Polylactic acid molding with improved impact strength

Abstract

To provide a resin material which gives light weight and high strength to final products including automobiles and mobile phones, while having biodegradability.SOLUTION: A molding includes 100 pts.wt. of polylactic acid (A), 1 to 40 pts.wt. of a modifier (B), and 0.1 to 10 pts.wt. of a nucleating agent (C), the molding having an absolute crystallinity of 28 to 40%, wherein the polylactic acid (A) has a melt flow rate (MFR) of 3 to 30 and, in addition, preferably has a D-form content of 10% or less, and wherein the modifier (B) is preferably a copolymer comprising a (meth)acrylic acid ester or a core-shell graft copolymer comprising a (meth)acrylic acid ester.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polylactic acid molded article having improved impact strength. [Background technology]

[0002] In recent years, biodegradable polymers that decompose in the natural environment have attracted attention and are being studied worldwide in order to protect the global environment. Aliphatic polyesters such as polylactic acid, polyhydroxybutyrate, and polycaprolactone are known as biodegradable polymers. Among these, polylactic acid, in particular, is a highly biosafe and environmentally friendly polymeric material because it is made from lactic acid or its derivatives obtained from biological sources. Therefore, its use as a general-purpose polymer, including in stretched films, fibers, and injection-molded products, is being considered.

[0003] However, polylactic acid resins are brittle and hard, limiting their applications, and have hardly been used in fields such as daily necessities, home appliance parts, and automobile parts. Even when they are molded into injection-molded articles, they suffer from problems such as insufficient mechanical strength, such as insufficient flexibility and impact resistance, and are therefore not currently used. Furthermore, polylactic acid has a low crystallization rate and a slow molding cycle, resulting in poor productivity, significantly limiting the scope of its practical application.

[0004] Patent Document 1 discloses a resin composition containing a polyolefin resin, a biodegradable resin (aliphatic polyester-based biodegradable polymer), and an acid- or epoxy-group-containing polyolefin. Patent Document 1 states that the use of an acid- or epoxy-group-containing polyolefin makes it possible to provide a composition and molded article having an excellent balance of physical properties such as processability, impact resistance, and elastic modulus. However, the resin composition described in Patent Document 1 requires the provision of multiple kneading sections, making the manufacturing method complicated, and the mechanical strength of the resulting molded article not meeting the desired level. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-077063 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a polylactic acid molded article (polylactic acid molded product) having excellent mechanical strength, particularly impact resistance. The molded article of the present invention is suitable for applications requiring high impact resistance, such as components for vehicles, ships, electronic devices, home appliances, and building materials, as well as for daily necessities, sporting goods, and stationery. Furthermore, the polylactic acid used in the present invention is a biomass plastic derived from plants, etc., and is preferably used as a resin molded product with low environmental impact. [Means for solving the problem]

[0007] The present invention includes the following inventions. [1] Polylactic acid (A) 100 parts by weight, 1 to 40 parts by weight of a modifier (B), and Nucleating agent (C) 0.1 to 10 parts by weight and the absolute crystallinity of the molding is 28 to 40%. [2] The molded article according to [1], wherein the polylactic acid (A) has a melt flow rate (MFR) of 3 to 30 and a D-isomer content of 10% or less. [3] The molded article according to [1] or [2], wherein the modifier (B) comprises at least one selected from a copolymer containing a (meth)acrylic acid ester and a core-shell type graft copolymer containing a (meth)acrylic acid ester. [4] The molded article according to any one of [1] to [3], wherein the modifier (B) has a glass transition point of −10° C. or lower and contains 15 to 100% by weight of a (meth)acrylic acid ester relative to the modifier. [5] The molded article according to any one of [1] to [4], wherein the nucleating agent (C) comprises at least one selected from organic sulfonates, organic metal salts, organic hydrazide compounds, carboxylic acid ester compounds, phthalocyanine compounds, melamine compounds, layered silicates, amide compounds, metal oxides, metal carbonates, talc, silica, and the like. [6] The molded product according to any one of [1] to [5], further comprising an additive (D), which is at least one selected from the group consisting of a catalyst, a neutralizing agent, an antioxidant, an ultraviolet absorber, a lubricant, an antistatic agent, an antiblocking agent, a processing aid, a colorant, a foaming agent, a plasticizer, a brightness enhancer, an antibacterial agent, and a light diffusing agent. [7] A method for producing the molded article according to any one of [1] to [6], Polylactic acid (A), modifier (B) and nucleating agent (C) are mixed together to obtain a mixture, A manufacturing method in which the mixture is molded. [Effects of the Invention]

