CA1232214A

CA1232214A - Preform with internal barrier and products made from the same

Info

Publication number: CA1232214A
Application number: CA000469653A
Authority: CA
Inventors: Suppayan M. Krishnakumar; Thomas E. Nahill
Original assignee: Continental Plastic Containers LLC
Current assignee: Continental Plastic Containers LLC
Priority date: 1984-02-17
Filing date: 1984-12-07
Publication date: 1988-02-02
Also published as: AU3639984A; EP0392571B1; MX169495B; JPH079488A; EP0392571A3; US4710118A; ATE114268T1; AU573661B2; US4609516A; EP0392571A2; JPH0785894B2; JPH0442967B2; DE3584898D1; DE3587947T2; EP0153120A3; DE3587947D1; US4781954A; JPS60189407A; ATE70490T1; EP0153120B1

Abstract

PREFORM WITH INTERNAL BARRIER
AND PRODUCTS MADE FROM THE SAME
ABSTRACT OF THE DISCLOSURE

This relates to laminated preforms, the method of forming such preforms and products which may be bene-ficially formed utilizing such preforms. Most particularly, this relates to a preform which has formed as part of the injection molding thereof two layers of barrier material which are disposed within two layers of thermoplastic resin and having received therebetween a solid core of thermoplastic resin. The specific method of forming the preform permits the barrier material layers to be of a greatly reduced thickness as compared to such layer thick-nesses permissible in the past, with the result that the barrier material layers in the blow molded articles are of a thickness recognized to be acceptable for the barrier function. The barrier material layers may be selectively terminated along the length of the preform so as to permit portions of the resultant blow molded article to be removed and reused. This abstract forms no part of the specification of this application and is not to be con-strued as limiting the claims of the application.

* * * *

Description

~.Z3~

PREFORM WITH INTERNAL BARRIER
AND PRODUCTS MADE FROM THE SAME
This invention relates in general to new and useful improvement in preforms formed by injection molding thermoplastic materials and which preforms are utilized in the forming of blow molded articles.
This invention particularly relates to the forming of a preform of a thermoplastic material having incorporated therein a layer of barrier material.
Currently multi-layer containers are produced commercially utilizing the phyla methods of processing:
a: Coextrusion blow molding by Coextrusion stretch blow molding I Tube coextrusion and reheat stretch blow molding d. Sequential injection molding of preforms in multi-station injection molds and stretch blow molding.
Among the methods listed above, method "d" is the only one which yields finished cold multi-layer preforms.
But this method is still not practical for producing multi-layer preforms with one of the layers having a thickness of .003 to owls inch.
There has been developed a method of forming a preform by injection molding wherein there is incorporated therein a central layer of barrier material. This is disclosed in US patent application No. AYE of Toy Basque Kabushiki Couch (Trading as Tub Co. Ltd.), published 4 August, 1982. Elowever, because of the cost of the barrier material, the thickness of the barrier layer which is pro sidle in accordance with that patent application is too great to be commercially feasible.
$
.:

~32~

Barrier materials which are suitable for use in the forming of containers have 2 to 3 magnitudes higher gas barrier and are to 8 times more expensive when come pared to thermoplastic materials suitable for use in the forming of containers. The thickness of the barrier layer required in a container wall for the majority of the pack-aging applications is on the order of OKAY to .0015 inch.
This would, assuming a 10 times wall thickness reduction during the biaxial orientation I blow molding a preform, translates to a .005 to .015 inch layer thickness of the barrier material in the wall of a multi layer preform.
This invention in particular relates to the forming of a multi-layer preform which has five layers including inner and outer first layers of thermoplastic resin, inner and outer second layers of barrier material within the first layers and a central or second layer of thermoplastic material between the layers of barrier material. Further, the sums of the thicknesses of the two layers YE barrier material may be as low as .006 inch.
2Q In accordance with this invention, one takes advantage of mold filling phenomenon which comprises:
1. I,aminar flow

2. The development of elongation Al and shear fields in the advancing melt front between two parallel cold walls

3. The formation of oriented solidified layers on the cold wall and the tunnel flow of molten material between the solidified layers.
A further feature of this invention is thy ability to provide two very thin barrier layers instead of one thick layer and the advantages resulting therefrom.
With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings.

.

