Method of making a covered elastic yarn

Abstract

The present invention relates to a method of making a covered elastic yarn with an elastic thread as a core yarn, and a continuous thermoplastic multifilament thread as a sheath yarn, wherein the respective filaments forming said covered elastic yarn are respectively tangled with each other to retain flux form, and at the same time to form the sheath-core system, and said sheath yarn wraps the outer periphery of said core yarn but is reversed irregularly and intermittently in said direction, and said sheath yarn and said core yarn are substantially twistless.

Parent Case Text

This is a division of application Ser. No. 143,940, filed May 17, 1971, now U.S. Pat. No. 3,807,162.

Description

BACKGROUND OF THE PRESENT INVENTION:

A novel elastic invention relates a method of making this yarn.

The yarn according to the method of this invention is a covered yarn wherein a multi-filament, continuous filament thread as a sheath yarn wraps a core yarn in such a manner that said multi-filament thread wraps round said elastic thread, and said core yarn and said sheath yarn are substantially twistless.

In conventional covered elastic yarns which are generally used at present rubber yarn or polyurethane elastic fiber yarn is used as the elastic core yarn, and the other filament yarn or spun yarn is twisted around said core, or said yarns are associated and twisted thereon.

In addition, elastic yarn such as rubber yarn or polyurethane elastic filament yarn is used as the core in the convection of ejected fluid, and other filament yarns are tangled therewith, or elastic yarn and thermoplastic filament yarn are associated, and the associated yarns are crimped in "twisting-heat setting-untwisting type" method so called "Italian type" twister to produce over-untwisting yarn. While, the conventional covered elastic yarns have excellent characteristics, they have the following drawbacks.

First of all, in the case of single or double covered yarn prepared either in such a manner that non-elastic yarn wound on a bobbin mounted on a rotating hollow spindle is wound onto the rubber or polyurethane elastic core filament as that filament is drawn through the spindle, or in another case of single covered yarn prepared in such a manner that non-elastic sheath yarn and rubber or polyurethane elastic core filament yarn are twisted under tension in a ring twister, excellent covering properties can be obtained but it is necessary to carry out appropriate thermal setting for power down and the setting of twisting torque because of the high torque attributable to the twisting operation. Other problems include excessive stretch power and, in addition, there is a limitation to the spindle speed in the experimental calculation of the productivity of fine yarn (total denier 90 denier,) there is no such a case that the processing speed should go beyond 20m/min even when the number of revolutions of the spindle is adjusted to be 10,000 rpm, the number of twists is adjusted to 10,000 rpm, and the number of twists is adjusted to 500 turns/m.

On the other hand, in addition to the foregoing drawbacks, there is a crimped yarn such as wooly yarn to be used as covering yarn must be separately prepared.

In addition, in the case of the conventional sheath core type bulked elastic yarn prepared in such a manner that polyurethane elastic filament yarn and other filament yarn are passed through ejected fluid convection, wherein the filaments are disturbed around said polyurethane elastic filament yarn to be tangled, the covering yarn is not twisted, and therefore the tangling property thereof is poor, and not satisfactory, and there is a fear that the core yarn may be exposed, and at the same time the cost of air is expensive. In addition to these this process drawbacks, as above, has a remarkable over-all drawback in the cost of labor attributable to the complicated processes, and the cost of processing is therefore high.

On the other hand, in the case of over twisted yarn produced from the associated elastic yarns and thermoplastic filament yarns by using the Italian type twister, the covering property is excellent but in view of the ordinary twisting process which is required in this case, the productivity thereof is not more than that of single covered yarn, at the same time, the number of processes is increased, and the cost of production is high, and therefore over-twisted yarn produced by the Italian type twister is not practical.

Thus, there is no twistless covered elastic yarn although there are those conventional covered elastic yarns having actual twists, or poor tangling property caused by fluidal convection.

It is a principal object of this invention to remove the above mentioned drawbacks of the prior arts, and to provide a novel covered elastic yarn having fast elasticity and remarkably excellent covering property.

It is another object of this invention to provide a method for producing the above mentioned novel covered elastic yarn.

In order to attain the above described objects of this invention, the present invention has the following structure.

This invention relates to a covered elastic yarn comprising an elastic thread as a core yarn and a multi-filament continuous filament thread as a sheath yarn, wherein the respective filaments forming said covered elastic yarn are tangled to retain the fluxability and at the same time to form sheath-core state, and said sheath yarn wraps the outer periphery of said core yarn, and is reversed intermittently and irregularly in said direction, and said sheath yarn and said core yarn are substantially twistless.

The present invention is explained more in detail in the following paragraphs;

The yarn of this invention is produced by using elastic thread having remarkably high elongation and recovery, such as rubber yarn or polyurethane filament yarn, as the core yarn. Said core yarn may be monofilament but it is preferable to use a plural number of associated filaments, i.e., multi-filament; and as a matter of course it is most preferable that the number of filaments should be great.

The reason for this is that the tangling property of core yarn against sheath yarn increases as the number of filaments in the core yarn increases.

On the other hand, as the above mentioned elastic yarn, crimped yarn or such elastic yarn having shrink-ability attained by chemicals, can be used.

