Polyester resin composition and molded article comprising the same

Abstract

To provide a polyester resin composition which contains a biomass material and is excellent in hydrolysis resistance, impact resistance, and heat resistance.SOLUTION: The polyester resin composition contains (C) 0.1-3 pts.mass of a carbodiimide compound, (D) 0.1-10 pts.mass of a silicone-based resin, and (E) 5-100 pts.mass of an inorganic fiber reinforcement material based on 100 pts.mass of a polyester component containing (A) 25 mass% or more and less than 50 mass% of a polylactic acid resin and (B) 75 mass% or less and more than 50 mass% of a thermoplastic polyester resin different from the polylactic acid resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic polyester resin composition containing a biomass material, and more particularly to a biomass-containing polyester resin composition having hydrolysis resistance, high impact resistance, and high heat resistance. [Background technology]

[0002] In recent years, from the perspective of global environmental conservation, attention has been focused on biomass materials derived from non-petroleum sources and biodegradable resins that are decomposed in the natural environment by the action of microorganisms present in soil and water, and a variety of environmentally friendly material resins have been developed.

[0003] Polylactic acid resins are biomass materials derived from starch, such as corn, and are biodegradable. They are relatively inexpensive and have a melting point of approximately 170°C. This makes them promising as non-petroleum-derived, melt-processable biodegradable resins. Traditionally, polylactic acid resins have been used in civil engineering, agricultural applications, stationery, and everyday items. Research and development efforts to biodegrade them and return them to nature after use have led to some practical applications. Recently, as polylactic acid production has become even more cost-effective, its use as a general-purpose resin has also been explored. However, polylactic acid resins have issues with durability, such as a low deflection temperature under load (approximately 55°C) and poor heat resistance. Furthermore, compared to polyester resins, they are prone to loss of molecular weight and strength due to hydrolysis, which hinders their use in industrial parts.

[0004] To address this issue, Patent Document 1 proposes blending polybutylene terephthalate with polylactic acid to improve heat resistance and crystallization properties. However, because polybutylene terephthalate and polylactic acid are simply blended, the compatibility between them is poor, and the dispersion of each resin component is coarse. Furthermore, evaluation was based solely on deflection temperature under load, and simply blending the two resins does not necessarily improve hydrolysis resistance. Patent Document 2 also reports that blending glycidyl methacrylate improves the compatibility between polybutylene terephthalate and polylactic acid. A polyester resin composition containing polybutylene terephthalate and / or its copolymer blended with a polylactic acid-based resin and a glycidyl methacrylate copolymer provides a biomass material with high impact resistance, high heat resistance, and low warpage. However, as with Patent Document 1, the level of hydrolysis resistance is not disclosed, and the method of Patent Document 2 leaves room for improvement in terms of hydrolysis resistance.

[0005] Patent Document 3 discloses a thermoplastic resin composition having excellent hydrolysis resistance, mechanical properties, and heat resistance, and a molded article made from the same, which is prepared by blending a mixture of an epoxy compound and a carbodiimide compound as an end-capping agent with a thermoplastic resin mainly composed of a polylactic acid resin. However, the heat resistance is low, and the level is still insufficient for use as an industrial material.

[0006] Patent Document 4 mentions that a polyester resin composition that suppresses hydrolysis, a drawback of polyester resins, can suppress the deterioration of physical properties of polyester resins widely used in films, sheets, beverage containers, etc. by using at least one selected from carbodiimide compounds, isocyanate compounds, and oxazoline compounds as a hydrolysis inhibitor and hydrotilesite as a hydrolysis inhibitor assistant, and is therefore industrially useful. However, the resins that have been shown to be effective in improving hydrolysis resistance are limited to those produced from glycolic acid, isophthalic acid, and ethylene glycol. Therefore, it has not been found that these resins have an effect on the hydrolysis resistance of polylactic acid.

[0007] Patent Document 5 discloses a composition comprising a polylactic acid resin and an aromatic polyester resin, in which hydrolysis resistance has been improved by a blending technique using hydrotalcite, which is said to adsorb to an acid that serves as a catalyst for the hydrolysis reaction of polylactic acid, as in Patent Document 4. However, although an improvement in hydrolysis resistance was demonstrated, heat resistance was insufficient.

