JPS608061B2 - Coating composition for hot dip coating of aluminum and aluminum alloys - Google Patents

Description

[Detailed Description of the Invention] In recent years, aluminum or aluminum alloys have been used for sashes,
Applications for architecture and building materials such as gates are increasing, and the surface treatment is usually after anodizing, followed by sealing treatment, or without sealing treatment, and painting methods such as electrodeposition, electrostatic, heat dipping, etc. Accordingly, coating is performed using coating compositions that have been passed through various coating methods.

Among these coatings, the present invention relates to a coating composition for aluminum or aluminum alloy used in the heat soaking method. A coating method using a heated coating composition includes heating a coating composition in which the coating film-forming components are dissolved in a chlorinated hydrocarbon solvent to a temperature close to the boiling point of the chlorinated hydrocarbon solvent. A generally known method is to immerse the object to be coated in the composition and pull it up through a vapor layer of the chlorinated hydrocarbon solvent generated on the liquid surface of the composition to form a uniform coating film. ing.

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.

In addition, as a composition using thermosetting acrylic resin,
11Q, B-A composition mainly composed of N-methylol or alkoxymethyl derivatives of ethylenically unsaturated carboxylic acid amide (Japanese Patent Publication No. 47-45176), (1) A similar composition with an intrinsic viscosity of 0.005 to 0.017 Composition(
Special 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, and nitrogen is added to the highly reactive side chain. The use of an acrylic resin made of monomers that do not contain hydroxyl groups promotes the decomposition of the chlorinated hydrocarbon solvent used,
Alternatively, they are excluded from resin compositions because they cause deterioration due to thermal decomposition products of chlorinated hydrocarbons. Therefore, it is necessary to increase the baking temperature when baking the coating film. If the brazing temperature is increased, the acrylamide resin used will yellow significantly because it contains nitrogen atoms.
In reality, it is necessary to set the temperature at 180℃ to 200qC for 2 minutes to 30 minutes, and as a result, it is difficult to achieve the pencil hardness of the paint film for more than 4 days, which is required for building material applications. However, it was not possible to avoid the drawback that the coating film was easily damaged. In addition, a composition containing phenolic and thioether stabilizers (Japanese Patent Publication No. 52-488) has been proposed as a stable composition for hot coating, and hydroxyalkyl ester acrylate resin is also used in combination with the above stabilizers. It is considered possible. 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 and have a Gardner color number of 4 to 5.
In some cases, the coating film was colored up to 6 to 7, and it was possible to determine that the formed coating film was clearly colored from the initial stage even when compared with the naked eye. The present inventors have conducted research to improve the above-mentioned drawbacks, and as a result A a Q,
B-ethylenically unsaturated carboxylic acid, b Q,8-ethylenically unsaturated carboxylic acid alkyl ester and c acrylic acid and/or methacrylic acid hydroxyalkyl ester are copolymerized as essential components, and the carboxyl group is copolymerized. When a composition prepared by dissolving a mixture of an acrylic resin partially or completely neutralized with an organic amine and an aminoplast in a chlorinated hydrocarbon solvent is used for heat-durable coating of aluminum and aluminum alloys. , to provide a coating film with excellent low-temperature crosslinking properties, improved coating film hardness, and excellent coating film hardness, weather resistance, chemical resistance, etc., and to add a stabilizer. The present invention was completed based on the discovery that it is stable against long-term heating without significant thickening or coloring.

Among the components constituting the composition of the present invention, acrylic resin as component A (a) Q,8-ethylenically unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, etc. and elbow Q , 8-alkyl esters of ethylenically unsaturated carboxylic acids, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isoptyl acrylate. , isobutyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, etc., and [c
'Copolymerization of hydroxyalkyl esters of acrylic acid and/or methacrylic acid, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, etc. It is obtained by neutralizing part or all of the carboxyl groups with an organic amine.