[0008] The molded article of the present invention has significantly higher impact strength. DETAILED DESCRIPTION OF THE INVENTION

[0009] A resin composition for producing a molded article, and the molded article, (A) polylactic acid, (B) a modifier, and (C) Nucleating agent comprising or consisting essentially of: In one embodiment, a resin composition for producing a molded article, and the molded article, (A) polylactic acid, (B) a modifier; (C) a nucleating agent, and (D) Additives comprising or consisting essentially of:

[0010] The molded product preferably has an absolute crystallinity of 10 to 50%, 20 to 45%, 28 to 40%, 30 to 38%, or 32 to 36%.

[0011] The absolute crystallinity of the molded product may be 10% or more, 15% or more, 20% or more, 25% or more, 26% or more, 27% or more, 28% or more, 29% or more, 30% or more, 31% or more, 32% or more, 33% or more, 34% or more, 35% or more, 36% or more, 37% or more, 38% or more, or 39% or more, or may be 50% or less, 45% or less, 40% or less, 39% or less, 38% or less, 37% or less, 36% or less, 35% or less, 34% or less, 33% or less, 32% or less, 31% or less, or 30% or less. The degree of crystallinity varies depending on the components of the resin composition, the temperature of the mold, and the like.

[0012] The absolute crystallinity Dc (%) is calculated by the following formula: Absolute crystallinity (%) = [△Hm-(△Hc1+△Hc2) / 93] x 100 △Hc1 Crystallization energy detected around 90℃ △Hc2 Crystallization energy detected around 160℃ △Hm Melting energy detected around 175℃ Theoretical heat of complete crystallization 93J / g

[0013] The heat of fusion (melting energy) and the heat of crystallization (crystallization energy) can be obtained by differential scanning calorimetry (DSC). For example, if a molded product is heated at a rate of 10°C / min, the crystallization energy (△Hc1) resulting from crystallization seen at around 90°C, the crystallization energy (△Hc2) resulting from crystallization seen at around 160°C, and the melting energy (△Hm) resulting from crystallization seen at around 175°C are obtained. On the other hand, the theoretical heat of complete crystallization is a theoretical value, and since the heat of melting of a complete crystal cannot be observed itself, it is a value theoretically determined assuming a completely crystallized state.

[0014] In the present invention, high impact resistance (particularly high Charpy impact strength) can be obtained. Charpy impact strength is 5kJ / m 2 More than 10 kJ / m 2More preferably, 15 kJ / m 2 That's all. Charpy impact strength can be measured in accordance with ISO179.

[0015] <(A) Polylactic acid> "Polylactic acid (PLA)" refers to a polymer composed of lactic acid units. Polylactic acid is usually produced by the condensation of lactic acid, but can also be obtained by the ring-opening polymerization of lactide.

[0016] In the present invention, polylactic acid may contain other component units as long as the performance is not impaired. Examples of other component units other than lactic acid units include polycarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, etc. Specific examples include polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, and 5-tetrabutylphosphonium sulfoisophthalic acid, or derivatives thereof, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, and ethyl acetate in trimethylolpropane or pentaerythritol. Examples of suitable polyols include polyhydric alcohols obtained by adding ethylene oxide or propylene oxide to bisphenol, aromatic polyhydric alcohols obtained by an addition reaction of ethylene oxide to bisphenol, polyhydric alcohols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol, and derivatives thereof; hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid; and lactones such as glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone.