[0008] Patent Document 6 discloses a method for improving the hydrolysis resistance of polyester resins by blending polybutylene terephthalate with a carbodiimide compound as a hydrolysis inhibitor, a glycidyl ester compound or a glycidyl ether compound as a chain extender, one of talc, calcium carbonate, and mica as an inorganic nucleating agent, and low-molecular-weight polytetrafluoroethylene as an organic nucleating agent and water vapor blocking agent. In particular, low-molecular-weight polytetrafluoroethylene is used as an organic nucleating agent to improve the crystallinity of polybutylene terephthalate, resulting in a more compact structure and improved hydrolysis resistance. Its distribution on the resin surface also blocks water vapor, further improving hydrolysis resistance. Furthermore, its lubricating properties are known to improve the retention length of glass fibers and improve rigidity. However, the resin used is limited to polybutylene terephthalate, and no mention is made of its effects on other polyester resins.

[0009] Furthermore, conventional hydrolysis resistance tests have not been conducted under sufficient temperature and humidity conditions or for sufficient time periods, such as temperatures of 60°C to 90°C, humidity of 85% to 90%, and test times of 100 to 500 hours, and evaluation of whether the hydrolysis resistance is at a level that allows it to be used as an industrial material has been insufficient.On the other hand, in order to apply resin materials made from ecologically excellent biomass materials as industrial parts, there is a demand for materials that demonstrate excellent hydrolysis resistance, heat resistance, and impact resistance under test conditions that meet sufficient conditions. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-36818 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-209226 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-266432 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-219567 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-254899 [Patent Document 6] China patent CN113667283B Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made to solve the above problems, and an object of the present invention is to provide a polyester resin composition that contains a biomass material and has excellent hydrolysis resistance, impact resistance, and heat resistance. [Means for solving the problem]

[0012] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention provides the following.

[0013] [1] A polyester resin composition characterized by comprising, relative to 100 parts by mass of a polyester component containing (A) 25% by mass or more but less than 50% by mass of a polylactic acid resin and (B) 75% by mass or less but more than 50% by mass of a thermoplastic polyester resin different from the polylactic acid resin, 0.1 to 3 parts by mass of (C) a carbodiimide compound, 0.1 to 10 parts by mass of (D) a silicone-based resin, and 5 to 100 parts by mass of (E) an inorganic fiber reinforcing material. [2] The polyester resin composition according to [1], wherein the thermoplastic polyester resin (B) different from the polylactic acid resin is polybutylene terephthalate. [3] The polyester resin composition according to [1] or [2], wherein the carbodiimide compound (C) is an aromatic carbodiimide compound. [4] The polyester resin composition according to any one of [1] to [3], wherein the silicone resin (D) is a modified silicone resin having an ester group or an acrylic group. [5] The polyester resin composition according to any one of [1] to [4], wherein the inorganic fiber reinforcing material (E) is glass fiber. [6] A molded article made of the polyester resin composition according to any one of [1] to [5]. [Effects of the Invention]

[0014] Molded articles made from the polyester resin composition of the present invention have flexural strength, notched Charpy impact strength, and deflection temperature under load at levels suitable for use as industrial materials, and are excellent in hydrolysis resistance. The effect of the present invention is to significantly improve the hydrolysis resistance and heat resistance of a polyester resin composition while maintaining its excellent mechanical properties by using a terminal blocking agent (carbodiimide compound) or a silicon-based additive (silicone-based resin) as a hydrolysis inhibitor for the polyester resin system. Furthermore, the polyester resin composition of the present invention is a biomass-based polyester resin composition that contains 25% by mass or more of a biomass component in the polyester component, while exhibiting improved impact strength, heat resistance with a deflection temperature under load of 200°C or higher, and excellent hydrolysis resistance. As such, it is a resource-saving material that can be recycled and molded, and has a low environmental impact. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that redundant explanations may be omitted as appropriate, but this does not limit the gist of the invention.

[0016] The present invention provides a polyester resin composition containing a polyester component that contains 25% by mass or more but less than 50% by mass of (A) polylactic acid resin and more than 50% by mass or less of (B) a thermoplastic polyester resin different from the polylactic acid resin (hereinafter, when a numerical range is expressed using "to" in this specification, the range includes the upper and lower limits). The polyester resin composition also contains, per 100 parts by mass of the polyester component, 0.1 to 3 parts by mass of (C) a carbodiimide compound, 0.1 to 10 parts by mass of (D) a silicone-based resin, and 5 to 100 parts by mass of (E) an inorganic fiber reinforcing material.

