JP2862200B2 - Foamable fluoro rubber composition and fluoro rubber foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a foamable fluororubber composition, in particular, having excellent heat resistance, chemical resistance and mechanical strength. The present invention relates to an expandable fluororubber composition for producing a fluororubber foam used in the field, and a fluororubber foam molded therefrom by normal-pressure hot air vulcanization.

[0002]

2. Description of the Related Art Polyurethane foams have been widely used in various fields as a typical example of plastic foams, but have the disadvantage of poor heat resistance and chemical resistance. For this reason, silicone rubber foams having excellent heat resistance have been industrialized, but this has the disadvantage that it expands with most organic solvents. Therefore, the heat resistance of this foam,
Fluororubber foam sponged from fluororubber with excellent chemical resistance has also been proposed, but this fluororubber has poor processability, is expensive, and it is impossible to obtain molded products with a hardness of 50 or less. Therefore, expandable fluororubbers having reduced hardness and reduced cost per unit volume have been industrialized.

[0003]

However, there are amine-based and polyol-based crosslinked forms of this fluororubber besides peroxide crosslinking, but these crosslinked forms include alkaline substances such as magnesium oxide and calcium hydroxide. However, these have an adverse effect on the stability of the foaming agent, and have the disadvantage that the amine-crosslinked fluororubber composition itself is inferior in storage stability in the amine type.

On the other hand, in the case of this polyol type compound, it is necessary to incorporate an onium salt or an iminium salt as a crosslinking accelerator which acts as a catalyst together with the polyol crosslinking agent, and these compounds are required to interact with the blowing agent. There is a disadvantage of deteriorating the stability of the fluororubber composition. For this reason, this foamable fluororubber composition is generally used in a peroxide-crosslinking type, but the crosslinking in the peroxide-crosslinking type is insufficient due to insufficient pressure during molding. And the formation of a skin layer becomes difficult, and this is also caused by hot-air vulcanization under normal pressure (abbreviated as HAV).
There is a drawback that foaming and formation of a stable skin layer cannot be performed by the cross-linking by the method.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a foamable fluororubber composition and a foam which solve the above disadvantages and drawbacks. The foamable fluororubber composition comprises 100 parts by weight of a polyol crosslinked fluororubber. Polyol crosslinking agent in which at least one OH group in one molecule is silylated
0.1 to 10 parts by weight of an acid acceptor, 1 to 20 parts by weight of a catalyst, 0.1 to 10 parts by weight of a catalyst and 3 to 20 parts by weight of a foaming agent. The rubber composition is formed by foaming by hot air vulcanization under normal pressure.

That is, the present inventors have conducted various studies to develop a foamable fluororubber composition which has good stability, can easily form a surface skin layer, and can be crosslinked with HAV. In a known foamable fluororubber composition comprising a rubber, a polyol crosslinker, an acid acceptor, a catalyst and a foaming agent, a polyhydroxy aromatic compound or a fluorinated polyaliphatic compound as a polyol crosslinker used herein is used. If at least one of the OH groups in the molecule is silylated, this composition does not adversely affect the stability of the foaming agent even if an alkaline compound such as magnesium oxide or calcium hydroxide is added as an acid acceptor, Even if a catalyst such as an onium salt or an iminium salt is added, the stability of the composition does not deteriorate, and the formation of the surface skin layer becomes easy. , Further not only die molding HA
The present inventors have found that V-crosslinking can be performed, and have advanced the research on the mixing ratio of each component used here, thereby completing the present invention. This is described in more detail below.

[0007]

The present invention relates to a foamable fluororubber composition and a fluororubber foam. The foamable fluororubber composition is, as described above, a polyol-crosslinked fluororubber.
00 parts by weight, 0.1 to 10 parts by weight of a polyol crosslinking agent in which at least one OH group in one molecule is silylated,
20 parts by weight, 0.1 to 10 parts by weight of a catalyst, and 3 to 20 parts by weight of a foaming agent.
Although it is characterized by being crosslinked, this foamable fluororubber composition has high stability, it is easy to form a surface skin layer, and it is possible not only to mold but also to crosslink HAV. This fluororubber foam has the advantage of good cell uniformity and no pinholes or wrinkles in the skin layer.

The foamable fluororubber composition of the present invention comprises a polyol crosslinked fluororubber, a polyol crosslinker, an acid acceptor, a catalyst and a foaming agent. The polyol crosslinked fluororubber is highly fluorinated. Elastic copolymer of vinylidene fluoride and hexafluoropropene, vinylidene fluoride and tetrafluoroethylene, pentafluoropropene,
Elastic copolymers with one or more of trifluoroethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether) and the like are exemplified, and among these, vinylidene fluoride-hexaene is exemplified. Fluoropropene binary elastic copolymers and vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary elastic copolymers are preferred.

