JP2012207170A - Polylactic acid-based resin composition and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition excellent in mechanical strength including a real use, heat resistance, and moist heat resistance by a cross-linked poly lactic acid resin, and to provide a molding in which a real use is possible.SOLUTION: The polylactic acid-based resin composition includes: 0.01-10 pts.mass of a carbodiimide compound based on 100 pts.mass of the total amount of 70-99 pts.mass of a polylactic acid resin in which the D-form content is at most 1.0 mole% or at least 99.0 mole% and which is crosslinked, and 30-1 pts.mass of an aramid fiber and/or an LCP fiber.

Description

  The present invention relates to a polylactic acid-based resin composition and a molded body using the same composition, and more particularly to a resin composition reinforced with aramid fibers and LCP fibers and a molded body using the same composition.

  In recent years, biodegradable polyester resins have attracted attention from the viewpoint of environmental conservation. Among these, polylactic acid is a crystalline polymer, and has a higher melting point and higher heat resistance than other biodegradable polyester resins. In addition, since it can be mass-produced, the cost is low and the utility is high. Furthermore, polylactic acid can be produced using plants such as corn and sweet potato as raw materials, and can contribute to saving resources that may be depleted of oil or the like.

However, polylactic acid has not only a long molding cycle because of its low crystallization rate, but also has the disadvantage that the resulting molded article is inferior in mechanical strength and heat resistance.
As a method for improving the crystallization rate of a polylactic acid resin, for example, a method of adding ordinary talc, silica, calcium lactate or the like as a crystal nucleating agent to a lactic acid polymer has been developed (see, for example, Patent Document 1). However, even in this case, the crystallization rate is still slow, and the obtained molded article has low heat resistance of 100 ° C. or less.

  It has also been proposed to add a low molecular weight compound having an amide group to polylactic acid and a layered clay mineral organized with an organic onium salt to improve the crystallization speed and heat resistance of polylactic acid by their synergistic effect. (For example, refer to Patent Document 2).

  However, in this case, although an improvement in crystallization speed and heat resistance is recognized, the effect is still insufficient, and therefore a molding cycle during injection molding is long, and heat resistance that can withstand actual use is imparted. It has not reached.

  Moreover, in order to improve the crystallization speed, what added the (meth) acrylic acid ester compound to the biodegradable polyester resin is also developed (for example, refer patent document 3). However, in this case, although the crystallization speed is improved, the effect is not sufficient.

  Further, a polylactic acid containing an aramid fiber and / or an LCP fiber and a hydrolysis inhibitor and improving the heat resistance, rigidity and durability by a synergistic effect thereof has been proposed (for example, Patent Document 4). reference). However, in this case, although improvement in heat resistance, rigidity and durability was observed, the effect was still insufficient.

JP-A-8-193165 JP 2003-226801 A JP 2003-128901 A JP 2005-023250 A

  The present invention is intended to solve the above-described problems, and has a high crystallization speed, excellent heat resistance, and further has excellent mechanical strength, impact resistance, and moist heat resistance. It is an object to provide a composition and a molded body obtained by molding the resin composition.

  As a result of intensive studies to solve the above problems, the present inventors have used a polylactic acid resin having a specific D-form content and a cross-linked polylactic acid resin and an aramid fiber. And it discovered that the said subject was solved by using together an LCP fiber and a carbodiimide compound, and reached | attained this invention. That is, the gist of the present invention is as follows.

(1) 70 to 99 parts by mass of a crosslinked polylactic acid resin having a D-form content of 1.0 mol% or less, or 99.0 mol% or more, and an aramid fiber and / or LCP fiber The polylactic acid-type resin composition characterized by mix | blending 0.01-10 mass parts of carbodiimide compounds with respect to 100 mass parts of total amounts with 30-1 mass parts.
(2) The polylactic acid resin composition according to (1), wherein 0.01 to 20 parts by mass of a (meth) acrylic acid ester compound is contained in 100 parts by mass of the polylactic acid resin.
(3) The polylactic acid resin composition according to (1) or (2), wherein the carbodiimide compound has an isocyanate group as a terminal group.
(4) A molded article obtained by molding the polylactic acid resin composition according to any one of (1) to (3).