[0017] Polylactic acid can contain only one of the optical isomers, L-lactic acid (L-form) or D-lactic acid (D-form), or both the L- and D-forms. Polylactic acid preferably contains L-lactic acid as the main structural unit. For example, polylactic acid can contain 0.1 to 10% by weight, preferably 0.1 to 5% by weight or 0.1 to 2% by weight of D-lactic acid units (based on the weight of the polylactic acid), with the remainder being L-lactic acid units. The amount of D-isomer lactic acid units may be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, or 1.0 wt% or more, and may be 10 wt% or less, 8 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, 1.5 wt% or less, 1.2 wt% or less, 1 wt% or less, 0.8 wt% or less, 0.6 wt% or less, or 0.5 wt% or less, based on the polylactic acid. From the viewpoint of the molding cycle, the amount of D-isomers is preferably 1 wt% or less or less than 1 wt% based on the polylactic acid.

[0018] The melt flow rate (MFR) of the polylactic acid may be 2 g / 10 min or more, 3 g / 10 min or more, 5 g / 10 min or more, 6 g / 10 min or more, 7 g / 10 min or more, 8 g / 10 min or more, 9 g / 10 min or more, 10 g / 10 min or more, 11 g / 10 min or more, 12 g / 10 min or more, 13 g / 10 min or more, 14 g / 10 min or more, or 15 g / 10 min or more, and may be 50 g / 10 min or less, 40 g / 10 min or less, 30 g / 10 min or less, 25 g / 10 min or less, 20 g / 10 min or less, or 1 g / 10 min or less. From the viewpoint of injection moldability, the melt flow rate (MFR) of the polylactic acid is preferably 9 to 30 g / 10 min, 9 to 25 g / 10 min, or 9 to 20 g / 10 min. The melt flow rate was measured in accordance with ISO1133 at a temperature of 190°C and a load of 2.16 kg.

[0019] The polylactic acid (A) may be a single one or a combination of at least two kinds.

[0020] Alternatively, the amount of polylactic acid (A) may be 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, relative to the resin composition, and may be 99% by weight or less, 98% by weight or less, 97% by weight or less, 95% by weight or less, 92% by weight or less, 90% by weight or less, 88% by weight or less, or 85% by weight or less. The amount of polylactic acid (A) is preferably 82 to 96% by weight or 84 to 94% by weight relative to the resin composition. Further alternatively, the amount of polylactic acid (A) may be the "balance" (or 100 parts by weight) of the resin composition excluding the modifier (B), the nucleating agent (C), and, if present, the other component (D). That is, the resin composition may comprise or consist (essentially) of the modifier (B), the nucleating agent (C), if present, the other component (D), and the balance (or 100 parts by weight) of polylactic acid (A).

[0021] The resin composition may or may not contain a thermoplastic resin other than polylactic acid, particularly a polyester resin other than polylactic acid, such as a non-biodegradable polyester resin. Preferably, the resin composition does not contain a polyester resin other than polylactic acid (or a thermoplastic resin other than polylactic acid). Examples of polyester resins other than polylactic acid include copolymer polyester resins, such as polymers obtained by copolymerizing polycarboxylic acids and polyhydric alcohols, specifically polyethylene terephthalate and polybutylene terephthalate.

[0022] <(B) Modifier> The modifier (B) is preferably a polymer containing a (meth)acrylic acid ester, for example, a normal polymer (particularly, a copolymer) containing a (meth)acrylic acid ester (not a core-shell type graft copolymer), or a core-shell type graft copolymer containing a (meth)acrylic acid ester. In one embodiment, the modifier (B) is a polymer that is not a core-shell type graft copolymer and that contains a (meth)acrylic acid ester. The term "(meth)acrylic acid ester" refers to an acrylic acid ester and / or a methacrylic acid ester.

[0023] The polymer containing a (meth)acrylic acid ester may be a homopolymer, a copolymer of two or more (meth)acrylic acid esters, or a copolymer of a (meth)acrylic acid ester and another monomer (other than a (meth)acrylic acid ester). The other monomer may be, for example, an olefin monomer such as ethylene, a diene monomer such as butadiene, or an aromatic monomer such as styrene.

[0024] In a polymer (particularly, a copolymer) containing a (meth)acrylic acid ester, the (meth)acrylic acid ester is preferably an ester of (meth)acrylic acid and an alkyl alcohol (the alkyl group may have 1 to 12 or 1 to 5 carbon atoms) (the alkyl group is derived from the alkyl alcohol) (i.e., a (meth)acrylic acid alkyl ester). Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. The (meth)acrylic acid ester may also be an alicyclic, aromatic, heterocyclic, and / or vinyl group-containing ester, a hydroxy-containing ester, a carboxylic acid-containing ester, or a halogen-containing ester.

