JP2012097182A - Polyamide resin composition and polyamide resin foamed molded object - Google Patents

Abstract

[PROBLEMS] To provide a good foam that has excellent heat resistance, is sufficiently lightweight, has low water absorption, exhibits excellent dimensional stability and load resistance even in a high humidity environment, and also has light scattering properties. Provided is a polyamide resin composition capable of obtaining a polyamide resin foam molded article in a state by an easy method.
A specific glycidyl group-containing styrene copolymer (B) 0 to 10 parts by mass and an inorganic reinforcing material (C) 0 to 350 parts by mass with respect to 100 parts by mass of an amorphous polyamide resin (A). The non-crystalline polyamide resin (A) has an alicyclic group and has a storage elastic modulus (unit) obtained by melt viscoelasticity measurement in the linear region at a frequency of 10 to 100 rad / s. : Pa) is plotted on a logarithmic graph of frequency (x) and storage modulus (y), and the multiplier (y = ax ^α, where a is a constant) is assumed to be α value, and the measurement is performed at 260 ° C. The α value obtained from the melt viscoelasticity measurement is α (0), and after the melt viscoelasticity measurement, the α value obtained from the melt viscoelasticity measurement performed again after the residence at the same temperature for 30 minutes is α (30). Α (0) <1.20 and α (0) −α (30)> .20 is.
[Selection figure] None

Description

  The present invention has the excellent heat resistance of a polyamide resin, can be sufficiently reduced in weight in a good foamed state, has excellent water absorption, and exhibits excellent dimensional stability and load resistance even in a high humidity environment. In addition, the present invention relates to a polyamide resin composition capable of obtaining a molded article excellent in light scattering characteristics, and a polyamide resin foam molded article using the same.

  Polyamide resins generally have a low melt viscosity, so when foam molding is performed, the walls between the foam cells are broken during the cell growth process, and the cells tend to become coarse, making it difficult to produce a polyamide resin foam molded article with a uniform and fine foam structure. It is known.

  As a method for producing a polyamide resin foam molded article, a method using a chemical foaming agent is common. 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, a crystalline polyamide having a high solidification rate has a short time for maintaining an appropriate viscoelastic state, and thus it has been difficult to form uniform foamed cells by this method.

  On the other hand, polyamide resins are known to be useful as resin materials having light scattering properties, and methods for obtaining resin materials having light scattering properties using polyamide porous particles are described in Patent Documents 6 and 7. ing. However, here, polyamide is prepared as a light-scattering filler, and a method for easily obtaining a light-scattering polyamide molded body by injection molding is not disclosed.

  By the way, nylon 6 and nylon 66, which are general-purpose polyamides, easily absorb water and increase in mass when exposed to a high humidity environment. And if it absorbs water, a molded object will expand and load resistance will fall. Therefore, there is a need for a polyamide-type molded article having lower water absorption that is less susceptible to deterioration of properties in a high-humidity environment.

JP 2009-249549 A JP 2006-35687 A JP 2005-126545 A JP 2006-69215 A JP 2006-212945 A JP 2007-219183 A JP 2010-132768 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyamide resin composition for foam molding that can obtain a polyamide resin foam molded article in a good foamed state by an easy method. Polyamide foam molding with excellent heat resistance and light weight, excellent water absorption, excellent dimensional stability and load resistance even in high humidity environments, and light scattering To provide a body.

  As a result of intensive studies to achieve the above object, the present inventors have found that specific parameter values (α (0), α (30)) obtained by measuring the melt viscoelasticity of the polyamide resin satisfy a predetermined relationship. If it is a foamed product of a specific polyamide resin composition, the rheological properties necessary for foam molding are enhanced, the solidification speed of the polyamide resin is controlled, foaming moldability is improved, heat resistance is excellent, and weight is sufficiently reduced Further, it has been found that a foamed molded article having low water absorption, dimensional stability at the time of water absorption and load resistance, and light scattering properties can be easily obtained. As one means for obtaining parameter values (α (0), α (30)) satisfying a predetermined relationship, an alicyclic group formed by polycondensation of an aliphatic dicarboxylic acid and an alicyclic diamine. Amorphous polyamide resin having a group, in particular an aliphatic dicarboxylic acid selected from dicarboxylic acids having 12 to 18 carbon atoms, bis (4-amino-cyclohexyl) methane, bis (3-amino-cyclohexyl) methane Formed by polycondensation with an alicyclic diamine selected from the group consisting of bis (3-methyl-4-amino-cyclohexyl) methane and 2,2-bis (4-amino-cyclohexyl) propane It has also been found that a polyamide resin may be used as a polyamide resin. Furthermore, when a specific vinyl copolymer containing a glycidyl group or an inorganic reinforcing material is blended with such an amorphous polyamide resin, the rheological properties necessary for foam molding are further enhanced, and each of the above-mentioned properties can be obtained. It has been found that further improvement. The present invention has been completed based on these findings.

