JP2005120528A - Polylactic acid-based hydrophilic fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based hydrophilic fiber having sufficient water absorption and moisture-absorbing and releasing properties derived from a hydroxy group while being a synthetic fiber, usable in various kinds of applications, and not requiring incineration or the disposal as an industrial waste at the disposal after use because of having biodegradability. <P>SOLUTION: The polylactic acid-based hydrophilic fiber comprises a polylactic acid-based resin containing a modified polyvinyl alcohol resin. The polylactic acid-based hydrophilic fiber is a core-sheath type conjugate fiber in which the core part or the sheath part comprises the polylactic acid-based resin containing the modified polyvinyl alcohol resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polylactic acid-based hydrophilic fiber comprising a polylactic acid-based resin containing a modified polyvinyl alcohol resin and having hydrophilicity, hygroscopicity, moisture release, and biodegradability.

  Conventionally, various fibers have been proposed in the field of apparel, daily life, and industrial materials as fibers obtained by imparting hydrophilicity, hygroscopicity, and moisture release properties to synthetic fibers.

  For example, Patent Document 1 proposes a polyamide fiber in which polyvinyl pyrrolidone or polyether ester amide is contained in polyamide to exhibit moisture absorption / release properties (having moisture absorption and moisture release properties). Further, Patent Document 2 proposes a fiber in which a thermoplastic water-absorbing resin composed of a crosslinked product of polyethylene oxide is contained in polyamide or polyester to exhibit moisture absorption and desorption.

  However, since the hygroscopic component contained in these fibers does not have a hydroxyl group, these fibers do not have the water-absorbing and hygroscopic properties derived from hydroxyl groups like natural fibers. Depending on the intended use, water absorption and moisture absorption / release performance may be insufficient.

  Moreover, since these do not have biodegradability, they had to be incinerated at the time of disposal or treated as industrial waste.

On the other hand, Patent Document 3 proposes a fiber that exhibits moisture absorption / release properties by kneading a thermoplastic water-absorbing resin composed of a crosslinked product of polyethylene oxide into a biodegradable aliphatic polyester. Since the thermoplastic water-absorbing resin composed of a cross-linked product of oxide does not have biodegradability, it remains after the aliphatic polyester is decomposed, and also in this fiber, the moisture-absorbing and releasing component does not have a hydroxyl group. It does not have water-absorbing and moisture-absorbing / releasing properties derived from a hydroxyl group like natural fibers, and depending on the application to be used, the water-absorbing and moisture-absorbing / releasing properties may be insufficient.
JP-A-7-150414 JP-A-8-260244 JP-A-9-95823

  The present invention solves the problems as described above, has a sufficient water absorption and moisture absorption and desorption performance derived from hydroxyl groups while being a synthetic fiber, and can be used for various applications, and after use. Has a technical problem to provide a polylactic acid-based hydrophilic fiber that is biodegradable and therefore does not need to be incinerated at the time of disposal or treated as industrial waste.

The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.
That is, the gist of the present invention is a polylactic acid-based hydrophilic fiber comprising a polylactic acid-based resin containing a modified polyvinyl alcohol resin.

  Since the polylactic acid-based hydrophilic fiber of the present invention contains a modified polyvinyl alcohol having a hydroxyl group as a water-absorbing substance, it can be a hydrophilic fiber with improved water absorption and moisture absorption / absorption, and sweat absorption and moisture absorption. It has excellent physical properties and also has physical properties such as practical strength and elongation. For this reason, it can be used in various fields such as clothing, inner construction, socks, ski wear, civil engineering construction materials, and marine products. It becomes possible to use it. Furthermore, since it is biodegradable, it is biodegraded in water or in the soil after use, so there is no need to incinerate or treat it as industrial waste at the time of disposal.

Hereinafter, the present invention will be described in detail.
First, as a polylactic acid-based resin as a main component constituting the fiber of the present invention, poly L-lactic acid, poly D-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or these A mixture can be suitably used, and the number average molecular weight is preferably 30,000 to 150,000, more preferably 90,000 to 110,000.

  When the number average molecular weight is less than 30,000, not only fiberization by melt extrusion becomes difficult, but also the mechanical strength of the fiber tends to decrease. Further, even when the number average molecular weight exceeds 150,000, melt extrusion may be difficult.