According to the present invention, since the polylactic acid resin has a specific D-form content and is crosslinked, the crystallization speed and heat resistance of the resin composition can be improved. Moreover, the moist heat resistance of a resin composition can be improved by containing a carbodiimide compound. Furthermore, by containing an aramid fiber and / or LCP, the mechanical strength, heat resistance, and impact resistance of the resin composition can be improved.
Thus, since the polylactic acid-type resin composition of this invention has the outstanding performance, industrial utility value is very high. In addition, since a biodegradable resin derived from a natural product is used, it can contribute to saving of depleted resources such as oil.
The polylactic acid-based resin composition of the present invention can be formed into various molded bodies by various molding methods, and various molded bodies obtained by molding such a polylactic acid-based resin composition of the present invention are various. Can be used for products.

Hereinafter, the present invention will be described in detail.
First, the polylactic acid resin in the present invention is required to have a D-form content of 1.0 mol% or less or a D-form content of 99.0 mol% or more. It is preferably 1 to 0.6 mol% or 99.4 to 99.9 mol%. When the D-form content is within this range, the crystallinity is excellent, the crystallization speed is improved, and the heat resistance is also improved. If the D-form content is outside this range, the effect of improving the crystallization speed and heat resistance will be insufficient.

  In the present invention, the D-form content of the polylactic acid resin is a ratio (mol%) occupied by the D lactic acid unit in the total lactic acid units constituting the polylactic acid resin. Therefore, for example, in the case of a polylactic acid resin having a D-form content of 1.0 mol%, this polylactic acid resin has a ratio of D lactic acid units of 1.0 mol% and a ratio of L lactic acid units of 99. 0.0 mol%.

  In the present invention, the D-form content of the polylactic acid resin is such that L lactic acid and D lactic acid obtained by decomposing the polylactic acid resin are all methyl esterified, and the methyl ester of L lactic acid and the methyl ester of D lactic acid are gas chromatographed. It is calculated by a method of analyzing with a graphic analyzer.

  As the polylactic acid resin used in the present invention, among various commercially available polylactic acid resins, a polylactic acid resin having a D-form content defined by the present invention can be used. In addition, among lactides, which are cyclic dimers of lactic acid, L-lactide having a sufficiently low D-form content or D-lactide having a sufficiently low L-form content is used as a raw material, and a known melt polymerization method is used. Alternatively, those produced by further using a solid phase polymerization method can be used.

  The polylactic acid resin in the present invention satisfies the above-mentioned D-form content and is crosslinked (hereinafter sometimes referred to as a crosslinked polylactic acid resin). The cross-linked polylactic acid resin in the present invention includes divinylbenzene, diallylbenzene, divinylnaphthalene, divinylphenyl, divinylcarbazole, divinylpyridine, and their nucleus-substituted compounds and related homologues; ethylene glycol diacrylate, butylene glycol. Polyfunctional acrylic acid compounds such as diacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, tetramethylol methane tetraacrylate; ethylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol dimethacrylate, Tetraethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10 Multifunctional methacrylic acid compounds such as decanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate; aliphatic or aromatic such as divinyl phthalate, diallyl phthalate, diallyl malate, bisacryloyloxyethyl terephthalate Polyvinyl carboxylic acid, such as polyvinyl ester, polyallyl ester, polyacryloyloxyalkyl ester, polymethacryloyloxyalkyl ester; polyvinyl of aliphatic or aromatic polyhydric alcohol such as diethylene glycol divinyl ether, hydroquinone divinyl ether, bisphenol A diallyl ether, etc. Ethers or polyallyl ethers; cyanurates such as triallyl cyanurate and triallyl isocyanurate Allyl ester of isric acid or isocyanuric acid, triallyl phosphate, trisacryloxyethyl phosphate, maleimide compounds such as N-phenylmaleimide, N, N'-m-phenylenebismaleimide, dipropargyl phthalate, maleic acid A polyfunctional monomer such as a compound having two or more triple bonds such as dipropargyl can be used.

