Modifiers for polyamide resins and polyamide resin compositions

Abstract

To provide a modifier for polyamide resins that suppresses the decrease in fluidity during melting of polyamide resin compositions while sufficiently improving their impact strength at room temperature and low temperature. [Solution] A modifier for polyamide resins comprising polymer particles, wherein the polymer particles have a core-shell structure consisting of a shell layer and one or more core layers, at least one of the core layers is composed of polybutadiene or poly(butadiene-styrene), the shell layer is composed of a polymer of 50% by weight or more of methacrylic acid ester monomer and 0 to 50% by weight of other monomer copolymerizable with the methacrylic acid ester monomer, the polymer particles contain maleic anhydride as a constituent monomer, and the content of maleic anhydride is 0.3 to 2.5% by weight of the total polymer particles, the modifier for polyamide resins.

Description

Technical Field

[0001] The present invention relates to a modifier for polyamide resins and a polyamide resin composition containing the modifier.

Background Art

[0002] Conventionally, as a technique for improving the impact resistance of thermoplastic resins, a method of blending a graft copolymer containing a rubber component with a thermoplastic resin is known.

[0003] However, when the thermoplastic resin is a polyamide resin, generally, the polyamide resin and the rubber-containing graft copolymer have low compatibility. Therefore, the rubber-containing graft copolymer is not sufficiently dispersed in the polyamide resin, and the effect of improving the impact strength of the polyamide resin by blending the rubber-containing graft copolymer is not always sufficient. In addition, when the rubber-containing graft copolymer is blended to improve the impact strength of the polyamide resin, the fluidity during melting decreases, and as a result, there is a problem of poor moldability.

[0004] In Patent Document 1, as a modifier for polyamide resins that can improve the impact strength while suppressing the decrease in colorability and fluidity of polyamide resin compositions, it has a core-shell structure, a specific volume average particle diameter, the core layer is composed of polybutadiene or poly(butadiene-styrene), the shell layer is composed of a polymer containing a specific amount of methacrylic acid ester monomer, and a modifier composed of polymer particles containing a specific amount of carboxyl group-containing vinyl monomer as a constituent monomer is described.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, there was room for improvement in the effect of suppressing the decrease in fluidity during melting of polyamide resin compositions, and in the effect of improving impact strength at room temperature and low temperatures, especially at low temperatures. The present invention aims to provide a modifier for polyamide resins that can sufficiently improve the impact strength at room temperature and low temperatures while suppressing the decrease in fluidity during melting of polyamide resin compositions. [Means for solving the problem]

[0007] The present invention relates to a modifier for polyamide resins comprising polymer particles, wherein the polymer particles have a core-shell structure consisting of a shell layer and one or more core layers, at least one of the core layers is composed of polybutadiene or poly(butadiene-styrene), the shell layer is composed of a polymer of 50% by weight or more of a methacrylic acid ester monomer and 0 to 50% by weight of another monomer copolymerizable with the methacrylic acid ester monomer, and the polymer particles contain maleic anhydride as a constituent monomer, with the maleic anhydride content being 0.3 to 2.5% by weight of the total polymer particles. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a modifier for polyamide resins that can sufficiently improve the impact strength at room temperature and low temperature while suppressing the decrease in fluidity during melting of the polyamide resin composition. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below. (Modifier for polyamide resins) The modifier for polyamide resin according to this embodiment is composed of polymer particles that are graft copolymers. The polymer particles have a core-shell structure consisting of a shell layer and one or more core layers. The shell layer refers to the polymer layer located on the surface side of the polymer particle and is also called the graft layer. The core layer refers to the polymer layer located inside the polymer particle from the shell layer and is composed of a rubbery polymer. The core layer may be only one layer, or it may consist of two or more layers with different monomer compositions. The shell layer covers the surface of the core layer, but is not limited to covering the entire surface of the core layer; it is sufficient if it covers at least a part of the surface of the core layer.

[0010] (Core layer) The core layer of the polymer particles is composed of a rubbery polymer. At least one layer of the core layer may be composed of polybutadiene or poly(butadiene-styrene). Alternatively, the entire core layer may be composed of polybutadiene or poly(butadiene-styrene).

[0011] Preferably, at least one layer of the core layer is composed of polybutadiene or poly(butadiene-styrene), and more preferably, the entire core layer is composed of polybutadiene or poly(butadiene-styrene). This improves the refractive index of the core layer compared to, for example, the case where acrylic rubber is used, bringing it closer to the refractive index of the polyamide resin. As a result, the appearance of the polyamide resin composition is improved, the decrease in appearance of the polyamide resin due to the blending of polymer particles is suppressed, and in addition, the effect of improving the impact strength of the polyamide resin composition at room temperature and low temperature is also excellent. Here, the appearance of the polyamide resin composition refers to its color development and gloss. Even when polymer particles are blended into a polyamide resin colored with a coloring agent containing a dark coloring component including black such as carbon black, its color development can be maintained, the increase in brightness can be suppressed, and its gloss can be preserved.

