JP2501044B2 - Liquid foamable fluororubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid expandable fluororubber composition, particularly a liquid, which has a wide processing range and excellent storage stability. The obtained foam is a closed cell, which is heat resistant and resistant. The present invention relates to a liquid foamable fluororubber composition which is useful as a seal member for automobiles, electric / electronic parts, building materials, cushioning materials, coating agents and the like because it has chemical properties and flame retardancy.

[0002]

BACKGROUND ART Various types of plastic foams have been known so far, but urethane foam as a typical example has insufficient heat resistance and chemical resistance, and therefore silicone sponge as a heat resistant foam. Has the disadvantage that most of them swell in organic solvents. Therefore, it is said that the most stable foam is a fluororubber sponge, but the fluororubber sponges currently on the market are obtained by kneading a foaming agent into a polyol-crosslinking fluororubber. Is processability, storage stability,
Since there is a problem in the uniformity of foaming, a known urethane foam is impregnated with a fluororubber composition,
A method has also been proposed in which the solvent is removed and then cured to form a fluororubber film on the urethane surface to improve the defects of the urethane foam.

[0003]

However, since the foam obtained by this method becomes an open-cell body, it has no sealing property, and it is difficult to form a fluororubber film stably. It has the disadvantages that its use range is limited and stable production becomes difficult. Further, it has been pointed out that this fluororubber has poor workability, and there is a high risk of scorch due to the heat generated during roll kneading. It is said that it is difficult to obtain such a molded product, and it is difficult to set its hardness to Hs 50 ° or less.

Regarding the crosslinking of this fluororubber,
When a solution-processing fluororubber is crosslinked, it is foamed at the time of crosslinking, or surface tack is generated, so that it is extremely unlikely to be crosslinked with an organic peroxide, which is usually performed by using an amine or a polyol. In this case, it is difficult to completely remove the solvent, and when amine and polyol are used as the cross-linking agent, the reaction progresses even at room temperature, the solution changes in viscosity, and there is a risk of gelation, resulting in lack of storage stability. There are many problems in practical application.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a liquid foamable fluororubber composition which has solved such disadvantages, and it is a peroxide crosslinkable fluororubber composition having 0.1 to 30 weight% thereof. % Of the foaming agent is dissolved in an organic solvent to form a liquid.

That is, the present inventors have conducted various studies to develop a fluororubber composition in which the foam obtained therefrom has excellent storage stability and becomes a closed cell, and as a result, the fluororubber composition was peroxidized. If the product is crosslinked, a foaming agent is added to it, and it is dissolved in an organic solvent to form a liquid, this product is a liquid, so the processing range can be expanded. Since it is a cross-linking type, it has good storage stability, and this does not require complete removal of the solvent during the cross-linking process.
The foam obtained from this is a closed cell and can be molded without leaving a tacky surface condition, and it was found that this product has excellent heat resistance, chemical resistance, and flame retardancy. The present invention was completed by conducting research on the types and blending amounts of fluororubber compositions, foaming agents, and solvents used for. This will be described in detail below.

[0007]

The present invention relates to a liquid expandable fluororubber composition, which comprises a peroxide-crosslinking fluororubber composition containing a foaming agent and dissolved in an organic solvent to form a liquid. It was done.

The fluororubber as a main component constituting the liquid expandable fluororubber composition of the present invention is a peroxide cross-linking type. This peroxide-crosslinking fluororubber is a vinylidene fluoride-hexafluoropropene binary elastic copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary elastic copolymer, pentafluoropropene-trifluoroethylene diisocyanate. Organic peroxides such as elastic copolymers consisting of one or two kinds of original copolymer, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether), etc. It is said to be a mixture of

As the fluororubber, vinylidene fluoride-hexafluoropropene binary elastic copolymer and vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary copolymer are preferred, and as the organic peroxide, Is benzoyl peroxide
De, dicumyl peroxide, di -t- butyl peroxide, t- butyl peroxy acetate, t- butyl peroxybenzoate, 2,5-dimethyl -t- butyl peroxy hexane, 2,4 - dichlorobenzoyl peroxide , 1,1-bis (t-butylperoxy)
Examples include 3,3,5-trimethylchlorohexane, 1,1-bis (t-butylperoxy) chlorohexane, cyclolohexanone peroxide, methyl ethyl ketone peroxide, and the like.