Ed IN THE Drunks:
Figure 1 is a schematic sectional view taken thrown injection mold cavity, and shows the manner in which material is directed into the cavity to form a preform in accordance with this invention.
Figure 2 is an enlarged fragmentary schema-tic view showing the manner in which a first quantity of thermoplastic resin is injected Pinto the bottom of the mold cavity and the resultant cooling upon contact with cold wall surfaces.
Figure 3 is a schematic sectional view similar to Figure 2, and shows the injection of a barrier material into the bottom of the mold cavity and the resultant tunnel flow of both the first quantity of thermoplastic resin and the barrier material.
Faker 4 is a schematic fragmentary sectional view similar to FicJures 2 and 3, and shows the progressive flow ox a second quantity of thermoplastic resin into and therewith Claris of the first thermoplastic resin and the barrier material.
Figure 5 is an enlarged fragmentary radial sectional view showing the flow of the thermoplastic material forming the first layers of the laminated preform.
Figure 6 is a diagram plotting the injection of the materials into the mold cavity against time.
FieJure 7 is another diagram plotting pressure within the mold cavity against time.
Figure is an enlarged radial sectional view through the neck finish end of a preform in accordance with this invention or forming a blow molded mottle, and shows one arrangement of material layers within the preform.
Figure 9 is a fragmentary sectional view similar to Figure 8, but showing another relationship of the material layers in the area of the neck finish.
Figure 10 us yet another enlarged fragmentary sectional view similar to Figure 8, and shows yet another arrangement of the material layers within the preform.

...

I

Figure 11 is an enlarged fragmentary sectional view similar to Figure 8, jut through a slightly different type of preform, and shows the arrangement of the layers therein.
Figure 12 is yet another enlarged fragmentary sectional view similar to Figure 8, but with respect to a preform of the type shown in Figure 11 and showing yet another arrangement of material layers Figure 13 is a vertical sectional view taken through an intermediate article of manufacture utilizing a preform such as that shown in Figures 11 and 12.
Figure 14 is a fragmentary enlarged radial sectional view taken generally along the line 14-14 of Figure 13, and shows the arrangement of the layers of material within the article.
Figure 15 is an enlarged fragmentary sectional view similar to Figure 14, and shows a different arrange-mint of the material layers.
Figure 16 is a vertical sectional view Tony through a bottle or like container formed utilizing one of the preforms of Figures 8-10.
Figure 17 is an enlarged fragmentary radial sectional view taken generally along the line 17-17 of Figure 16, and shows the relationship of layers of material I in the finished bottle.
Referring now to the drawings in detail, it will be seen that there is illustrated in Figure 1 a conventional injection mold generally identified by the numeral 20. It is to be understood that this is a schematic showing in that a ; 3Q conventional injection mold for forming a preform will in-elude numerous cavities, fox example sixteen or more, arranged in rows and columns. Such an injection mold is generally of a solid construction and each injection mold unit will include a mold cavity 22. Each mold unit 20 will also include a neck ring 24 which forms an extension of the mold cavity 22 and defines a neck finish. The neck ring 24 may be of .

~Z3~

a split construction. Further, each mold unit 20 is provided with a core 26.
It will be seen that the neck ring 24 in conjunct lion with the core 26 closes what may be considered to be the upper end of the mold cavity 22 while the lower end of the mold cavity is provided with an opening 28 which may receive in sealed relation the nozzle of an extrude.
In accordance with the present invention, in lieu of the nozzle of the extrude being directly received within the opening 28, a nozzle-like end 30 of a rotary valve member 32 us received in the opening 28 in sealed relation. The valve member 32 is mounted in sealed rota-lion within a valve block 34 which has formed therein a first passage 36 which receives the conventional nozzle 40 of a plasticizer or injection head. The passage 36 opens radially toward the rotary valve member 32. The rotary valve member 32 has a through passage 42 which at one end terminates in a generally radial passage 44 which can be aligned with the passage 36. There is also associated with the valve block 34 a second material dispenser 46 which in its simplest form may include a dispensing piston 48 and which has a flow passage 50 exiting therefrom toward the valve block 34. The valve block 34 has a radial passage 52 which is axially aligned with and in con~unication with the passage 50. The passage 52 term-notes at the valve member 32. The valve member 32 has a further passage 54 extending generally radially from the passage 42 and so circumferential spaced from the past sage 44 such that when the passage 44 is aligned with- the passage 36 the passage 54 is spaced from the passage 52 in a circumferential direction. my rotating the valve member 32, the passage 44 may be moved out of communication with the passage 36 and the passage 54 moved into commune-cation with the passage 52. Thus material may be selectively supplied from either the plasticizer or from the supply device 46.

