JP2014189773A - Ethylene-vinyl acetate copolymer resin composition, crosslinked foam, and footwear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylene-vinyl acetate copolymer resin composition yielding a low-glossiness crosslinked foam excellent in terms of adhesion and mechanical characteristics; a crosslinked foam including the resin composition; and footwear including the crosslinked foam.SOLUTION: The provided ethylene-vinyl acetate copolymer resin composition includes: an ethylene-vinyl acetate copolymer; a swellable clay including alkyl ammonium cations expressed by the formula (1); a foaming agent; and a crosslinking agent: (in the formula (1), R expresses a hydrocarbon group having 1-30 carbon atoms).

Description

  The present invention relates to an ethylene-vinyl acetate copolymer resin composition, a cross-linked foam containing the resin composition, and footwear.

  As the foam for a shoe sole, a foam of polyurethane or ethylene-vinyl acetate copolymer is used. In recent years, improvement in the expansion ratio has been studied for reducing the weight of the foam, but there is a problem that mechanical properties deteriorate when the expansion ratio is increased. Therefore, Patent Document 1 discloses using a foam using an ethylene-α-olefin copolymer for the purpose of improving mechanical properties.

  Moreover, the foam for shoes soles is produced by metal mold | die foam molding, such as a compression mold and an injection mold. The foam molded in this way has a high surface gloss, but in the field where design properties are required, a reduction in the gloss of the surface is desired. In order to solve this problem, it is known that a foam molded by a compression mold is formed excluding the foam surface, but there is a problem that the cost is high and the process is complicated. In addition, the injection mold is advantageous in terms of cost and process because a foam can be formed at one time, but it is a problem to reduce the gloss of the molding surface. Therefore, Patent Document 2 discloses that a physical surface treatment method is used to reduce the gloss of the foam surface.

JP 2011-001545 A Japanese Patent No. 3613866

  However, in patent document 1, the adhesive properties are not sufficient. Since the adhesive property affects the durability of the shoe, a foam having an excellent balance between the adhesive property and the mechanical property is desired for further weight reduction. Moreover, in patent document 2, the complexity of a process cannot be avoided, but there exists a subject in cost and a process surface.

  The present invention has been made in view of the above problems, and has a low glossiness, an ethylene-vinyl acetate copolymer resin composition that provides a crosslinked foam having excellent adhesive properties and mechanical properties, and the resin composition An object of the present invention is to provide a cross-linked foam containing, and footwear containing the cross-linked foam.

  As a result of intensive studies to solve the above problems, the present inventors have found that a swellable clay containing an ethylene-vinyl acetate copolymer and a specific ammonium cation (hereinafter also referred to as “organized swellable clay”). The present inventors have found that the above-described problems can be solved by using a resin composition that contains the present invention, and have completed the present invention.

That is, the present invention is as follows.
[1]
An ethylene-vinyl acetate copolymer;
A swellable clay comprising an alkylammonium cation represented by formula (1);
A blowing agent;
A crosslinking agent;
including,
Ethylene-vinyl acetate copolymer resin composition.
(In the formula (1), R represents a hydrocarbon group having 1 to 30 carbon atoms.)
[2]
The ethylene-vinyl acetate copolymer resin composition according to [1] above, wherein a content of the vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 3 to 50% by mass.
[3]
The ethylene-vinyl acetate copolymer resin composition according to [1] or [2] above, wherein the swellable clay is synthetic fluorine mica.
[4]
A crosslinked foam comprising the ethylene-vinyl acetate copolymer resin composition according to any one of [1] to [3] above.
[5]
Footwear comprising the cross-linked foam according to [4] above.

  According to the present invention, an ethylene-vinyl acetate copolymer resin composition that provides a crosslinked foam having low gloss and excellent adhesive properties and mechanical properties, a crosslinked foam containing the resin composition, and the crosslinked foam Footwear can be provided.

  Hereinafter, although the form for implementing this invention (henceforth "this embodiment") is demonstrated in detail, this invention is not limited to this, Various in the range which does not deviate from the summary. Deformation is possible.

