JPS6058266B2 - Composition for powder coating - Google Patents

Description

[Detailed description of the invention] The present invention relates to a polyurethane powder coating composition.

More specifically, the present invention relates to a polyurethane powder coating composition that has superior coating performance and lower baking temperature than conventional polyurethane powder coatings. Since powder coatings do not contain organic solvents, they are increasingly expected to have a promising future as resource-saving, labor-saving, and non-polluting coatings. Due to these problems, the expansion of the field of application is currently being restricted.

Particularly when painting thin steel plates, there is a strong desire to lower the baking temperature, since high-temperature baking of 200° C. or higher can lead to deformation of the steel plate and melting of the solder. In order to lower the baking temperature, it is necessary to accelerate the curing reaction rate, but if the curing rate is too fast, the fluidity of the powder coating during melting will be inhibited and a smooth surface will not be obtained.

In addition, with powder coatings, the curing reaction must proceed after the paint is melted by heating to form a smooth children's painting, so the selection and combination of resin, curing agent, and curing reaction catalyst are important factors. Among them, the catalyst is extremely important because it is an element that balances the heated flow of the paint and the progress of the curing reaction during the coating film formation process. It is already known that an organotin compound is added to a blocked polyisocyanate compound as a curing reaction catalyst. etc. are used.

However, although these tin compounds have the effect of lowering the curing temperature, it cannot be said that the smoothness of children's paintings and the performance of the coating film are sufficient, and there is a strong demand for the development of catalysts that solve these problems. Ta. The present inventors have conducted various intensive studies to solve such problems and have arrived at the present invention.

That is, the present invention has a hydroxyl value of 20 to 200 and a softening point of 50 to 200.
This is a powder coating composition characterized by comprising a hydroxyl group-containing polymer having a temperature of 150°C, a blocked polyisocyanate compound, and an organotin compound represented by the following general formula (1). (In the formula, R is an alkyl group having 1 to 18 carbon atoms, a cyclohexyl group, a vinyl group, a phenyl group, or a benzyl group, X and Y are a phenoxy group or a benzyloxy group, and X and Y are the same It's okay to be hot.

) The hydroxyl group-containing organic polymer used in the present invention includes hydroxyl group-containing polyester, hydroxyl group-containing polyether,
Examples include hydroxyl group-containing polyester ether, hydroxyl group-containing polyurethane, hydroxyl group-containing polyester urethane, hydroxyl group-containing alkyd resin, hydroxyl group-containing epoxy resin, and hydroxyl group-containing vinyl polymer.