, Jo `:
:
:

I

In accordance with this invention, the material delivered by the plasticizer will be a suitable Thor-plastic resin in the form of a hot melt This resin may be such materials as PET, PUP, PEW PVC and PC. The barrier material which is supplied ho the supply device 46 may ye of any conventional known tarrier material including, for example EVIL, EVE, POOH and the like, or such barrier materials as may be developed in the future.
With respect to the foregoing, it is to be noted that EVIL alas barrier properties on the order of one hundred times that of PET; OH has barrier properties on the order of one hundred to two hundred times that of PET:
and POOH has barrier properties on the order of two thousand times that of PET. Accordingly, only a very thin layer of these barrier materials is required, and from a commercial standpoint it is highly desirable to maintain such very thin layers because of the much higher cost of the barrier materials than the acceptable thermoplastic resins including PET.
It is also to be understood that the external the~noplastic resin layers must be of sufficient thickness to protect the barrier layer. On the other hand, in the case of a bottle for beverages or other products containing COY, the innermost layer of the thermoplastic material, i.e. that which defines the interior of the container, must be relatively thin so as not to absorb COY.
With the foregoing requirements in mind, the manner in which a laminated preform is formed in accordance with this invention will be described in detail.
referring first to Figure 2, it will be seen that a preselected limited amount of a first thermoplastic resin 56 will be injected into the bottom of the mold cavity 22 and as it flows through the mold cavity, due to the relatively cool temperature of the mold unit 20 include in the core 26, there will be solidification of the thermos plastic resin 56 both externally and internally of the mold ~.23~

cavity 22 to define inner and outer layers 58, 6Q of the first thermoplastic resin.
Reference is particularly made to Figure 5 at this time wherein it will be seen that the thermoplastic resin 56 has a luminary flow with the velocity of the advancing thermoplastic resin being the greatest in the center and diminishing toward zero adjacent the mold components The velocity of the advancing thermoplastic resin 56 is generally indicated by an arrow schematic arrangement 62.
It is to be understood that as the thermoplastic resin 56 solidifies upon contacting the mold components, the flow of the thermoplastic resin will discontinue adjacent the walls of the mold cavity 22 and there will be a tunnel flow effect between the layers 58, 6Q. Further, due to the relatively cool air within the mold cavity 22( there will be a slight cooling of the advancing front of the thermos plastic resin 56, which errant is identified by the numeral 64.
It is to be understood that the thickness of the layers 56, 60 will be varied depending upon factors such as:
1. Material properties (.viscoelastic and thermal 2. Cavity dimensions 3. Injection velocity (prosier.
It is to be ~derstood that a precise amount of the first thermoplastic resin 56 will be injected into the mold cavity 22 over a selected period of time, with this being schematically shown in Figure 6, and at a low pros-sure as indicated in Figure 7. The quantity of the thermos plastic resin which is injected into the mold cavity may be controlled in many conventional manners. Basically, in-section of the thermoplastic resin is effected by axially advancing the feed screw of a plasticizer, and a suitable stop may by provided to limit thy advance of the. feed screw.
There also will be the timed rotation of the valve member 32 to move the passage 44 out of alignment with the passage 36 and thus the quantity of thermoplastic resin 56 injected into the mold cavity 22 may be controlled by the timing of the actuation of the valve member 32.
As is schematically shown in Figure 6, the barrier material which is next injected into the mold cavity and is identified by the numeral 66, is fed toward the mold cavity in slightly overlapping relation with respect to the thermos plastic resin 56. It is to be understood that mechanism for lo feeding the barrier material 66, as schematically shown in Figure l, may be of a single shot type so as to inject the exact amount of barrier material required.
With respect to figure 7, it will be seen that the barrier material 66 will be injected into the mold cavity 22 a a pressure only slightly higher than the pressure of the thermoplastic resin 56 with there being a very slight pros-sure drop as at 67 between -the discontinuation of injecting the thermoplastic resin 56 and the initiation of the inject lion of the barrier material 66. The overlap in injection is to eel the pressure drop to a minimum.
Rerun now to Figure 3, it will be seen that the barrier material 66 will have a tunnel flow through the cavity defined between the layers 58, 60 and at the same time will advance the previously injected thermoplastic material 56.
Normally the barrier material will have a lower melting them-portray than the thermoplastic resin 56, and therefore the cooling effect of the thermoplastic resin layers 58, 60 on the barrier material 66 will not be as great as the mold surfaces on the thermoplastic material 56. Thus, while there will be 3Q a solidification of the barrier material 66 as it contacts the solidified layers 58, 60 and there will be formed inner and outer solidified layers 68, 70 of the barrier material, these layers will be materially thinner than the layers 58, 60. For example, the layers 58, 60 will have a thickness varying from .010 to .040 inch, while the barrier material layers 68, 70 will have a thickness as low as .003 inch.

