JP7769641B2 - Additive for polyamide resin and polyamide resin composition - Google Patents

Description

The present invention relates to an additive for polyamide resins and a polyamide resin composition containing the additive.

Polyamide resins such as nylon-6, nylon-6,6, and nylon-12 have excellent physical properties such as heat resistance and abrasion resistance, and also have excellent resistance to hydrocarbon solvents such as gasoline and oil, so they are used in a variety of molding applications, including mechanical parts, automotive parts, and electrical and electronic parts.

However, polyamide resins have the property that their melt viscosity and melt tension drop significantly at temperatures above their melting point. This can make molding difficult when applied to melt processing methods carried out at temperatures above their melting point, such as blow molding, extrusion molding, and foam molding. Specifically, blow molding and extrusion molding can cause the molded product to have uneven wall thickness due to drawdown, while foam molding can cause the cells to become uneven.

Patent Document 1 describes adding a thickener (B) to a polyamide resin to increase the melt viscosity of the polyamide resin. The thickener (B) comprises 100 parts by weight of reactive polymer particles (B-1) having a glass transition temperature of 60°C or higher and a volume average particle diameter in the range of 50 to 500 μm, coated with 0.5 to 30 parts by weight of polymer particles (B-2) having a volume average particle diameter of 0.01 to 0.5 μm. In the examples, a monomer (glycidyl methacrylate) having an epoxy group is used to produce the polymer particles (B-1), and therefore the polymer particles (B-1) contain epoxy groups. The patent also discloses that the weight average molecular weight of the polymer particles is 52,000 to 67,000.

Patent Document 2 does not disclose melt viscosity, but describes the use of a core-shell polymer in combination with 80 to 99 parts by weight and a copolymer of alkyl (meth)acrylate and unsaturated carboxylic acid as an impact modifier for polyamide resin. There is no disclosure of the molecular weight of the copolymer.

Japanese Patent Application Laid-Open No. 2007-31607 Japanese Unexamined Patent Publication No. 63-61013

As described above, polyamide resins are required to have improved moldability during melt processing, and at the same time, they are also required to have improved tensile properties of the resulting molded articles.
However, the techniques described in Patent Documents 1 and 2 are insufficient to improve moldability during melt processing and further to improve the tensile properties of molded articles.

In view of the above-mentioned current situation, the present invention aims to provide an additive for polyamide resins that can improve the moldability of polyamide resins during melt processing and improve the tensile properties of molded articles containing polyamide resins, and a polyamide resin composition containing the additive.

The inventors discovered that by blending a copolymer containing specific constituent monomers and having an average molecular weight within a specific range into a polyamide resin, the moldability of the polyamide resin during melt processing is improved, and further, the tensile properties of the resulting molded body are improved, leading to the present invention.

That is, the present invention is an additive for polyamide resins, comprising a first polymer, the first polymer comprising, as constituent monomers, (i) a carboxyl group-containing vinyl monomer, and
(ii) a (meth)acrylic acid ester monomer and/or an aromatic vinyl monomer;
wherein the first polymer has a weight average molecular weight of 2,000 to 25,000.
Preferably, the carboxyl group-containing vinyl monomer accounts for 15% by weight or more and 50% by weight or less of 100% by weight of the first polymer.
Preferably, the first polymer is a copolymer containing, as constituent monomers, (i) a carboxyl group-containing vinyl monomer and (ii) a (meth)acrylic acid ester monomer.
Preferably, the composition further comprises a second polymer having a weight average molecular weight of 100,000 or more.
Preferably, the first polymer forms particles, and at least a portion of the second copolymer is located outside the particles.
Preferably, the second polymer is a polymer containing, as a constituent monomer, a methacrylic acid ester monomer and/or an aromatic vinyl monomer.
Preferably, the total of the methacrylic acid ester monomer and the aromatic vinyl monomer accounts for 80% by weight or more and 100% by weight or less of 100% by weight of the second polymer.
Preferably, the first polymer and/or the second polymer are non-rubbery polymers.
Preferably, the first polymer and the second polymer are each a non-rubber polymer, the first polymer forms particles, and at least a portion of the second polymer is located outside the particles.
The present invention also relates to a modifier for polyamide resins, comprising the additive and an impact modifier. Preferably, the impact modifier is a core-shell type impact modifier. Preferably, the impact modifier is a polyolefin elastomer.
The present invention further relates to a polyamide resin composition containing a polyamide resin and the additive for polyamide resin, wherein the proportion of the additive is 0.1 to 10% by weight based on 100% by weight of the total of the polyamide resin and the additive; and also relates to a polyamide resin composition containing a polyamide resin and the modifier for polyamide resin, wherein the proportion of the modifier is 1 to 40% by weight based on 100% by weight of the total of the polyamide resin and the modifier.
Preferably, the polyamide resin composition further contains a reinforcing material, and the proportion of the reinforcing material is 10 to 60% by weight relative to 100% by weight of the total of the polyamide resin and the reinforcing material.
Furthermore, the present invention also relates to pellets or molded articles made from the polyamide resin composition.

The present invention provides an additive for polyamide resins, which can improve the moldability of polyamide resins during melt processing and the tensile properties of molded articles containing polyamide resins, and a polyamide resin composition containing the additive. The additive for polyamide resins according to a preferred embodiment of the present invention can reduce the fluidity of polyamide resins when melted, and can also increase the melt viscosity or melt tension of polyamide resins. Furthermore, the additive for polyamide resins can be blended with an impact modifier into polyamide resins, thereby further enhancing the impact-improving effect of the impact modifier in addition to the aforementioned effects.

Embodiments of the present invention are described in detail below.

(Additives for polyamide resins)
The polyamide resin additive of this embodiment contains at least a first polymer. A preferred embodiment of the polyamide resin additive preferably contains a second polymer in addition to the first polymer, since this additive has excellent granulation properties during additive production. The polyamide resin additive is used by blending it with a polyamide resin, and may be a molecular chain extender for the polyamide resin, an agent for improving the moldability of the polyamide resin during melt processing, or an agent for improving the tensile properties of a polyamide resin-containing molded article.

(first polymer)
The first polymer is a copolymer containing, as constituent monomers, a carboxyl group-containing vinyl monomer, and a (meth)acrylic acid ester monomer and/or an aromatic vinyl monomer.

The first polymer has carboxyl groups derived from the carboxyl group-containing vinyl monomer. When the polyamide resin and the first polymer are mixed by melt kneading or the like, the carboxyl groups of the first polymer can react with the terminal amino groups of the polyamide resin. This reaction elongates the molecular chain of the polyamide resin and can also introduce a branched structure into the polyamide resin. It is believed that this mechanism improves the moldability of the polyamide resin during melt processing and further improves the tensile properties of the resulting molded article. On the other hand, as shown in the comparative example below, when a polymer having epoxy groups rather than carboxyl groups was blended with the polyamide resin, the effect of improving the moldability of the polyamide resin during melt processing was insufficient.

The carboxyl group-containing vinyl monomer is not particularly limited, but examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. One of these may be used alone, or two or more may be used in combination. Of these, acrylic acid and/or methacrylic acid is preferred, with methacrylic acid being more preferred.

