JPH01259042A - Production of molded article - Google Patents

Abstract

PURPOSE:To readily produce a molded article having excellent heat resistance, dimensional stability and beautiful surface in low cost by mixing specific components such as ethylene-based polymers, a foaming agent in specific ratio, blending, foaming and molding at respective specific temperatures. CONSTITUTION:(A) Ethylene-based polymer is mixed with (B) copolymer comprised at least ethylene and at least one monomer of alpha,beta-unsaturated monocarboxylic acid and alpha,beta-unsaturated dicarboxylic acid (anhydride), (C) copolymer comprising at least ethylene and ethylenic monomer containing hydroxyl group or epoxy group and (D) a foaming agent degrading at 100-250 deg.C, in the ratios of 70-99.9wt.% component A in the total mixture, 1-99wt.% component B in the components B+C, (carboxyl group + carboxylic acid anhydride group in the component B):(hydroxyl group + glycidyl group in the component C)=0.2:1-5:1 (molar ratio) and 0.001-5.0pts.wt. component D to 100pts.wt. of components A+B+C, blended at >=100 deg.C, foamed at <=300 deg.C and molded to afford a molded article.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a foam of an ethylene polymer mixture. In more detail, surface 1 thermal strength (not only is it excellent, but the surface of the resulting foam (molded product) does not have any sink marks or warpage, and the surface of the molded product is beautiful even when the force is applied. The present invention relates to a method for manufacturing an ethylene polymer foam (molded body) using a simple method.

[Prior art] Ethylene-based polymers have good processability, with a tf force of 1, but also excellent heat resistance and chemical resistance, as well as good mechanical strength such as rigidity, and a tf force of 1. Due to its excellent hardness, it is used in many different fields.

However, ethylene polymers have high crystallinity (therefore, they hardly flow below their melting point. Once the melting point is exceeded, their viscosity and elasticity rapidly decrease as the temperature rises, and they become extremely fluid. Therefore, it is difficult to obtain a molded product with no sink marks on the surface and a beautiful surface.On the other hand, in mixtures containing a blowing agent, the air bubbles generated by the blowing agent are uniform. Because it is difficult to maintain the material within a temperature range where it exhibits appropriate viscoelasticity and does not disperse and scatter out of the system, expansion occurs at inappropriate temperatures.
It is difficult to obtain a beautiful molded product because the foamed foam is exposed on the surface of the molded product. Styrenic polymers, which are non-grade resins, are easy to manufacture into beautiful molded products because their viscosity and elasticity decrease little due to temperature maintenance.
Widely used industrially. However, its drawbacks are poor heat resistance and impact resistance.

In other words, in the process of obtaining molded products of ethylene polymers that have excellent heat resistance and cold resistance, molded products of styrene polymers that undergo crystallization and solidify, resulting in changes in density that are non-standard resins. It becomes much larger than when you get . As a result, especially when performing injection molding, there are drawbacks such as the finished dimensions of the mold becoming smaller, sink marks occurring when obtaining thick molded products, and warping due to anisotropy of shrinkage rate. .

[Problems to be Solved by the Invention] Conventionally, methods for improving these drawbacks include methods for obtaining molded products using special molds, methods for highly filling inorganic materials,
A method of molding under special molding conditions, a method of adding an ordinary chemical blowing agent, etc. have been proposed.

However, the method using a special mold increases costs and limits the design of the molded product. Furthermore, in the method of highly filling inorganic substances, the physical properties (particularly impact strength) of the molded product decrease, the cost increases due to increasing the density of the resin, and the fluidity deteriorates. Furthermore, in the method of molding under special molding conditions, the molding cycle becomes longer.

Furthermore, the conventional method of adding a chemical foaming agent has drawbacks such as foaming on the surface of the molded product and roughening of the surface of the molded product.

From the above, the present invention does not have these drawbacks (problems), that is, it is an ethylene polymer foam (molded product) that has excellent dimensional stability, not only does not have sink marks on its surface, but also has no warpage and no wrinkles. ) in a simple way.