These hydroxyl group-containing organic polymers have a hydroxyl value of 20 to 2.
00, the softening point is 50-150°C. Hydroxyl value is 20~
If it is outside the range of 200, the coating film performance will not be sufficient. Further, if the softening point is outside the range of 50 to 150°C, the storage stability as a powder coating will not be sufficient, and the fluidity during baking will not be sufficient. In order to avoid foaming during baking, it is preferable to keep the acid value as low as possible. The blocked polyisocyanate compound used in the present invention is an addition compound of a polyisocyanate compound and a blocking agent. Examples of polyisocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate,
Aromatic, aliphatic, and alicyclic compounds such as naphthalene diisocyanate, benzene triisocyanate, metaphenylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, bis(isocyanatemethyl)cyclohexane, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and bis(isocyanatemethyl)benzene. group, araliphatic polyisocyanate compounds and these polyisocyanate compounds and polyols, polyamines, hydroxyl group-containing amines, water,
Examples include terminal isocyanate group-containing compounds obtained by reacting with ammonia, urea, hydroxyl group-containing polyethers, hydroxyl group-containing polyesters, hydroxyl group-containing polyurethanes, etc., as well as biuret and allophanate compounds thereof. Blocking agents include phenol, cresol, P
- Phenols such as oxybenzoate, active methylene compounds such as acetylacetone and acetoacetate, oximes such as acetoxime and methyl ethyl ketone oxime, lactams such as ε-caprolactam, monomers such as cyclohexanol and t-butyl alcohol. There are known blocking agents such as alcohols. The blocked polyisocyanate compound used in the present invention is obtained by reacting these polyisocyanate compounds with a blocking agent by a conventional method,
There is no method limitation to this invention. Next, examples of the organotin compound represented by the general formula (1) used in the present invention include tetramethyl-1-3-diphenoxy distanoxane, tetra-n-propyl-1,3-diphenoxy distanoxane, and tetra-n-propyl-1,3-diphenoxy distanoxane. n-butyl-1,3-diphenoxydistanoxane, tetra n-octyl-1,3
- Diphenoxy distanoxane, tetralauryl 1
, 3-diphenoxy-distanoxane, tetramethyl-1,3-dibenzyloxy-distanoxane, tetra-n-propyl-1,3-dibenzyloxy-distanoxane, tetra-n-butyl-1,3-dibenzyloxy-distano xane, tetran-octyl-1,3-dibenzyloxydistanoxane, tetralauryl-1
, 3-dibenzyloxydistanoxane, Tetra n
-butyl-1-phenoxy-3-dibenzyloxy-distanoxane, tetra-n-octyl-1-phenoxy-3-benzyloxy-distanoxane, 1-di-n-
Butyl-1-Phenoxy-3-G-n-Octyl-3-
Benzyloxydistanoxane, 1-di-n-octyl-1-phenoxy-3-di-n-butyl-3-benzyloxydistanoxane, tetra-cyclohexyl-1,3-diphenoxydistanoxane, tetracyclohexyl- 1,3-dibenzyloxy-distanoxane, tetraphenyl-1,3-diphenoxy-distanoxane, tetraphenyl-1,3-dibenzyloxy-distanoxane, tetradibenzyl-1,3-diphenoxy Examples include distanoxane, tetrabenzyl-1,3-dibenzyloxydistanoxane, and the like. The organic tin compound used in the present invention is not limited to these specific examples. Two or more of these compounds can be used in combination. Hydroxyl group-containing organic polymer (A) in the present invention, blocked poly)isocyanate compound (
The blending ratio of B) and the organotin compound (C) represented by the general formula (1) is (A) (B) (C) = 100:
10-50: 0.01-5.0 (parts by weight) is suitable.

The blending ratio can be freely selected depending on the purpose. The above three components are further blended with known additives such as leveling agents, pigments, weathering agents, etc. if necessary, melted and mixed at a temperature of 80 to 140°C, cooled and solidified, and then crushed to be used as a powder coating. . The powder coating composition of the present invention not only has superior coating surface smoothness and coating performance compared to conventional powder coatings containing organic tin compounds as curing reaction catalysts, but also exhibits superior coating performance at lower temperatures. It can be baked and has excellent storage stability.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

In the examples, parts simply indicate parts by weight.

The softening point was determined using a fully automatic melting point measuring device (manufactured by METI'LER,
MODELFP-1), and the molecular weight was measured using a molecular weight measuring device (manufactured by Hitachi, Ltd.) using chloroform as a solvent.
115 type). The smoothness and appearance of the coating film were visually evaluated. The Erichsen value was measured according to JISZ2247, and the DuPont impact value (112'', 1KG) was measured according to JISK54OO.Water resistance was measured using a humidity cabinet (manufactured by Toyo Seiki Seisakusho) compliant with NDS-K-2601. ℃ and humidity of 98% or more
After standing for 00 hours, it was measured by a cross-over test according to ASTM D3359. Production Example 1 In a reaction vessel equipped with a thermometer, a stirrer, and a partial reflux condenser, 358 parts of dimethyl terephthalate and 58 parts of dimethyl isophthalate were added. , 936 parts of neopentyl glycol, 684 parts of ethylene glycol, 121 parts of trimethylolpropane, and 0.9 parts of zinc acetate were charged, the temperature was gradually raised, and the mixture was reacted at 220° C. for about 3 hours.

