US3511677A - Process for preparation of a sized zero-twist synthetic fiber yarn and product thereof - Google Patents

Description

May 12,1970 A. J. STROHMAIER ETAL 3,511,677

PROCESS FOR PREPARATION OF A SIZED ZERO-TWIST SYNTHETIC FIBER YARN AND PRODUCT THEREOF Filed June 25, 1968 ALFRED J. STROHIAIER ROBERT W. WHITMAN ATTORNEY United States Patent O PROCESS FOR PREPARATION OF A SIZED ZERO- TWIST SYNTHETIC FIBER YARN AND PRODUCT THEREOF Alfred J. Strohmaier and Robert W. Whitman, Seaford,

Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Continuation-impart of application Ser. No. 435,361

Feb. 25, 1965, which is a continuation-in-part of application Ser. No. 261,852, Feb. 28, 1963. This application June 25, 1968, Ser. No. 739,727

Int. Cl. D06m 3/42; B32b 27/02 US. Cl. 1177 8 Claims ABSTRACT OF THE DISCLOSURE A process for preparing a coherent zero-twist continuous filament yarn comprising applying a coating of a volatile medium containing a thermoplastic film-forming polymeric material to an undrawn yarn, drawing the yarn while wet with the volatile medium and then heating the drawn yarn to dry the coating before winding the yarn on a package. The yarn produced exhibits a high degree of filament parallelism within the yarn bundle.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of our pending application Ser. No. 435,360, filed Feb. 25, 1965, and now abandoned, which is in turn a continuation-in-part of application Ser. No. 261,852, filed Feb. 28, 1963, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to novel synthetic textile yarns and to a method for their preparation. More particularly, it relates to a coherent, zero-twist synthetic fiber yarn and to a novel and efiicient process for preparing the yarn. While the invention is applicable to any drawable synthetic polymer yarn, it will be particularly described with reference to the preferred polyamide textile yarns.

Polyamide textile yarns, e.g., those prepared from polyhexamethylene adipamide and polycaproamide, are wellknown articles of commerce, with numerous variations in structure and form being known and sold, and many variations in manufacturing processes being proposed. Re cently, considerable interest has developed in zero-twist multifilament textile yarns because of their higher degree of opacity in woven fabrics combined with the considerable saving in manufacturing costs achieved by the elimination of twisting operations. In the preparation of zerotwist yarns, the manufacturer is free to use high-speed surface driven package windups, such as that disclosed by Peterson in US. Pat. No. 2,789,774. Unfortunately, zerotwist yarns are subject to filament snagging, ballooning at guides, and filament transfer between adjacent yarn bundles. Heretofore, these problems have been overcome either by following the procedure of interlacing in an air jet as described by Bunting and Nelson in US. Pat. No. 2,985,995 or by twisting and applying a sizing composition. Such sizing compositions are usually applied after the yarn is drawn as a final step in the preparation of yarn for various textile fabrication processes. Although sizing or interlacing treatments have permitted the use of zerotwist yarns as filling yarns in the weaving of fabrics, they are not completely satisfactory. For example, interlacing is found to give nonuniform yarn bundle characteristics which lead to flashes in fabrics and a drawn zero-twist yarn which is subsequently sized has been found to have 3,511,677 Patented May 12, 1970 SUMMARY OF THE INVENTION The present invention provides Zero-twist polyamide textile yarns suitable for use, without further treatment, as filling yarns in woven fabrics. Another provision is a zerotwist multifilament polyamide yarn having reduced friction and improved running characteristics. The invention also provides a zero-twist yarn characterized by a coherent yarn bundle structure and an efiicient and economical process for preparing coherent zero-twist multifilament nylon yarns.

These provisions are realized by a process for preparing a coherent zero-twist multifilament polyamide textile yarn comprising supplying to a drawing step a zero-twist multifilament undrawn yarn prepared from a synthetic linear polycarbonamide, applying to the undrawn yarn a liquid finish comprising a major amount of a volatile inert liquid and a minor amount of a thermoplastic filmforming polymeric material which is adherent to polyamide structures, immediately drawing the yarn to the desired degree of orientation before the volatile liquid evaporates, heating the drawn yarn (under tension) to an elevated temperature for a suflicient time to evaporate the residual volatile liquid and dry the finish coating, and then winding the yarn into a package without twisting.

Operation of the above process provides a coherent zero-twist multifilament synthetic textile yarn in which the filaments are held together and protected throughout their length by a thin nontacky covering of a size-like nature. The yarn is resistant to snagging, ballooning, and filament transfer between adjacent yarn bundles, and is capable of being wound on a quill and used as a filling yarn in woven fabrics without additional preparation. Furthermore, the yarn exhibits reduced friction and improved luster uniformity which permits the production of fabrics showing a markedly reduced incidence of both flashes and tension-induced fabric nonuniformities. Close examination reveals that the sized yarn bundle has a somewhat flattened cross section but is not spread out to a single-filament-thick band.

