JPS608060B2 - Coating composition for hot dip coating of aluminum or aluminum alloys - Google Patents

Description

[Detailed Description of the Invention] In recent years, aluminum or aluminum alloys have been used for sashes,
Applications for architectural materials such as gates are increasing, and the surface treatment is usually after anodizing and sealing treatment, or without sealing treatment, and painting methods such as haze deposition, electrostatic coating, and heating bonding are used. Accordingly, coating compositions suitable for each coating method are applied.

Among these coatings, the present invention relates to a coating composition for aluminum or aluminum alloy used in the heated eel thin coating method. Using a heated coating composition,
The coating method is to flood a coating composition in which film-forming components are dissolved in a chlorinated hydrocarbon solvent to a temperature close to the boiling point of the chlorinated hydrocarbon solvent, and then add the coating composition into the composition. A method is generally known in which a material is immersed and pulled up through a vapor layer of the chlorinated hydrocarbon solvent generated on the liquid surface of the composition to form a uniform coating film.

This coating method has many advantages, such as uniform coating thickness, no uneven coating, and no risk of fire. In order to achieve this, the above-mentioned composition is required to have long-term heat stability, that is, to have no increase in viscosity, gelation, change in hue, or deterioration in coating performance.

As compositions meeting these objectives, compositions using various synthetic resins such as thermoplastic acrylic resins, alkyd resins, and epoxy resins are known.

Also, as a composition using thermosetting acrylic resin,
1-Q, 8-ethylenically unsaturated carboxylic acid amide N
- Compositions based on methylol or alkoxymethyl derivatives (Japanese Patent Publication No. 47-45176), '2} Similar compositions with an intrinsic viscosity of 0.005 to 0.017 (Japanese Patent Publication No. 49-9082) etc. have been proposed.
However, in these thermosetting acrylic resin compositions, the acrylic resin used is an amide type, and the functional group contained is an N-methylol group or an N-alkoxymethyl group, which has a highly reactive side chain. The use of acrylic resins made of monomers that do not contain nitrogen but contain hydroxyl groups may accelerate the decomposition of the chlorinated hydrocarbon solvents used or cause deterioration due to thermal decomposition products of the chlorinated hydrocarbons. Excluded from resin compositions. Therefore, it is necessary to increase the baking temperature when baking the paint film.If the baking temperature is increased, the acrylamide resin used will yellow significantly because it contains nitrogen atoms, and in reality ~20-30 for 200qo
As a result, it is difficult to obtain a pencil hardness of 4 days or more for the paint film required for building material applications.
However, it was not possible to avoid the disadvantage that the coating film was easily damaged because the coating film was very thin. Furthermore, a composition containing phenolic and thioether stabilizers (Japanese Patent Publication No. 52-488) has been proposed as a stable composition for hot coating, and acrylic acid hydroxyalkyl ester resin can also be used in combination with the above stabilizers. It is said to be available for use. However, the use of stabilizers increases the cost of the composition, and it has not been possible to provide an inexpensive composition for hot coating. Furthermore, these compositions become colored with the passage of heating time, reaching a Gardner color number of 4 to 5, or even 6 to 7 in some cases, and the formed coating films are clearly colored from the beginning even when compared with the naked eye. It was possible to determine that The inventors of the present invention should improve the above-mentioned drawbacks.As a result of research,
A resin and aminoplast obtained by copolymerizing a hydroxyalkyl ester of acrylic acid and/or methacrylic acid, a Q,8-ethylenically unsaturated carboxylic acid, and an alkyl ester of Q,8-ethylenically unsaturated carboxylic acid as essential components. A mixture consisting of 55 to 95% by weight of a chlorinated hydrocarbon solvent and 45 to 5% by weight of an alcoholic solvent.
When a composition dissolved in a mixed solvent consisting of The present invention was developed based on the discovery that it provides a coating film with excellent performance in terms of weather resistance, chemical resistance, etc., is stable against long-term heating without adding a stabilizer, and does not cause significant aging or discoloration. completed.

Hydroxy alkyl ester of acrylic acid and/or methacrylic acid used in the present invention, obtained by copolymerizing an alkyl ester of Q'8-ethylenically unsaturated carboxylic acid and Q,8-ethylenically unsaturated carboxylic acid as essential components. The resin (hereinafter referred to as hydroxyl group-containing acrylic resin) is an ester of acrylic acid and/or methacrylic acid and glycol such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate. Q,3-ethylenically unsaturated carboxylic acids and their alkyl esters copolymerizable with monomers, such as unsaturated acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, methyl acrylate, Copolymerization of esters such as methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, ethylhexyl acrylate, and ethylhexyl methacrylate. In addition, if necessary, styrene,
It is also possible to add polymerizable unsaturated monomers containing a hydroxyl group in the molecule, such as vinyl monomers such as vinyltoluene, and monoallyl ethers of allyl alcohols and polyhydric alcohols. Furthermore, in the resin used in the present invention, it is also possible to copolymerize vinyl acetate with other acrylic monomers and then introduce hydroxyl groups into the acrylic resin by hydrolyzing the vinyl acetate unit. The amount of hydroxyl groups in the hydroxyl group-containing acrylic resin is not particularly limited, but
The hydroxyl value of the resin is preferably from 40 to 200 in terms of heat stability, reactivity with aminoplast, and performance of the coating film formed.