[Ethylene-vinyl acetate copolymer resin composition]
The ethylene-vinyl acetate copolymer resin composition (hereinafter, also simply referred to as “resin composition”) according to this embodiment.
An ethylene-vinyl acetate copolymer;
A swellable clay comprising an alkylammonium cation represented by formula (1);
A blowing agent;
And a crosslinking agent.
(In the formula (1), R represents a hydrocarbon group having 1 to 30 carbon atoms.)

[Ethylene-vinyl acetate copolymer]
The ethylene-vinyl acetate copolymer used in the present embodiment is not particularly limited, and a known one can be used. The content of the vinyl acetate monomer in the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 3 to 50% by mass, more preferably 5 to 33% by mass, and further preferably 6 to 28% by mass. By using such an ethylene-vinyl acetate copolymer, it tends to be more excellent in flexibility, heat resistance, and processability. In addition, content of the vinyl acetate monomer in an ethylene-vinyl acetate copolymer can be measured based on JISK7192.

  Further, the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer used in the present embodiment is preferably 0.1 to 50 g / 10 min, more preferably 0.5 to 40 g / 10 min. More preferably, it is 1-30 g / 10min. When the MFR is within the above range, the processability tends to be superior. The MFR of the ethylene-vinyl acetate copolymer can be measured according to JIS K7210 code D.

  Further, the ethylene-vinyl acetate copolymer used in the present embodiment may be modified with an unsaturated monomer. Examples of such unsaturated monomers include, but are not limited to, mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; unsaturated carboxylic acid derivatives that are anhydrides of mono- or dicarboxylic acids ; (Meth) acrylic acid esters such as hydroxyethyl (meth) acrylate, glycyl (meth) acrylate, aminoethyl (meth) acrylate; vinyl groups such as vinyltrimethoxysilane and γ-propyltrimethoxysilane γ- Examples thereof include alkoxysilane.

  In addition, ethylene-vinyl acetate copolymer may be used individually by 1 type, or may use 2 or more types together.

(Swelling clay)
The resin composition according to the present embodiment includes a swellable clay containing an alkylammonium cation represented by the formula (1). This swelling clay fulfills the function of improving the mechanical properties, low gloss, and adhesion of the resin composition by being dispersed in the ethylene-vinyl acetate copolymer.

The swellable clay used in the present embodiment contains an alkylammonium cation represented by the formula (1). Specifically, there is no particular limitation as long as the cation contained between the layers of the swellable clay is an ammonium cation represented by the formula (1). Such a swellable clay can be produced by ion exchange of cations contained between layers with ammonium ions represented by the formula (1).
(In the formula (1), R represents a hydrocarbon group having 1 to 30 carbon atoms.)

  Although it does not specifically limit as swelling clay used by this embodiment, For example, bentonite, montmorillonite, vermiculite, mica etc. are mentioned. Among these, synthetic fluorine mica is preferable. Although it does not specifically limit as a synthetic fluorine mica, For example, a somasif (a product name, the product made by Coop Chemical Co., Ltd., a synthetic swelling fluorine mica) etc. are mentioned. By using such swellable clay, the aspect ratio tends to increase and the mechanical properties tend to be superior. Synthetic fluorine mica can be produced by a dry synthesis method.

  The ion-exchangeable cations existing between the layers of the swellable clay are ions such as sodium and lithium, and these ions easily exchange with a cationic substance. Therefore, the swellable clay can introduce various substances having a cationic property between the layers. The swellable clay used in this embodiment is obtained by exchanging ions existing between layers with alkylammonium cations represented by the formula (1). The exchange method is not particularly limited, and a known method can be used. Specific examples include the methods described in the examples. Note that the amount of ion-exchanged organic matter can be measured from the weight loss by thermal analysis.

