JPS6037203B2 - Manufacturing method of water-absorbing artificial fiber - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing water-absorbing artificial fibers.

Synthetic fibers such as polyester, polyamide, and polyacrylonitrile have poor water absorbency, and improvements are desired. In order to improve the water absorption of synthetic fibers, many attempts have been made to introduce hydrophilic groups into the polymers that form them or to mix hydrophilic substances with them, but it is difficult to increase the water absorption rate sufficiently with this method. However, when the water absorption rate can be increased, the quality of the thread deteriorates significantly and is often impractical. Many methods have been proposed for attaching hydrophilic substances to the fiber surface, but
Although this method improves the hydrophilic properties of the fibers, such as their wettability, the water absorption properties are hardly improved, and the durability is often poor due to the shedding of the hydrophilic substances.

On the other hand, another substance is mixed with the fiber-forming polymer in the form of fine particles,
Many proposals have been made to obtain porous water-absorbing fibers by extracting and removing the particulate matter after forming the fibers.

Although this porous fiber can be obtained with considerably excellent water absorption, it requires a technically difficult method of mixed spinning, and the strength and elongation of the obtained fiber are insufficient, and it is difficult to obtain because of the diffused reflection of light. It has the disadvantage of lacking transparency and sharpness of dyeing.

The purpose of the present invention is to improve the shortcomings of these conventional water-absorbing synthetic fibers, that is, to develop a new synthetic fiber that has sufficient water absorption, has little deterioration in yarn quality such as strength and elongation, and is easy to manufacture. We are proposing synthetic fibers.

Further objects will become apparent from the description below. The present invention is directed to an artificial fiber that is made of a fiber-forming polymer and has at least one hollow part, and the hollow part is closed on the side surface of the fiber by cracks. A composite fiber consisting of a sheath of a formable polymer and a core of a polymer more soluble or degradable is subjected to torsional strain by false twisting to create cracks on the fiber sides, and then at least It is characterized by dissolving or decomposing a part of it.

Here, cracks are cracks that do not exist during spinning, but are generated due to mechanical strain or the like in subsequent steps.

The water absorbency of the fiber of the present invention is obtained by the hollow portions and cracks.

That is, water enters the hollow space inside the fiber from the surface of the fiber through cracks and is retained there. Furthermore, the water held in the hollow portion can be released to the outside through the cracks or evaporated. Therefore, in general, the water absorption capacity (saturated water absorption amount) is proportional to the size of the hollow portion, that is, the hollowness ratio, and the water absorption or water discharge rate is proportional to the degree of crack opening. It is fully expected that the hollow portions of hollow fibers will have the ability to retain water.

The problem is that it is extremely difficult to provide a passage for water to enter and exit the hollow part. However, as will be described later, the inventors of the present invention have found a method for easily producing fibers having cracks as passages connecting the hollow portion and the outside world, and have completed the present invention. The hollowness ratio of the fiber of the present invention can be arbitrarily selected depending on the purpose of use. For example, to obtain a normal water absorption capacity, the hollowness ratio can be set to 10-60%, especially 20-50%, and to obtain a particularly high water absorption capacity, the hollowness ratio can be set to 30-90%, especially 40-80%. It can be done. The hollow portions of the fibers of the present invention may be continuous in the length direction of the fibers or may be discontinuous. However, in general, when cracks are continuous, the fibers tend to become excessively soft and the cracks tend to deform, for example, the cracks open and the hollow part is opened, which tends to reduce the water retention capacity. In other words, cracks that are intermittent are better and more desirable. Cracks in the fibers of the present invention are generally along the length of the fibers. The larger the inside of the crack is, the easier water can pass through it, but if the inside of the crack becomes too large, the distinction between the hollow part and the outside world disappears, and the ability to retain water is lost. Therefore, inside the crack, the diameter of the hollow part (in the case of a non-circular cross section, the diameter of a circle with the same area) is 50% or less, especially 30%.
Below, in most cases, 1 to 20% is preferred. Of course,
Since cracks are long and narrow, the cracks inside vary depending on the location, and the above is an average. Similarly, the inside of the crack is less than 5mm (5 x 10 - wholesale), especially 3mm to 0.
Approximately 1 French m is suitable. If the inside of the crack becomes too small, for example less than 0.1 m, particularly less than 0.01 m, the water passing rate becomes too low, which may be undesirable. Of course, cracks deform and change when external forces such as twisting or bending are applied to the fibers. Therefore, it is inappropriate to grasp the inside of a crack in a fixed manner. It is desirable to take care so that the inside of the crack can reach the above values during use. The number of cracks is usually from 1 to about 10,000 per 1m of the total length of a single machine, preferably in the range of 1 to 100, particularly in the range of 10 to 50.