[0025] The (meth)acrylic acid ester may be a reactive group-containing (meth)acrylic acid ester. The reactive group is preferably an epoxy group, a carboxyl group, an acryloyl group, a methacryloyl group, a hydroxyl group, or an episulfide group, and more preferably an epoxy group (e.g., a glycidyl group). From the viewpoint of imparting impact resistance, the (meth)acrylic acid ester is preferably glycidyl (meth)acrylate, particularly glycidyl methacrylate.

[0026] The copolymer containing a (meth)acrylic acid ester may contain an olefin. The olefin may be an olefin having 2 to 8 or 2 to 5 carbon atoms, such as ethylene, propylene, or butylene. The amount of the olefin may be 30 to 90% by weight or 50 to 80% by weight based on the copolymer.

[0027] A preferred example of the copolymer containing a (meth)acrylic acid ester is a copolymer of an olefin with a (meth)acrylic acid alkyl ester and / or a reactive group-containing (meth)acrylic acid ester. The amount of the (meth)acrylic acid alkyl ester and / or the reactive group-containing (meth)acrylic acid ester may be 3 to 60% by weight or 5 to 50% by weight, and the amount of the olefin may be 97 to 40% by weight or 95 to 50% by weight, based on the copolymer.

[0028] Particularly preferred examples of the copolymer containing a (meth)acrylic acid ester are a copolymer of a (meth)acrylic acid alkyl ester, a reactive group-containing (meth)acrylic acid ester, and an olefin, and a copolymer of a reactive group-containing (meth)acrylic acid ester and an olefin. In the copolymer of a (meth)acrylic acid alkyl ester, a reactive group-containing (meth)acrylic acid ester, and an olefin, the amount of the (meth)acrylic acid alkyl ester may be 5 to 50 wt%, 10 to 40 wt%, or 15 to 30 wt%, the amount of the reactive group-containing (meth)acrylic acid ester may be 2 to 20 wt%, 3 to 15 wt%, or 5 to 12 wt%, and the amount of the olefin may be 40 to 90 wt%, 50 to 85 wt%, or 55 to 80 wt%, based on the weight of the copolymer. In the copolymer of a reactive group-containing (meth)acrylic acid ester and an olefin, the amount of the reactive group-containing (meth)acrylic acid ester may be 2 to 30% by weight, 3 to 20% by weight, or 5 to 15% by weight, and the amount of the olefin may be 70 to 98% by weight, 80 to 97% by weight, or 85 to 95% by weight, based on the weight of the copolymer.

[0029] The core-shell graft copolymer has a so-called core-shell structure, which is composed of a core layer surrounded by a shell layer, with adjacent layers composed of different polymers. Each of the core layer and the shell layer may be composed of a single layer, or two or more layers. The core-shell type graft copolymer is preferably obtained by graft polymerizing the shell component in the presence of the core component.

[0030] The core component forming the core layer is preferably a rubber component. The type of rubber component is not particularly limited, as long as it is composed of a polymer component having rubber elasticity. Examples of polymer components having rubber elasticity include rubbers composed of an acrylic component, a silicone component, a styrene component, a nitrile component, a conjugated diene component, a urethane component, or a polymerized component such as ethylene or propylene. For example, the rubber is composed of a polymerized component of an acrylic component such as ethyl acrylate units or butyl acrylate units, a silicone component such as dimethylsiloxane units or phenylmethylsiloxane units, a styrene component such as styrene units or α-methylstyrene units, a nitrile component such as acrylonitrile units or methacrylonitrile units, or a conjugated diene component such as butadiene units or isoprene units. Rubbers made by copolymerizing two or more of these components may also be used, including rubbers made by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a silicone component such as dimethylsiloxane units or phenylmethylsiloxane units, rubbers made by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a styrene component such as styrene units or α-methylstyrene units, rubbers made by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a conjugated diene component such as butadiene units or isoprene units, and rubbers made by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a silicone component such as dimethylsiloxane units or phenylmethylsiloxane units with a styrene component such as styrene units or α-methylstyrene units. Furthermore, rubbers made by copolymerizing and crosslinking crosslinkable components such as divinylbenzene units, allyl acrylate units, or butylene glycol diacrylate units in addition to these components can also be used.

