JP4765724B2 - Aliphatic polyester staple fiber - Google Patents

Description

  The present invention relates to an aliphatic polyester staple fiber having excellent hydrolysis resistance and excellent durability after hot-press molding.

  Polyesters typified by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polylactic acid, polycaprolactone, polybutylene succinate, etc. are excellent in mechanical properties and chemical properties. Depending on the characteristics of each polyester, they are used for clothing and industrial materials, for example. In the case of PET, for example, in the case of PET, an aromatic polyester having aromatic dicarboxylic acid and alkylene glycol as main components as a typical polyester is bis ((esterification) by esterification or transesterification of terephthalic acid or dimethyl terephthalate with ethylene glycol. 2-hydroxyethyl) terephthalate is produced and industrially produced by a polycondensation method in which this is polycondensed using a catalyst at a high temperature under vacuum. On the other hand, polylactic acid contained in aliphatic polyester is produced by ring-opening polymerization of lactide or direct polymerization of lactic acid.

  Among these, aliphatic polyesters have poor mechanical strength and thermal properties compared to aromatic polyesters, but are not raw materials such as biomass raw materials, transparency and flexibility. Yes, application development is progressing in various fields.

  However, aliphatic polyesters generally have a high hydrolysis rate and easily decrease in molecular weight, so that it is difficult to maintain the mechanical strength of the molded product. In particular, the tendency is remarkable under conditions of high temperature and humidity, which has been an obstacle to practical use. In particular, in the field of fibers, the specific surface area is generally larger than that of other molded products, and therefore, the fiber is easily subjected to hydrolysis.

  Therefore, for example, Patent Document 1 discloses a technique for substituting the COOH terminal or alcohol terminal of an aliphatic polyester with another compound to suppress hydrolysis. The technique described in this document describes that a carbodiimide compound or an epoxy compound is used as a terminal blocking agent. However, these epoxy compounds have only a slight effect on improving durability, and the problem that the molecular weight is further reduced and the durability is lowered by melt-molding the melt-formed fiber again is not recognized and solved. Was not.

On the other hand, a method cited in Patent Document 2 is described as such a compound having few problems. Since the compound described in Patent Document 2 is trifunctional, it is described that the gas barrier property is improved by increasing the viscosity at the time of melt molding even at a low draw ratio. However, Patent Document 2 relates to a film, and the fiber has not been studied.
JP-A-8-120520 (page 3, paragraph 0014) JP 2005-314444 A (page 2)

  An object of the present invention is to provide an aliphatic polyester staple fiber that can drastically improve hydrolysis resistance and crystallization characteristics, and further increase the molecular weight after heat treatment to improve the durability of the final molded product. Is.

That is, the present invention is composed of an aliphatic polyester, talc having an average particle size D ₅₀ of 5 μm or less, and a trifunctional or higher functional epoxy compound, and the aliphatic polyester and the trifunctional or higher functional epoxy compound are at least partially reacted. and has the COOH terminal group concentration of the aliphatic polyester is from 1 to 20 Ri eq / t der, an aliphatic polyester staple fibers that are used in thermal molding, heat pressing of 220 ° C. the staple fiber sample 5g The weight average molecular weight of the aliphatic polyester extracted from the molded article after hot pressing when the pressing process is performed for 5 minutes at a pressing pressure of 5 MPa to form a press film is the staple before molding. It is an aliphatic polyester staple fiber characterized by an increase compared to the fiber.

  As the aliphatic polyester used in the present invention, those obtained by polycondensation of saturated dicarboxylic acid and diol, or those obtained by polycondensation of hydroxycarboxylic acid are preferably used. Examples of aliphatic polyesters obtained by polycondensation include polylactic acid, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate) copolymer, polycaprolactone, Polypivalolactone, or a polyester composed of glycol such as ethylene glycol or 1,4-butanediol and dicarboxylic acid such as succinic acid or adipic acid may be used.

  Although these aliphatic polyesters have the disadvantage that they are hydrolyzed faster than aromatic polyesters, the raw materials are easily derived from natural products, and are excellent in transparency and flexibility as compared with aromatic polyesters. Of these aliphatic polyesters, polylactic acid is further superior to other aliphatic polyesters in terms of mechanical properties and heat resistance, and is particularly preferably used.

  In addition, two types of polylactic acid that are particularly preferably used in the present invention are known, one mainly composed of L-lactic acid and one mainly composed of D-lactic acid. Lactic acid may be used. If the optical purity of lactic acid in polylactic acid is 97% or more, the melting point of the resin can be increased and the heat resistance is excellent, which is preferable. In general, polylactic acid decreases in crystallinity when the optical purity is lowered. Therefore, the obtained molded product generally has a reduced heat resistance, and a practical molded product cannot be obtained. For this reason, polylactic acid having an optical purity of 98% or more is preferably used. When the optical purity in one polymer molecule satisfies the above value, for example, polylactic acid obtained by melt-mixing a polymer mainly composed of L-lactic acid and a polymer mainly composed of D-lactic acid can be used. In this case, the polylactic acid molecular chain mainly composed of L-lactic acid and the polylactic acid molecular chain mainly composed of D-lactic acid form a stereocomplex crystal, and the crystal has a higher melting point than the homopolymer. In view of this, the staple fiber of the present invention and, further, the final molded product produced therefrom is preferable because of its excellent heat resistance.

