US3314919A - Process of melt spinning roughsurfaced fibers - Google Patents

Description

United States Patent 3,314,919 PROCESS OF MELT SPINNKNG RUUGH- SURFACED FlIBER Elmer E. Most, Kinston, N.C., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware No Drawing. Filed May 22, W62, fier. No. 196,615

2 Claims. (Cl. 260-4515) This invention relates to melt spun synthetic linear condensation polymer textile fibers, and is more particularly concerned with modification of such fibers to provide improved resistance to pilling and lower dynamic friction without adversely affecting other desirable properties.

Synthetic linear condensation polyester and polyamide textile fibers are well-known in the art and, because of their outstanding properties, have found application in many different end uses. These fibers are produced by melt-spinning the polymer into filaments and orienting the filaments by drawing to several times the as-spun length. Textile yarns comprise either these continuous fibers or staple fibers formed therefrom, as by cutting to lengths roughly corresponding to the better grades of cotton or wool. The natural fibers have rough surfaces, Whereas melt-spun fibers have had a smooth, shiny surface. This surface has made processing into fabric more difiicult, because of the higher dynamic friction, and has also been objectionable when an appearance similar to that of natural fibers is desired.

The appearance of melt-spun fibers has been improved .by the use of spinnerets which provide non round cross sections and by incorporating internal delustrants, such as finely-divided TiO in the polymer prior to spinning.

Graves US. Patent 2,205,722. and Dickson et al. British Patent 610,137 disclose the use of a variety of internal delustrants which are insoluble in the polymer and have a different refractive index. These function by scattering light which passes into the fiber but do not appreciably modify the fiber surface. They do not overcome the problem of high dynamic friction and create a new problem by increasing the rate of light aging.

A further problem with the melt spun condensation polymers, when used in the form of staple fibers, is the tendency to form pills on textile fabrics. These are small but unsightly balls of snarled fiber ends which. form when the surface of the fabric is rubbed during normal wearing. Extensive efforts have been made to overcome this problem without achieving fully satisfactory results.

An object of this invention is to produce melt spun fibers which are improved in the above respects without adversely affecting other desirable properties. Gther objects will become apparent from the specification and claims.

In accordance with this invention I have found that fibers, produced by melt-spinning a synthetic linear condensation polymer and drawing the spun filaments into oriented fibers, are improved by incorporating in the polymer 0.1 to 5% of a finely-divided (up to 100 micron) terephthalate salt of a metal of atomic number 20 to 56 from Group II of the Mendeleeff Periodic Table, e.g., calcium terephthalate, barium terephthalate, cadmium terephthalate and zinc terephthalate. Manganese terephthalate is also suitable. The preferred salt is calcium terephthalate. The preferred condensation polymers are polyethylene terephthalate and polyhexamethylene adipamide, which may be modified with minor amounts of copolymerizable components in accordance with commercial practice.

Addition of the metal terephthalate has been found to decrease the dynamic friction of the fibers and to increase the resistance to pilling of the staple fibers, as illustrated in the examples. This is accompanied by a surface roughening which can be observed by examination with a microscope. Since the salt is compatible with the polymer and does not differ appreciably in refractive index, the effect is unlike that of the internal delustrants mentioned above. However, the surface roughening produced by the metal terephthalate makes it possible to reduce the amount of internal delustrant without impairing the appearance of fabric composed of the fibers. The resistance to light aging has been found to be greatly improved.

The terephthalate salt may be added to the reactants before the polymerization, during the polymerization, or to the polymer melt at the end of the polymerization prior to melt spinning. It may be added to, or coated onto, the solid polymer flake before melting. In the polymerization of polyethylene terephthalate it is preferred to add the terephthalate salt as a glycol slurry in the early stages of the polymerization.

The average particle size required depends on the denier of the yarn and may be between 0.1 and 100;]. and prefably between 3 and 30 The particle size referred to is that measured before the terephthalate salt is added to the polymer. The polymers may be spun into fibers with round or non-round cross section, e.g., ribbon-like and trilobal.

