JPH04100872A - Heat-resistant coating material - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant coating material which gives a film excellent in heat and corrosion resistance and having high hardness by dispersing or dissolving a carbosilane polymer, a silicone resin, an inorganic filler, and an alkali metal silicate in an organic solvent. CONSTITUTION:A polycarbosilane [an organosilicon compound consisting mainly of bonding units of formula I (wherein R<1> is H or alkyl; R<2> is alkyl or phenyl)] and/or polycarbosilastyrene [an organosilicon compound consisting of units of bonding formula I and those of formula II (wherein R<3> and R<4> are each H, alkyl or phenyl) and in some cases having a partially crosslinked linkage], a silicone resin (e.g. dimethylpolysiloxane), an inorganic filler, and an alkali metal silicate (e.g. sodium metasilicate nonahydrate) are dispersed or dissolved in an organic solvent (e.g. xylene) to give a heat-resistant coating material. This coating material can give a film excellent in heat and corrosion resistance and having high hardness.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a heat-resistant paint that can withstand use at high temperatures.

(Prior Art and its Problems) JP-A-62-235370 discloses a heat-resistant paint in which a polycarbosilane, a silicone resin, and an inorganic filler are dispersed or dissolved in an organic solvent.

The heat-resistant paint described in the above-mentioned publication can be baked in air, and the coating film obtained therefrom has the advantage of not only excellent heat resistance but also good corrosion resistance and impact resistance.

On the other hand, the coating film obtained by curing the polymetallocarbosilane by heating the paint described in the above publication at a temperature of 250 to 450°C, which is the temperature commonly used for baking, has a pencil hardness of 2H to 450°C.
3H, has a relatively low hardness, and has the problem of easily scratching the coating film.

(Technical means for explaining the problem) The present invention provides a heat-resistant paint that has excellent heat resistance and corrosion resistance and can provide a coating film with high hardness.

According to the present invention, a heat-resistant paint is provided in which polycarbosilane and/or polycarbosilastyrene, a silicone resin, an inorganic filler, and an alkali metal silicate are dispersed or dissolved in an organic solvent.

The polycarbosilane in the present invention is mainly of the following formula (
It is an organosilicon polymer consisting of carbosilane bonding units represented by I).

-+Si CHz ← (IllR2 (In the formula, R1 represents a hydrogen atom or an alkyl group, and R2 represents an alkyl group or a phenyl group.) The polycarbosilastyrene in the present invention is a bonding unit represented by the above formula (I) and silastyrene bonding units of the following formula [■],
It is an organosilicon polymer with optionally partially crosslinked bonds.

CH, C, Hs (In the formula, R3 and R4 each represent a hydrogen atom, an alkyl group, or a phenyl group.)
It can be prepared according to the method described in Japanese Patent No. 39617. The description of this publication is incorporated herein by reference.

In the following description, polycarbosilane and polycarbosilastyrene may be collectively referred to as "carbosilane polymer."

Specific examples of the silicone resin in the present invention include dimethylpolysiloxane, methylphenylpolysiloxane,
Pure silicone resins such as diphenylpolysiloxane, pure silicone resins, alkyd resins, polyester resins,
Examples include modified silicones reacted with modifying resins such as acrylic resins and epoxy resins.

The blending ratio of silicone resin is 10 parts of carbosilane polymer.
0 parts by weight, 10 to 900 parts by weight, especially 50 to 50 parts by weight
Preferably, it is 0 parts by weight. If the blending ratio of silicone resin is too small, the flexibility of the coating film will be reduced due to baking, and if the ratio is too high, the heat resistance and corrosion resistance of the coating film will be reduced due to baking.

The inorganic filler in the present invention is at least one selected from oxides, borides, phosphates, silicates (excluding alkali metal silicates), silicides, borides, nitrides, and carbides. is used. For example,
Magnesium, calcium, barium, titanium, zirconium, chromium, manganese, iron, cobalt, nickel,
Examples include oxides, carbides, nitrides, silicides and borides of copper, zinc, boron, aluminum and silicon, borates, phosphates and silicates of magnesium, calcium or zinc.

The blending ratio of the inorganic filler is preferably 10 to 900 parts by weight, particularly 50 to 500 parts by weight, per 100 parts by weight of the carbosilane polymer. By incorporating an inorganic filler, the adhesion of the coating film to the substrate during baking is improved, but if the proportion of the inorganic filler is too high, the flexibility of the coating film decreases.

As the alkali metal silicate in the present invention,
MZO・n5ioz・xHz.

[In the formula, the gate is Li, Na, K or NP, 4 (R
represents an alkyl group), n is 0.5 to 4, and is 0
-10. ] Compounds represented by the following are generally used.

Specific examples thereof include sodium metasilicate nonahydrate, sodium orthosilicate hydrate, potassium metasilicate hydrate, and lithium metasilicate hydrate.

The blending ratio of the alkali metal silicate is 5 to 100 parts by weight, particularly 10 to 100 parts by weight, per 100 parts by weight of the carbosilane polymer.
Preferably, it is 50 parts by weight. If the blending ratio of alkali metal silicate is too small, the hardness of the paint film will not be sufficient, and even if the ratio is increased excessively, there is a limit to the increase in hardness, and conversely, the flexibility of the paint film will decrease. .

As the organic solvent in the present invention, any solvent can be used as long as it is capable of dissolving the carbosilane polymer and silicone resin. Specific examples include toluene, xylene, n-butanol, isobutanol, butyl acetate, mineral spirit, solvent naphtha, ethyl cellosolve, and cellosolve acetate.

