JP3088939B2 - Primer for powder coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for coating a synthetic resin such as a thermoplastic resin and a thermosetting resin on a metal surface having a shape such as a pipe, a wire, a rod or a plate via a specific primer. The present invention relates to a method for producing a synthetic resin-coated metal body having excellent aesthetics, corrosion resistance, metal insulation, abrasion resistance, and weather resistance, as well as significantly improved adhesion to metal, and a primer for powder coating. .

[0002]

2. Description of the Related Art A diene polymer such as polybutadiene has already been used as a primer for powder coating of thermoplastic resin powder, especially nylon powder (JP-B-53-5045). Tokiko Sho 55
-41631). Since these primers are applied and dried and then baked in a high-temperature furnace, those using a halogenated hydrocarbon such as trichloroethane as a medium have been used from the viewpoint of drying properties and fire prevention. However, due to global environmental requirements such as protection of the ozone layer, the use of halogenated hydrocarbons such as chlorofluorocarbon and trichloroethane has been restricted. Low-grade aliphatic or aromatic hydrocarbons can be considered as alternatives, but there are many problems in terms of low flash point, disaster prevention such as toxicity to human body, and work environment.

The present inventor has already developed a water-based primer having an adhesive property equal to or higher than that of a conventional product by mixing a partially acid-modified diene-based polymer with an organic amine or ammonia (see, for example, Japanese Patent Application Laid-Open No. H11-157556). JP-A-7-18858
No. 4). The water-based primer is pollution-free and excellent in safety,
In addition, the adhesiveness between the metal and the synthetic resin film is excellent. However, for the production of parts that come into contact with water or an aqueous solution for a long time or at a high temperature, for example, pipes for water and sewage, water tank panels, etc., the water resistance is insufficient, and improvement has been demanded.

As a result of intensive studies for the purpose of improving the water resistance of the primer coating layer, the present inventors have used a water-based primer obtained by mixing an aliphatic amine and an aromatic polyamine with an acid-modified diene polymer. The present inventors have found that the water resistance required for products used in the above-mentioned humid environment can be sufficiently satisfied, and that the addition of an inorganic filler to this system further improves the water resistance.

[0005]

SUMMARY OF THE INVENTION Namely, the present invention is an acid-modified diene polymer, an aliphatic amine or ammonia, primer powder coating comprising an aromatic polyamine and water,
And acid-modified diene polymer, an aliphatic amine or ammonia, an aromatic polyvalent Amin, an inorganic filler and water
For powder coating primer containing, and these primers were applied to a metal surface, with baked, a method for producing a synthetic resin coated metal body which covers the synthetic resin thereon. In the present invention
Is a synthetic resin-coated metal obtained by such a method.
Primer for powder coating is applied to the body, that is, the metal surface.
Synthetic resin coated gold that is clothed and coated with synthetic resin
The genus is also included.

In general, the introduction of a crosslinked structure into a coating film increases the mechanical strength of the coating film to improve the resistance to thermal expansion and shrinkage, and as a result, improves the adhesion of the coating film to an adherend. . The present invention relates to a water-based primer composed of a partially acid-modified diene-based polymer and an aliphatic amine or ammonia, further added with an aromatic polyamine, to thereby provide a carboxyl group of the acid-modified diene-based polymer. An active group such as a carboxyl group, an aldehyde group, or an epoxy group, which is generated by oxidizing a group and an acid anhydride group or a double bond, and an aromatic polyamine cause a cross-linking reaction in a curing and baking process to form a strong primer layer. Is to give.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The acid-modified diene polymer referred to in the present invention is a compound having a conjugated double bond such as butadiene or isoprene, for example, acrylic acid, methacrylic acid,
After copolymerizing with a carboxylic acid or carboxylic anhydride such as maleic anhydride, or polymerizing a compound having a conjugated double bond, the polymer obtained by treating the obtained polymer with maleic anhydride or the like is used. It is united.

