Polylactic acid resin composition

Abstract

To provide a polylactic acid resin composition excellent in characteristics caused by a filler, capable of preventing a thermal degradation in a melt kneading process, and deterioration due to hydrolysis under a moist heat environment, and excellent also in productivity during working (shorter molding cycle).SOLUTION: A polylactic acid resin composition of the present invention comprises a polylactic acid resin, a filler, a hydrolysis inhibitor, a filler dispersant and / or a filler dispersing polymer, where a content of the filler in the lactic acid resin composition is 10 wt.% to 70 wt.%, and the content of the hydrolysis inhibitor in the polylactic acid resin composition is 0.1% to 5 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polylactic acid resin composition. [Background technology]

[0002] Polylactic acid is a plant-derived resin known as a biodegradable resin. Polylactic acid is sometimes crystallized for use to improve heat resistance, but the crystallization rate of polylactic acid is slow, resulting in problems such as low productivity during molding, such as a long molding cycle in injection molding.

[0003] Furthermore, attempts have generally been made to obtain molded articles with improved properties by blending various fillers into resin compositions. Blending fillers at high concentrations is extremely difficult due to production problems (e.g., feed necks when adding fillers to a kneader) and filler dispersibility problems. For example, Patent Document 1 discloses blending polylactic acid and a filler to obtain a resin composition, but even when the filler content is about 30% by weight, the feed necks make it difficult to perform stable melt-kneading with high productivity.

[0004] Furthermore, conventional polylactic acid resin compositions have the problem that, due to the high concentration of filler blended therein, they are susceptible to thermal degradation during the melt-kneading process and hydrolysis in a humid and hot environment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-352844 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, conventional polylactic acid resin compositions, which have difficulty in incorporating a high concentration of filler, have the problem that the filler-attributable properties (e.g., rigidity, heat resistance, and shape stability) are not fully exhibited and are susceptible to the effects of hydrolysis. The present invention has been made to solve this problem, and an object of the present invention is to provide a polylactic acid resin composition that has excellent filler-attributable properties, is prevented from thermal degradation during the melt-kneading process and degradation due to hydrolysis in a humid and hot environment, and also has excellent productivity during molding (shortened molding cycle). [Means for solving the problem]

[0007] The polylactic acid resin composition of the present invention is a polylactic acid resin composition comprising a polylactic acid resin, a filler, a hydrolysis inhibitor, and a filler dispersant and / or a filler dispersion polymer, wherein the content of the filler in the polylactic acid resin composition is 10% by weight to 70% by weight, and the content of the hydrolysis inhibitor in the polylactic acid resin composition is 0.1% by weight to 5% by weight. In one embodiment, the hydrolysis inhibitor is a compound having one or more functional groups of at least one type selected from the group consisting of a carbodiimide group, an oxazoline group, and an epoxy group. In one embodiment, the filler dispersing agent is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids. In one embodiment, the filler dispersion polymer is at least one selected from the group consisting of polyolefin-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyalkylene glycol-based resins, polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, acrylic-based resins, urethane-based resins, epoxy-based resins, and water-soluble polysaccharides. In one embodiment, the filler dispersion polymer is at least one selected from the group consisting of polyvinyl alcohol-based resins, polyalkylene glycol-based resins, polyvinylpyrrolidone-based resins, and water-soluble polysaccharides. In one embodiment, the total content of the filler dispersant and the filler dispersion polymer in the polylactic acid resin composition is 0.1% by weight to 30% by weight. In one embodiment, the filler is at least one selected from talc and mica. In one embodiment, the polylactic acid resin composition further comprises an impact modifier. In one embodiment, the impact resistance improver is at least one selected from the group consisting of aliphatic polyester resins, aliphatic-aromatic polyester resins, polyvinyl alcohol resins, and natural rubbers. According to another aspect of the present invention, there is provided a method for producing the polylactic acid resin composition, which comprises melt-kneading a polylactic acid resin, a filler granule, and a hydrolysis inhibitor, the filler granule containing the filler, the filler dispersant, and / or the filler dispersion polymer, and the filler content in the filler granule is 80 to 99.9 parts by weight per 100 parts by weight of the filler granule. According to yet another aspect of the present invention, there is provided an injection-molded article formed from the polylactic acid resin composition. According to yet another aspect of the present invention, there is provided an extrusion molded article formed from the polylactic acid resin composition described above. According to yet another aspect of the present invention, there is provided a sheet-shaped material formed from the polylactic acid resin composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polylactic acid resin composition that has excellent filler-attributable properties, in which degradation of the polylactic acid resin due to hydrolysis is suppressed, and that also has excellent productivity during molding (e.g., shortened molding cycle), as well as a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] A. Polylactic acid resin composition A-1. Overview of polylactic acid resin composition The polylactic acid resin composition of the present invention contains a polylactic acid resin, a filler, a hydrolysis inhibitor, and a filler dispersant and / or a filler dispersion polymer. The filler content in the polylactic acid resin composition is 10% to 70% by weight. The impact modifier content in the polylactic acid resin composition is 0.1% to 5% by weight. The content ratios of components in the polylactic acid resin composition, including the "filler content in the polylactic acid resin composition" and the "hydrolysis inhibitor content," are weight ratios based on the total solid content in the polylactic acid resin composition.