  That is, the present invention has the following configuration.

(1) Amorphous polyamide resin (A) With respect to 100 parts by mass, two or more glycidyl groups are contained per molecule, the weight average molecular weight is 4000 to 25000, and the epoxy value is 400 to 2500 equivalent / 1 ×. It is a polyamide resin composition for a foamed molded article containing 0 to 10 parts by mass of a glycidyl group-containing styrene copolymer (B) that is 10 ⁶ g and 0 to 350 parts by mass of an inorganic reinforcing material (C). The amorphous polyamide resin (A) has an alicyclic group, and the melt viscoelasticity measurement of the amorphous polyamide resin (A) has a frequency in the range of 10 to 100 rad / s in the linear region. Multiplier when the storage elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement is plotted on a logarithmic graph of frequency (x) and storage elastic modulus (y) (y = ax ^α ; where a is a constant) Α value The α value obtained from the melt viscoelasticity measurement performed at 260 ° C. is defined as α (0), and after the melt viscoelasticity measurement is retained for 30 minutes at the same temperature, the melt viscoelasticity measurement is performed again. A polyamide resin composition satisfying the following formulas (i) and (ii) when α value is α (30).
α (0) <1.20 (i)
α (0) −α (30)> 0.20 (ii)

  (2) The non-crystalline polyamide resin (A) is an aliphatic dicarboxylic acid selected from dicarboxylic acids having 12 to 18 carbon atoms, bis (4-amino-cyclohexyl) methane, bis (3-amino- Obtained by polycondensation with an alicyclic diamine selected from the group consisting of (cyclohexyl) methane, bis (3-methyl-4-amino-cyclohexyl) methane and 2,2-bis (4-amino-cyclohexyl) propane The polyamide resin composition for foam molded articles according to (1), which is a product.

  (3) The polyamide resin composition according to (1) or (2), wherein the amorphous polyamide resin (A) is a resin having no aromatic group.

  (4) Glycidyl group-containing styrenic copolymer (B) is (X) 20-99% by mass vinyl aromatic monomer, (Y) 1-80% by mass glycidyl alkyl (meth) acrylate, and (Z) The polyamide resin composition according to any one of (1) to (3), 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.

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

  (6) The polyamide resin composition in a molten state is melted together with a chemical foaming agent and / or an inert gas in a supercritical state in a cavity formed by melting the polyamide resin composition and clamped with a plurality of molds. Said (5) description obtained by injecting, filling, and expanding the cavity volume by moving at least one mold in the mold opening direction when a non-foamed skin layer having a thickness of 100 to 800 μm is formed on the surface layer. Polyamide resin foam molding.

  (7) The polyamide resin foam molded article according to (5) or (6), which is used as an automobile-related part.

  (8) The polyamide resin foam molded article according to (5) or (6), which is used as a light scattering component.

  According to the polyamide resin composition of the present invention, an excellent foamed polyamide resin foamed molded article can be obtained by an easy method. In such a polyamide resin composition, rheological properties for obtaining a homogeneous foamed state can be obtained by staying during foam molding, so that cell growth due to foam breakage can be suppressed during the growth process of the foamed cell by the gas of the foaming agent. As a result, it is a polyamide resin foam that combines excellent lightness and load resistance, has low water absorption, exhibits excellent dimensional stability and load resistance even in high humidity environments, and has light scattering properties. A molded body can be obtained by an easy method. The polyamide resin foam molded article of the present invention thus provided is suitably used as a design functional component requiring high functional properties and a resin functional component having high required characteristics, for example, in applications such as automobile parts and household appliance parts. Moreover, since the polyamide resin foam molded article of the present invention receives light and scatters and emits light, it is extremely useful as an optical molded article for the purpose of energy saving.

FIG. 1 is a cross-sectional photograph of a polyamide resin foam molded article according to one embodiment (Example 1) of the present invention. FIG. 2 is a cross-sectional photograph of the polyamide resin foam molded article of Comparative Example 2. 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 the frequency dependence data of the storage elastic modulus obtained initially in the melt viscoelasticity measurement of the amorphous polyamide resin (A1: MACM · 14) used in Examples 1, 4, 7 to 10. . FIG. 5 shows the frequency of the storage modulus obtained by re-measurement after 30-minute residence time in the melt viscoelasticity measurement of the amorphous polyamide resin (A1: MACM · 14) used in Examples 1, 4, 7 to 10. It is a graph of dependence data. FIG. 6 is a graph of the frequency dependence data of the storage elastic modulus obtained by the initial measurement and the remeasurement after the residence for 30 minutes in the melt viscoelasticity measurement of the crystalline polyamide resin (A4: polyamide 6) used in Comparative Examples 1 to 5. It is.

  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 specific amorphous polyamide resin (A) and, if necessary, a specific glycidyl group-containing styrene copolymer (B) and an inorganic reinforcing material (C).