The content of the carboxyl group-containing vinyl monomer can be appropriately set based on factors such as the moldability improvement effect during melt processing, the tensile properties of the molded product, and productivity. The content may be, for example, 10% by weight or more, based on 100% by weight of the first polymer. It is preferably 15% by weight or more, and more preferably 20% by weight or more. This range provides a particularly excellent effect in improving moldability during melt processing. However, if the content of the carboxyl group-containing vinyl monomer is too high, the water content of the first polymer increases, complicating post-processing during production. Therefore, the content is preferably 50% by weight or less, and more preferably 45% by weight or less.

From the viewpoint of productivity, the first polymer contains, as constituent monomers, a carboxyl group-containing vinyl monomer as well as one or both of a (meth)acrylic acid ester monomer and an aromatic vinyl monomer. It is preferable that the first polymer contain a (meth)acrylic acid ester monomer, as this is effective in improving the moldability of the polyamide resin during melt processing and in improving the tensile properties of the molded article.

The (meth)acrylic acid ester monomer is not particularly limited, but examples include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; and (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate. Of these, (meth)acrylic acid alkyl ester monomers are preferred, (meth)acrylic acid alkyl ester monomers in which the alkyl group has 1 to 4 carbon atoms are more preferred, and methyl methacrylate is particularly preferred.

The aromatic vinyl monomer is not particularly limited, but examples include styrene, α-methylstyrene, p-methylstyrene, etc. Among these, styrene is preferred.

A higher molecular weight of the first polymer is preferable from the standpoint of improving moldability during melt processing and the tensile properties of the molded article. Specifically, the weight-average molecular weight of the first polymer is preferably in the range of 2,000 to 25,000, as measured by gel permeation chromatography (GPC) in terms of polystyrene. If the weight-average molecular weight is less than 2,000, the thermal stability of the polymer may be insufficient. If the weight-average molecular weight exceeds 25,000, the stability of the latex during polymer production may decrease, making efficient production difficult. Polymers with a weight-average molecular weight of 25,000 or less can be suitably produced using a chain transfer agent during polymerization.

The first polymer is preferably a non-rubber polymer. A non-rubber polymer is a polymer that does not have a crosslinked structure between its molecular chains. When the first polymer is a non-rubber polymer, the reaction between the carboxyl groups of the first polymer and the terminal amino groups of the polyamide resin proceeds more efficiently, making it easier to achieve improved moldability during melt processing and improved tensile properties of the molded body.

(Second double combination)
The second polymer is an optional component capable of improving granulation properties during production. Because the first polymer has a small molecular weight, powdering it alone can result in a fine powder that is difficult to handle. Therefore, in order to obtain the first polymer as a powder of an appropriate particle size that is easy to handle, it is desirable to produce the first polymer together with a second polymer having a large molecular weight and isolate the first polymer together with the second polymer. Furthermore, the presence of the second polymer improves the dispersibility of the first polymer in the polyamide resin, allowing the reaction between the polyamide resin and the first polymer to proceed efficiently, thereby further improving the moldability of the polyamide resin during melt processing.

From the viewpoint of improving granulation properties, the weight average molecular weight of the second polymer is 100,000 or more, as measured by GPC in terms of polystyrene. Preferably, it is 150,000 or more, and more preferably 180,000 or more. There is no particular upper limit, but it is preferably 1,000,000 or less, more preferably 700,000 or less, and even more preferably 500,000 or less.

The monomers constituting the second polymer are not particularly limited, but preferably contain a methacrylic acid ester monomer and/or an aromatic vinyl monomer. From the viewpoints of improving moldability during melt processing and improving the tensile properties of molded articles, it is more preferable to contain an aromatic vinyl monomer. Furthermore, from the viewpoints of polymerization conversion rate and granulation ability, it is more preferable to contain a methacrylic acid ester monomer.

The methacrylic acid ester monomer is not particularly limited, but examples include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate; and hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate. Among these, alkyl methacrylate monomers are preferred, with alkyl methacrylate monomers in which the alkyl group has 1 to 4 carbon atoms being more preferred, and methyl methacrylate being particularly preferred.

The aromatic vinyl monomer is not particularly limited, but examples include styrene, α-methylstyrene, p-methylstyrene, etc. Among these, styrene is preferred.

The total content of the methacrylic acid ester monomer and aromatic vinyl monomer is preferably 80% by weight or more and 100% by weight or less, more preferably 82% by weight or more and 99% by weight or less, and even more preferably 84% by weight or more and 98% by weight or less, of 100% by weight of the second polymer.

From the viewpoint of improving granulation properties, it is preferable that the second polymer contains an acrylic acid ester monomer in addition to a methacrylic acid ester monomer and/or an aromatic vinyl monomer.

The acrylic acid ester monomer is not particularly limited, but examples include alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; and hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate. Among these, alkyl acrylate monomers are preferred, with alkyl acrylate monomers in which the alkyl group has 1 to 4 carbon atoms being more preferred, and butyl acrylate being particularly preferred.

From the viewpoint of improving granulation properties, the content of the acrylic acid ester monomer is preferably 0% by weight or more and 20% by weight or less, more preferably 1% by weight or more and 18% by weight or less, and even more preferably 2% by weight or more and 16% by weight or less, of 100% by weight of the second polymer.

The second polymer is preferably a non-rubber polymer. When the second polymer is a non-rubber polymer, the reaction between the carboxyl groups of the first polymer and the terminal amino groups of the polyamide resin proceeds more efficiently, making it easier to achieve improved moldability during melt processing and improved tensile properties of the molded body.

A preferred embodiment of the additive for polyamide resins may contain the first polymer and the second polymer, and the relationship between the two polymers is not particularly limited. However, from the viewpoint of improving granulation properties, it is preferred that the first polymer constitutes particles and at least a portion of the second polymer is located on the outside of the particles. At least a portion of the second polymer may coat the outer surface of the particles. Alternatively, a portion of the second polymer may be located on the outside of the particles, and the remainder may be impregnated into the interior of the particles.
Furthermore, it is preferable that the first polymer and the second polymer are not chemically bonded to each other. In this case, it is considered that by kneading the additive with the polyamide resin, the first polymer and the second polymer exist separately from each other in the polyamide resin matrix.

The polyamide resin additive of this embodiment is blended with polyamide resin and used to improve the moldability of polyamide resin during melt processing and the tensile properties of polyamide resin-containing molded articles. The amount of the additive blended with the polyamide resin can be set as appropriate, but it is preferable that the ratio of the additive to the total of the polyamide resin and the additive be 0.1% by weight or more and 10% by weight or less. A ratio within this range of additive can favorably improve the moldability during melt processing and the tensile properties of molded articles while maintaining the unique physical properties of polyamide resin. The ratio is more preferably 0.2 to 8% by weight, and even more preferably 0.3 to 5% by weight. Furthermore, due to the significant effect of improving the tensile properties of molded articles, it is particularly preferable that the ratio be 1.5% by weight or more.

(Method for producing additives for polyamide resin)
The method for producing the additive for polyamide resins can be a conventional polymerization method and is not particularly limited. For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used, with emulsion polymerization being preferred. When producing the first polymer, it is preferable to carry out polymerization in the presence of a chain transfer agent to control the molecular weight. Furthermore, when producing the first polymer and the second polymer continuously, first, a latex of the first polymer is produced by emulsion polymerization, and then the monomer components for the second polymer, a polymerization initiator, etc. are added to the latex to polymerize the monomer components.