  The cation exchange capacity of the swellable clay used to obtain the organically swellable clay used in this embodiment is not particularly limited, but is preferably 50 to 200 mm equivalent / 100 g, such as 85 to 140 mm. The amount is more preferably 100 g, more preferably 90 to 140 mm equivalent / 100 g. When the cation exchange capacity is in the above range, the mechanical properties tend to be further improved. The cation exchange capacity can be measured by the Schollenberger method.

  In the formula (1), R is not particularly limited as long as it is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and may be linear or branched, and may be a saturated hydrocarbon or an unsaturated hydrocarbon. Such hydrocarbon group is not particularly limited, but for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl And aliphatic hydrocarbon groups such as a group, undecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, octadecyl group, lauryl group, stearyl group, and behenyl group.

  The content of the organically swellable clay in the resin composition according to this embodiment is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and 1 to 15% by mass. More preferably. When the content is within the above range, the mechanical properties tend to be more excellent.

  In addition, swelling clay may be used individually by 1 type, or may use 2 or more types together.

[Foaming agent]
The foaming agent used in the present embodiment is not particularly limited, and known ones can be used. Such a foaming agent is not particularly limited. For example, sodium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, azobisisobutyronitrile. And benzenesulfonyl hydrazide. In addition, a foaming agent may be used individually by 1 type, or may use 2 or more types together.

  The content of the foaming agent in the resin composition according to this embodiment is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and 1 to 15% by mass. Is more preferable. When the content is within the above range, the expansion ratio becomes better and the moldability tends to be better.

[Crosslinking agent]
There is no restriction | limiting in particular as a crosslinking agent used by this embodiment, A well-known thing can be used. Such a crosslinking agent is not particularly limited, and for example, an organic peroxide or a sulfur-based crosslinking agent can be used. Examples of the organic peroxide include, but are not limited to, dicumyl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, cyclohexane peroxide, and t-butylperoxybenzoate. , T-butyl cumyl oxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) octane, di-t-butyl peroxide and the like. It is done. Moreover, it does not specifically limit as a sulfur type crosslinking agent, For example, sulfur, sulfur chloride, 4,4'- dithiodimorpholine etc. are mentioned. In addition, a crosslinking agent may be used individually by 1 type, or may use 2 or more types together.

  The content of the crosslinking agent in the resin composition according to the present embodiment is preferably 0.1 to 20% by mass, more preferably 0.3 to 10% by mass, and 0.3 to 5% by mass. % Is more preferable. When the content is within the above range, the foam moldability tends to be more excellent.

[Other ingredients]
The resin composition according to the present embodiment may contain other polymers and additives as necessary.

  Examples of such a polymer include, but are not limited to, polyethylene, polypropylene, an ethylene copolymer, a polypropylene copolymer, a diene copolymer, and the like.

  The polyethylene is not particularly limited, and examples thereof include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, and ultra low density polyethylene.

  The ethylene-based copolymer is not particularly limited. For example, other than ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-vinyl ester copolymer, ethylene-acrylic acid copolymer. Examples thereof include a polymer, an ethylene-methacrylic acid copolymer, an ethylene-acrylic acid ester copolymer, and an ethylene-methacrylic acid ester copolymer. More specifically, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-vinyl alcohol resin, ethylene-propylene copolymer, ethylene-vinyl acetate. Examples thereof include a saponified copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene-ethyl methacrylate copolymer.

  Although it does not specifically limit as said polypropylene-type copolymer, For example, a polypropylene block copolymer, a polypropylene random copolymer, etc. are mentioned.

  The diene copolymer is not particularly limited, and examples thereof include styrene butadiene rubber.

  The additive is not particularly limited. For example, a heat stabilizer, a crosslinking aid, a foaming aid, a processing aid, a lubricant, a colorant (pigment, dye, etc.), silicone oil, other oils, an inorganic filler ( Calcium carbonate, talc, magnesium hydroxide, silica, barium sulfate, glass filler, etc.), flame retardants, crystal nucleating agents, ultraviolet absorbers and the like.