The concentration of terephthalate salt required depends somewhat on the particle size and on the end use of the yarn. In staple yarn, a concentration of between 0.5 and 2.5% of the salt with particle size between 1 and 25a is suitable if a cotton-like staple is desired. In staple for worsted fabrics with cover, between 1.0 and 4.0% by weight of the salt with particle size between 1 and 50 1. is preferred. In general, the aesthetics increase with increasing concentration and particle size of the terephthalate within these ranges.

Example 1 The terephthalates of Ca, Ba, Mn, Zn, and Cd are prepared as follows: A quantity of dimethyl terephthalate is heated overnight on the steam bath with a 10% excess of 10% sodium hydroxide containing methyl alcohol. The excess caustic is neutralized to phenolphthalein with hydrochloric acid, and the metal terephthalate is precipitated in a finely-divided condition by addition of a concentrated, aqueous solution of the appropriate metal salt. Yields of the dry salt are between and 182 grams (4% by weight based on the weight of the polymer) of each of the metal terephthalates prepared above are tumbled with ten pounds of semi-dull (0.3% TiO polyethylene terephthalate flake. Each ten pound batch of flake is melt spun and drawn to give a 70-denier, 34-filament, ribbon cross-section yarn. The ribbon crosssection is produced with a spinneret having orifices of the type shown in FIGURE IX of Pamm et al. US. Patent No. 2,816,349. Two control yarns are prepared with only 0.3% TiO present as the insoluble material for comparison purposes. Examination of the filaments produced, under a microscope, reveals that those containing the metal terephthalate salt have a rough surface and an uneven profile, whereas the yarn containing only TiO are relatively smooth surfaced and have a uniform profile.

Friction measurements on the above yarns give coemcients of dynamic friction below 0.5 for all the yarns containing metal terephthalate salt, while the control yarns have coefficients above 0.65 in the same test.

Each batch of yarn is cut into 2 /2 inch staple and processed separately into a spun yarn on the cotton system. The processability of the yarns containing the metal terephthalate salts is markedly better than that of the control yarns, showing reduced running tensions, im proved draftability, reduced roll wrapping, and the like.

Each of the spun yarns is woven into a 2 x 2 twill fabric. The fabric samples containing the metal terephthalate salts are characterized by a handle which is definitely dryer (less slick) than the control sample. This fabric is then subjected to the ASTM Test for Pilling Resistance of Textile Fabrics, described in D137559T, Section E, Random Tumble Pilling Tester. There are 620 pills per 35 square inches with the control containing TiO but no calcium terephthalate. When 4% calcium terephthalate is present there are 460 pills per 35 square inches, a marked improvement in resistance to pilling. Substantially the same result is obtained for each of the other metal terephthalates.

Example 2 Polyethylene terephthalate containing 0.5, 1.0, and 1.5% calcium terephthalate is melt-spun into trilo-bal cross section, 1.5 denier per filament yarn (modification ratio 1.6). The coefiicient of dynamic friction is measured and compared to a control yarn prepared from polyethylene terephthalate without calcium terephthalate. The data in Table I clearly indicate the reduction in friction obtained by the addition of calcium terephthalate to the polymer.

TABLE I Coeflicient of Calcium terephthalate: dynamic friction None 0.69 0.5% 0.545 1.0% 0.445 1.5% 0.33

Substantially equivalent results are obtained with each of the other metal terephthalates of Example 1 and when the procedure is repeated using in place of polyethylene terephthalate a copolyester of 10% ethylene isophthalate and 90% ethylene terephthalate.

The coefficient of dynamic friction used here is conveniently measured by draping a single filament over a cylindrical polished mandrel (180 contact) with one end of the filament attached to a strain gauge, and the other end attached to a free-hanging weight of about 0.3 gram. The surface of the mandrel is flooded with No. 50 mineral oil and the mandrel rotated at a surface speed of about 120 cm./sec. in a direction which exerts tension on the strain gauge. The coefficient of friction f is calculated from the equation where T is the output tension, T is the input tension, and

a is the angle of wrap in radians.

ratings are made on a 1-5 scale where 1 is very bad, is

excellent, and 3 is borderline. The results are presented in Table II along with the results of similar tests on fabrics prepared from polyethylene terephthalate fiber 5 containing no calcium terephthalate.

