JP2847852B2 - Fluoro rubber vulcanizing composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composition for vulcanizing fluororubber.

[Prior art] A copolymer obtained by copolymerizing vinylidene fluoride, propylene and ethylene tetrafluoride, which are fluorine-containing elastomers having excellent engine oil resistance and chemical resistance, can be prepared by various polymerization methods such as emulsion polymerization and solution polymerization. It is known that it is produced by an appropriate means such as a radiation polymerization method and a redox catalyst polymerization method (for example, Japanese Patent Publication Nos. 60-19324 and 60-19325).

Further, as a polymerization initiator, a fluorine-containing catalyst comprising a redox catalyst comprising (1) water-soluble persulfate, (2) water-soluble iron salt, (3) hydroxymethanesulfinate and (4) ethylenediaminetetraacetic acid or a salt thereof. A method for producing a polymer is known (for example, JP-B-61-8806). Examples of the composition for vulcanizing a polyol of fluororubber include a) an elastic copolymer containing vinylidene fluoride, b) a hydroxide and / or oxide of a divalent metal, c) a polyhydroxy aromatic compound and d) 1,8
Combinations of diaza-bicyclo [5.4.0] undecene-7 with vulcanization accelerators such as inorganic and organic acid salts, quaternary ammonium salts, and quaternary phosphonium salts are known (eg, Kaisho 47-191, JP-B 52-38072).

[Problems to be Solved by the Invention] A fluororubber vulcanizing composition using a polyhydroxyaromatic compound as a vulcanizing agent using a fluorinated elastic copolymer obtained by a method of the prior art has a problem that Large variations in vulcanizability occurred. Furthermore, when each composition is examined, there has been a problem that variations occur between production lots of the fluorine-containing elastic copolymer, and it is difficult to obtain reproducibility of polyol vulcanization.

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, that is, a fluororubber exhibiting stable and excellent vulcanizability and excellent vulcanizate properties. It is intended to provide a composition for vulcanization, a) a copolymer obtained by copolymerizing vinylidene fluoride, propylene and ethylene tetrafluoride, having a heat of fusion of 0.3 J b) hydroxides and / or oxides of divalent metals, c) polyhydroxyaromatic compounds or alkali metal or alkaline earth metal salts thereof, and d) It is intended to provide a fluororubber vulcanizing composition comprising a sulfur accelerator.

The a) fluorine-containing elastic copolymer of the present invention is preferably one obtained by copolymerizing vinylidene fluoride, propylene and ethylene tetrafluoride at a reaction molar ratio of 10 to 60/20 to 50/20 to 60, respectively.
In particular, when the reaction molar ratio of vinylidene fluoride / propylene / ethylene tetrafluoride is from 20 to 50/20 to 40/30 to 50, good results with excellent engine oil resistance and cold resistance can be obtained. If the amount of vinylidene fluoride is too small, the effect of improving cold resistance becomes insufficient, while if the amount is too large, the resistance to engine oil and polar solvents is impaired. If the propylene content is too low, the rubber elasticity of the copolymer is lost.

The fluorinated elastic copolymer has a heat of fusion at the melting peak of 0.3 J / g or less in a thermometric analysis. The heat of fusion of the melting peak in the thermal quantitative analysis is the measurement result of the melting peak generated at 100 to 150 ° C., and DSC7 manufactured by Perkin Elmer Co., Ltd.
It is measured using a mold at a sample amount of 10 mg and a heating rate of 10 ° C./min. In particular, a copolymer having a heat of fusion of 0.1 (J / g) or less provides high polyol vulcanizability and excellent reproducibility of polyol vulcanizability.