  The amorphous polyamide resin (A) used in the present invention has an alicyclic group. That is, the amorphous polyamide resin (A) is preferably a monomer in which at least one monomer constituting the polyamide has an alicyclic group. Examples of the alicyclic group include a cyclohexyl group, a substituted cyclohexyl group, and a piperazine ring. In the present invention, “non-crystalline” means a material that does not exhibit a clear melting point when DSC measurement is performed at a heating rate of 20 ° C./min in accordance with JIS-K7121.

  The amorphous polyamide resin (A) is preferably a polyamide resin formed by polycondensation of an aliphatic dicarboxylic acid and an alicyclic diamine. Thereby, the conditions (i) and (ii) relating to the α value described later can be satisfied, and as a result, the rheological properties necessary for foam molding are improved. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid (hereinafter sometimes abbreviated as “12”), tridecanedioic acid, tetradecanedioic acid (hereinafter referred to as “14”). And the like, and aliphatic dicarboxylic acids having a linear or branched chain having 4 to 36 carbon atoms. Examples of the alicyclic diamine include bis (4-amino-cyclohexyl) methane (hereinafter sometimes abbreviated as “PACM”), bis (3-amino-cyclohexyl) methane, and bis (3-methyl-4-amino-cyclohexyl). ) Methane (hereinafter sometimes abbreviated as “MACM”), 2,2-bis (4-amino-cyclohexyl) propane, isophoronediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (amino) Methyl) cyclohexane, 3-aminocyclohexyl-4-aminocyclohexylmethane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis (aminopropyl) piperazine, bis (aminoethyl) piperazine and the like. .

  As a combination of the aliphatic dicarboxylic acid and the alicyclic diamine constituting the non-crystalline polyamide resin (A), the aliphatic dicarboxylic acid is undecanedioic acid, dodecanedioic acid (12), tridecanedioic acid, tetradecanedioic acid ( 14) dicarboxylic acids having 12 to 18 carbon atoms such as alicyclic diamines such as bis (4-amino-cyclohexyl) methane (PACM), bis (3-amino-cyclohexyl) methane, and bis (3-methyl-). A combination selected from the group consisting of 4-amino-cyclohexyl) methane (MACM) and 2,2-bis (4-amino-cyclohexyl) propane has good melt flow characteristics, and the conditions regarding the α value described later ( It is particularly preferable for satisfying i) and (ii). In particular, as the non-crystalline polyamide resin (A), a resin in which bis (3-methyl-4-amino-cyclohexyl) methane (MACM) and dodecanedioic acid (12) are combined (hereinafter abbreviated as “MACM12”). Resin having a combination of bis (3-methyl-4-amino-cyclohexyl) methane (MACM) and tetradecanedioic acid (14) (hereinafter sometimes abbreviated as “MACM14”) has a water absorption rate. This is preferable in that a molded product having a low water absorption dimension change is obtained. Among them, MACM14 can be molded at a molding temperature of 300 ° C. or less, and has a good thin-wall moldability and burr generation suppression even at a mold temperature of about 100 ° C., and is excellent in strength, rigidity, impact resistance, and toughness. Is preferable in that it is easily obtained.

  In addition to the aliphatic dicarboxylic acid and alicyclic diamine described above, monomers constituting the amorphous polyamide resin (A) include lactams such as ε-caprolactam and ω-laurolactam, 6-aminocaproic acid, 11 Aminocarboxylic acids such as aminoundecanoic acid, 12-aminododecanoic acid, tetramethylenediamine, hexamethylenediamine, undecanemethylenediamine, dodecanemethylenediamine, 2,2,4- (or 2,4,4-) trimethylhexa Aliphatic diamines such as methylenediamine and 5-methylnonamethylenediamine may be included.

  The amorphous polyamide resin (A) is preferably a resin having no aromatic group. That is, it is preferable that all of the monomers constituting the amorphous polyamide resin (A) do not contain an aromatic group. Thus, the molded object which has favorable toughness is obtained by not having an aromatic group.

  The amorphous polyamide resin (A) preferably has a glass transition temperature of 125 to 160 ° C. More preferably, it is 130-155 degreeC, More preferably, it is 135-153 degreeC. If the glass transition temperature of the non-crystalline polyamide resin (A) is less than 125 ° C, the glass transition temperature is further lowered by water absorption, so the rigidity of the molded product in a high temperature and high humidity environment is lowered, and problems such as deformation occur. This is not preferable. On the other hand, when the glass transition temperature of the amorphous polyamide resin (A) exceeds 160 ° C., impact resistance and toughness tend to be lowered. Further, when the glass transition temperature is high, the filling property is difficult, so it is necessary to set the mold temperature and the resin temperature at the time of molding extremely high, which is not preferable in terms of energy saving. In the present invention, the glass transition temperature can be measured, for example, by the method described in Examples described later.

  Although the molecular weight of an amorphous 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 of the molded article 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.

