JP4609091B2 - Polylactic acid fiber - Google Patents

Description

  The present invention relates to a binder fiber that is easy to manufacture and whose durability is dramatically improved by subsequent melt molding.

  In general, aliphatic polyesters are easily hydrolyzed, and further, thermal decomposition proceeds in heat treatment, resulting in a problem that durability is insufficient in actual use. On the other hand, a technique is known in which a terminal reactive agent is added to an aliphatic polyester to increase the molecular weight of the entire resin to improve durability. For example, Patent Document 1 discloses a specific polyfunctional aziridine compound. Techniques for reacting and crosslinking are disclosed. However, in this method, when melt spinning using an aliphatic polyester to which a polyfunctional aziridine compound is added and fiberized, the cross-linked product has already been formed, so that elongation deformation on the spinning line is inhibited. Fluidity and stringiness will be insufficient. Furthermore, in melt spinning, the resin and chemicals react to a high degree because of the length of time from the melting of the molten resin to fiberization, the so-called residence time. In ordinary melt spinning, the pipe pressure of the melt molding machine and the spinning pack are used. The pressure of the nozzle became too high, and the resin could not be discharged stably from the nozzle. For this reason, it has been difficult to stably fiberize the above technique.

  Moreover, as a means for suppressing the reaction at the time of melting, Patent Document 2 discloses a technique of adding a crosslinkable monomer that reacts with active energy rays into a resin. In this technique, it becomes possible to eliminate the poor fluidity in melt molding, and the resulting molded product can be made high molecular weight by irradiating active energy rays such as X-rays or electron beams. However, the method using active energy rays is expensive due to the high introduction cost of the irradiation device. Furthermore, the safety restrictions are large for X-rays and the work is complicated, and there is a problem of the irradiation depth for electron beam irradiation. The final product could not be provided at a low price because the shape of the molded body was considerably restricted.

  Further, there is a method of obtaining a high-molecular-weight heat-adhesive fiber by reducing the amount of the terminal reactive drug added and arranging an aliphatic polyester to which the drug is added to the core part or the sheath part of the core-sheath composite fiber or the like It is described in Patent Document 3. However, as described above, it is very difficult to mold a resin in which the weight average molecular weight of the aliphatic polyester is 200,000 or more by adding a chemical. Patent Document 3 is characterized in that the core portion and the sheath portion have a melting point difference. However, in a binder fiber having a melting point difference of 20 ° C. or more between the core portion and the sheath portion, for example, the core portion has a high melting point and the sheath portion. In the case where the melting point is low, when the melt molding is performed at a high temperature in accordance with the melting point of the core part, the sheath part having a low melting point is deteriorated by heat. In addition, when melt molding is performed at a low temperature in accordance with the low melting point sheath, the high melting point component disposed in the core does not flow sufficiently, resulting in insufficient strength of the molded body.

Because of these problems, the conventional technique has a good spinnability, and a high molecular weight molded article cannot be obtained by melt-molding the obtained fiber.
Japanese Patent Application Laid-Open No. 07-90071 Japanese Patent Laid-Open No. 10-147720 Japanese Patent Laid-Open No. 06-248516

  The present invention is intended to provide a binder fiber that is easy to manufacture and whose durability is dramatically improved by subsequent melt molding.

The problem of the present invention is that the solution specific viscosity (ηr) after performing the pressure heat treatment at a pressure of 1.5 MPa for 2 minutes at 220 ° C. is 1.05 to 4 times that before the heat treatment , and the functional group Theoretical addition of reacting the total amount of COOH end group-reactive and / or OH end group-reactive agent C having two or more with respect to COOH end group concentration and / or OH end group concentration of polylactic acid based on The resin A to which 5 times or more of the amount is added and the resin B mainly composed of polylactic acid not substantially containing the drug C are combined, and the difference in melting point between the resin A and the resin B is 20 ° C. Achieved by polylactic acid fiber characterized by being less than.

  According to the present invention, it is possible to obtain a binder fiber that is easy to manufacture and whose durability is dramatically improved by subsequent melt molding.

  The resin used for the fiber of the present invention is polylactic acid. Among these, polylactic acid is mainly composed of L-lactic acid and / or D-lactic acid because of its high heat resistance and excellent properties such as mechanical properties and biodegradability.

  In the method for producing polylactic acid used in the present invention, L-lactic acid, D-lactic acid, and DL-lactic acid (racemic) are used as raw materials to once generate lactide which is a cyclic dimer, and then ring-opening polymerization is performed 2 A two-stage lactide method and a one-stage direct polymerization method in which the raw material is directly subjected to dehydration condensation in a solvent are known.

  Polylactic acid may be obtained by any production method, but in the case of a polymer obtained by the lactide method, the cyclic dimer contained in the polymer is vaporized at the time of molding, and at the time of melt spinning, yarn irregularities are produced. It causes the reaction and reacts with unreacted chemicals and inhibits high molecular weight, so the content of the cyclic dimer contained in the polymer at the stage of molding or before melt spinning is 0.5 wt. % Or less, and more preferably 0.3 wt% or less.

