JPH0692502B2 - Method for producing fluorosilicone-treated silica - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing fluorosilicone-treated silica.

[Conventional technology]

Organopolysiloxane compositions such as silicone rubber, silicone grease, and silicone oil compounds have fluidity control, mechanical strength reinforcement, releasability and adhesion improvement, and compression set, heat resistance and chemical resistance. Silica fine powder is blended for the purpose of improving. Examples of the fine silica powder include fumed silica produced by hydrolyzing a silicon compound in an oxyhydrogen flame, and wet process silica produced by hydrolyzing and neutralizing sodium silicate in water. However, since all of these silica fine powders have a large number of silanol groups on the surface thereof, if they are directly mixed and kneaded in the organopolysiloxane composition,
Pseudo-crosslinking called structuring, creep hardening, etc. occurs during storage, resulting in problems such as a marked decrease in fluidity and consistency of the composition, and an extremely large plasticization reversion in rubber. So, conventionally,
These silica fine powders are preliminarily represented by the formula: R ⁵ ₃ SiCl (in the formula, R ⁵ is a monovalent hydrocarbon group containing no fluorine) or the like, and the formula: (R ⁵ ₃ Si) ₂ NH (In the formula, R ⁵ is the same as above) and the like, and is mixed with organopolysiloxane as treated silica in which silanol groups on the surface are silylated by reacting with silazane compound; silica fine powder and silicone rubber are kneaded Then, when a silazane compound, a dialkylsilanediol, an alkoxysilane or the like is added and reacted at the time of forming a composition, a method of silylating silanol groups on the surface of silica fine powder in the composition is performed. According to such a method, structuring during storage of the resulting organopolysiloxane composition can be prevented.

[Problems to be Solved by the Invention]

However, the organopolysiloxane composition containing fine silica powder in which silanol groups are silylated by the above-mentioned conventional method has insufficient releasability and transparency.

Therefore, an object of the present invention is to provide a method capable of obtaining a novel fluorosilicone-treated silica which can be incorporated into an organopolysiloxane composition such as silicone rubber to improve its releasability and transparency. is there.

[Means for Solving the Problems]

MEANS TO SOLVE THE PROBLEM This invention solves the said subject by making (B) Formula (I): 100 parts by weight of silica fine powder having a specific surface area of 50 m ² / g or more. [Wherein, Rf is a formula: FCqF ₂ qOn (wherein q is an integer of 1 to 3 and n is an integer of 1 to 4)] The number of carbon atoms containing a perfluoroalkyl ether group. 3 to 15 represents a fluorine-containing organic group, and R ¹ is a substituted or unsubstituted 1 having 1 to 10 carbon atoms and containing no fluorine atom.
A valent hydrocarbon group, R ² represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and a is 0, 1 or 2] a silazane compound 1 having a molecular weight of 3000 or less containing a group represented by
To 200 parts by weight and 0 to 50 parts by weight of (C) water are provided.

Examples of the (A) fine silica powder used in the method of the present invention include dry silica such as fumed silica; wet silica. The specific surface area of this fine powder silica is 50 m ² / g or more, preferably 100 m ² / g or more, and in particular, in order to obtain a high tear strength when compounded with silicone rubber, the specific surface area is 200 to 400 m ² / g. Is preferred. When the specific surface area of the silica fine powder used is less than 50 m ² / g, a sufficient reinforcing effect cannot be obtained even if the treated silica obtained in the present invention is blended with the silicone rubber. A specific example of this silica fine powder is Aerosil-13 from Degussa.
0, 200, 300, 380; MS-5 and MS-7 from Cabot Corp .; Nipsyl VN-3, LP, E220, A-330 from Nihon Silica Corp. and the like.

The silazane compound (B) used in the method of the present invention contains a group represented by the above formula (I).
Is a general formula: FCqF ₂ qOn (wherein q is an integer of 1 to 3 and n is an integer of 1 to 4) and has a perfluoroalkyl ether group and has 3 to 15 carbon atoms. Indicates a fluorine-containing organic group, for example, the following formula: (Where n is an integer of 1 to 4) (Here, n is an integer of 1 to 4). As a specific example of this Rf, for example, the following formula: F (CF ₂ CF ₂ CF ₂ O) ₂ CF ₂ CF ₂ CH ₂ O−, CF ₃ CF ₂ O (CF ₂ CF ₂ O) ₂ CF ₂ OCF ₂ CF ₂ O− Can R ¹ has ¹ carbon atom
~ 10 represents a substituted or unsubstituted monovalent hydrocarbon group containing no fluorine atom, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group; a vinyl group, an allyl group, a cyclopentenyl group, a hexenyl group, etc. An aliphatic or alicyclic unsaturated hydrocarbon group; an aromatic hydrocarbon group such as a phenyl group, a tolyl group, and a xylyl group; a substituted hydrocarbon group such as a chloroethyl group, a chloropropyl group, a cyanoethyl group, and a methoxyethyl group. R ² has 2 to 10 carbon atoms, preferably 2 to
8 divalent hydrocarbon groups such as ethylene group, ethylidene group, trimethylene group, phenylethylene group or formula: And a group represented by. a is 0, 1 or 2.