On the other hand, as said sheath yarn, a crimped yarn composed of multi-filament yarn composed of thermoplastic filaments can be used.

Said sheath yarn covers and is twisted around said core yarn, and the core yarn is placed almost in the centre of said covering elastic yarn, and in regard to the direction of twisting of said sheath yarn, said sheath yarn is twisted in such a direction that said sheath yarn is twisted with random interval and intermittently in the lengthwise direction of said covered elastic yarn, and either filaments themselves forming said sheath or the filaments forming said sheath yarn and said core yarn are is mutually tangled to retain fluxability.

Sometimes, it is possible to partially melt the filaments forming said sheath yarn in order to improve the fluxability further.

When thermoplastic synthetic yarn is used as the core yarn, random untwisting or slight crimping can be observed intermittently in the same manner as in the case of said sheath yarn.

In such a structure as described above, it is possible for said sheath yarn to be more excellently tangled against said core yarn.

For a better understanding of the nature of this invention, reference should be had to the following detailed description fo specific embodiments thereof, when read in conjunction with the accompanying drawings forming a part thereof, wherein:

FIG. 1 (A) is a schematic view of a length of conventional covered elastic yarn, in its fully, or nearly fully elongated condition.

FIG. 1 (B) is a schematic view of a length of the yarn of FIG. 1 (A), contracted more than in FIG. 1 (A).

FIG. 2 is a schematic view of a length of covered elastic yarn prepared by a conventional false-twisting method, in its fully, or nearly fully elongated condition. FIG. 2 (B) is a schematic view of a length of the yarn of FIG. 2 (A) contracted more than in FIG. 2 (A).

FIG. 2 (C) is a schematic view of a length of the yarn of FIG. 2 (B) further twisted.

FIG. 3 (A) is a schematic view of a length of the yarn in accordance with this invention, in its fully, or nearly fully elongated condition.

FIG. 3 (B) is a schematic view of a length of the yarn of FIG. 3 (A) contracted more than in FIG. 3 (A).

FIG. 4 (A) is an enlarged cross sectional view of the yarn of FIG. 2 (A);

FIG. 4 (B) is an enlarged cross sectional view of the yarn of FIG. 2 (B);

FIG. 5 (A) is an enlarged cross sectional view of the yarn of FIG. 3 (A);

FIG. 5 (B) is an enlarged cross sectional view of the yarn of FIG. 3 (B).

FIG. 6 (A) is a schematic view of partly cut off false-twisting apparatus shown partially in cross-section which can be used to make the yarn in accordance with the present invention.

FIG. 6 (B) is a vertical sectional view of a guide (10) in the apparatus shown in FIG. 6 (B).

FIG. 7 (A) is a schematic view, partially in cross-section, of modified false twisting apparatus which can be used to make the yarn in accordance with this invention.

FIG. 7 (B) is a vertical sectional view of a star-wheel type pulley usable for FIG. 7 (A).

Referring first to FIG. 1 (A), FIG. 1 (A) is a schematic view of the covered elastic yarn twisting two yarns 2 and 2' on the core yarn 1 by a conventional spinning machine or a conventional twister, in elongated state. FIG. 1 (B) is a model schematic view of the covered elastic yarn of FIG. 1 (A) contracted by 30%.

As is apparent from FIG. 1 (A), the filaments of the sheath yarns 2, 2' of the covered yarn are regularly twisted and therefore the covering property of the covered elastic is remarkably excellent, but since the filaments of the covered yarns 2, 2' are controlled by twisting, and therefore the space occupied by said filaments becomes narrower, and the bulkiness thereof deteriorated, and this is a drawback.

FIG. 2 (A) is a schematic view of a covered yarn under tension prepared by simply associating and conventional false-twisting the core yarn 1 and the covering yarns 2, 2', and FIG. 2 (B) is a schematic view of the same yarn shown in FIG. 2 (A) contracted by 30%.

As is apparent from FIG. 2 (B), the core yarn 1 and the covering yarns 2, 2' have no twist at all, and it is very bulky but there is no contact of the filaments composing the core yarn and the covering yarn see FIG. 4 described below.

Therefore, the covering property is very poor, and the core yarn and the covering yarn can be separated by a slight external effect when the covered yarn passes through a guide or tensioner, and the separated core yarn and the covering yarn are not restored to their original state, and this is a serious drawback.

Therefore additional twisting is required after false twisting, or pre-twisting is required before false twisting.

FIG. 2 (C) shows the form of the yarn after such additional twisting or pre-twisting. The increase of the number of processes, in making this yarn and its poor bulkiness are accounted to be drawbacks.

FIG. 3 (A) and FIG. 3 (B) show the covered elastic yarns obtained in accordance with the present invention in comparison with the covered elastic yarns obtained in accordance with the prior art.

FIG. 3 (A) shows the covered elastic yarn of the present invention under tension in the same manner as in FIG. 1 (A) and FIG. 2 (A), and FIG. 3 (B) shows said yarn contracted by about 30%.

FIG. 3 (B) is a schematic view of the structure which makes use of the merits of the yarn of FIG. 2 (B) and FIG. 1 (B), so as to compensate for the respective drawbacks thereof.

