JPH0482013B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a foam obtained by hot air crosslinking, which has a large expansion ratio, is lightweight, and has good cushioning properties and
Expected to have excellent breathability, sound insulation, etc.1.
2-polybutadiene (hereinafter abbreviated as 1,2-PBO)
system and ethylene vinyl acetate copolymer (hereinafter referred to as
(abbreviated as EVA) system cross-linked foam. [Prior art] Crosslinked foams include natural rubber, synthetic rubber,
Foams using 1,2-PBD, ethylene-vinyl acetate copolymer (EVA), and the like are known. However, most of these are manufactured by a method in which the raw material compound is 100% filled in a mold, the blowing agent is decomposed and crosslinked, and then the foam is foamed outside the mold. The manufacture of foams by hot air crosslinking without the use of molds has been attempted to a small extent with natural and synthetic rubbers. However, the natural rubber and synthetic rubber foams obtained by this crosslinking method have low expansion ratios and are currently unsatisfactory in terms of cushioning properties and breathability. [Problems to be Solved by the Invention] An object of the present invention is to use a specific 1,2-PBD having thermoplasticity as a foam raw material by hot air crosslinking.
By selecting EVA and EVA, the present invention aims to provide a crosslinked foam that can be expected to have a high expansion ratio, be lightweight, and have excellent cushioning properties and breathability. [Means for solving the problems] The present invention provides: (A) a vinyl bond content of 70% or more and a crystallinity of 5%;
and intrinsic viscosity [η] (30℃ in toluene)
(B) 1 selected from natural rubber, diene synthetic rubber, and non-diene synthetic rubber; Seed and above raw rubber 0-80
(C) 0 to 300 parts by weight of a rubber softener (D) 0 to 600 parts by weight of an inorganic filler (E) Foaming agent 3 The present invention provides a crosslinked foam obtained by crosslinking and foaming a composition containing ~30 parts by weight and (F) sulfur or an organic peroxide in hot air. The 1,2-PBD of component (A) used in the present invention is:
In order to obtain appropriate hardness and cushioning properties,
The 1,2 bond content is 70% or more, preferably 85% or more, and the crystallinity is 5% or more, preferably 10 to 40%. Although the molecular weight can be selected over a wide range, in order to obtain a foam with a high magnification, which is the objective of the present invention, [η] (toluene, 30°C) should be 0.5.
It is necessary that it is dl/g or more. The amount of 1,2-PBD (A) in the above [(A) + (B)] component is 20 to 100% by weight, preferably 40 to 100% by weight, and if it is less than 20% by weight, the magnification is high. It is difficult to obtain a foam. Also, it is also used for component (A).
EVA preferably has a vinyl acetate content of 10% or more to obtain appropriate hardness and cushioning properties.
It is 15-30%. Although the molecular weight can be selected over a wide range, in order to obtain a foam with a high magnification, which is the objective of the present invention, the melt index (JISK6760-
1966, unit: g/min) must be 0.5 or more. The amount of EVA (A) in the above [(A) + (B)] component is 20 to 100
The amount is preferably 40 to 100% by weight, and if it is less than 20% by weight, it is difficult to obtain a foam with a high magnification. As component (A), 1,2-PBD is more desirable than EVA in terms of crosslinking efficiency. In the present invention, component (B) of natural rubber, diene synthetic rubber, and non-diene rubber is in the range of 0 to 80% by weight, preferably 0 to 60% by weight, mainly for adjusting the elasticity and crosslinking rate of the foam. used. Typical examples include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), acrylonitrile rubber (NBR), and chloroprene rubber (CR).
Diene rubber such as ethylene-propylene rubber (EPM), ethylene-propylene terpolymer (EPDM), acrylic rubber (ACM, ANM),
Examples include non-diene rubbers such as fluorocarbon rubber.
Among these, preferred are NR and IR. The rubber softener (C) used in the present invention includes process oils (aromatic, naphthenic, paraffinic), lubricating oils, paraffin, liquid paraffin,
Petroleum based softeners such as petroleum asphalt and petrolatum; Coal tar based softeners such as coal tar and coal tar pitch; Fatty oil based softeners such as castor oil, linseed oil, rapeseed oil and coconut oil; Tall oil;
Examples include waxes such as beeswax, carnauba wax, and lanolin; fatty acids and fatty acid salts such as ricinoleic acid, palmitic acid, barium stearate, calcium stearate, and zinc laurate; and synthetic polymeric substances such as petroleum resins. The process oil is a mineral oil-based rubber softener generally called process oil or extender oil, and is a mixture of aromatic rings, naphthenic rings, and paraffin chains.
