JP2006328583A - Sea-island type conjugate fiber having excellent anti-transparent property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sea-island type conjugated fiber which has suitable fiber physical properties capable of providing high density woven fabrics having excellent anti-transparent property, softness and dyeability, and can easily be split. <P>SOLUTION: This sea-island type conjugated fiber comprising a polyester A consisting mainly of polylactic acid and a polyester B consisting mainly of polytrimethylene terephthalate is characterized in that the polyester A occupies the whole surface of the fiber, and the content of titanium oxide contained in the polyester B is 1.5 to 7.0 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sea-island type composite fiber that has suitable fiber properties that can provide a high-density fabric excellent in see-through property, softness, dry touch, and color developability and that can be easily sea-islanded.

  A method for obtaining ultrafine fibers by reducing the weight of sea-island composite fibers composed of a plurality of components is widely known. However, most of them are composite fibers using polyethylene terephthalate (hereinafter referred to as PET) polymer, and ultrafine fibers obtained by reducing the amount of the composite fibers need to be dyed at a high temperature of 100 ° C. or higher. Color development was not obtained, and there was a restriction on product development in dark colors. Furthermore, since the Young's modulus of PET itself is high, the softness is insufficient, and the fiber shrinkage rate is also low, so even if titanium oxide is contained, the density does not increase even as a high-density fabric, It was not obtained.

  In contrast, polytrimethylene terephthalate (hereinafter referred to as 3GT) obtained by polycondensation of lower alkyl ester of terephthalic acid represented by terephthalic acid or dimethyl terephthalate and trimethylene glycol (1,3-propanediol). ) Has attracted attention in recent years because it has characteristics such as a low Young's modulus and easy dyeability compared to PET and polybutylene terephthalate (hereinafter referred to as PBT).

  As for 3GT ultrafine fibers, a technology for reducing the amount of alkali of 5-sodium sulfoisophthalic acid copolymerized PET and 3GT sea-island composite fiber is disclosed (see Patent Documents 1 and 2). PET has a higher melting point than 3GT. Since 3GT is a polymer with low heat resistance and easily decomposes under temperature conditions above the melting point, only composite fibers with low strength can be obtained when co-spun with copolymerized PET as in Patent Document 1, At the same time, the fiber shrinkage also decreases, so that it is not possible to obtain a fabric having high anti-penetration properties as intended by the present invention. Furthermore, it was revealed that yarn breakage frequently occurred in terms of the yarn forming property, and the productivity was inferior.

On the other hand, for sea-island type composite fibers using biodegradable polylactic acid (hereinafter referred to as PLA) as a component to be reduced and decomposed, composite fibers of PLA and PET, or PLA and isophthalic acid copolymerized PET (patent document) 3) and PLA / PBT composite fibers (see Patent Document 4) are technically disclosed, but the case of using 3GT has not been clarified, and as described above, ultrafine fibers using PET or PBT. However, since the softness is insufficient and the fiber shrinkage is low, a soft fabric with good anti-peeling property cannot be obtained.
JP 2001-348735 A (Claims) JP 2001-89940 A (Claims) JP-A-11-302926 (Claims) JP-A-8-35121 (Claims)

  The present invention is intended to solve the above-mentioned conventional problems, and has suitable fiber physical properties capable of providing a fabric excellent in see-through property, softness, dry touch, and dyeability, and easily decomposes. It is to provide a possible sea-island type composite fiber.

The present invention is achieved by employing the items described in the following (1) to (5).
(1) A composite fiber composed of polyester A containing polylactic acid as a main component and polyester B containing polytrimethylene terephthalate as a main component. Polyester A occupies the entire surface of the fiber, and titanium oxide contained in polyester B A sea-island type composite fiber characterized in that the amount is 1.5 to 7.0% by weight.
(2) The sea-island type composite fiber according to (1), wherein the polyester B is composed of polytrimethylene terephthalate containing 0 to 1.0% by weight of titanium oxide and polyester C containing 2 to 60% of titanium oxide. .
(3) When the sea-island type composite fiber according to (1) is produced, the sea-island type is characterized in that, after the polyester B is melted, it is subjected to other-stage filtration at least twice in the process until it is discharged from the mouthpiece hole. A method for producing a composite fiber.
(4) When the sea-island type composite fiber according to (2) is produced, polytrimethylene terephthalate and polyester C are separately melted and then kneaded in a molten state to form polyester B. Manufacturing method.
(5) When producing the sea-island type composite fiber according to (2), polytrimethylene terephthalate and polyester C are mixed before melting, and after mixing chips are melted, they are kneaded in a molten state to obtain polyester B. A method for producing a sea-island composite fiber.

