JP2824044B2 - Heat resistant insulating coating composition - 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 insulating coating composition, and more particularly to a heat-resistant insulating coating composition having good adhesion to a metal material having a large thermal expansion property and having a temperature of 150 to 180.degree.
The present invention relates to a heat-resistant insulating coating composition which can be cured by heating in a relatively intermediate temperature range and can obtain a coating film having excellent heat resistance, electric insulation, moisture resistance and the like.

[0002]

2. Description of the Related Art In recent years, among metal or nonmetallic materials, those used for a long time in a high temperature range of 200 ° C. or more have been increasing, and the need for heat-resistant paints used for these materials has been increasing. It is diversifying. In order to respond to these needs, many organopolysiloxane-based paints, inorganic-organic composite paints composed of an organopolysiloxane and an organic resin, and heat-resistant organic resin-based paints such as polyimide resins have been reported. For example, JP
JP-A-2-37378 and JP-A-62-122133 disclose that a silicone polymer-based coating material having a ladder structure using an alkyl silicate as a binder has a temperature of 300 ° C to 5 ° C.
It is reported that by baking at 00 ° C., a coating film having a high coating film hardness and an excellent insulating property can be obtained.

[0003] JP-A-63-135462 discloses an inorganic heat-resistant paint in which an inorganic powder is dispersed in a sol obtained by partially hydrolyzing and polycondensing tetraalkoxysilane or organoalkoxysilane. ,
JP-B-58-50658 also discloses a heat-resistant coating compounded with polyborosiloxane, but all of them have problems in water resistance, moisture resistance, etc., and in particular, the former simultaneously satisfies both heat resistance and insulation. However, the appropriate thickness range is small and it is difficult to control the thickness. In addition, Japanese Unexamined Patent Publication No.
No. 153283 discloses a heat-resistant insulating coating composition comprising polycarbosilane, polysilazane, a silazane compound, and inorganic powder, which is baked at a high temperature of 250 ° C. or more in air to provide adhesion, heat resistance, and insulation. It is reported that a coating film excellent in properties, moisture resistance and the like can be obtained.

[0004] However, these organopolysiloxane-based paints are compared with the above-mentioned heat-resistant organic resin-based paints such as polyimide resin and inorganic-organic composite paints represented by silicon-modified polyester resin and silicon-modified epoxy resin. , Heat resistance, heat yellowing, adhesion to substrate after heat treatment, insulation, etc.
The adhesiveness, insulation and moisture resistance of the coating film in an oxidizing atmosphere of 00 ° C. or more are not simultaneously satisfied.

[0005] Even if the cured coating is a heat-resistant paint having excellent heat resistance, insulation and moisture resistance, baking at a high temperature of 250 ° C to 500 ° C is generally required in order to obtain the properties of the coating. And there is a problem in economics.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a heat-cured coating film simultaneously satisfies adhesiveness, heat resistance, insulation and moisture resistance, and has a low curing temperature, and is easily and inexpensively manufactured. It is an object of the present invention to provide a heat-resistant insulating coating composition which is excellent in economical efficiency.

[0007]

Heat-resistant insulating coating composition SUMMARY OF THE INVENTION The present invention relates to compounds of the general formula _{(A) R n Si (OR} ') 4-n ( wherein, R is an alkyl group having 1 to 4 carbon atoms, R 'represents a methyl group or an ethyl group, and n is any one of 0, 1, and 2.) 100 parts by weight of one or more selected from alkoxysilanes represented by the following formula: From 3 parts by weight to 5 parts by weight of the organopolysiloxane (B) having
The formula (C) M (OR) _4-n (where R is an alkyl group having 1 to 4 carbon atoms) based on 100 parts by weight of the partial co-hydrolysate in the state of coexistence at 0 parts by weight. , M represents a metal selected from titanium, zirconium, or aluminum. When M is titanium or zirconium, n
Is 0, and n is 1 when M is aluminum. 1) or 2 or more selected from the metal alkoxides represented by the formula (3) to 20 parts by weight, and
The formula (D) R ″ (R _n ) Si (OR) _3-n (wherein R is a methyl or ethyl group, and R ″ is an epoxy group Represents an organic group, n is 0, 1, or 2.) An organo group obtained by reacting an epoxy group-containing silane coupling agent represented by the following formula in the presence of a catalyst in a proportion of 0.01 to 30 parts by weight. An inorganic powder is blended at a ratio of 30 parts by weight to 500 parts by weight with respect to 100 parts by weight of the polysiloxane (E).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The binder in the heat-resistant insulating coating composition of the present invention will be described. First, a partial co-hydrolyzate of a mixture of the alkoxysilane and the organopolysiloxane (B) represented by the general formula (A) (hereinafter referred to as an organopolysiloxane (a)) is a siloxane bond (Si) having excellent heat resistance. -O-Si), and an unreacted alkoxy group and a reactive hydroxyl group (silanol group; Si
Since (OH) is contained in the molecular structure, it is cured by a dealcoholization reaction or the like, and bears heat resistance, insulation, and moisture resistance, which are the main performances of the heat resistant insulating coating composition of the present invention.

