density of the compacted chopped strands being greater than the bulk density of the chopped strands prior to agglomerating. The use of the term “compacted chopped strand” should be understood to comprise a chopped strand having a cross-section with more filaments than the chopped strand had prior to agglomerating, a chopped stand having a cross-section with more filaments per unit area after agglomerating than the chopped strand had prior to agglomerating, a chopped strand having a cross-sectional area that is larger than the cross-sectional area of the chopped strand prior to agglomerating, and/or a rounded chopped strand. Various embodiments of compacted chopped strands can comprise one or more of these features (e.g., some embodiments can comprise only one such feature; some embodiments can comprise any two of these features; some embodiments can comprise any three of these features; some embodiments can comprise each of these features; etc.).
In some embodiments, agglomerating can result in the rounding of chopped strands. As used herein, the terms “round” or “rounded” when used to describe chopped fiber glass strands or compacted chopped fiber glass strands refer to the cross-section of the fiber glass strands, such that the fiber glass strands are more like a cylinder in shape than a small piece of flat paint brush. Chopped strands prior to agglomerating can be generally flat due, in part, to the chopping apparatus. The combination of agglomerating with the sizing composition on the fiber glass strands can result in the chopped strands picking up loose filaments, partial chopped strands, or other chopped strands during agglomeration. Continuous fiber glass strands having a particular number of filaments are supplied to the chopping apparatus, and the chopping of the strands can result in at least some of the filaments, individually and/or in groups as partial chopped strands, being separated from the chopped strands. The individual loose filaments or partial chopped strands that reach the device used to agglomerate the chopped strands can also aid in producing compacted chopped strands that are round.
Agglomerating, in some embodiments, can result in a plurality of the chopped strands, or portions thereof, adhering to, or otherwise combining, to form compacted chopped strands that are larger than the chopped fiber glass strands prior to agglomerating. The compacted chopped strands may be larger in diameter than the chopped strands due to loose filaments adhering to the chopped strands, due to chopped strands adhering to one another, and/or due to partial chopped strands adhering to the chopped strands or other partial chopped strands. As the chopped strands can be more flat than round due to the chopping step, a comparison of the diameters of compacted chopped strands and chopped strands may not be feasible since a flatter strand would not have a substantially uniform diameter. Thus, it may be useful to compare the chopped strands and the compacted chopped strands based on their cross-sectional areas.
Another useful measure for comparing the size of the compacted chopped strands with the size of the chopped strands is the weights of the strands. The weights can be expressed in terms of “Tex”, which refers to the mass in grams per 1,000 meters of yarn. The compacted chopped strands, in some embodiments, can have a greater weight than chopped strands. Another useful measure for comparing the size of the compacted chopped strands with the size of the chopped strands is the number of filaments in each strand.
Compacted chopped strands of certain sizes (in terms of diameter, cross-sectional area, and/or weight) may be more desirable for downstream handling and subsequent processing. A number of factors can affect the size of compacted chopped strands including, without limitation, the composition and components of the sizing composition applied, agglomerating technique, the LOI of the strand, the distribution of the sizing composition on the strand, the amount of moisture applied, and others.
Some embodiments of the present invention relate to sizing compositions adapted to produce compacted chopped strands having desirable sizes and shapes. As discussed in more detail below, the use of alkylene oxide polymers in some sizing compositions can result in compacted chopped strands having desirable sizes, shapes, and other properties after agglomerating.
In some embodiments, a compacted chopped strand of the present invention comprises a plurality of fiber glass filaments and a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: a film-former, a coupling agent, and at least one alkylene oxide polymer, the alkylene oxide polymer comprising at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. In some embodiments, the compacted chopped strand has a cross-sectional area that is larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, the compacted chopped strand comprises a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand. The compacted chopped strand, in some embodiments, comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments the compacted chopped strands can have a cross-sectional area that is between about one and about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. Compacted chopped strands can exhibit a flow index of at least 1.0 in some embodiments, at least 1.2 in other embodiments, and at least 1.5 in still other embodiments.
In some embodiments of compacted chopped strands, the alkylene oxide polymer comprises polyethylene oxide. The polyethylene oxide can comprise up to about five weight percent of the sizing composition on a total solids basis in some embodiments. In some embodiments, up to about five weight percent polyethylene oxide has proven to be an effective amount in a sizing composition for use in producing compacted chopped strands. However, for other embodiments, it may be practical to include more than five weight percent polyethylene oxide in the sizing composition. For example, and without limitation, more polyethylene oxide might be used if certain components and/or amounts of certain components are used in a sizing composition. The cost of polyethylene oxide might be another non-limiting example of a factor relevant to selecting an amount of polyethylene oxide to use.
As will be discussed in more detail below, in some embodiments of compacted chopped strands, the sizing composition can comprise a second film-former, different from and in addition to a first film-former. In some embodiments, a film-former can comprise an epoxy polymer. In further embodiments where a first film-former comprises an epoxy polymer, the sizing composition can further comprise a second film-former and the second film-former can comprise a polyurethane. Film-formers, including the different types of film-formers, combinations, and amounts, will be discussed in more detail below.
The sizing composition utilized in some non-limiting embodiments of compacted chopped strands can further comprise other components, such as a lubricant.
In some embodiments, a plurality of compacted chopped strands of the present invention can exhibit a bulk density of greater than 700 grams per liter. A plurality of compacted chopped strands, in some embodiments, can exhibit a flow index of at least 1. In other embodiments, the flow index can be at least 1.2 and, in other embodiments, the flow index can be at least 1.5.
Some embodiments of compacted chopped strands of the present invention can have a substantially round cross-section. In some embodiments, compacted chopped strands can have a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strands that were chopped prior to forming the compacted chopped strands. Compacted chopped strands, in some embodiments, can have a cross-sectional area that is greater than about 1.0 and up to about three times larger than the cross-sectional area of the continuous strands that were chopped prior to forming the compacted chopped strands. Compacted chopped strands having cross-sectional areas that are greater than about 1.0 and up to about three times larger than the cross-sectional areas of the continuous strands that were chopped prior to forming the compacted chopped strands are believed to perform better in some downstream applications. For example and without limitation, in some downstream applications, compacted chopped strands having cross-sectional areas that are greater than about 1.0 and up to about three times larger than the cross-sectional areas of the chopped strands are believed to have more desirable flow properties and/or more desirable disperability.
In embodiments where compacted chopped strands are generally cylindrical in shape or where the compacted chopped strands have a length dimension, the length of compacted chopped strands in embodiments of the present invention can vary depending on the application. The length of the compacted chopped strands will generally depend on the length of the chopped strand prior to agglomerating. While generally dependent on the desired end use and the chopper used, chop lengths of chopped strands can be between about three and about fifteen millimeters although continuous strands can be chopped to other lengths if so desired. In some embodiments, compacted chopped strands can have a length of up to about fifteen millimeters. Compacted chopped strands, in some embodiments, can have a length of greater than about three millimeters. In some embodiments, compacted chopped strands can have a length of up to about five millimeters.
In some embodiments, the present invention relates to a compacted chopped strand comprising: a plurality of fiber glass filaments and a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: at least one film-former in an amount up to about 90 weight percent on a total solids basis, at least one coupling agent in an amount up to about 50 weight percent on a total solids basis, and up to about 5 weight percent polyalkylene oxide on a total solids basis. In some embodiments, the polyalkylene oxide comprises polyethylene oxide.
Embodiments of a compacted chopped strand of the present invention can comprise a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising: a film-former, a coupling agent, and at least one alkylene oxide polymer. Alkylene oxide polymers useful in some embodiments of the present invention can generally have the following structure:
X—[—(CH2)_nO—]_n—Y
