JP5263370B2 - Polyamide resin composition and polyamide resin foam molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide resin composition which can provide an expanded molding having excellent heat resistance, a satisfactorily light weight and high load resistance by a simple molding process. <P>SOLUTION: The polyamide resin composition contains a polyamide resin (A), a glycidyl group-containing styrene-based copolymer (B) containing at least two glycidyl groups per molecule, a weight-average molecular weight of 4,000-25,000 and an epoxy value of 400-2,500 equivalents/1&times;10<SP POS="POST">6</SP>g and an inorganic reinforcing material (C) at such a ratio that the content of the glycidyl group-containing styrene-based copolymer (B) is 0.2-25 pts.mass and the content of the inorganic reinforcing material (C) is 0-350 pts.mass relative to 100 pts.mass of the polyamide resin (A). <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a polyamide resin composition capable of giving a foamed molded article having a light weight and high load resistance without damaging the heat resistance of the polyamide resin by a simple molding method, and a polyamide resin foamed molded article using the same. .

  As a method for producing a polyamide resin foam molded article, a method using a chemical foaming agent is generally known. The chemical foaming method is a method in which foaming molding is performed by mixing a raw material resin and an organic foaming agent that decomposes by heating to generate a gas, and heating it to a temperature equal to or higher than the decomposition temperature of the foaming agent. For example, in Patent Document 1, a polyamide terpolymer is used, and a polyamide foam molded article having a specific gravity of 1.2 is obtained by a chemical foaming agent. However, this polyamide foam has a low expansion ratio and cannot fully satisfy weight reduction.

  In addition, as a method for producing a polyamide resin foam molded article other than a method using a chemical foaming agent, Patent Document 2 discloses that a polyamide molded article is made to absorb a carbon dioxide in advance and heated in a post-process to obtain a polyamide with a double expansion ratio. A method for obtaining a foamed molded article has been proposed. However, the polyamide foam molded body obtained by this method is still not sufficiently lightweight, and the molding process and the foaming process are substantially separate processes, which is complicated and poor in productivity. There are drawbacks.

  Further, Patent Document 3 discloses a method for producing a foamed polyamide molded body in which a supercritical fluid of nitrogen or carbon dioxide is dissolved in a molten resin and injection molded. However, this method also has a low expansion ratio of 1.25, and it has not been possible to realize a sufficient weight reduction.

  On the other hand, Patent Document 4 discloses a method of obtaining a foamed molded article having a fine average cell diameter using polystyrene resin, but in order to obtain a desired foamed molded article, in addition to a general injection molding machine. In addition, a special injection plunger and a special injection device are separately required, and there is a drawback that it lacks versatility. In addition, the foam molded articles reported in the literature are only those using polystyrene resins that are relatively easy to foam even in existing foam molding methods, and this method was applied to polyamide resins that are difficult to foam. However, the actual situation is that a desired foamed molded article cannot be easily obtained.

  Further, in Patent Document 5, when the molten resin filled in the mold becomes a certain viscoelastic state during the cooling process, the core side mold is moved in the mold opening direction and the resin in the mold is inactive in a critical state. A method for obtaining a foamed molded article by directly injecting gas has been proposed. However, in this method, it is difficult to form uniform foamed cells because the crystalline polyamide having a high solidification rate has a short time for maintaining an appropriate viscoelastic state.

JP 2009-249549 A JP 2006-35687 A JP 2005-126545 A JP 2006-69215 A JP 2006-212945 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide a polyamide resin composition that can provide a foamed molded article having excellent heat resistance and sufficiently light weight and high load resistance by a simple molding method, An object of the present invention is to provide a polyamide resin foam molded article using the same.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor aims to control the solidification rate of the polyamide resin and increase the effect of mitigating deformation in the linear-nonlinear region at the time of melting. It was found that a specific glycidyl group-containing styrene copolymer may be contained in a predetermined ratio together with the polyamide resin. If a polyamide resin composition containing such a specific glycidyl group-containing styrenic copolymer is used as a raw material for injection molding, a foam molded article having excellent heat resistance, sufficiently light weight and high load resistance can be obtained. It was confirmed. Furthermore, when manufacturing a foaming molding, it also discovered that if the process of extending a metal mold | die immediately after injection molding is applied, lightness and load resistance can be improved more. The present invention has been completed based on these findings.

  That is, the present invention has the following configuration.

(1) Polyamide resin (A) and glycidyl group containing 2 or more glycidyl groups per molecule, having a weight average molecular weight of 4000 to 25000, and having an epoxy value of 400 to 2500 equivalents / 1 × 10 ⁶ g The glycidyl group-containing styrene copolymer (B) is 0.2 to 25 with respect to 100 parts by mass of the polyamide resin (A) and the styrene copolymer (B) and the inorganic reinforcing material (C). A polyamide resin composition comprising a mass part and the inorganic reinforcing material (C) in a proportion of 0 to 350 parts by mass.

  (2) The polyamide resin (A) comprises a crystalline polyamide resin (a) and an amorphous polyamide resin (b), and the ratio is (a) :( b) = 0-100: 100-0 (mass) The polyamide resin composition as described in (1) above.

  (3) The glycidyl group-containing styrene copolymer (B) is (X) 20 to 99% by mass of vinyl aromatic monomer, (Y) 1 to 80% by mass of glycidyl alkyl (meth) acrylate, and (Z). The polyamide resin composition according to (1) or (2), wherein the polyamide resin composition is a copolymer composed of a vinyl group-containing monomer other than (X) and not containing 0 to 79% by mass of an epoxy group.

(4) Plotting storage elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in the frequency range of 10 to 100 rad / s in a logarithmic graph of frequency (x) and storage elastic modulus (y) The loss modulus (unit: Pa) obtained by melt viscoelasticity measurement in the frequency range of 10 to 100 rad / s in the linear region, where ^{α is} a multiplier (y = ax ^α ; where a is a constant), Polyamide resin (A) and glycidyl, where β is a multiplier (y ′ = bx ′ ^β ; where b is a constant) when plotted on a log-log graph of frequency (x ′) and loss modulus (y ′) Any of (1) to (3) above, wherein α of the matrix composition comprising the group-containing styrene-based copolymer (B) is less than 1.4 and the absolute value of α-β is 0.5 or less. The polyamide resin composition described in 1.

  (5) A polyamide resin foam molded article obtained by using the polyamide resin composition according to any one of (1) to (4).

  (6) A foamed layer composed of a resin continuous phase and independent foamed cells having an average cell diameter of 10 to 300 μm, and a non-foamed skin layer having a thickness of 100 to 800 μm laminated on the foamed layer are formed by the polyamide resin composition. The polyamide resin foamed molded article according to (5), which is formed and has a specific gravity of 0.2 to 1.0.

  (7) The polyamide resin foam molded article according to (6), which has a sandwich structure in which the non-foamed skin layer is provided on both surfaces of the foamed layer.

  (8) The polyamide resin composition in a molten state is injected and filled together with a chemical foaming agent and / or an inert gas in a supercritical state into a cavity formed by a plurality of molds clamped, and the surface layer has a thickness of 100. The method according to any one of (5) to (7), which is obtained by moving at least one mold in the mold opening direction to enlarge the volume of the cavity when a non-foamed skin layer of ˜800 μm is formed. Polyamide resin foam molding.

  According to the present invention, there is provided a polyamide resin composition capable of giving a foam molded article having excellent heat resistance, sufficiently light weight and high load resistance by a simple molding method, and a polyamide resin foam molded article using the same. can do. Such a polyamide resin foam molding has a uniform and high foaming ratio, and has both excellent lightness and load resistance. Therefore, it is a resin having high required characteristics in applications such as automobile parts and home appliance parts. It can be suitably used as a functional part or a design part that requires functionality.

FIG. 1 is a cross-sectional photograph of a polyamide resin foam molded article according to one embodiment (Example 27) of the present invention. FIG. 2 is a cross-sectional photograph of the polyamide resin foam molded article of Comparative Example 9. FIG. 3 is a schematic configuration diagram for explaining an example of a method for producing a polyamide resin foam molded article of the present invention. FIG. 4 is a graph of frequency-dependent data of storage elastic modulus and loss elastic modulus obtained by melt viscoelasticity measurement of the matrix composition in Example 4. FIG. 5 is a graph of frequency-dependent data of storage elastic modulus and loss elastic modulus obtained by melt viscoelasticity measurement of the matrix composition in Comparative Example 1.

  Hereinafter, the polyamide resin composition of the present invention and the foamed molded article using the same will be described in detail.

(Polyamide resin composition)
The polyamide resin composition of the present invention contains a polyamide resin (A), a specific glycidyl group-containing styrene copolymer (B), and an inorganic reinforcing material (C) as necessary.

  The polyamide resin (A) used in the present invention is a raw material of lactam, ω-aminocarboxylic acid, dicarboxylic acid, diamine, etc., and a polyamide resin obtained by polycondensation of such an amine component and an acid component, Or these copolymers and blends.

