Polyamide resin composition for welding and molded article thereof

Abstract

A polyamide resin composition for welding according to the present invention contains a polyamide resin that contains a crystalline polyamide resin (A), and a thermoplastic elastomer that contains a polyolefin polymer (B) modified with an epoxy group and has a reactive functional group capable of reacting with a terminal group and / or a main chain amide group of the crystalline polyamide resin (A). The content of the resin (A) is 70-90 mass parts and the content of the polymer (B) is 10-30 mass parts per 100 total mass parts of the resin (A) and the polymer (B). The thermoplastic elastomer is dispersed in a matrix of the polyamide resin. The polyamide resin composition has a melt viscosity difference at a predetermined temperature difference of 4.0×101 (Pa∙S) expressed as the absolute value of the amount of change per 1°C, can be applied for injection molding, has excellent welding processability in addition to impact resistance and moldability, and can provide a molded article from the composition.

Description

Polyamide resin composition for welding and molded article thereof

[0001] The present invention relates to a weldable polyamide resin composition. The weldable polyamide resin composition of the present invention is suitable for use as a polyamide resin composition for injection molding, and is a polyamide resin composition that not only has excellent impact resistance and moldability but also has excellent weldability. The present invention also relates to a molded article made using the weldable polyamide resin composition.

[0002] One of the excellent properties of polyamide resins is toughness, and one indicator of this toughness is impact strength. The impact strength of polyamide resins increases significantly upon moisture absorption, but is not necessarily sufficient immediately after molding or at low temperatures below 0°C. Specifically, when inserting metal into a product immediately after molding or in cold regions during the winter, problems such as cracking or chipping of the product may occur. One method for achieving excellent impact strength even under such conditions or environments is known to involve blending a polymer that is highly flexible even at temperatures below 0°C with a polyamide resin and dispersing the polymer in the resin (Non-Patent Document 1).

[0003] Such polymer blends are not simply mixtures of polymers, but are highly designed polymer composite systems, and are called polymer alloys, following the example of metal alloys. Non-Patent Document 2 reports examples of blending polyamide resins with rubber or polyolefins to obtain polyamide resin compositions with high impact resistance. Specific examples include binary systems in which polyamide 6 is blended with ethylene-methacrylic acid copolymer, ethylene-vinyl acetate acrylic acid copolymer, maleic anhydride-grafted ethylene propylene rubber, etc., and blends of polyamide 6 and maleic anhydride-grafted polypropylene. By using such techniques and adjusting the kneading conditions, it is possible to stabilize a uniform dispersion structure by using the reaction product as a compatibilizer, even if the affinity between the polymers is extremely low.

[0004] This technology has also made it possible to produce polyamide resin compositions with extremely high impact resistance by adding large amounts of rubber or polyolefin. However, with the recent rapid spread of battery electric vehicles (BEVs) around the world and the research and development efforts of automobile manufacturers to improve the performance of fuel cell vehicles (FCVs), there has been a demand for materials with even higher added value that, in addition to the high impact resistance described above, have not only the fluidity to accommodate the larger and longer products that require flexibility, but also excellent moldability to achieve more complex product shapes and secondary processability such as welding.

[0005] For example, proposed methods for welding synthetic resin members include a method for welding synthetic resin members that can weld together synthetic resin members that have high laser light absorption properties and that can set the welding strength to be high (Patent Document 1), and a welding device for welding the joining surfaces of difficult-to-weld fluororesin materials (Patent Document 2).

[0006] As seen in these and other inventions, it has become possible to provide resin molded products with improved weldability using processing methods and equipment. However, with the rapid spread of battery electric vehicles (BEVs) in recent years around the world, the increasing performance of fuel cell vehicles (FCVs), and the advanced and highly efficient part design proposals made by automobile manufacturers through research and development efforts, there is a growing demand for materials with even higher added value that not only have high impact resistance but also secondary processability that can accommodate the complex structure of products that require flexibility.

[0007] Various polyamide resin compositions for injection molding have been proposed. For example, a polyamide resin composition for sliding parts has been proposed (Patent Document 3), which contains a crystalline polyamide resin (A), a modified polyolefin resin (B) having reactive functional groups capable of reacting with terminal groups and / or main chain amide groups of the polyamide resin (A), a thermoplastic elastomer (C) having reactive functional groups capable of reacting with terminal groups and / or main chain amide groups of the polyamide resin (A), an antioxidant (D), and a mold release agent (E), in which the modified polyolefin resin (B) and the thermoplastic elastomer (C) are dispersed in a matrix of the polyamide resin (A) in the form of domains with particle sizes of 5 μm or less.

[0008] Osamu Fukumoto, "Lecture on Plastic Materials

[16] Polyamide Resin," Nikkan Kogyo Shimbun (1970) Takayuki Okada, Satoru Hosoda, "Morphology and Function of Polymer Alloys," Polymers, Vol. 37, February issue (1988)

[0009] Patent No. 6884664 Specification Patent No. 6501702 Specification Patent No. 6872155

[0010] However, although the polyamide resin composition of Patent Document 3 is excellent in moldability, heat resistance stability, and sliding properties, it does not have satisfactory weldability.

[0011] An object of the present invention is to provide a polyamide resin composition for welding that is applicable to injection molding and that is excellent in impact resistance, moldability, and also in welding processability. Another object of the present invention is to provide a molded article using the polyamide resin composition for welding.

[0012] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0013] The present invention has the following configuration [1]: [1] A polyamide resin composition comprising a polyamide resin and a thermoplastic elastomer having a reactive functional group capable of reacting with a terminal group and / or a main chain amide group of the polyamide resin (hereinafter, this may be simply referred to as the thermoplastic elastomer), wherein the polyamide resin comprises a crystalline polyamide resin (A), and the thermoplastic elastomer comprises a polyolefin polymer (B) modified with an epoxy group, wherein the crystalline polyamide resin (A) is 70 parts by mass or more and 90 parts by mass or less and the epoxy group-modified polyolefin polymer (B) is 10 parts by mass or more and 30 parts by mass or less relative to a total of 100 parts by mass of the crystalline polyamide resin (A) and the epoxy group-modified polyolefin polymer (B), the thermoplastic elastomer is dispersed in a matrix of the polyamide resin with an average particle size of 500 nm or less, and the polyamide resin composition has a molecular weight distribution (Mw / Mn) of 5.0 or more, The polyamide resin composition was measured using a capillary flow tester having a capillary length of 10 mm and a capillary diameter of 1 mm under the condition of a shear rate of 60.8 (1 / sec) at temperatures of 250°C and 310°C. The difference in melt viscosity, expressed as an absolute value of the change per 1°C, was 4.0 x 10 １ (Pa·S) or less.

[0014] The present inventors have found that achieving [1] makes it possible to provide a polyamide resin composition that not only has high impact resistance but also has improved weldability. Specifically, a polymer alloy material in which the thermoplastic elastomer containing the epoxy-modified polyolefin polymer (B) is dispersed in a polyamide resin matrix containing the crystalline polyamide resin (A) while maintaining the above-mentioned molecular weight distribution range can maintain viscosity at relatively low shear rates without relying on introducing a special structure such as a branched structure into the polyamide resin. Furthermore, while suppressing the formation of significantly coarse welded bumps (hereinafter referred to as "beads"), the viscosity can also be suppressed at relatively high shear rates, such as during pressure welding. This has the effect of suppressing the formation of voids due to air entrapment at the weld interface, thereby enabling the production of well-welded molded products. Furthermore, the melt viscosity of the polyamide resin composition measured at temperatures of 250°C and 310°C at a shear rate of 60.8 (1 / sec) is 4.0 x 10, where Δη, expressed as the absolute value of the change per 1°C, is 4.0 x 10. １ By controlling each of these factors as described below, it is possible to suppress the difference in viscosity of the polyamide resin composition depending on the processing temperature during welding, thereby making it possible to broaden the appropriate temperature range for achieving a good welding state. As described above, it has been discovered that it is possible to propose a polyamide resin composition for welding that takes into consideration the reduction of the reject rate and the risk of defects during welding processing. As described above, by using a thermoplastic elastomer containing a polyolefin polymer (B) modified with epoxy groups, it is possible to impart high fracture toughness to a molded article obtained from the polyamide resin composition at the welded portion.