Chain transfer agents that can be used in the production of the first polymer are not particularly limited, but include primary mercaptan chain transfer agents such as n-butyl mercaptan, n-octyl mercaptan, n-hexadecyl mercaptan, n-dodecyl mercaptan, and n-tetradecyl mercaptan; secondary mercaptan chain transfer agents such as sec-butyl mercaptan and sec-dodecyl mercaptan; tertiary mercaptan chain transfer agents such as t-dodecyl mercaptan; and mercaptan compounds, 2-ethyl mercaptan ... Examples of suitable chain transfer agents include thioglycolic acid esters such as hexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris(thioglycolate), and pentaerythritol tetrakis(thioglycolate), thiophenol, tetraethylthiuram disulfide, pentanephenylethane, acrolein, methacrolein, allyl alcohol, carbon tetrachloride, ethylene bromide, styrene oligomers such as α-methylstyrene dimer, and terpinolene. These may be used alone or in combination of two or more. The amount of chain transfer agent used may be appropriately determined depending on the desired weight average molecular weight of the first polymer.

The emulsifier (dispersant) that can be used in emulsion polymerization is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used.
Among the above-mentioned emulsifiers, the anionic surfactant is not particularly limited, and examples thereof include the following compounds: fatty acid soaps such as 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 soda soap, semi-hardened beef tallow fatty acid soda soap, and castor oil potassium soap; alkoxylated surfactants such as sodium dodecyl sulfate, higher alcohol sodium sulfate, triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and sodium 2-ethylhexyl sulfate; alkyl sulfate salts; sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; sodium dialkylsulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalenesulfonates; sodium alkyldiphenyletherdisulfonates; potassium alkylphosphate salts; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalenesulfonate formalin condensates; polycarboxylic acid type polymeric anions; sodium acyl (beef tallow) methyl taurate; sodium acyl (coconut) methyl taurate; sodium cocoyl isethionate; sodium α-sulfofatty acid ester salts; sodium amidoethersulfonate; oleyl sarcosine; sodium lauroyl sarcosine; rosin acid soap, etc.

Furthermore, among the above-mentioned emulsifiers, nonionic surfactants 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 copolymers, etc.

Furthermore, among the above emulsifiers, cationic surfactants are not particularly limited, but examples include the following compounds: alkylamine salts such as coconut amine acetate, stearyl amine acetate, octadecyl amine acetate, and tetradecyl amine acetate; quaternary ammonium salts such as lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, alkyl benzyl dimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, and behenyl trimethyl ammonium chloride.

Furthermore, among the above emulsifiers, amphoteric surfactants are not particularly limited, but examples include the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethyl glycine; amido betaine; imidazoline; lauryl carboxymethyl hydroxyethyl imidazolinium betaine, etc.

These emulsifiers (dispersants) may be used alone or in combination of two or more.

When emulsion polymerization is used, known polymerization initiators, such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate, can be used as thermal decomposition initiators.

Redox initiators can also be used that combine peroxides such as organic peroxides such as t-butylperoxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide; or inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate, with, if necessary, a reducing agent such as sodium formaldehyde sulfoxylate or glucose, and, if necessary, a transition metal salt such as iron (II) sulfate, and, if necessary, a chelating agent such as disodium ethylenediaminetetraacetate, and, if necessary, a phosphorus-containing compound such as sodium pyrophosphate.

When a redox initiator is used, polymerization can be carried out at low temperatures where the peroxide does not substantially decompose thermally, making it preferable because the polymerization temperature can be set over a wide range. Among these, organic peroxides such as cumene hydroperoxide, dicumyl peroxide, and t-butyl hydroperoxide are preferably used as redox initiators. The amount of the initiator used, and when a redox initiator is used, the amount of the reducing agent, transition metal salt, chelating agent, etc. used, can be within known ranges. Furthermore, when polymerizing a monomer having two or more radically polymerizable double bonds, known chain transfer agents can be used within known ranges. Surfactants can also be used, but these amounts are also within known ranges.

The solvent used during emulsion polymerization may be any solvent that allows the emulsion polymerization to proceed stably, and for example, water can be suitably used.

The temperature during emulsion polymerization is not particularly limited as long as the emulsifier is dissolved uniformly in the solvent, but is, for example, 40 to 75°C, preferably 45 to 73°C, and more preferably 49 to 71°C.

When the polyamide resin additive is produced by emulsion polymerization, the additive can be separated from the aqueous medium by, for example, coagulating the additive by mixing a latex of the additive 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, followed by heat treatment, dehydration, washing, and drying according to known methods. The resulting additive is preferably washed with water and/or an organic solvent.

Alternatively, a water-soluble organic solvent such as an alcohol (e.g., methanol, ethanol, or propanol) or acetone can be added to the additive latex to precipitate the additive. The additive can then be separated from the solvent by centrifugation, filtration, or other methods, and then dried and isolated. Another method involves adding a slightly water-soluble organic solvent (e.g., methyl ethyl ketone) to the additive latex to extract the additive in the latex into an organic solvent layer, which can then be separated and mixed with water or other liquid to precipitate the additive.

Alternatively, the additive latex can be directly powdered by spray drying. The resulting powder is preferably washed with water and/or an organic solvent. Alternatively, calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, etc., preferably as an aqueous solution, can be added to the resulting powder, and the powder can be re-dried as needed, to achieve the same effect as the above-mentioned washing.

(Modifier for polyamide resin)
The polyamide resin modifier of this embodiment contains the above-mentioned additive for polyamide resins and an impact modifier. The impact modifier is not particularly limited and may be a conventionally known one. Specific examples include one or more selected from the group consisting of a core-shell impact modifier, a polyolefin elastomer, a polyester elastomer, and a polyamide elastomer. Among these, a core-shell impact modifier or a polyolefin elastomer is preferred.

The core-shell impact strength improver is composed of polymer particles that are graft copolymers. The polymer particles consist 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 more inward on the polymer particle than the shell layer and is composed of a rubbery polymer. The core layer may consist of only one layer, or may consist of two or more layers with different monomer compositions. The shell layer covers the surface of the core layer, but it is not limited to covering the entire surface of the core layer, as long as it covers at least a portion of the surface of the core layer.

(Core layer)
The core layer is composed of a rubbery polymer, which preferably contains at least one selected from the group consisting of natural rubber, diene rubber, acrylate rubber, and polyorganosiloxane rubber, and more preferably contains at least one selected from the group consisting of diene rubber, acrylate rubber, and polyorganosiloxane rubber.

(Diene rubber)
The diene rubber is an elastomer containing a constituent unit derived from a diene monomer as a constituent unit. The core layer more preferably contains a diene rubber, and particularly preferably is a diene rubber, because the glass transition temperature of the resulting elastomer can be lowered, the impact resistance of the resulting molded article of the polyamide resin composition is improved, and the raw material cost is low.

Examples of diene monomers include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), and 2-chloro-1,3-butadiene. These diene monomers may be used alone or in combination of two or more.

The diene rubber may further contain, as a structural unit, a structural unit derived from a vinyl monomer other than the diene monomer that is copolymerizable with the diene monomer.

