Method For Producing Mixed Filaments

Abstract

Synthetic fibers having natural fiber-like touch, gloss, texture and appearance are produced by spinning a polyester and a polyamide through a common spinneret simultaneously to form mixed filaments consisting of multisegment-filaments, in each of which the polyester is divided by the polyamide into at least 3 segments, and polyester single component filaments, drawing the mixed filaments and then subjecting the drawn mixed filaments to a false twisting to fibrillate the multisegment filaments.

Description

The present invention relates to a method for producing mixed filaments consisting of polyester and polyamide, which have different cross-sectional shapes.

Conventional polyester or polyamide fibers are excellent in dynamic properties but the fineness and cross-sectional shape of each of the single component filaments are simple and therefore the touch, gloss, texture and appearance thereof are more simple than natural fibers.

In order to overcome this drawback, various attempts have been heretofore made but satisfactory results have not been obtained. For example, attempts have been made to spin filaments having different deniers from a common spinneret. The smallest denier of the monofilament obtained in this process is up to 1.5 denier, usually more than 2 deniers considering the operability, and from such filaments, it is difficult to obtain the desirable texture, touch and the like. As filaments provided with the natural fiber-like excellent properties, it is desirable to have a large number of filaments of non-circular cross-section of extremely fine denier (for example, about 0.5 denier), and in order to keep a moderate resiliency and excellent dynamic properties, it is desired to have filaments having a denier of several times as large as the extremely fine filaments.

Even if such filaments can be spun by the above described process, the filaments of an extremely fine denier and the filaments having a large denier are different in behaviour in this spinning step (for example, solidification, speed, and the like), and it is difficult to find out the drawing condition suitable for any filaments in the subsequent drawing step, so that finally filaments poor in the dynamic property are formed.

The object of the present invention is to provide a novel method for readily producing the filaments provided with both the preferable properties of synthetic fibers and natural fibers.

The present invention consists in a method for producing mixed filaments (D), which comprises spinning a polyester and a polyamide through a common spinneret simultaneously to form an intermediate mixed filament product (C) consisting of multisegment filaments, in each of which the polyester is divided in cross-section by the polyamide into at least 3 segments, and (B) polyester monofilaments, so as to satisfy the following definitions,

1. THE RATIO OF THE MULTISEGMENT FILAMENTS (A) to in the total mixed filaments (C) is 40-70 percent by weight,

2. THE RATIO OF POLYAMIDE IN EACH OF THE MULTISEGMENT FILAMENTS (A) is less than 40 percent by weight, preferably less than 30 percent by weight and the ratio of polyamide in the total mixed filament product (C) is less than 30 percent by weight, preferably less than 25 percent by weight,

3. The polyamide in each multisegment filament (A) forms thin layers having an even thickness which diverge radially in the cross-section of said multisegment filament (A), and

4. each polyester segment in the multisegment filament (A) is less than 1 denier, preferably less than 0.7 denier and the polyester monofilament (B) is more than 2 deniers, preferably more than 3 deniers,

drawing the spun mixed filament product (C) and then subjecting the drawn mixed filament product (C) to a false twisting to fibrillate the multisegment filaments (A) contained therein and, thereby produce mixed filament product (D).

The term "segment" used herein means that portion constituting the multisegment filament, which substantially extends evenly along the longitudinal direction of the filament. The term "forming the thin layers having an even thickness diverging radially" means a thin layer structure extending in at least three directions radially from one point, such as the Y-shape as shown in FIG. 1, the X-shape as shown in FIG. 2, and the six branches as shown in FIG. 3. Such radial thin layer structure can be easily formed as mentioned hereinafter and such multisegment filaments can be efficiently separated by a false twisting and easily fibrillated.