In addition, from the viewpoint of heat stability, the weight average molecular weight of the resin is approximately 7.
Preferably, the range is from 000 to about 200,000. Next, the aminoplast used in the present invention may be one that coexists with the hydroxyl group-containing acrylic resin and has the effect of forming a strong coating film through reaction crosslinking during coating film formation, i.e., during drying. Therefore N-Methi.

-alkyl etherified melamine and/or N-methylolalkyl etherified penzoguanamine, such as methoxymethylated melamine, ethoxymethylated melamine, butoxymethylated melamine, isobutoxymethylated melamine, methoxymethylated penzoguanamine, ethoxymethylated pen Monomers such as zoguanamine, butoxymethylated penzoguanamine, isobutoxymethylated penzoguanamine, polymers of double or higher, and mixtures thereof can be used. It shall also include bodies and oligomers. Preferably, mixed ether type methoxymethyl/butoxymethylated melamine, methoxymethyl/isobutoxymethylated melamine, methoxymethyl/butoxymethylated penzoguanamine, methoxymethyl/isobutoxymethylated penzoguanamine, etc. can be used. The degree of alkyl etherification of these aminoplasts is 2 to 2 per triazine ring.
It is desirable that the number is six. These are available in the market;
For example, Sumimaru M-100C, M-50 manufactured by Sumitomo Chemical Co., Ltd.
, M-40 and M-30 (methylated melamine aminoplast), M-6 cord (mixed methylated and butylated melamine aminoplast); Nikaratsuk MW-30 and MX-40 (melamine Aminoplast); Melan 20, 22, 25, 26 manufactured by Hitachi Chemical
'27, 28 and 29 (butylated melamine/plast); Super Becca Miso J manufactured by Dainippon Ink Co., Ltd.
-1820 -16 G-821 -16 L-101 -6 L-109-65 (butylated melamine aminoplast), Super Beckamine TD-126 (butylated penzoguanamine aminoplast); Mitsui Toshosha Co., Ltd. Reuban 2 female B (butylated melamine aminoplast),
Yuban 90 and 91-55 (benzoguanamine aminoplast), Cymel 1123, 1124 and 1
125 (benzoguanamine aminoplast), etc. The mixing ratio of the hydroxyl group-containing acrylic resin and aminoplast is 50% of the hydroxyl group-containing acrylic resin.
Preferably, the amount is 50 to 5 parts by weight of aminoplast to 95 parts by weight. The chlorinated hydrocarbon solvents in the mixed solvent used in the present invention include trichlorethylene, 1,
Preferably, those having a boiling point of 50 to 130 qo and being non-flammable include 1,1-trichloroethane, perchlorethylene, carbon tetrachloride, chloroform, and ethylene dichloride.

The alcoholic solvent that is the other component of the mixed solvent is not particularly limited, but it is desirable to use one having 1 to 6 carbon atoms.

That is, methyl alcohol, ethyl alcohol, inpropyl alcohol, butyl alcohol, isobutyl alcohol, secondary butyl alcohol, amyl alcohol, hexyl alcohol, diacetone alcohol and the like are preferred. The mixing ratio of the chlorinated hydrocarbon solvent and the alcohol solvent in the above mixed solvent is 5% of the chlorinated hydrocarbon solvent.
It is necessary that the content of the solvent be 5 to 95% by weight, and the alcoholic solvent should be 45 to 5% by weight.

If the amount of the chlorinated hydrocarbon solvent in the mixed solvent is less than 55% by weight, it will be difficult to form a vapor layer of the chlorinated hydrocarbon on the liquid surface during heating and carinizing coating, and the so-called vapor wash effect will be reduced. This makes it difficult to form a uniform coating. In addition, the amount of chlorinated hydrocarbon solvent is 95% by weight.
If it exceeds this, the heating stability of the composition after a long period of time deteriorates, and the composition has a tendency to cause thickening and gelation. Furthermore, if a stabilized chlorinated hydrocarbon solvent is used as the chlorinated hydrocarbon solvent, the stability will naturally be further improved. The nonvolatile content in the composition of the present invention is preferably 10 to 5% by weight. The composition obtained according to the present invention does not cause a significant increase in viscosity or gelation even after long-term heating in the range of 60 to 120 oo, has excellent discoloration resistance compared to conventional coating compositions, and
It is possible to bake under a wide range of baking conditions of 10 to 5 minutes at ~230 qo, particularly preferably at a lower temperature of 15 to 40 minutes at 14,000 to 180 qo, and the hardness of the formed coating film can be as long as 4 days depending on the case. It is possible to obtain a coating film with excellent spots.

