JP2909879B2 - Powder paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating suitable for the inner surface coating of a metal can.

[0002]

2. Description of the Related Art It is well known that powder coatings have less volatile components and odors than solvent coatings and are very useful in terms of pollution control and environmental regulations. In recent years, with the expanding use of powder coatings, the quality of powder coatings for the inner surface coating of metal cans containing various liquid chemicals is strictly required. It is necessary to have mechanical strength such as above and excellent chemical resistance. On the other hand, conventional powder coatings for this type of application are made of an epoxy resin as a base resin, which is uniformly kneaded with an acid anhydride, a curing agent such as dicyandiamide, an additive such as a pigment and a filler, and then pulverized. Things have been proposed. Of these, the epoxy resin, the main component, is often a bisphenol A glycidyl ether type, but in addition to this, it has flexibility such as cresol novolak glycidyl ether type or phenol novolak type epoxy resin for imparting heat resistance. Epoxy resins such as glycidyl dimer acid and glycidyl ether of polyoxyalkylene glycol have been proposed.
However, the conventional powder coating cannot provide a coating film satisfying both mechanical strength and chemical resistance. In particular, in the conventional powder coating, the particle layer is 2 to 2.
Unless the coating thickness of three or more layers is about 50 μm, a good smooth and uniform coating surface and a coating film having sufficient mechanical strength and chemical resistance for practical use cannot be obtained. However, it has not been satisfied with the demands such as shortening the curing process by reducing the film thickness and reducing the overall cost of powder coating.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a powder coating material which satisfies both excellent mechanical strength and chemical resistance. It is an object of the present invention to provide a powder coating which can have sufficient mechanical strength and excellent chemical resistance even in a thin film.

[0004]

The present invention provides a powder coating comprising at least a binder resin and a curing agent, wherein the binder resin has a methylol index of 15 to 45 and a tertiary butylphenol resin and bisphenol A. And an epoxy resin, and wherein the curing agent is m
-A powder coating characterized by being diphenylenediamine or diaminodiphenylmethane.

Hereinafter, the present invention will be described in detail. The powder coating of the present invention comprises powder particles containing at least a binder resin and a curing agent. The binder resin in the present invention is bisphenol A having excellent adhesion and flexibility between a paratertiary butyl phenol resin having excellent chemical resistance and a metal having a methylol index of 15 to 45 as a raw material. And a type epoxy resin. The methylol index indicates the amount of methylol groups contained in the p-tert-butylphenol resin as an index. The methylol index was obtained by using a 50% acetone solution of paratertiary butylphenol resin, and measuring the infrared absorption spectrum by infrared spectroscopy.
The characteristic absorption of the benzene nucleus at 600 Kaiza and 100
The ratio of the strength of the methylol group to the characteristic absorption of 0 to 1050 kaiza is expressed as a percentage. The methylol index can be adjusted by the mixing ratio of phenols and formaldehydes of the p-tert-butylphenol resin and the condensation / cooling process optionally controlled. If the methylol index of the p-tert-butylphenol resin is less than 15, the powder coating will not be solidified, resulting in poor pulverizability during production and storage stability. On the other hand, if it exceeds 45, the strength of the resin itself of the paratertiary butylphenol resin is low, and thus the coating film strength is inferior.

