JPS584744B2 - Huntai Triyousosaibutsu - Google Patents

Description

Detailed Description of the Invention The present invention provides a thermosetting acrylic powder coating that can significantly improve the finished appearance (hereinafter referred to as "finished appearance") in terms of both gloss and smoothness of the coating, especially when applied in a thin film. composition for use.

Recently, in the field of baking paints, powder paints have been in the spotlight because of their ability to prevent air pollution caused by solvents, to obtain thick coatings with one application, and to save labor.

As for the above powder coatings, epoxy resin powder coatings have traditionally been the most widely used in practical use, but their use is limited due to their poor weather resistance.Thermosetting acrylic powders have overcome this defect. As shown in Japanese Patent Publication No. 48-38617, paints include acrylic esters such as methyl acrylate and ethyl acrylate, and/or methacrylic esters such as methyl methacrylate and ethyl methacrylate, and glycidyl acrylate and glycidyl methacrylate. A solid copolymer consisting of a monomer containing a glycidyl group such as acrylate in a specific composition ratio and having a specific secondary transition point and number average molecular weight is combined with a saturated fat such as pimelic acid, sebacic acid, etc. A thermosetting acrylic powder coating composition containing a specific proportion of a crosslinking agent such as a group dicarboxylic acid is known.

With conventional thermosetting acrylic powder coatings such as those mentioned above, it is possible to paint a thick film of 50μ or more in one application to the extent that the finished appearance of the paint film is practically satisfactory, but if a thin film of less than 50μ is applied. If the finished appearance of the paint film is not sufficiently satisfactory for practical use, that is, if it is applied to a thin film of 20 to 40 μm, which is equivalent to the conventional solvent-based paint, it may be applied to a thick film of 50 μm or more. In this case, the finished appearance of the coating film becomes significantly worse and cannot be of a practically satisfactory quality.

As a result of intensive research, the present inventors have discovered that a specific crosslinking agent not specifically disclosed in the above-mentioned publication can be used as a solid crosslinking agent as described in Japanese Patent Publication No. 48-38617. A powder coating with extremely high practical value that, when used in combination with a polymer, can eliminate the practical disadvantages already mentioned in the thermosetting acrylic powder coating described in the publication without impairing the practical disadvantages. The present invention provides a composition for use.

That is, the object of the present invention is to
As in the thermosetting acrylic powder coating composition described in Publication No. 7, weather resistance, chemical resistance, metal adhesion, etc. of the coating film formed when it is put to practical use as a thermosetting acrylic powder coating. Not only is it excellent, but it also maintains its practical advantages as a powder coating composition, such as excellent locking properties when stored as a powder coating before being put to practical use, and in particular, it It is an object of the present invention to provide a powder coating composition constituting a thermosetting acrylic powder coating that significantly improves the finished appearance of a coating when applied as a thin film.

Therefore, the present invention provides: (A) (a-1) a monomer having the structure of the general formula (R is an alkyl group or cycloalkyl group having 1 to 20 carbon atoms), and (a-2) Monomer 5 having the structure of the general formula (in the formula, R is H or CH9)
40 weight percent and (a-3) the monomers (a-1) and (a-2) copolymerizable monomers 0 to 65 weight percent. a solid copolymer with a point of 20 to 80°C; (B) 0.6 per epoxy group in the copolymer;
1,24- in an amount providing ~1.2 carboxyl groups
This is a powder coating composition characterized by comprising tetracosane diacid.

The general formula shown in (a-1) above (wherein R1 is H
or CH3, R2 is an alkyl group or cycloalkyl group having 1 to 20 carbon atoms), for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, Ethylhexyl, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tridecyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, stearyl methacrylate, etc. are commonly used.

If the amount of these monomers used is less than 30% by weight of the total monomers, the weather resistance will be reduced and the inherent advantages of the thermosetting acrylic powder coating will be lost, making it unsuitable for the present invention.

The above (A) is a constituent component of the solid copolymer (A) above.
Examples of monomers having the structure represented by a-2) (wherein R is H or CH3) include glycidyl acrylate, glycidyl meccrylate, β-methylglycidyl acrylate, and β-
There are methylglycyler methacrylate, etc., which form a heat-cured coating film by reaction with the 1,24-tetracosane diacid (B), but these monomers account for less than 5 weight percent of the total monomers. If the weight ratio exceeds 1 to 40, the chemical resistance will deteriorate and the powder coating will be unsuitable for the present invention.
Even when coating a thin film with a thickness of less than 0μ, a coating film with a good finished appearance cannot be obtained and is therefore unsuitable for the present invention.

Furthermore, the monomers (a-1) and (a-2) shown in (a-3) above are constituent components of the solid copolymer in (3) above.
Examples of monomers copolymerizable with and include styrene, α
-Methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, β-hydroxyethyl acrylate, β-hydroxybubutyl methacrylate, etc., and these monomers are copolymerized in a range of 65% by weight or less of the total monomers. However, if the weight exceeds 65%, the weather resistance decreases and it is unsuitable for the present invention.

These above monomers (a-1), (a-2) and (a
The above solid copolymer (5) obtained by copolymerizing -3) must have a secondary transition point in the range of 20-80°C.

In other words, if the secondary transition point is less than 20°C, the powder coating has poor locking properties during storage and cannot be put to practical use.
If the temperature exceeds 1.80°C, a coating film with a good finished appearance cannot be obtained by thin film coating as described above, which is inappropriate for the present invention.