  Specifically, as the amine component constituting the polyamide resin (A), for example, 1,2-ethylenediamine, 1,3-trimethylenediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 2-methyl-1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 2-methyl-1, 8-octamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,16-hexadecamethylenediamine, 1 , 18-octadecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexa Aliphatic diamines such as tylenediamine; alicyclic diamines such as piperazine, cyclohexanediamine, bis (3-methyl-4-aminohexyl) methane, bis- (4,4′-aminocyclohexyl) methane, isophoronediamine; And aromatic diamines such as metaxylylenediamine, paraxylylenediamine, paraphenylenediamine and metaphenylenediamine, and hydrogenated products thereof.

  Examples of the acid component constituting the polyamide resin (A) include polyvalent carboxylic acids and acid anhydrides. Examples of the polyvalent carboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 2,2′-diphenyl. Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 5-sulfonic acid sodium isophthalic acid, 5-hydroxyisophthalic acid; fumaric acid, maleic acid, succinic acid, itaconic acid, adipic acid, azelaic acid, Sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,18-octadecanedioic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohex Njikarubon acids, aliphatic and alicyclic dicarboxylic acids such as dimer acid; and the like.

  In addition, as a component constituting the polyamide resin (A), lactams such as ε-caprolactam and aminocarboxylic acid, undecane lactam, or lauryl lactam, which is a ring-opened structure thereof, and a structure in which these are ring-opened 11- Examples also include aminoundecanoic acid and 12-aminododecanoic acid. Polyamide resins (A) polymerized from these components include polycaproamide (nylon 6), polyundecamide (nylon 11), polylauramide (nylon 12), polytetramethylene adipamide (nylon 46), polyhexamethylene azide. Pamide (nylon 66), polyundecamethylene adipamide (nylon 116), polymetaxylylene adipamide (nylon MXD6), polyparaxylylene adipamide (nylon PXD6), polytetramethylene sebacamide (nylon) 410), polyhexamethylene sebamide (nylon 610), polydecamethylene adipamide (nylon 106), polydecamethylene sebamide (nylon 1010), polyhexamethylene dodecamide (nylon 612), polydecamethylene dodeca Mid (Nai 1012), polyhexamethylene isophthalamide (nylon 6I), polytetramethylene terephthalamide (nylon 4T), polypentamethylene terephthalamide (nylon 5T), poly-2-methylpentamethylene terephthalamide (nylon M-5T), Polyhexamethylene terephthalamide (nylon 6T), polyhexamethylene hexahydroterephthalamide (nylon 6T (H)), polynonamethylene terephthalamide (nylon 9T), polyundecamethylene terephthalamide (nylon 11T), polydodecamethylene terephthalate Amide (nylon 12T), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide (nylon 6T6I), polybis (3-methyl-4-aminohexyl) methane tele Talamide (nylon PACMT), polybis (3-methyl-4-aminohexyl) methane isophthalamide (nylon PACM • I), polybis (3-methyl-4-aminohexyl) methane dodecamide (nylon PACM12), polybis (3- In addition to polyamides such as methyl-4-aminohexyl) methane tetradecamide (nylon PACM 14), copolymers of these polyamide groups and / or blend compositions thereof may be mentioned.

  The polyamide resin (A) is a blend of a crystalline polyamide resin (a) that is rapidly crystallized and an amorphous polyamide resin (b) that has the effect of reducing the crystallization speed of the crystalline polyamide resin (a). It is preferable to control the crystallization rate. Examples of the crystalline polyamide resin (a) include, but are not limited to, crystalline aliphatic polyamides such as nylon 6, nylon 66, and nylon 46. As the non-crystalline polyamide resin (b), a polyamide having high compatibility with the crystalline polyamide resin (a) is preferable. From this viewpoint, for example, nylon 6T6I, nylon PACM14, nylon PACM12, nylon PACM12 · I, etc. preferable. The effect of lowering the crystallization rate can be evaluated by the crystallization temperature (Tc2) when the DSC is lowered, and the polyamide resin (A) is preferably 200 ° C. or lower, more preferably 190 ° C. or lower.

  When the polyamide resin (A) is a blend composition of the crystalline polyamide resin (a) and the amorphous polyamide resin (b), the DSC melting point of at least one resin is 150 ° C. or higher and 350 ° C. or lower from the viewpoint of heat resistance. It is preferable that If the melting point is less than 150 ° C., the heat resistance tends to be insufficient. If the melting point exceeds 350 ° C., there is a high possibility of decomposition in the molding process, making it difficult to obtain good moldability and a stable foamed molded product. . Examples of the resin having such a melting point include polycaproamide (nylon 6), polyundecamide (nylon 11), polylauramide (nylon 12), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46). ) Is included.

  When the main component of the polyamide resin (A) (80% by mass or more of all the polyamide resins (A)) is the amorphous polyamide resin (b), the glass transition temperature is 120 ° C. or more and 200 ° C. or less. Amorphous polyamide is preferred. If the glass transition temperature is less than 120 ° C, the heat resistance may be insufficient. If the glass transition point exceeds 200 ° C, the solidification temperature is too high, so that the foaming method for expanding the mold described later is difficult to apply. Become.

  When the polyamide resin (A) has a blend composition of the crystalline polyamide resin (a) and the amorphous polyamide resin (b), the ratio between the two is as follows: crystalline polyamide resin (a): amorphous polyamide resin (b ) = 0-100: 100-0 (mass ratio), preferably crystalline polyamide resin (a): amorphous polyamide resin (b) = 97: 3-50: 50, more preferably 95 : 5 to 50:50.

  The relative viscosity (RV) measured at 20 ° C. in 96% concentrated sulfuric acid of the polyamide resin (A) is preferably 0.4 to 4.0, more preferably 1.0 to 3.5, still more preferably 1.5. ~ 3.0. Examples of a method for setting the relative viscosity of the polyamide within a certain range include a means for adjusting the molecular weight. In addition, all the relative viscosities (RV) described in the present specification are measured at 96C in 96% concentrated sulfuric acid.

  The polyamide resin (A) can adjust the amount of end groups and the molecular weight of the polyamide by a method of polycondensation by adjusting the molar ratio of amino groups to carboxyl groups or a method of adding a terminal blocking agent. When polycondensation is performed at a constant ratio of amino groups to carboxyl groups, the molar ratio of all diamines to all dicarboxylic acids used is diamine / dicarboxylic acid = 1.00 / 1.05 to 1.10 / 1. It is preferable to adjust to a range of 0.00.

  When the end of the polyamide resin (A) is blocked, the timing for adding the end-capping agent may be at the time of raw material charging, at the start of polymerization, at the end of polymerization, or at the end of polymerization. The end capping agent is not particularly limited as long as it is a monofunctional compound having reactivity with the amino group or carboxyl group at the end of the polyamide, but monocarboxylic acid, monoamine, acid anhydride (phthalic anhydride, etc.) , Monoisocyanates, monoacid halides, monoesters, monoalcohols, and the like can be used. Specifically, as the end-capping agent, for example, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, isobutyric acid Aliphatic monocarboxylic acids such as cycloaliphatic carboxylic acids; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid Carboxylic acid; acid anhydrides such as maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride; methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine , Aliphatic compounds such as dibutylamine And alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine and naphthylamine;

The acid value and amine value of the polyamide resin (A) are both preferably 0 to 200 equivalents / 1 × 10 ⁶ g, more preferably 0 to 100 equivalents / 1 × 10 ⁶ g. When terminal functional groups is more than 200 equivalents / 1 × 10 ⁶ g, not only the gelation and degradation tends to occur during melt retention, even under the use environment, there is a fear of causing coloration and hydrolysis such problems. In particular, when a reactive compound such as glass fiber or maleic acid-modified polyolefin is compounded, the acid value and / or amine value may be 5 to 100 equivalents / 1 × 10 ⁶ g in accordance with the reactivity and the reactive group. preferable.

  Although the molecular weight of a polyamide resin (A) is not specifically limited, It is preferable that the number average molecular weights measured with the method as described in the Example mentioned later are the range of 3000-40000. If the number average molecular weight is less than 3000, the mechanical strength is lowered. Conversely, if the number average molecular weight is more than 40000, the molecular weight becomes too high and the moldability may be impaired.

  Examples of the glycidyl group-containing styrene copolymer (B) used in the present invention include (X) vinyl aromatic monomer, (Y) glycidyl alkyl (meth) acrylate, and (Z) epoxy group as required. It is possible to use those obtained by polymerizing a monomer mixture containing a vinyl group-containing monomer other than the above (X) that does not contain (hereinafter referred to as “other vinyl group-containing monomer”). In the present invention, by including the glycidyl group-containing styrenic copolymer (B), by increasing the molecular weight and exhibiting the effect of increasing the melt elongation viscosity, the processing condition control range is expanded, and as a result, the heat resistance is increased. The intended purpose of obtaining a foamed molded article having excellent light weight and load resistance can be achieved.

