JPH0395238A - Foam - Google Patents

Abstract

PURPOSE:To obtain a thermally expansive foam rubber advantageous in both storage and transportation cost and excellent in workability by compressing a vulcanized foam rubber containing a thermoplastic resin at a specified temperature and then cooling it. CONSTITUTION:A foam obtained by compressing a vulcanized foam rubber containing a thermoplastic resin at a temperature above the softening point of the thermoplastic resin and then cooling it. As the rubber, those generally used can be utilized; however, an ethylene/alpha-olefin rubber is particularly useful in the field of application where heat and weather resistances are required. The ethylene/alpha-olefin rubber to be used is an ethylene/alpha-olefin/nonconjugated diene rubber, preferably comprising a copolymer of ethylene and an alpha-olefin at a weight ratio of (90:1) to (40:60). As the alpha-olefin, propylene, butene-1, etc., may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a foam used for purposes such as cushioning, sealing, and heat insulation in the fields of automobiles, architecture, and industry.

BACKGROUND TECHNOLOGY Conventionally, vulcanized rubber foams have been molded into a shape according to their intended use, transported to a place of use, and then installed and used.

In other words, it is compressed and processed into a small volume during vulcanization and foaming,
There was no known technology for restoring it to its original shape during use.

Problems to be Solved by the Present Invention> Vulcanized rubber foam is bulky due to its low specific gravity and takes up a large amount of space during storage and transportation, making it disadvantageous compared to non-foam products in terms of storage and shipping costs. There was a need for improvement.

In addition, when applying sealants, etc., there are problems such as the volume of the foam is large relative to the space to be installed, making it difficult to install, and the adhesion and railing properties are not necessarily sufficient, and improvements have been desired.

<Means for Solving the Problems> As a result of research to solve the above-mentioned problems with vulcanized rubber foam, the present inventors found that it has a high specific gravity, a small capacity for storage, transportation, use,
This led to the development of a thermally expandable shape memory vulcanized rubber foam that can be returned to its original shape by heating during installation. That is, the present invention relates to a rubber foam that is advantageous in storage and transportation costs, has excellent workability, and has thermal expandability, and comprises the following invention.

(1) A thermally expandable rubber foam obtained by compressing a vulcanized rubber foam containing a thermoplastic resin at a temperature equal to or higher than the softening point of the thermoplastic resin and cooling.

(2) A thermally expandable rubber foam, wherein the vulcanized rubber foam is an ethylene-α-olefin vulcanized rubber foam containing a thermoplastic resin.

The rubber used in the present invention is not particularly limited, and commonly used rubbers can be used. For example, in addition to natural rubber, synthetic rubbers such as ethylene-4-olefin rubber, sterene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, and chlorobresci rubber, or a blend of two or more of these rubbers can be used. Among these, ethylene-α-olefin rubber is particularly useful in fields where heat resistance and weather resistance are required.

The ethylene-α-olefin rubber used in the present invention is an ethylene-α-olefin non-military diene rubber, preferably a copolymerization of ethylene and d-olefin in a weight ratio of 90:10 to 40:60. <As the s'-olefin, propylene, butene-1, etc. are used. Examples of non-conjugated dienes used include norbornenes, cyclic dienes, and aliphatic dienes, among which 5-ethylidene-2-norbornene, cyclopentadiene, and 1,4-hexadiene are representative.

The thermoplastic resin used in the present invention is blended into the foam to fix the shape after heating, pressure and cooling, and its type is not necessarily limited, but from practical drawings, Vicat softening Those with a temperature of 60 to 200°C are preferred, and include polyethylene-ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate copolymers, various ethylene copolymers, polypropylene, propylene-α-olefins. Examples include copolymers, styrene-butadiene block copolymers, and the like.

The blending amount of the thermoplastic resin is 5 to 100 parts by weight per 100 parts by weight of ethylene (1-olefin rubber,
Particularly preferred is 0-50 parts by weight.

If the amount of thermoplastic resin blended is less than this, the shape fixing performance during heating, compression, and cooling will be poor, and if it is greater than this, problems such as poor moldability during heating and foaming will occur.

A blowing agent is used to produce the vulcanized rubber foam used in the present invention. As a blowing agent, dinitropentamethylene tetrasulfur, azodicarbonamide, P, P
Oxybisbenzenesulfonyl hydrazide and the like are used, and if necessary, a foaming aid such as urea can also be used in combination.

In the present invention, in addition to the ethylene-olefin rubber, thermoplastic resin, and blowing agent, compounding agents such as fillers, softeners, vulcanizing agents, vulcanization accelerators, and activators can be used.

