JPS6323975A - Heat-resistant paint composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. which gives a coating film having excellent rust proofness and heat resistance even in a high-temperature atmosphere, by blending scaly mica powder having a specified size with scaly aluminum powder and a modified polysiloxane component. CONSTITUTION:A polysiloxane having silanol or alkoxy groups is condensed with a modified resin having hydroxyl or carboxyl group in a weight ratio of 20/80-80/20 to obtain a modified polysiloxane component (A) which is a curable resin having an MW of 500-80,000 and functional groups such as silanol, alkoxysilane, hydroxyl, carboxyl, epoxy, oxidatively polymerizable unsaturated double bond, etc. 100pts.wt. component A or mixture thereof with 20-50wt% (based on the amount of the component A) crosslinking agent (B) is dissolved in a solvent and the soln, is blended with 120-180pts.wt. scaly mica powder (C) having a length of 0.01-5mu and a thickness of not more than 3000Angstrom and 30-70pts.wt. scaly aluminum powder (D) having a length of 1-50mu and a specific surface area of not smaller than 1.0m<2>/g.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a heat-resistant coating composition.

[Prior Art] It has been conventional practice to apply a heat-resistant paint to the surface of iron materials such as exhaust mufflers, engine parts, heaters, stoves, plants, heat exchangers, etc. to prevent rusting.

As the heat-resistant paint, a paint made of polysiloxane containing aluminum powder is generally used. This material is characterized by the fact that the siloxane bonds in polysiloxane are stable against heat and that the aluminum powder has a high melting point (65
It is useful as a heat-resistant paint because it is stable against heat at a temperature of 9°C.

[Problems to be Solved by the Invention] The coating film formed from the #thermal paint described above has good rust prevention properties below the decomposition temperature of polysiloxane (approximately 250°C).
It exhibits heat resistance, but when exposed to temperatures higher than its decomposition temperature, as polysiloxane itself has high oxygen permeability, the oxygen that passes through the coating reacts with the iron metal of the material, producing iron oxide. It has the disadvantage that it forms a layer, which deteriorates the adhesion of the coating and causes the coating to peel, and it also has the disadvantage that the coating becomes brittle and collapses under the slightest external force. However, as a method to improve this drawback, a two-coat coating film in which a polysiloxane coating film containing a high concentration of zinc powder is formed as a primer between the heat-resistant paint coating film and the material described above can be considered. #The reality is that a coating film that is satisfactory in both heat resistance and rust prevention properties has not been obtained.

[Means for Solving the Problems] As a result of intensive research in order to solve the drawbacks of conventional heat-resistant coating compositions, the present inventors added flaky mica powder and flaky aluminum powder to modified polysiloxane. The present invention was completed based on the discovery that the containing coating composition forms a fused coating layer with a metal or non-metal having excellent rust prevention properties on the surface of an iron substrate under high-temperature atmospheric conditions, which solves the above-mentioned drawbacks. I ended up doing it.

That is, in the present invention, the modified polysiloxane component is 100 parts, and the length in the longitudinal direction is 0.01 to 5 pots.

Scale-like mica powder 120 to 18 with a thickness of 3000A or less
0 parts by weight and longitudinal dimension 1 to 50 pL, specific surface J&
1. Scale-like aluminum powder of Om″/g or more 30~
It relates to a heat-resistant coating composition containing 70 parts by weight.

The modified polysiloxane used in the present invention is a conventionally known modified polysiloxane obtained by condensing a polysiloxane having a silanol group or an alkoxy group with a modified resin having a water M group or a carboxyl group. Examples of such modified polysiloxanes include polyester-modified polysiloxanes, alkyd-modified polysiloxanes, acrylic-modified polysiloxanes, epoxy-modified polysiloxanes, melamine-modified polysiloxanes, and phenol-modified polysiloxanes. Among them, polyester-modified polysiloxane is preferred.

As the polysiloxane, an organopolysiloxane having one or more silanol groups or alkoxy groups in one molecule is used.

In addition, the above-mentioned resins are used as the modified resin, but to give an example of the raw materials for these resins, for example, for polyester, phthalic acid (anhydride), isophthalic acid, terephthalic acid, adipic acid, and cepatic acid are used. Polybasic acids such as benzoic acid, P-tert-butylbenzoic acid, etc.; Polyhydric alcohols such as ethylene glycol μ, neopentyl glycol μ, 1,6-hexanedioh μ, trimethylolpropane, etc. For alkyd resins, linseed oil, safflower oil, soybean oil, coconut oil, and their fatty acids can be used in addition to the raw materials for polyester, and for acrylic resins, methyl (meth)acrylate, ethyl ( Examples include meth) acrylate, butyl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide, glynosidyl (meth) acrylate, styrene, etc. For epoxy resins, Epicoat 828, Epicoat 1004
, times 1007. Examples include bisphenol A type such as 1009 (manufactured by Shell Chemical Co., Ltd., trade name).