[0017] [(A) Polylactic acid resin] The polylactic acid resin (A) used in the present invention is a biomass material. Hereinafter, polylactic acid may be abbreviated as PLA. The polylactic acid resin (A) is obtained by ring-opening polymerization of lactide, a dimer of lactic acid. From the viewpoints of heat resistance and moldability, it is preferable to use a polylactic acid having a high optical purity of the lactic acid component as the lactic acid used in the present invention. That is, the polylactic acid resin (A) is preferably poly-L-lactic acid and / or poly-D-lactic acid, or a stereocomplex PLA, which is a structural complex of poly-L-lactic acid and poly-D-lactic acid. In poly-L-lactic acid, the molar ratio of L-lactic acid to D-lactic acid (percentage molar ratio) is preferably 100 to 90 / 0 to 10, and most preferably 100 to 95 / 0 to 5 from the viewpoint of injection molding. The same can be said for poly-D-lactic acid, in which the ratio of L-lactic acid to D-lactic acid is reversed. Compared to poly-L-lactic acid (poly-D-lactic acid), stereocomplex PLA has a higher melting point and a faster crystallization rate, resulting in better physical properties such as heat resistance and hydrolysis resistance. The mass ratio of the poly-L-lactic acid and poly-D-lactic acid components in stereocomplex PLA is preferably 30-70 / 70-30, more preferably 40-60 / 60-40, even more preferably 45-55 / 55-45, and most preferably 50 / 50 from the viewpoint of injection molding. The melting point of the (A) polylactic acid resin is preferably from 150 to 180°C, more preferably from 160 to 180°C, from the viewpoint of the heat resistance of the polyester resin composition of the present invention.

[0018] [(B) Thermoplastic polyester resin different from polylactic acid resin] Hereinafter, "(B) a thermoplastic polyester resin different from polylactic acid resin" may be referred to as "(B) a thermoplastic polyester resin." The (B) thermoplastic polyester resin used in the present invention is a thermoplastic polyester resin different from polylactic acid resin, and is preferably at least one selected from polyesters composed of an aromatic dicarboxylic acid component and an alkylene glycol component having 2 to 6 carbon atoms. The aromatic dicarboxylic acid component is preferably terephthalic acid or 2,6-naphthalenedicarboxylic acid. The (B) thermoplastic polyester resin is particularly preferably polybutylene terephthalate. While there are no particular limitations on the polybutylene terephthalate, a homopolymer composed mainly of terephthalic acid and 1,4-butanediol is used. The amount of terminal carboxyl groups in the polybutylene terephthalate is preferably 40 eq / ton or less. The melting point of the polybutylene terephthalate is preferably 180°C to 230°C. The intrinsic viscosity of the polybutylene terephthalate is preferably 0.5 to 1.8 dl / g, more preferably 0.6 to 1.5 dl / g. The intrinsic viscosity is a value (unit: dl / g) measured at 30° C. using an Ubbelohde viscometer after dissolving 0.1 g of a sample in 25 ml of a mixed solvent of phenol / tetrachloroethane (mass ratio 6 / 4).

[0019] [Polyester component] The present invention uses a polyester component containing 25% by mass or more but less than 50% by mass of (A) polylactic acid resin and 75% by mass or less but more than 50% by mass of (B) a thermoplastic polyester resin different from the polylactic acid resin. If the (A) polylactic acid resin is less than 25% by mass relative to 100% by mass of the polyester component, the biomass content is low, the resource-saving effect is reduced, and the object of the present invention is not achieved. Furthermore, if it is 50% by mass or more, the deflection temperature under load is less than 150°C, which is also not achieved, and this is not preferred. When the (B) thermoplastic polyester resin is polybutylene terephthalate, the deflection temperature under load of the polyester resin composition can be made 150°C or higher, which can be said to have high heat resistance.

[0020] [(C) Carbodiimide compound] The carbodiimide compound (C) used in the present invention is not particularly limited as long as it has a carbodiimide group (-N=C=N-) in the molecule. In the carbodiimide compound (C) used in the present invention, the group bonded to the carbodiimide group is not particularly limited, and examples thereof include aliphatic groups, alicyclic groups, aromatic groups, and groups to which these organic groups are bonded (e.g., benzyl groups, phenethyl groups, 1,4-xylylene groups, etc.). Examples of carbodiimide compounds suitable for use in the present invention include aliphatic carbodiimide compounds in which an aliphatic group is bonded to a carbodiimide group, alicyclic carbodiimide compounds in which an alicyclic group is bonded to a carbodiimide group, and aromatic carbodiimide compounds in which an aromatic group or a group containing an aromatic group is bonded to a carbodiimide group. The carbodiimide compound (C) may be used alone or in combination of two or more.

[0021] Specific examples of aliphatic carbodiimide compounds include diisopropylcarbodiimide and dioctyldecylcarbodiimide, and specific examples of alicyclic carbodiimide compounds include dicyclohexylcarbodiimide and poly(4,4'-dicyclohexylmethanecarbodiimide).