On the other hand, the bisphenol A type epoxy resin constituting the binder resin in the present invention preferably has an epoxy equivalent of 900 to 2100, a softening point of 90 to 130 ° C., and a glass transition point of 50 to 90 ° C. The reason is that the epoxy equivalent, the softening point, and the glass transition point may be inferior in storage stability as a powder when each is lower than the above range, and when the coating strength is inferior when it is higher than the above range. There is. The content of the para-tert-butyl phenol resin is preferably 50 to 95% by weight based on the total amount of the para-tert-butyl phenol resin and the bisphenol A-type epoxy resin. It is preferably 5 to 50% by weight based on the total amount of the paratertiary butyl phenol resin and the bisphenol A type epoxy resin. If the content of the p-tert-butylphenol resin is less than 50% by weight, the chemical resistance may be poor, and if it exceeds 95% by weight, the strength of the coating film may be poor.
The powder coating of the present invention may contain a resin such as an acrylic resin, a xylene resin, a urea resin, a melamine resin, and a polyester resin in addition to the binder resin. As the curing agent in the present invention, m-diphenylenediamine or diaminodiphenylmethane is applied. By using these curing agents, in addition to imparting the above-mentioned mechanical strength and chemical resistance to the coating film, it is possible to secure safety against toxicity when a liquid for food or the like is incorporated in a metal can. In addition, an effect that the curing speed is higher than that of other curing agents can be expected. The powder coating of the present invention may contain a curing agent other than m-diphenylenediamine or diaminodiphenylmethane. Since the powder coating of the present invention uses the binder resin and the curing agent, sufficient mechanical strength and chemical resistance can be obtained. In particular, this property is effective even for a thin film having a coating thickness of 30 μm or less. Becomes In order to reduce the thickness of the coating film surface, the powder coating material of the present invention preferably has an average particle size of 5 to 20 μm. The average particle diameter of the powder coating means a 50% volume diameter measured by a Coulter Counter TAII. In this case, the powder coating is suspended in water using a surfactant, dispersed for 30 seconds by an ultrasonic disperser, and measured at a concentration of 5 to 9%. A powder coating having a volume 50% diameter of less than 5 μm may be easily aggregated due to an increase in interparticle force due to van der Waals force or the like, and may have poor fluidity. Further, when attempting to produce powder particles having such a small particle size by a general melt-kneading and pulverizing / classifying method, a large energy is required in the pulverizing / classifying step, so that the production cost may be increased. On the other hand, the volume 50% diameter is 20 μm
If it exceeds, a thin and uniform powder-adhered layer cannot be obtained on the surface to be coated, and a smooth and uniform coated surface may not be obtained. In addition, the powder coating of the present invention includes fillers such as barium sulfate, calcium carbonate, aluminum oxide, and calcium silicate, acrylic oligomers, spreading agents such as silicone, titanium oxide, chromium oxide, iron oxide, and carbon black. A coloring agent, an antifoaming agent, and the like may be appropriately added. In the present invention, the above composition is dry-mixed, and after hot-melt kneading,
The composition may be obtained by pulverization and classification, or the composition may be obtained by a polymerization method such as a suspension polymerization method or an emulsion polymerization method. In the present invention, an external additive may be attached to the surface of the powder coating as described above. Examples of the external additive include hydrophobic silica, titanium oxide, alumina, polyvinylidene fluoride, and metal. Soaps, nonionic surfactants and the like can be mentioned, and among these, hydrophobic silica, titanium oxide and alumina having a primary particle diameter of less than 1 μm are preferable because they are favorably adhered to the powder surface. If the primary particle diameter of the external additive is larger than 1 μm, it tends to fall off from the surface of the powder particles, easily causing agglomeration of the powder coating, uneven charging, and roughening of the coating film surface. Become. In order to make the external additive adhere to the surface of the powder coating, there is a method of dry-mixing the two with a high-speed mixer such as a Henschel mixer manufactured by Mitsui Miike and a super mixer manufactured by Kawada Seisakusho. Furthermore, the glass transition point of the powder coating of the present invention is preferably 55 ° C. or higher, since the storage stability of the powder coating is improved. The glass transition point may be measured using a DSC measurement device.

[0007]

The present invention will be described below with reference to examples. In the following, “parts” means “parts by weight”. <Example 1> 60 parts of p-tertiary butyl phenol resin (trade name: TO-EP5, methylol index 23, manufactured by Lignite) 7.5 parts of bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei) Bisphenol A 7.5 parts of epoxy resin (trade name: YD-014 manufactured by Toto Kasei) 0.5 parts of m-diphenylenediamine (trade name: m-diphenylenediamine manufactured by Mitsui Toatsu Chemicals) 25 parts of titanium oxide (Ishihara) Sangyo Co., Ltd. product name: CR-90) Flow-off agent 1 part (BASF Co., Ltd. product name: Acronal 4F) Raw materials having the above mixing ratios are mixed with a super mixer, and heat-melted by self-heating with a Buss uniter. After kneading, the mixture was pulverized by a jet mill, and then classified by a dry air classifier so that the 50% volume became 10 μm to obtain powder particles. Next, 0.5 part of hydrophobic silica (trade name: R-972, manufactured by Aerosil Co.) was added to 100 parts of the powder particles, and the mixture was stirred and mixed with a Henschel mixer to obtain a powder coating of the present invention. <Example 2> 60 parts of p-tert-butylphenol resin (trade name: TO-EP5, manufactured by Lignite, methylol index 23) 7.5 parts of bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei) Bisphenol A 7.5 parts of epoxy resin (trade name: YD-014, manufactured by Toto Kasei) 1 part of diaminodiphenylmethane (trade name: diaminodiphenylmethane, manufactured by Nippon Urethane Co.) 25 parts of titanium oxide (trade name: CR-90 manufactured by Ishihara Sangyo Co., Ltd.) Flowing agent 1 part (product name: Acronal 4F, manufactured by BASF) The raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded by self-heating with a buss-made uniter, pulverized by a jet mill, and thereafter. The particles were classified by a dry air classifier so that the 50% volume diameter became 10 μm to obtain powder particles. Next, 0.5 part of hydrophobic silica (trade name: R-972, manufactured by Aerosil Co.) was added to 100 parts of the powder particles, and the mixture was stirred and mixed with a Henschel mixer to obtain a powder coating of the present invention.