It is preferred that the process conditions be adjusted to give a yarn bearing at least about 0.01 weight percent to as much as 0.05 to 0.8 weight percent film-forming polymer. Where the amount of the film-forming material is too small, it does not provide suflicient coherence for a useful yarn. The application of more than about 0.8% film-former leads to processing difliculties associated with the formation of deposits on guides and rolls. However, more than 0.8% film-former may be used with specialized guide and roll surfaces, for example, Teflon 1 fluorocarbon resin or silicone-coated surfaces. Other lubricants and yarn dressing agents in addition to the film-forming polymer may be present in the dried coating, but the total finish solids loading preferably will not exceed about 3% by weight on the yarn.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic illustration of an apparatus arrangement used in practicing the preferred process of the invention.

DETAILED DESCRIPTION OF THE DRAWING 1 Registered Du Pont trademark.

and a thermoplastic polymeric film-forming material is incorporated in the spin finish normally applied to the undrawn filaments immediately after quenching.

As shown in the drawing, molten polymer is extruded through spinneret 1 to form filaments 2 which are quenched and then passed over finish applicator roll 3 where a size-containing finish is applied to the discrete filaments. The filaments are then converged in guide 4 and proceed as a bundle to and around feed roll 5, with its accompanying separator roll 6. The yarn next passes to and around first draw roll 7 and associated separator roll 8, which is moving at a higher peripheral speed than feed roll 5, and then proceeds to and around heated second-stage draw rolls 9, 10 which are rotating at a peripheral speed higher than that of first-stage draw roll 7. Dried, sized, drawn yarn 11 then optionally passes in contact with finish applicator roll 12, where a secondary finish many be applied, and then passes through a traversing guide 13 to windup bobbin 14 driven by drive roll 15.

In this preferred embodiment a polyamide is converted, in one continuous operation, from molten polymer into a drawn sized textile yarn suitable for use directly as filling in the weaving of fabrics. The drawing takes place in two stages in zones 16, 17 and the drawn yarn is heated to an elevated temperature under tension as it passes around heated rolls 9, 10 to evaporate the residual volatile liquid and dry the finish coating before winding into package 14. Surprisingly, the sized multifilament yarn produced by this preferred process, when woven and dyed, yields fabrics having a degree of uniformity higher than has been observed With any prior nylon yarn. The virtual absence of visual defects, spots, flashes, and the like, is readily apparent even to an untrained observer. Close examination of the warns in such fabrics reveals an extremely low level of occurrence of filament intermingling, filament entanglement, and filament crossovers which cause non-uniform reflectance of light in fabrics made from conventional yarns. Inspection reveals also that the high degree of filament parallelism in these yarns allows the yarn bundle to spread uniformly into the spaces available in the fabric weave structure. This uniform spreading of the yarn bundle, in addition to increasing uniformity of appearance, provides a fabric with more opacity and less porosity than equivalent fabrics prepared from prior art yarns. Higher opacity and lower porosity are valuable fabric attributes in many end uses.

Although zero-twist yarns with moderately low levels of filament intermingling have been known previously, sized zero-twist yarns have had fairly high levels of filament intermingling. This is because conventional methods of sizing a yarn always introduce an appreciable degree of filament intermingling due to added handling of the yarn no matter how much care is taken in the sizing operation. In the preferred process of the present invention, size is applied to lock the filaments in place before an appreciable amount of filament intermingling can occur.

The term zero-twist yarn as used herein refers to a yarn which has no measurable twist in several yards of length.

The term undrawn yarn refers to yarn which exhibits spinning orientation only. Usually undrawn yarn has a birefringence value less than 0.012. Birefringence is determined according to the method of Heyn, Textile Research Journal, 22, 513 (1952), and is a measure of crystalline orientation.

The term multifilament yarn as used herein refers to a textile denier yarn having at least five filaments in the yarn bundle. The yarn may contain as many as 200 filaments or more in the bundle, but most common textile denier yarns contain fewer than 100 filaments.

The degree of filament parallelism in a multifilament yarn, or absence of filament entanglement, may be measured automatically by the apparatus of Hitt described in U.S. Pat. No. 3,290,932. The apparatus measures the length of yarn, in centimeters, which can be passed through a test point before entangled or intermingled filaments deflect a needle projecting transversely through the moving yarn bundle. This length of yarn, usually an average of 10 determinations, is reported as the automatic pin drop count, or APDC number (in centimeters). For meaningful measurements on sized yarns, of course, the size must be softened with a solvent sufficiently so that the size itself does not cause a deflection of the sensing needle. For the results reported in the examples, the Hitt apparatus shown in FIG. 1 of the patent is modified by inserting a device for wickin-g a solvent (usually water) onto the yarn between the tension device 14 and needle probe 18. The tension device is set to provide a tension of 10 gms. in the test yarn, and the yarn passed through the apparatus at a speed of 100 inches per minute. The apparatus is adjusted so that a force of 8 gms. is required to trip the needle probe.

