Modifier for polyamide resin and polyamide resin composition

Abstract

Provided is a modifier for a polyamide resin, which is capable of sufficiently improving impact strength at normal temperature and low temperature while suppressing a decrease in fluidity of a polyamide resin composition during melting. A modifier for a polyamide resin, the modifier comprising polymer particles having a core-shell structure comprising a shell layer and one or more core layers, at least one of the core layers comprising polybutadiene or poly (butadiene-styrene), the shell layer is composed of a polymer comprising 50 wt% or more of a methacrylic acid ester monomer and 0-50 wt% of another monomer copolymerizable with the methacrylic acid ester monomer, the polymer particles contain maleic anhydride as a constituent monomer, and the content of the maleic anhydride is 0.3-2.5 wt% with respect to the entire polymer particles.

Description

Technical Field

[0001] This invention relates to modifiers for polyamide resins and polyamide resin compositions comprising the modifiers. Background Technology

[0002] Previously, as a technique to improve the impact resistance of thermoplastic resins, a method of incorporating graft copolymers containing rubber components into thermoplastic resins was known.

[0003] However, when the thermoplastic resin is a polyamide resin, the compatibility between polyamide resin and rubber-containing graft copolymers is generally low. Therefore, the rubber-containing graft copolymers cannot be fully dispersed in the polyamide resin, and the effect of improving the impact strength of the polyamide resin by incorporating rubber-containing graft copolymers may not be sufficient. In addition, if rubber-containing graft copolymers are used to improve the impact strength of polyamide resin, there is a decrease in melt flowability, resulting in poor molding processability.

[0004] In Japanese Patent Application Publication No. 2021-130777, a modifier for polyamide resin that can suppress the decrease in color development and flowability of polyamide resin compositions and improve impact strength is disclosed. The modifier is composed of polymer particles having a core-shell structure and a specific volume average particle size. The core layer is composed of polybutadiene or poly(butadiene-styrene), and the shell layer is composed of a polymer containing a specific amount of methacrylate monomer and a specific amount of carboxyl-containing vinyl monomer as a constituent monomer. Summary of the Invention

[0005] However, there is still room for improvement in the effect of suppressing the decrease in fluidity of the polyamide resin composition during melting, and in the effect of improving the impact strength at room temperature and low temperature, especially at low temperature. The object of this invention is to provide a polyamide resin modifier that can suppress the decrease in fluidity of the polyamide resin composition during melting and can sufficiently improve the impact strength at room temperature and low temperature.

[0006] This invention relates to a modifier for polyamide resins, comprising polymer particles having a core-shell structure consisting of a shell and one or more core layers, wherein at least one of the core layers is composed of polybutadiene or poly(butadiene-styrene), and the shell layer is composed of a polymer consisting of at least 50% by weight of methacrylate monomer and 0 to 50% by weight of other monomers capable of copolymerizing with the methacrylate monomer. The polymer particles contain maleic anhydride as a constituent monomer, and the content of maleic anhydride relative to the total polymer particles is 0.3 to 2.5% by weight.

[0007] According to the present invention, a modifier for polyamide resins is provided that can suppress the decrease in fluidity of polyamide resin compositions during melting and can sufficiently improve the impact strength at room temperature and low temperature. Detailed Implementation

[0008] The following embodiments of the present invention will be described in detail.

[0009] (Modifier for polyamide resin)

[0010] The polyamide resin modifier involved in this embodiment is composed of polymer particles as a graft copolymer. 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, also called the graft layer. The core layer refers to the polymer layer located further inside the polymer particle than the shell layer, and is composed of a rubbery polymer. The core layer can be a single layer or can consist of two or more layers with different monomer compositions. The shell layer covers, but is not limited to, the entire surface of the core layer, but can cover at least a portion of the surface of the core layer.

[0011] (Nuclear layer)

[0012] The core layer of the aforementioned polymer particles is composed of a rubbery polymer. At least one of the core layers may be composed of polybutadiene or poly(butadiene-styrene). Alternatively, the entire core layer may be composed of polybutadiene or poly(butadiene-styrene).

[0013] By making at least one layer of the core layer composed of polybutadiene or poly(butadiene-styrene), preferably the entire core layer composed of polybutadiene or poly(butadiene-styrene), the refractive index of the core layer can be increased to approach that of the polyamide resin compared to the case of using, for example, acrylic rubber. This results in improved appearance of the polyamide resin composition. Furthermore, the decrease in appearance of the polyamide resin can be suppressed by incorporating polymer particles, and the impact strength of the polyamide resin composition at both room temperature and low temperature is also excellent. Here, the appearance of the polyamide resin composition refers to color development and gloss. Even when using a colorant containing dark-colored components such as carbon black, including black, and incorporating polymer particles into the polyamide resin, its color development can be maintained, the increase in lightness can be suppressed, and its gloss can be preserved.

