JPH0977876A - Foaming agent masterbatch for polyacetal resin, its production and production of expanded molding using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a foaming agent masterbatch capable of providing a polyacetal resin expanded molding having fine and uniform cells and excellent mechanical properties without any defects such as delamination. SOLUTION: This foaming agent masterbatch is obtained by blending (A) 100 pts.wt. graft copolymer prepared by grafting (b) one or more grafting components of vinylic polymers or ethereal polymers onto (a) an olefinic polymer as a main chain component with (B) 1-100 pts.wt. thermal decomposition type foaming agent which is a solid at 20 deg.C temperature and has >=170 deg.C decomposition temperature and melt kneading the resultant blend. The polyacetal resin expanded molding is prepared by mixing (C) 100 pts.wt. polyacetal resin with 0.1-20 pts.wt. resultant masterbatch, heating the produced mixture above the decomposition temperature of the foaming agent contained in the foaming agent masterbatch and molding the mixture.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a foaming agent masterbatch for polyacetal resin, a method for producing the foaming agent masterbatch, and a method for producing a polyacetal resin foam-molded article using the foaming agent masterbatch. .

[0002]

2. Description of the Related Art In a injection molding method, a polyacetal resin is blended with a pyrolytic foaming agent to produce a foamed molded article having a foaming ratio of 1.1 to 2.5 by a short shot method, and a full shot method. Foaming ratio is 1.0
Methods for producing a molded product having an extremely low foaming ratio of 1 to 1.03 are all known. When producing such a foam-molded article, the powder or pellets of the polyacetal resin is blended with a powdery foaming agent, and when subjected to molding, (a) the powdery foaming agent is easily scattered, Deteriorates the environment, and (b) the uniformly mixed pellets of polyacetal resin and the powdery foaming agent are different in diameter, specific gravity, etc. when the blended product is being transported or when it is put in the hopper of a molding machine. There are drawbacks such that the composition ratio of the both changes, and when they are extremely large, the two separate, and a uniformly foamed molded product cannot be obtained.

As a method for solving the above-mentioned drawbacks (a) and (b), when a powdery foaming agent is mixed with a polyacetal resin, a polyhydric alcohol is added to improve the adhesion and the mixing property between the two. A method has been proposed (Japanese Patent Laid-Open No. 61-57).
631 publication). However, the proposed method is (c)
The powdery foaming agent and the polyhydric alcohol may form a paste-like mass, and it is unavoidable that the composition ratio of the foaming agent varies, and (d) the polyhydric alcohol is the inner surface of the hopper of the molding machine. However, there is another problem such that the cleaning and removing work is burdened with this, and it cannot be said to be an advantageous method.

[0004]

As a method for solving the above disadvantages (c) to (d), a foaming resin composition prepared by kneading a large amount of a foaming agent into a base resin in advance, that is, a so-called foaming agent masterbatch is prepared. A method of blending this with powder or pellets of a polyacetal resin and molding is proposed and put into practical use. Conventionally, a low density polyethylene (LDPE) is generally used as a base resin used for preparing a blowing agent masterbatch for a polyacetal resin. According to this method, the above problems (a) to (d) are all solved, but the affinity and compatibility of the polyacetal resin and the low-density polyethylene are poor, so delamination occurs on the surface of the molded product. Alternatively, there is a drawback that the interface between the two becomes a starting point of fracture and the mechanical properties of the molded product deteriorate.

The inventors of the present invention have made earnest studies in view of such circumstances, and as a result, by using a specific foaming agent masterbatch, it has fine and uniform bubbles, is free from surface defects such as delamination, and is excellent. It is possible to obtain a polyacetal resin foam-molded product having mechanical properties, and particularly, the expansion ratio is 1.
The inventors have found that a polyacetal resin foam-molded product having excellent mechanical properties can be obtained with a ratio of 01 to 2.5 times, and completed the present invention.

