JPH0819329B2 - Room temperature curable polysiloxane composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating material for general construction. More specifically, the present invention relates to a polysiloxane coating material having excellent transparency, weather resistance, water resistance and stain resistance.

(Prior Art) A large number of compositions have heretofore been disclosed for room temperature curable polysiloxane coating materials.

When used as a coating material for general construction, these compositions have the general formula Si (OR ² ) ₄ or the general formula R ¹ Si (OR ² ) ₃ (R ¹ , R
⁽² is an alkyl group) A low condensate obtained by hydrolysis of an alkoxysilane represented by (1) is prepared in advance, and such a low condensate is further polycondensation-cured before use. Examples of catalysts used at this time include acids, alkalis, amines such as inorganic acids such as hydrochloric acid and paratoluenesulfonic acid, organic acids; octenoates such as zinc, cobalt and tin, naphthenates; sodium acetate, thiocyanate. Alkali metal salts such as sodium; Aliphatic polyamines such as triethanolamine, choline hexoate, triethylenetetramine, tetraethylenepentamine; quaternary ammonium salts such as tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide; tetra Butylphosphonium hydroxide, 1,8-diazabicyclo (5,4,0) undecene-7 and the like can be mentioned.

(Problems to be Solved by the Invention) As described above, the conventional product requires a two-step reaction for film formation. Further, since the drying time at room temperature curing is long and the chargeability is large even after curing, dust in the air is easily adsorbed by the electrostatic suction action. Further, since the surface hardness is low, there is a problem that the surface is easily scratched.

An object of the present invention is to solve the above problems and to provide a polysiloxane liquid coating material having a short drying time, excellent conductivity, transparency, water resistance, stain resistance, weather resistance, and large surface hardness. To provide.

(Means for Solving Problems) As a result of various investigations, the present inventors have improved the above-mentioned various properties by hydrolyzing an alkoxysilane using an oxy compound of Group IVB of the periodic table as a catalyst, and have a production method. The present invention has been completed by finding that an advantageous coating material can be obtained also in. The present invention comprises (a) a compound represented by the general formula R ¹ Si (OR ² ) ₃ as an essential component, and is represented by the general formula ▲ R ¹ ₂ ▼ Si (OR ² ) ₂ and the general formula Si (OR ² ) ₄ . An alkoxysilane having the compound as an optional component (wherein R ¹ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group, R ² represents an alkyl group having 1 to 4 carbon atoms), (b) water, (c) A room temperature curable polysiloxane composition comprising 0.05 to 5 mol% of an oxy compound of Group IVB of the periodic table, and (a), (b) and (c) per 1 mol of the alkoxy group of the component (a). It is a thing.

As the above-mentioned alkoxysilane, ▲ R ¹ ₂ against R ¹ Si (OR ² ) ₃
▼ Si (OR ² ) ₂ can be added in the range of 15 mol% or less, Si (OR ² ) ₄ in the range of 20 mol% or less, and instead of Si (OR ² ) ₄ , its partial hydrolysis-condensation product, for example, Commercially available ethyl silicate 40
(Product name) etc. can be added.

When (R ¹ ₂ ) Si (OR ² ) ₂ is added, cracks are less likely to form in the coating film, but if it exceeds the above range, the drying time becomes long and the film-forming property becomes poor. Further, by adding Si (OR ² ) ₄ , the hardness of the coating film increases and the drying time is shortened, but if it exceeds the above range, cracks are likely to occur.

Examples of the compound represented by the general formula R ¹ Si (OR ² ) ₃ include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, methyltrii-propoxysilane, ethyltrin-butoxysilane, phenyltrimethoxysilane. Examples of compounds represented by the general formula R ¹ Si (OR ² ) ₂ such as methoxysilane and phenyltriethoxysilane include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, and dimethyltrii-.
Propoxysilane, diphenyl n-butoxysilane, etc.
Examples of the compound represented by the general formula Si (OR ² ) ₄ include tetraethoxysilane, tetramethoxysilane, tetra i-propoxysilane and the like.

The water of the component (b) is appropriately in the range of 0.8 to 2.5 mol, preferably 1.5 to 2 mol, relative to 1 mol of the alkoxy group of the component (a), and the film forming property is lost outside this range.

