JP2598982B2 - Manufacturing method of molded body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a molded article of a polyamide resin mixture. In more detail, not only is the heat resistance excellent, but also the surface of the obtained molded body is free of sink marks and warpages, so the surface of the molded product is beautiful, and the molding of the polyamide resin obtained by a simple method. It relates to a method for producing a body.

[Conventional technology]

Polyamide resins are used in various fields because they have not only good workability but also good mechanical strength such as heat resistance and rigidity, and excellent hardness.

However, since polyamide resins generally have high crystallinity, they hardly flow below the melting point. When the temperature exceeds the melting point, the viscosity and elasticity decrease sharply with increasing temperature,
It becomes remarkably fluid. Therefore, there is no sink on the surface of the molded product, and it is difficult to obtain a molded product with a beautiful surface. On the other hand, in a mixture containing a foaming agent, bubbles generated from the foaming agent are uniformly dispersed, and it is difficult to maintain the material in a temperature range that exhibits an appropriate viscoelasticity that does not fly out of the system. It is difficult to obtain a beautiful molded product by expanding at a temperature and exposing foamed foam on the surface of the molded product. Styrene-based polymers, which are amorphous resins, are easy to produce beautiful molded products due to small decrease in viscosity and elasticity due to temperature maintenance, and are widely used industrially. However, a disadvantage is poor heat resistance.

In other words, in the process of obtaining a molded article of a polyamide resin having excellent heat resistance, the solidification accompanied by crystallization causes a change in density compared to the case of obtaining a molded article of a styrene-based polymer that is an amorphous resin. Very large.
As a result, particularly when performing injection molding, there are drawbacks in that the finished dimensions with respect to the mold are reduced, and when a thick molded product is obtained, sinks occur or warpage due to shrinkage anisotropy occurs. .

Conventionally, as a method of improving these disadvantages, a method of obtaining a molded product using a special mold, a method of highly filling an inorganic substance, a method of adding a nucleating agent, a method of molding under special molding conditions, a general chemical method A method of adding a foaming agent has been proposed.

However, a method using a special mold leads to an increase in cost and limits the design of a molded product. In addition, in the method of highly filling an inorganic substance, the physical properties (particularly, impact strength) of the molded article and the gloss of the surface of the molded article are reduced. Furthermore, in the method of adding a nucleating agent,
The improvement effect is not sufficient and the molding temperature is very limited. Further, in the method of molding under special molding conditions, the molding cycle becomes longer. Furthermore, in the method of adding a normal chemical foaming agent, foaming foam is generated on the surface of the molded product,
In addition, there are drawbacks such as rough surface of the molded product.

From these facts, the present inventors have proposed (A) a propylene polymer, (B) at least ethylene and an α, β-unsaturated monocarboxylic acid, an α, β-unsaturated dicarboxylic acid, an anhydride thereof and a half ester. A copolymer comprising at least one monomer selected from the group consisting of: (C) a copolymer comprising at least ethylene and an ethylenically unsaturated monomer containing a hydroxyl group or an epoxy group; and (D) a foaming agent. An application has already been filed for a method for producing a foam of a mixture (Japanese Patent Laid-Open No. 62-325349).

[Problems to be solved by the invention]

As described above, when the polyamide resin is foamed, sink and warp are generated in the molded body (foam). Therefore, it is an object of the present invention to obtain a molded article free from sink marks and warpage as in the invention previously proposed.

Therefore, the present invention is free from these drawbacks (problems), that is, not only has no sink mark on the surface, but also has no warp, and is capable of producing a polyamide resin molded article (foam) having excellent dimensional stability by a simple method. Is to get.

[Means and actions for solving the problem]