[0006]

That is, according to the first aspect of the present invention, an olefin polymer is used as a main chain component (a),
It is a solid at a temperature of 20 ° C. and has a decomposition temperature of 170 ° C. with respect to 100 parts by weight of a graft copolymer (A) in which a vinyl polymer is grafted as a graft component (b).
A blowing agent masterbatch for a polyacetal resin is provided, which is prepared by blending 1 to 100 parts by weight of the above thermal decomposition type blowing agent (B) and melt-kneading.

According to the second aspect of the present invention, a graft copolymer (A) 100 obtained by grafting a main chain component (a) of an olefin polymer and a graft component (b) of a vinyl polymer. Is solid at a temperature of 20 ° C.,
And a pyrolysis type foaming agent (B) 1 having a decomposition temperature of 170 ° C. or higher
A method for producing a foaming agent masterbatch for a polyacetal resin is provided, which comprises blending 100 parts by weight to 100 parts by weight and then melt-kneading at a temperature not higher than the thermal decomposition of the thermal decomposition type foaming agent (B).

Further, according to the third aspect of the present invention, 0.1 part of the blowing agent masterbatch for polyacetal resin of the first aspect of the present invention is added to 100 parts by weight of the polyacetal resin (C).
The present invention provides a method for producing a polyacetal resin foam-molded product, which comprises mixing 20 to 20 parts by weight and heating the mixture to a temperature not lower than the decomposition temperature of the foaming agent contained in the foaming agent masterbatch for molding.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the present invention, the graft copolymer (A) {hereinafter sometimes referred to as the copolymer (A)} is a thermal decomposition type foaming agent (B).
{Hereinafter, it may be referred to as a foaming agent (B)}, which functions as a base resin that melts at a decomposition temperature of a foaming agent (B) or less and holds the foaming agent (B) without decomposing, and at the same time, forms a polyacetal resin (C ) {Hereinafter, it may be referred to as resin (C)} and has a function of enhancing excellent affinity and compatibility.

This copolymer (A) is composed of an olefin polymer as a main chain component (a) and a vinyl polymer as a graft component (b), which has a branched structure by intermolecular reaction, or It is a graft copolymer chemically crosslinked.

The olefin-based polymer constituting the main chain component (a) of the copolymer (A) is a homopolymer such as polyethylene, polypropylene or polybutene, and monomers constituting these polymers. A copolymer of each other,
And copolymers of these monomers as the main components with other copolymerizable monomers. Other copolymerizable monomers include glycidyl esters of acrylic acid, glycidyl methacrylate, glycidyl methacrylate, and the like, glycidyl esters of α, β-unsaturated acids, α, acrylic acid, methacrylic acid, and the like. Examples include β-unsaturated carboxylic acids and their alkyl esters. Specific examples of the copolymer include ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / ethyl acrylate copolymer, and ethylene / α, β-unsaturated acid glycidyl ester copolymer. Can be mentioned. Among the olefin polymers constituting the main chain component (a) exemplified above, polyethylene, ethylene.α, β-
Most preferred are glycidyl ester copolymers of unsaturated acids.

The graft component (b) which can be grafted onto the main chain component (a) is a vinyl polymer, and the main chain component (a) is grafted with the graft component (b) by an interpolymer reaction. As a result, the copolymer (A)
And the compatibility and compatibility of the polyacetal resin (C) for molding with are greatly improved.

Examples of vinyl polymers include polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polyethyl methacrylate, 2-ethylhexyl polymethacrylate, polystyrene, polyacrylonitrile,
Acrylonitrile / styrene copolymer, butyl acrylate / methyl methacrylate copolymer, butyl acrylate /
Styrene copolymers and the like can be mentioned. These may be one kind or a mixture of two or more kinds. Particularly preferred as the graft component (b) are polymethylmethacrylate, acrylonitrile / styrene copolymer and the like.

