JPH03126780A - Coating composition - Google Patents

Abstract

PURPOSE:To provide the title composition excellent in water retention stability, comprising an alumina-contg. and organopolysiloxane, as a condensate through hydrolysis, obtained by reaction between each specified amount of a specific organoalkoxysilane, water and colloidal alumina. CONSTITUTION:The objective composition capable of giving a coating film of excellent characteristics on metallic or ceramic substrate surfaces, 3000-50000 in average molecular weight in terms of polystyrene, comprising a condensate through hydrolysis, obtained by reaction between (A) 100 pts.wt. of an organoalkoxysilane of the formula (R is 1-8C organic group; R<1> is 1-5C alkyl or 1-4C acryl), (B) 0.01-4 pts.wt. colloidal alumina on a solid basis with feathery alumina particles, and (C) water (1.0-4.0mol in the total amount throughout the reaction system).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides heat-resistant,
Concerning a silicone-based coating composition that has excellent abrasion resistance, chemical resistance, weather resistance, etc., can form a thick coating film with high hardness, high gloss, and nonflammability, and has excellent long-term storage stability. .

(Prior art) The surfaces of various molded objects such as metals and ceramics are coated with silicone-based polymer compositions to provide smoothness, scratch resistance, chemical resistance, and corrosion resistance.

Efforts are being made to improve weather resistance, water resistance, etc.

For example, Japanese Patent Publication No. 53-5042 discloses a reaction condensate obtained by adding methyltrimethoxysilane to aqueous colloidal silica and adjusting the pH with an organic acid.

A coating composition containing a pigment (extender pigment) and a pigment (extender pigment) is disclosed. When an acid is added to the mixture of methyltrimethoxysilane and colloidal silica, hydrolysis and condensation proceed, and at the same time, active silanol on the surface of the silica particles of colloidal silica also participates in the condensation reaction. Therefore, if the hydrolysis/condensation reaction is allowed to proceed excessively, the active silanol on the surface of the silica particles becomes involved in the reaction, which tends to cause aggregation/gelation of the silica particles. Therefore, it is necessary to set the two reaction conditions to extremely mild conditions. Moreover, the resulting coating has poor stability due to the presence of much more water than is required for hydrolysis and therefore must be used within 24 hours after preparation.

Furthermore, since the degree of condensation of methyltrimethoxysilane condensate, which is a film-forming component when forming a coating film, is low,
If the film thickness is greater than that, there is a drawback that cranking occurs. It also has poor alkali resistance.

Japanese Patent Publication No. 63-45752 discloses a coating composition for preventing corrosion of metals. This composition consists of a reaction mixture obtained by adding an aqueous solution of an acid to a mixture of methyltrimethoxysilane, triisopropoxyaluminum, isopropanol, and colloidal silica. This coating composition is composed of A1□0. Because it contains
The coating film obtained using this has excellent corrosion resistance. However, this &1IFf! , the above-mentioned Japanese Patent Application Publication No. 52-5042
Like the composition described in the above publication, it has the drawbacks of lacking stability and not being able to form a thick coating.

JP-A-61-268770 discloses a coating composition comprising a reaction condensate obtained from a mixture of methyltrimethoxysilane, aqueous colloidal alumina, acid 1 and alcohol. This paint coats the surface of glass, metal, plastics, etc. and positively charges the surface of the base material, thereby preventing the surface of the base material from being contaminated by dust, dirt, etc. This is due to the action of particles with strong positive charges. The paint is prepared by mixing methyltrimethoxysilane, aqueous colloidal alumina acid and alcohol at room temperature. In order to uniformly disperse the alumina in the paint, an aqueous colloidal alumina is used, as described above. Here, if it is attempted to add the required amount of alumina in order to ensure the above-mentioned antistatic performance, the amount of water will inevitably increase. this is.

The upper limit of the solid content of aqueous colloidal alumina is approximately 25
%. The amount of water mentioned above is much larger than the amount of water required for hydrolysis of methyltrimethoxysilane, so when mixing each component and performing a polycondensation reaction, the reaction must be controlled under mild conditions. There is a need. Furthermore, the resulting paint has poor stability even when diluted with alcohol or the like.