[0014] Among these considerations, considering the good improvement in impact strength at both room temperature and low temperatures, as well as raw material costs, polybutadiene is particularly preferred. The proportion of styrene in the poly(butadiene-styrene) is not particularly limited, but is preferably 0 to 50% by weight. It should be noted that 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, above -40°C.

[0015] The aforementioned polybutadiene or poly(butadiene-styrene) may or may not contain vinyl monomers other than butadiene and styrene. Examples of such vinyl monomers include, for instance, aromatic vinyl monomers such as α-methylstyrene (excluding styrene); (meth)acrylic acid and (meth)acrylic acid alkyl esters 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.

[0016] The above-mentioned polybutadiene or poly(butadiene-styrene) can be polymerized using multifunctional monomers such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate.

[0017] Furthermore, the aforementioned polybutadiene or poly(butadiene-styrene) can be polymerized without the use of a chain transfer agent, but polymerization is preferably carried out in the presence of a chain transfer agent. By using a chain transfer agent, the polyamide resin composition according to this embodiment exhibits increased impact strength at both room temperature and low temperature, a reduced incidence of brittle fracture in impact tests at both room temperature and low temperature, and a tendency to increase the incidence of ductile fracture. There are no particular limitations on the chain transfer agents that can be used; examples include alkyl thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, tert-decyl mercaptan, n-decyl mercaptan, and n-octyl mercaptan, and alkyl ester thiols such as 2-ethylhexyl mercaptoacetate.

[0018] When using a chain transfer agent, there is no particular limitation on its amount, but it is preferably 0.01 to 3% by weight of the total amount of polybutadiene or poly(butadiene-styrene). If the amount of chain transfer agent used is within the above range, the effect of improving the impact strength of polyamide resin at room temperature and low temperature by co-regulating polymer particles can be increased. The above-mentioned amount is more preferably 0.05 to 2% by weight, and even more preferably 0.1 to 1% by weight.

[0019] The refractive index of the core layer is 1.50 or higher. By using a core layer exhibiting such a refractive index, the appearance of the polyamide resin composition can be further improved, and the decrease in the appearance of the polyamide resin caused by the coagulated 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; for example, it is preferably 1.58 or lower, and more preferably 1.57 or lower.

[0020] (shell)

[0021] The aforementioned shell layer is composed of a polymer comprising 50% or more of methacrylate monomers and 0 to 50% by weight of other monomers capable of copolymerizing with the aforementioned methacrylate monomers. Because the shell layer is composed of a polymer comprising 50% or more of methacrylate monomers, its glass transition temperature is higher, the polymer particles are less prone to coarsening, and the latex of the polymer particles exhibits better mechanical stability, making it suitable for industrial production.

[0022] The methacrylate monomers constituting the aforementioned shell layer are not particularly limited, and examples include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, benzyl methacrylate, and other alkyl methacrylates. Methyl methacrylate is preferred. Furthermore, to avoid generating isobutylene gas, which is flammable, during the melt processing of the polyamide resin composition, tert-butyl methacrylate is preferably not used.

[0023] The methacrylate monomer constitutes 50-100% by weight of the total monomer component of the polymer forming the shell layer. By ensuring that the methacrylate monomer accounts for more than half of the polymer particle shell layer, the polymer particles are less prone to coarsening during the pulverization process of obtaining polymer particle powder from latex. Therefore, the obtained polymer particles are easily and uniformly dispersed in the polyamide resin. Furthermore, the latex containing the polymer particles also exhibits good mechanical stability. The above proportion is preferably 60-99% by weight, more preferably 70-97% by weight, and even more preferably 75-95% by weight.

[0024] In addition to methacrylate monomers, the monomer components of the polymer constituting the shell of the polymer particles may also include other monomers capable of copolymerizing with methacrylate monomers. There are no particular limitations on such monomers, but alkyl acrylates are preferred, except for maleic anhydride, which will be described later. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, and benzyl acrylate. Butyl acrylate is preferred.

[0025] The proportion of the other copolymerizable monomers in the total monomer component of the polymer constituting the shell layer is 0 to 50% by weight. The preferred proportion is 1 to 40% by weight, more preferably 3 to 30% by weight, and even more preferably 5 to 25% by weight.

[0026] From the perspective of the compatibility between polymer particles and polyamide resin, and from the perspective of the effect of improving impact strength at room temperature and low temperature, the weight ratio of the shell layer in the total polymer particles is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, and even more preferably 10 to 30% by weight.

[0027] (maleic anhydride)

[0028] The aforementioned polymer particles contain maleic anhydride as a constituent monomer. The maleic anhydride is preferably a constituent monomer of the polymer constituting the shell layer. In this case, it may be contained only in the shell layer and not in the core layer, or it may be contained in both the core layer and the shell layer. Specifically, maleic anhydride only needs to be contained in the polymer particles; it may be contained only in the core layer and not in the shell layer.