The copolymer (A) can be easily produced by a generally known radical reaction. As a specific production method, (i) a method in which the olefin polymer constituting the main chain component (a) is melt-kneaded with the monomer constituting the graft component (b) and the radical catalyst to cause a graft reaction. (Ii) A catalyst such as peroxide is added to the olefin polymer constituting the main chain component (a) to generate a free radical, and the polymer of the graft component (b) is added thereto and melt-kneaded. A method of performing a graft reaction, (iii) a catalyst such as a peroxide is added to the polymer of the graft component (b) to generate a free radical, which is melt-kneaded with an olefin polymer constituting the main chain component (a). And a graft reaction is performed.

The kneading ratio of the main chain component (a) and the graft component (b) in producing the copolymer (A) is 95: 5.
It is preferable to select in the range of 5:95. Graft component (b)
If the ratio of (b) is small, the affinity and compatibility between the copolymer (A) and the polyacetal resin (C) for molding will not be improved, which is not preferable, and if the ratio of the graft component (b) is too large, thermal decomposition type foaming will occur. It is not preferable because it becomes difficult to melt-knead the agent (B) without decomposing it. Within the above range, 80:20 to 20:80 is preferable, and 60:40 to 40:60 is particularly preferable.

According to the experiments by the present inventors, the foaming agent (B)
It has been found that the melting temperature of the copolymer (A) is preferably 170 ° C. or lower in order to retain it in the copolymer (A) without decomposing it and to function as a blowing agent masterbatch for polyacetal resin. . The melting temperature of the copolymer (A) of 170 ° C. or lower can be easily achieved by selecting the main chain component (a) or the graft component (b) and the kneading ratio of both.

In the present invention, the heat-decomposable foaming agent (B) has a function of thermally decomposing and foaming a molded article when the molding polyacetal resin (C) is molded. The thermal decomposition type foaming agent (B) needs to be solid at a temperature of 20 ° C. and have a decomposition temperature of 170 ° C. or higher. When it is solid at a temperature of 20 ° C., the problems (c) to (d) do not occur when the foaming agent masterbatch is prepared by mixing with the copolymer (A). Further, when the decomposition temperature is 170 ° C. or higher, the foaming agent masterbatch is not thermally decomposed when the foaming agent masterbatch is prepared, and a foaming agent masterbatch having good foaming efficiency is obtained.

The heat-decomposable foaming agent (B) may be any of conventionally known organic foaming agents, inorganic foaming agents, etc., so long as they satisfy the above requirements.
It is selected and used according to the purpose and application.

As organic foaming agents, azo compounds, nitroso compounds, sulfonyl compounds, tetrazole compounds and the like are known, and specific examples thereof include azodicarbonamide, 5-phenyltetrazole and dinitrosopentamethylenetetramine. To be Examples of the inorganic foaming agent include zinc oxide, zinc carbonate, sodium bicarbonate, sodium citrate and the like. These may be used alone or as a mixture of two or more kinds, and may be used in combination with other foaming agents not exemplified. Of these, preferred is azodicarbonamide, a tetrazole compound, sodium bicarbonate, sodium citrate alone or 2 selected from these.
Combinations of more than one species.

When the foaming agent masterbatch is prepared, other auxiliary agents can be added, if necessary, in order to adjust the decomposition temperature of the foaming agent. Other auxiliary agents include salicylic acid, stearic acid, adipic acid, urea, calcium stearate, cadmium stearate, zinc stearate and the like. These may be used alone or as a mixture of two or more kinds. In addition, when preparing the foaming agent masterbatch, a dispersibility improving agent for the foaming agent, a nucleating agent, a lubricant, a coloring agent, an anticorrosive agent and the like may be added, if necessary.

