JP7542933B2 - Polyamide resin composition for welding and molded article using same - Google Patents

Description

The present invention relates to a polyamide resin composition for welding, which is made by blending specific amounts of polyamide resin, amide-based wax, and glass fiber, and to a molded article obtained by molding the same.

Polyamide resins are widely used as injection molded products in the fields of automobiles and machine parts, taking advantage of their excellent injection moldability, heat resistance, toughness, oil and gasoline resistance, and abrasion resistance. The development of polyamide resins in the above fields has been mainly as a replacement for metal materials, and their practical use has progressed from parts with many advantages such as light weight and rust prevention. Furthermore, with the recent improvement in the performance of polyamide resin materials and the development of molding and processing technologies, the application of polyamide resins to parts that are large and complex in shape and that were difficult to resinify using conventional technologies has been considered. In order to resinify such difficult parts, a single molding technique such as injection molding, extrusion molding, or blow molding is not sufficient, and a combination of post-processing techniques such as cutting, bonding, and welding is required. However, the design of conventional polyamide resin materials cannot be said to take into consideration the applicability to such post-processing, and for example, when glass fiber reinforced polyamide resin molded products consisting of two or more parts are used by welding, there was a problem that their use was limited due to insufficient tensile strength of the welded parts.

As a material that has excellent flowability and high cycleability during molding and also has high strength when used with various welding methods, for example, a polyamide resin composition consisting of a crystalline polyamide resin with a specific amino terminal group concentration and an inorganic filler has been investigated (for example, see Patent Document 1).

In addition, as a material that can exhibit welding characteristics that prevent the welded part from becoming a strength defect and can also improve the durability of the welded joint, for example, polyxylene adipamide, a polyamide copolymer of hexamethylene diamine, terephthalic acid, and ε-caprolactam, and a polyamide-based molding material made of a filler, is being considered (for example, see Patent Document 2).

JP 2002-30215 A JP 2009-96903 A

When a molded article made of a glass fiber reinforced polyamide resin composition is welded for use, for example as a high-pressure tank liner that is subject to distortion during use, there is a problem that even if the tensile strength of the welded part is high, if the tensile elongation is insufficient, cracks will occur at the welded part, limiting its use. Therefore, in applications where distortion is applied during use, not only high tensile strength but also high tensile elongation of the welded part is required.

However, the polyamide resin composition described in Patent Document 1 has a problem in that although the tensile strength of the welded portion is high, the tensile elongation is low.

Similarly, the polyamide molding material described in Patent Document 2 has the same problem of high tensile strength at the welded parts, but low tensile elongation.

In view of the problems with the conventional technology described above, the present invention aims to provide a polyamide resin composition that can produce molded products with an excellent balance between the tensile strength and tensile elongation of the welded parts.

To achieve the above objective, the present invention has the following configuration.

A polyamide resin composition for welding, which is made by blending 3 to 9 parts by weight of glass fiber (C) with a total of 100 parts by weight of 90 to 99.99 parts by weight of polyamide resin (A) and 0.01 to 10 parts by weight of amide wax (B).

The present invention includes a molded article having a welded portion made of the above polyamide resin composition.

The present invention includes a method for manufacturing a molded article in which a molded article having the above-mentioned welded portion is joined by any one of a welding methods selected from hot plate welding, infrared welding, vibration welding, laser welding, and infrared/vibration welding.

The polyamide resin composition for welding of the present invention has an excellent balance between tensile strength and tensile elongation at the welded part, and can suppress the occurrence of cracks at the welded part even when used in an environment where distortion is applied, making it possible to develop it into a useful molded product with a welded part.

The present invention will be described in more detail below.

The polyamide resin composition for welding of the present invention (hereinafter, sometimes referred to as "polyamide resin composition") is made by blending 3 to 9 parts by weight of glass fiber (C) to a total of 100 parts by weight of 90 to 99.99 parts by weight of polyamide resin (A) and 0.01 to 10 parts by weight of amide wax (B). By blending a specific amount of amide wax (B) with polyamide resin (A), which has an excellent balance of moldability, rigidity, and toughness, dense and uniform crystals are formed, resulting in excellent tensile elongation at the welded part. Furthermore, by blending a specific amount of glass fiber (C), which has excellent rigidity, a molded product with an excellent balance of tensile strength and tensile elongation at the welded part can be obtained. On the other hand, a combination of only polyamide resin (A) and glass fiber (C) or a large amount of glass fiber (C) improves the tensile strength of the welded part, but reduces the tensile elongation.