[Means and effects for solving the problems] According to the present invention, these problems are solved by: (A) an ethylene polymer; (B) at least ethylene and an a,β-unsaturated monocarboxylic acid; - Copolymers (I) and (C) consisting of at least one monomer selected from the group consisting of unsaturated dicarboxylic acids and their anhydrides; (C) an ethylenically unsaturated monomer containing at least ethylene and a hydroxyl group or an epoxy group; - A method for producing a foam of a mixture consisting of a copolymer (II) consisting of and (D) a blowing agent that can be decomposed in a temperature range of 100 to 250 ° C. The mixing ratio of polymer is 70
~99.9% by weight, and the mixing ratio of copolymer (I) in the total amount of copolymer (I) and copolymer (II) is 1 to 99% by weight, but copolymer The molar ratio of the total amount of carboxyl groups and carboxylic acid anhydride groups in (I) to the total amount of hydroxyl groups and glycidyl groups in copolymer (II) is from 0.2:1 to 5:1. Yes, melt flow index of ethylene polymer (JI
Measured under conditions 4 according to S K7210, hereinafter referred to as “M
FRJ) is 0. The copolymerization ratio of ethylene in these copolymers is 30 to 99.5ffl12%, and the copolymerization ratio of monomers having polar groups is 0.1 to 200 g/10 minutes. 1-70
% by weight, and the mixing ratio of the blowing agent to 100 parts by weight of the total amount of the ethylene polymer, copolymer (I) and copolymer (II) is 0.001 to 5.0 parts by weight. 100° C. or higher, but producing a mixture such that the extraction residue of toluene at the boiling point of the copolymer (I) and copolymer (II) is at most 10% by weight;
Injection molding the mixture at 300° C. or lower while foaming only the inside of the molded product so that the extraction residue is at least 70% by weight for the copolymer (I) and copolymer (II). The problem can be solved by a method for producing a molded body characterized by: The present invention will be specifically explained below.

(A) Ethylene polymer The ethylene polymer used in the present invention is a polymer containing ethylene as a main component, and ethylene homopolymers and random and block copolymers of ethylene and α-olefin are preferred. It is used. The total copolymerization ratio of α-olefins in the random and block copolymers is at most 30% by weight, preferably 25% by weight or less, particularly preferably 20% by weight or less. Also, α
-As an olefin, the number of carbon atoms is at most 12 α~
Olefins are preferred, especially 3-8 α-olefins. Suitable alpha-olefins include propylene, butene-1, heptene-1,4-methylpentene-1 and hexene-1.

The MFR of the ethylene polymer is usually 0.001 to 500.
g/10 minutes and 0. O1 to 80 g/10 min is preferable, and 0.1 to 70 g/10 min is particularly preferable. If an ethylene polymer having an MFR of less than 0.001 g/10 minutes is used, a good molded product cannot be obtained due to poor moldability when producing a molded product by injection molding. On the other hand, if an ethylene polymer exceeding 500 g/10 minutes is used, the impact resistance of the molded product will be poor and the molded product will not be suitable for practical use.

(B) Copolymer (I) The copolymer (I) used in the present invention is at least selected from the group consisting of ethylene, a, β-unsaturated monocarboxylic acid, a, β-unsaturated dicarboxylic acid, and anhydride thereof. It is a copolymer consisting of at least one selected monomer. Examples of the copolymer include the following polymers.

(I) Copolymer of ethylene and a,β-unsaturated monocarboxylic acid [hereinafter referred to as "ethylene copolymer (a)"] and (2) Copolymer of ethylene and a,β-unsaturated dicarboxylic acid and/or or a copolymer with its anhydride [hereinafter referred to as "ethylene copolymer (b)"] These copolymers (I) are 1
It is desirable that the material melts at a temperature of 50° C. or lower and has fluidity.

(I) Ethylene copolymer (a) Ethylene copolymer (a) contains at least ethylene and a,
It is a copolymer with β-unsaturated monocarboxylic acid, and in order to ensure the above-mentioned fluidity properties, a radically polymerizable comonomer having a polar group (hereinafter referred to as the "third component") is copolymerized. Preferably.

The third component is copolymerized as a comonomer, thereby having a monomer corresponding to the third component copolymerized into the ethylene copolymer (a).