In order to prepare the foaming agent masterbatch according to the present invention, first, 100 parts by weight of the copolymer (A) as a base is mixed in the range of 1 to 100 parts by weight of the foaming agent (B). When the blending amount of the foaming agent (B) with respect to the copolymer (A) is less than 1 part by weight, the amount of the foaming agent is too small and it is necessary to blend a large amount at the time of producing a molded product, and the function of the masterbatch is fulfilled. It is not preferable because it is not available. When the blending amount of the foaming agent (B) with respect to the copolymer (A) exceeds 100 parts by weight, the amount of the foaming agent (B) is too large and it becomes difficult to prepare the foaming agent masterbatch, which is not preferable. Within the above range, the blowing agent (B) is added to 100 parts by weight of the copolymer (A).
The range of 5 to 50 parts by weight is preferable, and particularly preferable is the blowing agent (B) based on 100 parts by weight of the copolymer (A).
It is in the range of 10 to 30 parts by weight.

To prepare the foaming agent masterbatch according to the present invention, the blended copolymer (A) and foaming agent (B) are melt-kneaded at a temperature not higher than the thermal decomposition of the foaming agent (B).
This is because the foaming agent (B) is thermally decomposed at a high temperature during preparation of the foaming agent masterbatch, and the product does not function as a foaming agent masterbatch. There is no limitation on the kneading machine that can be used in the melt kneading, and examples include conventionally known ones such as a Σ blade type kneading machine, a mixing roll, a Banbury mixer, a high-speed twin-screw continuous mixer, and an extruder.

In order to prepare a foaming agent masterbatch without thermally decomposing the foaming agent (B), for example, melt-kneading with an extruder and the following method can be used. (1) The cylinder temperature of the extruder is set to 140 to 170 ° C. (2-1) Kneading is performed using a single-screw extruder equipped with a full flight screw. (2-2) In the case of a twin-screw extruder, in order to suppress the heat generation of the resin due to the mutual shearing action of the two screws, a full flight half meshing screw is equipped and they are rotated in different directions. (3) The copolymer (A) is charged into a hopper and melted,
The foaming agent (B) is introduced through a hole formed in the middle of the cylinder and melt-kneaded with the copolymer (A) to form extruded pellets.

In order to produce a polyacetal resin foam-molded article using the foaming agent masterbatch prepared by the above method, first, the molding polyacetal resin (C) 1
0.1 parts by weight of the above blowing agent masterbatch to 100 parts by weight.
Mix ~ 20 parts by weight. When the compounding amount of the foaming agent masterbatch is less than 0.1 part by weight with respect to 100 parts by weight of the resin (C), the amount of the foaming agent with respect to the resin (C) is too small and the target expansion ratio is 1.01. The above molded products cannot be obtained. When the blending amount of the blowing agent masterbatch exceeds 20 parts by weight, the amount of the blowing agent with respect to the resin (C) is too large, and the expansion ratio becomes too high, which is not preferable. The blending amount of the blowing agent masterbatch is 0.5 within the above range.
-5 parts by weight are preferred.

There is no limitation on the mixer that can be used for mixing the foaming agent masterbatch with the resin (C), and conventionally known ones such as a ball mill, a blender, a tumbler, a Henschel mixer, and a crusher can be used. To be

The resin (C) is a raw material resin for the foamed molded product and refers to a polyacetal resin for molding. The molding polyacetal resin is a homopolymer consisting only of oxymethylene units, and a copolymer (copolymer) containing oxymethylene units as a main component and other copolymerized units such as oxyethylene units as a subcomponent. ) Is known. Further, it may be a polymer cross-linked by a known method or a graft-copolymerized one.

When mixing the foaming agent masterbatch with the resin (C), various ordinary resin additives may be added, if desired. Resin additives that can be blended include
Antioxidant, flame retardant, flame retardant aid, antistatic agent, release agent,
Examples thereof include colorants such as dyes and pigments, lubricants, plasticizers, crystallization accelerators, heat resistance stabilizers, weather resistance stabilizers, ultraviolet absorbers, rust inhibitors, and fillers such as glass fibers and carbon fibers. The resin additive is not limited to those exemplified above. These resin additives can be blended with the resin (C) in advance by kneading.