In other words, in the yarn structure of FIG. 3 (B) the filaments composing the sheath yarns (2), (2') covering the core yarn (1), are reversed in twist direction at random intervals.

Point a of FIG. 3 (A) and FIG. 3 (B) shows the twist reversing point of said filaments.

The above described phenomena are demonstrated by all of the filaments forming the sheath yarn, and therefore the covered elastic yarn as a whole has remarkably excellent covering property, and at the same time, the filaments forming the sheath yarn have almost no contact against the core filaments attributable to twisting because the filaments forming the core yarn and sheath yarn are substantially twistless, and therefore excellent bulkiness can be attained.

In addition, a covered elastic yarn of FIG. 2 (A), (B), produced in accordance with a conventional false-twisting method is covered with the covering yarn not being closely adhered on the elastic yarn (1) as is apparent from FIG. 4 (A), (B), in a covered elastic yarn produced in accordance with the present invention, as is apparent from FIG. 5 (A), (B), the thermoplastic continuous multifilament thread is partially laid in the elastic thread (1) in such a manner that the thermosetting continuous multifilament thread is inserted into said elastic thread.

Therefore, the yarn of the present invention has remarkably excellent fluxability, and the slipping-off of the core yarn (1) is reduced when the yarn is subjected to tension and pulling, and the covering property is not at all deteriorated.

Namely, in accordance with this invention, an elastic thread is taken off its package under tension, and a thermoplastic continuous multi-filament thread and said elastic thread are associated together, and thus associated thermoplastic; continuous multi-filament and the elastic thread are passed through a fluxing guide, and are arranged in such a manner that said elastic thread can becomes the core and that said multifilament thread wraps around said elastic thread, and the thus obtained combined and associated yarns are then supplied into a false twisting machine, to carry out a twisting, heat setting and untwisting process.

The method of the present invention is explained in more detail in the following paragraphs.

In supplying elastic thread and thermoplastic multifilament thread simultaneously to the same false twisting machine, the relation of said elastic thread and thermoplastic multi-filament thread is such that the filaments of said thermoplastic multifilament thread are arranged in such a manner that the elastic thread can be wrapped by said filaments, and the covered elastic yarn thus obtained has elastic thread within the fiber flux of the crimped thermoplastic multi-filaments by means of false twisting, and the elastic thread is covered with the crimped multi-filament, and therefore the two cannot be easily separated.

Moreover, in regard to the covered elastic yarn thus obtained the elastic thread as the core yarn and the filaments forming the sheath yarn are substantially untwisted, and the generation of torque and kink can be hardly observed.

In regard to the determination of the temperature at which the false twisting is carried out in accordance with the present invention, it is a matter of course that temperature should be adjusted to be sufficient to fix the desirable crimping of the thermoplastic multi-filament to be used as the sheath thread, but it is necessary that the kind of the elastic thread used as the core yarn should be taken into consideration.

For example, when an elastic thread which is subject to thermal deterioration (such as natural rubber) is used, the temperature at which false twisting is carried out must be adjusted to be low so as not to damage the elastic thread or said elastic thread must be protected by the sheath thread, and therefore it is a matter of course that the conditions such as the kind of the sheath thread, temperature and the number of twisting turns should be taken into consideration.

On the other hand, when a thermoplastic elastic thread, such as polyurethane fibers, is used as the core yarn, and the elastic thread is supplied under a high tension or high elongation in a high temperature zone, the elongation of the covered elastic yarn product is less; on the contrary, when the elastic thread is supplied under less tension or at low elongation, the elongation of the covered elastic yarn product is larger.

Conversely when the elastic thread is supplied under a high tension or at high elongation, in a low temperature zone, the elongation of the covered elastic yarn becomes larger, while if the elastic thread is supplied under a low tension or at low elongation, the elongation of the covered elastic yarn product becomes small. Therefore in accordance with the method of the present invention, it is possible to select the tension of the core yarn elastic thread and the temperature at which false twisting is carried out to meet the object of this invention.

Furthermore, it is possible to select the temperature at which false twisting is carried out in such a manner that the fibers forming the sheath strand can be partially melted and adhered to each other.

In addition, when polyurethane elastic yarn, as the core yarn is subjected to the false twisting treatment at a temperature in the neighbourhood of the melting point of the core yarn, i.e. if the heat-setting of the false twisting is carried out at a temperature ranging from 180.degree.C to 200.degree.C, or more preferably at 190.degree.C, the polyurethane elastic yarn is softened, and, in addition, the twists attributable to the false twisting is generated on the surface of said polyurethane elastic yarn, and therefore the fibers forming said sheath strand are laid into the concave portions produced by the twisting of said elastic yarn.

Therefore, the covering property of the covered elastic yarn which can be obtained as described above, can be further improved, and at the same time the migration of said sheath thread cannot be brought about by the external frictional force.

What is important in the method of the present invention is that in supplying the elastic thread as the core yarn and the thermoplastic multi-filament thread as the sheath yarn to the same false twisting machine, the filaments forming the thermoplastic multi-filaments should be parallelly arranged in such a manner as to wrap the core yarn.

