US3516239A - Artificial fiber having voids and method of manufacture thereof - Google Patents

Description

June 23, 1970 KENJI FUKUDA ET AL 3,516,239

ARTIFICIAL FIBER HAVING vows AND METHOD OF MANUFACTURE THEREOF Filed March 13, 1967 4 Sheets-Sheet 1 June 23, 19,0 KENJ] FUKUDA EIAL 3,515,239

. ARTIFICIAL FIBER HAVING VOID S AND METHOD OF MANUFACTURE THEREOF Filed March 13, 1967 4 Sheets-Sheet 2 June 23, 1970 KENJI FUKUDA ETAL 3,516,239

ARTIFICIAL FIBER HAVING VOIDS AND METHOD OF MANUFACTURE THEREOF Filed March 13, 1967 4 Sheets-Sheet 5 F79! 5 m I F 1 E3 '20 f? 55100 111 3 80 1V E5 V 60- VI LI 0 0 W REMOVAL RATIO OF POLYETHYLENE TEREPHTHALATE 1%) Q- 657 E I IZO H lOO 111 W1 E W E5 LIJ 0 2O 4O 6O I00 REMOVAL RATIO OF POLYETHYLENE TEREPHTHALATE June 23, 1970 KENJI FUKUDA ET AL Filed March 13, 1967 4 Sheets-Sheet 4.

VIII F/ 6b 9 g \40 I E 11 I m 111 1v 2: 80 2 2 E 6O ES 40 W E Q 20 z 0 20 40 6O 80 I00 REMOVAL RATIO OF POLYETHYLENE TEREPHTHALATE F/g. 6c

INDEX OF PHYSKIAL PROPERTIES REMOVAL RATlO OF POLYETHYLENE TEREPHTHALATE (/o) United States Patent 3,516,239 ARTIFICIAL FIBER HAVING VOIDS AND METHOD OF MANUFACTURE THEREOF Kenji Fukuda, Suita-shi, and Yujiro Okamoto, Ibarakishi, Japan, assignors to Teijin Limited, Osaka, Japan, a corporation of Japan Filed Mar. 13, 1967, Ser. No. 622,636 Claims priority, application Japan, Mar. 15, 1966, 41/ 16,248 Int. Cl. D06m 9/02; D02g 3/02; D0611 1/02 US. Cl. 57-140 11 Claims ABSTRACT OF THE DISCLOSURE Artificial fiber which comprises a linear polymer having voids characterized in that the whole of the fiber or the whole of the fiber excluding the central axial neighborhood of the fiber uniformly contains a plurality of thin voids extending lengthwise axially of the fiber and method of manufacturing the foregoing fiber.

This invention relates to a new artificial fiber and a method of manufacturing the same. More particularly, this invention relates to an artificial fiber which comprises a linear polymer having voids characterized in that the Whole of the fiber or the whole of the fiber excluding the central axial neighborhood of the fiber uniformly contains a plurality of thin voids extending lengthwise axially of the fiber. The invention also concerns a method of manufacturing the foregoing fiber.

The fiber obtained by spinning a blend of at least two classes of fiber-forming linear polymers which are incompatible (hereinafter also referred to as composite fibers) conjointly possesses the characteristics that are possessed by the constituent polymers as fibers. For example, the composite fiber obtained by spinning and draw ing a blend consisting of nylon 6 chips in a major proportion and polyethylene terephthalate chips in a minor proportion possesses the excellent dyeability, tenacity maintainability and crimp elasticity of nylon 6 and, in addition, possesses the high Youngs modulus and high dimensional stability of polyethylene terephthalate, de pending upon the proportion of the blend. This is due to the fact that, as a characteristic of fiber-forming linear polymers, not only the nylon 6 which is to become the predominant component but also the polyethylene terephthalate which is blended therewith both possess a fibrous structure and each fiber is formed in such a state wherein the polyethylene terephthalate having a fibrous structure is uniformly dispersed in the predominant component the nylon 6 having a fibrous structure.