Regarding the amount of the organic peroxide added to the fluororubber, if the organic peroxide is less than 1 part by weight relative to 100 parts by weight of the fluororubber, the crosslinking is not stable, and if it exceeds 20 parts by weight, the foaming is not stable. However, the resulting crosslinked product loses the original properties of the fluororubber.
Although it is required that the amount is parts by weight, the preferable range is 3 to 10 parts by weight. Further, this organic peroxide may be added alone, but it is necessary to select it in consideration of the decomposition temperature of the foaming agent described later,
Since foaming may not be stable with only one type, it is desirable to use two or more types together.

The peroxide-crosslinking fluororubber composition thus obtained can easily change its viscosity depending on moisture, temperature, etc. when the fluororubber composition which is crosslinked by using a known amine or polyol is made into a solution. However, it can be stored for a long period of time because it gels or gels, and it can be stored stably unless it is heated considerably.

A foaming agent is then added to the peroxide cross-linking agent fluororubber composition in order to make it foamable. As the foaming agent, N, N '
-Dimethyl-N, N'-dinitrosoterephthalamide,
Examples include dinitrosopentamethylenetetramine, azobisisobutyronitrile, azodicarboxylic acid amide, paratoluenesulfonyl hydrazide, p, p′-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl semicarbazide, and trihydrazinotriazine. .

These foaming agents may be used in combination of two or more thereof in order to stabilize the foaming state, but if the addition amount is less than 0.1 parts by weight with respect to 100 parts by weight of the above-mentioned fluororubber, foaming will occur. Is not stable and crosslinking inhibition occurs when the amount is more than 30 parts by weight. Therefore, it is necessary to set the range to 0.1 to 30 parts by weight, but the preferable range is 1 to 20 parts by weight. In addition, it is optional to add a urea-based auxiliary agent, an organic acid-based auxiliary agent, and a metal salt-based auxiliary agent to the composition in order to adjust the decomposition temperature.

The expandable fluororubber composition thus obtained requires the addition of a cross-linking aid to stabilize its cross-linking, and further to improve the physical properties of the resulting foam. A filler, an acid acceptor, a plasticizer, a lubricant and the like may be added to the above.

Examples of the crosslinking aid include diallyl ether of glycerin, triallyl phosphoric acid, diallyl adipate,
Examples include diallyl melamine, triallyl isocyanurate, triallyl isocyanate, etc.
It may be added in an amount of 20 parts by weight, preferably 2 to 10 parts by weight.

Examples of the filler include carbon black, alumina, silica, clay, calcium carbonate, titanium oxide, iron oxide, polytetrafluoroethylene powder, and the addition amount thereof suppresses the hardness of the foaming agent. Therefore, the amount may be 60 parts by weight or less, preferably 20 parts by weight or less, based on 100 parts by weight of the fluororubber.

Further, as the acid acceptor added here,
Magnesium oxide, calcium oxide, calcium hydroxide, barium stearate, sodium stearate,
Examples of lead oxide include 20 parts by weight or less, preferably 10 parts by weight, based on 100 parts by weight of fluororubber.
It is preferable to use less than or equal to parts by weight.

The plasticizers and lubricants added here are added for the purpose of lowering the hardness of the fluororubber and improving the workability, but these are fluorine-based oils or greases that have good compatibility with the fluororubber. , Fatty acid ester, carnauba wax, etc., which are fluororubber 100
30 parts by weight or less, preferably 10 parts by weight or less may be added to the parts by weight.

The liquid expandable fluororubber composition of the present invention is prepared by dissolving the expandable fluororubber composition obtained as described above in a solvent. The solvent is one which dissolves the fluororubber. Since it is required to be present, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, alcohols such as methanol and ethanol, dimethylformamide, and freon are exemplified. And from the volatility after application, acetone,
Methyl ethyl ketone and the like are preferred, and since this solvent also participates in foaming, it may be used as a mixture of two or more kinds, but from the viewpoint of stability, it is not very economical, but a chlorofluorocarbon solvent is used. It is also good.