The a,β-unsaturated monocarboxylic acid that can be used to produce the ethylene copolymer (a) generally has 3 to 20 carbon atoms, preferably 3 to 16 carbon atoms. . Typical examples include acrylic acid, methacrylic acid, crotonic acid, monoalkyl maleate, and monoalkyl fumarate.

Further, the third component is a radically polymerizable vinyl compound containing H and a polar group, and typical examples include unsaturated carboxylic acid ester, vinyl ester, and alkoxyalkyl acrylate.

The unsaturated carboxylic acid ester usually has 4 to 40 carbon atoms, particularly preferably 4 to 20 carbon atoms. As typical examples, those with good thermal stability such as methyl (meth)acrylate and ethyl (meth)acrylate are preferred.

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

In the ethylene copolymer (a), the amount of the third component is 2
It is preferably 5 mol% or less, particularly preferably 2 to 20 mol%. Although the characteristics of the present invention can be achieved even if the content exceeds 25 mol%, it is not necessary to exceed 25 mol%, which is not preferable from the viewpoint of production and economy.

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

The a,β-unsaturated monocarboxylic acid is a copolymer (I
It is used as a crosslinking reaction point with I) and to provide adhesiveness to a wide variety of base materials, and there is no need for it to be present in excess from either point of view. If the amount increases, water absorption increases, which not only has negative effects such as foaming during molding and deterioration of electrical properties due to water absorption after molding, but also production problems such as safety, separation, and recovery, and economic problems. This is also disadvantageous and undesirable. On the other hand, if it is less than 0.5 mol %, there is no problem in terms of adhesion, but foaming bubbles are likely to be exposed on the surface of the molded product during molding, making it impossible to obtain a beautiful molded product.

(2) Ethylene copolymer (b) Also, the ethylene copolymer (b) used in the present invention
) may result in a copolymer of ethylene and an a,β-unsaturated dicarboxylic acid and/or its anhydride (which may also contain the third component). That is, it is a direct copolymerization of ethylene, a, β-unsaturated dicarboxylic acid and/or its anhydride, or these and the third component.

Examples of the third component include the same type of compound as the ethylene copolymer (a).

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

The a,β-unsaturated dicarboxylic acid usually has at most 20 carbon atoms, preferably 4 to 16 carbon atoms. Typical examples of the dicarboxylic acid include maleic acid,
Examples include fumaric acid, itaconic acid, citraconic acid, and 3,8-endomethylene-1,2,3,8-tetrahydro-cis-phthalic acid (nadic acid@)).

"a,β-unsaturated dicarboxylic acid or its anhydride" (
The bonding amount of the ethylene copolymer (b) (hereinafter referred to as "unsaturated dicarboxylic acid component") is 0.5 mol% or more, 20
It is preferably less than mol%.

More preferably, it is 1.0 to 15 mol%.

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

(I) Saponified product obtained by saponifying part or all of a copolymer of ethylene and vinyl ester [hereinafter referred to as "ethylene copolymer (C)"] (hereinafter referred to as "hydroxyl compound") or "ethylenic unsaturated hetamine having epoxy group" (hereinafter referred to as "epoxy compound"); and copolymers of these and the third component described above [hereinafter referred to as ethylene copolymer (d)] (I) ethylene copolymer (c) Furthermore, the ethylene copolymer used in the present invention can be produced by saponifying part or all of a copolymer of ethylene and vinyl ester.

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

In saponifying this copolymer to produce an ethylene copolymer part, a commonly used saponification method may be used. The degree of saponification is usually 80% or more, preferably 85% or more, and particularly preferably 90% or more.

(2) Ethylene-based copolymer (d) Furthermore, 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; It may also be a multicomponent copolymer with a third component.

Examples of the hydroxyl compound which is a comonomer component of the copolymer include hydroxyalkyl (meth)acrylate (alkyl group usually has 1 to 25 carbon atoms) and α-alkenyl alcohol having 3 to 25 carbon atoms. . Typical examples of the hydroxyl compounds include hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, and allyl (a
l Iyl) alcohol.

Further, representative examples of epoxy compounds include those in which -the formula is represented by the following formulas [Formula (I) and Formula (II)].