Having observed that when a composite fiber of this sort obtained from a blend of at least two classes of incompatible polymers having fiber-forming ability is treated with chemicals which does not act on at least one component and is capable of dissolving or destroying other components the attack by the chemicals gradually proceeds into the interior of the fiber from its outer part depending upon the concentration of said treating chemicals treatment temperature and time, we conceived of utilizing this phenomenon in the art of textile processing.

An object of this invention is therefore to provide a method of processing a composite fiber in a manner that a composite fiber is provided with new properties and characteristics without essential impairment of its intrnisic qualities.

Other objects will become apparent from the following description.

In explaining this invention in detail in the following, we shall, for the sake of convenience, refer mainly to a composite fiber composed of two classes of fiber-forming linear polymers which are incompatible with each other. It should be understood however that the same explanatron holds good with respect to a composite fiber composed of more than two components. By the term fiberforming linear polymer used in this invention is meant a polymer from which monofilament of 0.5 to 5 denier can be easily formed by spinning, the said filaments having a tenacity of at least 0.8 g./de. and other properties ordinarily required of textile fibers.

According to this invention, fibers composed of a uniform blend of 5-50% by weight of a fiber-forming linear polymer (component A) and 50% by weight of another fiber-forming linear polymer (component B) not compatible with the former, in the form of either filaments, yarn or knit or woven fabrics, is removed of at least a part, say, 10-l00% of the component A by being brought into contact with and dissolved or destroyed by chemicals which acts on only component A and not on component B to remove the former from the fiber. The chemicals attack the fiber beginning at its outer layer and gradually proceeds to the interior of the fiber. Hence, component A which is present in the zone beginning at the outer layer of the fiber and extending to a desired depth can be dissolved or destroyed and removed by the chemicals by a suitable choice of the concentration of the chemicals, the treatment temperature and treatment time. The sites from which component A has been removed, in consequence of the fact that component A had a fibrous structure become thin voids extending lengthwise axially of the fiber. Hence, when of component A has been removed from a composite fiber composed of 55-50% by weight of component A and 95-50% by weight of component B, the resulting fiber becomes of such a structure that the fiber consisting of only component B contains uniformly distributed over the whole of the fiber with a porosity of about 5-50%, a plurality of thin voids extending lengthwise axially of the fiber. On the other hand, when 10% of component A has been removed from the composite fiber, the peripheral portion of the fiber having an apparent sectional area corresponding to 10% of the total sectional area of the fiber becomes of a structure consisting of only component B and containing therein with a porosity of about 550% the voids such as hereinabove described, whereas that zone on the inner side of the peripheral portion retains intact its compact composite fiber structure. Namely, in the latter case there is formed a fiber having a structure wherein the core is compact and about this core there is a zone having a plurality of voids which are thin and long. In any case, the size of these long and thin voids differs depending upon such factors as the type and proportion of the polymers A and B that constitute the fiber, and the spinning drawing conditions for the fiber. But in general, the diameter is 10m to 10p, and the length is at least three times the diameter. Especially preferable are voids substantially having a diameter of 10111;]. to 1 and a length at least 5 times as long as the diameter. The hereinabove used terminology: the peripheral portion of the fiber having an apparent sectional area corresponding to 10% of the total sectional area of the fiber is meant that the sectional area of the peripheral portion inclusive of the sectional area occupied by the voids present is 10% of the total sectional area of the fiber inclusive of the sectional area of said voids.

The composite fiber from which 1096% of component A has been removed is enhanced in its softness and is imparted a silky handle and a pearl-like luster, as compared with the original composite fiber. In spite of the enhancement of softness, the bending resilience of the composite fiber is maintained. This eifect is most pronounced when the removal ratio of component A is 1090%. When 100% of component A has been removed, the fiber becomes very pliant and the whiteness and luster are enhanced. From the standpoints of structure and effects the characteristics of the fibers in which the removal of component A exceeds 96; is substantially the same. as those of the fibers whose removal ratio is 100%. In either case, the resulting fibers suffer a slight loss in tenacity, but it is not such as to cause any practical difficulties and as to the many other practically useful physical properties there is no essential change, if not an improvement, as compared with the original composite fiber.