[0012] Among these, polybutadiene is particularly preferred from the viewpoint of its high effect in improving impact strength at room temperature and low temperature, and from the viewpoint of raw material cost. The proportion of styrene in poly(butadiene-styrene) is not particularly limited, but is preferably 0 to 50% by weight. In this disclosure, room temperature refers to a temperature of approximately 20°C to 30°C, and low temperature refers to a temperature lower than room temperature, for example, -40°C or higher.

[0013] The aforementioned polybutadiene or poly(butadiene-styrene) may not contain vinyl monomers other than butadiene and styrene, or it may contain such vinyl monomers. Examples of such vinyl monomers include aromatic vinyl monomers (excluding styrene) such as α-methylstyrene; (meth)acrylic acids and alkyl (meth)acrylates such as acrylic acid, methacrylic acid, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate; and unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile.

[0014] The aforementioned polybutadiene or poly(butadiene-styrene) may be obtained by using polyfunctional monomers such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, or 1,3-butylene dimethacrylate during polymerization.

[0015] Furthermore, the polybutadiene or poly(butadiene-styrene) may be polymerized without the use of a chain transfer agent, but it is preferable that it be polymerized in the presence of a chain transfer agent. By using a chain transfer agent, the impact strength of the polyamide resin composition according to this embodiment is improved at room temperature and low temperature, the incidence of brittle fracture decreases and the incidence of ductile fracture tends to increase in impact tests at room temperature and low temperature. The usable chain transfer agent is not particularly limited, but examples include alkyl mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, t-decyl mercaptan, n-decyl mercaptan, and n-octyl mercaptan, and alkyl ester mercaptans such as 2-ethylhexyl thioglycolate.

[0016] When using a chain transfer agent, the amount used is not particularly limited, but it is preferably 0.01 to 3% by weight of the total amount of polybutadiene or poly(butadiene-styrene). When the amount of chain transfer agent used is within the above range, the effect of improving the impact strength of the polyamide resin at room temperature and low temperature due to the blending of polymer particles can be enhanced. The amount used is more preferably 0.05 to 2% by weight, and even more preferably 0.1 to 1% by weight.

[0017] The core layer preferably has a refractive index of 1.50 or higher. By using a core layer with such a refractive index, the appearance of the polyamide resin composition is further improved, and the deterioration of the appearance of the polyamide resin due to the incorporation of polymer particles can be further suppressed. The refractive index of the core layer is more preferably 1.51 or higher, and even more preferably 1.52 or higher. The upper limit of the refractive index is not particularly limited, but for example, it is preferably 1.58 or lower, and more preferably 1.57 or lower.

[0018] (Shell layer) The aforementioned shell layer is composed of a polymer of 50% by weight or more of a methacrylic acid ester monomer and 0 to 50% by weight of another monomer copolymerizable with the methacrylic acid ester monomer. Because the shell layer is composed of a polymer in which 50% by weight or more of the methacrylic acid ester monomer constitutes 50% by weight or more, the glass transition temperature of the shell layer is high, the polymer particles are less likely to become coarse, and the mechanical stability of the latex of the polymer particles is also good, making it suitable for industrial production.

[0019] The methacrylate ester monomers constituting the aforementioned shell layer are not particularly limited, but examples include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, and behenyl methacrylate. Among these, methyl methacrylate is preferred. Furthermore, it is preferable not to use t-butyl methacrylate in order to avoid the generation of isobutylene gas, which is a flammable gas, during the melting process of the polyamide resin composition.

[0020] The proportion of the methacrylic acid ester monomer in the total monomer components of the polymer constituting the shell layer is 50 to 100% by weight. When the methacrylic acid ester monomer accounts for more than half of the shell layer of the polymer particles, the polymer particles are less likely to become coarse during the powdering process to obtain the polymer particle powder from the latex. This results in the advantage that the obtained polymer particles are easily dispersed uniformly in the polyamide resin, and the mechanical stability of the polymer particle latex is also good. The proportion is preferably 60 to 99% by weight, more preferably 70 to 97% by weight, and even more preferably 75 to 95% by weight.

[0021] The monomer component of the polymer that constitutes the shell layer of the polymer particles may contain, in addition to the methacrylic acid ester monomer, other monomers copolymerizable with the methacrylic acid ester monomer. Such monomers are not particularly limited, but in addition to maleic anhydride described later, alkyl acrylates are preferred. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, behenyl acrylate and the like. Among them, butyl acrylate is preferred.

[0022] The proportion of the other copolymerizable monomer in the total monomer component of the polymer that constitutes the shell layer is 0 to 50% by weight. The proportion is preferably 1 to 40% by weight, more preferably 3 to 30% by weight, and still more preferably 5 to 25% by weight.

[0023] From the viewpoints of the compatibility between the polymer particles and the polyamide resin and the improvement effect of the impact strength at normal temperature and low temperature, the weight ratio of the shell layer in the whole polymer particles is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, and still more preferably 10 to 30% by weight.