The composition of the present invention can be used as a clear without dispersing pigments, etc., and can also be used with inorganic pigments that do not react with chlorinated hydrocarbon solvents, such as titanium oxide, iron oxide, lead oxide, zinc oxide, etc. It is also possible to use it by coloring it with metal oxides such as silicates, talc, silica, mica, carbon, calcium carbonate, barium sulfate, etc., as well as organic pigments such as phthalocyanine compounds, or organic dyes. Furthermore, surfactants, plasticizers, and other additives commonly used in the art may be added to improve workability, coating finish, coating performance, etc. The composition of the present invention can be used not only at high temperatures near the boiling point of the chlorinated hydrocarbon solvent used as described above, but also at lower temperatures, such as around room temperature, depending on the case.

The aluminum or aluminum alloy to be coated can be processed into shapes such as window frames, plates, rods, wires, films, etc. by extrusion, rolling, drawing, etc., and can be used as is, or by degreasing, etching, boehmite, phosphorus, etc. Surface treatments such as chemical conversion treatment with acid salts, or electrolytic anodization treatment using one or more types of sulfuric acid, phosphoric acid, organic acids, etc., are used.

After anodizing, it is further electrolytically colored in a metal salt bath such as nickel or tin with direct current or alternating current, or dyed with a case containing conventionally known inorganic or organic dyes.
It is also possible to use products that have been washed with hot water, with or without containing basic substances such as metal salts and amines. Furthermore, in order to avoid bringing moisture into the heated coating, it is preferable to drain and dry at a temperature of 80 to 150 degrees Celsius after the treatment, and cool to near the temperature at which the coating is applied before applying the coating to the coating. When applying heat bond coating to aluminum or aluminum alloy using the composition of the present invention, the coating made of the composition of the present invention is heated to near the boiling point of the chlorinated hydrocarbon solvent used. Then, aluminum or aluminum alloy with or without surface treatment as described above is soaked and pulled up through a vapor layer of chlorinated hydrocarbons formed on the surface of the coating bath, and 130 qo
This is done by baking at ~230oo x 10-50 minutes. The present invention will be specifically explained below with reference to Production Examples and Examples.

Production Example 1 In a four-necked flask equipped with a condenser, a reflux condenser, a thermometer, and a dropping funnel, 19 parts of isopropyl alcohol and 41 parts of xylene are charged and heated to reflux temperature.

A mixture of 4 parts of acrylic acid, 32 parts of butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 49 parts of methyl methacrylate, and 15 parts of azobisisobutyronitrile was then added to the flask under reflux over a period of 4 hours. Drip inside. After the dropwise addition was completed, refluxing was continued for another 2 hours to complete the reaction. After removing the polymerization solvent by heating and reducing the pressure, n-butyl alcohol was added to obtain a resin solution with a nonvolatile content of 70%. The obtained acrylic resin had a hydroxyl value of 64.7 and a weight average molecular weight of about 15,000. Production Example 2 60 parts of n-butyl alcohol, 66 parts of methacrylic acid, 59 parts of methyl methacrylate, 104 parts of styrene,
A copolymerization reaction was carried out in the same manner as in Production Example 1 with a composition of 20 parts of inbutyl acrylate, 157 parts of ethyl acrylate, 28 parts of 2-hydroxyethyl methacrylate, and 15 parts of azobisisobutyronitrile, and the nonvolatile content was 70 parts. %
An acrylic resin liquid was obtained.

The obtained acrylic resin had a hydroxyl value of 86.5 and a weight average molecular weight of about 19,500. Production Example 3 Using 25 parts of isobutyl alcohol and 45 parts of xylene as the polymerization solvent, 33 parts of acrylic acid, an essential part of butyl acrylate, 14 parts of 2-hydroxyethyl methacrylate,
637 parts of methyl methacrylate, 17 parts of styrene, and 20 parts of azobisisoputilonitrile were polymerized in the same manner as in Production Example 1, and then the solvent was replaced with n-butyl alcohol,
The nonvolatile content was 70%.