If necessary, a part of the hydroxyalkyl ester of acrylic acid and/or methacrylic acid may be replaced with another monomer containing a hydroxyl group, such as allyl alcohol or monoallyl ether of polyhydric alcohol, which can be copolymerized with these. is also possible. Furthermore, if necessary, it is also possible to copolymerize with the above monomers a vinyl monomer such as styrene, vinyltoluene, vinyl acetate, etc. that can be copolymerized with the above monomers. Q
, 8-ethylenically unsaturated carboxylic acid, alkyl ester of Q,8-ethylenically unsaturated carboxylic acid, hydroxyalkyl ester of acrylic acid and/or methacrylic acid, and other monomers added as necessary. The amount of carboxyl groups and hydroxyl groups in the acrylic resin obtained by copolymerization (hereinafter abbreviated as carboxyl group- and hydroxyl group-containing acrylic resin) is not particularly limited, but it depends on thermal stability, reactivity with the aminoplast described below, From the viewpoint of the performance of the coating film formed, the carboxyl group should have an acid value of 5 to 100, and the hydroxyl group should have a hydroxyl value of 40.
It is desirable that it be in the range of ~200. It is necessary to neutralize part or all of the carboxyl groups of the carboxyl group- and hydroxyl group-containing acrylic resin with an organic amine in order to improve the heat stability of the composition. If unneutralized, long-term heating tends to cause thickening, gelation, etc. The type of organic amine used for neutralization is not limited, but it is desirable that it be liquid at normal temperature and pressure, and have a boiling point of 70 qo to 170 qo.

For example, triethylamine, dipropylamine, diisopropylamine, n-butylamine, di-n-butylamine, monoisobutylamine, diisobutylamine, dimethylaminopropylamine, diethylaminopropylamine, diethylaminoethylamine, monoethanolamine, monoisopropanolamine, methylethanolamine, morpholin. , methylmorpholine, ethylmorpholine, etc. can be preferably used. Next, the aminoplast used in the present invention coexists with the carboxyl group- and hydroxyl group-containing acrylic resin and has the effect of forming a strong coating film through reaction crosslinking during coating film formation, that is, during competitive drying. Therefore, N-methylol alkyl etherified melamine and/or N-methylol alkyl etherified penzoguanamine, e.g.
Single plants or Dimers or higher multimers and mixtures thereof can be used.

Therefore, the aminoplast includes not only the usual amino resin but also the above-mentioned monomers and oligomers.
Preferably, mixed maple 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 6 per triazine ring.
It is desirable that the number of These are available on the market, such as Sumimaru M-1000 and M-5 manufactured by Sumitomo Chemical Co., Ltd.
u M-40 and M-30 (methylated melamine aminoplast), M-6 spots (mixed ether type melamine aminoplast); Nikalac MW manufactured by Sanwa Chemical Co., Ltd.
-30 and MX-40 (melamine aminoplast)
; Hitachi Chemical Melan 20, 22, 25, 26, 27,
28 and 29 (butylated melamine aminoplasts); Supervecamine J-820 manufactured by Dainippon Ink Co., Ltd.
-6 stop G-821-6 L-101-60, L-1
09-65 (butylated melamine aminoplast)
, Supervetsukamine TD-126 (butylated penzoguanamine aminoplast); Mitsui Tosho Co., Ltd. Yuban 2
Examples include Eaves B (butylated melamine aminoplast), Yuban 90 and 91-55 (benzoguanamine aminoplast), and Cymel 11231124 and 1125 (benzoguanamine aminoplast). In the composition of the present invention, the mixing ratio of the acrylic resin as the component (■) and the aminoplast as the 'B' component is 50 to 50% of the acrylic resin as the bad component.
Preferably, the amount of aminoplast is 50 to 5 parts by weight to 95 parts by weight. Chlorinated hydrocarbon solvents that can be used in the present invention include trichloroethyl, 1,1,1-trichloroethane, perchlorethylene, carbon tetrachloride, chloroform, ethylene dichloride, etc. whose boiling point is 5000 to 1.
Those that are not flammable at 30°C are preferred, and mixtures of two or more of these can also be used.

Furthermore, if a stabilized chlorinated hydrocarbon solvent is used as the chlorinated hydrocarbon solvent, it is natural that the heating stability of the composition will be further improved. Preferably, the non-volatile content in the composition of the invention is between 10 and 5% by weight. The composition according to the present invention does not cause a significant increase in viscosity or gelation due to long-term heating in the range of 60°C to 12,000°C, has excellent discoloration resistance compared to conventional coating compositions, and has a heating temperature of 130°C to 230°C. under a wide range of simulated conditions, preferably at 140°C to 180qo for 1 to 50 minutes.
It is possible to bake at a relatively low temperature for 5 to 40 minutes, and the hardness of the formed coating film can range from rough to rough, and in some cases can have excellent coating hardness.