In the present invention, the carboxylic acid unit introduced into the polymer is introduced to disperse the diene polymer in water.
Desirably, it is in the range of mgKOH / g. Acid value is 5
In the case of not more than mgKOH / g, even if a salt is formed by mixing an aliphatic amine or ammonia, the solubility in water is low and a stable aqueous solution is not formed. Acid value is 500mg
An acid-modified diene-based polymer exceeding KOH / g is not only difficult to produce, but also undesirably because the hydrophilicity of the primer layer is higher than necessary, and the adhesiveness after hot water treatment is reduced.

The molecular weight of the acid-modified diene polymer used in the present invention is at least 500 or more, preferably about 1,000 to 5,000. If the molecular weight is too low, the adhesion is not sufficient, and if it is too high, the viscosity of the obtained primer is high, and the amount of application to the adherend may exceed an appropriate value. The appropriate amount of the acid-modified diene polymer to be applied to the iron plate is in the range of about 0.2 to 2.5 mg / cm ² , preferably 0.3 to 1.5 mg / cm ² .

The aliphatic amine or ammonia used in the present invention is used to form a salt by acting on the carboxyl group of the acid-modified diene polymer to improve the water solubility of the polymer. The produced salt is decomposed in the drying or baking step, forms an aliphatic amine or ammonia again, and is discharged out of the system. Therefore, the aliphatic amine used in the present invention is not particularly limited as long as it has a low molecular weight. However, the addition of a divalent or higher polyvalent aliphatic amine causes the formation of a salt with a plurality of acid-modified diene-based polymers in an aqueous solution to cause gelation, resulting in precipitation of the acid-modified diene-based polymer. The use of monovalent aliphatic amines is preferred.

The aliphatic amine used in the present invention can be any of primary, secondary and tertiary amines. However,
Primary and secondary aliphatic amines may cause a dehydration reaction with a carboxyl group in the drying or baking step to generate a hydrophilic amide group, which may cause a problem in terms of water resistance of the primer coating layer. There is. In that respect, tertiary amines are more preferred.

The aliphatic amine used in the present invention includes, specifically, allylamines, isopropylamines, ethylamines, isobutylamines, n-butylamines, sec-butylamines, t-butylamines, and n-butylamines.
-Propylamines, 2-ethylhexylamines, morpholines, piperidines, amino alcohols and the like. Stability in aqueous solutions of aliphatic amines, drying,
Amino alcohols such as N, N-dimethylaminoethanol and N, N-diethylaminoethanol are particularly preferably selected from the viewpoint of volatility in the baking step. Ammonia can also be used in place of the aliphatic amine.

The aromatic polyamine used in the present invention is an aromatic organic compound having a plurality of amino groups directly bonded to an aromatic ring and / or nitrogen atoms incorporated in the aromatic ring. Since it contributes to the crosslinking reaction in the baking step, it is necessary that the compound has low volatility and does not scatter in the baking step. The amino group of the aromatic polyvalent amine used in the present invention may be primary, secondary, or tertiary.
Primary and secondary amino groups that can react with a carboxyl group to form an amide or imide group are more preferred. Since the basicity of the aromatic amine is lower than the basicity of the aliphatic amine, if the amino group of the aliphatic amine is present in an equivalent amount or more with respect to the carboxyl group of the acid-modified diene polymer, a plurality of amino groups are formed. Even when the aromatic amine is added, precipitation of the acid-modified diene polymer does not occur.

The aromatic polyamine used in the present invention is:
Specifically, phenylenediamines, toluylenediamines, diaminodiphenylmethanes, diaminodiphenylethers, diaminobenzanilides, diaminodiphenylsulfones, dianisidines, aminopyridines, imidazoles, melamines, pyrazines, guanamines, etc. Is mentioned. Toluylenediamines, diaminodiphenylmethanes, diaminodiphenylethers, diaminobenzanilides, and diaminodiphenylsulfones are particularly preferred from the viewpoints of reactivity to carboxyl groups, volatility, and water resistance of the resulting film.