[0024] (Maleic anhydride) The polymer particles contain maleic anhydride as a constituent monomer. The maleic anhydride is preferably a constituent monomer of the polymer that constitutes the shell layer. At this time, it may not be contained in the core layer and may be contained only in the shell layer, or may be contained in both the core layer and the shell layer. However, maleic anhydride only needs to be contained in the polymer particles and may not be contained in the shell layer and may be contained only in the core layer.

[0025] The inclusion of maleic anhydride as a constituent monomer in the polymer particles suppresses the decrease in fluidity during melting of the polyamide resin composition while enabling a sufficient improvement in impact strength at room temperature and low temperatures. Furthermore, the maleic anhydride contained in the polymer particles imparts reactivity with the polyamide resin to the polymer particles, thereby improving the dispersibility of the polymer particles in the polyamide resin. It is presumed that the reaction of the maleic anhydride contained in the polymer particles with the terminal amino groups of the polyamide resin to form imides with strong intermolecular forces contributes to both the suppression of the decrease in fluidity during melting of the polyamide resin composition and the sufficient improvement in impact strength at room temperature and low temperatures.

[0026] An embodiment in which the shell layer contains maleic anhydride as a constituent monomer is preferable because it can particularly enhance the reactivity between the maleic anhydride and the polyamide resin, further improving the dispersibility of polymer particles in the polyamide resin, thereby further enhancing both the suppression of the decrease in fluidity during melting of the polyamide resin composition and the effect of improving impact strength at room temperature and low temperature.

[0027] The content of maleic anhydride is 0.3 to 2.5% by weight relative to the total polymer particles. Within this range, the impact strength at room temperature and low temperature can be sufficiently improved while suppressing the decrease in fluidity of the polyamide resin composition during melting. The lower limit of the percentage may be 0.3%, 0.4%, 0.5%, 0.7%, or 0.8% by weight. The upper limit of the percentage may be 2.5%, 2.2%, 2.0%, 1.7%, or 1.5% by weight.

[0028] When the shell layer contains maleic anhydride as a constituent monomer, the content of maleic anhydride in the shell layer is preferably 1.5 to 11.5% by weight relative to the total constituent monomers of the polymer constituting the shell layer. The lower limit of the percentage may be 1.5%, 1.8%, 2.2%, 3.2%, or 3.6% by weight. The upper limit of the percentage may be 11.5%, 10%, 9%, 8%, or 7% by weight.

[0029] (Volume-average particle diameter of polymer particles) The volume-average particle diameter of the polymer particles is preferably 100 nm or more, 120 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, or 170 nm or more, in that order, in order to achieve better impact strength. On the other hand, as the particle diameter of the polymer particles increases, the polymerization reaction takes longer and productivity tends to decrease, so the volume-average particle diameter is preferably 400 nm or less, more preferably 350 nm or less, even more preferably 300 nm or less, even more preferably 250 nm or less, and particularly preferably 200 nm or less. The volume-average particle diameter of the polymer particles is a value measured using a particle diameter measuring device in the latex state of the polymer particles, as shown in the Examples section. The volume-average particle diameter of the polymer particles can also be calculated from a transmission electron microscope (TEM) image of the polyamide resin composition. The particle diameter of the polymer particles can be controlled by the type and amount of polymerization initiators, chain transfer agents, redox agents, emulsifiers, etc., polymerization temperature, polymerization time, etc.

[0030] (Method for manufacturing polymer particles) The method for producing the polymer particles can be a conventional method and is not particularly limited. For example, bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization can be employed, but emulsion polymerization, i.e., emulsion graft polymerization, is preferred. Specifically in emulsion graft polymerization, first, a latex of polymer particles corresponding to the core layer is produced by emulsion polymerization, and then monomer components for the shell layer and polymerization initiators are added to the latex to polymerize the monomer components.

[0031] The emulsifier (dispersant) that can be used in emulsion polymerization is not particularly limited, and anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. may be used. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used. Among the emulsifiers mentioned above, the anionic surfactant is not particularly limited, but examples include the following compounds: potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid sodium soap, semi-hardened beef tallow fatty acid sodium soap, castor oil potassium soap, and other fatty acid soaps; sodium dodecyl sulfate, higher alcohol sodium sulfate, dodecyl sulfate triethanolamine, dodecyl sulfate ammonium, polyoxyethylene alkyl ether sulfate sodium, polyoxyethylene alkyl ether sulfate triethanolamine, polyoxyethylene alkylphenyl ether sulfate sodium, 2-ethylhexyl sulfate sodium, and other alcohols. Sodium methyl sulfate; sodium alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; sodium dialkyl sulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalene sulfonate; sodium alkyldiphenyl ether disulfonate; potassium alkyl phosphate; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalene sulfonic acid formalin condensate; polycarboxylic acid type polymer anions; sodium acyl(tallow)methyltaurate; sodium acyl(coconut)methyltaurate; sodium cocoyl isethionate; sodium α-sulfo fatty acid esters; sodium amide ether sulfonate; oleyl sarcosine; sodium lauroyl sarcosinate; rosinic acid soap, etc.