The Schiefer frosting test is a modification of the Schiefer abrasion test, ASTM-D117561T, Section E. In the modified test the fabric sample to be tested is dyed a deep navy blue, mounted on a round stationary sample holder, and abraded by a crosscut-surfaced steel head with an eccentric circular motion using a 2-pound head weight and a 3,000 cycle exposure. Frosting, in the abraded area of the sample, shows up as a lighter blue color against the deep blue of the unabraded background.

It is known that the use of low viscosity polymer overcomes the pilling problem while at the same time introducing a frosting problem. The data in the table show that, by the use of calcium terephthalate, both the pilling 3O problem and the frosting problem are overcome.

Example 4 A solution of hexamethylene diammonium adipate is polymerized to polyhexamethylene adipamide in a conventional melt polymerization (see U.S. Patent No. 2,163,636). During the polymerization, at a temperature of 210 C. and a pressure of 250 pounds per square inch gage, calcium terephthalate in a aqueous slurry 4 is added. Two polymers were prepared, one having 2% calcium terephthalate in the 15 particle-size range, and the other having 2% calcium terephthalate in the 6-95n particle-size range. These polymers (26 and 33 relative viscosity, respectively) were extruded, cast, cut to flake, and the melt-spun yarn drawn (2.9-3.2 draw ratio) to 70 denier/34 filament round cross-section yarns. The finish free yarn-over-yarn hydrodynamic friction (f light durability (Weather-Ometer tenacity half-life, T and appearance of these yarns was determined. For comparison two controls were run, one with 2% and another with 0.02% O.1-5,u. particle size TiO The results are shown in Table III.

TABLE III 1 Light r'ty Additive Hydro- SUbJOClZlVG Rating of Item Additive Particle dynamic fi gP g Appearance Size in [L Friction fh (g/d.) T1

in Hours 1 2% calcium terephthalate. 1-5 0. 42 600-700 Equivalent to 0.3% TiO;

(semidull) delustered. 2 2% calcium terephthalate 6-95 0. 42 600-700 66- nylon with highlights. 3 2% T102 0.1-5 0.55 -100 Verl ly 520d covering power but c a y. 4 0.02% T102 0.1-5 0.70 150-200 Poor covering power.

Example 3 Example 5 2% Calcium terephthalate (based on the weight of the polymer) is tumbled with polyethylene terephthalate flake having a relative viscosity of 20. The flake is then spun into a 3 denier filament, 200 filament round cross-section yarn, the yarn cut into a 2 /2 inch staple and the staple spun into yarn and made into a 2 x 2 twill fabric. The fabric is rated for pilling in the Random Tumble Pilling Tester ofASTM D-1375-59T, Section E, and for frost- A solution of hexamethylene diammonium adipate is polymerized to polyhexamethylene adipa'mide of fiberforming viscosity in a conventional melt polymerization.

70 The polymer is extruded in the form of a ribbon, quenched with water, and cut to flake. The polymer flake is tumbled with 2% by weight of finely-divided calcium terephthalate in which the size of the particles ranges from 2 to 30 microns. The mixture of polymer flake and ing by the Schiefer Frosting Rating (at 3000 cycles). The calcium terephthalate powder is then melt spun and drawn in a conventional fashion to give a IS-clenier, monofilament yarn having the normal commercial physical properties, i.e., a tenacity of 5.9 g.p.d. at 28% elongation.

A second yarn sample is prepared by introducing the calcium terephthalate as a water slurry into the partially polymerized polyhexamethylene adipamide and then further polymerizing the mixture to produce a fiberforming polymer. The polymer is extruded as a ribbon, quenched, cut to flake, and then melt spun and drawn to give a 15-denier monofilament as described above.