The polyamide resin (A) used in the present invention is a resin made of a polymer having an amide bond, and is made mainly of amino acids, lactams, or diamines and dicarboxylic acids. Representative examples of such raw materials include amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid, lactams such as ε-caprolactam and ω-laurolactam, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine, 5-methylnonamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis(4-aminomethyl)cyclohexane, and bis(4-aminomethyl)cyclohexane. Examples of the polyamide resins include aliphatic, alicyclic, and aromatic diamines such as bis(3-methyl-4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine, and aminoethylpiperazine, and aliphatic, alicyclic, and aromatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodiumsulfoisophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid. In the present invention, polyamide homopolymers or copolymers derived from these raw materials can be used alone or in the form of a mixture. Two or more of such polyamide resins may be blended.

Specific examples of polyamide resins (A) that are particularly useful in the present invention include polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polypentamethylene adipamide (polyamide 56), polytetramethylene adipamide (polyamide 46), polyhexamethylene sebacamide (polyamide 610), polypentamethylene sebacamide (polyamide 510), polyhexamethylene dodecamide (polyamide 612), polyundecaneamide (polyamide 11), polydodecanamide (polyamide 12), polycaproamide/polyhexamethylene terephthalamide copolymer (polyamide 6/6T), polyhexamethylene adipamide/polyhexamethylene terephthalamide copolymer (polyamide 66/6T), polyhexamethylene adipamide/polyhexamethylene isophthalamide copolymer (polyamide 66/6I), polyhexamethylene Polyhexamethylene adipamide/polyhexamethylene isophthalamide/polycaproamide copolymer (polyamide 66/6I/6), polyhexamethylene terephthalamide/polyhexamethylene isophthalamide copolymer (polyamide 6T/6I), polyhexamethylene terephthalamide/polydodecanamide copolymer (polyamide 6T/12), polyhexamethylene adipamide/polyhexamethylene terephthalamide/polyhexamethylene Examples include polyisophthalamide copolymer (polyamide 66/6T/6I), polyxylylene adipamide (polyamide MXD6), polyhexamethylene terephthalamide/poly-2-methylpentamethylene terephthalamide copolymer (polyamide 6T/M5T), polyhexamethylene terephthalamide/polypentamethylene terephthalamide copolymer (polyamide 6T/5T), and mixtures or copolymers thereof.

Particularly preferred examples include polyamide 6 resin, polyamide 66 resin, polyamide 610 resin, polyamide 11 resin, polyamide 12 resin, polyamide 6/66 copolymer, and polyamide 6/12 copolymer. Particularly preferred examples include polyamide 6 resin, polyamide 66 resin, and polyamide 610 resin, and more preferably polyamide 6 resin. Furthermore, it is practically suitable to use these polyamide resins as a mixture.

There are no particular restrictions on the degree of polymerization of these polyamide resins (A), and the relative viscosity measured at 25°C in a 98% concentrated sulfuric acid solution with a sample concentration of 0.01 g/ml is preferably in the range of 1.5 to 7.0. If the relative viscosity is 1.5 or more, the melt viscosity of the polyamide resin composition during molding will be appropriately high, which will suppress air entrapment during molding and further improve moldability. The relative viscosity is more preferably 1.8 or more. On the other hand, if the relative viscosity is 7.0 or less, the melt viscosity of the polyamide resin composition during molding will be appropriately low, which will further improve moldability.

The amount of amino terminal groups in the polyamide resin (A) is not particularly limited, but is preferably in the range of 1.0×10 ⁻⁵ to 10.0×10 ⁻⁵ mol/g. If the amount of amino terminal groups is in the range of 1.0×10 ⁻⁵ to 10.0×10 ⁻⁵ mol/g, a sufficient degree of polymerization can be obtained, and the mechanical strength of the molded product can be improved. Here, the amount of amino terminal groups in the polyamide resin can be determined by dissolving the polyamide resin in a phenol-ethanol mixed solvent (83.5:16.5 (volume ratio)) and titrating with a 0.02N hydrochloric acid aqueous solution.

The amide wax (B) used in the present invention includes amide compounds obtained by reacting a monocarboxylic acid with a diamine, amide compounds obtained by reacting a monoamine with a polybasic acid, and amide compounds obtained by reacting a monocarboxylic acid, a polybasic acid, and a diamine. These can be obtained by the dehydration reaction of the corresponding amine and carboxylic acid.

The monoamine is preferably a monoamine having 5 or more carbon atoms, and specific examples thereof include pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, stearylamine, cyclohexylamine, and benzylamine, and two or more of these may be used in combination. Among these, higher aliphatic monoamines having 10 to 20 carbon atoms are particularly preferred. If the carbon number is more than 20, the compatibility with the polyamide resin (A) decreases, and there is a risk of precipitation.

