JPS5830905B2 - Fuck you - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyurethane coating composition suitable for powder coating.

More specifically, the present invention relates to a polyurethane powder coating composition which has a lower baking temperature and superior coating performance than conventional polyurethane powder coating compositions.

It is known that a powder composition consisting of a polyester resin containing two or more hydroxyl groups and a polyisocyanate blocked with a phenol such as phenol or cresol, or an alcohol such as ethyl alcohol or cellophane can be used as a powder coating.

However, the disadvantage of these compositions is that the baking temperature 5 (180~
The temperature is as high as 220°C, and phenomena such as bubble formation or discoloration are observed in the coating, which may render the coating worthless.

It is also known that a powder composition of a polyester resin containing two or more hydroxyl groups and having a melting point of 40 DEG C. or higher and a polyisocyanate blocked with ε-caprolactam can be used as a powder coating.

The disadvantage of this composition is that the baking temperature is between 200 and 220°.
C, which is high, and the performance of the resulting coating film is poor.

In view of these circumstances, the present inventors have been conducting research and development on powder coating compositions that have low baking temperatures and excellent coating performance, and have developed an aromatic diisocyanate in which an isocyanate group is directly linked to the nucleus. (hereinafter simply referred to as aromatic diisocyanate) using a specific blocking agent as the polyisocyanate fraction. The present invention was completed based on this new knowledge.

That is, the present invention is based on the general formula % formula % () (wherein R1 is a phenyl group, furyl group or tetrahydrofuryl group which may be substituted with an alkyl group,
is a powder coating composition containing an aromatic diisocyanate blocked with a compound represented by (representing a hydrogen atom or an alkyl group) or an adduct thereof, and a polyol resin having a melting point of 40° C. or higher.

The composition of the present invention does not undergo gelation during storage,
It is extremely stable.

Moreover, it is possible to perform baking coating in a short time at a low temperature of about 160° C. or less, and the resulting coating film does not cause any fading or foaming, and has good physical properties.

Such excellent effects can be attributed to methanol, ethanol, and
This cannot be obtained when alcohols such as butanol and ethyl cellosolve are used as blocking agents.

In the compound represented by the general formula (I) used in the present invention, R1 represents a phenyl group, a furyl group, or a tetrahydrofuryl group which may be substituted with an alkyl group, and the alkyl group as the substituted valve is a lower Alkyl groups include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., with 1 to 4 carbon atoms.
Preferably.

Further, R2 represents a hydrogen atom or an alkyl group, and examples of the alkyl group include lower alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl, among which those having 1 to 4 carbon atoms are preferred.

Specific examples of the compound represented by general formula (1) include benzyl alcohol, α-methylbenzyl alcohol,
-ethylbenzyl alcohol, α-propylbenzyl alcohol, α-n-)'f rubenzyl alcohol, α
-tert-butylbenzyl alcohol, 3-methylbenzyl alcohol, 2-methyl-α-phenylethyl alcohol, 4-ethyl-benzyl alcohol, furfuryl alcohol, methyl-α-furyl-carbinol, ethyl-α-furyl-carbinol Nor, furopyru-α-furyl-carbinol, isoamyl-α-furyl-carbinol, tetrahydrofurfuryl alcohol, ethyl-tetrahydrofurfuryl-(2)-carbinol, butyl-tetrahydrofurfuryl-(2)-carbinol, etc. can be given.

Aromatic diisocyanates or adducts thereof used in the present invention include, for example, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, diphenyl diisocyanate, dimethyldiphenyl diisocyanate, dimethyldiphenylmethane diisocyanate, dimethoxydiphenyl diisocyanate, phenylene diisocyanate, triphenylmethane triisocyanate. or an excess of this diisocyanate, such as ethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, trimethylolpropane, hexanetriol, chrycerin, sorbitol, pentaerythritol, castor oil, ethylenediamine, hexamethylenediamine, ethanol amine, jetanolamine,
Polyisocyanates obtained by reacting low-molecular active hydrogen compounds such as triethanolamine, water, ammonia, and urea, or high-molecular active hydrogen compounds such as various polyether polyols, polyester polyols, and acrylic polyols, or their allophanates and biurets. These include polyisocyanates obtained by phosgenating a compound or a condensed amine of aniline and formalin.

Among these aromatic diisocyanates, tolylene diisocyanate and adducts thereof are particularly preferred.