The fiber obtained according to this invention possesses a plurality of thin voids extending lengthwise axially of the fiber. These long and thin voids are present in great numbers in the fiber stacked against each other radially of the fiber. Hence, the fiber posseses an optical structure similar to the multilayered structure of pearl. That the invention multicellular fiber having a core has, as hereinbefore noted, a pearl-like luster is believed due to the complex reflection and transmission of light based on this pearl-like structure. On the other hand, that the invention multicellular fiber not having a core excels in its whiteness and luster is believed to be due to the fact that the transmission of light becomes greater in view of the absence of a core.

US. Pat. No. 3,085,987 (British Pat. No. 898,289, German Pat. No. 1,152,257 and French Pat. No. 1,267,725) discloses the preparation of a porous fiber from a synthetic linear condensation polyester consisting of a mixture of certain aromatic ethers. The object of this prior art resides in the improvement of the dyeability of the fiber by means of the minute pores which are left behind in the fiber after .evaporation of the aromatic cthers. The minute pores in this disclosure differ from the structure of the thin voids of this invention which extend lengthwise axially of the fiber and in which the voids in great numbers are disposed adjacently of each other radially of the fiber as in a stack. In the case of the fiber according to this prior art, the provision of a pearl-like luster or an increase in whiteness cannot be expected as in the case with the fiber of this invention. The specific differences between the foregoing prior disclosure and the present invention are shown in Example 5.

In the accompanying drawings and photographs,

FIG. 1 is a cross-sectional view out at right angles to the axis of the fiber, illustrating schematically an embodimentv of the invention fiber;

FIG. 2 is an electronic photomicrograph illustrating that portion of FIG. 1 enclosed with broken line 11 of the product obtained in the hereinafter given Example 3;

FIG. 3 is an electronic photomicrograph illustrating the longitudinal section taken along lines III-III of FIG. 1 of the product obtained in the hereinafter given Example 3;

1 FIG. 4 is a cross-sectional view, as in FIG. 1, illustrating schematically another embodiment of the invention fiber;

FIG. 5 is a graph to explain Example 1; and

FIGS. 6a, b and c are graphs for explaining Example 3.

This invention will now be described more specifically with reference to FIGS. 1-4.

- FIG. 1 is a cross-sectional view cut at right angles to the axis of a fiber 1 having a circular section. This fiber was obtained by dissolving and removing by means of chemicals 50% of component A from a composite fiber composed of 30% of component A and 70% of component B. In the peripheral portion of the fiber 1 are shown the numerous thin voids 2 extending lengthwise axially of the fiber, which have been left behind after removal of component A. The peripheral zone 3 of the fiber 1 containing the numerous voids 2 is made up substantially of only component B. The apparent sectional area (the total area of the annular portion inclusive of the total sectional area. of the voids 2) of this peripheral zone corresponds to 50% of the apparent sectional area of the fiber 1 (the total area of the circle inclusive of the total sectional area of the voids 2). The total sectional area of the numerous voids 2 corresponds to about 30% of the apparent sectional area of the peripheral zone 3. In other words, the peripheral zone 3 containing the numerous thin voids extending lengthwise in the axial direction has a porosity of 30%. The portion neighboring the central axis of the fiber 1 which had not been attacked by the chemicals, i.e. the core portion 4, has a circular section and has a sectional area corresponding to 50% of the apparent sectional areas of the fiber 1. Since component A has not been removed from this portion, this portion retains intact the compact state of the original fiber composed of 30% of component A and of component B.

The fact that products of any mode can be obtained by varying the proportion of components A and B making up the fiber and the ratio of removal of component A should be readily understandable from the illustration shown in FIG. 1.

Further, it should be understood that the aforesaid FIG. 1 is a rough schematic view and that actually the voids 2 are thinner than those shown and moreover are present in a greater number.