It will be realized that the probability of filament intermingling in a yarn bundle is a direct function of the number of filaments in the bundle. Hence, the chiliculty of preparing a yarn with a high degree of filament parallelism increases as the number of filaments increases. The multifilament sized yarns of this invention, not available heretofore, have average APDC values (measured as described above) higher than the expression (l000-10N) cm., where N is the number of filaments in the range of 5 to about in the yarn bundle, and APDC values above 100 cm. for yarns having about 90 to about 210 filaments. The preferred yarns of this invention, giving the best performance in fabrics, usually and APDC values above 100 cm. for yarns having about The term synthetic linear polycarbonamide is intended to include any linear polymer having recurring units of the formula as integral parts of the main polymer chain, wherein R is hydrogen or a monovalent hydrocarbon radical, the average number of carbon atoms separating the amide groups being at least 2, said polycarbonamide having an intrinsic viscosity of at least about 0.4, as defined in U.S. 2,130,948. Particular polycarbonamides including among those which are useful in this invention are as follows: polyhexamethylene adipamide, polyhexamethylene sebacamide, polymerized 6-aminocaproic acid, polytetramethylene .sebacamide, polytetramethylene adipamide, polymetaxylyleneadipamide, the polyamide from bis(4-aminocyclohexyl)methane and azelaic acid, sebacic acid, decamethylene-1,10'-dicarboxylic acid or dodecane- 1,12-dioic acid, and the polyamide from Z-methylhexamethylene diamine and terephthalic acid. The invention is also applicable to other polymers and various copoly-mers, either block or random, such as the copolyrner of polyhexamethylene adipamide and polyhexamethylene isophthalamide and the copolyrner of polyhexamethylene adipamide, and polyhexamethylenet-butyl isophthalamide. Other suitable polycarbonamides are disclosed in U.S. Pats. Nos. 2,071,251 and 2,071,253.

The liquid finish of this invention comprises a major amount of an inert volatile liquid. By major amount is meant at least 60% of the total mixture. If desired, the volatile liquid may comprise up to or more of the finish composition. Suitable volatile liquids are those which have boiling points above room temperature but below the temperature of the heating step which follows the yarn drawing step. Removal of the volatile liquid is accomplished by heating the yarn to a temperature above the boiling point of the liquid but below the melting point of the polymer for a short period, generally less than a second in duration. Liquids particularly suitable include water and low molecular weight alcohols such as ethanol. Other liquids which may be suitable for particular variations of the process include volatile esters such as methyl acetate, ethers such as dibutyl ether, ketones such as methylethyl ketone, hydrocarbons such as kerosene, and other volatile inert liquids which will be apparent to those skilled in the art. Mixtures of liquids may be used, if desired.

The liquid finish also contains, as an essential component, a minor amount of a thermoplastic film-forming polymeric material which forms a coherent bond with polyamide structures. By minor amount is meant concentrations of the order of 0.25 to 5% of the total finish composition. By film-forming polymer is meant a polymer capable of being formed into a self-supporting film. The film-forming polymeric material may either be dissolved or dispersed in the volatile carrier liquid. A preferred film-forming polymeric material is polyacrylic acid, because of its excellent adherency to polyamides. Other film-forming materials which may be used include monomeric and polymeric phenol-formaldehyde resins, polyvinyl alcohol, polyvinyl acetate, polyacrylates, polymethacrylates, poly(methylvinylether/maleic anhydride) interpolymer, polyitaconic acid, and copolymers of vinylidene chloride and acrylic acid. Copolymers and mixtures of polymers may be used. In general, any film-forming material suitable as a sizing agent for nylon yarns is operable in the process of this invention.

The liquid finish containing the film-forming polymeric material may also include other yarn dressing agents, if desired. When the film-forming polymeric material is applied to the yarn as a component of spin finish in a coupled spinning and drawing process, it is usually desirable for the finish to contain lubricants, emulsifiers, and wetting agents. Examples of lubricants which may be used include mineral, animal, or vegetable oils, esters, synthetic oils such as polyethylene oxide derivatives, silicone oils and similar materials. Suitable emulsifiers include soaps such as the alkali metal salts of oleic or stearic acid, sulfonated petroleum oils, and esters such as sorbitan trioleate and sorbitan monolaurate. Suitable wetting agents include anionic materials such as the dioctyl ester of sodium sulfosuccinate as well as nonionic materials such as condensation products of alkyl phenols with ethylene oxide. Bactericides such as Dowicide A (sodium salt of phenylphenate) may be added if desired. Antistatic agents such as trialkylphosphates may also be present.