The acid value and amine value of the amorphous polyamide resin (A) are both preferably 0 to 200 equivalent / 1 × 10 ⁶ g, and more preferably 0 to 100 equivalent / 1 × 10 ⁶ g. When the terminal functional group exceeds 200 equivalents / 1 × 10 ⁶ g, not only gelation or deterioration is likely to occur during the melt residence, but also there is a possibility of causing problems such as coloring and hydrolysis in the use environment. 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 adjusted to 5 to 100 equivalents / 1 × 10 ⁶ g in accordance with the reactivity and the reactive group. preferable.

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

  When the end of the amorphous 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 amorphous polyamide resin (A) used in the present invention has a storage elastic modulus (unit: Pa) obtained by melt viscoelasticity measurement in a frequency range of 10 to 100 rad / s in a linear region, and a frequency (x). The α value obtained from the melt viscoelasticity measurement performed at 260 ° C. with the multiplier (y = ax ^α ; where a is a constant) plotted on the logarithmic graph of the storage elastic modulus (y) as α value. Is α (0), and the α value obtained from the melt viscoelasticity measurement performed again after the melt viscoelasticity measurement at the same temperature for 30 minutes is α (30), the following formulas (i) and ( It satisfies ii).
α (0) <1.20 (i)
α (0) −α (30)> 0.20 (ii)

  Nylon 6 and nylon 66 have a behavior close to 2 with respect to the α value, and do not change greatly due to retention, so α (0) −α (30) is almost zero. Moreover, compared with the case where the α value increases with retention due to molecular chain scission due to deterioration, the amorphous polyamide resin (A) used in the present invention has a frequency (x) and a storage elastic modulus (y). As particularly shown in the log-log graph, the relaxation behavior is slow in deformation at the time of melting, and the melting behavior in the foaming process is more suitable for foam molding. Therefore, it is excellent in moldability of foam molding and productivity of foam molded products, and fine and uniform foam molding even in non-crystalline polyamide resin (so-called engineering plastics) with a glass transition temperature of 125 ° C or higher and high heat resistance. You can get a body. That is, the non-crystalline polyamide resin (A) having an alicyclic group of the present invention is accompanied by a decrease in molecular weight due to deterioration during melt residence as compared to “polyamide 6” and “polyamide 66” used in the comparative examples. Not only does the relaxation behavior not be faster, but the relaxation behavior of the system becomes slower due to appropriate residence conditions, indicating that the rheological properties are suitable for foaming without increasing the viscosity. Furthermore, when the glycidyl group-containing styrene copolymer (B) is added to the non-crystalline polyamide resin (A) having an alicyclic group, rheological properties more suitable for foam molding can be obtained. The behavior of α (0) when the glycidyl group-containing styrene copolymer (B) is added to the amorphous polyamide resin (A) having a group is well shown.

  In general, foaming in foam molding is controlled by a resin cooling process, and the growth of foamed cells is formed by deformation of the molten resin under a relatively low shear rate. For this reason, if the relaxation behavior in the molten state is too fast, the walls between the foamed cells cannot withstand extension, and the adjacent cells become identical and the foamed cells become coarse. When α (0) obtained by measurement of melt viscoelasticity of 10 to 100 rad / s, which is less affected by change over time within the measurement time, is 1.2 or more, the relaxation behavior against melt deformation due to entanglement of molecular chains is sufficiently slow. However, when foaming, the cells tend to be integrated with adjacent cells and become coarse. As for α (30) obtained by melt viscoelasticity measurement after 30-minute residence, if α (0) -α (30) is 0.20 or less, the relaxation behavior against melt deformation due to entanglement of molecular chains It cannot be said that it is slow enough, and when foaming, the cells tend to be integrated with adjacent cells and become coarse. Further, when α (0) <α (30), the molecular weight is lowered due to the deterioration of the resin, and the relaxation effect due to the entanglement of molecular chains is reduced, which causes the cell to become coarse in foam molding.

  The glycidyl group-containing styrenic copolymer (B) contains, for example, (X) a vinyl aromatic monomer, (Y) a glycidyl alkyl (meth) acrylate, and, if necessary, (Z) an epoxy group not contained. Those obtained by polymerizing a monomer mixture containing a vinyl group-containing monomer other than (X) (hereinafter referred to as “other vinyl group-containing monomer”) can be used. In the present invention, when the glycidyl group-containing styrenic copolymer (B) is contained, the molecular weight increases and the effect of increasing the melt extensional viscosity is easily expressed, and the processing condition control range is widened. A foamed molded article having excellent lightness and load resistance can be obtained.

  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) acrylate 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 (Z) can also be used as other vinyl group-containing monomers.

  The glycidyl group-containing styrenic copolymer (B) comprises (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. It is preferable that it is a copolymer which consists of a mass% other vinyl group containing monomer. 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. Here, (X) + (Y) + (Z) = 100 mass%. Since these compositions affect the functional group concentration contributing to the reaction with the amorphous 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 amorphous polyamide resin (A). It is. 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 crosslinked product, and the 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 amorphous 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.

