US3115744A - Process for the manufacture of crimped yarn - Google Patents

Description

Dec. 31, 1963 c. c. NOTT 3,115,744

PROCESS FOR THE MANUFACTURE OF CRIMPED YARN Filed July 22, 1960 Inventor Come/v 619/9245: /Varr Attorneys United States Patent M 3,115,744 PROCESS FGR THE MANUFACTURE OF CRIMPED YARN Conan Charles Nott, Town Centre, Cwrnbran, England,

assignor to British Nylon Spinners Limited, Pontypool,

England Filed July 22, 1960, Ser. No. 44,597 Claims priority, application Great Britain July 24, N59 6 Claims. (Cl. 57-157) This invention relates to yarn comprising synthetic linear polymers, and more particularly to yarn consisting of or containing a synthetic linear polyamide, and to processes for manufacturing said yarn.

The present yarn consists of continuous filaments; it is composed at least mainly, of a synthetic linear polymer of the type which can be melt-spun, for example, a polyamide or a polyester. The filaments may consist wholly of polyhexamethylene adipamide, but other synthetic linear polymers may form the material of the filaments, for instance, polyureas, e.g. polyhexamethylene urea, polyurethanes, e.g. polybutylene. glycol hexamethylene dicarbamate, polyesters, e.g. polyethylene terephthalate, stereospecific polyolefines, e.g. polypropylene or the following polyamides namely, polyhexamethylene sebacamide, polykappa-aminoundecanoic acid, poly-epsilon-caprolactam. The yarn of the present invention may thus include filaments of other textile material besides synthetic linear polymers provided that the latter constitute at least the major proportion of said yarn.

Yarn consisting of synthetic linear polymer filament, for example, a polyamide yarn made of polyhexamethylene adipamide, possesses many properties eagerly sought after for textile purposes and, in particular, a high degree of strength expressed as the tenacity at the point of rupture. Such yarn is accordingly manufactured commercially on a large scale, the high tenacity being attained by submitting the filaments to a process of drawing whilst they are in the solid state, a process frequently referred to as cold-drawing. Thus the filaments, in their undrawn condition after being solution-spun or melt-spun from the required polymer, are elongated in the solid state, commonly by passage between two pairs of rolls, the second pair revolving faster than the first. Between the rolls the filaments may, if desired, pass round a snubbing pin so as to locate the point at which drawing takes place.

During the last decade the employment of synthetic linear polymer yarn, notably polyamide yarn and later polyester yarn, in various textile fields formerly depending on natural fibres or conventional rayon yarn such as viscose or cellulose acetate, has continuously increased. Yarn composed of a synthetic linear polymer possesses numerous excellent properties among which high tenacity, resistance to abrasion and uniformity are especially to be reckoned. Nevertheless such yarn is apt to be regarded, in the case of some end uses, as inadequate or capable of improvement in respect of aquality known as handle, feel, loftiness, bulk or fullness, a characteristic which is not easy to define because it is largely subjective and consequently a matter of personal opinion. The reason for the lack of bulk or fullness seems to reside at least in some measure in the normal smoothness of synthetic linear polymer filaments. Be this as it may, however, this quality of fullness is of great importance because it is understood to be related to the power of fabrics made from the yarn to absorb moisture and afford warmth. Consequently efforts have frequently been made in the past, to enhance the fullness of synthetic linear polymer yarn, by increasing its bulk by means of numerous crimping processes or by giving it a hairy or fuzzy nature in various ways. Yet it is ditficult to obtain quite the desired effect. For not only must the yarn present the right 3,115,744 Patented Dec. 31, 1963 appearance to the eye and possess the correct feel, but it is essential that it have the necessary mechanical properties as well. For example, a crimped yarn of suitable fullness and appearance, may lose these qualities on being wovenowing to the tension exerted in the loom pulling out the crimps. Hot wet treatment. as, for instance, in dyeing, is also liable to interfere with the physical nature of the yarn.