  According to the present invention, it is possible to provide a polyester sea-island type composite fiber that is excellent in softness and dyeability that could not be achieved by the prior art, and that is highly transparent even if it is a thin fabric.

  Hereinafter, the present invention will be described in detail.

  First, the sea-island type composite fiber of the present invention will be described. The composite fiber is a sea-island composite fiber composed of polyester A containing PLA as a main component and polyester B containing 3GT as a main component, and polyester B is divided into a plurality of segments by polyester A, as shown in FIG. Such a sea-island type composite fiber is mentioned as an example. What is important in the present invention is that the entire surface of the fiber is covered with polyester A. As will be described later, the polyester B contains titanium oxide at a high concentration. When the polyester B is exposed on the fiber surface, the titanium oxide causes problems such as guide wear and the productivity deteriorates. The number of sea islands and the fineness are not particularly specified, and should be set in consideration of the target final product and productivity.

  Polyester A, which is one component of the composite fiber, is a polyester mainly composed of PLA and is a component eluted by alkali treatment. By using PLA for polyester A, the spinning temperature can be set low, and thermal degradation of polyester B (3GT) can be minimized. Furthermore, since 3GT and PLA are similar in tension and shrinkage behavior in the spinning process, very good process stability can be obtained during composite spinning. In addition, unlike PET in which a conventional organic metal salt is copolymerized, an acid treatment step is not required for weight reduction, so that it is possible to reduce the environmental load without discharging an acidic solvent. At the same time, the elution process can be shortened, which is preferable.

Here, PLA used in the present invention is a polymer in which 90 mol% or more is a repeating unit having — (O—CHCH ₃ —CO) n— as a repeating unit, and is obtained by polymerizing lactic acid or its oligomer. However, a copolymerization component, a polyfunctional compound, etc. may be added in the range of 10 mol% or less. Examples of copolymer components include biologically biodegradable aliphatic compounds such as diols such as ethylene glycol, butanediol, hexanediol, and octanediol, and aliphatic groups such as succinic acid, hydroxyalkylcarboxylic acid, pivalolactone, and caprolactone. Lactones are preferred. As the polyfunctional compound, a polymer obtained by reacting glycerin, pentaerythritol, trimellitic acid, pyromellitic acid or the like to form an appropriate branch or weak crosslink in the polymer can be used. Furthermore, inorganic particles such as titanium oxide may be added in order to reduce the frictional resistance of the fibers and increase the process passability.

  Since lactic acid has two types of optical isomers, D-lactic acid and L-lactic acid, the polymer is poly (D-lactic acid) consisting only of D isomer and poly (L-lactic acid) consisting only of L isomer, and There is polylactic acid consisting of both. The optical purity of D-lactic acid or L-lactic acid in polylactic acid is lowered, the crystallinity is lowered, and the melting point drop is increased. Therefore, the optical purity is preferably 90% or more in order to improve heat resistance. A more preferable optical purity is 93% or more, and a still more preferable optical purity is 97% or more. As described above, the optical purity has a strong correlation with the melting point. The optical purity is about 90%, the melting point is about 150 ° C., the optical purity is 93%, the melting point is about 160 ° C., the optical purity is 97%, and the melting point is about 170 ° C. It becomes. In addition to the system in which two types of optical isomers are simply mixed as described above, the two types of optical isomers are blended and formed into a fiber, and then subjected to high-temperature heat treatment at 140 ° C. or higher. A stereo complex in which a racemic crystal is formed is more preferable because the melting point can be dramatically increased.

  The other component, polyester B, is a polymer mainly composed of 3GT, and is a component that constitutes ultrafine fibers after the alkali weight loss treatment. In the present invention, by setting polyester B to 3GT, it is possible to obtain softness and dyeability that could not be obtained with conventional ultrafine fibers of PET or PBT, and to exhibit excellent windproof properties during fabric formation. it can. 3GT used in the present invention is 3GT composed of 50 mol% or more of repeating units of trimethylene terephthalate. Here, 3GT has terephthalic acid as the main acid component and 1,3-propanediol as the main glycol component. The resulting polyester. However, it may contain a copolymer component capable of forming another ester bond at a ratio of less than 50 mol%, or may be blended with other polyesters represented by PET. Examples of copolymerizable compounds include dicarboxylic acids such as isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, and sebacic acid, while glycol components include, for example, ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol. , Polyethylene glycol, polypropylene glycol and the like can be mentioned, but are not limited thereto. Furthermore, the polyester that can be blended is not particularly limited as long as it is a fiber-forming polyester, but PET and polybutylene terephthalate (hereinafter referred to as PBT) are preferable. Moreover, a hindered phenol derivative, a coloring pigment, etc. can be added as needed as fine particles of silica or alumina as a lubricant, and an antioxidant.