[0015] In the present invention, the following configurations [2] to

[11] are preferred.

[0016] [2] The polyamide resin composition for welding according to [1], characterized by having at least one crystallization temperature peak at 185° C. or higher. According to [2], the polyamide resin composition having the above properties not only ensures adhesion but also makes it possible to control the amount of beads generated around the welded part during welding within an appropriate range, thereby making it possible to suppress early breakage of the welded part or the vicinity of the welded part due to distortion of the bead.

[0017] [3] The polyamide resin composition for welding according to [1] or [2], characterized in that the crystalline polyamide resin (A) contains at least one crystalline polyamide resin having a melting point of 230° C. or less. According to [3], by using a crystalline polyamide resin having the above properties as the crystalline polyamide resin (A), it is possible to facilitate melting of the welded portion during welding processing of the polyamide resin composition and to maintain a good welded portion condition.

[0018] [4] The polyamide resin composition for welding according to any one of [1] to [3], wherein the epoxy-modified polyolefin polymer (B) has a glass transition temperature of −30° C. or lower. According to [4], since the epoxy-modified polyolefin polymer (B) has a glass transition temperature in the above range, impact resistance and fracture toughness can be more effectively improved, and a molded article obtained from the polyamide resin composition can exhibit high fracture toughness in a welded portion even in a low-temperature environment expected when used in cold regions.

[0019] [5] The polyamide resin composition for welding according to any one of [1] to [4], wherein the epoxy-modified polyolefin polymer (B) has a melt flow rate (MFR) of 10 g / 10 min or more when measured in accordance with ISO 1133A at a temperature of 230°C and a load of 2.16 kg. According to [5], the presence of the above properties of the epoxy-modified polyolefin polymer (B) in addition to the crystalline polyamide resin (A) makes it possible to obtain a polyamide resin composition for welding that not only has high fracture toughness at the welded portion of a molded article obtained from the polyamide resin composition, but also has excellent spreading of the molten material during molding or bonding of the welded portion, which is often a trade-off in polymer alloys.

[0020] [6] The polyamide resin composition for welding according to any one of [1] to [5], further comprising an antioxidant (C). According to [6], the use of the antioxidant (C) can suppress a decrease in the molecular weight of the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B) as well as the polyamide resin containing the crystalline polyamide resin (A) constituting the polyamide resin composition during heating during welding, thereby making it possible to effectively suppress embrittlement of the welded portion.

[0021] [7] The polyamide resin composition for welding according to any one of [1] to [6], further comprising a mold release agent (D). According to [7], the inclusion of the mold release agent in the polyamide composition makes it easy to remove a molded product from a mold when the polyamide composition is molded in a mold.

[0022] [8] A polyamide resin composition for welding according to [7], characterized in that when injection molding is performed using a 14,000-grit polished mold at a molding temperature of 260°C and a mold temperature of 80°C, followed by cooling for 65 seconds and demolding to consecutively obtain 20 semi-cylindrical molded articles each having a radius of 75 mm, a width of 50 mm, a draft angle of 3°, and an average thickness of 3 mm, none of the molded articles is distorted or deformed, and the pressure applied to the ejector pins at the end and center of the semi-cylindrical article upon demolding is less than 120 MPa. According to [8], by achieving the above, it is confirmed that the polyamide resin composition not only has the welding properties described above, but also possesses the inherent function of mold releasability that the polyamide resin composition should have during injection molding, and not only is excellent impact resistance and weldability excellent, but molded articles can be easily removed from the mold even if they are long or have a complex shape, and a stable injection molding cycle can be maintained.

[0023] [9] The polyamide resin composition for welding according to any one of [1] to [8], characterized in that the rate of change [{(MFR2-MFR1) / MFR1} x 100] between the melt flow rate (MFR1) measured in accordance with ISO 1133A after 5 minutes of residence at 280°C under a load of 10 kg and the melt flow rate (MFR2) measured after 20 minutes of residence under the same conditions as above is less than 100%. According to [9], the above-mentioned characteristic suppresses decomposition or viscosity reduction of the polyamide resin composition caused by heat applied from a heat source to melt the weld, making it possible to maintain a good weld condition.

[0024]

[10] A molded article obtained from the polyamide composition for welding according to any one of [1] to [9].

[0025]

[11] A welded molded article obtained by welding molded articles obtained from the polyamide composition according to any one of [1] to [9].

[0026] The weldable polyamide resin composition of the present invention is suitable for injection molding, and in particular, is excellent in impact resistance, moldability, and weldability. Furthermore, the weldable polyamide resin composition of the present invention can provide a good weld without any problems during processing, and the welding conditions can be stably and easily adjusted during production, making it possible to provide the above-mentioned excellent molded products.

[0027] Hereinafter, embodiments of the present invention will be described in detail.

[0028] <Polyamide Resin Composition> The weldable polyamide resin composition of the present invention contains a polyamide resin and a thermoplastic elastomer having a reactive functional group capable of reacting with a terminal group and / or a main chain amide group of the polyamide resin.

[0029] <Polyamide Resin Containing Crystalline Polyamide Resin (A)> The polyamide resin in the weldable polyamide resin composition of the present invention contains a crystalline polyamide resin (A). The crystalline polyamide resin (A) is preferred in that it can improve the mechanical properties of the weldable polyamide resin composition. The polyamide is a polymer having an amide bond (—NHCO—) in the main chain.

[0030] Examples of the crystalline polyamide (A) include polyamide 6 (PA6), polyamide 66 (PA66), polyamide 46 (PA46), polyamide 56 (PA56), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 510 (PA510), polyamide 610 (PA610), polyamide 612 (PA612), polymetaxylylene adipamide (PAMXD6), hexamethylenediamine-terephthalic acid polymer (PA6T), hexamethylenediamine-terephthalic acid, and adipic acid polymer. Examples of suitable crystalline polyamides include PA6T / 66, hexamethylenediamine-terephthalic acid and ε-caprolactam copolymer (PA6T / 6), trimethylhexamethylenediamine-terephthalic acid polymer (PATMD-T), metaxylylenediamine, adipic acid, and isophthalic acid copolymer (PAMXD6 / MXDI), trihexamethylenediamine, terephthalic acid, and ε-caprolactam copolymer (PATMDT / 6), and diaminodicyclohexylenemethane, isophthalic acid, and lauryllactam copolymer. These may be used alone or in combination of two or more. Furthermore, as a crystalline polyamide (A), polyamide resins obtained by polymerization of plant-derived raw materials may also be used. Among these, polyamide 6 is preferred due to its excellent moldability, melt flowability, and mechanical properties.

[0031] Polyamide 6 is preferably a polyamide whose main raw material is ε-caprolactam. Polyamides whose main raw material is ε-caprolactam can be obtained by polycondensation. Polyamide 6 may be copolymerized with other monomers. Examples of such monomers include amino acids such as 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid; lactams such as ω-laurolactam; aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, and 5-methylnonamethylenediamine; aromatic diamines such as metaxylylenediamine and paraxylylenediamine; 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, and bis(4-aminocyclohexyl) alicyclic diamines such as 2,2-bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, bis(aminopropyl)piperazine, and aminoethylpiperazine; aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodiumsulfoisophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid. Two or more of these may be copolymerized.