[0032] Furthermore, the nonionic surfactants among the emulsifiers mentioned above are not particularly limited, but examples include the following compounds: polyoxyethylene alkyl allyl ethers or polyoxyethylene alkyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene oleyl ether, and polyoxyethylene lauryl ether; polyoxyethylene sorbitan esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monostearate; polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monostearate, and polyethylene glycol monooleate; oxyethylene / oxypropylene block copolymer, etc.

[0033] Furthermore, the cationic surfactants among the emulsifiers mentioned above are not particularly limited, but examples include the following compounds: alkylamine salts such as coconutamine acetate, stearylamine acetate, octadecylamine acetate, and tetradecylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, distearyldimethylammonium chloride, alkylbenzyldimethylammonium chloride, hexadecyltrimethylammonium chloride, and behenyltrimethylammonium chloride.

[0034] Furthermore, while the amphoteric surfactants among the emulsifiers mentioned above are not particularly limited, examples include the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethylglycine; amide betaine; imidazoline; lauryl carboxymethyl hydroxyethyl imidazolinium betaine, etc.

[0035] These emulsifiers (dispersants) may be used individually or in combination of two or more. By adjusting the amount of emulsifier used, the average particle size of the polymer particles can be controlled.

[0036] When employing emulsion polymerization, known polymerization initiators, namely 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate, can be used as thermal decomposition initiators.

[0037] In addition, redox initiators can be used in combination with peroxides such as organic peroxides including t-butyl peroxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide; and inorganic peroxides including hydrogen peroxide, potassium persulfate, and ammonium persulfate, along with, if necessary, reducing agents such as sodium formaldehyde sulfoxylate and glucose, and, if necessary, transition metal salts such as iron(II) sulfate, and, if necessary, chelating agents such as disodium ethylenediaminetetraacetate, and, if necessary, phosphorus-containing compounds such as sodium pyrophosphate.

[0038] When a redox-type initiator is used, polymerization can be carried out even at low temperatures in which the peroxide does not substantially decompose thermally, and the polymerization temperature can be set over a wide range, which is preferable. In particular, it is preferable to use organic peroxides such as cumene hydroperoxide, dicumyl peroxide, and t-butyl hydroperoxide as redox-type initiators. The amount of the initiator used, and when a redox-type initiator is used, the amounts of the reducing agent, transition metal salt, chelating agent, etc. can be used within a known range. Furthermore, when polymerizing monomers having two or more radically polymerizable double bonds, known chain transfer agents can be used within a known range. Surfactants can also be used in addition, but this is also within a known range.

[0039] Any solvent that allows emulsion polymerization to proceed stably is acceptable as the solvent used during emulsion polymerization; for example, water can be suitably used.

[0040] The temperature during emulsion polymerization is not particularly limited as long as the emulsifier is uniformly dissolved in the solvent, but for example, it is 40 to 75°C, preferably 45 to 70°C, and more preferably 49 to 65°C.

[0041] When the polymer particles are produced by emulsion polymerization, for example, the polymer particles can be coagulated by mixing the latex of the polymer particles with an acid such as hydrochloric acid or a divalent or higher metal salt such as calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, or calcium acetate. Then, the polymer particles can be separated from the aqueous medium by heat treatment, dehydration, washing, and drying according to a known method. The obtained polymer particles are preferably washed with water and / or an organic solvent.

[0042] Alternatively, alcohols such as methanol, ethanol, and propanol, or water-soluble organic solvents such as acetone, can be added to the latex of the polymer particles to precipitate them. After separating the polymer particles from the solvent by centrifugation or filtration, they can be dried and isolated. Another method involves adding a slightly water-soluble organic solvent such as methyl ethyl ketone to the latex of the polymer particles to extract the polymer particles from the latex into the organic solvent layer. After separating the organic solvent layer, it can be mixed with water or the like to precipitate the polymer particles.

[0043] Alternatively, the latex of the polymer particles can be directly powdered by spray drying. The resulting powder is preferably washed with water and / or an organic solvent. Alternatively, the same effect as the washing described above can be obtained by adding calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, etc., to the resulting powder, preferably as a solution such as an aqueous solution, and re-drying as necessary.

[0044] (Amount of modifier added) The modifier for polyamide resin according to this embodiment, comprising the polymer particles detailed above, is used by being blended with a polyamide resin and has the effect of improving the impact strength of the polyamide resin at room temperature and low temperature while suppressing the decrease in fluidity of the polyamide resin composition during melting. The amount of modifier blended with the polyamide resin can be set as appropriate, but preferably the ratio of the modifier to the total of the polyamide resin and modifier is 1 to 40% by weight. When the ratio of the modifier is within the above range, the effect of improving the impact strength of the polyamide resin at room temperature and low temperature due to the blending of the modifier can be obtained while maintaining the physical properties unique to the polyamide resin and suppressing the decrease in fluidity of the polyamide resin composition during melting. The above ratio is more preferably 3 to 30% by weight, and even more preferably 5 to 25% by weight.