  The weight average molecular weight of polylactic acid is preferably 80,000 or more from the viewpoints of heat resistance and moldability. By setting the weight average molecular weight to 80,000 or more, not only the mechanical properties of the resulting molded article are improved and a product having excellent durability can be obtained, but also the fluidity and crystallization characteristics at the time of melting are in a preferable range. Therefore, stable production is possible even when the staple fiber of the present invention is obtained. For this reason, the weight average molecular weight is more preferably in the range of 80,000 to 400,000, and most preferably in the range of 100,000 to 250,000.

  The amount of unreacted monomers and oligomers contained in the polylactic acid particularly preferably used in the present invention is preferably in the range of 0.01 to 0.3% by weight. Unreacted monomers and oligomers may bleed during melt molding and contaminate the device, or react with the epoxy compound of the present invention to reduce the activity of the epoxy compound, but if there is a very small amount, It acts as a so-called plasticizer and can improve moldability. Therefore, the amount of the monomer and oligomer is preferably in the range of 0.01 to 0.2% by weight, and more preferably in the range of 0.01 to 0.15% by weight.

  The aliphatic polyester used in the present invention may contain other modifiers, additives and other polymers as long as the characteristics are not changed. These modifiers, additives and other polymers may be added at the time of polymerization, may be in the form of master pellets previously kneaded, or may be directly mixed with aliphatic polyester pellets and melt molded. Furthermore, the aliphatic polyester of the present invention can be copolymerized with other monomers as long as the characteristics are not changed. Examples of the copolymer component include dicarboxylic acid, diol, hydroxycarboxylic acid, and modified products thereof. The content of these copolymerization components is not particularly limited, but if the copolymerization is carried out in a range not exceeding 40 mol% with respect to the aliphatic polyester, the characteristics of the aliphatic polyester as a substrate are significantly changed. Therefore, the modification effect is preferable.

  Further, in the fiber of the present invention, a trifunctional or higher functional epoxy compound is contained, and the trifunctional or higher functional epoxy compound is allowed to react with at least a part of the aliphatic polyester, preferably at least a part of the end of the aliphatic polyester. It is important to make it react. The trifunctional or higher functional epoxy compound has three or more epoxy groups in one molecule of the compound. The reason for having 3 or more epoxy groups per molecule of the compound is that melt-kneading with an aliphatic polyester, part of the compound reacts with the aliphatic polyester when a staple fiber is obtained, and melt molding is performed again. When the epoxy group remaining during the reaction further reacts with the aliphatic polyester, the molecular weight increases, and the durability of the final molded product can be drastically improved. In addition, by using an epoxy compound as a material to be added to the aliphatic polyester, the reaction rate is lower than that of other terminal reactive materials such as carbodiimide compounds. In addition to being able to easily obtain staple fibers, it is difficult to form a structure in which all epoxy groups react with aliphatic polyester, and unreacted epoxy groups remain in aliphatic polyester staple fibers. It becomes easy to make a structure. Further, in order to have a structure in which the epoxy compound is reacted at least partially with the aliphatic polyester, the staple fiber of the present invention is preferably produced by melt spinning, and the melt residence time of the aliphatic polyester in melt spinning is 2 to 2. 40 minutes is preferred. By setting the melt residence time to 2 minutes or longer, the aliphatic polyester and the epoxy compound can be reacted to form a structure in which both are at least partially reacted. Moreover, it is preferable that the melt residence time be 40 minutes or less because the thermal decomposition of the aliphatic polyester itself can be suppressed and a staple fiber having excellent quality can be obtained. For these reasons, it is more preferable to set the melt residence time in the range of 3 to 30 minutes.

  The trifunctional or higher functional epoxy compound of the present invention is characterized by having at least one glycidyloxycarbonyl group or N- (glycidyl) amide group in one molecule. Preferably, it is preferable to have at least one structure of the following formula (I) or (II) in one molecule.

(In the formula, R1 represents a functional group having a hydrocarbon skeleton containing a saturated bond / unsaturated bond / substituent or a functional group containing a saturated bond / unsaturated bond / substituent containing a covalent bond atom other than carbon. R2 represents a functional group having a hydrocarbon skeleton containing a saturated bond / unsaturated bond / substituent or a functional group containing a saturated bond / unsaturated bond / substituent containing a covalent bond atom other than carbon, and R1 In the formula, 1 to 3 are attached for the sake of explanation of the reactivity of the glycidyl group.)

  It was found that the epoxy compound having the structure of the above formula (I) or (II) has a particularly high reactivity. The cause of this is not clear, but it is thought as follows. The oxygen of the carbonyl group has a high electron density, and this mainly takes the form of attacking 1 carbon in the formula of the glycidyl group. As a result, it can take a pseudo 6-membered ring structure in which the epoxy ring is opened. That is, it is considered that the energy required for ring opening of the epoxy ring is lower than that of the compound not having the pseudo 6-membered ring structure, and thus the reactivity is specifically high. Therefore, in the present invention, it is preferable to use a compound having at least one structure of the above formula (I) or (II) in one molecule as a tri- or higher functional epoxy compound.