  In the present invention, the polyester B contains titanium oxide particles in an amount of 1.5 to 7.0% by weight in order to impart anti-permeability. By setting the titanium oxide to 1.5% by weight or more, it is possible to obtain a fabric having good see-through properties. The titanium oxide content is more preferably 2.0% by weight or more, and further preferably 2.5% by weight or more. Moreover, by setting the titanium oxide content to 7.0% by weight or less, it is possible to produce composite fibers with good yarn-making properties, and an appropriate lightweight feeling can be obtained when a fabric is obtained. A more preferable titanium oxide content is 6.0% by weight or less. The titanium oxide suitable for the present invention is preferably an anatase type in which the maximum secondary particle size is 5.0 μm and the proportion of the particle size of 1.0 μm or less is at least 50.0% by weight or more. Further, as another effect of containing titanium oxide, a dry feeling, a pastel dyeing feeling, and the like are obtained.

  In order to obtain 3GT containing titanium oxide, it is also preferable to blend with 3GT having a titanium oxide content of 0 to 1.0% by weight and polyester C having a titanium oxide content of 2 to 60% by weight. The polyester C here is not particularly limited as long as it is a fiber-forming polyester, but PET and PBT are preferable in view of compatibility with 3GT and titanium oxide. In 3GT, titanium oxide is very easy to aggregate. On the other hand, PET and PBT are superior to agglomeration. By containing titanium oxide at a high concentration and kneading in a spinning process to obtain polyester B, a high concentration 3GT excellent in dispersibility can be obtained. it can. It is important that the mixing ratio of 3GT and polyester C is within a range that does not impair the characteristics of 3GT. The mixing ratio of polyester C is 50% by weight or less, which is the same as the requirement for polyester B.

  The preferable intrinsic viscosity of 3GT in the present invention is 0.7 to 2.0, and when the intrinsic viscosity is 0.7 or more, it becomes easy to produce a fiber having sufficient strength and elongation. A more preferable intrinsic viscosity is 0.8 or more. Further, when the intrinsic viscosity is 2.0 or less, production stability is easily obtained. A more preferable intrinsic viscosity is 1.5 or less.

  The composite weight ratio of polyester A and polyester B can be arbitrarily set, but in the range of 1: 9 to 5: 5 in consideration of the splitting property and the product amount loss due to the weight loss of polyester A (PLA). More preferably, it is in the range of 2: 8 to 4: 6. By making the composite ratio of the polyester A 10% or more, it is possible to avoid a composite abnormality with the polyester B and to shorten the passage time of the pipe after the polyester A is melted. Improvement is possible. Moreover, when the composite ratio of polyester A is 50% or less, the loss of product amount due to weight loss can be reduced.

  Next, the physical properties of the sea-island composite fiber of the present invention will be described.

  The fiber shrinkage is preferably 9 to 20% in order to develop excellent anti-peeling properties and softness when the conjugate fiber of the present invention is made into a fabric. By setting the fiber shrinkage within this range, the tissue density is increased by heat set shrinkage in the high-order processing after the formation of the fabric, and it is possible to obtain excellent see-through properties.

  In order to obtain a fabric having an appropriate windproof property and softness, the shrinkage stress peak value is preferably 0.2 to 0.5 cN / dtex, and more preferably 0.23 cN / dtex or more. Is good. The initial tensile resistance of the composite fiber is preferably 20 to 40 cN / dtex. By setting the initial tensile resistance to 40 cN / dtex or less, a soft texture fabric can be obtained without impairing the softness of the 3GT polymer. Other physical properties are not particularly specified, but in order to obtain a composite fiber utilizing the characteristics of 3GT, the strength is preferably 3.0 to 5.0 cN / dtex, and the elongation is 30 to 60%. A composite fiber excellent in color developability and good handling in post-processing can be obtained. In order not to impair the characteristics of 3GT, it is easy to obtain good color developability when the elongation is 35% or more. The sea-island type composite fiber obtained in the present invention, when it is a high-density woven fabric, exhibits a very good anti-peeling property, and when it is raised, a dense suede-like material in the raised direction can be obtained. .