Examples of vinyl monomers other than diene monomers that can be copolymerized with diene monomers (hereinafter also referred to as vinyl monomer A) include: (a) aromatic vinyl monomers such as styrene, α-methylstyrene, monochlorostyrene, and dichlorostyrene; (b) vinyl carboxylic acids such as acrylic acid and methacrylic acid; (c) alkyl (meth)acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; (d) methacrylic acid; (e) hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; (f) glycidyl group-containing vinyl monomers such as glycidyl methacrylate and 4-hydroxybutyl acrylate glycidyl ether; (g) unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; (h) vinyl acetate; (i) alkenes such as ethylene, propylene, butylene, and isobutylene. The above-mentioned vinyl monomer A may be used alone or in combination of two or more.

The content of structural units derived from vinyl monomer A in diene rubber is not particularly limited. It is preferable that diene rubber contains 50 to 100% by weight of structural units derived from diene monomers and 0 to 50% by weight of structural units derived from vinyl monomer A, based on 100% by weight of structural units.

The diene rubber may further contain structural units derived from multifunctional monomers such as diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butylene dimethacrylate. In other words, these multifunctional monomers may be used in the polymerization of the diene rubber.

Suitable examples of diene rubbers include butadiene rubber (polybutadiene rubber), styrene/butadiene copolymer rubber (poly(styrene/butadiene) rubber), poly(acrylonitrile/butadiene) rubber, and butadiene/acrylic acid ester copolymer. Butadiene rubber is an elastomer that contains 50 to 100% by weight of structural units derived from 1,3-butadiene out of 100% by weight of structural units.

The diene rubber is preferably a butadiene rubber containing 50 to 100% by weight of structural units derived from 1,3-butadiene and 0 to 50% by weight of structural units derived from vinyl monomer A, and more preferably a 1,3-butadiene homopolymer containing 100% by weight of structural units derived from 1,3-butadiene.

It is further preferable that the core layer contains butadiene rubber, and butadiene rubber is particularly preferable, because this can lower the glass transition temperature of the resulting elastomer, has a significant effect of improving the impact resistance of the molded article of the resulting polyamide resin composition, and has low raw material costs.

(Acrylate rubber)
The acrylate rubber is an elastic material containing, as a structural unit, a structural unit derived from a (meth)acrylate monomer.

Examples of (meth)acrylate monomers include: (a) (meth)acrylic acid alkyl esters having an alkyl group containing 1 to 22 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate; (b) aromatic ring-containing (meth)acrylic acid esters, such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; (c) (meth)acrylic acid hydroxyalkyl esters, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; (d) glycidyl group-containing (meth)acrylic acid esters, such as glycidyl (meth)acrylate and glycidyl alkyl (meth)acrylate; and (e) (meth)acrylic acid alkoxyalkyl esters. These (meth)acrylate monomers may be used alone or in combination of two or more.

The acrylate rubber may further contain, as a structural unit, a structural unit derived from a vinyl monomer other than a (meth)acrylate monomer that is copolymerizable with the (meth)acrylate monomer. Examples of the vinyl monomer other than a (meth)acrylate monomer that is copolymerizable with the (meth)acrylate monomer include (a) the diene monomers described above, and (b) vinyl monomers A other than (meth)acrylate monomers.

The acrylic rubber has a crosslinked structure. To introduce the crosslinked structure, for example, a crosslinking agent and/or a grafting agent can be used when synthesizing the core layer polymer by polymerizing the monomer components. Examples of crosslinking agents and grafting agents include: (a) allyl alkyl (meth)acrylates such as allyl (meth)acrylate and allyl alkyl (meth)acrylate; (b) polyfunctional (meth)acrylates such as monoethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; and (c) polyfunctional monomers such as diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and divinylbenzene. These crosslinking agents and grafting agents may be used alone or in combination of two or more.

Suitable examples of acrylate rubbers include polybutyl acrylate rubber and butyl acrylate/2-ethylhexyl acrylate copolymer rubber. Polybutyl acrylate rubber is an elastomer containing 50 to 100% by weight of structural units derived from butyl acrylate out of 100% by weight of structural units.

Suitable examples of polyorganosiloxane-based rubbers include silicone rubber and silicone/acrylate-based rubber.

Examples of silicone rubbers include polymethylsilicone rubber and polymethylphenylsilicone rubber. Examples of silicone/acrylate rubbers include polyorganosiloxane/butyl acrylate copolymer.

In one embodiment, it is preferable that the core layer contains one or more materials selected from the group consisting of butadiene rubber, styrene/butadiene copolymer rubber, acrylate rubber, and silicone rubber.

(shell layer)
The shell layer is preferably formed from a polymer containing a structural unit derived from a vinyl monomer, such as an aromatic vinyl compound, a vinyl cyanide compound, an unsaturated carboxylic acid ester, an acrylamide monomer, or a maleimide monomer.

Suitable examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, α-methylvinyltoluene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and dibromostyrene.

Suitable examples of the vinyl cyanide compound include acrylonitrile, methacrylonitrile, and ethacrylonitrile.

Suitable examples of the unsaturated carboxylic acid esters include: (a) alkyl acrylate esters having an alkyl group containing 1 to 22 carbon atoms, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, and behenyl acrylate; (b) alkyl methacrylate esters having an alkyl group containing 1 to 22 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, and behenyl methacrylate; and (c) alkoxyalkyl (meth)acrylate esters having an alkyl group containing 1 to 22 carbon atoms and an alkoxyl group, such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate.

Suitable examples of the acrylamide-based monomer include acrylamide, methacrylamide, and N-methylacrylamide.

Suitable examples of the maleimide-based monomer include N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-hexylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide.

The polymer constituting the shell layer preferably contains, as a constituent monomer, one or more selected from acrylic acid alkyl esters and methacrylic acid alkyl esters. These may be used alone or in combination of two or more.

Furthermore, it is preferable that the polymer constituting the shell layer further contains, as a constituent monomer, at least one reactive vinyl monomer selected from the group consisting of carboxyl group-containing vinyl monomers, hydroxyl group-containing vinyl monomers, and glycidyl group-containing vinyl monomers. By including the reactive vinyl monomer as a constituent monomer in the shell layer, the core-shell impact modifier can be made reactive with the polyamide resin, thereby improving the dispersibility of the core-shell impact modifier in the polyamide resin and enhancing the impact strength improvement effect. At the same time, the dispersibility of the additive in the polyamide resin can also be improved. Among the reactive vinyl monomers, carboxyl group-containing vinyl monomers are preferred because of their particularly good reactivity with polyamide resins. The reactive vinyl monomers may be used alone or in combination of two or more.

Suitable examples of the carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, isocrotonic acid, vinyloxyacetic acid, allyloxyacetic acid, 2-(meth)acryloylpropanoic acid, 3-(meth)acryloylbutanoic acid, 4-vinylbenzoic acid, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyethyl maleic acid, 2-methacryloyloxyethyl phthalic acid, and 2-methacryloyloxyethyl hexahydrophthalic acid. Among these, acrylic acid and/or methacrylic acid are preferred, with methacrylic acid being more preferred.

Suitable examples of the hydroxyl group-containing vinyl monomer include (meth)acrylic acid hydroxyalkyl esters having an alkyl group with 1 to 22 carbon atoms and a hydroxyl group, such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

Examples of the glycidyl group-containing vinyl monomer include glycidyl (meth)acrylate.