Those in which the number of carbon atoms in the paraffin ring accounts for 50% or more of the total carbon are called paraffin type, those in which the number of carbon atoms in the naphthene ring is 30 to 45% are called naphthenic, and those in which the number of aromatic carbon atoms is more than 30% are called paraffin type. It is considered aromatic. The mineral oil-based rubber softener used as component (C) of the present invention is preferably a naphthenic or aromatic one in the above category from the viewpoint of compatibility with component (A). The blending amount of component (C) softener is component [(A) + (B)] 100
0 to 300 parts by weight, preferably 50 to 300 parts by weight
It is 150 parts by weight. If the amount is 300 parts by weight or more, the softener tends to bleed and kneading becomes difficult. Examples of inorganic fillers for component (D) used in the present invention include light calcium carbonate, heavy calcium carbonate, various surface-treated calcium carbonates, as well as talc, magnesium hydroxide, mica, clay, barium sulfate, and natural silica. Acid, synthetic silicic acid (white carbon), titanium oxide, various carbon blacks, etc. can be used. Among these inorganic fillers, heavy calcium carbonate is preferable because it is economically advantageous. The blending amount of the inorganic filler is 0 to 600 parts by weight, preferably up to 400 parts by weight, based on 100 parts by weight of components [(A)+(B)]. When the amount exceeds 600 parts by weight, it is difficult to obtain high foamability, and the mechanical strength of the resulting foam is significantly reduced. As the blowing agent (E) used in the present invention, known inorganic or organic blowing agents can be used. It is also possible to use them together. Specific examples of blowing agents include sodium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DNPT), dinitrosoterephthalamide, azobisisobutyronitrile, azo barium dicarboxylate, sulfonyl hydrazide,
Examples include toluenesulfonyl hydrazide. These foaming agents may be used in combination with known foaming aids such as urea and urea derivatives. The amount of blowing agent used is 3 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of components [(A) + (B)].
Parts by weight. If the blowing agent is less than 3 parts by weight, only a foam with a low expansion ratio will be obtained, and if it is more than 30 parts by weight, a large amount of gas will be generated due to the decomposition of the blowing agent, making it difficult to obtain a foam with a good appearance. do not have. In addition to the components (A) to (E) described above, a crosslinking agent is added to the foam-forming composition of the present invention to cause crosslinking and foaming. Also,
Crosslinking foaming using energy such as electron beams and ultraviolet rays is also possible. Crosslinking agents include sulfur and various organic peroxides. Specific examples of organic peroxides include dicumyl peroxide,
1,1-bis(t-butylperoxy)3,3,
5-trimethylcyclohexane, t-butylperoxybenzoate, 2,5-dimethyl 2,5-
Bis(t-butylperoxy)hexane, t-butylperoxyisopropyl carbonate, and the like. In the case of sulfur vulcanization, various vulcanization accelerators are added at the same time to cause crosslinking and foaming. Specific examples of vulcanization accelerators include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and N-oxyzoethylene-2- These include benzothiadylsulfenamide (DBS), tetramethylthiuram disulfide (TMTD), and tetramethylthiuram monosulfide (TMTM). Note that from the viewpoint of crosslinking efficiency, sulfur vulcanization is more desirable than organic peroxide crosslinking. Further, in addition to the above-mentioned additives, crosslinking aids, anti-aging agents, processing aids, adhesives, plasticizers, etc. may be added as appropriate. There are no particular restrictions on the method of mixing the above (A) to (E) and other compounding agents, and mixing methods used for general rubber compounds such as a Banbury mixer, pressure kneader, open roll, etc. can be used. be. The uncrosslinked mixture thus obtained is molded, for example, into a sheet shape, if necessary, and then subjected to crosslinking and foaming in hot air. Crosslinking and foaming is performed in hot air at a temperature in the range of 130 to 180°C, preferably 140 to 170°C, and heated to a temperature above the decomposition temperature of the blowing agent to crosslink the compound and decompose the blowing agent. At this time, there is no particular need to apply pressure, and crosslinking and foaming can be carried out under atmospheric pressure. This crosslinking and foaming operation can be performed batchwise or continuously. The crosslinked foam according to the present invention can be expected to have a