[0032] Of the total 100 mol % of monomer units constituting polyamide 6, the units derived from ε-caprolactam are preferably 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and even more preferably 90 mol % or more. This may be 100 mol %.

[0033] The relative viscosity of the crystalline polyamide resin (A) is preferably 1.5 or higher, more preferably 1.8 or higher, and even more preferably 2.0 or higher. A relative viscosity of 1.5 or higher can further improve strength. The relative viscosity of the crystalline polyamide resin (A) is preferably 4.5 or lower, more preferably 4.0 or lower, and even more preferably 3.6 or lower. A relative viscosity of 4.5 or lower can suppress excessive decrease in fluidity when the polyamide resin composition is melted and allowed to flow, and can improve the dispersibility of the sintered body. The relative viscosity is a value measured in accordance with JIS K6920-2:2009 using 98% sulfuric acid at 25°C with a sample (i.e., polyamide) of 1 g / dL.

[0034] The polyamide resin composition for welding of the present invention contains the crystalline polyamide resin (A) as a polyamide resin, but in this embodiment may further contain an amorphous polyamide resin. The content of the crystalline polyamide resin (A) in 100% by mass of the polyamide resin contained in the weldable polyamide resin composition of this embodiment is preferably 80% by mass or more. The content of the crystalline polyamide resin (A) may be 90% by mass or more, 95% by mass or more, 98% by mass or more, or even 100% by mass.

[0035] When the polyamide resin composition for welding of the present invention contains an amorphous polyamide resin, transfer to a molded article (i.e., mold transfer) becomes easier when the polyamide resin composition is injection molded. The amorphous polyamide resin can be a polyamide that does not show a crystalline melting peak in a thermogram measured by differential scanning calorimetry (DSC). Examples of amorphous polyamides include polymers obtained by polycondensation of diamines such as 4,4'-diamino-3,3'-dimethyldicyclohexylmethane (CA), 4,4'-diaminodicyclohexylmethane (PACM), metaxylylenediamine (MXD), trimethylhexamethylenediamine (TMD), isophoronediamine (IA), 4,4'-diaminodicyclohexylpropane (PACP), and hexamethylenediamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, and, if necessary, lactams such as caprolactam and lauryllactam. These may be used alone or in combination of two or more. Of course, other monomers may also be copolymerized into the amorphous polyamide resin.

[0036] In particular, the amorphous polyamide preferably contains an aromatic component, since crystallization is easily suppressed. As the amorphous polyamide containing an aromatic component, polyamide 6T / 6I made from terephthalic acid, isophthalic acid, and adipic acid as raw materials, and polyamide 6T / 66 made from terephthalic acid, adipic acid, and hexamethylenediamine as raw materials are preferred. Among them, polyamide 6T / 6I is more preferred in terms of moldability.

[0037] The crystalline polyamide resin (A) used in the present invention preferably uses at least one crystalline polyamide resin having a melting point of 230°C or less, as measured by a differential scanning calorimeter as described in the Examples section. Using a crystalline polyamide resin (A) having a melting point of 230°C or less allows the heat source temperature during processing to be set low, thereby preventing decomposition, burning, and gas generation on the melt surface due to thermal decomposition of the polyamide resin containing the crystalline polyamide resin (A) and the thermoplastic elastomer containing the epoxy-modified polyolefin polymer (B). This is preferable in that it can prevent poor adhesion or embrittlement of the welded portion and the generation of voids due to gas accumulation at the welded interface.

[0038] The amine terminal group concentration of the crystalline polyamide resin (A) used in the present invention is preferably 10 eq / ton or more, more preferably 20 eq / ton or more, and particularly preferably 30 eq / ton or more. When the amine terminal group concentration is 10 eq / ton or more, the dispersibility of the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B) present in the polyamide resin containing the crystalline polyamide resin (A) tends to be sufficient, which is preferable.

[0039] The carboxylic acid terminal group concentration of the crystalline polyamide resin (A) used in the present invention is not particularly limited, but is preferably 180 eq / ton or less, more preferably 160 eq / ton or less, and particularly preferably 140 eq / ton or less. When the carboxylic acid terminal group concentration is 180 eq / ton or less, deterioration of the crystalline polyamide resin (A) due to thermal history during processing is unlikely to occur, which is preferable.

[0040] <<Thermoplastic Elastomer Comprising Epoxy-Modified Polyolefin Polymer (B)>> The polyamide resin composition for welding of the present invention contains, in addition to the polyamide resin containing the crystalline polyamide resin (A), a thermoplastic elastomer containing an epoxy-modified polyolefin polymer (B). The basic structure of the thermoplastic elastomer is a substance that is elastic at room temperature (23°C). Among thermoplastic elastomers, those having reactive functional groups capable of reacting with the terminal groups and / or main-chain amide groups of the polyamide resin containing the crystalline polyamide resin (A) are preferred, and among these, epoxy-modified polyolefin polymer (B) is preferred. Epoxy groups are preferred from the viewpoint of their good reactivity with the acid and amine terminals of the polyamide resin containing the crystalline polyamide resin (A). The epoxy groups of the polyolefin polymer (B) are obtained by introducing functional groups such as epoxy groups into the basic structure of a polyolefin elastomer such as a polyolefin polymer.

[0041] Preferred examples of the polyolefin polymer forming the polyolefin elastomer, which is the basic structure of the epoxy-modified polyolefin polymer (B), include homopolymers or copolymers of ethylene, propylene, and α-olefins having 3 or more carbon atoms, and copolymers of the α-olefins with other unsaturated compounds having double bonds, such as alkyl (meth)acrylates, or non-conjugated dienes. Examples include homopolymers of α-olefins such as polyethylene, polypropylene, polybutene-1, polypentene-1, and polymethylpentene. Further examples include polyolefin copolymers obtained by radical polymerization of at least one of α-olefins such as ethylene, propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and isobutylene, and non-conjugated dienes such as 1,4-hexadiene-dicyclopentadiene, 2,5-norbornadiene, 5-ethylidenenorbornene, 5-ethyl-2,5-norbornadiene, and 5-(1'-propenyl)-2-norbornene, using a conventional metal catalyst or a high-performance metallocene catalyst. 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, and unhydrogenated or hydrogenated polybutadiene.

[0042] The method for introducing epoxy groups into the polyolefin polymer is not particularly limited, and methods such as copolymerization of a monomer having an epoxy group or graft reaction of an unmodified polyolefin polymer using a radical initiator can be used. In the case of copolymerization, the amount of these epoxy group-containing components introduced is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 12 parts by mass, per 100 parts by mass of all olefin monomers forming the modified polyolefin polymer. When the amount of the epoxy group-containing component introduced is 0.1 parts by mass or more, sufficient impact resistance tends to be imparted, while when it is 20 parts by mass or less, the melt viscosity stability is good. In the case of graft reaction, the amount is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 6 parts by mass, per 100 parts by mass of the modified polyolefin polymer. The same effects as those of copolymerization can be achieved within the above ranges in the case of graft reaction.