According to the present invention, these objects are attained from the group consisting of (A) polyamide resins, (B) at least ethylene and α, β-unsaturated monocarboxylic acids, α, β-unsaturated dicarboxylic acids and anhydrides thereof. A copolymer (I) comprising at least one selected monomer, (C) a copolymer (II) comprising at least ethylene and an ethylenically unsaturated monomer having a hydroxyl group or an epoxy group, and (D) This is a method for producing a molded product of a mixture of a foaming agent which decomposes at a temperature at which a polyamide resin melts but can decompose at a maximum of 300 ° C., wherein the total amount of the copolymer (I) and the copolymer (II) is The mixing ratio of the copolymer (I) in the copolymer is 1 to 99% by weight, but the total amount of the carboxyl groups and the carboxylic anhydride groups in the copolymer (I): the hydrid in the copolymer (II) The ratio of the total amount of the loxyl group and the epoxyl group is from 0.2: 1 to 5: 1 in molar ratio, the copolymerization ratio of ethylene in these copolymers is 30 to 99.5% by weight, and The copolymerization ratio of the monomer having a group is 0.1 to 70% by weight,
Polyamide resin, copolymer (I) and copolymer (II)
The mixing ratio of the foaming agent to the total amount of 100 parts by weight is 0.001.
To 5.0 parts by weight of the copolymer (I) and the copolymer (II) so that the extraction residue of toluene at the boiling point is at most 10% by weight. Degree is at least 10% and 98% sulfuric acid
Dissolve 1g in 100cc, the relative viscosity measured at a temperature of 20 ℃ 0.5-5.0 polyamide resin in the whole polymer
The mixture is dry-blended to 70 to 99.9% by weight, and the resulting mixture is at a temperature of 400 ° C. or lower, and the extraction residue of the copolymer (I) and the copolymer (II) is at least 70%.
The injection molding is performed while foaming only the inside of the molded body so as to obtain the weight% of the molded body. Hereinafter, the present invention will be described specifically.

(A) Polyamide resin The polyamide resin used in the present invention is a linear polymer compound having an acid amide bond (-CONH-), and is roughly classified into a polyamide obtained by polycondensing a dibasic acid and a diamine. Polyamides obtained by self-polycondensation of cyclic lactams and amino acids are known. Representative examples of the former include polycondensates of hexamethylene and adipic acid (nylon 6-6) and polycondensates of hexamethylene diamine and sebacic acid (nylon 6
-10), polycondensate of hexamethylenediamine and dodecanoic acid (nylon 6-12), polycondensate of hexamethylenediamine and terephthalic acid (nylon 6T), polycondensate of xylenediamine and adipic acid (XD -6 nylon) and a polycondensate of xylene diamine and sebacic acid (XD-10
Nylon). Representative examples of the latter include self-condensation products of caprolactam (nylon 6), 10
Self-polycondensates of aminoundecanoic acid (nylon 11) and self-polycondensates of laurinlactam (nylon 12).

Relative viscosity of the polyamide resin (concentrated sulfuric acid 10
Dissolve 1 g of the resin in 0 cc and measure at a temperature of 20 ° C.
[Η]) is 0.5 to 5.0, preferably 0.6 to 4.8. When molded using a polyamide resin having a relative viscosity of less than 0.5, it is difficult to obtain a molded product having excellent mechanical strength.
On the other hand, when using a polyamide resin resin exceeding 5.0,
Moldability is not good.

Also, the degree of crystallinity is at least 10%, especially
% Or more is desirable. If a polyamide resin having a crystallinity of less than 10% is used, the production method of the present invention is not effective because sink marks and warpage are originally small.

These polyamide resins are industrially manufactured and used in various fields, and their manufacturing methods, types, various physical properties, and molding methods are described in "Plastic Handbook" edited by Shunsuke Murahashi, Ryohei Oda, Minoru Imoto (Asakura Shoten, published in 1984), pages 521 to 548, and the like.

(B) Copolymer (I) The copolymer (I) used in the present invention comprises at least ethylene and an α, β-unsaturated monocarboxylic acid, α,
A copolymer comprising at least one monomer selected from the group consisting of β-unsaturated dicarboxylic acids and anhydrides. Examples of the copolymer include the following polymers.

(1) a copolymer of ethylene and an α, β-unsaturated monocarboxylic acid (hereinafter referred to as “ethylene copolymer (a)”); and (2) ethylene and an α, β-unsaturated dicarboxylic acid or a mixture thereof. Copolymer with anhydride [hereinafter referred to as "ethylene copolymer (b)"] It is desirable that these copolymers (I) melt at a temperature of 150 ° C or lower and have fluidity.

(1) Ethylene-based copolymer (a) The ethylene-based copolymer (a) is a copolymer of at least ethylene and an α, β-unsaturated monocarboxylic acid. Is preferably a copolymer obtained by copolymerizing a radical polymerizable comonomer having a polar group (hereinafter, referred to as "third component").

By copolymerizing the third component as a comonomer, a multi-component copolymer having a monomer corresponding to the third component copolymerized in the ethylene-based copolymer (a) can be obtained [the ethylene-based copolymer described below]. The same applies to the case of the combination (b) or the ethylene copolymer (d)].

The α, β-unsaturated monocarboxylic acid that can be used in the production of the ethylene copolymer (a) generally has 3 to 20, preferably 3 to 16 carbon atoms. Representative examples include acrylic acid, methacrylic acid, crotonic acid, monoalkyl malates, monoalkyl fumarate, and the like.