The inventors have already found that such multisegment filament (filaments having the cross-sections as shown in FIGS. 1 to 3) is useful as proposed in Japanese Patent Application No. 29,925-1970. These fibers are very favorable on account of being similar to natural fibers in the texture, touch and gloss, but the fibers are poor in other respects. Namely, these fibers are too soft for use in gentleman's suit cloth or lady's thick suit cloth which requires a certain degree of resiliency, and are not suitable for them. If the fineness of the segment is enlarged (for example, 3 deniers) in order to overcome this drawback, the preferable properties as described above are lost.

The inventors have found that when the multisegment filaments polyester single component filaments are simultaneously spun, the features of the above described multisegment filament are maintained and further a moderate resiliency can be obtained.

Namely, in order to attain the object of the present invention, the weight ratio of the multisegment filaments in the total mixed filaments simultaneously spun is 40-70 percent by weight. When the ratio of the multisegment filaments is less than 40 percent by weight, the excellent natural fiber-like properties cannot be obtained and when the rate is more than 70 percent by weight, the resulting fibers are too soft and deficient in the dimensional stability. That is, the ratio of the multisegment filaments must be selected within the above range depending upon the object.

Polyamide and polyester are different in their shrinkability, and in general polyamide is greater in shrinkage than polyester, that is, polyamide has less dimensional stability than polyester. Of course, if polyester is drawn at a low temperature, the shrinkability increases and may become the same as the shrinkability of polyamide, but yarn breakage occurs in the drawing step, and the drawing becomes unstable. When the mixed filaments composed of the multisegment filaments consisting of polyester and polyamide and the polyester single component filaments are drawn under a condition suitable for the polyester, the multisegment filaments are more highly shrunk and cause loose filaments (floating thread) and these filaments are not only entangled on the guide or traveller in the drawing but also cause hindrance in the after-treatments, such as false twisting, warp beaming, warping and the like. Consequently, in order to solve this problem, the ratio of polyamide to the multisegment filament must be decreased. As the result of various investigations, it has been found that the ratio of polyamide in the multisegment filaments must be less than 40 percent by weight, preferably less than 30 percent by weight and further the ratio of polyamide in the total mixed filaments must be less than 30 percent by weight, preferably less than 25 percent by weight.

In order to divide the polyester into at least 3 segments by the polyamide and to make small the ratio of polyamide in the multisegment filaments as far as possible, it is most reasonable that the polyester and the polyamide are bonded in such a state that the polyamide forms thin layers having a substantially even thickness which diverge radially, in the cross-section of each of the above described multisegment filaments.

The filaments having the cross-sections as shown in FIGS. 1 to 4 can be produced while maintaining a very stable bonding form as explained hereinafter. On the contrary, a filament as shown in FIG. 5, in which a component is divided with another component forming very uneven thin layers, is liable to cause aggregation of polymer in the spinning and a slight variation of the melt viscosity of both the components influences upon the bonded shape and it is difficult to produce such a filament having a uniform cross-sectional structure along the longitudinal direction and the fibrillation of the resulting filament is not effected efficiently.

In order to improve the fibrillation of the filamenet having such a cross-section, it is necessary to increase the rate of thin layer component, while in the filaments as shown in FIGS. 1 to 4 wherein a filament forming component is bonded by the radially diverged thin layers having an even thickness, it is easy to decrease the ratio of thin layer component to less than 30 percent by weight and even if the ratio is reduced to about 10 percent, it is possible to maintain an even cross-sectional structure along the longitudinal direction of the filament.

The larger the number of the polyester segments in each of the multisegment filaments, the higher is the advantage in view of the fibrillation, but when the number of segments is increased too much, the production is difficult and further it is difficult to divide the polyester evenly with a small amount of polyamide. In general, the number of polyester segments in each of the multisegment filaments is preferred to be 3-8, preferably 3-6.