[0010] The polylactic acid resin composition of the present invention contains a high filler content, and therefore, although the polylactic acid resin is the main component, it is possible to form a molded article having excellent mechanical properties (for example, rigidity and dimensional stability (low molding shrinkage, low linear expansion coefficient, low warpage)). Furthermore, the polylactic acid resin composition can be advantageously used from the viewpoints of heat resistance (heat distortion temperature resistance), appearance, colorability (ability to be colored to bright colors), filler dispersibility, and composition uniformity. The polyester resin composition is particularly advantageous in that it has a good balance of rigidity, heat resistance, and impact resistance. The polylactic acid resin composition also has an excellent production speed when produced by melt-kneading. Furthermore, the polylactic acid resin composition is significantly improved in terms of thermal degradation during the melt-kneading process and degradation due to hydrolysis in a humid and hot environment.

[0011] Furthermore, the polylactic acid resin composition exhibits a rapid crystallization rate, providing excellent moldability during injection molding and shortening the molding cycle. The degree of crystallization of the polylactic acid resin composition can be evaluated by differential scanning calorimetry (DSC). Differential scanning calorimetry involves measuring the endothermic heat of melting and the exothermic heat of recrystallization of polylactic acid crystals during a series of operations: heating a 5-10 mg sample from room temperature to 200°C at a constant heating rate, holding the sample at 200°C for 5 minutes, and then cooling it to room temperature at a constant cooling rate. The faster the exothermic peak of recrystallization occurs during the cooling process, or the higher the temperature range at which it occurs, the more likely crystallization will occur during molding, allowing for a faster molding speed (molding cycle). In the polylactic acid resin composition, the exothermic peak due to crystallization is preferably 10 J / g or more, more preferably 20 J / g or more, and even more preferably 25 J / g or more, in terms of polylactic acid. When the exothermic peak due to crystallization is 10 J / g or more in terms of polylactic acid, excellent heat resistance can be exhibited due to the progress of crystallization. Note that the term "polylactic acid equivalent" used here refers to the value obtained by dividing the heat generation amount of the exothermic peak by the content of polylactic acid contained in the resin composition sample.

[0012] The polylactic acid resin composition of the present invention, which has the above-described excellent properties, can be obtained, for example, by forming a filler granule containing the above-described filler and a filler dispersant and / or a filler dispersion polymer, and then mixing the filler granule with a polylactic acid resin (e.g., by melt-kneading). The adoption of such a production method significantly improves the workability of filler addition and filler dispersibility, making it possible to incorporate a high filler content.

[0013] In one embodiment, a molded article is provided that is formed from the polylactic acid resin composition. The flexural modulus of the molded article at 23°C is preferably 3 GPa or more, more preferably 5 GPa or more, and even more preferably 7 GPa or more. The flexural modulus is measured in accordance with ISO 178. The molded article can be obtained, for example, by injection molding pellets of the polylactic acid resin composition, as described below.

[0014] The deflection temperature under load of 0.45 MPa of a molded article formed from the polylactic acid resin composition is preferably 100° C. or higher, more preferably 110° C. or higher, even more preferably 120° C. or higher, and particularly preferably 130° C. or higher. The deflection temperature under load is measured in accordance with ISO 75 using a dumbbell-shaped test piece (Type 1A multipurpose test piece).

[0015] The tensile strength of a molded article formed from the polylactic acid resin composition at 23°C is preferably 35 MPa or more, more preferably 40 MPa or more, and even more preferably 50 MPa or more. The tensile strength and critical elongation described below are measured using a dumbbell-shaped test piece (Type 1A multipurpose test piece) in accordance with ISO 527 at a pulling rate of 5 mm / min.

[0016] In the polylactic acid resin composition, the higher the temperature at which the exothermic peak of recrystallization occurs during the cooling process, the shorter the molding cycle can be, which is preferable. According to the DSC measurement described above, when the temperature is lowered from 200°C at a rate of 10°C / min, the exothermic peak of recrystallization is preferably 95°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher.

[0017] A-2. Polylactic acid resin The polylactic acid resin may be any suitable polylactic acid resin, which has properties and conditions equivalent to those of synthetic resins under normal use conditions and is degradable under specific disposal conditions.

[0018] The polylactic acid resin may be a polylactic acid (homopolymer) or a copolymer containing structural units derived from lactic acid. In one embodiment, the polylactic acid resin may be a copolymer of lactic acid and a hydroxycarboxylic acid. Examples of hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxycaproic acid. Polylactic acid resins with a high L-lactic acid content are preferably used because of their high melting point. The L-lactic acid content of the polylactic acid resin is preferably 96% or more, more preferably 98% or more, and even more preferably 98.6% or more.

[0019] The content of the polylactic acid resin in the polylactic acid resin composition is preferably 29.8% by weight to 90% by weight, more preferably 35% by weight to 80% by weight, even more preferably 40% by weight to 75% by weight, and particularly preferably 50% by weight to 70% by weight.

[0020] A-3. Filler As the filler, any appropriate filler can be used depending on the desired properties.

[0021] Examples of properties and effects that can be imparted by the above fillers include weight increase or weight reduction, reinforcement (increased rigidity, increased elastic modulus, increased strength), dimensional stability, molding cycle (crystallization rate), crystallinity, thermal conductivity, electrical conductivity, magnetism, piezoelectricity, vibration damping, sound insulation, sliding properties, heat insulation, electromagnetic wave absorption, light reflectivity, light scattering, heat radiation, flame retardancy, radiation protection, ultraviolet protection, moisture removal, dehydration, deodorization, gas absorption, gas barrier, anti-blocking, oil absorption, antibacterial properties, promotion of biodegradation, and increased bio-content (increased proportion of naturally derived components).