  Examples of the (X) vinyl aromatic monomer include styrene and α-methylstyrene. Examples of (Y) glycidyl alkyl (meth) acrylate include (meth) acrylic acid glycidyl, (meth) acrylic acid ester having a cyclohexene oxide structure, (meth) acrylic glycidyl ether, and the like. (Meth) acrylic acid glycidyl is preferable at a high point. (Z) Other vinyl group-containing monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( (Meth) acrylic acid having an alkyl group having 1 to 22 carbon atoms such as cyclohexyl (meth) acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, etc. (the alkyl group may be linear or branched) Alkyl ester, (meth) acrylic acid polyalkylene glycol ester, (meth) acrylic acid alkoxyalkyl ester, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylic acid dialkylaminoalkyl ester, (meth) acrylic acid benzyl ester, ( Meth) acrylic acid phenoxyalkyl ester Ether, (meth) acrylic acid isobornyl ester, and (meth) acrylic acid alkoxysilyl alkyl ester. Also, (meth) acrylamide, (meth) acrylic dialkylamide, vinyl esters such as vinyl acetate, vinyl ethers, aromatic vinyl monomers such as (meth) allyl ethers, and α-olefin monomers such as ethylene and propylene Can also be used as other vinyl group-containing monomers.

  The glycidyl group-containing styrenic copolymer (B) is a glycidyl group-containing styrenic copolymer (B) in which (X) 20 to 99 mass% vinyl aromatic monomer, (Y) 1 to 80 mass% glycidyl. It is preferably a copolymer comprising alkyl (meth) acrylate and (Z) 0 to 79% by mass of other vinyl group-containing monomers. More preferably, the copolymer (X) is 20 to 99% by mass, (Y) is 1 to 80% by mass, and (Z) is 0 to 40% by mass, and more preferably (X) is 25 to 90%. It is a copolymer comprising 10% by mass, (Y) 10 to 75% by mass, and (Z) 0 to 35% by mass. Since these compositions affect the functional group concentration contributing to the reaction with the polyamide resin (A), it is preferable to appropriately control the composition within the above range.

  Specific examples of the glycidyl group-containing styrene copolymer (B) include, for example, styrene / methyl methacrylate / glycidyl methacrylate copolymer, bisphenol A type, cresol novolac, phenol novolac type epoxy compounds, and the like. Of course, the glycidyl group-containing styrenic copolymer (B) may be used alone or in a mixture of two or more.

  It is important that the glycidyl group-containing styrene copolymer (B) contains two or more glycidyl groups per molecule as a functional group capable of reacting with the amino group or carboxyl group of the polyamide resin (A). As a result, it is possible to quickly introduce a partial cross-link into the entire resin, and the reaction between the amino group or carboxyl group of the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B) during melt extrusion. A part becomes a cross-linked product, and an effect of improving the melt extensional viscosity can be obtained. In addition, the glycidyl group in a glycidyl group containing styrene-type copolymer (B) may exist in any of the principal chain of a polymer, a side chain, and the terminal, for example.

  In order to control the glycidyl group-containing styrenic copolymer (B) so that the melt extensional viscosity can be adjusted, it is important that the weight average molecular weight is 4000 to 25000. A weight average molecular weight becomes like this. Preferably it is 5000-15000, More preferably, it is 6000-10000. When the weight average molecular weight of the glycidyl group-containing styrene copolymer (B) is less than 4000, the unreacted glycidyl group-containing styrene copolymer (B) is volatilized in the molding process or bleeds out on the surface of the molded product. In addition, the adhesiveness of the product may be reduced and the surface may be contaminated. Further, burnt dust is generated due to an excessive reaction between the glycidyl group-containing styrene copolymers (B), leading to a decrease in productivity during kneading and a decrease in quality of the final product. On the other hand, when the weight average molecular weight of the glycidyl group-containing styrene copolymer (B) exceeds 25,000, not only the reaction during kneading extrusion is delayed and the effect of maintaining the molecular weight is lowered, but also the glycidyl group-containing styrene copolymer. Since the compatibility between (B) and the polyamide resin (A) is deteriorated, the possibility that the durability such as heat resistance inherent in the polyamide resin (A) is lowered is increased.

It is important that the epoxy value of the glycidyl group-containing styrene-based copolymer (B) is 400 to 2500 equivalents / 1 × 10 ⁶ g. Preferably it is 500-1500 equivalent / 1x10 < ⁶ > g, More preferably, it is 600-1000 equivalent / 1x10 < ⁶ > g. If the epoxy value is less than 400 equivalents / 1 × 10 ⁶ g, the target rheology control effect may not be exhibited. If the epoxy value exceeds 2500 equivalents / 1 × 10 ⁶ g, the thickening effect becomes excessive and the moldability is increased. May be adversely affected.

  Content of a glycidyl group containing styrene-type copolymer (B) is 0.2-25 mass parts with respect to 100 mass parts of polyamide resins (A). Preferably it is 0.2-15 mass parts, More preferably, it is 0.3-12 mass parts. If the amount is less than 0.2 parts by mass, it may be difficult to achieve the targeted rheological control effect. If the amount exceeds 25 parts by mass, the thickening effect becomes excessive and adversely affects the moldability. There is a tendency to affect the mechanical properties.

  The inorganic reinforcing material (C) used in the present invention is the one that most effectively improves physical properties such as strength, rigidity, and heat resistance. Specifically, glass fiber, carbon fiber, aramid fiber, alumina fiber, Examples thereof include fibrous materials such as silicon carbide fibers and zirconia fibers, whiskers such as aluminum borate and potassium titanate, acicular wollastonite, and milled fibers. Besides these, glass beads, glass flakes, glass balloons, silica, talc, kaolin, wollastonite, mica, alumina, hydrotalcite, montmorillonite, graphite, carbon nanotubes, fullerenes, zinc oxide, indium oxide, tin oxide, Iron oxide, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, red phosphorus, calcium carbonate, potassium titanate, lead zirconate titanate, barium titanate, aluminum nitride, boron nitride, zinc borate, aluminum borate Further, fillers such as barium sulfate, magnesium sulfate, and layered silicate subjected to organic treatment for delamination can also be used as the inorganic reinforcing material (C). Among these, glass fiber, carbon fiber and the like are preferably used. These inorganic reinforcing materials (C) may be used alone or in combination of two or more.

  For example, as a glass fiber, the chopped strand shape cut | disconnected by the fiber length about 1-20 mm can be used preferably. As the cross-sectional shape of the glass fiber, a glass fiber having a circular cross section or a non-circular cross section can be used. Non-circular cross-section glass fibers include those that are substantially oval, substantially oval, and substantially bowl-shaped in a cross section perpendicular to the length direction of the fiber length, in which case the flatness is 1.5 to 8 is preferable. Here, the flatness is assumed to be a rectangle with the smallest area circumscribing a cross section perpendicular to the longitudinal direction of the glass fiber, the length of the long side of the rectangle is the major axis, and the length of the short side is the minor axis. It is the ratio of major axis / minor axis. The thickness of the glass fiber is not particularly limited, but the minor axis is about 1 to 20 μm and the major axis is about 2 to 100 μm.

  In order to improve the affinity with the polyamide resin (A), the inorganic reinforcing material (C) is pretreated with a coupling agent such as an organic silane compound, an organic titanium compound, an organic borane compound, or an epoxy compound. And those that easily react with carboxylic acid groups and / or carboxylic acid anhydride groups are particularly preferable. As the coupling agent, any of a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and the like may be used. Among them, aminosilane coupling agents, epoxy silane coupling agents and the like are particularly preferable. Silane coupling agents are preferred. For example, a polyamide resin composition containing glass fibers treated with a coupling agent is preferable because a molded product having excellent mechanical characteristics and appearance characteristics can be obtained. In addition, although it is preferable to perform the process by a coupling agent beforehand, a coupling agent can also be added after use and used.

  Content of an inorganic reinforcement material (C) is 0-350 mass parts with respect to 100 mass parts of polyamide resins (A). Preferably it is 0-150 mass parts, More preferably, it is 0-120 mass parts. When the inorganic reinforcing material (C) exceeds 350 parts by mass, the elongation of the molten resin at the time of foaming becomes low, and adjacent cells are easily bonded and coarsened.

  In the present invention, the content ratios of the polyamide resin (A), the glycidyl group-containing styrene copolymer (B) and the inorganic reinforcing material (C) are the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B). And the total amount of the inorganic reinforcing material (C) is 100% by mass, the polyamide resin (A) is 30 to 99% by mass, the glycidyl group-containing styrene copolymer (B) is 0.2 to 10% by mass, and the inorganic reinforcement It is preferable that a material (C) is 0-65 mass%. More preferably, the polyamide resin (A) is 40 to 95% by mass, the glycidyl group-containing styrene copolymer (B) is 0.5 to 10% by mass, and the inorganic reinforcing material (C) is 0 to 55% by mass. . More preferably, the polyamide resin (A) is 50 to 90% by mass, the glycidyl group-containing styrene copolymer (B) is 1.2 to 10% by mass, and the inorganic reinforcing material (C) is 0 to 45% by mass. Particularly, the polyamide resin (A) is preferably 60% by mass or more. By including the polyamide resin (A), the glycidyl group-containing styrene copolymer (B) and the inorganic reinforcing material (C) at the above-mentioned ratios, the effect of the targeted rheology control can be expressed more effectively. Thus, it is possible to obtain a foamed molded article having excellent heat resistance and light weight and load resistance.