[0022] Specific examples of aromatic carbodiimide compounds include diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, N-tolyl-N'-phenylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-p-methoxyphenylcarbodiimide, di-3,4-dichlorophenylcarbodiimide, di-2,5-chlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, p-phenylene-bis-di-o-tolylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, and p-phenylene-bis-dicyclohexylcarbodiimide. Examples of the carbodiimide compounds include mono- and dicarbodiimide compounds such as methyl-4,4'-diphenylcarbodiimide and ethylene-bis-diphenylcarbodiimide, and polycarbodiimide compounds such as poly(4,4'-diphenylmethanecarbodiimide), poly(3,5'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide).

[0023] When the (C) carbodiimide compound is a polycarbodiimide compound, its molecular weight (number average molecular weight) is preferably at least 2000. By using a polycarbodiimide compound with such a molecular weight, retention stability during melting tends to be improved.

[0024] In the present invention, the amount of the (C) carbodiimide compound is not particularly limited as long as it does not impair the object of the present invention. However, within a range that does not impair the flowability of the polyester resin composition, 0.1 to 3 parts by mass is blended per 100 parts by mass of the polyester component. The blending amount is the same as the content of the polyester resin composition (the same applies to the following explanations of each component). The blending amount of the (C) carbodiimide compound is preferably 0.3 to 2 parts by mass, more preferably 0.35 to 1.6 parts by mass. The (C) carbodiimide compound is thought to react with the (A) polylactic acid resin and the (B) thermoplastic polyester resin, thereby acting as a compatibilizer for them, improving hydrolysis resistance, and reducing gas generation during molding. However, if the amount is less than 0.1 part by mass, it is difficult to obtain the desired properties. Conversely, if the amount is more than 3 parts by mass, the reaction between the (A) polylactic acid resin and the (B) thermoplastic polyester resin terminals tends to increase viscosity, which may result in a decrease in flowability. Furthermore, in the polyester resin composition of the present invention, the (C) carbodiimide compound surprisingly also contributes to improving impact strength. When the (C) carbodiimide compound is a polycarbodiimide compound and its content is within the preferred range, a compatibilizing effect between the (A) polylactic acid resin and the (B) thermoplastic polyester resin and a moderate thickening effect are obtained, which is expected to not only inhibit hydrolysis but also improve the impact strength of the polyester resin composition.

[0025] [(D) Silicone resin] The (D) silicone-based resin in the present invention is not particularly limited as long as it is a compound having a siloxane group in its molecule. The (D) silicone-based resin may be a modified silicone resin (siloxane). From the viewpoint of compatibility with the (A) polylactic acid resin and the (B) thermoplastic polyester resin, the (D) silicone-based resin is preferably a modified silicone resin having an ester group or an acrylic group, and more preferably a modified silicone resin containing an ester group. Among these, polyester-modified silicone resins (polyester-modified siloxanes) are particularly preferred. (D) silicone-based resins are known for their low water affinity due to the silicone moiety, excellent hydrophobicity and water repellency, and are also used as mold release agents and lubricants due to their excellent sliding properties. Furthermore, (D) silicone-based resins are effective in improving the scratch resistance, abrasion resistance, impact resistance, and blocking resistance of not only engineering resins but also TPEs and polyolefins, and are known as additives for various base polymers. In the present invention, it was discovered that the (D) silicone-based resin has the effect of improving hydrolysis resistance. The silicone resin (D) is blended in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the polyester component. By blending an amount within this range, the above-mentioned effects can be achieved. The blending amount of the silicone resin (D) is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass.

[0026] [(E) Inorganic fiber reinforcement] Examples of the inorganic fiber reinforcing material (E) in the present invention include, but are not limited to, commonly used wollastonite and acicular wollastonite, glass fiber, carbon fiber, whiskers such as aluminum borate and potassium titanate, and milled fiber, which is a short glass fiber having an average particle size of about 4 to 20 μm and a cut length of about 35 to 80 μm. Wollastonite is most superior in terms of the appearance of the molded product, while glass fiber is most superior in terms of strength and rigidity. These inorganic fiber reinforcing materials (E) may be used alone or in combination of two or more types, but glass fiber is preferred mainly from the perspective of rigidity and deflection temperature under load.