  The polylactic acid in the present invention may contain a small amount of chain extender, for example, an organic peroxide, a bisoxazoline compound, a diisocyanate compound, an epoxy compound, an acid anhydride, etc. for the purpose of increasing the molecular weight. Good.

  Furthermore, the polylactic acid in the present invention may be blended with an aliphatic-aromatic copolymer polyester in order to impart flexibility to the fiber. That is, polylactic acid has a property that it is hard and brittle at room temperature, but flexibility can be imparted by using it together with an aliphatic-aromatic copolymer polyester. At this time, by blending the aliphatic-aromatic copolymer polyester, considering the provision of flexibility and the decrease in strength, (polylactic acid) / (aliphatic-aromatic copolymer polyester) = 95 in mass ratio. It is preferable to blend at a ratio of / 6 to 50/50 (mass%). The aliphatic-aromatic copolymer polyester is a copolymer polyester having at least an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and an aliphatic diol as constituent components, and the glass transition temperature thereof is 0 ° C. or less. Preferably, it is −20 ° C. or lower.

  Examples of the aliphatic dicarboxylic acid constituting such an aliphatic-aromatic copolymer polyester include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like. Furthermore, examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like.

  Then, by selecting and polycondensing at least one or more of these, the desired aliphatic-aromatic copolymer polyester can be obtained, and if necessary, isocyanate, acid anhydride, epoxy compound, organic peroxide The jump-up and long-chain branching can be given structurally using the above. In addition, a urethane bond, an amide bond, an ether bond, or the like may be introduced as long as the biodegradability is not affected.

  In the present invention, the polylactic acid-based resin as described above includes various inorganic particles such as titanium oxide, silicon oxide, calcium carbonate, silicon nitride, clay, talc, and crosslinked polymer particles, if necessary. In addition to particles such as various metal particles, conventionally known antioxidants, antioxidants, anti-coloring agents, light-proofing agents, inclusion compounds, anti-static agents, various coloring agents, various surfactants, various reinforcing fibers, etc. Various additives may be added within a range not impairing the effects of the present invention.

  The fiber of the present invention is a polylactic acid resin containing a modified polyvinyl alcohol resin as described above, but the modified polyvinyl alcohol resin may be blended and contained in the polylactic acid resin. preferable. That is, it is preferable that the modified polyvinyl alcohol resin is not uniformly present in the polylactic acid-based resin, but is substantially uniformly mixed in the polylactic acid-based resin. The fiber is preferably a fiber obtained by spinning such a blend. Thereby, it can prevent that a modified polyvinyl alcohol resin peels off and elutes from a fiber, and durability of water absorption and moisture absorption / release property improves.

  And it is preferable that content of modified polyvinyl alcohol shall be 3-40 mass% with respect to fiber mass, and also 5-30 mass%. When the content is less than 3% by mass, it is difficult to obtain a fiber having sufficient water absorption and moisture absorption / release properties. On the other hand, if it exceeds 40% by mass, it is not preferable because the yarn-making property is inferior and the physical properties such as the strength and elongation tend to be lowered.

  Next, the modified polyvinyl alcohol resin contained in the fiber of the present invention is preferably an oxyalkylene group-containing polyvinyl alcohol. Specifically, oxyalkylene group-containing polyvinyl alcohol is a copolymer of vinyl acetate and polyoxyalkylene (meth) allyl ether such as polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, It is then obtained by saponification. In this case, the copolymerization ratio (content) of the polyoxyalkylene (meth) allyl ether is preferably 0.1 to 20 mol%, more preferably 0.1 to 5 mol%. The degree of condensation of the polyoxyalkylene is 1 to 300, preferably 3 to 50, and the proportion of oxyalkylene units in the entire oxyalkylene group-containing polyvinyl alcohol is preferably 3 to 40% by mass. This indicates that there is an optimum range for the degree of localization-delocalization of oxyalkylene units and the length of oxyalkylene units in the copolymer.

  The saponification degree of vinyl acetate units in the oxyalkylene group-containing polyvinyl alcohol is preferably 50 to 100 mol%, more preferably 70 to 99 mol%, and the average polymerization degree of polyvinyl alcohol is preferably 150 to 1500, and more preferably 200 to 1000. In addition, components other than polyoxyalkylene (meth) allyl ether may be contained as a copolymerization component as long as the object of the present invention is not impaired. For example, α-olefin (ethylene, propylene, long chain α-olefin, etc.) , Ethylenically unsaturated carboxylic acid monomers (acrylate, methacrylate, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl ether, etc.) may be contained as long as they are about 30 mol% or less.