Furthermore, since methyltrimethoxysilane has a low molecular weight, when it is hydrolyzed and then polycondensed, a large amount of water is eliminated by a dehydration reaction. Therefore, the coating film formed by applying the paint has a large volume shrinkage upon curing, and if the coating film is thick, cracks are likely to occur.

JP-A-63-46272 discloses an organopolysiloxane which is a condensation product of methyltrimethoxysilane and has a polystyrene equivalent weight average molecular weight of 3,000 to 50,000, aqueous colloidal alumina, water and alcohol. A coating composition comprising a reaction condensate formed from a mixture of the following is disclosed. This composition contains essentially the same components as the above-mentioned JP-A No. 61-288790, but a comparative composition obtained by polycondensing methyltrimethoxysilane while controlling the molecular weight to a predetermined molecular weight. Contains an organopolysiloxane with a relatively high molecular weight. Therefore, the rate of volumetric shrinkage due to dehydration reaction during curing is small, making it difficult for cranks to form. Therefore, it is also possible to form a relatively thick film. However, for example, in order to obtain the desired strength and antistatic function, it is necessary to contain a certain amount of alumina, and if the necessary amount of alumina is contained, as described above.

The amount of water will inevitably increase. The amount of water contained in this coating composition is 5 to 3.4 moles per mole of the organoborisiloxane.

This paint contains acids such as hydrochloric acid, nitric acid, and acetic acid that were present as stabilizers in colloidal alumina.

The presence of these acids and the excess water makes the hydrolysis/polycondensation reaction of organoalkoxysilane extremely rapid. Therefore, when mixing and reacting each portion of the paint,
Alternatively, during storage of the paint, the hydrolysis/polycondensation reaction proceeds rapidly, resulting in easy gelation.

Therefore, when a coating film is formed using such a paint,
The resulting film lacks transparency, becomes cloudy, or exhibits a whitening phenomenon.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and its purpose is to provide a silicone-based coating composition for coating the surfaces of metals, ceramic extrusions, etc. The object of the present invention is to provide a coating composition having the following properties: ■ A coating composition that has excellent storage stability and can be stored for a long time without gelling; ■ A coating composition that can be stored at high temperatures when preparing a coating film. A coating composition that does not require long curing treatment and does not cause cracks even when forming a relatively thick coating film; A coating composition that can form a coating film with excellent adhesion to a substrate.

■Alkali resistance, acid resistance, water resistance, and scratch resistance.

A coating composition that can form a coating film with excellent nonflammability.

(Means and Effects for Solving the Problems) The coating composition of the present invention is a coating composition containing an aluminum-containing organopolysiloxane.

The aluminum-containing organopolysiloxane.

An organoorganic compound represented by the general formula R51(OR')3 (where R is an organic group having 1 to 8 carbon atoms, and R'' is an alkyl group having 1 to 5 carbon atoms or an acyl group having 1 to 4 carbon atoms) It is a hydrolyzed condensate of alkoxysilane, water and colloidal alumina.

The alumina particles of the colloidal alumina have a feather-like shape, and the alumina-containing organopolysiloxane contains 100 parts by weight of the organoalkoxysilane;
01 to 4 parts by weight of the colloidal alumina; and 1.0 to 4.0 mol of water in a total amount in one reaction system per mol of the organoalkoxysilane.

Obtained from.

The alumina-containing organopolysiloxane has an average molecular weight in terms of polystyrene of 3,000 to 50,000.

This achieves the above objective.

The alumina-containing organopolysiloxane contained in the composition of the present invention is a condensate obtained by hydrolyzing and condensing organoalkoxysilane and colloidal aluminum, and its weight average molecular weight in terms of polystyrene is 3,000.
~50,000.

