JPS588430B2 - Fun Taiyoyouji Yushisoseibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermosetting polyester resin composition for powder coatings.

More specifically, 2-methyl-1,3-butanediol (
The present invention relates to a thermosetting polyester resin powder coating composition containing as constituent elements terephthalic acid (hereinafter abbreviated as TA) or dimethyl terephthalate (hereinafter abbreviated as DMT).

In recent years, there has been an increasing social demand for paints that do not use organic solvents that cause environmental pollution, and powder paints that do not use organic solvents at all are becoming more important.

Various types of powder coatings, such as acrylic and epoxy, are available, but the former are expensive, have poor chemical resistance, and have the characteristic odor of acrylic when cured, while the latter has poor weather resistance.

Powder coatings are also required to not cause blockage (clumping) during storage after manufacture.

To achieve this, the base resin must have a high softening point, while the coating film must have good flowability during curing, which are contradictory conditions that must be met.

Furthermore, in the process of preparing a powder coating, it is desired that it be easy to mix with a pigment, and that it is easy to crush and classify.

Powder coatings prepared in this manner are required to have good fluidity during baking, to be cured at low temperatures, and to be free from pinholes and blisters.

It is desired that the coating film has good smoothness, gloss, bending resistance, chemical resistance, stain resistance, and water resistance.

By using a polyester resin containing IPG and TA or DMT as a base resin, the present inventors have found that the formed coating film surface does not block during storage, has good flowability during curing, has smoothness, gloss, and bending resistance on the surface of the formed coating film. It has been found that a powder coating can be obtained that exhibits excellent performance in adhesion, stain resistance, chemical resistance, and salt water spray tests, and particularly has very good boiling water resistance.

One of the features of the present invention is that a powder coating composition with good flowability upon curing can be obtained, resulting in a thin coating film.

The polyester resin of the present invention can be obtained by a conventional polyesterification reaction method using the following raw materials.

Although it is essential to use IPG and TA or DMT in the present invention, it is possible to mix other dihydric alcohols, trihydric or higher polyhydric alcohols, and other dibasic acids during esterification.

Suitable other dihydric alcohols include, for example, ethylene glycol, fluoropylene glycol, 1,3-butylene glycol, neopentyl glycol, 1,6-hexanediol, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc. Examples of the trivalent or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolfuropane, pentaerythritol, and dipentaerythritol.

Examples of dibasic acids other than TA and DMT include isophthalic acid, phthalic anhydride, succinic acid, adipic acid, sepacic acid, and 1,10-decanedicarboxylic acid.

The polyesterification reaction can be carried out under normal pressure, increased pressure, or reduced pressure.

As the catalyst used for esterification or transesterification, for example, metal compounds such as tin, titanium, antimony, zinc, lead, and aluminum can be used in the esterification reaction.

In addition, in order to prevent side reactions during esterification, such as ether production reactions, weakly alkaline substances such as alkali metal salts or alkali metal salts, amines, etc. can be added.

Note that the average molecular weight and softening point of the polyester can be adjusted by performing a vacuum treatment during the esterification.

The polyester resin used in the present invention contains at least 30 mol%, preferably at least 40 mol%, of IPG units as its polyhydric alcohol component, and at least 50 mol%, preferably 55 mol%, of TA units as its polybasic acid component. or more, with a softening point of 80 and a free alcoholic hydroxyl group.
~150°C polyester.

The crosslinking agent added to such a polyester resin may be any compound that can undergo a crosslinking reaction with the polyester.

Among these, amine resins include methylolated amino compounds such as methylolated melamine, methylolated urea, and methylolated penzoguanamine obtained by reacting formaldehyde with amine compounds such as melamine, urea, and penzoguanamine, and their carbon numbers. It is an alkoxy compound having a molecular weight of 4 or less, and is commonly referred to as a melamine resin, a urea resin, a penzoguanamine resin, or the like.