Examples of the oxy compound of Group IVB of the periodic table, which is the component (c), include oxy compounds of titanium, zirconium, and hafnium, and the oxy compound of zirconium is particularly preferable. Examples of such compounds include TiOCl ₂ , ZrOCl ₂ , Hf
Specific examples thereof include OCl ₂ , TiO (NO ₃ ) ₂ , ZrO (NO ₃ ) ₂ and HfO (NO ₃ ) ₂ . The amount thereof is 0.05 to 5 mol%, preferably 0.1 to 3 mol% with respect to 1 mol of the alkoxy group of the component (a),
If it exceeds this range, the pot life will be extremely short and it will be unsuitable for practical use. If it is less than this range, the reaction does not proceed. When an acid catalyst such as sulfuric acid or hydrochloric acid is used in place of the component (c), a condensate which gives a coating film that can be used practically is not formed. In order to carry out the present invention, a solution as the component (a) and a solution in which the component (c) is dissolved in an appropriate amount of water (b) are separately prepared, and mixed and stirred at the time of use to react. Good. Further, by adding an alcoholate of another metal, for example, Ti (OR) ₄ , Zr (OR) ₄ , B (OR) ₃ , Al (OR) ₃ or the like to this coating system, hydrolysis is promoted or alkali resistance, It is possible to improve chemical resistance and the like. In addition, a solvent such as ethanol or ethylene glycol monoethyl ether, a pigment, an antifungal agent, etc. can be appropriately added to this coating system. As a coating method, spraying, brush coating, coating with a roll coater, etc. can be used as is. Curing time is about 30 minutes, and touch-drying is possible, and complete drying is about 12 hours. The present invention will be described below with reference to examples and comparative examples.

Examples 1 to 3 and Comparative Example 1 A polysiloxane coating agent was prepared with the following composition.

Comparative Example 1 200 g of water in which 700 g (3.9 mol) of CH ₃ Si (OC ₂ H ₅ ) ₃ and 1 g of ZrOCl ₂ 8H ₂ O (0.03 mol% relative to 1 mol of alkoxy group) were dissolved
(0.95 mol per mol of alkoxy group) was forcibly stirred, but the reaction did not proceed while the siloxane and water were separated into two layers.

Comparative Example 2 162 g of Si (OC ₂ H ₅ ) ₄ and 125 g of (CH ₃ ) ₃ Si (OC ₂ H ₅ ) and 187 g of ethyl alcohol were added, and the contents were heated to 80 ° C. with stirring, and 10 g of 0.2N hydrochloric acid was added. The mixture was added and reacted at 80 ° C. for 10 hours (first reaction). 10 g of triethylamine was added to this reaction product, and the condensation reaction was carried out at 80 ° C for 2 hours.
100 g was added and the solvent was removed until the non-volatile matter became 40%.

A reaction product prepared by separately preparing a solution prepared by mixing one or more kinds of the alkoxysilanes of the above-mentioned examples and a solution prepared by dissolving a catalyst in water, and forcibly stirring the two to react with each other.
Table 2 shows the coating film performance when the product obtained in Comparative Example 2 was spray coated on a slate plate with a spray gun.

○ Water resistance test: Completely submerge in running water for 7 days and visually observe changes in gloss, whitening, peeling, blistering, etc.

○ Weather resistance test… Leave it on an exposure test stand facing south at 45 ° for 6 months, and visually observe deterioration such as gloss, whitening, peeling, and blistering.

○ Transparency: Visually observe after drying at room temperature for 24 hours.

○ Contamination resistance test ... Attach a test plate to the inner wall of a 400 m long tunnel and leave it for 6 months to attach dirt such as exhaust gas, sewage and mud. It is evaluated by the recovery rate of diffuse reflection before and after washing with a washing machine.

○ Measurement of surface hardness: The pencil hardness was measured according to JIS-K-5400.

(Effects of the Invention) The composition of the present invention has an appropriate pot life (bot life) and forms a coating film excellent in various properties such as water resistance, weather resistance and stain resistance in a relatively short time. There are features. Further, unlike the conventional polysiloxane composition, a two-step reaction is not required, which is advantageous in the process. Its high transparency makes it highly useful as a top coat for building exteriors, decorative panels, and Tonanru inner walls.

Claims (1)

[Claims] (A) A compound represented by the general formula R ¹ Si (OR ² ) ₃ is used as an essential component, and a compound represented by the general formula ▲ R ¹ ₂ ▼ Si (OR ² ) ₂ and the general formula Si (O 2
An alkoxysilane having a compound represented by R ² ) ₄ as an optional component (wherein R ¹ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group, R ² represents an alkyl group having 1 to 4 carbon atoms), (b ) Water, (c) 0.05 to 5 mol% of an oxy compound of Group IVB of the periodic table, and (a), (b), and (c) above, relative to 1 mol of the alkoxy group of the above component (a). Room temperature curable polysiloxane composition.