The above organoalkoxysilane has the general formula R3i (O
Represented by R. In the above formula, R is an atom group having 1 to 8 carbon atoms, and R'' is an alkyl group having 1 to 5 carbon atoms or an acyl group having 1 to 4 carbon atoms.The prime number of R and R' is too large. When this occurs, the hydrolysis rate described below becomes extremely slow, and in some cases, hydrolysis hardly progresses.The above R includes alkyl groups such as methyl, ethyl, propyl, and butyl; phenyl, tolyl,
Aryl groups such as xylyl groups; cycloalkyl groups such as cyclohexyl groups; other γ-chloropropyl groups, vinyl groups, γ-glycidoxypropyl groups, γ-methacryloyloxypropyl groups, T-mercaptopropyl groups, T-aminopropyl groups group, 3,4-epoxycyclohexyl group, and the like. Examples of R'' include methyl group, ethyl group, propyl group, 2-butyl group, 2-acetyl group, etc. Examples of such organoalkoxysilane include methyltriethoxysilane.

Methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane propyltrimethoxysilane 1 propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane 0 run 1 γ-glycidoxypropyltrimethoxysilane, T-glycidoxypropyl]-liethoxysilane, T
Examples include -mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and 3,4-epoxycyclohexylethyltrimethoxysilane. Preferably, methyltrimethoxysilane and/or methyltriethoxysilane are used. These organoalkoxysilanes can be used alone or in combination of two or more.
The two can also be used together.

The colloidal alumina used in the composition of the present invention is. Usually, it is an alumina sol with a pH in the range of 2.0 to 6.0 using water as a dispersion medium. This contains alumina, alumina hydrate, etc. in a proportion of about 5 to 25% by weight, and acids such as hydrochloric acid, nitric acid and acetic acid are used as dispersion stabilizers. The average particle size of the above alumina sol is 5 xxo-
'~2.5 XIO-'μm. Preferably 1. X10-
The shape of the alumina particles in the alumina sol is granular, rod-like, feather-like, etc., but the feather-like shape is particularly preferable in the composition of the present invention. Examples of the products include Alumina Sol-100 and Argo Na Sil-200 (both manufactured by Nissan Chemical Industries, Ltd.). Alumina sol is used for the purpose of increasing the surface hardness of the coating film obtained using the coating composition of the present invention or for improving the durability. Improves chemical properties,
Used to improve adhesion to the base material.

The proportion of the colloidal alumina in the composition is from 0.01 parts by weight to 4 parts by weight, preferably from 0.05 parts by weight to 1 part by weight, in terms of solid content, per 100 parts by weight of the organoalkoxysilane. When the amount exceeds 4 parts by weight, the amount of water and the amount of acid blended as a stabilizer increase accordingly. As a result, the paint tends to gel and lack stability. Furthermore, the resulting coating film has poor transparency and is cloudy. Conversely, if it is less than 0.01 part by weight, the adhesion of the coating film to the substrate will be poor. Poor alkali resistance. Furthermore, it becomes difficult to form a thick coating film, and the coating film is more likely to crack.

2 An alkali-containing organopolysiloxane is formed from the organoalkoxysilane and colloidal alumina through hydrolysis and polycondensation. For example, first, a double organoalkoxysilane is prepared, and a water-soluble organic solvent is added thereto as required.

Examples of water-soluble organic solvents include alcohol solvents, cellosolve solvents, and cellosolve acetate solvents.

Examples include glyme-based solvents. Add 2 colloidal alumina and water, stabilizer, etc. to this,
The hydrolysis/polycondensation reaction is carried out by heating at a temperature of about 20°C or higher up to the reflux temperature, preferably at 50 to 80°C for about 30 minutes to about 20 hours.

Here, the hydrolysis and condensation of organoalkoxysilane. It is shown by the following formula. From this equation, it can be seen that the theoretical amount of water required for hydrolysis is 1.5 times the mole of organoalkoxysilane.