  Subsequently, the preferable manufacturing method of the composite fiber of this invention is demonstrated.

  The conjugate fiber of the present invention can be produced by any known method, but considering the stability and productivity of the composite structure, the production by the melt spinning method is the best. In the production by the melt spinning method, the yarn can be produced in any process, such as a method in which spinning and drawing processes are continuously performed, a method in which an undrawn yarn is wound once and then drawn, or a high-speed spinning method. Depending on, yarn processing such as false twisting or air entanglement may be performed. As an example, the production by the direct spinning drawing method will be described in detail below.

  In melt spinning the conjugate fiber of the present invention, polyester B containing 3GT as a main component, which is one component, has a temperature of 240 to 280 ° C. when 3GT containing 1.5 to 7.0% by weight of titanium oxide is used. And are preferably melted. In the melting, a pressure melter method and an extruder method can be mentioned, and melting by an extruder is preferable from the viewpoint of uniform melting and prevention of stagnation. The molten polymer passes through the piping, and after being measured, flows into the base pack. Under the present circumstances, it is preferable that piping passage time is 5 to 30 minutes from a viewpoint of suppressing thermal deterioration. Furthermore, since the titanium oxide particles in 3GT are likely to agglomerate and have a great influence on the yarn forming property, it is preferable to perform multistage filtration twice or more before the polymer is discharged from the nozzle discharge hole. This multi-stage filtration makes it possible to disperse and remove titanium oxide aggregates, and when it is made into a fabric, it is possible to obtain fibers with more uniform see-through properties. In general, in the case of multistage filtration, for example, the filter for the first stage filtration is 20 μm, the filter for the second stage filtration is 10 μm, and the second stage is a finer filter than the filter used for the first stage filtration. However, when dispersibility is taken into consideration, the effect can be obtained even if the accuracy of the first stage, the second stage, and the subsequent filters is comparable. The filter is preferably a stainless steel nonwoven fabric filter. In addition to a filter made of stainless steel, a filter of a type in which stainless powder is sintered may be used in consideration of dispersibility. The filter accuracy is determined in consideration of the yarn forming property and the titanium oxide dispersibility, but it is preferable to use a filter having an accuracy of 3 to 25 μm.

  On the other hand, as polyester B, when using what mixed 3GT containing 0 to 1.0% by weight of titanium oxide and polyester C containing 2 to 60% by weight of titanium oxide, the following two methods are preferable.

  In the first method, 3GT containing 0 to 1.0% by weight of titanium oxide and polyester C containing 2 to 60% by weight of titanium oxide are separately melted and blended after melting. In this case, the melting temperature of 3GT is preferably 240 to 280 ° C., and the melting temperature of polyester C is preferably 250 to 300 ° C. when PET is used, and 240 to 280 ° C. when PBT is used. After melting, 3GT and polyester C are mixed in the pipe and then kneaded by a mixer. By this kneading, 3GT polyester B in which titanium oxide is appropriately dispersed can be obtained.

  In the second method, 3GT containing 0 to 1.0% by weight of titanium oxide and polyester C containing 2 to 60% by weight of titanium oxide are mixed in the form of chips, and the mixed chip is represented by one extruder. The polyester B is obtained by melting with a melting machine. In this case as well, 3GT polyester B having excellent dispersibility can be obtained by kneading with a mixer after melting. In this case, the melting temperature is preferably adjusted to the higher melting point polyester of 3GT and polyester C, but generally a melting temperature of 240 to 300 ° C. is taken.

  On the other hand, polyester A which is the other component is PLA, and is preferably melted at 200 to 240 ° C. using an extruder as in 3GT. Also in this case, it is preferable that the pipe passage time is 5 to 30 minutes from the viewpoint of suppressing thermal degradation.

  The polymers of polyester A and polyester B that have flowed into the pack are joined together by a die, are combined into a sea-island shape by a known technique, and are discharged from the die.

  At this time, the spinning temperature is suitably 240 to 280 ° C. If it is this range, the composite fiber which utilized the characteristic of 3GT can be manufactured.