The composition of the present invention can be used in clears without dispersing pigments, etc., and can also contain inorganic pigments such as titanium oxide, iron oxide, lead oxide, zinc oxide, etc. that do not react with chlorinated hydrocarbon solvents. In addition to metal oxides, silicates, talc, silica, mica, carbon, calcium carbonate, barium sulfate, etc., it can also be colored with 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, and coating performance. 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.

Aluminum and aluminum alloys used as coatings are processed into shapes such as window frames, plates, bars, films, etc. by extrusion, rolling, drawing, etc., and can be used as they are, or by degreasing, etching, boehmite, etc. Surface treatments such as chemical conversion treatment with a phosphate or anodization treatment with one or more electrolytes such as sulfuric acid, phosphoric acid, and organic acids are used.

After anodizing, it can be electrolytically colored with metal salts such as nickel and tin using direct current or alternating current, or dyed with conventionally known inorganic dyes.
It is also possible to use products that have been washed with hot water, with or without containing metal salts of o, basic substances such as amines, etc. Furthermore, in order to avoid bringing moisture into the heated bonding coating, it is desirable to drain and dry at a temperature of 80 qC to 15,000 ℃ after the above-mentioned treatment, cool it to near the temperature of the coating bath, and then soak it into the coating. . When performing hot bond coating of aluminum and aluminum alloys using the composition of the present invention, the coating bath made of the composition of the present invention is heated to near the boiling point of the chlorinated hydrocarbon solvent used. , aluminum and aluminum alloys with or without surface treatment as described above are soaked and pulled up through a vapor layer of chlorinated hydrocarbons formed on the surface of the coating bath, 130
It is carried out by dovetailing at 00 to 230 oo for 1 minute to 50 minutes.

The present invention will be specifically described below with reference to Production Examples and Examples.

Parts and percentages are by weight. Production example 1 dropping funnel,
15 parts of n-butyl alcohol and 35 parts of xylene are charged into a four-way flask equipped with a thermometer, a thermometer, and a reflux condenser, and heated to reflux temperature.

Next, 3 parts of acrylic acid, 10 parts of ethyl acrylate, 20 parts of butyl acrylate, 17 parts of 2-hydroxyethyl methacrylate, 35 parts of methyl methacrylate, 15 parts of styrene, and 1 part of azobisisobutyronitrile.
5 parts of the mixture were added dropwise under reflux over a period of 4 hours. After the dropwise addition was completed, refluxing was continued for another 2 hours to complete the polymerization. The reaction solvent was removed under reduced pressure while heating, and trichloroethylene was added to obtain a trichloroethylene solution of an acrylic resin containing carboxyl groups and hydroxyl groups with a nonvolatile content of 70%. The resulting resin had an acid value of 23.4 and a hydroxyl value of 73.4. Production Example 2 In the same manner as in Production Example 1, 60 parts of n-butyl alcohol was used as the reaction solvent, 66 parts of methacrylic acid, 20 parts of butyl acrylate, and 27 parts of 2-hydroxyacrylate.
59 parts of methyl methacrylate, 134 parts of styrene, 157 parts of ethyl acrylate, and 2 parts of azopisisobutyronitrile were copolymerized.

The reaction solvent was replaced with trichlorethylene in the same manner as in Production Example 1 to obtain a trichloroethylene solution of a carboxyl group- and hydroxyl group-containing acrylic resin with a nonvolatile content of 70%. The resulting resin had an acid value of 30.4 and a hydroxyl value of 92.1.
Met. Reference Example 1 60 parts of n-butyl alcohol was charged into the apparatus used in Production Example 1 and heated to reflux temperature.