  Further, in the case of the direct polymerization method, there is substantially no problem due to the cyclic dimer, so that it is more preferable from the viewpoint of moldability or yarn production. The weight average molecular weight of the polylactic acid of the present invention is preferably 100,000 to 300,000, more preferably 150,000 to 250,000. When the weight average molecular weight is in such a range, the strength properties when formed into a molded article such as a fiber or a film can be improved. Furthermore, by using polylactic acid having a molecular weight adjusted within this range as a raw material, the amount of drug C added to improve durability can be relatively reduced. For example, when polylactic acid having a weight average molecular weight of 10,000 is used as a starting material and when polylactic acid having a weight average molecular weight of 100,000 is used as a starting material, it generally depends on the concentration of end groups. The theoretical addition amount of the drug C is greatly different. That is, by setting the concentration of the drug C added to the resin to a relatively low concentration, it is preferable from the viewpoint of suppressing the cost of the drug C and suppressing the bleeding out of the drug C. In general, it is difficult to make the polylactic acid have a weight average molecular weight of 300,000 or more only by the polymerization step.

  Further, the value obtained by dividing the weight average molecular weight of polylactic acid by the number average molecular weight, that is, the degree of dispersion of the polymer is preferably 2.0 or less. When the degree of dispersion is 2.0 or less, a product having excellent durability obtained by uniformly reacting the molded product after the crosslinking reaction can be obtained. The degree of dispersion is more preferably 1.8 or less, and most preferably 1.7 or less. The degree of dispersion can be adjusted to the above range by a method of removing a low molecular weight compound, that is, a residual monomer during the polymerization reaction by a solvent extraction operation or the like.

  A lower COOH end group concentration is preferable because the heat resistance of the resin is improved, but it is generally difficult to obtain a COOH end group concentration of 5 equivalent / t or less only by polycondensation of aliphatic polyester. The preferable range of the COOH end group concentration is 5 to 50 equivalent / t, and more preferably 7 to 45 equivalent / t.

  The polylactic acid used in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other monomer components having ester forming ability in addition to L-lactic acid and D-lactic acid. Examples of copolymerizable monomer components include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, and other hydroxycarboxylic acids, as well as ethylene glycol, propylene glycol, and butane. Compounds containing a plurality of hydroxyl groups in the molecule such as diol, neopentyl glycol, polyethylene glycol, glycerin, pentaerythritol or derivatives thereof, succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2 , 6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid and the like, or compounds containing a plurality of carboxylic acid groups in the molecule. In order to reduce the melt viscosity of polylactic acid, aliphatic polyester polymers such as polycaprolactone, polybutylene succinate, polyethylene succinate and polyhydroxybutyrate can be used as an internal plasticizer or as an external plasticizer. .

  Furthermore, it is known that the polylactic acid used in the present invention forms a stereocomplex crystal of poly-L lactic acid mainly composed of L-lactic acid and poly-D lactic acid mainly composed of D-lactic acid. The stereocomplex crystal is known to have an improved melting point as compared to poly L-lactic acid or poly-D lactic acid alone resin, and is also known to improve chemical resistance due to the increased crystal perfection. . In order to improve the heat resistance and chemical resistance after melting, it is preferable to use this technique. The mixing ratio of poly L lactic acid and poly D lactic acid is preferably 30/70 to 70/30 for the formation of stereocomplex crystals. Furthermore, the difference in weight average molecular weight between poly L lactic acid and poly D lactic acid is preferably 100,000 or less. When the difference in weight average molecular weight is 100,000 or less, the difference in melt viscosity between poly-L lactic acid and poly-D lactic acid is small, and poly-L lactic acid and poly-D lactic acid are sufficiently mixed, so that the formation of a stereo complex proceeds smoothly. Preferably, when the difference in weight average molecular weight is 10,000 or more, the stress at the time of spinning is concentrated on the molecular chain having a large weight average molecular weight in poly L lactic acid or poly D lactic acid. Orientation proceeds in a form that follows. That is, it is preferable because a precursor that can easily form a stereocomplex crystal can be formed. From these, the difference in weight average molecular weight is more preferably in the range of 10,000 to 100,000, and more preferably in the range of 10,000 to 50,000.

  The polylactic acid resin used in the present invention may contain a component other than the aliphatic polyester as long as the effects of the present invention are not impaired and the spinnability is not impaired. For example, plasticizers, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, yarn friction reducing agents, mold release agents, antioxidants, ion exchange agents, or coloring Examples of the pigment include inorganic fine particles, such as titanium oxide, calcium carbonate, clay, bentonite, diatomaceous earth, mica, sericite, and talc, and an organic compound may be added as necessary.

  In particular, polylactic acid fibers generally have poor wear resistance, so peeling, scraping, fibrillation, etc. at contact points such as yarn path guides, needles, cards, rollers, heaters, and pins installed in various processes May occur, and there is a concern that process passability is deteriorated. Therefore, it is preferable to avoid these problems by reducing yarn friction. The yarn friction reducing agent added to polylactic acid is not limited as long as it is stable to heat, does not react with OH end groups or COOH end groups of polylactic acid, and reduces yarn friction. However, fatty acid amides and / or fatty acid esters are preferably used. Of these compounds, fatty acid bisamides and alkyl-substituted fatty acid monoamides are preferably used. Fatty acid bisamides and alkyl-substituted fatty acid monoamides are less reactive than amides of ordinary fatty acid monoamides, so that they do not easily react with polylactic acid during melt molding, and are also heat resistant due to their high molecular weight. It is high and hardly sublimates by melt molding, so that it exhibits excellent slipperiness when it is made into a fiber without impairing the function as a lubricant.