The present invention concerns a new process for producing a full or lofty synthetic linear polymer yarn starting with undrawn yarn, which depends on the incorporation in the drawing process of a heat treatment whereby part of the yarn when it has been drawn, is subjected to a raised temperature, the yarn being held substantially at constant length during the heat treatment. The heated part of the yarn then has a reduced tendency to shrink; in other words it is dimensionally more stable than the other part. After the two parts are twisted together and shrunk, the heated part of the yarn forms loose convolutions around the unheated part which remains substantially straight. If desired, a plurality of different heat treatments may be provided so as to subject various parts of the yarn to different raised temperatures.

The undrawn yarn may be twistless; but in any case it is essential that there should be no twist between those parts of the yarn which must be parted from each other in the form of separate strands to permit them to be given different heat treatment, or no heat treatment.

Accordingly this invention relates to a process for the manufacture of yarn comprising drawing undrawn or incompletely drawn synthetic linear polymer multifilarnent yarn between a feed roll and draw roll, which process is characterised in that the yarn after passage round the feed roll and the draw roll, is separated into two or more parts, which parts are subjected to different temperatures whilst their length is maintained substantially constant, the parts of the yarn being then twisted together by conventional means.

If desired, the undrawn or incompletely drawn multifilament yarn may comprise filaments of more than one denier. In the case of two deniers, when only the lighter denier filaments are heated after drawing, the heavier denier filaments shrink more and when the heated and unheated parts of the multifilament yarn are twisted together or doubled, the heavier denier part forms a core which is clad by the filaments of lighter denier.

The separation of the yarn may, for example, be effected by providing the draw roll with two separator rolls, so that the yarn, after passage round the feed roll and the draw roll and one of the separator rolls, is separated into two parts, one of which continues to run round the aforesaid separator roll and draw roll, whilst the other part of the yarn then runs round the draw roll and the second separator roll, and is subjected during its passage between these two rolls to a heat treatment whilst its length *is maintained substantially constant.

Another way of separating the yarn is by spreading" it out as a ribbon, so that only part of the ribbon may receive the heat treatment. In this case the separate strands, though distinct, are adjacent. It has already been stated that the yarn may be divided into more than two parts for the purpose of various heat treatments; in such cases the draw roll is equipped with a corresponding number of separator rolls when this method of separating the yarn is employed.

As already indicated, a snubbing pin, if desired, be located between the food roll and the draw roll.

The invention includes yarns manufactured in accordance with the above process.

The heat treatment can be applied by causing the yarn to run over a hot plate so as to subject it to the required temperature. Some other means for heating the yarn are hot nitrogen, steam, infra-red radiant heat, hot molten metal or a high frequency electrical field. It is evident that the temperature reached must not be so high as to melt the polymer, and the melting points of the polymers already mentioned above are therefore now quoted as a guide:

C. Polyhexamethylene adipamide 248 Polyhexamethylene urea 270 Polybutylene glycol hexamethylene dicarbamate 178 Polyethylene terephthalate 255 Stereospecific polypropylene 165 Polyhexamethylene sebacamide 209 Poly-kappa-a-minoundecanoic acid 187 Poly-epsilon-caprolactam 2l4 It will be understood that when the yarn is referred to as passing round the feed roll, and the like, the yarn may make one or more turns or wraps round the said roll in accordance with known textile practice.

The fullness or bulk of the present yarn is enhanced or its development accelerated by heating the yarn, especially in the presence of water, egg. by immersion in water at 60 C. or by steaming. The invention includes the bulked yarn when so treated. Its loftiness is stable to tension. When the yarn is first woven into a fabric and the fabric then heated in the aforesaid manner, a crepe effect is produced.

The yarns of the present invention may be, if desired, subsequently doubled, braided, looped, set by heat, hot water or steam, dyed, sized or otherwise conventionally treated to prepare them for use in knitting, warp-knitting, weaving or other textile manufacturing process. These yarns are eminently suited for blouses or lingerie.

