JPH07108809B2 - Heat resistant inorganic sheet material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant inorganic sheet material containing no asbestos, more specifically, a heat-resistant inorganic material containing no asbestos, which is useful for gaskets, electric insulating plates, heat shield plates and the like. It relates to a sheet material.

[0002]

2. Description of the Related Art Asbestos products having excellent heat resistance and airtightness have been used for a long time as gaskets, electric insulating plates, heat shield plates, etc. in machines used at high temperatures such as internal combustion engines. However, in recent years, the use of asbestos products has been regulated for well-known environmental hygiene reasons,
Heat resistant inorganic sheet materials that do not contain asbestos are required in various fields.

[0003]

Therefore, the present invention provides a heat-resistant inorganic sheet material that is as good as an asbestos product, particularly a non-asbestos heat-resistant inorganic sheet material that is suitable as a gasket material used at high temperatures. Is what you are trying to do.

[0004]

The non-asbestos heat-resistant inorganic sheet material successfully provided by the present invention is obtained by heating a mixture of mica, wollastonite, and hydraulic cement by heating in an autoclave after papermaking. To form a sheet-like product by subjecting the resulting sheet-like formed product (after punching if necessary) to impregnating with an alcoholic silica sol or impregnating with an alkyl silicate and then hydrolyzing the alkyl silicate. By filling the voids in the molded product with silica sol, heating and drying, and baking.

[0005]

The inorganic sheet material according to the present invention is capable of producing asbestos by the synergistic action of the inorganic raw materials in the above-mentioned unique combination and the action of reinforcing silica gel filled in the fine voids of the sheet, improving water repellency, improving dimensional stability and the like. Despite not containing it, it has suitable compression characteristics for use in gaskets, etc. and excellent heat resistance, bending strength, water repellency and heat shielding properties,
Furthermore, it has excellent electrical insulation.

To produce the inorganic sheet material of the present invention,
First, the raw materials preferably mixed in the following ratios are dispersed in water for papermaking (the values in parentheses are particularly desirable ratios). Mica 10-50% by weight (20-40% by weight) Wollastonite 5-40% by weight (8-20% by weight) Silica raw material 5-30% by weight (10-25% by weight) Hydraulic cement 5-50 % By weight (20-40% by weight)

The mica used here may be any of muscovite, phlogovite, biotite, etc.,
A flake diameter of about 10 to 600 μm is suitable.
As the wollastonite, so-called fibrous wollastonite with needle crystals is used. Silica powder, silicon dust and the like are suitable as the siliceous raw material. Also, as hydraulic cement, in addition to ordinary Portland cement,
Alumina cement can be used.

The dispersion of the papermaking raw material further contains a fibrous material for improving the papermaking property and reinforcing it in an amount not exceeding about 20% by weight of the total raw material, and if necessary, an organic or inorganic material as a molding aid. The binder is added in an amount not exceeding about 30% by weight of the total raw materials. As the fiber to be added,
Pulp, alkali-resistant glass fiber and the like are suitable, as the binder, acrylonitrile-butadiene rubber, acrylic rubber, styrene-butadiene rubber, chloroprene rubber, urethane rubber, fluororubber, silicone rubber, vinyl acetate, latex such as starch, Well-known binders for sheet formation such as emulsions and aqueous solutions can be used.

The liquid in which the above various raw materials are dispersed is mixed well, and if necessary, a fixing agent and a coagulant are added to form flocs. This is paper-made by a paper-making machine to make a sheet having a thickness of about 1 to 6 mm. This green sheet is put in an autoclave, heated to about 120 to 160 ° C., and then dried. In this autoclave treatment, a hydration reaction of hydraulic cement and a reaction between the cement and the siliceous raw material occur, and the sheet hardens. The sheet-shaped molded article is then impregnated with an alcoholic silica sol (a suspension of silica sol produced in the hydrolysis of an alkyl silicate in alcohol), or the alkyl silicate is hydrolyzed by a method such as steam exposure after impregnation. And a silica sol is generated. In the case of a gasket or the like that needs to be finished in a specific shape, punching is performed prior to the impregnation treatment so as to have a predetermined shape.