~32Z~
g Referring now to Figure 4, in the illustrated ; embodiment of the mechanism for feeding the thermoplastic resin, an additional supply of the same thermoplastic resin identified by the numeral 56 is injected into the mold cavity. This additional supply of thermoplastic resin is generally identified by the numeral 72. The thermoplastic resin 72 as it advances within the confines of the layers 68, 70 of the barrier material will remelt the tarrier material and advance it together with the barrier material lo melt 66 through the tunnel defined my the layers 68, 70, thereby reducing the thickness of the layers 68, 7Q. As will be apparent from Figure 4, the advancing thermos plastic resin 72 will advance the barrier material 66 which, in turn, will continue to advance the thermoplastic : 15 resin 56.
further with respect to Figure 4, it will be seen that the advancing large quantity of the thermoplastic resin 72 as it engages the layers 58, 68 at the end of the core 26, wit]. melt portions of the solidified layers 58, 68 2Q. and advance the same with the result that there may be no portion of either the layer 58 or the layer 68 at the extreme end of the core 26.
Referring next to figure 6/ it will be seen that the thermoplastic resin 72 is advanced in slightly over-lapping relation with the barrier material 66. It is lobe understood that once the injection of the barrier material 66 has been completed the valve member 32 will be rotated to a position to receive the thermoplastic resin 72. In the illustrated embodiment, the valve member 3Q 32 will be returned to its starting position since the thermoplastic resin 72 is delivered from the same supply as the thermoplastic resin 56.
With respect to the diagram of Figure 7, to will be seen that the thermoplastic resin 72 will ye. in-35 jetted first at a gradually increasing pressure. above th~pressure of the injection of the barrier material 66. with ` assay a slight initial pressure drop as indicated at 74. Then, when the cavity 22 has been filled, there will be a pros-sure boost, as at 76, followed by a holding period 78 wherein the pressure of the hot melt material injected into the mold cavity will gradually decrease as the thermos plastic material 72 gradually solidifies.
Depending upon usage of the preform which is formed in the manner described above, the amount of the thermoplastic resin 56 and the barrier material 66 injected into the mold cavity 22 will vary. Further, the shape of the preform at the front end thereof will vary.
In Figures 8, g and lo there are illustrated preforms which are particularly adapted to be used in their entireties in the slow molding of bottles and like con-trainers wherein a small diameter closure is applied Bohemians of screw threads.With respect to Figure 8, the illustrated preform portion is part of a preform identified by the numeral 80 and includes a laminated body I which terminates if a pa neck finish generally identified by the numeral 84. The neck finish 84 includes injection molded threads 86 and a shoulder member 88 by means of which the preform 80 is sup-ported during reheating and blow molding.
In the preform 80, the quantity of thermoplastic resin 56 injected into the mold cavity is sufficient to have the layers 58, 60 extend to the extreme end of the preform 80 and to form at the extreme end an end wall 59. Further, the quantity of barrier material injected into the mold cavity is sufficient to have the layers 68, 70 extend to a point adja-pa cent the extreme end of the preform and to form an end Wylie adjacent the end wall 59. The thermoplastic resin 72 will also extend to a point adjacent the extreme end of the pro-form 80 as permitter by the end wall 69.
In Figure 9 there is illustrated a preform 90 which will be of the same configuration as the preform 80. Further, while the quantity of the thermoplastic resin 56 directed ,, :