The monocarboxylic acid is preferably an aliphatic monocarboxylic acid or hydroxycarboxylic acid having 5 or more carbon atoms, and specific examples thereof include valeric acid, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, montanic acid, 12-hydroxystearic acid, and benzoic acid, and two or more of these may be used in combination. Among these, higher aliphatic monocarboxylic acids having 10 to 30 carbon atoms are particularly preferred. If the carbon number is more than 30, the compatibility with the polyamide resin (A) decreases, and there is a risk of precipitation.

Specific examples of the diamine include ethylenediamine, 1,3-diaminopropane, 1,4-diaminopropane, tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, metaxylylenediamine, paraxylylenediamine, tolylenediamine, phenylenediamine, and isophoronediamine, and two or more of these may be used in combination. Of these, ethylenediamine is particularly preferred.

The polybasic acid is a dibasic or higher carboxylic acid, and specific examples thereof include aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, sebacic acid, pimelic acid, and azelaic acid, aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and cyclohexylsuccinic acid, and two or more of these may be used in combination.

Among them, amide compounds obtained by reacting higher aliphatic monocarboxylic acids, polybasic acids, and diamines are particularly suitable, and examples thereof include amide compounds obtained by reacting stearic acid, sebacic acid, and ethylenediamine. In this case, the mixing ratio of each component is preferably in the range of 0.18 mol to 1.0 mol of polybasic acid and 1.0 mol to 2.2 mol of diamine per 2 mol of higher aliphatic monocarboxylic acid, and more preferably in the range of 0.5 mol to 1.0 mol of polybasic acid and 1.5 mol to 2.0 mol of diamine per 2 mol of higher aliphatic monocarboxylic acid.

The glass fiber (C) used in the present invention is not particularly limited, and any known glass fiber can be used. By blending glass fiber with the polyamide resin composition of the present invention, the mechanical strength of the molded product can be increased. Glass fibers are available in the form of chopped strands cut to a predetermined length, roving strands, milled fibers, and the like, and any of these may be used. There is no particular limit to the fiber diameter, but a diameter of 4 to 20 μm is preferred. If the fiber diameter is 4 μm or more, the filling rate in the thin wall part of the molded product can be increased. On the other hand, if the fiber diameter is 20 μm or less, the number of glass fibers in the polyamide resin composition can be increased, and the reinforcing effect of the glass fibers can be easily obtained, thereby increasing the mechanical strength. Here, the fiber diameter of the glass fiber refers to the number average value of the fiber diameter of each glass fiber, and can be determined by the following method. The cross section of the glass fiber (a surface perpendicular to the length direction of the fiber) is observed using a SEM (scanning electron microscope), the maximum diameter and the minimum diameter are measured, and the average value is taken as the fiber diameter of each glass fiber. The fiber diameter of the glass fiber can be determined by calculating the number average value of the fiber diameters of 10 randomly selected glass fibers. When chopped strands are used, there are no particular restrictions on the fiber length, but glass fibers with a strand length of 3 mm are preferably used, as they have high extrusion kneading workability. When roving strands are used, they can be compounded by a known technique of directly feeding the roving strands into an extruder. Two or more of these glass fibers may be used in combination.

The glass fibers are preferably surface-treated with a known coupling agent (e.g., a silane-based coupling agent, a titanate-based coupling agent, etc.) or other surface treatment agent, which can further improve the mechanical strength of the molded product. Examples of silane-based coupling agents include aminosilane, epoxysilane, and acrylicsilane.

The glass fibers are preferably coated with a binder, which can improve workability during melt-kneading. In addition, this can also have the effect of further improving the mechanical strength of the molded product. Examples of binders include urethane resins, epoxy resins, acrylic acid resins, amino resins, vinyl acetate resins, and polyolefin resins.

The polyamide resin composition of the present invention is made by blending 3 to 9 parts by weight of glass fiber (C) with 90 to 99.99 parts by weight of polyamide resin (A) and 0.01 to 10 parts by weight of amide wax (B) for a total of 100 parts by weight.