By using a polylactic acid resin as a crosslinked polylactic acid resin, mechanical strength and heat resistance are improved, and dimensional stability is also improved. And as a crosslinking agent, a (meth) acrylic acid ester compound is especially desirable. When the polylactic acid resin is cross-linked by this component, particularly mechanical strength, heat resistance, and dimensional stability are improved.
The (meth) acrylic acid ester compound has high reactivity with the polylactic acid resin, and it is difficult for the monomer to remain, and the resin is less colored, so that it has two or more (meth) acrylic groups in the molecule, or 1 Compounds having one or more (meth) acryl groups and one or more glycidyl groups or vinyl groups are preferred. Specific compounds include glycidyl methacrylate, glycidyl acrylate, glycerol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, allyloxy polyethylene glycol monoacrylate, allyloxy polyethylene glycol monomethacrylate, polyethylene glycol dimethacrylate, polyethylene glycol. Examples include diacrylate, polypropylene glycol dimethacrylate, polypropylene glycol diacrylate, and polytetramethylene glycol dimethacrylate. Further, these alkylene glycol portions may be alkylene copolymers having various lengths. Furthermore, butanediol methacrylate, butanediol acrylate and the like can be mentioned.

  When a (meth) acrylic acid ester compound is used, the content in the resin composition is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the polylactic acid resin, and more preferably 0.05 to 10 parts by mass. Part, preferably 0.1 to 5 parts by weight.

  When a (meth) acrylic acid ester compound is blended with a polylactic acid resin, it is preferable to use a peroxide in combination because the crosslinking reaction is promoted. Specific examples of peroxides include benzoyl peroxide, bis (butylperoxy) trimethylcyclohexane, bis (butylperoxy) cyclododecane, butylbis (butylperoxy) valerate, dicumyl peroxide, butylperoxybenzoate, dibutyl Examples thereof include peroxide, bis (butylperoxy) diisopropylbenzene, dimethyldi (butylperoxy) hexane, dimethyldi (butylperoxy) hexyne, and butylperoxycumene. 0.1-20 mass parts is preferable with respect to 100 mass parts of polylactic acid resin, and, as for the compounding quantity of a peroxide, it is preferable that it is 0.1-10 mass parts especially. Although it can be used even if it exceeds 20 parts by mass, it is disadvantageous in terms of cost. In addition, since such a peroxide decomposes | disassembles at the time of mixing with resin, even if it is used at the time of a mixing | blending, it may not be contained in the obtained resin composition.

  Examples of means for blending the (meth) acrylic acid ester compound with the polylactic acid resin include a melt kneading method using a general extruder. In order to improve the kneading state, it is preferable to use a twin screw extruder. The kneading temperature is preferably in the range of the melting point of the polylactic acid resin + 5 ° C. to the melting point of the polylactic acid resin + 100 ° C., and the kneading time is preferably 20 seconds to 30 minutes. If the temperature is lower or shorter than this range, the kneading or reaction becomes insufficient, and if the temperature is higher or longer, the resin may be decomposed or colored. When blending, if the (meth) acrylic ester compound is in a solid state, a method of supplying it using a dry blend or a powder feeder is preferable. In the case of a liquid state, it is injected from the middle of an extruder using a pressure pump. The method is preferred. A peroxide can be blended in the same manner.

  As a preferable method when the (meth) acrylate compound and the peroxide are used in combination, a method in which the (meth) acrylate compound and / or the peroxide is dissolved or dispersed in a medium and injected into a kneader. As a result, the operability can be remarkably improved. That is, a (meth) acrylic acid ester compound solution or dispersion is injected during the melt kneading of the polylactic acid resin component and the peroxide, or the (meth) acrylic acid ester compound is melted during the kneading of the polylactic acid resin. It is possible to melt and knead by injecting a solution or dispersion liquid of benzene and peroxide.

  As a medium for dissolving or dispersing the (meth) acrylic acid ester compound and / or the peroxide, a general one is used, and is not particularly limited, but is a plasticizer excellent in compatibility with the polylactic acid resin of the present invention. Is preferred. For example, one or more selected from aliphatic polycarboxylic acid ester derivatives, aliphatic polyhydric alcohol ester derivatives, aliphatic oxyester derivatives, aliphatic polyether derivatives, aliphatic polyether polycarboxylic acid ester derivatives, etc. Examples include plasticizers. Specific compounds include dimethyl adipate, dibutyl adipate, triethylene glycol diacetate, methyl acetyl ricinoleate, acetyl tributyl citric acid, polyethylene glycol, dibutyl diglycol succinate, glycerol diacetomonocaprylate, glycerol diacetomonolaurate, etc. Is mentioned. The amount of the plasticizer used is 30 parts by mass or less, preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the biodegradable resin polyester resin. When the reactivity of the crosslinking agent is low, it is not necessary to use a plasticizer. However, when the reactivity is high, it is preferable to use 0.1 parts by mass or more. In addition, since this medium may volatilize at the time of mixing with resin, even if it uses it at the time of manufacture, this medium may not be contained in the obtained resin composition.