  The content of the glycidyl group-containing styrene copolymer (B) can be appropriately set according to the molecular weight and the number of introduced functional groups, but is 0 to 10 parts by mass with respect to 100 parts by mass of the polyamide resin (A). More preferably, it is 0-9 mass parts, More preferably, it is 0-5 mass parts. When the glycidyl group-containing styrenic copolymer (B) exceeds 10 parts by mass, the thickening effect becomes excessive and adversely affects the moldability, and tends to affect the mechanical properties and transparency of the molded body. is there.

  The glycidyl group-containing styrene copolymer (B) has high miscibility with the amorphous polyamide resin (A), is well dispersed in the amorphous polyamide resin (A), and has a relatively high molecular weight. The reaction with the non-crystalline polyamide resin (A) produces a relatively loose cross-linked or branched structure that does not lead to a gel. This reaction product is considered to increase the molecular chain entanglement effect in the polyamide resin composition in the molten state, increase the melt viscosity, and develop the effect of slowing the relaxation behavior in a wide shear rate region.

  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 1 to 20 μm and the major axis is about 2 to 100 μm.

  In order to improve the affinity with the amorphous polyamide resin (A), the inorganic reinforcing material (C) is previously coated with a coupling agent such as an organic silane compound, an organic titanium compound, an organic borane compound, or an epoxy compound. Those that have been subjected to a coupling treatment are preferred, and those that easily react with carboxylic acid groups and / or carboxylic anhydride groups are particularly preferred. 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 article 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. However, since the light scattering characteristics may deteriorate when the above-described coupling treatment is performed, a transparent inorganic reinforcing material (C) that is not subjected to the coupling treatment when importance is attached to transparency and light scattering characteristics. ) Should be used.

  Content of an inorganic reinforcement material (C) is 0-350 mass parts with respect to 100 mass parts of non-crystalline polyamide resin (A). Preferably it is 20-150 mass parts, More preferably, it is 30-120 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.

  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 amorphous 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 composition.

  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 with respect to 100 parts by mass of the amorphous polyamide resin (A). -30 mass parts.

  Examples of the release agent include long chain fatty acids or esters thereof, metal salts, amide compounds, polyethylene wax, silicone, polyethylene oxide, and the like. As the long chain fatty acid, 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 may be partially or fully carboxylic acid monoglycol or 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 non-crystalline polyamide resin (A).

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

  The polyamide resin composition of the present invention may contain a thermoplastic resin other than the amorphous polyamide resin (A) as long as the effects of the present invention are not impaired. Examples of the thermoplastic resin other than the non-crystalline polyamide resin (A) include, for example, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), aramid resin, polyether ether ketone (PEEK), polyether ketone (PEK), Polyetherimide (PEI), Thermoplastic polyimide, Polyamideimide (PAI), Polyetherketone ketone (PEKK), Polyphenylene ether (PPE), Polyethersulfone (PES), Polysulfone (PSU), Polyarylate (PAR), Polyethylene Terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate (PC), polyoxymethylene (POM), polypropylene (PP), polyethylene (PE), polymethyl Pentene (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 non-crystalline polyamide resin (A) is low, a compatibilizing agent such as a reactive compound or a block polymer may be added as necessary, or other thermoplastics may be added. The resin may be modified (particularly acid modification is preferred). Other thermoplastic resins may be blended in a melted state by melt-kneading with the amorphous polyamide resin (A), or other thermoplastic resins are formed into fibers or particles to form an amorphous polyamide. You may disperse | distribute in resin (A). When other thermoplastic resins are contained, the content is preferably 0 to 50 parts by mass, more preferably 0 to 35 parts by mass, and more preferably 100 parts by mass of the amorphous polyamide resin (A). Preferably it is 0-20 mass parts.

  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.

  The polyamide resin composition of the present invention has good miscibility between the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B), and the glycidyl group-containing styrene copolymer (B) is added to the polyamide resin (A). Is easy to disperse and the molecular weight of the glycidyl group-containing styrene copolymer (B) is relatively high, so that the gel is not reached in the reaction between the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B). Not relatively loose crosslinks or branched structures can be produced. It is considered that this reaction product contributes to an increase in the molecular chain entanglement effect in the molten state, increases the melt viscosity, and develops the effect of slowing the relaxation behavior in a wide shear rate region.

  In preparing the polyamide resin composition of the present invention, the method of mixing the amorphous 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 above, 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) above, It is desirable that the polyamide resin (A) in which the glycidyl group-containing styrene copolymer (B) and the like are uniformly dispersed and mixed is heated and remelted to increase the melt viscosity.