Alkylene oxide polymers useful in embodiments of the present invention can include, in some embodiments, at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. The terminal groups X and Y can generally be any functional group that will not adversely interfere with the alkylene oxide's performance in the sizing composition, with the compatibility of the alkylene oxide with other components in the sizing composition, with the ability of the sizing composition to at least partially coat the filaments, and/or other factors important in selecting components of a sizing composition. Some commercially available polyalkylene oxides that can be used in some embodiments of the present invention comprise a terminal hydroxy (—OH) group.
While the alkylene oxide polymer can be a straight chain polymer in some embodiments, the alkylene oxide polymer can be a branched polymer in some embodiments. The alkylene oxide polymer can comprise functional groups in some embodiments. For example, when an ethylene glycol initiator is used to synthesize the alkylene oxide polymer, the potential for hydroxy functional groups increases. Persons of skill in the art will recognize the need, in some instances, to minimize or avoid the presence of certain functional groups on the alkylene oxide polymer to the extent that such functional groups might adversely affect the performance of the alkylene oxide polymer, the performance of the sizing composition, the performance of the continuous, chopped, or compacted chopped strands, and/or otherwise be undesirable.
In some embodiments, the alkylene oxide polymer can be a homopolymer, although a copolymer comprising alkylene oxide can be used in other embodiments. An alkylene oxide homopolymer can be advantageous as it can maximize the amount of water molecules complexed per molecular chain, which assists in water solubility and other features. In some embodiments, the alkylene oxide polymer can include other monomers so long as such monomers do not have a substantial undesirable effect on the performance of the alkylene oxide polymer, the performance of the sizing composition, the performance of the continuous, chopped, or compacted chopped strands, and/or other properties.
As discussed below, the inclusion of alkylene oxide polymers in sizing compositions for embodiments of the present invention can provide a number of advantages. In selecting a particular alkylene oxide polymer for use in embodiments of the present invention, a number of factors can be considered including, without limitation, the compatibility of the alkylene oxide with water, the adhesive properties of the alkylene oxide polymer when wet, the non-adhesive properties of the alkylene oxide polymer when dry, and other factors discussed herein. For example, such factors can be important in selecting a molecular weight of the alkylene oxide polymer, considering the number of alkylene oxide groups to include in each polymer, considering whether the alkylene oxide polymer should be a homopolymer, considering whether reactive or non-reactive functional groups would be advantageous/disadvantageous, etc.
The use of alkylene oxide polymers in some sizing compositions can result in compacted chopped strands having desirable sizes, shapes, and other properties after agglomeration. For example, alkylene oxide polymers can be useful in sizing compositions that, without alkylene oxide, may not absorb or retain enough moisture through chopping for the chopped strands to increase in bulk density and in cross-sectional area during agglomeration. Thus, the inclusion of alkylene oxide polymer in sizing compositions used in embodiments of the present invention can assist in increasing the size of the compacted chopped strands. Similarly, alkylene oxide polymers can be included in sizing compositions for compacted chopped strands which may not, in the absence of alkylene oxide polymers in the sizing composition, substantially increase in size during agglomeration. The inclusion of alkylene oxide polymers in such sizing compositions is believed to result in chopped strands at least partially coated with the sizing composition which are more likely to agglomerate with or collect loose filaments or other chopped strands to result in larger compacted chopped strands. Similarly, alkylene oxide polymers in embodiments of sizing compositions can also be useful in producing more round compacted chopped strands.
Alkylene oxide polymers can also assist in modifying the rheology or viscosity of sizing compositions in some embodiments. The ability of an alkylene oxide polymer to hydrogen bond with water molecules results in it being water soluble and can allow the alkylene oxide polymer to provide lubricious properties to the sizing composition.
In addition to the above benefits that can be provided by alkylene oxide polymers in sizing compositions for compacted chopped strands in some embodiments of the present invention, alkylene oxide polymers can also advantageously have a minimal effect on other properties of the compacted chopped strands in some embodiments. For example, the inclusion of alkylene oxide polymers may not adversely affect the color of the compacted chopped strands in some embodiments. As another example, the inclusion of alkylene oxide polymers may not adversely affect mechanical properties of the compacted chopped strands in some embodiments. As another example, the inclusion of alkylene oxide polymers may not adversely affect mechanical properties of composites that are reinforced by compacted chopped strands in some embodiments.
The molecular weight of alkylene oxides useful in some embodiments of the present invention can vary. The molecular weight of the alkylene oxides to be used in a particular sizing composition can be selected based on a number of factors including, without limitation, the adhesive and lubricating characteristics of the alkylene oxide, the other components of the sizing composition and relative amounts thereof, the desired size of the compacted chopped strands, the desired viscosity of the sizing composition, the moisture retention properties of the alkylene oxide, the commercial availability and cost of the alkylene oxide, and others. For example, alkylene oxide polymers having higher molecular weights are believed to have stronger adhesive and lubricating properties, which can be factors in producing larger compacted chopped strands. Because alkylene oxide polymers can modify the rheology of sizing compositions, the molecular weights of the alkylene oxide polymers used in some embodiments of the present invention can be selected based on the desired viscosity of the sizing composition. For example, if a need exists to increase the viscosity of the sizing composition using alkylene oxide, alkylene oxide polymers having higher molecular weighs can be selected.
In some embodiments, the alkylene oxide polymers used in the sizing composition can have a molecular molecular weight greater than about 100,000. In further embodiments, the alkylene oxide polymers can have a molecular weight greater than about 2,000,000. The alkylene oxide polymers, in some embodiments can have a molecular weight up to about 10,000,000. In embodiments where the polyalkylene oxide comprises polyethylene oxide, the polyethylene oxide can have a molecular molecular weight greater than about 100,000 in some embodiments, greater than about 2,000,000 in other embodiments, and up to about 10,000,000 in still other embodiments. Desirable results have been observed in embodiments where polyalkylene oxides, such as polyethylene oxide, having molecular weights of up to about 10,000,000 have been utilized. Polyalkylene oxides and polyethylene oxides having molecular weights greater than 10,000,000 can be used in some embodiments if such polymers are available, are economically feasible, and/or would not have undesirable effects.
The number of methylene (—CH₂—) groups in the monomer comprising the alkylene oxide polymer can be important in some embodiments. For example, the unshared pair of electrons on the oxygen atom in the alkylene oxide monomer is believed to contribute to the adhesive properties of the alkylene oxide polymer. Thus, at least theoretically, increasing the number of methylene groups in the alkylene oxide in the monomer increases the distance between the oxygen atoms in a polymer formed from a plurality of the alkylene oxide monomers, such that the adhesive characteristics of the alkylene oxide polymer could potentially be reduced. The following alkylene oxide polymers are particularly well-suited for use in some embodiments of the present invention as their inclusion in a sizing composition provides or is expected to provide desirable adhesive properties: polyethylene oxide, polypropylene oxide, polybutylene oxide, and combinations thereof.
Polyethylene oxide is particularly useful in some embodiments of the present invention. A non-limiting example of a polyethylene oxide that can be used in some embodiments of the present invention is POLYOX WSR-301 from the Dow Chemical Company, which is a water-soluble polyethylene oxide having an approximate molecular weight of 4,000,000. Another non-limiting example of a polyethylene oxide that can be used in some embodiments of the present invention is POLYOX WSR-303 also from the Dow Chemical Company, which is a water-soluble polyethylene oxide having an approximate molecular weight of 8,000,000. Other examples of polyethylene oxides that can be used in some embodiments of the present invention are available from the Dow Chemical Company under the POLYOX trade name, from Rita Corporation under the Rita PEO trade name, and from other well-known chemical suppliers.