[0027] Among the (E) inorganic fiber reinforcements, glass fibers preferably have a chopped strand shape cut to a fiber length of approximately 1 to 20 mm. Glass fibers with circular or noncircular cross sections can be used. Glass fibers with circular cross sections have an average fiber diameter of approximately 4 to 20 μm and a cut length of approximately 3 to 6 mm, and are generally usable. Glass fibers with noncircular cross sections also include those that are approximately elliptical, approximately oval, or approximately cocoon-shaped in a cross section perpendicular to the fiber length, and preferably have a flatness of 1.5 to 8. Here, flatness refers to the ratio of the major axis to the minor axis, where the length of the long side of a rectangle with the smallest area circumscribing the cross section perpendicular to the longitudinal direction of the glass fiber is the major axis and the length of the short side of this rectangle is the minor axis. The thickness of the glass fiber is not particularly limited, but glass fibers with a minor axis of approximately 1 to 20 μm and a major axis of approximately 2 to 100 μm can be used.

[0028] These glass fibers are preferably treated in advance with a conventionally known coupling agent such as an organosilane compound, an organotitanium compound, an organoborane compound, or an epoxy compound. The surface treatment method is not particularly limited, and any conventional treatment method can be used.

[0029] The blending amount of (E) inorganic fiber reinforcing material in the present invention is 5 to 100 parts by mass, preferably 10 to 80 parts by mass, and more preferably 15 to 60 parts by mass, per 100 parts by mass of the polyester component. If it is less than 5 parts by mass, the effect of improving heat resistance is small, and if it exceeds 100 parts by mass, the fluidity decreases, and it may be impossible to obtain thin-walled or large molded products. By blending (E) inorganic fiber reinforcing material within this range, it becomes possible to satisfy various properties.

[0030] In industrial applications, thermoplastic polyester resins are blended with inorganic fiber reinforcements such as glass fiber. While this improves strength and heat resistance, it also increases the anisotropy of mold shrinkage due to the orientation of the inorganic fiber reinforcement during molding, resulting in significant warpage, making them unsuitable for precision parts. However, polyester resin compositions blended with thermoplastic polyester resin (B), (A) polylactic acid resin, (C) carbodiimide compound, and (D) silicone resin surprisingly exhibit very little warpage in the resulting molded products, even when blended with inorganic fiber reinforcement (E), making them suitable for precision parts. This is thought to be due to the effect of finely dispersed polylactic acid resin (A) alleviating internal stress.

[0031] [Polyester resin composition] The polyester resin composition of the present invention contains (C) a carbodiimide compound, which reacts with the terminal groups that cause hydrolysis of the polyester resin, thereby suppressing hydrolysis. Furthermore, by using an appropriate amount, not only can hydrolysis be suppressed, but also a compatibilizing effect and a moderate thickening effect can be obtained, thereby improving the impact strength of the polyester resin composition. Furthermore, by using an appropriate amount of (D) a silicone-based resin, the hydrolysis resistance of the polyester resin composition can be further improved. Furthermore, by including (E) an inorganic fiber reinforcing material, particularly glass fiber, the rigidity and deflection temperature under load can be improved.

[0032] The polyester resin composition may further contain (F) a glycidyl group-containing copolymer and (G) a non-fibrous inorganic filler, which will be described later. The polyester resin composition of the present invention preferably contains (A) a polylactic acid resin, (B) a thermoplastic polyester resin, (C) a carbodiimide compound, (D) a silicone resin, and (E) an inorganic fiber reinforcing material in total at least 85 mass%, more preferably at least 90 mass%, and even more preferably at least 95 mass%.

[0033] [(F) Glycidyl group-containing copolymer] In the present invention, the glycidyl group-containing copolymer (F) is preferably blended in an amount of 1 to 20 parts by mass relative to 100 parts by mass of the polyester component. The blending amount of the glycidyl group-containing copolymer (F) is more preferably 3 to 15 parts by mass, even more preferably 4 to 12 parts by mass, and particularly preferably 5 to 12 parts by mass. From the viewpoints of improving hydrolysis resistance, compatibilization, and impact resistance, the blending amount described above is preferred.

[0034] The (F) glycidyl group-containing copolymer is preferably a glycidyl methacrylate copolymer. Furthermore, the monomer other than glycidyl methacrylate in the (F) glycidyl group-containing copolymer preferably includes one or more selected from ethylene, styrene, vinyl acetate, acrylic acid esters, and methacrylic acid esters. Among these, ethylene is particularly preferred. The glycidyl methacrylate copolymer is not limited to glycidyl group-containing ethylene copolymers, but specific examples include ethylene-methyl acrylate-glycidyl methacrylate copolymers and ethylene-butyl acrylate-glycidyl methacrylate copolymers. The glycidyl methacrylate copolymer inhibits hydrolysis by reacting with the terminal groups that cause hydrolysis of the polyester component. Furthermore, the terminal groups of the (A) polylactic acid resin and the (B) thermoplastic polyester resin react with the glycidyl methacrylate copolymer to form a branched structure, increasing the melt viscosity and thereby acting as a compatibilizer. Thus, blocking the terminal groups that cause hydrolysis and forming bridges between the two polyester resins is believed to improve hydrolysis resistance.