The polyol crosslinking agent used in the present invention has at least one OH group in one molecule silylated as described above. The silylated polyol crosslinking agent may be a polyhydroxy aromatic compound or a fluorinated polyaliphatic compound, including bisphenol A, bisphenol B, bisphenol AF,
3,5-trihydroxybenzene, hydroxyresorcin, 2-t-butylhydroquinone, 2-methylresorcin, 1,5-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2, -bis (4-hydroxyphenyl) butane , 3,3,5,5-tetrachlorobisphenol A, 4,4-dihydroxydiphenyl, CF ₂ (CF
₂ CH ₂ OH) ₂ , HOCH ₂ (CF ₂ ) ₄ OCF (CF ₃ ) CH ₂ OH, CF ₂ (CFHCF ₂ CH ₂ O
H) ₂ , (CF ₂ ) ₃ (CFHCF ₂ CH ₂ OH) _{2 and the} like are exemplified, and particularly preferred are bisphenol A, bisphenol B, bisphenol AF, hydroquinone and the like.

Since these polyol crosslinking agents are required to have at least one OH group contained in one molecule thereof silylated, they are

Embedded image [R ¹ , R ² , and R ³ are organic groups that do not react with the OH group or organic groups containing silicon, specifically, methyl, ethyl, propyl, phenyl, vinyl, trifluoropropyl, Or a group such as -OSi (CH ₃ ) ₃ , where X is O
-H, -Cl, -OH, -N
HR ⁴ (R ⁴ is an organic group or an organic group containing silicon)].

The preferred silylating agent is hexamethyldisilazane, which can react with a polyhydroxy compound at ordinary temperature to silylate it. Preferably, all the OH groups in the molecule are silylated, but this may be at least one OH group in the molecule silylated. The silylated polyol crosslinking agent is represented by the following formula:

Embedded image

Embedded image

Embedded image

Embedded image (Here the monovalent organic group for R ⁵ is 1 to 10 carbon atoms the same or different, such as methyl group, ethyl group, vinyl group, a methoxy group, group or a hydrogen atom is exemplified by an ethoxy group, R ⁶
Are exemplified by F or H).

The silylated polyol crosslinking agent is preferably represented by the following formula:

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Embedded image

Embedded image

Embedded image

Embedded image

Embedded image (Where R ⁵ is the same or different and is a monovalent organic group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, a vinyl group, a methoxy group, an ethoxy group, or a hydrogen atom, and R ⁶ is F or H) The ones shown are preferred.

When the amount of the silylated polyol crosslinking agent is 0.1 parts by weight or less based on 100 parts by weight of the polyol-crosslinked fluororubber, the fluororubber produced from this composition has poor mechanical physical properties. However, the addition of more than 10 parts by weight does not give further superiority in physical properties to the produced fluororubber, and rather causes the danger of bleeding.Therefore, it is necessary to set this in the range of 0.1 to 10% by weight. However, the preferred range is 0.5 to 5 parts by weight. Since the polyol cross-linking agent is silylated by the above-described method, the stability of the foaming agent described below is not affected even if an acid acceptor described below is added to the foamable fluororubber composition to which the polyol crosslinking agent is added. This gives the advantage that the surface skin layer can be easily formed and HAV crosslinking can be performed.

Next, the acid acceptor constituting the foamable fluororubber composition may be a known acid acceptor, such as magnesium oxide, calcium oxide, lead oxide, calcium hydroxide, barium stearate, sodium stearate and the like. These may be exemplified, and may be blended alone or in combination of two or more. However, the addition amount may be 1 to 20 parts by weight based on 100 parts by weight of the polyol cross-linked fluororubber.

Further, it is necessary to add a catalyst which acts as a crosslinking accelerator for the foamable fluororubber composition to the foamable rubber composition, and the catalyst may be a known one.

Embedded image Wherein R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are monovalent hydrocarbon groups having 1 to 20 carbon atoms, Z is P or N, and Y is a halogen atom, or a compound represented by the general formula (R ¹¹ ) _{3 P = N = P (R} 12) 3 + Y - ( wherein the R ^11, R ¹² is a monovalent hydrocarbon group having 1 to 20 carbon atoms,
Y may be an onium salt or an iminium salt represented by the following formula: benzyltriphenylphosphonium chloride or bromide as the onium salt, and bisbenzyldiphenylphosphineiminium chloride as the iminium salt. The addition amount is based on 100 parts by weight of the polyol crosslinked fluororubber
The amount may be 0.1 to 10 parts by weight, preferably 0.2 to 3 parts by weight.