  There are no particular limitations on the heating and remelting method, and any method known to those skilled in the art may be employed. For example, a single screw extruder, a twin screw extruder, a pressure kneader, a Banbury mixer, or the like can be used. Among these, a twin screw extruder is particularly preferably used. The operating conditions and the like of the twin screw extruder vary depending on various factors such as the type of the amorphous polyamide resin (A) and the type and amount of each component, and cannot be uniquely determined. For example, the processing temperature may be set within the range of 300 ° C. or less and the glass transition temperature (125 to 160 ° C.) of the amorphous polyamide resin (A) +50 to 150 ° C. or so. 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. As for the screw configuration of the extruder, it is preferable that several kneading disks with excellent kneading are incorporated.

  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 usually comprises a non-foamed skin layer present in the surface layer and a foamed layer present in the inner layer. These non-foamed skin layer and foamed layer are the above-described polyamide resin of the present invention. Since it is formed with the composition, it has a foam structure in a uniform cell state, 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 cell is preferably equal to or 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 foam 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. However, as a molding method capable of obtaining molding cycle performance and cost, and uniform foaming, the drawings are shown below. A foaming method (mold expanding method) for expanding a mold, which will be described using, is preferably employed. Of course, the foamed molded article 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”). In this method, the mold 2 is moved in the mold opening direction to enlarge the volume of the cavity 3 to obtain a foam molded article. Specifically, after filling the cavity 3 with the polyamide resin composition M and the foaming agent, a non-foamed skin layer is formed on the surface of the polyamide resin composition M filled in the cavity 3 by heating at a predetermined temperature. Is done. When the non-foamed skin layer reaches a predetermined thickness (100 to 800 μm), the mold 2 is moved in the mold opening direction to expand the volume of the cavity 3.

  The foaming agent that can be used in obtaining the foamed molded article of the present invention is added to a resin melted in a resin melting zone of a molding machine as a gas component that becomes a foaming nucleus 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, and among these, ADCA is preferable. 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 base material made of a thermoplastic resin having a melting point lower than the decomposition temperature of the chemical foaming agent in order to uniformly disperse the amorphous polyamide resin (A). It can also be used as a foaming agent 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 amorphous polyamide resin (A) may increase so much that the physical properties may be deteriorated. It becomes difficult to make a masterbatch due to the problem of stability

  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 with respect to 100 parts by mass of the thermoplastic resin composition (resin component in the polyamide resin composition). Furthermore, it is preferable that it is 0.1-20 mass parts. 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, you may mix arbitrarily according to the state of a 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 specific gravity larger than that of a gas and a viscosity smaller than that of 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.

  Since the polyamide resin foam molded article of the present invention has both heat resistance and light weight, it is useful as, for example, an automobile-related part such as an interior part, an exterior part, a cover, a casing, or a load support system part. Moreover, since the polyamide resin foam molded article of the present invention has good light scattering properties, it is also useful as a light scattering component.

  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.

<Melting point (Tm) and glass transition temperature (Tg)>
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 addition, the temperature at the intersection of the base line extension below the glass transition point and the tangent line indicating the maximum slope from the peak rising portion to the peak apex in the second temperature increase process is expressed as the glass transition temperature ( Tg).

<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

<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.

<Skin layer thickness and foamed state>
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 cross-sectional observation sample image | photographed with the scanning electron microscope or the stereomicroscope was image-processed, and the thickness of the integrated non-foaming layer seen in a surface layer part was measured as skin layer thickness.

  In the foamed cross-sectional image, “○” indicates that a cavity having a length of 1/2 or more of the total thickness of the foam molded body is not observed in the foam layer between the upper and lower skin layers. A case where a cavity having a length of ½ or more of the entire thickness of the foamed molded product was observed in the foam layer in between was evaluated as “x”.

<Productivity>
In obtaining a polyamide resin composition, when there was no particular problem during melt-kneading, it was evaluated as “◯”, and when the viscosity was too high and extrusion was difficult, it was evaluated as “x”.

<Dimensional stability during water absorption (95% RH water absorption dimension increase)>
Using the obtained polyamide resin foamed molded article (width 100 mm × length 250 mm), a water absorption test was carried out by measuring the change over time by standing in an environment of 80 ° C. and 95% RH. When it disappeared, it was regarded as equilibrium water absorption, and the dimension at this time (dimension when 95% RH water was absorbed) was measured. Then, the dimensional change rate was obtained from the following formula, and the case where the dimensional change rate was less than 0.1% was evaluated as “◯”, and the case where the dimensional change rate was 0.1% or more was evaluated as “x”. In addition, in the following formula | equation, the dimension at the time of drying is an initial dimension of the polyamide resin foam molded product before being subjected to a water absorption test. The dimensions were measured by measuring the dimension (mm) in the width direction and the dimension (mm) in the length direction of the polyamide resin foamed molded article, and taking the average value as the dimension during 95% RH water absorption or drying.
Dimensional change rate (%) = [(95% RH water absorption-dry size) / dry size] × 100

<Load resistance retention characteristics at the time of water absorption>
A test piece having a width of 10 mm and a length of 100 mm was cut out from the obtained molded polyamide resin foam, and the maximum load when a three-point bending test was performed at a span length of 50 mm and a load speed of 2 mm / min was X (N). The maximum load when a three-point bending test was conducted at a temperature of 80 ° C. and a humidity of 95% for 200 hours and a span length of 50 mm and a load speed of 2 mm / min was defined as Y (N). Those having a value of 0.8 or more were evaluated as “◯”, and those having a value less than 0.8 were evaluated as “×”.