Long ones are effective even if they are small in number, while short ones require a large number of them. For example, the total length of cracks is 1 skin or more, preferably 5 skin to 50 cracks per 1m of single fiber length.
A range of 0c, particularly 10 to 100 skins, is suitable. The fiber of the present invention can be easily produced.

That is, at least two types of spinning materials are formed into a core/sheath type composite paper yarn, stretched as necessary, and then subjected to torsional strain by a method such as false twisting to cause cracks in at least a portion of the sheath; Next, by melting or decomposing and removing at least a portion of the core paper thread material, it is possible to obtain a fiber having a hollow part, which is closed to the fiber surface by cracks. The first step of producing the fiber of the present invention is core-sheath composite spinning. The paper thread material used for the core portion may be any material that can be used as a composite grade thread and is convenient for the subsequent core and polymer removal process.
Not particularly limited. Polymers useful for the removal process include polymers that are soluble in water, polymers that can be decomposed and dissolved in aqueous alkaline solutions, polymers that can be dissolved in acids, and polymers that can be dissolved in non-aqueous solvents. Preference is given to those which can be dissolved or decomposed in aqueous solution. There are a number of water-soluble polymers, including polyalkylene oxides, such as polyethylene oxide, polyethylene oxide/polypropylene oxide copolymers, derivatives thereof, segmented copolymers of other polymeric (e.g. polyester or polyamide) segments. Polymers, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl polymers such as polyacrylates, water-soluble polyamides such as polypisproboxyethaneazibamide, polybisproboxypiverazineazibamide, and the like.

Polymers that can be decomposed and dissolved in alkaline aqueous solution include:
Examples include fiber-forming polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene oxybenzoate, and their polymers and modified products. In particular, 1 to 60% (by weight) of the above polyester
degree, preferably 2-30%, most preferably 5-20%
% of polyalkylene oxides are easy to composite spin, are easily decomposed by alkaline aqueous solution, and are moderately soft, so they do not cause cracks in the sheath component when false-twisting etc. It is easy to use, inexpensive and easily available, and is one of the most advantageous for the purpose of the present invention. Similarly, a mixture of about 5 to 50%, especially about 10 to 30%, of aliphatic polyester with a low melting point (200° C. or less) to aromatic polyester is also very suitable as a core component. Polyesters used for this purpose include polylactones such as polycaprolactone,
Polyalkylene alkylates such as polyethylene adipate, polyethylene sebacate, polybutylene adipate, polybutylene sebacate, polyhexamethylene adipate and polyhexamethylene sebacate, and their mutual copolymers, etc. Examples include polymers with components such as Examples of acid-soluble polymers include 6 nylon, 66 nylon, 610 nylon, 612 nylon, 1
Examples include polyamides such as nylon 2 and copolymers thereof.

Examples of non-aqueous solvents include chlorides such as tricrene and perchlorene, aromatic compounds such as toluene and xylene, dimethylformamide, and acetone. Examples of polymers that can be dissolved in these solvents include polyethylene and polypropylene. , polystyrene, polyvinyl chloride, polyacrylonitrile polymers, etc. As the polymer used for the sheath portion, any fiber-forming polymer can be used. For example, many polymers can be used, such as polyolefins, polyvinyls, polyacrylonitrile, polyamides, polyesters, polyethers, polycarbonates, polyureas, and polyurethanes. Among them, polyacrylonitrile-based, polyamide-based and polyester-based polymers are useful. Furthermore, hydrophilic polymers having hydrophilic groups such as ether bonds, hydroxyl groups, amino groups, carboxyl groups, sulfonate groups, phosphoric acid groups, etc. are suitable because they improve the water absorption rate. Of course, the sheath polymer itself may have a high water absorbency, but it may also have a low water absorbency. Rather, it is preferable to use fibers that have low water absorption, are not watery, and are easily wetted by water, since this will increase the water absorption of the final fiber of the present invention. This hydrophilicity, or wettability, can be evaluated by producing a weave with a normal round cross section (about 3 denier) from the polymer and measuring the water absorption rate of the knitted or woven fabric made of the fiber. . In order to obtain fibers with particularly excellent water absorption ability, it is necessary to determine that the water wicking height for 5 minutes measured using the method described below is IQ.
It is preferable to use a highly hydrophilic polymer as the sheath component, which exhibits a diameter of more than 200 m, particularly 2 or more, most preferably 3 or more. Examples of suitable polymers with such improved hydrophilicity include polyalkylene oxides with 1
-10%, especially about 2-8%, of copolymerized or mixed polymers. The combination of core and sheath components is an important issue.