The molecular weight of the (B) silazane compound used in the present invention is 30.
It is 00 or less, preferably 1000 or less. When a silazane compound having a molecular weight of more than 3000 is used, the reactivity decreases due to steric hindrance and the like, and the silanol group on the silica surface cannot be sufficiently silylated, or the unreacted silazane compound or its decomposition by-product after the reaction is completed. May become difficult to remove, which may cause inconvenience.

Specific examples of this silazane compound include the following formulas: And the like.

The above silazane compounds may be used alone or in combination of two or more. Also, for example, the formula: [(CH ₃ ) ₃
Si] ₂ NH, may be used by mixing at an appropriate ratio and then not silazane compound containing _{[CH 2 = CH (CH 3)} 2 Si ] fluorine-containing organic group represented by ₂ NH or the like.

The silazane compound used in the present invention is, for example, a corresponding chlorosilane, for example, methylene chloride, dichloroethane, trichloroethane, trichlorotrifluoroethane, dissolved in a chlorinated solvent or fluorinated solvent such as metaxylene hexafluoride, ammonia gas. Can be reacted by blowing in, and the resulting ammonium chloride can be removed by filtration or washing with an alkaline aqueous solution, and then purified by distillation or the like to obtain a simple substance or a mixture.

The amount of the silazane compound used in the present invention is 1 to 200 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of the silica fine powder. If the amount of the silazane compound used is less than 1 part by weight, the silanol groups on the silica surface will be insufficiently silylated, and if it exceeds 200 parts by weight, it will be expensive, and unreacted substances and decomposition by-products will be generated after the reaction is completed. The removal requires a large number of processing steps, which is economically disadvantageous.

In the method of the present invention, it is desirable to carry out the reaction between the fine silica powder and the silazane compound in the presence of water. The water used here has a function of promoting the reaction between the silica fine powder and the silazane compound, and promoting the silylation of silanol groups on the surface of the silica fine powder. The use of water at a temperature of room temperature or higher is convenient because it can promote the decomposition of the silazane compound and promote the volatilization of ammonia.

The amount of water used in the present invention is 0 to 50 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of silica fine powder.
If the amount of water used is too large, it takes a lot of time and energy to remove the residual water after the reaction is completed, which is economically disadvantageous.

Further, in the method of the present invention, a wetting agent can be used in order to moisten the surface of the silica fine powder to be used and sufficiently carry out the reaction between the silica fine powder and the silazane compound. Examples of the wetting agent include the following general formula: (CH ₃ ) Si (RO ⁴ ) ₂ , CH ₃ Si (RO ⁴ ) ₃ , [In the formula, R ⁴ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, a methoxyethyl group or the like, and s and t are positive integers. There is a compound represented by This humectant is usually
Those having a molecular weight of 3800 or less, and more preferably 1000 are preferable.

When a wetting agent is used, its amount is usually 30 parts by weight or less, preferably 0 to 10 parts by weight per 100 parts by weight of silica fine powder.
Parts by weight.

The method for producing the fluorosilicone-treated silica of the present invention is
Even if a predetermined amount of the above (A) silica fine powder is charged into a reactor and the (C) silazane compound is added dropwise or by spraying while stirring at room temperature, it usually produces mild heat and liberates ammonia gas. While the reaction proceeds. In this state, after aging for several hours to several days, by removing ammonia, low molecular weight silanol compounds, by-products such as siloxane compounds or unreacted silazane compounds under heating or reduced pressure, fluorosilicone-treated silica can be obtained. . Here, in order to sufficiently react the silanol group on the surface of the silica fine powder with the silazane compound and to sufficiently silate the silanol group, water may be added dropwise or by spraying before adding the silazane compound. Although the reaction proceeds even at room temperature, it can be promoted by further heating it to a temperature of room temperature to 200 ° C., for example, the reaction time can be shortened within 2 hours.

The fluorosilicone-treated silica obtained by the method of the present invention is mixed with an organopolysiloxane and kneaded to control fluidity, strengthen strength, improve releasability and adhesiveness, and compression set, heat resistance and chemical resistance. It is possible to improve the sex. Mixing and kneading of organopolysiloxane and fluorosilicone-treated silica is carried out by adding the treated silica obtained by the above method to organopolysiloxane, for example, in a proportion of 1 to 100 parts by weight relative to 100 parts by weight of organopolysiloxane. Good.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example 1 10 g of silica fine powder (specific surface area 200 m ² / g, Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) was charged into a flask and kept at room temperature.
After slowly adding 1.0 g of ion-exchanged water while stirring,
The following formula: When 9.9 g of disilazane represented by the above formula was gradually added dropwise to react, a mild exotherm and generation of ammonia odor were observed. The mixture was stirred under a closed atmosphere for 1 hour. Then, at room temperature,
After aging for a period of time, the reaction mixture was transferred to a enamel dish, air-dried for about 6 hours in a draft, and then 150 ° C in a hot air circulation furnace.
After heat treatment for about 16 hours, volatile components such as ammonia produced as a by-product were removed to obtain 14.3 g of white fine powdery treated silica.