The preferred mixing ratio of each component is 5 to 50 parts by weight of an aliphatic amine or ammonia, preferably 15 to 30 parts by weight, based on 100 parts by weight of an acid-modified diene polymer.
3 to 30 parts by weight of aromatic polyamine, preferably 5 to 20
Parts by weight, and 300 to 1500 parts by weight of water, preferably 400 to 900 parts by weight. In consideration of the stable dispersibility of the primer, shortening of the drying time, selection of the solid content concentration, etc.
The mixing ratio is adjusted within the above range, and it can be preferably carried out.

By adding an aromatic polyvalent amine,
The water resistance of the primer coating layer is greatly improved, but when higher water resistance is required, the addition of an inorganic filler is effective. It is considered that the addition of the inorganic filler effectively alleviates the shrinkage strain due to the decrease in the coefficient of thermal expansion of the primer layer, and consequently delays the decrease in adhesiveness when immersed in hot water.

As the inorganic filler used in the present invention, those which hardly react with water and have a surface isoelectric point of 7 or more are preferable, and include various metal oxides, metal hydroxides, carbon black and the like. Can be Specifically, zinc oxide,
Iron oxide, copper oxide, nickel oxide, cobalt oxide, tin oxide, various carbon blacks and the like can be used.

These inorganic fillers have a negatively charged surface under an environment having a pH below the isoelectric point due to the formation of a functional group on the solid surface or a metal hydroxide due to hydration. A strong interaction occurs with the acid (Heisei Murase, Colorants, 60, 225 (1987)).

It has been clarified that the diene polymer reacts with oxygen in the air in the step of baking to a metal to form a carboxyl group. Therefore, when the diene polymer is baked in the presence of the inorganic filler whose surface is negatively charged, a primer layer in which the diene polymer and the inorganic filler are firmly bonded to each other is generated, and this results in adhesion. It is thought to contribute.

The appropriate amount of the inorganic filler to be added to the primer depends on the required water resistance and the ratio to the aromatic polyamine, but the amount is preferably 2 parts by weight per 100 parts by weight of the diene polymer.
0 to 120 parts by weight, more preferably 50 to 90 parts by weight. If the amount is less than 20 parts by weight, the degree of decrease in the coefficient of thermal expansion of the primer layer is low, and the shrinkage strain cannot be sufficiently reduced, and as a result, sufficient water resistance cannot be obtained. If the amount exceeds 120 parts by weight, not only is a stable dispersion not obtained, but also the primer layer obtained after baking becomes brittle and the adhesion is reduced.

The primer of the present invention using water as a medium may further contain other components. For example, ethyl cellosolve, butyl cellosolve, or the like can be used as an auxiliary for improving the wettability of the primer and the fluidity of the coating film when applied to a metal. Also, a small amount of a water-soluble rust inhibitor may be added for the purpose of preventing excessive rust generation.

In order to accelerate the oxidation reaction during the baking treatment, cobalt or manganese ions can be added to the primer solution. The cobalt or manganese ion to be added is preferably added in the form of a compound which is uniformly dissolved in the primer solution, such as cobalt naphthenate, cobalt octylate and the like. The amount of addition is such that the total amount of cobalt ions and manganese ions is the acid-modified diene polymer 1
With respect to 00 parts by weight, 0.01 to 1.00 parts by weight is good,
Preferably it is 0.05 to 0.6 parts by weight. The method for producing a synthetic resin-coated metal body using the primer for powder coating of the present invention is as follows: a metal, which has been degreased and washed as required, is uniformly coated with a primer by a conventional method such as dipping, dried, and then subjected to high-frequency heating, The primer is baked on the metal surface using a heating means such as a furnace, and the synthetic resin is coated thereon using a fluid immersion method or an electrostatic coating method. like this
The synthetic resin-coated metal body obtained in
Synthetic resin coated via powder coating primer of the invention
Have been.