[0022] For example, calcium carbonate, talc, silica, and clay are suitable for weight increase. For reinforcement, wollastonite, potassium titanate, xonotlite, gypsum fiber, aluminum borate, fibrous magnesium compound (MOS), aramid fiber, various fiber systems, carbon fiber, glass fiber, talc, mica, glass flakes, polyoxybenzoyl whiskers, and the like are suitable. For antibacterial properties, catechin, silver ion-supported zeolite, copper phthalocyanine, and the like are suitable. For gas barrier properties, synthetic mica, clay-synthetic mica nanofillers, and the like are suitable. For weight reduction, balloon systems such as silica balloons, glass balloons, cenospheres, perlite, and shirasu balloons are suitable. For conductivity, carbon black, graphite, carbon fiber, metal powder, metal fiber, and metal foil are suitable. For the purpose of imparting magnetism, various magnetic materials, various ferrites, magnetic iron oxide, samarium-cobalt (Sm-Co), Nd-Fe-B, etc. are suitable. For the purpose of imparting thermal conductivity, alumina, AlN, BN, BeO, etc. are suitable. For the purpose of imparting piezoelectricity, barium titanate, lead zirconate titanate (PZT), etc. are suitable. For the purpose of imparting vibration damping properties, mica, graphite, potassium titanate, xonotlite, carbon fiber, ferrite, etc. are suitable. For the purpose of imparting sound insulation properties, iron powder, lead powder, barium sulfate, etc. are suitable. For the purpose of imparting sliding properties, graphite, hexagonal BN, molybdenum sulfide, Teflon (registered trademark) powder, talc, high molecular weight polyethylene, etc. are suitable. For the purpose of imparting electromagnetic wave absorption, electromagnetic wave absorbing ferrite, graphite, charcoal powder, carbon microcoil (CMC), carbon nanotubes (CNT), PZT, etc. are suitable. For the purpose of imparting light reflection and light scattering, titanium oxide, glass beads, calcium carbonate, aluminum powder, mica, etc. are suitable. For the purpose of imparting heat radiation, magnesium oxide, hydrotalcite, MOS, alumina, charcoal powder, etc. are suitable. For the purpose of flame retardancy, antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc borate, red phosphorus, zinc carbonate, hydrotalcite, dawsonite, bromine-based flame retardants, phosphorus-based flame retardants, etc. are suitable. For the purpose of radiation protection, lead powder, barium sulfate, etc. are suitable.For the purpose of UV protection, titanium oxide, zinc oxide, iron oxide, etc. are suitable. For the purpose of dehumidification and dehydration, calcium oxide, magnesium oxide, etc. are suitable. For the purpose of deodorization and gas absorption, zeolite, activated clay, etc. are suitable. For the purpose of anti-blocking (preventing film from being pressed together), silica, calcium carbonate, talc, spherical microparticles (silicone or acrylic beads), etc. are suitable. For the purpose of oil absorption (printing ink absorption, quick-drying, etc.), algae-like calcium carbonate, algae-like xonotlite, etc. are suitable. For the purpose of water absorption, water-absorbing polymer gels, calcium oxide, magnesium oxide, etc. are suitable. For the purpose of improving the bio content, cellulosic materials (wood flour, wood fiber, sawdust, wood chips, newsprint, paper, flax, hemp, wheat straw, rice husks, kenaf, jute, sisal, peanut shells, soybean husks, etc.), starch, natural rubber, etc. are suitable.

[0023] The size of the filler can be any appropriate size. The particle diameter of the filler is, for example, 10 nm to 100 μm. The size of the filler can be determined by laser diffraction.

[0024] In one embodiment, a silicate compound is used as the filler. Examples of preferred silicate compounds include talc, mica, and wollastonite. In one embodiment, the filler is at least one selected from talc and mica. Talc is particularly preferred. The silicate compound not only functions as a reinforcing material for the polylactic acid resin composition, but also functions as a crystal nucleating agent for polylactic acid. Use of this silicate compound increases the degree of crystallization of polylactic acid and simultaneously increases the crystallization rate. As a result, the heat resistance of the polylactic acid resin composition can be increased and the solidification time can be shortened, thereby improving moldability.

[0025] As described above, the filler content in the polylactic acid resin composition is 10 to 70% by weight, preferably 15 to 65% by weight, and more preferably 20 to 60% by weight.

[0026] A-4. Filler dispersant In one embodiment, the filler dispersant is a compound comprising a hydrophobic group and a hydrophilic group. The hydrophilic / hydrophobic balance can be controlled by adjusting the degree of esterification of the filler dispersant compound, the type of fatty acid (presence or absence of a hydroxyl group, saturated or unsaturated fatty acid, alkyl chain length), and the degree of polymerization. Use of a filler dispersant can improve the dispersibility of the filler in the polylactic acid resin composition, as well as improve productivity (discharge rate) and the ease of cleaning the processing machine in the production of filler granules described below.

[0027] Examples of the filler dispersant include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamides, polyhydric alcohol fatty acid esters, polyglycerin fatty acid esters, etc. One type of filler dispersant may be used alone, or two or more types may be used in combination.

[0028] In one embodiment, the filler dispersing agent is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

[0029] The polyhydric alcohol fatty acid ester is an ester compound composed of a polyhydric alcohol and a fatty acid. Examples of the polyhydric alcohol fatty acid ester include esters of polyhydric alcohols such as pentaerythritol and glycerin with fatty acids having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms).