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

The copolymerization ratio of ethylene in this 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. In addition, the copolymerization ratio of the hydroxyl compound is usually 0.1 to 0.1 for the same reason as in the case of the ethylene copolymer (a).
70% by weight, preferably from 0.5 to 70% by weight, particularly preferably from 0.5 to BO% by weight. Furthermore, in the case of a multicomponent copolymer, the copolymerization ratio of the third component is generally at most 69 for the same reason as for the ethylene copolymer (a).
．． 9% by weight, preferably 65% by weight or less, particularly preferably 60% by weight or less.

These proportions are the copolymers of ethylene and unsaturated carboxylic acid esters used to produce ethylene copolymers (a), ethylene copolymers (b), and ethylene copolymers (d). Copolymers of ethylene and vinyl esters used to produce ethylene-based copolymer sources are both processed at temperatures of 120-260°C under high pressures of 50-2,500 kg/al. It can be produced by copolymerizing a comonomer (including a third component) that copolymerizes with ethylene in the presence of a comonomer (including a third component). This copolymerization method is a well known method.

The MFR of these ethylene copolymers (a) to ethylene copolymers (d) is generally 0.01 to 1000.
g/10 minutes, preferably 0.05 to 500 g/10 minutes, particularly preferably 0.1 to 500 g/10 minutes.

MFR is 0. When an ethylene copolymer having an O content of less than 1 g/10 minutes is used, it is difficult to mix the mixture uniformly when producing the mixture of the present invention, and the moldability is also poor.

To produce the mixture of the present invention, the above ethylene polymer, copolymer (I), copolymer (II), and blowing agent are uniformly mixed within the mixing ratio range described below. . Alternatively, the copolymer (I), the copolymer (II), and the blowing agent may be mixed in advance to prepare a masterbatch, and the ethylene copolymer may be mixed with this masterbatch (triblending may also be performed). However, by further mixing the reaction accelerator described later, the above-mentioned copolymer (I) and copolymer (I
The crosslinking of I) can be promoted.

(D) Reaction accelerator The reaction accelerator used in the present invention is widely known as a curing agent for epoxy resins. Publication) pages 26 to 29, pages 32 to 35
Examples include those described on pages 109 to 128, pages 185 to 188, pages 330 and 331.

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

(I[I) In formulas and (IV), Ra, R7゜R and R may be the same or different, and each represents a hydrogen atom, an alkyl group having 1 to 32 carbon atoms, an aryl group,
A hydrocarbon group selected from alkaryl and aralkyl groups, but not all hydrogen atoms at the same time. X is a halogen atom. In these formulas, R to R9
A hydrocarbon group having 12 or less carbon atoms is preferred. Also,
X is preferably a chlorine atom or a bromine atom.

Typical examples of the reaction accelerator include ethanolamine, jetanolamine, triethanolamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, n-butylamine, N,N-dimethylaminoethanol, N,N- Diethylaminoethanol, morpholine, piperidine, pyridine, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminomethacrylate, N,N-diethylaminoethyl acrylate, trimethylamine, triethylamine, tri-n-
Butylamine, N,N-dimethylbenzylamine, hexamethylenetetramine, triethylenediamine, N,N
- tertiary amines such as dimethylpiperazine and N-methylmorpholine, acidic or alkaline compounds such as p-toluenesulfonic acid and potassium hydroxide and trimethylbenzylammonium chloride,
Mention may be made of ammonium halogen salts such as tetraethylammonium bromide, tetrabutylammonium chloride and cetyltrimethylammonium chloride, as well as zinc chloride. Particularly preferred are N,N-dimethylbenzylamine and p-toluenesulfonic acid.