In addition, blocked polyisocyanates include, for example, phenols, cabbage lactams, aliphatic alcohols, tolylene diisocyanate, isophorone diisocyanate,
Polyisocyanate compounds such as hexamethylene diisocyanate and condensates of diisocyanates and trimethylolpropane condensates are used.

The blending amounts of the polyester resin and crosslinking agent used in the present invention are such that a coating film with good performance is obtained and storage stability as a powder coating is achieved.

Specifically, the blending amount of the polyester resin and crosslinking agent is 5
0-98% by weight and 2-50% by weight, preferably 60-9%
6% by weight and 4-40% by weight.

When the composition of the present invention is used as a powder coating, various additives such as pigments, flow control agents, and curing accelerators are mixed with these resin compositions.

At that time, additives such as pigments may be mixed into the molten resin composition, or these additives may be blended with the resin composition and then melt-mixed.

Pigments include common organic and inorganic pigments such as titanium oxide, zinc oxide, carbon black, iron oxide, aluminum powder, cyanine blue, and phthalocyanine green.

The flow control agent is used to adjust the flowability of the coating film during baking, and is, for example, Modaflow (trade name).

The hardening accelerator accelerates hardening during baking, and includes, for example, tertiary amines and organic tin compounds.

The present invention will be explained below with reference to Examples.

Example 1 A 3L glass separable flask with an electromagnetic stirrer,
A reactor equipped with a thermometer, partial condenser, total condenser, and nitrogen blowing tube was charged with IPG9.
05 mol, trimethylolpropane 2.25 mol, TA
Add IO mol and 4 g of siftirtin oxide,
After heating and stirring at 50 to 230°C and distilling off a theoretical amount of produced water, the contents of the flask were lowered to 210°C and heated for 15 minutes.
Polycondensation was carried out under reduced pressure of mmHg.

The acid value of the obtained polyester was 5.0, and the softening point was 110.
It was ℃.

To 100 parts (by weight) of this polyester, 10 parts of hexamethoxymethylmelamine, 45 parts of titanium oxide, and 0.5 parts of Modaflow were melt-kneaded using heated rolls at 140°C for 20 minutes.

After cooling, it was pulverized and classified to obtain a powder with an average particle size of 45 μm.

A mild steel plate (0.8 mm x 5
0 mm x 150 mm) and baked at 200° C. for 30 minutes to obtain a cured coating film with a thickness of about 60 μm.

This coating has excellent surface smoothness, a 60° mirror finish, and a gloss level of 95.
Above, bending resistance passed 4mm, pencil hardness 2H impact resistance (Dupont type) 1/2 x 500g 40 Helichsen extrusion value 9mm, lattice test 1oO/100, boiling water resistance no abnormality after 2 hours, lattice after 2 hours boiling 100/100,
It passed the 300-hour salt spray test.

Example 2 Using the reaction apparatus used in Example 1, 8.8 mol of IPG,
2.5 mol of trimethylolpropane, 8.0 mol of TA and 3 g of tetraptoxytitanate at 150-230°C
After heating and stirring and distilling off the theoretical amount of produced water,
2.0 mol of isophthalic acid was added and the mixture was heated and stirred at 150 to 230°C, and a theoretical amount of produced water was distilled off.

Lower the temperature inside the flask to 210℃ and further increase the temperature by 15mmH.
g Polycondensation was carried out under reduced pressure.

The acid value of the obtained polyester was 4.6 and the softening point was 104.
It was ℃.

90 parts of this polyester, 10 parts of hexamethoxymelamine
1, 45 parts of titanium oxide, and 0.5 part of Modaflow were melt-kneaded at 140° C. for 20 minutes using a heating roll.

After cooling, it was pulverized and classified to obtain a powder with an average particle size of 40 μm.

This powder was coated in the same manner as in Example 1 to obtain a coating film having the performance shown in the table.