[0035] [(G) Non-fibrous inorganic filler] A small amount of (G) non-fibrous inorganic filler promotes the crystallization of crystalline resins, forming uniform, fine crystals, which is effective in improving not only rigidity but also heat resistance and hydrolysis resistance. Examples of (G) non-fibrous inorganic fillers include talc, mica, montmorillonite, graphite, carbon black, silica, dolomite powder, silicates, quartz powder, diatomaceous earth, alumina, unspecified or spherical calcium carbonate, magnesium carbonate, hydrotalcite, magnesium oxide, calcium oxide, zinc oxide, aluminum oxide, neodymium oxide, aluminum hydroxide, magnesium hydroxide, calcium sulfate, and barium sulfate. These can be used alone or in combination. Calcium carbonate, in particular, is weakly alkaline and neutralizes the acid produced by hydrolysis of polyester, which is thought to suppress molecular weight loss due to hydrolysis. There are no particular limitations on the type of calcium carbonate; it can be soft calcium carbonate (synthetic calcium carbonate), heavy calcium carbonate, or surface-treated calcium carbonate. There are no particular restrictions on the particle size of the (G) non-fibrous inorganic filler, but it is believed that the finer the particle size, the greater the effect as a nucleating agent. The particle size of the (G) non-fibrous inorganic filler is preferably 0.05 μm to 10 μm, and more preferably 0.05 μm to 5 μm. The amount of the (G) non-fibrous inorganic filler to be blended is usually preferably 0.01 to 3 parts by mass, more preferably 0.01 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, per 100 parts by mass of the polyester component.

[0036] [Other additives] Furthermore, the polyester resin composition of the present invention may contain various known additives, as necessary, within the range that does not impair the properties of the present invention. Examples of known additives include a mold release agent, a modifier, a heat stabilizer, an antioxidant, an ultraviolet absorber, a light stabilizer, a plasticizer, a modifier, an antistatic agent, a flame retardant, a dye, and a pigment.

[0037] Examples of release agents include long-chain fatty acids or their esters or metal salts, amide compounds, polyethylene wax, silicone, and polyethylene oxide. Long-chain fatty acids are particularly preferably those having 12 or more carbon atoms, such as stearic acid, 12-hydroxystearic acid, behenic acid, and montanic acid. The carboxylic acid may be partially or entirely esterified with monoglycol or polyglycol, or may form a metal salt. Examples of amide compounds include ethylene bis-terephthalamide and methylene bis-stearylamide. These release agents may be used alone or in combination.

[0038] These various additives may be contained in a total amount of up to 5 parts by mass when the total of (A), (B), (C), (D), and (E) is 100 parts by mass.

[0039] If the composition falls outside the specific range of the present invention, phase separation occurs during melt processing, and transesterification reactions are likely to occur when kneaded with high shear torque, resulting in a lack of stable structure and physical properties. The reason for this is thought to be that, when comparing (A) polylactic acid resin and (B) thermoplastic polyester resin, the two have different solubility indices based on differences in chemical structure, as well as a large difference in melting point. That is, when (A) polylactic acid resin has an extremely low melt viscosity at the kneading temperature and (B) thermoplastic polyester resin is polybutylene terephthalate, the viscosity difference with (B) thermoplastic polyester resin is such that the viscosity at a shear rate of 500 to 5,000 s ―1 During melt mixing, the ratio increases by 10 to 30 times, which causes variations in the (A) polylactic acid resin fraction in the melt mixed state, resulting in large localized drawdown and making it difficult to form strands or pellets after compounding.

[0040] The polyester resin composition of the present invention can be produced by premixing all of the above-mentioned components and, if necessary, various additives, followed by melt-kneading. Any melt-kneading method known to those skilled in the art can be used, including a single-screw extruder, twin-screw extruder, pressure kneader, Banbury mixer, etc. A twin-screw extruder is particularly preferred. Typical melt-kneading conditions for a twin-screw extruder include a cylinder temperature of 230 to 250°C and a kneading time of 2 to 15 minutes.

[0041] The applications of the polyester resin composition of the present invention are not particularly limited. The polyester resin composition of the present invention is ecologically excellent in that it can suppress an increase in the carbon dioxide concentration in the atmosphere because it uses a biomass component as a raw material. This ecologically excellent polyester resin composition of the present invention is used for industrial applications such as automobiles, electrical and electronic equipment, office automation equipment, household appliances, hoses, and tubes, which require heat resistance and low-temperature flexibility. [Example]

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0043] <Examples 1 to 9 and Comparative Examples 1 to 6> In Examples 1 to 9 and Comparative Examples 1 to 6, the following materials were used as components of the polyester resin compositions.