In the general formula (A), R has 1 to 4 carbon atoms.
Alkyl group such as methyl group, ethyl group, n-
A propyl group and an i-propyl group. Also,
R 'represents a methyl group or an ethyl group. General formula (A)
Specific examples of the alkoxysilane represented by are tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltrisilane. Ethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane and the like, preferably tetramethoxysilane, tetraethoxysilane, Methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane. These alkoxysilanes are used alone or as a mixture of two or more.

The alkoxysilane represented by the general formula (A) is preferably dimethyldialkoxysilane such as dimethyldimethoxysilane or dimethyldiethoxysilane in which at least 30 mol% of the total Si concentration constituting the alkoxysilane is n = 2) is preferable.

The organopolysiloxane (B) having a reactive hydroxyl group is a ladder silicone or a straight silicone having a side chain group of a methyl group or a phenyl group and having a reactive hydroxyl group in a molecular structure.
The hydroxyl value is from 30 mgKOH / g to 500 mgKOH
/ G, preferably 40 mg KOH / g to 400 mg KO
H / g, particularly preferably 60 mg KOH / g to 300 m
gKOH / g, and a weight average molecular weight (Mw) in terms of polystyrene of 1,000 to 50,000, preferably 2,000 to 30,000, particularly preferably 3,000 to 15,000. You may want to select one.

When the hydroxyl value is less than 30, the adhesion and curing rate of the obtained coating film decrease, and when it exceeds 500, the storage stability of the composition is poor, and the resulting coating film cracks after baking. Tends to be easier. When the molecular weight is less than 1,000, the adhesion and moisture resistance of the obtained coating film are reduced, and cracks are easily generated after baking.
If it exceeds 000, the compatibility with the alkoxysilane decreases, and the adhesion and curing speed of the obtained coating film decrease.

Examples of commercially available and easily available products include, for example, KR-220 manufactured by Shin-Etsu Chemical Co., Ltd.
L, KR-240, KR-242A, KR-311, K
R-2610B and the like. One of these may be used alone or a mixture of two or more may be used.

The partial cohydrolysis / polycondensation reaction can be carried out by mixing the alkoxysilane represented by the general formula (A) and the organopolysiloxane (B) and adding water adjusted to an acidic side. To produce an organosiloxane oligomer or an organosiloxane polymer. At this time, the amount of water is preferably 0.5 mol to 1.5 mol per 1 mol of the alkoxysilane. The mixing ratio of the alkoxysilane represented by the general formula (A) to the organopolysiloxane (B) is preferably 3 parts by weight to 50 parts by weight, relative to 100 parts by weight of the alkoxysilane represented by the general formula (A). Is from 5 to 40 parts by weight, particularly preferably from 8 to 30 parts by weight. If the amount is less than 3 parts by weight, the adhesion and the moisture resistance are reduced, and if it exceeds 50 parts by weight, the compatibility with the alkoxysilane is reduced. The cracks tend to occur after baking.

However, even when only the organopolysiloxane component thus prepared is used as a binder, the curing speed in a medium temperature range (150 ° C. to 180 ° C.) is slow, and it takes a long time to obtain a predetermined coating film performance. Requires heating.

Therefore, in the heat-resistant insulating coating composition of the present invention, the organopolysiloxane (a) obtained above is added to the above-mentioned general formula for the purpose of increasing the curing rate by heating in a medium temperature range. The metal alkoxide represented by (C) is composited, and the coating film is primarily crosslinked. In that case,
3 parts per 100 parts by weight of organopolysiloxane (a)
It is from 5 parts by weight to 20 parts by weight, preferably from 5 parts by weight to 15 parts by weight, particularly preferably from 7 parts by weight to 10 parts by weight. When the amount is less than 3 parts by weight, the curing speed is slow. Gelling occurs due to poor storage stability, and adhesion of the coating film is poor even when coating is performed using the obtained composition.

As the metal alkoxide represented by the general formula (C), Ti (OR) ₄ , Zr (OR) ₄ , Al (O
R) _{3 and the} like, wherein R is an alkyl group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl And the like. Specific examples of these metal alkoxides include titanium tetraethoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, zirconium tetraethoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, and aluminum trimethoxide. , Aluminum triethoxide, aluminum triisopropoxide, and aluminum tri-n-butoxide. These metal alkoxides are used alone or in combination of two or more.