[0029] The aforementioned polymer particles, by incorporating maleic anhydride as a constituent monomer, can suppress the decrease in flowability during melting of the polyamide resin composition and sufficiently improve the impact strength at both room temperature and low temperature. Furthermore, by utilizing the maleic anhydride contained in the aforementioned polymer particles, the polymer particles can be imparted with reactivity to the polyamide resin, thereby improving the dispersibility of the polymer particles in the polyamide resin. It is speculated that the maleic anhydride contained in the aforementioned polymer particles reacts with the terminal amino groups of the polyamide resin to form imides with strong intermolecular forces, which contributes to both suppressing the decrease in flowability during melting of the polyamide resin composition and sufficiently improving the impact strength at both room temperature and low temperature.

[0030] The shell layer containing the aforementioned maleic anhydride as a constituent monomer can particularly improve the reactivity of the maleic anhydride with the polyamide resin, further improve the dispersibility of polymer particles in the polyamide resin, and further improve the effect of suppressing the decrease in fluidity of the polyamide resin composition during melting and improving the impact strength at room temperature and low temperature, and is therefore preferred.

[0031] The content of maleic anhydride relative to the total polymer particles is 0.3 to 2.5% by weight. Within this range, the decrease in the fluidity of the polyamide resin composition during melting can be suppressed, and the impact strength at room temperature and low temperature can be sufficiently improved. The lower limit of the above proportion can be 0.3% by weight, 0.4% by weight, 0.5% by weight, 0.7% by weight, or 0.8% by weight. Furthermore, the upper limit of the above proportion can be 2.5% by weight, 2.2% by weight, 2.0% by weight, 1.7% by weight, or 1.5% by weight.

[0032] When the shell layer contains maleic anhydride as a constituent monomer, the content of maleic anhydride in the shell layer relative to the total constituent monomers of the polymer constituting the shell layer is preferably 1.5 to 11.5% by weight. The lower limit of the above ratio can be 1.5% by weight, 1.8% by weight, 2.2% by weight, 3.2% by weight, or 3.6% by weight. Furthermore, the upper limit of the above ratio can be 11.5% by weight, 10% by weight, 9% by weight, 8% by weight, or 7% by weight.

[0033] (Volume average particle size of polymer particles)

[0034] To achieve superior impact strength, the volume average particle size of the polymer particles is more 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. On the other hand, if the particle size of the polymer particles increases, the polymerization reaction time tends to increase, leading to a decrease in productivity. Therefore, the volume average particle size is preferably 400 nm or less, more preferably 350 nm or less, further preferably 300 nm or less, even more preferably 250 nm or less, and particularly preferably 200 nm or less. It should be noted that the volume average particle size of the polymer particles, as shown in the examples, is a value measured using a particle size measuring device in the latex state of the polymer particles. Alternatively, the volume average particle size of the polymer particles can also be calculated from a transmission electron microscope (TEM) image of the polyamide resin composition. The particle size of the polymer particles can be controlled by the type or amount of polymerization initiator, chain transfer agent, redox agent, emulsifier, etc., the polymerization temperature, and the polymerization time.

[0035] (Methods for manufacturing polymer particles)

[0036] The method for manufacturing the aforementioned polymer particles can be a conventional method and is not particularly limited. For example, any of the following methods can be used: bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, with emulsion polymerization, i.e., emulsion graft polymerization, being preferred. Specifically, in emulsion graft polymerization, firstly, a latex corresponding to the core layer polymer particles can be manufactured by emulsion polymerization, and then a monomer component for the shell layer or a polymerization initiator is added to the latex to polymerize the monomer component.

[0037] There are no particular limitations on the emulsifiers (dispersants) that can be used in emulsion polymerization; anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., can be used. Additionally, dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives can be used. There are no particular limitations on the anionic surfactants used as emulsifiers mentioned above; for example, the following compounds can be cited: potassium laurate, potassium coconut fat, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid sodium soap, semi-cured tallow fatty acid sodium soap, castor oil potassium soap, etc.; sodium lauryl sulfate, sodium higher alcohol sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, 2-ethylhexyl sulfate, etc. Alkyl sulfate salts such as sodium hexyl sulfate; sodium alkylbenzene sulfonate such as sodium dodecylbenzene sulfonate; sodium dialkyl succinate sulfonate such as sodium di(2-ethylhexyl) succinate; sodium alkyl naphthalene sulfonate; sodium alkyl diphenyl ether disulfonate; potassium alkyl phosphate; phosphate salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalene sulfonic acid formaldehyde condensate; polycarboxylic acid type polymer anions; sodium (tallow) acyl methyl taurate; sodium (coconut oil) acyl methyl taurate; sodium cocoyl hydroxyethanesulfonate; sodium α-sulfo fatty acid ester salts; sodium amide ether sulfonate; oleoyl sarcosine; sodium lauroyl sarcosine; rosin acid soap, etc.