<Light scattering characteristics>
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 as a comparison object was produced under the same conditions as in the above.

  When the obtained polyamide resin foamed molded product and the polyamide resin non-foamed molded product (comparative object) obtained above are irradiated with light having a wavelength of 440 nm, the irradiated light is scattered within the molded product, and the entire molded product emits light. The case where the degree of visible light is more noticeable than that of the non-foamed molded article is “◯”, the case where the degree of light emission is equivalent to that of the non-foamed molded article, or the light transmission itself is poor, The case where light was not transmitted to the side opposite to the light source of the molded body or the amount of transmitted light was small and light emission due to light scattering inside the molded body was not recognized was evaluated as “x”.

<Measurement of melt viscoelasticity (α value)>
In order to obtain the above-mentioned α value in the melt viscoelasticity measurement of the amorphous polyamide resin (A), melt viscoelasticity measurement is performed in the frequency range of 10 to 100 rad / s in the linear region, and the frequency (x) and the storage elastic modulus Frequency-dependent data was acquired as a log-log graph of (y).

The melt viscoelasticity measurement (dynamic viscoelasticity measurement) is performed under the following conditions using “ARES” manufactured by TA Instruments and a parallel plate of 25 mmφ as a measurement jig, and the frequency (ω) −storage elastic modulus (G ′ ) Was obtained. The graph which shows the result of the amorphous polyamide resin (A1: MACM * 14) used in Example 1, 4, 7-10 is shown in FIG. 4, FIG. 5, The crystalline polyamide resin ( A graph showing the results of A4: polyamide 6) is shown in FIG. When determining the slope (α value) of the storage elastic modulus from the plot, a straight line was obtained on the plot using the power approximation formula of the obtained data points, and the slope of the straight line was determined. The measurement was 260 ° C. in all examples, 240 ° C. in the comparative example using “polyamide 6 (A4)”, 275 ° C. in the example using “polyamide 66 (A5)”, and “polyamide 6T6I (A6)”. Was performed at 280 ° C.
Strain = 10%
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)>
(Amorphous polyamide resin having an alicyclic group in the present invention; A1 to A3)
A1: MACM · 14 ((polycondensate of bis (3-methyl-4-amino-cyclohexyl) methane and tetradecanedioic acid); “G350” manufactured by Arkema, glass transition temperature (Tg) 146 ° C., number average molecular weight 14200
A2: MACM · 12 ((Condensate of bis (3-methyl-4-amino-cyclohexyl) methane and dodecanedioic acid); “TR-90” manufactured by EMS, glass transition temperature (Tg) of 155 ° C., number Average molecular weight 13300
A3: MACM · 12 · I (polycondensate of bis (3-methyl-4-amino-cyclohexyl) methane, dodecanedioic acid and isophthalic acid); “TR-55” manufactured by EMS, glass transition temperature (Tg ) 162 ° C., number average molecular weight 18600
(Comparative polyamide resin; A4 to A6)
A4: Polyamide 6; “Nylon T-820” manufactured by Toyobo, 6 nylon with relative viscosity RV = 3.1, number average molecular weight 25400, melting point 225 ° C.
A5: Polyamide 66; “Amilan (registered trademark) CM3001N” manufactured by Toray, 66 nylon with relative viscosity RV = 2.8, number average molecular weight 17900, melting point 265 ° C.
A6: Polyamide 6T6I (polycondensate of polyhexamethylene terephthalamide and polyhexamethylene isophthalamide); “Grivory G21” manufactured by EMS, 6T / 6I = 33/67 (mol%), Tg 125 ° C., number average molecular weight 15100 , Amorphous

<Glycidyl group-containing styrene copolymer (B)>
(B1: Styrene polymer 1)
The oil jacket temperature of a 1 liter pressurized stirred tank reactor 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 temperature inside 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 polymer (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)
A styrenic polymer (in the same manner as in the production of the styrenic polymer (B1) except that a monomer mixed solution consisting of St77 parts by mass, GMA 23 parts by mass, Xy 15 parts by mass, and DTBP 0.3 parts by mass was used. 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: Glass beads; “EMB-10” manufactured by Potters Barotini

<Other additives>
Stabilizer 1: Cupric bromide (manufactured by Nacalai Tesque, reagent)
Stabilizer 2: “Irganox B1171” manufactured by Ciba Specialty Chemicals
Mold release agent: “Montanic acid ester wax WE40” manufactured by Clariant Japan