The blending ratio of polysiloxane and modified resin (including crosslinking agent) is 20/80 to 80/20, preferably 4
It is 0/60 to 60/40. If the proportion of polysiloxane is less than 20, the organic matter in the resin will begin to decompose.
The film stability is poor at high temperatures of C or higher, and if the 1 ratio of polysiloxane is more than 80, the adhesion to the substrate tends to be poor at high temperatures.

Such modified polysiloxanes have 500~go, o
oo, preferably has a molecular weight in the range of 1,000 to 50.000.0 If a modified polysiloxane with a molecular weight of less than 500 is used, film-forming property etc. will be poor, and on the contrary, it will be greater than 80.000. Modified polysiloxanes with high molecular weight tend to have poor coating workability.

The modified polysiloxane described above includes a silanol group, an alkoxysilane group, a hydroxyl group, a carboxyl group, an epoxy group,
Alkoxy group, methylol group.

It is a curable resin having one or more functional groups such as a phenol group and an oxidatively polymerizable unsaturated double bond. The modified polysiloxane can be used alone or in combination with a crosslinking agent, and examples of the crosslinking agent include melamine resin, polyincyanate, and epoxy resin. Further, the crosslinking agent can be blended in an amount of about 20 to 50% by weight based on the modified resin.

The scale-like mica powder used in the present invention is a powder having a scale-like external shape with a longitudinal dimension of 0.01 to 5W, preferably 0.1 to 3W, and a thickness of 3000 Å or less. The longitudinal dimension of the flaky mica powder is o, o
When it is smaller than tg, the film stability at high temperatures is poor, and on the other hand, when it is larger than 5 g, film forming properties are poor. Furthermore, if the thickness of the scale-like mica powder is greater than 3,000 mm, film-forming properties and the like are poor.

As the scale-like mica powder described above, for example, mica S
-100 (■ Yamaro Mica Industries), Mica A-100 (■
Examples include Mica A-11 (Yamaro Mica Industries), Mica A-150 (Yamaro Mica Industries), and the like.

In addition, flaky mica powder generally contains crystal water, but from the viewpoint of forming a denser coating film during firing, it is preferable to use mica powder from which crystal water has been removed by firing, such as mica S- It is advantageous to use 100.

The amount of scale-like mica powder blended is within the range of 120 to 180 ton h parts, preferably 140 to 160 parts by weight, per 100 parts by weight of the modified polysiloxane solid content. If the amount of the scale-like mica powder blended is less than 120, film stability at high temperatures is poor, and on the other hand, if it is more than 180, film forming properties are poor.

The flaky aluminum powder used in the present invention has a longitudinal dimension of 1 to 50 mm, preferably 5 to 45 mm, and a specific surface area of 1.0 m'/g or more, preferably 1.5 rrf/g.
The powder has the above leafing type or non-leafing type scale-like external shape. If the dimension in the longitudinal direction of the scale-like aluminum powder is smaller than 1 μm, the film stability at high temperatures is poor, and on the other hand, if it is larger than 50, the film forming property is poor. Further, when the specific surface area of the flaky aluminum powder is smaller than 1.0 m'/g, the film forming property is poor.

Furthermore, it is advantageous to use powder with a smooth surface because it forms a smooth and dense fusion layer. , aluminum paste 52
-568 (Toyo Aluminum @), aluminum paste 52
-402 (Toyo Aluminum v4), aluminum paste 5
2-566 (Toyo Aluminum ■) and the like.

The amount of flaky aluminum powder to be blended is within the range of 30 to 70 parts by weight, preferably 40 to 60 parts by weight, based on 100@i parts of the modified polysiloxane solid content. If the blending amount of the flaky aluminum powder is less than 30, the film stability at high temperatures will be poor, and on the other hand, if it is more than 70,
Poor film-forming properties at high temperatures.

The method for preparing the heat-resistant coating composition of the present invention can be carried out according to a known coating preparation method.
A heat-resistant coating composition can be obtained by dissolving or dispersing the above-described modified polysiloxane in an appropriate solvent, adding scale-like mica powder and scale-like aluminum powder, and dispersing with a disperser such as a high-speed stirrer. can. The solvent that can be used is not particularly limited as long as it can dissolve or disperse the modified polysiloxane, and examples include alcohol solvents, ketone solvents, ester solvents,
Examples include aromatic hydrocarbon solvents.