The partial co-hydrolysis thus obtained
A coating film obtained by using a polycondensate (hereinafter referred to as an organopolysiloxane (b)) as a binder undergoes primary cross-linking in a medium temperature range, and thus has excellent initial adhesion, insulating properties, and heat resistance.

However, in the case of the organopolysiloxane (b) in which the organopolysiloxane (a) is combined with the metal alkoxide represented by the general formula (C), the ratio of each hydroxyl group or the reaction between the hydroxyl group and the alkoxy group is low. In particular, the reaction cannot be expected so much when the heating is performed in the middle temperature range. In other words, since these unreacted hydroxyl groups and alkoxy groups remain, the coating film tends to cure and shrink further when exposed to a high temperature of 250 ° C. or higher, and the adhesion of the coating film decreases in the subsequent air-cooling / water-cooling spall test. It has been found that there is a problem in water resistance and moisture resistance when the hydroxyl group and the alkoxy group remain.

Therefore, the present inventors considered that the temperature range from 150 ° C. to 180 ° C.
The hydroxyl group or the hydroxyl group and the alkoxy group are positively reacted with each other by heating in a medium temperature range of ℃, that is, the hydroxyl group or the alkoxy group of the alkoxysilane represented by the general formula (A) and the organopolysiloxane (B) It was examined whether bonding with a highly active hydroxyl group in a varnish or at the time of curing can improve the adhesion and moisture resistance of the coating film.

As a result, after the primary cross-linking using the above-mentioned metal alkoxide, the cross-linked product is reacted with the epoxy group-containing silane coupling agent represented by the general formula (D) in the presence of a catalyst. It was found that this could solve this problem.

As the epoxy group-containing silane coupling agent represented by the general formula (D), R represents a methyl group or an ethyl group, and R ″ represents an organic group containing an epoxy group. For example, glycidoxymethyl group, β-glycidoxyethyl group, γ-glycidoxypropyl group, 3,
Examples thereof include a 4-epoxycyclohexyl group. Specific examples include glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, β-
Glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyl (methyl) dimethoxysilane, Examples thereof include γ-glycidoxypropyl (dimethyl) methoxysilane, γ-glycidoxypropyl (ethyl) dimethoxysilane, and 3,4-epoxycyclohexylmethyltrimethoxysilane.

The amount of the epoxy group-containing silane coupling agent is 0.01 to 30 parts by weight, particularly preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the organopolysiloxane (b). Parts are preferred. If the amount exceeds 30 parts by weight, the curing reaction of the binder becomes slow, and the coating properties such as moisture resistance and adhesiveness deteriorate.

The catalyst has a function of accelerating the bonding reaction between the epoxy group in the epoxy group-containing silane coupling agent and the hydroxyl group or the alkoxy group in the partial co-hydrolysis / polycondensation product. Suitable are heterocyclic amines, metal acetyl acetate compounds and the like.

Examples of suitable catalysts include piperazine and imidazole as heterocyclic amines,
Examples of the metal acetyl acetate compound include aluminum acetyl acetate, chromium acetyl acetate, titanyl acetyl acetate, nickel acetyl acetate, and the like.

The amount of the catalyst is 0.01 to 10 parts by weight, particularly preferably 1 to 5 parts by weight, per 100 parts by weight of the epoxy group-containing silane coupling agent (D). If it exceeds this range, the compatibility will be reduced and the coating properties such as adhesion will be reduced.

Hereinafter, a method of preparing the organopolysiloxane (E) as a binder in the heat-resistant insulating coating composition of the present invention will be described.

The alkoxysilane (A) / organopolysiloxane (B) is mixed at a predetermined composition ratio in a reaction vessel equipped with a reflux condenser and a stirrer, and then used alone or in combination.
A homogeneous solution adjusted to an arbitrary concentration using at least one kind of solvent is obtained. Next, while stirring at room temperature, distilled water adjusted to pH 2 with hydrochloric acid was added dropwise to partially co-hydrolyze and simultaneously carry out a polycondensation reaction to obtain an organopolysiloxane (a). Further, one or two or more metal alkoxides such as Ti, Zr, and Al are added and reacted at room temperature to obtain an organopolysiloxane (b). By adding the contained silane coupling agent and further reacting by adding a catalyst,
An organopolysiloxane (E) was prepared.

However, the partial cohydrolysis reaction of these binders and the like is usually carried out at room temperature, but it is necessary to shorten the synthesis time, replace the solvent, and increase the degree of condensation of the organopolysiloxane to increase the viscosity. In such a case, heating may be performed with 130 ° C. as the upper limit.