[0044] [(A) Polylactic acid resin] A-1: Polylactic acid resin (REVODE290, manufactured by Zhejiang Hisun Biomaterials Co., Ltd.), poly-L-lactic acid, L-lactic acid / D-lactic acid (molar ratio): 99 / 1, melting point: 173°C A-2: Polylactic acid resin (D120, manufactured by Total Corbion), poly-D-lactic acid, L-lactic acid / D-lactic acid (molar ratio): 1 / 99, melting point: 175°C A-3: Polylactic acid mixture resin (REVODE290, manufactured by Zhejiang Hisun Biomaterials Co., Ltd., and D120, manufactured by Total Corbion, mixed using a twin-screw extruder), stereocomplex PLA

[0045] [(B) Thermoplastic polyester resin] B: Polybutylene terephthalate (manufactured by Toyobo), intrinsic viscosity: 0.87 dl / g

[0046] [(C) Carbodiimide compound] C-1: Carbodiimide compound (Stabaxol (registered trademark) P, manufactured by Rhein Chemie), aromatic polycarbodiimide C-2: Carbodiimide compound (Stabaxol (registered trademark) I, manufactured by Rhein Chemie), aromatic monocarbodiimide

[0047] [(D) Silicone Resin] D-1: Modified silicone resin having an ester group (polyester-modified siloxane, TEGOMER (registered trademark) H-Si 6440 P, manufactured by Evonik) D-2: Modified silicone resin with acrylic groups (silicone-acrylic copolymer resin, Chaline 175S, manufactured by Nissin Chemical Industry Co., Ltd.)

[0048] [(E) Inorganic fiber reinforcement] E-1: Glass fiber (T-120H, manufactured by Nippon Electric Glass Co., Ltd., average fiber length 3 mm, average fiber diameter 11 μm) E-2: Glass fiber (T-127H, manufactured by Nippon Electric Glass Co., Ltd., average fiber length 3 mm, average fiber diameter 11 μm), water-resistant glass fiber

[0049] [(F) Glycidyl Group-Containing Copolymer] F: Glycidyl methacrylate copolymer (Bondfast (registered trademark) 7M, manufactured by Sumitomo Chemical)

[0050] [(G) Non-fibrous inorganic filler] G: Calcium carbonate (Whiton P-10, manufactured by Toyo Fine Chemical Co., Ltd.), heavy calcium carbonate

[0051] 〔Other additives〕 H: As the stabilizer, an antioxidant (IRGANOX 1010, manufactured by BASF) was used. This stabilizer was contained at 0.1 part by mass with respect to a total of 100 parts by mass of component (A) and component (B). I: As the mold release agent, LICOWAX-OP, manufactured by Clariant, was used. This mold release agent was contained at 0.3 part by mass with respect to a total of 100 parts by mass of component (A) and component (B).

[0052] The components shown in Table 1 and Table 2 were dry-blended at the ratios of the contents (parts by mass) shown in the table, and using a twin-screw extruder (any one of STS35, TEM26SS, TEX34αIII), melt kneading was performed under the conditions of a cylinder temperature of 245 to 250 °C, a discharge rate of 20 kg / hr, and a screw rotation speed of 180 rpm to produce pellets of the polyester resin composition. Test pieces were produced using the obtained pellets, and the measurement results of flexural strength, flexural strength after PCT, hydrolysis resistance (retention rate), notched Charpy impact strength, and heat distortion temperature were confirmed. The measurement results of the polyester resin compositions of Examples 1 to 9 are shown in Table 1. Also, the measurement results of flexural strength, flexural strength after PCT, hydrolysis resistance (retention rate), Charpy impact strength, and heat distortion temperature of Comparative Examples 1 to 6 are shown in Table 2. Incidentally, each physical property of the polyester resin composition was measured according to the following method.

[0053] <Flexural strength> Using an injection molding machine (manufactured by the company, J110AD) whose temperature was adjusted to 2,45 °C and a mold compliant with ISO 294 whose temperature was adjusted to 80 °C, a multipurpose test piece was obtained. Using the obtained test piece, measurement was performed in accordance with ISO-178. The test piece was injection molded under the conditions of a cylinder temperature of 245 °C and a mold temperature of 80 °C.

