JPH05155943A - Production of fluororubber - Google Patents

Abstract

PURPOSE:To provide the subject process whereby the vulcanizability of a fluororubber in polyol vulcanization can be improved because an organic onium compound which has been heretofore easily available but little effective as a polyol vulcanization accelerator can be used, and a heretofore usable organic onium compound is effective even when used in a markedly reduced amount. CONSTITUTION:The objective process comprises the step of mixing and dispersing an organic onium compound in a polymerization reaction solution of a fluororubber comprising vinylidene fluoride, tetrafluoroethylene and propylene.

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 fluororubber, and more particularly to a method for producing fluororubber having improved vulcanizability.

[0002]

2. Description of the Related Art A fluororubber obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene and propylene is a conventional vinylidene fluoride and hexahexene compound in a polyol vulcanization formulation using a combination of a polyhydroxy compound and a vulcanization accelerator. The vulcanizability was poor as compared with the copolymerized fluororubber made of fluoropropylene. Several methods are known as means for solving this problem (Japanese Patent Publication No. 1-15530, Japanese Patent Laid-Open No. 1-29986).
0).

Japanese Patent Publication No. 15530/1989 describes a method of introducing an unsaturated group by acting an aqueous alkali solution containing an onium compound in the state of an aqueous dispersion, and JP-A-1-299860 discloses a method. A method of kneading (that is, dry mixing) an onium compound and a polyhydroxy compound with a fluoroelastomer gum is described.

However, in practice, onium compounds that can be used as vulcanization accelerators are not always readily available by these methods, and it is necessary to use a large amount of onium compounds in order to obtain a sufficient vulcanization rate. However, there is a problem that the vulcanization rate is difficult to stabilize because the dispersibility of the onium compound is not good when the onium compound is mixed with the fluororubber.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the prior art as described above, and is a method for producing a fluororubber comprising vinylidene fluoride, tetrafluoroethylene and propylene, which is excellent in vulcanizability. It is intended to provide.

[0006]

The present invention comprises a step of mixing and dispersing an organic onium compound in a polymerization reaction liquid of an elastic copolymer obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene and propylene. The present invention provides a method for producing a fluororubber containing the same.

The elastic copolymer obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene and propylene in the present invention is obtained by a conventionally known polymerization method of fluororubber, and the copolymerization ratio thereof is Vinylidene, tetrafluoroethylene, and propylene having a content of 10 to 70, 20 to 60, and 20 to 50 mol% respectively are vulcanizates, rubber properties of vulcanized rubber, mechanical properties, engine oil resistance, etc. Is preferred.

The polymerization method is not particularly limited, but a method of producing a copolymer in an aqueous medium by a method such as emulsion polymerization or suspension polymerization and using the latex or the aqueous dispersion obtained there as it is is a stepwise process. It is advantageous. For these polymerizations, a catalytic polymerization method using a free radical initiator,
Ionizing radiation polymerization method, redox polymerization method and the like can be appropriately adopted.

The organic onium compound used in the present invention is an essential component for accelerating the polyol vulcanization of fluororubber, and includes phosphonium, arsonium and sulfonium, including ammonium compounds in which the central element of the cation is nitrogen. Various compounds such as oxonium, selenonium, stanonium, and iodonium compounds can be adopted, but quaternary ammonium compounds and quaternary phosphonium compounds are preferable from the viewpoint of availability.

Such suitable compounds include tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride, tributylallylphosphonium chloride, tributylallylphosphonium bromide, tributyl (2- Methoxypropyl) phosphonium chloride,
Benzyltributylphosphonium chloride, benzyltrioctylphosphonium bromide, 8-methyl-1,8
-Diaza-bicyclo (5,4,0) -7-undecenium chloride, 8-ethyl-1,8-diaza-bicyclo (5,4,0) -7-undecenium bromide, 8-benzyl-1 , 8-diaza-bicyclo (5,4,0) -7
-Undecenium chloride, 1,8-diaza-bicyclo (5,4,0) undecene-7 p-toluenesulfonate, 1,8-diaza-bicyclo (5,4,0) -undecene octyl acid Salt and the like. These may be used alone or as a mixture of two or more.

By mixing the organic onium compound in the polymerization reaction liquid, the organic onium compound can be uniformly dispersed in the fluororubber. The amount of the organic onium compound used is determined according to its molecular weight and vulcanization reactivity and is not particularly limited, but is 0.01 to 20 parts by weight, preferably 0.1 to 1 part by weight per 100 parts by weight of the fluororubber.
Used in the range of 0 parts by weight. As a result, it becomes possible to use a compound that has little effect as a conventional vulcanization accelerator, or it is possible to significantly reduce the compounding amount of a conventional vulcanization accelerator.

Further, when the organic onium compound is mixed in the polymerization reaction liquid, alkali should not be present together. When an alkali is allowed to coexist, the method is the same as that disclosed in Japanese Patent Publication No. 15530, and an unsaturated group is introduced into the elastic copolymer. In this case, as described in the section of the prior art, vulcanization becomes insufficient when the usual vulcanization compounding is performed.