That is, a combination is required in which cracks are likely to occur in the sheath due to torsional strain such as false twisting, and a combination is required in which the sheath component is not substantially degraded during the process of dissolving or decomposing and removing the core component. In core-sheath type composite fibers, the probability of cracks occurring in the sheath due to torsional strain such as false twisting depends on the properties of both components, especially mechanical properties such as hardness (softness),
The larger the difference in torsional modulus, compression modulus, elongation modulus, elastic recovery modulus, etc., the greater the difference.

Cracks also tend to occur when fibers that are easily fibrillated, such as polypropylene, polyacrylonitrile, polyethylene terephthalate, or modified products thereof, are used in the sheath component. Cracks also tend to occur when the affinity between the core component and the sheath component is poor. Similarly, the higher the degree of molecular orientation, the more likely cracks will occur. On the other hand, if the properties of both components are similar, cracks are less likely to occur. Taking these things into consideration, it is necessary to roughly mix the ingredients so that cracks will occur appropriately. Finally, when the core component is dissolved or decomposed after composite spinning into a core/sheath type and pre-combusted, and the sheath component is subjected to a treatment that does not substantially dissolve or decompose, the rate at which the core component is removed ( The amount of cracks can be evaluated by measuring the rate of weight loss). When the speed of core component removal is high, there are many cracks, and when this speed is low, there are few cracks. If the core component is extracted through the saddle component even if there is no crack, the degree of crack can be evaluated by comparing the extraction speed before and after false twisting. Furthermore, since cracks can be observed as clear cracks using a scanning electron microscope, the shape, size, and number of cracks can be confirmed. The composite yarn of the core component and the sheath component can be produced by a well-known method.

FIGS. 1 to 6 are examples of cross sections of core-sheath type composite fibers that can be used for producing the fibers of the present invention. The composite may be concentric as in FIG. 1 or eccentric as in FIG. The core may be circular or non-circular as shown in FIG.
The sheath may be circular as shown in FIGS. 1-3 or non-circular as shown in FIG. 4. The number of cores may be one as shown in FIGS. 1 to 4, or a plurality of cores as shown in FIG. 5. However, as the number of cores increases, the transparency of the fibers and the sharpness during dyeing tend to decrease, and a more complicated composite thread cap is required. The number is usually 1 to 3, with 1 being the most practical. The core may have a double structure or a multilayer mixed structure consisting of two types of polymers 2 and 2' as shown in FIG.

The greater the eccentricity of the core and the more uneven the thickness of the core, the more likely cracks will occur. FIGS. 7 to 11 are examples of cross sections of cracks caused by torsional strain such as false twisting.
FIG. 7 shows an example in which a soft core is deformed by strong strain, rupturing the sheath (creating a crack) and exposing a portion of it to the surface. FIG. 8 shows an example in which the soft core protrudes further from the crack. Figure 9 shows that the core is hard and does not deform much.
An example is shown in which the sheath is deformed and cracked. FIG. 10 shows an example in which two cracks were formed, and FIG. 11 shows an example in which two cores each formed one crack. The volume ratio (volume occupancy) occupied by the core in a core-sheath composite fiber is closely related to the hollowness ratio and water absorption capacity (saturated water absorption amount) of the target water-absorbing fiber.