The smallest polyester segment in the multisegment filament must be less than 1 denier. The extremely fine filaments obtained by fibrillation of such a filament have desirable texture, appearance and gloss similar to natural fibers. In general, the multisegment filaments composed of polyester segments having an even cross-section as shown in FIGS. 1 to 3 are useful, but in some cases, the multisegment filament as shown in FIG. 4, wherein the area and cros-sectional shape of the polyester segments are different, is preferable, because various forms of fibrils can be formed.

The polyester filaments spun simultaneously with the multisegment filaments serve to provide the moderate resiliency and excellent dynamic properties, which are characteristics of synthetic fibers, to the resulting fibers and a relatively large fineness, that is more than 2 deniers, usually about 3-10 deniers, is preferred.

The mixed filaments in which extremely fine fibrillated filaments and usual filaments (monofilament of 2-10 deniers) are fully entangled, develop an excellent effect. These mixed filaments can be obtained by producing the multisegment filaments and single component filaments simultaneously and when the separately produced filaments are mixed, both the filaments are not fully entangled.

For a better understanding of the invention, reference is made to the accompanying drawings, wherein:

FIGS. 1 to 5 show embodiments of cross-sections of filaments;

FIG. 6 is a vertical cross-sectional view of spinneret which can produce the mixed filaments of the present invention;

FIG. 7 is a cross-sectional view of the spinneret as shown in FIG. 6 in the arrow direction on lines X--X'; and

FIG. 8 is a cross-sectional view of the spinneret as shown in FIG. 6 in the arrow direction on lines Y--Y'.

The mixed fibers obtained by the method of the present invention can be produced in a high evenness of the cross-sectional structure by a relatively simple apparatus.

Referring to FIG. 6, an inner spinneret plate 100 is superposed on a spinneret plate 110.

A part of the melted polyester is extruded from inner orifices 5 through a supplying chamber 2 and a passage 3 and the melted polyamide is extruded from channels 8 through a supplying chamber 1, passage 6 and a reservoir 7. Both the polymers are bonded at an inlet of a conduit 9 and spun from an orifice 111 through the conduit 9. On the other hand, a part of the remaining polyester is spun from an orifice 111 through a supplying chamber 2, a passage 4 and a conduit 9. Part number 120 is a supporter.

FIG. 7 is a cross-sectional view of the spinneret as shown in FIG. 6 in an arrow direction on lines X--X' and shows the bottom of the inner spinneret 100. The inner orifices 5 and the passages 4 are opened at the projecting portion of the bottom of the inner spinneret plate 100 corresponding to the spinning orifices 111 in the spinneret plate 110. The inner orifices 5 consist of four small holes. At the top face of the projecting portion in the bottom of the inner spinneret plate where each of the four small holes opens, channels 8 are provided between the outlets of the adjacent small holes.

FIG. 8 is a cross-sectional view of the spinneret as shown in FIG. 6 in an arrow direction on lines Y--Y' and shows the upper face of the spinneret plate 110 provided with circular spinning orifices 111.

The spinneret as shown in FIGS. 6 to 8 provides the mixed filaments consisting of 3 multisegment filaments in which polyester is divided with four radially diverged polyamide thin layers into 4 segments and 3 polyester monofilaments.

By using a non-circular cross-sectional spinning orifice, non-circular cross-sectional filament can be easily obtained. However, considering the operability, the cross-section of the filament is preferred to be substantially circular. Furthermore if the numbers of the inner orifices 5 and the channels 8 are varied, the multisegment filaments having the cross-section as shown in FIGS. 1, 3 and 4 can be easily obtained. The deniers of the multisegment filaments and the polyester single component filament may be either the same or different, but when both the filaments have the same denier, the filaments having improved dynamic properties are apt to be obtained. The denier ratio of both the filaments is preferred to be about 10/7-7/10. A given value of the denier ratio of both the filaments can be obtained by selecting the diameter or length of the orifice 111.

When the filaments obtained by the above described method are applied to a false twisting, the segments in the multisegment filaments are separated into fibrils and the polyester single component filaments and the fibrillated segments are fully entangled to form the desired mixed filaments.