The amount of alkylene oxide utilized in some non-limiting embodiments of the present invention can be an amount effective to form compacted chopped strands having a desirable size and shape. References herein to the amounts of various components of the sizing compositions should be understood to refer to the amount of the component in the sizing composition prior to application of the sizing composition to the glass filaments. In some non-limiting embodiments, up to about five weight percent polyalkylene oxide has proven to be an effective amount in a sizing composition for use in producing compacted chopped strands. However, for other embodiments, it may be practical to include more than five weight percent polyalkylene oxide in the sizing composition. For example, and without limitation, more polyalkylene oxide might be used if certain components and/or amounts of certain components are used in a sizing composition. The cost of polyalkylene oxide might be another non-limiting example of a factor relevant to selecting an amount of polyalkylene oxide to use. In some non-limiting embodiments wherein the polyalkylene oxide comprises polyethylene oxide, the amount of polyethylene oxide can comprise up to about five (5) weight percent of the sizing composition based on total solids. In other non-limiting embodiments, the amount of polyethylene oxide can comprise up to about one (1) weight percent of the sizing composition based on total solids. In other non-limiting embodiments, the amount of polyethylene oxide can comprise more than about 0.005 weight percent of the sizing composition based on total solids. In other non-limiting embodiments, the amount of polyethylene oxide can comprise more than about 0.1 weight percent of the sizing composition based on total solids. The amount of polyethylene oxide, in other non-limiting embodiments, can comprise between about 0.1 weight percent and about one (1) weight percent.
The sizing composition used to at least partially coat the fiber glass filaments further comprises a film-former in some embodiments. The film-former can be selected from among a variety of art recognized materials for fiber glass sizing compositions. Important factors in selecting a film-former for use in some embodiments of the present invention are the film-former's compatibility with the resin to be reinforced, the film-former's compatibility with other components in the sizing composition, the adhesive characteristics of the film-former and potential effects on the sizes of the compacted chopped strands, and others. In some embodiments, the sizing composition used can comprise two or more film-formers. Two or more film-formers can be desirable in some embodiments as different film-formers can impart different properties to the sizing composition and to composites reinforced with the compacted chopped strands.
Synthesis of film-forming polymers are well know to those skilled in the art and will not be discussed here. A comprehensive discussion can be found in “The Chemistry of Organic Film Formers”, D. H. Solomon, Robert E. Krieger Publishing Company, 1977.
Examples of film-formers that can be used in some embodiments of the present invention can include, without limitation, polyesters, polyurethanes, epoxy polymers, vinyl esters, and others, including copolymers thereof and variants thereof having substituted functional groups. In some embodiments of the present invention, the film-former can comprise an epoxy polymer. Epoxy polymers can be useful in some embodiments of the present invention because epoxy polymers have good adhesive characteristics and are useful in reinforcing polyethylene or polybutylene terephthalate resins (an example of an application where compacted chopped strands may be particularly useful). In some embodiments, the epoxy polymer can be a urethane modified epoxy polymer. Urethane modified epoxy polymers can be useful in some embodiments of the present invention, for example, to balance the properties of the compacted chopped strands produced and of composites reinforced with the compacted chopped strands.
Epoxy film-formers are usually available as non-ionic, aqueous emulsions and “epoxy dispersion” will refer to one or more epoxy polymers dispersed as an aqueous emulsion.
An example an epoxy polymer useful as a film-former in non-limiting embodiments of the present invention is EPI-REZ 5520-W-60, commercially available from Resolution Performance Products LLC of Houston, Tex. EPI-REZ 5520-W-60 is a nonionic aqueous dispersion of urethane modified epoxy resin having a typical epoxide equivalent weight of about 540. Other examples of suitable epoxy polymers can include EPI-REZ 3522-W-60, also commercially available from Resolution Performance Products LLC, and Araldite® XU GY 281.
In embodiments of the present invention utilizing an epoxy polymer as a film-former, some embodiments can further comprise a second film-former. In such embodiments, the second film-former can comprise polyesters, polyurethanes, other epoxy polymers, and others. The second film-former can comprise polyurethane in some embodiments. Polyurethanes can be useful in embodiments where the compacted chopped strand might be used to reinforce polyamide resins. Polyurethanes can be useful as a second film-former in embodiments where the epoxy polymer comprises a urethane modified epoxy polymer.
Various polyurethane dispersions may be useful including, without limitation, aqueous solutions of polyurethane polymers formed by a reaction between an organic isocyanate or polyisocyanate and an organic polyhydroxylated compound or hydroxyl terminated polyether or polyester polymer. The polyurethane dispersion can contain a crosslinking group in some embodiments. The polyurethane can be part of a dispersion comprising a polyurethane and a blocked isocyanate in some embodiments. A non-limiting example a polyurethane film-former useful in some embodiments of the present invention is Witcobond W-290H commercially available from Crompton Corporation. Another non-limiting example of a polyurethane film-former useful in some embodiments of the present invention is Baybond 2011L commercially available from Bayer Corporation.
The amount and type of film-formers present in the sizing composition can be determined by various factors including, but not limited to, the film-former's compatibility with the resin to be reinforced, the film-former's compatibility with other components in the sizing composition, the adhesive characteristics of the film-former and potential effects on the sizes and shapes of the compacted chopped strands, the cost of a film-former such that the sized glass fibers are a commercially viable product, and others. The lower limit of the amount of film-former can be determined by the lowest amount effective to protect the glass fibers from damage during processing or by the lowest amount effective to promote greater adhesion between the glass fibers or by the lowest amount effective to produce compacted chopped strands that are not too small. The upper limit of the amount of film-forming material can be determined by a viscosity of the wet sizing composition suitable for application to glass fibers or by the amount of film-former necessary to provide acceptable strength in a reinforced polymeric resin or by the amount of film-former necessary to produce compacted chopped strands that are not too large. In some embodiments, the total amount of film-former that can provide a wet sizing composition having a useful viscosity can be up to about 90% by weight based on total solids of the sizing compositions. In other embodiments, the total amount of film-former can be greater than about 60% by weight based on total solids of the sizing composition. In other embodiments, the amount of film-former can be between about 60 and about 90% by weight based on total solids of the sizing composition.
In embodiments that comprise an epoxy polymer as a first film-former and a polyurethane as a second film-former and wherein the total amount of film-former in the sizing composition is from about 60 weight percent to about 90 weight percent based on the total solids of the sizing composition, the ratio of epoxy film-former to polyurethane film-former can generally be from about 2:1 (e.g., the total film-former comprises about 67 weight percent epoxy film-former) to about 4:1 (e.g., the total film-former comprises about 80 weight percent epoxy film-former). In some non-limiting embodiments, the ratio of epoxy film-former to polyurethane film-former can be about 3:1 (e.g., the total film-former comprises about 75 weight percent epoxy film-former).
The sizing composition used to at least partially coat the fiber glass filaments for forming compacted chopped strands further comprises one or more coupling agents in some embodiments. Non-limiting examples of coupling agents that can be used in the sizing compositions of the present invention can include organo-silane coupling agents, transition metal coupling agents, amino-containing Werner coupling agents, chrome coupling agents, and mixtures thereof. These coupling agents typically have multiple functionality. Each metal or silicon atom has attached to it one or more groups which can react with the glass fiber surface or otherwise be chemically attracted, but not necessarily bonded, to the glass fiber surface. A coupling agent also interacts and/or reacts with a resin or resins that may be used in an end product, such that the coupling agent can facilitate adhesion between the glass fibers and the resin or resins.
The coupling agent can comprise organo-silane coupling agents in some embodiments. Non-limiting examples of useful functional organo silane coupling agents can include epoxy (e.g., SILQUEST® A-187 gamma-glycidoxypropyltrimethoxysilane), methacrylate (e.g., SILQUEST® A-174 gamma-methacryloxypropyltrimethoxysilane), and amino (e.g., A-1100 gamma-aminopropyl-triethoxysilane) silane coupling agents, each of which are commercially available from GE Advanced Materials of Tarrytown, N.Y. Other examples of useful silane coupling agents are set forth in K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibres at page 263 (2d Ed. New York 1983), which is hereby incorporated by reference.
Non-limiting examples of organo-silane coupling agents that may be particularly suitable for some applications can include amino-functional silanes, such as SILQUEST® A-1108 and SILQUEST® A-1120 from GE Advanced Materials of Tarrytown, N.Y. and DYNASYLAN® AMEO from Degussa AG of Dusseldorf, Germany. SILQUEST® A-1120 is an N-(beta(Aminoethyl)-gamma-aminopropyltrimethoxysilane. While the complete structure of SILQUEST® A-1108 is not publicly available, SILQUEST® A-1108 is also understood to be an amino-functional silane. DYNASYLAN® AMEO is 3-aminopropyltriethoxysilane.
The amount of the coupling agent in the sizing composition can depend upon various factors such as, but not limited to, the type and amount of film-former that may be included in the sizing composition, the coupling agent's affinity for a particular resin, and/or the coupling agent's compatibility with the other components of the sizing composition. In some embodiments, where one or more amino-functional coupling agents are used, the total amount of coupling agent can comprise up to about 50 weight percent of the sizing composition on a total solids basis. The total amount of coupling agent, in some embodiments, can comprise up to about 40 weight percent of the sizing composition on a total solids basis. In further embodiments, the total amount of coupling agent can comprise greater than about 10 weight percent of the sizing composition on a total solids basis. In further embodiments, the total amount of coupling agent can comprise between about 1 and about 40 weight percent of the sizing composition on a total solids basis.