  The polylactic acid-based resin composition of the present invention can improve mechanical strength, heat resistance, and impact resistance by blending aramid fibers and / or LCP fibers with a crosslinked polylactic acid resin.

  The aramid fiber in the present invention is a fiber made of a resin having an aromatic amide structure such as polyparaphenylene terephthalamide or copolyparaphenylene 3.4'oxydiphenylene terephthalamide. Specific examples include “Kevlar” manufactured by DuPont, “Technola” manufactured by Teijin Techno Products, and “Twaron”. These are usually formed into fibers by dissolving an aramid raw material in sulfuric acid or N-methylpyrrolidone and performing wet spinning.

In the present invention, LCP (Liquid Crystalline Poly
esters)) fiber is a fiber made of a resin exhibiting liquid crystallinity when melted, and usually refers to a fiber formed of polyester exhibiting liquid crystallinity when melted. Polyester that exhibits liquid crystallinity when melted means that light is transmitted in a flowable temperature range when a polyester sample powder is placed on a heated sample stage between two polarizing plates that are orthogonal to each other by 90 ° and heated. It means what has the property which can be done.

  Examples of such polyester include aromatic polyester. The aromatic polyester is composed of an aromatic dicarboxylic acid, an aromatic diol and / or an aromatic hydroxycarboxylic acid, or a derivative thereof. In some cases, these and the alicyclic dicarboxylic acid, an alicyclic diol, an aliphatic diol, Copolymers with these derivatives are also included.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 4,4′dicarboxydiphenyl, 2,6-dicarboxynaphthalene, 1,2-bis (4-carboxyphenoxy) ethane, and their alkyl and aryl. , Alkoxy, and halogen substituted groups of halogen groups.

  Aromatic diols include hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylethane, 2,2-bis (4 -Hydroxyphenyl) propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, etc., and alkyls thereof , Nuclear substituents such as aryl, alkoxy and halogen groups.

  Examples of aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxynaphthalene-6-carboxylic acid, 1-hydroxynaphthalene-5-carboxylic acid, and their alkyl, aryl, alkoxy, and halogen. And a nuclear substitute of the group.

  Examples of the alicyclic dicarboxylic acid include trans-1,4-dicarboxycyclohexane, cis-1,4-dicarboxycyclohexane and the like, and substituted products of these alkyl, aryl, and halogen groups.

  Examples of the alicyclic and aliphatic diols include trans-1,4-dihydroxycyclohexane, cis-1,4-dihydroxycyclohexane, ethylene glycol, 1,4-butanediol, and xylylenediol.

  LCP fibers are usually obtained by melt spinning these polyester raw materials. Specific examples of the LPC fiber include “Vectrane” manufactured by Kuraray, which is composed of hydroxybenzoic acid and hydroxynaphthalene carboxylic acid, “Sumika Super Fiber” manufactured by Sumitomo Chemical Co., Ltd., which is mainly composed of hydroxybenzoic acid, and the like.

  The content of the aramid fiber and / or LCP fiber needs to be 1 to 30 parts by mass with respect to 99 to 70 parts by mass of the crosslinked polylactic acid resin. Preferably, it is 5-20 mass parts (crosslinked polylactic acid resin 95-80 mass parts). If the content is less than 1 part by mass, the effect of improving the mechanical strength, heat resistance, impact resistance, etc. cannot be obtained sufficiently. If the content exceeds 30 parts by mass, the fluidity of the resin composition is inferior, and the operability deteriorates, such as clogging during operation. Moreover, the moldability is also impaired.