[0031] From the viewpoint of dispersibility and compatibility with polylactic acid, it is preferable that the methacrylic acid ester forms the shell layer. When using a core-shell type graft copolymer, it is preferable not to use metal oxides, such as tin oxide.

[0032] The glass transition point of the modifier (B) may be -100°C or higher or -50°C or higher, and may be 0°C or lower, -5°C or lower, -10°C or lower, -15°C or lower, -20°C or lower, -25°C or lower, or -30°C or lower. Since this increases impact resistance, the glass transition point is preferably -10°C or lower (for example, -100°C to -10°C or -50°C to -10°C). The glass transition point can be determined from the tan δ peak calculated from dynamic viscoelasticity. Measurement can be performed using a dynamic viscoelasticity device, with a starting temperature of -150°C, a heating rate of 2°C / min, and a frequency of 1 to 11 Hz.

[0033] In the modifier (B), the total amount of the acrylic acid ester and the methacrylic acid ester may be 15 to 100% by weight relative to the modifier. The amount of the acrylic acid ester and the methacrylic acid ester may be 15% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, or 70% by weight or more relative to the modifier, and may be 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 35% by weight or less, or 30% by weight or less. The amount of the acrylic acid ester and the methacrylic acid ester may be 15 to 40% by weight or 20 to 33% by weight relative to the modifier. From the viewpoint of improving impact resistance, the amount of the acrylic acid ester and the methacrylic acid ester is preferably 15 to 60% by weight or 20 to 50% by weight relative to the modifier.

[0034] The modifier (B) may be used alone or in combination of two or more. The amount of the modifier (B) may be 2 parts by weight or more, 3 parts by weight or more, 5 parts by weight or more, 8 parts by weight or more, or 10 parts by weight or more, and may be 40 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, or 40 parts by weight or less, preferably 5 to 15 parts by weight, per 100 parts by weight of the polylactic acid (A). Alternatively, the amount of modifier (B) may be 2% by weight or more, 4% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, 10% by weight or more, or 12% by weight or more, and may be 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, or 10% by weight or less, based on the resin composition. The amount of modifier (B) is preferably 2 to 17% by weight, 4 to 16% by weight, or 7 to 15% by weight based on the resin composition.

[0035] <(C) Nucleating Agent> Nucleating agents (C) that can be used include various types of organic sulfonates, organic metal salts, organic hydrazide compounds, carboxylic acid ester compounds, phthalocyanine compounds, melamine compounds, layered silicates, amide compounds, metal oxides, metal carbonates, talc, silica, etc. Among these, organic sulfonates are preferred from the viewpoint of their crystallization-promoting effect.

[0036] The organic component of the organic sulfonate may be an alkyl compound or an aromatic compound, but is preferably an aromatic compound. The aromatic compound may have a substituent on the benzene ring. Examples of the substituent include an alkyl group, a hydroxyl group, a carboxyl group, an ester group, an amide group, and an aldehyde group. An ester group (especially an alkyl ester group (an alkyl group having 1 to 12 or 1 to 4 carbon atoms)) is particularly preferred, and it is particularly preferred that the compound have two or more ester groups. Specific examples of aromatic compounds include dimethyl isophthalate and diethyl isophthalate. The organic sulfonate is preferably a metal salt, such as a barium salt, calcium salt, strontium salt, potassium salt, rubidium salt, or sodium salt. A particularly preferred organic sulfonate is potassium dimethyl 5-sulfoisophthalate.

[0037] The resin composition (or modifier (B)) may or may not contain a metal oxide. It is preferable that the resin composition (or modifier (B)) does not contain a metal oxide, for example, tin oxide.