  The polymer discharged from the die is cooled and solidified, and after the oil is applied, it is taken out. The take-up speed is possible at any speed of 1000-5500 m / min. In the case of drawing in an undrawn yarn or partially oriented yarn region of 100 to 4000 m / min, a method of pre-winding, drawing, and heat-treating to make a drawn yarn without winding is used. In the direct spinning drawing method described above, the draw ratio is suitably set so that the drawn yarn elongation is in the range of 30 to 60%. Further, in any of the spinning and drawing processes, it is possible to perform entanglement using a known entanglement device up to winding. If necessary, it is possible to increase the number of confounding by giving multiple times. Furthermore, it is also possible to add an oil agent immediately before winding.

  An outline of the apparatus preferably used is shown in FIG. The yarn once taken up at 1000 to 4000 m / min by the hot roller 8 heated to 40 to 80 ° C. is wound on the hot roller 8 for several turns for preheating, and the speed is 3800 to 5500 m / min. Then, it is drawn to the hot roller 9 and stretched. At this time, the hot roller 9 is heated to 110 to 170 ° C. and wound by several turns to perform heat setting. After provision of the entanglement, the tension is adjusted together with the cooling of the yarn by the two godet rollers 11 and 12, and it is wound around the package by a winder. In the winder, the package winding tension is adjusted by the contact roll 13 in contact with the package.

  By setting the contact roll speed to be 1.001 to 1.01 times faster than the winding speed of the package, it is possible to easily obtain a good bulge rate and ear height rate of the package. By setting the overfeed of the contact roll speed to be 1.001 or more, it is possible to reduce the tension when being wound around the package, and it is possible to suppress the swelling rate and the ear height rate. A more preferable range is 1.0015 or more. Moreover, the thread fall from a package end surface can be prevented by setting it as 1.01 or less, and favorable unwinding property can be ensured. A more preferable overfeed range is 1.008 or less. Furthermore, the yarn tension at the contact roll inlet is preferably 0.1 to 0.3 cN / dtex. By setting the tension to 0.1 cN / dtex or more, the yarn sway between the godet roller and the winder can be reduced, and the yarn can be stably wound even when the winding speed is increased. A more preferable tension is 0.12 cN / dtex or more. Further, when the tension is 0.3 cN / dtex or less, the tension control with the contact roll becomes easy and a good package foam can be obtained. A more preferable tension is 0.25 cN / dtex or less. Furthermore, the winding speed is preferably 3800 to 5000 m / min. By setting it as this range, high production efficiency can be maintained without impairing the physical properties of the composite fiber. A more preferable speed range is 3900 to 5000 m / min.

Hereinafter, an example is given and it demonstrates concretely. In addition, the main measured value of the Example was measured with the following method.
(1) Intrinsic viscosity Intrinsic viscosity [η] is a value determined based on the following defining formula.

Ηr in the definition formula is a value obtained by dividing the viscosity at 25 ° C. of a diluted solution of 3GT dissolved in O-chlorophenol having a purity of 98% or more by the viscosity of the solvent itself measured at the same temperature. Is defined. C is the solute weight value in grams in 100 ml of the solution.
(2) Strength and elongation Measured according to JIS L1013 (1999).
(3) Fiber shrinkage rate Fiber shrinkage rate (%) = {(L0−L1) / L0} × 100
L0: skein of 1m × 10 turns of raw yarn, skein length at a measurement load of 0.029 cN / dtex L1: raw yarn is treated with boiling water at 100 ° C. for 15 minutes under no load, and air-dried Thereafter, the skein length when a measurement load of 0.029 cN / dtex was applied (4) Shrinkage stress peak value It was measured with a thermal stress measuring instrument manufactured by Kanebo Engineering Co., Ltd. at a heating rate of 150 ° C./min. The sample was a 10 cm × 2 loop, and the initial tension was fineness (decitex) × 0.9 × (1/30) gf.
(5) Yarn breakage The rate of occurrence of yarn breakage during yarn production is converted to the value when produced by an eight-spindle winder, and one with a thread breakage of 1 / t or less passes (XX), 2 times / T or less was accepted (O), and more than 2 times / t was rejected (x).
(6) A zokkoki fabric having a transmittance warp density of 5280 / m, a weft density of 3580 / m, and a raw machine width of 1.30 m was prepared, refined at 95 ° C., and polyester A with a 3% by weight sodium hydroxide aqueous solution. More than 95% by weight of the component was removed by alkali reduction. Furthermore, after drying once at 130 ° C., finish heat setting was performed at 160 ° C. and a width of 110 cm. The total light transmittance of the fabric thus obtained was measured in accordance with JIS K7105 (1981) light transmittance A method.
(7) Permeability The perforation resistance of the Zokki fabric obtained by the above method was subjected to a sensory test and evaluated in four stages. In addition, a pass level is more than (circle).