Rsi(OR')] +31120÷RSi(O
il) 3 +3R' OHnRSi(Off):+
-shi(RSiO+.s)n+1.5nll□0 By summarizing this equation, the following equation is obtained.

nRSi(OR'): +-1-1.5nl+20 (
=±(RSiO+.s)n +3nR11 ■ The amount of water mentioned above is 2 Usually, about 1.0 to 4.0 mol, preferably 1.5 to 3 mol, per 1 mol of organoalkoxysilane.
．． It is 0 mole. If this ratio is less than about 1.0 mole, there will be a large amount of residual alkoxy groups. Even when the resulting paint is applied to a base material, it may not cure sufficiently, and the adhesion and hardness between the paint film and the base material decrease. On the other hand, the blending ratio of 1 is 4.
If it exceeds 0 mol.

The presence of excess water in the reaction solution makes it difficult to control the reaction, resulting in poor storage stability of the resulting solution.

The water required above is as follows. Water contained in the colloidal alumina is mainly used. Depending on this need.
Tap water, distilled water, ion exchange water, etc. are added to adjust the amount of water. Preferably distilled water or ion-exchanged water is used.

The molecular weight of the product obtained by such hydrolysis/polycondensation is. It is about 3,000 to about 50,000, preferably about 4,000 to about 30,000. Here, the molecular weight is a value calculated using a polystyrene conversion method using gel permeation chromatography. (4) When the molecular weight is less than about 3.000, the resulting paint has a high silanol content. Therefore, if a thick coating film is formed using this paint, cracks are likely to occur. On the other hand, if the molecular weight exceeds about 50,000, the resulting paint tends to gel and lacks storage stability.

Furthermore, the adhesion between the coating film and the base material decreases.

The composition of the present invention further contains various additives as necessary. For example, it can be used as a colored enamel by adding one-body pigments or colored pigments, or it can be used as a paint to form anti-rust films, electrical insulation films, heat radiation films, conductive films, etc. by adding appropriate fillers. It is also possible.

Other additives include various surfactants, silane coupling agents 2, titanium coupling agents, and polyamines.

Examples include various conventionally known additives such as alkali metal salts, organometallic compounds, heterocyclic compounds containing a nitrogen atom, various metal alkoxides, aluminum compounds such as aluminum acetylacetonate, and dyes.

The coating composition containing "double alumina-containing organopolysiloxane, water" 5 and various additives as necessary may be diluted or concentrated with an organic solvent as appropriate to adjust the solid content before storage or use. Ru. Examples of diluting solvents include alcohol solvents, cellosolve solvents, and cellosolve acetate solvents.

A glyme-based solvent or the like is used, and the solid content is usually adjusted to 5% to 40% by weight, preferably 20 to 30% by weight.

A desired coating film is formed by coating and curing a coating material containing the composition of the present invention on various substrates.

Substrates that may be used include metals, ceramics, glass, plastics, paper, fiber wood, and the like. The solid content in the resulting paint has sufficient performance as an inorganic binder for the paint, so even when the paint does not contain the above additives and is directly applied to the surface to be painted and cured, it remains relatively thick at 50 to 100 μm. A covering layer is formed. The paint hardens at approximately 80 to 200°C.
This can be done under relatively mild conditions of up to 60 minutes, and it is possible to form a relatively thick coating film without cracking or peeling during curing. In paints containing extender pigments or colored pigments, it is also possible to form a coating film with a thickness of 100 μm or more without causing cracks or peeling. Therefore, 1 e.g. foamed plastics, wood 2
Even porous substrates with large surface roughness such as paper and fibers can be impregnated with paint or coated with paint to provide water resistance, weather resistance, dimensional stability, high hardness, and It is possible to impart flammability, etc. In addition, unlike organic paints, as inorganic nonflammable paints, regardless of whether the base material is flammable, flame retardant, or nonflammable (a wide range of materials from plastics to inorganic materials),
Their surfaces can also be coated to impart flame-resistant properties.