<Example 3> 45 parts of p-tert-butylphenol resin (trade name: TO-EP5, manufactured by Lignite, methylol index 23) 15 parts of bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei) Bisphenol A-type epoxy resin 15 parts (Toto Kasei Co., Ltd. product name: YD-014) Diaminodiphenylmethane 2 parts (Nippon Urethane Co., Ltd. product name: diaminodiphenylmethane) Titanium oxide 2.5 parts (Ishihara Sangyo Co., Ltd. product name: CR-90) 1 part of spreading agent (trade name: Acronal 4F, manufactured by BASF) The raw materials having the above mixing ratios are mixed by a super mixer, hot-melt kneaded by self-heating with a Buss unit, and pulverized by a jet mill. Thereafter, the powder was classified by a dry air classifier so that the volume 50% diameter became 10 μm to obtain powder particles. Next, 0.5 part of hydrophobic silica (trade name: R-972, manufactured by Aerosil Co.) was added to 100 parts of the powder particles, and the mixture was stirred and mixed with a Henschel mixer to obtain a powder coating of the present invention. <Example 4> 80 parts of p-tert-butyl phenol resin (trade name: TO-EP5, methylol index 23, manufactured by Lignite) 10 parts of bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei) Bisphenol A type epoxy Resin 10 parts (Toto Kasei Co., Ltd. product name: YD-014) Diaminodiphenylmethane 1.5 parts (Nippon Urethane Co., Ltd. product name: diaminodiphenylmethane) Flow agent 1 part (BASF product name: Acronal 4F) The raw materials having the above ratios are mixed with a super mixer, hot-melt kneaded by self-heating in a Buser unit, pulverized by a jet mill, and then classified by a dry air classifier so that the 50% volume becomes 10 μm in diameter. Particles were obtained. Next, 0.5 part of hydrophobic silica (trade name: R-972, manufactured by Aerosil Co.) was added to 100 parts of the powder particles, and the mixture was stirred and mixed with a Henschel mixer to obtain a powder coating of the present invention.

Comparative Example 1 A comparative powder coating was obtained in the same manner as in Example 1, except that the bisphenol A type epoxy resin was replaced by 75 parts of para-tert-butylphenol resin. <Comparative Example 2> A comparative powder was prepared in the same manner as in Example 1, except that the bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei Co., Ltd.) was used in an amount of 75 parts, except for the p-tert-butylphenol resin. Paint was obtained. <Comparative Example 3> A comparative example was prepared in the same manner as in Example 1 except that the p-tert-butylphenol resin was replaced with 60 parts of a p-tert-butylphenol resin having a methylol index of 12 (trade name: TO-EP10, manufactured by Lignite). A powder coating was obtained. <Comparative Example 4> A comparative example was prepared in the same manner as in Example 1, except that the paratertiary butyl phenol resin was replaced with 60 parts of a paratertiary butyl phenol resin having a methylol index of 49 (trade name: TO-EP11, manufactured by Lignite). A powder coating was obtained. <Comparative Example 5> A powder coating for comparison was obtained in the same manner as in Example 1, except that the paratertiary butyl phenol resin was replaced with 60 parts of a resol type phenol resin (trade name: TOR-1000, manufactured by Lignite). . Comparative Example 6 A powder coating for comparison was obtained in the same manner as in Example 1, except that the paratertiary butyl phenol resin was replaced with 60 parts of a novolak type phenol resin (trade name: TO-100, manufactured by Lignite). . <Comparative Example 7> In Example 1, a bisphenol A type epoxy resin (trade name: YD-017, manufactured by Toto Kasei Co., Ltd.)
7.5 parts of bisphenol A type epoxy resin (trade name: YD-014 manufactured by Toto Kasei Co., Ltd.) 7.5 parts of novolak type epoxy resin (trade name: YDCN- manufactured by Toto Kasei Co., Ltd.)
701S) A powder coating for comparison was obtained in the same manner except that 15 parts were replaced.