The term "false twisting" used herein means that the filaments are twisted and then partially untwisted. The "false twisting" includes a usual false twisting (abbreviated to as FT process) wherein twisting and untwisting are effected continuously and a process wherein after twisting, twisting in the reverse direction is made (referred to as multi-step process). In general, FT process is preferred in view of the working efficiency and therefore an explanation will be made with respect to this process.

The object of the false twisting lies in fibrillation of the multisegment filament as mentioned above. The multisegment filament is readily fibrillated and therefore it is not necessary to determine the number of twistings (when a spindle is used, rotation number of spindle/yarn velocity) exactly as in the usual twisting.

For the object of the present invention, the number of twist (false twisting) necessary per meter of filament is 0.1X-1.5X, particularly 0.5X-1.2X (provided that, X=270,000/d+60+800, d=denier of original fiber).

In the same manner, the twisting may be effected at room temperature (for example, 20.degree.C) or by heating (for example, 190.degree.C) and the feed ratio (velocity of feed roller/velocity of delivery roller) may be 0.8-2.0.

The above explanation was made with respect to FT process but FT process may be effected more than two times and further after the false twisting by FT process, a heat-setting and conventional twisting may be effected. Then, an explanation will be made with respect to the multi-step process.

This process may combine two steps of twisting--reverse twisting, three steps of twisting--heat setting--reverse twisting, four steps of twisting--heat setting--reverse twisting--heat setting or may combine further many steps.

In this case, the number of twists for effecting fibrillation (usually the first step) is the same as in the above described FT process. The number of twists in the reverse direction effected thereafter may be the same as or different from the original number of twists but is preferred to be at least 50, preferably at least 70 percent of the original number of twists. When the original number of twists is different from the number of reverse twists, the fibers are actually twisted and the number of actual twists and the direction thereof can be selected depending upon the object.

The false twisting effected in FT process may be carried out by a conventional false twisting machine provided with a false twisting portion consisting of a spindle between a feed roller and a delivery roller and a heating portion consisting of an electric heater or may be carried out by providing a false twisting portion between a delivery roller of a drawing apparatus and a winding up appartus to effect the drawing and false twisting continuously.

As the false twisting portion, use may be made of conventional means, for example, a spindle a means for applying false twists to filaments directly by contacting the filaments with a rotating roller, that is a means for applying twists directly by a friction and air jet type means which applies false twists to filaments by a rotating flow of compressed air.

As the heating portion, use may be made of conventional plate-shaped or tube-shaped heating elements but as mentioned above; any heating element may not be used depending upon the purpose. In the multi-step process, conventional twisters (double twister, uptwister and the like) may be used. The heat-setting may be effected by the following means. That is, a bobbin wound with filaments is heated with steam or hot water or the running filament is heated by a metal heater or a heater tube. By the method of the present invention, various fibers can be obtained.

As polyesters to be used in the present invention, mention may be made of polyethylene therephthalate, polyethylene oxybenzoate, polytetramethylene terephthalate, polydimethylcyclohexane terephthalate, polypivalolactone and copolyesters containing the components of these polyesters.

As polyamides to be used in the present invention, mention may be made of nylon 6, nylon 66, nylon 11, polymethaxylene adipamide and copolymers containing the components of these polyamides.

The combination of polyester and polyamide to be used in the present invention can be selected optionally depending upon the object but when highly crimped filaments are to be obtained by applying false twists, it is preferred to combine polyester and polyamide, which are equal in the appropriate false twisting conditions, for example, a combination of polyethylene terephthalate and nylon 66.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof.