Next, the inorganic powder in the heat-resistant insulating coating composition of the present invention will be described. The inorganic powder is used for improving various properties such as adhesion, thickening, insulation, and heat resistance of the obtained coating film, and is an essential component in the heat-resistant insulating coating composition of the present invention. . Examples of the inorganic powder include metal oxides, carbides, nitrides, and the like in the form of particles, flakes, and fibers, and the particles mainly improve various properties such as insulation, heat resistance, and adhesion. For the purpose,
In addition, scaly and fiber-like materials are used mainly for the purpose of increasing the film thickness and improving crack resistance. Specific examples include silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, silicon carbide,
Silicon nitride, boron nitride, aluminum nitride, zircon, spinel, mullite, perovskite compound, sialon, clay, talc, mica, bentonite, alumina fiber, zirconia fiber, etc. Used. In use, for the purpose of improving the wettability with a binder and the like, a surface-modified one with various known silane coupling agents may be used as necessary. The average center particle size of the inorganic powder is not particularly limited,
1 μm to 100 μm, preferably 0.1 μm to 50 μm
m, more preferably 1 μm to 20 μm, and a purity of 90% or more is preferable.

The content of the inorganic powder in the heat-resistant insulating coating composition of the present invention is from 30 parts by weight to 500 parts by weight based on 100 parts by weight of the organopolysiloxane (E) as a binder.
Parts by weight, preferably 50 to 300 parts by weight, more preferably 80 to 200 parts by weight. If the content of the inorganic powder is lower than 30 parts by weight, the film forming property of the obtained coating film is low, and pinholes are generated, which causes a decrease in insulation. If the amount is more than 500 parts by weight, it is difficult to control the film thickness and it is difficult to obtain a uniform coating film, so that the adhesion and the moisture resistance are reduced.

Further, the heat-resistant insulating coating composition of the present invention includes:
A solvent such as alcohol can be added for the purpose of uniformly dispersing the inorganic powder, further preventing gelation, and improving coating (painting) properties. Suitable solvents include alcohols, ketones, esters, cellosolves, cyclic ethers, and the like. For alcohols, lower alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; for ketones, acetone, methyl ethyl ketone, methyl isobutyl ketone; for esters, ethyl acetate and butyl acetate; for cellosolve, methyl cellosolve, ethyl cellosolve, and butyl cellosolve , A cyclic ether is tetrahydrofuran,
4-dioxane or the like can be used alone or as a mixture. These solvents also include alcohols released by a partial cohydrolysis reaction or a polycondensation reaction such as an organoalkoxysilane.

The use amount of these solvents is adjusted so that the solid content concentration in the heat resistant insulating coating composition is 30% by weight to 80% by weight.

Further, the heat-resistant insulating coating composition of the present invention contains a dispersing agent, an antifoaming agent,
Paint additives such as leveling agents and thickeners can be added.

The heat-resistant insulating coating composition of the present invention is prepared by dispersing an inorganic powder or the like in a binder by a known dispersion method such as a sand mill or a ball mill.

The heat-resistant insulating coating composition of the present invention is applied to a surface of a metal substrate surface-treated by a known method such as sand blasting by a method such as spray coating, dip coating, and spin coating. By baking for 20 to 40 minutes in a medium temperature range of from ℃ to 180 ℃, a coating film having excellent adhesion, heat resistance, insulation and moisture resistance can be obtained.
After baking, the thickness of the obtained coating film is 10 μm to 150 μm.
m, preferably 30 μm to 120 μm, more preferably 40 μm to 100 μm. 10μ after baking
When the thickness is smaller than m, the adhesiveness and heat resistance are excellent, but pinholes are easily generated and the insulation property is reduced.
If it exceeds m, the distortion of the coating film will increase and the adhesion and heat resistance will decrease, so that there is a problem that the coating film partially peels off during baking or air-cooled / water-cooled spall tests after high-temperature heating.

Hereinafter, the present invention will be described in detail with reference to examples.

[0038]

EXAMPLES In this example, heat-resistant insulating coating compositions were prepared according to the formulations shown in Tables 1 to 5 below. In addition, all the numbers in a table | surface are shown by a weight part. Further, the present invention is not limited to these examples.

All the obtained paints were stable without any change for three months or more. Further, the obtained coating material was applied to a surface-treated stainless steel plate SUS304 having a size of 70 mm × 70 mm × 2 mm by dip coating so as to have a film thickness of 70 μm after drying, and dried in air for 180 μm.
Baking at 30 ° C. for 30 minutes to give a standard test plate.