Particularly preferred among these adducts are adducts at the incyanate group at the 4-position.

The reaction between the above-mentioned aromatic diisocyanate or its adduct and the compound represented by the general formula (1) is carried out by a known method in or without an active hydrogen-containing solvent.

In the reaction, known catalysts such as tertiary amines and organic metals may be used.

If a solvent is used and it is necessary to remove it after the completion of the reaction, it can be distilled off using a spray dryer, drum dryer, thin film evaporator, or the like.

In this way, a solid block polyisocyanate is produced.

The melting point of this block polyisocyanate is about 40-20
0°C1 is preferably about 60-150°C.

In the present invention, this block polyisocyanate and a polyol resin having a melting point of 40°C or higher are mixed to form a coating composition, and the mixing ratio of both is such that the equivalent ratio of recycled incyanate groups to hydroxyl groups of the block polyisocyanate is 0. ．．
It is adjusted to 5 to 2.01, preferably 0.6 to 1.5.

Examples of the polyol resin with a melting point of 40° C. or higher used in the present invention include polyester resins, acrylic polyol resins, epoxy resins, polyether resins, polyether ester resins, and mixtures thereof, particularly polyester resins, acrylic polyol resins, etc. is preferred.

Examples of the polyester resin include polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sepacic acid, azelaic acid, and trimethic acid, and polybasic acids such as ethylene glycol, diethylene glycol, propylene glycol, Dipropylene glycol, 1.3 butanediol, 1,4-butanediol, 1.5-bentanediol, neopentyl glycol, hexamethylene glycol, decamethylene glycol, hydroquinone bis(hydroxyethyl ether), hydrogenated bisphenol A1 tri Methylolethane, trimethylolpropane, hexanetriol,
It can be obtained by condensing polyols such as glycerin, pentaerythritol, tris(hydroxyethyl)in cyanurate, and cyclohexane dimetatool under conditions with an excess of hydroxyl groups by a conventional method.

In this case, it is also possible to use two or more types of acids or polyols in combination.

Also, castor oil, higher fatty acids, etc. may be used in combination to form a so-called oil-modified polyester polyol.

The polyester resin obtained by combining the above raw materials has a molecular weight of 500 to 4,000, preferably 1,000.
~3,000. Hydroxyl value: 10-300°, preferably 20
~2001 Those having an acid value of 1 to 30 and a melting point of 60 to 120°C are preferably used.

If the melting point is below 40°C, blocking of the composition will occur, and if it is above 120°C, gelation will occur easily during melt blending.

Examples of the acrylic polyol resin include (1) 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol,
Keihi alcohol, crotonyl alcohol, or
For example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, and itaconic acid, ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, 1,4-cyclohexyl dimetatool, It is a reaction product with phenyl glycidyl ether, chrycidyl decanoate, etc.

A hydroxyl group-containing monomer and (2) for example methyl acrylate,
Ethyl acrylate, n-propyl acrylate, isopropyl acrylate, lobutyl acrylate, t acrylate
Acrylic acid esters such as ert-butyl, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, 2-methacrylate - Methacrylic acid esters such as ethylhexyl, styrenic monomers such as styrene, vinyltoluene, and α-methylstyrene; Other vinyl acetate, vinyl propionate, acrylonidonyl, vinyl stearate, acrylic acetate, diallyl adipate, dimethyl itaconate, Diethyl maleate, vinyl chloride, vinylidene chloride, ethylene, glycidyl methacrylate, N-methylolacrylamide, N-
It is obtained by copolymerizing copolymerizable α,β-ethylenically unsaturated monomers such as butoxymethylacrylamide, acrylamide, diaseptane acrylamide, etc., and its hydroxyl value is about 10 to 300. Preferably about 20~
It is 200.

In addition, its melting point is about 40 to 150°C1, preferably about 6
It is 0-120°C.

The epoxy resin has at least two hydroxyl groups in one molecule, and is usually a condensed epoxy resin obtained by reacting bisphenol A and epichlorohydrin.

This epoxy resin has the following chemical structure.

Among the above epoxy resins, those with n7% of about 2 to 12 are particularly preferable, while those with an epoxy equivalent of 42
5 to 10,000, particularly preferably 425 to 4,000.

Further, its melting point is about 40 to 200°C, preferably about 60 to 200°C.
It is 150'C.

Furthermore, in addition to the above-mentioned epoxy resins, for example, epoxy ester resins obtained by reacting soybean oil fatty acids and epoxy resins can also be used.