One embodiment of the process according to the invention is illustrated by the accompanying diagrammatic drawings wherein the numbers have the following meanlngs:

When the present process is operated, the undrawn yarn 10 is passed between the nip roll 1 and feed roll 2 and then round the snubbing pin 3; thence it goes around the draw roll 4 and separator roll 5 once or several times. When the yarn arrives at point 111 it is separated into two parts, one part continuing to run around rolls 4 and 5 whilst the other part passes to separator roll 6 and back over the hot plate '7 to the draw roll 4. The two parts of the original yarn, reunited, then traverse the guide 8 and are wound up and twisted at 9.

The following examples which are by way of illustrating but not limiting the invention describe some specific ways in which the above apparatus can be operated.

Nip roll Feed roll Snubbing pin Draw roll First separator roll Second separator roll Electrically heated hot plate Yarn guide Conventional bobbin for winding up yarn Yarn Example 1 An undrawn yarn comprising two multifilament strands (not twisted together), each strand containing 60 filaments and having turn per inch 2 twist, is drawn at 90 feet per minute and at a mechanical draw ratio of 4.06 by means of the apparatus described above.

The yarn path is as follows. The yarn, after passing between rolls 1 and 2 and twice around the snubbing pin 3, goes three times round rolls 4 and 5. The yarn has now been drawn. At point 11 the two strands are separated; One continues to pass round rolls 4 and 5, making three more circuits. The other strand is taken thrice round rolls 4 and 6. This strand passes over the hot plate 4 7 which is 6 inches long and maintained at 160 C. Thus the total number of wraps on the draw roll is 6.

The yarn is finally wound up and given 4.3 Z turns per inch twist at 9 after passing through the yarn guide 8. When relaxed in hot water (60 C.) the yarn is found to be full and has a good handle. Its denier is 2624.

Example 2 An undrawn yarn of polyhexamethylene adipamide, comprising four strands, each of 60 filaments twisted with 34, 2 turn per inch is drawn at feet per minute at a mechanical draw ratio of 4.06 as in Example 1, with the use of the same apparatus as therein referred to.

All four strands proceed 3 times round rolls 4 and 5. At point 11 two of the strands are separated from the other two, one pair making three more circuits round rolls 4 and 5 and the other pair going thrice round rolls 4 and 6 and over the heater 7. The strands are then united and wound up and twisted (4 2 turns per inch).

The resultant yarn is finally steamed under negligible tension, when a bulked yarn of pleasant handle results. Its denier is 5764.

Example 3 An undrawn yarn of polyhexamethylene adipamide comprises two strands, each consisting of 60 filaments twisted together with turn per inch. The total denier is 826.

The yarn is drawn on the apparatus previously described except that the snubbing pin 3 is omitted. The mechanical draw ratio is 3.09 and the temperature of the hot plate is 200 C. One strand is passed six times round rolls 4 and 5, the other strand three times round rolls 4 and 5 and three times round rolls 4 and 6. The combined strands are wound up and given 2 /2 2 turns per inch twist.

The resulting yarn which has a denier of 285 is woven as weft against a warp consisting of a polyhexamethylene adipamide yarn of 34 filaments (total denier twisted with 7 turns per inch 8 twist.

The resulting fabric is immersed in an aqueous bath containing 0.2% sodium carbonate and 0.2% soap at room temperature. The bath is heated up to 60 C. during 30 minutes and maintained at this temperature for a further 30 minutes. The fabric is rinsed and dried; it possesses a well-defined crepe effect.

The fabric is heat set by submitting it to a temperature of 215 C. for '27 seconds on a stenter, adjusted to permit 3% shrinkage in both the warp and weft directions.

The fabric is subsequently dyed with Multamine Navy Blue 28 (obtainable from Imperial Chemical Industries, Ltd.) and retains its crepe appearance.

Example 4 A yarn comprising six strands of polyhexamethylene adipamide each containing filaments twisted together with Z turn per inch, is drawn on a conventional drawing machine, that is, as illustrated in the accompanying drawing, the roll 6 and the heater 7 being absent.

The rate of drawing is 325 feet per minute and the mechanical draw ratio is 5.45.