In other words, the hollowness ratio of the water-absorbing fiber is, in most cases, equal to the volume occupancy of the core of the core-sheath composite fiber. The volume occupancy of the core portion may be arbitrarily selected depending on the purpose of use of the water-absorbing fiber, but it is usually 10 to 90%, particularly 20 to 80%, and most preferably 30 to 70%. Core-sheath composite fibers are subjected to torsional strain, which causes cracks in the sheath. Torsional strain can be imparted by methods such as twisting, twisting/untwisting, etc., but false twisting, in which heating and untwisting are performed continuously, is most useful.
False twisting can be carried out in the same manner using a normal false twisting machine for the purpose of crimping. In order to provide both cracks and crimping, it is sufficient to pre-combust under heating, and in order to provide only cracks without crimping, it is sufficient to pre-combust at room temperature or a relatively low temperature. The number of twists is usually 1,000 to 10,000 times per 1m, particularly 2,000 to 50,000 times, and the larger the number of twists, the more likely cracks will occur. When the purpose is to provide both crack and crimp, false twisting is carried out at a temperature between the softening point of the sheath polymer (usually 10 to 30° C. lower than the melting point) and a temperature about 50° C. lower than the softening point. For example, when the sheath is made of nylon 6, the suitable temporary combustion temperature is in the range of 150°C to 2000°C, in the case of nylon 66, 180 to 240°C, and in the case of polyethylene terephthalate, the range is 180°C to 240qo. This false-twisting may be performed only with core/sheath composite filaments, but for other fiber examples, ordinary single-component filaments and double yarns (including mixed weaves) may be temporary-twisted to create a mixed false-twisted yarn (combined false-twist yarns). A twisted yarn) can be obtained, which is also extremely useful. If the softening point of the mating fiber is high in this mixed false twisting, the false twisting temperature can be higher than the softening temperature of the source fiber. Composite fibers whose sheaths have cracks due to torsional strain such as false twisting are made into threads or into fiber structures such as knitted fabrics or nonwoven fabrics, and then at least a portion of the core component is removed.

The core component is removed by dissolving it in an aqueous or non-aqueous solvent or decomposing it with a decomposing agent. It is not necessary to remove all of the core component. Depending on the desired water absorption power, it may be sufficient to remove, for example, about 20 to 90% of the core. Of course, in this removal step, it is desirable to take care to minimize the deterioration of the sheath component, but it is actually possible to substantially prevent the sheath component from deteriorating. Many examples have already been given of the solvent or decomposer to be applied to the combination of the core component and the sheath component, and the selection is easy for experts. In particular, the core component is a polymer that is easily decomposed by an aqueous alkali solution (e.g., caustic soda), such as a modified polyester, and the degree of resistance to the aqueous alkali solution;
After cracking a core-sheath composite filament whose sheath component is a polymer such as unmodified or low-density polyester, polyamide, polyacrylonitrile, polyolefin, etc. using an aqueous polisher, crack the core polymer (at least partially) with an alkaline aqueous solution. ) removal method is the most practical. FIGS. 12 to 16 are examples of cross-sectional views of cracked portions of the fibers of the present invention.

In the figure, 3 indicates a crack, and 4 indicates a hollow portion created by removing the core component. Fig. 12 shows an example with one crack, Fig. 13 shows an example where part of the core component 2 remains, Figs. 14 and 15 show an example with multiple cracks, and Fig. 16 shows the same as shown in Fig. 6. An example in which component 2' remains in the core having a multilayer structure will be shown. FIG. 17 shows an example of the cross section and side surface of the fiber of the present invention, in which there are cracks 3 in the part A, but there are no cracks in the part B, and the fiber has a completely hollow structure. As described above, one of the major features of the present invention is that it is possible to easily obtain fibers having both a hollow structure and a hollow structure portion opened to the surface by cracks. Furthermore, by adjusting the method for removing the core component, it is possible to have only the cracked part A have a hollow part, while the B part retains its original core-sheath structure. Therefore, in the fiber of the present invention, parts having cracks and hollow parts, parts having complete hollow parts, and parts having the original core/sheath structure can coexist. This completely hollow part and core/sheath structure have functions such as maintaining the shape of the fiber, maintaining crimping, and maintaining appropriate hardness, and the ratio of each part can be adjusted to achieve the desired use. A major feature of the present invention is that it can be adapted to the following. The fibers of the present invention can be used in the form of continuous filaments, cut staples, etc., in yarns, yarns, knitted fabrics, woven fabrics, non-woven fabrics, felts, papers, leather-like sheets, and all other fibrous structures and products.