If the amount of polyamide resin (A) is less than 90 parts by weight, the toughness of the molded product made of the polyamide resin composition obtained is reduced. The amount of polyamide resin (A) is preferably 93 parts by weight or more, more preferably 95 parts by weight or more. On the other hand, if the amount of polyamide resin (A) is more than 99.99 parts by weight, the mold releasability during molding of the obtained polyamide resin composition, and the tensile strength and tensile elongation at the welded part during welding are reduced. The amount of polyamide resin (A) is preferably 99.95 parts by weight or less, more preferably 99.9 parts by weight or less. The amount of amide wax (B) is 0.01 to 10 parts by weight, preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more. Also, 7 parts by weight or less, more preferably 5 parts by weight or less. If the amount of amide wax (B) is less than 0.01 parts by weight, the mold releasability during molding of the obtained polyamide resin composition, and the tensile strength and tensile elongation at the welded part during welding are reduced. On the other hand, if the amount of the amide wax (B) is more than 10 parts by weight, the toughness of the molded product made of the obtained polyamide resin composition is reduced. If the amount of the glass fiber (C) is less than 3 parts by weight per 100 parts by weight of the total of the polyamide resin (A) and the amide wax (B), the tensile strength of the welded part of the obtained polyamide resin composition when welded is reduced. The amount of the glass fiber (C) is preferably 4 parts by weight or more. On the other hand, if the amount of the glass fiber (C) is more than 9 parts by weight, the tensile elongation of the welded part of the obtained polyamide resin composition when welded is reduced. The amount of the glass fiber (C) is preferably 8 parts by weight or less.

The polyamide resin composition preferably further contains an impact-resistant material (D). By adding the impact-resistant material (D), the impact resistance of the molded product can be improved.

Examples of impact-resistant materials (D) include olefin-based resins, acrylic rubbers, silicone rubbers, fluorine-based rubbers, styrene-based rubbers, nitrile rubbers, vinyl rubbers, urethane rubbers, polyamide elastomers, polyester elastomers, and ionomers. Two or more of these may be blended.

Among these, olefin resins are preferably used because they have excellent compatibility with polyamide resins (A) and amide waxes (B) and have a high impact resistance improving effect. Olefin resins are thermoplastic resins obtained by polymerizing olefin monomers such as ethylene, propylene, butene, isoprene, and pentene. They may be copolymers of two or more olefin monomers, or copolymers of these olefin monomers with other monomers. Specific examples of olefin resins include polymers or copolymers of polyethylene, polypropylene, polystyrene, poly1-butene, poly1-pentene, polymethylpentene, etc.; ethylene/α-olefin copolymers, ethylene/α,β-unsaturated carboxylic acid ester copolymers, α-olefin/α,β-unsaturated carboxylic acid ester copolymers, polyolefins obtained by hydrolyzing at least a portion of a copolymer of (ethylene and/or propylene) and vinyl alcohol ester, copolymers of (ethylene and/or propylene) and (unsaturated carboxylic acid and/or unsaturated carboxylic acid ester), polyolefins obtained by converting at least a portion of the carboxyl groups of a copolymer of (ethylene and/or propylene) and (unsaturated carboxylic acid and/or unsaturated carboxylic acid ester) to a metal salt, block copolymers of conjugated dienes and vinyl aromatic hydrocarbons, or hydrogenated products thereof. Among these, ethylene/α-olefin copolymers and ethylene/α,β-unsaturated carboxylic acid ester copolymers are more preferred, and ethylene/α-olefin copolymers are even more preferred.

The olefin resin may be modified with an unsaturated carboxylic acid and/or a derivative thereof. Here, the derivative of an unsaturated carboxylic acid is a compound in which the hydroxyl group of the carboxyl group of an unsaturated carboxylic acid is replaced with another substituent, and includes metal salts, acid halides, esters, acid anhydrides, amides, and imides of unsaturated carboxylic acids. By using such a modified olefin resin, the compatibility with the polyamide resin (A) and the amide wax (B) is further improved, and the impact resistance can be further improved. Examples of unsaturated carboxylic acids or derivatives thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, methyl maleic acid, methyl fumaric acid, mesaconic acid, citraconic acid, glutaconic acid, and metal salts of these carboxylic acids; methyl hydrogen maleate, methyl hydrogen itaconate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethacryloyl methacrylate, dimethyl maleate, dimethyl methacrylate ... unsaturated carboxylic acid esters such as ethyl and dimethyl itaconate; acid anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride, endobicyclo-(2,2,1)-5-heptene-2,3-dicarboxylic acid, and endobicyclo-(2,2,1)-5-heptene-2,3-dicarboxylic acid anhydride; maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, glycidyl citraconate, and 5-norbornene-2,3-dicarboxylic acid. Among these, unsaturated dicarboxylic acids and their acid anhydrides are preferred, with maleic acid or maleic anhydride being particularly preferred.