The third component is a radically polymerizable vinyl compound containing a polar group, and is an unsaturated carboxylic acid ester,
Representative examples include vinyl esters and alkoxyalkyl (meth) acrylates.

The unsaturated carboxylic acid ester usually has 4 to 40 carbon atoms, and particularly preferably 4 to 20 carbon atoms. As a typical example, those having good heat stability such as methyl (meth) acrylate and ethyl (meth) acrylate are preferable, and those having poor heat stability such as t-butyl (meth) acrylate cause foaming and the like, and thus are preferable. Absent.

Furthermore, the alkoxyalkyl acrylate usually has at most 20 carbon atoms. The alkyl group preferably has 1 to 8 (preferably 1 to 4) carbon atoms, and the alkoxy group has 1 to 8 carbon atoms (preferably 1 to 4 carbon atoms).
4) are desirable. Representative examples of preferred alkoxyalkyl acrylates include methoxyethyl acrylate, ethoxyethyl acrylate, and butoxyethyl acrylate. The vinyl ester generally has at most 20 carbon atoms (preferably 4 to 16 carbon atoms).
). Typical examples thereof include vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate.

In the ethylene copolymer (a), the amount of the third component is
It is preferably at most 25 mol, particularly preferably 2 to 20 mol%. Even if it exceeds 25 mol%, the characteristics of the present invention are exhibited, but it is not necessary to exceed 25 mol%, which is not preferable in terms of production and economy.

The binding amount of the α, β-unsaturated monocarboxylic acid in the ethylene copolymer (a) is preferably 0.5 mol% or more and 25 mol% or less, and particularly preferably 1.0 mol% to 15 mol%. is there.

The α, β-unsaturated monocarboxylic acid serves as a cross-linking reaction point with the copolymer (II) described later and for imparting adhesion to a wide variety of base materials. There is no need to be in excess. As the water content increases, the water absorption increases, which not only has a negative effect on the deterioration of electrical properties due to foaming during molding and water absorption after molding, but also has problems in manufacturing such as safety, separation, recovery, etc. Is also disadvantageous. On the other hand, if it is less than 0.5 mol%, there is no problem in terms of adhesiveness, but foamed foam tends to be exposed on the surface of the molded article during molding, and a beautiful molded article cannot be obtained.

(2) Ethylene copolymer (b) The ethylene copolymer (b) used in the present invention is a copolymer of ethylene and an α, β-unsaturated dicarboxylic acid or an anhydride thereof. (May include the third component). That is, ethylene and an α, β-unsaturated dicarboxylic acid or its anhydride or those obtained by directly copolymerizing the third component with them.

Examples of the third component include compounds of the same type as the ethylene-based copolymer (a).

When the ethylene copolymer (b) is produced by a direct copolymerization method, an α, β-unsaturated dicarboxylic acid or an anhydride thereof is selected as a copolymer comonomer.

 The α, β-unsaturated dicarboxylic acid usually has a large carbon number.
At least 20 and especially 4 to 16 are preferred.
You. Representative examples of the dicarboxylic acid include maleic acid and phthalic acid.
Malic acid, itaconic acid, citraconic acid, 3,6-endomethyi
Len-1,2,3,6-tetrahydro-cis-phthalic acid (nadine
Dic acid ).

"Α, β-unsaturated dicarboxylic acid or anhydride thereof"
The binding amount of the unsaturated copolymer (hereinafter referred to as “unsaturated carboxylic acid component”) in the ethylene-based copolymer (b) is preferably 0.5 mol% or more and 20 mol% or less. More preferably 1.0-1
5 mol%.

(C) Copolymer (II) Further, the copolymer (II) used in the present invention is a copolymer comprising at least ethylene and an ethylenically unsaturated monomer containing a hydroxyl group or an epoxy group. Examples of the copolymer include the following polymers.

(1) A saponified product obtained by saponifying a part or all of a copolymer of ethylene and a vinyl ester [hereinafter referred to as “ethylene copolymer (c)”] (2) Ethylene and a hydroxyl group Copolymers with "ethylenically unsaturated monomers having an epoxy group" (hereinafter referred to as "hydroxyl compounds") or "ethylenically unsaturated monomers having an epoxy group" (hereinafter referred to as "epoxy compounds") and Multicomponent copolymer with three components [hereinafter referred to as “ethylene copolymer (d)”) (1) Ethylene copolymer (c) Further, the ethylene copolymer used in the present invention is ethylene and vinyl. It can be produced by saponifying a part or all of a copolymer with an ester.

As the vinyl ester which is a comonomer component of the copolymer, the same kind as the above-mentioned third component is preferably used, and vinyl acetate is particularly preferable.

