JP2000212473A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with an adhesive layer between a base material and a photocatalyst layer and improve the weatherability, the stainproofness, the capability of being cleaned up, and the self-cleaning properties by using an alkali silicate and/or a colloidal silica, a fibrous titanium oxide, and a silane compound as the constituents. SOLUTION: At least one compound selected from alkali silicates and water- base colloidal silicas having a silica content of 15-45 wt.% is blended with 2-97 wt.%, preferably 5-70 wt.%, fibrous titanium oxide having a mean diameter of 0.1-5 μm, a mean length of 3-150 μm and a mean aspect ratio of 3 to 200, and 2-80 wt.%, preferably 5-60 wt.%, silane compound of the formula: SiR1n(OR2)4-n. In the formula, n is 0 to 3; R1 is H, a halogen, a 1-8C alkyl, a 3-8C alkenyl, amino, glycidoxy, (meth)acryloyloxy, aminoalkylamino or the like; and R2 is a 1-8C alkyl, a 1-8C alkoxy, or a 1-8C alkyl substituted by an alkoxy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an antifouling property, a purifying property,
The present invention relates to a coating composition having excellent self-cleaning properties and weather resistance.

[0002]

2. Description of the Related Art Titanium oxide is known for its photocatalytic activity, and as a coating material utilizing such photocatalytic activity, a material comprising titanium oxide powder, a silicon compound and a metal oxide sol has been proposed (particularly, sol.). Kaihei 9-3100
No. 39).

[0003]

However, in this case, since powdery titanium oxide is used as the photocatalyst, it is essential to provide an adhesive layer between the substrate and the photocatalyst layer in order to support the powder. Therefore, there is a drawback that it takes time and labor when constructing, and the construction cost increases. Also, its photocatalytic activity was not yet sufficient. An object of the present invention is to provide a coating composition which does not require an adhesive layer between a substrate and a photocatalyst layer, and is excellent in weather resistance, antifouling property, purifying property and self-cleaning property.

[0004]

The present invention comprises (A) at least one member selected from the group consisting of alkali silicate and colloidal silica, (B) fibrous titanium oxide, and (C) a silane compound. It relates to a coating composition. The present invention also relates to the coating composition using monoclinic titanium oxide as the fibrous titanium oxide.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples of alkali silicates include, for example, sodium silicate, potassium silicate, lithium silicate, ammonium silicate and amine silicate. The colloidal silica has a silica content of 1
Examples of the aqueous colloidal silica and organosilica sol of 5 to 45% by weight can be given. As the fibrous titanium oxide, anatase-type titanium oxide, rutile-type titanium oxide, monoclinic titanium oxide, and a mixture thereof can be used.
Above all, monoclinic titanium oxide or a mixed titanium oxide of monoclinic titanium oxide and another crystalline titanium oxide is preferably used because of its high activity. Among them, monoclinic titanium oxide can be produced, for example, according to the method disclosed in Japanese Patent No. 2704351. That is, for example, a titanium dioxide hydrate fiber obtained by acid-treating potassium tetratitanate fiber is heat-treated at 80 to 350 ° C., and then heated to 360 to 6 ° C.
It can be produced by heat treatment at 50 ° C.

The shape of the fibrous titanium oxide that can be used in the present invention includes an average fiber diameter of 0.1 to 5 μm and an average fiber length of 3
A fibrous material having a thickness of about 150 to 150 μm and an average aspect ratio of about 3 to 200, particularly 7 or more is preferable. The fibrous titanium oxide used in the present invention uses a material treated with a surface treating agent such as a silane-based, titanate-based, aluminum-based, zirconium-based, or phosphorus-based coupling agent to improve the affinity with a binder. You may. The amount of the fibrous titanium oxide to be added is preferably 2 to 97% by weight in terms of solid content in the coating composition of the present invention. More preferably, 5 to 70% by weight is added. If it is less than 2% by weight, the photocatalytic activity may be insufficient.
Even if added in an amount larger than 7% by weight, the self-cleaning property and the film strength may be insufficient.