  The polyamide resin composition of the present invention can contain various additives conventionally used in polyamide resins in addition to the above-mentioned ones. Examples of additives include stabilizers, impact modifiers, flame retardants, mold release agents, slidability improvers, colorants, plasticizers, crystal nucleating agents, and the like. In addition, a hydrotalcite-based compound can be used as an additive for the purpose of preventing metal corrosion of a mold or the like. Only one type of additive may be used, or two or more types of additives may be used.

  As stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, phosphite compounds, thioether compounds, heat stabilizers, hindered amines, benzophenones, Examples include imidazole-based light stabilizers, ultraviolet absorbers, metal deactivators, and the like. In addition, as one of the heat stabilizers, copper compounds (specifically, cuprous chloride, cuprous bromide, cuprous iodide, cupric chloride, cupric bromide, cupric iodide) , Copper salts of organic carboxylic acids such as cupric phosphate, cupric pyrophosphate, copper sulfide, copper nitrate, and copper acetate) can prevent long-term heat aging that is effective in a high-temperature environment of 120 ° C or higher. Useful. Furthermore, this copper compound is preferably used in combination with an alkali metal halide compound. Examples of the alkali metal halide compound include lithium chloride, lithium bromide, lithium iodide, sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium fluoride, potassium chloride, potassium bromide, potassium iodide and the like. Can be mentioned. When the stabilizer is contained, the content is preferably 0 to 5 parts by mass with respect to 100 parts by mass of the polyamide resin (A). In particular, when the stabilizer is a copper compound, the amount is preferably 0.005 to 0.5 parts by mass, more preferably 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the polyamide resin (A).

  Although it does not restrict | limit especially as a flame retardant, For example, the combination of a halogenated flame retardant and an antimony compound is preferable. Examples of halogen flame retardants include brominated polystyrene, brominated polyphenylene ether, brominated bisphenol type epoxy polymer, brominated styrene maleic anhydride polymer, brominated epoxy resin, brominated phenoxy resin, decabromodiphenyl ether, decabromo. Biphenyl, brominated polycarbonate, perchlorocyclopentadecane, brominated cross-linked aromatic polymer and the like are preferable, and as the antimony compound, antimony trioxide, antimony pentoxide, sodium antimonate and the like are preferable. Among them, a combination of dibromopolystyrene and antimony trioxide is preferable from the viewpoint of thermal stability. Non-halogen flame retardants can also be used as the flame retardant, and specific examples include melamine cyanurate, red phosphorus, phosphinic acid metal salts, nitrogen-containing phosphoric acid compounds, and the like. In particular, a combination of a phosphinic acid metal salt and a nitrogen-containing phosphate compound (including, for example, melamine, a condensate of melamine such as melam and melon and a reaction product of polyphosphoric acid or a mixture thereof) is preferable. When the flame retardant is contained, the content is preferably 0 to 50 parts by mass, more preferably 0 to 40 parts by mass, and still more preferably 0 to 30 parts by mass with respect to 100 parts by mass of the polyamide resin (A). Part.

  Examples of the release agent include long chain fatty acids or esters thereof, metal salts, amide compounds, polyethylene wax, silicon, polyethylene oxide, and the like. As long-chain fatty acids, those having 12 or more carbon atoms are particularly preferable, and examples thereof include stearic acid, 12-hydroxystearic acid, behenic acid, and montanic acid. These include partially or fully carboxylic acids such as monoglycol and polyglycol. May be esterified or may form a metal salt. Examples of the amide compound include ethylene bisterephthalamide and methylene bisstearyl amide. Only one type of release agent may be used, or two or more types may be used. When it contains a mold release agent, it is preferable that the content shall be 0-5 mass parts with respect to 100 mass parts of polyamide resins (A).

  Examples of the sliding property improving material include high molecular weight polyethylene, acid-modified high molecular weight polyethylene, fluorine resin powder, molybdenum disulfide, silicon resin, silicon oil, zinc, graphite, mineral oil, and the like. When the slidability improving material is contained, the content thereof is preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the polyamide resin (A).

  The polyamide resin composition of the present invention includes an olefin having a carboxylic acid group and / or a carboxylic acid anhydride group for the purpose of increasing the reaction efficiency of the glycidyl group-containing styrene copolymer (B) and improving impact resistance. A base polymer (modified polyolefin) may be contained. This modified polyolefin is an α-olefin (co) polymer in which a monomer having a carboxylic acid group and / or a carboxylic anhydride group is contained in the molecular chain of the unmodified polyolefin by copolymerization or graft polymerization. .

  Examples of the unmodified polyolefin that can be used for obtaining the above-mentioned olefin polymer include homopolymers such as polyethylene, polypropylene, polybutene-1, polypentene-1, polymethylpentene, ethylene, propylene, butene-1, Α-olefins such as pentene-1, 4-methylpentene-1, hexene-1, octene-1, isobutylene, 1,4-hexadiene dicyclopentadiene, 2,5-norbornadiene, 5-ethylidene norbornene, 5-ethyl- Obtained by radical polymerization of at least one nonconjugated diene such as 2,5-norbornadiene and 5- (1′-propenyl) -2-norbornene using a normal metal catalyst or a metallocene high-performance catalyst. Mention may be made of polyolefins. Specific examples include ethylene / propylene copolymer, ethylene / butene-1 copolymer, ethylene / hexene-1 copolymer, ethylene / propylene / dicyclopentadiene copolymer, ethylene / propylene / 5-ethylidene-2. -Norbornene copolymer, unhydrogenated or hydrogenated polybutadiene, unhydrogenated or hydrogenated styrene / isoprene / styrene triblock copolymer, unhydrogenated or hydrogenated styrene / butadiene / styrene triblock copolymer, etc. It is done. Among these, the diene elastomer is an AB type or ABA ′ type block copolymer elastic body composed of a vinyl aromatic hydrocarbon and a conjugated diene, and the end blocks A and A ′ are the same. Or thermoplastic homopolymers or copolymers derived from vinyl aromatic hydrocarbons, which may be different and the aromatic moiety may be monocyclic or polycyclic, examples of such vinyl aromatic hydrocarbons. Examples thereof include styrene, α-methylstyrene, vinyl toluene, vinyl xylene, ethyl vinyl xylene, vinyl naphthalene, and mixtures thereof. The intermediate polymer block B is composed of a conjugated diene hydrocarbon, and examples thereof include polymers derived from 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, and mixtures thereof. In addition, it is also possible to use a block copolymer obtained by subjecting the intermediate polymer block B to a hydrogenation treatment.

  The method for introducing a carboxylic acid group and / or a carboxylic acid anhydride group into an unmodified polyolefin is not particularly limited, and it is possible to use a method such as copolymerization or graft introduction into an unmodified polyolefin using a radical initiator. it can. In the case of copolymerization, the introduction amount of these functional group-containing components is in the range of 0.1 to 20 mol%, preferably 0.5 to 12 mol%, based on the entire olefin monomer in the modified polyolefin, In the case of grafting, the content is in the range of 0.1 to 10% by mass, preferably 0.5 to 6% by mass based on the mass of the modified polyolefin. If the introduction amount of the functional group-containing component is too small, the reaction promoting effect of the glycidyl group-containing styrene copolymer (B) may not be sufficiently obtained or the impact resistance may not be sufficiently imparted. If it is too high, the stability of the melt viscosity may be impaired.

  Specific examples of the olefin polymer (modified polyolefin) having a carboxylic acid group and / or a carboxylic acid anhydride group include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, ethylene / acrylic acid copolymer, ethylene / methacrylic acid. Acid copolymers, and some or all of the carboxylic acid moieties in these copolymers as salts with sodium, lithium, potassium, zinc, calcium, ethylene / methyl acrylate copolymers, ethylene / acrylic acid Ethyl copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl methacrylate copolymer, ethylene / ethyl acrylate-g-maleic anhydride copolymer (where “-g-” represents graft ( The same shall apply hereinafter)), ethylene / methyl methacrylate-g-maleic anhydride 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 Examples thereof include hydrogenated styrene / isoprene / styrene-g-maleic anhydride copolymer. Among these, a (co) polymer having a carboxylic acid anhydride group having high reactivity with an amine is preferable.