○○: Very good ○: Excellent △: Slightly transparent and unsatisfactory ×: Transparent Example 1
Polyester A is poly-L-lactic acid having an optical purity of 98.0%, Polyester B is an intrinsic viscosity 1.1, and a homo 3GT having a titanium oxide content of 1.5% by weight is 210 ° C. and 250 ° C. using an extruder. After melting at, the mixture was measured with a pump and poured into a known base at 250 ° C. in order to form a sea-island type composite form as shown in FIG. The composite weight ratio was 3GT7 with respect to polylactic acid 3. The passage time of each polymer for piping was 20 minutes for polylactic acid and 11 minutes for 3GT. Polyester B was filtered in two stages, and the first stage was a 15 μm stainless steel non-woven fabric filter, and the second stage was a 10 μm stainless steel non-woven filter. The yarn discharged from the base is cooled by the apparatus shown in FIG. 2 and applied with an oil agent, and then taken up by the first hot roller 8 heated to 55 ° C. at a speed of 2700 m / min. The film was drawn around the second hot roller 9 heated to 150 ° C. at a speed of / min, and stretched and heat set. Further, after drawing the two godet rollers 11 and 12 at 4200 m / min, the tension at the contact roll inlet is 0.13 cN / dtex, the contact roll speed is 4080 m, and the package winding speed is 4072 m / min, that is, overfeed. Was wound up as 1.0020 to obtain 8 island-in-sea composite fibers of 64 dtex-36 filaments. The property evaluation results of this composite fiber are as shown in Table 1, and the yarn forming property was good. Further, since the fiber shrinkage rate and the shrinkage stress value are sufficient, when it is made into a fabric, it has a high density and has excellent anti-penetration properties.

Example 2
As polyester B, a composite fiber was obtained under the same conditions as in Example 1 except that homo-3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 2.0% by weight was used. Furthermore, a fabric having excellent anti-penetration properties could be obtained.

Example 3
As polyester B, a composite fiber was obtained under the same conditions as in Example 1 except that homo-3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 6.0% by weight was used. Furthermore, a fabric with excellent anti-penetration properties could be obtained, and even thin fabrics had a sufficiently high anti-penetration effect.

Example 4
Example 1 except that the base was changed, a 70 island type sea-island composite base was used, and as polyester B, a homo 3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 3.0% by weight was used. A composite fiber was obtained under the following conditions. The fabric obtained from a fiber with a small number of islands and a fineness was also highly effective in see-through.

Example 5
Polyester B was melted separately as follows: Homo 3GT with an intrinsic viscosity of 1.1 and titanium oxide content of 0.3% by weight and Homo PET with an intrinsic viscosity of 0.6 and titanium oxide content of 5.0% by weight. A composite fiber was obtained under the same conditions as in Example 1 except that a blended and kneaded mixture at 5: 5 was used and one-stage filtration was performed using a 10 μm stainless steel nonwoven fabric filter. Although the shrinkage characteristics were slightly inferior to those of Example 4 due to the characteristics of PET, the see-through property was satisfactory.

Example 6
As polyester B, a homo 3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 0.3% by weight and a homo PET having an intrinsic viscosity of 0.6 and a titanium oxide content of 5.0% by weight in a chip state are 5 weight ratios. : A composite fiber was obtained under the same conditions as in Example 5 except that the mixture kneaded and melted at 5 and kneaded was used. Since the transmittance was good and there was some uneven dispersion of titanium oxide, a satisfactory fabric was obtained although the anti-penetration by sensory test was inferior to Example 5.

Example 7
As polyester B, a homo 3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 0% by weight and a homo PET having an intrinsic viscosity of 0.5 and a titanium oxide content of 50.0% by weight were separately melted, and a weight ratio of 1: A composite fiber was obtained under the same conditions as in Example 5 except that the one blended and kneaded in No. 9 was used. Since the composite ratio of 3GT is high, the characteristics of 3GT are fully utilized, and since the shrinkage characteristics are sufficient, a fabric with high anti-penetration properties can be obtained. Further, the yarn forming property was very good despite containing high concentration titanium oxide.
Example 8
Polyester B was melted separately as follows: Homo 3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 1.0% by weight and homo PET having an intrinsic viscosity of 0.6 and a titanium oxide content of 2.0% by weight. Two-stage filtration similar to Example 1 was performed using what was blended and kneaded at 5: 5. Other than that, composite fibers were obtained under the same conditions as in Example 1. Although the shrinkage characteristics were slightly inferior to those of Example 1 due to the characteristics of PET, the see-through property was still satisfactory.