The solid copolymer (3) used in the present invention has a number average molecular weight of usually 1,500 to 30,000, particularly 30.
A range of 00 to 10,000 is desirable.

The 1,24-tetracosane dioic acid shown in (B) above plays a role as a crosslinking agent in the powder coating composition of the present invention, and in the baking process of the powder coating, the above-mentioned solid copolymer is The thermosetting acrylic powder coating using 1,24-tetracosane diacid of (B) above of the present invention reacts with the glycidyl group or β-methylglycidyl group contained in Surprisingly, it is impossible to achieve commercial value with conventional thermosetting acrylic powder coatings using crosslinking agents such as pimelic acid, sebacic acid, and brassylic acid. ~
The finished appearance of the formed coating film is dramatically improved when a thin film such as 40μ is applied, and even when it is coated with a thin film such as S, it is at least equivalent to the solvent-based paint commonly used in the past, and it can be made into a thick film of 50μ or more. A coating film having a practically satisfactory finished appearance as in the case of painting can be obtained.

The amount of 1,24-tetracosane diacid (B) used in the present invention is 0.6 to 1.2 carboxyl groups per epoxy group in the solid copolymer (A). If the amount is less than 0.6 or more than 1.2, the coating film formed by thin film coating as described above will have commercial value and a good finished appearance. This method is unsuitable for the present invention because a film cannot be obtained.

As is clear from the above description, the present invention is based on ■, 24-
Tetracosane diacid is a specific copolymer as previously described (
There is a practical significance in that it is blended into the solid copolymer of A) in a specific proportion.

The solid copolymer of the above-mentioned (A) of the present invention and the above-mentioned (B) 1
, 24-tetracosanedioic acid, it is necessary to use crosslinking agents conventionally used in the composition, such as pimelic acid, sebacic acid, and brassylic acid, from a practical point of view. It is possible to use the present invention in small amounts that do not inhibit the effects described above.
Further, in order to increase the crosslinking rate of the powder coating composition in the baking step, a small amount of a catalyst such as tertiary amines, imizoles, metal salts of organic carboxylic acids, and tetraalkylammonium salts may be used in combination.

In addition, when putting the powder composition of the present invention into practice, a small amount of a resin component such as an epoxy resin, a polyester resin, a ketone resin, a melamine resin, or a cellulose derivative such as cellulose acetate butyrate may be used in combination. In addition, known fluidity regulators such as silicone oil, Modaflow (trade name of Monsite Co., Ltd.) and FC-430 (trade name of 3M Co., Ltd.), antistatic agents such as alkyl polyoxyethylene phosphate esters, titanium oxide, iron oxide, etc. Inorganic pigments such as , and other organic pigments may be mixed as appropriate.

The powder coating composition of the present invention is applied to an object to be coated, such as a base material made of a metal material, by a known coating method such as an electrostatic powder spray method or a fluidized dipping method, and is usually applied at a temperature of 160 to 240°C.
It was baked in a hot air oven for 10 to 60 minutes and put into practical use.
The unique advantages of thermosetting acrylic powder coatings include excellent blocking properties during storage as mentioned above, as well as excellent weather resistance, chemical resistance, and metal adhesion, and the finish when applied in a thin film. It is possible to obtain a powder coated film with an outstanding appearance.

Next, an example will be described.

Example (4) Each of the powder coatings of experiment numbers (1) to (6), which are powder coating compositions prepared by the method described above, was treated with zinc phosphate using an electrostatic spray coating machine for powder coating. 9.8mm with
A thick matte steel plate was coated with a film thickness as shown in Table 3, and then baked at 200° C. for 20 minutes to obtain six types of test plates.

Each of these test plates was tested and evaluated for the finished appearance, weather resistance, chemical resistance, and metal adhesion of the formed coating film, and the above-mentioned conditions were evaluated using the electrostatic spray coating machine for powder coating. The blocking properties of the powder coatings were tested and evaluated, and the results are also shown in Table 3.

In addition, the following experiment was conducted.

To 100 parts by weight of the copolymer D, 19.6 parts by weight of 1,24-tetraconsandioic acid (1 epoxy group in copolymer D)
A composition for a powder coating was obtained in exactly the same manner as in the example described above, except that 0.07 carboxyl groups were added (corresponding to an amount equivalent to providing 0.7 carboxyl groups per carboxyl group) (abbreviated as composition according to an example of the present invention). .

Furthermore, 189 parts by weight of brassylic acid was added to 100 parts by weight of the copolymer D.
Part by weight (1.1 per epoxy group in copolymer D)
A composition for a powder coating was obtained in exactly the same manner as in the above-mentioned Examples, except that the amount corresponding to the amount providing carboxyl groups was added (abbreviated as composition according to comparative example).

The composition according to the example of the present invention was evaluated for its characteristics by various tests shown in Table 3, and the test number (4) shown in Table 3 was
Furthermore, the evaluation of the properties of the composition according to the above comparative example by the various tests shown in Table 3 was substantially the same as that of Experiment No. (6) shown in Table 3.

Claims (1)

[Claims] 1(A) (a-1) General formula is an alkyl group or cycloalkyl group having 1 to 20 carbon atoms)
(a-2) Monomers 5 to 4 having the structure of the general formula (in the formula, R or H is CH3)
(a-3) Monomers copolymerizable with monomers (a-1) and (a-2), O to 65 weight percent, and (a-3) secondary Transition point is 20~80C
(B) 0.6 per epoxy group in the copolymer;
1,24- in an amount providing ~1.2 carboxyl groups
A powder coating composition characterized by comprising tetracosane diacid.