[0030] The fatty acid amide is a compound having a structure formed by dehydration condensation of a fatty acid with ammonia or a primary or secondary amine. Examples of the fatty acid amide include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

[0031] The polyglycerol fatty acid ester is an ester compound composed of polyglycerol and a fatty acid, and examples of the polyglycerol fatty acid ester include diglycerol palmitate, diglycerol stearate, diglycerol oleate, decaglycerol palmitate, decaglycerol stearate, and decaglycerol oleate.

[0032] The polyglycerol fatty acid ester, condensed hydroxy fatty acid, and alcohol ester of condensed hydroxy fatty acid may be commercially available products. Examples of commercially available products include "Tirabazole P-4," "Tirabazole VR-01," and "Tirabazole VR-08" (polyglycerol fatty acid ester), and "Tirabazole H-818" (alcohol ester of condensed hydroxy fatty acid), manufactured by Taiyo Kagaku Co., Ltd. These may be used alone or in combination of two or more.

[0033] The content of the filler dispersant in the polylactic acid resin composition is preferably 0.1 to 15% by weight, more preferably 1 to 10% by weight, and even more preferably 1 to 5% by weight.

[0034] The total content of the filler dispersant and filler dispersion polymer in the polylactic acid resin composition is preferably 0.1% by weight to 30% by weight, more preferably 1% by weight to 25% by weight, and even more preferably 1% by weight to 15% by weight. Within these ranges, a resin composition with excellent filler-attributable properties can be obtained, and a polylactic acid resin composition with excellent productivity and filler dispersibility can be obtained. Note that the "total content of the filler dispersant and filler dispersion polymer" refers to the content of the filler dispersion polymer when the polylactic acid resin composition does not contain a filler dispersant, and refers to the content of the filler dispersant when the polylactic acid resin composition does not contain a filler dispersion polymer.

[0035] A-5. Filler dispersion polymer The polylactic acid resin composition may contain a filler dispersion polymer to enhance filler dispersibility, which may also have the effect of improving interfacial adhesion between the filler and the polylactic acid resin.

[0036] The filler dispersion polymer may be at least one selected from the group consisting of polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyalkylene glycol resins, polyvinylpyrrolidone resins, polyester resins, polyamide resins, acrylic resins, urethane resins, epoxy resins, and water-soluble polysaccharides. In one embodiment, the filler dispersion polymer is at least one selected from the group consisting of polyvinyl alcohol resins, polyalkylene glycol resins, polyvinylpyrrolidone resins, and water-soluble polysaccharides. These resins are particularly preferred because they have excellent compatibility with polylactic acid resins, excellent filler dispersion properties, and are themselves biodegradable.

[0037] Specific examples of the polyvinyl alcohol resin used as a filler dispersion polymer include ethylene-vinyl alcohol copolymer (EVOH; EVAL (registered trademark) manufactured by Kuraray Co., Ltd.), butenediol-vinyl alcohol copolymer (BVOH; Nichigo G Polymer (registered trademark) manufactured by Mitsubishi Chemical Corporation), etc.

[0038] The water-soluble polysaccharide refers to a water-soluble compound composed of long chains of monosaccharides such as glucose and mannose. In one embodiment, the water-soluble polysaccharide is a water-soluble carbohydrate composed of 10 or more monosaccharides bound together. In one embodiment, the water-soluble polysaccharide may be a naturally occurring polymeric substance. For example, water-soluble polysaccharides derived from plants (seeds, sap, fruits, etc.), seaweed, or microorganisms may be used. Specific examples of the water-soluble polysaccharide include pullulan, dextrin, chitosan, tamarind seed gum, guar gum, locust bean gum, gum arabic, karaya gum, pectin, cellulose, konjac mannan, soybean polysaccharides, carrageenan, agar, tragacanth gum, alginic acid, xanthan gum, gellan gum, Agrobacterium succinoglycan, carboxymethylcellulose, and cationized guar gum. Among these, pullulan or dextrin is preferred, and pullulan is more preferred.

[0039] Commercially available filler dispersion polymers may be used, including Chemipearl (registered trademark) manufactured by Mitsui Chemicals, Inc., HYPOD (registered trademark) manufactured by The Dow Chemical Company, AQUACER (registered trademark) manufactured by BYK Japan, ZAIKXEN (registered trademark) manufactured by Sumitomo Seika Chemicals, Saiden Glue (registered trademark) manufactured by Saiden Chemical, and Saivinol (registered trademark) manufactured by Saiden Chemical.

[0040] The content of the filler dispersion polymer in the polylactic acid resin composition is preferably 0.1 to 15% by weight, more preferably 1 to 10% by weight, and even more preferably 1 to 5% by weight.

[0041] A-6. Hydrolysis inhibitors The hydrolysis inhibitor can be blended to improve the processing stability, long-term heat resistance, and long-term moist heat resistance of the polylactic acid resin composition. The hydrolysis inhibitor has the function of suppressing a decrease in the molecular weight of the polylactic acid resin and stabilizing it by capturing carboxylic acids generated by hydrolysis of the polylactic acid resin.

[0042] In one embodiment, the hydrolysis inhibitor is a compound having at least one functional group selected from the group consisting of a carbodiimide group, an oxazoline group, and an epoxy group. The compound may be a polymer.

[0043] Examples of the compound containing the carbodiimide group include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, N,N'-di-2,6-diisopropylphenylcarbodiimide, 2,6,2',6'-tetraisopropyldiphenylcarbodiimide, as well as cyclic carbodiimides and polycarbodiimides such as Carbodilite (registered trademark: manufactured by Nisshinbo Chemical Inc.) and Stavaxol (registered trademark: manufactured by Rhein Chemie AG).