The fluororubber obtained by the present invention is mixed with an organic onium compound in a polymerization reaction solution and then subjected to a usual treatment (for example, when the polymerization reaction solution is an emulsion, it is agglomerated with sodium chloride and then dried. )) To obtain raw rubber, which can be vulcanized by mixing a polyhydroxy compound and an acid acceptor.

As the polyhydroxy aromatic compound,
2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) perfluoropropane [bisphenol AF],
Examples thereof include hydroquinone, catechol, resorcin, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) butane, and preferably bisphenol A, bisphenol AF, hydroquinone and the like. These may also be in the form of alkali metal salts or alkaline earth metal salts. These polyhydroxy aromatic compounds are used in an amount of 0.5 to 10 parts by weight, preferably 0.5 to 6 parts by weight, based on 100 parts by weight of the fluororubber.

As the acid acceptor, a metal oxide or a metal hydroxide is generally used, and examples thereof include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide and zinc oxide.

Of these, magnesium oxide and calcium hydroxide are preferably used. These can be used alone or in combination of two or more, and fluororubber 100
It is used in the range of 2 to 25 parts by weight.

The fluororubber obtained according to the present invention includes reinforcing agents such as carbon black, fine silica, clay and talc, which are usually used in the production of conventional vulcanized rubber, other fillers, pigments, antioxidants, You may add and mix a stabilizer etc.

In producing the fluororubber composition obtained by the present invention, it is desirable to uniformly mix the fluororubber, the polyhydroxy aromatic compound, the acid acceptor and, if necessary, other additives. Such mixing can be performed by a rubber kneading roll, Banbury mixer, or the like which has been conventionally used. The working conditions during mixing are not particularly limited, but the additive composition can be sufficiently dispersed and mixed in the fluororubber by kneading at a temperature of about 30 to 80 ° C. for about 10 to 60 minutes.

It is also possible to appropriately dissolve and disperse the additive formulation in a solvent to prepare a suspension solution. Furthermore, so-called wet mixing in which the mixing is performed in the medium from the beginning is also possible. In such a case, a solution-form compound can be obtained by using a mixer such as a roll, a ball mill and a homogenizer. In addition, it is desirable that the working conditions and operations during the mixing are performed by selecting the optimum conditions according to the kinds of the raw materials used and the compounding agents and the purpose.

The fluororubber composition obtained by the present invention can be formed into a sheet, a pipe, a rod or a tube by a continuous compression molding method such as injection molding, extrusion molding, transfer molding, roll coating, brush coating or impregnation in addition to ordinary compression molding. It can be molded into molded products such as angle, channel, draped cloth and coated plate, and can be molded into other shaped products and special molded products such as sponge rubber by various molding methods. .. The composition of the fluororubber obtained by the present invention which has been molded and processed in this manner is appropriately vulcanized by a vulcanizing means as described below to obtain a vulcanized rubber product.

As an operation for vulcanization, an operation usually used conventionally can be adopted. For example, an operation of heating while pressurizing in a mold may be adopted, and an operation of extruding, molding with a calender roll and the like and then heating in a heating furnace or a steam pot may be adopted. Regarding the working conditions during heating, it is desirable to select the optimum conditions according to the raw materials used and the composition. The temperature during vulcanization is usually about 80 to 250 ° C, preferably about 120 to 200 ° C.
The heating time is not particularly limited, but is in the range of 1 minute to 3 hours, preferably 5 minutes to, depending on the combination of the polyhydroxy aromatic compound and the organic onium compound.
It is selected within the range of 2 hours. If you raise the heating temperature,
The heating time can be shortened. Reheat treatment of the obtained vulcanized product can also be adopted, which is useful for improving physical properties. For example, 150 to 300 ° C, preferably 180
A reheat treatment at a temperature of ~ 250 ° C for about 2 to 25 hours may be employed.

[0022]

In the present invention, the mixing of the organic onium compound in the polymerization reaction liquid generally means that the organic onium compound is soluble in water or an organic solvent, and the polymerization reaction liquid, especially the aqueous solution after emulsion polymerization or suspension polymerization Since it is easily uniformly dissolved in the dispersion liquid and has a high affinity for organic substances, it is considered that the vulcanization in the polyol vulcanization is remarkably improved by being easily dispersed in the fluororubber.

[0023]

EXAMPLES Next, the present invention will be explained by examples. In the examples, "parts" means "parts by weight". In addition, in the following examples and comparative examples, the vulcanizability and vulcanizate properties of the compositions were measured as follows. (1) Vulcanization characteristics A vulcanization curve was measured with a Monsanto Rheometer ODR 2000 model, and based on this, the minimum torque TRm.
In, maximum torque TRmax, effective torque ΔTR, vulcanization start time T10, and effective vulcanization time T90 were calculated. (2) Physical properties of vulcanized sheet 2 mm thick sheet using vulcanized composition, pressure 100 kg / c
After molding and vulcanization under conditions of m ² G and temperature of 170 ° C for 20 minutes
Secondary vulcanization was performed at 30 ° C. for 24 hours, and the measurement was performed according to JIS K6301.