I

into the mold cavity will be sufficient for the layers 58,60 to go to the extreme end of the preform including a neck finish portion 92 thereof and to form the end wall, the quantity of the barrier material 66 injected into the mold cavity will be such that the layers 68, 70 will terminate interiorly of the preform short of the neck finish 92 into : that area of the resultant bottle which becomes the shoulder of the bottle, as will be described in detail hereinafter.
With respect to Figure 10, the preform 94 thereof is also of an identical configuration to the preform 80.
However, the quantity of the thermoplastic resin 56 intro-duped into the mood cavity will be only sufficient for the layers 58, 60 to extend to a point adjacent to the neck finish 96 of the preform I Thus, the neck finish part of the preform I will be formed solely by the thermos plastic resin 72. Further, the quantity of the barrier material 66 injected into the mold cavity will be such that the layers I 70 terminate internally of the preform short owe the termination of the layers 58, 60.
In figures 11 and 12 there are illustrated pro-forms for pheromone containers and like hollow articles other than bottles or containers with small diameter neck finishes. on extreme end portion only in radial section of such preform is illustrated in each of Figures 11 and 12.
With particular reference to Figure 11, it will be seen that there is illustrated a preform 98 having an open end portion 100 which may include a supporting flange or collar 102. Inasmuch as the end portion 100, as will be described in detail hereinafter is utilized solely as a support in the blow molding of the preform 98 into a tubular shape, it is not necessary that the barrier material 66 extend into the end portion 100. Therefore, only sufficient barrier material is injected into the mold cavity of the preform 98 so as to permit the layers 68, 70 to terminate adjacent the end portion 100. In a like manner, the quantity of thermoplastic resin 56 injected ~.~32'~

into the mold cavity will be only sufficient to have the layers I 60 extend generally into the area of the end portion lQQ, Thus, the end portion 100 will be formed entirely by the thermoplastic resin 72.
In Figure 12 there is illustrated yet another profane 104 which is identical to the preform 98 including an end portion 106 and a flange or collar 108, except that the end portion 106 it formed entirely by the thermoplastic resin 56 and the layers formed by the resins 66 and 72 terminate in relatively great spaced relation to the end portion 106. The preform lQ4 is advantageous in forming a container or like tubular body wherein an intermediate article of manufacture is involved.
Referring now to Figure 13, it will be seen that there is illustrated an intermediate article of menu-lecture generally identified by the numeral 110 and blow molded from a preform such as the preform 98 or the pro-form 104. The intermediate article of manufacture includes a base portion 112 in the form of a container. The base 2Q portion 112 includes a tubular body 114 having an integral bottom 116 and terminating in a closure receiving portion 118. The illustrated closure receiving portion 118 is in the form of a flunk adapted to be engaged by a con-ventional metal end unit and forming part of a convent tonal double seam securing the metal end unit (not shown) to the base portion 112 which when separated from the remainder of the intermediate article of manufacture 110, becomes a container.
Although it has not been so illustrated, the 3Q intermediate article of manufacture 110 may have the closure receiving portion 118 in the form of a neck finish which may be threaded or otherwise modified to receive a closure unit. At this time it is to be understood that except for the fact that it is formed from a laminated preform the intermediate article of manufacture 110 has - been formed prior to this invention.

. . .

:~232~

It will be teen that the intermediate article of : manufacture also includes an upper blow molded portion 120 which terminates in an end portion 122 which will correspond to the end portions 100; 106 of the preform 98, 104.
With respect to Figure 14, the intermediate article of manufacture illustrated therein was formed from a preform such as the preform 104 of Figure 12. It is to be understood that the upper portion 120 is to be separated from the base portion 112 by a cutting action, such as a fusion cutting action, with. the removal of a portion 124.
It will be seen that in this embodiment of the invention the layers 68, 70 terminate. in the closure receiving portion 118 and that the layer formed by the thermoplastic material 72 terminates entirely within the base portion 112. Thus all of the intermediate article of manufacture.ll0 which it to be severed from the base portion 112 will be formed by the thermoplastic resin 56 and may be reconditioned and reused.
On the other hand, with respect to Figure 15, there may be occasions whole it is desired that the barrier material layers 68, 70 extend beyond the closure receiving portion into the upper portion 120. Thus, when the base portion 112 is removed from the remainder of the intermediate article of manufacture 110, the layers 68, 70 of the barrier material will extend through the cut edge of the base portion 112 into the upper portion 120. In a like manner, the layers 58, 60 of the first thermoplastic resin will also extend into the upper portion 120. Thus, when the base portion 112 is severed 30 - from the remainder of the intermediate article of menu-lecture 110 by removal of the material in the area 126, the intermediate article of manufacture 110 illustrated in Figure 15 may be formed, for example, from the preform of Figure 11. When the cutting action involves heat fusion of the cut layers to one another may be effected at the end of the base portion 120.