The above mentioned arrangement determines the superiority of the covering property of the covered elastic yarn of this invention.

In order to arrange the respective filaments to be supplied to the false twisting zone, it is necessary that the relation of the respective threads, at the same time when they are supplied, be sufficiently taken into consideration.

First of all, in order to place the elastic thread in the center, said elastic thread should be supplied under tension to prevent the free slipping-off thereof, and furthermore the multi-filament thread should be supplied under low tension to wrap said elastic thread.

When the respective threads are supplied in such a manner as described above, the fibers which are to become sheath form the outer side, and the elastic thread which is to can become the core thread is placed in the center.

In the above described embodiment, it is necessary to have a guide for fluxing the threads, i.e. a U or V shaped yarn guide or a star-wheel type pulley guide having a U or V shaped concave portion on the periphery thereof to arrange the filaments in the neighbourhood of the twist-starting point, to prevent, from that point backward, the twisting of the fluxed threads which abruptly starts beyond that point, using a nip roller guide to define that point.

In other words, in the present invention, the elastic thread and non-elastic thread are directly introduced into a false twisting machine after they have been associated, but it is necessary to keep said elastic thread and non-elastic thread in the associated state for a predetermined time, and said elastic thread is introduced into the center of said non-elastic thread by the above mentioned treatment.

Therefore, a U or V shaped guide is preferable.

In other words, in accordance with the present invention, said core yarn and said sheath yarn are doubled, and thereafter, the doubling state is retained for a predetermined distance, while a tension difference is maintained therebetween in a yarn introducing zone of a false-twisting apparatus, in which the yarn is false-twisted while the backward travel of twist is controlled, and thereby said core yarn is sufficiently placed into said sheath yarn.

FIG. 6 and FIG. 7 are diagrams showing embodiments for carrying out the process and for making the porudct of the present invention.

In FIG. 6 (A), the elastic thread 5 which is positively released from the package 3 thereof by the roller 4, is supplied to a pair of feed rollers 6 of the false-twisting machine while being subjected to tension.

On the other hand, the thread 8 which is released from package 7 of the thermoplastic multi-filament yarn which becomes the sheath yarn passes through the guide 9, and is supplied to the feed roller 6 of the false-twisting machine, and is associated with the elastic thread (5).

The elastic thread (5) supplied by the feed rollers (6), and the continuous multi-filament thread (8) are arranged by the grooved guide (10) having a V shaped groove in the lateral cross section perpendicular to the running direction of said threads (5) and (8) in such a manner that said thread (5) is arranged within the central portion of said continuous multi-filament thread (8). Said elastic thread (5) and continuous multi-filament thread (8) are then subjected to false twisting by means of the false twisting spindle (13), and the twisted portion thereof is thermally set by means of the heater (12), and when said threads have passed through said spindle (13), they are untwisted, and are drawn out by a pair of delivery rollers (14), and said threads pass through the guide (15), and are taken up into a package (17) by means of a take up device such as drum type winder.

In other words, the false twisting is perfectly stopped by a nip roller (11), and the two threads keep their associated state between the feed roller (6) and nip roller (11). This prevents twist from travelling backward to grooved guide (10) or said feed rollers (6) so that the state of core-sheath of the two threads is not destroyed thereby.

FIG. 6 (B) is a diagram showing the cross sectional form of grooved guide (10) in the plane perpendicular to the running direction of the threads 5, 8, and said elastic thread 5 is arranged into the central portion fo said continuous multi-filament thread 8 in said groove.

On the other hand, FIG. 7 is a diagram showing a modified form of the apparatus of FIG. 6 (A), (B). In FIG. 7 (A), the elastic thread 5 released by the positive feed-roller 4 from the package 3 thereof is elongated by a predetermined degree between said feed roller 4 and delivery roller 14.

Said elastic thread 5 is associated with the thermoplastic multi-filament thread 8 released from the package 7 thereof in an almost tensionless state, and is supplied into the star-wheel type pulley 18.

FIG. 7 (B) is a cross sectional view of said star-wheel pulley across the center of said star-wheel type pulley. Said star-wheel type pulley is light and is rotated in the running direction of the threads 5, 8 of the shaft 20 by contact with the threads.

The peripheral portion 21 of said pulley (as seen in FIG. 7 (B) has a shaped groove, and that helps said two threads take on a sheath-core form without adding high tension to said continuous multifilament thread which becomes sheath thread by using said pulley and said elastic thread 5 arranged in the central portion of said continuous multi-filament thread 8 therein.

Further, in FIG. 6 (A), a pair of nip rollers 11 is provided in order to prevent the travelling of the twist of the false-twisting machine during the false twisting process, but when a pair of the nip rollers 11 is used, there is a fear that the sheath-core arrangement of the threads 5, 8 attained by the groove guide 10, may be upset thereby.

On the other hand, the star wheel type pulley as is shown in FIG. 7 (A) is rotated along with the running of the threads 5, 8, and therefore it is not necessary to use such a pair of nip rollers 11 as is shown in FIG. 6 (A) because there is no fear that the twist of the false twisting machien may arrive at the entrance portion of the groove 21 of said pulley 18, and only the guide 19 for converting the running direction suffices.