  The polyamide resin composition of the present invention may contain a thermoplastic resin other than the polyamide resin (A) as long as the effects of the present invention are not impaired. Examples of the thermoplastic resin other than the polyamide resin (A) include polyphenylene sulfide (PPS), liquid crystal polymer (LCP), aramid resin, polyether ether ketone (PEEK), polyether ketone (PEK), and polyether imide. (PEI), thermoplastic polyimide, polyamideimide (PAI), polyether ketone ketone (PEKK), polyphenylene ether (PPE), polyethersulfone (PES), polysulfone (PSU), polyarylate (PAR), polyethylene terephthalate, poly Butylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate (PC), polyoxymethylene (POM), polypropylene (PP), polyethylene (PE), polymethylpentene TPX), polystyrene (PS), polymethyl methacrylate, acrylonitrile - styrene copolymer (AS), acrylonitrile - butadiene - styrene copolymer (ABS) and the like. If the compatibility between these other thermoplastic resins and the polyamide resin (A) is low, a compatibilizing agent such as a reactive compound or a block polymer may be added or other thermoplastic resins may be modified as necessary. (Especially acid modification is preferable). The other thermoplastic resin may be blended in a melted state by melt kneading with the polyamide resin (A), or the other thermoplastic resin is formed into a fiber shape or a particle shape, and is added to the polyamide resin (A). It may be dispersed. When other thermoplastic resins are contained, the content thereof is preferably 0 to 50 parts by mass, more preferably 0 to 35 parts by mass, and still more preferably 0 with respect to 100 parts by mass of the polyamide resin (A). ˜20 parts by mass.

  In the polyamide resin composition of the present invention, a compound or polymer having a substituent that reacts with the amino group or carboxyl group of the polyamide resin (A) is used as any of the optional components described above. Such reactive substituents may be introduced to increase the degree of crosslinking. Examples of the reactive substituent include functional groups such as a glycidyl group, a carboxyl group, a carboxylic acid metal salt, an ester group, a hydroxyl group, an amino group, and a carbodiimide group, and a polyester terminal such as a lactone, lactide, and lactam, and a ring opening. Examples thereof include functional groups that can be added, and among these, a glycidyl group or a carbodiimide group is preferred from the viewpoint of the speed of the reaction. There may be only one kind of such a substituent, or two or more kinds, and it may have different kinds of functional groups in one molecule. In addition, when a reactive substituent is introduced, the introduction amount is preferably set in a range in which gel or the like does not occur due to advanced crosslinking.

  In the polyamide resin composition of the present invention, a relatively loose cross-linked or branched structure that does not reach a gel is generated by the reaction of the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B). For this reason, the entanglement effect of molecules can be increased in the molten state of the polyamide resin composition. This reaction product is considered not only to increase the melt viscosity but also to exhibit the effect of slowing the relaxation behavior in a wide shear rate region as a long-term relaxation component when strained in the molten state.

Multiplier when storage elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in the frequency range of 10 to 100 rad / s in the linear region is plotted on a logarithmic graph of frequency (x) and storage elastic modulus (y). (Y = ax ^α ; where a is a constant) α, and loss elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in the frequency range of 10 to 100 rad / s in the linear region is frequency (x ′). Polyamide resin (A) and glycidyl group-containing styrenic copolymer (β) with respect to multiplier (y ′ = bx ′ ^β ; where b is a constant) β plotted on a log-log graph of loss modulus (y ′) When a relaxation component is generated for a long time by the reaction of B), the value of α changes because the shear rate dependence of the storage elastic modulus changes. In addition, the value of α in the case of instantaneous relaxation after applying strain is theoretically α = 2, and the value of α of the polyamide resin in the case of not containing the glycidyl group-containing styrene copolymer (B) is Generally, α = 1.5 to 2.0. Therefore, when the α value is less than 1.4 due to the reaction between the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B), the polyamide resin (A) and the glycidyl group-containing styrene copolymer are used. It shows that a relaxation component is generated for a long time by reaction with (B). Moreover, since the value of β does not greatly depend on the reaction between the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B), the melt viscoelasticity tendency that the absolute value of α-β becomes smaller is It shows a tendency to increase the melt tension, especially at low shear, due to the generation of relaxation components for a long time, and it is a modification that can suppress cell coarsening due to cell bubble breakage in the cell growth process in foam molding. Indicates. As described above, in the present invention, the cells are in a molten state in which the cells do not break up and become coarse in the foaming process, so that the moldability and productivity of foam molding are excellent, and a fine and uniform foam molded body can be obtained. I guess. Conversely, when the α value is 1.4 or more, the polyamide resin has no relaxation component for a long time and is not suitable for foam molding. Furthermore, the fact that the absolute value of α-β exceeds 0.5 means that the dependence on the molecular weight and structure of β is small, and in a low shear region where the foam cell grows, it is a molten state closer to a viscous body. This indicates that the melted state in foaming is not preferable because the wall between the foamed cells is easily broken.

  In order to satisfy the condition that the α value is less than 1.4 and the absolute value of the α value-β value is 0.5 or less, the polyamide resin (A) and a glycidyl group-containing styrene copolymer ( The reaction of B) may be carried out under appropriate conditions. Specifically, although it depends on the type and amount of the polyamide resin (A), the glycidyl group-containing styrene copolymer (B), and further the inorganic reinforcing material (C), it is preferably represented by the present invention (A). To the content of each component of (C) (polyamide resin (A), glycidyl group-containing styrene copolymer (B) and, if necessary, inorganic reinforcing material (C)), polyamide resin (A) and Time required for reaction with the glycidyl group-containing styrene copolymer (B), extruder screw configuration capable of applying sufficiently high shear stress to the matrix composition, temperature setting, screw rotation speed, extrusion amount per hour, etc. It is sufficient to select the compound conditions.

  In general, foaming in foam molding is most efficiently controlled by a resin cooling process. Since the growth of the foam cell involves deformation of the molten resin at a relatively low shear rate, if the relaxation behavior in the molten state is too early, the walls between the foam cells cannot withstand extension and the adjacent cells become identical and become minute. A matrix composition that cannot form a foam cell but has the above-described behavior (that is, having an α value and a β value in the above-mentioned range) relaxes in deformation upon melting, as can be seen from the range of the α value. It has been modified so that the behavior is slow, and the melting behavior in the foaming process is more easily foamed. Therefore, a fine and uniform foam molded article can be obtained even in a resin having a high heat resistance level called engineering plastic, which is excellent in moldability and productivity of foam molding.

  In preparing the polyamide resin composition of the present invention, the method of mixing the polyamide resin (A) with the glycidyl group-containing styrene copolymer (B) and other optional components is not particularly limited. For example, the glycidyl group-containing styrenic copolymer (B) and other optional components (inorganic reinforcing material (C), additives, etc.) can be added to the polyamide resin (A) after polymerization. Specifically, 1) it is added into the polymerization machine after completion of the polymerization, 2) it is directly added to the polyamide resin in a molten state immediately after leaving the polymerization machine and kneaded, or 3) it is solidified (for example, powder, A method of melt kneading after adding to the polyamide resin (A) in the form of pellets or the like can be applied. In the method 1) or 2), since the polyamide resin is in a molten state, the melt viscosity is increased as it is by adding the glycidyl group-containing styrene copolymer (B), but in the method 3) It is desirable that the polyamide resin (A) in which the glycidyl group-containing styrene copolymer (B) or the like is uniformly dispersed and mixed is heated and remelted to increase the melt viscosity.

  There is no restriction | limiting in particular in the heating remelting method, Any method well-known to those skilled in the art may be employ | adopted, For example, a single screw extruder, a twin screw extruder, a pressure kneader, a Banbury mixer etc. can be used. Among these, a twin screw extruder is particularly preferably used. The operating conditions of the twin screw extruder vary depending on various factors such as the type of polyamide resin (A) and the type and amount of each component, and are not uniquely determined. For example, the operating temperature is the melting point of the polyamide resin ( Generally, it may be set at around + 25 ° C. It may be considered that the operation time is within 10 minutes, for example, 1 to several minutes, and the target melt viscosity is sufficiently reached. The screw configuration of the extruder preferably incorporates several kneading disks with excellent kneading.

  The polyamide resin composition of the present invention thus obtained has high viscosity stability in the molten state, and has melt rheological properties particularly suitable for foam molding.

(Polyamide resin foam molding)
The polyamide resin foam molded article of the present invention is obtained using the above-described polyamide resin composition of the present invention. Such a polyamide resin foam molded article of the present invention comprises a non-foamed skin layer present in the surface layer and a foamed layer present in the inner layer, and these non-foamed skin layer and foamed layer are the above-described polyamide resin composition of the present invention. Therefore, it has a uniform cellular foam structure and can exhibit excellent lightness and load resistance.

  The foam layer is composed of a resin continuous phase and independent foam cells having an average cell diameter of 10 to 300 μm. Here, the resin continuous phase means a portion having no void formed by a cured polyamide resin composition. Since the diameter of the foamed cell (cell diameter) is uniform and does not vary, it exhibits different characteristics regardless of whether it is small or large, and thus is useful in any case. For example, when the average cell diameter is small, higher rigidity can be exhibited with the same weight, and when the average cell diameter is large, appropriate energy absorption characteristics in cushioning and destruction can be obtained. However, since a foam structure having an average cell diameter equal to or greater than the thickness of the non-foamed skin layer is disadvantageous in terms of load resistance, the average cell diameter of the foamed cells is preferably less than the thickness of the non-foamed skin layer. Specifically, the average cell diameter is preferably 10 to 300 μm as described above, and more preferably 10 to 200 μm. When the average cell diameter is less than 10 μm, the internal pressure of the molded product is low, the pressure at the time of forming the non-foamed skin layer is insufficient, and the appearance such as sink marks may be deteriorated. On the contrary, there may be a case where the cell cannot be grown due to the external pressure. However, in this case, it is not preferable because the cell growth is excessively suppressed and the target low specific gravity structure may not be obtained. On the other hand, when the average cell diameter exceeds 300 μm, the load resistance is low, and the reinforcing effect of the inorganic reinforcing material (C) on the scale of several μm to several 100 μm cannot be expected. When the average cell diameter is within the above range, an appropriate pressure can be applied to the non-foamed skin layer from the inside of the molded body, and molding can be performed with an external pressure that does not inhibit cell growth.