The hydroxyl value of the resin is 43.1, and the weight average molecular weight is approximately 200.
It was 00. Production Example 4 Using 20 parts of butyl alcohol, 40 parts of xylene as a polymerization solvent, 110 parts of butyl acrylate, 27 parts of 2-hydroxyethyl methacrylate, 26 parts of methyl methacrylate, 20 parts of styrene, and 10 parts of ethyl acrylate.
Kato, 10 parts of ethylhexyl methacrylate, 5 parts of acrylic acid, and 3 parts of azobisisobutyronitrile were polymerized in the same manner as in Production Example 1, then the solvent was replaced with isobutyl alcohol, and the nonvolatile content was 70 parts. % acrylic resin liquid was obtained.

The hydroxyl value of the resin is 116.5, and the weight average molecular weight is approximately 95.
It was 00. Comparative Example 1 In Production Example 1, the solvent was
Instead of replacing with butyl alcohol, the reaction mixture was replaced with trichlorethylene to obtain a trichloroethylene solution of acrylic resin with a non-volatile content of 70%.

Comparative Example 2 (Production of N-methylolamide-containing acrylic resin) 600 parts of n-butyl alcohol was charged into the four-necked flask used in Production Example 1 and heated to reflux temperature.

Next, a mixture consisting of 210 parts of n-methylol acrylamide, 28 parts of methacrylic acid, 56 parts of methyl methacrylate, 14 parts of styrene, 392 parts of isobutyl methacrylate, and 17 parts of azobisisobutyronitrile was added dropwise over 4 hours under reflux. do. After the dropwise addition is completed, the reflux temperature is maintained for another 2 hours to complete the copolymerization. The nonvolatile content of the obtained resin liquid was 69%. Example 1 Coating compositions were obtained by mixing the resin liquids of Production Examples 1 to 4 and Comparative Examples 1 and 2 as follows.

As a result, a coating composition for heat-curable bond coating with a nonvolatile content of 21.5% was obtained.

The proportion of trichlorethylene in the solvent of each composition except Comparative Example 1 was 90%. 10 of these each
0 ratio. c. A thermal stability test was conducted at 80° C. for 180 feeding hours in a test flask with a condenser attached to the top of a round glass container.

The results of the thermal stability test are shown in Table 1. Furthermore, each composition was placed in a heating bond coating device equipped with a cooling device above the liquid level and flooded to 70 to 7yo, and the end-sealed plate obtained by anodizing 6$ aluminum was immersed. 17 for Production Examples 1 to 4 and Comparative Example 1.
000 is 3 times, and for comparative example 2, 170oo is 30 minutes.
20 minutes of kneeling was performed at 19,000 minutes and 19,000 minutes. Table 1 shows the performance of each coating film. Furthermore, 80qo is 18
A coating film performance test similar to that described above was conducted for each composition except for Comparative Example 1 after the 0 field time thermal stability test.

Regarding Comparative Example 1, the viscosity increased from 12.4 seconds to 33.7 seconds during the 180 field time thermal stability test, so a coating performance test after the thermal stability test was not conducted. The results are shown in Table 1. A ghost.

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Cloud Fu ↑ 〇Yano Toin N Small size g Shimobata Gunden Yotsuya Tatsumi day is also Kenb and dish loss loss loss unemployment As above, the composition obtained by the present invention is the composition of Comparative Example 2 which has been used conventionally. Even though the scale temperature is 20 oo lower than that of the original product, it is superior in pencil hardness, sulfur dioxide gas resistance, weather resistance, and coloration of the coating film after the thermal stability test, and is equivalent in other respects.

In addition, in Comparative Example 1 in which an alcohol-based solvent was not used as the solvent, the viscosity changed from the initial 12.4 seconds to 33.0 seconds in a thermal stability test at 80°C and 180 feeding hours. The viscosity increased in ten thousand seconds. Examples 2 to 4
and Comparative Example 3 n of the acrylic resin obtained in Production Example 1
-Butyl alcohol solutions were made into paints using the following formulations.

As in Example 1, each of the above compositions was subjected to a thermal stability test and a coating test on an aluminum profile having a length of 30 skins and a length of 6 dollars.

The results of the coating test are shown in Table-2.

In Comparative Example 3, in which the proportion of trichlorethylene in the mixed solvent was 5% by weight, there was a difference of about 5 cm in coating film thickness between the upper and lower parts of the object to be coated with 30 skins, and the effect of paper washing was not obtained. There wasn't.

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Claims (1)

[Claims] 1 A resin obtained by copolymerizing a hydroxyalkyl ester of acrylic acid and/or methacrylic acid, an α,β-ethylenically unsaturated carboxylic acid, and an alkyl ester of α,β-ethylenically unsaturated carboxylic acid as essential components, and an amino acid. A hot dip coating composition for aluminum or aluminum alloy, characterized in that a mixture consisting of plastic is dissolved in a mixed solvent consisting of 55 to 95% by weight of a chlorinated hydrocarbon solvent and 45 to 5% by weight of an alcoholic solvent. thing.