EXAMPLE 1

By using the spinneret as shown in FIG. 6, provided that 18 orifices 111 are arranged in a circumference of a spinneret plate 110 and 9 groups of inner orificies 5 and channels 8, and 9 passages 4 are opened on the bottom of the inner spinneret 100 alternately corresponding to the orifices 111, polyethylene terephthalate (PET) having an intrinsic viscosity of 0.71 in o-chlorophenol solution at 30.degree.C and polyhexamethylene adipamide (nylon 66) having an intrinsic viscosity of 1.05 in metacresol at 30.degree.C are melted separately and the melted PET and the melted nylon 66 are supplied to a supplying chamber 2 and a supplying chamber 1 in a weight ratio 7/1 by metering pump respectively. The temperature of the spinneret is maintained at 290.degree.C and both the melted polymers are spun from circular orifices, each having a diameter of 0.25 mm, and cooled in air and the spun filaments are wound up at a velocity of 700 m/min, while oiling, drawn to 3.6 times on a drawing pin at 105.degree.C, and wound up while contacting with a metal plate at 165.degree.C for about 0.1 sec. to obtain drawn yarns of 75 denier/18 filament, which is referred to as yarn F.sub.1. The yarn F.sub.1 is composed of 9 polyester single component filaments and 9 multisegment filaments having the cross-section as shown in FIG. 2 wherein PET is divided by thin layers of nylon 66 into 4 segments and 4 segments are uniformly dispersed (conjugate ratio of PET/nylon 66 being 3/1).

For comparison, the multisegment filament and the polyester single component filament are separately spun and drawn.

Namely, by using a spinneret as shown in FIG. 6, provided that 18 orifices 111 are arranged on a spinneret plate 110 and 18 groups of inner orifices 5 and channels 8 corresponding to said orifices 111 are provided on the inner spinneret plate 100, PET and nylon 66 are spun and drawn in the same manner as in the production of yarn F.sub.1, provided that the feed ratio of PET/nylon 66 is 3/1 by weight, whereby multisegment filament of 75 denier/18 filament are obtained, which is referred to as yarn F.sub.2.

Separately, PET is spun in a conventional process to form PET filaments having 75 denier/18 filament, which is referred to as yarn F.sub.3.

Yarns F.sub.1, F.sub.2 and F.sub.3 are false twisted and then fed into a metal tube heater having an inner diameter of 3 mm and a length of 50 cm heated at 215.degree.C and taken out at a rate of 60 m/min through a spindle rotating at 200,000 rpm and wound up at a rate of 55 m/min.

After the false twisting, the yarns F.sub.1 and F.sub.2 are completely fibrillated and in the yarn F.sub.1 the fibrillated segments and the polyester single component filaments are thoroughly entangled and dispersed homogeneously, each of the above false twisted yarns is S-twisted and Z-twisted and these twisted yarns are mixed and then formed into a plain knitted goods by a circular knitting machine of 20 gauge and these knitted goods are refined, dyed and steam set to form suit cloths.

The resulting suit cloths are estimated and the results are shown in the following Table 1.

Table 1 ______________________________________ Shape Yarn Bulkiness Resiliency Softness retaining property ______________________________________ F.sub.1 Present Invention o o o o F.sub.2 Comparative .DELTA. .times. o .times. F.sub.3 Comparative .DELTA. o .times. o ______________________________________

In the above Table, the bulkiness, resiliency and softness are feeling estimation and the shape retaining property is estimated by classifying the deformation after a square form of the suit cloth is washed 5 times into three classes.

As seen from Table 1, the suit cloth obtained by using the mixed yarn F.sub.1 produced by the method of the present invention is rich in bulkiness and has a moderate resiliency and further softness and an excellent shape retaining property and is provided with the features of natural fibers and synthetic fibers.

EXAMPLE 2

The mixed filaments are produced in substantially the same manner as in the yarn F.sub.1 in Example 1, provided that the feed ratio of PET/nylon 66 is varied to 3/1, 5/1, 7/1 and 9/1. When the feed ratio of PET/nylon 66 is 3/1, the conjugate ratio of PET/nylon 66 in the multisegment filament is substantially 1/1. When the feed ratios are 5/1, 7/1 and 9/1, the conjugate ratios are substantially 2/1, 3/1 and 4/1, respectively. When the conjugate ratio of PET/nylon 66 of multisegment filament is 1/1 and 2/1, that is when the rate of polyamide in the multisegment filament is 50 percent and 33 percent, the yarns wound on bobbins after drawing float loose filaments and cause hindrance in the following false twisting step.