. , ~.;23~
-14~

In Figure 16 there is illustrated a conventional bottle which may be formed from any one of the preforms of Figures 8, 9 and lo. The bottle is generally identified by the numeral 128 and includes a tubular body 130 having an integral bottom 132. The body 130 at its upper end is connected by way of a shoulder 134 to a neck finish 136.
It is to be understood that the neck finish 136 will be identical to top neck. finish. of the respective preform from which the bottle 128 is blow molded. Further, it will be seen that the termination of the layers 68, 70 of the barrier material may be at the extreme end of the neck finish 136 when the preform of Figure 8 its utilized.
On the other hand, when the preform of Figure 2 is utilized, the layers 68, 70 of the barrier material will terminate in the shoulder 134 adjacent the neck finish 136. Finally with respect to the use of the preform of Figure 10., both the layers 68, 70 of the barrier material and the layers 58, 60 of the first thermoplastic resin will terminate in the shoulder 134 adjacent the neck finish.l36~
I With.parti.. cuter reference to the bottle 128, it is to be understood that in the normal blow molding of such bottle the body portion 130 will be very thin, having been reduced in thickness on the. order of one-tenth. or less so that the material forming the body 130 will have a positive and desired biaxial orientation. On the other hand, the material of the bottle 128 in the shoulder 134 closely adjacent the neck finish 136 will have only a minor reduction in thickness while the material in the neck finish 136 will not be reduced in thickness at all. Thus 30. the barrier material 66 may beneficially terminate in the shoulder 134 as described above It is also pointed out here that the extreme center of the bottom 132 is of ,. such greater thickness than the body 130, and therefore the absence of barrier material in the central part of the bottom 132 will not be a material omission.

.. ..

2~3~

Reference is finally made to Figure 17 which is a radial cross section of the body 130 and shows inner and outer layers 58, 60 of the first thermoplastic material 56, inner and outer layers 68, 70 ox the barrier material 66, and a central core of the other thermoplastic material 72.
Inasmuch as there is a reduction in thickness of the lam-noted preform on the order of ten times, the thickness ox the layers 58, 60 in the bottle 12~ will be on the order of .001 to .004 inch, while the thickness of the barrier material layers 68, 70 will be on the order of .0003 inch.
The thickness of the layer 58 will be sufficient to protect the barrier layer 68 against the contents of the bottle 128 including available COY.
Further, it has been found that when the barrier material 66 does not have properties which permit the heat bonding thereof to the thermoplastic resin and the thick-news of the layers 68, 70 have been relatively great as required by known practices, when the blow molded article has been Wormed there has been a positive delamination of the layers of barrier material from the remainder of the blow molded article. However, when the barrier material layers in the preform are very thin, as described herein-above, Kit has been wound that the prior pronounced delamina-lion does not occur. A conventional test for delamination is the squeezing of the body of a blow molded article, and if there is delamination there will be a squeaking noise emitted. When the barrier material layers are very thin at the start, the blow molded articles utilizing such a preform do not emit the squeaking noise and do not show pa evidence of a complete delamination.
There has recently been developed by others a five-layer tubular prison which is formed as an extruded tube. Such prison does have a barrier layer which is thin, but which is not directly bonded to the thermoplastic resins which form the primary layers of the prison. The method of forming such a multi-layer prison is not conducive to ~23~