Examples of the polyether resin include polymers such as paraformaldehyde, α-polyoxymethylene, eupolyoxymethylene, and trioxane, polytetramethylene ether glycol, and polyhexamethylene ether glycol, and the molecular weight thereof is approximately 500 to 4. ,000
．． Hydroxyl value approximately 20-200. Those having a melting point of about 60 to 120°C are preferably used.

Examples of the polyether ester resin include (1) polyether polyol having a hydroxyl value of about 45 to 200, (2
) For example, phthalic anhydride, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, 3,6-nindomethylenetetrahydrophthalic anhydride, 3,6-nindomethylenetetrachlorophthalic anhydride, tetrachlorophthalic anhydride, tetrabromo Obtained by reacting a dibasic acid anhydride such as phthalic anhydride with (3) an oxirane compound such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, phenyl glycidine ether, allyl glycidyl ether, etc. by a known method. Those having a molecular weight of about 500 to 4,000, a hydroxyl value of about 20 to 200, and a melting point of about 60 to 120° C. are preferably used.

Any conventionally known method may be used to produce a composition suitable for powder coating from a blocked polyisocyanate and a polyol resin.

That is, a method in which both fractions are dissolved and mixed in the presence of a solvent, pigments, leveling agents, dissociation catalysts, stabilizers, etc. are mixed therein as required, and then this is made into fine powder using a spray dryer, or A method is adopted in which both solid fractions are heated and mixed at 80 to 140° C. in a molten state, pigments and other additives are kneaded therein, and the mixture is cooled to solidify and then finely pulverized.

The particle size of the powder is 5 to 500 microns, more preferably 1
It is 0 to 300 microns.

In practicing the present invention, it is desirable to use a block polyisocyanate dissociation catalyst for the purpose of lowering the baking temperature.

Further, it is desirable to use a stabilizer for the purpose of improving heat resistance and weather resistance.

As the catalyst, any known catalyst such as amine type, metal type, etc. can be used.

The amount of catalyst added is preferably 0.01 to 5% by weight of the coating composition.

As the stabilizer, any known stabilizer such as phenol type, phosphorus type etc. can be used, but (in the formula, alkylene is an alkylene group having 1 to 5 carbon atoms,
is an integer of 1 to 5) is preferable.

The amount of stabilizer added is preferably 0.01 to 5% by weight of the coating composition.

Examples of the above-mentioned phosphorus compounds include tetraphenyldipropylene glycol diphosphite, tetraphenylbutylene glycol diphosphite, and tetraphenyldiethylene glycol diphosphite.

The resin composition thus obtained is useful as a powder coating, and for powder coating, it is applied to the object by a method such as fluid coating or electrostatic coating, and then coated with a powder coating of about 150 to 17
If baking is performed at 0'C, crosslinking will occur due to the reaction between the regenerated incyanate groups and hydroxyl groups, resulting in a tough film.

The resulting coating film shows no so-called discoloration or thermal deterioration, and has good physical properties.

EXAMPLES The present invention will be specifically explained below using Examples.

In the examples, parts and % indicate parts by weight and % by weight, respectively.

Example ■ 388 parts of dimethyl terephthalate, 93 parts of ethylene glycol, ■, 3-butylene IJ: ] -/L/13
5 parts, 36 parts of trimethylolpropane at 180℃~22
After heating to 0°C and reacting for 4 hours while continuously removing generated methanol from the system, phthalic anhydride 148
The mixture was further reacted at 240°C for 4 hours while separating and removing by-product water to obtain an acid value of 8.01, a hydroxyl value of 77, and a melting point of 72.
℃ polyester resin was obtained.

On the other hand, a 75% ethyl acetate solution of an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane
Add 114 parts of benzyl alcohol to 92 parts, and make 78~
When reacted at 80°C for 4 hours, free NCO groups were reduced to 0.1
% or less.

Ethyl acetate was then completely removed by heating at 120°C or lower under reduced pressure to obtain a blocked isocyanate with a melting point of 90 to 100°C.

335 parts of this blocked isocyanate, 728 parts of the above polyester resin (NCO10H ratio is 1.o), 530 parts of titanium oxide, 5 parts of Modaflow, 1,1,3,3-tetrabutyl-1,3-diacetoxydiscutuxaf 3 Department,
Two parts of tetraphenyldipropylene glycol diphosphite were premixed in a Henschel mixer for 5 minutes.