Further, in order to make the foamable fluororubber composition foamable, it is necessary to add a foaming agent. However, this is an organic foaming agent because of the stability of cells. These include well-known N, N-dimethyl-N, N-dinitrosoterephthalamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, azodicarbonamide, paratoluenesulfonylhydrazide, P, P-oxy Bisbenzenesulfonyl hydrazide, paratoluenesulfonyl semicarbazide, trihydrazinotriazine, etc. are exemplified.In order to adjust the decomposition temperature, urea-based, organic acid-based, even if a metal salt-based auxiliary is added Alternatively, an organic foaming agent containing a foaming aid and having a controlled foaming temperature may be used. In addition,
The amount of the foaming agent was 100
When the amount is less than 3 parts by weight, the amount is too small to stabilize foaming, and when the amount is more than 20 parts by weight, crosslinking inhibition occurs in the fluororubber composition. The preferred range is 5 to 15 parts by weight.

The foamable fluororubber composition of the present invention comprises the above polyol crosslinked fluororubber, a polyol crosslinker in which at least one OH group in one molecule is silylated, an acid acceptor, a catalyst and a foaming agent. A fixed amount can be obtained by mixing and uniformly kneading them using a two-roll for rubber, a kneader, a pressure kneader, a Banbury mixer, and the like, which includes silica, carbon black, alumina as a filler, Bengala, clay, calcium carbonate, titanium oxide, polytetrafluoroethylene powder, various conductive fillers, various heat dissipating fillers, etc. may be added, but from the viewpoint of reinforcing properties, this filler is silica or carbon black. It is preferable that MT carbon black is particularly preferable, but the present invention aims at sponge formation. The amount of Rukoto is desirably small, so this may be a 30 parts by weight or less.

The foamable fluororubber composition of the present invention thus produced has excellent storage stability since at least one OH group in one molecule of the polyol crosslinking agent is silylated. However, a molding device for obtaining a fluororubber foam from this may be any conventionally used rubber processing machine, such as mold molding by a rubber press, HAV by a calender roll and an extruder, and the like. Molding by steam cross-linking is exemplified, but these can be easily processed without using a special device because of good workability in each case.

[0019]

EXAMPLES Examples of the present invention and comparative examples will now be described.
The polyol-crosslinked fluororubber 1 used in the examples is a vinylidene fluoride-hexafluoropropene binary copolymer FC2260 [trade name of Sumitomo 3M Ltd.],
The polyol cross-linked fluororubber 2 is a vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer / FC2650 [trade name of Sumitomo 3M Ltd.], and the polyol cross-linking agent is bisphenol AF.
(Manufactured by Riedel-dehaen), the silylating agent is hexamethylsilazane LS-7150 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.),
The acid acceptor is magnesium oxide / Kyomag 150 # (trade name, manufactured by Kyowa Chemical Co., Ltd.), calcium hydroxide [reagent, manufactured by Kanto Chemical Co., Ltd.], and the catalyst (crosslinking accelerator) is benzylphenylphosphonium chloride [Kanto Chemical Reagent], foaming agent CELLMIC CAP 250 [trade name, manufactured by Sankyo Co., Ltd.], carbon black: THERMAX MT [trade name, manufactured by Harbor Co., Ltd.], peroxide: Perhexa 25B [Nippon Yushi Co., Ltd. Trade name], the cross-linking agent is TAIC [Nippon Kasei Co., Ltd.
Product Name].

Example 1 33.6 g (0.1 mol) of bisphenol AF was added to a solution obtained by adding 10 g of toluene to 19.3 g (0.12 mol) of a silylating agent, and the mixture was stirred. Bisphenol AF generated powder
Was observed. It is presumed that hexamethylsilazane, a silylating agent, was decomposed to generate ammonia and silylated the OH group of bisphenol AF. However, after dissolution was completed, the pressure was reduced to remove the toluene and volatile components. Was analyzed by FT-TR.
The chart shown in FIG. 3 was obtained, and the absorption of OH groups was not measured.
Was confirmed to be silylated.