In producing the ethylene-based copolymer (d) by saponifying the copolymer, a generally used saponification method may be applied. The degree of saponification is usually 80% or more, preferably 85% or more, and particularly preferably 90% or more.

(2) Ethylene-based copolymer (d) Further, the ethylene-based copolymer (d) used in the present invention may be a copolymer of ethylene and a hydroxyl-based compound or an epoxy-based compound. May be a multi-component copolymer with the third component.

Examples of the hydroxyl compound which is a comonomer component of the copolymer include hydroxyalkyl acrylate (the alkyl group usually has 1 to 25 carbon atoms) and 3 to 25 carbon atoms.
Α-alkenyl alcohols. Representative examples of the hydroxyl compound include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyhexyl acrylate and allyl (al
lyl) alcohol.

Further, as a typical example of the epoxy-based compound, a compound represented by the following general formula [Formula (I) and Formula (II)] can be given.

Representative examples of the epoxy compounds represented by the formulas (I) and (II) include glycidyl methacrylate, glycidyl acrylate, α-methylglycidyl acrylate, α-methylglycidyl methacrylate, vinyl glycidyl ether, and allyl glycidyl ether. And methacryl glycidyl ether.

The copolymerization ratio of ethylene in the copolymer (II) is generally 30 to 99.5% by weight, preferably 30 to 99.0% by weight, and particularly preferably 35 to 99.0% by weight. Further, the copolymerization ratio of the hydroxyl compound is usually 0.1 to 70% by weight for the same reason as in the case of the ethylene copolymer (a),
It is preferably from 0.5 to 70% by weight, particularly preferably from 0.5 to 60% by weight. Further, in the case of a multi-component copolymer, the copolymerization ratio of the third component is generally at most 69.9% by weight for the same reason as the ethylene-based copolymer (a), and is preferably 65% by weight or less, particularly preferably It is preferably at most 60% by weight.

These ethylene-based copolymers (a), ethylene-based copolymers (b) and ethylene-based copolymers (d) and ethylene-vinyl copolymers used for producing the ethylene-based copolymers (c) All copolymers are 50 to 25
Manufactured by copolymerizing comonomers (including third components) that copolymerize with ethylene in the presence of a chain transfer agent (eg, organic peroxide) at a temperature of 120-260 ° C. at a high pressure of 00 kg / cm ² can do. This copolymerization method is a well-known method.

The melt index of these ethylene copolymers (a) to (d) (measured according to JIS K7210 under condition 4, hereinafter referred to as "MFR") is generally 0.01 to 1000 g / 10 minutes. Yes, 0.05 to 500 g / 10 min is desirable, and 0.1 to 500 g / 10 min is particularly preferable. MFR 0.01g
If an ethylene copolymer of less than / 10 minutes is used, not only is it difficult to uniformly mix the mixture of the present invention when producing the mixture, but also the moldability is poor.

The mixture of the present invention can be produced by uniformly mixing the above polyamide resin, copolymer (I), copolymer (II) and foaming agent within the mixing ratio described below. At this time, the copolymer (I), the copolymer (II) and the blowing agent are mixed in advance to form a masterbatch, which can be obtained by dry blending a polyamide resin with the masterbatch. By mixing the above reaction accelerator, the crosslinking between the copolymer (I) and the copolymer (II) can be promoted.

(D) Reaction Accelerator The reaction accelerator used in the present invention is widely known as a curing agent for epoxy resin, and a typical example thereof is “epoxy resin” edited by Hiroshi Kakiuchi (Shokodo, 1979 Pages 26 to 29, 32 to 35, 10
Pages 9 to 128, pages 185 to 188, pages 330 and 331 are mentioned.

Typical examples of the reaction accelerator include primary, secondary or tertiary amines, acids,
Examples thereof include alkaline compounds and ammonium salts represented by the formula (IV).

In the formulas (III) and (IV), R ⁶ , R ⁷ , R ⁸ and R ⁹ may be the same or different, and each represents a hydrogen atom, an alkyl group having 1 to 32 carbon atoms, an aryl group, or an alkaryl group. And hydrocarbon groups selected from aralkyl groups, but not all hydrogen atoms at the same time. X is a halogen atom. In these formulas, the carbon number of R ⁶ to R ⁹ is
Up to 12 hydrocarbon groups are preferred. X is preferably a chlorine atom or a bromine atom.