[0045] (Polyamide resin) The polyamide resin according to this embodiment is not limited to polymers having an acid amide bond (-CONH-), but examples include polymers obtained by polycondensation of a diamine and a dibasic acid, polymers obtained by polycondensation of a diamine derivative such as diformyl and a dibasic acid, polymers obtained by polycondensation of a dibasic acid derivative such as a dimethyl ester and a diamine, polymers obtained by reaction of dinitrile or diamide with formaldehyde, polymers obtained by polyaddition of diisocyanate and a dibasic acid, polymers obtained by self-condensation of amino acids or their derivatives, polymers obtained by ring-opening polymerization of lactams, and the like. The polyamide resin may also contain a polyether block. One type of polyamide resin may be used alone, or two or more types may be used in mixture form.

[0046] Specific examples of polyamide resins include the aliphatic polyamides nylon 4, nylon 6, nylon 66, nylon 7, nylon 9, nylon 11, nylon 12, nylon 46, nylon 56, nylon 410, nylon 412, nylon 610, nylon 612; the semi-aromatic polyamides nylon 6T, nylon 6I, nylon 9T, nylon 10T, nylon M5T, nylon MXD6; and the copolymer polyamides nylon 6 / 66, nylon 6 / 12, nylon 6 / 66 / 12, nylon 6 / 6T, nylon 66 / 6T, nylon 6 / 6I, nylon 6T / 6I, nylon 6T / 12, nylon 66 / 6T / 6I, etc. Among these, nylon 6, nylon 6,6, nylon 11, and nylon 12 are preferred from the viewpoint of versatility.

[0047] (Other resins) The polyamide resin composition according to this embodiment may or may not contain thermoplastic resins other than polyamide resin. When thermoplastic resins other than polyamide resins are included, the thermoplastic resin is not particularly limited, but examples include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, ABS resin, AS resin, acrylic resin, polyacetal, polycarbonate, modified polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, cyclic polyolefin, etc. The amount of other thermoplastic resins is not particularly limited, but for example, it is 0 to 100 parts by weight, preferably 0 to 50 parts by weight, more preferably 0 to 30 parts by weight, and even more preferably 0 to 10 parts by weight per 100 parts by weight of polyamide resin.

[0048] (Other additives) The polyamide resin composition according to this embodiment may appropriately contain additives that can be incorporated into general thermoplastic resin compositions, as long as they do not impair the effects of the present invention. Such additives are not particularly limited, but examples include colorants, flame retardants, flame retardant aids, anti-dripping agents, reinforcing agents, fillers, antioxidants, conductivity imparting agents, hydrolysis inhibitors, thickeners, plasticizers, lubricants, antioxidants, ultraviolet absorbers, antistatic agents, flow improvers, mold release agents, compatibilizers, and heat stabilizers.

[0049] Examples of colorants include masterbatches, colored pellets, colored compounds, dry colors, paste colors, and liquid masterbatches. Colorants also include pigments such as carbon black.

[0050] The amount of coloring component can be set as appropriate, but from the viewpoint of good color development and efficient usage, 0.0.1 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, and even more preferably 0.5 to 1.5 parts by weight per 100 parts by weight of the polyamide resin composition is preferred.

[0051] From the viewpoint of improving impact strength at room temperature and low temperature, the polyamide resin composition according to this embodiment preferably further contains a reinforcing material. Examples of reinforcing materials include glass fibers, carbon fibers, boron fibers, asbestos fibers, polyvinyl alcohol fibers, polyester fibers, acrylic fibers, fully aromatic polyamide fibers, polybenzoxazole fibers, polytetrafluoroethylene fibers, kenaf fibers, bamboo fibers, hemp fibers, bagasse fibers, high-strength polyethylene fibers, alumina fibers, silicon carbide fibers, potassium titanate fibers, brass fibers, stainless steel fibers, steel fibers, ceramic fibers, basalt fibers, etc. Among these, glass fibers, carbon fibers, and metal fibers are preferred, and glass fibers are more preferred, due to their high effect in improving impact strength. The reinforcing material may be used alone or in combination of two or more types.

[0052] The amount of reinforcing material can be set as appropriate, but from the viewpoint of improving impact strength with efficient use, 1 to 50 parts by weight, more preferably 10 to 40 parts by weight, and even more preferably 25 to 35 parts by weight per 100 parts by weight of the polyamide resin composition is preferred.

[0053] (Method of manufacturing the composition) The method for producing the polyamide resin composition according to this embodiment is not particularly limited, and a general method for producing thermoplastic resin compositions can be applied. For example, the polyamide resin composition can be obtained by mixing the raw materials using a Henschel mixer or a tumbler mixer, and then performing melt kneading. A kneader such as a single-screw or twin-screw extruder, a Banbury mixer, a pressure kneader, or a mixing roll can be used for this melt kneading. Pellets made of the polyamide resin composition can be produced by such melt kneading.

[0054] The polyamide resin composition according to this embodiment can be molded into a predetermined shape to form a molded article. The molding method is not particularly limited, and for example, injection molding, extrusion molding, blow molding, calendering, inflation molding, rotational molding, press molding, etc., can be used.

