JPH0449860B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a crosslinked foam having a high expansion ratio and excellent hardness, tear strength, impact resistance, and elasticity. [Prior art] Crosslinked foams using 1,2 polybutadiene (1,2-PED), ethylene-vinyl acetate copolymer (EVA), natural rubber, synthetic rubber, etc. are known as crosslinked foams with rubber elasticity. It is being Among these, it is difficult to obtain a high expansion ratio with crosslinked foams using natural rubber and synthetic rubber, and dimensional accuracy is poor due to large shrinkage after crosslinking. Furthermore, it has a drawback in mold flowability. On the other hand, foams using 1,2-PED and EVA are generally known to be able to obtain foams with a high expansion ratio without shrinkage problems with only one step of crosslinking, such as the midsole of sports shoes,
It is widely used in applications that require weight reduction, such as outer soles and inner soles. [Problems with the conventional technology] However, in order to reduce weight, it is essential to increase the foaming ratio to 3 times or more, but on the other hand, the mechanical strength such as hardness, tear strength, and tensile strength of the resulting foam decreases. do. In addition, in recent years there has been an increasing trend toward weight reduction, and the demand for high foaming with a foaming ratio of 5 times or more is increasing. However, the physical properties of a foam with an expansion ratio of 5 times or more are lower than those of a foam with an expansion ratio of 3 times or more. However, the hardness, tear strength, and impact resistance of foam, along with adhesive strength, are particularly important properties for the sole material of sports shoes. When using shoes, please note that abnormal phenomena such as settling (deformation) may occur, and if foam with low tear strength is used as a sole material, breakage such as cracking may occur during use, reducing the durability of the shoe. This becomes a big problem and reduces the value of the product. [Purpose of the Invention] As a result of various studies to solve the above problems, the inventors found that by blending specific thermoplastic resins and elastomers, a material with high rubber elasticity and extremely light weight ( specific gravity 0.2 or less),
It was discovered that a foam having excellent hardness, impact resistance, and tear strength can be obtained, and based on this knowledge, the present invention was completed. [Structure of the Invention] This invention provides: (A) 1,2 bond content of 70% or more and crystallinity of 5%;
Intrinsic viscosity [η] (measured at 30℃ in toluene)
1,2-polybutadiene with a content of 0.5 dl/g or more30
~95% by weight, (B) 5 to 50% by weight of at least one selected from natural rubber, diene synthetic rubber, and non-diene rubber; and (C) polyethylene polymer, ethylene-vinyl acetate copolymer resin, polystyrene. based resin, ionomer resin, polybutene-1, polyester elastomer, polyurethane elastomer,
The present invention relates to a crosslinked foam obtained by crosslinking and foaming a mixture containing 1 to 19% by weight of at least one selected from polypropylene polymers in the presence of a blowing agent. The present invention will be explained in detail below. The 1,2 PED of component (A) used in the invention has a 1,2 bond content of 70% or more, preferably 85% or more, and a crystallinity of 5% or more in order to obtain a foam with a uniform cell structure. , preferably 10-40%. Although the molecular weight can be selected over a wide range, [η] (toluene at 30°C) must be
It is necessary that it is 0.5 dl/g or more. 1.0 more
A 1.2-PBD of ~3.0 is more preferred. The amount of 1,2 PBD is 30-95% by weight, preferably 50