Non-limiting embodiments of sizing compositions of the present invention can also comprise a plurality of coupling agents. The multiple coupling agents can advantageously result in the sizing composition being compatible with a variety of resins, or can enhance the compatibility of the sizing composition with particular resins. The amount and type of each coupling agent used in a sizing composition of the present invention may be selected based on resin compatibility, effect on fiber glass strand properties (e.g., lower broken filaments, abrasion resistance, strand integrity, and strand friction), and/or compatibility with other components of the sizing composition.
In some embodiments where multiple coupling agents are used, each of the coupling agents can comprise an amino-functional silane. The amino-functional coupling agents can be used in various combinations and amounts, and can include coupling agents comprising a primary amine only, coupling agents comprising a primary amine and a secondary amine, coupling agents comprising a secondary amine only, and others.
In some embodiments, a sizing composition can comprise a first coupling agent comprising a primary amine and a secondary amine, a second coupling agent comprising a primary amine, and a third coupling agent comprising a third amino-functional coupling agent. In some embodiments, each of the three coupling agents can comprise up to about twenty-five weight percent of the sizing composition on a total solids basis. In other embodiments, each of the three coupling agents can comprise greater than about five weight percent of the sizing composition on a total solids basis. In some embodiments, each of the three coupling agents can comprise up to about fifteen weight percent of the sizing composition on a total solids basis. In some embodiments comprising three coupling agents, the coupling agent comprising a primary amine and a secondary amine can be SILQUEST® A-1120, the coupling agent comprising a primary amine can be DYNASYLAN® AMEO, and the third amino-functional coupling agent can comprise SILQUEST® A-1108.
The sizing composition used to at least partially coat the fiber glass filaments for forming compacted chopped strands can further comprise a lubricant in some embodiments. Lubricants can be provided in sizing compositions for a number of reasons including, for example, to assist with internal lubrication (e.g., reduce filament-to-filament or glass-to-glass abrasion) as well as to provide external lubrication (e.g., protect against glass-to-contact point abrasion during manufacturing). In embodiments of the present invention comprising lubricants, the lubricants can be lubricants which are different from any film-former used in the sizing composition. As used herein, the phrase “lubricants which are different from any film-former in the sizing composition” means that while lubricants may have film-forming properties, the lubricant(s) selected for a particular sizing composition are chemically different from any film-formers included in the same sizing composition.
Useful lubricants can include cationic, non-ionic, or anionic lubricants, and mixtures thereof. Non-limiting examples of such lubricants can include glass fiber lubricants which include amine salts of fatty acids (which can, for example, include a fatty acid moiety having 12 to 22 carbon atoms and/or tertiary amines having alkyl groups of 1 to 22 atoms attached to the nitrogen atom ), alkyl imidazoline derivatives (such as can be formed by the reaction of fatty acids with polyalkylene polyamines), acid solubilized fatty acid amides (for example, saturated or unsaturated fatty acid amides having acid groups of 4 to 24 carbon atoms such as stearic amide), acid solubilized polyunsaturated fatty acid amides, condensates of a fatty acid and polyethylene imine and amide substituted polyethylene imines, such as Emery 6717, a partially amidated polyethylene imine commercially available from Cognis Corporation of Cincinnati, Ohio.
A non-limiting example of a useful alkyl imidazoline derivative is Cation X, which is commercially available from Rhone Poulenc of Princeton, N.J. Other non-limiting example of useful lubricants include, without limitation, RD-1135B epoxidized polyester commercially available from Borden Chemical of Louisville, Ky., and Ketjenlube 522 partially carboxylated polyester which is commercially available from Akzo Chemicals, Inc. of Chicago, Ill.
In non-limiting embodiments of a sizing composition utilizing a lubricant, the total amount of lubricant can comprise up to 99.9 weight percent of the sizing composition based on total solids. In other non-limiting embodiments, the total lubricant can comprise up to about 50 weight percent of the sizing composition based on total solids. The total lubricant, in other non-limiting embodiments, can comprise up to about 10 weight percent of the sizing composition based on total solids.
Other components used in sizing compositions that would not adversely affect the performance of the sizing composition and that would not adversely affect the sizes, shapes, and physical properties of the compacted chopped strands can be also be used in sizing compositions for some embodiments of compacted chopped strands. Examples of components that might adversely affect the performance of the sizing composition can include components that might adversely affect the sizes and shapes of the compacted chopped strands, components that might adversely affect the physical properties of the compacted chopped strands, and components that might adversely affect the compacted chopped strands performance in reinforcing resins. As non-limiting examples, anti-static agents or biocides might be included if they would not adversely affect the sizing composition, the compacted chopped strands, or performance of the compacted chopped strands.
As noted above, sizing compositions comprising the above-referenced components or various combinations thereof can be used to at least partially coat at least one of a plurality of fiber glass filaments in forming compacted chopped strands of the present invention. In some embodiments, the sizing composition comprises at least one film-former in an amount up to about 90 weight percent on a total solids basis, at least one coupling agent in an amount up to about 50 weight percent on a total solids basis, and up to about five weight percent of at least one alkylene-oxide polymer on a total solids basis, wherein the alkylene oxide polymer comprises at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. In further embodiments, the sizing composition can comprise a second film-former and the ratio of the amount of first film-former to the amount of second film-former is between about 2:1 and about 4:1. In further embodiments, the sizing composition can comprise a lubricant in an amount up to about 50 weight percent on a total solids basis.
In some embodiments, the sizing composition comprises at least one film-former in an amount up to about 90 weight percent on a total solids basis, at least one coupling agent in an amount up to about 40 weight percent on a total solids basis, and up to about five weight percent of at least one alkylene oxide polymer on a total solids basis, wherein the alkylene oxide polymer comprises at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. In further embodiments, the sizing composition can comprise a second film-former and the ratio of the amount of first film-former to the amount of second film-former is between about 2:1 and about 4:1. In further embodiments, the sizing composition can comprise a lubricant in an amount up to about 10 weight percent on a total solids basis.
In some embodiments, the sizing composition comprises at least one film-former in an amount ranging from about 60 weight percent to about 90 weight percent on a total solids basis, at least one coupling agent in an amount ranging from about 10 weight percent to about 50 weight percent on a total solids basis, and at least one alkylene oxide polymer ranging from about 0.1 weight percent to about 1 weight percent on a total solids basis, wherein the alkylene oxide polymer comprises at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide. In further embodiments, the sizing composition can comprise a second film-former and the ratio of the amount of first film-former to the amount of second film-former is between about 2:1 and about 4:1. In further embodiments, the sizing composition can comprise a lubricant in an amount up to about 10 weight percent on a total solids basis.
In some embodiments, the sizing composition comprises two film-formers in a total amount of up to about 90 weight percent of the sizing composition on a total solids basis, a first film-former comprising an epoxy polymer and a second film-former comprising a polyurethane wherein the ratio of the epoxy polymer to the polyurethane is between about 2:1 and about 4:1, at least one coupling agent in an amount up to about 50 weight percent on a total solids basis, and up to about five weight percent of polyethylene oxide on a total solids basis. In further embodiments, the epoxy polymer comprises a urethane-modified epoxy polymer. In other embodiments, the at least one coupling agent comprises two amino-functional coupling agents. The at least one coupling agent can comprise three amino-functional coupling agents in some embodiments. In other embodiments, the sizing composition can comprise a lubricant in an amount up to about 50 weight percent on a total solids basis.
In some embodiments, the sizing composition comprises two film-formers in a total amount of greater than about 60 weight percent of the sizing composition on a total solids basis, a first film-former comprising an epoxy polymer and a second film-former comprising a polyurethane wherein the ratio of the epoxy polymer to the polyurethane is between about 2:1 and about 4:1, at least one coupling agent in an amount up to about 40 weight percent on a total solids basis, and up to about five weight percent of polyethylene oxide on a total solids basis. In further embodiments, the epoxy polymer comprises a urethane-modified epoxy polymer. In other embodiments, the at least one coupling agent comprises two amino-functional coupling agents. The at least one coupling agent can comprise three amino-functional coupling agents in some embodiments. In other embodiments, the sizing composition can comprise a lubricant in an amount up to about 10 weight percent on a total solids basis.