[0038] The nucleating agent (C) may be used alone or in combination of two or more. The amount of the nucleating agent (C) may be 0.1 to 10 parts by weight, 0.2 to 4 parts by weight, or 0.2 to 3 parts by weight relative to 100 parts by weight of the polylactic acid (A). Alternatively, the amount of nucleating agent (C) may be 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, or 6% by weight or more, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, or 3% by weight or less, based on the resin composition. The amount of nucleating agent (C) is preferably 0.2 to 5% by weight or 0.5 to 3% by weight based on the resin composition.

[0039] <(D) Other Ingredients> The molded product (resin composition) may contain another component (D). Other components, such as additives, may be used. Examples of additives include catalysts (especially transesterification catalysts), neutralizing agents, antioxidants, ultraviolet absorbers, lubricants, antistatic agents, antiblocking agents, processing aids, colorants (inorganic pigments, organic pigments, pigment dispersants, etc.), foaming agents, plasticizers, flame retardants, brightness enhancers, antibacterial agents, and light diffusing agents. It is preferable that the additive is not a flame retardant. These additives may be used alone or in combination of two or more.

[0040] The amount of other component (D) (particularly, additives) may be 50% by weight or less, 0.1 to 30% by weight, 0.3 to 20% by weight, 0.5 to 10% by weight, or 1 to 5% by weight relative to the molded product (resin composition).

[0041] A resin composition containing the components of the present invention is melted and molded to obtain a molded product.

[0042] <Method of manufacturing resin composition> The resin composition for forming the molded article can be produced by premixing polylactic acid (A), modifier (B), and nucleating agent (C) as needed, followed by melt-kneading. Premixing may be dry blending using a premixer such as a ribbon blender, Henschel mixer, or V blender. Melt kneading may be performed using a melt kneader equipped with a heating mechanism, such as a Banbury mixer, mixing roll, single-screw or twin-screw extruder, or kneader. The melt kneader may be equipped with a filter having an opening of 1 mm or less, for example, 0.01 to 0.5 mm, particularly 0.05 to 0.3 mm.

[0043] The melt-kneading temperature is preferably equal to or higher than the melting point so that the polylactic acid (A) melts.

[0044] <Step of molding the resin composition> The molding can be carried out by injection molding, extrusion molding, blow molding, etc. The molding is preferably injection molding or direct blow molding.

[0045] <Manufacturing method for injection molded products> The present invention also relates to a method for producing an injection-molded article, which includes a step of injection-molding a resin composition. For injection molding, a conventional injection molding machine is used, and the melt-kneaded resin composition is supplied to the injection molding machine.

[0046] As the injection molding machine, a known one can be used, such as a hydraulic injection molding machine, an electric injection molding machine, etc. The injection molding machine can be appropriately selected depending on the size of the injection-molded article to be obtained and the size of the mold to be used. The clamping pressure can be appropriately selected depending on the size of the mold used and the resin capacity. The mold can be heated using an electric heater or a heat medium circulating mold temperature controller. In particular, it is preferable to heat the mold by embedding a heat medium circulating pipe inside the mold, as this allows for accurate and rapid control of the surface temperatures of the mold and the molded body.

[0047] The mold temperature may be 60°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, or 85°C or higher, or 160°C or lower, 150°C or lower, 145°C or lower, 140°C or lower, 135°C or lower, 130°C or lower, 125°C or lower, 120°C or lower, 115°C or lower, 110°C or lower, 105°C or lower, 100°C or lower, or 95°C or lower. In order to develop high impact strength, the mold temperature is preferably 80 to 100°C or 75 to 95°C. The retention time in the mold may be 20 to 300 seconds, preferably 25 to 200 seconds.

[0048] <Manufacturing method for extrusion molded products> The present invention also relates to a method for producing an extrusion molded article, which includes a step of extruding a resin composition. For extrusion molding, a typical T-die extruder, inflation molding machine, etc. is used. These extruders are connected to a kneader. The melt-kneaded resin composition is supplied to the extruder. Alternatively, an apparatus in which a kneader and an extruder are integrated may be used. Examples of the apparatus in which a kneader and an extruder are known, and include, but are not limited to, a continuous intensive mixer; a continuous kneader such as a kneading-type twin-screw extruder (same-rotation or counter-rotation); a continuous kneading device using a rotating disk with a grinding mechanism; a single-screw extruder equipped with a kneading section (Dulmage, CTM, etc.); and a twin-screw kneading extruder with a kneading disk or kneading rotor. Two or more types of kneaders may be used in combination.