It can also be used by mixing with other fibers by doubling, mixed twilling, intercalating, blending, knitting, interweaving, or other means, if necessary. The mixing ratio can be selected arbitrarily depending on the purpose of use, but 5
~95%, especially 10-90%, most often 20-80%
A range of is suitable. By mixing, it is possible to impart sufficient water absorbency to the textile product, and to compensate for the disadvantages of the fibers of the present invention, such as low transparency, softness, and weak stiffness. The first feature of the fiber of the present invention is its excellent water absorbency. The saturated water absorption amount can be controlled by changing the hollow portion, and can easily be adjusted to, for example, 10 to 300% of the fiber weight. In particular, fibers with a large hollowness ratio, for example 40~
It has been extremely difficult to manufacture fibers with a hollowness ratio of 90%, but according to the present invention, fibers with such a high hollowness ratio can be easily obtained. When the hollowness ratio is 50%, the saturated water absorption amount is 100%, and when the hollowness ratio is 90%, the saturated water absorption amount is 900%.
It can even be %. A second feature of the fibers of the present invention is that they can be easily crimped by false twisting. Ordinary hollow fibers are deformed during the false twisting process, and the hollowness is often substantially close to $. Furthermore, fibers that have water absorption properties due to their non-circular cross-sections often become deformed in cross-section due to false twisting and lose their original shape. In contrast, according to the present invention, the fibers are handled in almost the same way as ordinary fibers, not only in the false twisting process but also in processes such as bran mills, and the core component is removed from the final product, resulting in a high hollowness ratio and low crimping. A hollow fiber product with low deformation can be obtained. The fibers of the present invention can be used in applications that require water absorption, such as clothing such as underwear, shirts, sportswear, and socks; It is suitable for a wide range of uses, including household goods such as towels, sheets, and cleaning supplies, office supplies such as felt bags and blotting paper, and various industrial materials.

Furthermore, the fibers of the present invention, especially those made of lipophilic polymers (eg, polyolefins, aromatic polyesters, etc.), exhibit high oil absorption.

By taking advantage of this property, we can produce oil supply devices, lamp wicks, oil-absorbing fences,
Suitable for oil dish towels, etc. The third feature of the fiber of the present invention is that it has high heat insulation properties.

Taking advantage of the feature that it is easy to obtain products with a high hollowness ratio, which is extremely difficult to achieve using other methods, it is suitable for applications such as cold-proof clothing, heat-resistant clothing, general clothing, futon wire, and heat insulating materials. On the other hand, the fiber of the present invention has a smaller apparent specific gravity and is lighter. For example, when the hollowness ratio is 50 to 60, the apparent specific gravity is about 0.5 to 0.7, which is suitable for various uses. Examples are shown below,
The present invention will be explained in more detail, but of course the present invention is not limited thereto.

In the examples, % or % represents a weight ratio unless otherwise specified. Solution viscosity of polymers (relative viscosity and intrinsic viscosity)
In the case of polyester or polyether, a mixture of 6 parts of phenol and 4 parts of tetrachloromethane is used as a solvent, and in the case of nylon, 95% sulfuric acid is used as a solvent.
Less than 1 ta of polymer was dissolved in 100 ml of solvent and measured at 20°C using an Ostwald viscometer.

Water wicking height J
was determined according to the Byrek method.

)・The measured value after 5 minutes is shown. In addition, the water absorption rate, which indicates the water retention capacity, is based on German standard (DIN) 5 spots 14.
Measurements were taken after dehydration for 20 minutes at a centrifugal force of 100. Further, the frictional charging voltage, which is a measure of antistatic property, was measured as follows. After removing the oil and other substances adhering to the outside of the sample with a detergent, drying it in an 8000 ventilation dryer, and drying it in a 25q.
o After leaving the sample in a room with a relative humidity of 33% for more than 6 hours, cut the sample into a 6-inch diameter tube with a diameter of 6 mm in the center, 12 cm in length, 20 cm in length, and 1 rib in thickness.
Insert it into the metal plate holder with the circular hole and secure it by holding it with a metal plate cover of the same size. Place a raised wooden board in the center that is in close contact with the circular hole under the sample in the circular hole, and use a piece of wool (cotton cloth, synthetic fiber cloth, etc.) stretched over the friction body of the blackboard eraser from above. Then, rub the metal plate and material lightly by hand 12 times, and immediately place the metal plate and the material on a rotating sector type electrostatic detector at a distance of about 30 degrees, and measure and record the charged voltage. The measured values after sanding are shown in each table.The strength of the fibers was measured in a conventional manner using a tensile tester manufactured by Instron.