  Examples of the fatty acid amide preferably used in the present invention include lauric acid amide, palmitic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, methylol stearic acid amide, methylol behenic acid amide, dimethylol oil amide, and dimethyl laurin. A compound having two amide bonds in one molecule, such as acid amide, dimethyl stearamide, saturated fatty acid bisamide, unsaturated fatty acid bisamide, aromatic bisamide, etc., for example, methylene biscaprylic amide, methylene biscapric amide , Methylene bis lauric acid amide, methylene bis myristic acid amide, methylene bis palmitic acid amide, methylene bis stearic acid amide, methylene bis isostearic acid amide, methylene bis behenic acid amide, methylene bis Oleic acid amide, methylene biserucic acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bismyristic acid amide, ethylene bispalmitic acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid Amide, Ethylene bis behenic acid amide, Ethylene bis oleic acid amide, Ethylene bis erucic acid amide, Butylene bis stearic acid amide, Butylene bis behenic acid amide, Butylene bis oleic acid amide, Butylene bis erucic acid amide, Hexamethylene Bistearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bisoleic acid amide, hexamethylene biserucic acid amide, m-xylylene bisstearic acid amide, m-key Rylene bis-12-hydroxystearic acid amide, p-xylylene bis stearic acid amide, p-phenylene bis stearic acid amide, p-phenylene bis stearic acid amide, N, N'-distearyl adipic acid amide, N, N'- Distearyl sebacic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide, N, N′-distearyl isophthalic acid amide, N, N′-distearyl terephthalic acid amide, Examples include methylene bishydroxystearic acid amide, ethylene bishydroxystearic acid amide, butylene bishydroxystearic acid amide, and hexamethylene bishydroxystearic acid amide.

  The alkyl-substituted fatty acid monoamide preferably used in the present invention refers to a compound having a structure in which an amide hydrogen such as a saturated fatty acid monoamide or an unsaturated fatty acid monoamide is replaced with an alkyl group, such as N-lauryl lauric acid amide, N-palmityl palmitic acid amide, N-stearyl stearic acid amide, N-behenyl behenic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N -Oleyl palmitic acid amide etc. are mentioned. The alkyl group may have a substituent such as a hydroxyl group introduced into its structure. For example, methylol stearamide, methylol behenic acid amide, N-stearyl-12-hydroxystearic acid amide, N- Oleyl 12 hydroxystearic acid amide and the like are also included in the alkyl-substituted fatty acid monoamide of the present invention.

  Furthermore, the fatty acid ester preferably used in the present invention includes, for example, lauric acid cetyl ester, lauric acid phenacyl ester, myristic acid cetyl ester, myristic acid phenacyl ester, palmitic acid isopropylidene ester, palmitic acid dodecyl ester, palmitic acid Aliphatic monocarboxylic acid esters such as tetradodecyl ester, palmitic acid pentadecyl ester, palmitic acid octadecyl ester, palmitic acid cetyl ester, palmitic acid phenyl ester, palmitic acid phenacyl ester, stearic acid cetyl ester, behenic acid ethyl ester; Monoesters of ethylene glycol such as glycol monolaurate, glycol monopalmitate, glycol monostearate, glycol dilaurate Diesters of glycols such as glycol dipalmitate and glycol distearate; Monoesters of glycerol such as monolauric acid glycerin ester, monomyristylic acid glycerin ester, monopalmitic acid glycerin ester, monostearic acid glycerin ester; dilauric acid glycerin ester Glycerin diesters such as glyceryl dimistilate, glyceryl dipalmitate, glyceryl distearate; glyceryl trilaurate, glyceryl trimistilate, glycerin tripalmitate, glyceryl tristearate, palmitodiolein, palmi Examples include triesters of glycerin such as todistearin and oleodistearin. That.

  Among these fatty acid amides and / or fatty acid esters, fatty acid bisamides can be used more preferably because the reactivity of the amides is even lower, and it is more preferable to use ethylene bisstearic acid amide.

  The fatty acid amide and / or fatty acid ester described above may be contained in either the resin A or the resin B, but is preferably contained in the resin that forms the fiber surface. Moreover, if the addition amount is 0.001-2.0 weight%, since the reduction effect of fiber surface friction is fully exhibited, it is preferable. If the addition amount is 2.0% by weight or less, it becomes possible to maintain good spinnability, and if the addition amount is 0.001% by weight or more, the effect of reducing the fiber surface friction is sufficiently exhibited. . Therefore, the addition amount is more preferably 0.05 to 1.0% by weight.

  Color pigments include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, and quinocridone. Organic pigments such as thioindigo can be used. Moreover, modifiers such as calcium carbonate and silica can also be used.