[0044] Examples of commercially available products of the compound having the epoxy group include "Celloxide 2021P" manufactured by Daicel Corporation, "Denacol" manufactured by Nagase ChemteX Corporation, and "Epofriend" manufactured by Daicel Corporation.

[0045] An example of a commercially available product of the compound having the oxazoline group is "Epocross" manufactured by Nippon Shokubai Co., Ltd.

[0046] The content of the hydrolysis inhibitor in the polylactic acid resin composition is preferably 0.1 to 5% by weight, more preferably 0.3 to 4% by weight, and even more preferably 0.5 to 3% by weight.

[0047] A-7. Other ingredients The polylactic acid resin composition may further contain any other appropriate components (additives) as needed. Examples of additives include antioxidants, light stabilizers, foaming agents, UV absorbers, antiblocking agents, heat stabilizers, antibacterial agents, compatibilizers, plasticizers, tackifiers, processing aids, lubricants, coupling agents, flame retardants, oxygen scavengers, and colorants. The additives may be added at any appropriate time during the production process of the polylactic acid resin composition, for example, in the form of liquid, powder, pellets, granules, or masterbatch.

[0048] In one embodiment, the polylactic acid resin composition may further contain a resin other than a polylactic acid-based resin. Examples of such resins include aliphatic polyester-based resins (e.g., homopolymers or copolymers of polycaprolactone, polyethylene succinate, polybutylene succinate adipate, polyhydroxyvalerate, etc., or modified homopolymers or copolymers thereof), aliphatic-aromatic polyester-based resins (e.g., block or random polymers of aliphatic carboxylic acids or hydroxy acids, aromatic dicarboxylic acids, and 1,3-propanediol, etc.), and polyvinyl alcohol-based resins (e.g., polyvinyl alcohol, polyvinyl acetate, polyvinyl butyrate, ethylene-vinyl alcohol copolymers, etc.). Naturally derived biodegradable resins such as natural rubber and eucommia elastomers can also be used. In one embodiment, the polylactic acid resin composition further contains an impact modifier. The above resins can serve as impact modifiers in polylactic acid-based resin compositions. In particular, polybutylene adipate terephthalate (PBAT) resin and amorphous polyhydroxyalkanoate (amorphous PHA), which are aliphatic or aromatic polyester resins, are preferred as impact modifiers. Other preferred impact modifiers include polyolefin elastomers, SEBS, SEPS, and core-shell rubber. In one embodiment, the impact modifier is at least one selected from the group consisting of aliphatic polyester resins, aliphatic or aromatic polyester resins, polyvinyl alcohol resins, and natural rubber. When an impact modifier is used in a polylactic acid resin composition, the content of the impact modifier in the polylactic acid resin composition is 5% by weight to 50% by weight, more preferably 10% by weight to 40% by weight, and even more preferably 15% by weight to 30% by weight.

[0049] B. Method for producing polylactic acid resin composition In one embodiment, the polylactic acid resin composition can be obtained by melt-kneading the polylactic acid resin, the filler, the filler dispersant and / or filler dispersion polymer, and the hydrolysis inhibitor. Any appropriate method can be used for melt-kneading. For example, a kneader, a Banbury mixer, a roll, or a single-screw or multi-screw extruder having two or more screws can be used. Preferably, a twin-screw extruder is used. The melt-kneaded composition can be pelletized. In one embodiment, melt-kneading is performed at a temperature range of 80°C to 170°C (preferably 100°C to 160°C).

[0050] In one embodiment, the polylactic acid resin composition is obtained by melt-kneading the filler granules containing the filler, a filler dispersant, and / or a filler dispersion polymer with the polylactic acid resin and a hydrolysis inhibitor. This manufacturing method significantly improves the workability of filler addition and filler dispersibility, enabling a high filler content. More specifically, the filler granules are remarkably stable when introduced into an extruder or other device. Therefore, their use can dramatically improve the productivity (hourly compound processing rate) of filler-containing resin compositions. Furthermore, the use of the filler granules improves filler dispersibility and molding processability (fluidity). Therefore, polylactic acid resin compositions obtained using the filler granules can be obtained by melt-kneading via low-load extrusion, i.e., by suppressing excessive heat generation in the resin, even when containing a high concentration of filler. As a result, the polylactic acid resin composition exhibits excellent mechanical properties and moldability, with reduced thermal degradation of the resin. Furthermore, adding a hydrolysis inhibitor during melt-kneading facilitates adjustment of the blending amount. The hydrolysis inhibitor can also be blended during the granulation process of the filler granules.

[0051] (Filler granules) The filler granules can be produced by any appropriate method. The filler granules can be obtained, for example, by subjecting a mixture containing the filler, the filler dispersant, and / or a binder component to a semi-wet granulation method. More preferably, the filler granules can be obtained by subjecting a mixture containing the filler, the filler dispersant, and a binder component to a semi-wet granulation method. The filler and filler dispersant described in Section A can be used.

[0052] The content of the filler in the filler granules is preferably 80 to 99.9 parts by weight, more preferably 82 to 99 parts by weight, even more preferably 85 to 98 parts by weight, particularly preferably 87 to 97 parts by weight, and most preferably 90 to 96 parts by weight, relative to 100 parts by weight of the filler granules.

[0053] In one embodiment, the filler-dispersing polymer is mixed in the form of a polymer liquid (polymer solution or polymer dispersion) containing the filler-dispersing polymer.