On the other hand, when the conjugate ratio is 3/1, that is when the rate of polyamide in the multisegment filament is 25 percent, the amount of the loose filaments is small and there is no hindrance in the following step. In the yarn of a conjugate ratio of 4/1 wherein the rate of polyamide in the multisegment filament is 20 percent, there is no loose filament.

EXAMPLE 3

.epsilon.- polycaproamide (nylon 6, intrinsic viscosity in the metacresol solution at 30.degree.C being 1.1) and PET are spun and drawn in the same manner as described in Example 1 in a feed ratio of PET/nylon 6 being 9/1 to obtain yarn F.sub.4 of 75 denier/18 filament. The resulting yarn F.sub.4 is false twisted. The thus treated yarns are fed at a rate of 60 m/min without using a heater and taken out at a rate of 60 m/min through a false twisting spindle rotating at 1,900,000 rpm and wound up at a rate of 61.2 m/min.

The multisegment filaments in the yarn F.sub.4 after the false twisting are fibrillated. The yarn F.sub.4 after the false twisting is not substantially crimped and is flexible and has a moderate resiliency and shows silk-like gloss.

Claims

What is claimed is:

1. A method for producing a yarn consisting of a mixture of (A) fibrillated multisegment composite filaments consisting of polyester and polyamide and (B) polyester monofilaments, said polyamide being selected from the group consisting of polyhexamethylene adipamide, polycaproamide and copolyamides thereof, said polyester being selected from the group consisting of polyetheylene terphthalate and copolyesters thereof which comprises simultaneously and separately spinning through a common spinneret (1) monofilaments of polyester having a denier of more than 2 to form component (B) and (2) composite filaments of polyester and polyamide in which the polyester of each composite filament is divided into at least three separate segments by thin interesecting polyamide layers having a substantially uniform thickness throughout their length and which extend radially and diverege in a direction away from their intersection toward the periphery of said composite filament, said polyester segments having a denier of less than 1, said composite filaments being from 40 to 70 percent by weight based on the sum of the weights of said monofilaments and composite filaments, said polyamid being less than 40 percent by weight based on the weight of said composite filaments and said polyamide being less than 30 percent by weight based on the sum of the weights of said monofilaments and composite filaments,

combining the monofilaments and composite filaments, drawing the combined filaments and then false twisting the combined filaments to fibrillate said composite filaments whereby to form a yarn in which the fibrillated segments of said composite filaments and said polyestere monofilaments are entangled and are homogeneously dispersed.

2. A method as claimed in claim 1, wherein said polyamide in the total mixed filaments is less than 25 percent by weight.

3. A method as claimed in claim 1, wherein said polyamide in the composite filaments is less than 30 percent by weight.

4. A method as claimed in claim 1, wherein said polyamide in the composite filament is of X-shaped form, Y-shaped form or six-arm radial-shaped.

5. A method as claimed in claim 1, wherein the polyester segments in the composite filament are is less than 0.7 denier.

6. A method as claimed in claim 1, wherein the polyester monofilament is 3-10 deniers.

7. A method as claimed in claim 1, wherein the polyester is polyethylene terephthalate.

8. A method as claimed in claim 1, wherein the polyamide is polyhexamethylene adipamide.

9. A method as claimed in claim 1, wherein the polyamide is .epsilon.-polycaproamide.

10. A method according to claim 1, in which the feed ratio of polyester to polyamide fed to said spinneret is 7/1 or less and the conjugation ratio of polyester to polyamide in said composite filament is 3/1 or less.