Next, 210 parts of N-methylol acrylamide, 28 parts of acrylic acid, 560 parts of methyl methacrylate, 14 parts of styrene, 392 parts of imbutyl acrylate, and azobisisobutylene. A mixture consisting of 1 $ part of nitrile was added dropwise to the flask under reflux over a period of 4 hours. After the dropwise addition was completed, the mixture was kept under reflux for 2 hours to completely react the remaining monomers and complete the polymerization. In the same manner as in Production Example 1, the solvent was replaced with trichlorethylene to obtain a resin liquid with a nonvolatile content of 70%. Examples 1 to 5, Comparative Example 1 Triethylamine was added to the resin liquid obtained in Production Example 1,
10% of carboxyl groups of acrylic resin (Example 1),
30% (Example 2), 50% (Example 3), 70% (Example 4), and 100% (Example 5) were neutralized, and each was made into a paint using the following formulation.

Resin liquid (70% non-volatile content) 52.2 Sumimaru M-100C 6.4 (manufactured by Sumitomo Chemical Co., Ltd.) Trichlorethylene
141.4 Total 200.0 Further, as Comparative Example 1, a neutralized acrylic resin liquid was made into a paint in the same manner as in the above formulation.

As a result, coating compositions for heat-curable bond painting each having a non-volatile content of 21.5% were obtained. These are each 100 ratio.
c. A thermal stability test was conducted at 80° C. for 180 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 put into a heating bond coating device equipped with a cooling device above the liquid level and flooded to 7,000 to 75 oo, and the end-sealed plate obtained by anodizing 6 $ aluminum was immersed. , pulled up through the solvent vapor layer formed on the liquid surface and immediately dried in a hot air drying oven.
A coating film performance test was conducted with 3 females competing at 70qo. 80
After conducting a thermal stability test for 180 feeding hours at 2C, each composition was similarly coated on an unsealed plate obtained by anodizing 6$ aluminum and subjected to a performance test.

The thermal stability test, coating film performance, and coating film performance after the thermal stability test are shown in Table 1. ! Funaba oath L.

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Japan R total Hitomi and Kasumi Keishizuku. As shown in Table 1, in Comparative Example 1 using an unneutralized acrylic resin, the viscosity increased in the thermal stability test.

Example 6 Mono-ethanolamine was added to the resin liquid obtained in Production Example 2 to neutralize 50% of the carboxyl groups of the acrylic resin, and a paint was prepared using the following formulation.

Resin liquid (70% non-volatile content) 52.2 parts Sumimaru M-68B 6.4 (manufactured by Sumitomo Chemical Co., Ltd.) Trichloroethylene
141.4 total 200.0 A coating composition for heat dipping thin coating with a nonvolatile content of 21.5% was obtained.

This composition was subjected to a thermal stability test, a coating film performance test, and a coating film performance test after the thermal stability test in the same manner as in Example 1.

The results are shown in Table-2. Comparative Example 2 The resin liquid obtained in Reference Example 1 was made into a paint with the following formulation to obtain a composition with a nonvolatile content of 21.5%.

Resin liquid (70% non-volatile content) 52.2 parts Sumimaru M-6 string 6.4 (manufactured by Sumitomo Chemical Co., Ltd.) Trichlorethylene 14
1.4 total 200.0 This composition was subjected to a thermal stability test, a coating film performance test, and a coating film performance test after the thermal stability test in the same manner as in Example 1. 20 minutes at 190qC and 170
It was at the 2/30 level at midnight.

The results are shown in Table-2. Table-2 Lost 1 1. Day. S.

Measured in a cup at a temperature of 20°C. Husband 2: Based on Gardner color meter. Husband 3: 48 hours in sulfur dioxide gas atmosphere.

*4 According to JIS 1A River 4706K.

X-5 Sunshine Weatherometer exam 500 hours.

Loss 6 Judgment by visual inspection. As described above, the composition obtained from the present invention has better thermal stability than Comparative Example 2, which is used in its predecessor, and is particularly excellent in discoloration resistance, and has a high pencil hardness even at a 20 oo lower competition. It has excellent sulfur dioxide gas resistance and weather resistance, and is comparable in other respects.

Claims (1)

[Claims] 1 A a α,β-ethylenically unsaturated carboxylic acid b
Acrylic acid copolymerized with an alkyl ester of α,β-ethylenically unsaturated carboxylic acid and a hydroxyalkyl ester of acrylic acid and/or methacrylic acid as essential components, and in which part or all of the carboxyl groups are neutralized with an organic amine. A coating composition for hot dip coating of aluminum and aluminum alloys, characterized in that a mixture of a resin and an aminoplast is dissolved in a chlorinated hydrocarbon solvent.