The amount of the reactive vinyl monomer used can be appropriately set depending on the desired effect and is not particularly limited. However, when the reactive vinyl monomer is a carboxyl group-containing vinyl monomer, the proportion of the carboxyl group-containing vinyl monomer in the entire polymer particles of the core-shell impact strength modifier is preferably 0.05 to 1.4 wt%. Having this proportion within this range enhances the impact strength improvement effect of the polyamide resin due to the incorporation of the core-shell impact strength modifier. The lower limit of this proportion is preferably 0.1 wt%, more preferably 0.2 wt%. The upper limit of this proportion is preferably 1.2 wt%, more preferably 1.0 wt%, even more preferably 0.9 wt%, even more preferably 0.7 wt%, particularly preferably 0.6 wt%, and most preferably 0.5 wt%.

The weight proportion of the shell layer in the entire polymer particle of the core-shell impact strength modifier is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, and even more preferably 10 to 30% by weight, from the viewpoint of compatibility between the core-shell impact strength modifier and the polyamide resin, and the impact strength improving effect.

(Particle size of core-shell type impact strength improver)
The particle size of the polymer particles that are the core-shell impact strength improver can be set as appropriate, but the volume average particle size of the polymer particles is usually 100 nm or more. Since larger particle sizes tend to improve impact strength, especially at low temperatures, the volume average particle size is preferably 130 nm or more, more preferably 150 nm or more, more preferably 160 nm or more, and even more preferably 170 nm or more. On the other hand, since larger particle sizes of the polymer particles tend to increase the time required for the polymerization reaction and reduce productivity, the volume average particle size is preferably 400 nm or less, more preferably 350 nm or less, even more preferably 300 nm or less, and even more preferably 250 nm or less. The volume average particle size of the polymer particles is a value measured using a particle size measuring device in the state of the polymer particles in a latex state, as shown in the Examples section. The volume average particle size of the polymer particles can also be calculated from transmission electron microscope (TEM) images of the polyamide resin composition. The particle size of the polymer particles can be controlled by the types and amounts of the polymerization initiator, chain transfer agent, oxidation-reduction agent, emulsifier, etc., the polymerization temperature, the polymerization time, etc.

(Method for producing polymer particles that are core-shell type impact strength improvers)
The polymer particles that are the core-shell type impact strength improver can be produced by a conventional method and is not particularly limited.For example, any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be adopted, but emulsion polymerization, i.e., emulsion graft polymerization, is preferred.In emulsion graft polymerization, specifically, first, a latex of particles that correspond to the core layer is produced by emulsion polymerization, and then monomer components and polymerization initiators for the shell layer are added to the latex to polymerize the monomer components.

(Polyolefin elastomer)
Examples of the polyolefin elastomer include polyolefin elastomers and hydrogenated styrene thermoplastic elastomers. Specific examples include ethylene/propylene copolymers, ethylene/butene-1 copolymers, ethylene/hexene-1 copolymers, ethylene/propylene/dicyclopentadiene copolymers, ethylene/propylene/5-ethylidene-2-norbornene copolymers, unhydrogenated or hydrogenated styrene/isoprene/styrene triblock copolymers, unhydrogenated or hydrogenated styrene/butadiene/styrene triblock copolymers, ethylene/methacrylic acid copolymers, and copolymers in which a part or all of the carboxylic acid moieties in these copolymers are converted into salts with sodium, lithium, potassium, zinc, or calcium; ethylene/methyl acrylate copolymers; Ethylene/ethyl acrylate copolymer, ethylene/methyl methacrylate copolymer, ethylene/ethyl methacrylate copolymer, ethylene/ethyl acrylate-g-maleic anhydride copolymer (where "g" represents graft, the same applies hereinafter), ethylene/methyl methacrylate-g-maleic anhydride copolymer, ethylene/ethyl acrylate-g-maleimide copolymer, ethylene/ethyl acrylate-g-N-phenylmaleimide copolymer, or partially saponified products of these copolymers; ethylene/glycidyl methacrylate copolymer, ethylene/vinyl acetate/glycidyl methacrylate copolymer, ethylene/methyl methacrylate /glycidyl methacrylate copolymer, ethylene/glycidyl acrylate copolymer, ethylene/vinyl acetate/glycidyl acrylate copolymer, ethylene/glycidyl ether copolymer, ethylene/propylene-g-maleic anhydride copolymer, ethylene/butene-1-g-maleic anhydride copolymer, ethylene/propylene/1,4-hexadiene-g-maleic anhydride copolymer, ethylene/propylene/dicyclopentadiene-g-maleic anhydride copolymer, ethylene/propylene/2,5-norbornadiene-g-maleic anhydride copolymer, ethylene/propylene-g-N-phenylmaleimide copolymer Examples of the copolymer include ethylene/butene-1-g-N-phenylmaleimide copolymer, hydrogenated styrene/butadiene/styrene-g-maleic anhydride copolymer, hydrogenated styrene/isoprene/styrene-g-maleic anhydride copolymer, ethylene/propylene-g-glycidyl methacrylate copolymer, ethylene/butene-1-g-glycidyl methacrylate copolymer, ethylene/propylene/1,4-hexadiene-g-glycidyl methacrylate copolymer, ethylene/propylene/dicyclopentadiene-g-glycidyl methacrylate copolymer, and hydrogenated styrene/butadiene/styrene-g-glycidyl methacrylate copolymer. Examples of industrially usable elastomers include TAFMER MH7020, MH7010, and MA8510 manufactured by Mitsui Chemicals, Inc., HIMILAN 1706 manufactured by DuPont-Mitsui, SEBS TUFTEC M1943 manufactured by Asahi Kasei Corporation, and PA-bond 959, PA-bond 969, and PA-bond 979 manufactured by Polymer Asia Co., Ltd.

The polyamide resin modifier of this embodiment contains the additive of this embodiment and an impact modifier, and the proportion of the additive contained in the modifier can be determined appropriately by one skilled in the art. However, from the perspective of balancing the effects achieved by the additive and the effects achieved by the impact modifier, the proportion of the additive relative to the total amount of the additive and impact modifier is preferably 0.1% by weight or more and 25% by weight or less, more preferably 0.5% by weight or more and 15% by weight or less, and even more preferably 1% by weight or more and 10% by weight or less.

The polyamide resin modifier of this embodiment can be produced by mixing the additive of this embodiment with an impact modifier. When producing the modifier, the additive and impact modifier may be mixed in powder form, but it is preferable to mix the additive and impact modifier in latex form and then dry them to obtain a powder. In particular, when the impact modifier is a core-shell impact modifier, mixing it in latex not only improves the impact strength, but also dramatically improves the melt tension of the polyamide resin composition, which is effective in improving parison retention during blow molding. This is thought to be because the additive is more compatible with the shell portion of the core-shell impact modifier during latex blending. As a result, when the modifier is kneaded with the polyamide resin, the additive is uniformly dispersed in the polyamide resin along with the dispersion of the core-shell impact modifier.

(Amount of modifier blended)
The polyamide resin modifier of this embodiment is blended with a polyamide resin to improve its moldability during melt processing, the tensile properties of molded articles, and the impact strength of the polyamide resin. The amount of modifier blended with the polyamide resin can be set as appropriate, but the proportion of modifier relative to the total of the polyamide resin and modifier is preferably 1% by weight or more and 40% by weight or less. A modifier proportion within this range can favorably improve moldability during melt processing, the tensile properties of molded articles, and the impact strength of the polyamide resin while maintaining the physical properties unique to the polyamide resin. The proportion is more preferably 3 to 30% by weight, and even more preferably 5 to 25% by weight.