Since the specific gravity of the solvent varies depending on the type of solvent, it may be determined on the basis of the viscosity of the target liquid expandable fluororubber composition. If the viscosity of the liquid foamable fluororubber composition is less than 1 poise, there is a disadvantage that it is necessary to heat the solvent for volatilizing it or to leave it for a long time, and if it is 1,000,000 poise or more. Since uniform dissolution becomes difficult and workability during coating becomes poor, the viscosity is 1 to 1,000,000.
The viscosity may be in the range of 10 to 500,000 poise, and the solvent may be efficiently volatilized and the coating step may be performed. You can choose freely.

The liquid expandable fluororubber composition of the present invention can be obtained by uniformly mixing the above-mentioned fluororubber, foaming agent, crosslinking aid, filler, acid acceptor, plasticizer, lubricant and solvent. However, since this mixing requires that each of these components be sufficiently dispersed, after solid components are kneaded using a two-roll, kneader, pressure kneader, Banbury mixer, etc. It suffices to dissolve it in a mixing mixer using a solvent.
Although this mixing mixer can shorten the processing time, in this case, there is still concern about the complete dispersion of each component. Therefore, it is better to completely disperse this with a three-roll mill or the like. At the time of dissolution, heat treatment may be performed for the purpose of shortening the time.

The liquid foamable fluororubber composition of the present invention thus obtained is applied to a target object to be treated, foamed and crosslinked and cured. It may be performed by bar coating, screen printing, spraying, or the like. In this foaming and cross-linking curing, it is preferable to volatilize the solvent in advance as much as possible, but since the residual solvent acts as a foaming agent, the required amount of the solvent having an arbitrary boiling point is left and the expansion ratio is increased. It may be adjusted. The residual amount of the solvent may be 50% or less by volume, preferably 20% or less.

The conditions for foaming and cross-linking and hardening of this coating film are the organic peroxide contained in this composition, the decomposition temperature of the foaming agent,
It may be set in consideration of the boiling point of the solvent, etc., but this is usually heated to 100 to 300 ° C. Therefore, for this foaming and crosslinking / curing, a dryer or the like is used for foaming and hot air crosslinking is performed. Infrared crosslinking or high frequency crosslinking may be performed, but press crosslinking may be performed in the mold.

Since the fluororubber film obtained by foaming and cross-linking and curing the liquid expandable fluororubber composition of the present invention may have self-adhesiveness, this is used when adhering to other materials. However, it is possible to use the known fluororubber primer when adhesion is required when it does not exhibit self-adhesion. In addition, when the composition is molded in a mold and adhesiveness is not particularly required, a target commercially available release agent can be used to easily obtain a target fluororubber foam. it can.

[0025]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Examples 1 to 3 Fluororubber Daiel G801 [trade name manufactured by Daikin Co., Ltd.] (hereinafter abbreviated as fluororubber I), or fluororubber Doyton GF [trade name manufactured by DuPont, USA] (hereinafter abbreviated as fluororubber II) In addition, organic peroxide Niper B [trade name of NOF Corporation], organic peroxide Niper 3M [trade name of NOF Corporation], organic peroxide Perhexa 2-5B Nippon Oil & Fats Co., Ltd. product name], Foaming agent / Selmike CAP [Sankyo Kasei Co., Ltd. product name], Foaming agent / Selmike CAP250 [Sankyo Kasei Co., Ltd. product name], Crosslinking aid / Tyke Nippon Kasei Product Name],
Filler-Thermax MT [Harbor Company trade name], Filler-Aerosil 200 [Nippon Aerosil Co., Ltd. trade name], and acid acceptor Ca (OH) ₂ were added in the weights shown in Table 1 and 2 After thoroughly kneading with this roll, acetone and methyl ethyl ketone were added thereto in the amounts shown in Table 1,
It was completely melted with a mixing mixer to prepare a liquid expandable fluororubber composition.

Then, this composition was dispensed on a polyimide film Kapton 75 [mu] m thick (trade name, manufactured by DuPont, USA) with a nozzle inner diameter of 1 to 4 mm using a constant-quantity discharge device [manufactured by Yasukawa Electric Co., Ltd.]. Coating speed 4m
When discharging was performed under the condition that the nozzle height was 2 / min and the nozzle height was 2 mm, it was possible to discharge with good workability.