Examples of the silane compound include, for example, the general formula (1) SiR ¹ _n (OR ² ) _4-n , wherein n is 0,
R ¹ represents a hydrogen atom,
Substituted with a halogen atom, a C ₁ -C ₈ alkyl group, a C ₂ -C ₈ alkenyl group, or an amino group, a glycidoxy group, a (meth) acryloxy group, an aminoalkylamino group, a halogen atom, a mercapto group or a carboxyl group Represents a C ₁ -C ₈ alkyl group, and R ² represents C ₁ -C ₈
Alkyl _group, an alkoxy group, or an alkyl group of _C 1 -C ₈ substituted with an alkoxy group of C 1 -C ₈₎
And the hydrolyzed condensates thereof (particularly, organopolysiloxanes), modified products thereof, and various compounds known as silane coupling agents.

More specifically, R¹Is a methyl group,
Group, vinyl group, γ-glycidoxypropyl group, γ-
Tacryloxypropyl group, γ- (2-aminoethyl) a
Minopropyl group, γ-chloropropyl group, γ-mercap
Tripropyl group, γ-aminopropyl group or γ-
A compound of the general formula (1), which is a riloxypropyl group, ²
Is methyl, ethyl, methoxy, ethoxy, β-
Methoxyethyl group, β-ethoxyethyl group, 2-ethyl
The compound of the general formula (1) which is a hexyl group and its hydrolyzate
Decomposed products such as dimethylpolysiloxane and vinyltrisiloxane
Chlorosilane, vinyltrimethoxysilane, γ- (meta
Acryloyloxypropyl) trimethoxysilane, γ-
Glycidyloxypropyltrimethoxysilane, γ-g
Lysoxypropylmethyldiethoxysilane, γ-amido
Coupling agents such as propyltriethoxysilane
I can do it. These silane compounds may be used alone or in combination.
More than one species can be used.

The silane compound is preferably added to the coating composition of the present invention in an amount of 2 to 80% by weight in terms of solid content. More preferably, 5-6
It is preferable to add 0% by weight. If the amount is less than 2% by weight, it is difficult to form a film, and the strength of the coating film decreases. 80
When the amount is more than the weight%, the coating solution is settled to deteriorate the workability, and the photocatalytic activity may not be sufficiently imparted.

In the present invention, if necessary, a small amount of a water-soluble or water-dispersible polymer such as polyvinyl alcohol, methylcellulose, carboxymethylcellulose soda, sodium acrylate, acrylate emulsion, acetate, etc. It is also possible to use a vinyl emulsion, an ethylene-vinyl acetate emulsion or the like in combination, but the amount of these used is 10% in terms of solid content from the viewpoint of securing the weather resistance of the coating film.
% By weight or less.

The coating composition of the present invention may contain various pigments. Specific examples thereof include titanium oxide, zinc white, titanium yellow, red iron oxide, chromium oxide green, ultramarine, cadmium red, and iron black. Etc. can be exemplified. The coating composition of the present invention may contain various inorganic fillers, and specific examples thereof include talc, mica, clay, silica, calcium carbonate and the like. Further, in the coating composition of the present invention, an alkali titanate may be used as a film-forming auxiliary. Examples of the alkali titanate include lithium titanate, sodium titanate, potassium titanate, and the like. Among them, a fibrous material is preferable, and potassium octitanate fiber is particularly preferable.

When it is necessary to improve water dispersibility, a small amount of a wetting agent generally used for water-based paints (water-soluble and water-dispersible paints) can be added. It is possible to mix a small amount of an antifoaming agent to erase foam generated at the time of application, as well as to defoam the stock solution. Further, if necessary, an antifreezing agent, a water repellent and the like may be appropriately blended to improve the stability of the stock solution at a low temperature and the water repellency of the film.

The production of the coating composition of the present invention can be carried out in accordance with a usual method for producing a water-based paint, and no special process or apparatus is required. The coating composition of the present invention may be used as an undiluted solution or, if necessary, about 5 to 5 times.
It is preferable to dilute by adding 15% by weight of water, and apply by water brush, roll brush, air spray, airless spray or the like. Depending on the material to be coated, dip coating is also possible. After coating, the coating composition of the present invention can be air-dried and dried, and if necessary, may be forcibly dried using hot air or the like.