(Polyamide resin)
The polyamide resin in this embodiment is not limited as long as it is a polymer having an acid amide bond (—CONH—). Examples include polymers obtained by polycondensation of diamines and dibasic acids, polymers obtained by polycondensation of diamine derivatives such as diformyl with dibasic acids, polymers obtained by polycondensation of dibasic acid derivatives such as dimethyl ester with diamines, polymers obtained by reaction of dinitriles or diamides with formaldehyde, polymers obtained by polyaddition of diisocyanates with dibasic acids, polymers obtained by self-condensation of amino acids or derivatives thereof, and polymers obtained by ring-opening polymerization of lactams. 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 mixed and used.

Specific examples of polyamide resins include aliphatic polyamides such as nylon 4, nylon 6, nylon 6,6, 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. Among these, nylon 6, nylon 6,6, nylon 11, and nylon 12 are preferred from the perspective of versatility.

(Other resins)
The polyamide resin composition of this embodiment may or may not contain a thermoplastic resin other than the polyamide resin. When a thermoplastic resin other than the polyamide resin is contained, the thermoplastic resin is not particularly limited, but examples thereof 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, and cyclic polyolefin. The amount of the other thermoplastic resin is not particularly limited, but is, for example, 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 the polyamide resin.

(Other additives)
The polyamide resin composition of the present embodiment may contain, as appropriate, additives that can be blended into general thermoplastic resin compositions, including, but not limited to, flame retardants, flame retardant auxiliaries, anti-dripping agents, reinforcing materials, fillers, antioxidants, pigments, dyes, conductivity-imparting agents, hydrolysis inhibitors, thickeners, plasticizers, lubricants, UV absorbers, antistatic agents, flow improvers, release agents, compatibilizers, and heat stabilizers.

From the viewpoint of improving impact strength, it is preferable that the polyamide resin composition of this embodiment further contains a reinforcing material. Examples of reinforcing materials include glass fiber, carbon fiber, boron fiber, asbestos fiber, polyvinyl alcohol fiber, polyester fiber, acrylic fiber, wholly aromatic polyamide fiber, polybenzoxazole 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 due to their high impact strength-improving effect, and glass fiber is more preferred. The reinforcing materials may be used alone or in combination of two or more types.

The amount of reinforcing material to be added can be set as appropriate, but it is preferable that the proportion of the reinforcing material relative to the total of 100% by weight of the polyamide resin and the reinforcing material is 10 to 60% by weight, more preferably 15 to 50% by weight, and even more preferably 20 to 40% by weight.

(Method for producing the composition)
The method for producing the polyamide resin composition of this embodiment is not particularly limited, and a general method for producing a thermoplastic resin composition can be applied. For example, the raw materials can be mixed using a Henschel mixer, a tumbler mixer, or the like, and then melt-kneaded to obtain the polyamide resin composition. For the 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. By such melt-kneading, pellets made of the polyamide resin composition can be produced.

The polyamide resin composition of this embodiment can be molded into a predetermined shape to form a molded article. The molding method is not particularly limited, and examples that can be used include injection molding, extrusion molding, blow molding, foam molding, calendar molding, inflation molding, rotational molding, and press molding.

(Application)
The polyamide resin composition of the present embodiment and molded articles thereof are useful in 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, optical fiber cable coating materials, power tools, and electric wire ties; hydraulic and pneumatic connectors and tubes, bearings, covers and housings, and shafts. Examples of applications include, but are not limited to, mechanical applications such as receivers, pressure-resistant hoses, and cable ties; building material applications such as curtain rail parts, 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 snorkels; packaging materials and container applications such as shrink wrapping film, food packaging film, alcoholic beverage bottles, and pesticide bottles; daily necessities applications such as toothbrushes, chair legs and armrests, combs, and knives and forks; and medical applications such as medical catheters and pipes, medical packs, and sutures.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

(Weight average molecular weight)
The weight-average molecular weight was determined by dissolving a sample in tetrahydrofuran (THF), filtering the soluble fraction through a 0.2 μm filter, and then using a high-speed GPC apparatus (HLC-8220, manufactured by Tosoh Corporation) (sample solution: 20 mg sample/10 mL THF, columns: one TSKguard column Super HZ-H and two TSKgel Super HZM-H, both manufactured by Tosoh Corporation, column temperature: 40° C., detector: differential refractometer, flow rate: 0.35 mL/min, injection volume: 10 μL, calibration curve: standard polystyrene).

(Volume average particle diameter of polymer particles)
The volume average particle size of the polymer particles was measured in the state of polymer particle latex using a Nanotrac Wave manufactured by Nikkiso Co., Ltd. as a measuring device.

(Polymerization Conversion Rate)
A part of the obtained latex was sampled and precisely weighed, and dried in a hot air dryer at 120°C for 1 hour, and the weight after drying was precisely weighed as the solid content. Next, the ratio of the weighed results before and after drying was calculated as the solid content ratio in the latex. Finally, using this solid content ratio, the polymerization conversion rate was calculated by the following formula.
Formula: Polymerization conversion rate = (total weight of charged raw materials x solid component ratio - total weight of raw materials other than monomers) / charged monomer weight x 100 (%)

(Example of additive manufacturing)
As a representative method for producing additives, the production procedure for the additives used in Examples 1 and 2 is shown below. The additives used in the examples and comparative examples other than Examples 1 and 2 were produced in accordance with the following description for Examples 1 and 2, except that the types and amounts of the monomers used and the amount of the chain transfer agent were changed according to the descriptions in the table.

<Production of additive latex>
A glass reactor equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer and emulsifier adding device was charged with 100 parts by weight of deionized water, 0.147 parts by weight of sodium hydroxide, and 1.353 parts by weight of polyoxyethylene lauryl ether phosphate, and the temperature was raised to 70°C while stirring in a nitrogen stream.
0.0025 parts by weight of disodium ethylenediaminetetraacetate, 0.0015 parts by weight of ferrous sulfate heptahydrate, 0.3 parts by weight of sodium formaldehyde sulfoxylate, and 0.01 parts by weight of t-butyl hydroperoxide were added to the mixture and stirred.
To this was added a mixture of 11.05 parts by weight of methacrylic acid (hereinafter referred to as MAA), 38.95 parts by weight of styrene (hereinafter referred to as ST), 0.9 parts by weight of t-dodecyl mercaptan (chain transfer agent), 0.9 parts by weight of n-dodecyl mercaptan (chain transfer agent), and 0.451 parts by weight of polyoxyethylene lauryl ether phosphate over 150 minutes. During the addition, aqueous sodium hydroxide solution was added as needed to maintain the pH at 6.5 to 7.0, and t-butyl hydroperoxide was added as needed to promote polymerization. After completion of the addition of the mixture, the mixture was stirred for 30 minutes while cooling the temperature from 70°C to 50°C, and t-butyl hydroperoxide was added as needed during stirring to promote polymerization. As a result, a first polymer was formed at a polymerization addition rate of 97%.
Thereafter, a mixture of 43.28 parts by weight of ST, 6.72 parts by weight of butyl acrylate (hereinafter referred to as BA), 0.451 parts by weight of polyoxyethylene lauryl ether phosphate, and 0.08 parts by weight of t-butyl hydroperoxide was added over 150 minutes. During the addition, aqueous sodium hydroxide solution was added as needed to maintain the pH at 6.5 to 7.0. After the addition was completed, 0.01 parts by weight of t-butyl hydroperoxide was added three times every 10 minutes, followed by stirring for 30 minutes to form a second polymer at a polymerization conversion rate of 98%. As a result, an additive latex containing the first polymer and the second polymer was obtained.
<Obtaining white resin powder as an additive>
650 parts by weight of deionized water and 3.5 parts by weight of a 25% by weight aqueous calcium chloride solution were heated to 70°C while stirring, and the additive latex was added thereto to obtain a slurry containing coagulated latex particles. Thereafter, the coagulated latex particle slurry was heated to 95°C, dehydrated, and dried to obtain a particulate additive containing the first polymer and the second polymer as a white resin powder.