  As the polymerization method for obtaining the oxyalkylene group-containing polyvinyl alcohol, a solution polymerization method is usually employed, and in some cases, a suspension polymerization method, an emulsion polymerization method or the like can also be employed. As the saponification reaction, an alkali saponification method, an acid saponification method or the like is employed.

  In addition to the above, polyvinyl alcohol containing oxyalkylene group includes vinyl acetate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamide, polyoxypropylene allylamide, polyoxyethylene vinylamide, polyoxypropylene vinylamide Etc. can be obtained by copolymerization and then saponification.

  In addition, the oxyalkylene group-containing polyvinyl alcohol can also be obtained by reaction of alkylene oxide with polyvinyl alcohol, or polymerization of vinyl acetate with polyoxyalkylene glycol and subsequent saponification.

  The oxyalkylene group-containing polyvinyl alcohol thus obtained is further one of (1) a phenol compound having a melting point of 50 to 250 ° C., (2) a thioether compound, and (3) a phosphite compound. The above is preferably added in an amount of 0.01 to 5.0 mass%, particularly 0.1 to 0.5 mass% with respect to the oxyalkylene group-containing polyvinyl alcohol. Thereby, thermal stability can be improved. If the amount added is less than 0.01% by mass, improvement in thermal stability cannot be expected, and if it exceeds 5.0% by mass, the hydrophilicity tends to decrease.

  (1) Phenol compounds having a melting point of 50 to 250 ° C. include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4′-thiobis- (6 -T-butylphenol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxy Phenylpropionate] methane, octadecyl-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate, 4,4′-thiobis- (6-tert-butylphenol), N, N ′ Hexamethylene-bis (3,5-di-t-butyl-4'-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t -Butyl-4-hydro Cibenzyl) benzene, pentaerythryl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,1,3-tris (2-methyl-4-hydroxy-5-t) -Butylphenyl) butane and the like.

  (2) As thioether compounds, pentaerythritol-tetrakis- (β-laurylthiopropionate), tetrakis [methylene-3- (dodecylthio) propionate] methane, bis [2-methyl-4- {3-n- Alkylthiopropionyloxy} -5-t-butylphenyl] sulfide and the like.

  (3) Phosphite compounds include triphenyl phosphite, tris (p-nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, diphenylisooctyl phosphite, diphenylisodecyl Phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, triisooctyl phosphite, tristearyl phosphite, other tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylenephosphonite And di (2,4-di-t-butylphenyl) pentaerythritol diphosphite.

  Furthermore, the oxyalkylene group-containing polyvinyl alcohol in the present invention includes (4) at least one of fatty acids having 10 or more carbon atoms or salts thereof, fatty acid amide compounds, and fatty acid ester compounds, and oxyalkylene group-containing polyvinyl alcohols. It is preferable to add 0.01 to 3.0% by mass, particularly 0.1 to 0.5% by mass, and the thermal stability is further improved.

  (4) Fatty acids having 10 or more carbon atoms or salts thereof are higher fatty acids such as lauric acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, arachidinic acid, behenic acid, erucic acid, hydroxystearic acid, hydroxyricinol Examples thereof include hydroxy fatty acids such as acids, and metal salts such as magnesium, calcium, strontium, barium, and zinc, among which stearic acid, magnesium stearate, calcium stearate, and magnesium behenate are practical. The fatty acid amide compound (4) is a fatty acid amide such as stearic acid amide, palmitic acid amide, oleic acid amide, behenic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide or the like. An alkylene bis fatty acid amide is mentioned. Furthermore, fatty acid ester compounds include fatty acid esters of monohydric alcohols such as butyl stearate and butyl palmitate, and fatty acid esters of polyhydric alcohols such as ethylene glycol monostearate.

  As a method of adding the compounds (1) to (4) to the oxyalkylene group-containing polyvinyl alcohol, a conventional method, that is, a melt can with a stirrer, an extruder, a roll kneader, etc. Is preferable. The melt mixing temperature is preferably 160 to 250 ° C, more preferably 180 to 230 ° C.