In producing the mixture of the present invention, the copolymer (I) is a copolymer consisting of ethylene and a monomer having an a,β-unsaturated dicarboxylic acid group, that is, ethylene and a,
An ethylenically unsaturated dicarboxylic acid copolymer containing ethylene and an epoxy group as the copolymer (II), using an ethylenic multicomponent copolymer consisting of an anhydride of β-unsaturated dicarboxylic acid or these and the third component. A copolymer consisting of ethylene and a heptamine represented by formula (I) or (II), or an ethylene-based multicomponent copolymer consisting of these and the third component. Moreover, when the reaction accelerator is not used, copolymer (I) and copolymer (II) are not crosslinked, and a molded mixture having good heat resistance cannot be obtained. In this case, the copolymer ( I) and copolymer (II) can be crosslinked. As the polymer, the ethylene copolymer (
a), ethylene copolymer (b), ethylene and a,β-unsaturated monocarboxylic acid and/or a,β-
Copolymers with unsaturated dicarboxylic acids (these copolymers may also be ethylene-based multicomponent copolymers containing a third component)
, saponified copolymers of ethylene and vinyl acetate, copolymers of ethylene and hydroxyalkyl (meth)acrylates, and copolymers (including homopolymers) containing ethylene or propylene as main components, as well as the above-mentioned ethylene-based copolymers. a,β-unsaturated monocarboxylic acid, a,β- used in producing copolymer (a) and ethylene copolymer (b)
Examples include modified olefin polymers obtained by graft polymerization of unsaturated dicarboxylic acids or their anhydrides. Furthermore, examples of organic compounds include ethylene glycol, polyethylene glycol, propylene glycol, glycerin, and polypropylene glycol.

(E) Foaming agent The foaming agent used in the present invention decomposes in the temperature range of 100 to 250°C, and moreover, the foaming agent itself and the gas generated by decomposition are
Discuss iye polymerization, copolymer (I) and copolymer (II)
There is no particular limitation as long as it does not react with any of the above, but those with a decomposition temperature of 110°C or higher are particularly desirable, and those with a decomposition temperature of 130°C or higher are particularly preferred. Suitable blowing agents include organic blowing agents such as dinitropentamethylenetetramine, azobisisobutyronitrile, azodicarbonamide, paratoluenesulfonylhydrazide and hydrazine.

Also, inorganic compounds (e.g., sodium bicarbonate) and organic acids (e.g., salicylic acid, phthalic acid, fumaric acid, maleic acid, itaconic acid, stearic acid, lauric acid) and boronic acids which meet the above conditions in the above temperature range may be used. Blowing agents in combination with acids can also be used.

In producing the mixture of the present invention, these blowing agents alone may be used as the blowing agent, but further effects can be obtained by using a blowing agent and a blowing aid in combination. The foaming aids cannot be further specified because they vary depending on the type of foaming agent used, but examples of foaming aids for azodicarbonamide include zinc white (zinc oxide), tribasic lead sulfate, urea, and stearin. Foaming aids for dinitrosopentamethylenetetramine include salicylic acid, phthalic acid, boric acid, and urea resin.

(F) Mixing ratio In producing the mixture of the present invention, the mixing ratio of the ethylene polymer in the total amount of the ethylene polymer, copolymer CI) and copolymer (II) is 70 to 99.9. % by weight [i.e., copolymer (I) and copolymer (II)
The mixing ratio of ) is 80 to 0.01% by weight as a total amount]
and preferably 75 to 99.8% by weight, particularly 80 to 99.8% by weight.
99.7% by weight is preferred. If the mixing ratio of the ethylene polymer to the total amount of the ethylene polymer, copolymer (I), and copolymer (II) is less than 70% by weight, injection molding will be difficult and a good molded product will not be obtained. is not obtained. On the other hand, if it exceeds 99.9% by weight, viscosity retention during foaming is poor and good molded products cannot be obtained.

The mixing ratio of copolymer (I) in the total amount of copolymer (I) and copolymer (II) is 1 to 99% by weight, preferably 5 to 95% by weight, particularly 10 to 95% by weight. 90% by weight is preferred. Copolymer (I) and copolymer (II)
Even if the mixing ratio of copolymer (I) in the total amount of is less than 1% by weight or more than 99% by weight, viscosity retention is poor during foaming, and a beautiful molded product with no bubbles on the surface can be obtained. I can't.

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

In addition, when adding a reaction accelerator, the mixing ratio thereof is generally a large amount (both 5.0 parts by weight) per 100 parts by weight of the total amount of the ethylene polymer, copolymer (I), and copolymer (II). 0 parts by weight, preferably 0.01 to 5.0 parts by weight, and particularly preferably 0.01 to 2.0 parts by weight.

