JPH07278335A - Production of foamed fluororubber - Google Patents

Abstract

PURPOSE:To perform mass-production of a foamed fluororubber containing uniform cells and having excellent cushioning property and heat-insulation at a low cost by kneading a fluororubber with a foaming agent and a vulcanizing agent and successively foaming and vulcanizing the mixture using a specific method. CONSTITUTION:This foamed material is produced by kneading (A) a fluororubber (e.g. tetrafluoroethylene-propylene rubber) with (B) a foaming agent and (C) a vulcanizing agent, heating the kneaded mixture under pressure at or above the decomposition temperature of the component B and vulcanizing at the vulcanization temperature of the component A. The component B is preferably the single use of thermally expandable microcapsule or a combination of the microcapsule with a decomposition-type foaming agent such as azodicarbonamide. The component C is e.g. calcium hydroxide when the component A is a polyol-vulcanization type and is e.g. dicumyl peroxide when the component A is a peroxide-vulcanization type.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluororubber foam, and particularly to a cushioning property having uniform cells while preventing the vulcanization of fluororubber from being unnecessarily accelerated. The present invention relates to a method for producing a fluororubber foam.

[0002]

2. Description of the Related Art As a conventional method for producing foams of natural rubber and synthetic rubber of this kind, azodicarbonamide of an azo compound and N, N'- of a nitroso compound are used in natural rubber or synthetic rubber. By kneading a decomposition type foaming agent such as dinitrosopentamethylenetetramine together with a vulcanizing agent, etc., and then foaming by heating under pressure at a temperature at which decomposition of this decomposition type foaming agent occurs, or at a temperature higher than that. , Produced natural and synthetic rubber foams.

[0003]

However, when a fluororubber, which is a kind of synthetic rubber, is foamed with a decomposing type foaming agent and a vulcanizing agent as in the conventional case, a crack is generated on the surface. However, there is a problem that it is extremely difficult to produce a fluororubber foam having an excellent cushioning property with uniform air bubbles because of the unevenness formed on the surface or the accumulation of gas inside. As described above, the reason why it is difficult to foam the fluororubber is that when a decomposing type foaming agent that decomposes at a temperature equal to or lower than the vulcanization temperature is used, the heat of decomposition of the foaming agent is generated. It is considered that this is because the vulcanization of fluororubber is significantly accelerated.

The present invention is a completely new technique developed in view of the above-mentioned problems of the conventional technique, and in particular, the fluororubber is treated so that the heat of decomposition of the foaming agent does not adversely affect the vulcanization of the fluororubber. It is intended to provide a technique for producing a fluororubber foam which is foamed, has uniform cells, and is rich in cushioning properties.

[0005]

The method for producing a fluororubber foam according to the present invention is a technique which has fundamentally improved the above-mentioned conventional problems, and the gist of the first invention is fluororubber. It is produced by kneading a blowing agent and a vulcanizing agent, pressurizing and heating at a temperature at which decomposition of the blowing agent occurs or at a temperature higher than that, and then vulcanizing at a vulcanizing temperature of fluororubber. A method for producing a fluororubber foam characterized by the above.

Further, the gist of the second invention of the manufacturing method according to the present application is that the foaming agent is composed of only thermally expandable microcapsules, or a combination of the thermally expandable microcapsules and the decomposed foaming agent. The method for producing a fluororubber foam of the first invention is characterized by the above. Furthermore, the gist of the third invention is that the generation of heat of decomposition of the foaming agent can be set as small as possible,
A method for producing a fluororubber foam according to the first invention and the second invention, characterized in that the fluororubber is foamed while preventing the vulcanization of the fluororubber by heat of decomposition.

[0007]

The function of producing the fluororubber foam according to the present invention is as follows.
As described above, the heat-expandable microcapsules were used alone in the fluororubber, or the heat-expandable microcapsules and the decomposing foaming agent were used in combination to foam. The fluororubber can be easily foamed by the expansion of the heat-expandable microcapsules without promoting vulcanization, and a fluororubber foam having uniform bubbles and rich cushioning properties can be produced.

Further, as in the invention of the present application, the generation of the decomposition heat of the foaming agent can be set to be as small as possible, and the foaming is performed while the vulcanization of the fluororubber is not promoted by the decomposition heat, so that uniform foaming can be smoothly performed. You can do it.

[0009]

EXAMPLES Specific examples of the fluororubber, the foaming agent, the vulcanizing agent, the foaming aid, the reinforcing agent and the like used in the method for producing a fluororubber foam according to the present invention will be described below. .