[0043] Specific examples of the modified polyolefin copolymer (B) having an epoxy group include ethylene-glycidyl methacrylate copolymer, ethylene-propylene-glycidyl methacrylate copolymer, ethylene-butene-1-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate copolymer, ethylene-acrylic acid-glycidyl methacrylate copolymer, ethylene-methacrylic acid-glycidyl methacrylate copolymer, ethylene-methyl acrylate-glycidyl methacrylate copolymer, ethylene-ethyl acrylate-glycidyl methacrylate copolymer, ethylene-methyl methacrylate-glycidyl methacrylate copolymer, ethylene-ethyl methacrylate-glycidyl methacrylate copolymer, copolymer, ethylene-methyl maleate-glycidyl methacrylate copolymer, ethylene-ethyl maleate-glycidyl methacrylate copolymer, ethylene-methyl fumarate-glycidyl methacrylate copolymer, ethylene-ethyl fumarate-glycidyl methacrylate copolymer, ethylene-vinyl chloride-glycidyl methacrylate copolymer, ethylene-vinylidene chloride-glycidyl methacrylate copolymer, ethylene-styrene-glycidyl methacrylate copolymer, ethylene-acrylonitrile-glycidyl methacrylate copolymer, ethylene-isobutyl vinyl ether-glycidyl methacrylate copolymer, ethylene-acrylamide-glycidyl methacrylate copolymer, and the like.

[0044] Examples of the modified polyolefin copolymer (B) having an epoxy group include "BONDFAST" (ethylene-glycidyl (meth)acrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd. and "MODIPER C1430G" (polycarbonate-g-GMA / AS copolymer) manufactured by NOF Corporation.

[0045] The epoxy group-containing modified polyolefin copolymer (B) may be modified with a reactive functional group other than the epoxy group that can react with the terminal group (amino group or carboxy group) and / or main chain amide group of the polyamide resin including the crystalline polyamide resin (A), in addition to the modification with the epoxy group. Examples of the reactive functional group other than the epoxy group include a carboxy group, an acid anhydride group, an oxazoline group, an amino group, an isocyanate group, etc.

[0046] The polyamide resin composition for welding of the present invention contains the modified polyolefin copolymer (B) having epoxy groups. However, in this embodiment, it may also contain a thermoplastic elastomer (b) other than (B) that has a reactive functional group capable of reacting with the terminal group and / or main chain amide group of the polyamide resin. The content of the thermoplastic elastomer (b) contained in the weldable polyamide resin composition of this embodiment is preferably 30% by mass or less, based on a total of 100% by mass including the modified polyolefin copolymer (B) having epoxy groups. The content of the thermoplastic elastomer (b) may be 20% by mass or less, 10% by mass or less, 5% by mass or less, 2% by mass or less, or even 0% by mass.

[0047] The thermoplastic elastomer (b) has a basic structure that is an elastic material at room temperature (23° C.), and is a natural or synthetic polymer material. Specific examples of materials constituting the thermoplastic elastomer (b) include natural rubber, conjugated diene compound polymers, aromatic compound-conjugated diene copolymers, hydrogenated aromatic compound-conjugated diene copolymers, polyester elastomers, polyurethane elastomers, polyamide elastomers, and elastomers having a core-shell structure.

[0048] Furthermore, aromatic compound-conjugated diene copolymers and hydrogenated aromatic compound-conjugated diene copolymers are A-B or A-B-A' type block copolymer elastomers composed of vinyl aromatic hydrocarbons and conjugated dienes, where the terminal blocks A and A' may be the same or different. Thermoplastic homopolymers or copolymers derived from vinyl aromatic hydrocarbons, whose aromatic moieties may be monocyclic or polycyclic, are also included. Examples of such vinyl aromatic hydrocarbons include styrene, α-methylstyrene, vinyltoluene, vinylxylene, ethylvinylxylene, vinylnaphthalene, and mixtures thereof. The intermediate polymer block B is composed of a conjugated diene hydrocarbon, such as a polymer derived from 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, or a mixture thereof. Hydrogenation of the intermediate polymer block B of the above-mentioned block copolymers is also possible. Specific examples include unhydrogenated or hydrogenated styrene / isoprene / styrene triblock copolymers and unhydrogenated or hydrogenated styrene / butadiene / styrene triblock copolymers.

[0049] The thermoplastic elastomer (b) preferably has a reactive functional group capable of reacting with the terminal group (amino group or carboxy group) and / or the main chain amide group of the crystalline polyamide resin (A). Examples of the reactive functional group include a carboxy group, an acid anhydride group, an oxazoline group, an amino group, and an isocyanate group.

[0050] The method for introducing a functional group such as a carboxylic acid group or a carboxylic anhydride group into the basic structure of the thermoplastic elastomer (b) such as the aromatic compound-conjugated diene copolymer can be the same as the method for introducing an epoxy group into the basic structure of the polyolefin polymer. The amount of the functional group-containing component to be introduced is the same for the aromatic compound-conjugated diene copolymer, etc.

[0051] Specific examples of modified polyolefin copolymers having carboxylic acid groups and / or carboxylic acid anhydride groups include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, and copolymers in which part or all of the carboxylic acid moieties in these copolymers have been converted into salts with sodium, lithium, potassium, zinc, or calcium, ethylene / ethyl acrylate-g-maleic anhydride copolymer (here, "-g-" represents graft (the same applies hereinafter)), ethylene / methyl methacrylate-g-anhydride copolymer, and Examples of the copolymer include maleic acid 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, hydrogenated styrene / butadiene / styrene-g-maleic anhydride copolymer, and hydrogenated styrene / isoprene / styrene-g-maleic anhydride copolymer.

[0052] The epoxy-modified polyolefin polymer (B) preferably has as high a fluidity as possible. Specifically, the high fluidity of the epoxy-modified polyolefin polymer (B) itself makes it possible to prevent a loss of the fluidity of the entire polyamide resin composition when it is blended with a polyamide resin containing a crystalline polyamide resin (A). The melt flow rate (MFR) is an index used to quantitatively measure the fluidity of the epoxy-modified polyolefin polymer (B). For example, when polyamide 6, which is preferred as the blended crystalline polyamide resin (A), is used, measurement is preferably performed at a temperature at which it fully melts, preferably 230°C or higher, and the load applied as a weight during measurement is preferably 2.16 kg. The melt flow rate of the epoxy-modified polyolefin polymer (B) assumed under the above conditions is preferably in the range of 10 g / 10 min or higher, more preferably 12 g / 10 min or higher. By using an epoxy group-modified polyolefin polymer (B) having a melt flow rate of 10 g / 10 min or more, it becomes possible to easily impart not only high fracture toughness at the welded portion to a molded article obtained from the polyamide resin composition but also excellent spreading of the molten material onto the bonding surface during molding or welding.

[0053] The glass transition temperature of the epoxy-modified polyolefin polymer (B), measured by a method using a dynamic viscoelasticity measuring device described in the Examples section below, is preferably −30° C. or lower, more preferably −35° C. or lower, and even more preferably −40° C. or lower. By including an epoxy-modified polyolefin polymer (B) satisfying the above glass transition temperature, a polyamide resin composition having excellent toughness in a low-temperature environment can be obtained.

[0054] The polyamide resin composition of the present invention comprises a polyamide resin containing the crystalline polyamide resin (A) and the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B). The total proportion of the crystalline polyamide resin (A) and the epoxy group-modified polyolefin polymer (B) in the polyamide resin composition of the present invention is preferably 90 mass% or more, more preferably 95 mass%, even more preferably 99 mass%, and may be 100 mass%.

[0055] The blending amount of the crystalline polyamide resin (A) is 70 parts by mass or more and 90 parts by mass or less relative to 100 parts by mass of the total of the crystalline polyamide resin (A) and the epoxy group-modified polyolefin polymer (B). The blending amount of the crystalline polyamide resin (A) is preferably 72.5 parts by mass or more, more preferably 75 parts by mass or more, and is preferably 87.5 parts by mass or less, more preferably 85 parts by mass or less. When the blending amount of the crystalline polyamide resin (A) is 70 parts by mass or more, a morphology structure in which the crystalline polyamide resin (A) is a continuous phase tends to be stably formed in the microstructure of a molded article made of the polyamide resin composition, which is preferable.