  Moreover, as a specific example of the compound which can take this pseudo 6-membered ring structure, the compound of Formula (I) is 7,8-dimethyl-1,7,8,14-tetradecane tetracarboxylic acid tetrakis (oxiranyl). Methyl), 7-oxabicyclo [4.1.0] heptane-3,4-dicarboxylate diglycidyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] ethylene, bis [ 2- (Glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,3-propanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1 , 4-Butanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid 1,5-pentanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,6-hexanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy -1-cyclohexanecarboxylic acid] 1,7-heptanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,8-octanediyl, bis [2- (glycidyloxycarbonyl) ) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,9-nonanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,10-decanediyl, bis [ 2- (Glycidyloxycarbonyl) -4,5-epoxy-1-cyclohe Suncarboxylic acid] 1,11-undecanediyl, bis [2- (glycidyloxycarbonyl) -4,5-epoxy-1-cyclohexanecarboxylic acid] 1,12-dodecanediyl, 4-cyclohexene-1,2-dicarboxylic acid bis (Oxiran-2-ylmethyl), 4,4-bis [4- (2,3-epoxypropan-1-yloxy) phenyl] pentanoic acid 2,3-epoxypropan-1-yl, 4,4-bis [4 -(2,3-epoxypropan-1-yloxy) phenyl] pentanoic acid 2,3-epoxypropan-1-yl and modified products thereof. Examples of the compound of the above formula (II) include tri (methylglycidyl) isocyanurate, triglycidyl isocyanurate and modified products thereof. Other compounds having the structure of formula (I) include glycidyl acrylate, glycidyl methacrylate, norborna-2,5-diene-2,3-dicarboxylate, 2-methyl-3-glycidyl, and 2-phenylnorborna-2. , 5-Diene-3-carboxylate glycidyl, 2- (piperidinocarbonyl) norborna-2,5-diene-3-carboxylate glycidyl, 2- (dipropylcarbamoyl) norborna-2,5-diene-3- Glycidyl carboxylate, methyl 2-methylenebutanoate (2-ethyloxiran-2-yl), glycidyl 3-pentenoate, glycidyl 4-pentenoate, glycidyl 5-hexenoate, glycidyl 6-heptenoate, glycidyl 7-octenoate , A polymer using a monomer containing at least one glycidyl 8-nonenate and a modified product thereof Etc., and the like.

  In the case of using a monomer among the above as the trifunctional or higher functional epoxy compound of the present invention, 7,8-dimethyl-1,7,8,14-tetradecane is considered in consideration of heat resistance and reaction efficiency due to the epoxy index. Tetracarboxylic acid tetrakis (oxiranylmethyl), 7-oxabicyclo [4.1.0] heptane-3,4-dicarboxylic acid diglycidyl, and triglycidyl isocyanurate are preferable, and are more reactive and excellent in handleability. It is particularly preferable to use triglycidyl isocyanurate as a monomer. Triglycidyl isocyanurate is a powder having a melting point of about 100 ° C., and is easy to handle. In addition, triglycidyl isocyanurate melts into the aliphatic polyester when melt-mixed with the aliphatic polyester of the present invention. A structure in which a trifunctional or higher functional epoxy compound is finely dispersed can be obtained, and the melt viscosity and molecular weight unevenness of the resin can be reduced, and the staple fiber of the present invention can be stably produced. Furthermore, since the compound itself is excellent in crystallinity, it is preferable because it is possible to suppress fuming due to scattering of the epoxy compound, particularly in the production of a melt-molded article using the aliphatic polyester staple fiber of the present invention. is there. In addition, since it has the structure of formula (II) and has carboxyl groups on both sides of nitrogen to which glycidyl group is bonded, it is easy to form the above-described pseudo 6-membered ring structure, and it is estimated that the reactivity is particularly high. Is done.

  Moreover, when using a polymer among the above as an epoxy compound more than trifunctional of this invention, the reactivity and compatibility with aliphatic polyester are considered, and glycidyl acrylate, glycidyl methacrylate, norborna-2,5-diene is considered. 2-methyl 3-glycidyl 2,3-dicarboxylate, 2-phenylnorborna-2,5-diene-3-glycidyl 2-carboxylate, 2- (piperidinocarbonyl) norborna-2,5-diene-3- Glycidyl carboxylate, 2- (dipropylcarbamoyl) norborna-2,5-diene-3-carboxylate, glycidyl 2-methylenebutanoate (2-ethyloxylan-2-yl) methyl, glycidyl 3-pentenoate, 4- Glycidyl pentenoate, glycidyl 5-hexenoate, glycidyl 6-heptenoate, glycidyl 7-octenoate , 8-nonene acid glycidyl and of these modified products, it is preferable that a polymer containing at least one as a reactive monomer. Furthermore, among these compounds, it is easy to obtain and easy to polymerize, and since the resulting polymer is excellent in compatibility with aliphatic polyester, glycidyl acrylate and glycidyl methacrylate are used as reactive monomers. It is preferable to use it. Moreover, what adjusted the compatibility and reactivity with aliphatic polyester and copolymerized monomers other than the said reactive monomer are used suitably. The copolymer component is not particularly limited as long as it is a component having a carbon-carbon double bond or a carbon-carbon triple bond and copolymerizable with the above monomer. For example, ethylene, propene, 2- Butene, 1,3-butadiene, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2-methylpropene, isoprene, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid n -Butyl, tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, phenyl acrylate, benzyl acrylate, naphthyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl N-butyl acid, t-butyl methacrylate, n-pentyl methacrylate, methacrylate Hexyl acid n-, phenyl methacrylate, benzyl methacrylate, and the like methacrylic acid-naphthyl and these modified products.