[0038] Furthermore, the nonionic surfactant used as the emulsifier mentioned above is not particularly limited. For example, the following compounds can be cited: polyoxyethylene nonylphenyl ether, polyoxyethylene oil-based ether, polyoxyethylene lauryl ether, and other polyoxyethylene alkyl allyl ethers or polyoxyethylene alkyl ethers; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, and other polyoxyethylene sorbitan esters; polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol monooleate, and other polyoxyethylene fatty acid esters; oxyethylene / oxypropylene block copolymers, etc.

[0039] Furthermore, the cationic surfactants used as the emulsifiers mentioned above are not particularly limited. Examples include alkylamine salts such as cocoyl acetate, stearylamine acetate, octadecylamine acetate, and tetradecylamine acetate; and quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, distearate dimethylammonium chloride, alkylbenzyldimethylammonium chloride, hexadecyltrimethylammonium chloride, and benzyltrimethylammonium chloride.

[0040] Furthermore, the amphoteric surfactant used in the aforementioned emulsifiers is not particularly limited, and examples include the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethyl glycinate; amide betaine; imidazoline; and lauryl carboxymethyl hydroxyethyl imidazoline. Betaine, etc.

[0041] These emulsifiers (dispersants) can be used alone 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.

[0042] When using emulsion polymerization, well-known polymerization initiators such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate can be used as thermally decomposable initiators.

[0043] Alternatively, redox initiators can be used, which include organic peroxides such as isopropyl tert-butyl peroxide, p-menthol peroxide, cumene peroxide, dicumene peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, and tert-hexyl peroxide; inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate; reducing agents such as sodium formaldehyde sulfoxylate and glucose as needed; transition metal salts such as ferric sulfate (II) as needed; chelating agents such as disodium ethylenediaminetetraacetate as needed; and phosphorus-containing compounds such as sodium pyrophosphate as needed.

[0044] When using a redox initiator, polymerization can be achieved at low temperatures where the peroxides do not substantially decompose thermally, allowing for a wide range of polymerization temperatures to be set, which is therefore preferable. Organic peroxides such as cumene hydroperoxide, dicumene peroxide, and tert-butyl hydroperoxide are preferred as redox initiators. The amount of the initiator used, and the amount of the reducing agent / transition metal salt / chelating agent used when using a redox initiator, can be used within known ranges. Furthermore, when polymerizing monomers having two or more free radical polymerizable double bonds, known chain transfer agents can be used within known ranges. Surfactants can also be added, and these are also within known ranges.

[0045] As a solvent used in emulsion polymerization, any solvent that can stably carry out emulsion polymerization is acceptable; for example, water is preferred.

[0046] The temperature during emulsion polymerization is not particularly limited as long as the emulsifier is uniformly dissolved in the solvent. For example, it is 40 to 75°C, preferably 45 to 70°C, and more preferably 49 to 65°C.

[0047] When manufacturing the polymer particles via emulsion polymerization, for example, the polymer particles can be coagulated by mixing the latex of the polymer particles with acids such as hydrochloric acid, calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, or calcium acetate, which are divalent or higher metal salts. The polymer particles are then subjected to heat treatment, dehydration, washing, and drying according to known methods to separate them from the aqueous medium. Preferably, the obtained polymer particles are washed with water and / or an organic solvent.

[0048] Alternatively, water-soluble organic solvents such as methanol, ethanol, propanol, or acetone can be added to the latex of the polymer particles to precipitate the polymer particles. The polymer particles can then be separated from the solvent by centrifugation, filtration, etc., and dried. Other methods include adding water-soluble organic solvents such as methyl ethyl ketone to the latex of the polymer particles, extracting the polymer particles from the latex into an organic solvent layer, separating the organic solvent layer, and then mixing it with water to precipitate the polymer particles.

[0049] Alternatively, the latex of the aforementioned polymer particles can be directly powdered using spray drying. It is preferable to wash the resulting powder with water and / or an organic solvent. Alternatively, calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, etc., can be added to the resulting powder, preferably in the form of an aqueous solution, and then re-dried as needed to achieve the same effect as the washing described above.

[0050] (Amount of modifier)

[0051] The polyamide resin modifier described in this embodiment, composed of the polymer particles detailed above, is used in conjunction with the polyamide resin to suppress the decrease in fluidity during melting of the polyamide resin composition and to improve the impact strength of the polyamide resin at room temperature and low temperature. The amount of modifier relative to the polyamide resin can be appropriately set, and preferably, the ratio of modifier to the total of the polyamide resin and modifier is 1 to 40% by weight. If the ratio of modifier is within the above range, the following effects can be obtained: while maintaining the unique physical properties of the polyamide resin, the decrease in fluidity during melting of the polyamide resin composition is suppressed, and the impact strength of the polyamide resin at room temperature and low temperature is improved by the addition of the modifier. More preferably, the ratio is 3 to 30% by weight, and even more preferably, 5 to 25% by weight.