In some embodiments, the sizing composition comprises two film-formers in a total amount of between about 60 weight percent and about 90 weight percent of the sizing composition on a total solids basis, a first film-former comprising a urethane-modified epoxy polymer and a second film-former comprising a polyurethane wherein the ratio of the urethane-modified epoxy polymer to the polyurethane is between about 2:1 and about 4:1, a first coupling agent in an amount up to about 15 weight percent on a total solids basis, a second coupling agent in an amount up to about 15 weight percent on a total solids basis, a third coupling agent in an amount up to about 15 weight percent on a total solids basis, polyethylene oxide in an amount up to about 1 weight percent on a total solids basis, and a lubricant in an amount up to about 10 weight percent on a total solids.
Other sizing compositions incorporating the components discussed above and in the varying amounts discussed above may also be prepared.
The present invention relates to compacted chopped strands which comprise, in some embodiments, a plurality of fiber glass filaments and a residue of a sizing composition (as discussed above) at least partially coating at least one of the filaments. In various embodiments, the compacted chopped strands can comprise a number of characteristics including those set forth below separately or in various combinations. In some embodiments, compacted chopped strands can have a cross-sectional area that is greater than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, compacted chopped strands can have a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand. Compacted chopped strands can have a cross-sectional area that is greater than about 1.0 and up to about three times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand in some embodiments. In some embodiments, compacted chopped strands can comprise a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand. Compacted chopped strands, in some embodiments, can comprise a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand. In some embodiments, compacted chopped strands can have a substantially round cross-section. A plurality of compacted chopped strands can exhibit a bulk density of greater than 700 grams per liter in some embodiments. A plurality of compacted chopped strands can exhibit desirable flow indexes, such as a flow index of at least 1 in some embodiments, a flow index of at least 1.2 in other embodiments, and a flow index of at least 1.5 in still other embodiments.
Compacted chopped strands of the present invention and various properties of such strands will be discussed in more detail below. Methods and systems for forming compacted chopped strands are generally known to those of ordinary skill in the art. Examples of such methods and systems are described in U.S. Pat. Nos. 4,840,755, 5,578,535, 5,693,378, 5,868,982, 5,945,134, and 6,743,386, in U.S. Patent Publication No. 2004/0089966, and in PCT Publication No. WO 03/097543.
Exemplary methods and systems comprise providing a supply of generally continuous fiber glass strand. The strand can be supplied directly from a forming operation as part of a “direct chop” process or from one or more packages of continuous fiber glass strands as part of a “remote wet chop” process using techniques known to those of ordinary skill in the art.
As used herein, the term “strand” means a plurality of continuous filaments or fibers that can be twisted or untwisted. The number of individual filaments in a fiber strand can vary although the number typically ranges from about 50 to about 8000 filaments. The diameters of the individual filaments in the strand can vary but typically range from about 5 microns (designated “D” fiber strand) to about 24 microns (designated “T” fiber strand). If more information on strand and fiber designations is desired, see Loewenstein, (3rd. Ed. 1993) at page 27, which is hereby incorporated by reference.
The generally continuous strand can be provided to a chopping assembly or similar apparatus which can sever the strand into a plurality of chopped strands. Such chopping assemblies are well known in the art and commercially available such as, for example, the Model 90 chopper from Finn and Fram, Inc. of San Fernando, Calif. Examples of suitable chopping assemblies are also described in U.S. Pat. No. 6,148,641 and U.S. Patent Publication No. 2003/0162452, published on Aug. 28, 2003, each of which are hereby incorporated by reference.
As noted above, in a direct chop process, a generally continuous, glass fiber strand (or plurality of strands) is fed directly from a fiber forming assembly into a chopping assembly where the strand is chopped. In other embodiments, such as remote chop processes, the generally continuous fiber glass strand (or plurality of strands) can be supplied from a package (or plurality of packages). As used herein, the term “package” refers to any package containing a supply of generally continuous fiber strand such as forming packages, roving packages, and bobbins. For example, the supply of generally continuous fiber glass strand can be provided by one or more creels or carriers containing one or more packages of generally continuous fiber glass strand. Such processes are often referred to as indirect processes or remote chop processes.
The use of chopping assemblies to sever or chop generally continuous fiber glass strand to form wet, chopped strands is well known to those of skill in the art. For additional information related to chopping of fiber glass strands, see Loewenstein, (3rd. Ed. 1993) at pages 193-94, 325-26, U.S. Pat. No. 6,148,641, and U.S. Patent Publication No. 2003/0162452.
Typically, the wet, chopped strands have a flatter profile after chopping due to the operation of the chopping assembly. FIG. 1 illustrates an example of a cross-section of a chopped strand upon leaving a chopping assembly and prior to agglomerating. Further, the operation of the chopping assembly can result in filaments separating from the chopped strands, either as loose individual filaments or as smaller groups of filaments (e.g., partial chopped strands). These loose filaments or partial chopped strands may continue downstream in the process and adhere to other chopped strands, other partial chopped strands, and/or other filaments.
From a chopping assembly, the wet, chopped strands can be agglomerated. The chopped strands can be provided to a device for agglomerating the chopped strands into compacted chopped strands using conventional techniques.
The chopped strands can be agglomerated in any number of ways using techniques known to those of skill in the art as set forth below. For example, and without limitation, the chopped strands can be agglomerated by tumbling, mixing, shaking, rolling, vibrating, or otherwise moving the chopped strands amongst other chopped strands and loose filaments. Non-limiting examples of ways in which the chopped strands can be agglomerated are set forth in U.S. Pat. Nos. 4,840,755, 5,578,535, 5,693,378, 5,868,982, 5,945,134, and 6,743,386, in U.S. Patent Publication No. 2004/0089966, and in PCT Publication No. WO 03/097543. In general, agglomerating the chopped strands can be accomplished by moving the chopped strands relative to other chopped strands, partial chopped strands, and/or loose filaments in a manner that can result in chopped strands, partial chopped strands, and/or loose filaments agglomerating into compacted chopped strands. Factors that can be important in agglomeration, as understood by those of ordinary skill in the art, can comprise the amount of moisture on the chopped strands, the sizing composition applied to the chopped strands, the agglomerating device, and others.
After agglomeration, the compacted chopped strands may be dried. In some embodiments, a conveyor may be provided to transport the compacted chopped strands to a drying device. The compacted chopped strands may be dried using techniques known to those of skill in the art, including drying at room temperature or at elevated temperatures. In some embodiments, the compacted chopped strands can be dried using a vibrating bed dryer.
The foregoing description of the manner in which compacted chopped strands can be formed can be adapted for any number of products using techniques known to those of ordinary skill in the art. For example, persons of ordinary skill in the art, when provided with the sizing composition of the present invention, will be able to readily select the appropriate method and system for manufacturing compacted chopped strands, such as direct chop, remote chop, and others.
The moisture content of the fiber glass strands can be important in producing compacted chopped strands having a desired size and shape. For example, in both direct chop and remote wet chop processes, the moisture content can affect the diameter of the compacted chopped strands, the shape of the compacted chopped strands, the density of the compacted chopped strands, the amount of loose filaments and/or partial chopped strands collected by the chopped strands, and/or other properties of the compacted chopped strands. Persons of ordinary skill in the art can readily determine an appropriate moisture content based on the desired properties of the compacted chopped strands. Further, the moisture content of the continuous strands, the chopped strands, and/or the compacted chopped strands can be measured and/or adjusted using techniques known to those of ordinary skill in the art in order to achieve a desired moisture content and to produce a compacted chopped strand having desired properties.
The components of the sizing composition can also be an important factor in the size and shape of the compacted chopped strands. Some sizing compositions may not absorb or retain enough moisture through chopping for the chopped strands to reach a desirable size. In accordance with embodiments of the present invention, alkylene oxide polymers can be included in sizing compositions to result in compacted chopped strands having desirable sizes and other properties after agglomerating. For example, alkylene oxide polymers can be useful in sizing compositions to increase the bulk density and the cross-sectional area of the compacted chopped strands after agglomerating. Another factor in the size of the compacted chopped strands produced by embodiments of the present invention is the distribution of the sizing composition on the strands and the content of the sizing composition as applied.