FIGS. 2 and 3 are electronic photomicrographs illustrating in section the composite fiber actually obtained from 30 parts by weight of polyethylene terephthalate and 70 parts by weight of poly-e-caprolactam by means of Example 3 of this invention. Namely, FIG. 2 shows a cross-section corresponding to precisely the portion enclosed by the broken line II in FIG. 1, of the actual product, whereas FIG. 3 shows in longitudinal section taken precisely along broken lines III-III of FIG. 1. The round patterns seen in FIG. 2 as white spots are the cross-sections of the thin voids 2 which extend in the axial direction of the fiber. On the other hand, the long thin patterns seen in the manner of white needle leaves in FIG. 3 are the voids 2 in longitudinal section. The round patterns seen as grayish spots in FIG. 2 are the cross-sections of component A which remain in component B, not having been attacked by the chemicals. The zone con taining these grayish patterns is the core portion which is compactly composed of components A and B. That the components A and B are photographed as distinguishable grayish patterns in the compactly composed core portion in these electronic photomicrographs is due to the fact that the components A and B are incompatible and component A is distributed in component B as a fiberous structure.

FIG. 4 is a schematic view in cross-section of a fiber 1 having a circular section, which has been obtained by dissolving and removing by means of chemicals all of component A from a composite fiber which had been composed of 20% of component A and of component B. In a product of this mode in this invention, the numerous axially extending thin voids that remain after removal of component A are present uniformly in the whole of the fiber, and hence, as shown in FIG. 4, the voids 2 are distributed uniformly over the whole area of the circular cross-section of the fiber 1. The substance 3 of the fiber 1 containing the numerous voids 2 is essentially composed of only the component B. The total sectional area of the numerous voids 2 corresponds to about 20% of the apparent cross-sectional area of the fiber 1. In other words, the fiber 1 containing the numerous axially extending thin voids has a porosity of about 20%.

Although an electronic photomicrograph of the product of this mode will not be given, it should be readily understandable that the photomicrograph of this product would correspond to one wherein the grayish patterns shown in FIG. 2 have all been converted to the white patterns.

Combinations of fiber-forming linear polymers which are mutually incompatible and hence conveniently usable in this invention include such as polyester and polyamide, polyester and polyacrylonitrile, polyester and polycarbonate, polyester and polyolefin, polyamide and polyacrylonitrile, polyamide and polycarbonate, polyamide and polyolefin, polyamide and polyvinyl chloride, and polyester and polyvinyl chloride. In these combinations, the choice as to which will be used as component A and which as component B will be determined by the chemicals which is to be used for the treatment. For example, in the case of the combination of polyester and polyamide, an aqueous solution of caustic soda dissolves the polyester but does not act on the polyamide. Hence, when the caustic soda aqueous solution is used as the treating chemicals the polyester becomes component A while the polyamide becomes component B. On the other hand, since formic acid attacks polyamide but does not act on polyester, when formic acid is used as the treating chemicals the polyamide become component A while polyester becomes component B. Not only for this combination but for all other combinations where polyester is used as component A the caustic soda aqueous solution is suitably used as the treating chemicals. On the other hand, the known polyamide solvents such as formic acid and glacial acetic acid are conveniently used as the treating chemicals in the case of those combinations where polyamide are used as component A. The suitable treating chemicals for the combination using polyvinyl chloride as component A is methylene chloride. In the combination of polyamide and polycarbonate where the polycarbonate are com ponent A, caustic soda aqueous solution, cyclohexane, methylene chloride, chloroform, etc., are used as the treating chemicals whereas in the combination of polyester and polycarbonate where the polycarbonate are component A, benzene, xylene, toluene, etc., become the treating chemicals.

An example of a combination of three classes of polymers is that of polyester, polyamide and polycarbonate. By choosing an appropriate chemical from the above-mentioned various treating chemicals, one or two of these three components can be component A, and two or one can be component B. As examples of a composite fiber composed of four classes of polymers, we can cite a combination of nylon 6 and nylon 66 as component A with polyethylene terephthalate and polycarbonate as component B, and that of polycarbonate as component A with nylon 6, polypropylene and modified polyethylene terephthalate (having an improved dyeability) as component B. When at least 2 classes of incompatible polymers are to be removed from at least 3 polymers, the polymers are subjected to a treatment consisting of at least 2 steps. In this case, the polymers to be removed are designated as component A.