<Evaluation> Each of the powder coatings obtained above was applied to a corona spray gun charged with negative ions, and was subjected to a bright finish of 0.8 mm × 150 mm × 70 mm.
And then baked at 200 ° C. for 20 minutes. Then, the following items are tested,
The results are shown in Tables 1 and 2. (1) Storage stability Leave for 1 week in an environment of a temperature of 40 ° C and a humidity of 60% RH,
The state of blocking between particles was visually confirmed. Those without blocking were evaluated as good, and those with blocking were evaluated as poor. (2) Coating film thickness This is a value measured by a film thickness meter. (3) Leveling Property (Smoothness and Homogeneity) The coating film surface was visually checked. (4) Bending resistance Based on JIS-K-5400 (8, 1). (5) Ericssen JIS-K-5400 (8, 2). In this evaluation, 1 or more is a practically usable range. (6) Impact resistance Based on JIS-K-5400 (8, 3, 2) Dupont method. In this evaluation, 20 mm or more is a practically usable range. (7) Pencil hardness Based on JIS-K-5400 (8, 4, 2). In this evaluation, 3H or more is a practicable range. (8) Adhesive strength to the surface to be coated This was based on the JIS-K-5400 (8, 5, 2) grid method. In this evaluation, 80/100 or more is a practically usable range. (9) Chemical resistance 5% caustic soda, 5% sulfuric acid, diethyl sulfate, animal oil, vegetable oil, silicone emulsion, glycidyl ether, trichlene and formalin
It was immersed for a month, and the state of the coating film thereafter was visually checked.

[0011]

[Table 1]

[Table 2]

As is clear from Tables 1 and 2, it was confirmed that all the powder coatings of Examples 1 to 4 of the present invention had good results in each test. In contrast,
In Comparative Example 1, it was confirmed that storage stability was inferior, and that bending resistance, Erichsen, impact resistance, and adhesive strength were inferior. In Comparative Example 2, it was confirmed that the pencil hardness was inferior, and that the coating film was softened to glycidyl ether, trichlene and formalin, resulting in inferior chemical resistance. In Comparative Example 3, it was confirmed that the storage stability was poor and the coating film was softened to glycidyl ether and the chemical resistance was poor. In Comparative Example 4, it was confirmed that the flex resistance, Erichsen and adhesive strength were inferior. In Comparative Example 5, it was confirmed that the storage stability was poor, spots were formed on the coating film surface, the leveling property was poor, and the pencil hardness was poor. In Comparative Example 6, it was confirmed that the coating film surface was in a matte state, the leveling property was poor, cracking occurred with respect to the bending resistance, and the pencil hardness was inferior. It was also confirmed that the coating film was peeled or blistered with respect to glycidyl ether and formalin, resulting in poor chemical resistance. In Comparative Example 7, it was confirmed that the coating film surface had a matte state and the leveling property was poor, and that Ericksen and the pencil hardness were poor, and that the coating film was peeled or blistered against glycidyl ether and formalin, resulting in poor chemical resistance. .

[0013]

As described above, according to the present invention, a coating film having excellent mechanical strength and chemical resistance while maintaining good coating condition and storage stability, and having a thin coating film thickness. Thus, a powder coating having the above-mentioned effects can be obtained.

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 5/03 C09D 161/00-161/16 C09D 163/00-163/10

Claims (3)

(57) [Claims] 1. A powder coating comprising at least a binder resin and a curing agent, wherein the binder resin contains a paratertiary butyl phenol resin having a methylol index of 15 to 45 and a bisphenol A type epoxy resin. And the curing agent is m-diphenylenediamine or diaminodiphenylmethane. 2. The content of the para-tert-butylphenol resin in the total amount of the para-tert-butylphenol resin and the bisphenol A type epoxy resin is 50 to 9%.
The powder coating according to claim 1, wherein the content is 5% by weight. 3. The powder coating according to claim 1, wherein the average particle size of the powder coating is 5 to 20 μm.