To achieve the effects of the present invention, it is essential that the liquid finish be applied to the undrawn yarn and then the yarn drawn while the finish is still in the liquid state. Immediately thereafter, the finishcoated yarn must be heated so that a dry coherent film is formed on the yarn before it is wound up.

The drawn yarn may be heated to any temperature sufficient to drive off the volatile liquid and provide a dry coherent film. Temperatures between 80 C. and 220 C. are suitable. For high speed operations with relatively short heating times, temperatures in the range 180 210 C. are particularly suitable.

Where the coherent zero-twist yarn of this invention is to be subjected to severe abrasive conditions, it may be desirable to apply to the drawn yarn an additional overlay finish. For this purpose, any conventional polyamide dressing composition may be used.

In the following examples which are illustrative of the invention, the parts and percentages are given by weight.

EXAMPLE I A master finish mixture is prepared by mixing the following ingredients in the indicated proportions:

Parts Trialkyl phosphate (Zelec UT) 41.7 Ethanol 488.2 Potassium hydroxide (45% solution) 16 Parts Polyethylene glycol di(2-etl1ylhexoate) (Flexol 4 GO) 439.4 Oleic acid 14.6 Water 127.5

This master mix, which contains 44.6% solids by weight is used to prepare the following test solutions:

ture in the range of 40-5 0 C.

The three test mixtures and the control are used, consecutively, as spinning finishes in the preparation of polyamide yarns as follows.

Polyhexamethylene adiparnide is melt spun into a 34-filament yarn having a polymer intrinsic viscosity of 1.1 using the apparatus of Greenwalt, U.S. Pat. No. 2,217,743, and the filaments quenched with cross-flow cooling air according to the method of Brand, U.S. Pat. No. 3,067,459. The quenched undrawn filaments are then contacted with a rotating finish roller (U.S. Pat. No. 3,067,458) which is bathed in the finish mixture supplied (Table I). The yarn is then converged and passed around a feed roll rotating with a surface speed of 834 y.p.m., then through a first draw Zone and around a first draw roll rotating with a surface speed of 1870 y.p.m. The yarn is then passed through a second draw zone to and around a pair of combination draw-anneal rolls heated to a temperature of 200 C. and rotating at a surface speed of 3000 y.p.m. In passing over the latter rolls, the yarn is heated to a temperature approaching roll temperature. It is then advanced to a surface driven bobbin windup and wound into a package without being twisted, i.e., into a zero-twist package. All of the yarn samples produced, both control and test, have a denier of 701-2, a tenacity of 5.11025 g.p.d. and an elongation of 20.5- 1.5% under a load of 300 gm.

In contrast to the control yarn samples, the samples bearing the test finishes exhibit a coherent bundle structure capable of passing over guides and through eyelets without snagging or ballooning and without transfer of filaments between adjacent yarn bundles. Measurement of the yarn profile as the yarn in passed over a sharp edge indicates that the yarn bundle is several filaments thick, as if it were a slightly interlaced yarn as described in U.S. Pat. No. 2,985,995. However, closer examination, and other tests such as the APDC test, reveal an extremely low level of filament intermingling. In addition, the lightly coated test yarns show no shedding of finish and leave no deposits on guide surfaces. Examination of the filaments of the test yarns by means of an electron microscope using surface replication techniques reveals that the filaments have a very thin microwrinkled skin which is removable by scouring. The filaments of the control yarn, in contrast, exhibit a smooth surface when examined in this manner. The unexpected roughness of the microwrinkled skin of the filaments of the test yarn is believed to be due to the explosive evaporation of the solvent when the process is run at high speeds over a very hot drying roll.

The coefficient of friction is measured for each yarn, on both an Alsimag and a chrome pin, with the results shown in Table II. Also, samples of each yarn are wound on a quill using a quilling tension of 20 grams and then 7 inserted as filling in a plain weave fabric which is subsequently rated for quill barr using a 1 to 5 scale where 1 indicates no barr and 5 indicates severe barr. These results are also shown in Table II. The data clearly show the reduction in friction and in quill barr achieved by the yarns of the present invention.

The coeflicient of friction is measured by passing a test yarn at a speed of 250 y.p.m. over a %-inch diameter stationary pin, using a wrap angle of approximately 164, and measuring input and output threadline tensions. Calculations are based on the standard formula where T is input tension, T is output tension, f is the coefficient of friction, and 6 is the wrap angle in radians.