No particular restrictions are imposed on the treatment conditions of the composite fiber by these chemicals so long as the conditions are such that the desired removal ratio of component A can be achieved without any adverse clfects on component B. A suitable concentration for the chemicals treatment temperature and treatment time are chosen within these limits. Taking, for example, the case where polyester is removed as component A from a composite fiber composed of polyester and polyamide, using caustic soda aqueous solution, the suitable conditions in this case would be generally as follows: a concentration of the caustic soda aqueous solution of 5-10O grams per liter, treatment temperature of 50 C.boil and treatment time of 10- 400 minutes. For achieving a given removal ratio, the higher the concentration of the solution or the higher the temperature is, the shorter will be the treatment time. For example, for removing 50% of polyester from a fiber composed of 20% of polyester and 80% of polyamide, the treatment must be carried out for minutes with boiling caustic soda aqueous solution of a concentration 30-40 grams per liter. To be sure, the treatment conditions required for achieving the same removal ratio will be milder in the case of a fiber whose content of polyester is lower. On the other hand, taking as an example the treatment with formic acid of a fiber containing 20% of polyamide as component A, in this case about 30% of the polyamide can be removed by treating the fiber for 3 minutes at room temperature using formic acid aqueous solution. The same end can also be achieved by carrying out the treatment over an extended period of time, say about 30 minutes, using a formic acid aqueous solution of such a low concentration as is not usually used in practice as solvents for polyamide.

The following nonlimitative examples are given for further illustrating this invention. The parts and percentages are on a weight basis, unless otherwise noted.

The values of the physical properties given in the examples were determined in the following manner.

TENSILE STRENGTH AND ELONGATION The top and bottom of a specimen of a fabric 3.5 cm, long and 5 cm, wide are fitted to the chucks of a Shopper-type tensile tester so that the specimen length becomes 20 cm. The specimen is pulled and the strength and elongation at break are read.

SURFACE ABRASION SURFACE FRICTION COEFFICIENT A head mounted with a specimen of a fabric 10 cm. long and 5 cm. wide is moved at a uniform velocity while contacting the surface of a specimen 50 cm. long and 11 cm. wide mounted atop a fiat block. The resistance at this time is read with a U-gauge and computation is made in accordance with the following equation:

a (surface friction coefiicient T (U-gauge reading) R weight of head plus specimen) CREASE RECOVERY A specimen 4 cm. long and 1.5 cm. wide is folded in its middle and applied a 500 gram load for 5 minutes. After removal of the load, the specimen is set in a Monsanto-type crease recovery tester and 5 minutes later the recovery angle is checked.

BENDING STIFFNESS A specimen of a fabric 5 cm. long and 5 cm. wide is passed through a 4-mm. slit made by two bars each 10 mm. in diameter and 70 mm. long while pulling it up by a bar 70 mm. long and 1.4 mm. in diameter. The resistance incurred at this time is read with a U-gauge.

BEND'ING RESILIENCE A fabric specimen 5 cm. long and 2 cm. wide is bent at an angle and the two ends thereof are fitted to the chucks of the movable block of an Instron-type tensile and elongation tester. The movable block is moved upwardly and the specimen is gradually applied pressure by means of a pressure member fitted at the top of the tester. The hysteresis curve of the force of resistance of this time is recorded and the repulsive force is calculated.

TEAR STRENGTH Measurement is made with respect to a specimen 10 cm. long and 6.3 cm. wide by using an Elemendorf-type tear strength tester.

7 of these filaments, a plain fabric of 120 ends x 1'00 picks was woven.

Next, this fabric was scoured for 30 minutes at 60 C.

WHITENESS A specimen of a fabric 5 cm. long and 5 cm. wide is set in a Spectrophotometer, after which light having a Wavelength of 480 my. is applied. The amount of light reflected at this time is measured and the ratio between this and that of a standard white card is computed.

LUSTER A specimen 5 cm. long and 5 cm. wide is set in a Goniophotometer, after which rays of all wavelengths from a white light source were directed against the surface of the specimen at a 60 degree angle. The amount of reflected light is measured and the ratio between this and that of a standard card is computed.