The compositions of the present invention include 1 alumina-containing organopolysiloxane as described above. In this alkoxysilane-containing organopolysiloxane, the alkyl group simultaneously participates in the reaction during the hydrolysis/polycondensation reaction of alkoxysilane, and alumina is incorporated into some of the siloxane bonds produced. It's Ma. When a paint containing such an alumina-containing organopolysiloxane is applied and cured, hydrolysis and polycondensation further proceed, forming a polymer in which alumina is incorporated into the siloxane bonds. In the present invention, 1
Since feather-like alumina with a large surface area is used, the reaction area with the alkoxysilane is large even if the amount is small.

Incorporating feather-like alumina into the polymer physically strengthens the polymer. In this way, a coating film having hardness, chemical resistance, weather resistance, heat resistance, etc. comparable to conventional coatings can be formed using a smaller amount of alumina than conventional coatings. Since the amount of alumina is small, a glossy coating film with excellent transparency is obtained.

As described above, in the present invention, since the amount of alumina sol used is small, the amount of water present in the reaction system is small. Therefore, the reaction for forming an alumina-containing organopolysiloxane from an organoalkoxysilane can be easily controlled by adding water as needed. Since such a small amount of alumina sol is used, kelization does not occur during the production of the alumina-containing organopolysiloxane and during storage of the paint containing the polysiloxane.

Additionally, organopolysiloxanes containing aluminum.

Rather than a low molecular weight monomer, as mentioned above, 3,00
Since it is an oligomer having a predetermined molecular weight of 0 to 50,000, it exists stably during storage and is less prone to gelation.

When a coating material containing the composition of the present invention is applied to a substrate and cured by heating, a uniform, glossy coating film is formed on the surface of the substrate. As mentioned above, this coating film has a form in which feather-like alumina is bonded to the polymer skeleton of organopolysiloxane. Therefore, this coating film has high hardness and excellent adhesion to the substrate. It is possible to form a thick coating film without shrinking or cranking the coating film during curing. In this way, by using the coating composition of the present invention, a coating film having gloss, high hardness, heat resistance, weather resistance, chemical resistance, alkali resistance, acid resistance, water resistance, etc. can be obtained. The result is 9.

(Example) The present invention will be explained below with reference to Examples. In the examples, all parts are by weight.

Practical Flaming (a) Preparation of alumina-containing organopolysiloxane: In a reaction vessel equipped with a reflux condenser and a stirrer, 100 parts of methyltrimethoxysilane and 1 part of alumina sol-100 (manufactured by Nissan Chemical Industries, Ltd., hydrochloric acid stabilized aqueous dispersion) were added. Contains feather-like alumina; solids concentration 10% by weight) 1 part, and 20 parts water
The mixture was heated to 60°C with stirring, and reacted for about 3 hours. This was then cooled to room temperature to obtain an alumina-containing organopolysiloxane having a 2 weight average molecular weight of about 6.200. The molecular weight was measured by a polystyrene conversion method using Gelper Aesigon chromatography.

(b) Preparation of coating composition: (125 parts of isopropanol was added to the alumina-containing organopolysiloxane obtained in Section 81 to obtain coating composition A.

(C) Evaluation of coating composition: (The coating coating composition obtained in section b1 was evaluated on the following items. and Tables 1 and 2, respectively, along with the evaluation results of the coating compositions obtained in Comparative Examples 1 to 5.
Shown below.

[Storage Stability] Place the coating composition in a sealed container,
After being left at 0°C for 2 weeks, the presence or absence of gelation of the two compositions was examined.

Regarding the following items, a cured coating film was formed on a cold rolled stainless steel plate (JIS G43055US-CP) in the following manner and evaluated. First, using a spray device, apply the coating composition to a coating film with a dry coating thickness of 50 μm.
Coat it on the stainless steel plate so that it becomes . This was heated at 150°C for 30 minutes, and the resulting cured coating film was evaluated.

[Coating film appearance] Evaluate the surface condition by visual observation.

[Adhesion] Evaluated by JIS K5400 substrate grain.

[Hardness] Evaluated by JTS K5400 pencil hardness.

[Solvent resistance] Soak gauze in toluene and apply 301 to the coating film. Observe the condition after the rubbing test.