As described above, compacted chopped strands of the present invention can be rounded in some embodiments, meaning that the cross-sections of compacted chopped strands are generally round, particularly when compared to chopped strands prior to agglomerating. FIG. 2 is a cross-sectional view of an embodiment of a compacted chopped strand of the present invention that has a substantially round cross-section. The rounding of the compacted chopped strand of FIG. 2 is evident when compared to the cross-sectional view of the chopped strand prior to agglomerating shown in FIG. 1. Accordingly, in some embodiments of the present invention, compacted chopped strands can have substantially round cross-sections, such that the compacted chopped strands are more like a cylinder in shape than a small piece of flat paint brush.
With regard to the size of the compacted chopped strands of the present invention, the compacted chopped strands, in some embodiments, will generally have a larger bulk density than the chopped strands prior to agglomerating. As used herein, “bulk density” refers to the weight of the strands that fill a predetermined volume. Thus, the compacted chopped strands filling a given volume, in some embodiments, will generally weigh more than chopped strands filling the same volume. In some embodiments of the present invention, compacted chopped strands can have bulk densities of greater than about 700 grams per liter. In other embodiments, compacted chopped strands can have bulk densities of between about 700 and about 1000 grams per liter (or other relevant unit of measure). The aforementioned range of bulk densities can be desirable for some applications. For example, and without limitation, for some applications, compacted chopped strands with a bulk density of substantially less than about 700 grams per liter may not flow as well in downstream applications. As another example, and without limitation, compacted chopped strands with a bulk density of substantially greater than about 1000 grams per liter may not disperse well in a resin.
Compacted chopped strands of the present invention in some embodiments can also generally weigh more than chopped strands prior to agglomerating. The weights can be expressed in terms of “Tex”, which refers to the mass in grams per 1,000 meters of yarn. Thus, in some embodiments, a compacted chopped strand of the present invention can generally be expected to weigh more than a chopped strand. In some embodiments, compacted chopped strands can weigh greater than about 500 Tex per compacted chopped strand. Compacted chopped strands, in some embodiments, can weigh less than about 3,000 Tex per compacted chopped strand. In some embodiments of the present invention, compacted chopped strands can weigh between about 500 and about 3,000 Tex per compacted chopped strand. The size of the compacted chopped strands can be an important factor in the flow properties and dispersion properties of the compacted chopped strands, and the aforementioned range of sizes can be appropriate for some downstream applications.
The size of compacted chopped strands of the present invention can also be considered in terms of cross-sectional area. Compacted chopped strands in some embodiments of the present invention can generally be expected to have larger cross-sectional areas than chopped strands prior to agglomerating. The desired sizes of the compacted chopped strands can vary, but are typically less than about four times larger than the size of the chopped strands prior to agglomerating. The cross-sectional areas of some embodiments of compacted chopped strands can be greater than about 1.0 and up to about four times the cross-sectional areas of the chopped strands prior to agglomerating in some embodiments. The cross-sectional areas of compacted chopped strands, in some embodiments, can be greater than about 1.0 and up to about three times the cross-sectional areas of the chopped strands prior to chopping in some embodiments. The compacted chopped strands, in other embodiments, can have cross-sectional areas greater than about 1.0 and up to about one and one-half times larger than the chopped strands prior to agglomerating.
The length of compacted chopped strands can be a variety of lengths depending on the application. The lengths of the compacted chopped strands will generally depend on the length of the chopped strand prior to agglomerating. While generally dependent on the desired end use and the chopper used, chop lengths of chopped strands can be between about three and about fifteen millimeters although continuous strands can be chopped to other lengths if so desired. In some embodiments, compacted chopped strands can have a length of up to about fifteen millimeters. Compacted chopped strands, in some embodiments, can have a length of greater than about three millimeters. In some embodiments, compacted chopped strands can have a length of up to about five millimeters.
With regard to downstream uses of compacted chopped strands (e.g., uses by a customer of the compacted chopped strand manufacturer), compacted chopped strands of the present invention can be more easily processed than conventional chopped strands in some embodiments. The improved processability of the compacted chopped strands can be due to the shape and size of the strands as discussed. Another factor that can improve the processability of the compacted chopped strands is flowability. As used herein, the term “flowability” characterizes the performance of the dry compacted chopped strands when poured or emptied from a container and is measured by the slump test described herein.
The flowability of compacted chopped strands is an indicator of how the compacted chopped strands will perform in downstream operations. For example, compacted chopped strands can be used to reinforce thermoplastic resins. In such applications, the compacted chopped strands are mixed with a polymeric resin. After mixing, the mixture of resin and compacted chopped strands can be provided to a molding device (e.g., injection molding or compression molding device), where the mixture is formed into an article.
It can be important for the compacted chopped strands to flow well when delivered to the polymeric resin for mixing. Compacted chopped strands that do not flow well can slow, back-up, or plug the delivery channel to the mixing chamber. Flow problems can also trigger equipment malfunction, downtime, and poor product quality. No-flow conditions such as arching or ratholing, erratic flow, overflow, limited discharge, and segregation are also examples of flow problems.
A slump test has been developed to measure the flowability of the compacted chopped strands. The slump test provides a flow index value which is an indicator of flowability. Compacted chopped strands having higher flow indexes under the slump test are believed to generally perform better in downstream operations where the strands are poured or emptied from a container than strands having lower flow indexes.
FIG. 3 illustrates an apparatus 200 that can be used for the slump test to calculate the flow index of chopped strands and compacted chopped strands. The apparatus 200 includes a sample cylinder 202, having a diameter of 8.02 centimeters and a height of 7.62 centimeters, a platform, a scale, a deflector, and receiving tray. The cylinder 202 can be positioned on a platform having the same diameter and filled with chopped strands. The cylinder 202 can be lifted to release the chopped strands to the platform so that excess chopped strands fall onto an excess strand deflector 206. A receiving tray 210 collects the excess chopped strands. A scale 212 is used to measure the initial weight of the chopped strands and the weight of the excess chopped strands in the receiving tray 210.
The slump test may be performed under standard ambient laboratory conditions in the following manner. The cylinder assembly 202 is placed on the scale 212 and the scale is tared to a zero reading. The cylinder assembly 202 is then placed on a vibrating tray (Model No. US-100 from Vibco). The cylinder assembly 202 is filled with chopped strands until it is full. The vibratory setting of the vibrating tray is set to level #5 and turned on for thirty seconds. As the tray vibrates, the cylinder 202 should continue to be filled with chopped strands until it is full (the vibrating of the tray will allow more strands to be added). The top surface of the cylinder 202 is then leveled with a square edge. The full cylinder 202 is placed on the scale and the weight is recorded as W₁(grams). The cylinder is raised, which allows the chopped strands to slide off the platform. Many of the excess chopped strands hit the excess strand deflector 206 and slide into the receiving tray 210. Any excess chopped strands in the deflector tray that do not slide into the receiving tray 210 should be brushed down into the receiving tray 210 using a brush.
An empty collecting cup is then placed on the scale 212 and the reading is then tared to zero. The excess chopped strands are poured from the receiving tray 210 into the collecting cup. The cup containing the excess chopped strands is then placed on the scale 212 and the weight is recorded as W₂(grams).
The flow index is calculated using the following equation: $\begin{matrix} Flow Index = \frac{W_{1}^{2}}{K (W_{1} - W_{2})} & (Eq . 1) \end{matrix}$
wherein K is a constant that is a function of the cylinder size (e.g., the cylinder radius and the cylinder height). This equation reflects the relationship between the bulk density of the chopped strands and the angle of repose (the angle of the pile of compacted chopped strands remaining on the platform relative to a horizontal plane). The constant K can be calculated by the following equation:
K=3V ₁ ²/(πr ³)=3πrh ₁ ² (Eq. 2)
where V₁is the volume of the test cup in cubic centimeters, h₁is the height of the cup in centimeters, and r is the radius of the measuring table in centimeters. The sensitivity of K to the cup size (assuming a radius of 4.01 centimeters) is shown in Table 1.