(Examples 1 to 15 and Comparative Examples 1 to 3) Preparation of Polyamide Resin Compositions Pellets and test pieces composed of a composition containing a polyamide resin and the white resin powder of the additive were prepared according to the following description, and MFR, tensile properties, Izod impact strength, and HDT were measured. However, in Comparative Example 1, evaluation was performed without using the white resin powder of the additive. MFR or melt tension was used as an index of moldability during melt processing. A smaller MFR value indicates lower fluidity during melt processing and better moldability during melt processing. Furthermore, a larger melt tension value indicates better moldability during melt processing.

(Pellet and test piece preparation conditions)
(a) 99.0 parts by weight or 98.0 parts by weight of polyamide 6 resin (Durethan B29 manufactured by Lanxess) (b) 1 part by weight or 2 parts by weight of white resin powder of the additive (c) 0.1 part by weight of hindered phenol-based antioxidant (Irganox 1076 manufactured by BASF) (d) 0.2 part by weight of phosphorus-based processing stabilizer (Irgafos 168 manufactured by BASF)

The mixture of (a) to (d) was kneaded and extruded in a twin-screw extruder (TEX44SS manufactured by The Japan Steel Works, Ltd.) heated to a barrel temperature of 230 to 260°C at a screw rotation speed of 100 rpm to obtain pellets.
The pellets were dried in a dryer at 80°C for 12 hours to sufficiently reduce the moisture content, and then test specimens were produced using an injection molding machine (FAS100B manufactured by Fanuc Corporation) at a molding temperature of 270 to 290°C and a mold temperature of 80°C.

(MFR)
The pellets prepared under the above conditions were dried in a hot air dryer at 120°C for 12 hours, and then the MFR value was measured in accordance with JIS K7210 Method A under conditions of a measurement temperature of 280°C and a load of 5 kg.

(Melt tension)
The melt tension was determined by measuring the stress when the pellets prepared under the above conditions were melted and stretched at a constant acceleration, and was measured under the following conditions. The melt tension was measured for Examples 7-8 and 16 and Comparative Examples 1 and 4-5.
[Measurement conditions]
Model used: Capillary rheometer (RG25, manufactured by Gottfert)
Capillary die: diameter 2 mm, length 20 cm
Winding speed: 17 mm/s
Acceleration: (Table 1) 6mm/s ² , (Table 2) 12mm/s ²
Measurement temperature: (Table 1) 228°C, (Table 2) 238°C

(Tensile properties)
The 3.2 mm thick ASTM D638-1 type test piece prepared by the above-mentioned method was subjected to measurement of tensile properties (tensile modulus, tensile yield stress, tensile breaking stress, and tensile breaking strain) in an absolute dry state at 23°C at a test speed of 50 mm/min by a method conforming to the ASTM D638 standard.

(Izod impact strength)
The Izod impact strength of the test piece with a length of 63.5 mm, a width of 12.7 mm, and a thickness of 3.2 mm, and having a V-notch, prepared by the method described above, was measured in an absolute dry state at −30° C. and 23° C. by a method conforming to the ASTM D256 standard.

(HDT)
The test pieces, each having a length of 127 mm, a width of 12.7 mm, and a thickness of 6.4 mm, were annealed at 100°C for 1 hour, and then the HDT was measured at a load of 18.6 kgf/ ^cm2 according to the method of ASTM D648.
The results of the above measurements are shown in Table 1.

Table 1 shows that Examples 1 to 15 have significantly smaller MFR values than Comparative Examples 1 to 3, meaning that they have good moldability during melt processing. Furthermore, the tensile properties of the molded bodies are also good compared to Comparative Examples 1 and 2. Among the Examples, Examples 7 to 15 are particularly good. Furthermore, Examples 7 and 8 have higher melt tension values than Comparative Example 1, which also indicates good moldability during melt processing. Comparative Example 1 does not contain any additives, and the additives used in Comparative Examples 2 and 3 do not contain methacrylic acid, a carboxyl group-containing vinyl monomer, but instead contain glycidyl methacrylate, an epoxy group-containing vinyl monomer.

(Production of core-shell impact strength improver)
<Production of polybutadiene rubber latex (core layer)>
A pressure-resistant polymerization reactor was charged with 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. The mixture was thoroughly degassed with stirring to remove oxygen, and then 100 parts by weight of butadiene (hereinafter referred to as BD) was added to the system, and the temperature was raised to 45°C. 0.05 parts by weight of sodium formaldehyde sulfoxylate and 0.03 parts by weight of paramenthane hydroperoxide were added to initiate polymerization. At 6, 10, 14, and 17 hours after the start of polymerization, 0.014 parts by weight of paramenthane hydroperoxide was added. After 20 hours of polymerization, residual monomers were removed under reduced pressure to devolatilize and terminate the polymerization, yielding a polybutadiene rubber latex composed primarily of polybutadiene rubber and having a volume average particle size of 180 nm.

<Production of polymer particle latex>
A glass reactor equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer and emulsifier adding device was charged with 30 parts by weight of deionized water and the above-mentioned polybutadiene rubber latex so that the solids content was 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, and 0.04 parts by weight of sodium formaldehyde sulfoxylate were charged. A mixture of 19.62 parts by weight of methyl methacrylate (hereinafter referred to as MMA), 2.18 parts by weight of BA, 0.2 parts by weight of MAA, and 0.024 parts by weight of t-butyl hydroperoxide was added thereto over 68 minutes. Five minutes after the completion of the addition, 0.015 parts by weight of sodium formaldehyde sulfoxylate was added, and after another 5 minutes, 0.01 parts by weight of t-butyl hydroperoxide was added, and after another 5 minutes, 0.01 parts by weight of t-butyl hydroperoxide was added. This process was repeated twice, and the mixture was stirred for 50 minutes to obtain a polymer particle latex with a polymerization conversion rate of 100%.

(Production of modifier containing additive and polymer particles)
The polymer particle latex containing 3.0 parts by weight of the hindered phenol antioxidant IRGANOX-1076 [n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate] was blended with the additive latex used in Examples 7 and 8 in a solids ratio of 98:2 (by weight) to obtain a blended latex. 760 parts by weight of deionized water and 3.5 parts by weight of a 25% by weight aqueous calcium chloride solution were heated to 60°C with stirring, and the blended latex was added to the mixture to obtain a slurry containing coagulated latex particles. The coagulated latex particle slurry was then heated to 90°C, dehydrated, and dried to obtain a modifier containing the additive and polymer particles (core-shell impact strength modifier) as a white resin powder.
Also, polymer particles (core-shell type impact strength modifier) alone were obtained as a white resin powder in the same manner except that the additive latex was not used.