TABLE II a A second PAA-sized yarn prepared exactly as described above is examined for filament intermingling in the APDC test and found to give an average APDC value of 4022 cm., indicating a very high level of filament parallelism. Taffeta fabric prepared with this test yarn as filling, using the procedure for fabrics listed in Table VIIIa, is found to be significantly lower than a control fabric in air permeability and light transmittance, indicating that the Finish Coeificient of friction Fabric Roll PAA 1 on Finish 2 on speed, yarn, yarn, Alsimag r.p.m. percent percent pin, In

1-D (control).

Chrome P In EXAMPLE II For comparison, the general procedure of Example I is repeated using control finish l-D, but with the exception that the drawn yarn passes through an interlacing jet as described in U.S. 2,985,995 before it is wound up. The yarn produced has a moderately coherent bundle structure with measured coefiicients of friction falling between those of the control and test yarns of Example 1. The yarn is quilled and woven as filling into a plain weave fabric. Close examination of the fabric reveals numerous flashes. The fabric is given a quill barr rating of 4.5 in contrast to the ratings of 1.5 achieved with the test yarns of Example I.

EXAMPLE III A 70-denier, 34-filament, zero-twist, 66 nylon yarn is prepared according to the general procedure of Example I using as a spin finish a mixture having the following composition:

Parts Polyacrylic acid 10.0 Water 400.0 Polyethylene glycol-di(Z-ethylhexoate) 79.5 Sorbitan monolaurate 4.4 Sorbitan trioleate 4.4 Dioctyl ester of sodium sulfosuccinate 1.7

A control yarn is prepared using a spin finish of essentially the same composition but with on polyacrylic acid present.

The test yarn so produced is a zero-twist, lightly sized yarn having a somewhat flattened coherent bundle structest yarn provides a marked improvement in cover power.

Similar results are obtained when the above spin finish mixture is diluted with an equal volume of water before using.

When the test is repeated with yarns of semidull luster containing 0.5% by weight TiO and mid-dull luster containing 0.9% TiO similar results are obtained.

It has also been discovered that certain processing advantages can be achieved upon separate application of film-forming and spin finish components. This practice is demonstrated in the following examples (IV, V and VI).

EXAMPLE IV The general yarn preparation procedure of Example I is repeated with the exception that the single rotating finish roller of that example is replaced with a pair of rotating finish rollers operating in tandem so that the quenched, undrawn yarn contacts first one roller and then the other and then proceeds to the feed roller. The first finish roller is bathed in a mixture of film forming agent and volatile solvent (Finish A) having the following composition:

TABLE III Composition of Finish A Parts Water 98.75 Polyitaconic acid (35% solution) 1.22 Sodium dioctylsulfosuccinate .04

The second finish roller is bathed in a spin finish (Finish B) having the following composition:

TABLE IV Composition of Finish B Parts Isopropyl alcohol 60.0 Triethyleneglycol-di(Z-ethylhexoate) 38.8 Stearic acid 0.4 Methylphenylpolysiloxane 0.8

The yarn prepared with this dual-finish-roll system is found to be a coherent, low-friction, zero-twist yarn substantially equivalent in all performance aspects to the test yarns prepared in Example I. The amount of polyitaconic acid coating on the yarn is found to be 0.22% by weight, with Finish B ingredients adding another 0.32%. The coeflicient of hydrodynamic friction f measured on a chrome pin, is 0.44. In an extended period of operation the dual-finish-roll process of this example is found to be superior to that of Example I in that fewer size deposits are built up on the draw rolls and fewer broken filaments and roll wraps are encountered.

A second test yarn prepared as above is woven as filling in a taffeta fabric, scoured, dyed, and finished using the procedure used for those fabrics rated in Table VIIIa. The test fabric is found to have an average air permeability of 25.1 cu. ft./min./ft. compared with a value of 45.0 for a similarly prepared control fabric woven from an unsized filling yarn. Likewise, in a light transmittance test, the test fabric gives a value of 2.56% transmittance compared with a value of 3.35% for the control fabric. These data show the superior covering power of the test fabric.

EXAMPLE V The procedure of Example IV is repeated using in place of Finish A an alternative finish mixture having the composition in Table V. Similar results are obtained.

TABLE V Composition of Finish C Parts Water 95.95

Sodium dioctylsulfosuccinate (75%) 0.05 Vinylidene chloride/acrylic acid 70/30 copolymer EXAMPLE VI The general procedure of Example IV is repeated using two alternative finish mixtures. Finish A is replaced With Finish D having the following composition:

TABLE VI Composition of Finish D Parts Water 98.75 Sodium dioctylsulfosuccinate (75 0.04 Poly(methylvinylether/maleic anhydride) 1.22

Finish B is replaced with Finish E having the composition of Table VII.

Finish composition (parts) Water (87.0)

The yarn produced is substantially equivalent to the test yarns produced in Example IV, being a coherent, zero-twist yarn with the low coefficient of friction f of 0.52, measured on a chrome pin. Total finish pickup is 0.14% by weight. The yarn holds together as if it were twisted as much as 3 turns per inch.