Example 1 was carried out using the composition and reaction conditions shown in Table 1 to obtain a coating composition BE. The composition and evaluation results of the obtained coating composition are shown in Tables 1 and 2, respectively.

Comparative Flaming Soil 2i A coating composition F-J was obtained by the same procedure as in Example 1 using the composition and reaction conditions shown in Table 1. The composition and evaluation results of the obtained coating composition are shown in Tables 1 and 2, respectively.

(The following is a blank space) 2 24 Real 40 Paint obtained in Example 1 & 100 parts of container A Titanium oxide (manufactured by Ishiya Sangyo ■, Taibake R-3)
80) 20 parts were blended and dispersed in a 5-sand mill for 1 hour to obtain a coating composition K.

Next, the obtained coating composition K was applied onto a cold-rolled stainless steel copper plate (JIS G43055US-CP) using a spray device so that the dry coating film had a thickness of 100 μm, and heated at 150° C. for 30 minutes. A cured coating was formed. In addition to the evaluation items shown in Example 1, these cured coating films were evaluated on the following items. The results are shown in Table 3 together with the evaluation results of coating compositions obtained in Examples 7 to 10 and Comparative Examples 6 to 8, which will be described later.

[Boiling Water Resistance] The coated stainless steel plate was immersed in boiling water at 100°C for 24 hours, and then its condition was observed.

[Drop 1 ml of acid-resistant 13% sulfuric acid aqueous solution onto the coating film, let it stand for one day in a petri dish with a lid, wash with water, and observe the condition.

[Alkali Resistance] 1 ml of a 1% aqueous solution of 1-lium hydroxide was dropped onto the coating film, and after standing for 1 day in a petri dish with a lid, it was washed with water and the condition was observed.

[Weather Resistance] A 1,000 hour irradiation test was carried out using a weatherometer according to JIS K 5400, and the condition was observed.

The coating composition was prepared in the same manner as in Example 6, except that coating composition B-E prepared in Examples 2 to 5 was used instead of coating composition A. A sample L~0 was obtained and evaluated in the same manner. The results are shown in Table 3.

Comparative Examples 1 and 3 were used instead of coating composition A on the comparison side. The coating composition P was prepared in the same manner as in Example 6, except that coating compositions F, H, and
-R was obtained and evaluated in the same manner. The results are shown in Table 3.

(The following is a blank space) G 7 (Effects of the invention) According to the present invention, a coating film with excellent properties can be easily formed on the surface of a metal or ceramic substrate, and a coating film with excellent storage stability can be formed. A silicone-based coating composition is provided. The coating film obtained using the coating paint obtained by this method has high hardness, excellent scratch resistance, gloss, and has heat resistance, weather resistance, water resistance, chemical resistance, etc. Extremely good at In particular, it maintains high gloss even when left outdoors or under corrosive conditions, and does not discolor or deteriorate, which is an excellent property not found in conventional silicone-based coating paints. Therefore, for example, 2g of exterior wall material exposed to sunlight 2g of equipment used under conditions where it is easy to eat
It can be advantageously used as a paint for coating building materials that require cosmetic properties.

that's all

Claims (1)

[Claims] 1. A coating composition containing an alumina-containing organopolysiloxane, wherein the alumina-containing organopolysiloxane has the general formula RS
i(OR')_3 (where R is an organic group having 1 to 8 carbon atoms, R' is an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 4 carbon atoms)
is a hydrolyzed condensation product of an organoalkoxysilane represented by (an acyl group of Part by weight of the organoalkoxysilane: 0.0% in terms of solid content.
01 to 4 parts by weight of said colloidal alumina; and water in a total amount of 1.0 to 4.0 mol in the entire reaction system per 1 mol of said organoalkoxysilane, said alumina-containing organopolymer. A coating composition for coating, wherein the average molecular weight of the siloxane in terms of polystyrene is 3,000 to 50,000. 2. The colloidal alumina uses water as a dispersion medium, and the average particle size of the alumina is 5 x 10^-^3 to 2.5 x 10^-
The coating composition according to claim 1, which has a thickness of 1 μm.