  As described above, when the modified polyvinyl alcohol resin is added and mixed in the polylactic acid resin, after preparing pellets containing various components in the modified polyvinyl alcohol, added to the polylactic acid resin, Although it may be melt-mixed, each component of (1) to (4) is not a pellet that has been previously melt blended in modified polyvinyl alcohol, modified polyvinyl alcohol resin, each component of (1) to (4), A polylactic acid resin may be added and directly melt mixed.

  In addition, other polymers can be blended in the modified polyvinyl alcohol resin as long as the effects of the invention are not impaired, and various additives such as plasticizers, fillers, colorants, and stabilizers are blended. You can also

  Furthermore, the fiber of the present invention may be a core-sheath type composite fiber. In this case, either the core part or the sheath part is made of a polylactic acid resin containing a modified polyvinyl alcohol resin. And it is preferable that the other core part or sheath part which does not contain modified polyvinyl alcohol resin shall consist of polylactic acid-type resin.

  When the modified polyvinyl alcohol resin is contained in the polylactic acid resin in the core or sheath of the composite fiber, it is preferable to contain 3 to 50% by weight of the modified polyvinyl alcohol resin in the mass of the core or sheath. Moreover, it is preferable that the core-sheath composite ratio (mass ratio) is core / sheath = 80/20 to 20/80.

  When the core-sheath composite ratio and the content of the modified polyvinyl alcohol are outside the above ranges, it is difficult to obtain a fiber having sufficient water absorption and moisture absorption / release properties, or the yarn-making property is inferior, such as high elongation. The physical property value tends to decrease, which is not preferable.

  The modified polyvinyl alcohol and polylactic acid constituting the fiber of the present invention are both biodegradable, and the biodegradation rate of the modified polyvinyl alcohol is slightly slower than that of polylactic acid, but the product using the fiber of the present invention After being used, it is completely decomposed after a certain period of time if it is left in an environment (in the soil or in water) where microorganisms exist.

  The fiber of the present invention may be either a multifilament or a monofilament, and the cross-sectional shape of the single fiber constituting the fiber may be any, for example, a circle, an ellipse, a triangle, a multileaf shape, a square, a rectangle, a rhombus, a saddle type , Horseshoe type and the like can be mentioned, and these shapes may be partially changed. These various cross-sectional fibers can be used in appropriate combination.

  When the fiber of the present invention is a multifilament, the fineness of the single yarn constituting the multifilament is preferably 3.3 to 22 dtex, and the total fineness of the multifilament is preferably 55 to 2200 dtex.

  When the fiber of the present invention is a monofilament, the single yarn fineness is preferably 55 to 1100 dtex, more preferably 220 to 670 dtex, from the viewpoints of bundling property, durability and weaving property.

  And the fiber of this invention can be used conveniently for both a clothing use and an industrial material use. And it can be used as a woven or knitted fabric or a non-woven fabric, or it can be used as a net by making a net, or it can be made into a rope or the like by making a string. At this time, it is preferable to use a product of 100% of the fiber of the present invention, but it may be used after knitting, weaving, or twisting with other fibers depending on the application. In view of the biodegradability of the product obtained, it is preferable to use biodegradable fibers as other fibers.

  Moreover, when using as an industrial material using the characteristic of the fiber of this invention, it is especially suitable for a fishery material use. In other words, by containing the modified polyvinyl alcohol resin, it has excellent hydrophilicity derived from hydroxyl groups, and has good adhesion to laver and seaweeds, thereby improving the adhesion and growth of these spores. The yield is improved. When using for such a use, when setting it as a core-sheath composite fiber, it is preferable that the modified polyvinyl alcohol resin contains in a sheath part.

  As described above, when the net of the present invention is used to net aquaculture nets such as seaweeds and laver, a plurality of the nets of the present invention can be used in a concentrated manner. Depending on the purpose such as adhesion of seaweeds, thinning properties of seaweed spores and adjustment of specific gravity, they may be used by twisting with biodegradable fibers other than the present invention. In this case, it is preferable that the polylactic acid fiber of the present invention is used at 30% or more of the total fineness of the net yarn.

Next, the manufacturing method of the fiber of this invention is demonstrated.
The polylactic acid-based resin containing the modified polyvinyl alcohol resin obtained as described above can be produced using a conventional melt spinning apparatus. In the case of a core-sheath type composite fiber, it can be produced using a conventional composite fiber spinning device.