First, the fluororubber used in the present invention includes vinylidene fluoride type two-component type and three-component type polyol vulcanization / peroxide vulcanization / polyamine vulcanization types. Examples thereof include ethylene-propylene rubber. In the foaming agent used in the present invention, examples of the heat-expandable microcapsules include heat-expandable microcapsules containing low-boiling hydrocarbons (softening temperature of shell wall: 80 to 140 ° C., expansion ratio). 60 to 70 times)
Is used.

Further, among the foaming agents used in the present invention,
As the decomposition type foaming agent, for example, azo compound asodicarbonamide (decomposition temperature 200 ° C., decomposition heat amount 10 kcal /
mol), N, N'-dinitrosopentamethylenetetramine of nitroso compound (decomposition temperature 200 ° C 155 kcal / mol)
Hydragit-based compounds p. Organic compounds such as p'-oxybisbenzenesulfonyl hydrazide (decomposition temperature 150 ° C, decomposition heat amount 43.5 kcal / mol) and inorganic compounds such as sodium bicarbonate (decomposition temperature 90 ° C) are used.

The amount of these foaming agents used is appropriately determined according to the foaming ratio of the intended product, but is generally about 3 to 15 parts by weight per 100 parts by weight of the fluororubber. Further, these foaming agents can be used by adjusting the decomposition temperature in combination with a foaming auxiliary. As the foaming aid, a urea compound, an organic acid salt compound such as zinc stearate, or an inorganic compound such as basic zinc carbonate or zinc oxide can be used.

The vulcanizing agent used in the present invention includes calcium hydroxide and highly active magnesium oxide in the polyol vulcanizing type of fluororubber, and the half-life of 1 minute in the peroxide vulcanizing type. Temperature is 179-183 ℃
Organic peroxides are used. For example, dicumyl peroxide.2.5 dimethyl-2.5 bis (t-butylperoxy) hexane.1.3-bis (t-butylperoxyisopropyl) benzene and the like can be mentioned.

The amount of the vulcanizing agent used is 3 parts by weight of calcium hydroxide per 100 parts by weight of the polyol vulcanizing type fluororubber.
-8 parts by weight and 1-5 parts by weight of highly active magnesium oxide are used. Peroxide vulcanizing type is fluororubber 10
0.5 to 2.0 parts by weight of 2.5 dimethyl-2.5-bis (t-butylperoxy) hexane is used per 0 parts by weight, and at the same time, 1 to 4 parts by weight of triallyl isocyanurate as a vulcanization aid. Can be used.

As other reinforcing agents and colorants, carbon black, titanium oxide, silica, etc. can be used, and if necessary, liquid fluororubber, dioctyl sebacate, tricresyl phosphate, etc. are optionally added as plasticizers. I can do things.

A plurality of specific examples of the method for producing a fluororubber foam of the present invention using the above-mentioned fluororubber, a foaming agent, a vulcanizing agent, a foaming aid, a reinforcing agent and the like will be shown. It is as follows.

[Example 1] 100 parts by weight of fluororubber (trade name: Daier G-755L, polyol vulcanization binary system, manufactured by Daikin Industries, Ltd.), MT carbon black (trade name: Thermax N-990, CANCARB Ltd 10 parts by weight, highly active magnesium oxide (trade name: Kyowamag M)
A-150, Kyowa Chemical Industry Co., Ltd.) 3 parts by weight, calcium hydroxide (trade name: CALDIC-2000, Omi Chemical Industry Co., Ltd.) 6 parts by weight, heat-expandable microcapsules (trade name: Matsumoto Micros) 6 parts by weight of FAIR F-30, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., and 4 parts by weight of azodicarbonamide (trade name: Celmic CAP-250, manufactured by Sankyo Kasei Co., Ltd.) as a decomposing foaming agent are rolled. Kneading with a water-cooled open roll at a temperature of 35 ° C or less, and a mold in a press heated to 160 ° C (150 * 100 * 8.5
mm) is filled with the above mixture and heated under pressure for 15 minutes to obtain a foam. Furthermore, when this foam was heated in an oven at 170 ° C for 7 minutes to complete vulcanization, the size of the fluororubber foam was 225 * 150 * 14 mm, and uniform foam and cushioning foam were obtained. I was able to manufacture it.

[Example 2] In the above-mentioned [Example 1],
Except that no heat-expandable microcapsules were added, the same procedure as in [Example 1] was carried out, and the obtained foam had a size of 165 * 110 * 10.3 mm and was cushioned with fine bubbles. It was a foam with little property.

[Example 3] Same as [Example 1] except that 15 parts by weight of liquid fluororubber (trade name: Daiel G-101, manufactured by Daikin Industries, Ltd.) was added in [Example 1]. When the same procedure was performed under the same conditions, the size of the foam was 240 * 160 * 15 mm as in [Example 1], and it was possible to produce a fluororubber foam having uniform bubbles and cushioning properties.

