JPS5945361A - Method for forming inorganic coating film - Google Patents

Abstract

PURPOSE:To form an inorganic coating film having excellent film properties, by applying and curing a coating containing a film-forming component consisting of a high-polymeric condensate obtained by hydrolyzing a specific organic silicon compound or its oligocondensate with an acid, and condensing the product. CONSTITUTION:The organic silicon compound of formula (R is 1-8C hydrocarbon group) (e.g. tetramethoxysilane) and/or its oligocondensate is hydrolyzed in the presence of an acid catalyst such as hydrochloric acid. The pH of the system is adjusted to >=7 e.g. by adding sodium hydroxide, etc. and the hydrolyzed product is condensed to obtain a high-polymeric condensate free from silanol group and having a condensation degree of >=20 and a molecular weight of about >=2,000. A coating containing the above condensate as a film-forming component is applied to the substrate, if necessary added with a strongly basic catalyst, etc., and cured with moisture to obtain an inorganic coating film. EFFECT:Excellent corrosion resistance, solvent resistance, heat resistance and weatherability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an inorganic coating film, and more specifically, an inorganic binder containing silicon is used as a film-forming component.

The present invention relates to a method for forming a coating film using a paint that has been prepared using a paint.

Conventionally, many paints that use silicate as a binder have been proposed and have been proposed, such as corrosion-resistant paints such as alkyl silicate-based zinc-rich paints and alkali-silicate-based zinc-rich paints, and organosilicon-based heat-resistant paints such as polydimethylsiloxane. is well known.

Alkyl silicate zinc rich paint uses an organosilicon compound or (and) low condensate represented by the following general formula % () (where R represents a hydrocarbon group having 1 to 8 carbon atoms) as a starting material, and uses hydrochloric acid Hydrolyzed in the presence of an acid catalyst such as, and partially condensed, this is used as a binder, and a large amount of zinc dust is added to this.

This binder has many silanol groups at its terminals due to acid hydrolysis, and these silanol groups are metastable in the acidic region. Before painting, zinc powder is added and mixed to consume the acid catalyst and react with the binder to cause crosslinking and hardening. Although the above hydrolyzate differs depending on the amount of reaction water and the reaction conditions (therefore, the degree of progress of the condensation reaction), a high condensate is not produced in an acid-catalyzed reaction (in an acidic region). However, the stability usually decreases after 3 to 6 months, and it tends to thicken and gel.Also, paints that use this binder as a film-forming component have a pot life of about 5 to 10 hours after adding zinc dust. The curing reaction is based on the reaction between zinc powder and the silanol group of the binder, and when a non-reactive general pigment is used in place of zinc powder, the coating thickness is 1/(hereinafter referred to as "2"). No film can be formed, and the coating performance is extremely poor, making it impractical.

On the other hand, Japanese Unexamined Patent Application Publication No. 11676/1983 discloses a one-component zinc-rich paint using a low condensed alkyl silicate and adding alkyl titanate or alkyl zirconate as a moisture curing aid. In the reaction, a large amount of alcohol is produced as a by-product due to moisture curing, and as the alcohol evaporates, a large volume shrinkage occurs. Therefore, it is difficult to use this type of paint for purposes other than zinc-rich paints containing a large amount of zinc powder, and it cannot be used as clear paints or paints for forming thick films.

Moisture-curable clear paints and inorganic paints such as zinc-free enamels have also been developed that use organosilicon resins such as polydimethylsiloxane as binders, but these binder components contain many alkyl Because it has a base, it does not have a high degree of heat resistance, and the cohesive force of the paint film is small, and it is difficult to apply another paint on top of the formed paint film. It is only used for more limited purposes.

It is also known to use highly hard organosilicon resins for surface modification of plastics, but in all cases the crosslinking functional group is silanol.

The present inventor has been conducting research to solve the problems of paints using this type of silicon-containing compound, and in this research, the organosilicon compound represented by the above general formula [I] or (and) After hydrolyzing the low condensate in the presence of an acid catalyst and then condensing the resulting product at a pH of 7 or higher, the resulting condensate is a high condensate that does not have silanol groups. discovered that when applied to an object to be coated, it is cured by moisture in the air, resulting in a coating film with excellent physical properties, and also that the above-mentioned problems of the conventional method could be overcome, leading to the completion of the present invention. That is, the present invention uses an organosilicon compound and/or a low condensate thereof represented by the following general formula, R-0-5i-0-R (where R is an O hydrocarbon group having 1 to 8 carbon atoms), and an acid catalyst. After hydrolysis in the presence of silanol, a high condensate having no silanol group obtained by condensation with a pn of 7 or more is applied as a film-forming component to an object to be coated, and the film is cured by moisture. The present invention relates to a method for forming an inorganic coating film characterized by the following.