[0056] The amount of the epoxy-modified polyolefin polymer (B) is 10 to 30 parts by mass per 100 parts by mass of the total of the crystalline polyamide resin (A) and the epoxy-modified polyolefin polymer (B). The amount of the epoxy-modified polyolefin polymer (B) is preferably 12.5 parts by mass or more, more preferably 15 parts by mass or more, and preferably 27.5 parts by mass or less, more preferably 25 parts by mass or less. When the amount of the epoxy-modified polyolefin polymer (B) is 10 parts by mass or more, the effect of imparting toughness is good. When the amount of the epoxy-modified polyolefin polymer (B) is more than 30 parts by mass, the rigidity is reduced and the viscosity of the epoxy-modified polyolefin polymer (B) increases, resulting in poor flowability during molding and poor mold releasability. Furthermore, the dispersed particle size of the epoxy-modified polyolefin polymer (B) becomes large, which may cause strand pulsation during extrusion, making pelletizing difficult.

[0057] In the polyamide resin composition of the present invention, the thermoplastic elastomer containing the epoxy-modified polyolefin polymer (B) is dispersed with an average particle size of 500 nm or less in a matrix mainly composed of a polyamide resin containing the crystalline polyamide resin (A). That is, the thermoplastic elastomer containing the epoxy-modified polyolefin polymer (B) forms a particulate dispersed phase (dispersed particles) in a continuous phase mainly composed of a polyamide resin containing the crystalline polyamide resin (A). The number-average particle size of the dispersed particles of the thermoplastic elastomer containing the epoxy-modified polyolefin polymer (B) is preferably 500 nm or less, more preferably 450 nm or less, and even more preferably 400 nm or less. From the viewpoints of high toughness and physical property stability, it is preferable to keep the particle size within the above-mentioned range. From the viewpoint of flowability, the number-average particle size of the dispersed particles is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more.

[0042] When the dispersed particle size is within the above range, there is an effect of suppressing the change in melt viscosity in the low shear rate region, and Δη is also reduced. When the thermoplastic elastomer (b) is used in combination with the epoxy group-modified polyolefin polymer (B), the thermoplastic elastomer can form a dispersed phase (dispersed particles) in a form including the thermoplastic elastomer (b), and the epoxy group-modified polyolefin polymer (B) and the thermoplastic elastomer (b) may each form an independent dispersed phase (dispersed particles), or the forms may be combined.

[0058] The molecular weight distribution (Mw / Mn) of the polyamide resin composition of the present invention is 5.0 or more across all peaks obtained by GPC (gel permeation chromatography) as described in the Examples section, preferably 5.5 or more, more preferably 6.0 or more, and particularly preferably 7.0 or more.

[0059] A molecular weight distribution of 5.0 or higher enhances non-Newtonian properties, thereby preventing the formation of significantly coarse beads by maintaining viscosity at low shear rates, without relying on the introduction of special structures such as branched structures into the polyamide resin containing the crystalline polyamide resin (A). This allows for reduced viscosity at relatively high shear rates, such as during pressure welding, thereby preventing the formation of voids due to air entrapment at the weld interface, thereby enabling the production of well-welded molded products. It also effectively suppresses changes in melt viscosity at low shear rates, resulting in a small Δη. More specifically, the molecular weight distribution is enhanced when the proportion of the peak area for a weight-average molecular weight of 10,000 or less to the total is at least 5%, preferably at least 6%, and more preferably at least 7%. Furthermore, a proportion of the peak area for a weight-average molecular weight of 80,000 or more to the total tends to improve the toughness of the polyamide resin composition, which is preferred. A proportion of 22% or more is more preferred, with 25% or more being particularly preferred.

[0060] The molecular weight distribution of the above-mentioned polyamide resin composition is greatly affected by the molecular weight distribution of the polyamide resin containing the crystalline polyamide resin (A), so as the crystalline polyamide resin (A), the crystalline polyamide resin (A) having the above-mentioned molecular weight distribution can be used alone, or in order to obtain the polyamide resin containing the crystalline polyamide resin (A) having the above-mentioned molecular weight distribution, it can be prepared by blending two or more kinds of pellets of the crystalline polyamide resin (A) having different relative viscosities when kneading.For example, when adjusting the molecular weight distribution using two kinds of crystalline polyamide resins (a1) and (a2) having different relative viscosities, it is preferable to mix the crystalline polyamide resin (a1) having a relative viscosity of 3.4 or more and 3.8 or less with the crystalline polyamide resin (a2) having a relative viscosity of 2.4 or less and 2.8 or less in a mass ratio of (a1):(a2)=90:10 to 70:30, thereby achieving the above-mentioned molecular weight distribution. Even when the polyamide resin contains an amorphous polyamide resin, the above molecular weight distribution can be achieved by blending it with a crystalline polyamide resin (A) during kneading, provided that the properties are not significantly impaired.

[0061] The polyamide resin composition of the present invention is measured using a capillary flow tester having a capillary length of 10 mm and a capillary diameter of 1 mm under the condition of a shear rate of 60.8 (1 / sec) at temperatures of 250°C and 310°C. The difference in melt viscosity Δη of the polyamide resin composition is 4.0 × 10, expressed as an absolute value of the change per 1°C. １ (Pa·S) or less. １ (Pa·S) or less is preferable, and 3.0×10 １ (Pa·S) or less is more preferable, and 2.5×10 １ (Pa·S) or less is particularly preferred, and 2.0×10 １The following is more preferable. By satisfying the above range, it is possible to suppress variations in viscosity change of the polyamide resin composition due to processing temperature during hot plate welding, thereby increasing the degree of freedom in temperature conditions during hot plate welding. As a result, even if unevenness in temperature occurs due to welding equipment, a welded body with a uniform thickness of the molten part (bead) can be obtained, resulting in excellent welding processability. There is no particular restriction on the lower limit of the difference in welding viscosity, but it is preferably 0.5 × 10 １ (Pa·S) or more. １ If the viscosity is less than (Pa·S), there is a concern that it may be difficult to adjust the fluidity during injection molding, such as the fluidity in the mold not increasing when desired during injection molding.

[0062] Δη is 4.0 × 10 １ In order to achieve a viscosity of (Pa·S) or less, it is necessary to use the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B), to have a molecular weight distribution (Mw / Mn) of 5.0 or more of the polyamide resin composition, and to disperse the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B) in an average particle size of 500 nm or less in a matrix of the polyamide resin containing the crystalline polyamide resin (A).

[0063] The polyamide resin composition of the present invention preferably has at least one crystallization temperature of 185°C or higher, as measured by a method using a differential scanning calorimeter, which will be described in the Examples section. By having at least one crystallization temperature of 185°C or higher, the time required for the polyamide resin composition to crystallize from a molten state does not become too long, and excessive discharge of beads outside the molded article can be suppressed. This makes it possible to prevent beads from unintentionally adhering to non-welded portions and the generation of points prone to stress concentration in the vicinity.

[0064] The polyamide resin composition of the present embodiment may contain an antioxidant (C). The antioxidant (C) can suppress oxidative degradation of the polyamide resin composition.