Example 1 Ten parts of polyethylene terephthalate and 90 parts of poly-e-caprolactam (nylon 6), both in the form of small chips, were mixed and uniformly melted. The melt was then spun by the conventional spinning method by being extruded through an extruder 25 mm. in diameter. The die temperature at this time was 280 C. The spun filaments were drawn 4.5 X and made into a 50 denier-l2 filaments. These filaments had a tenacity of about 7.2 grams per denier, an elongation of about 30% and a Youngs modulus of about 350 kg. per mm. 100 twist per meter were imparted to these filaments, after which by the use Example 2 A 50 denier-12 filaments were made by spinning a melt blend of 85 parts of polyethylene terephthalate and 15 parts of polyhexamethylene adipamide (nylon 66), as in Example 1, and drawing the freshly spun filaments 3.2 After imparting a twist of 3 00 turns per meter to these filaments and steaming the so obtained twisted yarn for minutes at 120 C. under a state in which its shrinkage was restricted, it was wound up onto a reel. The yarn, while still .wound on the reel, was immersed for 3 minutes at room temperature in 85% formic acid aqueous solution (bath ratio 1250) followed by washing with water and drying. As-a result of this treatment, the weight of the yarn decreased 3.8%. This signifies that about 25% of the nylon 66 (component A) in the yarn was removed. The yarn obtained by this treatment had silky handle and a pearl-like luster,'and it did not have the mineral-like handle and luster possessed by the usual synthetic fibers. A monofilament was taken out of this yarn for testing. This was designated as Sample 2.

For purpose of comparison, the aforesaid yarn, before being treated as hereinabove described, was immersed for one hour in room temperature water followed by drying. A monofilament for testing was taken out of this yarn. This was designated as Contrast 2.

The physical properties of Sample 2 and Contrast 2 are shown in Table II.

TABLE II Friction Denier of Young's Qoefliciency mono- Tenacity, Elongation, modulus, (Roder methwhiteness filament g./d. percent kgJmmJ 0d) 10 percent Sample 2. 4. 1 5. 2 21. 5 1, 210 0. 453 84. 5 Contrast 2 4.2 I 5. 5 21.2 1,250 0.401 78.3

soap and one gram per liter of a nonionic synthetic deter- Example 3 in a bath containing one gram per liter of a fatty acid gent (bath ratio 1:40), following which it was heat set for 1 minute at 180 C.

This scoured fabric was then immersed in caustic soda aqueous solution of a concentration of 40 grams per liter (bath ratio 1:10) and boiled for 60' minutes in a jigger. As a result of this treatment, 4.2% decrease is the weight of the fabric occurred. This means that 42% of the polyethylene terephthalate (component A) in the fiber was removed.

The physical properties of this fabric (Sample 1) obtained by means of the treatment with caustic soda aqueous solution, which has a soft and silky handle and a pearl-like luster, are compared in Table I and FIG. 5

with those of the scoured fabric before being given the aforesaid treatment (Contrast 1).

A 50 denier-12 filamentswere prepared by spinning a melt blend of 10 parts of polyethylene terephthalate (component A) and 90 parts of poly-e-caprolactam (component B), as in Example 1, followed by drawing the freshly spun filaments 4 This yarn was imparted a twist of 100 turns per meter, following which the yarn was used and a plain fabric of 120 ends x 100 picks was woven.

This fabric was scoured as in Example 1, after which it was heated at 98-100 C. in a tensionless state in a beaker containing caustic soda aqueous solution of a concentration of 80 g./liter (bath ratio 1:50). Various changes in the physical properties resulting in the fabric obtained by varying the treatment time in the range of 10-300 minutes were investigated. FIG. 6a is a graphic representation of these results.

TABLE I Crease Tensile Elongation Surface recovery strength (Warp diabrasion (warp di- Bending (warp direction) tenacity reotion) stiffness, Whiteness reetion) kg. percent; cycle percent g. percent Sample 1 51. 4 41. 3 360 86. 3 3. 6 85. 2 Contrast 1-... 58. 9 40. 1 279 84. 6 4. 7 78. 5

FIG. 5 is a graph showing the changes in the various physical properties when the time and temperature for the treatment by means of the aforesaid caustic soda aqueous solution were changed and the removal ratio of the polyethylene terephthalate was increased further. The index of physical properties on the vertical axis indicates the relative values of the properties of samples of this invention when the property values of the contrast sample was taken as 100. In FIG. 5, curve I is a curve repersenting the changes in the surface friction coefficient, curve II, that of whiteness, curve III, that of crease recovery, curve component A and parts of component B and given the same treatment ashereinabove described.

