JP2000265017A - Rubber foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber foam excellent in tan δand free from stickiness, which foam comprises a vulcanized foam of a composition essentially consisting of EPDM, PIB, a vulcanizer, and an organic blowing agent and containing EPDM and PER in a specified weight ratio. SOLUTION: The foam composition contains 100 pts.wt., in total, EPDM and PIB, at most 10 pts.wt. vulcanizer such as sulfur or a sulfur compound, 0.1-10 pts.wt. vulcanization accelerator such as a thiazole, 0.1-20 pts.wt. organic blowing agent selected from among a fluoroalkane, an azo compound, a hydrazine compound, etc., 0.1-20 pts.wt. blowing aid such as urea, at most 50 wt.% thermoplastic polymer such as an acrylic polymer, and additives such as a plasticizer, a filler, an antioxidant, and a colorant. This composition is subjected to vulcanization foaming to obtain a foam having an expansion ratio of 1.1-150. The EPDM used has an ethylene content of 40-60 wt.% and a Mooney viscosity of 10-60 and is used in an EPDM/PIB ratio of 85/15 to 50/50 by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber foam excellent in tan δ and suitable as a material for reducing vibration such as soundproofing and vibration suppression.

[0002]

2. Description of the Related Art Conventionally, a butyl rubber-based foam has been known as a rubber foam excellent in tan δ and preferably used as a material for reducing vibration such as soundproofing and vibration suppression. However, there is a problem in that the adhesiveness tends to cause self-fusion during storage and adhesion to other members, which makes it difficult to handle, and that it is easily contaminated with dust and the like, and the contamination is difficult to remove.

[0003]

An object of the present invention is to develop a rubber foam having excellent tan δ and exhibiting no tackiness.

[0004]

According to the present invention, there is provided an EPDM comprising at least EPDM, PIB, a vulcanizing agent and an organic foaming agent.
/ PIB used ratio is 85 / 15-50 based on weight ratio
The present invention provides a rubber-based foam comprising a vulcanized foam of an admixture of / 50.

[0005]

According to the vulcanized foam having the above-mentioned composition, while achieving a high tan .delta.
PDM and PIB are well compatible with each other and can be vulcanized and foamed via a vulcanizing agent such as sulfur, so that a highly durable rubber foam having no tackiness can be obtained.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber-based foam of the present invention is EPD
It comprises a vulcanized foam of an admixture containing at least M, PIB, a vulcanizing agent and an organic foaming agent, wherein the use ratio of the EPDM / PIB is 85/15 to 50/50 based on the weight ratio.

As EPDM (ethylene-propylene-diene rubber) and PIB (polyisobutylene), appropriate ones can be used without any particular limitation. EP
As the DM, those having an ethylene composition ratio of 40 to 60% by weight and a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10 to 60 are preferably used in view of the physical properties of the obtained vulcanized foam.

[0008] The use ratio of EPDM and PIB is EPDM
85/15 to 50/50 based on weight ratio by / PIB
It is said. When the EPDM usage rate exceeds 85,
tanδ is poor, and if it is less than 50, the vulcanization density is poor and a foam is hardly formed. The use ratio of EPDM / PIB, which is preferable from the viewpoint of achieving a high tan δ and forming a foam, is 83/17 to 55/45, preferably 80/20 to 6
0/40.

As the vulcanizing agent, any suitable vulcanizing agent can be used. Among them, sulfur and sulfur compounds are preferred in view of the physical properties such as the vulcanizability and durability due to foaming properties and the non-adhesiveness of the obtained foam. , Especially sulfur, can be preferably used. The amount of vulcanizing agent used is
Per 100 parts by weight of EPDM and PIB in total, 10 parts by weight or less, preferably 0.5 to 5 parts by weight from the viewpoint of the above-mentioned properties and the like.

As the organic foaming agent, any suitable one can be used, and there is no particular limitation. Incidentally, examples thereof include fluorinated alkanes such as trichloromonofluoromethane and dichloromonofluoromethane, azo compounds such as azobisisobutyronitrile and azodicarboxylic amide (ADCA), barium azodicarboxylate, and paratoluenesulfonyl. Hydrazide or diphenyl sulfone
Hydrazine compounds such as 3,3'-disulfonylhydrazide, 4,4'-oxybis (benzenesulfonylhydrazide), and allylbis (sulfonylhydrazide) can be mentioned.

Semicarbazide compounds such as ρ-toluylenesulfonyl semicarbazide and 4,4′-oxybis (benzenesulfonyl semicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; Organic foaming agents such as N-nitroso-based compounds such as N'-dinitrosopentamethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide are also included.