-90% by weight, and if it is less than 30% by weight, it will be difficult to obtain a foam with a high expansion ratio, and the shrinkage will also increase. On the other hand, if it exceeds 95% by weight, (B) of other ingredients,
The amount of (C) used becomes small, and a foam with excellent hardness and tear strength, which is the object of the present invention, cannot be obtained. In the present invention, the component (B) of natural rubber, diene synthetic rubber, and non-diene rubber is 5 to 50% by weight, preferably 5% by weight.
It is used in the range of ~30% by weight and is used to adjust the elasticity of the foam. Typical examples include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, acrylonitrile rubber, diene rubber such as chloroprene rubber, ethylene-propylene rubber, ethylene-propylene-nonconjugated diene rubber, acrylic rubber, Examples include non-diene rubbers such as fluorocarbon rubber. Among these, diene rubber is preferred, and natural rubber and polyisoprene rubber are more preferred.
By blending these rubber components, the elasticity of the foam can be adjusted and it also provides resistance to cracking and peeling. If the amount of rubber used is less than 5% by weight, the elasticity will be impaired and the foam will be prone to cracking and poor peeling. If it exceeds 50% by weight, a foam with a high expansion ratio and low shrinkage cannot be obtained by only one-stage vulcanization. In addition, component (C) is low density polyethylene (density
0.9~0.929, abbreviated as LDPE), medium density polyethylene (density 0.93~0.941, abbreviated as MDPE), high density polyethylene (density 0.942~0.980, abbreviated as HDPE),
Linear low density polyethylene (density 0.915 to 0.945, L-
(abbreviated as LDPE), polyethylene polymers such as
Polystyrene resins (hereinafter abbreviated as PS) such as ethylene-vinyl acetate copolymer (preferably vinyl acetate content 5-50% by weight, abbreviated as EVA), polystyrene, styrene-MMA copolymer, styrene-acrylonitrile copolymer, etc. ), ionomer resin (hereinafter abbreviated as ION), polybutene-1 (hereinafter abbreviated as PE-1), polyester elastomer (hereinafter abbreviated as PES)
), polyurethane elastomer (hereinafter referred to as PU
Polypropylene polymers (hereinafter abbreviated as PP) such as polypropylene, polypropylene, and modified polypropylene are thermoplastic resins or thermoplastic elastomers that are available on the market and have excellent physical properties at room temperature even without crosslinking. It is a polymer that exhibits plastic fluidity when processed at high temperatures. Examples of polyethylene include the following. Produced by high pressure polymerization method with density 0.9~0.929
LDPE, MDPE with a density of 0.93 to 0.941 or density 0.942 produced by medium-low pressure polymerization using a catalyst
Examples include HDPE having a density of 0.980 to 0.980, and low-density α-olefin-ethylene copolymer (L-LDPE) having a density of 0.915 to 0.945 produced by medium-low pressure polymerization using a combination of α-olefin and ethylene (L-LDPE). The ethylene-vinyl acetate copolymer resin preferably has a vinyl acetate content of 5 to 50% by weight. Polystyrene resin is a thermoplastic resin whose main component is an aromatic vinyl compound, such as polystyrene, high impact polystyrene, and ABS resin.
Examples include AS resin and styrene-MMA copolymer. Ionomer resin (ION) is an ionic copolymer with ionic cross-bonds.
For example, it is a copolymer of α-olefin such as ethylene or propylene and acrylic acid, methacrylic acid, maleic acid, etc., which is neutralized with a metal compound. Polybutene-1 is a polymer containing butene-1 as a main component, and is a crystalline thermoplastic polymer having high molecular weight and isotacticity obtained by regular polymerization at low pressure, for example. Polyester elastomer is an elastomer that has a hard segment made of polyester and a soft segment made of polyether. In the hard segment