The applied primer is oxidized by oxygen in the air in the baking step to generate active groups. If the baking conditions are mild, the formation of active groups is insufficient,
If the conditions are too severe, carbonization proceeds and the adhesion decreases. The baking temperature is suitably from 250 to 400 ° C., and the baking time depends on the baking temperature.

Examples of the coated synthetic resin for which the primer of the present invention can be used include polyamide, polyolefin, polyester, polyvinyl chloride, fluororesin and the like as thermoplastic resins, and epoxy resins and the like as thermosetting resins. It is not something to be done.

As the metal body, various metal industrial materials such as iron, steel, aluminum and zinc can be used.

[0026]

The present invention will be described below in detail with reference to examples.

Example 1 150 g of liquid polybutadiene BN1015 manufactured by Nippon Soda (molecular weight: about 1500, acid value: 130 mgKOH / g), 30 g of dimethylaminoethanol, and 30 g of butyl cellosolve
Was mixed well, and 4.5 g of cobalt naphthenate and 850 of water were mixed.
g was added to obtain a uniform aqueous solution. Further, 15 g of 4,4'-diaminodiphenylmethane was added and mixed.

After derusting and degreasing, the above primer is applied to an iron plate by a dipping method.
Dried for hours. Next, after heating in an electric furnace at 350 ° C. for 7 minutes, nylon 12 powder (Diamid Z2073 ash)
For 7 seconds, air-cooled for 1 minute, and water-cooled for several minutes. After immersing the obtained nylon-coated iron plate in hot water at 95 ° C. for a predetermined period, a cut was made with a cutter knife to evaluate the adhesiveness. Table 1 shows the results.

Example 2 In place of 4,4'-diaminodiphenylmethane in Example 1, 15 g of 1,3-diaminobenzene (m-phenylenediamine) was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 3 In place of 4,4'-diaminodiphenylmethane of Example 1, 15 g of 1,2-diaminobenzene (o-phenylenediamine) was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 4 In place of 4,4'-diaminodiphenylmethane of Example 1, 15 g of 2,4-diaminotoluene (m-toluylenediamine) was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 5 In place of 4,4'-diaminodiphenylmethane in Example 1, 15 g of 4,4'-diaminodiphenylsulfone was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 6 In place of 4,4'-diaminodiphenylmethane in Example 1, 15 g of 4,4'-diaminodiphenyl ether was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 7 In place of 4,4'-diaminodiphenylmethane of Example 1, 15 g of melamine was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 8 In place of 4,4'-diaminodiphenylmethane of Example 1, 15 g of benzoguanamine was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Comparative Example 1 Liquid polybutadiene BN1015 manufactured by Nippon Soda (molecular weight: about 1500, acid value: 130 mgKOH / g) 150 g, dimethylaminoethanol 30 g, butyl cellosolve 30 g
Was mixed well, and 4.5 g of cobalt naphthenate and 850 of water were mixed.
g was added to obtain a uniform aqueous solution.

Using this primer, a nylon-coated iron plate was prepared, and the adhesion was evaluated after immersion in hot water. Details are the same as in the first embodiment.

Comparative Example 2 In place of 4,4'-diaminodiphenylmethane of Example 1, 15 g of m-xylylenediamine was added. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Comparative Example 3 In place of 4,4'-diaminodiphenylmethane in Example 1, polyallylamine (manufactured by Nitto Boseki Co., Ltd .;
000) 15 g. The other primer components and the evaluation of the adhesion were the same as in Example 1.

Example 9 150 g of liquid polybutadiene BN1015 manufactured by Nippon Soda (molecular weight: about 1500, acid value: 130 mgKOH / g), 30 g of dimethylaminoethanol, 30 g of butyl cellosolve
Was mixed well, and 4.5 g of cobalt naphthenate and 850 of water were mixed.
g was added to obtain a uniform aqueous solution. Further, 15 g of 4,4'-diaminodiphenylmethane and 105 g of zinc oxide were added and mixed.