  Among these copolymerizable components, ethylene, propene, 2-butene, 1, are considered in consideration of reactivity with the above reactive monomer and compatibility with aliphatic polyester, and availability. 3-butadiene, styrene, isoprene, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, methacrylic acid , Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, ethylene, styrene, isoprene, acrylic acid Methyl, ethyl acrylate, propyl acrylate, n-butyl acrylate, acrylic acid t Butyl, n-pentyl acrylate, n-hexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, n-to methacrylate Xylyl and modified products thereof are more preferably used. In particular, when polylactic acid that is suitably used in the present invention is used among aliphatic polyesters, a structure having acrylic acid or methacrylic acid as a skeleton should have a structure excellent in compatibility with polylactic acid. It is more preferable because it can be uniformly added and reacted in the resin.

  The composition of the monomer that is a copolymerization component with respect to the reactive monomer can be arbitrarily determined, but the epoxy index of the epoxy compound, compatibility with the aliphatic polyester, thermal and physical properties It is preferable to determine appropriately according to the purpose. The epoxy index of the epoxy compound is preferably in the range of 500 to 15000 equivalent / t. By adding a trifunctional or higher functional epoxy compound having an epoxy index within the above range to the staple fiber of the present invention, the aliphatic polyester partially reacts, and the one having no problem of thickening or gelation can be stabilized. It becomes possible to manufacture. In general, in melt spinning, when the thickening occurs, the yarn production stability tends to be impaired and the yield tends to deteriorate, but if the compound has an epoxy index in the above range, there is no problem as described above, and the effect of the present invention, That is, when the aliphatic polyester staple fiber is melt-molded again, the remaining epoxy group reacts with the end of the aliphatic polyester, whereby the weight average molecular weight is increased and the durability of the final molded product is improved. From this, the epoxy index is preferably within the above range in order to achieve the effects of the present invention and to perform stable spinning, and the above range is more preferably 1000 to 12000 equivalents / t, more preferably 3000 to 12000 equivalents / t. Most preferably in the range of t.

Further, talc of the present invention, it is important that the average particle diameter D ₅₀ is 5μm or less. By the average particle diameter D ₅₀ of the talc and 5μm or less, after the production of staple fibers of the present invention, to enhance dramatically the crystallinity of the final molded product by heat molding or the like, filtering pressure rises in reeling In addition, it is necessary to be 5 μm or less in order to ensure spinnability and stretchability. As will be described later, the smaller the talc particle size, the larger the specific surface area, and the effect as a crystal nucleating agent is dramatically improved. Therefore, the particle diameter of talc is preferably 4 μm or less, and more preferably 3 μm or less. Most preferably, it is 1.5 μm or less. Incidentally, it is not limited in particular lower limit of the average particle diameter D ₅₀ of the talc, the higher the a cohesive particle size decreases, it is 0.2μm or more because the dispersibility in the polymer becomes poor preferable. In addition, a form modified with an organic substance is preferably applied to improve the dispersibility of the talc surface.

  In addition, talc having a particle diameter of 10 μm or more contained in talc is preferably 0 to 34.5% by volume or less based on the total amount of talc. When the staple fiber of the present invention is used for clothing and industrial materials, a single fiber having a fiber diameter of 7 to 50 μm is required as a general-purpose grade. In our study, it was found that when the fiber diameter was less than twice the particle diameter of the added talc, the fiber strength decreased rapidly and the broad distribution shifted to the low strength side. For example, when the fiber having a reduced strength is blended with natural fiber, thread breakage occurs, causing a process abnormality. Therefore, the content of talc having a particle diameter of more than 10 μm is preferably 0 to 34.5% by volume or less based on the total amount of talc. Preferably it is 0-23 volume%, More preferably, it is 0-12 volume%, Most preferably, it is 0 volume%.

Furthermore, the specific surface area (BET method) of talc is preferably 10 m ² / g or more. The larger the specific surface area, the greater the effect as a crystal nucleating agent, which is preferable. However, when the specific surface area is too large, aggregation of particles tends to occur. From this, the preferable range of the specific surface area is 10 to 50 m ² / g, and more preferably 15 to 40 m ² / g.

The average particle diameter D ₅₀ of the talc used in the present invention is an average value obtained from particle size distribution measured in (Ltd.) using a Shimadzu SALD-2000J, laser diffraction method.

  Talc is preferably contained in an amount of 0.1 to 2% by weight based on the staple fiber of the present invention in order to increase the crystallization rate. If it exceeds 2% by weight, the increase in the crystallization promoting effect is hardly observed due to the aggregation of talc, but the pack life is shortened due to an increase in the filtration pressure during spinning, and fluffing and yarn breakage frequently occur during spinning and stretching. Therefore, the amount of talc added is preferably 0.2 to 2% by weight, and more preferably 0.3 to 1.5% by weight.

  Further, the staple fiber of the present invention was heated to the melting point Tm + 30 ° C. of the aliphatic polyester at a heating rate of 16 ° C./min and a sample amount of 10 mg using a differential scanning calorimeter (DSC) “2920 modulated DSC” manufactured by TA Instruments. Thereafter, the sample is stored for 5 minutes, and when the sample is cooled at a temperature decrease rate of 16 ° C./min, the temperature decrease crystallization temperature Tc ′ and the temperature decrease crystallization heat amount ΔH ′ at that time are determined. The cooling crystallization heat quantity ΔH ′ is preferably 90 to 120 ° C. and 5 to 50 J / g, respectively. The staple fiber of the present invention is suitably used as a binder fiber when obtaining a molded article having an increased molecular weight and excellent durability and mechanical properties after hot pressing, but cooling after pressing during hot pressing. In the process, it is effective in improving the mechanical properties of the hot-press molded product from which crystallization can proceed. It is a parameter that represents the crystallization rate in the cooling step. The higher the temperature-falling crystallization temperature Tc ′, the earlier the temperature-falling crystallization in the cooling process proceeds, and the higher the temperature-falling crystallization heat amount ΔH ′, the higher the ultimate crystallinity of the aliphatic polyester in the molded product obtained. Indicates high. Therefore, the higher the Tc ′ and the higher the ΔH ′, the faster the crystallization speed and the higher the ultimate crystallinity, so that a molded product having excellent mechanical properties can be obtained even with a short heat treatment. Tc 'is preferably 80 to 120 ° C, and most preferably 95 to 120 ° C. Moreover, although ΔH ′ is better as it is higher, 50 J / g is close to the upper limit at present. Therefore, ΔH ′ is preferably 15 to 50 J / g, more preferably 20 to 50 J / g, and most preferably 25 to 50 J / g.