  The non-foamed skin layer is laminated on the foamed layer and preferably has a thickness of 100 to 800 μm. When the thickness of the non-foamed skin layer is less than 100 μm, there is a tendency that a good appearance cannot be obtained. On the other hand, when the thickness exceeds 800 μm, the specific gravity of the foamed molded product as a whole is 0 because the specific gravity of the foamed layer is too low. There is a possibility that the foamed structure of 2 to 1.0 cannot be obtained in a uniform cell state. More preferably, the thickness of the non-foamed skin layer is 120 to 700 μm, and more preferably 150 to 500 μm.

  The foamed molded product of the present invention usually has a sandwich structure in which non-foamed skin layers are provided on both sides of the foamed layer (in other words, a structure in which the foamed layer is sandwiched between the non-foamed skin layers from both sides). .

  The specific gravity of the foamed molded product of the present invention is preferably 0.2 to 1.0. Since the specific gravity of general non-reinforced polyamide and inorganic reinforced polyamide is approximately 1.0 to 1.8, it can be said that the foamed molded product of the present invention is sufficiently lightened. More preferably, it is 0.3-0.9. If the specific gravity is less than 0.2, the mechanical properties as a load-bearing structure tend to be too low, and if it exceeds 1.0, it cannot be said that sufficient weight reduction has been achieved.

  The foam molding method for obtaining the foam molded article of the present invention is not particularly limited, and a known method can be adopted. Hereinafter, a foaming method (mold) for expanding a mold described with reference to the drawings. The extended method) is preferably employed. Of course, the foamed molded product of the present invention is not limited to those obtained by the method.

  As shown in FIG. 3, the foaming method for expanding a mold is a process in which a polyamide resin composition M in a molten state is placed in a cavity 3 formed by a plurality of molds 1 and 2 that are clamped and a chemical foaming agent and At least one non-foamed skin layer having a thickness of 100 to 800 μm is formed on the surface layer by injection and filling with an inert gas in a supercritical state (hereinafter sometimes collectively referred to as “foaming agent”). This is a method of obtaining a foamed molded article by moving a mold 2 (hereinafter also referred to as an “operating mold”) 2 in the mold opening direction (core back) to enlarge the volume of the cavity 3. Specifically, after filling the polyamide resin composition M and the foaming agent in the cavity 3, a non-foamed skin layer is formed on the surface layer of the polyamide resin composition M filled in the cavity 3. When the non-foamed skin layer reaches a predetermined thickness (100 to 800 μm), the working mold 2 is moved in the mold opening direction to expand the volume of the cavity 3. In order to move the working mold 2 when the non-foamed skin layer reaches a predetermined thickness (100 to 800 μm), for example, after the polyamide resin composition M is filled, the working mold 2 is operated within an optimum delay time. The mold 2 may be moved (core back). As a result, a more uniform cellular foam structure can be formed.

  The moving speed (core back speed) of the working mold 2 is preferably in the range of 2 to 10 mm / second when the core back distance is from 0 mm to 0.5 mm, and the core back amount is from 0.5 mm. The distance up to a predetermined core back distance is preferably in the range of 0.5 to 5 mm / second. If the core back speed is within the above range, a more uniform cell-like foam structure can be formed. The core back speed is not necessarily constant as long as it is within the above range, and may be changed as appropriate.

  The foaming agent that can be used in obtaining the foamed molded article of the present invention is added to a resin that is melted in a resin melting zone of a molding machine as a gas component serving as a foam core or a generation source thereof.

  Specifically, as the chemical foaming agent, for example, inorganic compounds such as ammonium carbonate and sodium bicarbonate, and organic compounds such as azo compounds, sulfohydrazide compounds, nitroso compounds, and azide compounds can be used. Examples of the azo compound include diazocarbonamide (ADCA), 2,2-azoisobutyronitrile, azohexahydrobenzonitrile, diazoaminobenzene, etc. Among them, ADCA is preferred and used. Examples of the sulfohydrazide compound include benzenesulfohydrazide, benzene 1,3-disulfohydrazide, diphenylsulfone-3,3-disulfonehydrazide, diphenyloxide-4,4-disulfonehydrazide and the like. Examples of the nitroso compound include N, N-dinitrosopentaethylenetetramine (DNPT), N, N-dimethyl terephthalate, and the like. Examples of the azide compound include terephthalazide, P-tert-butylbenzazide, and the like.

  When a chemical foaming agent is used as the foaming agent, the chemical foaming agent is a foaming agent based on a thermoplastic resin having a melting point lower than the decomposition temperature of the chemical foaming agent in order to be uniformly dispersed in the polyamide resin (A). It can also be used as a masterbatch. The thermoplastic resin used as the base material is not particularly limited as long as it has a melting point lower than the decomposition temperature of the chemical foaming agent, and examples thereof include polystyrene (PS), polyethylene (PE), and polypropylene (PP). In this case, it is preferable that the compounding ratio of the chemical foaming agent and the thermoplastic resin is 10 to 100 parts by mass of the chemical foaming agent with respect to 100 parts by mass of the thermoplastic resin. If the chemical foaming agent is less than 10 parts by mass, the amount of the masterbatch mixed with the polyamide resin (A) may be excessive, leading to a decrease in physical properties. Master batching becomes more difficult.

  When carbon dioxide and / or nitrogen in a supercritical state is used as the blowing agent, the amount thereof is 0.05 to 30 parts by mass, more preferably 0.1 to 100 parts by mass of the resin component in the polyamide resin composition. It is preferably ~ 20 parts by mass. If the carbon dioxide and / or nitrogen in the supercritical state is less than 0.05 parts by mass, it becomes difficult to obtain uniform and fine foam cells, and if it exceeds 30 parts by mass, the appearance of the molded body surface tends to be impaired. .

  In addition, although the supercritical carbon dioxide or nitrogen used as a blowing agent can be used alone, carbon dioxide and nitrogen may be mixed and used. Nitrogen tends to be more suitable for forming finer cells than polyamide, and carbon dioxide is more suitable for obtaining a higher expansion ratio because a relatively large amount of gas can be injected. Therefore, carbon dioxide or nitrogen in a supercritical state may be arbitrarily mixed depending on the state of the foam structure. When mixing carbon dioxide and nitrogen, the mixing ratio is preferably in the range of 1: 9 to 9: 1 in terms of molar ratio.

  In order to inject the molten polyamide resin composition M into the cavity 3 together with the foaming agent, the molten polyamide resin composition M and the foaming agent may be mixed in the injection molding machine 4. In particular, when supercritical carbon dioxide and / or nitrogen is used as the foaming agent, for example, as shown in FIG. 3, the carbon dioxide and / or nitrogen in the gaseous state is pressurized directly or by a pressure pump 6 from a gas cylinder 5. A method of injecting into the injection molding machine 4, a method of injecting liquid carbon dioxide and / or nitrogen into the injection molding machine 4 with a plunger pump, and the like can be employed. These carbon dioxide and / or nitrogen must be in a supercritical state inside the molding machine from the viewpoints of solubility, permeability, and diffusibility in the polyamide resin composition in the molten state.

  Here, the supercritical state can eliminate the distinction between the gas phase and the liquid phase in a certain temperature range and pressure range when increasing the temperature and pressure of the substance generating the gas phase and the liquid phase. It means a state, and the temperature and pressure at this time are called critical temperature and critical pressure. In other words, since a substance has both gas and liquid characteristics in a supercritical state, a fluid generated in this state is called a critical fluid. Since such a critical fluid has a higher density than a gas and a lower viscosity than a liquid, it has a characteristic that it is very easy to diffuse in a substance. Incidentally, carbon dioxide has a critical temperature of 31.2 ° C. and a critical pressure of 7.38 MPa, and nitrogen has a critical temperature of 52.2 ° C. and a critical pressure of 3.4 MPa. As a result, it becomes a supercritical state and behaves as a critical fluid.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
In addition, the measured value described in the Example is measured by the following method.