As described so far in the foregoing paragraphs, the respective threads 5, 8 associated in the sheath-core state, are taken up on the package 17 after they are subjected to the process for twisting-heatsetting-untwisting.

The covered elastic yarn thus obtained is an elastic yarn having remarkably strong covering property, and the covering cannot be destroyed even if it is used over and over again, and partial exposure of the core yarn thereof can be hardly observed, and the covered elastic yarn has a very uniform shape in the lengthwise direction thereof.

In addition, when the thermoplastic filaments are slightly melted and adhered by raising the temperature of the heater of the false-twisting machine, it is needless to mention here that faster covering can be attained and the covering becomes more compact.

The covered elastic yarn of the present invention has almost the same processability as the ordinary crimped yarns, and it is possible to adjust the crimping degree by adjusting the temperature of the heater of the false-twisting machine and the strich power thereof is almost the same as that of thermatic set single covered yarn, or core spun yarn.

Since the covered elastic yarn of the present invention is twistless yarn, and snarls and kinks are in easily formed in the yarn of this invention when compared with the conventional single covered yarn to say nothing of the conventional false twisted crimped yarn.

Thus, the hank reeling property, hank dyeing property, hank winding property, cone-up property, preparing property for weaving, and preparing property for knitting of the covered elastic yarn of the present invention are the same as or more excellent than those of the conventional false twisted crimped yarns or single covered yarns.

The woven or knit fabrics obtained from the covered elastic yarn of the present invention can present the soft touch of wooly yarn by crimping process of the thermoplastic filaments and twistless covering process into the elastic filament yarn attained thereby, without being controlled by twist thereof, and has a special appearance as woven or knit goods.

The covered elastic yarn of the present invention can be directly used for producing the ordinary knit goods, longitudinally stretchable woven fabric, and laterally stretchable woven fabric, without employing any heat setting process or twisting process, and this is accounted to be an advantage of the present invention.

In particular, in the case of the longitudinally stretchable woven fabric, it is possible to omit sizing process by using the covered elastic yarn prepared by slightly melting and adhering the thermoplastic filaments at the time when false twisting is carried out.

When the covered elastic yarn of the present invention is used for knit goods, there is a remarkable advantage that the yarn having the same stretch power as that of the conventional thermoplastic yarn can be directly woven from the cheese of the false-twisted yarns since in accordance with the prior art, the covered elastic yarn is used by thermally setting the same in most cases.

In addition, the processing speed of the covered elastic yarn of the present invention is from 5 to 10 times the speed of the conventional yarns, and it is apparent that the present invention can greatly reduce the cost of production.

On the other hand, the method of this invention can be easily worked out directly on the conventional false twisting machine, or by a simple improvement of the conventional devices, and the operation required for working out the method of this invention is hardly different from that of the conventional methods.

The following are the examples to further illustrate the present invention.

The method for measuring the elongation and covering property, and coefficient of feeding as described in the following examples of the present invention are explained below;

1. METHOD FOR MEASURING ELONGATION

The yarn of the present invention was wound on the periphery of a 50 cm frame for 10 times, and thermal treatment was carried out with 60.degree.C hot water for 30 minutes.

After having dried the yarn for 24 hours, 40 g a weight of par a yarn was suspended thereon for 30 seconds, and the length l.sub.1 was read. Thereafter, the load was removed, and the yarn was left out to be shrunk for 20 seconds, and then a weight of 0.16 g par a yarn was suspended thereon for 30 seconds, and the length l.sub.2 was read. ##EQU1##

2. METHOD FOR MEASURING THE COVERING PROPERTY

A weight of 40 g was suspended on the yarn of the present invention for 30 seconds, and the length of 50 cm was marked on the yarn, and thereafter the weight was removed, and then the yarn was left out to be shrunk for 120 seconds, and then, a weight of 0.5 g was suspended thereon so to separate the core yarn and the sheath yarn thereof.

The length l.sub.1 of the yarn with the weight hanging down is read. ##EQU2##

3. DETERMINATION OF COEFFICIENT OF FEEDING ##EQU3##

DEFINITION OF POLYURETHANE ELASTIC THREAD USED IN RESPECTIVE EXAMPLES

A polyurethane elastic thread 40 denier-1 filament used in the following examples and comparative examples is a monofilament in which six polyurethane elastic filaments are coalesced, and a polyurethane elastic thread 70 denier-1 filament is a monofilament in which 18 polyurethane elastic filaments are coalesced.

EXAMPLES 1, 2, and 3,

1. Examples 1 and 2

A polyurethane elastic thread 40 denier-1 filament elongated by 3.5 times of the original length thereof and Nylon-6, 70 denier-34 filaments being tensioned by 0.1g were associated with each other, and thereafter the associated filaments were supplied into the apparatus embodiment as shown in FIG. 6. (A), (B), and treated under conditions as shown in items EX-1 and EX-2 of Table-1.

The results as shown in items EX-1 and EX-2 of Table- 2 were obtained.