  In addition, the staple fiber of the present invention has a trifunctional or higher epoxy compound added, at least partly reacts with the aliphatic polyester, and the COOH end group concentration in the aliphatic polyester is in the range of 1 to 20 equivalent / t. It is important to be in The reason why the COOH end group concentration of the aliphatic polyester is 20 equivalents / t or less is that it is possible to improve the durability of the aliphatic polyester that is susceptible to degradation due to hydrolysis during storage or transportation by sea. It can be mentioned. For this reason, for example, the staple fiber of the present invention can be stored for a long time and has durability. Further, it is important that the COOH end group concentration is 1 equivalent / t or more. The staple fiber of the present invention can be suitably used as a heat-bonding fiber when, for example, a board formed by hot pressing after blending with various natural fibers and / or synthetic fibers is used. The remaining COOH end group reacts with an unreacted trifunctional or higher functional epoxy compound to increase the molecular weight, thereby improving the durability of the final molded product. From these facts, the COOH end group concentration is preferably 2 to 18 equivalent / t, and most preferably 3 to 15 equivalent / t.

In addition, the trifunctional or higher functional epoxy compound added to the staple fiber of the present invention is added in an amount larger than the added amount with which the total amount reacts with respect to the COOH end group concentration of the aliphatic polyester before the epoxy compound is added. Is preferred. Specifically, it is preferable to determine the addition amount of the epoxy compound according to the following formula (III).
W (wt%)> PA / PE × 100- (III)
(Wherein, W is the amount of the epoxy compound added, PA is the COOH end group concentration of the aliphatic polyester before the epoxy compound is added, and PE is the epoxy index of the epoxy compound. The units of COOH end group concentration and epoxy index are Both are equivalent / t.)

  The aliphatic polyester adjusted to the range of the above formula (III) is preferably easy to have a form partially reacted with the COOH end group of the aliphatic polyester when the staple fiber of the present invention is used. It is possible to dramatically improve the durability of the final molded product by further increasing the molecular weight during hot-press molding after blending, which is an aspect. The weight average molecular weight of the aliphatic polyester extracted from the molded article after hot pressing is preferably 1.05 times or more that of the staple fiber of the present invention from the viewpoint of improving durability, and 1.1 times or more. More preferably, it is 1.2 times or more.

  The staple fiber of the present invention can be used for various applications, and it is particularly preferable to use the staple fiber once melted. That is, the unreacted trifunctional or higher functional epoxy compound remaining in the staple fiber reacts with the end of the aliphatic polyester by heat treatment and further improves the molecular weight, thereby suppressing the decrease in molecular weight due to hydrolysis over time, It becomes possible to maintain the strength of the molded body for a long time. From this, the staple fiber of the present invention is preferably heat-treated at a temperature equal to or higher than the melting point of the aliphatic polyester, and can be particularly suitably used for a molded product produced through the heat treatment step.

  In the aliphatic polyester staple fiber of the present invention, it is important that talc and an epoxy compound coexist in the aliphatic polyester which is a constituent resin. Talc is a naturally-occurring mineral having magnesium oxide as a constituent unit, and the above component acts as an epoxy ring-opening catalyst. From this fact, it becomes possible to further improve the reactivity of the epoxy compound to the COOH end group of the aliphatic polyester by using talc and the epoxy compound together, and when the aliphatic polyester staple fiber is melt-formed again. The effect of increasing the weight average molecular weight can be enhanced.

  Preferred examples of natural fibers used when blending with various natural fibers and / or synthetic fibers mentioned as preferred methods of using the staple fibers of the present invention include cotton fibers, hemp fibers, bamboo fibers, wood fibers, kenaf fibers, and jute. Fiber, banana fiber, plant fiber such as coconut fiber or pulp or cellulose fiber processed from these plant fibers and fibrous fiber such as animal fibers such as silk, wool, Angola, cashmere, camel, etc. It is preferable to select and use one or more of them. In addition, preferable examples of the synthetic fiber include polyethylene terephthalate fiber, polypropylene terephthalate fiber, polybutylene terephthalate fiber, polyacrylic fiber, polyamide fiber, polypropylene fiber, acetate fiber, and regenerated cellulose fiber. The above can be selected and used.

For this reason, the single yarn fineness of the staple fiber of the present invention is not particularly limited, but is preferably set in the range of 0.01 to 25 dtex from the viewpoint of ease of production and ease of handling.
In addition, the cross section of the staple fiber of the present invention is not particularly limited, and can be freely designed such as a round cross section, a trilobal cross section, a cross section, a W-shaped cross section, a hollow cross section and a tabular hollow cross section, A round cross section is preferred because of ease of manufacture.