  The solution specific viscosity (ηr2) after subjecting the fiber obtained by the present invention to pressure heat treatment at 220 ° C. for 2 minutes is 1.05 to 4 with respect to the solution specific viscosity (ηr1) of the fiber before the heat treatment. It is important to double. In general, the solution specific viscosity is used as a standard for estimating the molecular weight of the polymer, and the larger the value of the parameter, the higher the molecular weight. That is, the fiber of the present invention is designed so that the molecular weight of the fiber-constituting resin is increased by applying heat treatment at a temperature at which the resin melts as described above, so that crosslinking or chain connection proceeds. The fiber designed in this way has never existed before, and is achieved for the first time by the method described later. In addition, such a fiber design suppresses an increase in molecular weight in melt spinning, so that the spinnability is high and the productivity is good, and the molecular weight can be freely increased by a subsequent heat treatment. In addition, when the polylactic acid used in the present invention is made into a fiber as it is, pyrolysis proceeds easily by a normal heat treatment, so that ηr after heating also decreases. However, in the fiber of the present invention, ηr increases after the heat treatment due to the effect of the diffusion and reaction of the drug C described later. In other words, the durability of the final product can be dramatically increased by increasing the molecular weight. From this, when ηr after pressure heat treatment is in the range of 1.05 to 4 times, it becomes possible to impart sufficient flexibility and durability to the obtained molded product, and the polylactic acid The characteristic biodegradability is not impaired. Furthermore, ηr2 / ηr1 is preferably 1.10 to 3.5 times, and most preferably 1.20 to 2.5 times. That is, by optimizing each of the resin A, the resin B, and the medicine C in the present invention, the above requirement is achieved, and the above requirement is a method for evaluating the durability of the final product to be obtained.

Melting point difference between the resin A and the resin B in the present invention is Ru der below 20 ° C.. When the melting point difference is less than 20 ° C., melting and spinning can be performed under the condition that the thermal decomposition of the resin A or the resin B can be suppressed, and a stable fiber can be manufactured. In addition, when the obtained fiber is hot-pressed, the heated fiber quickly melts, so when it is combined with other materials, the melted fiber is efficiently filled, and the drug C is sufficiently melted. It can diffuse into the body and increase the strength of the molded product. The difference in melting point is preferably less than 15 ° C and most preferably less than 12 ° C. In addition, the melting points of the resin A and the resin B in the present invention are preferably 130 ° C. or higher because the handleability of the obtained fiber is excellent and the heat resistance of the obtained molded body is improved. The melting points of Resin A and Resin B are each preferably 150 ° C. or higher.

The COOH end group-reactive and / or OH end group-reactive agents added to the polylactic acid resin used in the present invention include oxazoline compounds, oxazine compounds, aziridine compounds, glycidyl groups, acid anhydride groups, imide groups. are needed use those having two or more crosslinkable functional groups such as isocyanate groups. Further, even a cyclic compound having crosslinkability such as an aziridine compound is preferable because the end of the aliphatic polyester resin can be sufficiently crosslinked. Furthermore, it is preferable that the compound having two or more functional groups described above has a weight average molecular weight of 500 to 30,000 because of excellent heat resistance during melt molding. In addition, if the compound having these functional groups is a copolymer grafted to the main chain of the polymer, it becomes possible to introduce a large number of functional groups into one molecule, In general, the thermal properties such as the melting point are stable, and the handling property is excellent, which is preferable. The polymer to which this functional group is grafted can be arbitrarily selected, but from the viewpoint of ease of synthesis, acrylates such as polyester polymer, polyacrylate, polymethyl methacrylate, poly (alkyl) methacrylate, etc. It can select suitably from groups, such as a polymer, a polystyrene polymer, and a polyolefin polymer.

  Among the agents that can be used in the present invention, as an example of an oxazoline compound, polyfunctionality is important from the viewpoint of crosslinkability, and therefore, a compound having a plurality of oxazoline rings in one molecule is selected. . Similarly, for aziridine compounds and oxazine compounds, it is preferable from the viewpoint of crosslinkability to select a compound having a plurality of rings in one molecule. Further, these compounds are preferably used from the viewpoint of heat resistance and handleability, such as those synthesized so as to have a molecular weight in the range of 500 to 30,000, such as compounds graft-polymerized to the main chain. It is done.

  Among the drugs that can be used in the present invention, as an example of the carbodiimide compound, polyfunctionality is important from the viewpoint of crosslinkability. For this reason, it is preferable that the carbodiimide compound contains a plurality of carbodiimide groups in the molecule. A polycarbodiimide compound obtained by polymerizing a compound having a carbodiimide group so as not to lose the activity of the carbodiimide group is preferable because thermal stability at the time of melting is increased and handling properties are excellent.

Of the drugs that can be used in the present invention, the compound having a glycidyl group is not particularly limited as long as it has two or more glycidyl groups, but from the balance of thermal stability and reactivity during melting. , A polymer having a monomer unit of a compound having a glycidyl group, a compound in which a glycidyl group is graft-copolymerized to a polymer as a main chain, and further having a glycidyl group at the end of a polyether unit. Preferably there is.
Furthermore, examples of the monomer unit having a glycidyl group described above include glycidyl acrylate and glycidyl methacrylate. In addition to these monomer units, a long-chain alkyl acrylate or the like may be copolymerized to control the reactivity of the glycidyl group. Furthermore, when the polymer having the glycidyl group as a monomer unit or the average molecular weight of the polymer as the main chain is in the range of 500 to 50,000, the increase in melt viscosity when high concentration is added can be suppressed. This is preferable because the heat resistance of the drug can be secured. The weight average molecular weight is more preferably in the range of 1000 to 30000, and most preferably in the range of 2000 to 20000.