On the other hand, methods for producing a copolymer of vinylidene fluoride, propylene and ethylene tetrafluoride having a heat of fusion of 0.3 J / g or less include emulsion polymerization, solution polymerization, radiation polymerization, and redox catalyst system. Although various polymerization methods such as polymerization can be adopted, it is important that, at the end of the polymerization, the operation of stopping the polymerization such as stopping the supply of the monomer and collecting the monomer be performed after the activity of the polymerization catalyst is sufficiently reduced. Well-known methods of lowering the polymerization catalyst activity include lowering the polymerization temperature and adding a polymerization terminator. However, dimethyldithiocarbamate as a terminator is not preferable because it has a bad influence on the polyol vulcanizability. On the other hand, a method of decreasing the polymerization catalyst activity by stopping the supply of one of the reducing agent or the oxidizing agent in the oxidation-reduction catalyst system is preferably used.
Particularly, in a redox catalyst system comprising (1) a water-soluble persulfate, (2) a water-soluble iron salt, (3) hydroxymethanesulfinate and (4) ethylenediaminetetraacetic acid, a hydroxymethanesulfinate as a reducing agent Is preferably used.

b) Examples of the hydroxide and / or oxide of the divalent metal include hydroxides and oxides such as magnesium, calcium, lead, and zinc. The amount of these metal hydroxides and oxides to be used is preferably 1 to 20 parts by weight, particularly preferably 2 to 10 parts by weight, per 100 parts by weight of the fluorinated elastic copolymer.

c) As polyhydroxy aromatic compounds, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) perfluoropropane [bisphenol AF], hydroquinone, catechol, Resorcin, 4,4'-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) butane and the like can be mentioned, and preferably, bisphenol A, bisphenol AF, hydroquinone and the like are used. They may also be in the form of alkali metal salts or alkaline earth metal salts. The amount of these porin hydroxy aromatic compounds or salts thereof is preferably 0.5 to 10 parts by weight, particularly preferably 0.5 to 6 parts by weight, per 100 parts by weight of the fluorinated elastic copolymer.

d) As a vulcanization accelerator, 1,8-diazabicyclo [5.
4.0] Undesane-7 inorganic and organic acid salts, quaternary ammonium salts and quaternary phosphonium salts can be used. Specifically, 1,8-diazabicyclo [5.4.0] undecene-
Examples of the inorganic or organic acid salt of 7 include 1,8-diazabicyclo [5.4.0] undecene-7 paratoluenesulfonate (U-CAT SA-506) and octylate (U-CAT).
SA-102).

Examples of the quaternary ammonium salt include tetrabutylammonium bromide, tetrabutylammonium chloride, methyltrioctylammonium chloride, benzyltriethylammonium chloride, tetrahexylammonium tetrafluoroborate, 8-ethyl-1,8-diazabicyclo [5.
4.0] Undec-7-enium bromide, 8-benzyl-
1,8-diazabicyclo [5.4.0] undec-7-enium chloride and the like.

Examples of the quaternary phosphonium salt include tetrabutyl phosphonium bromide, tetrabutyl phosphonium chloride, benzyl triphenyl phosphonium bromide, tributyl allyl phosphonium chloride, tributyl allyl phosphonium bromide, benzyl tributyl phosphonium chloride, and benzyl trioctyl phosphonium bromide. .

The amount of these vulcanization accelerators used is the amount of the fluorine-containing elastic copolymer.
It is preferably 0.01 to 20 parts by weight, particularly 0.1 to 10 parts by weight, per 100 parts by weight.

In the composition of the present invention, conventionally in the production of vulcanized rubber,
Reinforcing agents such as carbon black, fine silica, clay and talc, other fillers,
Pigments, antioxidants, stabilizers and the like may be added and blended.

In producing the composition of the present invention, a fluorine-containing elastic copolymer, a polyhydroxy aromatic compound or a salt thereof, a vulcanization accelerator, a hydroxide and / or an oxide of a divalent metal, and if necessary, other Is desirably mixed sufficiently uniformly. Such mixing can be carried out by a rubber kneading roll or a Banbury mixer, which is conventionally ordinarily used. The working conditions at the time of mixing are not particularly limited, but usually by kneading at a temperature of about 30 to 80 ° C. for about 10 to 60 minutes, the added compound can be sufficiently dispersed and mixed in the fluorinated elastic copolymer.