The diffusion bonding of a barrier layer to a conventional thermoplastic resin layer by way of pressure when the materials of the two layers are not normally heat bondable together in that the components of such a tubular prison are extruded at a low pressure on the order of 2000 to 5000 pi and as soon as the tube leaves the extrusion head, at which tire all components are hot the pressure is no-lived and as the components cool they shrink and tend to separate.
On the other hand, as its schematically shown in Figure 7, wren the various materials are introduced into the mold kowtow 22 by a conventional injection molding process, the barrier layers 68, 70, in addition to being very thin and thus relatively incompressible, are clamped between the core 72 and the layers 58, 60 at a very high pressure on the order of 15,000 to 17,000 pi There-fore, while the barrier layers 68, 70 may not be heat bond-able to the thermoplastic resin layers 58, 60 and the core 72, there is a considerable diffusion bonding effected Boone thus layers at the high forming temperatures and pressures. Further, as is also shown in Figure 7, after the injection step has been completed there is a maintaining of a high pressure on the materials previously injected into the mold cavity and thus the pressure is maintained between the layers as the materials of the layers shrink, thereby pro-venting any tendency to separate due to relative shrinkage.
Since the thickness of the barrier layers 68, 70 May be as low as .0Q3 inch, it will be apparent -that it is of a relatively incompressible thinness. Further, as disk closed herein before, the preform, at least in the body port lion of the resultant blow molded hollow member, will be stretched on the order of ten times, thereby reducing the thickness of the barrier layers 68, 70 to be as low as .0003 inch, which thinness results in the resultant barrier layers as being extremely thin and thus incompressible for all practical purposes. The net result is that in the resultant blow molded hollow member the barrier layers ~232~1~

68, 70 maintain a pressure bond with the thermoplastic resin layers 58, 6Q and the core 72.
Although specific materials have been described as being beneficially acceptable, it is to be understood that the possibilities of utilizing barrier materials which are not commercially acceptable at this time definitely exist because of the ability to maintain the thickness of the barrier material layers in the blow molded article one which provides or the desired barrier char-acteristics without utilization of an excess amount of the otherwise prohibitively expensive material.
Although only several preferred embodiments of the invention have been specifically illustrated and described herein, it is to be understood that material layers within the preforms may be varied in accordance with the desired uses of the preforms and the resultant blow molded articles.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of forming laminated preforms of the type including an interior barrier layer, said method com-prising the steps of providing an injection mold for a preform wherein the injection mold includes a core with there being a cavity surrounding the core, providing separate supplies of at least one flowable thermoplastic resin and a flowable barrier material, injecting into that end of said mold cavity which defines a preform bottom a limited quantity of said thermoplastic resin with the sur-face portions of said limited quantity of thermoplastic resin cooling due to contact with said mold and said core to define first solidified layers while there is tunnel flow of the thermoplastic resin between said solidified layers, injecting a limited quantity of said barrier material into said mold cavity behind said limited quantity of thermo-plastic resin with said barrier material forcing said thermo-plastic resin further into said cavity with said barrier material having tunnel flow between said thermoplastic resin solidified layers with surface portions of said barrier material in contact with said thermoplastic resin solidified layers also cooling and forming second solidified layers, and then injecting other flowable thermoplastic resin into said mold cavity behind said barrier material sufficient to complete filling of said mold cavity with said other flow-able thermoplastic resin forcing said limited quantities of said thermoplastic resin and said barrier material to flow toward the other end of said mold cavity, and permitting all of the injected material to solidify.

2. A method according to claim 1 wherein said barrier material has a melting temperature lower than that of said other thermoplastic resin with said other thermo-plastic resin as it flows between the layers of barrier material heating contacted layers of said barrier material and forcing portions thereof forwardly into said mold cavity to thereby effect thinning of the layers of barrier material.

3. A method according to claim 2 wherein the combined thickness of the barrier material layers is as low as 0.006 inch.

4. A method according to claim 1 wherein the injected quantity of the barrier material is insufficient for the barrier layers to extend the full length of said mold cavity.

5. A method according to claim 1 wherein the injected quantity of the barrier material is insufficient for the barrier layers to extend the full length of said mold cavity, and said barrier layers terminating internally of the resultant preform between said layers of thermo-plastic resin and said other thermoplastic.

6. A method according to claim 1 wherein the injected limited quantity of said thermoplastic material is sufficient for the first solidified layers to extend the full length of said mold cavity.

7. method according to claim 1 wherein said quantity of thermoplastic resin and said other thermoplastic resin are provided from a common source.

8. A method according to claim 1 wherein said barrier material has a melting temperature lower than that of said quantity of thermoplastic resin.

9. A method according to claim 1 wherein the thickness of said first solidified layers is at least in part controlled by controlling the temperature of said core and said injection nold and thus the rate of cooling of said thermoplastic resin forming said first solidified layers.

10. A method according to claim 1 wherein the thickness of said first solidified layers is at least in part controlled by controlling the temperature of said core and said injection nold and thus the rate of cooling of said thermoplastic resin forming said first solidified layers, and by the temperature of the injected thermoplastic resin forming said first solidified layers.