Even if the reaction accelerator is blended in an amount exceeding 5.0 parts by weight,
Although the low-temperature crosslinking promoting effect appears, the reaction accelerator itself may not only inhibit crosslinking adhesion, but also cause the reaction accelerator to bleed onto the surface of the molded product, making it difficult to obtain a good molded product. It is undesirable because it cannot be used.

Furthermore, when producing the mixture of the present invention, when blending the above-mentioned organic compound and/or polymer having a hydroxyl group or carboxyl group, the mixing ratio thereof should be adjusted to the above-mentioned ethylene polymer, copolymer (I) and copolymer (I). Usually at most 20 parts by weight, preferably from 0.1 to 20 parts by weight, preferably from 0.5 to 20 parts by weight, especially 1.0 parts by weight, based on 100 parts by weight of the total amount of polymer (II).
~15 parts by weight is preferred.

Further, the mixing ratio of the blowing agent to 100 parts by weight of the total amount of the ethylene polymer, copolymer (I) and copolymer (II) is o,oot~10 parts by weight, and 0.002~10 parts by weight.
The amount is preferably 5.0 parts by weight, and preferably 0.005 to 4.0 parts by weight. If the mixing ratio of the blowing agent to 100 parts by weight of the total amount of the ethylene polymer, copolymer (I) and copolymer <n> is less than 0.001 parts by weight, the amount of foaming will be small and sink marks will occur on the surface of the molded product. This not only causes warpage and warpage, but also makes it impossible to improve dimensional stability. On the other hand, 1
If it exceeds 0 parts by weight, it is not preferable because the viscosity of the ethylene polymer mixture cannot be maintained and bubbles are generated on the surface of the molded product.

(G) Production of mixture In producing the mixture of the present invention, the purpose can be achieved by uniformly mixing the above polymers or these with an organic compound and a blowing agent.
Fillers (e.g. calcium carbonate, talc, mica)
Additives such as heat, light and oxygen stabilizers, flame retardants, plasticizers, nucleating agents, colorants (pigments) and antistatic agents may be added depending on the intended use of the resulting mixture. good.

The mixing method is an extruder or mixing roll that is commonly used in the field of olefin polymers.

There is a method of kneading the polymer in a molten state using a mixer such as a kneader, roll mill, Banbury mixer, or continuous mixer. A more homogeneous mixture can be obtained by mixing the mixture using the same or different types of mixers. In addition, a more homogeneous mixture can be obtained by triblending these mixtures in advance using a mixer such as a drum tumbler or a Henschel mixer, and then melting and kneading the resulting mixture. . Furthermore, a part of these mixed components may be mixed in advance to produce a so-called masterbatch, and the resulting masterbatch (mixture) and the remaining mixed components may be mixed.

At this time, the blowing agent, copolymer (I) and copolymer (I)
It is desirable to prepare pellets by pre-mixing with I) and mixing the remaining mixing components into the resulting mixture. Alternatively, the blowing agent and copolymer (II) or the blowing agent and copolymer (I) and copolymer (II) may be mixed in advance, and each of the resulting mixtures may be mixed with the remaining mixed components. .

When melt-kneading, it is necessary that copolymer (I) and copolymer (II), which are mixed components, are not substantially crosslinked (if crosslinked, the resulting mixture may be molded as described below). Formability deteriorates.From this,
The melt-kneading temperature varies from room temperature (20°C) to 15°C, depending on the type and amount of copolymer (I) and copolymer (II) used, as well as whether or not the reaction accelerator is added.
The temperature is preferably 0°C, and preferably 140°C or lower.

As a guideline for "substantially no crosslinking", the total amount of copolymer (I) and copolymer (II) in the mixture should be "extracted in boiling toluene for 3 hours, Generally, it is preferable that the "residue having a size of 0.1 un or more" (hereinafter referred to as "extraction residue") is less than 2% IO,
It is preferably 8 Wffi% or less, and preferably 5 wt% or less.