[0054] In one embodiment, the method for producing the filler granules includes a mixing step of mixing the filler with the filler dispersion polymer component and / or the filler dispersant, a granulation step of granulating the mixture obtained through the mixing step to obtain a granule precursor, and a drying step of drying the granule precursor.

[0055] In the mixing step, water may be further mixed in. The water to be added is not particularly limited, and examples thereof include tap water, distilled water, ion-exchanged water, hard water, and soft water.

[0056] The amount of water mixed is usually 1 to 30 parts by weight, preferably 3 to 25 parts by weight, and more preferably 5 to 20 parts by weight, per 100 parts by weight of filler in the filler granules.

[0057] In the mixing step, the components are preferably blended at room temperature and homogenized using any suitable mixer, such as a Henschel mixer, a powder kneader (KDH, KDA, CKD, CPM) (Dalton), a Spartan mixer (SPM) (Dalton), or an SP granulator (SPG) (Dalton).

[0058] The mixing time in the mixing step can be any appropriate time depending on the type of components, the type of mixer, the component blending ratio, etc. The mixing time in the mixing step is set so that each component is uniformly dispersed. A high-speed mixer such as a Henschel mixer or a Spartan mixer can be used for processing in 1 to 10 minutes. On the other hand, a powder kneader may require processing times of several minutes to 60 minutes.

[0059] In the granulation step, a compression granulation method is preferably used. Also, in the granulation step, a semi-wet granulation method can be preferably used. Examples of the compression granulation method / semi-wet granulation method include a disk pelleting method, a tableting method, and a briquetting method. From the viewpoint of the balance between productivity and the quality of the resulting filler granules, the disc pelletizer method is preferably employed.

[0060] The basic structure of a disc pelletizer consists of one or two discs with numerous 2-30 mm holes and a roller for pressure-feeding raw materials through the holes in the disc. The raw materials supplied between the disc and roller, or between two discs, are forced into the holes in the disc as the roller rotates, forming a cylindrical extrudate. The disc holes are tapered, and compressive stress is applied from the outer periphery of the die hole as the filler mixture passes through the holes. The length of this tapered hole is called the effective length. The extruded granule precursor is cut by a cutter or other device on the backside of the disc to obtain pellet-shaped filler granules. The length of the granule precursor (and thus the filler granules) can be adjusted by adjusting the distance between the backside of the disc and the cutter and the rotation speed of the roller.

[0061] More specifically, disc pelleting methods include roller-disc die methods, roller-ring die methods, double die methods, flat die methods, etc. Commercially available disc pelleting machines include the Disc Pelletter F Series manufactured by Dalton.

[0062] Any suitable drying method can be used in the drying step. After the drying step, a filler granule from which fine powder has been removed can be obtained using a vibrating sieve or the like. Any suitable drying equipment can be used in the drying step. For example, a vibrating fluidized bed dryer is preferred because it can dry efficiently in a short time, and examples of such equipment include the VDF series vibrating fluidized bed dryers manufactured by Dalton.

[0063] In the present invention, various molded articles are provided using the polylactic acid resin composition. For example, injection molded articles, extrusion molded articles, sheets, 3D printer shaped articles, etc. can be provided. Furthermore, shaped articles (vacuum molded articles, press molded articles, sheet-like shaped articles, etc.) can be obtained from the sheets. [Example]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Parts and percentages are by weight unless otherwise specified.

[0065] [Production Example 1] Production of filler granule MB-1 20 parts by weight of a filler dispersion polymer (polyolefin aqueous dispersion (aqueous PE dispersion); manufactured by Mitsui Chemicals, Inc., trade name "Chemipearl A100"; polyolefin solids concentration: 40% by weight; average particle size of polyolefin particles: 4 μm; in the table, "D-1") and 3 parts by weight of a filler dispersant (polyglycerol condensed hydroxy fatty acid ester; manufactured by Taiyo Kagaku Co., Ltd., trade name "Chirabazole H818"; in the table, "C-1") were placed in a 1 L plastic container and stirred at room temperature for 20 minutes using a stirring blade to obtain mixture A. Next, 100 parts by weight of filler (talc powder, manufactured by Asada Flour Milling Co., Ltd., product name "JM-300"; in the table, "B-1") was added to a powder kneader (KDHJ-10), and while stirring with a stirring blade at a rotation speed of 30 rpm, Mixture A was added to the powder kneader. After that, stirring was carried out for 6 minutes, and Mixture B was obtained. Mixture B was placed in a disc pelleter (Dalton, product name "Disc Pelleter F-5 / 11-175") to obtain a pellet-shaped granulated precursor. The die hole diameter was 3 mm, the die plate thickness was 15 mm, the effective length of the die hole was 10 mm, and the roller rotation speed of the dispelleter was 108 rpm. The obtained granule precursor was dried at 140°C for 6 hours using a hot air circulation dryer to obtain filler granule MB-1.

[0066] [Production Example 2] Production of filler granule MB-2 Filler granule MB-2 was obtained in the same manner as in Production Example 1, except that 20 parts by weight of a filler dispersion polymer (aqueous polyolefin dispersion (aqueous PE dispersion); manufactured by Mitsui Chemicals, Inc., trade name "Chemipearl A100") was used instead of 20 parts by weight of a filler dispersion polymer (a 15% aqueous solution of water-soluble vinyl alcohol resin (BVOH) (manufactured by Mitsubishi Chemical Corporation, trade name "Nichigo G-polymer AZF8035Q"; saponification degree 98.0 mol% or more; melting point: 172°C; polymer concentration: 15 wt%; in the table, "D-2")). The ingredients used in Production Examples 1 and 2 are shown in Table 2.