[0049] <Manufacturing method for blow molded products> The present invention also relates to a method for producing a blow-molded article, which comprises a step of blow-molding a resin composition. For the blow molding, a normal injection blow molding machine or a direct blow molding machine is used. The melt-kneaded resin composition is supplied to the blow molding machine. As the blow molding machine, a known machine can be used and can be appropriately selected.

[0050] <Pellet manufacturing method> A case where the resin composition is in the form of pellets will be described. The melt-kneaded resin composition may be supplied to a die device. The die device has a supply port to which the extruder is connected, and the melt-kneaded resin composition is supplied from the extruder to the supply port of the die device.

[0051] The resin composition supplied from the extruder to the die device is then fed to the extrusion molding section of the die device. The resin composition is extruded from the extrusion opening of the extrusion molding section to form strands. The diameter of the strands is not particularly limited and can be changed appropriately depending on the purpose, but is, for example, in the range of 0.2 to 10 mm or 0.5 to 5 mm.

[0052] The strands can be cooled as needed and then cut into pellets using a pelletizer. The most commonly used cooling method is to introduce the extruded strand into a water bath and immerse the strand in the cooling water in the water bath. The strands after cooling are preferably fed to a pelletizer after removing moisture adhering to the surface using a water drainer. The pelletizer cuts the strands by driving a rotary blade or the like. The length of the strands to be cut is not particularly limited and can be changed appropriately depending on the purpose, but is, for example, in the range of 0.5 to 10.0 mm or 1.0 to 5.0 mm. The shape of the pellets can be cylinders, prisms, etc., but cylinders are preferred because they are easy to manufacture and handle.

[0053] The pellets can be used to obtain molded articles, which can be produced by the above-mentioned methods for producing injection-molded articles, the above-mentioned methods for producing extrusion-molded articles, blow molding, vacuum molding, inflation molding, calendar molding, slush molding, dip molding, foam molding, and the like.

[0054] In this specification, the symbol "~" indicating a range of numerical values ​​generally includes the lower limit and upper limit written before and after the symbol "~", but may not include one or both of the lower limit and upper limit. That is, "1 to 10" generally means "1 or more and 10 or less", but may also mean "more than 1 and 10 or less", "1 or more and less than 10", or "more than 1 and less than 10". As used herein, the terms "comprise" or "contain" refer to all of "comprising," "essentially consisting of," and "consisting of." For example, "the composition comprises components 1 to 3" also encompasses "the composition consists (essentially) of components 1 to 3." [Example]

[0055] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, %, parts and ratios mean % by weight, parts by weight and ratios by weight, respectively, unless otherwise specified.

[0056] The test methods, raw materials and manufacturing methods used below are as follows:

[0057] [Raw materials] Polylactic acid resin (A) A-1: Total Corbion's "Luminy (registered trademark) L-130" D-isomer content: less than 1%, Melt flow rate (190℃): 10g / 10min

[0058] Modifier (B) B-1: Ethylene / glycidyl methacrylate / methyl acrylate copolymer (weight % of constituent monomers: ethylene 68% / glycidyl methacrylate 8% / methyl acrylate 24%, Tg: -20°C, (meth)acrylic acid ester component amount: 32%) B-2: Ethylene / glycidyl methacrylate / butyl acrylate copolymer (weight percent of constituent monomers: ethylene 67% / glycidyl methacrylate 8% / butyl acrylate 25%, Tg: -50°C, (meth)acrylic acid ester component amount: 33%) B-3: Ethylene / glycidyl methacrylate copolymer (weight percent of constituent monomers: ethylene 92% / glycidyl methacrylate 8%, Tg: -10°C, (meth)acrylic acid ester component amount: 8%)

[0059] Nucleating Agent (C) C-1: 5-Sulfoisophthalic acid dimethyl potassium salt

[0060] [Holding time] The resin composition pellets were injection molded using an IS80EPN-2A injection molding machine manufactured by Shibaura Machine Co., Ltd. at a molding temperature of 190 to 210°C, an injection time of 15 seconds, and the mold temperature shown in Table 1. The holding time was compared to determine the time during which the molded article could be easily removed from the mold and no distortion or bending occurred in the shape of the molded article.