Representative examples of the reaction accelerator include ethanolamine,
Diethanolamine, triethanolamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, n-butylamine, N, N-dimethylaminoethanol, N, N-diethylaminoethanol, morpholine, biperidine, pyridine, N, N-dimethylamino Ethyl acrylate, N, N-dimethylamino methacrylate, N, N-diethylaminoethyl acrylate, trimethylamine, triethylamine, tri-n-butylamine, N, N-dimethylbenzylamine, hexamethylenetetramine, triethylenediamine, N, N-dimethylpiperazine And tertiary amines such as N-methylmorpholine, acidic or alkaline compounds such as p-toluenesulfonic acid and potassium hydroxide, and trimethylbenzyl ammonium chloride. Id, tetraethylammonium bromide, tetrabutylammonium chloride and cetyltrimethylammonium halide ammonium salt such as chloride, zinc chloride and the like more. Among them, N, N-dimethylbenzylamine and p-toluenesulfonic acid are preferred.

In producing the mixture of the present invention, the copolymer (I)
A copolymer comprising ethylene and a monomer having an α, β-unsaturated dicarboxylic acid group, that is, an ethylene-based multi-component copolymer comprising ethylene and an anhydride of an α, β-unsaturated dicarboxylic acid or these and the third component Using a polymer,
And a copolymer comprising ethylene and an ethylenically unsaturated monomer containing an epoxy group as the copolymer (II), that is, a copolymer of ethylene and a monomer represented by the above formula (I) or (II) or When an ethylene-based multi-component copolymer comprising these components and the third component is used, and the reaction accelerator is not used, the copolymer (I) and the copolymer (II) do not crosslink, and the heat resistance is high. , A molded article of a good mixture cannot be obtained. In this case, an organic compound or polymer having a boiling point of 150 ° C. or higher and a hydroxyl group (−
OH group) or a carboxyl group (—COOH group) is blended (mixed) to obtain the copolymer (I).
And the copolymer (II). The polymer is selected from the group consisting of ethylene and α, β-unsaturated monocarboxylic acid and α, β-unsaturated dicarboxylic acid among the ethylene-based copolymer (a) and the ethylene-based copolymer (b). Copolymers with selected monomers (these copolymers may be ethylene-based multi-component copolymers containing a third component), saponified copolymers of ethylene and vinyl acetate, ethylene and hydroxyalkyl acrylate And a copolymer having ethylene or propylene as a main component (including a homopolymer), which was used in producing the ethylene copolymer (a) and the ethylene copolymer (b). α, β-unsaturated monocarboxylic acid,
Modified olefin polymers obtained by graft polymerization of an α, β-unsaturated dicarboxylic acid or its anhydride are exemplified. Examples of the organic compound include ethylene glycol, polyethylene glycol, propylene glycol, glycerin, and polypropylene glycol.

(E) Blowing agent The blowing agent used in the present invention decomposes at the temperature at which the polyamide resin melts, but at most 300 ° C.
Can be decomposed. Moreover, there is no particular limitation as long as the foaming agent itself and the gas generated by decomposition do not react with any of the polyamide resin, the copolymer (I) and the copolymer (II). In particular, those having a decomposition temperature of 190 to 300 ° C, particularly 220 to 300 ° C, are suitable. Suitable foaming agents include azodicarbonamide-based organic foaming agents and inorganic compounds (for example, sodium bicarbonate) and organic acids (for example, salicylic acid, stearic acid, lauryl acid) and borane that satisfy the above conditions in the above temperature range. Blowing agents in combination with acids can also be used.

(F) Mixing ratio In producing the final mixture of the present invention, the mixing ratio of the polyamide resin in the total amount of the polyamide resin, the copolymer (I) and the copolymer (II) is 70 to 99.9% by weight.
[That is, the mixing ratio of the copolymer (I) and the copolymer (II) is 30 to 0.01% by weight in total.]
It is preferably 99.5% by weight, particularly preferably 75 to 99.0% by weight. The mixing ratio of the polyamide resin in the total amount of the polyamide resin, the copolymer (I) and the copolymer (II) is
If it is less than 70% by weight, injection molding is difficult, and a good molded product cannot be obtained. On the other hand, if it exceeds 99.9% by weight, the viscosity retention during foaming is poor, and a good molded product cannot be obtained.

The mixing ratio of the copolymer (I) in the total amount of the copolymer (I) and the copolymer (II) is 1 to 99% by weight, preferably 5 to 95% by weight, more preferably 10 to 95% by weight. 90% by weight is preferred. Even when the mixing ratio of the copolymer (I) in the total amount of the copolymer (I) and the copolymer (II) is less than 1% by weight or more than 99% by weight, the viscosity is maintained during foaming. Bad, no beautiful molded body with no bubbles on the surface.