2. Examples 3

On the other hand, a polyurethane elastic thread 40 denier-1 filament elongated 2.8 times the original length thereof and Nylon-6, 70 denier-34 filaments being tensioned by 1.0g were associated with each other, and thereafter the associated filaments were supplied into the apparatus embodiment as shown in FIG. 6.(A), (B) and treated under conditions as shown in item EX-3 of Table-1.

The results as shown in item EX-2 of Table-2 were obtained.

TABLE 1 __________________________________________________________________________ EX-1 EX-2 EX-3 __________________________________________________________________________ materials polyurethane thread (denier-filament) 40-1 40-1 40-1 Nylon-6 multi filament (denier-filament) 70-34 70-34 70-34 elongating degree of elastic thread (times) 3.5 3.5 2.8 doubling tension of Nylon-6 multi-filament (g) 0.1 0.1 1.0 existence of grooved guide be exist be exist yes coefficient of feeding of processing (%) +1 +2 -1 conditions number of rotations of false-twisting spindle 20.times.10.sup.4 20.times.10.sup.4 20.times.10.sup.4 of processing (r.p.m.) - number of false-twisting 3600 s/Meter) 3600 3600 temperature of heater (.degree.C) 190 180 170 length of heater (mm) 900 900 900 tension of twisting (g) 7 7 7 tension of untwisting (g) 14 16 20 a number of true twist (Turns/Meter) 0 0 0 __________________________________________________________________________

TABLE 2 __________________________________________________________________________ EX-1 EX-2 EX-3 __________________________________________________________________________ number of filaments of Nylon-6 multi-filament adhered to polyurethane elastic thread 22 16 0 (number/an optional cross section of the covered elastic yarn) multi-filament not adhered to polyurethane elastic thread 12 18 34 (number/an optional cross section of the covered elastic yarn) a weight of 0.5g 97 87 12 covering property (%) a weight of 2.0g 94 80 0 *CI: a coefficient of recovery of elasticity (%) 54 58 60 coefficient of elongation (%) 179 190 191 index of torque 11 8 6 an existence of the twisting mass produced by rubbing motion yes yes do. __________________________________________________________________________ *CI value: It is based on the rule of JIS.

3. Considerations

As is apparent from EX-1 and EX-2 of Table-2, the covered elastic yarns of the present invention, in the production of which there is a relatively high difference between the tension of the polyurethane elastic thread and that of the Nylon-6 multi-filament, and heat-setting of the false-twisting is carried out at a temperature ranging from 180.degree.C, to 200.degree.C have excellent covering property, because the respective filaments of Nylon-6 are adhered to the outer surface of the polyurethane elastic thread.

On the other hand, the covered elastic yarn in accordance with Example-3, produced with only slight differential tension between of the polyurethane elastic thread and the Nylon-6 multi-filament and with heat-setting of the false-twisting at a temperature lower than 180.degree.C, i.e. 170.degree.C, has poor covering property, because the respective filaments of Nylon-6 are generally not adhered to the outer surface of the polyurethane elastic thread.

EXAMPLES 4 and 5

1. Example 4

A polyurethane elastic thread 40 denier-1 filament elongated by 3.6 times the original length thereof and Nylon-6, 70 denier-24 filaments, under 0.2 grams tension were associated with each other, and thereafter the associated filaments were supplied into and treated in apparatus of the embodiment as shown in FIG. 7(A), (B) under in conditions as shown in item EX-4 of Table- 3.

The results as shown in item EX-4 of Table-4 were obtained.

2. Example 5

The associated filaments as mentioned above were supplied into and treated in apparatus of the embodiment as shown in FIG. 6(A), (B) under conditions as shown in item EX-5 of Table-3.

The results as shown in item EX-5 of Table-4 were obtained.

TABLE 3 __________________________________________________________________________ EX-4 EX-5 __________________________________________________________________________ Materials polyurethane thread (denier-filament) 41 41 Nylon-6 multi filament (denier-filament) 70-24 70-24 elongating degree of elastic thread (times) 3.6 3.6 doubling tension of Nylon-6 multi-filament (g) 0.2 0.2 ratio of tension between an entry and an exit of 1.06 -- star-wheel type grooved guide existence of a grooved guide yes yes coefficient of feeding of processing (%) -- -1 conditions number of rotations of false-twisting spindle 20.times.10.sup.4 20.times.10.sup.4 of processing (r.p.m.) number of false-twisting (Turns/Meter) 3,300 3,300 temperature of heater (.degree.C) 195 195 length of heater (mm) 900 900 tension of twisting (g) 12 11 tension of untwisting (g) 22 20 number of true twist (Turns/Meter) 0 0 __________________________________________________________________________

TABLE 4 __________________________________________________________________________ EX-4 EX-5 __________________________________________________________________________ number of filaments of Nylon-6 multi-filament adhered to polyurethane elastic thread 14 10 (number/an optional cross section of the covered elastic yarn) multi-filament not adhered to polyurethane elastic-thread 10 14 (number/an optional cross section of the covered elastic yarn) weight of 0.5g 100 98 covering property (%) weight of 2.0g 99 96 *CI: coefficient of recovery of elasticity (%) 57 58 coefficient of elongation (%) 147 151 index of torque 9 8.2 existence of the twisting mass produced by rubbing motion none none __________________________________________________________________________ *CI value: It is based on the rule of JIS.