Methods for introducing these unsaturated carboxylic acids or their derivatives into olefin-based resins include, for example, copolymerizing an olefin monomer with an unsaturated carboxylic acid and/or its derivative, and grafting an unsaturated carboxylic acid and/or its derivative onto an unmodified olefin-based resin using a radical initiator.

As the ethylene/α-olefin copolymer, a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is preferred. Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl α-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene, etc. Two or more of these may be used. Among these α-olefins, α-olefins having 3 to 12 carbon atoms are preferred from the viewpoint of improving mechanical strength. Furthermore, at least one of 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 may be copolymerized. A copolymer of ethylene modified with an unsaturated carboxylic acid and/or its derivative and an α-olefin having 3 to 12 carbon atoms is more preferred because it can further improve the compatibility with the polyamide resin (A) and the amide wax (B) and further improve the impact resistance. The α-olefin content in the ethylene/α-olefin copolymer is preferably 1 to 30 mol%, more preferably 2 to 25 mol%, and even more preferably 3 to 20 mol%.

The structure of the impact-resistant material (D) is not particularly limited, and may be, for example, a multi-layer structure called a core-shell type, which is composed of at least one layer of rubber and one or more layers of a different polymer. The number of layers constituting the multi-layer structure may be two or more, and may be three or more or four or more, but it is preferable to have one or more rubber layers (core layers) inside. The type of rubber constituting the rubber layer of the multi-layer structure is not particularly limited, and examples include rubbers obtained by polymerizing acrylic components, silicone components, styrene components, nitrile components, conjugated diene components, urethane components, ethylene components, propylene components, isobutene components, etc. The type of different polymers constituting the layers other than the rubber layer of the multi-layer structure is not particularly limited as long as they are polymers having thermoplasticity, but polymers having a higher glass transition temperature than the rubber layer are preferred. Examples of polymers having thermoplastic properties include polymers containing unsaturated carboxylic acid alkyl ester units, unsaturated carboxylic acid units, unsaturated glycidyl group-containing units, unsaturated dicarboxylic acid anhydride units, aliphatic vinyl units, aromatic vinyl units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units, and other vinyl units.

The amount of impact-resistant material (D) in the polyamide resin composition is preferably 1 to 50 parts by weight per 100 parts by weight of the total of polyamide resin (A) and amide wax (B). Impact resistance can be further improved by making the amount of impact-resistant material (D) 1 part by weight or more. The amount of impact-resistant material (D) is more preferably 5 parts by weight or more, and even more preferably 10 parts by weight or more. On the other hand, rigidity can be further improved by making the amount of impact-resistant material (D) 50 parts by weight or less. The amount of impact-resistant material (D) is more preferably 45 parts by weight or less, even more preferably 40 parts by weight or less, and even more preferably 35 parts by weight or less.

The polyamide resin composition may contain other components in addition to the components (A), (B), (C) and (D) as necessary, provided that the properties of the composition are not impaired. Examples of other components include fillers other than the components (A) to (D), thermoplastic resins and various additives.

For example, by blending a filler as another component in the polyamide resin composition, the strength and dimensional stability of the resulting molded product can be further improved. The filler referred to here does not include glass fiber (C). The filler may be fibrous or non-fibrous, and a combination of fibrous and non-fibrous fillers may be used. Examples of fibrous fillers include carbon fibers, potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, and metal fibers. Examples of non-fibrous fillers include silicates such as wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, and alumina silicate; metal oxides such as alumina, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, and iron oxide; metal carbonates such as calcium carbonate, magnesium carbonate, and dolomite; metal sulfates such as calcium sulfate and barium sulfate; metal hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; glass flakes, glass beads, ceramic beads, boron nitride, and silicon carbide. These may be hollow. In addition, it is preferable to pretreat these fibrous and/or non-fibrous fillers with a coupling agent before use in the sense of obtaining better mechanical properties. Examples of coupling agents include isocyanate compounds, organic silane compounds, organic titanate compounds, organic borane compounds, and epoxy compounds.

Examples of thermoplastic resins include polyester resin, polyphenylene sulfide resin, polyphenylene oxide resin, polycarbonate resin, polylactic acid resin, polyacetal resin, polysulfone resin, polyethylene tetrafluoride resin, polyetherimide resin, polyamideimide resin, polyimide resin, polyethersulfone resin, polyetherketone resin, polythioetherketone resin, polyetheretherketone resin, styrene-based resins such as polystyrene resin and ABS resin, polyalkylene oxide resin, etc. It is also possible to blend two or more of such thermoplastic resins.

Examples of various additives include color inhibitors, antioxidants such as hindered phenols and hindered amines, release agents, plasticizers, heat stabilizers, lubricants, UV inhibitors, colorants, flame retardants, and foaming agents.