(IO injection molding method) The ethylene polymer mixture obtained in this way is foamed with a blowing agent using an injection molding machine used in the field of general synthetic resins to form copolymer (I) and copolymer. 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 copolymer (I) and copolymer (II) in the mixture, copolymer (I), copolymer (
II) and the type of blowing agent, whether or not a crosslinking accelerator is used, the mixing ratio when used, and the type thereof, but the ethylene polymer, copolymer (I), and copolymer (II) melt. The temperature is such that these do not thermally decompose, and the blowing agent used decomposes. For these reasons, the molding temperature is generally 180 to 300°C, particularly preferably 190 to 270°C. During this injection molding step, copolymer (I) and copolymer (II) are crosslinked.

The extraction residue of copolymer (I) and copolymer (II) in the thus obtained molded product is at least 70%
%, preferably 75% or more, particularly 78% or more. Copolymer (I) and copolymer (II)
If the extraction residue is less than 70%, the ethylene polymer mixture cannot maintain its viscosity, resulting in foaming on the surface of the molded product, which is not preferable.

In the above injection molding, the expansion ratio varies depending on the type of blowing agent and its mixing ratio, but is generally 1.0.
01 to 1.50 times (preferably 1.002 to 1.45 times). If the expansion ratio is less than 1.001 times, sink marks and warpage occur, making it impossible to obtain a beautiful molded product. On the other hand, if it exceeds 1.5 times, bubbles will be generated on the surface of the molded product, which is not preferable.

[Examples and Comparative Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in Examples and Comparative Examples, the dimensional stability test was conducted at a temperature of 230° C. and a mold size of 6.5 mm in thickness.
It was injection molded using a 200 mm x 200 am flat plate mold. The thickness of each obtained molded body was actually measured and evaluated.

The physical properties and mixing ratio of the ethylene polymer, the mixture obtained by tri-blending copolymer (I) and copolymer (II), and the blowing agent used in the examples and comparative examples are as follows. show.

[(A) Ethylene polymer]

As an ethylene polymer, an ethylene homopolymer having a density of 0.985 g/cJ and an MFR of 1.0 g:/10 min [hereinafter referred to as "P E (a)]", a density of 0.9
45 g/-, an ethylene homopolymer with an MFR of Bor/10 min [hereinafter referred to as rPE(b)J], and a density of 0.920. /cIa, the copolymerization ratio of butene-1 is 10% by weight, and the MFR is 10g/10
Ethylene-butene-1 copolymer [hereinafter referred to as rPE (
c) J) was used.

[(B) Mixture (A)]

Further, a mixture of copolymer (I) and copolymer (II) [hereinafter referred to as "mixture (A)"] is shown below.

As the mixture, a polyethylene-acrylic acid copolymer having an MFR of 300 g/10 min (density 0.954 g/ct+1
, an acrylic acid copolymerization ratio of 20% by weight, hereinafter referred to as rEAAJ) and a vinyl acetate copolymerization ratio of 28% by weight.Saponified product obtained by saponifying an ethylene-vinyl acetate copolymer [Saponification degree 97.5%] , MFR75g
/10 minutes, density 1.19 g/C111, hereinafter referred to as "saponified material"] [mixing ratio 50:50 (weight ratio), hereinafter referred to as "mixture (I)"], MFR is 20
A mixture of ethylene-methacrylic acid copolymer (density 0.950 g/Cl11, methacrylic acid copolymerization ratio 25% by weight) with a saponification degree of 0 g/10 min and the above saponification degree [mixing ratio 50:50 (weight ratio), below] "Mixture (■)"), an ethylene-ethyl acrylate-maleic anhydride ternary copolymer with an MFR of 212 g/10 min (ethyl acrylate copolymerization ratio 30.7% by weight, maleic anhydride copolymerization ratio 1.7% by weight, hereinafter referred to as rEAMJ)
and an ethylene-methyl methacrylate-hydroxy methacrylate ternary copolymer with an MFR of 123 g/10 min (copolymerization ratio of methyl methacrylate 20.7% by weight).
, hydroxy methacrylate (copolymerization ratio 11.7% by weight) [mixing ratio 50:50 (weight ratio)
, hereinafter referred to as "mixture (■)"] and an MFR of 10
Ethylene-methyl methacrylate at a concentration of 5 g/lO
A terpolymer of maleic anhydride (copolymerization ratio of methyl methacrylate: 20.5ffi, copolymerization ratio of maleic anhydride: 381% by weight) and a terpolymer of ethylene-methyl methacrylate-glycidyl methacrylate (methyl methacrylate) Using a mixture [mixing ratio 30:70 (weight ratio), hereinafter referred to as "mixture (■)"] with a copolymerization ratio of 18.6% by weight and a copolymerization ratio of glycidyl methacrylate 12.7% by weight, [hereinafter referred to as "mixture (■)"] , "Blowing agent (^)"], dinitrosopentamethylenetetramine (hereinafter referred to as "Blowing agent (^)")
Foaming agent (B)] and sodium bicarbonate (hereinafter referred to as "Blowing agent (C)"); and as blowing aids, zinc stearate (hereinafter referred to as "Blowing aid (I)"), salicylic acid [hereinafter referred to as "Blowing aid (I)"]. "Foaming aid (I1) J" and fumaric acid (hereinafter referred to as "foaming aid (III) J") were used.