Examples 1 to 9 and Comparative Examples 1 to 3 Copolymerized polyethylene terephthalate containing 17% polyether segments obtained by cocondensing polyethylene glycol with an average molecular weight of 8000 (relative viscosity 2.2, heat resistant agent Firganox 1010, Bonding ratio: 1:10, 1:5, 1:3, 1:2 with polyethylene terephthalate (relative viscosity: .7) as the core and sheath (containing 0.3%)
, 1:1, 2:1, 3:1, 5:1, 10:1, and 150 denier/4 at 3.2 to 3.5 times.
A composite yarn of 8 filaments was obtained.

The processed yarn obtained by pre-combusting these at a yarn speed of 10 h/mic, a number of twists of 2400/m, and a temperature of 200 qo is
After making it into a thin circular knitted fabric using a 12mm round rope machine, it was refined using a 90mm hot water bath. Sodium hydroxide
% and an alkaline aqueous solution at 80° C. for different times to obtain samples with various weight loss rates, but the weight loss rate was faster than the polyethylene phthalate single yarn, reflecting the occurrence of cracks in the sheath. However, it was clear that the rate of weight loss was different for each filament, and the ease with which cracks occurred was different. The water absorbency, charging voltage, and mechanical strength of each alkali-treated knitted fabric or the yarn obtained by unraveling them are shown in the following table.

For comparison, individual yarns of the above-mentioned polyethylene terephthalate and copolymerized polyethylene terephthalate were made with the same twill configuration, processed into yarns in almost the same way, knitted, scoured,
The results of alkali treatment are also shown (Comparative Example 2)
.

Furthermore, a case was also shown in which a hollow fiber having the same weave structure with a hollowness ratio of about 30% was obtained using the polyethylene terephthalate, processed into a processed thread, knitted into a fabric, and then treated with a scouring alkali. (Comparative Example 3) Only Examples have useful water absorbency and practical strength, and it can be seen that weight loss ratios of 10 to 20% or more and 80% or less are preferable.

Incidentally, in many examples, the weight loss rate and the increase in water absorption rate are proportional, and it can be considered that the weight loss rate and the hollowness ratio correspond to each other. However, if the crack width is large, the bonding ratio is large, or the alkali weight loss rate is large, the weight loss does not necessarily correspond to an increase in hollowness. In addition, the frictional charging voltage may be significantly lower than that of a single yarn, which indicates that there are parts of the copolymer containing electrically conductive polyether segments that are not strongly attacked by alkali. It has become clear that cracks are quite ubiquitous, and that they are often useful. Figure 18 shows Example 3 (core/sheath ratio 1/3, alkali weight loss 22%)
This is a scanning electron micrograph of a cross section of a fiber. As is clear from the figure, the hollow portion has a hollowness ratio close to that of the composite ratio, and it also shows that there is a portion that is not hollow (the core remains completely). FIG. 19 is a scanning electron micrograph of the side surface of the fiber of Example 5 (core/sheath ratio = 1/1, weight loss rate 45%), and shows an example of cracks occurring on the side surface. First surface charge polarity: Negative Examples 10 to 14 and Comparative Example 4 Instead of polyethylene terephthalate used in the sheath part in Examples 1 to 9, 3 mol% sodium 3,5-dicarboxybenzenesulfonate was copolymerized. A so-called cationic beam polyethylene terephthalate (intrinsic viscosity 0.60, hereinafter referred to as CD-PET) with improved hydrophilicity was used, while the same copolymerized polyethylene terephthalate as in Examples 1 to 9 was used for the core part. A core-sheath type composite multifilament was obtained by melt spinning.

However, the joining ratios are 1:10, 1:5, 1:3, 1:2
, 1:1, and for comparison, a CD-P with the same ayado configuration.
A single ET yarn was obtained. In addition, all grade compositions are approximately 1 after stretching.
50 denier/48 filaments. Each drawn yarn was subjected to a false twisting process in the same manner as in Examples 1 to 9), except that it was subjected to a false twisting process at 190oC to obtain a circular knitted fabric, which was then subjected to scouring and alkaline treatment, and its water absorption, antistatic properties, and strength were measured. did. The results are shown in Table 2, and compared to polyethylene terephthalate, CD-PET, which has increased hydrophilicity, has excellent water absorption, even when the core bonding ratio is small (thick sheath). Cracks tend to occur during false twisting, and Alka*IJ
It can be seen that the weight loss time is significantly shortened. Table 2 Examples 15 to 19 and Comparative Examples 5,6 Average molecular weight 20
000 polyethylene glycol, 910 parts, Bisu 8
-Hydroxyethyl terephthalate 8 parts This is a sterically hindered phenol compound, Irganox 1010 (Ciba).
A polyether ester with a relative viscosity of 4.2, which was melt-polymerized using antimony oxide as a catalyst, was blended with 10% polyether ester as an antistatic agent into the core polyester, and on the other hand, A composite multifilament was melt-spun using the same polyester for the sheath part.