[0055] (Application) The polyamide resin composition and molded articles according to this embodiment have several applications, taking advantage of their benefits such as oil resistance, non-conductivity, and excellent color development without surface coating. These applications include: automotive applications such as cylinder head covers, engine covers, intake manifolds, radiator tanks, oil pans, accelerator pedals, canisters, fuel tubes, air brake tubes, exhaust gas tubes, hydrogen injectors, ducts, industrial fasteners, and door mirror stays; electrical and electronic applications such as coil bobbins, connectors, gears, sockets, switches, electric blanket coated wires, fiber optic cable coatings, power tools, wire binding materials, and chargers; and hydraulic and pneumatic connectors. Examples of applications include, but are not limited to, mechanical applications such as tubes, bearings, covers / housings, bearings, pressure-resistant hoses, and cable ties; building materials such as curtain rail components, aluminum sash corners, door rollers, handrails, curtain rollers, and door handles; sports and leisure applications such as sports shoe soles, ski and snowboard equipment, reels, and diving / snorkeling equipment; packaging materials and containers such as shrink wrap film, food packaging film, alcoholic beverage bottles, and pesticide bottles; daily necessities such as toothbrushes, chair legs and armrests, combs, knives and forks; and medical applications such as medical catheters and pipes, medical packs, and sutures.

[0056] The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A modifier for polyamide resins, comprising polymer particles, The polymer particles have a core-shell structure consisting of a shell layer and one or more core layers. At least one of the core layers is composed of polybutadiene or poly(butadiene-styrene), The shell layer is composed of a polymer of 50% by weight or more of a methacrylic acid ester monomer and 0 to 50% by weight of another monomer copolymerizable with the methacrylic acid ester monomer. The polymer particles contain maleic anhydride as a constituent monomer. A modifier for polyamide resins, wherein the content of maleic anhydride is 0.3 to 2.5% by weight relative to the total polymer particles. [Item 2] The modifier for polyamide resins according to item 1, wherein the maleic anhydride is a constituent monomer of the polymer constituting the shell layer. [Item 3] The core layer is a modifier for polyamide resins according to item 1 or 2, exhibiting a refractive index of 1.50 or higher. [Item 4] A modifier for polyamide resins as described in any one of items 1 to 3, having a volume-average particle diameter of 100 nm or more. [Item 5] A modifier for polyamide resins according to any one of items 1 to 4, wherein the ratio of the shell layer to the total polymer particles is 1 to 50% by weight. [Item 6] It contains a polyamide resin and a polyamide resin modifier described in any one of items 1 to 5. A polyamide resin composition in which the modifier accounts for 1 to 40% by weight of the total amount of the polyamide resin and the modifier. [Item 7] The polyamide resin composition according to item 6, further comprising 0.0.1 to 3 parts by weight of a coloring component per 100 parts by weight of the polyamide resin composition. [Item 8] The polyamide resin composition according to item 6 or 7, further comprising 1 to 50 parts by weight of a reinforcing material per 100 parts by weight of the polyamide resin composition. [Item 9] Pellets comprising the polyamide resin composition described in any one of items 6 to 8. [Item 10] A molded article comprising a polyamide resin composition as described in any one of items 6 to 8. [Examples]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] (Refractive index of the core layer) The refractive index of the core layer was measured using an Abbe Refractometer 2T manufactured by Atago, in accordance with the JIS K7142 standard.

[0059] (Average particle size of polymer particles) The average particle size of polymer particles was measured as the volume-average particle size in the polymer latex state. A Nanotrac Wave manufactured by Nikkiso Co., Ltd. was used as the measuring device.

[0060] (polymerization rate) A portion of the obtained polymer particle latex was sampled and accurately weighed, then dried in a hot air dryer at 120°C for 1 hour. The weight after drying was accurately weighed as the solid content. Next, the ratio of the weighing results before and after drying was determined as the solid component ratio in the latex. Finally, the polymerization conversion rate was calculated using this solid component ratio according to the following formula. Formula: Polymerization conversion rate = (Total weight of raw materials × Solid component ratio - Total weight of raw materials other than monomers) / Weight of monomers × 100 (%)

[0061] <Method for manufacturing the core layer> In a pressure polymerization reactor, 170 parts by weight of deionized water, 0.002 parts by weight of disodium ethylenediaminetetraacetate, 0.0012 parts by weight of ferrous sulfate heptahydrate, and 0.13 parts by weight of sodium dodecylbenzenesulfonate were added. After thoroughly degassing and removing oxygen while stirring, 100 parts by weight of butadiene (hereinafter referred to as BD) was added to the system and the temperature was raised to 45°C. Then, 0.05 parts by weight of sodium formaldehyde sulfoxylate and 0.03 parts by weight of paramenthane hydroperoxide were added to start polymerization. At 6, 10, 14, and 17 hours from the start of polymerization, 0.014 parts by weight of paramenthane hydroperoxide were added, respectively. At 20 hours from the start of polymerization, the remaining monomer was defoliated and removed under reduced pressure to terminate polymerization and obtain a polybutadiene rubber latex (core layer) mainly composed of polybutadiene rubber. The volume-average particle size of the polybutadiene rubber particles in the obtained latex was adjusted as appropriate by changing the initial amount of sodium dodecylbenzenesulfonate added.