For comparison purposes, a control 15-denier monofilament yarn is prepared which contains 0.3% TiO but no calcium terephthalate.

These yarns are then knit into ladies seamless hosiery using the IS-denier monofilament in the knee, calf, ankle, and foot sections. A similarly prepared 40-denier, 13- filament yarn is used in the welt, heel and toe sections. During knitting it is foundthat the lower, more uniform surface friction of the yarn containing calcium terephthalate affords better control of yarn running tension which results in improved control of the leg length of the hosiery. The yarn containing calcium terephthalate is found to give a variation in leg length of i% inch for all hosiery knitted from one yarn package. In contrast, the control yarn gives a leg length variation of :15 inch for hosiery knitted from a single yarn package. Improved length control is obviously a great advantage to the manufacturer of ladies hosiery.

As an additional advantage it is found that the hosiery knitted from yarn containing calcium terephthalate has a markedly drier and less slick hand than the control.

The above experiment in which calcium terephthalate is added by tumbling the powder with polymer flake is repeated with calcium terephthalate concentrations of 0.25% and 0.1% by weight. The described improvement in length control in knitted hosiery is achieved in both yarns.

Substantially equivalent results are obtained when the yarns are prepared from polycaproamide instead of polyhexamethylenediamine adipamide.

Similar results are obtained with hosiery yarns prepared from polyundecanoamide.

Example 6 Finely-divided calcium terephthalate, having a particle size in the 2-5 micron range, is added to hot caprolactam in suflicient quantity to give a slurry having a concentration of by weight. Fifteen percent water is then add-ed to prevent crystallization of the caprolactam upon cooling, and the slurry run through a colloid mill to complete the dispersion of the calcium terephthalate and render the slurry stable to settling. The caprolactam slurry is then polymerized in the usual fashion to give a low molecular weight polymer, which is extruded as a ribbon and cut to flake.

Eight parts of the flake prepared above is blended with 92 parts of a nylon 66/6 (875/125 parts by weight) random copolymer which is free of TiO (The 66/6 copolymer is prepared by copolymerization of caprolactam and the adipic acid salt of hexamethylene diamine, using the general process described by Spanagel in US. Patent No. 2,163,636.) The blended flake is melt spun using apparatus of the type described by Waltz in US. Patent No. 2,571,975, and then drawn according to the teachings of Babcock in US. Patent No. 2,289,232. The yarn produced is a 20-denier monofilament having a tenacity of 6 g.p.d. at a break elongation of 28%.

Examination of the filaments under a microscope shows that the yarn contains a random dispersion of particles ranging in size from about 2 microns to about 50 microns. Most of the particles at the surface of the filament are found to be covered by a thin skin of polymer. The internal particles are each associated with a void which is larger than the particle. The surface of the filament is visibly rough.

The coefficient of friction is determined on a rotating chrome pin flooded with mineral oil to give an f value of 0.69. In the same test a 66/6 copolymer yarn containing no calcium terephthalate and n0 TiO gave an value of 0.91, and a similar filament containing only 0.3% TiO gave an f value of 0.86.

Example 7 Nylon 66/6 (87.5/ 12.5) random copolymer flake of fiber-forming molecular Weight is tumbled with a methanol dispersion of 2% calcium terephthalate containing 0.4% polyvinyl-pyrrolidone as an adhesive. The methanol is removed by vaporization and the polymer melt spun as in US. Patent 2,571,975 and drawn as in US. Patent No. 2,289,232 to give a 20-denier monofilament. Measurement of the coefficient of friction gives an f value of 0.57, in contrast to the high value of 0.86 given by a control yarn containing 0.3% TiO in place of the calcium terephthalate.