high expansion ratio, be lightweight, and have excellent cushioning properties, air permeability, etc. despite hot air crosslinking under atmospheric pressure. The crosslinked foam of the present invention can be widely used in footwear materials, industrial products, cushioning materials, sealing materials, etc. Next, the present invention will be specifically explained by showing Examples and Comparative Examples. In the Examples and Comparative Examples, tensile strength and elongation were measured according to JIS K-6301, hardness was measured using a rubber tester type C (Kobunshi Keiki sponge hardness tester), specific gravity was measured using the buoyancy method, and foaming ratio was measured using a rubber tester type C (Kobunshi Keiki sponge hardness tester). was calculated from the thickness ratio of the sample before and after foaming. Examples 1-2 1,2-PBD (Japan Synthetic Rubber Co., Ltd., JSR RB820,
Vinyl bond content 92%, crystallinity 25%, [η] toluene (30°C = 1.25) and other ingredients were mixed in a BR type Banbury mixer at the proportions shown in Table 1, and then placed in hot air at 160°C for 20 minutes. A foam was obtained by cross-linking and foaming. The physical property test results are shown in Table 1. Example 3 Other than changing the type of 1,2-PBD (Japan Synthetic Rubber Co., Ltd., JSR RB810, vinyl bond content 92%,
A foam was obtained in the same manner as in Example 1, crystallinity 18%, [η] toluene 30°C = 1.25). The physical property test results are shown in Table 1. Example 4 Using 80 parts by weight of 1,2-PBD (JSR RB820) and 20 parts by weight of natural rubber, the amounts of heavy calcium carbonate, naphthenic oil, vulcanization accelerator, and blowing agent were changed as shown in Table 2. Other than that, a foam was obtained in the same manner as in Example 1. The physical property test results are shown in Table 2. Example 5 Using 80 parts by weight of 1,2-PBD (JSR RB820) and 20 parts by weight of styrene-butadiene rubber (JSR SBR1507), the amounts of heavy calcium carbonate, naphthenic oil, vulcanization accelerator, and blowing agent were adjusted. A foam was obtained in the same manner as in Example 1 except for the changes shown in Table 2. The physical property test results are shown in Table 2. Example 6 The blowing agent was a combination of an organic blowing agent and an inorganic blowing agent,
A foam was obtained in the same manner as in Example 1, except that the amounts of heavy calcium carbonate, naphthenic oil, and vulcanization accelerator were changed as shown in Table 2. The physical property test results are shown in Table 2. Comparative Example 1 The polymer used was 100 parts by weight of natural rubber,
A foam was obtained in the same manner as in Example 1, except that the amounts of the vulcanization accelerator and sulfur added were changed as shown in Table 1. The physical property test results are shown in Table 1. Comparative Example 2 The polymer used was styrene-butadiene rubber.
A foam was obtained in the same manner as in Example 1, except that the amount of the vulcanization accelerator was changed as shown in Table 1. The physical property test results are shown in Table 1. Comparative Example 3 The polymer composition was changed to natural rubber beyond the scope of the present invention.
A foam was obtained in the same manner as in Example 4, except that 85 parts by weight and 15 parts by weight of 1,2-PBD (JSR RB820) were used, and the amounts of the vulcanization accelerator and sulfur were changed as shown in Table 2. Ta. The physical property test results are shown in Table 2. Comparative Example 4 The polymer composition was changed beyond the scope of the present invention to 85 parts by weight of styrene-butadiene rubber, 1,2-PBD (JSR
A foam was obtained in the same manner as in Example 4, except that 15 parts by weight of RB820) was used and the vulcanization accelerator was changed as shown in Table 2. The physical property test results are shown in Table 2. From Tables 1 and 2, it can be seen that the compositions of Examples 1 to 6 according to the present invention have larger expansion ratios and are lighter in weight than Comparative Examples 1 to 4, which are outside the scope of the present invention. [Effects of the Invention] The crosslinked foam composition of the present invention contains 1,2-polybutadiene whose vinyl bond content, degree of crystallinity, and intrinsic viscosity are within specific ranges, and whose vinyl acetate content and melt index are within specific ranges. An EVA
By blending with other specific types of rubber in a specific range of ratios and cross-linking and foaming in hot air,
It has the following excellent performance that has not been available before. In other words, it has a high foaming ratio and is lightweight.