  In the case of a multifilament, first, melt spinning is performed from a usual spinning device, the melt-spun yarn is cooled by a cooling device, a spinning oil is applied, and the undrawn yarn is taken up by a take-up roller. The temperature and air volume of the cooling air, the speed of the take-up roller, etc. are not particularly limited and are appropriately selected. A two-step method in which the unstretched yarn is once wound and then stretched, a method of obtaining a highly oriented unstretched yarn by winding at a high speed without stretching the yarn, and a direct spinning stretch method in which the yarn is continuously stretched without being scraped. To obtain the desired fiber. When stretching, it can be performed by a single-stage or two-stage or more multi-stage stretching method. The stretching method, stretching temperature, stretching ratio, etc. are the type of polymer constituting the fiber, the desired strength and elongation characteristics, etc. Is selected appropriately. The stretched yarn is subjected to heat treatment or relaxation treatment as necessary.

  In the case of monofilaments, melt spinning is performed from a conventional spinning device, the spun monofilament is cooled with a liquid or the like, and then the cooled and solidified monofilament is once wound or stretched without being wound. Stretching can be performed in a single stage or multiple stages including two or more stages. After stretching, it is subjected to relaxation heat treatment in a gas and wound up.

Hereinafter, the present invention will be described specifically by way of examples. Various characteristic values in the examples were measured and evaluated as follows.
A. Fiber strength (cN / dtex) and elongation (%): Measured according to JIS L-1013 using Shimadzu Autograph DSS-500 at a grip interval of 25 cm and a tensile speed of 30 cm / min.
B. Moisture absorption / release (%): Sample obtained by knitting the obtained fiber into a knitted fabric with a basis weight of 150 g / m ² using an interlock structure using a 33 "28G circular knitting machine (LPJ-H type manufactured by Fukuhara Seiki Co., Ltd.) This was dried for 2 hours at a temperature of 105 ° C. and the mass W0 was measured, and the sample was conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and the mass W1 was measured. The initial moisture content M0 was determined from the equation (1), and then the sample was allowed to absorb moisture for 24 hours under conditions of a temperature of 34 ° C. and a relative humidity of 90%, and then the mass W2 was measured. After that, the sample was left to stand for another 24 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then the mass W3 was measured, and the moisture content M2 after moisture release was calculated according to the following equation 3). Asked.
M0 (%) = [(W1-W0) / W0] × 100 1)
M1 (%) = [(W2-W0) / W0] × 100 2)
M2 (%) = [(W3-W0) / W0] × 100 3)
C. Water absorption (cm): Using a 33 "28G circular knitting machine (LPJ-H type, manufactured by Fukuhara Seiki Co., Ltd.), the obtained fiber is knitted into a knitted fabric having a basis weight of 150 g / m ² using an interlock structure. The sample was conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then the water after 10 minutes according to the Bilec method described in JIS L-1907 (Textile Absorption Test Method). The wicking height was measured.
D. Number of spores attached: Cut the obtained fiber into 5cm length to make a sample yarn, put a beaker with water and seaweed spores in an incubator maintained at 18 ° C, and put it in the sea water in the beaker Suspend the entire length of the sample yarn in the seawater in the beaker, irradiate 3000 lux light for 10 hours a day, repeat this for 1 week to attach the laver spores, The number of spores in one visual field when observed under a microscope at a magnification of 100 was counted in total, and the number of spores per visual field was determined as an average value to obtain the number of spores attached.
E. Spore remaining rate: The obtained fiber was cut to a length of 5 cm to obtain a sample yarn, and the sample yarn to which the spore was adhered by the method D above and 300 cc seawater were placed in a 500 cc beaker, and 300 rpm with a magnetic stirrer. For 2 weeks. Thereafter, a total of 10 spores in one visual field when the sample yarn surface was observed under a microscope at a magnification of 100 times were counted, and the number of spores per visual field was determined as an average value to obtain the number of remaining spores. The spore residual rate (calculated by the following formula) was determined from the ratio of the number of residual spores to the number of spores attached.
Spore remaining rate (%) = (number of remaining spores / number of adhered spores) × 100