Example 1 The copolymerization ratio of vinylidene fluoride / tetrafluoroethylene / propylene was 35/40/25 by the emulsion polymerization method.
A latex containing 30% by weight of fluororubber (molar ratio) was produced. To 1 kg of this latex, 2 g of tetrabutylammonium bromide was dissolved in 5 g of water and added, and the mixture was mixed for 3 minutes. This was coagulated with sodium chloride and then dried to obtain raw rubber.

With respect to 100 parts of the raw rubber obtained here,
Bisphenol AF 2 parts, Kyowamag 150 (manufactured by Kyowa Chemical Industry Co., Ltd., magnesium oxide) 3 parts, hydroxide hydroxide carbit (Omi Chemical Co., Ltd., calcium hydroxide) 6 parts,
30 parts of MT carbon was kneaded with a double roll to obtain a vulcanizing composition. The vulcanization characteristics and vulcanization physical properties of this are shown in Table 1.

Comparative Example 1 The latex used in Example 1 was coagulated with sodium chloride and dried to obtain raw rubber. To 100 parts of this raw rubber, 2 parts of bisphenol AF, 5 parts of tetrabutylammonium bromide, 3 parts of Kyowamag 150, 6 parts of carbite and 30 parts of MT carbon were kneaded with a two-roll mill to obtain a vulcanizing composition. The vulcanizability of this composition is shown in Table 1. However, the vulcanization was slow and it was not suitable for practical use.

Comparative Examples 2 and 3 Japanese Patent Publication No. 1-155301 for the latex used in Example 1.
An unsaturated bond was introduced using tetrabutylammonium bromide and sodium hydroxide by the method described in 1. to obtain a raw rubber. To 100 parts of this raw rubber, 2 parts of bisphenol AF, 2 parts of tetrabutylammonium bromide,
3 parts of Kyowamag 150, 6 parts of carbite, and 30 parts of MT carbon were kneaded by a two-roll mill to obtain a vulcanizing composition. The vulcanization characteristics of this composition are shown in Table 1, but the vulcanization was insufficient and it was not suitable for practical use. Also,
A vulcanizing composition was obtained in exactly the same manner except that the amount of tetrabutylammonium bromide was 5 parts. The vulcanization characteristics and vulcanization physical properties of this composition were good.

Example 2 A vulcanizing composition was obtained in the same manner as in Example 1 except that 4 g of triphenylbenzylphosphonium chloride was used instead of 2 g of tetrabutylammonium bromide. The vulcanization characteristics and vulcanization properties are shown in Table 1.

Comparative Example 4 A vulcanizing composition was obtained in the same manner as in Comparative Example 1, except that 7 parts of triphenylbenzylphosphonium chloride was used instead of 5 parts of tetrabutylammonium bromide. The vulcanization characteristics of this composition are shown in Table 1, but they were hardly vulcanized and were not suitable for practical use.

Examples 3 and 4 Instead of using tetrabutylammonium bromide in Example 1, tetrabutylphosphonium chloride or 8-
Methyl-1,8-diaza-bicyclo (5,4,0) -7
A vulcanizing composition was obtained in exactly the same manner except that undecenium chloride was used. The vulcanization characteristics and vulcanization physical properties are shown in Table 1.

[0031]

[Table 1]

In Table 1, TBAB is tetrabutylammonium bromide, TPBPCl is triphenylbenzylphosphonium chloride, TBPCl is tetrabutylphosphonium chloride, and DBU is 8-methyl-1,8-.
It is diaza-bicyclo (5,4,0) -7-undecenium chloride.

[0033]

INDUSTRIAL APPLICABILITY The present invention remarkably improves the vulcanizability of a fluororubber composed of vinylidene fluoride, tetrafluoroethylene and propylene, which is excellent in engine oil resistance, in a polyol vulcanization formulation. It is also extremely economically useful. Further, the fluororubber obtained by the present invention is a crankshaft seal for automobile parts, an O-ring around an engine, a gasket, a tube, etc. based on excellent vulcanization physical properties such as heat resistance, engine oil resistance and chemical resistance. Gaskets and tubes around radiators, heat exchange gaskets for food and chemical plants,
It is useful in a wide range of applications such as diaphragms, gaskets, and sealing materials.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Saito 3-474-2 Tsukakoshi, Saiwai-ku, Kawasaki-shi, Kanagawa Asahi Glass Co., Ltd. Tamagawa branch room

Claims (3)

[Claims] 1. A method for producing a fluororubber, which comprises a step of mixing and dispersing an organic onium compound in a polymerization reaction liquid of an elastic copolymer obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene and propylene. 2. The method for producing a fluororubber according to claim 1, wherein the organic onium compound is a quaternary ammonium salt or a quaternary phosphonium salt. 3. The method for producing a fluororubber according to claim 1, wherein the copolymerization method is emulsion polymerization or suspension polymerization.