  The diameter of the aramid fiber and / or LCP fiber is preferably 1 to 40 μm, and more preferably 5 to 20 μm. Below this range, the price of the fiber increases and the economic efficiency decreases, and the handling property decreases due to the decrease in bulk density. On the other hand, when it exceeds, the strength improvement effect of the resin composition is lowered.

  The length of the aramid fiber and / or LCP fiber is preferably 0.5 to 30 mm, more preferably 1 to 10 mm, and still more preferably 2 to 6 mm. Below this range, the effect of improving the mechanical strength, heat resistance, and impact resistance of the resin composition is poor.On the other hand, when it exceeds the above range, workability is reduced, such as bridging by the hopper of the molding machine, and melting characteristics are reduced. This causes problems such as significant inhibition.

  The form of the aramid fiber and / or LCP fiber may take any form such as a staple, a cut filament, a chopped strand, a chopped strand mat, and a pulp as long as the diameter and length are within the above ranges.

  For the purpose of improving dispersibility and adhesion to the crosslinked polylactic acid resin, a surface treatment agent can be applied to the aramid fiber and / or the LCP fiber. Examples of the surface treatment agent include compounds having two or more epoxy groups, carboxyl groups, carbonyl groups, oxazonyl groups, hydroxyl groups, amino groups, such as acid anhydride modified polyolefins, EGMG, epoxy resins, acid anhydride modified polyesters, Phenogine resin, dinitroamine, acid anhydride-modified polyester and the like are preferable.

  The method of adding the aramid fiber and / or LCP fiber to the crosslinked polylactic acid resin is not particularly limited, but the following two methods are particularly preferable. The first method is a method of preparing a compound by kneading cut fibers or staples having a predetermined length in advance into a crosslinked polylactic acid resin using a twin screw extruder or a melt mixer. At this time, when feeding the fiber to the extruder, only the cross-linked polylactic acid resin is first melted, and then the fiber may be fed from the middle of the twin screw extruder by a side feeder or the like.

  The second method is a method using a so-called pultrusion method in which a continuous filament or continuous staple yarn is unwound and a lactic acid resin is extruded from a crosshead die, and at the same time, the above fibers are coated and impregnated with the resin. . The pultruded strand is cut into an appropriate size by a pellet cutter or the like to form resin pellets. The length of the fiber contained in the resin pellet is controlled substantially equal to the length of the resin pellet.

  Furthermore, the polylactic acid-type resin composition of this invention contains a carbodiimide compound, and moist heat resistance improves by containing a carbodiimide compound.

  Examples of the carbodiimide compound used in the present invention include 4,4'-dicyclohexylmethane carbodiimide, tetramethylxylylene carbodiimide, N, N-dimethylphenylcarbodiimide, N, N'-di-2,6-diisopropylphenylcarbodiimide and the like. The carbodiimide compound having one or more carbodiimide groups in the molecule is not particularly limited.

  Such a carbodiimide compound can be produced by a conventionally known method, and can be produced by a carbodiimide reaction accompanied by a carbon dioxide removal reaction using a diisocyanate compound as a raw material. If the end-capping treatment is not performed, the end group has an isocyanate group.

  As the carbodiimide compound used in the resin composition of the present invention, it is preferable to use a carbodiimide compound having an isocyanate group as a terminal group from the viewpoint of improvement in heat resistance and mechanical properties. The isocyanate group has a higher reactivity than the carbodiimide group, and a higher effect is obtained.

  The content of the carbodiimide compound in the polylactic acid resin composition of the present invention is 0.01 to 10 parts by mass with respect to 100 parts by mass in total of the crosslinked polylactic acid resin and the aramid fiber and / or LCP fiber. Is required and is preferably 0.1 to 5 parts by mass. When the content is less than 0.01 parts by mass, the effect of improving the heat and moisture resistance of the resin composition of the present invention is not seen, whereas when it exceeds 10 parts by mass, the heat resistance and moldability are lowered.

  In addition, glass fibers may be added to the resin composition of the present invention for the purpose of improving mechanical strength and heat resistance. The amount is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the resin composition. As the glass fiber, a normal glass fiber is sufficient, and a surface treatment may be performed in order to enhance the adhesion to the resin. As an addition method, it can be added from a hopper in an extruder or from the middle of kneading using a side feeder. Moreover, it can also use by diluting with a base resin at the time of shaping | molding by carrying out a masterbatch process of glass fiber.

