JPH04239075A - Heat-resistant coating composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant paint that can withstand use at high temperatures.

0002

[Prior art and its problems] Japanese Patent Application Laid-Open No. 57-20046
Publication No. 2 discloses a heat-resistant paint in which polyborosiloxane, a silicone resin, and an inorganic filler are dispersed or dissolved in an organic solvent. The heat-resistant paint described in this 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, when a coating film formed from the coating material described in the above-mentioned publication is exposed to a temperature of about 500° C. or higher, the volume shrinks as the polyborosiloxane converts into an inorganic substance, causing pinholes to reach the base material. may be generated. The pinholes that occur in this paint film limit its use in applications where it is exposed to corrosive gases, which is a problem that needs to be solved.

0004

[Technical means for explaining the problem] The present invention is a heat-resistant paint that has excellent heat resistance and can provide a coating film in which pinholes are not generated or are significantly suppressed even at high temperatures. I will provide a. According to the present invention, a polyborosiloxane, a silicone resin, an inorganic filler, and a softening point of 4
A heat-resistant paint is provided in which a glass frit having a temperature of 00 to 600°C is dispersed or dissolved in an organic solvent.

The polyborosiloxane used in the present invention is a known organosilicon polymer, for example, as disclosed in Japanese Patent Publication No. 58-473.
It can be prepared according to the method described in Publication No. 2. The number average molecular weight of polyborosiloxane is usually 500 to 10
000, preferably 1000-5000.

Specific examples of silicone resins used in the present invention include pure silicone resins such as dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane, and modified pure silicone resins such as alkyd resins, polyester resins, acrylic resins, and epoxy resins. For example, modified silicone reacted with a commercially available resin.

The blending ratio of the silicone resin is preferably 10 to 900 parts by weight, particularly 50 to 500 parts by weight, per 100 parts by weight of the polyborosiloxane. If the blending ratio of silicone resin is too small, the flexibility of the baked coating will decrease, and if the proportion is too high, the heat resistance and corrosion resistance of the baked coating will decrease.

As the inorganic filler in the present invention, at least one selected from oxides, borides, phosphates, silicates, silicides, borides, nitrides and carbides is used. Examples include oxides, carbides, nitrides, silicides of magnesium, calcium, barium, titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, zinc, boron, aluminum, and silicon.
borides, lithium, sodium, potassium, magnesium, calcium or zinc borates, phosphates;
Examples include silicates.

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 polymetallocarbosilane. By blending an inorganic filler, the adhesion of the baked coating film to the base material is improved, but if the blending ratio becomes too high, the flexibility of the coating film decreases.

[0010] Examples of the glass material for the glass frit having a softening point of 400 to 600°C in the present invention include phosphate glass, borosilicate glass, and lead glass. Among these, lead glass is toxic, so heat-resistant paints containing it should be refrained from use in civilian applications such as cooking utensils. On the other hand, phosphate glasses, borosilicate glasses, etc. are non-toxic and can all be used in a variety of applications, including consumer use. Glass frit can be prepared according to a method known per se, in which molten glass is sprayed into water and quenched. There are no particular restrictions on the particle size of the glass frit, but it is generally 2 to 20 μm.

The blending ratio of glass frit is preferably 10 to 200 parts by weight, particularly 20 to 100 parts by weight, per 100 parts by weight of polyborosiloxane. If the blending ratio of glass frit is too small, the chemical resistance at high temperatures, that is, the durability against corrosive gases will not be sufficient, and if the ratio is increased too much, the flexibility of the coating will decrease. When the softening point of the glass frit is lower than 400° C., the glass frit melts and aggregates during coating baking, resulting in a decrease in the adhesion of the paint film and a decrease in mechanical strength. If the softening point is higher than 600°C, the effect of preventing pinholes in the coating film will be reduced.

As the organic solvent in the present invention, any solvent can be used as long as it is capable of dissolving polymetallocarbosilane 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 metal substrates, electric wires, or non-metallic substrates such as ceramics and refractory bricks by means known per se such as brush coating, roll coating, spraying, and dipping, and then dried and baked.

[0014] The amount of heat-resistant paint applied is 20 to 100 g/m.
It is preferable that it is 2. 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, cracks are likely to occur in the coating film when the coating film is exposed to high temperatures or to cooling/heating cycles.

[0015] The baking temperature is 150°C or higher, especially 200°C.
It is preferable that it is above. If the baking temperature is too low, polymetallocarbosilane, which is one of the paint components, will not be sufficiently cured, resulting in lower strength and impact resistance of the paint film. In addition, the temperature of the object to be coated after painting is 150℃.
When placed in the above usage environment, the baking step can be omitted.

[0016]

[Example] Examples and comparative examples are shown below. Unless otherwise specified below, "%" and "parts" refer to "% by weight" and "parts by weight," respectively.

The heat resistance of the coating film was evaluated as follows. After holding 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, cross cuts with a pitch of 1 mm were made in the coating film using a cutter knife, and adhesive cellophane tape was pasted on this area, and the presence or absence of peeling of the coating film was examined after the adhesive cellophane tape was rapidly peeled off. 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.

The presence or absence of pinhole-like peeling portions in the coating film was evaluated as follows. The object to be coated is heated to 1000℃ for 20 minutes.
After being kept in an air oven for 0 hours, it was removed from the oven and slowly cooled, and then sprayed with salt water for 200 hours.
The coating film was observed under a 50x microscope to see if corrosion had formed. Rust formation and blistering of the paint film were observed on those with pinhole-like peeling.

Example 1 Polybolysiloxane with a number average molecular weight of 1500 prepared according to the method described in Japanese Patent Publication No. 58-4732.
% xylene solution, 50% xylene solution of methylphenylpolysiloxane (manufactured by Toshiba Silicone Co., Ltd., TSR
-116) 100 parts, silicon carbide powder 100 parts, phosphate glass frit (manufactured by Nippon Fellow, 01-4102M
) 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.

[0020] The heat-resistant paint was applied to the base material to a thickness of about 30 μm using a spray gun, and then heated in an air oven for 300 μm.
After baking at ℃ for 25 minutes, it was slowly cooled. The heat resistance of the resulting coating film was "good" and no pinhole-like peeling was observed.

Example 2 Example 1 was repeated except that 50 parts of borosilicate glass frit (manufactured by Nippon Fellow, 12-3615) was used in place of the borate glass frit. The heat resistance of the resulting coating film was "good" and no pinhole-like peeling was observed.

Comparative Example 1 Example 1 was repeated except that a borate glass frit was included. Although the heat resistance of the resulting coating film was "good", pinhole-like peeling was observed.

Claims (1)

[Claims] 1. A heat-resistant paint comprising polyborosiloxane, silicone resin, inorganic filler, and glass frit having a softening point of 400 to 600°C dispersed or dissolved in an organic solvent.