[0065] Examples of the antioxidant (C) include organic antioxidants such as phenolic antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants, as well as heat stabilizers, with phenolic antioxidants being preferred. Furthermore, it is more preferred that the phenolic antioxidant be a phenolic antioxidant having a hindered structure. Examples of hindered phenolic antioxidants include N,N'-hexamethylene-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, bis(3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid) glycol ester, 2,1'-thioethylbis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), and triethylene glycol-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate. These may be used alone or in combination of two or more. The use of a phenolic antioxidant having a hindered structure slows down the radical scavenging rate that causes oxidative deterioration of the surface of a molded article, and makes it possible to impart an effect that lasts even in a high-temperature environment for a long period of time.

[0066] In the polyamide resin composition of this embodiment, the content of the antioxidant (C) is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. When the content is 0.05% by mass or more, oxidative deterioration of the polyamide resin composition over time can be prevented. On the other hand, the content of the antioxidant is preferably 1.0% by mass or less, more preferably 0.5% by mass or less.

[0067] The polyamide resin composition of the present embodiment may contain a mold release agent (D). When the polyamide resin composition contains a mold release agent, when the polyamide resin composition is molded in a mold, it becomes easy to remove the molded product from the mold.

[0068] The release agent (D) is not particularly limited, and examples thereof include higher fatty acid ester compounds, higher fatty acid metal salts, amide compounds, polyethylene wax, silicone, and polyethylene oxide. Among these, higher fatty acid ester compounds and higher fatty acid metal salts are preferred. Note that higher fatty acids are fatty acids having more than 10 carbon atoms, preferably fatty acids having 11 to 30 carbon atoms. These may be used alone or in combination of two or more.

[0069] In the polyamide resin composition of this embodiment, the content of the mold release agent (D) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. If it is 0.01% by mass or more, when the polyamide resin composition is injected into a mold, it is possible to prevent the polyamide resin composition from sticking to the mold and wrinkles that may occur on the surface of the molded product upon mold release. On the other hand, the content of the mold release agent is preferably 2.0% by mass or less, more preferably 1.0% by mass or less. If it is too high, decomposition gases derived from the mold release agent and the like will inhibit welding.

[0070] The polyamide resin composition of the present invention is injection molded using a 14,000-grit mold at a molding temperature of 260°C and a mold temperature of 80°C, cooled for 65 seconds, and then demolded from the mold to obtain 20 consecutive semi-cylindrical molded articles each having a radius of 75 mm, a width of 50 mm, a draft angle of 3°, and an average thickness of 3 mm, at a 120° angle. It is preferable that none of the molded articles are distorted or deformed, and that the pressure exerted on the ejector pins at the end and center of the semi-cylinder during demolding is less than 120 MPa. By controlling the demolding pressure within the above range, molded articles with not only simple shapes but also shapes that are prone to mold-release defects due to shrinkage or excessive transfer within the mold, such as cylindrical structures, are easily demolded, enabling long-term continuous molding and resulting in excellent productivity. On the other hand, if the pressure is 120 MPa or more, when continuously molding a complex shape such as the cylindrical molded product mentioned above, it may cause problems such as poor mold release from the mold and severe wrinkles on the molded product, which may affect productivity and the quality of the molded product.Furthermore, the shape may not be maintained due to deformation during ejection, which may also affect weldability.

[0071] The polyamide resin composition of the present invention preferably has a melt flow rate (MFR1) measured in accordance with ISO 1133A after 5 minutes of residence at 280°C under a load of 10 kg, and a melt flow rate (MFR2) measured after 20 minutes of residence under the same conditions as above, with the change rate [{(MFR2-MFR1) / MFR1} x 100] of less than 100%. By maintaining the change rate within this range, it is possible to prevent the viscosity of the welded portion from becoming extremely low and causing sagging when a molded article of the polyamide resin composition is hot plate welded.

[0072] The polyamide resin composition of the present embodiment may contain, for example, a heat aging resistance improver such as carbon black, copper oxide, or a halide, an antistatic agent, a pigment, a dye, a heat dissipation aid, etc., within the range not impairing the inherent functions and physical properties of the polyamide resin composition of the present invention. Of course, the polyamide composition of the present embodiment may contain a resin other than polyamide, as long as the inherent functions and physical properties are not impairing, as described above.

[0073] The polyamide resin composition of the present invention can be produced by kneading a polyamide resin containing at least a crystalline polyamide resin (A), the thermoplastic elastomer containing an epoxy-modified polyolefin polymer (B), and, if necessary, an antioxidant (C), a mold release agent (D), and the like, in a kneading device. For kneading, an extruder (e.g., a single-screw extruder or a twin-screw extruder), a pressure kneader, or the like can be used. Among these, an extruder is preferred, and a twin-screw extruder is more preferred. The kneading temperature can be 220°C to 300°C. The kneading time can be, for example, about 2 minutes to 15 minutes.

[0074] For example, the polyamide resin composition of the present embodiment can be produced by melt-kneading a polyamide resin containing at least the crystalline polyamide resin (A), the thermoplastic elastomer containing the epoxy group-modified polyolefin polymer (B), and, as necessary, an antioxidant (C), a mold release agent (D), and the like, in a twin-screw extruder, extruding the resulting strand, and, as necessary, cooling and cutting the strand.

[0075] The shape of the polyamide resin composition of the present embodiment can be appropriately set. The polyamide composition of the present embodiment may be, for example, in the form of pellets, strands, or powder, or may be molded into any shape. Among these, the pellet shape is preferred.

[0076] The polyamide resin composition of the present embodiment can be used as a raw material for molded articles that require high impact resistance and low-temperature toughness. In particular, it can be suitably used as a raw material for automobile parts, electrical and electronic parts, aircraft parts, industrial parts, and other parts that require high impact resistance and have complex shapes. Examples of such parts include parts used in fuel duct parts, water-cooling pipe parts, fuel tank parts, and the like.

[0077] The molded article of the present invention can be obtained by molding the polyamide composition of the present invention described above. That is, the molded article of this embodiment can be obtained from the polyamide composition of this embodiment described above. Examples of molding methods include injection molding, extrusion molding, and blow molding. Among these, injection molding is preferred because it can achieve complex shapes. The molded article has good fusion properties, and a welded molded article can be obtained by welding molded articles together.

[0078] The present invention will be described in more detail below with reference to examples and comparative examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0079] The following raw materials were used:

[0080] <Crystalline Polyamide Resin (A)> A1: "ZISAMIDE TP6603" manufactured by Zhi Sheng Industrial Co., Ltd. (polyamide 6, relative viscosity 2.5, melting point 225°C) A2: "ZISAMIDE TP4208" manufactured by Zhi Sheng Industrial Co., Ltd. (polyamide 6, relative viscosity 3.6, melting point 225°C) A3: Polyamide 6 / 66 copolymer (relative viscosity 3.5, melting point 195°C)

[0081] <Thermoplastic elastomers> <Epoxy group-modified polyolefin polymer (B)> B1: "Bondfast (registered trademark) BF-7L" (ethylene-glycidyl (meth)acrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd. (Tg = -33°C, MFR (230°C, 2.16 kg) = 20 g / 10 min) B2: "Bondfast (registered trademark) BF-7M" (ethylene-glycidyl (meth)acrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd. (Tg = -33°C, MFR (230°C, 2.16 kg) = 16 g / 10 min) <Thermoplastic elastomer (b)> b1: "Tafmer (registered trademark) MH5020" (modified EBR) manufactured by Mitsui Chemicals, Inc. (Tg = -42°C, MFR (230°C, 2.16 kg) = 16 g / 10 min) b2: "Tuftec (registered trademark) M1943" (maleic anhydride-modified SEBS) manufactured by Asahi Kasei Corporation (Tg = -43°C, MFR (230°C, 2.16 kg) = 5.4 g / 10 min) b3: "Tuftec (registered trademark) M1913" (maleic anhydride-modified SEBS) manufactured by Asahi Kasei Corporation (Tg = -43°C, MFR (230°C, 2.16 kg) = 5.4 g / 10 min)

[0082] <Antioxidant> C1: "ANOX20" (hindered phenol antioxidant) manufactured by SI Group

[0083] <Release Agent> D1: "N.P.1500-S" (magnesium stearate) manufactured by Tannan Chemical Industry Co., Ltd. D2: "Recorb WE-40" (aliphatic ester) manufactured by Clariant Japan Co., Ltd.