<Number average molecular weight>
2 mg of each sample was weighed, dissolved in 4 mL of hexafluoroisopropanol (HFIP) / sodium trifluoroacetate 10 mM solution, filtered through a 0.2 μm membrane filter, and the obtained sample solution was gel permeated under the following conditions. The number average molecular weight was calculated | required by performing the chromatography (GPC) analysis. The molecular weight was calculated in terms of standard polymethyl methacrylate, and those having a molecular weight of 1000 or less were excluded as oligomers.
Equipment: “HLC-8220GPC” manufactured by TOSOH
Column: “TSKgel SuperHM-H × 2”, “TSKgel SuperH2000” manufactured by TOSOH
Flow rate: 0.25 mL / min Concentration: 0.05% by mass
Temperature: 40 ° C
Detector: RI

<Epoxy value>
A sample was weighed in a 100 mL Erlenmeyer flask, 10-15 mL of methylene chloride was added, and the mixture was stirred and dissolved with a magnetic stirrer. 10 mL of tetraethylammonium bromide reagent was added, 6-8 drops of crystal violet indicator were added, and titrated with 0.1 N perchloric acid. The end point was changed from blue to green and stable for 2 minutes. The amount of perchloric acid required for titration (mL) was A, the sample mass was W (g), the normality of the perchloric acid reagent was N, and the epoxy value was calculated based on the following formula.
Epoxy value (equivalent / 1 × 10 ⁶ g) = (N × A × 1000) / W

<Melting point (Tm)>
A sample (polyamide resin) that was dried under reduced pressure at 105 ° C. for 15 hours was weighed in an aluminum pan (“Product Number 900793.901” manufactured by TA Instruments), and was measured with an aluminum lid (“Product Number 900794.901” manufactured by TA Instruments). After sealing, using a differential scanning calorimeter (“DSCQ100” manufactured by TA Instruments), the temperature was raised from room temperature to 20 ° C./minute, held at 350 ° C. for 3 minutes, then the pan was taken out and immersed in liquid nitrogen. It was cooled rapidly. Thereafter, the pan was taken out from the liquid nitrogen and allowed to stand at room temperature for 30 minutes, and then the temperature was raised from room temperature to 350 ° C. at 20 ° C./min using the differential scanning calorimeter, and the endothermic peak temperature due to melting at that time Was the melting point (Tm). In the present invention, the non-crystalline polyamide (b) does not show a clear endothermic peak temperature in this melting point measurement.

<Specific gravity>
A test piece of 25 mm × 25 mm × thickness having cut surfaces on four sides was cut out from the foamed molded product, and the specific gravity was measured according to the solid specific gravity measurement method described in JIS-Z8807. In addition, when the test piece is divided into a plurality of parts, for example, when the foam layer is not sufficiently formed in the sandwich structure of the skin layer / foam layer / skin layer and the upper and lower skin layers are separated, Specific gravity was measured simultaneously using the separated cut specimens.

<Average cell diameter, cell uniformity>
First, after embedding in a visible light curable resin and polishing to expose the foamed cross section, or after immersing the molded body prepared so as to expose the foamed cross section by breaking with a notch in liquid nitrogen for 10 minutes A sample for cross-sectional observation was obtained by exposing the foamed cross section by impact destruction.

  The average cell diameter is obtained by subjecting a photograph of the foamed cross-section of the sample for cross-section observation taken with a scanning electron microscope to image processing, and taking the equivalent circle diameter of at least 100 adjacent cells as the cell diameter, and averaging the 100 values This was performed at any three locations, and the average of the three average values obtained at the three locations was taken as the average cell diameter.

The uniformity of the cells is obtained by image processing of the foamed cross-section photograph of the sample for cross-sectional observation taken with a scanning electron microscope, and averaged at three arbitrary points of 500 μm to 2000 μm square including at least 20 adjacent cells. When the cell diameter is 300 μm or less and there is no cavity having a length continuity of 800 μm or more, “◯” is given, and the others are “x”.
When the cell uniformity was “x” and there was a cavity with a length continuity of 800 μm or more, the average cell diameter was not measurable.

<Skin layer thickness>
After embedding in a visible light curable resin and polishing to expose the foamed cross section, or after immersing the molded body prepared in advance so as to expose the foamed cross section by notching and breaking in liquid nitrogen for 10 minutes, impact fracture By exposing the foamed cross section, a cross section observation sample was obtained. And the photograph of the foaming cross section of the said sample for cross-sectional observation image | photographed with the scanning electron microscope was image-processed, and the thickness of the integrated non-foaming layer seen by the surface layer part was measured as skin layer thickness.

<Productivity>
When obtaining a polyamide resin composition, when the strand was pelletized with a strand cutter, if the pellet was obtained without any problem, “○”, and if the strand property was not stable and could not be pelletized, “×” evaluated.

<Load resistance improvement rate>
First, the polyamide foam molding to be measured, except that no foaming agent (nitrogen or carbon dioxide) is used and the mold is molded without moving the mold in the mold opening direction (without expanding the mold). A polyamide resin non-foamed molded article to be compared was produced using a flat plate mold having a width of 100 mm, a length of 250 mm, and a thickness of 2 mm under the same production conditions.

  The obtained polyamide foam molded product and the polyamide resin non-foamed molded product (comparative object) obtained above were allowed to stand for 24 hours in an environment of a temperature of 80 ° C. and a humidity of 95%, and then each 10 mm wide × 100 mm long. A test piece was cut out. The maximum load of the non-foamed molded product when the three-point bending test was carried out with a span length of 50 mm and a load speed of 2 mm / min for this cut-out test piece is X (N), and the maximum load of the foamed molded product is Y (N). , Y / X value is 1.5 or more, “◯”, 1 or more, less than 1.5, “△”, less than 1, or upper foam layer is hollow Therefore, the case where the lower non-foamed skin layer and the foamed layer were not destroyed at the same time and only the upper non-foamed skin layer was destroyed was evaluated as “x”.

<Measurement of melt viscoelasticity>
In order to obtain the above-mentioned α value and β value in the melt viscoelasticity measurement of the matrix composition comprising the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B), a frequency range of 10 to 100 rad / s in the linear region Measure melt viscoelasticity at, and obtain logarithmic graphs of frequency (x) and storage modulus (y) and logarithmic graphs of frequency (x ') and loss modulus (y') as frequency-dependent data did. The matrix composition used for the measurement was prepared in the same manner as in each Example and Comparative Example except that the inorganic reinforcing material (C) and the additives (stabilizer, mold release agent, black pigment) were not used.

The melt viscoelasticity measurement (dynamic viscoelasticity measurement) is performed under the following conditions using “ARES” manufactured by TA Instruments and a 25 mm parallel plate as a measurement jig, and the frequency ω (x) −storage elastic modulus G ′. A log-log plot of (y) and a log-log plot of frequency ω (x ′) and loss modulus G ′ ′ (y ′) were obtained. A graph showing the results of Example 4 is shown in FIG. 4, and a graph showing the results of Comparative Example 1 is shown in FIG. When calculating the slope of storage elastic modulus (α value) and the slope of loss elastic modulus (β value) from the plot, obtain a straight line on the plot using the power approximation formula of the obtained data points, and obtain the slope of the straight line. It was. The measurement was performed at 230 ° C. in an example using “polyamide 11” as the polyamide resin (A), 240 ° C. in an example using “polyamide 6-1 or 6-2”, and in an example using “polyamide 66”. Conducted at 280 ° C.
Strain = 10%
Temperature = DSC melting point at least 10 ° C. Initial Frequency = 100 rad / s
Final Frequency = 10 rad / s
Gap = 0.7-1.5mm
Geometry Type = Parallel Plate (Diameter = 25mm)

  In the examples and comparative examples, the following raw materials were used.

<Polyamide resin (A)>
a1: Polyamide 6-1; “Nylon T-820” manufactured by Toyobo, 6 nylon with relative viscosity RV = 3.1, number average molecular weight 25400, melting point 225 ° C.
a2: Polyamide 6-2; “Nylon T-840” manufactured by Toyobo, 6 nylon with relative viscosity RV = 2.4, number average molecular weight 17700, melting point 225 ° C.
a3: Polyamide 66-1; “Amilan (registered trademark) CM3001N” manufactured by Toray, 66 nylon of relative viscosity RV = 2.8, number average molecular weight 17900, melting point 265 ° C.
a4: Polyamide 11; “Rilsan (registered trademark) B BMNO” manufactured by Arkema, 11 nylon with relative viscosity RV = 2.1, melting point 187 ° C.
b1: Polyamide 6T6I; “Grivory G21” manufactured by EMS, 6T / 6I = 33/67 (mol%), Tg 125 ° C., number average molecular weight 15100, non-crystalline b2: Polyamide PACM14; Arkema “G350”, Tg 146 ° C. Number average molecular weight 14200, non-crystalline b3: Polyamide MACM12 · I; “TR-55” manufactured by EMS, Tg 162 ° C., number average molecular weight 18600, non-crystalline

<Glycidyl group-containing styrene copolymer (B)>
B1: Styrene polymer 1; produced as follows.
That is, the oil jacket temperature of a pressurized stirred tank reactor having a capacity of 1 liter equipped with an oil jacket was kept at 200 ° C. On the other hand, a monomer comprising 89 parts by mass of styrene (St), 11 parts by mass of glycidyl methacrylate (GMA), 15 parts by mass of xylene (Xy), and 0.5 parts by mass of ditertiary butyl peroxide (DTBP) as a polymerization initiator. The mixed solution was charged into the raw material tank. This is continuously supplied from the raw material tank to the reactor at a constant supply rate (48 g / min, residence time: 12 minutes), and the reaction solution is discharged at the outlet of the reactor so that the content liquid mass of the reactor becomes constant at about 580 g. Extracted continuously. At this time, the internal temperature of the reactor was kept at about 210 ° C. After 36 minutes from the stabilization of the temperature inside the reactor, the extracted reaction solution was led to a thin film evaporator maintained at a reduced pressure of 30 kPa and a temperature of 250 ° C., and continuously removed volatile components. A coalescence (B1) was obtained. The styrene copolymer (B1) had a weight average molecular weight of 8500 and a number average molecular weight of 3300 according to GPC analysis (polystyrene conversion value). The epoxy value is 670 equivalents / 1 × 10 ⁶ g, the epoxy value (the average number of epoxy groups per molecule) is 2.2, and it has two or more glycidyl groups in one molecule. .