The proportion of the organic solvent to be used varies depending on the type and blending proportion of the film-forming components, and can be appropriately determined by those skilled in the art in accordance with the disclosure of the present invention.

The heat-resistant paint of the present invention is applied to a metal substrate or a non-metal substrate such as ceramic or firebrick by a known method such as brush coating, roll coating, spraying, or dipping, and then dried. Burned in.

The amount of heat-resistant paint applied is preferably 20 to 100 g/rrf. If the coating amount is too small, pinholes are likely to occur in the coating film, resulting in decreased corrosion resistance.

On the other hand, if the coating amount is excessively large, the coating film is likely to crack when exposed to high temperatures or cold/heat cycles.

The baking temperature is preferably 150°C or higher, particularly 200°C or higher. If the baking temperature is too low, the carbosilane polymer, which is one of the paint components, will not be sufficiently cured, resulting in lower strength and impact resistance of the paint film.

Incidentally, if the object to be coated is placed in a usage environment of 150° C. or higher after coating, the baking step may be omitted.

(Example) Examples and comparative examples are shown below. Unless otherwise specified in the examples, "%" and "parts" refer to "% by weight" and "parts by weight," respectively.

The pencil hardness of the formed coating film was measured according to JIS K 5400.

Further, the heat resistance of the coating film was evaluated as follows.

After keeping the object to be coated in an air oven at 1000°C for 200 hours, it was taken out from the oven and slowly cooled in the air.
Next, crosscuts were made in the paint film with a pitch of one plate using a cutter knife, adhesive cellophane tape was pasted on this area, and the tape was violently peeled off to check whether the paint film had peeled off or not. The heat resistance was rated as "good" if no peeling of the coating film was observed, and the heat resistance was rated as "poor" if any peeling was observed.

Reference Example 1 2.5 liters of anhydrous xylene in a 5j2 three-ring flask! and 400 g of sodium were heated under a nitrogen gas stream to the boiling point of xylene, and then 11 of dimethyldichlorosilane was added.
It dripped in time. After the dropwise addition was completed, the mixture was heated under reflux for 10 hours to form a precipitate. This precipitate was filtered and washed first with methanol and then with water to obtain 420 g of white powder polydimethylsilane.

On the other hand, 750 g of diphenyldichlorosilane and 124 g of boric acid were mixed in n-butyl ether under a nitrogen gas atmosphere.
530 g of polyborodiphenylsiloxane was obtained by heating at 100-120°C and further heating the resulting white resinous material in vacuo at 400°C for 1 hour.

Next, 8.27 g of the above polyborodiphenylsiloxane was added to 250 g of the above polydimethylsilane, mixed, and heated to 350°C under a nitrogen stream in a 22 quartz tube equipped with a reflux tube. Polycarbosilane partially containing siloxane bonds was obtained by polymerization for a period of time.

After cooling the product, add xylene to take it out as a solution, filter it, and then evaporate the xylene to reduce the number average molecular weight to 1.
500 polycarbosilane was obtained.

Reference Example 2 (Synthesis of polycarbosilastyrene) Equimolar amounts of dichloromethylsilane and dichloromethylphenylsilane were mixed in a toluene solvent in the presence of a Na dispersed catalyst,
A polymerization reaction was carried out at 10"C to obtain polysilastyrene having a softening point of 86 to 94C.

This polysilastyrene was heat-treated at 420°C for 15 minutes under reduced pressure to have a softening point of 175-185°C, a number average molecular weight of 4.
500 polycarbosilastyrene was obtained.

Example 1 100 parts of a 50% xylene solution of the polycarbosilane obtained in Reference Example 1, 10 parts of a 50% xylene solution of methylphenylpolysiloxane (manufactured by Toho Silicone Co., Ltd., TSR-116)
0 parts, 100 parts of silicon carbide powder, 30 parts of sodium metasilicate nonahydrate, and 50 parts of xylene were mixed in a mixer to prepare a heat-resistant paint.

Separately, a stainless steel plate (SUS 316L) with a thickness of 0.6 mm was degreased with acetone as a base material and then air-dried.

Approximately 30μ of the heat-resistant paint is applied to the base material using a spray gun.
It was coated to a thickness of 100 ml, baked in an air oven at 300°C for 25 minutes, and then slowly cooled.

The pencil hardness of the formed coating film was 8H. Furthermore, the heat resistance of this coating film was "fair".

Comparative Example 1 Example 1 was repeated except that sodium metasilicate nonahydrate was not blended.

The pencil hardness of the resulting coating film was 2H, and the heat resistance was "good".
Met.

Example 2 Example 1 was repeated except that 30 parts of sodium orthosilicate hydrate was used instead of sodium metasilicate nonahydrate.

The pencil hardness of the resulting coating film was 8H, and the heat resistance was "good".
Met.

Example 3 Example 1 was repeated except that 200 parts of silicon nitride powder was used instead of silicon carbide powder.

The pencil hardness of the resulting coating film was 8H, and the heat resistance was "good".
Met.

Example 4 Example 1 was repeated except that 50 parts of zirconium oxide powder was used instead of silicon carbide powder.

The pencil hardness of the resulting coating film was 8H, and the heat resistance was "Good J".
Met.

Example 5 Example 1 was repeated except that 100 parts of the 50% xylene solution of polycarbosilastyrene obtained in Reference Example 2 was used instead of the 50% xylene solution of polycarbosilane.

The pencil hardness of the formed coating film was 8H. Moreover, the heat resistance of this coating film was "good".

Claims (1)

[Claims] A heat-resistant paint characterized in that polycarbosilane and/or polycarbosilastyrene, a silicone resin, an inorganic filler, and an alkali metal silicate are dispersed or dissolved in an organic solvent.