In the organosilicon compound represented by the above general formula CI used as a raw material in the present invention, R is the same or different hydrocarbon group having 1 to 8 carbon atoms, and the hydrocarbon group in this case is an alkyl group. group, a phenyl group with or without a substituent, a cycloalkyl group, etc. Examples of substituents include methyl and ethyl groups. Specific examples of the compound include tetramethoxysilane, tetraethoxysilane, deI-labrovimexisilane, tetrabutoxysilane, and tetraphenoxysilane. Further, the term "low-synthesize product" means an oligomer having a degree of polymerization of 10 or less.

When condensing the organosilicon compound represented by the general formula [1,] or (and) its low condensate, the compound or (and) its low condensate is added to a water-soluble solvent, and hydrochloric acid, sulfuric acid, In the presence of a mineral acid such as phosphoric acid or an organic acid such as formic acid or acetic acid, water is added at a ratio of 0.2 to 2 tnc# per mole of R (> group) bonded to Si, and 20 to 20
At about 0.06C: React for about 30 minutes to 10 hours with stirring, then add inorganic bases such as sodium hydroxide, potassium hydroxide, aliphatic amines such as monoethylamine, diethylamine, triethylamine, ammonia, etc. The pII of the system is set to 7 or higher to allow the condensation reaction to proceed.

After the reaction is completed, the desired high condensate can be easily obtained by removing remaining water by distillation, azeotropy, or the like.

The high condensate thus obtained is a three-dimensional condensate with a degree of condensation of at least 20 or more and a molecular weight of about 2,000 or more, and has sufficient performance as an inorganic binder for paints. A coating film with a thickness of about 20/7 can be formed.

It hardens due to moisture in the air about 10 minutes to 10 hours after application, and rapidly hardens within a few minutes when brought into active contact with coating water. At this time, the curing properties can be further improved by adding a strong base catalyst or a metal alkoxide such as titanium or aluminum.

In the present invention, a one-component rust-preventing paint can be obtained by adding a metal bed, for example, zinc powder, or an enamel can be obtained by adding only ordinary extender pigments or coloring pigments. In addition, if a large amount of paint is added at this time, it is possible to apply thick coatings of 100 μm or more without causing any flaking or peeling.

The inorganic coating film formed by the method of the present invention has superior coating performance compared to conventional silicate coatings, and is especially excellent in corrosion resistance, solvent resistance, heat resistance, and weather resistance.

EXAMPLES The present invention will be specifically described below with reference to Examples.

Example 1 Tetraethyl silicate 208y is placed in the reaction vessel.

Ethyl alcohol 208y and 0.2NI￥A acid 72f
7 was added and the contents were then allowed to react at 40°C for 2 hours with stirring. The obtained reaction product is hereinafter referred to as "reaction product A-1".

Further, 50y of triethylamine was further added to the above reaction product A-1 to raise the pH to 7 or more to carry out a condensation reaction, and then benzene 502 was added and the temperature was raised to 70-76°C.
The solvent was removed for 150y. The reaction product thus obtained had a resin non-volatile content of 22.1% (dried at 105°C for 30 minutes in a nitrogen stream, the same applies hereinafter), and did not change at all even after being stored at 30°C for 60 days, exhibiting excellent storage stability. showed his sexuality. Hereinafter, this product will be referred to as [reaction product A-2-1].

Then, apply the above reaction product A-2 solution to a polished steel plate to a film thickness of 1
It was painted 0μ and placed in a room with a temperature of 200C and humidity of 75% for 7 days. No cracks were observed in the coating film thus formed, and there was no change at all even after immersion in toluene for 24 hours.

Comparative Example 1 The reaction product A-1 solution obtained in Example 1 was coated in the same manner as in Example 1, but the coated film cracked after 3 hours and could not be formed. In addition, the reaction product “A-1 solution” was
When stored at 0°C for 60 days, it turned into a gel.