TABLE 1

Cup Height, cm K

5.08 975

7.62 2194

10.16 3900
For cylinders having a radius of 4.01 centimeters, heights of five centimeters or larger generally provide more accurate results. In the procedure described above, the cylinder 202 had a height of 7.62 centimeters, so the constant (K) in the equation would be 2194.
The procedure described above can generally be used to calculate the flow index of compacted chopped strands having nominal lengths of about thirteen millimeters or less.
As used herein, the term “flow index” refers to the flow index calculated using the slump test described above. Embodiments of compacted chopped strands of the present invention can have a flow index of 1.0 or greater. In other embodiments, compacted chopped strands can have a flow index of 1.2 or greater. In other embodiments, compacted chopped strands of the present invention can have a flow index of 1.5 or greater.
Embodiments of the present invention will now be illustrated in the following specific, non-limiting examples.

EXAMPLES

Sizing compositions were prepared in accordance with the formulations set forth in Table 2. Sizing composition A represents a comparative sizing composition, while sizing composition 1 represents a non-limiting embodiment of a sizing composition for use with compacted chopped strands of the present invention.

TABLE 2


Formulations of Comparative Sizing Composition
[pounds (weight percent solids)]

Component

		A	1

First Silane¹	13.28	(10.74%)	13.28	(10.71%)
Second Silane²	13.28	(10.74%)	13.28	(10.71%)
Third Silane³	13.28	(10.74%)	13.28	(10.71%)
Cold Water for Silanes⁴	45 gallons	(0.0%)	45 gallons	(0.0%)
Alkylene Oxide Polymer⁵			0.34	(0.27%)
Hot Water for Alkylene	12 gallons	(0.0%)	12 gallons	(0.0%)
Oxide Polymer⁶
First Film-Former⁷	102.4	(48.84%)	102.4	(48.71%)
Second Film-Former⁸	37.2	(18.04%)	37.2	(18.00%)
Lubricant⁹	5.31	(0.90%)	5.31	(0.90%)

¹DYNASYLAN ® AMEO 3-aminopropyltriethoxysilane commercially available from Degussa AG of Dusseldorf, Germany.
²SILQUEST ® A-1108 amino-functional silane commercially available from GE Advanced Materials of Tarrytown, NY.
³SILQUEST ® A-1120 N-(beta(Aminoethyl)-gamma-aminopropyltrimethoxysilane commercially available from GE Advanced Materials of Tarrytown, NY.
⁴Deionized water.
⁵POLYOX WSR-301 polyethylene oxide commercially available from the Dow Chemical Company.
⁶Deionized water.
⁷EPI-REZ 5520-W-60 urethane modified epoxy resin commercially available from Resolution Performance Products LLC of Houston, Texas.
⁸Witcobond W-290H polyurethane dispersion commercially available from Crompton Corporation.
⁹RD-1135B epoxidized polyester commercially available from Borden Chemical of Louisville, Kentucky.

The amounts of the components listed in Table 2 represent the amounts that can be used to prepare 100 gallons of the sizing composition. Other volumes of the sizing composition can be prepared by adjusting the amounts shown.
Preparation of Sizing Compositions

Each of the sizing compositions in Table 2 can be generally prepared according to the exemplary procedure described below. The amount of water used to prepare the individual components prior to adding the components to the main mix tank may vary depending on the technician preparing the sizing composition. Water is precisely added at the end of the procedure to dilute the sizing composition to the desired final volume.
The specified amount of cold water (˜75° F.+/−15° F.) is added to a main mix tank. The specified amount of the first silane, the second silane, and the third silane are then added to the main mix tank. The silane mix is then agitated slowly for at least twenty minutes or until the solution is clear.
To prepare the alkylene oxide polymer, the specified amount of hot water (150° F. +/−10° F.) is added to a premix tank. The specified amount of alkylene oxide polymer is weighed into a dry container. The disc mixer in the premix tank is started on high speed and an eductor is used to transfer the alkylene oxide polymer to the premix tank. The alkylene oxide polymer is mixed in the premix tank for ten minutes and then transferred to the main mix tank. The premix was inspected to insure proper mixing devoid of large particles and was then transferred to the main mix tank. As sizing composition A does not include alkylene oxide polymer, this step was not part of the preparation of sizing composition A.
The specified amount of the first film-former is then added to the main mix tank and agitated for at least five minutes. The specified amount of the second film-former is then added to the main mix tank and agitated for at least five minutes. The specified amount of the lubricant is then added to the main mix tank and agitated for five minutes on high speed. The mix tank agitator is then returned to a slow speed.
The final mix was agitated while adding the amount of cold water (75+/−15° F.) required to bring the sizing composition to the correct volume. The lid of the main mix tank is closed and the sizing composition is agitated for at least ten minutes. The final temperature of the sizing composition prior to use in a fiber glass forming operation is 85+/−25° F. The sizing composition has a nominal percent solids of 13.00% +/−0.95% and a nominal pH of 10.0+/−0.50.
Preparation of Compacted Chopped Strands
Each of the sizing compositions was prepared according to the above mix procedure.
A fiber glass strand comprising a plurality of thirteen micron diameter (“K”) filaments was provided from a bushing using techniques known to those of skill in the art for producing E-glass. Upon exiting the bushing, the filaments were sprayed with water from a plurality of spray nozzles.
After spraying with water, the filaments were at least partially coated with one of the two sizing compositions provided in Table 2. The sizing composition was applied using an applicator roll. The applicator roll applied the sizing composition to achieve a nominal loss on ignition of 0.9. As used herein, the term “loss on ignition” or “LOI” means the weight percent of dried coating (sizing composition) present on the fiber glass as determined by Equation 1:
LOI=100×[(W _dry −W _bare)/W _dry] (Eq. 3)
wherein W_dryis the weight of the fiber glass plus the weight of the coating after drying in an oven at 220° F. (about 104° C.) for 60 minutes, and W_bareis the weight of the bare fiber glass after heating the fiber glass in an oven at 1150° F. (about 621° C.) for 20 minutes and cooling to room temperature in a dessicator.
After the filaments were at least partially coated with the sizing composition, the filaments were gathered into a continuous strand. The continuous strand was then delivered to a chopping assembly as a direct chop operation. The nominal chop length for the continuous strands was set to ⅛ of an inch (˜3 millimeters).
After chopping, the chopped strands were agglomerated by tumbling to form compacted chopped strands.
The compacted chopped strands were then dried using a vibrating bed dryer in accordance with techniques known to those of ordinary skill in the art.

Example 1

Compacted chopped strands were prepared as described above in order to compare the bundle size distributions of compacted chopped strands coated with comparative sizing composition A and sizing composition 1.
The bundle size distribution is determined using a sieve with a Tyler #5 screen size. One hundred grams of compacted chopped strands were placed on the screen and shaken for ten seconds. A percentage of large bundles for each one hundred gram sample was determined by weighing the amount of compacted chopped strands that did not pass through the screen.
The percentage of large bundles is an indicator of bundle size distribution. In general, a plurality of compacted chopped strands with a low percentage of large bundles is believed to disperse better in a resin.
For this example, five pound samples of compacted chopped strands were collected from the exit end of the dryer every hour. A total of forty-eight samples of compacted chopped strands prepared using comparative sizing composition A (“Control #1”) were collected. The average percentage of large strands for Control #1 was 0.95%. A total of sixty-one samples of compacted chopped strands prepared using sizing composition 1 (“Sample #1”) were collected. The average percentage of large strands for the Sample # 1, which represent an embodiment of the present invention, was 0.37%. This data suggest that embodiments of compacted chopped strands of the present invention which incorporate an alkylene oxide polymer into the sizing composition exhibit a lower bundle size distribution than compacted chopped strands without an alkylene oxide polymer in the sizing composition. Such embodiments of compacted chopped strands of the present invention are also expected to disperse better in a resin.

Example 2

In this Example, physical properties of compacted chopped strands prepared using the sizing compositions in Table 1 were compared to determine whether the presence of the alkylene oxide polymer would have a negative effect on the properties.
Four sets of samples were prepared according to the “Preparation of Compacted Chopped Strands” section above. Two of the sample sets were control samples (using sizing composition A from Table 2) and two were sets of compacted chopped strands according to an embodiment of the present invention (using sizing composition 1 from Table 2). Two additional sample sets were also prepared according to the “Preparation of Compacted Chopped Strands” section above using sizing composition 1 from Table 2, except the compacted chopped strands were not dried inline. These sample sets were dried remotely using a Rexnord dryer. For the purpose of comparing physical properties, the samples dried using the Rexnord dryer are comparable to the samples dried using the inline dryer such that the differences in drying techniques should not be considered a factor that might affect the physical properties being measured. The nominal chop lengths of the compacted chopped strands were ⅛ of an inch (˜3 millimeters). The nominal LOI for each sample set was 0.9. A significant number of compacted chopped strands from each sample set were tested to determine a number of physical properties.
Tensile strength was measured according to ISO Method 527-2. The notched charpies (i.e., impact resistances) of the compacted chopped strands were measured using ISO Method 179-1. The percentages of glass content of the compacted chopped strands were measured using ISO Method 1172.

Table 3 provides the average values of the physical properties for each sample set.

TABLE 3


Physical Properties

	Sizing		Tensile	Notched	Glass
Sample	Composition	Dryer	Strength	Charpy	Content

Control #2	Composition A	Inline	129	12.7	30.1
Control #3	Composition A	Inline	129	12.7	30
Sample #2	Composition 1	Inline	132	13	30.1
Sample #3	Composition 1	Inline	130	12.7	30
Sample #4	Composition 1	Rexnord	132	13	30.1
Sample #5	Composition 1	Rexnord	132	12.9	29.9

As evidenced by Table 3, the compacted chopped strands prepared using alkylene oxide polymer as a component of the sizing composition exhibited comparable physical properties to the compacted chopped strands prepared without using alkylene oxide polymer as a component of the sizing composition.