The amount of the organic foaming agent used can be determined as appropriate, but generally, from the viewpoint of the physical properties of the obtained foam, particularly the physical properties required for a vibration reducing material, the total amount of EPDM and PIB per 100 parts by weight , 0.1 to 20 parts by weight, especially 0.1.
It is 5 to 15 parts by weight, especially 1 to 12 parts by weight.

The preparation of the admixture is at least EPDM, P
The mixing can be carried out by mixing the components consisting of IB, vulcanizing agent and organic foaming agent by an appropriate method such as a method of mixing via a kneader such as a kneader or a mixing roll. At this time, a mixing method in which the temperature is raised to such an extent that vulcanization proceeds is not preferable.

In preparing the admixture, an appropriate compounding agent according to the related art can be added for the purpose of adjusting the viscosity and vulcanizability, adjusting the physical properties such as the strength of the obtained foam, and the like.
By the way, for the purpose of accelerating vulcanization, for example, guanidines and thiazoles, sulfenamides and tulams, dithiocarbamic acids and xanthogenic acids, aldehyde ammonia and aldehyde amines, vulcanization accelerators such as thioureas, and more A vulcanization accelerator may be added. The amount of vulcanization accelerator used is EPDM and PIB
0.1 to 10 parts by weight per 100 parts by weight is suitable, but not limited thereto.

For the purpose of promoting foaming, for example, a foaming aid such as a urea-based, salicylic-acid-based or benzoic acid-based foaming agent can be blended. The amount of foaming aid used is EPDM and PIB
0.1 to 20 parts by weight per 100 parts by weight of the total is suitable, but not limited thereto.

Further, an acrylic polymer such as a poly (meth) acrylic acid alkyl ester, polyvinyl chloride, polyethylene, polypropylene, ethylene / polyethylene, etc. may be added to the admixture for the purpose of controlling physical properties such as strength of the obtained foam.
Suitable non-rubber-based thermoplastic polymers such as vinyl acetate copolymers, polyvinyl acetates, polyamides and polyesters, chlorinated polyethylenes and urethane-based polymers, styrene-based polymers and silicone-based polymers, and epoxy-based resins can also be blended. . The amount used is preferably 50% by weight or less, more preferably 30% by weight or less, and particularly preferably 15% by weight or less of the total amount of EPDM and PIB from the viewpoint of maintaining the rubber-like properties of the foam.

In addition, the admixture may contain an organic acid such as phthalic anhydride, benzoic acid or salicylic acid, N-nitroso-diphenylamine, N-nitroso-phenyl-β- A vulcanization retarder comprising an amine such as naphthylamine may be blended to retard vulcanization in the opposite manner to the vulcanization accelerator described above.

The admixture may further contain paraffins such as chlorinated paraffin, waxes, naphthenes, aromas, asphalts, etc.
Drying oils such as linseed oil, animal and vegetable oils, petroleum oils and various low-molecular-weight polymers, phthalates and phosphates, stearic acid and its esters, alkylsulfonic acid esters and tackifiers For example, a softening agent composed of the following may be added. In addition, stearic acid and its esters are also useful as a lubricant and the like, and are therefore examples of components that can also contain various lubricants.

In addition, the admixture includes talc, calcium carbonate, clay and mica powder, aluminum hydroxide and magnesium hydroxide, zinc white and bentonite, carbon black and silica, alumina and aluminum silicate, acetylene black and aluminum powder. If necessary, a suitable compounding agent such as a filler, a plasticizer, an antioxidant, an antioxidant, a pigment, a colorant, and a fungicide can be added. The zinc white is useful as a stabilizer, and carbon black is also useful as a reinforcing agent. Accordingly, examples of the components that can also contain various stabilizers and reinforcing agents are given.

Each of the above-mentioned components comprising EPDM and PIB, a vulcanizing agent and an organic foaming agent, and other compounding agents as required, may be used alone or in combination of two or more in preparing a mixture.

The rubber-based foam according to the present invention can be formed by heating and vulcanizing and foaming the above-mentioned admixture. When forming the admixture, the admixture may be formed, if necessary, into a predetermined form such as a sheet. , And then heat-treat the molded body to form a vulcanized foam. In that case, the molded body may be formed into an arbitrary form by an appropriate method, and the form is not particularly limited.

Therefore, the mixture may be formed into a sheet by an appropriate method such as a mixing roll, a calender roll, or extrusion molding, or may be appropriately formed by injection molding or press molding through a predetermined mold. It may be formed into a predetermined form having irregularities or the like by any suitable method.