[0052] (Polyamide resin)

[0053] The polyamide resin involved in this embodiment is not limited to any polymer having an acid amide bond (-CONH-). Examples include polymers obtained by condensation polymerization of diamine and diacid, polymers obtained by condensation polymerization of diamine derivatives such as diformyl and diacid, polymers obtained by condensation polymerization of diacid derivatives such as dimethyl ester and diamine, polymers obtained by reaction of dionitrile or diamide with formaldehyde, polymers obtained by addition polymerization of diisocyanate and diacid, polymers obtained by self-condensation of amino acids or their derivatives, and polymers obtained by ring-opening polymerization of lactams. Furthermore, the polyamide resin may contain polyether blocks. One type of polyamide resin may be used alone, or two or more types may be used in combination.

[0054] Specific examples of polyamide resins include aliphatic polyamides such as nylon 4, nylon 6, nylon 66, nylon 7, nylon 9, nylon 11, nylon 12, nylon 46, nylon 56, nylon 410, nylon 412, nylon 610, and nylon 612; semi-aromatic polyamides such as nylon 6T, nylon 6I, nylon 9T, nylon 10T, nylon M5T, and nylon MXD6; and copolymer polyamides such as 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, and nylon 66 / 6T / 6I. From a general applicability perspective, nylon 6, nylon 66, nylon 11, and nylon 12 are preferred.

[0055] (Other resins)

[0056] The polyamide resin composition according to this embodiment may or may not contain a thermoplastic resin other than polyamide resin. When it contains a thermoplastic resin other than polyamide resin, there is no particular limitation on the thermoplastic resin, and 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 polyolefins, etc. The amount of other thermoplastic resins is not particularly limited, for example, it is 0 to 100 parts by weight relative to 100 parts by weight of polyamide resin, 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.

[0057] (Other additives)

[0058] To the extent that it does not impair the effects of the present invention, the polyamide resin composition according to this embodiment may suitably contain additives that are typically incorporated into thermoplastic resin compositions. Such additives are not particularly limited, and examples include colorants, flame retardants, flame retardant aids, anti-dripping agents, reinforcing materials, fillers, antioxidants, conductivity imparting agents, hydrolysis inhibitors, thickeners, plasticizers, lubricants, antioxidants, ultraviolet absorbers, antistatic agents, flow improvers, release agents, compatibilizers, heat stabilizers, etc.

[0059] Examples of colorants include masterbatches, coloring particles, coloring compounds, color powders, color pastes, and liquid masterbatches. Additionally, examples of coloring components included in colorants include pigments such as carbon black.

[0060] The amount of coloring component can be appropriately set. From the viewpoint of good color development and effective usage, it is preferably 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, relative to 100 parts by weight of the polyamide resin composition.

[0061] From the viewpoint of improving impact strength at both 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 fiber, carbon fiber, boron fiber, asbestos fiber, polyvinyl alcohol fiber, polyester fiber, polyacrylonitrile fiber, fully aromatic polyamide fiber, and polybenzoyl peroxide. Reinforcing materials include azole fiber, polytetrafluoroethylene fiber, kenaf fiber, bamboo fiber, hemp fiber, bagasse fiber, high-strength polyethylene fiber, alumina fiber, silicon carbide fiber, potassium titanate fiber, brass fiber, stainless steel fiber, steel fiber, ceramic fiber, and basalt fiber. Among these, glass fiber, carbon fiber, and metal fiber are preferred for their ability to improve impact strength, with glass fiber being the most preferred. Reinforcing materials can be used alone or in combination of two or more types.

[0062] The amount of reinforcing material can be appropriately set. From the viewpoint of improving impact strength with an effective amount, it is preferably 1 to 50 parts by weight, more preferably 10 to 40 parts by weight, and even more preferably 25 to 35 parts by weight, relative to 100 parts by weight of the polyamide resin composition.

[0063] (Method for manufacturing the composition)

[0064] The method for manufacturing the polyamide resin composition described in this embodiment is not particularly limited, and general methods for manufacturing thermoplastic resin compositions can be used. For example, the polyamide resin composition can be obtained by mixing the raw materials using a Henschel mixer, a drum mixer, or similar equipment and then performing melt mixing. This melt mixing can be performed using a single-screw or twin-screw extruder, a Banbury mixer, a pressure kneader, a mixing roller, or other similar mixer. Particles composed of the polyamide resin composition can be manufactured through such melt mixing.

[0065] The polyamide resin composition described in this embodiment can be molded into a predetermined shape to form a molded article. There are no particular limitations on the molding method; for example, injection molding, extrusion molding, blow molding, calendering, blow molding, rotational molding, compression molding, etc., can be used.