  The foaming aid is not particularly limited, and examples thereof include zinc oxide and salicylic acid. The processing aid is not particularly limited, and examples thereof include stearic acid and calcium stearate. Although it does not specifically limit as a pigment, For example, a titanium oxide etc. are mentioned.

[Method for producing ethylene-vinyl acetate copolymer resin composition]
It does not restrict | limit especially as a manufacturing method of the ethylene-vinyl acetate copolymer resin composition of this embodiment, A well-known method can be utilized. For example, a melt kneading method is used using a general kneader such as a Banbury mixer, a kneader, a roll, a single screw extruder, a twin screw extruder, or a multi-screw extruder.

(Crosslinked foam)
The crosslinked foam according to the present embodiment includes the resin composition. “Crosslinking” refers to partial bonding of polymers.

  Although it does not specifically limit as a manufacturing method of the crosslinked foamed material which concerns on this embodiment, For example, the heat crosslinking foaming method and the electron beam crosslinking foaming method can be mentioned. Examples of the heat-crosslinking foaming method include a method of filling a resin composition into a mold with an injection molding machine and heat-crosslinking foaming, and a method of heat-crosslinking and foaming a resin composition melt-kneaded with a kneader with a hot press. . Examples of the radiation crosslinking foaming method include a method of foaming after the sheet is crosslinked by electron beam irradiation.

  The crosslinked foam containing the ethylene-vinyl acetate copolymer resin composition of the present embodiment has a low gloss and can provide a foam excellent in mechanical properties. Such a crosslinked foam can be suitably used for automobile parts, civil engineering and building applications, household electrical appliance members, sports equipment, and the like.

〔footwear〕
The footwear according to the present embodiment includes the crosslinked foamed body. The cross-linked foam is suitable as a shoe sole for footwear because it can achieve both high foamability and mechanical properties.

  The present embodiment will be described based on examples. Note that the present embodiment is not limited to these examples. The physical properties in Examples and Comparative Examples were evaluated by the following methods.

[Ethylene-vinyl acetate copolymer]
Ethylene-vinyl acetate copolymer 1: Suntec EVA EF0910 (product name, manufactured by Asahi Kasei Chemicals Corporation, vinyl acetate monomer content 9% by mass, MFR = 1.0 g / 10 min)
Ethylene-vinyl acetate copolymer 2: Suntech EVA EF1531 (product name, manufactured by Asahi Kasei Chemicals Corporation, vinyl acetate monomer content 15 mass%, MFR = 3.0 g / 10 min)
Ethylene-vinyl acetate copolymer 3: Suntec EVA EM7830 (product name, manufactured by Asahi Kasei Chemicals Corporation, vinyl acetate monomer content 28% by mass, MFR = 30.0 g / 10 min)

[Swelling clay]
Somasif ME-100 (product name, manufactured by Coop Chemical Co., Ltd.)

[Ethylene-α-olefin copolymer]
TAFMER DF810 (product name, manufactured by Mitsui Chemicals, MFR = 1.2g / 10min)

[Evaluation method]
(1) Specific gravity Specific gravity of the cross-linked foams produced in Examples and Comparative Examples was measured according to ASTM D297.

(2) Gloss Using the surface of the sample after heat-crosslinking foaming, the crosslinked foams produced in Examples and Comparative Examples using a product name micro-gloss meter (BYK-Gardner) according to ASTM D2457 The 60 ° gloss was measured.

(3) Tensile strength The surface of the cross-linked foam prepared in Examples and Comparative Examples was cut out, and a measurement sample having a thickness of 3 mm was cut out. Using ASTM D412, the tensile strength of the measurement sample was measured in a 23 ° C. constant temperature room using a universal material testing machine (manufactured by A & D Co., Ltd.).

(4) Tear strength After cutting off the surface of the crosslinked foam produced in the examples and comparative examples, a measurement sample having a thickness of 10 mm was cut out. According to ASTM D3574, the tear strength of the measurement sample was measured in a 23 ° C. constant temperature room using a universal material testing machine (manufactured by A & D Co., Ltd.).