When the specific surface area, carbon content and fluorine content of the obtained treated silica were measured, they were 105 m ² / g, 9.5% by weight and 14.9% by weight, respectively. Further, when this treated silica was put into a glass bottle together with water and shaken for a wetting test with water, it was found that all of the treated silica floated above the water surface and had water repellency.

Example 2 As disilazane, 4.9 g of disilazane used in Example 1
A treated silica was obtained in the same manner as in Example 1 except that a mixture consisting of and 0.9 g of hexamethyldisilazane was added dropwise.

The obtained treated silica is in the form of white fine powder and has a specific surface area,
When the carbon content and the fluorine content were measured, they were 115 m ² / g, 5.3% by weight and 7.5% by weight, respectively. When subjected to a wetting test with water in the same manner as in Example 1, it showed water repellency.

Example 3, Comparative Example 1 Treated silica obtained in Examples 1 and 2 and treated silica prepared in the same manner as in Example 1 except that hexamethyldisilazane was used as the silazane compound (specific surface area 12
0 m ² / g, carbon content 3.5% by weight) (Comparative Example 1), using the following composition: General formula: Which has a viscosity of 5000 cSt and has vinyl groups at both ends, dimethylpolysiloxane 100 parts by weight Treated silica 10 parts by weight Formula: 0.5 parts by weight of a substantially chlorine-free platinum catalyst prepared from vinyl siloxane and chloroplatinic acid (Pt concentration: 1.0% by weight, toluene solution) Formula: [(CH ₂ = CH) .CH _A mixture of 0.05 parts by weight of cyclotetrasiloxane represented by ₃ SiO] ₄ was uniformly kneaded with a three-roll mill and dispersed uniformly. To this, the general formula: A uniform amount of 0.2 parts by weight of a cross-linking agent represented by the following is obtained to measure the transparency and viscosity of the obtained composition, and the composition is subjected to a releasability test according to the following method, and after curing. Was measured for strength and specific gravity. The results are shown in Table 1.

Releasing Test The vacuum degassed composition was applied to the mirror surface of a 5 × 5 × 0.5 cm mirror-like metal block placed in a 7 × 7 × 1.5 cm box-shaped mold. After allowing to stand at room temperature for 16 hours to cure, it was taken out of the mold and aged and cured for another 2 days to obtain a female mold made of a cured product of the composition. A molded product obtained by pouring a resin composition obtained by mixing a curing agent having triethylenetetramine as a main component as a cross-linking agent into a bisphenol type liquid epoxy resin into the obtained female mold and curing the mixture at 80 ° C. for 30 minutes The operation of demolding was repeated to measure the releasability and the releasability.

Releasability The releasability of the female mold prepared from the composition obtained in each example was evaluated according to the following criteria. A: There is almost no resistance when demolding a cured molded product.

B: Intermediate between A and C C: There is some resistance when releasing the cured molded product from the mold.

Mold release durability As the gloss of the molded product decreases with the deterioration of the female surface of the rubber, the demolding operation was repeated until the gloss of the surface of the molded product decreased, and the number of repetitions was shown.

Strength after curing Put the composition in a mold of 12 × 15 × 0.3 cm, smooth the upper surface with a stainless steel plate, leave it for 16 hours at room temperature to cure, then remove from the mold Further, it was aged and cured for 2 days to obtain a molded sheet. The hardness, elongation and tensile strength of this molded sheet were measured according to JIS K6301.

From the above results, it can be seen that the silicone rubber composition prepared by adding the fluorosilicone-treated silica produced by the method of the present invention has excellent releasability.

[Effects of the Invention] According to the method of the present invention, it is possible to produce a fluorosilicone-treated silica which can be blended with an organopolysiloxane to obtain an organoposiloxane composition having excellent releasability and transparency.

Claims (1)

[Claims] 1. To 100 parts by weight of (A) silica fine powder having a specific surface area of 50 m ² / g or more, (B) formula (I): [In the formula, Rf is the number of carbon atoms containing a perfluoroalkyl ether group represented by the formula: FCqF ₂ qOn (wherein q is an integer of 1 to 3 and n is an integer of 1 to 4). 3-
15 represents a fluorine-containing organic group, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms and containing no fluorine atom, and R ² is a divalent carbon group having 2 to 10 carbon atoms. Indicates a hydrogen group,
a is 0, 1 or 2] A silazane compound 1 having a molecular weight of 3,000 or less containing a group represented by
˜200 parts by weight and (C) 0 to 50 parts by weight of water are reacted to produce a fluorosilicone-treated silica.