  Moreover, the strength of the staple fiber of the present invention is preferably 0.8 cN / dtex or more. When the strength is 0.8 cN / dtex or more, yarn breakage hardly occurs during blending or storage, and stable processing becomes possible. The upper limit is not particularly specified, but considering the normal strength of the aliphatic polyester, there is no problem if it is 8 cN / dtex or less. Therefore, the strength of the staple fiber of the present invention is more preferably in the range of 1.0 to 8 cN / dtex.

  In addition, as a preferred production example of the staple fiber of the present invention, first, trifunctional or higher functional epoxy compound and talc are melt-mixed with an aliphatic polyester by a conventionally known method, for example, a biaxial kneading extruder, and finely dispersed. A pellet having the above structure may be prepared, or a master pellet to which an epoxy compound and talc are added at a high concentration may be prepared, diluted, and used. In preparing the master pellet, it is preferable to match the base aliphatic polyester and its particle size (unit: mg / piece, average weight per 100 pellets). By combining the base aliphatic polyester pellets and the particle size thereof, separation from the base aliphatic polyester pellets is less likely to occur in the melt-spinning storage hopper, so that the staple fibers obtained can be uniform. It becomes possible. Furthermore, a method of adding an epoxy compound and talc in the extruder part of the direct spinning machine is also suitable. Thereafter, the polymer extruded by the melt extruder is metered to a predetermined discharge amount by a metering pump, filtered by a spinning pack, spun from a base, applied with an oil agent, and taken up as a sub-tow by a can. Thereafter, it is preferable to produce the staple fiber of the present invention by performing drawing, heat treatment, and mechanical crimping in a drawing process, and then cutting to a predetermined length. At this time, it is preferable to perform mechanical crimping as necessary. Although the cut length can be arbitrarily selected, it is preferable to match the fiber length of the partner to be mixed. The standard for the cut length is 2 to 100 mm.

  Preferred embodiments of the present invention are shown below, but the present invention is not limited to these descriptions.

A. Weight average molecular weight 10 mg of the staple fiber sample or press film sample of the present invention was dissolved in 4 ml of chloroform (for high performance liquid chromatograph) and filtered using a membrane filter having an opening of 0.15 μm to obtain a sample solution. Then, using a water permeation chromatography (GPC) “Waters2690” manufactured by Waters, measured at 25 ° C. with an injection sample volume of 200 μl at a chloroform (for high performance liquid chromatograph) flow rate of 1.0 ml / min. Using a polystyrene 6 sample as a standard substance, the weight average molecular weight was calculated in terms of the main dispersion peak.

B. Epoxy index of epoxy compound The epoxy index is obtained by measuring the amount of epoxy groups according to JIS K7236 (2001), calculating the epoxy index EI (unit: equivalent / kg), and multiplying this by 1,000 to determine the epoxy index (equivalent / t ).

C. The aliphatic staple fiber sample or press film sample of the present invention precisely weighed to a COOH end group concentration of 0.5 g of the aliphatic polyester is dissolved in an o-cresol (5% moisture) adjustment solution, and an appropriate amount of dichloromethane is added to this solution. Then, it measured by titrating with a 0.02N KOH methanol solution. At this time, since the oligomer of the aliphatic polyester is hydrolyzed to produce COOH end groups, the COOH end group concentration of the polymer, the COOH end group concentration derived from the monomer, and the COOH end group concentration derived from the oligomer are all added. Is obtained.

D. Strength of fiber A tensile elongation curve was drawn with a sample length of 10 mm and a tensile speed of 10 mm / min with “Tensilon UCT-100” manufactured by Orientec, and the stress value at the maximum point was defined as the strength of the fiber.

E. Melting point and crystallization characteristics of aliphatic polyester Using DSC “2920 modulated DSC” manufactured by TA Instruments, a melting point peak was obtained at a heating rate of 16 ° C./min and a sample amount of 10 mg, and the peak top position was taken as the melting point. In addition, the temperature was lowered for 5 minutes at the melting point Tm + 30 ° C. of the aliphatic polyester, and the cooling crystallization temperature Tc ′ when the sample was cooled at a cooling rate of 16 ° C./min and the cooling crystallization heat amount ΔH ′ at that time were determined. .

F. Wet heat aging characteristics The press films obtained in Examples and Comparative Examples were subjected to a heat and heat aging treatment for 1,000 hours in an environment of 50 ° C. × 95% RH. . The weight average molecular weight retention before and after the treatment (unit:%, the ratio of the weight average molecular weight before and after the treatment) is calculated, and 70% or more is indicated by ６０, 60% or more by ○, and 50% or less by ×. The above was regarded as passing.

[Example 1]
Nitrogen in the presence of 99.8% pure L-lactic acid (D-lactic acid content 0.2%) as a starting material and bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1) Polymerization was performed at 180 ° C. for 140 minutes in an atmosphere. Thereafter, the mixture was cut in a cooling solvent to obtain polylactic acid pellets P1 having a weight average molecular weight of 140,000, a dispersity of 1.7, a particle size of 35 mg / piece, and a COOH end group concentration of 25.2 equivalent / t. Further, the amount of lactide was measured and found to be 0.11% by weight.