[0062] As a typical method for producing polymer particle latex, the production procedure for the polymer particle latex in Example 1 is shown below. The polymer particle latex in the other examples and comparative examples was produced by changing the monomer composition of the shell layer according to the table, but the production procedure is the same as described below for Example 1.

[0063] <Method for manufacturing the shell layer in Example 1> In a glass reactor equipped with a thermometer, stirrer, reflux condenser, nitrogen inlet, and monomer and emulsifier addition device, 30 parts by weight of deionized water and the aforementioned polybutadiene rubber latex (core layer) were charged to a solid content of 78 parts by weight, and the temperature was raised to 60°C while stirring in a nitrogen stream. Next, 0.00032 parts by weight of disodium ethylenediaminetetraacetate, 0.00008 parts by weight of ferrous sulfate heptahydrate, and 0.04 parts by weight of sodium formaldehyde sulfoxylate were charged. A mixture of 19.4 parts by weight of methyl methacrylate (hereinafter referred to as MMA), 2.2 parts by weight of n-butyl acrylate (hereinafter referred to as BA), 0.5 parts by weight of maleic anhydride (hereinafter referred to as MAH), and 0.024 parts by weight of t-butyl hydroperoxide was added over 68 minutes. Five minutes after the completion of the addition, sodium formaldehyde sulfoxylate and t-butyl hydroperoxide were added as appropriate to obtain polymer particle latex (shell layer) with a polymerization conversion rate of 100%.

[0064] (Obtaining white resin powder from polymer particles in each example and comparative example) 760 parts by weight of deionized water and 3.3 parts by weight of a 25% by weight aqueous solution of calcium chloride were heated to 60°C while stirring. Then, 2.5 parts by weight of IRGANOX-1076 [n-octadecyl-3-(3',5',di-t-butyl-4'-hydroxyphenyl)propionate], a hindered phenol antioxidant, were added to each polymer particle latex to obtain a slurry containing coagulated latex particles. Subsequently, the slurry was heated to 90°C, dehydrated, and dried to obtain a white resin powder of polymer particles.

[0065] (Manufacturing of polyamide resin compositions) Pellets and test specimens were prepared from compositions containing polyamide resin and white resin powder of polymer particles according to the following description. Izod impact strength, MFR, isobutylene gas generation, and appearance (L value and gloss) were measured, and the results are shown in the respective tables. However, in Reference Example 1, white resin powder of polymer particles was not used, and in Comparative Example 7, a commercially available modifier was used instead of the white resin powder of polymer particles.

[0066] (Pellet and test specimen preparation conditions) • Examples and comparative examples (a) Nylon 6: Polyamide 6 resin (UBE1030B manufactured by UBE Corporation) 79.5 parts by weight (b) 20 parts by weight of polymer particles or commercially available modifier (c) Carbon Black 0.5 parts by weight ·Reference example (a) Nylon 6: Polyamide 6 resin (UBE1030B manufactured by UBE Corporation) 99.5 parts by weight (c) Carbon Black 0.5 parts by weight

[0067] The mixtures of (a), (b), and (c) or (a) and (c) were kneaded and extruded in a twin-screw extruder (TEX44SS manufactured by Japan Steel Works Ltd.) heated to a barrel temperature of 210 to 270°C at a screw rotation speed of 200 rpm to obtain pellets.

[0068] These pellets were dried in a vacuum dryer at 120°C for 12 hours to sufficiently reduce the moisture content. Then, test specimens were prepared using an injection molding machine (FANUC FAS100B) under the conditions of a molding temperature of 270°C and a mold temperature of 80°C.

[0069] (Izod impact strength) For test specimen 1, which was prepared using the method described above and had a thickness of 4.0 mm and a V-notch, the Izod impact strength was measured at -30°C, 0°C, and 23°C in a completely dry state, in accordance with the ASTM D256 standard.

[0070] (MFR) The pellets prepared under the aforementioned conditions were dried in a vacuum dryer at 120°C for 12 hours, and then the MFR value was measured according to JIS K7210 Method A, under conditions of a measurement temperature of 270°C and a load of 5 kg.

[0071] (Presence or absence of isobutylene gas generation) During the mixing of polyamide resin and polymer particles under the aforementioned conditions, the gas collected from the vent was analyzed using GCMS (Trace1300-ISQ-QD, Thermo Fisher Scientific) to confirm the presence or absence of isobutylene gas.

[0072] (L value) A 2mm thick color plate was obtained under the same conditions as those used to prepare the Izod impact strength test specimen. The reflectance L value of the obtained color plate was measured using a color difference meter (model: ZE 6000) manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with the JIS Z8741 standard. A lower L value indicates a deeper black color and better color development.

[0073] (Glossy) A 2 mm thick color plate was obtained under the same conditions as those used to prepare the Izod impact strength test specimen. The 60-degree specular gloss of the obtained color plate was measured using a color difference meter (model: VG 7000) manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with the JIS K8722 standard.