The joining ratio of core and sheath is 1:10, 1:5, 1:3, 1
:2, 1:1, and the antistatic agent was blended by passing the previously melted polymer through a static mixing element (Kenix type, 1-Kan element) immediately before spinning (bonding). As the polyester, so-called easily dyeable polyethylene terephthalate (ED-PET with an intrinsic viscosity of 0.60 or less), which has improved hydrophilicity and dyeability by copolymerizing 5% by weight of polyethylene glycol with an average molecular weight of 1000, was used. Therefore, a single multifilament made of only this ED-PET was spun. In addition, a single yarn containing 10% antistatic agent was also graded in the same manner as the core portion. The weave composition of each filament is 75 denier/72 filament (after stretching)
And so. Two of each drawn yarn was twisted in the same manner as in Examples 1 to 9) to form a circular knitted fabric, and then scouring and alkaline bath treatment were performed.

The water absorbency, antistatic property, and strength of each cracked hollow fiber obtained are shown in Table 3 together with the results of the single fiber of the comparative example. It can be seen that in the examples, both excellent water absorption and antistatic properties can be obtained. In addition, during false twisting, the cracks in the sheath were local, so the antistatic polyester part of the core was not uniformly dissolved away by the alkali treatment, and as a result, compared to Comparative Example 6, the antistatic polyester part of the core was not uniformly dissolved. Prevention properties have been obtained. Table 3 Charging polarity: Negative Examples 20 to 28 and Comparative Example 7 The core part was made of antistatic polyester containing the same antistatic agent (polyether ester) as in Examples 15 to 19, and the sheath part was Poly-caprolactam (hereinafter referred to as nylon 6) with a viscosity of 2.7 is used, and the bonding ratio between the core and sheath is 1:10, 1:5, 1:3, 1:2, 1:1, 2:1,
A core-sheath type composite multifilament was obtained by changing the ratio of 3:1, 5:1, and 10:1 to melt-grade yarn.

Separately, for comparison, 6 nylon single yarn with the same fineness configuration was also spun. Weave configurations are all 70 denier/36 filaments after stretching. After pre-combusting each drawn yarn at a temperature of 9,000 degrees with a yarn length of 12 hours/min, twisting rate of 2,600 times/m, and a temperature of 9,000 degrees, each drawn yarn was knitted in the same manner as in the examples described above, and subjected to scouring and alkaline treatment. Ta.

The water absorbency, charging voltage, and mechanical strength of each treated knitted fabric or the yarn obtained by starving it are summarized in Table 4. It can be seen that superior water absorption and antistatic properties were obtained compared to the comparative example.

Further, it is preferable that the sheath of nylon 6 is slightly less likely to cause cracks in polyester, and that the sheath ratio and thickness of the sheath be small. Table 4

[Brief explanation of the drawing]

Figures 1 to 6 are examples of cross sections of core-sheath composite fibers that can be used in the present invention, and Figures 7 to 11 are cross-sectional examples of core-sheath composite fibers that have cracked due to twisting strain. This is an example. FIGS. 12 to 16 are examples of cross sections of cracked portions of the fibers of the present invention, and FIG. 17 is examples of cross sections and side surfaces of the fibers of the present invention. FIG. 18 is an example of a scanning electron micrograph of a cross section of the fiber of the present invention, and FIG. 19 is an example of a scanning exposure micrograph of the fiber of the present invention. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19

Claims (1)

[Scope of Claims] 1. Torsional strain is applied by false twisting to a composite fiber consisting of a fiber-forming polymer sheath and a core of a polymer more soluble or degradable than the sheath to create cracks on the sides of the fiber. A method for producing a water-absorbing artificial fiber, which comprises tightening the core, and then dissolving or decomposing and removing at least a portion of the core. 2. The method according to claim 1, wherein the sheath is made of polyester or polyamide, and the core is made of polyester that has a higher decomposition rate with alkali than the sheath.