JPS60192735A - Foam body - Google Patents

Abstract

PURPOSE:A high-expansion ratio foam excellent in wet skid performance, mold flow and abrasion resistance, prepared by crosslinking and expanding a rubber composition containing a specified 1,2-polybutadiene, a styrene/butadiene random copolymer and other rubbers. CONSTITUTION:A rubber composition comprising (A) 30-90wt% 1,2-polybutadiene (1,2-bond content >=70wt%, crystallinity >=5%, and intrinsic viscosity in toluene at 30 deg.C>=0.5dl/g), (B) 5-60wt% styrene/butadiene random copolymer (combined styrene content of 3-30wt% and 1,2-bond content of the butadiene portion of 50-95%), and 0-50wt% at least one member selected from among natural rubber, diene rubbers (except the rubber of component B), and aromatic vinyl compound/conjugated diene compound block copolymers is mixed with a crosslinking agent and a blowing agent at about 70-140 deg.C. The obtained mixture is placed in a mold and crosslinked and expanded by heating to about 140- 170 deg.C under an elevated pressure.

Description

Detailed Description of the Invention The present invention relates to a crosslinked foam of butadiene polymer rubber that has excellent wet skid properties and mold flow properties, good abrasion resistance, and a high expansion ratio. Foams using 1,2-/IJ butadiene (1,2-PBD), ethylene/vinyl acetate copolymer (EVA), natural rubber, synthetic rubber, etc. as the body are known. Of these, natural
It is difficult to obtain a high expansion ratio with foams using rubber and synthetic rubber, and dimensional accuracy is poor due to large shrinkage after vulcanization. Furthermore, it has the disadvantage that it is difficult to mold using a complicated mold due to poor mold flowability.

On the other hand, it is generally known that foams using 1.2-PBD and EVA can be used with only one stage of crosslinking to obtain foams with a high expansion ratio and no shrinkage problems. It is widely used in applications that require weight reduction, such as soles, inner soles, and midsoles.

The main performance of outer soles is wet skid properties, which show the resistance to slipping on wet roads when walking or running, and abrasion resistance, but in recent years, lighter sponges have been used due to the demand for weight reduction. It's here. Furthermore, there is a demand for complex and deep designs for the soles of shoes, which has created a need for materials with good mold flow properties.

However, foams using EVA have a practical problem of poor wet skid properties, although foams can be obtained with fairly good mold flow properties.

In addition, although the foam using 1.2-PBD has improved the wet skid property, which is a drawback of EVA foam, it is not sufficient, and it may be difficult to balance mold flowability and abrasion resistance. It has one drawback.

An object of the present invention is to provide a crosslinked foam of butadiene polymer rubber which has excellent wet skid properties and mold flow properties, good grass pillow resistance, and has a high expansion ratio.

According to the present invention, (A) 1.2 The alloy content is 70% or more and the crystallinity is 5.
and intrinsic viscosity [η] (measured in toluene at 30°C)
1,2-polybutadiene 30 with 0.5 dt79 or more
~90% by weight, (B) 5-60% by weight of a random styrene-butadiene copolymer rubber containing 3-30% by weight of bound styrene and 50-95% of 1,2 bonds in the butadiene moiety, and (C) Natural rubber. , a diene-based synthetic rubber (excluding the copolymer rubber of (B) above), and a mixture consisting of O to 50% by weight of at least one selected from the group consisting of a block copolymer of an aromatic vinyl compound and a conjugated diene compound. A crosslinked foam of a sitadiene polymer is provided by crosslinking and foaming the same in the presence of a blowing agent.

In order to obtain a foam with a uniform cell structure, the 1.2-PBD component used in the present invention has a 1.2 bond content of 70%.
% or more, preferably 85% or more, crystallinity is 5% or more,
Preferably it is 1-0 to 40% 1.2-PBD. Although the molecular weight can be selected over a wide range, in order to obtain a uniform and fine foam, the above [η] must be 0.5.
It is necessary that it is 61777 or more, and more preferably 1 to 3 dL/I.