Then, using the silylated bisphenol AF as a cross-linking agent (treated cross-linking agent), the formulations shown in Table 1 were prepared. After preform molding into a 2 mm thick sheet at ℃ 3 minutes, this preform sheet is
When molded with a 4 mm-thick sheet mold under the conditions of ° C × 20 minutes, a uniform cell molded product having a good skin layer can be obtained. The hardness, specific gravity, and other physical properties are shown in Table 1.
Was shown. In addition, this preform sheet
When left in a dryer at 150 ° C. for 60 minutes, there was slight variation in thickness, but a sponge molded product having a good skin layer could be obtained. Further, the composition was left at 80 ° C. for 4 hours. Since there was no change in the molded product even in the subsequent molding, it was confirmed that the composition was excellent in storage stability. Also, this composition is
After forming a preform having a thickness of 2 mm in 3 minutes and leaving it in an oven at 150 ° C. for 10 minutes, a sponge molded product was obtained. Had no pinholes and few wrinkles.

[0022]

[Table 1]

Example 2 Using polyol-crosslinked fluororubber 2, the amount of the foaming agent was increased to 15 parts by weight and the amount of the treated crosslinking agent was reduced to 1.4 parts by weight, as shown in Table 1. When molding was performed under the same conditions as in the above, a good molded product could be obtained although the cells were slightly larger.

Example 3 The amount of the foaming agent was reduced to 5 parts by weight as shown in Table 1 using the polyol-crosslinked fluororubber 1, but the amount of the treated crosslinking agent was increased to 5.6 parts by weight. 2 in the same manner as in Example 1
When I made a preform sheet by mold molding with a thickness of mm,
Since the thickness was non-uniform, the preform sheet was molded with a thickness of 3 mm, and the same results as in Example 1 were obtained except that the cells became finer and the specific gravity increased.

COMPARATIVE EXAMPLE 1 A mixture having the same composition as in Example 1 was kneaded except that the treated crosslinker silylated with hexamethyldisilazane in Example 1 was changed to an untreated crosslinker that was not silylated. When molding was performed under the same conditions, a sponge-like molded body was obtained. However, as shown in Table 1, the uniformity of the cells was poor, and the formation of the skin layer was insufficient. The product obtained by leaving the product in a dryer at 80 ° C. for 4 hours and then sponge-molding has increased non-uniformity of foam and poor skin layer formation, and has uneven surface and poor storage stability. Had become something.

Comparative Example 2 The same composition as in Example 1 was used except that the amount of the blowing agent in Example 1 was increased to 25 parts by weight, and molding was performed under the same conditions as in Example 1. As shown in Table 1, it was in an uncrosslinked state due to crosslinking inhibition, and the formation of the skin layer was insufficient, and a satisfactory molded product was not obtained.

Comparative Example 3 The blending amounts of the polyol cross-linked fluororubber 1, the foaming agent and the carbon black were the same as those in Example 1, except that no acid acceptor and no catalyst were added and the peroxide and the crosslinking aid were added. Table 1
When blended as above and crosslinked with peroxide and molded,
As shown in Table 1, in this molded product, it was difficult to form a stable skin layer, and the cells were also non-uniform. For this composition, a sponge was molded by hot air vulcanization under normal pressure as in Example 1. However, although a molded product was obtained, it was confirmed that the cells were non-uniform, the skin layer had many wrinkles, and there were tears at several places.

[0028]

The present invention relates to a foamable fluororubber composition, which comprises 100 parts by weight of a polyol-crosslinked fluororubber as described above, and a polyol crosslinked having at least one silylated OH group in the molecule. 0.1 to 10 parts by weight of an acid acceptor, 1 to 20 parts by weight of an acid acceptor, 0.1 to 10 parts by weight of a catalyst, and 3 to 20 parts by weight of a foaming agent. Since at least one of the OH groups is assumed to be silylated, the stabilization of the foaming agent by the addition of an acid acceptor, the stability of this composition does not deteriorate, and the molded product obtained by molding The surface skin layer is easily formed.
The advantage is given that AV cross-linking is also possible.

[Brief description of the drawings]

FIG. 1 shows an FT-IR chart of silylated bisphenol AF obtained by silylating bisphenol AF as a polyol crosslinking agent produced in Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08J 9/00-9/42 C08L 15/00-15 / 02,27 / 12-27/20

Claims (2)

(57) [Claims] (1) 100 parts by weight of a polyol cross-linked fluororubber,
0.1 to 10 parts by weight of a polyol crosslinking agent in which at least one OH group in one molecule is silylated, 1 to 20 parts by weight of an acid acceptor,
A foamable fluororubber composition comprising 0.1 to 10 parts by weight of a catalyst and 3 to 20 parts by weight of a blowing agent. 2. A fluororubber foam obtained by foaming the foamable fluororubber composition according to claim 1 by hot air vulcanization under normal pressure.