Fillers include carbon black, calcium carbonate,
This can be done using talc, clay, finely powdered silicic acid, etc.

As the vulcanizing agent, sulfur, sulfur compounds, etc. can be used, and a vulcanization accelerator is usually used in combination. As a vulcanization accelerator,
Diteocarpamates, thiurams, thiazoles,
Examples include thioerias, guanidines, xanthates, aldehyde amines, and aldehyde ammonias.

In addition to sulfur vulcanization, quinoid vulcanization and organic peroxide vulcanization are also possible as vulcanization systems, including P-besizoquinone dioxime, P,P'-dibenzoquinone dioxime, and Peroxide, 2,5-dimethyl-2,6-di(t-butylperoxy)hexane, 2,5-dimethyl-2.5
-di(penzoylperoxy)hexane, 1.1-di-t-phtherperoxy-8.8.5-}limethyldimethylhexane, and the like can be used.

Examples of the activator include zinc white, zinc fatty acid, zinc carbonate, and stearic acid, and examples of the softener include various process oils and lubricating oils. In addition to the above-mentioned ingredients, processing aids, antioxidants, and the like can be added as necessary.

Next, the method for producing the vulcanized rubber foam of the present invention will be described. The mixing of rubber such as ethylene-α-olefin rubber, thermoplastic resin, etc. is carried out using a closed-type mixing machine such as Banbury 10xer or 2-der, or a wire mixing roll. Mixing of a blowing agent, vulcanizing agent, vulcanization accelerator, etc. is preferably carried out at a temperature of 100° C. or lower to prevent decomposition and scorch.

The blended composition obtained by cross-mixing is molded using an extruder, press, etc., and then vulcanized and foamed by heating continuously or in a vat type to produce a vulcanized rubber foam. Vulcanization ●Foaming methods include oven, PCM%UHF, LC
M, heat press, can vulcanization, etc.

The obtained vulcanized rubber foam is heated to a temperature higher than the softening point of the thermoplastic resin used for compounding, compressed into a small volume by pressurizing it using a mold, belt, etc., and in the compressed state, water etc. Cool rapidly. After cooling, the rigidity of the thermoplastic resin maintains its contracted shape even after the pressure of the mold and belt is released.

After the vulcanized rubber foam of the present invention produced by the method described above is transported to the place where it will be used and installed in equipment,
It is restored to its original shape by heating to a temperature above the softening point of the thermoplastic resin used.

By using the thermally expandable vulcanized rubber foam of the present invention,
It can reduce storage and transportation costs, improve the workability of installing it on equipment, and improve sealing properties.

The present invention will be specifically explained below with reference to Examples, but these are merely illustrative and the present invention is not limited thereto.

Examples> Examples 1, 2 and Comparative Examples The formulations shown in Table 1 were kneaded using a 1.71 Banbury 10 xer and a 10 inch Q Killengrol. Then, these blended compositions were mixed using a 45 mφ extruder to
It was extruded using a XIIX801l1 ribbon die, and then introduced into a continuous vulcanization tank where it was foamed and vulcanized at 200°C.

The obtained foam was heated to 120°C and molded into 1/8
The material was compressed to a thickness of 1, and in this state was immersed in water at 20° C. to rapidly cool it. Table 2 shows the specific gravity of the foam before and after pressure removal. moreover,
Table 2 shows the specific gravity of the foam after it was heated with hot air at 120°C.

The foam of Example 1.2 containing a thermoplastic resin was heated,
It can be seen that compression and cooling processes result in high specific gravity and small volume, and further heating restores the original specific gravity and volume.

Table 1 Mixture (part u) (Note) 1) Esplen 505 Sumitomo Chemical Industries (manufactured) EPDM 2) Seast SO Tokai Carbon (manufactured) carbon black 8) Sumikasen G806 Sumitomo Chemical Industries (manufactured) low-density polyethylene Ya N: Bit softening point 79℃ 4) Evatate H20 1 1 Sumitomo Chemical Co., Ltd. Ethylene-vinyl acetate Nil copolymer: Bit softening point 82℃ 5) Cell y Iku A Foaming agent DPT manufactured by Sankyo Kaoru 6) Zuruton NP Sankyo Kasei (manufactured) urea-based foaming aid

Claims (2)

[Claims] (1) A thermally expandable rubber foam obtained by compressing a vulcanized rubber foam containing a thermoplastic resin at a temperature equal to or higher than the softening point of the thermoplastic resin and cooling. (2) The thermally expandable rubber foam according to claim 1, wherein the vulcanized rubber foam is an ethylene-α-olefin vulcanized rubber foam containing a thermoplastic resin.