After derusting and degreasing, the above primer was applied to an iron plate by a dipping method.
Dried for hours. Next, the mixture was heated in an electric furnace at 350 ° C. for 7 minutes, immersed in a fluidized bed filled with nylon 12 powder (Diamid Z2073 ash) for 7 seconds, air-cooled for 1 minute, and then water-cooled for several minutes. After the obtained nylon-coated iron plate was immersed in hot water at 95 ° C. for a predetermined period, a cut was made with a cutter knife to evaluate the adhesiveness. Table 2 shows the results.

Example 10 In place of 4,4'-diaminodiphenylmethane of Example 9, 15 g of 1,3-diaminobenzene (m-phenylenediamine) was added.

Example 11 In place of 4,4'-diaminodiphenylmethane in Example 9, 15 g of 4,4'-diaminodiphenylsulfone was added.

Example 12 In place of 4,4'-diaminodiphenylmethane of Example 9, 15 g of 4,4'-diaminodiphenyl ether was added.

Example 13 In place of 4,4'-diaminodiphenylmethane of Example 9, 15 g of 2,4-diaminotoluene (m-toluylenediamine) was added.

Example 14 In place of the zinc oxide of Example 9, 105 g of Morocco H made by Columbia Carbon was added.

Comparative Example 4 150 g of liquid polybutadiene BN1015 manufactured by Nippon Soda (molecular weight: about 1500, acid value: 130 mg KOH / g), 30 g of dimethylaminoethanol, 30 g of butyl cellosolve
Was mixed well, and 4.5 g of cobalt naphthenate and 850 of water were mixed.
g was added to obtain a uniform aqueous solution. Further 105 g of zinc oxide
Was added and mixed.

After derusting and degreasing, the above primer was applied to an iron plate by a dipping method.
Dried for hours. Then, the mixture was heated in an electric furnace at 350 ° C. for 7 minutes, immersed in a fluidized bed filled with nylon 12 powder (Diamid Z2073 ash) for 7 seconds, air-cooled for 1 minute, and then water-cooled for several minutes. After the obtained nylon-coated iron plate was immersed in hot water at 95 ° C. for a predetermined period, a cut was made with a cutter knife to evaluate the adhesiveness. Table 2 shows the results.

Comparative Example 5 In place of the zinc oxide of Comparative Example 4, 105 g of Morocco H made of Columbia Carbon was added.

[0050]

[Table 1]

[Table 2]

[0051]

By using the primer for powder coating of the present invention, the low water resistance, which has been a problem of the conventional organic solvent-based and water-based primers, can be greatly improved. Further, since water is used as a medium, a manufacturing process of a synthetic resin-coated metal body that is desirable in terms of working environment or safety can be established.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 5/00 C09D 109/00 CA (STN) CAOLD (STN) REGISTRY (STN) WPIDS (STN)

Claims (6)

(57) [Claims] 1. A primer for powder coating comprising an acid-modified diene polymer, an aliphatic amine or ammonia , an aromatic polyamine and water. 2. A powder coating primer comprising 100 parts by weight of an acid-modified diene polymer, 5 to 50 parts by weight of an aliphatic amine or ammonia, 3 to 30 parts by weight of an aromatic polyamine and 300 to 1500 parts by weight of water. . 3. An acid-modified diene polymer, an aliphatic amine or ammonia, an aromatic polyamine , an inorganic filler and
Primer for powder coating containing a fine water. 4. 100 parts by weight of an acid-modified diene polymer, 5 to 50 parts by weight of an aliphatic amine or ammonia, 3 to 30 parts by weight of an aromatic polyamine, 20 to 120 parts by weight of an inorganic filler and 300 to 1500 parts by weight of water Primer for powder coating including parts. 5. The method according to claim 1, wherein the metal surface is
The primer for powder coating described is applied and synthesized on it
Synthetic resin coated metal body coated with resin. 6. A metal surface, the powder coating primer according to any one of claims 1 to 4 is applied, after attaching baked, the preparation of a synthetic resin coated metal body which covers the synthetic resin thereon .