In order to produce a polyacetal resin foam-molded article by using the mixture of the foaming agent masterbatch prepared by the above method and the resin (C), the foaming agent contained in the foaming agent masterbatch is Mold by heating above the decomposition temperature. A typical method for producing a foam-molded article is an injection molding method, but the method is not limited to this, and other molding methods for a thermoplastic resin, such as an extrusion molding method, depending on the type and shape of the molded article. Alternatively, a melt compression molding method may be used.

In order to produce a foam-molded article by the injection molding method, the resin (C), the foaming agent masterbatch and, if necessary, other resin additives are mixed and mixed, and the mixture is put into a hopper and the temperature is raised. For example, it is heated in a cylinder set at 190 to 220 ° C., injection-pressed into a mold, and cooled to obtain a desired molded product. There are no restrictions on the type of molded product,
Examples include electronic parts, home electric appliance parts, machine parts, automobile parts, office equipment parts, daily miscellaneous goods products, and the like.

[0030]

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[Examples 1 to 6, Comparative Examples 1 to 3] <Preparation of blowing agent masterbatch> Copolymer (A) having the characteristics shown in Table 1 or low density polyethylene 1 each
25 parts by weight of each azodicarbonamide-based foaming agent (decomposition temperature of about 190 ° C.) as a thermal decomposition type foaming agent (B) was weighed in an amount of 00 parts by weight and mixed by a tumbler to obtain a mixture.

The obtained mixture is a single-screw extruder equipped with a full-flight screw (extruder 1) and a twin-screw extruder equipped with a full-flight screw in a half meshing state and rotating in different directions (extruder 2). ), Or a three-thread screw equipped in a completely meshed state, and melt-kneaded by a twin-screw extruder (extruder 3) rotating in the same direction under the temperature conditions shown in Table 2 to produce a blowing agent masterbatch. Pellets A to E were prepared.

[0033]

[Table 1]

[0034]

[Table 2]

<Preparation of Blend for Producing Foamed Molded Article> Polyacetal resin (C) has a melting point of 165 ° C. and a melt index value (value measured at 190 ° C. according to ASTM D1238, value at 2.16 Kg load) of 9 The foaming agent master batches A to E prepared by the above method were added to a polyacetal copolymer of 0.2 (g / 10 minutes).
Blended in a ratio shown in 3 and mixed by a tumbler to obtain a blend for producing a foamed molded product. In addition, Comparative Example 2 and Comparative Example 3
In that case, instead of the foaming agent masterbatch, the foaming agent (B)
Only (Comparative Example 2) was mixed with the foaming agent (B) and glycerin (Comparative Example 3) in the proportions shown in Table-3.
In either case, the resin component 104 is added to 1 part by weight of the foaming agent.
The blending ratio was selected so that the weight part was {sum of components excluding foaming agent}.

<Production of foamed molded article> The obtained blended product was used to produce a molded article and a test piece by an injection molding machine by a short shot method and a full shot method. Evaluation was performed by the method described. (A) Short shot method The manufacturing conditions of the molded product were a cylinder temperature of 195 ° C., an injection speed of 100 mm / sec, a molten resin injection amount of about 80% of the mold cavity volume, a mold temperature of 30 ° C., and a cooling time of 40 seconds. .
The expansion ratio of the molded product is 1.25. (B) Full shot method The manufacturing conditions of the molded product are as follows: cylinder temperature 195 ° C, injection speed 100 mm / sec, molten resin injection amount is the same as mold cavity volume, holding pressure after injection of molten resin into the mold cavity. Was 500 kgf / cm ² , the mold temperature was 30 ° C., and the cooling time was 40 seconds. The expansion ratio of the molded product is 1.02 times.