[0067] [Table 1]

[0068] [Table 2]

[0069] <Evaluation> The filler granules obtained in Production Examples 1 and 2 were subjected to the following evaluations. The results are shown in Table 3. (1) Bulk density The dried surface-modified filler granules were allowed to fall naturally into a 1-liter measure, filled to the brim, and weighed to a volume of exactly 1 liter. The bulk density (unit: kg / L) of the surface-modified filler granules was calculated by measuring the weight. (2) Pellet size Twenty granules of the surface-modified filler granules were taken out, and the average length and diameter of the granules were measured using a vernier caliper. (3) Moisture content The amount of moisture (unit: weight %) remaining in the surface-modified filler granules was measured using an infrared moisture meter (FD-660 manufactured by Kett Electric Laboratory). (4) Collapse strength measurement The disintegration stress (unit: kg) of the surface-modified filler granules after drying was measured using a Kiya hardness tester (manufactured by Shiro Sangyo Co., Ltd., product name "WPF1600-B") The measured value was the average value of 25 granules. (5) Filler concentration in filler granules 1 to 3 g of the filler granules were collected and kept in a crucible in an electric furnace at 600° C. for 3 hours, and the filler concentration (wt %) was calculated from the ash weight.

[0070] [Table 3]

[0071] [Example 1] 55 parts by weight of filler granules MB-2, 45 parts by weight of polylactic acid (PLA; NatureWorks, Inc., product name "Ingeo 4032D"; melting point 155-170°C; in the table, "A-1"), and 1 part by weight of hydrolysis inhibitor (Nisshinbo Chemical, product name "Carbodilite HMV-5CA-LC"; in the table, "E-1") were quantitatively added to a twin-screw extruder (Toshiba Machine Co., Ltd., product name "TEM37SS"; L / D = 48) via a hopper located at the most upstream position of the extruder, using independent gravimetric feeders. Continuous melt-kneading (discharge: 20 kg / hr) was performed to obtain pellets of the resin composition. The cylinder temperature of the extruder from the middle stage onwards was set to 200°C. The rotation speed of the main screw of the twin-screw extruder was set to 100 rpm. The melt-kneaded resin composition was extruded in the form of a strand, cooled in a water-cooled bath, and formed into pellets having a length of about 3 mm.

[0072] [Examples 2 and 3, and Comparative Examples 1 to 3] Pellets of a polylactic acid resin composition were obtained in the same manner as in Example 1, except that the filler granules, polylactic acid, hydrolysis inhibitor, and impact modifier shown in Table 4 were used in the amounts shown in Table 4. Details of the polylactic acid and hydrolysis inhibitor used are as shown in Table 2. The impact modifier used in Example 3 was polybutylene adipate terephthalate (PBAT) resin (manufactured by BASF, product name "Ecoflex F Blend C1200"). In Comparative Examples 1 and 2, no filler dispersion polymer or filler dispersant was used, and no filler granules were formed, but powdered talc ("B-1" in Table 2) was used. In these Comparative Examples, bridging of powder B-1 occurred at the feed port, making it impossible to stably produce pellets of the polylactic acid resin composition. Comparative Example 3 is an example in which the hydrolysis inhibitor was omitted.

[0073] [Table 4]