It is also possible to appropriately dissolve and disperse such an additive in a solvent to form a suspension. Further, 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-type compound can be obtained by using a mixer such as a roll, a ball mill, and a homogenizer. It is desirable that the working conditions and operation at the time of mixing be performed by selecting optimum conditions according to the types and purposes of the raw materials and the compounding agents used.

The composition of the present invention can be produced by a continuous molding method such as extrusion, transfer, roll coating, brush coating, impregnation, etc., in addition to ordinary mold molding, by sheet, pipe, rod, tube, angle, channel, drawing cloth, It can be formed into a molded product such as a coated plate, and can also be formed into a deformed product or a special molded product such as a sponge-like rubber by various other forming methods. The composition of the present invention thus formed can be vulcanized by an appropriate vulcanizing means as described below. Thus, a vulcanized rubber product can be obtained from the composition of the present invention.

In the present invention, the operation at the time of vulcanization may employ an operation conventionally used conventionally. For example, an operation of heating while applying pressure in a mold is employed.
After molding by a calender roll or an injection molding method, an operation of heating in a heating furnace or a steam pot may be employed. It is desirable to select the optimal conditions for vulcanization, such as working conditions, depending on the raw materials used and the composition. The temperature at the time of vulcanization is usually about 80 to 250 ° C, preferably about 120 to 200 ° C. The vulcanization time is not particularly limited, but is in the range of 1 minute to 3 hours, and preferably in the range of 5 minutes to 2 hours, depending on the combination of the type of the polyhydroxy aromatic compound and the vulcanization accelerator. Is done. If the heating temperature is increased, the heating time can be shortened. In addition, a reheating treatment of the obtained vulcanized product can also be adopted, which is useful for improving physical properties. For example, 150-300 ° C, preferably 180-2
For example, a reheating treatment at a temperature of 50 ° C. for about 2 to 25 hours may be employed.

[Examples] In the following Examples and Comparative Examples, the polymer properties, vulcanization behavior and vulcanizate properties of the copolymer were measured as follows.

(1) Heat of fusion of melting peak (ΔH) Measured in a temperature range of 50 to 250 ° C at a heating rate of 10 ° C / min using a DSC7 type manufactured by PerkinElmer.

The heat of fusion (ΔH) of the melting peak generated in the range of 110 to 150 ° C. was determined. Sample amount 10mg.

(2) Vulcanization behavior Using a JSR II curameter manufactured by Imanaka Kikai Co., Ltd.
The vulcanization curve was measured at 170 ° C and the minimum torque T
R _min , maximum torque TR _MAX , effective torque ΔTR, vulcanization start time t ₁₀ , and effective vulcanization time t ₉₀ were calculated.

(3) Properties of vulcanized product Using a vulcanizing composition containing various polyol vulcanizing agents, a 1 mm thick sheet and a test piece for measuring compression set were subjected to a pressure of 100 kg / cm ² , a temperature of 170 ° C, and a temperature of 20 minutes. After press-molding vulcanization, secondary vulcanization at 230 ° C. for 24 hours was used as a test specimen for various measurements.

The measurement of tensile strength, elongation, 100% modulus and hardness is based on JIS K 6301, and the measurement of compression set is ASTM-
It measured according to 395-78.

Example 1 A polymerization tank provided with a stirring blade was charged with 370 ml of deoxygenated water, 56 g of t-butanol, 10.8 g of Na ₂ HPO ₄ .12H ₂ O, 2.7 g of sodium lauryl sulfate, and 0.74 g of NaOH. After nitrogen replacement deaeration, a redox catalyst was charged to touch FeSO ₄ · 7H ₂ O, ammonium persulfate, ethylenediaminetetraacetic acid aqueous solution to oxygen. Next, a mixed monomer of ethylene tetrafluoride (TFE) / propylene (P) / vinylidene fluoride (VDF) (molar ratio: 25/5/70) is introduced, and the pressure is adjusted to 23 (kg / cm ² ). After controlling the temperature of the polymerization tank to 25 ° C., the addition of hydroxymethanesulfinate (Rongalit) as a reducing agent is started, and the polymerization reaction is started. When the pressure drops due to the polymerization reaction, TF
E / P / VDF mixed gas (40/25/35 molar ratio) is supplied and the polymerization reaction is continued at a constant pressure. 0.07Nm mixed monomer supply
At the point of ³ , the addition of Rongalite was stopped, but the supply of the mixed monomer was continued. After 60 minutes, the supply of the monomer was stopped and the monomer was recovered.