[Examples 1 to 3]

1,2PED (manufactured by Japan Synthetic Rubber Co., Ltd., JSR RB830 vinyl bond content 92%, crystallinity 28%, [η] toluene 30℃ 1.25), polyisoprene (manufactured by Japan Synthetic Rubber Co., Ltd.,
JSR IR2200), LDPE (LS-30 manufactured by Mitsubishi Yuka Co., Ltd.) and other compounding agents were mixed in a pressure kneader at the proportions shown in the table, and vulcanized at 155°C for 22 minutes to obtain a foam. The results are shown in the table. [Examples 4 to 13] MDPE (Mitsubishi Yuka Co., Ltd. MS-
70), HDPE (Mitsubishi Yuka Co., Ltd. JX-10), L-LDPE
(Mitsui Petrochemical Industries, Ltd. 30100J), EVA (Mitsubishi Petrochemical Industries, Ltd.)
(EVA10S manufactured by Mitsubishi Plastics Co., Ltd.), PS (HF-55 manufactured by Mitsubishi Plastics Co., Ltd.),
ION (Himilan 1605 manufactured by Mitsui Polychemical Co., Ltd.),
PB-1 (manufactured by Adeka Argus Chemical Co., Ltd.)
WITRON6400), (PES (P-70B manufactured by Toyobo Co., Ltd.),
Other than changing the PU (E290FOND manufactured by Nippon Elastolan Co., Ltd.) and PP (BC-3 manufactured by Mitsubishi Yuka Co., Ltd.) as shown in the table,
Foams were obtained in the same manner as in [Examples 1 to 3]. The physical property results are shown in the table. It is clear from the results of Examples 1 to 13 that foams with a high expansion ratio and excellent hardness, tear strength, and impact resistance (settling) can be obtained in comparison with comparative examples. [Comparative Examples 1 to 5] Comparative Examples 1 and 5 are systems that do not contain the component (C) specified in the present invention, and are not preferable because they have defects in hardness and impact resistance (sagging). Comparative Example 2 is an ethylene-propylene rubber (made by Japan Synthetic Rubber Co., Ltd.) that is outside the range as component (C) specified in the present invention.
This is a system using JSR EP21), which is not desirable as it has defects in hardness and impact resistance (sagging). Comparative Example 3 is an example in which EVA, a commonly used foam material, was used instead of 1,2PBD, but this system had a defect in impact resistance (sagging) compared to the foam of the present invention. Not desirable. Comparative Example 4 is a system in which the amount of component (C) is outside the range measured in the present invention and has defects in tear strength and impact resistance (sagging) and is not preferable. From the above, Comparative Examples 1 to 5 are inferior to Examples 1 to 13 in any of the expansion ratio, hardness, tear strength, and impact resistance (sagging), and do not satisfy the requirements of the present invention. [Effects of the Invention] As shown in the Examples and Comparative Examples above, the crosslinked foam of the present invention has a high expansion ratio that could not be obtained with conventional foams, has moderate hardness, and has high tear strength and cyclic resistance. Since it has excellent stress resistance, it is suitable for use in footwear materials (outer soles, inner soles, midsoles, etc.), industrial products, cushioning materials, packaging materials, sealing materials, etc. by taking advantage of this excellent property. In addition, the crosslinked foam of the present invention has excellent dimensional accuracy,
It also has excellent durability, cushioning properties, and fluidity, so it can be suitably used in thermoformed sponges.

【table】

[Table] [Comparative Example 6] In Example 2, as 1,2-polybutadiene, 1,2 bond content was 92%, crystallinity was 0%, [η]
A crosslinked foam was obtained in the same manner as in Example 2 except that 30°C (toluene) = 1.25 was used. Its physical properties are shown in the table below. [Comparative Example 7] A crosslinked foam was produced in the same manner as in Example 2, except that polyisoprene, which is the component (B), was not used in Example 2, and 30 parts by weight of polyethylene, which was the component (C), was used instead. I got it. Its physical properties are shown in the table below.

【table】

【table】

Claims (1)

[Claims] 1(A) 1,2 bond content of 70% or more, crystallinity of 5
30 to 95% by weight of 1,2-polybutadiene with an intrinsic viscosity [η] (measured in toluene at 30°C) of 0.5 dl/g or more (B) Selected from natural rubber, diene-based synthetic rubber, and non-diene-based rubber and (C) polyethylene polymer, ethylene-vinyl acetate copolymer resin, polystyrene resin, ionomer resin, polybutene-1, polyester elastomer, polyurethane elastomer,
A crosslinked foam obtained by crosslinking and foaming a mixture consisting of 1 to 19% by weight of at least one selected from polypropylene polymers in the presence of a blowing agent.