The obtained polylactic acid pellets P1 were dried at a resin temperature of 80 ° C. under vacuum for 4 hours to obtain an absolutely dry state. Talc “SG-2000” (average particle diameter D50 = 1.0 μm, BET specific surface area 35 m ² / g) manufactured by Nippon Talc Co., Ltd. as a talc, 1.0 wt%, trifunctional or higher epoxy as polytalactic acid pellets P1 Compound “TEPIC-S” (substance name triglycidyl isocyanurate, epoxy index 10101 equivalent / t) 1.0 wt% as a compound is kneaded at a temperature of 200 ° C. in a twin screw extruder (KZW-15TWIN) manufactured by Technobel. After extruding, cooling and pelletizing were performed to obtain a polylactic acid resin composition P2.

  Thereafter, the polylactic acid resin composition P2 was dried at 100 ° C. under vacuum for 4 hours to obtain an absolutely dry state. Thereafter, the polylactic acid resin composition P2 was charged into the storage hopper, and a spinning speed of 1000 m / min, a single yarn fineness of 17.6 dtex, and an unstretched tow with a round cross section were obtained at a spinning temperature of 220 ° C. and a residence time of 15 minutes in the spinning machine. . Thereafter, the unstretched tows were aligned, stretched 3.6 times with a stretching machine having a hot water bath, cut to a fiber length of 51 mm, and a staple fiber having a single yarn fineness of 6.6 dtex was obtained.

  The physical property values of the obtained staple fiber are shown in Table 1. Thereafter, the staple fibers were dried with hot air at 80 ° C. for 2 hours. A 5 g staple fiber sample was weighed and subjected to a press treatment for 5 minutes with a 220 ° C. heat press (press pressure 5 MPa) to obtain a press film. The physical properties of the obtained sample are shown in Table 1. It was excellent in wet heat aging characteristics and also excellent in crystallization characteristics.

[Example 2]
Using the polylactic acid pellet P1 obtained in Example 1 in an absolutely dry state, 5% by weight of talc and 10% by weight of a tri- or higher functional epoxy compound were pelletized in the same manner as in Example 1 to obtain a polylactic acid resin. A composition P3 was obtained. Drying was performed for 4 hours under a vacuum at a resin temperature of 80 ° C. at a weight ratio P1: P3 = 9: 1 of P1 and P3 to obtain a mixed pellet P4. A staple fiber and a press film were obtained in the same manner as in Example 1 using the mixed pellet P4. The physical property values of the obtained sample are shown in Table 1. It was excellent in wet heat aging characteristics and also excellent in crystallization characteristics.

[Example 3]
A staple fiber and a press film were obtained in the same manner as in Example 2 except that the composition of the mixed pellets in Example 2 was P1: P3 = 19: 1. The physical properties of the obtained sample are shown in Table 1. Both wet heat aging characteristics and crystallization characteristics were good.

[Example 4]
Staple fibers and a press film were obtained in the same manner as in Example 2 except that the composition of the mixed pellets in Example 2 was P1: P3 = 4: 1. Slight thread breakage was observed when producing staple fibers, but production was possible without problems. The physical properties of the obtained sample are shown in Table 1, and both wet heat aging characteristics and crystallization characteristics were excellent.

[Example 5]
A staple fiber and a press film were obtained in the same manner as in Example 2 except that the composition of the mixed pellets in Example 2 was P1: P3 = 29: 1. The physical properties of the obtained sample are shown in Table 1. Both wet heat aging characteristics and crystallization characteristics were good.

[Example 6]
Staple fibers and a press film were obtained in the same manner as in Example 2 except that the composition of the mixed pellets in Example 2 was P1: P3 = 2: 1. Slight thread breakage was observed when producing staple fibers, but production was possible without problems. The physical properties of the obtained sample are shown in Table 1, and both wet heat aging characteristics and crystallization characteristics were excellent.

[Example 7]
A staple fiber and a press film were obtained in the same manner as in Example 1 except that the polylactic acid resin P7 added with 5.0% by weight of the epoxy compound of Example 1 was used. The physical properties of the obtained sample are shown in Table 2, and were excellent in wet heat aging characteristics and crystallization characteristics.

[Comparative Example 1]
Using the polylactic acid pellets P1 of Example 1, staple fibers and a press film were obtained in the same manner as in Example 1 without adding talc and an epoxy compound. The physical properties of the obtained sample are shown in Table 2, but both the wet heat aging characteristics and the crystallization characteristics were inferior.

[Comparative Example 2]
Using polylactic acid pellets P1 of Example 1, 0.5 wt% of talc was blended without adding an epoxy compound, and pelletizing was performed in the same manner as in Example 1 to obtain a polylactic acid resin composition P5. It was. A staple fiber and a press film were obtained in the same manner as in Example 1 using the P5. The physical properties of the obtained sample are shown in Table 2. Although the crystallization characteristics were excellent, the wet heat aging characteristics were inferior.

[Comparative Example 3]
Using polylactic acid pellets P1 of Example 1, talc was not added and 1.0% by weight of a trifunctional or higher functional epoxy compound was blended, and pelletized by the same method as in Example 1 to obtain a polylactic acid resin. Composition P6 was obtained. Using the P6, staple fibers and press films were obtained in the same manner as in Example 1. The physical properties of the obtained sample are shown in Table 2. Although the wet heat aging characteristics were excellent, the crystallization characteristics were inferior.

[Example 8]
A staple fiber and a staple fiber were prepared in the same manner as in Example 1 except that “SG-95” (average particle diameter D ₅₀ = 2.5 μm, BET specific surface area 15 m ² / g) manufactured by Nippon Talc was used as the talc of Example 1. A press film was obtained. The physical properties of the obtained sample are shown in Table 3, and were excellent in wet heat aging characteristics and good crystallization characteristics.