While not reflected in the above data, the compacted chopped strands of Samples 2-5 were observed to have similar color to Controls 2-3.

Example 3

In this Example, properties of compacted chopped strands prepared using sizing composition 1, which represent an embodiment of the present invention, were compared with uncompacted chopped strands prepared using comparative sizing composition A and compacted chopped strands prepared using comparative sizing composition A. Control #4 represents uncompacted chopped strands prepared using comparative sizing composition A. In the preparation of control #4, the chopped strands were not agglomerated by tumbling, but were dried directly after chopping, and are characterized as uncompacted chopped strands. Control #5 represents compacted chopped strands prepared as described above using comparative sizing composition A. Sample #6 represents compacted chopped strands according to one embodiment of the present invention prepared as described above using sizing composition 1. The nominal chop lengths of the chopped strands were ⅛ of an inch (˜3 millimeters). The nominal LOI for each sample set was 0.9.
For this example, five samples of five pounds each were collected from the exit end of the dryer for each of Control #4, Control #5, and Sample #6.
The bulk density of each sample was measured by filling a 0.0136 cubic foot vessel with the strands and weighing the strands to obtain bulk density in units of pounds per cubic feet. Five samples from each of Control #4, Control #5, and Sample #6 were measured. The average of the bulk densities for the five samples associated with Control #4, Control #5, and Sample #6 are shown in Table 4 below.
The flow index of each sample was measured using the slump test described above in connection with FIG. 3. Five samples from each of Control #4, Control #5, and Sample #6 were measured. The average of the flow indexes for the five samples associated with Control #4, Control #5, and Sample #6 are shown in Table 4 below.
The bundle size of each sample was measured by randomly selecting twenty individual compacted chopped strands, measuring the total weight of the subset, and dividing by twenty to get an average weight per compacted chopped strand. The average subset weight per chopped strand was divided by the nominal chopped length of the strands (⅛″) to calculate an average Tex of the subset. The Tex for five different subsets was calculated in this manner to provide a single bundle size data point. Five bundle size data points were calculated and averaged for each of Control #4, Control #5, and Sample #6. The average of the bundles sizes associated with Control #4, Control #5, and Sample #6 are shown in Table 4 below.

TABLE 4

Bulk

Sizing Compacted/ Density Flow Bundle

Sample Composition Uncompacted (lbs./ft³) Index Size (Tex)

Control #4 Composition A Uncompacted 35.06 0.186 416

Control #5 Composition A Compacted 47.86 0.913 812

Sample #6 Composition 1 Compacted 51.48 1.565 1090

As evidenced in Table 4, compacted chopped strands had a larger average bulk density, a larger average flow index, and a larger average bundle size than uncompacted chopped strands. Further, compacted chopped strands prepared using alkylene oxide polymer as a component of a sizing composition exhibited the largest average bulk density, the largest average flow index, and the largest average bundle size. This data suggest that the inclusion of alkylene oxide polymer as a component of the sizing composition in manufacturing compacted chopped strands can increase the density of the compacted chopped strands (e.g., increase the number of filaments per strand) while also providing an improvement in the flowability of the compacted chopped strands in downstream operations.
Desirable characteristics, which can be exhibited by embodiments of the present invention, can include, but are not limited to, the provision of compacted chopped strands having desirable properties; the provision of compacted chopped strands having desirable shapes; the provision of compacted chopped strands having desirable sizes; the provision of compacted chopped strands having improved flowability; the provision of compacted chopped strands having improved dispersability; the provision of compacted chopped strands having improved size uniformity; and others.
Various embodiments of the invention have been described in fulfillment of the various objects of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A compacted chopped strand, comprising:

a plurality of fiber glass filaments; and

a residue of a sizing composition at least partially coating at least one of the filaments, the sizing composition comprising:

a film-former;

a coupling agent; and

at least one alkylene oxide polymer, the alkylene oxide polymer comprising at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide, wherein the compacted chopped strand has a cross-sectional area that is larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

2. The compacted chopped strand of claim 1, wherein the alkylene oxide polymer comprises polyethylene oxide.

3. The compacted chopped strand of claim 2, wherein the polyethylene oxide comprises up to about five weight percent of the sizing composition on a total solids basis.

4. The compacted chopped strand of claim 2, wherein the polyethylene oxide has an average molecular weight of approximately 100,000 or greater.

5. The compacted chopped strand of claim 2, wherein the polyethylene oxide has an average molecular weight of approximately 10,000,000 or less.

6. The compacted chopped strand of claim 1, wherein the film-former comprises an epoxy polymer.

7. The compacted chopped strand of claim 6, wherein the sizing composition further comprises a second film-former and wherein the second film-former comprises polyurethane.

8. The compacted chopped strand of claim 1, wherein the sizing composition further comprises a lubricant.

9. The compacted chopped strand of claim 1, wherein the compacted chopped strand has a substantially round cross-section.

10. The compacted chopped strand of claim 1, wherein the compacted chopped strand has a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

11. The compacted chopped strand of claim 1, wherein the compacted chopped strand has a cross-sectional area that is greater than about 1.0 and up to about three times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

12. The compacted chopped strand of claim 1, wherein the compacted chopped strand has a length of up to about fifteen millimeters.

13. The compacted chopped strand of claim 1, wherein the compacted chopped strand comprises a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand.

14. The compacted chopped strand of claim 1, wherein the compacted chopped strand comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand.

15. A compacted chopped strand, comprising:

a plurality of fiber glass filaments; and

a film-former;

a coupling agent; and

at least one alkylene oxide polymer, the alkylene oxide polymer comprising at least one of polyethylene oxide, polypropylene oxide, and polybutylene oxide, wherein the compacted chopped strand comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand.

16. The compacted chopped strand of claim 15, wherein the compacted chopped strand has a cross-sectional area that is larger than the cross-sectional area of a continuous strand that was chopped prior to forming the compacted chopped strand.

17. The compacted chopped strand of claim 15, wherein the compacted chopped strand has a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

18. The compacted chopped strand of claim 15, wherein the compacted chopped strand has a cross-sectional area that is greater than about 1.0 and up to about three times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

19. The compacted chopped strand of claim 15, wherein the compacted chopped strand comprises a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand.

20. The compacted chopped strand of claim 15, wherein the polyethylene oxide has an average molecular weight of approximately 100,000 or greater.

21. The compacted chopped strand of claim 15, wherein the polyethylene oxide has an average molecular weight of approximately 10,000,000 or less.

22. The compacted chopped strand of claim 15, wherein the at least one film-former comprises an epoxy polymer.

23. The compacted chopped strand of claim 22, wherein the sizing composition further comprises a second film-former and wherein the second film-former comprises polyurethane.

24. The compacted chopped strand of claim 15, wherein the sizing composition further comprises a lubricant.

25. The compacted chopped strand of claim 15, wherein the compacted chopped strand has a substantially round cross-section.

26. The compacted chopped strand of claim 15, wherein the compacted chopped strand has a length of up to about fifteen millimeters.

27. A compacted chopped strand, comprising:

a plurality of fiber glass filaments; and

at least one film-former in an amount up to about 90 weight percent on a total solids basis;

at least one coupling agent in an amount up to about 50 weight percent on a total solids basis; and

up to about five weight percent polyalkylene oxide on a total solids basis.

28. The compacted chopped strand of claim 27, wherein the polyalkylene oxide comprises polyethylene oxide.

29. The compacted chopped strand of claim 27, wherein the compacted chopped strand comprises a larger number of filaments than the continuous strand that was chopped prior to forming the compacted chopped strand.

30. The compacted chopped strand of claim 27, wherein the compacted chopped strand has a cross-sectional area that is larger than the cross-sectional area of a continuous strand that was chopped prior to forming the compacted chopped strand.

31. The compacted chopped strand of claim 27, wherein the compacted chopped strand has a cross-sectional area that is greater than about 1.0 and up to about four times larger than the cross-sectional area of the continuous strand that was chopped prior to forming the compacted chopped strand.

32. The compacted chopped strand of claim 27, wherein the compacted chopped strand comprises a larger number of filaments per unit of cross-sectional area than the continuous strand that was chopped prior to forming the compacted chopped strand.