In addition, the random styrene-butadiene copolymer rubber of component (B) is, for example,
Further preferred for the purposes of the present invention are randomized A styrene-butadiene copolymer comb having a high degree of styrene-butadiene copolymer is prepared by combining styrene and butadiene monomers described in JP-A-52-101287 in a hydrocarbon solvent with ether or tertiary amine and -So, H group or -0805M group (M is Na,
It is obtained by polymerization using an organolithium compound as an initiator in the presence of an anionic surfactant having K). The copolymer rubber contains 3 to 30% by weight of bound styrene, preferably 5% by weight, from the viewpoint of wet skid properties and abrasion resistance.
~20% by weight, and the 1.2 bonds of the butadiene moiety are 50
~95% preferably 70-95% random styrene-
Butadiene copolymer rubbers include those with a branched or linear structure. Mooney viscosity can be selected from a wide range, but Mooney viscosity (ML, +4
100°C) 20 to 150 is preferable.Additional components (O is diene, system cured rubber (excluding the rubber of the above component (B)) include, for example, cis-4-liiso!lene rubber (
IR), / ribtadiengo A (BR), styrene-butadiene copolymer rubber (SBR) other than (B), high styrene rubber, acrylonitrile-butadiene copolymer rubber (
NBR), chloroprene rubber (CR), etc. Of these, natural rubber and cis4lyiso! are preferred. Rubber rubber, polybutadiene rubber, etc.

Ingredients (B) and ((5) are expressed in weight% (A)
43)/(c)=30-9015-6010-50, preferably 30-9015-6015-50, more preferably 40-80/20-5015-30.

When the amount of particles is less than 30 points, it is difficult to obtain a foam with a high expansion ratio, and the shrinkage becomes large. If the amount of component (B) is less than 5 layers, wet skid characteristics will not be improved.

If the weight of the component (Q) exceeds 50% by weight, it is difficult to obtain a foam with a high expansion ratio.

The crosslinking agent (referred to as component (D)) used in the present invention is not particularly limited, and includes sulfur, thiazoles such as dipenzothiazole disulfide, thiurams such as tetramethylthiuram monosulfide, and 2-mercaptoimisadrine. There are imidazoles such as , dithiocarbamates such as zinc dimethyl dithiocarbamate, guaenones such as diphenylguanidine, xanthates such as butyl xanthic disulfide, and organic peroxides such as dicumyl peroxide. Among these, combinations of sulfur and thiazoles such as dipenzothiazole disulfide, thiurams such as tetramethylthiuram monosulfide, or organic peroxides such as dicumyl peroxide are preferred.

In addition, there are no particular restrictions on the blowing agent (component), but
Sodium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, azodicarbonamide (ADC
A), dinitrosopentamethylenetetramine (DPT
), dinitrosoterephthalamide, azobisisobutyronitrile, azodical? Examples include barium phosphate, sulfonyl hydrazide, and the like. These foaming agents may be used in combination with known foaming aids such as urea and urea derivatives.

The amounts of the crosslinking agent and blowing agent used are not particularly limited, but can be determined as appropriate within the range commonly used in the fields of rubber, EVA, and the like.

In addition to the above-mentioned ingredients (6), the foam composition of the present invention also contains other compounding agents that are included in general rubber compositions, such as reinforcing agents, fillers, anti-aging agents, processing aids, and softening agents. , pigments, etc. may be added as appropriate.

There is no particular restriction on the method of mixing the above-mentioned rubber (g) and other compounding agents, and any mixing method used for general rubber compounds such as a nogunpari mixer, pressure kneader, or open roll may be used. Preferably, mixing is carried out at a temperature in the range of 70-140°C. The mixture thus obtained is fed into a tube mold,
130~iso℃ under pressure, preferably 140~170℃
C. and above the decomposition temperature of the blowing agent to effect crosslinking of the formulation and decomposition of the blowing agent.

The clamping pressure of the mold is required to substantially suppress the expansion of gas generated by decomposition of the blowing agent, and is usually 80 kg/kg/mold.
It is carried out under pressure of cm2 or more.

Next, the present invention will be specifically explained by showing Examples and Comparative Examples. In Examples and Comparative Examples, hardness (Is) ij rubber tester type C (manufactured by Kobunshi Keiki, Singi hardness tester)
The specific gravity was measured by the buoyancy method. Abrasion resistance is B5
The wet skid characteristics were measured by Akron abrasion according to 903, and the wet skid characteristics were evaluated on a five-point scale based on the feeling of slippage when running on a wet tile road surface while wearing jigging shoes.