The ratio of the sum of the carboxyl groups and carboxylic anhydride groups of the copolymer (I) and the sum of the hydroxyl groups and the epoxy groups of the copolymer (II) in the mixture is a molar ratio.
It is preferably from 0.2: 1 to 5: 1, particularly preferably from 0.3: 1 to 3: 1.

When a reaction accelerator is added, its mixing ratio is generally at most 5.0 parts by weight based on 100 parts by weight of the total amount of the polyamide resin, the copolymer (I) and the copolymer (II).
Parts by weight, preferably 0.01 to 5.0 parts by weight, especially
0.01 to 2.0 parts by weight are preferred. Even if the reaction accelerator is added in an amount exceeding 5.0 parts by weight, the effect of promoting the low-temperature crosslinking is exhibited, but not only the effect of inhibiting the crosslinking adhesion by the reaction accelerator itself, but also the effect of the reaction accelerator on the molded article is reduced. It is not preferable because it causes bleeding on the surface and the like, and a good molded body cannot be obtained.

Further, when the organic compound and / or polymer having a hydroxyl group or a carboxyl group is blended when producing the mixture of the present invention, the mixing ratio thereof is determined by the polyamide resin, the copolymer (I) and the copolymer. Usually at most 20 per 100 parts by weight of total (II)
Parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.5 to 20 parts by weight, particularly preferably 1.0 to 15 parts by weight.

Further, the mixing ratio of the foaming agent to the total amount of 100 parts by weight of the polyamide resin, the copolymer (I) and the copolymer (II) is 0.001 to 5.0 parts by weight, preferably 0.002 to 5.0 parts by weight, and 0.005 to 5.0 parts by weight. 4.0 parts by weight is preferred. Total amount of polyamide resin, copolymer (I) and copolymer (II) 100
If the mixing ratio of the foaming agent to the parts by weight is less than 0.001 part by weight, the foaming amount is small and not only sinks and warpages on the surface of the molded product are generated but also the dimensional stability cannot be improved. On the other hand, if the amount exceeds 5.0 parts by weight, the polyamide resin mixture cannot maintain the viscosity, so that foam due to foaming is generated on the surface of the molded product, which is not preferable.

(G) Production of Mixture In producing the mixture of the present invention, the above-mentioned polymer or an organic compound and a foaming agent can be uniformly mixed with the above-mentioned polymer, but the filler (for example, calcium carbonate) can be achieved. Talc, mica), heat, light and oxygen stabilizers, flame retardants, plasticizers, nucleating agents, colorants (pigments) and additives, such as antistatic agents, depending on the intended use of the mixture. It may be further added.

At this time, at least a copolymer (I) and a copolymer (II) or a mixture containing these copolymers and a foaming agent (if a reaction accelerator is blended, they may be blended) are produced in advance. Then, the resulting mixture (master batch) and the polyamide resin are dry-blended (a foaming agent and a reaction accelerator may be blended at this stage).

A method for producing a masterbatch is to knead a polymer in a molten state using a mixer, such as an extruder, a mixing roll, a kneader, a roll mill, a Banbury mixer and a continuous mixer, which are commonly used in the field of polyolefin resins. Although there is a method, a more uniform mixture can be obtained by previously mixing using one of these mixers and mixing the resulting mixture using the same or another type of mixer. Further, before performing these mixing, dry blending is previously performed using a mixer such as a drum tumbler and a Henschel mixer, and the resulting mixture is further melt-kneaded to obtain a more uniform mixture.
Furthermore, a so-called masterbatch may be manufactured by previously mixing a part of these mixed components, and the obtained masterbatch (mixture) and the remaining mixed components may be mixed. At this time, it is desirable that the foaming agent and the copolymer (I) and the copolymer (II) are preliminarily mixed to produce pellets, and the resulting mixture is mixed with the remaining mixed components. Further, the foaming agent and the copolymer (II) or the foaming agent and the copolymer (I) and the copolymer (II) may be mixed in advance, and the resulting mixture may be mixed with the remaining mixed components. .

During the melt-kneading, it is necessary that the copolymers (I) and (II), which are the mixed components, do not substantially cross-link (when cross-linking is performed, the resulting mixture is molded and processed as described below). The moldability is poor.
The temperature for melt-kneading is preferably room temperature (20 ° C.) to 150 ° C., depending on the type and amount of the copolymer (I) and copolymer (II) used and the presence or absence of the reaction accelerator. 140 ° C. or lower is preferred.

As a measure of the “substantially no cross-linking”, the total amount of the copolymer (I) and the copolymer (II) in the mixture is “extracted in boiling toluene for 3 hours. Residue having a size of 0.1 μm or more ”(hereinafter referred to as“ extraction residue ”) is generally preferably 10% by weight or less.
% By weight or less is preferred, and 5% by weight or less is optimal.