[0074] <Evaluation> The polylactic acid resin compositions obtained in the examples and comparative examples were subjected to the following evaluations, and the results are shown in Table 5. (1) Ash content measurement (unit: weight %) 1 to 3 g of pellets of the polylactic acid resin composition were collected and held in a crucible in an electric furnace at 600° C. for 3 hours, and the ash weight was calculated. (2) Dispersibility of filler Pellets of the polylactic acid resin composition were rolled in a hot press to form a sheet with a thickness of about 0.5 mm. The sheet was visually inspected for any remaining filler aggregates and evaluated according to the following criteria. AA: Good dispersion state with almost no filler agglomerates observed A: A state in which a small amount of relatively small filler aggregates remain BB: A state in which a considerable number of relatively small filler aggregates remain B: Large filler aggregates (Distribution ranking: AA>A>BB>B (Left good)) (3) Crystallization temperature (Tc) measurement (unit: °C) Using a differential scanning calorimeter (DSC) (DSC6220, manufactured by Hitachi High-Tech Science Corporation), 5 to 10 mg of a sample was heated from room temperature to 200°C at a constant heating rate, held at 200°C for 5 minutes, and then cooled to room temperature at a constant cooling rate of 10°C / min, and the recrystallization temperature of polylactic acid crystals was measured. (4) MFR (unit: g / 10 min) The melt mass flow rate (MFR) was measured in accordance with JIS K7210 using a "Melt Indexer" manufactured by Toyo Seiki Seisakusho, Ltd. The measurement conditions were 210°C and a load of 2.16 kg. (5) Tensile measurement The tensile strength (unit: MPa) and elongation at break (unit: %) were measured in accordance with ISO527 at a pulling rate of 5 mm / min. The test specimens used for the measurements were dumbbell-shaped test specimens (Type 1A multipurpose test specimens) molded from pellets of the polylactic acid resin composition using an injection molding machine (Toyo Machinery & Metal Co., Ltd., "SI-80W", mold clamping 100 tons) with a cylinder setting temperature of 200°C, a mold temperature of 110°C (both the fixed side and the moving side), and a cooling time of 60 seconds. (6) Bending measurement A bending test was carried out in accordance with ISO178 to measure the bending strength (unit: MPa) and bending modulus (unit: GPa). The test specimens used for the measurements were dumbbell-shaped test specimens cut out from the above-mentioned tensile measurements. (7) Heat deflection temperature measurement (unit: °C) The deflection temperature under load was measured under a load of 0.45 MPa in accordance with ISO 75. The test specimens used for the measurement were dumbbell-shaped test specimens cut out from the above-mentioned tensile measurement. (8) Charpy impact test (unit: KJ / m 2 ) The Charpy impact strength of notched test pieces formed from the polylactic acid resin composition was measured in accordance with ISO 179. The test pieces used for the measurement were dumbbell-shaped test pieces cut out from the above-mentioned tensile measurement. (9) Molding time of injection-molded specimen (dumbbell specimen) (unit: seconds) In the injection molding of the above-mentioned dumbbell-shaped test piece for the tensile test (Type 1A multipurpose test piece), the total number of seconds was counted, including the cooling time of 60 seconds, injection time, pressure holding time, and molded product ejection time. (10) Appearance of molded product The appearance of the dumbbell-shaped test pieces for the tensile test was classified into the following three categories. A: Glossy B: Dullness is observed C: Rough skin (Appearance ranking: A>B>C (Left good)) (11) Warpage of injection-molded specimens (dumbbell test specimens) The above-mentioned dumbbell-shaped test piece for the tensile test (Type 1A multipurpose test piece) was placed on a horizontal surface, and one end of the dumbbell was pressed against the horizontal surface. The lift (unit: mm) of the opposite end from the horizontal surface was measured and classified into the following three categories. AA: Almost no lifting is observed A: Floating less than 2mm B: Floating is 2mm or more but less than 4mm C: Floating of 5mm or more (Sled ranking: AA>A>B>C (Left good)) (12) Specific gravity The specific gravity of the resin composition was measured using a hydrometer (manufactured by Shinko Denshi Co., Ltd., "DMA220H"). (13) Moisture and heat resistance The test pieces were exposed to a humid and hot environment of 60°C and 95% relative humidity, and the change in flexural strength (unit: MPa) over time in the humid and hot environment was measured in accordance with ISO 178. The initial flexural strength was taken as 100, and the flexural strength was measured as the time (unit: Hr) required for the flexural strength to reach 50. The test pieces used for the measurements were dumbbell-shaped test pieces cut out from the tensile measurements.

[0075] [Table 5]

[0076] As shown in Table 5, Examples 1 to 3 have excellent rigidity (flexural modulus) and heat distortion temperature resistance. Furthermore, as the test specimens could be easily obtained by injection molding, the polylactic acid resin composition of the present invention has a high crystallization rate and improved moldability. Furthermore, the obtained polylactic acid resin composition not only has high rigidity and heat resistance, but also has excellent surface appearance (smoothness). Furthermore, the molded specimens have excellent dimensional stability (shrinkage rate, linear expansion coefficient, low warpage). A comparison between Example 1 and Comparative Example 3 demonstrates excellent moist heat resistance.

Claims

1. A polylactic acid resin composition comprising a polylactic acid resin, a filler granule containing a filler and a filler dispersant and / or a filler dispersion polymer, and a hydrolysis inhibitor, The content of the filler in the polylactic acid resin composition is 20% by weight to 60% by weight, the content of the hydrolysis inhibitor in the polylactic acid resin composition is 0.1% by weight to 5% by weight; The filler is talc. Polylactic acid resin composition.

2. 2. The polylactic acid resin composition according to claim 1, wherein the hydrolysis inhibitor is a compound having at least one functional group selected from the group consisting of a carbodiimide group, an oxazoline group, and an epoxy group.

3. 3. The polylactic acid resin composition according to claim 1, wherein the filler dispersing agent is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

4. 4. The polylactic acid resin composition according to claim 1, wherein the filler dispersion polymer is at least one selected from the group consisting of polyolefin-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyalkylene glycol-based resins, polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, acrylic-based resins, urethane-based resins, epoxy-based resins, and water-soluble polysaccharides.

5. 4. The polylactic acid resin composition according to claim 1, wherein the filler dispersion polymer is at least one selected from the group consisting of polyvinyl alcohol-based resins, polyalkylene glycol-based resins, polyvinylpyrrolidone-based resins, and water-soluble polysaccharides.

6. 6. The polylactic acid resin composition according to claim 1, wherein the total content of the filler dispersant and the filler dispersion polymer in the polylactic acid resin composition is 0.1% by weight to 30% by weight.

7. The polylactic acid resin composition according to claim 1 , further comprising an impact resistance improver.

8. 8. The polylactic acid resin composition according to claim 7, wherein the impact resistance improver is at least one selected from the group consisting of aliphatic polyester resins, aliphatic-aromatic polyester resins, polyvinyl alcohol resins, and natural rubber.

9. The method includes melt-kneading a polylactic acid resin, a filler granule, and a hydrolysis inhibitor, the filler granules contain the filler and the filler dispersant and / or the filler dispersion polymer, The content of the filler in the filler granules is 80 parts by weight to 99.9 parts by weight per 100 parts by weight of the filler granules. A method for producing the polylactic acid resin composition according to any one of claims 1 to 8.

10. An injection-molded article formed from the polylactic acid resin composition according to any one of claims 1 to 8.

11. An extrusion molded article formed from the polylactic acid resin composition according to any one of claims 1 to 8.

12. A sheet-like shaped product formed from the polylactic acid resin composition according to any one of claims 1 to 8.

Images