The yarn comprising the six strands forms on the draw roll a ribbon 1% inches wide. The yarn is taken round the draw roll 4 and separator roll 5 six times, but during the fourth circuit the yarn makes contact with a 10 inch long plate maintained at C. which is suitably positioned so that only half the ribbon of yarn i.e. A5 inch actually passes along the hot plate in contact therewith. The yarn is then twisted and wound up the twist inserted being 4% Z turns per inch. On relaxing the resulting drawn yarn in water at 60 C., a bulked yarn having a total denier of 5875 is obtained.

Example 5 An untwisted undrawn yarn of polyhexarnethylene adipamide comprising 34 filaments of 40 denier and 10 filaments of 50 denier (the total denier being 353) is drawn to 3.92 times its original length at 210 feet per minute on the same apparatus as that employed in Examples 1 and 2.

The whole yarn is passed 3 times round rolls 4 and 5. At point 11 the strand of lower denier is separated from that of heavier denier, the latter making 3 more circuits round rolls 4 and 5. The strand of lower denier passes from point 11 round roll 6, over the heater 7 and then twice round rolls 4 and 5. The two strands are combined and wound up at 9 with the insertion of 2 2 turns per inch twist. When relaxed in hot water (60 C.) the yarn becomes full and of a good handle, the strand of heavier denier tending to form a core which is clad by the strand of lighter denier.

What we claim is:

1. Process for the manufacture of yarn comprising: drawing continuous incompletely drawn melt-spun synthetic linear polymer multifilament yarn; separating the yarn into at least two strands; heating one of said strands to a temperature between slightly below its melting point and a temperature at which the tendency of the strand to shrink is reduced a substantial amount while maintaining its length substantially constant; simultaneously maintaining the other strand at a lower temperature than that to which said one strand is heated so that said other strand has a tendency to shrink which is greater than the tendency of said one strand to shrink; and twisting together said strands to form a yarn.

2. Process for the manufacture of yarn as claimed in claim 1 wherein the incompletely drawn mul-tifilament yarn comprises filaments of more than one denier.

3. Process for the manufacture of yarn as claimed in claim 1 wherein said one strand is heated by passage over a hot plate.

4. Process for the manufacture of yarn as claimed in claim 1 wherein the yarn, after the parts thereof have been twisted together, is heat-shrunk so as to become full or bulked.

5. Process for the manufacture of yarn as claimed in claim 4 wherein the step of heat-shrinking the yarn includes heating the yarn in the presence of water.

6. Process for the manufacture of yarn comprising: drawing continuous incompletely drawn melt-spun synthetic polymer multifilament yarn; separating the yarn into at least two strands; reducing the tendency of one of the strands to shrink by passing the same over a heated solid surface to heat it to a temperature between slightly below its melting point and a temperature at which the tendency of the strand to shrink is reduced a substantial amount while maintaining its length substantially constant; simultaneously maintaining the other strand at a lower temperature than that to which said one strand is heated so that said other strand has a tendency to shrink which is greater than the tendency of said one strand to shrink; twisting together the strands to form a yarn; heating the yarn in the presence of water to cause the previously heated strand to form loose convolutions around the previously unheated strand thereby forming a bulked yarn.

References Cited in the file of this patent UNITED STATES PATENTS 2,174,878 Hardy Oct. 3, 1939 2,789,340 Cresswell Apr. 23, 1957 2,855,749 Eshuis Oct. 14, 1958 2,956,330 Pitzl Oct. 18, 1960 2,979,883 Waltz Apr. 18, 1961 2,985,940 Weldon May 30, 1961

Claims (1)

1. PROCESS FOR THE MANUFACTURE OF YARN COMPRISING: DRAWING CONTINUOUS INCOMPLETELY DRAWN MELT-SPUN SYNTHETIC LINEAR POLYMER MULTIFILAMENT YARN; SEPARATING THE YARN INTO AT LEAST TWO STRANDS; HEATING ONE OF SAID STRANDS TO A TEMPERATURE BETWEEN SLIGHTLY BELOW ITS MELTING POINT AND A TEMPERATURE AT WHICH THE TENDENCY OF THE STRAND TO

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