[0066] (use)

[0067] As for the applications of the polyamide resin composition and its molded articles involved in this embodiment, due to their advantages such as oil resistance, non-conductivity, and excellent color development even without coating, examples include automotive applications such as cylinder head covers, engine covers, intake manifolds, radiator tanks, oil pans, accelerator pedals, charcoal canisters, fuel lines, air brake lines, exhaust pipes, hydrogen injectors, pipes, industrial fasteners, and car door rearview mirror brackets; and electrical / electronic applications such as coil frames, connectors, gears, sockets, switches, electric blanket sheathing wires, fiber optic cable sheathing materials, power tools, cable ties, and chargers. Applications: Mechanical applications such as hydraulic / pneumatic connectors / pipes, bearings, covers / housings, pressure-resistant hoses, and cable ties; building material applications such as curtain track components, aluminum window frame corners, door rollers, handrails, curtain rollers, and door handles; sports and leisure applications such as sports shoe soles, ski / ski equipment, reels, and snorkeling tubes; packaging materials / containers such as shrink wrap films, food packaging films, alcoholic beverage bottles, and pesticide bottles; daily necessities applications such as toothbrushes, chair legs or armrests, combs, and cutlery; medical applications such as medical catheters, medical kits, and sutures, etc., with no particular limitations.

[0068] Preferred embodiments of this disclosure are set forth in the following items, but the invention is not limited to these items.

[0069] [Project 1]

[0070] A modifier for polyamide resins, composed of polymer particles.

[0071] The aforementioned polymer particles have a core-shell structure consisting of a shell and one or more core layers.

[0072] At least one of the aforementioned core layers is composed of polybutadiene or poly(butadiene-styrene).

[0073] The aforementioned shell layer is composed of a polymer consisting of 50% by weight or more of methacrylate monomers and 0 to 50% by weight of other monomers capable of copolymerizing with the aforementioned methacrylate monomers.

[0074] The aforementioned polymer particles contain maleic anhydride as a constituent monomer.

[0075] The content of maleic anhydride is 0.3 to 2.5% by weight relative to the total polymer particles.

[0076] [Project 2]

[0077] According to the polyamide resin modifier of Project 1, the maleic anhydride is a constituent monomer of the polymer constituting the shell layer.

[0078] [Project 3]

[0079] According to the modifier for polyamide resin described in Project 1 or 2, the refractive index of the core layer is shown to be 1.50 or higher.

[0080] [Project 4]

[0081] The polyamide resin modifier according to any one of items 1 to 3, wherein the volume average particle size is 100 nm or more.

[0082] [Project 5]

[0083] The modifier for polyamide resin according to any one of items 1 to 4, wherein the proportion of the shell layer to the total polymer particles is 1 to 50 by weight.

[0084] [Project 6]

[0085] A polyamide resin composition comprising a polyamide resin and a polyamide resin modifier as described in any one of items 1 to 5.

[0086] The proportion of the modifier relative to the total of the polyamide resin and the modifier is 1 to 40 by weight.

[0087] [Project 7]

[0088] The polyamide resin composition according to Project 6 further comprises 0.1 to 3 parts by weight of a coloring component relative to 100 parts by weight of the above-mentioned polyamide resin composition.

[0089] [Project 8]

[0090] The polyamide resin composition according to item 6 or 7 further comprises 1 to 50 parts by weight of reinforcing material relative to 100 parts by weight of the above-mentioned polyamide resin composition.

[0091] [Project 9]

[0092] A type of particle, comprising the polyamide resin composition described in any one of items 6 to 8.

[0093] [Project 10]

[0094] A molded body comprising the polyamide resin composition described in any one of items 6 to 8.

[0095] Example

[0096] The following examples illustrate the invention in a more detailed manner, but the invention is not limited to these examples.

[0097] (Refractive index of the core layer)

[0098] The refractive index of the core layer was measured using an Abbe refractometer 2T manufactured by ATAGO, based on the JIS K7142 standard.

[0099] (Average particle size of polymer particles)

[0100] The volume average particle size was measured in the latex state of the polymer particles as the average particle size. The measuring apparatus used was a Nanotrac Wave manufactured by Nikkiso Corporation.

[0101] (Aggregation Conversion Rate)

[0102] A portion of the polymer particle latex collected / weighed was dried in a hot air dryer at 120°C for 1 hour, and its weight after drying was accurately measured as the solids content. Next, the ratio of the weighed results before and after drying was calculated as the solids ratio in the latex. Finally, the polymerization conversion rate was calculated using this solids ratio according to the following formula.

[0103] Formula: Polymerization conversion rate = (Total weight of raw materials input × Solid content ratio - Total weight of raw materials other than monomers) / Weight of input monomers × 100 (%)

[0104] <Methods for Manufacturing Core Layers>

[0105] In a pressure polymerizer, 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 thorough degassing to remove oxygen under stirring, 100 parts by weight of butadiene (hereinafter referred to as BD) were added to the system, and the temperature was raised to 45°C. Polymerization was initiated by adding 0.05 parts by weight of sodium formaldehyde sulfoxylate and 0.03 parts by weight of p-menthol peroxide. At the 6th, 10th, 14th, and 17th hours after the start of polymerization, 0.014 parts by weight of p-menthol peroxide were added respectively. At the 20th hour after the start of polymerization, residual monomers were removed by devolatilization under reduced pressure to terminate the polymerization, yielding a polybutadiene rubber latex (core layer) with polybutadiene rubber as the main component. It should be noted that the volume average particle size of the polybutadiene rubber particles in the obtained latex was appropriately adjusted by changing the initial addition amount of sodium dodecylbenzenesulfonate.