Example 4 100 parts by weight of fluororubber (trade name: Daier G-902, Percide vulcanization ternary system, manufactured by Daikin Industries, Ltd.), MT-carbon black (trade name: Thermax N-990, CANCARB Ltd Made) 10
Parts by weight, 2.5 dimethyl-2.5-bis (t-butylperoxy) hexane (trade name: Perhexa 25B, manufactured by NOF CORPORATION) 1.0 part by weight, triallyl isocyanurate (trade name: TAIC, 2 parts by weight of Nippon Oil & Fats Co., Ltd., heat-expandable microcapsules (trade name: Matsumoto Microsphere F-30, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.), 6 parts by weight, azodicarbonamide (trade name: Celmic CAP-250). , Sankyo Kasei Co., Ltd.) 4 parts by weight of a composition is kneaded with a water-cooled open roll having a roll temperature of 35 ° C. or lower, and then heated to 150 ° C. into a mold in a press (150 * 100 * 8.5 mm). Then, the above mixture is filled and heat-foamed under pressure for 15 minutes to obtain a foam. Furthermore, when this foam was heated in an oven at 170 ° C for 5 minutes to complete the vulcanization, the size of the fluororubber foam was 240 * 160 * 15mm, and uniform foam with cushioning properties was obtained. I was able to manufacture it.

[Example 5] The same procedure as in [Example 4] except that azodicarbonamide was not added in [Example 4], and the size of the foam was 210. *
It was possible to manufacture a fluororubber foam with 140 * 12mm and uniform air bubbles and cushioning properties.

Example 6 Under the same conditions as in Example 4 except that 6 parts by weight of azodicarbonamide was added without adding thermally expandable microcapsules in Example 4. When the same procedure was performed, the obtained foam had a gas trap inside, and the size of the foam was 18 due to non-uniform bubbles.
It was 5 * 125 * 11 mm, but it was not satisfactory as a fluororubber foam.

As is apparent from the above-mentioned specific examples, when foaming fluororubber, fluorine having uniform bubbles and rich cushioning property is used depending on whether the heat-expandable microcapsules are used as the foaming agent. It is clear that it is determined whether rubber foam can be produced.

When a decomposition type foaming agent is used for foaming the fluororubber, if the decomposition temperature of the foaming agent is set to 150 ° C. or higher, the heat of decomposition of the foaming agent is generated to vulcanize the fluororubber. Since it is remarkably accelerated, it is difficult to produce a fluororubber foam having uniform air bubbles and excellent in cushioning properties, but it is possible to use heat-expandable microcapsules alone or heat-expandable microcapsules. When used together with a decomposable foaming agent, the expansion of the heat-expandable microcapsules allows the fluororubber to be easily foamed, which makes it possible to minimize the generation of decomposition heat of the foaming agent. Thus, it is clear that the fluororubber can be foamed into a foam having uniform cushioning properties and excellent cushioning properties.

[0025]

Since the method for producing a fluororubber foam according to the present invention has the above-described structure and operation, the present invention has the following great effects.

(1) By carrying out the method of the present invention, the decomposition heat of the foaming agent can be set to a temperature as small as possible. (2) As a result, vulcanization of fluororubber can be suppressed. (3) The fluororubber can be easily foamed by the expansion of the thermally expandable microcapsules. (4) Therefore, it is possible to produce a fluororubber foam having uniform bubbles and rich in cushioning properties.

(5) The fluororubber foam produced by the method of the present invention has uniform bubbles, is excellent in cushioning properties and heat insulating properties, and can be mass-produced at low cost. Unlike rubber, it can be used for a wide range of purposes. (6) That is, for example, it can be used as packing for engine parts of automobiles, packing and gaskets for electric parts, OA equipment, chemical industry, building materials and the like.

Claims (3)

[Claims] 1. A kneading agent for a blowing agent and a vulcanizing agent is added to a fluororubber, and the mixture is pressurized and heated at a temperature at which the blowing agent is decomposed or at a temperature higher than that, and then the vulcanizing temperature of the fluororubber. A method for producing a fluororubber foam characterized by being produced by vulcanizing with. 2. The fluororubber foam according to claim 1, wherein the foaming agent is composed of only heat-expandable microcapsules, or is composed of a combination of the heat-expandable microcapsules and a decomposition type foaming agent. Body manufacturing method. 3. The method according to claim 1, wherein the generation of the heat of decomposition of the foaming agent can be set to be as small as possible, and the fluororubber is foamed while the vulcanization of the fluororubber is not accelerated by the heat of decomposition. 2. The method for producing a fluororubber foam according to 2.