It is clear from a comparison of FIGS. 6a, 0 that there is a tendency to demonstration of greater effects by the same treatment as the amount of component A contained in the fiber increases.

In FIGS. 6a, 0, the curves 1, II, III, IV, VII and VIII represent, respectively, surface friction coefficient, whiteness, crease recovery, bending resilience, bending stiffness and luster.

Example 4 90 parts of poly-e-caprolactam (nylon 6) and 10 parts of polycarbonate (a polymer with an average molecular weight of 32,000 containing 2,2-bis4-hydroxyphenyl propane as a dioxy component), both in the form of small chips, were mixed and uniformly melted. By spinning this melt and drawing the freshly spun filaments 2.5x, a 50 denier-12 filaments were obtained.

A crimped yarn was prepared by taking these filaments and imparting thereto a twist of 3000 turns per meter with a false twisting machine followed by heat setting the yarn at 150 C. and untwisting it.

This was followed by immersing this crimped yarn for 5 minutes at room temperature in methylene chloride, washing and drying.

A 6% loss was noted in the weight of the crimped yarn by this treatment. This signifies that 60% of the polycarbonate (component A) had been removed from the fiber. This crimped yarn was very soft and had an exceedingly high pearl-like luster.

Example 5 A melt blend of 90 parts of polyethylene terephthalate and 10 parts of poly-e-caprolactam (nylon 6) was spun in customary manner and drawn 3.5x to prepare a 50 denier-12 filaments. A twist of 100 turns per meter was imparted to these filaments, following which this twisted yarn was used to weave a plain fabric of 100 ends x 80 picks.

This fabric was immersed for 2 minutes at room tem perature in 80% formic acid aqueous solution (bath ratio 1:50), washed and dried.

As a result of this treatment, there was a decrease of 5% in the weight of the fabric, which meant that about 50% of the nylon 6 (component A) had been removed from the fiber. The so obtained fabric had silky handle and a pearl-like luster. This fabric was designated as Sample 3.

Separately, a melt blend of 90 parts of polyethylene terephthalate and 10 parts of 1,2-di-o-biphenyloxyethane was spun in customary manner and drawn 3.2x to prepare a 50 denier-l2 filaments. After imparting a twist of 100 turns per meter to this yarn, the twisted yarn was used and a plain fabric of 100 ends x 80 picks was woven. This fabric was heat set for one minute at 190 C. The so obtained fabric was designated as Contrast 3.

The physical properties of Sample 3 and Contrast 3 were compared. The results are presented in Table III. In Table III the indexes of the several physical properties of Contrast 3 are relative values taking 100 as the values of the physical properties of Sample 3.

TABLE III Surface Bending friction Whiteness Stiffness coefficient Dyeability Sample 3 lllll 100 100 100 100 Contrast 3 70 150 73 180 Example 6 80 parts of polyethylene terephthalate, 15 parts of polye-caprolactam (nylon 6) and 5 parts of polycarbonate (same as that used in Example 4), all in the form of small chips, were uniformly mixed and melted. The resulting melt was spun and drawn 2.7x to form 50 denier-12 filaments.

These filaments were immersed for 10 minutes in chloroform of 40 C., washed, and dried. A weight decrease of 4% was observed in the filaments as a result of this treat ment. This. means that of the polycarbonate component in the filaments had been removed. The obtained filaments had the properties of polyethylene terephthalate and poly-E-caprolactam, and possessed a soft and silky handle and a pearl-like luster.

It is also possible to subject these filaments to the treatment with the chemicals of Example 1 or 5 to remove at least a part of the nylon 6 or polyethylene terephthalate from the filaments.

Example 7 A 50 denier-12 filaments were prepared by spinning a melt blend of 80 parts of poly-e-caprolactam (nylon 6) and 20 parts of polyethylene terephthalate in a customary manner, followed by drawing the freshly spun filaments 4.5 X. Using these filaments, a plain fabric of 100 ends x 100 picks was Woven, which was designated as Contrast 4.