3. Considerations

As is apparent from items EX-4 and EX-5 of Table-4, the covered elastic yarn of the present invention can be obtained by either apparatus embodment as shown in FIG. 6 or as shown in FIG. 7. But the covering property of the covered elastic yarn of Example 4 produced with the apparatus embodiment of FIG. 7 which is provided with a star-wheel type guide, is more excellent than that of the covered elastic yarn of Example 5 produced with the apparatus embodiment of FIG. 6 which is provided with a simple grooved guide.

In both example mentioned above, it seems as if there is only a slight difference between the covering property of Example-4 and Example-5, but actually there is five fold difference in the mean value of the length differential used in calculating covering property % defined herein prior to the description of Example 1. As a matter of fact, in the covered elastic yarn produced in accordance with Example-4, as shown in Table-5, all of the five samples showed little tendency to permit slipping-off between said polyurethane elastic thread and Nylon-6 multi-filament thread, when a weight of 0.5g was suspended thereon.

On the other hand, in the covered elastic yarn produced in accordance with Example-5, as shown in Table-5, one of five samples showed about 20% (about 9.4 cm) of slipping of par length of 50 cm thereof between said polyurethane elastic thread and Nylon-6 multi-filament thread, when a weight of 0.5 g was suspended thereon.

As is apparent from the forgoing description, in the present invention, the method in accordance with Example-4 is more excellent than that in accordance with Example-5.

TABLE 5 ______________________________________ Examples number of EX-4 EX-5 measurement ______________________________________ X.sub.1 0.2 cm 0 cm X.sub.2 0.2 " 9.4 " X.sub.3 1.9 " 0.2 " X.sub.4 0 " 0.3 " X.sub.5 0.4 " 0 " X 0.54 cm 1.98 cm 50-X 49.5 cm 48.0 cm ______________________________________ ##EQU4##

EXAMPLES 6 and 7

A polyurethane elastic thread 40 denier-1 filament and Nylon-6, 70 denier-24 filaments were treated under conditions as shown in items EX-6 and EX-7 of Table-6 with the apparatus embodiment as shown in FIG. 7, and thereby the effects as shown in items EX-6 and EX-7 of Table-8. were obtained.

TABLE 6 __________________________________________________________________________ EX-6 EX-7 __________________________________________________________________________ Materials polyurethane thread (denier-filament) 40-1 40-1 Nylon-6 multi filament (denier-filament) 70-24 70-24 an elongating degree of elastic thread (times) 3.6 2.2 doubling tension of Nylon-6 multi-filament (g) 0.2 3.8 ratio of tension between an entry and an exit of 1.08 1.95 star-wheel type grooved guide existence of a grooved guide yes yes coefficient of feeding if processing (%) -- -- conditions number of rotations of false-twisting spindle 20.times.10.sup.4 20.times.10.sup.4 of processing (r.p.m.) number of false-twisting (Turns/Meter) 3400 3400 temperature of heater (.degree.C) 185 150 length of heater (mm) 900 900 tension of twisting (g) 13 28 tension of untwisting (g) 24 39 number of true twist (Turns/Meter) 0 0 __________________________________________________________________________

TABLE 7 __________________________________________________________________________ EX-6 EX-7 __________________________________________________________________________ number of filaments of Nylon-6 multi-filament adhered to polyurethane elastic thread 12 0 (number/an optional cross section of the covered elastic yarn) multi-filament not adhered to polyurethane elastic thread 12 24 (number/an optional cross section of the covered elastic yarn weight of 0.5g 89 0 covering property (%) weight of 2.0g 83 0 *CI: a coefficient of recovery of elasticity (%) 61 63 coefficient of elongation (%) 162 170.2 index of torque 7 7 existence of the twisting mass produced by rubbing motion none none __________________________________________________________________________ *CI value: based on the rule of JIS.

As is apparent from the forgoing discussion above described mention, in either a star-wheel type grooved pulley is used in both example 6 and in example 7 however, the covered elastic yarn in accordance with Example-6 in which the temperature of heat setting of false-twisting is the same as that of conventional false-twisting methods has a small covering property. Therefore, in order to obtain a covered elastic yarn having excellent covering property, it is preferable that the temperature of heat setting of false-twisting, as is in Example-6, is higher than that of conventional false-twisting methods.

EXAMPLES 8, 9, 10, 11 AND 12

1. Examples 8 and 9

A polyurethane elastic thread 70 denier-1 filament elongated by 3.6 times the original length thereof and Nylon-6, 70 denier-24 filaments under 0.1g tension were associated with each other, and thereafter the respective associated filaments were supplied to apparatus of the shown in FIG. 6 and FIG. 7 and treated under conditions as shown in items EX-8 and EX-9 of Table-8.

The results as shown in items EX-8 and EX-9 of Table-1 were obtained.

As is apparent from the foregoing discussion the covering property of the covered elastic yarn of Example 8 produced with the apparatus embodiment of FIG. 7 is better than that of the covered elastic yarn of Example 9 produced with the apparatus embodiment of FIG. 6.