<Evaluation of Foamed Molded Product> (a) Surface Condition of Molded Product (Peeling) A molded product having a size of 40 mm × 40 mm × 20 mm is molded by the short shot method, and the surface thereof is evaluated by visual observation. Is the way to do it. As long as the compatibility and affinity between the resin (C) and the resin contained in the foaming agent masterbatch are good, there is no peeling of the surface of the molded article. The evaluation results are displayed as follows. No surface peeling is observed: ○, surface layer floats: △, surface is completely peeled: ×

(B) Surface condition (smoothness) of molded product This is a method of touching the surface of the molded product with a fingertip and evaluating the feeling. If the foaming force is sufficient, the surface of the molded product is strongly pressed against the mold cavity surface, so that the surface of the molded product becomes smooth. The evaluation results are displayed as follows. Surface is smooth: ○, surface is rough: ×, intermediate between both: △

(C) Foamed structure 40 mm × 40 mm × 2 molded by the short shot method
This is a method in which a molded product having a size of 0 mm is cut, and the size, distribution, and uniformity of the foam cells appearing on the cut surface are visually observed. The evaluation results are displayed as follows. The size and distribution of the foam cells are uniform: ○, the size and distribution of the foam cells are not uniform: ×, intermediate between the two: △

(D) Tensile strength (unit: kgf / cm ² ) For test pieces molded by the short shot method, ASTM
It measured based on D638. (e) Tensile elongation (unit:%) For test pieces molded by the short shot method, ASTM
It measured based on D638.

(F) Tensile strength (with weld line) (unit: kgf / cm ² ) A mold having a gate at two locations and a weld line (melted resin flow end joint) at the center of the test piece. For the test pieces used and molded by the full shot method, ASTM D638
It measured according to. (g) Tensile elongation (with weld line) (unit:%) Using the same mold as above, a test piece molded by the full shot method was measured according to ASTM D638. (f)
In the test pieces of (g) and (g), a clear weld line was visually observed. The evaluation results of (a) to (g) above are shown in Table-3.

[0042]

[Table 3]

The following is clear from Table-3. (1) Molded articles produced using the foaming agent masterbatch according to the present invention are excellent in surface condition and foam structure, and also excellent in mechanical properties of the molded articles (see Examples 1 to 6). . Among them, using a graft copolymer obtained by grafting acrylonitrile-styrene copolymer on low-density polyethylene as a master batch resin, a single-screw extruder equipped with a full flight screw or a full flight screw is equipped in a semi-engaged state. When a blowing agent masterbatch prepared by using a twin-screw extruder that rotates in a direction is used, a more excellent molded product is obtained (Examples 4 to 5).
reference). (2) On the other hand, in Comparative Example 1 in which LDPE was used as the base resin of the foaming agent masterbatch, peeling occurred on the surface of the molded product, and the evaluation items (d), (f) and (g) were evaluated. , Inferior to those of the example. (3) Furthermore, the one in which the foaming agent is directly blended with the molding polyacetal resin (Comparative Example 2) does not meet the object of the present invention of obtaining a stable foamed molded article because the foamed structure is not constant. Although not shown in the table, scattering of the powdery foaming agent,
A tendency such as a change in the composition ratio due to the separation of the foaming agent was also observed. (4) A foaming agent directly blended with a polyhydric alcohol in a molding polyacetal resin (see Comparative Example 3) has a non-uniform foam size and distribution, and has a non-uniform foam structure, which is also stable foam molding. It does not meet the purpose of the present invention to obtain a product. This is because a part of the foaming agent becomes a pasty mass,
It shows that the uniformity and physical properties of the foam structure are adversely affected. Although not shown in the table, the behavior of the foaming agent adhering to the hopper of the molding machine together with the polyhydric alcohol was observed.