The polyamide resin is dry-blended with the mixture obtained in this manner so that the mixing ratio of the polyamide resin in the finally obtained molded article becomes the above-mentioned ratio.

(H) Injection molding method The copolymer (I) and the copolymer (I) are obtained by foaming a foaming agent by using an injection molding machine used in a general synthetic resin field with the polyamide resin mixture thus obtained. The molded article of the present invention can be produced by injection molding while crosslinking II).

The molding temperature depends on the mixing ratio of the copolymer (I) and the copolymer (II) in the mixture, the type of the copolymer (I), the copolymer (II) and the foaming agent, and whether or not a crosslinking accelerator is used. The temperature is such that the polyamide resin, the copolymer (I) and the copolymer (II) melt, but they do not thermally decompose, and vary depending on the mixing ratio and the type of the mixture used. The temperature at which the blowing agent decomposes. For these reasons, the molding temperature is 400 ° C or lower, preferably 240 to 400 ° C, and particularly preferably 240 to 380 ° C. In this injection molding step, the copolymer (I) and the copolymer (II) are crosslinked.

Extraction residue of copolymer (I) and copolymer (II) in the molded product thus obtained (after extraction with 98% sulfuric acid, the extraction residue was added to boiling toluene for 3 hours). The extraction residue after extraction is at least 70%, preferably at least 75%, and particularly preferably at least 78%. If the extraction residue of the copolymer (I) and the copolymer (II) is less than 70%, the viscosity of the polyamide resin mixture cannot be maintained, so that foam due to foaming is unpreferably generated on the surface of the molded product.

In the above injection molding, the expansion ratio varies depending on the type of the foaming agent and the mixing ratio thereof, but is generally 1.00.
It is 1 to 1.50 (preferably 1.002 to 1.45). When the expansion ratio is less than 1.001 times, sink marks and warpage occur, and a beautiful molded product cannot be obtained. Meanwhile, 1.
If it exceeds 5 times, bubbles are formed on the surface of the molded product, which is not preferable.

[Examples and Comparative Examples]

Hereinafter, the present invention will be described in more detail with reference to examples.

In the examples and the comparative examples, the dimensional stability test was performed at the temperatures shown in Table 2 so that the mold dimensions and the thickness were respectively different.
It was injection molded using a flat plate mold of 6.50 mm and 200 mm × 200 mm. The thickness of each obtained compact was measured and evaluated.

The physical properties and mixing ratios of the polyamide resin used in Examples and Comparative Examples, and the mixtures and foaming agents obtained by dry-blending the copolymer (I) and the copolymer (II) are shown below.

[(A) polyamide resin]

The polyamide resin has a relative viscosity of 2.5 and a crystallinity of 60% [nylon 6,6, hereinafter referred to as “PA (a)”], a relative viscosity of 1.2, and a crystallinity (density method). (Measured by the method of the present invention) is 55% [nylon 6, hereinafter referred to as "PA (b)"].

[(B) mixture (A)]

A mixture of the copolymer (I) and the copolymer (II) [hereinafter, referred to as “mixture (A)”] is shown below.

As the mixture, an ethylene-acrylic acid copolymer having an MFR of 300 g / 10 minutes (density 0.954 g / cm ³ , acrylic acid copolymerization ratio 20% by weight, hereinafter referred to as “EAA”) and vinyl acetate copolymerization ratio 28 Wt.% Of a saponified product obtained by saponifying an ethylene-vinyl acetate copolymer (a saponification degree).
97.5%, MFR (2) 75 g / 10 min, density 0.951 g / cm ³ , hereinafter referred to as “saponified” [mixing ratio 50: 5
0 (weight ratio), hereinafter referred to as “mixture (I)”], and MFR of 20
0 g / 10 min of ethylene-methacrylic acid copolymer (density
0.950 g / cm ³ , methacrylic acid copolymerization ratio 25% by weight) and the above-mentioned saponified product (mixing ratio 50:50 (weight ratio), hereinafter referred to as “mixture (II)”), MFR 212 g / 10 min Terpolymer of ethylene-ethyl acrylate-maleic anhydride (ethyl acrylate copolymerization ratio 30.7% by weight, maleic anhydride copolymerization ratio 1.7% by weight, hereinafter referred to as "EAM")
And a terpolymer of ethylene-methyl methacrylate-hydroxy methacrylate having an MFR of 123 g / 10 min (copolymerization ratio of methyl methacrylate 20.7% by weight, copolymerization ratio of hydroxy methacrylate 11.7% by weight) [mixing ratio 50 : 50 (weight ratio), hereinafter referred to as “mixture (III)”
A terpolymer of ethylene-methyl methacrylate-maleic anhydride having an MFR of 105 g / 10 min (copolymerization ratio of methyl methacrylate: 20.5% by weight, copolymerization ratio of maleic anhydride: 3.1% by weight) and ethylene-methyl methacrylate A mixture with a tertiary copolymer of glycidyl methacrylate (copolymerization ratio of methyl methacrylate 18.6% by weight, copolymerization ratio of glycidyl methacrylate 12.7% by weight) [mixing ratio 30:70 (weight ratio) or less, "mixture (IV) ] Was used.