In the above, in the formation of a foam having an uneven shape, the unvulcanized sheet is placed on a mold having unevenness and heated, and the mixture forming the unvulcanized sheet is formed on the unevenness of the mold. It is also possible to adopt a method of vulcanizing and foaming by flowing and infiltrating. Such a method has an advantage that the uneven shape can be accurately formed even in the case of a mold having a complicated and deep uneven structure having a fold structure.

Accordingly, the size of the molded article is arbitrary, and can be appropriately determined according to the desired form of the vulcanized foam. In the case of a sheet or the like, the thickness is 100 mm or less,
In particular, 1 μm to 80 mm, especially 10 μm to 50 mm is common.

The above-mentioned vulcanization / foaming treatment can be carried out under appropriate conditions according to the prior art, depending on the vulcanization starting temperature and foaming temperature of the vulcanizing agent or foaming agent used. General vulcanization foaming temperature is 450 ° C or less, especially 120-350 ° C,
Particularly, it is 150 to 300 ° C. Usually, the vulcanization and foaming treatment softens the admixture and expands the foaming agent to form a foamed structure, and vulcanization proceeds to form a desired vulcanized foam.

In the above, the foaming treatment and the vulcanization treatment can be performed under different temperature conditions, and appropriate treatment conditions can be adopted. The vulcanization / foaming treatment can also be performed under pressure for the purpose of adjusting the expansion ratio. The pressurization condition is
It can be according to the conventional.

The expansion ratio of the vulcanized foam to be formed is appropriately determined according to the purpose of use and the like, but is generally from 1.1 to 1.1.
It is 150 times, especially 1.5 to 100 times, especially 2 to 50 times. The expansion ratio can be controlled by the amount of the above-mentioned foaming agent, the processing time and temperature of vulcanization and foaming, and the like. In addition, by adjusting the expansion ratio, it is possible to control the foaming structure such as independent or continuous vulcanized foam to be obtained, or a mixture thereof.

The rubber-based foam according to the present invention can be used in various conventional applications such as cushioning materials, padding materials, sealing materials, heat insulating materials and waterproofing materials. In particular, since it has excellent tan δ, it can be preferably used as a material for reducing vibration such as soundproofing and vibration suppression.

[0029]

EXAMPLE 1 80 parts of EPDM (parts by weight, the same applies hereinafter), 20 parts of PIB,
2 parts sulfur, 2 parts tetramethylthiuram disulfide, 2 parts
-1 part of mercaptobenzothiazole, 7 parts of ADCA, 7 parts of urea-based foaming aid, 50 parts of heavy calcium carbonate, 30 parts of carbon, 20 parts of paraffinic oil, 5 parts of zinc oxide and 1 part of powdered stearic acid in a pressure kneader. The mixture was kneaded to obtain an admixture, which was sheeted with a mixing roll to obtain an unvulcanized sheet having a thickness of 5 mm. (3 times magnification) to obtain a rubber-based foam composed of a vulcanized foam having a closed cell structure.

Example 2 The amount of EPDM used was 60 parts and the amount of PIB used was 40 parts.
A rubber-based foam was obtained in the same manner as in Example 1 except that the above parts were used.

Comparative Example 1 A rubber foam was obtained in the same manner as in Example 1 except that the amount of EPDM was changed to 100 parts and PIB was not used.

Comparative Example 2 A rubber foam was obtained in the same manner as in Example 1 except that butyl rubber was used instead of EPDM and PIB.

Evaluation Test The rubber foams obtained in Examples and Comparative Examples were examined for the presence or absence of tackiness, and also for the tan δ at 10 ° C., 20 ° C. or 30 ° C.

The above results are shown in the following table. Adhesion tan δ 10 ° C 20 ° C 30 ° C Example 1 None 0.20 0.20 0.20 Example 2 None 0.21 0.21 0.21 Comparative Example 1 None 0.17 0.17 0.17 Comparative Example 2 Yes 0.24 0.24 0.24

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Takashi Nakamura 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nippon Denko Corporation F-term (reference) 4F074 AA25 AA26 AA98 AC03 BA13 BA14 BA15 BA16 BA17 BA18 BA20 BA28 BA54 BA55 BB05 BB06 CA12 CA25 CC04Y CC06X CC22X CC24X CC32Y DA40 4J002 BB151 BB182 DA046 EB067 EQ017 ES007 EU167 EV267 EV287 FD146 FD327

Claims (1)

[Claims] 1. A vulcanized foam of an admixture comprising at least EPDM, PIB, a vulcanizing agent and an organic foaming agent, wherein the use ratio of said EPDM / PIB is 85/15 to 50/50 based on the weight ratio. A rubber-based foam characterized by becoming.