The mixture was melt-blended in an extruder set at 110 to 120°C, cooled, and then ground to a particle size of 100μ or less in an atomizer.
Electrostatically coated to a film thickness of 100μ and heated at 160°C.
After baking for 0 minutes, a solid, glossy white coating was obtained.

The coating performance is shown in Table 1.

Example 2 174 parts of tolylene diisocyanate, 31 parts of trimethylolpropane, 14 parts of 1,3-butylene glycol, 128 parts of methylbenzyl alcohol, and 120 parts of ethyl acetate were reacted in the same manner as in Example 1, and the melting point was 85-95. °C blocked isocyanate was obtained.

350 parts of this blocked isocyanate, 730 parts of the polyester resin of Example 1 (NCO10H ratio is 1.0), 540 parts of titanium oxide, 5 parts of Modaflow, 1,1,3,3-
3 parts of tetrabutyl 1,3-diacetoxydistanoxane and 2 parts of tetraphenyldipropylene glycol diphosphite were melt-mixed and powdered in the same manner as in Example 1.
It was electrostatically coated on a mild steel plate at 60KV to a film thickness of 80-100μ and baked at 160°C for 30 minutes to obtain a robust, glossy white coating.

The coating performance is shown in Table 1.

Example 3 292 parts of the adduct of tolylene diisocyanate and trimethylolpropane used in Example 1, 107 parts of tetrahydrofurfuryl alcohol, and 0.1 part of dibutyltin dilaurate were reacted in the same manner as in Example 1, and the melting point was 90. -1
Blocked isocyanate at 00°C was obtained.

325 parts of this blocked isocyanate, epoxy resin (
Trade name: Epicoat 1004, manufactured by Shell Chemical Co., Ltd., epoxy equivalent: approximately 1.000. Melting point 95-104°C) 320
(NCO10H ratio is 1.0), 320 parts of titanium oxide,
3 parts of Modaflow, 2 parts of 1,1,3,3-tetrabutyl-1°3-diacetoxydistanoxane, and 1.3 parts of tetraphenylbutylene glycol diphosphite were melt-mixed and powdered in the same manner as in Example 1. 60KV on mild steel plate
Electrostatically coated to a film thickness of 80-100μ,
After baking at 0° C. for 30 minutes, a robust, glossy white coating was obtained.

The coating performance is shown in Table 1.

Example 4 125 parts of diphenylmethane diisocyanate, 155 parts of propylbenzyl alcohol, and 90 parts of ethyl acetate were reacted in the same manner as in Example 1 to obtain a blocked isocyanate with a melting point of 80-90°C.

660 parts of an acrylic polyol with a melting point of 77-84°C and a hydroxyl value of 85 obtained by copolymerizing 50 parts of styrene, 30 parts of n-butyl acrylate, and 20 parts of 2-hydroxyethyl methacrylate by a conventional method, and 280 parts of the above-mentioned blocked isocyanate. (NCO10H ratio is 1.0), titanium oxide 4
70 parts, Modaflow 4 parts, 1,1,3,3-tetrabutyl-1,3-diacetoxydistanoxane 2.5 parts, tetraphenyldipropylene glycol diphosphite 2
The components were melt-mixed, powdered in the same manner as in Example 1, electrostatically coated on a mild steel plate at 60KV to a film thickness of 80-100μ, and baked at 160°C for 30 minutes to make it solid and glossy. A white coating film was obtained.

The coating performance is shown in Table 1.

Example 5 210 parts of naphthalene diisocyanate, 31 parts of trimethylolpropane, 14 parts of 1,3-7' ethylene glycol, and 100 parts of furfuryl alcohol were reacted in the same manner as in Actual Stream 1 to produce a blocked isocyanate with a melting point of 95-1050C. I got it.

355 parts of this blocked isocyanate, 730 parts of the polyester resin of Example 1 (NCO10H ratio is 1.0), 540 parts of titanium oxide, 5.4 parts of Modaflow, ■, 1°3.
3.2 parts of 3-tetrabutyl-1,3-diacetoxydistanoxane and 2 parts of tetraphenyldiethylene glycol diphosphite were melt-mixed, powdered in the same manner as in Example 1, and powdered on a mild steel plate at 60 KV to a thickness of 80 to 100 μm. The film was electrostatically coated to a film thickness of , and baked at 160°C for 30 minutes to obtain a robust, glossy white film.