(Example 16 and Comparative Examples 4-5) Preparation of Polyamide Resin Compositions Pellets and test pieces composed of a composition containing a polyamide resin and the white resin powder of the modifier according to the formulations shown in Table 2 were prepared according to the methods described above, and the MFR, melt tension, tensile properties, and Izod impact strength were measured according to the methods described above. However, in Comparative Example 4, evaluation was performed without using the white resin powder of the modifier, and in Comparative Example 5, evaluation was performed using a white resin powder containing only the polymer particles (core-shell impact strength modifier) instead of the white resin powder of the modifier. The results obtained are shown in Table 2.
The polyamide resin used was polyamide 6 resin (UBE 1030B manufactured by Ube Industries, Ltd.).

From Table 2, it can be seen that Example 16 has a smaller MFR value and a larger melt tension value than Comparative Examples 4 and 5, meaning that it has good moldability during melt processing, and also has better tensile properties and Izod impact strength than Comparative Example 5.

(Examples 17 to 21 and Comparative Examples 6 to 8) Preparation of Polyamide Resin Compositions Pellets and test pieces composed of a composition containing a glass fiber reinforced polyamide resin, the additive white resin powder, and optionally a polyolefin elastomer according to the formulations shown in Table 3 were prepared as described below, and the MFR, tensile properties, Izod impact strength, and HDT were measured according to the methods described above. However, in each Comparative Example, evaluation was performed without using the additive white resin powder. The results obtained are shown in Table 3.

(Pellet and test piece preparation conditions)
(a) Glass fiber reinforced polyamide 6 resin (CM1016G-30 manufactured by Toray Industries, Inc., containing 30% by weight of glass fiber) Parts by weight shown in Table 3 (b) White resin powder of the additive used in Examples 7 and 8 Parts by weight shown in Table 3 (c) Maleic anhydride modified polyolefin elastomer (MH7020 manufactured by Mitsui Chemicals, Inc.) Parts by weight shown in Table 3 (d) Hindered phenol-based antioxidant (Irganox 1076 manufactured by BASF) 0.21 parts by weight (e) Phosphorus-based processing stabilizer (Irgafos 168 manufactured by BASF) 0.09 parts by weight

Pellets were obtained from the mixture of (a) to (e) using the method described above, and then test pieces were prepared.

From Table 3, it can be seen that Examples 17 to 19, in which the above-mentioned additives were blended into the glass fiber reinforced polyamide resin, had smaller MFR values than Comparative Example 6, which did not contain the above-mentioned additives, i.e., had good moldability during melt processing, and also had better tensile properties and Izod impact strength than the comparative example.
For the system in which a polyolefin elastomer is blended with a glass fiber reinforced polyamide resin, Example 20, which contains the additive, has a smaller MFR value and is better in both tensile properties and Izod impact strength than Comparative Example 7, which does not contain the additive. Example 21 also has a smaller MFR value and is better in both tensile properties and Izod impact strength than Comparative Example 8.

(Examples 22 to 27 and Comparative Examples 9 to 10) Preparation of Polyamide Resin Compositions Pellets and test pieces composed of compositions containing polyamide resin and the white resin powder of the additive according to the formulations shown in Table 4 were prepared as described below, and the MFR, tensile properties, Izod impact strength, and HDT were measured according to the methods described above. However, in each Comparative Example, evaluation was performed without using the white resin powder of the additive. The results obtained are shown in Table 4.

(Pellet and test piece preparation conditions)
(a) Polyamide 66 resin (Leona 1300 manufactured by Asahi Kasei Corporation or Leona 1700 manufactured by Asahi Kasei Corporation) Parts by weight shown in Table 4 (b) White resin powder of the additive used in Examples 7 and 8 Parts by weight shown in Table 4 (c) Hindered phenol-based antioxidant (Irganox 1076 manufactured by BASF Corporation) 0.21 parts by weight (d) Phosphorus-based processing stabilizer (Irgafos 168 manufactured by BASF Corporation) 0.09 parts by weight

Pellets were obtained from the mixture of (a) to (d) using the method described above, and then test pieces were prepared.

From Table 4, it can be seen that Examples 22 to 24, in which the additives were blended with nylon 6,6, had smaller MFR values than Comparative Example 9, which did not contain the additives, i.e., had good moldability during melt processing, and also had better tensile properties than Comparative Example 9.
Furthermore, it can be seen that in Examples 25 to 27, the MFR values are small and the tensile properties are good compared to Comparative Example 10.

Claims (12)

An additive for polyamide resins, comprising a first polymer and a second polymer ,
The first polymer contains, as constituent monomers, (i) a carboxyl group-containing vinyl monomer, and
(ii) a (meth)acrylic acid ester monomer and/or an aromatic vinyl monomer;
is a copolymer comprising
the first polymer has a weight average molecular weight of 2,000 to 25,000;
the second polymer is a polymer containing, as a constituent monomer, a methacrylic acid ester monomer and/or an aromatic vinyl monomer,
the second polymer has a weight average molecular weight of 100,000 or more,
The additive for polyamide resins, wherein the first polymer and the second polymer are each a non-rubber polymer, the first polymer constitutes particles, and at least a portion of the second polymer is located outside the particles . The additive for polyamide resins according to claim 1, wherein the carboxyl group-containing vinyl monomer accounts for 15% by weight or more and 50% by weight or less of 100% by weight of the first polymer. The additive for polyamide resins according to claim 1 or 2, wherein the first polymer is a copolymer containing, as constituent monomers, (i) a carboxyl group-containing vinyl monomer and (ii) a (meth)acrylic acid ester monomer. The additive for polyamide resins according to any one of claims 1 to 3, wherein the total of the methacrylic acid ester monomer and the aromatic vinyl monomer accounts for 80% by weight or more and 100% by weight or less of 100% by weight of the second polymer. A modifier for polyamide resins, comprising the additive according to any one of claims 1 to 4 and an impact strength improver. 6. The polyamide resin modifier according to claim 5 , wherein the impact modifier is a core-shell type impact modifier. 6. The polyamide resin modifier according to claim 5 , wherein the impact strength improver is a polyolefin elastomer. A polyamide resin and the additive for polyamide resins according to any one of claims 1 to 4 ,
The polyamide resin composition comprises the additive in an amount of 0.1 to 10% by weight based on 100% by weight of the total of the polyamide resin and the additive. A polyamide resin modifier comprising: a polyamide resin; and the modifier for polyamide resins according to any one of claims 5 to 7 ;
a polyamide resin composition in which the modifier accounts for 1 to 40% by weight relative to 100% by weight of the total of the polyamide resin and the modifier; 10. The polyamide resin composition according to claim 8 , further comprising a reinforcing material, wherein the proportion of the reinforcing material is 10 to 60% by weight relative to 100% by weight of the total of the polyamide resin and the reinforcing material. A pellet comprising the polyamide resin composition according to any one of claims 8 to 10 . A molded article made of the polyamide resin composition according to any one of claims 8 to 10 .