[(C) foaming agent]

Further, an azodicarbonamide-based blowing agent having a decomposition temperature of 250 ° C. (manufactured by Eiwa Kasei Kogyo Co., Ltd., blowing agent polystyrene ES # 201) was used as the blowing agent.

Examples 1 to 6, Comparative Examples 1 to 9 The mixture (A) and the foaming agent whose blending amounts and types are shown in Table 1 are dry-blended using a tumbler (internal volume 100) in advance, and then the resin Melt kneading was performed at a temperature of 140 ° C. Each mixture obtained in this manner (hereinafter referred to as "mixture (B)") and the polyamide resin whose type and amount are shown in Table 1 were dry-blended in the same manner as described above to obtain each mixture [hereinafter "mixture (B)". C) "). Each mixture obtained (C)
The mold size at the injection temperature shown in Table 2 is 6.50m thick
Injection molding was performed using an injection molding machine (8 ounce, manufactured by Toshiba Machine Co., Ltd.) using a flat mold having a length of 200 mm, a length of 200 mm and a width of 200 mm.

Take 100 g of the obtained molded product, dissolve it with 98% sulfuric acid, extract the residue with toluene at the boiling point using a Soxhlet extractor, and determine the amount of extraction residue before and after injection molding. Was. The apparent density was determined by measuring the specific gravity by the Archimedes method. Furthermore, the dimensional stability, sink mark, warp state, and the protrusion of foam on the surface of the molded product were visually observed and evaluated. Table 2 shows the results.

[Effects of the Invention] The following effects (features) are exhibited by implementing the method for producing a molded article of the present invention.

(1) Thick molded products (for example, various electronic parts and industrial parts such as brush handles and television receivers, various computers, facsimiles, housings for word processors, etc.) have good dimensional accuracy, and warpage and sink marks are generated. It can be molded without.

(2) Since a special mold is not used in molding a thick product, it is advantageous in terms of cost.

(3) For thick molding, no special molding conditions
In addition, molding can be performed with an increased molding cycle.

Claims (1)

(57) [Claims] (A) a polyamide resin; and (B) at least one monomer selected from the group consisting of at least ethylene and an α, β-unsaturated monocarboxylic acid, an α, β-unsaturated dicarboxylic acid and an anhydride thereof. (C) a copolymer (II) comprising at least ethylene and an ethylenically unsaturated monomer containing a hydroxyl group or an epoxy group; and (D) a temperature at which the polyamide resin melts. A method for producing a molded article of a mixture comprising a foaming agent which decomposes but can decompose at a temperature of at most 300 ° C. The copolymer (I) accounts for the total amount of the copolymer (I) and the copolymer (II) ) Is 1 to 99% by weight, but the total amount of carboxyl groups and carboxylic anhydride groups in copolymer (I): hydroxyl group and epoxy in copolymer (II) Is a molar ratio of 0.2: 1 to 5: 1, the copolymerization ratio of ethylene in these copolymers is 30 to 99.5% by weight, and the monomer having a polar group is All copolymerization ratios are 0.1 to 70% by weight,
Polyamide resin, copolymer (I) and copolymer (II)
The mixing ratio of the foaming agent to the total amount of 100 parts by weight is 0.001.
To 5.0 parts by weight of the mixture (copolymer (I) and copolymer (II)) so that the extraction residue of toluene at the boiling point is at most 10% by weight. Degree is at least 10% and 98% sulfuric acid
Dissolve 1g in 100cc, the relative viscosity measured at a temperature of 20 ℃ 0.5-5.0 polyamide resin in the whole polymer
The mixture is dry-blended to 70 to 99.9% by weight, and the resulting mixture is at a temperature of 400 ° C. or lower, and the extraction residue of the copolymer (I) and the copolymer (II) is at least 70%.
Injection molding while foaming only the inside of the molded body so as to obtain a weight percent.