It is preferable to add a copper compound to the polyamide resin composition, since this improves the long-term heat resistance. Examples of copper compounds include copper (I) chloride, copper (II) chloride, copper (I) bromide, copper (II) bromide, copper (I) iodide, copper (II) iodide, copper (II) sulfate, copper (II) nitrate, copper (II) phosphate, copper (I) acetate, copper (II) acetate, copper (II) salicylate, copper (II) stearate, copper (II) benzoate, and complex compounds of the inorganic copper halides with xylylenediamine, 2-mercaptobenzimidazole, benzimidazole, and the like. Two or more of these may be added. Among them, monovalent copper compounds, particularly monovalent copper halide compounds, are preferred, and copper (I) acetate, copper (I) iodide, and the like are preferred. The amount of copper compound added is preferably 0.01 parts by weight or more, more preferably 0.015 parts by weight or more, per 100 parts by weight of polyamide resin (A). On the other hand, from the viewpoint of suppressing coloration caused by liberation of metallic copper during molding, the amount of copper compound blended is preferably 2 parts by weight or less, and more preferably 1 part by weight or less.

Alkali halide compounds may also be blended with the copper compound. Examples of alkali halide compounds include lithium chloride, lithium bromide, lithium iodide, potassium chloride, potassium bromide, potassium iodide, sodium bromide, and sodium iodide. Two or more of these may also be blended. Potassium iodide or sodium iodide is particularly preferred.

The polyamide resin composition of the present invention can be produced in a molten state or in a solution state. From the viewpoint of productivity, production in a molten state is preferably used. For production in a molten state, melt kneading using an extruder, a Banbury mixer, a kneader, a mixing roll, etc. can be used, and from the viewpoint of productivity, melt kneading using an extruder that can produce continuously is preferably used. Examples of extruders include single-screw extruders, twin-screw extruders, multi-screw extruders such as four-screw extruders, and twin-screw single-screw composite extruders. A combination of these extruders may be used. From the viewpoint of improving kneading properties, reactivity, and productivity, multi-screw extruders such as twin-screw extruders and four-screw extruders are preferred, and twin-screw extruders are more preferred.

As an example of a melt-kneading method using a twin-screw extruder, polyamide resin (A), amide wax (B), glass fiber (C), and other components than (A), (B), and (C) as necessary are premixed, and the components are fed to a twin-screw extruder with a cylinder temperature set to the melting point of polyamide resin (A) or higher and melt-kneaded. There is no particular restriction on the order of mixing the raw materials, and any method may be used, such as a method of melt-kneading all the raw materials by the above method, a method of melt-kneading some of the raw materials by the above method and further blending and melt-kneading the remaining raw materials, or a method of mixing the remaining raw materials using a side feeder while melt-kneading some of the raw materials. A preferred method is to feed polyamide resin (A), amide wax (B), and other components than (A), (B), and (C) as necessary from the base of the extruder (the side where the raw materials are fed is the upstream side, and the side where the molten resin is discharged is the downstream side), melt-knead them, and then feed glass fiber (C) from the middle of the extruder using a side feeder and melt-knead them. Another method that is preferably used is to expose the extruder to a vacuum during the process to remove the gas that is generated.

The polyamide resin composition of the present invention can be molded by any method to obtain molded parts. Examples of molding methods include extrusion molding, injection molding, blow molding, calendar molding, compression molding, vacuum molding, foam molding, blow molding, and rotational molding. Examples of molded parts include injection molded parts, extrusion molded parts, blow molded parts, films, sheets, and fibers.

A molded product can be obtained by welding the molded parts thus obtained. Methods for welding the molded parts of the present invention include hot plate welding, infrared welding, vibration welding, laser welding, and infrared/vibration welding. Infrared/vibration welding is a welding method in which the welded part is heated with infrared rays and then vibration welding is performed. Among these, infrared welding, vibration welding, and infrared/vibration welding are preferred because they provide a better balance between tensile strength and tensile elongation at the welded part.

In the present invention, the above-mentioned various molded products can be used for various applications such as automobile parts, electrical and electronic parts, building parts, various containers, daily necessities, household goods, and sanitary products. In particular, the polyamide resin composition of the present invention has an excellent balance between tensile strength and tensile elongation at the welded parts, and is suitable as a high-pressure tank liner having a welded part, taking advantage of its property of being able to suppress the occurrence of cracks at the welded parts even when used in an environment where distortion is applied, and is particularly suitable as a high-pressure hydrogen tank liner.

The effects of the present invention will be explained in more detail below with reference to examples. Note that the present invention is not limited to the following examples. Evaluations of each example and comparative example were performed using the following methods.