[Example 9]
Staple fiber and press film were produced in the same manner as in Example 1 except that SG-200 (average particle diameter D ₅₀ = 3.2 μm, BET specific surface area 25 m ² / g) manufactured by Nippon Talc was used as the talc of Example 1. Got. The physical properties of the obtained sample are shown in Table 3, and were excellent in wet heat aging characteristics and good crystallization characteristics.

[Example 10]
Staples were produced in the same manner as in Example 1 except that “P-6” (average particle diameter D ₅₀ = 4.0 μm, BET specific surface area 10.5 m ² / g) manufactured by Nippon Talc was used as the talc of Example 1. Fiber and press film were obtained. When spinning staple fibers, although a slight increase in filtration pressure was confirmed, spinning was possible without problems. The physical properties of the obtained sample are shown in Table 3, and were excellent in wet heat aging characteristics and good crystallization characteristics.

[Comparative Example 4]
Staples were produced in the same manner as in Example 1 except that “P-2” (average particle diameter D ₅₀ = 7.0 μm, BET specific surface area 7.5 m ² / g) manufactured by Nippon Talc was used as the talc of Example 1. Fiber and press film were obtained. When spinning staple fibers, the increase in filtration pressure was significant and yarn breakage occurred frequently. Furthermore, the strength of the obtained staple fiber was remarkably lowered, and it could not withstand practical use. The physical properties of the obtained sample are shown in Table 3. Although it was excellent in wet heat aging characteristics, it was inferior in crystallization characteristics.

[Example 11]
As the epoxy compound of Example 1, “ARUFON UG-4030” (epoxy index 1800 equivalent / t, acrylic-styrene copolymer resin, weight average molecular weight 11,000) manufactured by Toagosei Co., Ltd. was used, and the amount added was 1.5. A staple fiber and a press film were obtained in the same manner as in Example 1 except that the weight% was used. The physical properties of the obtained sample are shown in Table 4. The wet heat aging characteristics were good, and the crystallization characteristics were also excellent.

[Example 12]
As the epoxy compound of Example 1, “ARUFON UG-4100” manufactured by Toagosei Co., Ltd. (epoxy index 1100 equivalent / t, acrylic-styrene copolymer resin, weight average molecular weight 9,200) was used, and the amount added was 2.3. A staple fiber and a press film were obtained in the same manner as in Example 1 except that the weight% was used. Slight smoke generation was observed during the manufacture of staple fibers, but yarn production was possible without any major problems. The physical property values of the obtained sample are shown in Table 4, and it was excellent in crystallization characteristics and wet heat aging characteristics.

[Example 13]
As the epoxy compound of Example 1, “Modiper A4200” (epoxy index 725 equivalent / t, ethylene-glycidyl acrylate-polymethyl methacrylate copolymer resin) manufactured by NOF Corporation was used, and the addition amount was 3.5% by weight. A staple fiber and a press film were obtained in the same manner as in Example 1 except for the above. A slight amount of smoke was observed during the production of staple fibers, but the yarn could be produced without any major problems. The physical property values of the obtained sample are shown in Table 4, and it was excellent in crystallization characteristics and wet heat aging characteristics.

[Comparative Example 5]
Staple fiber and press film were prepared in the same manner as in Example 1 except that “MA-DGIC” (monoallyl diglycidyl isocyanurate, epoxy index 8368 equivalent / t) manufactured by Shikoku Kasei Kogyo was used as the epoxy compound of Example 1. Got. The obtained press film had little effect of increasing the molecular weight and was inferior in wet heat aging characteristics.

Claims (5)

The aliphatic polyester, talc having an average particle size D ₅₀ of 5 μm or less, and a trifunctional or higher functional epoxy compound, wherein the aliphatic polyester and the trifunctional or higher functional epoxy compound are at least partially reacted; COOH terminal group concentration families polyester Ri 1 to 20 equivalents / t der, an aliphatic polyester staple fibers that are used in thermal molding, the heating press 220 ° C. the staple fiber sample 5 g (pressing pressure 5 MPa) The weight average molecular weight of the aliphatic polyester extracted from the molded product after hot-press molding is increased compared to the staple fiber before molding. An aliphatic polyester staple fiber . 2. The aliphatic polyester staple fiber according to claim 1, wherein the content of talc is 0.1 to 2.0% by weight of the whole fiber. The aliphatic polyester staple fiber according to claim 1 or 2, wherein the trifunctional or higher functional epoxy compound has at least one glycidyloxycarbonyl group or N- (glycidyl) amide group in one molecule. A trifunctional or higher functional epoxy compound is a polymer containing a glycidyl acrylate ester, a polymer containing a glycidyl methacrylate ester, a triglycidyl isocyanurate or a modified product thereof, and a glycidyl ester of a polyvalent carboxylic acid having a trifunctional or higher acid terminal. The aliphatic polyester staple fiber according to any one of claims 1 to 3, wherein the aliphatic polyester staple fiber is selected from at least one selected from the group consisting of: Aliphatic polyester extracted from a molded product after hot-pressure forming when 5 g of a staple fiber sample was subjected to press treatment for 5 minutes with a 220 ° C. heat press (press pressure 5 MPa) to form a press film. The aliphatic polyester staple fiber according to any one of claims 1 to 4, wherein the weight average molecular weight is 1.05 times or more that of the staple fiber before molding .