Next, the coating film thus obtained is allowed to stand at room temperature for 0.5 to 5 hours to volatilize the solvent by 50 to 98%, and then kept in a dryer heated to 200 ° C. for 30 minutes to foam. When cross-linked and molded, the results shown in Table 1 for the foamed state and the surface state were obtained. The foamed molded product thus obtained has self-adhesiveness and
Heat resistance of time and 2 at room temperature in gasoline, kerosene, and toluene
It showed the physical properties of being stable and nonflammable even after being left for 4 hours.

Examples 4 to 6 In addition to the above-mentioned two types of foaming agents as the foaming agent added to the fluororubber, a foaming agent Celmic C [trade name of Sankyo Kasei]
Was added to the fluororubbers I and II used in Examples 1 to 3.
The types and amounts of organic peroxides, blowing agents,
A liquid foamable fluororubber composition was prepared by adding a crosslinking aid, a filler and an acid acceptor, adding a solvent without using two rolls and mixing with a mixing mixer. Was partially agglomerated, and was kneaded again with a three-roll roll, and then treated in the same manner as in Examples 1 to 3, and the foamed state and surface state of the obtained foams were shown in Table 1.
The results are as shown in Example 1 and the foam is
The same physical properties as those of Nos. 3 to 3 were exhibited.

[0029]

[Table 1]

Comparative Example 1 In the liquid expandable fluororubber compositions of Examples 1 to 3, compositions without a foaming agent were prepared, and the solvent remaining therein was used as the foaming agent. When a foam was produced by treating in the same manner as in 1 to 3, in this case, uniform foaming could not be obtained, and a useful molded body could not be obtained.

Comparative Example 2 Liquid foamable fluororubber compositions obtained by adding organic peroxide, a foaming agent, a vulcanization aid, a filler, an acid acceptor and acetone as a solvent to the fluororubber I in Examples 1 to 3. A product was prepared and treated in the same manner as in Examples 1 to 3 to prepare a foam. In this case, since the amount of the foaming agent was as small as 0.05 parts by weight, it was slightly different from Comparative Example 1. Although the foaming was found to be uniform, a good foam could not be obtained.

Comparative Example 3 In the fluororubber I in Examples 1 to 3, the types and amounts of organic peroxides, blowing agents, vulcanization aids, and fillers shown in Table 2 were used.
Acetone was added as a solvent to prepare a liquid expandable fluororubber composition, which was treated in the same manner as in Examples 1 to 3 to form a foam. In this case, the amount of the foaming agent was 40 parts by weight. Therefore, a useful foam could not be obtained due to the inhibition of crosslinking.

Comparative Example 4 The fluororubber was a polyol crosslinkable one (hereinafter abbreviated as fluororubber III) which was not an organic peroxide crosslinkable one, and 100 parts by weight of acetone as a solvent was added to 100 parts by weight of this fluororubber. Then, when making the solution,
In this case, the reaction proceeds even at room temperature, and gelation occurs in about 1 hour, making it difficult to carry out coating and foam molding.

[0034]

[Table 2]

Comparative Example 5 When silicone rubber X-30-1293 [trade name of Shin-Etsu Chemical Co., Ltd.] was dipped in toluene, this product swelled significantly in about 1 hour.

Comparative Example 6 Urethane foam Polon (trade name, manufactured by Inoue MTP Co., Ltd.) was left at 200 ° C. for 4 hours, but it was significantly deformed and the original shape could not be maintained.

[0037]

INDUSTRIAL APPLICABILITY The present invention relates to a liquid expandable fluororubber composition, which comprises a peroxide-crosslinking fluororubber composition containing 0.1 to 30 parts by weight of a foaming agent. It is characterized by being dissolved in an organic solvent and liquefied, but since this is a liquid, it has a wide processing range, and because it is a peroxide crosslinked type, it has good storage stability. In addition, it is not necessary to completely remove the solvent during the cross-linking process, and the foam obtained by foaming and cross-linking it is a closed cell and can be molded without surface feeling tackiness. ,chemical resistance,
Since it will be excellent in flame retardancy,
It has an industrial advantage that it is useful as an electric / electronic component, a sealing member for building materials, a cushioning agent, and the like.

Claims (1)

(57) Reference number P031022 [Claims] 1. A liquid expandable fluororubber comprising a peroxide-crosslinked fluororubber composition blended with 0.1 to 30% by weight of a foaming agent and dissolved in an organic solvent to form a liquid. Composition.