A second sized test yarn is produced with poly(methylvinylether/maleic anhydride) as the cohesive agent in place of polyacrylic acid in the finish mixture of Example III. The general procedure of Example I is followed and the yarn product examined for filament intermingling. The yarn is found to give an average APDC value of 7624 cm. When the yarn is woven as filling in a plain weave fabric, dyed, and visually compared with dyed fabric of similar construction made with the best commercially available nylon yarns, the test fabric is found to be much superior in uniformity of appearance. Also, in air permeability tests, the test fabric gives an average value of 19.0 cu. ft./min./ft. compared to a value of 45.0 cu. ft./min./ft. for a control fabric, and in light transmittance tests the test fabric gives an average value of 2.19% transmittance compared with a value of 3.35% for a control fabric. These test results clearly show the improved cover power of the test fabric.

In the following examples a series of film-forming agents are applied to 66 nylon yarn in spin finish in the manner described in Example I. Seventy-denier, 34 filament, zero-twist yarns are prepared which are similar to the test yarns of Example I in coherency and reduced friction. The composition of the finish mixtures are presented in Table VIII along with approximate value for the amount of finish solids on the yarn, values for the coefficient of hydrodynamic friction measured on a chrome pin, and values for the average yarn bundle thickness as measured by a profile meter. Bundle thickness is an indication of coherency. A control sample, pre pared in the same manner but with no film-forming agent in the spin finish is included in the table for comparison. The control sample does not possess the coherency attributes of the test samples.

TABLE VIII Pickup, percent Total solids Film former Acrylate copolymer emulsion (40%) (Neocryl ETA) (5.0).

High melting mici-ocrystalline was (6.49)

Stearic acid (0.74)

Morpholine (0.56) 3, 4-dimethyl-1-hexyne-3-ol (0.22) VIII Water (84.0)

Polyvinylaeetate 25%) (so) Tringethylolpropane-tri-N-octanoate Phosphate ester of polyoxyethylenated alkylphenol (1.53).

Dirnethylpolysiloxane (0.10) Sodium dioetylsulfosuccinate (0.13). XI Water (87.22)

Pickup, percent Film Total Finish composition (parts) former solids is in. 10

Water (87.75) 0. 23 1. 52 0. 73 Polyvinylacetate emulsion (55%) (3.0) Coconut oil (4.5) Aluminum dihydroxystearate (0.26) High melting microerystalline wax (0.39) Pclygxyethylene sorbitol olcate laurate (2. 2). Polyoxyethylene lauryl ether (0.55) Mixed N'cctadecyl and -octadeceny1 betaine (1.50). Water (63.6) 0. 3 0. 46 Acrylazg 4emulsion (38%) (Rhoplex B- Oleic acid (7.0) Dimethylpolysiloxane (6.0)

Bundle thickness XII XIII (control) (no film former) A commercial aqueous finish containing solids of which the major ingredients are trialkylphosphate, oleic acid anl)polyethylene-glycol-di(Z-ethylhex- 0a e A second set of test samples for Examples VII through XII is prepared exactly as described above and tested for filament intermingling in the APDC test. The results, recorded in Table VlIIa, show the extremely low level of filament intermingling in these test yarns. Some of the test yarns are also woven, without further treatment, as filling in consecutive sections of a taffeta fabric, using a warp prepared from a commercial 7 O-denier 34-filament nylon twisted to 5 turns per inch Z and slasher sized in a conventional manner. The fabric is caustic secured on a jig, dyed gray with acid dyes, rinsed, dried and heat-set at 380 F. (194 C.) on a Tenter frame. A second fabric is prepared similarly and dyed red with a premetallized dye. The finished gray fabric has 111 ends per inch in the warp and 88 picks per inch in the fill. The red fabric has 106 ends per inch in the warp and 88 ends per inch in the fill. Each test fabric section is tested for air permeability and for percent light transmittance by methods described below. The results, summarized in Table VIIIa, indicate that the test yarn sections provide a significant improvement in cover power in comparison with a section woven from control yarn prepared in the same way but without the addition of size.

TABLE IX The yarn produced is a zero-twist, coherent yarn. Analysis shows a pickup of 0.03% by Weight of polyacrylic acid and a total finish solids loading of 0.15% by weight. The measured coefiicient of friction is f =0.49 for an Alsimag pin. In preparing quills for weaving, a low quilling tension is observed compared to a control sample containing no polyacrylic acid in the finish.

EXAMPLE XV This example illustrates the degree of filament intermingling and filament entanglement found in zero-twist yarns sized by prior art processes. Several conventionally TAB LE VIIIa Fabric cover power Air permeability, itfi/minJ fti Light transmittance, percent Yarn APD C, Example cm. Gray Red Av. Gray Red Av.