  In the resin composition of the present invention, the pigment, heat stabilizer, antioxidant, weathering agent, flame retardant, plasticizer, lubricant, mold release agent, antistatic agent, filler, A crystal nucleus material or the like can be added. Examples of heat stabilizers and antioxidants include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, and alkali metal halides. As the flame retardant, a halogen-based flame retardant, a phosphorus-based flame retardant, and an inorganic flame retardant can be used. However, in consideration of the environment, it is desirable to use a non-halogen flame retardant. Non-halogen flame retardants include phosphorus flame retardants, hydrated metal compounds (aluminum hydroxide and magnesium hydroxide), N-containing compounds (melamine and guanidine), and inorganic compounds (borate and Mo compounds). It is done. Inorganic fillers include talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, Examples thereof include zinc oxide, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, and carbon fiber. Examples of the organic filler include naturally occurring polymers such as starch, cellulose fine particles, wood flour, okara, fir shell, bran, and modified products thereof. Examples of the inorganic crystal core material include talc and kaolin. Examples of the organic crystal core material include a sorbitol compound, benzoic acid and a metal salt of the compound, a phosphate metal salt, and a rosin compound. In addition, the method of mixing these with the polyester resin composition of this invention is not specifically limited.

The polylactic acid resin composition of the present invention preferably has the following values as its mechanical properties: bending strength, flexural modulus, and bending fracture strain. The bending strength is preferably 120 MPa or more, particularly preferably 130 MPa or more, and more preferably 135 MPa or more. The flexural modulus is preferably 4.0 GPa or more, more preferably 5.0 GPa or more, and even more preferably 6.0 GPa or more. The bending fracture strain is preferably 4% or more, and more preferably 4.5% or more.
In addition, said bending strength, a bending elastic modulus, and bending fracture | rupture distortion use an injection molding machine (Toshiba IS-80G), melt | dissolve a resin composition at the molding temperature of 200-170 degreeC, and the mold temperature of 95 degreeC conditions. An ISO dumbbell-type test piece is prepared and measured based on ISO 178.

The polylactic acid-based resin composition of the present invention is excellent in impact resistance and preferably has a Charpy impact strength of 3.5 kJ / m ² or more, and more preferably 8.0 kJ / m ² or more. Furthermore, it is preferably 15.0 kJ / m ² or more.
The Charpy impact strength is measured based on ISO 179 by preparing an ISO dumbbell-shaped test piece in the same manner as described above.

And as a parameter | index which shows that the resin composition of this invention is excellent in heat resistance, it is preferable that heat deformation temperature is 130 degreeC or more, and it is preferable that it is 135 degreeC or more especially.
The heat distortion temperature is obtained by preparing an ISO dumbbell-shaped test piece in the same manner as described above and measuring the load at 0.45 MPa based on ISO 75.

As an index indicating that the crystallization speed of the polylactic acid resin composition of the present invention is improved, there is a molding cycle (second), and when the mold temperature is 95 ° C., it is 30 seconds or less. Among them, it is preferably 28 seconds or less.
In the same way as above, the injection cycle machine (Toshiba IS-80G) is used for the molding cycle, and the resin composition is melted at a molding temperature of 200 to 170 ° C., and an ISO dumbbell-shaped test piece is produced at a mold temperature of 95 ° C. In this case, after the resin composition is injected into the mold, the time (seconds) until the mold can be released satisfactorily (the molded body is fixed to the mold or without resistance) is obtained.

Furthermore, there is a strength retention as an index indicating that the polylactic acid resin composition of the present invention is excellent in heat and moisture resistance, and it is preferable that it exceeds 90%.
For the strength retention, after using the test piece for which the bending strength (pre-treatment bending strength) described above was measured and treated in an environment of temperature 60 ° C. and humidity 95% RH for 600 hours, bending strength (after treatment) Bending strength) is measured, and the strength retention is calculated by the following formula.
Strength retention (%) = (Bending strength after treatment / Bending strength before treatment) × 100