[0054] <Flexural strength after PCT [Pressure Cooker Test (HAST: High Accelerated Stress Test)]> The above test piece was placed in a thermostatic bath at 120°C for 10 minutes, and then in a thermostatic bath at 200°C for 20 minutes for annealing. Subsequently, using a test chamber (LSX-500, manufactured by Tommy Seiko), the conditions were set to 121°C, 24 hours, 100% RH, and 2 atm, and an accelerated humidity resistance test was conducted. Thereafter, the bending strength was measured in the same manner as above.

[0055] <Hydrolysis resistance (retention rate)> The calculation of hydrolysis resistance was performed by the following method. [Flexural strength of the test piece after PCT (MPa)] / [Flexural strength of the test piece (MPa)] × 100 = Hydrolysis resistance (retention rate) (%) Note that the "flexural strength of the test piece" refers to the flexural strength of the test piece before PCT.

[0056] <Notched Charpy impact strength> For the multi-purpose test pieces obtained in the same manner as above, using a notching tool manufactured by Toyo Seiki Co., Ltd., they were cut to the dimensions specified in ISO179-1 for notching. The obtained test pieces were measured in accordance with ISO179-1 using a Charpy impact tester (Digital Impact Tester manufactured by Toyo Seiki Co., Ltd.).

[0057] <HDT: Heat deflection temperature> Using an injection molding machine, under the conditions of a cylinder temperature of 245°C and a mold temperature of 80°C, multi-purpose test pieces of ISO-3167 were molded. For this multi-purpose test piece, in accordance with ISO-75, the heat deflection temperature when loaded at 0.45 MPa was measured.

[0058]

Table 1

Table 2

[0060] As is clear from Table 1, the polyester resin compositions of Examples 1 to 9 of the present invention satisfy the ranges specified in the present invention, and therefore have high impact resistance (Charpy impact strength) and high heat resistance (HDT: deflection temperature under load), and are able to suppress hydrolysis. It is clear from Examples 1 and 4 that the use of an appropriate amount of component (D) improves hydrolysis resistance. Furthermore, Examples 1 and 9 show that the use of a modified silicone resin having an ester group as the silicone resin (D) significantly improves hydrolysis resistance. From Examples 5 and 6, it can be seen that the use of components (F) and (G) further improves the hydrolysis resistance. In Examples 7 and 8, when either two types of polylactic acid or a mixture of two types of polylactic acid (stereocomplex PLA) was used as component (A), the hydrolysis resistance tended to be even better.

[0061] <Comparative Examples 1 and 2> On the other hand, in Comparative Examples 1 and 2, when only components (A) and (E) or only components (A), (C) and (E) were used, the hydrolysis resistance (retention rate) was not measurable, and the Charpy impact strength and the deflection temperature under load also showed low values.

[0062] <Comparative Examples 3 to 6> In Comparative Examples 3 to 6, even when only components (A), (B), and (E), only components (A), (B), (C) and (E), or only components (A), (B), (D) and (E) were used, an improvement in the deflection temperature under load was observed, but the hydrolysis resistance was lower than in the Examples.

[0063] Therefore, it is clear that the use of components (A), (B), and (E) and components (C) and (D) can provide a polyester composition having higher impact resistance, a high deflection temperature under load, and excellent hydrolysis resistance. [Industrial Applicability]

[0064] The present invention provides a biomass material that has high impact resistance, high heat resistance, and excellent hydrolysis resistance, which allows for the production of parts that use fewer natural resources and has a significantly lower environmental impact when disposed of. Therefore, it is expected to contribute greatly to industry while protecting the environment.

Claims

1. A polyester resin composition characterized by comprising, relative to 100 parts by mass of a polyester component containing (A) 25% by mass or more and less than 50% by mass of a polylactic acid resin, and (B) 75% by mass or less and more than 50% by mass of a thermoplastic polyester resin different from the polylactic acid resin, 0.1 to 3 parts by mass of (C) a carbodiimide compound, 0.1 to 10 parts by mass of (D) a silicone-based resin, and 5 to 100 parts by mass of (E) an inorganic fiber reinforcing material.

2. 2. The polyester resin composition according to claim 1, wherein the thermoplastic polyester resin (B) different from the polylactic acid resin is polybutylene terephthalate.

3. The polyester resin composition according to claim 1, wherein the carbodiimide compound (C) is an aromatic carbodiimide compound.

4. 2. The polyester resin composition according to claim 1, wherein the silicone resin (D) is a modified silicone resin having an ester group or an acrylic group.

5. The polyester resin composition according to claim 1, wherein the inorganic fiber reinforcing material (E) is glass fiber.

6. A molded article made from the polyester resin composition according to any one of claims 1 to 5.

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