Example 3 Using the same reaction apparatus as in Example 1, 8.0 mol of IPG,
2.5 mol of trimethylolpropane, 9.0 mol of TA and 3 g of tetraptoxytitanate at 150-230°C
The mixture was heated and stirred, and a theoretical amount of produced water was distilled off.

The contents of the flask were lowered to 140°C, 1 mol of adipic acid was added, and the mixture was heated and stirred at 150-190°C.

The obtained polyester had an acid value of 1.1 and a softening point of 83°C.

60 parts of this polyester, 40 parts of isophorone block isocyanate, 45 parts of titanium oxide, and 0.5 part of Modaflow (trade name) were melt-kneaded using an extruder.

After cooling, it was pulverized and classified to obtain a powder with an average particle size of about 45 μm.

This powder was coated in the same manner as in Example 1 to obtain a coating film having the performance shown in the table.

Example 4 Using the same reaction apparatus as in Example 1, 9.5 mol of IPG, 1 mol of trimethylolpropane, 10 mol of DMT, and 5 g of zinc acetate were heated and stirred at 150 to 230°C to remove distilled methanol.

The obtained polyester had a softening point of 110°C.

92 parts of this polyester, 8 parts of hexamethoxymelamine, 45 parts of titanium oxide, 0.5 parts of Motaflow (trade name),
0.5 part of phthalic anhydride was heated at 140°C at 20°C using a heating roll.
The mixture was melt-kneaded for a minute.

After cooling, it was pulverized and classified to obtain a powder with an average particle size of about 45 μm.

This powder was coated in the same manner as in Example 1 to obtain a coating film having the performance shown in the table.

Example 5 A reactor similar to Example 1 was charged with IPG6. O mol, 1.3
-2.5 moles of phthanediol, 2.0 moles of trimethylolpropane, 10 moles of DMT and 3 g of tetraptoxytitanium were heated and stirred at 150 to 210°C to remove distilled methanol.

The obtained polyester had a softening point of 99°C.

65 parts of this polyester, 45 parts of isophorone-based blocked diisocyanate, 45 parts of titanium oxide, and 0.5 part of Modaflow (trade name) were melt-kneaded.

After cooling, the powder was crushed and classified to obtain a powder with an average particle size of 45 μm.

This powder was coated in the same manner as in Example 1 to obtain a coating film having the performance shown in the table.

Example 6 65 parts of the polyester obtained in Example 1, 45 parts of isophorone-based blocked diisocyanate, 45 parts of titanium oxide, and 0.5 part of Modaflow (trade name) were melt-kneaded.

After cooling, the powder was crushed and classified to obtain a powder with an average particle size of about 45 μm.

This powder was coated in the same manner as in Example 1 to obtain a coating film having the performance shown in the table.

Comparative Example 1 Using the same reaction apparatus as in Example 1, 8.8 mol of neopentyl glycol, 2.23 mol of trimethylolpropane, 8.0 mol of TA, and 3 g of dibutyltin oxide were heated and stirred at 150 to 230°C.

Lower the temperature inside the flask to 210℃ and further increase the temperature to 15mmH.
g Polycondensation was carried out under reduced pressure.

The acid value of the obtained polyester was 8.7, and the softening point was 11.
The temperature was 1°C.

90 parts of this polyester, 10 parts of hexamethoxymethylmelamine, 45 parts of titanium oxide, and 0.3 parts of Modaflow (trade name) were melt-kneaded at 140° C. for 20 minutes with heated rolls.

After cooling, the powder was crushed and classified to obtain a powder with an average particle size of about 45 μm.

This powder was coated in the same manner as in the example to obtain a coating film having the performance shown in the table.

Claims (1)

[Claims] 1 (a) 30 mol% or more of the polyhydric alcohol component of the polyester is 2-methyl-1,3-butanediol units, and 50 mol% or more of the polybasic acid component is terephthalic acid units, a softening point of 80 50-98% by weight of polyester having free alcoholic hydroxyl groups at ~150°C;
(b) A resin composition for a powder coating comprising 2 to 50% by weight of a crosslinking agent.