2. Example 10

On the other hand, threads used in Examples 8 and 9 were treated by a conventional method.

The conventional method used as taught in (Japanese Patent Publication No. 25511/'67) comprises a first step of associating said elastic thread with said thermoplastic multi-filament thread, a second step of pre-twisting said associated threads, a third step of twisting said threads in the direction opposite to that of the original twist-heat setting- and untwisting said threads in the same direction as that of the original twist.

Conditions of treatment of the present example are shown in item EX-9 of Table-8 and the effects thereof are shown in item EX-9 of Table-9. As is apparent from the above result, the covered elastic yarn produced in accordance with Example-10 has practically rubbing resistance and forms a twisting mass in the longitudinal direction thereof directly after it was rubbed, because it is twisted slightly.

The covering property of said yarn of the present example has somewhat similar property to that of the yarn of the present invention.

The reason for said effect is that some of the original twist imparted by the pre-twisting process is retained after twisting-heat setting-untwisting.

However, in said covered elastic yarn, the elastic thread and the thermoplastic multi-filament thread are not substantially twistless as in the present invention.

Furthermore, in the present example, the covered elastic yarns treated without any pre-twisting process are not always the same in covering property as the above mentioned result as is apparent from the following examples (Examples 11 and 12).

3. Example 11

The covered elastic yarn of this example was obtained by the method of Example 10, but without any pre-twisting.

In the covered elastic yarn of this example, the elastic thread and the thermoplastic multi-filament were substantially twistless, but the covering property thereof was very poor as is apparent from item EX-11 of Table-9.

Furthermore, the covering properties of 38 with a weight of 0.5g) and 34 (with a weight of 2.0g) seem to some degrees of covering property, but as a matter of fact, the yarn obtained by this example is of almost no practical value, because the covered portions uncovered and with said thermoplastic multi-filament were randomly distributed along the longitudinal direction of said yarn.

Example 12

Furthermore, to make sure of the result reported in Example 11 the method of Example 11, but at the heatsetting temperature in the vicinity of Examples that in 8 and 9. As a result, the covering property of the covered elastic yarn of this example was more excellent than that of Example-11, but the covering property thereof was not completely perfect, and the coefficient of recovery of elasticity was lower than that of Examples 10 and 11.

TABLE 8 __________________________________________________________________________ EX-8 EX-9 EX-10 EX-11 EX-12 __________________________________________________________________________ Materials polyurethane thread (denier-filament) 70- 1 70- 70- 1 70- 1 70- 1 Nylon-6 multi filament (denier-filament) 70-24 70-24 70-24 70-24 70-24 elongating degree of elastic thread (times) 3.6 3.6 3.6 3.6 3.6 doubling tension of Nylon-6 multi-filament (g) 0.2 0.2 2.0 2.0 2.0 ratio of tension between an entry and an exit of 1.14 -- -- -- -- the star-wheel type grooved guide existence of a grooved guide yes yes none none none conditions coefficient of feeding of processing (%) -- -1 -1 1 1 of processing number of rotations of false-twisting spindle 20.times.10.sup.4 20.times.10.sup.4 20.times.10.sup.4 201 104 number of false-twisting (Turns/Meter) 3,300 3,300 2,300 2,300 2,300 temperature of heater (.degree.C 195 195 150 150 190 length of heater (mm) 900 900 900 900 900 tension of twisting (g) 16 15 14 14 14 tension of untwisting (g) 32 32 28 28 28 number of true twist (Turns/Meter) 0 0 300 0 0 __________________________________________________________________________

TABLE 9 __________________________________________________________________________ EX-8 EX-9 EX-10 EX-11 EX-12 __________________________________________________________________________ number of filaments of Nylon-6 multi-filament adhered to polyurethane 13 8 0 0 0 (number/an optional cross section of the covered elastic yarn) multi-filament not ahdered to polyurethane elastic thread 11 16 24 24 24 (number/an optional cross section of the covered elastic yarn) weight of 0.5g 100 81 100 38 71.6 covering property (%) weight of 2.0g 99 76 98.5 34 63.5 *CI: coefficient of recovery of elasticity (%) 62 59 61 64 51 coefficient of elongation (%) 167 163 159 172 143 index of torque 9 9 12 8 6 existence of the twisting mass produced by rubbing motion none none none none none __________________________________________________________________________ *CI value: It is based on the rule of JIS.

Claims

What we claim is:

1. Method for producing a covered elastic yarn comprising

1. arranging a plurality of thermoplastic heat-settable substantially inelastic filaments in the form of a running bundle,

2. applying tension to an elastic thread and continuously feeding and merging it with said thermoplastic filaments while maintaining said substantially inelastic filaments under a lower tension than that of said elastic thread, and positioning said elastic thread substantially in the center of said running bundle while maintaining said substantially inelastic filaments under a lower tension than that of said elastic thread,

3. twisting, heat-setting and detwisting the merged elastic thread and substantially inelastic filaments, said heating step being carried out at a temperature which is above the heat setting temperature of said inelastic filaments and which is sufficient to set the twist in said filaments substantially completely.