Next, the temperature was raised to 250°C, the pressure of the reaction system was gradually reduced, and the reaction was carried out for about 1 hour at 1 to 5 Hg to obtain a hydroxyl group-containing polyester (A-1) (hydroxyl group value 6 & softening point 70).
℃). Hydroxyl group-containing polyesters shown in Table 1 were obtained by the same procedure.

Production Example 2 1000 parts of xylene, 3 (1) parts of n-butyl alcohol,
Methyl methacrylate (9) parts, styrene 600 parts, 2
-200 parts of hydroxyethyl methacrylate, 150 tons of 2-ethylhexyl methacrylate! I), 5 parts of lauryl mercaptan, and w parts of benzoyl peroxide were charged and reacted at 90°C for about an hour, and then the solvent was distilled off under reduced pressure to obtain a hydroxyl group-containing vinyl polymer (A-4) (
Hydroxyl value 63s Softening point 65°C).

Production Example 3 444 parts of isophorodiisocyanate and ethylene glycol 6'5S were charged into a reaction vessel equipped with a thermometer, a stirrer, and a cooler, and the reaction was carried out at a reaction temperature of 100°C or less for about 3 hours, and then 226 parts of ε-caprolactam was added to the reaction system. was added and reacted at 130°C for about 3 hours to obtain a blocked isocyanate compound (B-1) (molecular weight 732, residual N
CO%ku1).

1,3-bis(isocyanatemethyl)cyclohexane using the same procedure? part, ethylene glycol 6? and m-
An isocyanate compound (B-2) blocked using 216 parts of cresol was obtained (molecular weight 66, residual NCO
%〈1.5).

Examples 1 to 8 Hydroxyl group-containing polyester (A-1) or vinyl polymer, blocked isocyanate compound (B-1), organotin compound of the present invention (12 parts as tin atom) in the amounts shown in Table 2. Rutile titanium oxide 400
1 part, Polyflow (manufactured by Kyoeisha Yushi Co., Ltd.) and 5 parts of benzoin were pulverized and mixed using a Henschel mixer, and then heated to 110 to 130°C using a Werner twin-screw extruder.
The mixture was melted and mixed, cooled and solidified, and then pulverized using a Hosokawa-type pulverizer.

The powder that passed through 100 mesh of the pulverized material was coated on a mild steel plate using an electrostatic powder coating machine (manufactured by Landsburk, -90K■) to a film thickness of 50 to 70μ, and then 170
Two-powder baking was carried out at ℃. Table 3 shows the performance of the resulting coating film.

Comparative Examples 1 to 4 Painting, painting, and baking were carried out in the same manner as in Example 1, except that hydroxyl group-containing polyester, blocked isocyanate compound, and organic tin compound were used in the proportions shown in Table 4.

Table 5 shows the performance of the resulting coating film. Table 3 and 5
As is clear from the table, the performance of the coating film containing the organic tin compound of the present invention is very excellent.

On the other hand, the performance of coating films containing known organic tin compounds lacks balance, and in particular, water resistance is extremely poor. Example 9
~12 Paint was prepared in the same manner as in Example 1, except that the hydroxyl group-containing polyester (A-2), the blocked isocyanate compound (B-1), and the organotin compound of the present invention were used in the proportions shown in Table 6. After coating and coating, it was baked under the baking conditions shown in Table 7.

Claims (1)

[Scope of Claims] 1. A powder characterized by comprising a hydroxyl group-containing organic polymer having a hydroxyl value of 20 to 200 and a softening point of 50 to 150°C, a blocked polyisocyanate compound, and an organotin compound represented by the following general formula. Painting composition. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R is an alkyl group having 1 to 18 carbon atoms, a cyclohexyl group, a vinyl group, a phenyl group, or a benzyl group, and X and Y are a phenoxy group or benzyloxy group, and X and Y may be the same.)