Examples 1-8. Comparative Examples 1 to 8 Mixtures (^), foaming agents, and foaming aids whose proportions and types are shown in Table 1 were triblended in advance using a tumbler (inner volume +00.Q). The thus obtained mixtures [hereinafter referred to as "mixtures (B)"] and the ethylene polymers whose types and blending ratios are shown in Table 1 were triblended in the same manner as described above to prepare each mixture [hereinafter referred to as "mixtures (B)"]. Mixture (C)] was prepared. Each of the obtained mixtures (C) was molded at the injection temperature shown in Table 2, and the mold dimensions were 6.50 am thick and 20011 mm long.
Injection molding was performed using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., 8 oz.) using a 11% flat plate mold with a width of 200 mm.

One g of the obtained molded product was extracted with toluene at the boiling point using a Soxhlet extractor, and the amount of extraction residue before and after injection molding was determined. Further, the apparent density was determined by measuring the specific gravity using the Archimedes method. Furthermore, the dimensional stability, sink marks, warpage, and the appearance of bubbles on the surface of the molded product were evaluated by observing with the naked eye. These results are shown in Table 2.

(The following is a blank space) [Effects of the Invention] By carrying out the method for producing a molded article of the present invention, the following effects (characteristics) are exhibited.

(I) Thick molded objects (for example, brush handles and housings for television receivers, various computers, facsimile machines, word processors, etc.)
It can be molded with good dimensional accuracy and without warping or sink marks.

(2) It is advantageous in terms of cost because no special mold is used in molding thick objects.

(3) When molding thick materials, there are no special molding conditions;
Moreover, the molding cycle can be increased.

Claims (1)

[Scope of Claims] (A) an ethylene polymer; (B) at least one selected from the group consisting of ethylene and α,β-unsaturated monocarboxylic acids, α,β-unsaturated dicarboxylic acids, and anhydrides thereof; A copolymer (I) consisting of one kind of monomer, (C) a copolymer (II) consisting of at least ethylene and an ethylenically unsaturated monomer containing a hydroxyl group or an epoxy group, and (D) 100 to 250°C A blowing agent that can be decomposed in a temperature range of
~99.9% by weight, and the mixing ratio of copolymer (I) in the total amount of copolymer (I) and copolymer (II) is 1 to 99% by weight, but copolymer The ratio of the total amount of carboxyl groups and carboxylic acid anhydride groups in (I) to the total amount of hydroxyl groups and glycidyl groups in copolymer (II) is from 0.2:1 to 5:1 in molar ratio. , the melt flow index of the ethylene polymer is 0.
The copolymerization ratio of ethylene in the copolymer is 30 to 99.5% by weight, and the copolymerization ratio of monomers having polar groups is 0.01 to 200g/10 minutes. 1 to 70% by weight, ethylene polymer,
Total amount of copolymer (I) and copolymer (II) 100
The mixing ratio of the blowing agent to parts by weight is 0.001 to 5.
0 parts by weight of the mixture at 100° C. or higher, but producing a mixture such that the extraction residue of toluene at the boiling point of the copolymer (I) and copolymer (II) is at most 10% by weight; The mixture is heated at a temperature below 300°C,
A method for producing a molded article, comprising injection molding the copolymer (I) and copolymer (II) while foaming only the inside of the molded article so that the extraction residue is at least 70% by weight.