"""Es' i's "5615 15.13 a 6i EXAMPLE XIV sized yarns containing one-half turn Z twist are also included for comparison. The example shows the effect on APDC test value of the number of filaments in a yarn bundle. Also, for comparison, sized yarns of various counts are prepared in accordance with the principles of the present invention and examined for degree of filament intermingling.

A series of 66 nylon yarns of various counts are prepared following the general procedure of Example I with the exceptions that the spin finish is substantially the same as that of Example III without polyacrylic acid and the roll speeds are adjusted to give a feed roll speed of 876 y.p.m., a first draw roll speed of 2212 y.p.m., and a second draw roll speed of 3113 y.p.m. The temperature of the second stage draw rolls is adjusted to 192 C. All of the yarns are wound on a bobbin as zero-twist (unsized) yarns. Each yarn is then sized with polyacrylic acid using a conventional single-end sizing procedure in which yarn is removed from its original package, passed around a 3%-in.-diameter feed roll (4 /2 wraps) running at 169 rpm, then passed over a 4-inch-diameter sizing roll bathed in the finish mixture of Example III, modified by adding about 2% silicone oil, and rotating at 5 rpm, then passed over an 8-inch hot plate maintained at 185 C. to dry the size, then passed around a 3 %1-inch-diameter draw roll (4 wraps) operating at 170 rpm. and finally proceeding to a surface-driven package windup which introduces no twist into the yarn. The process is carried out with great care to prevent, as much as possible, the introduction of filament intermingling by unnecessary handling. Each sized yarn is then examined for filament intermingling using the APDC test described previously, with the results shown in Table X.

A second series of yarns of varying yam counts are prepared in the above manner with the exception that the spin finish has the composition of that of Example III plus aproximately 2% of a 100 centistoke silicone oil. The yarns produced are zero-twist, sized yarns. Each of these yarns is then examined for filament intermingling with the APDC test and the results are recorded in Table X (test yarns). The data clearly show the much lower level of filament intermingling found in yarns prepared in accordance with the present invention.

For comparative purposes, several commercially available 66 nylon yarns having /2 turn Z twist per inch in the yarn are single-end sized by the above-outlined conventional sizing procedure and tested for filament intermingling using the APDC test. These results are also recorded in Table X and illustrate the fairly high level of filament intermingling observed in commercial yarns after a conventional sizing operation.

Air permeability of textile fabrics is determined according to the general procedure of ASTM method D737-46 using an Air Permeability Measuring Instrument supplied by the Sherman W. Frazer C0,, Washington, DC. Using a calibrated orifice, air flow through the fabric sample is measured under a differential pressure of 0.5 inch of water and reported in cubic feet per minute per square foot of fabric area. Test samples are preconditioned for testing by exposing the sample to moving air at 130-* -l0 F. (54i-5.5 C.) for 2 hours and then holding the sample at 70 F. (21 C.) and 65% relative humidity for 16 hours.

Light transmittance of textile fabrics, as reported herein, is measured by illuminating one side of a masked rectangular area of fabric with diffused white light and measuring the light transmitted through the fabric by means of a calibrated photoelectric cell. The sample is held flat for the test by being placed between two glass plates. Samples are preconditioned in the same manner as described above for the air permeability test. Results are reported as percent light transmitted and are the average of at least five determinations.

It will be apparent to those skilled in the art that the invention described herein is applicable to many types of synthetic fibers including those having non-round crosssections such as trilobal, hexalobal or cruciform; filaments containing either discontinuous or continuous longitudinal voids; filaments containing dispersed pigments of various types including those described in Belgian Pat. 646,680; filaments formed from melt blends of dissimilar polymers such as those described in British Pats. 918,637 and 963,320; mixed filaments of different polymers spun simultaneously from different holes of the same spinneret, e.g., 66 nylon cospun with a copolymer of adipic acid, isophthalic acid and hexamethylenediamine; composite filaments made up of two distinct polymeric components such as those described in British Pat. 805,033; and many other variations.

Although the coherent zero-twist yarn of this invention is designed to be used directly as a filling in fabrics, it is not so limited. If desired, the yarn may be interlaced or twisted and sized according to conventional procedures and used as warp yarns. Or, if sizing conditions and ingredients are properly chosen, direct slashing of the zerotwist yarn may be carried out. For most direct slashing procedures the cohesive agent in the finish and the cohesive agent in the slasher size should be mutually insoluble, and preferably both should be removable under normal scouring conditions.

Alternatively, no restriction on choice of cohesive agent is necessary if the direct slashing equipment is the type which keeps yarn ends separate from each other upon emerging from the size bath and in passing over the drying cans.