The latex obtained by the above polymerization reaction was aggregated with NaCl water, washed and dried to obtain 240 g of a copolymer. As a result of a thermal quantitative analysis (DSC) measurement of the copolymer, the heat of fusion (ΔH) of the melting peak around 120 ° C. was 0.020.
(J / g). To 100 parts by weight of the copolymer, 1.5 parts by weight of bisphenol AF, 2 parts by weight of a vulcanization accelerator FX-5166 (manufactured by 3M), 3 parts by weight of MgO ^# 150, 6 parts by weight of carbite, and 30 parts by weight of MT carbon were used. Using a roll, a fluororubber vulcanizing composition for polyol vulcanization was obtained. Table 1 shows the vulcanization behavior and vulcanizate properties of the vulcanizing composition.

(Example 2) In Example 1, the polyol vulcanization compounding formulation was 100 parts by weight of the copolymer, 1.5 parts by weight of bisphenol AF, 0.15 parts by weight of tetrabutylammonium bromide, U-CAT SA-506.
The same operation was performed except that 1 part by weight, 5 parts by weight of MgO ^# 150, 6 parts by weight of carbite, 1 part by weight of sodium stearate and 30 parts by weight of MT carbon were obtained, to obtain a composition for vulcanizing a fluororubber. Table 1 shows the vulcanization behavior and vulcanizate properties of the vulcanizing composition.

(Example-3) In Example-1, 45 g of Rongalit was added.
The same operation was carried out except that the monomer supply was stopped and the monomer was recovered after one minute, and the thermal quantitative analysis, the vulcanization behavior and the properties of the vulcanized product were measured. Table 1 shows the measurement results.

(Comparative Example-1) In Example-1, the introduction amount of the mixed monomer was 0.075N.
Stop adding Rongalit when m ³ is reached.
The same operation was performed except that the monomer supply was stopped and the monomer was recovered after 28 minutes, and the thermal quantitative analysis, the vulcanization behavior and the properties of the vulcanized product were measured. Table 1 shows the measurement results.

(Comparative Example-2) In Comparative Example-1, the polyol vulcanization compounding formulation was 100 parts by weight of the copolymer, 1.5 parts by weight of bisphenol AF, 0.5 part by weight of tetrabutylammonium bromide, and U-CAT SA-5061.
The same operation was performed except that the parts by weight were changed to 5 parts by weight of MgO ^# 150, 5 parts by weight of carbite, 1 part by weight of sodium atearate and 30 parts by weight of MT carbon, and the vulcanization behavior and vulcanizate properties were measured. Was. Table 1 shows the measurement results.

[Effect of the Invention] The fluororubber vulcanizing composition of the present invention provides a vulcanized polyol having excellent vulcanization properties and excellent heat resistance, engine oil resistance and mechanical properties. These vulcanized molded products are useful as seal materials for crankshaft seals, valve stem seals, power steering seals and the like in the automotive field.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification symbol FI C08F 214/18 C08F 214/18 (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 27/12 C08L 23/14 C08K 3/22 C08K 5/13

Claims (1)

(57) [Claims] 1. A) a copolymer comprising vinylidene fluoride, propylene and ethylene tetrafluoride copolymerized, wherein a fluorine-containing elastic copolymer having a heat of fusion at a melting peak of at least 0.3 J / g in a quantitative thermal analysis is obtained. A polymer, b) a hydroxide and / or oxide of a divalent metal, c) a polyhydroxy aromatic compound or an alkali metal or alkaline earth metal salt thereof, and d) a vulcanization accelerator. Fluorine rubber vulcanizing composition.