Regarding mold flowability, the details of the evaluation method are attached to the table, but
When a certain pressure is applied to rubber using a specific mold,
The evaluation was based on the distance of the rubber flowing into the mold.

Example-1 1,2-PBD (manufactured by Nippon Gosei Com Co., Ltd., JSRRB8
20゜1.2 Metal content 92%, crystallinity 25%, [η
[k17 = 1.25), random styrene-butadiene copolymer rubber 5DR-1 (5% by weight of bound styrene, 1
．． 2-bond metal content 86chi, Mooney viscosity ML, +41oo
℃=60), polyisozolene rubber (Japan Synthetic Rubber Co., Ltd.)
Co., Ltd., JSRlR2200) and other compounding agents were mixed in a pressure kneader at the proportions shown in the table, and heated at 160°C for 12 hours.
A foam was obtained by vulcanization for a minute. The physical property results are shown in the table.

Note that 1.2 The bond content was calculated using infrared absorption spectroscopy by Moreguchi et al.
8 (1959)). Further, the degree of crystallinity was determined by density measurement using a density gradient tube.

Example-2 Random styrene-butadiene copolymer rubber 5BR-2 (
20% by weight of bound styrene, 1.2% bound metal content, 62mm, Mooney viscosity m, +41°C = = 74).
Otherwise, a foam was obtained in the same manner as in Example-1. The physical property results are shown in the table @ Example-3 1,2-PBD (manufactured by Japan Synthetic Rubber Co., Ltd., JSRRB8
30゜1.2 The alloy content is 93%, the crystallinity is 29%, toluene [η3 = 1.25) and other additives are shown in the table.
A foam was obtained in the same manner as in Example-1 using C at a blending ratio of 1. The physical property results are shown in the table.

Comparative Example-1 Polybutadiene rubber with 1,2 bond J content of 5% or less and crystallinity of O (manufactured by Japan Synthetic Rubber Co., Ltd., JSRBROI)
A foam was obtained in the same manner as in Example-1, except that 1.2 PBD was used in Example-1. This foam had a higher specific gravity than Example 1, had poor foamability, and was poor in mold flowability.

Comparative Example 2 Foaming was carried out in the same manner as in Example 1, except that a styrene-butadiene copolymer rubber having 20% 1,2 bond content and 23.5% bonded styrene, which was beyond the scope of the present invention, was used. I got a body.

This foam has poor wet skid properties and abrasion resistance compared to Example-1.

Comparative Example-3 EVA (East 1-f: manufactured by Rodatsu Kogyo Co., Ltd., Ultracene 190°C UE631, vinyl acetate content 20%, M, I = 1.
52160, Fr Ir/10 minutes) and other compounding agents at the compounding ratio shown in the table were mixed using a pressurized knee gun and vulcanized at 160° C. for 20 minutes to obtain a foam. This foam has extremely poor wet skid properties compared to Example-1.

Water 6) As shown in the attached drawing, a rubber compound with the composition shown in the table above excluding the foaming agent was placed in part A of the mold and heated at 160°C using a hydraulic press at a pressure of 80 kg7cm2G.
When we add , the com becomes B-B'? It flows through a long, narrow channel and stops at a certain point.

The flow distance i1g+i at this time is determined in 6111, and the quality of the mold flow and flow is completely judged.

◎Best, ○Good, X Poor

[Brief explanation of the drawing]

The drawing is a plan view of the mold for planning the mold flow and flow resistance, and the mold thickness is 2 mm, the side length J is 90 mm, and the width of the channel (B-B'
) 8, and A is the injection part of the comb.

Claims (1)

[Claims] 1,2 bond content is 70 or more, crystallinity is 5 or more, and intrinsic viscosity [η] (measured in toluene at 30°C) is 0.
．． 5 di/l! The above 1,2-polybutadiene 30~
90% by weight, (B) 5 to 60% by weight of a random styrene-butadiene copolymer rubber with 3 to 30% by weight of bound styrene and 50 to 95% of 1,2 bonds in the butadiene moiety; and (C) natural rubber; At least one type O selected from diene-based synthetic rubber (excluding the copolymer rubber of (B) above) and a block copolymer of an aromatic vinyl compound and a conjugated diene compound
A crosslinked foam of a butadiene polymer obtained by crosslinking and foaming a 50% by weight mixture in the presence of a blowing agent.