[0014]

The present invention will be described in more detail with reference to the following examples. Example 1 Colloidal silica (product name: Snowtex S, manufactured by Nissan Chemical Industries, Ltd.) and fibrous titanium oxide (monoclinic titanium oxide, average fiber diameter of 0.2 μm, average fiber length of 10 μm, at the ratios shown in Table 1) Average aspect ratio 50, product name "MT
W ", Otsuka Chemical Co., Ltd.), silane compound (product name:
M coat 56 clear, manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed into a polybeaker and dispersed with a small disper for 10 minutes to obtain a coating composition of the present invention.

Example 2 Potassium octa titanate fiber (average fiber diameter: 0.4 μm, average fiber length: 12) was used in place of a part of the fibrous titanium oxide of Example 1.
μm, average aspect ratio 30, product name “Tismo-
D ", manufactured by Otsuka Chemical Co., Ltd.)
In the same manner as in the above, a coating composition of the present invention was obtained.

Example 3 A coating composition of the present invention was obtained in the same manner as in Example 1 except that sodium silicate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of the colloidal silica of Example 1. . Example 4 A coating composition of the present invention was obtained in the same manner as in Example 2 except that sodium silicate was blended in place of the colloidal silica of Example 2.

Comparative Example 1 The procedure of Example 1 was repeated except that the fibrous titanium oxide MTW of Example 1 was not used. Comparative Example 2 A powder was prepared in the same manner as in Example 1 except that powdery titanium oxide (product name: ST-01, manufactured by Ishihara Sangyo Co., Ltd.) was used instead of the fibrous titanium oxide MTW of Example 1. Comparative Example 3 Example 1 was repeated except that potassium titanate fiber (Tismo-D) was blended in place of the fibrous titanium oxide MTW of Example 1.
Prepared in the same manner as Comparative example 4 It prepared similarly to Example 3 except having replaced powdery titanium oxide (ST-01) instead of fibrous titanium oxide MTW of Example 3. Table 1 shows the compounding amounts of the components of Examples 1 to 4 and Comparative Examples 1 to 4. The unit is wt%.

[0018]

[Table 1]

Test Example 1 Each of the coating compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 was polished with a sandpaper (# 180) and washed with Tricrene to obtain a 0.8 × 70 × 150 mm steel plate. [JIS G3141 (SPCC-SB)] was applied with a brush and cured in a room for 4 days, and then its characteristics were measured.
Table 2 shows the results.

In Table 2, the state of the dried film was visually observed.
Those which did not form a film and partly dropped from the steel sheet were evaluated as x. The film thickness was measured with an elcometer. Hardness is JI
It was measured according to SK5400 8.4.2. The adhesiveness was measured by a cellophane tape peeling test using a 2 mm square, 10 × 10 squares. Accelerated weathering resistance is JIS K5400
According to 9.8.1, water was sprayed at a temperature of 63 ± 3 ° C. for 8 minutes for 120 minutes, and after a total time of 200 hours, it was measured by an adhesion test and a visual observation of a coating film state. (O: no change in coating film state, X: remarkable drop-off of the coating film) The photocatalytic property was measured by applying a cigarette tar to the coating film and irradiating with a 400 W mercury lamp for 120 hours, and then observing the fading state. (○: fading is remarkable, ×: no fading)

[0021]

[Table 2]

Table 2 shows that the examples of the present invention are sufficiently practical coating compositions. However, since Comparative Examples 1, 2, and 4 did not form a film, they were not suitable for a coating composition. Comparative Example 3 is inferior in photocatalytic properties.

[0023]

According to the present invention, it is possible to obtain a coating composition which does not require an adhesive layer between the substrate and the photocatalyst layer and is excellent in weather resistance, antifouling property, purifying property and self-cleaning property.

Claims (2)

[Claims] 1. A coating composition comprising (A) at least one member selected from the group consisting of alkali silicate and colloidal silica, (B) a fibrous titanium oxide, and (C) a silane compound. 2. The coating composition according to claim 1, wherein the fibrous titanium oxide is a monoclinic titanium oxide.