Example 8 A copolymer of polyethylene terephthalate containing 3 /2 mol percent of sodium-3,5-di(carbomethoxy)-benzenesulfonate is prepared according to the method of Grifling U.S. Patent No. 3,018,272, extruded as a ribbon and cut to flake. The flake is tumbled with 4% finelydivided calcium terephthalate and used as the sheath component in melt spinning a sheath-core yarn according to the teachings of Breen in US. Patent No. 2,931,091, using unmodified polyethylene terephthalate homopolymer as the core component. The filaments obtained show a high level of surface roughness, a spontaneous spiral crimp, and equilibrium crimp reversibility which depends upon humidity. Measurement of the coeflicient of friction on a smooth chrome pin at a yarn speed of y.p.m., with no mineral oil present, gives a value of 0.14. In contrast, a control yarn containing no calcium terephthalate, prepared in essentially the same way, gives a coefiicient value of 0.70.

The yarn prepared is cut to staple, blended with wool in a 55/45 ratio, spun into yarn, and woven into a tropical Weight fabric. In pilling tests, the fabric made from yarn containing calcium terephthalate is found to be equivalent to an all-Wool fabric, whereas fabric in which the polyethylene terephthalate fiber contains no calcium terephthalate is found to give objectionable pilling.

Polyamides to which this invention is applicable include: polycaproamide, polyhexamethylenediamine adipamide, polyhexamethylenediamine sebacamide, the polyamide from 1,8-diamino-n-octane and oxalic acid, the polyamide from bis-p-aminocyclohexylmethane and azelaic acid, the polyamide from 'bis-p-aminocyclohexylmethane and sebacic acid, the polyamide from m-xylylenediamine and azelic acid, the polyamide from p xylylenediamine and azelaic acid, the polyamide from m-xylylenediamine and adipic acid, the polyamide from Z-methyl-hexamethylenediamine and oxalic acid, and the polyamide from hexamethylenediamine and isophthalic acid. Polyesters useful in this invention include: the polymethylene terephthalates disclosed in US. Patent No. 2,465,319, poly(hexahydro-p-xylylene) terephthalate, copolymers of ethylene glycol with terephthalic acid and isophthalic acid, copolyesters containing 2 mol percent 5- sodium sulfoisophthalic acid, and the like.

Since many diflerent embodiments of the invention may be made Without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. In the production of textile fibers of polyhexamethyleneadipamide by melt-spinning the polymer and drawing the spun filaments into oriented fibers, which fibers are conventionally delustered by incorporating Ti0 in the polymer, the improvement for decreasing the dynamic friction of the fibers produced and increasing the resistance to Reierences Cited by the Examiner UNITED STATES PATENTS 2,238,949 4/1941 Sehlack 8-1 15.5 2,342,823 2/1944 Schlack 260-78 2,345,700 4/1944 Dreyfus 260-78 8 Spanagel 260-78 Whinfield et al. 260-75 Auspos et al. 260-75 Hostettler et a1. 260-783 Cramer 260-75 Matray et a1. 8-1155 Notarbartolo et a1. 260-783 LEON J. BERCOVITZ, Prim ry Examiner.

10 J. A. SEIDLECK, D. E. CZAIA, R. W. GRIFFIN,

Assistant Exan'ziners.

Claims (1)

1. IN THE PRODUCTION OF TEXTILE FIBERS OF POLYHEXAMETHYLENEADIPAMIDE BY MELT-SPINNING THE POLYMER AND DRAWING THE SPUN FILAMENTS INTO ORIENTED FIBERS, WHICH FIBERS ARE CONVENTIONALLY DELUSTERED BY INCORPORATING TIO2 IN THE POLYMER, THE IMPROVEMENT FOR DECREASING THE DYNAMIC FRICTION OF THE FIBERS PRODUCED AND INCREASING THE RESISTANCE TO LIGHT AGING WHICH COMPRISES REPLACING AT LEAST PART OF THE TIO2 WITH 0.1 TO 5%, BASED ON THE WEIGHT OF THE POLYMER, OF A FINELY-DIVIDED NORMAL TEREPHTHALATE SALT OF A METAL OF ATOMIC NUMBER 20 TO 56 FROM GROUP II OF THE PERIODIC TABLE.