(1) Tensile elongation of welded part Five test pieces, each 100 mm high and 10 mm wide, cut out from the molded product (thickness 3 mm) having a welded part obtained in each Example and Comparative Example so that the part joined by welding was the center in the height direction, were conditioned for 30 minutes under conditions of a temperature of 23°C and a humidity of 50%, and then the test pieces were set so that the welded part was the center of a tensile tester set to a chuck distance of 50 mm, and a tensile test was performed at a speed of 10 mm/min to evaluate the chuck distance at break. The average value measured for the five pieces was taken as the chuck distance at break. Using the measured chuck distance at break, the tensile elongation of the welded part was calculated according to the following formula.
Formula 1) x=100×(L-Lo)/Lo
x: Tensile elongation of welded part (%)
Lo: Distance between chucks before test (mm)
L: Distance between chucks at break (mm)

(2) Tensile strength of welded part Five test pieces, 100 mm high and 10 mm wide, were cut out from the molded products (thickness 3 mm) having welded parts obtained in each Example and Comparative Example so that the welded joint was at the center in the height direction. After conditioning for 30 minutes under conditions of a temperature of 23°C and a humidity of 50%, the test pieces were set so that the welded part was at the center of a tensile tester set to a chuck distance of 50 mm, and a tensile test was performed at a speed of 10 mm/min to evaluate the maximum strength until breakage. The average value measured for the five pieces was taken as the tensile strength of the welded part.

The raw materials and their abbreviations used in each of the Examples and Comparative Examples are shown below.
PA6: Polyamide 6 resin (melting point 223°C, relative viscosity 2.70 at 25°C in a 98% concentrated sulfuric acid solution with a resin concentration of 0.01 g/ml)
PA66: Polyamide 66 resin (melting point 265°C, relative viscosity 2.80 at 25°C in a 98% concentrated sulfuric acid solution with a resin concentration of 0.01 g/ml)
PA610: Polyamide 610 resin (melting point 226°C, relative viscosity 3.50 at 25°C in a 98% concentrated sulfuric acid solution with a resin concentration of 0.01 g/ml)
PA (MXD6): Polyamide MXD6 resin "Nylon T-600" (manufactured by Toyobo Co., Ltd.)
PA (6T/6): Polyamide 6T/6 resin "Ultramid" (registered trademark) T KR 4350 (manufactured by BASF, melting point 295°C)
Amide wax: Ethylenediamine-stearic acid-sebacic acid polycondensate "Light Amide WH-255" (manufactured by Kyoeisha Chemical Co., Ltd., melting point 255°C)
Impact-resistant material 1: Maleic anhydride-modified ethylene/1-butene copolymer "Tafmer" (registered trademark) MH7020 (manufactured by Mitsui Chemicals, Inc.)
Impact-resistant material 2: Glycidyl methacrylate-modified polyethylene copolymer "Bondfast" (registered trademark) 7L (manufactured by Sumitomo Chemical Co., Ltd.)
Impact-resistant material 3: Ionomer "Himilan" (registered trademark) 1706 (manufactured by DuPont)
Glass fiber: "T249H" (fiber diameter: 10.5 μm, fiber length: 3 mm, surface treated with a silane coupling agent) (manufactured by Nippon Electric Glass Co., Ltd.)
Glass flakes: "Micro Glass Flake REFG-101" (manufactured by Nippon Sheet Glass Co., Ltd.).

[Examples 1 to 4, 6 to 10, Comparative Examples 1 to 5]
Each of the raw materials shown in Tables 1 and 2 was melt-kneaded by feeding it to a twin-screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 240°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, and arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and the parallel faces were heated with infrared rays for 25 seconds, and then vibration was performed to melt the material to 2 mm to perform welding (infrared / vibration welding), and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are listed in Tables 1 and 2.

[Example 5]
Each of the raw materials shown in Table 1 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material supply port to the discharge port)) with a cylinder temperature set at 280°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 280 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, and arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and the parallel faces were heated with infrared rays for 25 seconds, and then vibration was performed to melt the material to 2 mm to perform welding (infrared / vibration welding), and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are listed in Table 1.

[Examples 11, 15 to 18]
Each of the raw materials shown in Table 1 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 240°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, and arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and the parallel faces were heated with infrared rays for 30 seconds, and then pressure was applied so that the penetration amount was 2 mm to perform welding (infrared welding), and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are listed in Table 1.

[Example 12]
Each of the raw materials shown in Table 1 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 240°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and vibration was performed to weld (vibration welding) so that the penetration amount was 2 mm, and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are listed in Table 1.