[0084] <Others> Stabilizer 1: Cupric bromide Stabilizer 2: Potassium iodide Stabilizer 3: ADEKA CORPORATION's "ADEKA STAB PEP36"

[0085] Examples 1 to 9 and Comparative Examples 1 to 8 <Polyamide resin composition: preparation of pellets> Each raw material was weighed according to the blending ratio of the polyamide resin composition shown in Tables 1 and 2, mixed in a tumbler, and then charged into a twin-screw extruder to obtain pellets. The twin-screw extruder was set at a temperature of 240°C to 300°C, and the kneading time was 5 to 10 minutes.

[0086] <Evaluation Methods> Various evaluations and measurements were carried out on the raw material crystalline polyamide resin (A), the thermoplastic elastomer (epoxy group-modified polyolefin polymer (B) and other thermoplastic elastomer (b)), and the obtained polyamide resin composition (pellets). The evaluation and measurement results are shown in Tables 1 and 2.

[0087] <Crystalline Polyamide Resin (A)> <Relative Viscosity (98% Sulfuric Acid Solution Method)> The relative viscosity of each of the above-described A1 to A4 was measured at 25° C. and 1 g / dL of polyamide using an Ubbelohde viscosity tube and 98% sulfuric acid in accordance with JIS K6920-2:2009.

[0088] <<Melting Point>> The melting points of the above A1 to A4 were measured using a differential scanning calorimeter ("EXSTAR 6000" manufactured by Seiko Instruments Inc.) at a temperature increase rate of 20° C. / min to determine the endothermic peak temperatures.

[0089] <Thermoplastic elastomer> <Glass transition temperature> The pellets of B1, B2, b1 to b3 were processed into a sheet (thickness: approximately 0.1 mm) using a hot press (200°C). A slice (width: approximately 4 mm, length: approximately 15 mm) was cut from the produced sheet as a sample, and the storage modulus E' and loss modulus E" were measured using a dynamic viscoelasticity measuring device Rheogel-E4000 (manufactured by UBM Corporation) at a frequency of 11 Hz and a heating rate of 2°C / min. The loss tangent tanδ (=E" / E') was calculated from the ratio of the storage modulus to the loss modulus, and the temperature at which tanδ reached its peak was taken as the glass transition temperature.

[0090] <<Melt Flow Rate (MFR)>> This was measured in accordance with ISO 1133A. The resins (B1 to B5 described above) placed in a cylindrical extrusion plastometer were heated to a temperature of 230°C, and the weight of a strand extruded from an orifice in 10 seconds using a weight load of 2.16 kg was measured in g / 10 min.

[0091] <Polyamide Resin Composition> <Crystallization Temperature> The endothermic peak temperature was determined by measuring at a temperature decrease rate of 10° C. / min using a differential scanning calorimeter (EXSTAR 6000 manufactured by Seiko Instruments Inc.).

[0092] <<Average particle size of dispersion>> A molded evaluation sample (approximately 10 mm × 3 mm) was cut out, and a cross section was prepared using a microtome equipped with a glass knife. The prepared cross section was observed with a differential interference microscope (Nikon ECLIPSE LV150N) and photographed (photographed area: 1.5 μm × 1.0 μm). In the micrograph, the 10 domains with the largest dispersion diameters were randomly selected from the domains of the dispersed thermoplastic elastomer, and the major axes of the selected domains were measured. The average value was calculated to obtain the average particle size.

[0093] <<Molecular Weight Distribution>> The obtained polyamide resin composition (pellets) was used as a sample. 2.5 mg of the sample was weighed and dissolved in 4 ml of a 10 mM HFIP / sodium trifluoroacetate solution. The solution was filtered through a 0.45 μm membrane filter, and GPC analysis of the filtrate was carried out under the following conditions. The molecular weight distribution (Mw / Mn) was calculated from the molecular weight calculated in terms of standard polymethyl methacrylate (PMMA). Apparatus: TOSOH HLC-8320 GPC Column: TOSOH TSKgel Super HM-H x 2 + TSKgel Super H2000 Solvent: 10 mM HFIP / sodium trifluoroacetate solution Flow rate: 0.2 ml / min Injection volume: 10 μl Temperature: 40°C Detector: RI

[0094] <<Change in Melt Flow Rate (MFR) (%)>> This was carried out in accordance with ISO 1133A. A resin composition (pellets) placed in a cylindrical extrusion plastometer was heated to 280°C and allowed to reside for 5 minutes, and then the weight of a strand extruded from the orifice in 10 seconds under a weight load of 10 kg was determined in units of g / 10 min to measure MFR1. MFR2 was also measured by determining the weight of a strand extruded from the orifice in 10 seconds under the same conditions as above but after an additional 20 minutes (total 25 minutes), and the weight of the strand extruded from the orifice in 10 seconds was determined in units of g / 10 min, and the rate of change [{(MFR2 - MFR1) / MFR1} x 100] was calculated.

[0095] <Δη> Using a capillary flow tester "Capillograph 1D" manufactured by Toyo Seiki Seisaku-sho, Ltd., with a capillary length of 10 mm and a capillary diameter of 1 mm, the melt viscosity of the polyamide resin composition was measured at a shear rate of 60.8 (1 / sec) at temperatures of 250° C. and 310° C. From the measurement results, the absolute value of the change per 1° C. was calculated as the absolute value (Pa·S) of the number obtained by subtracting the melt viscosity at 250° C. from the melt viscosity at 310° C. and dividing the result by the temperature difference of 60 (° C.).

[0096] <<Release Resistance Value and Demolding Properties>> A demolding resistance measuring device was attached, and a mold polished with a 14,000 mesh was used. A fully electric injection molding machine "EC130S" manufactured by Shibaura Machine Co., Ltd. was used. The molding speed was 40 mm / sec, injection peak pressure was 180 MPa, holding pressure was 65 MPa, holding pressure speed was 15 mm / sec, injection time was 18 sec, molding temperature was 260 ° C, mold temperature was 80 ° C, and cooling time was 65 seconds. A 120 ° semi-cylindrical molded product with a radius of 75 mm, width of 50 mm, and a draft angle of 3 ° was continuously injection molded. The average pressure applied to the ejector pins at the end and center of the semi-cylinder when demolded after 20 shots was measured and determined as the demolding resistance value (MPa). The demolding properties of the obtained molded products were evaluated by assigning "good" to cases where there was no distortion or deformation and "x" to cases where there was distortion or deformation.