Further, as other components that can be blended as necessary in the heat-resistant coating composition of the present invention, pigment dispersants, coating surface conditioner 1
Examples include colored pigments.

The heat-resistant coating composition of the present invention can be applied to the surface of an iron base by a coating method such as brush coating, spray coating, roller coating, curtain flow coating, or dip coating. Coating 1fi: There is no particular limit, but generally the dry film thickness is 20~
I think a range of 50 tiles is sufficient. The coating film can be dried at room temperature or by heating (approximately 100 to 250°C - approximately 10 to 60 minutes).

The heat-resistant paint composition of the present invention exhibits sufficient rust prevention properties in high-temperature atmospheres on untreated iron substrates and iron substrates that have been surface-treated with zinc phosphate, iron phosphate, chromic acid, etc. However, it is economically advantageous to apply it to untreated iron substrates.

[Function] The reason why the coating film formed from the #thermal coating composition of the present invention exhibits excellent heat resistance and rust prevention properties is as follows.

It can be considered as follows. That is, the coating film is exposed to a high temperature atmosphere (35
0°C or higher), the modified resin, which is an organic component, has a lower thermal decomposition temperature than polysiloxane, which contains a large amount of inorganic components, so it easily decomposes and volatilizes, and contains high concentrations of aluminum powder and mica powder. becomes. Subsequently, as the polysiloxane decomposes and the formation of 5i02 begins, the aluminum and mica in the coating fuse with the iron of the substrate, forming a coating of lacquer 1 to 5 on the surface of the substrate (coating film thickness 20 to 50 mm).
Forms a fused layer of iron, aluminum and silicon with anti-rust properties. Further, in the present invention, the above-mentioned fused layer can be easily formed by using specific aluminum powder and mica powder.

[Example] Next, Examples and Comparative Examples will be described in detail. In addition, parts in the following examples indicate parts by weight.

Examples 1 to 4 and Comparative Examples 1 to 4 After adding a solvent to the modified polysiloxane solution and diluting it,
While stirring the solution, flaky mica powder and flaky aluminum powder were gradually added and dispersed. Disparon 6900-20X (trade name, Kusunoki Kasei ■, inorganic thickener) was added to the resulting dispersion to adjust the viscosity, and coating compositions of Examples and Comparative Examples were obtained. Table 1 shows the raw materials and blending ratios used for blending.

Next, the above coating composition was spray-painted on an untreated polished cold-rolled steel plate, and then baked in a ventilation dryer at 200°C for 60 minutes to obtain a coated steel plate of about 30P. The test results of the painted steel plate are shown in Table-2.

(Mon) Modified polysiloxane Polyester modified polysiloxane: UD-460 (60%) Bayer Synthetic Silico-7 stock alkyd modified polysiloxane: TSR-184 (50%) Toshiba Silicone Ltd. Acrylic modified polysiloxane: TSR-171 (50%) ) Toshiba Silicone Co., Ltd. Epoxy-modified polysiloxane: TSR-194 (50%) Toshiba Silicone ■ (Small 2) Scale-like mica powder Mica S-100 [Yamaguchi Mica Industries ■ "Product name"] (0,1-3 end ) (House 3) Scale-shaped aluminum powder aluminum paste 52-568 Toyo Aluminum Co., Ltd. sieve residue (44 seats) 1.00% or less Test method A test plate coated on a heat-resistant Nibrite plate was heated at 250°350°.
．． Heating was continued at 450.550°C for 20 hours each, and immediately after the test plate was taken out of the furnace, it was cooled by pouring water.

As a result, the test plate had a good coating surface condition. Furthermore, it is attached with cellophane tape. Conduct a fitting test.

[Effects of the present invention] As explained above, the coating film obtained from the heat-resistant coating composition of the present invention has improved the problems that conventional coating films were unable to satisfy in terms of rust prevention and heat resistance. The effect is remarkable.

Claims (1)

[Claims] 100 parts by weight of a modified polysiloxane component, 120 to 180 parts by weight of scale-like mica powder with a longitudinal dimension of 0.01 to 5 μ and a thickness of 3000 Å or less, and a longitudinal dimension of 1 to 50
A heat-resistant coating composition containing 30 to 70 parts by weight of scale-like aluminum powder having a specific surface area of 1.0 m^2/g or more.