This fabric was immersed in a bath containing 60 grams per liter of caustic soda and 5 grams per liter of an ammonium salt type cationic surfactant (bath ratio 1:50), where it was boiled for 6 hours followed by washing and drying. The polyethylene terephthalate (component A) was completely removed from the fiber by this treatment. The so obtained fabric was designated as Sample 4.

As compared with Contrast 4, the whiteness of Sample 4 was improved by 15%, its luster, by 40% and its softness, by 70%. And its soft handle and pearl-like luster were more pronounced than any of the products obtained so far in the foregoing examples.

Further, when the dyeing of Sample 4 and Contrast 4 were carried out by boiling for 60 minutes in a dye bath containing 1% (O.W.F.) of Xylene Fast Blue PR (C.I. Acid blue 129, Sandoz) and 2% (O.W.C.) of acetic acid (bath ratio 1:100), Sample 4 was dyed a pronounced pastel-like color phase as compared with that obtained by Contrast 4.

As shown by the foregoing examples, the fiber of this invention possesses not only the physical properties possessed by the conventional textile fibers but also possesses unique and excellent properties not possessed by the conventional fibers. Hence, it demonstrates unique performances in the usual field of its use such as yarn, woven and knitted fabrics and nonwoven fabrics. For example, besides demonstrating exceptional dyeing effects owing to its high whiteness, as shown in the foregoing Example 7, it has the ability of being adhered very firmly with adhesives owing to the fact that voids contained in the fiber are relatively large in size and numerous. This ability makes the fiber of this invention valuable also for tire cords.

What is claimed is:

1. An artificial fiber having voids, said fiber comprising a compact core portion and a peripheral portion containing a plurality of voids, characterized in that said com pact core portion is a uniform blend of 5-5() percent by weight of fiber-forming linear polymers (component A) and -50 percent by weight of another fiber-forming linear polymer (component B) not compatible with said first-named polymers, said core portion having a sectional area corresponding to 49() percent of the total sectional area of the fiber, said plurality of voids in the form of thin voids extending lengthwise axially of the fiber being all contained in said peripheral portion uniformly distributed therein, said peripheral portion containing said voids being constituted of component B having a porosity of about 5-50 percent, said peripheral portion having an apparent sectional area corresponding to 10 96 percent of the total sectional area of the fiber.

2. A fiber according to claim 1 wherein one of the said fiber-forming linear polymers is a polyester, whereas the other of the said polymers is a polyamide.

3. A fiber according to claim 1 wherein one of said fiber-forming linear polymer is a polyamide, whereas the other of the said polymers is a polycarbonate.

4. A fiber according to claim 1 wherein one component is composed of polyamide and polycarbonate, and the other component is a polyester.

5. A fiber according to claim 1 wherein one component is composed of a polyamide and polyester, and the other component is a polycarbonate. Y

6. A fiber according to claim 1 wherein one component is composed of a polyester and polycarbonate, and the other component is a polyamide.

7. A yarn made from the fiber of claim 1.

8. A fabric made from the fiber of claim 1.

9. A method of manufacturing an artificial fiber having voids which comprises contacting a drawn fiber composed of a uniform blend of 5-50 percent by weight of fiber-forming linear polymers (component A) and 95-50 percent by weight of another fiber-forming linear poly mer (component B) not compatible with said first-named polymers with a chemical which is capable of acting only on said component A and not on said component B to remove at least a part of said component A from the fiber thereby forming in said fiber a plurality of thin voids extending lengthwise axially of the fiber.

-10. The'method according to claim 9 which comprises heating for 10-400 minutes at a temperature ranging between C. and the boiling point in caustic soda aqueous solution of a concentration of 5-100 grams per liter, a fiber composed of a uniorm blend of 5-50 percent by weight of a polyester and -50 percent by weight of polyamide, thereby removing at least a part of said polyester from the fiber.

11. The method according to claim 9 which comprises immersing in formic acid aqueous solution, a fiber composed of a uniform blend of 5-50 percent by weight of a polyamide and 95-50 percent by weight of a polyester, thereby removing at least a part of said polyamide from the fiber.

References Cited UNITED STATES PATENTS 8/1960 Jankens 161-178 4/1963 Abashian 8-55 X U.S. c1. X.R. 23-1145; 2876; 161178,

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