11. A method according to claim 1 wherein the thickness of said solidified layers of said barrier material is at least in part controlled by the temperature of said first solidified layers and thus the rate of cooling of said barrier material.

12. A method according to claim 1 wherein the thickness of said solidified layers of said barrier material is at least in part controlled by the temperature of said first solidified layers and thus the rate of cooling of said barrier material, and by the temperature of the injected barrier material.

13. A method according to claim 1 wherein the thickness of said solidified layers of said barrier material is at least in part controlled by the temperature of said first solidified layers and thus the rate of cooling of said barrier material, and by the temperatures of the injected barrier material and the injected other thermoplastic resin.

14. A laminated preform for forming blow molded articles and the like, said preform including a tubular wall having inner and outer surfaces, said tubular wall in radial cross section comprising inner and outer first layers of a thermoplastic resin inner and outer layers of a barrier material next to and between said inner and outer first layers, and a second layer of thermoplastic resin between said barrier material layers.

15. A laminated preform according to claim 14 wherein the combined thickness of said inner and outer layers of barrier material is as low as 0.006 inch.

16. A laminated preform according to claim 14 wherein said preform has a rounded base including an endmost part, and said endmost part is formed solely by the material of said first layers of thermoplastic resin.

17. A laminated preform according to claim 14 wherein said preform has an open end and said layers of barrier material terminate in said tubular wall remote from said open end.

18. A laminated preform according to claim 14 wherein said layers of barrier material terminate between said first and second layers of said thermoplastic resin.

19. A laminated preform according to claim 14 wherein said preform is for forming a blow molded container having a neck finish, said preform includes said neck finish, and said barrier material layers terminate adjacent to but short of said neck finish.

20. An intermediate article of manufacture comprising a blow molded article including a base portion in the form of a container having a bottom portion, a body and an open mouth defined by a closure receiving upper portion, said blow molded article further including an upper neck portion, and an expanded upper portion joining said closure receiving upper portion to said upper neck portion, said base portion having a wall of a laminated construction and which in radial cross section includes inner and outer first layers of a thermoplastic resin, inner and outer layers of a barrier material within and next to said inner and outer first layers, and a further layer of thermoplastic resin between said layers of barrier material, and said barrier material layers terminating in said intermediate article of manufacture in the general area of said closure receiving upper portion.

21. An intermediate article of manufacture according to claim 20 wherein said barrier material layers terminate in said base portion.

22. An intermediate article of manufacture according to claim 20 wherein said barrier material layers terminate in said expanded upper portion.

23. A blow molded container of the type including a bottom, a body, and said body terminating in a neck finish, at least said body being of a laminated construction and in radial cross section includes inner and outer first layers of a thermoplastic resin, inner and outer layers of a barrier material within and next to said inner and outer first layers, and a further layer of thermoplastic resin between said layers of barrier material.

24. A blow molded container according to claim 23 wherein said layers of barrier material have a combined thickness as low as 0.0006 inch.

25. A blow molded container according to claim 23 wherein said layers of barrier material extend through said neck finish.

26. A blow molded container according to claim 23 wherein said layers of barrier material extend into said neck finish.

27. A blow molded container according to claim 23 wherein said layers of barrier material extend to an area adjacent said neck finish.

28. A method of forming a blow molded hollow member having a laminated wall including at least one thin intermediate layer which is free of a heat bond with adjacent layers, said method comprising the steps of forming an injection molded laminated wall preform wherein the intermediate layer is tightly compressed between said adjacent layers to form a diffusion bond with said adjacent layers, blow molding the preform into a hollow member while biaxially stretching the layers and reducing the thickness of the layers with the thickness of said intermediate layer being reduced to a substantially incompressible thickness.

29. A method according to claim 28 wherein the thickness of said intermediate layer in said preform is as low as .003 inch.

30. A method according to claim 28 wherein the thickness of said intermediate layer in said hollow member is as low as .0003 inch.

31. A method according to claim 28 wherein in the forming of said preform said intermediate layer is compressed at a pressure of 15,000 to 17,000 p.s.i. to effect said diffusion bond.

32. A method according to claim 28 wherein in the forming of said preform said intermediate layer is compressed at a pressure of 15,000 to 17,000 p.s.i. to effect said diffusion bond, and a high pressure is maintained as said preform cools and sets to prevent separation between the layers due to shrinkage.