  Furthermore, for the purpose of promoting the crosslinking reaction of the compound having the glycidyl group, a metal salt of a carboxylic acid, particularly a catalyst in which the metal is an alkali metal or an alkaline earth metal can be added. The carboxylic acid to be used is not particularly limited, but when the catalyst is added to the polylactic acid used in the present invention, a catalyst based on lactic acid such as sodium lactate, calcium lactate or magnesium lactate should be used. Is preferred. Alternatively, a catalyst having a relatively large molecular weight such as a stearic acid metal salt can be used alone or in combination for the purpose of preventing the heat resistance of the resin from being lowered due to the addition of the catalyst. In addition, it is preferable to add the catalyst to the resin B that does not substantially contain the drug C because the glycidyl reaction during melt spinning can be controlled. The addition amount of the catalyst is preferably in the range of 0.001 to 0.5% by weight with respect to the fibers, from the viewpoint of keeping the dispersibility in a good state and controlling the reactivity. The addition amount of the catalyst is preferably 0.001 to 0.3% by weight.

  In addition, the method of adding the catalyst is not particularly limited, but a method of adding the catalyst in advance to the polylactic acid resin in the polymerization step, or after kneading in the resin B or mixing with the resin B before melt spinning The fiberizing method is preferable because the catalyst can be added uniformly. Alternatively, the catalyst may be dissolved in a fiber oil and added as an aqueous solution at any stage such as a melt spinning process or a stretching process.

The addition amount of the crosslinkable agent C added to the resin A is 5 of the theoretical addition amount in which the total amount is reacted with the COOH end group concentration and / or the OH end group concentration of the polylactic acid resin as the base material. It added more than doubled. When the drug C of the present invention is added to the resin A, since the crosslinking usually proceeds with respect to the added amount, the melt viscosity increases accordingly. However, the present inventor has intensively studied and found that when the drug C is added in an amount of 5 times or more the theoretical addition amount, the crosslinking reaction stops, the increase in melt viscosity stops, and further decreases. did. Although this principle is not clear, as one factor, when the concentration of the drug C serving as a cross-linking agent exceeds a certain range, it quickly reacts with the COOH end group and / or OH end group of polylactic acid, and the cross-linked structure is almost completely changed. It is conceivable that the reaction stops when it is not formed. Although there is no particular limitation on increasing the concentration of the drug C, the drug C often has poor heat resistance with respect to the aliphatic polyester, and volatilization, sublimation, etc. occur in the melt spinning stage, and the production apparatus is soiled. The work environment may be deteriorated. For this reason, it is preferable that the addition amount of the medicine C is up to 50 times. The addition amount of the drug C is preferably 7 to 40 times, more preferably 10 to 40 times the theoretical addition amount. The theoretical addition amount referred to in the present invention refers to the amount of the drug C necessary for completely reacting either the COOH end group or the OH end group. That is, when the COOH end group concentration in the polylactic acid resin is A and the OH end group concentration is B, the theoretical addition amount of the drug C with respect to the COOH end group is a value calculated only from A, whereas the drug with respect to the OH end group The theoretical addition amount of C is calculated from B alone. In particular, in the case of polylactic acid resin, A and B are substantially the same value, and in the present invention, the theoretical addition amount calculated based on the COOH end group concentration is used unless otherwise specified.
Further, in the fiber of the present invention, the composite ratio of the resin A and the resin B is adjusted so that the amount of the chemical C is 7 times or less the theoretical addition amount that reacts with all the end groups contained in the entire fiber. It is preferable. This means that the chemical C is 7 times or less of the theoretical addition amount that reacts with this end group with respect to the COOH end group concentration or OH end group concentration of the entire fiber formed by combining the resin A and the resin B. It shows that. When a large amount of unreacted drug C is present in the fiber, the COOH end group is blocked before the crosslinking reaction or chain linking reaction proceeds during the pressure heat treatment or melt molding. It becomes difficult to increase the molecular weight. Further, the addition amount of the agent C is 7 times or less, it becomes possible to sufficiently increase the molecular weight of the resulting molded article, also win the bleed-out from molded article of the drug C unreacted depression it can. Further, for the purpose of the present invention, the amount of the above-mentioned drug C added is preferably 1.1 times or more in order to sufficiently form a crosslinked structure of a molded body using the obtained fiber. The addition amount of the drug C is more preferably 1.2 times or more and 5 times or less, and further preferably 1.3 times or more and 4 times or less. From this, the composite ratio of the resin A and the resin B is not particularly limited for the fiber of the present invention, but any composite ratio can be selected from the amount of drug C added to the resin A and the ease of production. Resin A generally has a low spinnability, and has a high adhesiveness because it contains a large amount of unreacted drug C. From this, in order to ensure the spinnability and process passability, the composite ratio is preferably in the range of resin A / resin B = 2/98 to 60/40, preferably 5/95 to 40/60. It is more preferable to set the range.

  In the fiber of the present invention, the resin A containing the drug C and the resin B not containing the drug C have a composite structure. The melt viscosity of the resin A is sufficient to withstand melt spinning, but the spinnability is often low due to the crosslinking effect of the drug C. Therefore, by combining the resin B at each single fiber level, the spinning stability can be improved. It is preferable to give. The composite form is not particularly limited, but a core-sheath composite, a split composite, and the like are preferable from the standpoint of the stability of yarn production. However, among these composite forms, the core-sheath type composite is more preferable from the viewpoint of the yarn production stability. Examples of the core-sheath type composite include a multi-core type composite, an eccentric type composite, and a form in which the core of the composite is exposed on the surface of the fiber. Since C bleeds out during spinning, the simplest core-sheath composite form in which resin A is arranged in the center of the core and resin B completely covers resin A is preferable. Among them, by forming the resin A in the core of the core-sheath composite, the resin A disposed in the core by the pressure heat treatment in melt molding is quickly diffused into the resin B. It is preferable because the resin B can be sufficiently crosslinked. In addition, the unreacted drug C can be prevented from bleeding out during melt molding.