A preferred product prepared by the method of this invention is a coherent zero-twist yarn having a loading of film-forming agent in the range 0.01 to 0.40 percent by weight. Such yarns are exceptionally useful as feed yarns in the preparation of yarns having functional torque and twist without bulk by the method of Seem and Stoddard, US. Pat. No. 3,009,312.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a yarn production process including the coupled steps of spinning continuous synthetic linear polyamide filaments, advancing the spun filaments over spaced feed and draw rolls to draw them and winding the drawn filaments to a package as a zero-twist yarn bundle, the improvement comprising: applying a size finish mixture consisting essentially of a major percentage of a volatile inert liquid and a thermoplastic film-forming polymeric material to the undrawn filaments as they advance to said feed roll, said polymeric material being selected from the group consisting of polymeric phenolformaldehyde resin, polyvinyl alcohol, polyvinyl acetate, polyacrylates, polymethacrylates, polyacrylic acid, and copolymers of vinylidene chloride and acrylic acid and poly(methylvinylether and maleic anhydride), said liquid being selected from the group consisting of water, low molecular weight alcohols, esters, ethers, ketones and hydrocarbons, drawing said filaments before the evaporation of said liquid; and heating the drawn filaments under tension before said winding step, the time-temperature relationship of the heating step being sufficient to evaporate residual volatile liquid and dry said material before winding, said yarn production process providing a yarn having substantially parallel filaments as characterized by an APDC value greater than 2000 cm.

2. The process of claim 1, said polymeric material being present in the range of from 0.255% by weight of said finish mixture, said filaments bearing from 0.01- 0.8% by weight of said polymeric material after drying.

3. The process of claim 1, said volatile liquid being Water and comprising at least 60% of said finish mixture.

4. The process of claim 1 including the additional step of applying a lubricating spin finish to the filaments after the application of the film-forming polymeric material.

5. A sized coherent zero-twist yarn comprising: a plurality of continuous drawn synthetic linear polycarbonamide filaments, said filaments bearing a coating of from 0.010.8% by weight of a thermoplastic film-forming polymeric material said filaments being substantiall arallel as characterized by an average APDC value of said yarn greater than 2000 cm, said filaments being held to gether by said coating.

6. A yarn according to claim 5, said polymeric material 7 being selected from the group consisting of polymeric phenolformaldehyde resins, polyvinyl alcohol, polyvinyl acetate, polyacrylates, polymethacrylates, polyacrylic acid, and copolymers of vinylidene chloride andacrylic acid, and poly(methylvinylether and maleic anhydride).

7. A sized coherent zero-twist yarn comprising: a pin rality of continuous drawn synthetic linear polycarbonamide filaments, said filaments bearing a coating of from (Mil-8% by weight of polyacrylic acid said filaments being substantially parallel as characterized by an average APDC value of said yarn greater than 2000. cm, said filaments being held together by said coating. 1

8. In a yarn production process that includes the step of advancing synthetic linear polycarbonamide filaments over spaced feed and draw rolls and winding the drawn filaments to a package as a zero-twist yarn bundle, the improvement comprising: applying a size finish mixture consisting essentially of a major percentage of a volatile inert liquid and a thermoplastic film-forming polymeric material to the undrawn filaments as they advance to the feed roll, said polymeric material being selected from the group consisting of polymeric phenolformaldehyde resin, polyvinylalcohoi, polyvinyl acetate, polyacrylates, polymethacrylates, polyacrylic acid, and copolymers of vinylidene chloride and acrylic acid and poly(methylvinylether and maleic anhydride); drawing said filaments while wet with said mixture and heating the drawn fi aments before said Winding step, said liquid being selected from the group consisting of water, low molecular weight alcohols, esters, ethers, ketones and hydrocarbons, the time-temperature relationship of the heating step being sufiicient to evaporate residual volatile liquid and dry said material before winding, said yarn production process providing a yarn having substantially parallel filaments as characterized by an APDC value greater than 2000 cm.

References Cited UNITED STATES PATENTS 2,137,235 11/1938 Carothers 117-7 X 2,253,146 7/1941 Spanagel 161-227 X 2,509,741 5/1950 Miles 117-7 X 2,743,194 4/1956 Berner et al. 117-139.5 2,859,206 11/1958 Polansky et al. 117-138.8 X 2,899,341 7/1959 Dawson 117-1388 3,000,758 9/1961 Hennemann et al. 117-76 X 3,113,369 12/1963 Barrett et a1. 252-88 X 3,160,511 12/1964 Skeen et al. 117-7 3,236,685 2/1966 Caldwell et al. 117-161 X 2,985,995 5/ 1961 Bunting et a1.

3,221,088 '11/1965 Martin 264-210 X 3,259,681 7/1966 Bull et al. 264-210 X WILLIAM D. MARTIN, Primary Examiner J. E. MILLER, Assistant Examiner US. Cl. X.R.

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