[0074] [Table 1]

[0075] The abbreviations for the monomer compositions of the shell layers other than MMA, BA, and MAH in Table 1, and the details of the modifiers used in Comparative Example 7 are as follows. t-BMA: t-butyl methacrylate MAA: Methacrylic acid HEMA: 2-hydroxyethyl methacrylate MH7020: TAFMER MH7020 (α-olefin copolymer) manufactured by Mitsui Chemicals, Inc.

[0076] Compared to Reference Example 1, which did not contain polymer particles, Comparative Example 1, which contained polymer particles without maleic anhydride, was able to suppress the decrease in fluidity during melting of the polyamide resin composition, but it had almost no effect on improving impact strength at room temperature and low temperature.

[0077] The polyamide resin compositions of Comparative Examples 2 and 3, which did not contain maleic anhydride as a constituent monomer and instead contained polymer particles containing t-BMA and MAA respectively, showed improved impact strength at room temperature and low temperature compared to Comparative Example 1, but failed to suppress the decrease in fluidity during melting of the polyamide resin composition. Furthermore, in Comparative Example 2, isobutylene gas, a flammable gas, was generated during the kneading of the polyamide resin and polymer particles.

[0078] Comparative Example 4, a polyamide resin composition that did not contain maleic anhydride as a constituent monomer and incorporated polymer particles containing HEMA, showed an improvement in impact strength at room temperature compared to Comparative Example 1, but did not show much improvement in impact strength at low temperatures and failed to sufficiently suppress the decrease in fluidity of the polyamide resin composition.

[0079] The polyamide resin composition of Comparative Example 5, which incorporated polymer particles containing less than a specified amount of maleic anhydride as a constituent monomer, was able to suppress the decrease in the fluidity of the polyamide resin composition and showed an improvement in impact strength at room temperature and low temperature compared to Comparative Example 1, but the improvement was insufficient.

[0080] The polyamide resin composition of Comparative Example 6, which incorporated polymer particles containing a specific amount of maleic anhydride as a constituent monomer, showed improved impact strength at room temperature and low temperature compared to Comparative Example 1. However, the improvement in impact strength was insufficient, and the decrease in fluidity of the polyamide resin composition could not be sufficiently suppressed.

[0081] In Comparative Example 7, a polyamide resin composition using a commercially available modifier instead of the white resin powder of the polymer particles, showed improved impact strength at room temperature and low temperature compared to Comparative Example 1. However, the fluidity of the polyamide resin composition decreased significantly, and the addition of the modifier increased the L value, resulting in inferior color development and gloss.

[0082] On the other hand, the polyamide resin compositions of Examples 1 to 6, which are polymer particles containing a specific amount of maleic anhydride as a constituent monomer, exhibited excellent impact strength at room temperature and low temperature, suppressed a decrease in the fluidity of the polyamide resin composition, and furthermore, did not generate isobutylene gas, and showed excellent appearance with L value and gloss equivalent to Reference Example 1.

[0083] As described above, the polymer particles of Examples 1 to 6, compared to the polymer particles of Comparative Examples 1 to 7, can significantly improve the impact strength at room temperature and low temperature while suppressing the decrease in fluidity during melting of the polyamide resin composition, and furthermore, they do not impair the excellent appearance of the polyamide resin composition.

Claims

1. A modifier for polyamide resins, comprising polymer particles, The polymer particles have a core-shell structure consisting of a shell layer and one or more core layers. At least one of the core layers is composed of polybutadiene or poly(butadiene-styrene), The shell layer is composed of a polymer of 50% by weight or more of a methacrylic acid ester monomer and 0 to 50% by weight of another monomer copolymerizable with the methacrylic acid ester monomer. The polymer particles contain maleic anhydride as a constituent monomer. A modifier for polyamide resins, wherein the content of maleic anhydride is 0.3 to 2.5% by weight relative to the total polymer particles.

2. The modifier for polyamide resin according to claim 1, wherein the maleic anhydride is a constituent monomer of the polymer constituting the shell layer.

3. The core layer has a refractive index of 1.50 or more, as described in claim 1 or 2, for the modifier for polyamide resin.

4. A modifier for polyamide resins according to claim 1 or 2, wherein the volume average particle diameter is 100 nm or more.

5. The modifier for polyamide resin according to claim 1 or 2, wherein the ratio of the shell layer to the total polymer particles is 1 to 50% by weight.

6. The product contains a polyamide resin and the polyamide resin modifier described in claim 1 or 2. A polyamide resin composition in which the proportion of the modifier to the total amount of the polyamide resin and the modifier is 1 to 40% by weight.

7. The polyamide resin composition according to claim 6, further comprising 0.01 to 3 parts by weight of a coloring component per 100 parts by weight of the polyamide resin composition.

8. The polyamide resin composition according to claim 6, further comprising 1 to 50 parts by weight of a reinforcing material per 100 parts by weight of the polyamide resin composition.

9. Pellets comprising the polyamide resin composition described in claim 6.

10. A molded article comprising the polyamide resin composition described in claim 6.

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