[0097] <<Thickness Uniformity of Hot Plate Welded Portion>> A polyamide resin composition (pellets) was injection-molded into a shape equivalent to a dumbbell test piece as defined in JIS K7139, divided in half, to produce a molded article. The molded article was then placed in a hot plate welding machine. The half-section of the dumbbell test piece was then melted at a distance of 2 mm from the hot plate. After the surface temperatures reached 250°C and 310°C, respectively, the heat source was removed, and the specimen was immediately welded while applying a contact load of 0.4 kg. The specimen was then cooled for 30 seconds and then unloaded. The thickness of the central portion of the welding direction of the four molten portions (beads) that had formed on the surface of the welded portion by the above process was measured with a vernier caliper, and the average value was calculated. The thicknesses at surface temperatures of 250°C and 310°C were compared, and the difference between the average values ​​was determined. "Good": 1 mm or less; "Poor": Greater than 1 mm

[0098] <<Welding Strength Stability>> The polyamide resin composition (pellets) was injection-molded into a shape equivalent to a dumbbell test piece according to JIS K7139, divided in half, to produce a molded product. The molded product was then placed in a hot plate welding machine. The two halves of the dumbbell test piece were then heated at a heat source of 380°C, a hot plate distance of 2 mm, and a heating time of 150 seconds. After removing the heat source, the two halves were immediately welded together under a contact load of 0.4 kg. The welded parts were then cooled for 30 seconds and then unloaded. The molded parts with the welded joints obtained in the above process were gripped at both ends and subjected to a tensile test simulating ISO 527-1 at a tensile speed of 5 mm / min. Test pieces that showed good elongation of 50% or more even after the yield point and no fracture at or near the welded interface were compared with test pieces that fractured at or near the welded interface before and shortly after yielding. The test pieces were evaluated five times and evaluated according to the following criteria. The yield point represents the maximum point on the stress-strain curve in the tensile test. The stress at this yield point is defined as the tensile strength. ◯: Good in all five tests. ×: Early breakage or breakage thought to be due to poor welding occurred even in one test.

[0099]

[0100] In Examples 1 to 9, the rate of change per 1°C in melt viscosity at a shear rate of 60.8 (1 / sec) at 250°C and 310°C was 4.0 x 10 1(Pa·S) or less, which can suppress viscosity changes of the polyamide resin composition due to processing temperatures during welding, making it a resin composition that is expected to enable a wider temperature setting range during welding. In addition, since the crystallization temperature is 185°C or higher, the amount of beads generated around the weld during welding can be suppressed to a reasonable range. Furthermore, all of the polyamide resin compositions listed in the examples show a change in MFR measured after 5 minutes of residence at 280°C and 10 kg pressure compared to the MFR measured after 20 minutes of residence under the same conditions of less than 100%, which means that decomposition or viscosity reduction of the polyamide resin composition due to heat applied from a heat source to melt the weld is suppressed, and good weld quality can be expected to be maintained. Furthermore, the resistance during mold release is also suppressed, preventing deformation during ejection by an ejector pin and enabling the stable production of molded products with the designed dimensions.

[0101]

[0102] In Comparative Examples 1 to 7, the rate of change Δη per 1°C of melt viscosity at a shear rate of 60.8 (1 / sec) at 250°C and 310°C was 4.0 × 10 1(Pa·S), and the viscosity of the polyamide resin composition changes significantly depending on the processing temperature during welding. Therefore, the temperature conditions during welding are significantly limited, the thickness of the hot plate weld becomes uneven, and there is a high possibility of causing problems, which is not appropriate. In addition, the polyamide resin compositions of Comparative Examples 1 to 5 and 7 have a change rate of 100% or more between the MFR measured after 5 minutes of residence at 280°C and 10 kg and the MFR measured after 20 minutes of residence under the same conditions, which means there is a risk of problems during welding, such as decomposition of the molten material or drawdown due to a sudden drop in viscosity, which is not appropriate. Furthermore, in Comparative Examples 2, 4 and 8, the resistance during demolding is significantly high, so there is a possibility that the molded product will deform and deviate from the target dimensions during the ejection process using an ejector pin or air pressure, resulting in problems such as reduced production yield, which is also not appropriate. In Comparative Example 6, an epoxy-modified polyolefin polymer (B1) is used as the thermoplastic elastomer, but because the molecular weight distribution of the polyamide resin composition is narrow, the viscosity is not effectively suppressed in the relatively high shear rate range, and there is a risk of voids being generated due to air being entrained at the weld interface. In Comparative Example 8, the proportion of epoxy-modified polyolefin polymer (B1) used is high, the dispersed particle size is coarse and non-uniform, and the fluidity during extrusion molding is unstable, so the thickness of the hot plate weld is non-uniform and the mold release resistance is high.

[0103] The polyamide resin composition for welding of the present invention is suitable as a polyamide resin composition for injection molding, and since it not only has excellent impact resistance and moldability but also has excellent weldability in particular, it can be used for molded articles.

Claims

1. A polyamide resin composition comprising a polyamide resin and a thermoplastic elastomer having a reactive functional group capable of reacting with a terminal group and / or a main chain amide group of the polyamide resin, wherein the polyamide resin comprises a crystalline polyamide resin (A), and the thermoplastic elastomer comprises a polyolefin polymer (B) modified with an epoxy group, wherein the crystalline polyamide resin (A) is present in an amount of 70 to 90 parts by mass and the epoxy group-modified polyolefin polymer (B) is present in an amount of 10 to 30 parts by mass relative to a total of 100 parts by mass of the crystalline polyamide resin (A) and the epoxy group-modified polyolefin polymer (B), the thermoplastic elastomer is dispersed in a matrix of the polyamide resin with an average particle size of 500 nm or less, and the polyamide resin composition has a molecular weight distribution (Mw / Mn) of 5.0 or more, The polyamide resin composition was measured using a capillary flow tester having a capillary length of 10 mm and a capillary diameter of 1 mm under the condition of a shear rate of 60.8 (1 / sec) at temperatures of 250°C and 310°C. The difference in melt viscosity, expressed as an absolute value of the change per 1°C, was 4.0 x 10 １ (Pa·S) or less.

2. The polyamide resin composition for welding according to claim 1, characterized in that it has at least one crystallization temperature peak at 185°C or higher.

3. The polyamide resin composition for welding according to claim 1, wherein the crystalline polyamide resin (A) contains at least one crystalline polyamide resin having a melting point of 230°C or less.

4. The polyamide resin composition for welding according to claim 1, wherein the epoxy-modified polyolefin polymer (B) has a glass transition temperature of -30°C or lower.

5. A polyamide resin composition for welding according to claim 1, characterized in that the epoxy-modified polyolefin polymer (B) has a melt flow rate (MFR) of 10 g / 10 min or more when measured in accordance with ISO 1133A at a temperature of 230°C and a load of 2.16 kg.

6. The polyamide resin composition for welding according to claim 1, further comprising an antioxidant (C).

7. The polyamide resin composition for welding according to claim 1, further comprising a mold release agent (D).

8. A polyamide resin composition for welding according to claim 7, characterized in that when the composition is injection molded using a 14,000-grit polished mold at a molding temperature of 260°C and a mold temperature of 80°C, cooled for 65 seconds, and then demolded from the mold to consecutively obtain 20 semi-cylindrical molded articles having a radius of 75 mm, a width of 50 mm, a draft angle of 3°, an average thickness of 3 mm, and a 120° angle, none of the molded articles are distorted or deformed, and the pressure applied to the ejector pins at the end and center of the semi-cylindrical cylinder upon demolding is less than 120 MPa.

9. A polyamide resin composition for welding according to claim 1, characterized in that the rate of change [{(MFR2-MFR1) / MFR1} x 100] between the melt flow rate (MFR1) measured in accordance with ISO 1133A after a 5-minute residence time at 280°C under a 10 kg load and the melt flow rate (MFR2) measured after a 20-minute residence time under the same conditions as above is less than 100%.

10. A molded article obtained from the polyamide resin composition for welding according to any one of claims 1 to 9.

11. A welded molded article obtained by welding molded articles obtained from the polyamide resin composition according to any one of claims 1 to 9.

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