[0061] [Absolute crystallinity] 10 mg of the resin composition was filled into an aluminum cell, and the temperature was raised from room temperature to 200°C at a rate of 10°C / min using a differential scanning calorimeter (DSCvesta Smartloader, manufactured by Rigaku Corporation). The crystallization energies (ΔHc1, ΔHc2) detected near 90°C and 150°C, and the melting energy (ΔHm) detected near 175°C were measured. The absolute crystallinity was calculated using the measured values ​​and the theoretical heat of complete crystallization of 93 J / g as follows: Dc = {ΔHm - (ΔHc1 + ΔHc2)} / 93.

[0062] [Charpy impact test] Test specimens for evaluating physical properties were prepared under the following injection molding conditions. The pellets of the resin composition obtained above were injection molded using an IS80EPN-2A injection molding machine manufactured by Shibaura Machine Co., Ltd., at a molding temperature of 190 to 210°C, an injection time of 15 seconds, and an arbitrary mold temperature. The test specimens were then notched to a width of 10 mm, a thickness of 4 mm, and a notch height of 8 mm. The prepared test specimens were evaluated in accordance with ISO 179 using an IT-type impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd.

[0063] [Example 1] (Resin composition manufacturing example) Using a twin-screw kneading extruder, raw materials were supplied in the mixing ratio shown in Table 1 and melt-kneaded. The cylinder temperature was set to 50 to 190°C, the extrusion rate was 30 kg / h, and the screw rotation speed was 400 rpm to produce a resin composition.

[0064] [Example 2 and Comparative Examples 1 to 3] Using the same procedure as in Example 1, resin compositions containing the (meth)acrylic acid esters shown as modifiers B-2 and B-3 were produced. Molded articles were prepared from the resin compositions produced, and the holding time, absolute crystallinity, and Charpy impact strength were measured.

[0065] Examples 1 and 2 and Comparative Examples 1 to 3 are shown in Table 1 below. [Table 1] [Industrial Applicability]

[0066] The molded article of the present invention is suitable for applications requiring high impact resistance, such as components for vehicles, ships, electronic devices, home appliances, building materials, etc., as well as for daily necessities, sporting goods, stationery, etc. Furthermore, polylactic acid can be used as a resin molded article with low environmental impact from the viewpoint of carbon neutrality.

Claims

1. Polylactic acid (A) 100 parts by weight, 1 to 40 parts by weight of a modifier (B), and Nucleating agent (C) 0.1 to 10 parts by weight and the absolute crystallinity of the molding is 28 to 40%.

2. 2. The molded article according to claim 1, wherein the polylactic acid (A) has a melt flow rate (MFR) of 3 to 30 and a D-isomer content of 10% or less.

3. 2. The molded article according to claim 1, wherein the modifier (B) comprises at least one selected from a copolymer containing a (meth)acrylic acid ester and a core-shell type graft copolymer containing a (meth)acrylic acid ester.

4. 2. The molded article according to claim 1, wherein the modifier (B) has a glass transition point of −10° C. or lower and contains 15 to 100% by weight of a (meth)acrylic acid ester based on the modifier.

5. 2. The molded article according to claim 1, wherein the nucleating agent (C) comprises at least one selected from organic sulfonates, organic metal salts, organic hydrazide compounds, carboxylic acid ester compounds, phthalocyanine compounds, melamine compounds, layered silicates, amide compounds, metal oxides, metal carbonates, talc, silica, and the like.

6. The molded article also contains an additive (D), 2. The molded article according to claim 1, wherein the additive (D) is at least one selected from the group consisting of catalysts, neutralizing agents, antioxidants, ultraviolet absorbers, lubricants, antistatic agents, antiblocking agents, processing aids, colorants, foaming agents, plasticizers, brightness enhancers, antibacterial agents, and light diffusing agents.

7. A method for producing the molded article according to any one of claims 1 to 6, comprising: Polylactic acid (A), modifier (B), and nucleating agent (C) are mixed together to obtain a mixture, A manufacturing method in which the mixture is molded.

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