[0106] As a representative manufacturing method for polymer particle latex, the manufacturing steps of the polymer particle latex in Example 1 are shown below. The polymer particle latexes in examples other than Example 1 and comparative examples are manufactured by changing the monomer composition of the shell layer according to the table description, but the manufacturing steps are as described below in connection with Example 1.

[0107] <Method for manufacturing the shell in Example 1>

[0108] In a glass reactor equipped with a thermometer, stirrer, reflux cooler, nitrogen inlet, monomer and emulsifier addition device, 30 parts by weight of deionized water and the aforementioned polybutadiene rubber latex (core layer) were added to bring the solid content to 78 parts by weight. The mixture was heated to 60°C under a nitrogen flow while stirring. 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 added. Over a period of 68 minutes, a mixture of 19.4 parts by weight of methyl methacrylate (MMA), 2.2 parts by weight of n-butyl acrylate (BA), 0.5 parts by weight of maleic anhydride (MAH), and 0.024 parts by weight of tert-butyl hydroperoxide was added. Five minutes after the addition was complete, sodium formaldehyde sulfoxylate and tert-butyl hydroperoxide were added as appropriate, thereby obtaining polymer particle latex (shell layer) with a polymerization conversion of 100%.

[0109] (Obtaining the white resin powder from the polymer particles in each embodiment and comparative example)

[0110] While stirring 760 parts by weight of deionized water and 3.3 parts by weight of a 25% by weight calcium chloride aqueous solution, the temperature was raised to 60°C. Then, 2.5 parts by weight of each polymer particle latex containing IRGANOX-1076 [3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate n-octadecyl ester] as a hindered phenolic antioxidant was added to obtain a slurry containing coagulated latex particles. Subsequently, the slurry was heated to 90°C to dehydrate and dry, thereby obtaining a white resin powder containing polymer particles.

[0111] (Preparation of polyamide resin composition)

[0112] According to the following description, particles and test pieces composed of a white resin powder containing polyamide resin and polymer particles were prepared, and the Izod impact strength, MFR, isobutylene gas generation, L value and gloss as appearance characteristics were measured. These results are shown in the respective tables. In Reference Example 1, white resin powder containing polymer particles was not used, while in Comparative Example 7, a commercially available modifier was used instead of the aforementioned white resin powder containing polymer particles.

[0113] (Preparation conditions for granules and test pieces)

[0114] - Various embodiments and comparative examples

[0115] (a) 79.5 parts by weight of Nylon 6: Polyamide 6 resin (UBE1030B manufactured by UBE Corporation).

[0116] (b) 20 parts by weight of polymer particles or commercially available modifier

[0117] (c) 0.5 parts by weight of carbon black

[0118] -Reference Example

[0119] (a) 99.5 parts by weight of Nylon 6: Polyamide 6 resin (UBE1030B manufactured by UBE Corporation).

[0120] (c) 0.5 parts by weight of carbon black

[0121] Using a twin-screw extruder (TEX44SS manufactured by Nippon Steel Corporation) heated to a barrel temperature of 210–270°C, the mixture of (a), (b) and (c) or (a) and (c) was kneaded and extruded at a screw speed of 200 rpm to obtain granules.

[0122] The granules were dried at 120°C for 12 hours using a vacuum dryer to fully reduce the moisture content. Test pieces were then made using an injection molding machine (FANUC FAS100B) at a molding temperature of 270°C and a mold temperature of 80°C.

[0123] (Izod impact strength)

[0124] For the 4.0 mm thick test piece 1 with a V-notch prepared by the above method, the Izod impact strength at -30°C and 23°C was determined under absolutely dry conditions using a method based on ASTM D256.

[0125] (MFR)

[0126] The particles prepared under the above conditions were dried at 120°C for 12 hours using a vacuum dryer, and the MFR value was determined based on JISK7210 A method at a measurement temperature of 270°C and a load of 5 kg.

[0127] (Is isobutylene gas produced?)

[0128] The gas collected from the exhaust port during the mixing of polyamide resin and polymer particles under the above conditions was analyzed using GCMS (Trace1300-ISQ-QD manufactured by Thermo Fisher Scientific) to confirm the presence of isobutylene gas.

[0129] (L value)

[0130] Under the same conditions as those used in preparing the Izod impact strength test piece, a 2mm thick color swatch was obtained. The reflectance (L-value) of the obtained color swatch was measured using a colorimeter (model: ZE 6000) manufactured by Nippon Denshoku Kogyo Co., Ltd., based on the JIS Z8741 standard. It should be noted that a lower L-value indicates a deeper black, representing better color rendering.