[Examples 7 to 10] The blowing agent (B) was replaced with a tetrazole compound, sodium bicarbonate, sodium citrate and a mixture of azodicarbonamide and sodium bicarbonate.
In the same manner as in Example 4, a blowing agent masterbatch, a blend for producing a foamed molded product, and a foamed molded product were produced. The obtained foamed molded product was evaluated in the same manner as in Example 4 and the results are shown in Table 4. From Table 4, it can be seen that also in Examples 7 to 10, the same excellent foam-molded products as in Example 4 were obtained. In addition, the foam-molded articles produced by the same method as Comparative Examples 1 to 3 using these foaming agents had substantially the same results as Comparative Examples 1 to 3.

[0045]

[Table 4]

[0046]

The present invention has the following advantageous effects, and its industrial utility value is extremely large. 1. The foaming agent masterbatch according to the present invention does not cause the foaming agent to scatter and deteriorate the working environment. 2. Since the foaming agent masterbatch according to the present invention has no difference in diameter and specific gravity with the molding polyacetal resin, the blending state does not change during transportation after blending or when charged into the hopper of the molding machine. . 3. The foamed molded product obtained by using the foaming agent masterbatch according to the present invention does not cause breakage at the interface, and thus the molded product has excellent mechanical properties.

Claims (9)

[Claims] 1. A temperature of 20 ° C. with respect to 100 parts by weight of a graft copolymer (A) obtained by grafting an olefin polymer as a main chain component (a) and a vinyl polymer as a graft component (b). Solid at a decomposition temperature of 170
A foaming agent masterbatch for a polyacetal resin, which comprises 1 to 100 parts by weight of a pyrolyzable foaming agent (B) at a temperature of not less than 0 ° C. and is melt-kneaded. 2. The main chain component (a) constituting the graft copolymer (A) comprises polyethylene or a copolymer of ethylene and a glycidyl ester of an α, β-unsaturated acid. Foaming agent masterbatch for polyacetal resin. 3. The blowing agent master for a polyacetal resin according to claim 1, wherein the graft component (b) constituting the graft copolymer (A) is composed of polymethylmethacrylate or an acrylonitrile / styrene copolymer. batch. 4. The main chain component (a) constituting the graft copolymer (A) is polyethylene or a copolymer of ethylene and a glycidyl ester of an α, β-unsaturated acid, and the graft component (b) is Polymethylmethacrylate or acrylonitrile-styrene copolymer,
The foaming agent masterbatch for polyacetal resin according to claim 1. 5. The blowing agent masterbatch for a polyacetal resin according to claim 1, wherein the graft copolymer (A) is obtained by grafting an acrylonitrile / styrene copolymer on polyethylene. 6. The polyacetal according to claim 1, wherein the thermal decomposition type foaming agent (B) is one kind or a mixture of two or more kinds selected from azodicarbonamide, a tetrazole compound, sodium bicarbonate and sodium citrate. Foaming agent masterbatch for resin. 7. A main chain component (a) of an olefin-based polymer
And 100 parts by weight of the graft copolymer (A) grafted with the vinyl polymer graft component (b) are solids at a temperature of 20 ° C. and a decomposition temperature of 170 ° C. or more A method for producing a foaming agent masterbatch for a polyacetal resin, which comprises blending 1 to 100 parts by weight of the agent (B) and then melt-kneading at a temperature not higher than the thermal decomposition of the thermal decomposition type foaming agent (B). 8. The graft copolymer (A) and the thermal decomposition type foaming agent (B) are melt-kneaded using a single-screw extruder equipped with a full flight screw, or the full flight screw is in a semi-engaged state. The method for producing a foaming agent masterbatch according to claim 7, wherein the twin-screw extruder equipped in step 1 is used to melt-knead by rotating the screws in mutually different directions. 9. A foaming agent masterbatch for a polyacetal resin according to claim 1 is mixed in an amount of 0.1 to 20 parts by weight with respect to 100 parts by weight of the polyacetal resin (C) to prepare a foaming agent contained in the foaming agent masterbatch. A method for producing a polyacetal resin foam-molded article, which comprises heating at a decomposition temperature or higher and molding.