  The polylactic acid-based resin composition of the present invention is formed into various molded bodies by injection molding, blow molding, extrusion molding, inflation molding, and molding methods such as vacuum molding, pressure molding, and vacuum / pressure molding after sheet processing. Can do. In particular, it is preferable to use an injection molding method. In addition to a general injection molding method, gas injection molding, injection press molding, or the like can also be employed. As an example of injection molding conditions suitable for the resin composition of the present invention, the cylinder temperature is not lower than the melting point or flow start temperature of polylactic acid, preferably 180 to 250 ° C., optimally 190 to 240 ° C., and The mold temperature is suitably (melting point of the resin composition−20) ° C. or lower. If the molding temperature is too low, the operability becomes unstable, such as defective filling in the molded product, and it tends to be overloaded. On the other hand, when the molding temperature is too high, the resin composition is decomposed, and problems such as reduction in the strength of the resulting molded article and coloring may easily occur.

  The resin composition and molded product of the present invention can enhance their heat resistance by promoting crystallization. For example, the crystallization can be promoted by devising the mold temperature at the time of injection molding. In this case, the mold temperature is (the glass transition temperature of polylactic acid + 20) ° C. or more and the melting point of the resin composition. -20) It is preferable to cool to below the glass transition temperature of polylactic acid after being kept at a temperature not higher than ° C for a predetermined time. As a method for promoting crystallization after molding, after direct cooling to a temperature lower than the glass transition temperature of polylactic acid, heat treatment is performed again at a temperature not lower than the glass transition temperature of polylactic acid and not higher than (the melting point of the resin composition−20) ° C. It is preferable.

  Specific examples of the molded body of the present invention include: resin parts for electrical appliances such as various cases; agricultural materials such as containers and cultivation containers; resin parts for agricultural machines; resin parts for fishery business such as floats and processed fishery products containers ; Tableware and food containers such as dishes, cups and spoons; Medical resin parts such as syringes and infusion containers; Resin parts for drainage materials, fences, storage boxes, construction switchboards, etc .; Cooler boxes, Resin parts such as fan and toy, resin parts for general goods; resin parts for automobiles such as bumpers, instrument panels and door trims. Moreover, it can also be set as extrusion molded articles, such as a film, a sheet | seat, and a pipe, and a hollow molded article.

Hereinafter, the present invention will be described more specifically with reference to examples. The measurement methods used for the evaluation of the resin compositions of the following examples and comparative examples are as follows.
(1) Bending strength, bending elastic modulus, bending breaking strain As described above, the obtained test piece was used and measured based on ISO 178.
(2) Charpy impact strength:
As above-mentioned, it measured based on ISO 179 using the obtained test piece.
(3) Thermal deformation temperature (℃)
As described above, the obtained test piece was used and measured under a load of 0.45 MPa based on ISO 75.
(4) Moist heat resistance As described above, the bending strength retention after wet heat treatment was calculated and evaluated.
(5) Molding cycle As described above, the molding time for producing the test piece was measured.

The raw materials used in Examples and Comparative Examples of the present invention are shown below.
[Polylactic acid resin]
-Toyota brand name "S-12"; D-form content = 0.1 mol% (hereinafter sometimes referred to as "S-12")
・ Product name “TE-4000” manufactured by Unitika Ltd .; D-form content = 1.4 mol% (hereinafter sometimes referred to as “TE-4000”)
[Peroxide]
Di-t-butyl peroxide; manufactured by NOF Corporation, trade name “Perbutyl D” (hereinafter sometimes referred to as “PBD”)
[(Meth) acrylic acid ester compound]
-Ethylene glycol dimethacrylate; manufactured by Nippon Oil & Fats Co., Ltd., trade name "Blemmer PDE-50" (hereinafter sometimes referred to as "PDE")
[Aramid fiber]
-"Technora" manufactured by Teijin Techno Products; T-322EH3-12
[LCP fiber]
・ Kuraray "Vectran"; CF1670T
[Carbodiimide compound]
* "LA-1" manufactured by Nisshinbo Co., Ltd .; having an isocyanate group at the end group and having an isocyanate group content of 1 to 3% (hereinafter sometimes referred to as "LA-1")
・ Nisshinbo Co., Ltd. “HMV-8CA”; having no isocyanate group at the end group (hereinafter sometimes referred to as “HMV”)