[0131] (luster)

[0132] Under the same conditions as those used in the preparation of the Izod impact strength test piece, a color plate with a thickness of 2 mm was obtained. Based on the JIS K8722 standard, the 60-degree specular gloss of the obtained color plate was measured using a colorimeter (model: VG 7000) manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0133]

[0134] The abbreviations of the shell monomer components other than MMA, BA, and MAH in Table 1 and the details of the modifiers used in Comparative Example 7 are as follows.

[0135] t-BMA: tert-butyl methacrylate

[0136] MAA: Methacrylic acid

[0137] HEMA: 2-Hydroxyethyl methacrylate

[0138] MH7020: TAFMER MH7020 (α-olefin copolymer) manufactured by Mitsui Chemicals Co., Ltd.

[0139] Compared to Reference Example 1 which does not contain polymer particles, the polyamide resin composition of Comparative Example 1, which incorporates polymer particles that do not contain maleic anhydride, can suppress the decrease in the fluidity of the polyamide resin composition during melting, but has almost no effect on improving the impact strength at room temperature and low temperature.

[0140] Compared to Comparative Example 1, the polyamide resin compositions of Comparative Examples 2 and 3, which contained polymer particles free of maleic anhydride and respectively containing t-BMA and MAA as constituent monomers, showed improved impact strength at both room temperature and low temperature, but could not suppress the decrease in fluidity of the polyamide resin composition during melting. In Comparative Example 2, flammable isobutylene gas was further generated during the mixing of the polyamide resin and polymer particles.

[0141] Compared with Comparative Example 1, the polyamide resin composition of Comparative Example 4, which contains polymer particles that do not contain maleic anhydride but contain HEMA as a constituent monomer, has the effect of improving the impact strength at room temperature, but has almost no effect of improving the impact strength at low temperature, and cannot sufficiently suppress the decrease in the flowability of the polyamide resin composition.

[0142] The polyamide resin composition of Comparative Example 5, which incorporates polymer particles containing a small amount of maleic anhydride as a constituent monomer, can suppress the decrease in the flowability of the polyamide resin composition and improve the impact strength at room temperature and low temperature compared to Comparative Example 1, but the improvement effect is not sufficient.

[0143] Compared with Comparative Example 1, the polyamide resin composition of Comparative Example 6, which incorporates polymer particles containing a large amount of maleic anhydride as a constituent monomer, exhibits improved impact strength at room temperature and low temperature. However, the improvement in impact strength is insufficient, and it cannot adequately suppress the decrease in the flowability of the polyamide resin composition.

[0144] Compared with Comparative Example 1, the polyamide resin composition of Comparative Example 7, which uses a commercially available modifier instead of the above-mentioned polymer particles in the white resin powder, has the effect of improving the impact strength at room temperature and low temperature. However, the flowability of the polyamide resin composition is greatly reduced, and the L value is higher, resulting in poor color development and gloss due to the addition of the modifier.

[0145] On the other hand, the polymer particles containing a specific amount of maleic anhydride as a constituent monomer, namely the polyamide resin compositions of Examples 1 to 6, have excellent impact strength at room temperature and low temperature, can suppress the decrease in the flowability of the polyamide resin composition, and do not produce isobutylene gas. The L value and gloss are the same as those of Reference Example 1, showing excellent appearance.

[0146] As described above, it can be seen that, compared with the polymer particles of Comparative Examples 1 to 7, the polymer particles of Examples 1 to 6 can suppress the decrease in fluidity of the polyamide resin composition during melting, significantly improve the impact strength at room temperature and low temperature, and 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 and one or more core layers. In the core layer, at least one layer is composed of polybutadiene or poly(butadiene-styrene). The shell layer is composed of a polymer consisting of more than 50% by weight of methacrylate monomer and 0 to 50% by weight of other monomers capable of copolymerizing with the methacrylate monomer. The polymer particles contain maleic anhydride as a constituent monomer. The content of maleic anhydride relative to the total polymer particles is 0.3 to 2.5% by weight.

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

3. The modifier for polyamide resin according to claim 1 or 2, wherein, The refractive index of the core layer is greater than 1.

50.

4. The modifier for polyamide resin according to claim 1 or 2, wherein, The volume average particle size is above 100 nm.

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

6. A polyamide resin composition comprising a polyamide resin and a modifier for the polyamide resin according to claim 1 or 2. The proportion of the modifier relative to the total of the polyamide resin and the modifier is 1 to 40% by weight.

7. The polyamide resin composition according to claim 6, wherein, The polyamide resin composition further comprises 0.1 to 3 parts by weight of coloring component relative to 100 parts by weight.

8. The polyamide resin composition according to claim 6, wherein, The polyamide resin composition further comprises 1 to 50 parts by weight of reinforcing material relative to 100 parts by weight.

9. A particle comprising the polyamide resin composition of claim 6.

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

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