Comparative Example 1
As polyester B, a composite fiber was obtained under the same conditions as in Example 1, except that homo-3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 1.0% by weight was used. Since the content of titanium oxide is low, satisfactory see-through properties were not obtained.

Comparative Example 2
As polyester B, a composite fiber was obtained under the same conditions as in Example 1 except that homo-3GT having an intrinsic viscosity of 1.1 and a titanium oxide content of 8.0% by weight was used. Titanium oxide content is high, titanium oxide agglomeration cannot be dispersed even when three-stage filtration is used, and the yarn-making property is inferior. The results were not significantly different from those in Example 3.

Comparative Example 3
As polyester B, homo-PET having an intrinsic viscosity of 0.6 and a titanium oxide content of 5.0% by weight was used, and the same procedure as in Example 1 was conducted except that a 10-μm stainless fiber nonwoven fabric filter was used. A composite fiber was obtained under the following conditions. Since the main component of the polyester B is PET, it is inferior in shrinkage properties, a high-density fabric cannot be obtained, and is inferior in see-through properties.

Comparative Example 4
A composite fiber was obtained under the same conditions as in Comparative Example 3 except that PET having an intrinsic viscosity of 0.6 obtained by copolymerizing 4.5 mol% of 5-sodium sulfoisophthalic acid was used as polyester A. After all, the shrinkage property was inferior, and satisfactory see-through property was not obtained.

Comparative Example 5
As a filtration of polyester B, a composite yarn was obtained under the same conditions as in Example 2, except that one-stage filtration was performed using a 10 μm stainless fiber nonwoven fabric filter. Thread breakage due to dispersibility and aggregation of titanium oxide occurred frequently, and it was not at a practical level. Furthermore, the see-through property was slightly lower than that of Example 2.

Comparative Example 6
The yarn was produced under the same conditions as in Example 5 except that the mixer was removed and kneading was not performed, but the yarn-making property was inferior and there was uneven dispersion of titanium oxide, which was partially transparent when made into a fabric. Was seen and was not satisfactory.

Comparative Example 7
The yarn was produced under the same conditions as in Example 6 except that the mixer was removed and kneading was not performed, but the yarn production was also inferior and there was uneven dispersion of titanium oxide. As a result, she could see through and was not satisfied.

An example of a sea-island type composite fiber cross section is shown. An example of a spinning process (direct spinning drawing method) is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Area | region which consists of a polymer which has a polytrimethylene terephthalate as a main component 2 Area | region which consists of a polymer which has a polylactic acid as a main component 3 Base 4 Yarn cooling air blower 5 Oil supply device 6 Entanglement device 7 First hot roll 8 Second hot Roll 9 Entangling device 10 Gode roll 11 Gode roll 12 Contact roll 13 Package

Claims (5)

  A composite fiber composed of a polyester A containing polylactic acid as a main component and a polyester B containing polytrimethylene terephthalate as a main component, the polyester A occupying the entire surface of the fiber, and the amount of titanium oxide contained in the polyester B is 1 A sea-island type composite fiber, characterized in that it is 5 to 7.0% by weight.   2. The sea-island composite fiber according to claim 1, wherein the polyester B comprises polytrimethylene terephthalate containing 0 to 1.0% by weight of titanium oxide and polyester C containing 2 to 60% of titanium oxide.   The production of the sea-island type composite fiber according to claim 1, wherein the multi-stage filtration is performed at least twice in the process from melting the polyester B to discharging it from the die hole. Method.   A process for producing a sea-island type composite fiber according to claim 2, wherein polytrimethylene terephthalate and polyester C are separately melted and then kneaded in a molten state to obtain polyester B.   A sea-island type characterized in that, when the sea-island type composite fiber according to claim 2 is produced, polytrimethylene terephthalate and polyester C are mixed before melting, and the mixed chip is melted and kneaded in a molten state to form polyester B. A method for producing a composite fiber.

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