It is expected to have good cushioning properties and breathability, and can be suitably used for footwear materials, industrial products, cushioning materials, sealing materials, etc.

【table】

[Table] *2 Urea compound Manufactured by Eiwa Kasei Co., Ltd.

【table】

[Table] *1 Inorganic blowing agent manufactured by Eiwa Kasei Co., Ltd. Example 7 The following components were mixed in a BR type Banbury mixer and cross-linked and foamed in hot air at 160°C for 20 minutes to obtain a foam. . Physical properties were measured in the same manner as in Example 1. Ethylene-vinyl acetate copolymer 100 parts by weight Polyethylene glycol 3 SRF carbon black 3 Heavy carbon 250 Naphthene oil 80 Perhexa 3M (organic peroxide) 3 Azodicarbonamide blowing agent 8 Urea compound blowing aid 8 Total 455 ( Results) Expansion ratio: 4.5 times Specific gravity: 0.36 Tensile strength: 0.7 Kg/ ^cm2 Elongation: 70% Hardness: 30 Example 8 The following components were mixed using a BR type Banbury mixer, and crosslinked and foamed in hot air at 160°C for 20 minutes. A foam was obtained. Physical properties were measured in the same manner as in Example 1. 1,2-Polybutadiene (RB820) 50 parts by weight Natural rubber (RSS #3) 50 Silica filler (ZnO #3) 5 Stearic acid 3 SRF carbon black 3 Heavy carbon 250 Naphthene oil 80 Perhexa 3M 2 Azodicarbonamide foaming Agent 8 Urea compound foaming aid 8 Total 459 (Result) Expansion ratio 4 times Specific gravity 0.4 Tensile strength 0.9Kg/ ^cm2 Elongation 40% Hardness 22 Comparative example 5 The following components were mixed using a BR type Banbury mixer. After irradiating for 20 minutes from a distance of 40 cm using a 1KW high-pressure mercury lamp, the foam was heated at 160°C for 20 minutes to obtain a foam. Physical properties were measured in the same manner as in Example 1. 1,2-Polybutadiene (RB810) 100 parts by weight Silica filler (ZnO#3) 50 Paraffin oil 10 Azodicarbonamide blowing agent 8 Urea compound blowing aid 8 Total 176 (Result) Expansion ratio 3 times specific gravity 0.3 Tensile strength: 0.2 Kg/cm ² Elongation: 40% Hardness: 15 Test Examples The air permeability of the crosslinked foams obtained in Examples 1 to 8 and Comparative Examples 1 to 5 was measured by the following method. i.e. each 1.0 cm thick cross-linked foam with a diameter of 5.5
It was cut into a circular shape of 5 cm in diameter and packed in the center of a 5 cm diameter tube. After sealing the area where the crosslinked foam and the tube came into contact with paraffin wax, soapy water was applied to one side of the crosslinked foam. Next, apply a gauge pressure of 0.05 from the non-soaped side of the cross-linked foam.
Kg/cm ² of compressed air was introduced, and air permeability was evaluated based on the foaming state of soapy water. As a result, the crosslinked foams obtained in Examples 1 to 8 had extremely good air permeability, but Comparative Examples 1 to 5
The air permeability of the crosslinked foams obtained was poor. This is because in Comparative Examples 1 to 4, the foaming ratio was not sufficient because the polymer composition was outside the range of the present invention, and in Comparative Example 5, the crosslinking method was by ultraviolet rays, so the cells in the foam became closed cells. This is because there is.

Claims (1)

[Claims] 1 (A) Vinyl bond content is 70% or more, crystallinity is 5
% or more and intrinsic viscosity [η] (30℃ in toluene)
(B) 20 to 100% by weight of at least one selected from 1,2-polybutadiene and ethylene-vinyl acetate copolymer having a concentration of 0.5 dl/g or more; and (B) 1 selected from natural rubber, diene-based synthetic rubber, and non-diene-based synthetic rubber. For 100 parts by weight of a mixture [(A) + (B)] consisting of 0 to 80% by weight of raw rubber of 0 to 80% by weight, (C) 0 to 80% by weight of rubber softener (C)
A composition containing 300 parts by weight, (D) 0 to 600 parts by weight of an inorganic filler, (E) 3 to 30 parts by weight of a blowing agent, and (F) sulfur or organic peroxide is crosslinked and foamed in hot air. A cross-linked foam characterized by: