JPS6120591B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition for forming a polyurethane coating with good drying properties. The polyurethane coating 1 made of an aliphatic or alicyclic polyisocyanate compound and a polyhydroxyl compound has better water resistance, solvent resistance, chemical resistance, and stain resistance than conventional polyurethane coatings made from aromatic polyisocyanate compounds. Recently, it has been attracting attention in the field of paints because it has excellent properties and is stable against sunlight and ultraviolet rays. However, although these aliphatic or alicyclic polyisocyanate compounds provide polyurethane coatings with excellent properties as mentioned above, they react more slowly with polyhydroxy compounds than aromatic polyisocyanate compounds, and dry out more easily. It has the disadvantage of being inferior in quality. Conventionally, in a polyurethane composition consisting of a polyisocyanate compound and a polyhydroxyl compound, a method of adding a catalyst has been known in order to promote the reaction between the isocyanate group and the hydroxyl group, and examples of such a catalyst include, for example. Organometallic compounds such as dibutyltin dilaurate and tertiary amines such as triethylenediamine have been used (Ind. Eng. Chem. Vol. 52(7), No. 609-
610 pages, Special Publication No. 5057, Special Publication No. 35-5057
Publication No. 5058, Special Publication No. 13035, Special Publication No. 13035, Special Publication No. 13035
-16947). However, when such a catalyst is added to a composition for forming a polyurethane coating, although the drying property is improved,
The viscosity of the coating composition increases significantly and gels within a few hours or even minutes;
This will make painting work difficult. Therefore,
Compositions for forming polyurethane coatings containing such catalysts have short pot lives and have the drawback of limiting coating time. The present inventors have conducted extensive research in order to overcome the drawbacks of these conventional polyurethane coating compositions and develop a composition for forming polyurethane coatings that has a long pot life, short drying time, and has good workability. As a result of repeated research, we discovered that this objective could be achieved by further blending a certain aromatic carboxylic acid in a specific ratio into a composition of an aliphatic or alicyclic polyisocyanate and a polyhydroxy compound. Based on this knowledge, the present invention has been made. That is, the present invention provides (A) an aliphatic or alicyclic polyisocyanate compound having two or more isocyanate groups in the molecule, (B) a polyhydroxyl compound having two or more hydroxyl groups in the molecule, (C)
general formula (n in the formula is 0 or an integer of 1 to 4, X is a hydrogen atom, a sulfo group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group) or general formula (R in the formula is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), and the equivalent of the isocyanate group in component (A) to the hydroxyl group in component (B) Ratio (NCO/OH) is 0.8 to 1.5
Within the range, the amount of (C) is 0.1 to the total amount of (A) and (B).
The present invention provides a composition for forming a polyurethane coating, characterized in that the amount is in the range of 5.0% by weight, and the components (A) and (B) coexist with the component (C) in a substantially unreacted state. be. Aliphatic or alicyclic polyisocyanates having two or more isocyanate groups used as component (A) of the present invention include, for example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,4 ,4-trimethyl-1,
6-hexamethylene diisocyanate, 2,6-
Examples include diisocyanate caproate, 3-isocyanate methyl-,3,5,5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4'-diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated tolylene diisocyanate. In addition, isocyanate groups obtained by the reaction of these aliphatic or alicyclic diisocyanate compounds with polyhydric alcohols, such as ethylene glycol, polyethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, hexanetriol, and pentaerythritol. A polyisocyanate compound having a biuret structure obtained by the reaction of the diisocyanate and water can be used. Particularly preferred is a polyisocyanate compound having a biuret structure obtained from 1,6-hexamethylene diisocyanate and water, 1,6
- A polyisocyanate compound which is an adduct of hexamethylene diisocyanate and trimethylolpropane. Drying performance is also improved when aromatic polyisocyanates such as 2,4-tolylene diisocyanate, m-xylylene diisocyanate, and polyisocyanates obtained by reacting these aromatic diisocyanates with polyhydric alcohols are used. , is not preferable because there is a problem with the weather resistance of the resulting coating. On the other hand, polyhydroxy compounds having two or more hydroxyl groups used as component (B) of the present invention include polyhydroxy compounds commonly used in the urethane-related technical field, such as acrylic polyols, polyester polyols, and polycaprolactones. These include polyols and polyether polyols. The ratio of the polyisocyanate compound (A) to the polyhydroxyl compound (B) is NCO/OH
It is necessary that the equivalent ratio is in the range of 0.80 to 1.50, and particularly preferably in the range of 0.90 to 1.20. NCO／
If the OH equivalent ratio is less than 0.80, physical properties such as water resistance, solvent resistance, chemical resistance, weather resistance, etc. will deteriorate, and if it is greater than 1.50, drying will be too slow, which is not desirable in practice. do not have. Examples of aromatic carboxylic acids represented by the general formula () used as component (C) of the present invention include:
Benzoic acid, phenyl acetic acid, 3-phenylpropionic acid, 4-phenylbutyric acid, 5-phenylvaleric acid,
o-sulfobenzoic acid and the phenyl group of these aromatic substituted carboxylic acids, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary Examples include compounds having any substituent selected from a butyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a tert-butoxy group, and a sulfo group. Examples of the aromatic carboxylic acid represented by the general formula () include phthalic acid, isophthalic acid, terephthalic acid, and monomethyl esters, monoethyl esters, mono-n-propyl esters, monoisopropyl esters, and monoethyl esters of these compounds. mono-n
- Any compound selected from butyl esters, monoisobutyl esters, mono-tertiary butyl esters. Among these aromatic carboxylic acids, particularly preferred are 3-phenylpropionic acid and 4-phenylpropionic acid.
-phenylbutyric acid, 5-phenylvaleric acid, o-sulfobenzoic acid, o-methoxybenzoic acid, o-ethoxybenzoic acid, phthalic acid, phthalic acid monomethyl ester, and phthalic acid monoethyl ester. These aromatic carboxylic acids are added in an amount of 0.1 to 5.0% by weight based on the total amount of the polyisocyanate compound and the polyhydroxyl compound. If it is less than 0.1% by weight, no significant effect will be seen in promoting drying properties, and if it exceeds 5% by weight, the reaction between isocyanate groups and hydroxyl groups will be promoted too much and the pot life will be too short to be practical. The aromatic substituted carboxylic acid may be added after mixing the polyisocyanate compound and the polyhydroxyl compound, or may be added to the polyhydroxyl compound in advance and then mixed with the polyisocyanate compound. In any case, it is necessary for the aromatic carboxylic acid to coexist with the polyisocyanate compound and the polyhydroxyl compound in a substantially unreacted state, so that the aromatic carboxylic acid must be mixed with the polyisocyanate compound and the polyhydroxyl compound at least when they start the reaction. must have been done. Although aliphatic carboxylic acids promote the reaction between isocyanate groups and hydroxyl groups, no significant effect is observed in promoting drying properties. The coating composition of the present invention may optionally contain additives commonly used in the field of polyurethane coatings, such as:
Pigments, dyes, leveling agents, thixotropic agents, etc. can be included. Methods for drying after coating the coating composition of the present invention on a coated object include natural drying at room temperature;
Alternatively, a normal urethane paint drying method such as heat drying can be used. The present invention will be explained below with reference to Examples, but the scope of the present invention is not limited in any way. Polyisocyanate compounds used in the examples,
Polyhydroxyl compounds are as follows. (A) Polyisocyanate compound A polyisocyanate compound having a biuret structure obtained from 1,6-hexamethylene diisocyanate and water Isocyanate group content: 23.5% by weight Non-volatile content: 100% by weight Viscosity (25°C): 2000 centipoise ( B) Polyhydroxyl compound Acrylic polyol: Acrydik A-801 (manufactured by Dainippon Ink and Chemicals Co., Ltd.) Hydroxyl value: 50 Non-volatile content: 50% by weight All parts used in the examples are parts by weight. Example 1 Polyisocyanate compound 100 parts Polyhydroxyl compound 640 parts Ethyl acetate 200 parts N-Butyl acetate 130 parts Cellosolve acetate 50 parts Toluene 130 parts Xylene 150 parts To the above composition for forming a polyurethane coating, o-
The viscosity change of the coating-forming composition of the present invention to which 4.2 parts of sulfobenzoic acid has been added is shown in the drawing as curve a. Examples 2 to 7 In place of o-sulfobenzoic acid in Example 1, the first
A coating-forming composition containing 4.2 parts of the aromatic substituted carboxylic acid shown in the table was prepared, and the viscosity changes are shown in the drawings as curves b to g.

[Table] Comparative Examples 1 to 5 Polyisocyanate compound 100 parts Polyhydroxy compound 640 parts Ethyl acetate 200 parts N-Butyl acetate 130 parts Cellosolve acetate 50 parts Toluene 130 parts Xylene 150 parts Table 2 shows the above composition for forming a polyurethane coating. The viscosity change of the coating forming composition to which the conventionally known catalyst is added is shown in the drawing as a curve h~1.

[Table] Reference Example The compositions obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were each applied to a glass plate to a dry film thickness of 50μ, and after drying at 80°C or 120°C for 15 minutes, ℃
Place it in a drying room kept at a constant temperature, cover the paint film with gauze, place a 100g weight on top of it, leave it for 1 hour, remove the weight, and check the dryness by checking whether there are any traces of gauze left on the paint film. compared. The results are shown in Table 3. Table 3 also shows the gelation time, which is the time taken to lose fluidity when left at 25°C.

【table】

[Table] The symbols in the table have the following meanings. ◎: No traces of gauze remain on the coating film. ○: Some traces of gauze remain on the coating film. △: Approximately half of the gauze trace remains on the coating film. ×: Traces of gauze remain on the entire surface of the coating film. XX: Gauze adheres to the paint film. Example 8 Coating of a composition for forming a polyurethane coating consisting of 100 parts of polyisocyanate compound, 640 parts of polyhydroxyl compound, 200 parts of ethyl acetate, 130 parts of n-butyl acetate, 50 parts of cellosolve acetate, 130 parts of toluene, 150 parts of xylene, and 14 parts of o-methoxybenzoic acid. 7
Table 4 shows the physical properties of the coating film after several days. Comparative Example 6 Table 4 shows the physical properties of the coating 7 days after application of the same composition for forming a polyurethane coating as in Comparative Example 1.

【table】

【table】

【table】 [Brief explanation of the drawing]

1 is a graph showing changes in viscosity of coating forming compositions of Examples and Comparative Examples.

Claims (1)

[Claims] 1. (A) an aliphatic or alicyclic polyisocyanate compound having two or more isocyanate groups in the molecule; and (B) a polyhydroxyl compound having two or more hydroxyl groups in the molecule. , (C) General formula (In the formula, n is 0 or an integer of 1 to 4, X is a hydrogen atom, a sulfo group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group) or general formula (R in the formula is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), and the equivalent of the isocyanate group in component (A) to the hydroxyl group in component (B) Ratio (NCO/OH) is 0.8 to 1.5
In the range of , the amount of (C) is 0.1 relative to the total amount of (A) and (B).
5.0% by weight, and wherein components (A) and (B) coexist with component (C) in a substantially unreacted state. 2. The composition for forming a polyurethane coating according to claim 1, wherein the polyisocyanate compound is a polyisocyanate compound having a biuret structure obtained from 1,6,-hexamethylene diisocyanate and water. 3 (C) component is general formula (In the formula, n is 0 or an integer of 1 to 4, and X is a hydrogen atom, a sulfo group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group.) The composition for forming a polyurethane coating according to item 1. 4 The aromatic carboxylic acid of general formula () is 3-phenylpropionic acid, 4-phenyl n-butyric acid or o
- The composition for forming a polyurethane coating according to claim 3, which is sulfobenzoic acid. 5 (C) component is general formula The composition for forming a polyurethane coating according to claim 1, which is an aromatic carboxylic acid represented by the formula (R in the formula is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). 6. The composition for forming a polyurethane coating according to claim 5, wherein the aromatic carboxylic acid is phthalic acid, monomethyl phthalate, or monoethyl phthalate.