B2: Styrene polymer 2; produced as follows.
That is, the styrene-based polymer was prepared in the same manner as in the production of the styrene-based polymer (B1) except that a monomer mixed solution consisting of St77 parts by mass, GMA23 parts by mass, Xy15 parts by mass, and DTBP0.3 parts by mass was used. Combined (B2) was obtained. The styrene polymer (B2) had a weight average molecular weight of 9700 and a number average molecular weight of 3300 according to GPC analysis (polystyrene conversion value). The epoxy value is 1400 equivalent / 1 × 10 ⁶ g, the epoxy value (the average number of epoxy groups per molecule) is 4.6, and it has two or more glycidyl groups in one molecule. .

<Inorganic reinforcement (C)>
C1: Glass fiber 1; “CS3PE453” manufactured by Nitto Boseki Co., Ltd.
C2: Glass fiber 2; “CSG3PA810S” manufactured by Nitto Boseki Co., Ltd.
C3: Layered silicate; “Cloite 30B” manufactured by Southern Clay Products, organically treated montmorillonite C4: Glass beads; “GB731A-PN” manufactured by Potters Barotini

<Other additives>
Stabilizer: “Irganox B1171” manufactured by Ciba Japan
Mold release agent: “Montanic acid ester wax WE40” manufactured by Clariant Japan
Black pigment: “EPC8E313” manufactured by Sumika Color Co., Ltd.

(Examples 1-39, Comparative Examples 1-16)
The amount (parts by mass) of the raw materials (A) to (C) described above is as shown in Tables 1 to 6, and the amounts of other additives used are 0. 3 parts by mass, the release agent was 0.3 parts by mass, and the black pigment was 1.0 parts by mass. These were mixed in a 35φ twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.). Specifically, first, the polyamide resin (A), the glycidyl group-containing styrenic copolymer (B) and other additives are simultaneously added from a hopper at a screw speed of 100 rpm and melt-kneaded, and then the inorganic reinforcing material (C). Was fed by side feed. At this time, the cylinder temperature is 280 ° C. when polyamide 66-1 (a3) is used as the polyamide resin (A), and polyamide 6-1 (a1), polyamide 6-2 (a2), or polyamide 11 (a4). When using, the temperature was set to 250 ° C. Note that only when the layered silicate (C3) was used as the inorganic reinforcing material (C), delamination was performed in advance and the nano-order was dispersed in the polyamide resin (A). And after cooling the strand discharged from the extruder with the water tank, it pelletized with the strand cutter and dried at 125 degreeC for 5 hours, and the polyamide resin composition was obtained as a pellet.

  Next, using the polyamide resin composition obtained above, a foamed molded article was produced by the above-described mold expansion method. As the mold, a mold for making a flat plate made up of a fixing mold and an operation mold capable of forming a cavity having a width of 100 mm, a length of 250 mm, and a thickness of 2 mm when the mold was clamped was used. Specifically, in the plasticization region of an electric injection molding machine having a screw with a mold clamping force of 1800 kN, a diameter of 42 mm, and L / D = 30, the amount of nitrogen or carbon dioxide shown in each table in a supercritical state (Mass part: 100 parts by mass of resin component in the polyamide resin composition) Injected, injection-filled into a mold whose temperature was adjusted to a surface temperature of 40 to 60 ° C. (optimal conditions were selected during this period), and then a working metal By moving the mold in the mold opening direction by the length indicated as the core back amount (mm) in each table, the volume of the cavity was expanded to obtain a foam molded article. At this time, the delay time from the completion of injection to the start of the core back is set to 0 to 0.5 seconds (the optimum condition was selected during this time), and the moving speed of the working mold (core back speed) is the distance of the core back. Between 0 mm and 0.5 mm, an arbitrary speed in the range of 2 to 10 mm / second (optimal conditions were selected during this period), and the core back distance (mm) shown in each table from 0.5 mm to the core back distance The speed was arbitrarily set within a range of 0.5 to 5 mm / second (optimal conditions were selected during this period).

  The evaluation results of the polyamide resin foam molded articles obtained in Examples 1 to 39 and Comparative Examples 1 to 16 are shown in Tables 1 to 6.

  As is clear from Tables 1 to 6, the polyamide resin foam molded articles of Examples 1 to 39 have a uniform and fine foam cell structure, and are lightweight and excellent in load resistance. I understand. On the other hand, the foamed molded products of Comparative Examples 1 to 16 have low specific gravity, but the foamed cells tend to be non-uniform and coarse, and cannot exhibit stable load resistance, compared with Examples 1 to 39. Any of these evaluation items were inferior.

  Moreover, the foaming molding obtained in Example 27 and Comparative Example 9 was cut, and the cross section was observed with a scanning electron microscope. A cross-sectional photograph of the foamed molded product of Example 27 is shown in FIG. 1 ((A) is 25 times magnification, (B) is 120 times magnification), and a cross-sectional photograph (25 times magnification) of the foamed molded product of Comparative Example 9 is shown. It is shown in 2. 1 and 2, the polyamide resin foam molded article of the present invention has a uniform and fine foam cell structure, whereas the foam molded article of Comparative Example 9 has a non-uniform cell size. And it turns out that it is remarkably large compared with the polyamide resin foaming molding of this invention.

1 Mold (for fixing)
2 Mold (for operation)
3 Cavity 4 Injection molding machine 5 Gas cylinder 6 Booster pump 7 Pressure control valve

Claims (5)

A polyamide resin (A);
A glycidyl group-containing styrene copolymer (B) containing two or more glycidyl groups per molecule, having a weight average molecular weight of 4000 to 25000 and an epoxy value of 400 to 2500 equivalents / 1 × 10 ⁶ g;
Inorganic reinforcing material (C),
The ratio that the glycidyl group-containing styrene copolymer (B) is 0.2 to 25 parts by mass and the inorganic reinforcing material (C) is 0 to 350 parts by mass with respect to 100 parts by mass of the polyamide resin (A). A polyamide resin foam molded article obtained using a polyamide resin composition contained in
A foamed layer composed of a resin continuous phase and independent foamed cells having an average cell diameter of 10 to 300 μm, and a non-foamed skin layer of 100 to 800 μm thick laminated on the foamed layer are formed by the polyamide resin composition. A polyamide resin foamed molded article having a specific gravity of 0.2 to 1.0. The glycidyl group-containing styrenic copolymer (B) is (X) 20 to 99% by mass of vinyl aromatic monomer, (Y) 1 to 80% by mass of glycidyl alkyl (meth) acrylate, and (Z) 0 to 79. 2. The polyamide resin foam molded article according to claim 1, which is a copolymer composed of a vinyl group-containing monomer other than (X) which does not contain an epoxy group of mass%. When the storage elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in the frequency range of 10 to 100 rad / s in the linear region is plotted on a logarithmic graph of frequency (x) and storage elastic modulus (y). A multiplier (y = ax ^α ; where a is a constant) is α, and a loss elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in a frequency range of 10 to 100 rad / s in a linear region is expressed as a frequency (x Polyamide resin (A) and glycidyl group-containing styrene, where ^{β is} a multiplier (y ′ = bx ′ ^β ; where b is a constant) when plotted on a log-log graph of ') and loss modulus (y ′) The polyamide resin foam molded article according to claim 1 or 2 , wherein the matrix composition comprising the copolymer (B) has an α of less than 1.4 and an absolute value of α-β of 0.5 or less. The polyamide resin foam molded article according to any one of claims 1 to 3 , which has a sandwich structure in which the non-foamed skin layer is provided on both surfaces of the foam layer. The polyamide resin composition in a molten state is injected and filled together with a chemical foaming agent and / or an inert gas in a supercritical state into a cavity formed by a plurality of molds clamped, and the surface layer has a thickness of 100 to 800 μm. The polyamide resin foam molded article according to any one of claims 1 to 4 , which is obtained by moving at least one mold in the mold opening direction and expanding the volume of the cavity when the non-foamed skin layer is formed. .