The impregnation treatment includes dipping, spraying, coating, etc.
This can be done by any method. As a result, the silica sol is filled in the voids in the molded product. Then, by heating and drying, the filled silica sol is converted into silica gel, and by further firing, organic substances such as a binder are burned and removed, and the shrinkage during use of the product is reduced. It is desirable that the amount of silica gel produced does not exceed about 25% by weight, based on the weight of the product, with about 7-18% being particularly desirable. INDUSTRIAL APPLICABILITY The inorganic sheet according to the present invention makes use of features such as excellent strength, heat resistance, and water repellency, and is used as a gasket for an internal combustion engine, a sealing material for an exhaust gas recirculation control valve (EGR valve) of an automobile engine, a heat shield plate for a high temperature heating furnace It can be used for high withstand voltage electrical insulation boards, etc.

[0011]

[Examples] Example 1, Comparative Examples 1 and 2, Portland cement: 30 parts by weight Silica powder: 20 parts by weight Mica (phlogovite): 30 parts by weight Fibrous wollastonite (median particle size 19 μm or more): 1
0 parts by weight Alkali resistant glass fiber (12 mm long chopped strand): 2 parts by weight Rock wool: 5 parts by weight Softwood bleached kraft pulp: 3 parts by weight

The above raw materials were mixed in water, made into paper by a gauze paper making machine, then autoclaved and cured to form a sheet having a basis weight of 3400 g / m ² and a thickness of 2.5 mm. The obtained sheet-shaped molded product was punched into an annular shape having an outer diameter of 30 mm and an inner diameter of 5 mm and immersed in ethyl silicate (Comparative Example 2
Is not soaked), then put in an autoclave 3kg / c
Ethyl silicate was hydrolyzed by treatment with m ² steam. Hereinafter, after drying with hot air, firing was performed at 400 ° C. for 5 hours to obtain an annular sheet usable as a gasket (Comparative Examples 1 and 2 were not fired). Table 1 shows the processing conditions and the characteristic values of the products. In addition,
The test methods for water absorption rate and stress relaxation rate are as follows. Water absorption rate: After soaking in water at room temperature for 5 hours, the weight increase rate was measured. Stress relaxation rate: Measured according to ASTM F38-B.

[0013]

[Table 1] Example 1 Comparative example 1 Comparative example 2 Ethyl silicate impregnation amount (% by weight) 10 10 0 400 ° C firing Yes No No No Characteristic value Density (g / cm ³ ) 1.35 1.35 1.30 Bending strength (Kgf / cm ² ) 170 186 60 Water absorption (% by weight) 6 6 23 Stress relaxation rate (%) 13 32 25

[0014]

INDUSTRIAL APPLICABILITY The inorganic sheet material of the present invention made of mica, wollastonite, siliceous raw material and cement as raw materials has a heat resistance and a bending ability due to the synergistic action of the above-mentioned raw materials and the action of silica gel filled. Since it is excellent in strength, water repellency, heat shielding property, electric insulating property, etc., it is extremely useful as a gasket for internal combustion engine, heat shielding plate, electric insulating plate, etc., which can be used in place of asbestos products.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C09K 3/10 Q 21/02 C04B 35/16 C

Claims (3)

[Claims] 1. A sheet-shaped molded product obtained by molding a mixture of mica, wollastonite, a siliceous raw material, and hydraulic cement and then heating and curing in an autoclave to form a sheet. A heat-resistant inorganic sheet material obtained by filling silica sol in voids in a molded article by impregnating with an alcoholic silica sol or by impregnating with an alkyl silicate and then hydrolyzing the alkyl silicate, heating and drying and firing. 2. A mixture of mica, wollastonite, a siliceous raw material, and hydraulic cement is formed into a sheet and then heated in an autoclave to be cured to form a sheet. Punching into a desired shape, and then impregnating an alcoholic silica sol or impregnating an alkyl silicate and then hydrolyzing the alkyl silicate to fill the voids in the molded product with the silica sol,
A heat-resistant inorganic sheet material obtained by baking after heating and drying. 3. The method according to claim 1, wherein a mixture of 10 to 50% by weight of mica, 5 to 40% by weight of wollastonite, 5 to 30% by weight of siliceous raw material, and 5 to 50% by weight of hydraulic cement is produced. Item 2. A heat-resistant inorganic sheet material according to item 2.