Reference example <Method for producing modified polyvinyl alcohol resin>
After polyoxyethylene (meth) allyl ether having an average degree of condensation of oxyalkylene of 20 and vinyl acetate are copolymerized in methanol in the presence of azobisisobutyronitrile, and then the residual monomer is driven out, sodium hydroxide is added. Was saponified by adding a methanol solution. The copolymer is separated from the slurry produced by the saponification reaction, washed with methanol three times, and then added with 1.5 mol of acetic acid per mol of sodium acetate, and then washed again with methanol twice. The sodium acetate content was adjusted to 0.07% by mass and 0.026% by mass acetic acid (0.5 mol with respect to 1 mol of sodium acetate), and then dried to obtain an oxyalkylene group-containing polyvinyl alcohol resin (hereinafter referred to as “polyvinyl alcohol resin”) Abbreviated as EO-PVA).
The average degree of polymerization of this polymer is 270, the copolymerization ratio of the polyoxyethylene (meth) allyl ether unit is 1.0 mol%, the ratio of the oxyalkylene unit in the whole polymer is 16.1% by mass, the vinyl acetate component The degree of conversion was 96 mol%, the sodium acetate content was 0.07 mass%, and the acetic acid content was 0.026 mass%.
0.3 mass% of pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] having a melting point of 120 ° C. is added to the EO-PVA obtained above as a phenol compound. Then, it was supplied to a twin screw extruder equipped with a round die and extruded at a temperature of 210 ° C. to obtain a pellet-like modified polyvinyl alcohol resin.

Example 1
Polylactic acid having a melting point of 167 ° C., a molar ratio of D-lactic acid to L-lactic acid of D / L = 1.2 / 98.8, and a number average molecular weight of 99600 (manufactured by Cargill Dow, Nature Works) and the above reference example The modified polyvinyl alcohol obtained in (1) is dry blended so that the content of the modified polyvinyl alcohol is 20% by mass, continuously fed to a single-screw extruder, and is spun for a circular cross-section yarn through a spinning pack by a conventional method. It was melt spun from the die. At this time, the spinning temperature was 210 ° C., a 36-hole composite spinning die was used, the melt-spun yarn was cooled by blowing air at 15 ° C. with a cooling device, and after applying an oil agent, 1500 m / Taken with a take-up roller at a temperature of 90 ° C. at a speed of minutes, and then stretched 3.1 times on a final drawing roller at a temperature of 110 ° C. and wound at a speed of 4500 m / min, with a total fineness of 83 dtex and a filament count of 36 A multifilament with a round cross section was obtained.

Example 2
Polylactic acid having a melting point of 167 ° C., a molar ratio of D-lactic acid to L-lactic acid of D / L = 1.2 / 98.8, and a number average molecular weight of 99600 as a core component (manufactured by Cargill Dow, Nature Works) Using. As the sheath component, the same blend of polylactic acid and modified polyvinyl alcohol as in Example 1 was used. Then, except that a composite spinning apparatus having a spinneret having 36 spinning holes was used so that the core component and the sheath component had a mass ratio of (core component) / (sheath component) = 70/30. The same procedure as in Example 1 was performed to obtain a multifilament having a total fineness of 83 dtex, a filament count of 36, and a round cross section.

Comparative Example 1
The same as in Example 1 except that only polylactic acid having a melting point of 167 ° C., a molar ratio of D-lactic acid to L-lactic acid of D / L = 1.2 / 98.8, and a number average molecular weight of 99600 was used. A multifilament having a total fineness of 83 dtex and a filament count of 36 was obtained.

  Table 1 shows the results of measurement and evaluation of the strength, elongation, hygroscopicity, water absorption, spore adhesion number, and spore residual rate of the multifilaments obtained in Examples 1 and 2 and Comparative Example 1.

As is clear from Table 1, the fibers obtained in Examples 1 and 2 had sufficient strength and elongation, and were excellent in both moisture absorption and desorption and water absorption. Furthermore, the number of adhering laver spores and the spore survival rate were high, making them suitable for use in laver nets.
On the other hand, since the fiber of Comparative Example 1 was a fiber not containing modified polyvinyl alcohol, it did not have both moisture absorption and desorption properties and water absorption properties. Furthermore, the number of laver spores attached and the spore survival rate were low, and it was not suitable for use as a laver net.

Claims (2)

A polylactic acid-based hydrophilic fiber comprising a polylactic acid-based resin containing a modified polyvinyl alcohol resin. 2. The polylactic acid-based hydrophilic fiber according to claim 1, wherein the fiber is a core-sheath type composite fiber, wherein the core part or the sheath part is made of a polylactic acid-based resin containing a modified polyvinyl alcohol resin.