[Example 13]
Each of the raw materials shown in Table 1 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 240°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, and arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and the parallel faces were heated with a hot plate at a hot plate temperature of 280 ° C., and then pressure was applied so that the melt amount was 2 mm to perform welding (hot plate welding), and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are listed in Table 1.

[Example 14]
Each of the raw materials shown in Table 1 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 240°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thick on the laser beam transmission side was injection molded under the molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, and cooling time: 20 seconds using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. In addition, a material obtained by blending 0.4 parts by weight of carbon black with 100 parts by weight of the obtained pellets was used to injection mold a square plate molded product of 80 mm x 80 mm x 3 mm thick on the laser beam absorption side under the molding conditions of cylinder temperature: 240 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, and cooling time: 20 seconds. The obtained square plate molded product on the laser beam transmitting side and the square plate molded product on the laser beam absorbing side were arranged so that the 80 mm × 3 mm thick faces were facing each other and parallel to each other, and a laser beam was irradiated to the molded product so that the melting depth was 2 mm to perform welding (laser welding), thereby obtaining a molded product having a welded part. The results of evaluation of the obtained molded product by the above-mentioned method are shown in Table 1.

[Comparative Examples 6 and 7]
Each of the raw materials shown in Table 2 was melt-kneaded by feeding it to a twin screw extruder (TEX30α-35BW-7V manufactured by JSW) (L/D=45 (where L is the length from the raw material inlet to the discharge outlet)) with a cylinder temperature set at 300°C, a screw arrangement with two kneading zones, and a screw rotation speed of 200 rpm. The gut discharged from the die at a rate of 20 kg/h was quenched by passing it through a cooling bath filled with water adjusted to 10°C for 10 seconds, and then pelletized with a strand cutter to obtain pellets. The obtained pellets were vacuum-dried in a vacuum dryer at a temperature of 80°C for 12 hours to obtain pellets after drying. From the obtained pellets, a square plate molded product of 80 mm x 80 mm x 3 mm thickness was injection molded using an injection molding machine "SE75DUZ-C250" manufactured by Sumitomo Heavy Industries, Ltd. under molding conditions of cylinder temperature: 300 ° C., mold temperature: 80 ° C., injection speed: 40 mm / sec, holding pressure: 20 MPa, cooling time: 20 seconds. Two obtained square plate molded products were used, and arranged so that the 80 mm x 3 mm thick faces were facing each other and parallel, and the parallel faces were heated with infrared rays for 25 seconds, and then vibration was performed to melt the material to 2 mm to perform welding (infrared / vibration welding), and a molded product having a welded part was obtained. The results of evaluation by the above-mentioned method using the obtained molded product are shown in Table 2.

These results show that a molded article having a welded portion obtained by molding a polyamide resin composition obtained by blending polyamide resin (A), amide wax (B) and glass fiber (C) has an excellent balance between the tensile strength and tensile elongation of the welded portion.

Furthermore, it was found that a molded article having a welded portion obtained by molding a polyamide resin composition obtained by blending impact-resistant material (D) had superior tensile elongation.

The polyamide resin composition for welding of the present invention has an excellent balance between tensile strength and tensile elongation at the welded part, and can suppress the occurrence of cracks at the welded part even when used in an environment where distortion is applied, making it useful for development as a molded product with a welded part.

Claims (7)

A polyamide resin composition for welding, which is made by blending 3 to 9 parts by weight of glass fiber (C) with a total of 100 parts by weight of 90 to 99.99 parts by weight of polyamide resin (A) and 0.01 to 10 parts by weight of amide wax (B). The polyamide resin composition for welding according to claim 1, wherein the polyamide resin (A) is at least one selected from polyamide 6 resin, polyamide 610 resin, and polyamide 66 resin. The polyamide resin composition for welding according to claim 1 or 2 further comprises 1 to 50 parts by weight of an impact-resistant material (D) per 100 parts by weight of the total of the polyamide resin (A) and the amide wax (B). The polyamide resin composition for welding according to claim 3, wherein the impact resistant material (D) comprises an ethylene/α-olefin copolymer modified with an unsaturated carboxylic acid and/or its derivative. A molded article having a welded portion made of the polyamide resin composition according to any one of claims 1 to 4. A high-pressure tank liner having a welded portion made of the polyamide resin composition according to any one of claims 1 to 4. The method for manufacturing a molded product according to claim 5 or 6, wherein the welded portion is joined by any one of the welding methods selected from hot plate welding, infrared welding, vibration welding, laser welding, and infrared/vibration welding.