(5) Adhesion test Adhesive strength between the crosslinked foams produced in Examples and Comparative Examples and vulcanized rubber was measured. The surface of the crosslinked foam was washed with water and dried, and then a UV primer (P-7-2, manufactured by Dongsung NSC) was applied and dried. After this crosslinked foam was irradiated with UV, an aqueous primer (W104, manufactured by Dongsung NSC) was applied and dried, and further an aqueous adhesive (W01, manufactured by Dongsung NSC) was applied and dried again. Next, the surface of the vulcanized rubber was washed with methyl ethyl ketone and dried, and then an aqueous primer (PR505, manufactured by Dongsung NSC) was applied and dried again. A water-based adhesive was applied and dried, and then the crosslinked foam and vulcanized rubber were integrated by a press to obtain a measurement sample. The adhesive strength of the measurement sample was measured with a universal material testing machine.

Reference Example 1 Synthesis of Organized Swelling Clay 15 g of swellable clay (Somasif ME-100, manufactured by Coop Chemical Co., Ltd.) was dispersed in 500 mL of water. To this dispersion, an aqueous solution in which 9.2 g of trimethylstearyl ammonium chloride (Arcade 18-63, manufactured by Lion Corporation) was dissolved in 150 mL of water was added and stirred at room temperature for 2 hours. Thereafter, the resulting product was subjected to solid-liquid separation and washing to remove by-product salts, and then dried and ground to synthesize organically swellable clay.

[Example 1]
Using a Banbury mixer heated to 100 ° C., raw materials other than the crosslinking agent and foaming agent shown in Table 1 were melt-mixed and then cooled to room temperature. Then, the crosslinking agent and the foaming agent were added and mixed with a roll to prepare the ethylene-vinyl acetate copolymer resin composition of Example 1. The obtained resin composition was filled in a mold and heated and pressed at 170 ° C. for 10 minutes to obtain a crosslinked foam. After storage in a constant temperature room at 23 ° C. all day and night, the physical properties of the crosslinked foam were evaluated by the above evaluation.

[Examples 2-3]
Except having used the raw material shown in Table 1, operation similar to Example 1 was performed, the ethylene-vinyl acetate copolymer resin composition of Examples 2-3 was prepared, and the heat-crosslinked foam was obtained.

[Comparative Examples 1-4]
Except having used the raw material shown in Table 1, operation similar to Example 1 was performed, the ethylene-vinyl acetate copolymer resin composition of Comparative Examples 1-4 was prepared, and the heat-crosslinked foam was obtained.

  From Table 1, it was found that the cross-linked foam having low gloss and excellent adhesive properties and mechanical properties can be obtained with the ethylene-vinyl acetate copolymer resin composition of the present invention.

  Since the ethylene-vinyl acetate copolymer resin composition of the present invention exhibits the above-mentioned effects, it is possible to obtain a cross-linked foam with improved luster and improved texture in mold molding such as injection molding, and reduction in processing cost. Also effective. In addition, since it is excellent in mechanical properties and adhesive properties, it is useful as a material for various footwear such as outsole and midsole, and can be used for cushioning materials and various industrial products. In particular, the ethylene-vinyl acetate copolymer resin composition of the present invention has industrial applicability in the footwear field.

Claims (5)

An ethylene-vinyl acetate copolymer;
A swellable clay comprising an alkylammonium cation represented by formula (1);
A blowing agent;
A crosslinking agent;
including,
Ethylene-vinyl acetate copolymer resin composition.

(In the formula (1), R represents a hydrocarbon group having 1 to 30 carbon atoms.)   The ethylene-vinyl acetate copolymer resin composition according to claim 1, wherein the content of the vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 3 to 50 mass%.   The ethylene-vinyl acetate copolymer resin composition according to claim 1 or 2, wherein the swellable clay is synthetic fluorine mica.   The crosslinked foamed material containing the ethylene-vinyl acetate copolymer resin composition of any one of Claims 1-3.   Footwear comprising the crosslinked foam according to claim 4.