(Production of crosslinked polylactic acid resin)
Using a twin screw extruder (trade name “TEM37BS type” manufactured by Toshiba Machine Co., Ltd.), polylactic acid resin (100 parts by mass) is supplied from the root supply port of the extruder, and a pump is used from the middle of the kneader. Then, a solution in which a (meth) acrylic acid ester compound and a peroxide were mixed at a ratio shown in Table 1 was injected, and melt-kneading extrusion was performed at a processing temperature of 170 to 200 ° C. The molten resin discharged from the end of the extruder is taken up in a strand shape, passed through a vat filled with cooling water, cooled, and then cut into a pellet shape to form crosslinked polylactic acid resins (A-1) to (A-5) ) Was obtained.

Example 1
Using a twin screw extruder (trade name “TEM37BS type” manufactured by Toshiba Machine Co., Ltd.), 99 parts by mass of polylactic acid resin (A-1), 1 part by mass of aramid fiber, carbodiimide compound (100 parts by mass of polylactic acid resin and allied fiber) 1.5 parts by mass) is dry-blended and supplied from the root supply port of the extruder, while the barrel temperature is 190 ° C., the screw rotational speed is 200 rpm, and the discharge rate is 15 kg / h, while venting is effective. Melt extrusion was performed. The molten resin discharged from the extruder tip was taken up in a strand shape, passed through a vat filled with cooling water, cooled, and then cut into a pellet shape to obtain a resin composition pellet.
The obtained pellets were vacuum dried at 70 ° C. for 24 hours. Thereafter, using an injection molding machine (trade name “IS-80G type” manufactured by Toshiba Machine Co., Ltd.), an ISO-compliant test piece was prepared while adjusting the mold surface temperature to 95 ° C.

Examples 2-11, Comparative Examples 1-8
Except for changing the types and contents of polylactic acid resin, aramid fiber, LCP fiber, and carbodiimide compound to those shown in Table 2, pellets of the resin composition were obtained in the same manner as in Example 1, and in the same manner as in Example 1. A test piece was prepared.

  Table 2 summarizes the characteristic values and evaluation results of the polylactic acid resin compositions obtained in Examples 1 to 11 and Comparative Examples 1 to 8.

As is clear from Table 2, the polylactic acid resin compositions obtained in Examples 1 to 11 were not limited in bending properties, impact resistance, heat resistance, moist heat resistance, and molding cycle (crystallization rate). It was excellent.
On the other hand, since the resin composition of Comparative Examples 1 to 3 uses a polylactic acid resin whose D-form content is outside the range specified in the present invention, there is no effect of improving the crystallization speed and heat resistance, and the heat distortion temperature is low The molding cycle was long. Since the resin composition of Comparative Example 4 did not contain a carbodiimide compound, the result was inferior in heat and moisture resistance. Since the resin composition of Comparative Example 5 did not contain aramid fibers or LCP fibers, the results were inferior in all of bending properties, heat resistance, and impact resistance. Since the resin composition of Comparative Example 6 contained too much aramid fiber, the fluidity was deteriorated, poor feed to a molding machine was generated, and the resin composition could not be obtained. The resin composition of Comparative Example 7 did not use a cross-linked polylactic acid resin (S-12 was used as a polylactic acid resin without cross-linking), resulting in poor bending strength and heat resistance. Since the resin composition of Comparative Example 8 contained too much carbodiimide compound, the results were inferior in heat resistance and moldability compared to Examples 3 and 5 in which the carbodiimide compound was blended within the scope of the present invention.

Claims (4)

The D-form content is 1.0 mol% or less, or 99.0 mol% or more, and 70 to 99 parts by mass of a crosslinked polylactic acid resin, and aramid fibers and / or LCP fibers 30 to 1 The polylactic acid-type resin composition characterized by mix | blending 0.01-10 mass parts of carbodiimide compounds with respect to 100 mass parts of total amounts with a mass part. The polylactic acid resin composition according to claim 1, wherein 0.01 to 20 parts by mass of a (meth) acrylic acid ester compound is contained in 100 parts by mass of the polylactic acid resin. The polylactic acid resin composition according to claim 1 or 2, wherein the carbodiimide compound has an isocyanate group as a terminal group. A molded product, wherein the polylactic acid resin composition according to any one of claims 1 to 3 is molded.