Example 2 ES-40 (a low condensate of tetraethyl silicate manufactured by Nippon Colcoat Co., Ltd., trade name) 610y, 300y of ethyl alcohol, 52y of formic acid, and 36y of distilled water were added to a reaction vessel, and the contents were then heated at 80°C with stirring. 5 hours reaction time. The obtained reaction product will be referred to as "reaction product B-1" below.
”

N-methylmorpholine 507 was further added to the above reaction product B-1 to raise the plT to 7 or more and the mixture was heated to 40°.
The reaction was carried out at C for 5 hours, and then 100 y of toluene was added and the solvent was removed for 200 y. The reaction product thus obtained had a resin non-volatile content of 51.3 wt.
No change occurred even after storage for 0 days, showing excellent storage stability. This product is hereinafter referred to as reaction product B-21.

Then, a coating composition obtained by dispersing 50 parts by weight of talc in 100 parts by weight of the reaction product 13-2 was applied to a polished steel plate to a thickness of 100 μm and dried under the same conditions as in Example 1. No cracks were seen on the paint film, and it was immersed in seawater at 40°C.
There was no change even after immersion for 0 hours.

Comparative Example 2 The reaction product B-1 obtained in Example 2 was coated and coated in the same manner as in Example 2, and dried under the same conditions as in Actual hIL Example 1. Although no cracking was observed in the resulting coating film, peeling and dissolution were observed in the coating film after immersion in seawater at 40°C for 24 hours.

Moreover, the viscosity of the reaction product B-1 solution increased during storage between 306C160F1 and 306C160F1.

Example 3 Tetrabutyl silicate) 320y in the reaction vessel.

600 y of isopropanol and 144 y of 0.2N sulfuric acid were added, and the contents were then reacted at 40° C. for 1 hour with stirring. The obtained reaction product will be referred to as "reaction product C-" below.
1".

Further, potassium hydroxide 3y was further added to the above reaction product C-1 to raise the pH to 7 or more, and the mixture was heated to 1 at 30°C.
The reaction was carried out for 0 hours, and then 200!9' of toluene was added to remove the solvent for 400y. The reaction product thus obtained had a resin non-volatile content of 10.0% and showed excellent storage stability without any change even after storage at 30°C for 60 days. Hereinafter, this product will be referred to as "1 reaction product C-2".

Next, to 100 parts of the reaction product C=2; It was coated to a film thickness of 50μ and dried under the same conditions as in Example 1.
Shita. The coated plate was subjected to the Tsuruto spray test: ((It was subjected to a 10-hour test, but no damage was observed, although some white rust was observed in some areas.) The coating composition was stored at 130°C for 7F1. also showed no change.

Comparative Example 3 Using the reaction product C-t obtained in Example: 3, it was made into a paint and painted in the same manner as in Example 3 (2, dried under the same conditions as in Example 1. Although the paint composition was subjected to a spray test for 300 hours, no damage was observed, although white rust was observed in some areas.
Complete gelation occurred after 8 hours at °C. Moreover, the reaction product C-1 solution gelled when stored at 30°C for 160 days.

(From -1-) 1 Yumi Agent Patent attorney Eiji Saegusa, ,l,
],,, II Procedural Amendment (Voluntary) 1. Small (displayed as '1, 1982 Patent Application No. 157096, 2 shots) I
J1gp name Inorganic @ Film formation method 3? Relationship with Ili corrective case Patent applicant
h'su (1a o) Kansai Paint Co., Ltd. 4, agent 20 Hirano-cho, Higashi-ku, Osaka. ) 10 Sawa no Tsuru Hill Electric, T8 Jun 0
-203-0941 (Main) Spontaneous 6 Number of inventions increased by the amendment Contents of the amendment 1 The description in specification ν3 has been changed to the following 1'l';
sn)','jl, do.

(hereafter 10)

Claims (1)

[Claims] ■ An organosilicon compound and/or a low condensate thereof represented by the following general formula, R-0-5i-0-R (where R is 0 having 1 to 8 carbon atoms)
After hydrolyzing in the presence of an acid catalyst (hydrocarbon group), the pH is adjusted to 7 or higher and condensation is performed to form a film-forming component of a high condensate that does not have a silanol group. An inorganic coating film forming method characterized by curing the coating film with moisture.