  Although the cross-sectional shape of the fiber of the present invention can be arbitrarily selected, a known fiber cross-sectional shape such as a round cross-section, a multi-leaf cross-section, a flat cross-section, or a hollow cross-section can be adopted. Among these, a round cross section is preferable from the viewpoint of securing the spinnability.

  The fiber of the present invention may be produced by any known method as long as the resin A and the resin B are combined and melt-spun. Furthermore, it is preferable that the resin A and the resin B are dried before melt spinning because the thermal decomposition and hydrolysis at the time of melt spinning can be suppressed, so that the spinning stability is improved. The drying temperature is preferably a temperature at which the resin A or the resin B is not fused, and it is particularly preferable to perform the drying at a temperature of Tg to Tm-20 ° C. When drying the resin A or the resin B, specifically, drying at a temperature of 70 to 120 ° C. is preferable because there is no fusion and moisture, oligomers, and the like in the resin can be sufficiently removed. In addition, it is preferable to dry in a nitrogen atmosphere at the time of drying because it is possible to suppress the oxidation of the polymer. Alternatively, if the drying atmosphere is depressurized with a vacuum pump or the like, it is only possible to suppress the oxidation of the polymer. It is preferable because the drying efficiency is increased.

  Moreover, it is preferable to provide a known fiber oil to the melt-spun fibers of the present invention. In particular, it is preferable to reduce the coefficient of friction on the fiber surface in order to pass through the process of producing the textile product stably, and as the oil agent for fibers, an oil agent mainly composed of fatty acid esters is preferably used. The ratio of the fatty acid ester blended in the fiber oil is preferably 50% by weight or more because the effect of reducing the friction coefficient of the fiber surface can be exhibited. In addition, the oil agent for fibers may contain other antistatic agents, emulsifiers, mineral oils and other additives for the purpose of focusing and antistatic properties, as long as the effect of reducing the friction coefficient on the fiber surface is not impaired. preferable. Moreover, although the oil agent for fibers may be applied to the fiber as it is, it can also be applied as an aqueous emulsion having excellent handleability. In the case of an aqueous emulsion, the oil agent can be uniformly adhered to the fiber surface by adjusting the concentration of the fiber oil agent to a concentration in the range of 5 to 50% by weight. Furthermore, the oil for fibers can be applied at any time during the fiber production process such as the melt spinning process, the drawing process, and the crimping process. It is preferable to apply after cooling. It is preferable that the fiber oil is applied so as to adhere 0.3 to 2% by weight with respect to the fiber. By attaching the fiber oil within the above-mentioned range, it is possible to sufficiently reduce the friction coefficient of the fiber surface, and it is also possible to prevent the fiber oil from dropping off and contaminating the process in the subsequent process. . From this, it is more preferable that the fiber oil agent is adhered in a pure content of 0.5 to 1.5% by weight.

  The fiber of the present invention may be either a long fiber or a short fiber, but is preferably selected appropriately according to the final application. As a preferred example of long fibers, it is common to create and use structures such as woven fabrics and knitted fabrics. Examples of preferred short fibers include spun yarn, string, non-woven fabric, stuffed cotton, and composite binder fibers. In the case of a short fiber, since it becomes possible to make it excellent in the last name by making the cut length into the range of 2-100 mm, it is more preferable. Further, the single yarn fineness can be set to an arbitrary thickness, but may be appropriately determined within the range of 0.1 to 1000 dtex in view of ease of manufacturing.

Hereinafter, a specific method for obtaining the fiber of the present invention will be described. In addition, the measuring method of the various physical-property values measured in the present Example was described below.
A. Weight average molecular weight and dispersity of polylactic acid A sample solution in chloroform was mixed with THF to prepare a measurement solution. This was measured by GPC, and the weight average molecular weight was calculated in terms of polystyrene.
B. Melting | fusing point of polylactic acid The temperature which gives the extreme value of the melting endothermic curve obtained by measuring 20 mg of samples at the temperature increase rate of 16 degree-C / min using the differential scanning calorimeter DSC-7 type made from PerkinElmer, Inc. ).
C. Solution specific viscosity (ηr)
0.10 g of the sample resin was precisely weighed and dissolved in 10 ml of orthochlorophenol over 30 minutes at 100 ° C., and the flow time T0 of the solvent alone and the flow time T1 of the sample solution were determined with an Ostwald viscometer. Solution specific viscosity (ηr) was determined from / T0.
D. Lactide amount 1 ± 0.001 g of the sample is precisely weighed, and 20 ml of dichloromethane is added and ultrasonically dissolved. Thereafter, 5 ml of acetone is added, and the volume is adjusted to 50 ml with cyclohexane, and further ultrasonically dissolved. Thereafter, 20 μl of the supernatant was injected into the GC analyzer, and the amount of lactide was determined from the calibration curve determined in advance from the obtained chart.
E. COOH end group concentration A precisely weighed sample was dissolved in o-cresol (water 5%), and an appropriate amount of dichloromethane was added to this solution, followed by titration with a 0.02 N KOH methanol solution. At this time, an oligomer such as lactide, which is a cyclic dimer of lactic acid, is hydrolyzed to produce a COOH end group. Therefore, all of the COOH end group of the polymer, the COOH end group derived from the monomer, and the COOH end group derived from the oligomer are combined. The obtained COOH end group concentration is obtained.
F. Fineness Fiber was measured for a certain length, its weight W and length L were measured, and the fiber weight per 10000 m was determined to be the fineness (dtex).
G. Strength / Elongation The initial sample length was 200 mm and the tensile speed was 200 mm / min, and a load-elongation curve was obtained under the conditions shown in JIS L1013 (1999). Next, the load value at break was divided by the initial fineness and used as the strength. The elongation at break was divided by the initial sample length to obtain a strong elongation curve, and the strength at the maximum point was defined as the fiber strength.
H. Durability test Weighing 5 g of the sample fiber, preparing a 1 mm thick stainless steel plate with a 5 cm wide and 5 cm long hole, sandwiching the sample, 220 ° C, 1.5 MPa, 2 minutes The film was obtained by performing pressure heat treatment under these conditions. The ηr retention rate of 80% or more was obtained with the change in ηr (ηr retention rate) before and after treatment after 2000 hours of the film was kept at 50 ° C. × 90% RH for 2000 hours. Things were accepted.