(Examples 1-10, Comparative Examples 1-7)
The amount (parts by mass) of the raw materials (A) to (C) described above is as shown in Tables 1 and 2, and the amount of other additives used is 0 for the stabilizer 1 in each of the examples and comparative examples. 0.06 parts by mass, 0.3 parts by mass of stabilizer 2 and 0.4 parts by mass of the release agent, and these were melt-kneaded with a 35φ twin-screw extruder (manufactured by Toshiba Machine) at a screw speed of 100 rpm. . Specifically, raw materials other than glass fibers (inorganic reinforcing materials (C1) and (C2)) are mixed in advance and introduced from the main hopper, and glass fibers (inorganic reinforcing materials (C1) and (C2)) are placed from the vent port to the side. I put it in the feed. At this time, the cylinder temperature was 285 ° C. in the examples, 250 ° C. in the comparative example using “polyamide 6 (A4)”, 280 ° C. in the example using “polyamide 66 (A5)”, “polyamide 6T6I ( In the example using “A6)”, the temperature was set to 280 ° C. 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) After injecting and filling the mold temperature-controlled at 100 ° C., 100 to 800 μm of non-injection depending on the injection external pressure and the foaming pressure from the inside. At the stage where the foam skin layer is formed, the working mold is moved in the mold opening direction by the length indicated as the core back amount (mm) in each table, the cavity volume is expanded, Obtained.

  The evaluation result of the polyamide resin foaming molding obtained in Examples 1-10 and Comparative Examples 1-7 is shown in Tables 1-2.

  As is clear from Tables 1 and 2, the polyamide resin foam molded articles of Examples 1 to 10 have a good foamed state and excellent lightness, and have sufficient dimensional stability and load resistance even under water absorption. Further, it can be seen that the foamed molded article also has light scattering characteristics. On the other hand, some of the foamed molded articles of Comparative Examples 1 to 7 have a low specific gravity, but the low water absorption is poor, and any of the evaluation items is inferior to Examples 1 to 10. It was.

  Moreover, the foaming molding obtained in Example 1 and Comparative Example 2 was cut, and the cross section was observed with a scanning electron microscope or an optical microscope. A cross-sectional photograph (magnification 30 times) of the foamed molded product of Example 1 is shown in FIG. 1, and a cross-sectional photograph (magnification 20 times) of the foamed molded product of Comparative Example 2 is shown in FIG. 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 2 has a poor foamed state. .

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 (8)

For 100 parts by mass of the amorphous polyamide resin (A),
Glycidyl group-containing styrenic copolymer (B) 0 containing 2 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. 10 parts by mass;
A polyamide resin composition for a foamed molded article containing 0 to 350 parts by mass of an inorganic reinforcing material (C),
The amorphous polyamide resin (A) has an alicyclic group, and
In the melt viscoelasticity measurement of the non-crystalline polyamide resin (A), 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 expressed as frequency (x). And α obtained from a melt viscoelasticity measurement performed at 260 ° C., where a multiplier (y = ax ^α ; a is a constant) when plotted on a log-log graph of storage modulus (y) and α is a constant. When the value is α (0) and the α value obtained from the melt viscoelasticity measurement performed again after the melt viscoelasticity measurement for 30 minutes at the same temperature is α (30), the following formula (i) and A polyamide resin composition characterized by satisfying (ii).
α (0) <1.20 (i)
α (0) −α (30)> 0.20 (ii)   The non-crystalline polyamide resin (A) is an aliphatic dicarboxylic acid selected from dicarboxylic acids having 12 to 18 carbon atoms, bis (4-amino-cyclohexyl) methane, and bis (3-amino-cyclohexyl) methane. , Obtained by polycondensation with an alicyclic diamine selected from the group consisting of bis (3-methyl-4-amino-cyclohexyl) methane and 2,2-bis (4-amino-cyclohexyl) propane The polyamide resin composition for foam molded articles according to claim 1.   The polyamide resin composition according to claim 1 or 2, wherein the amorphous polyamide resin (A) is a resin having no aromatic group.   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. The polyamide resin composition according to any one of claims 1 to 3, wherein the polyamide resin composition is a copolymer comprising a vinyl group-containing monomer other than (X), which does not contain an epoxy group of mass%.   A polyamide resin foam molded article obtained by using the polyamide resin composition according to any one of claims 1 to 4.   Melting the polyamide resin composition and injecting and filling the polyamide resin composition in a molten state together with a chemical foaming agent and / or a supercritical inert gas into a cavity formed by a plurality of molds clamped The foamed polyamide resin according to claim 5, which is obtained by moving at least one mold in the mold opening direction and expanding the volume of the cavity when a non-foamed skin layer having a thickness of 100 to 800 µm is formed on the surface layer. Molded body.   The polyamide resin foam molded article according to claim 5 or 6, which is used as an automobile-related part.   The polyamide resin foam molded article according to claim 5 or 6, which is used as a light scattering component.