The following coating film evaluation test was performed on the standard test plate.

(1) Initial Insulating Property A silver paste is applied to a standard test plate and baked at 450 ° C. for 15 minutes to obtain an evaluation sample (hereinafter referred to as evaluation sample A).
And DC 500 V according to JIS-C-1303
Was measured.

(2) Insulation after heat resistance Evaluation sample A was heated in the air at 450 ° C. for 1 hour to produce an evaluation sample (hereinafter referred to as evaluation sample B). It was measured.

(3) Insulation after High Temperature and Humidity (a) The evaluation sample A was kept in an environment of 60 ° C. × 95% RH for 10 days, taken out, and left at room temperature for 24 hours.
It measured similarly to evaluation test (1).

(4) Insulating property after high temperature and high humidity (b) Evaluation sample B was kept in an environment of 60 ° C. × 95% RH for 10 days, taken out, and left at room temperature for 24 hours.
It measured similarly to evaluation test (1).

(5) Water resistance After the standard test plate was immersed in tap water for 30 days, the presence or absence of cracks and peeling of the coating film was evaluated.

(6) Heat resistance (a) A standard test plate was heated in air at 450 ° C. for 1 hour, and immediately cooled to room temperature by air cooling to evaluate the coating film adhesion and the presence or absence of cracks. .

(7) Heat resistance (b) After heating the standard test plate in air at 450 ° C. for 1 hour, immediately after being dropped into water, the coating film adhesion and the presence or absence of cracks were evaluated.

The evaluation results are shown in the following table. In the following table, ¹⁾ is manufactured by Shin-Etsu Chemical Co., Ltd., solid content concentration 100%, ²⁾ is manufactured by Shin-Etsu Chemical Co., Ltd., solid content concentration 50%, ³⁾ is γ- Glycidoxypropyltrimethoxysilane, ⁴⁾ β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, ^{5) 5} % of the catalyst marked with a circle with respect to the epoxy group-containing silane coupling agent (D) In ⁶⁾ , the unit is Ω · cm.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

[Table 5]

[0054]

According to the present invention, a mixture of a tetraalkoxysilane and a co-hydrolyzate of an organoalkoxysilane and an organopolysiloxane combined with a highly reactive metal alkoxide such as Ti can be obtained by short-time heat curing at a medium temperature range. In addition, since unreacted hydroxyl groups and alkoxy groups remain in the coating film, adhesion and insulation after the heat resistance test are reduced. Therefore, by adding an epoxy group-containing silane coupling agent in the presence of a catalyst, the epoxy group is opened in the varnish or at the time of curing, and reacts with the unreacted remaining hydroxyl group or alkoxy group. It is presumed that an advanced three-dimensional network structure including cross-linking between polymers is formed. Therefore, the heat-resistant insulating coating composition of the present invention can be cured only by heating in a middle temperature range of 150 ° C to 180 ° C, and the obtained coating film has excellent heat resistance, adhesion, and insulation, In particular, it has excellent insulation properties after a heat resistance test and a moisture resistance test. In addition, it is particularly useful for heat-resistant insulating coats of electric / electronic parts that require heat resistance and moisture resistance.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 183/04 C09D 5/25 C09D 183/14

Claims (1)

(57) [Claims] 1. A compound represented by the general formula (A): R _n Si (OR ′) _4-n (wherein, R represents an alkyl group having 1 to 4 carbon atoms, R ′ represents a methyl group or an ethyl group, and n represents 0 or 1). , 1 or 2), and 3 parts by weight of organopolysiloxane (B) having a reactive hydroxyl group with respect to 100 parts by weight of at least one selected from alkoxysilanes represented by the following formulas:
The formula (C) M (OR) _4-n (where R is an alkyl group having 1 to 4 carbon atoms) based on 100 parts by weight of the partial co-hydrolysate in the state of coexistence at 0 parts by weight. , M represents a metal selected from titanium, zirconium, or aluminum. When M is titanium or zirconium, n
Is 0, and n is 1 when M is aluminum. 1) or 2 or more selected from the metal alkoxides represented by the formula (3) to 20 parts by weight, and
The formula (D) R ″ (R _n ) Si (OR) _3-n (wherein R is a methyl or ethyl group, and R ″ is an epoxy group Represents an organic group, n is 0, 1, or 2.) An organo group obtained by reacting an epoxy group-containing silane coupling agent represented by the following formula in the presence of a catalyst in a proportion of 0.01 to 30 parts by weight. A heat-resistant insulating coating composition comprising 100 parts by weight of polysiloxane (E) and 30 parts by weight to 500 parts by weight of an inorganic powder.