ηr retention (%) = (post-treatment ηr) / (pre-treatment ηr) × 100
Example 1
Poly-L-lactic acid P1 having a weight average molecular weight of 150,000, ηr of 3.15, a COOH end group concentration of 25 equivalent / t, and a melting point of 170 ° C. was synthesized by a conventionally known method using L-lactic acid as a starting material. As the medicine C, polyethylene glycol diglycidyl ether (average molecular weight 500) was used. The theoretical reaction amount by which the total amount of COOH end groups present in the polylactic acid P1 of the drug C was reacted was 0.625% by weight. This drug C was melt-kneaded using a biaxial kneader at a kneading temperature of 200 ° C. at a ratio of 10% by weight with respect to polylactic acid P1 to obtain Resin A. The obtained resin A had a ηr of 3.20 and showed a slight increase in solution viscosity, but it showed a solution viscosity that could be sufficiently supplied to spinning. Resin B used polylactic acid P1 as it was. Resin A and Resin B are usually melted and weighed and filtered separately at a melting temperature and spinning temperature of 220 ° C. using a known spinning machine, and resin A is the core in the die. A spinning oil agent (containing 60% by weight of a fatty acid ester) prepared at a concentration of 15% by weight after being combined and discharged with the resin B as a sheath, cooled, and 1% by weight of the oil component is added to the fiber in a pure amount. The fiber of 300 dtex-24F was obtained at a spinning speed of 1000 m / min. The composite ratio of Resin A and Resin B was Resin A / Resin B = 10/90 by weight. The obtained fiber was stretched at a stretching ratio of 2.7 times between 1HR and 2HR at a stretching speed of 800 m / min with a 4-roller stretching machine at 1HR temperature of 80 ° C and 2HR temperature of 130 ° C, and 111 dtex- A 24F drawn yarn was obtained. The obtained drawn yarn had a strength of 4 cN / dtex, an elongation of 43%, and an ηr of 3.2, indicating excellent physical properties. The drawn yarns were drawn to 100000 dtex and formed into tows and then cut into short fibers having a cut length of 55 mm. Further, 5 g of this short fiber was weighed and sandwiched between stainless plates, and then pressed for 2 minutes with a hot press machine having a press temperature of 220 ° C. and a press pressure of 1.5 MPa to obtain a film sample having a thickness of 1 mm. . The film-like sample obtained had a ηr of 5.8, and had a highly advanced crosslinking reaction and excellent durability. As a durability evaluation, the film sample was placed in an environment of 50 ° C. and 90% RH for 2000 hours, and ηr was measured again. As a result, it was 5.5, and it was confirmed that the film actually showed excellent durability.

Example 2
A 111 dtex-24F drawn yarn was obtained in the same manner as in Example 1 except that the amount of the drug C in the resin A was changed to 5% by weight. At this time, ηr of Resin A was 3.7 and the solution viscosity was slightly increased, but spinning could be performed without any problem. Further, the film after being subjected to the pressure heat treatment in the same manner as in Example 1 was measured for ηr, which was 4.6, which was excellent in durability with sufficient progress of crosslinking. Moreover, when ηr was measured for the sample after the durability test, it was 4.4, which showed good durability.

Example 3
A 111 dtex-24F drawn yarn was obtained in the same manner as in Example 1 except that the amount of the drug C added to the resin A was 20% by weight. At this time, although the phenomenon that the drug C bleeds out and diffuses during spinning was confirmed, spinning and winding were completed without any problem. In addition, the film after being subjected to the pressure heat treatment in the same manner as in Example 1 was measured for ηr and found to be 3.8, which was excellent in durability with sufficient progress of crosslinking. Moreover, when ηr was measured for the sample after the durability test, it was 3.7, which showed good durability.

Comparative Example 1
Samples of drawn yarn and short fibers were obtained in the same manner as in Example 1 except that the resin A was replaced with the resin B and spinning was performed. When ηr was measured for the film subjected to the pressure heat treatment, it was lowered to 2.8 and was inferior in durability. In addition, when a durability test was performed, ηr was lowered to 2.0, and a product that could withstand actual use was not obtained.