The coating performance is shown in Table 1. Example 6 132 parts of dimethyldiphenyl diisocyanate and 13 parts of ethyl-tetrahydrofurfuryl-(2)-carbinol
0 parts was added and reacted in the same manner as in Example 1, resulting in a melting point of 90.
-100°C blocked isocyanate was obtained.

262 parts of this blocked isocyanate, 730 parts of the polyester resin of Example 1 (NCO10H ratio is 160), 500 parts of titanium oxide, 5 parts of Modaflow, 1,1,3,3-
Tetrabutyl-1゜3-diacetoxydistanoxane 3
1 part and 2 parts of tetraphenyldipropylene glycol diphosphite were melt-mixed, powdered in the same manner as in Example 1, and electrostatically coated on a mild steel plate at 60 KV to a film thickness of 80-100μ. After baking for 30 minutes at C, a robust, glossy white coating was obtained.

The coating performance is shown in Table 1.

Example 7 292 parts of the adduct of tolylene diisocyanate and trimethylolpropane used in Example 1 and 122 parts of 3-methylbenzyl alcohol were reacted in the same manner as in Example 1 to form a blocked isocyanate with a melting point of 85-95°C. Obtained.

340 parts of this blocked isocyanate, 660 parts of the acrylic polyol of Example 4 (NCO10H ratio is 1.0)
, 500 parts of titanium oxide, 4 parts of Modaflow, 1,1,3,
3 parts of 3-tetrabutyl-1,3-diacetoxydistanoxane and 2 parts of tetraphenyldipropylene glycol diphosphite were melt-mixed, powdered in the same manner as in Example 1, and powdered on a mild steel plate at 60 KV to 80-100 μm. Electrostatic coating was applied to a film thickness of , and baking was performed at 160°C for 30 minutes to obtain a robust, glossy white coating.

The coating performance is shown in Table 1. Comparative Example 1 292 parts of a 75% ethyl acetate solution of an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane was reacted with 46 parts of ethanol in the same manner as in Example 1 to produce a blocked isocyanate with a melting point of 90-100°C. I got it.

265 parts of this blocked isocyanate, 730 parts of the polyester resin of Example 1 (NC'010H ratio is 1, 0),
500 parts of titanium oxide, 5 parts of Modaflow, 1t 1.3
t 3-tetrabutyl-1,3-diacetoxydistannoki.

3 parts of tetraphenyldipropylene glycol diphosphite were melt-mixed, powdered in the same manner as in Example 1, and electrostatically coated on a mild steel plate at 60KV to a film thickness of 80-100μ. A white coating film was obtained by baking at 160°C for 30 minutes.

The coating performance is shown in Table 1.

Example 8 1,550 parts of dimethyl terephthalate, 560 parts of polypropylene glycol with a molecular weight of 560, 1,680 parts of hydrogenated bisphenol A, and 134 parts of trimethylolpropane were added to 18
Heating to 0-220°C and reacting for 8 hours while continuously removing methanol to remove insects from the system, acid value 1 or less,
A polyetherester resin having a hydroxyl value of 51 and a melting point of 69°C was obtained.

1100 parts of this polyether ester resin and 335 parts of the blocked isocyanate of Example 1 (NCO10H ratio is 1
．． 0), 550 parts of titanium oxide, 5 parts of Modaflow, 1,1
, 4 parts of 3,3-tetrabutyl-1゜3-diacetoxy distanoxane and 3 parts of tetraphenyl diethylene glycol diphosphite were melt-mixed and powdered in the same manner as in Example 1. After applying electrostatic coating to a thick layer and baking at 160°C for 30 minutes, a solid and glossy white coating was obtained.

The coating performance is shown below.

Gloss (60° specular reflection) 94% hardness (pencil) HB Bending test* LOtnmφ Passed Erichsen test 8 Solvent resistance (ethyl acetate) Passed *Conducted according to JIS K-5400.

Claims (1)

[Claims] 1 general formula % formula % (wherein R1 represents a phenyl group, a furyl group or a tetrahydrofuryl group which may be substituted with an alkyl group,
A powder containing an aromatic diisocyanate or an adduct thereof in which an isocyanate group blocked with a compound represented by (R2 represents a hydrogen atom or an alkyl group) or an adduct thereof and a polyol resin having a melting point of 40°C or higher Coating composition.