Comparative Example 2
Kneading was carried out to produce resin A in the same manner as in Example 1 with the addition amount of drug C in resin A being 2.5% by weight. However, since the molecular weight of the obtained resin A was too high, the strand during kneading Was not stable, pellets were not obtained, and fiber samples could not be produced.

Comparative Example 3
Kneading was carried out to produce resin A in the same manner as in Example 1 with the addition amount of drug C in resin A being 40% by weight. Since the addition amount of the medicine C was too large, the strands during kneading were not stabilized, and the pellets of the resin A could not be obtained, so that a fiber sample could not be produced.

Comparative Example 4
A stretched yarn of 111 dtex-24F was obtained in the same manner as in Example 1 except that the resin B was replaced with the resin A. Ηr of the obtained fiber was 3.3. When a film was produced from this sample in the same manner as in Example 1, ηr was not changed to 3.3, and no improvement in durability was observed.

Example 4
The drug C was a polyacrylate compound (the alkyl chain having 10 to 12 carbon atoms) having glycidyl methacrylate and alkyl methacrylate as structural units (average molecular weight 15000, theoretical drug amount 0.036% by weight per equivalent of terminal group, poly Fiber and film samples were produced in the same manner as in Example 1 except that the theoretical reaction amount with respect to lactic acid P1 was 0.9% by weight. The physical property values of the obtained fibers are shown in Table 2. The increase in viscosity during the kneading of the resin A was slight, and the yarn could be produced without any problem. Further, the obtained film sample had a sufficiently cross-linked structure and was excellent in durability, and when a durability test was actually performed, excellent results were obtained.

Example 5
Fiber and film samples were obtained in the same manner as in Example 4 except that the amount of the drug C added to the resin A was 20% by weight. The physical property values of the obtained fibers are shown in Table 2. The increase in viscosity during the kneading of the resin A was slight, and the yarn could be produced without any problem. Further, the obtained film sample had a highly crosslinked structure and was excellent in durability, and when a durability test was actually performed, excellent results were obtained.

Example 6
Except for using the drug C as a polycarbodiimide compound (carbodiimide equivalent 8, average molecular weight 2000, theoretical drug amount 0.028% by weight per equivalent of terminal group, theoretical reaction amount 0.7% by weight with respect to polylactic acid P1) Fiber and film samples were produced in the same manner as in Example 1. The physical property values of the obtained fibers are shown in Table 2. The increase in viscosity during the kneading of the resin A was slight, and the yarn could be produced without any problem. In addition, the obtained film sample showed a good durability having a sufficiently crosslinked structure for practical use. Furthermore, the durability test result was good.

Example 7
Drug C is polyglycerol polyglycidyl ether (Denacol EX-521, manufactured by Nagase ChemteX Corporation, average molecular weight 750, theoretical drug amount 0.015% by weight per equivalent of terminal group, theoretical reaction amount 0.375% by weight with respect to polylactic acid P1. Except for the above, fibers and film samples were produced in the same manner as in Example 1. The physical property values of the obtained fibers are shown in Table 2. The increase in viscosity during the kneading of the resin A was slight, and the yarn could be produced without any problem. Further, the obtained film sample had a sufficiently cross-linked structure and was excellent in durability, and when a durability test was actually performed, excellent results were obtained.

Example 8
Fiber and film samples were produced in the same manner as in Example 1 except that the composite ratio of Resin A and Resin B was Resin A / Resin B = 20/80. Although the drug C slightly bleeded out during spinning, spinning was possible without any problem. Further, the obtained film sample had a highly crosslinked structure, was excellent in durability, and the durability test result was also good.

Example 9
Fiber and film samples were produced in the same manner as in Example 1 except that the composite ratio of Resin A and Resin B was Resin A / Resin B = 7/93. The obtained film sample had a sufficiently cross-linked structure and good durability, and the durability test result was also good.

Example 10
Fiber and film samples were produced in the same manner as in Example 1 except that the composite ratio of Resin A and Resin B was Resin A / Resin B = 50/50. Although a bleed out of the drug C was observed at the time of spinning, spinning was possible. The obtained film sample had a highly cross-linked structure, but bleed out of the drug C was also observed during the pressure heat treatment by the unreacted drug C. Moreover, as a result of the durability test, it showed good durability.

Example 11
Fiber and film samples were produced in the same manner as in Example 1 except that the resin A was placed in the sheath and the resin B was placed in the core. Bleeding out of the drug C occurred during spinning, but spinning was possible. The obtained film sample had a crosslinked structure and good durability.

Example 12
Fiber and film samples were produced in the same manner as in Example 1 except that the resin A and the resin B were combined in the form of being bonded to a split mold. Bleeding out of the drug C occurred during spinning, but spinning was possible. The obtained film sample had a crosslinked structure and good durability.

It is the figure which illustrated the composite form which can take preferably about the fiber of this invention.

Explanation of symbols

1 Resin A
2 Resin B

Claims (1)

COOH end group reactivity having a solution specific viscosity (ηr) of 1.05 to 4 times that before the heat treatment and a functional group of 2 or more after heat treatment at 220 ° C. for 2 minutes at a pressure of 1.5 MPa . And / or OH end group-reactive chemical C is added to the COOH end group concentration and / or OH end group concentration of the polylactic acid used as the base material in an amount more than 5 times the theoretical addition amount. And a resin B mainly composed of polylactic acid substantially not containing the drug C, and the difference in melting point between the resin A and the resin B is less than 20 ° C. Polylactic acid fiber.

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