JPH093364A - Powder coating manufacturing method - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for easily and economically producing a powder coating having a very small particle size from a melt-kneaded resin composition for powder coating. [Composition] A method for producing a powder coating composition, which comprises melt-kneading a powder coating resin composition, cooling and pulverizing the resin composition, wherein a foaming agent is added to the powder coating resin composition in an amount of 0.1 to 0.1%. A method for producing a powder coating material, which comprises adding 0.5 parts by weight to prepare a porous pellet and then pulverizing the porous pellet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder coating, and more particularly to a method for easily producing a powder coating having a small particle size from a melt-kneaded resin composition for powder coating. .

[0002]

2. Description of the Related Art A method for producing a powder coating material includes a wet method in which powder coating particles are precipitated by adding another solvent having a low solubility to the solvated resin composition for powder coating material. After heat-melting and kneading the solid powder coating resin composition,
There is a dry method of solidifying by cooling and crushing. In the wet method, the particle size and grain shape are easily adjusted but the manufacturing cost is high. Therefore, the dry method is usually used because the manufacturing cost is low. In this dry method, in the pulverizing step of the melt-kneaded resin composition, a method of finely pulverizing by using a collision force and a shearing force of a pin mill or the like, or a method of finely pulverizing by using a collision force like a jet mill is used. To use. However, in the former method, although the energy required for pulverization is relatively small, heat is generated, so blocking occurs due to thermal denaturation of the resin powder, and it becomes difficult to obtain a powder having a desired particle size, and heat is not applied to the paint. A history may occur and the characteristics may change, and further, the problem that the fine metal powder is mixed into the powder coating material due to wear of the crushing equipment occurs. The latter method using a jet mill does not cause metal contamination, but it takes time to reduce the particle size of the powder coating,
Since a large amount of energy is required, there is a problem that the cost of the crushing process increases. In addition, JP-A-4-1372
No. 8 discloses a method for producing a powder coating composition by melt-kneading a resin composition and freeze-grinding the obtained solid, but in this method, the solid is treated with liquid nitrogen or the like. Since it is cooled, there are drawbacks such as high cost and complicated process. In recent years, powder coating materials having a small particle size have been required in the field of thin film beauty, and therefore an efficient method for producing a powder coating material without the above-mentioned drawbacks has been desired.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the conventional powder coating production methods, and easily and economically obtains a very small particle size from a melt-kneaded resin composition for powder coating. An object is to provide a method for producing a powder coating material.

[0004]

Means for Solving the Problems As a result of research to solve the above problems, the present inventors have found that a resin composition for powder coating is melt-kneaded, cooled, and then pulverized to obtain a powder. When a foaming agent is added to this resin composition to produce a porous solid when producing a paint, a powder paint with a small particle size can be produced easily and economically without being adversely affected by heat in the pulverization process. The present invention has been completed based on the finding that it is possible. Therefore, the present invention is a method for producing a powder coating composition in which a resin composition for powder coating composition is melt-kneaded, cooled, and then pulverized, and a foaming agent is added to the resin composition for powder coating composition. A method for producing a powder coating material is provided. The resin composition for powder coating of the present invention includes a resin for producing a coating, a curing agent,
It refers to a composition containing a pigment and various additives added as necessary, and used for producing a powder coating material. INDUSTRIAL APPLICABILITY The present invention can be widely applied to conventionally used powder coating compositions. First, the resin composition for powder coating will be described.

As the resin of the present invention, any resin conventionally used in the production of powder coating materials can be used without particular limitation. Specific examples thereof include polyester-
There are thermosetting resins such as urethane curing resin, polyester-epoxy curing resin, epoxy resin, acrylic resin, and acrylic-polyester resin, which can be used alone or in combination of two or more. .
If necessary, a modified resin such as a novolac resin, a phenoxy resin, a butyral resin, a ketone resin or a polyester resin, an epoxidized oil, or a plasticizer such as dioctyl phthalate may be appropriately added. Specific examples of the pigment used in the present invention include titanium dioxide, red iron oxide, iron oxide,
Zinc powder, carbon black, phthalocyanine blue,
There are coloring pigments such as phthalocyanine green, quinacridone pigments, azo pigments, isoindolinone pigments, and extender pigments such as silica, talc, precipitated barium sulfate, calcium carbonate, and glass fibers.

[0006] As the additive, an anti-sagging agent, a surface conditioner, a crosslinking promoting catalyst, an ultraviolet absorber, a light stabilizer, an antioxidant and the like can be used if necessary. The foaming agent used in the present invention is an organic foaming agent usually used in paints,
For example, azodicarbozamide (ADCA) system, azobisisobutyronitrile (AIBN) system, dinitrosopentamethylenetetramine (DPT) system, 4,4′-oxybisbenzenesulfonylhydrazide (OBSH) system, paratoluenesulfonyl There is a hydrazide (TSH) system,
Further, a gas such as nitrogen, helium, neon, argon, butane can be used. Among these organic foaming agents, those having a decomposition and foaming temperature of 170 ° C. or less are preferable, and particularly, those having a low decomposition and foaming temperature, such as AIBN type and TSH type are preferable. A foaming agent having a decomposition temperature of 170 ° C. or less is preferable because such a foaming agent completely completes the foaming reaction in the melt-kneading process and efficiently transforms the pellets of the powder coating composition into a porous solid. Because it does. If a foaming agent having a high decomposition temperature is used, this foaming agent tends to remain, and the residual foaming agent in the powder coating material is foamed in the baking step of the coating film, which is not preferable.

As the decomposition aid of the organic foaming agent,
DPT-based foaming agents include organic acids such as salicylic acid and phthalic acid, urea and urea compounds such as ADCA, ADCA-based foaming agents include zinc white, inorganic salts such as tribasic lead sulfate, zinc stearate, lead stearate, etc. It is also possible to use a mixture of the soap and the urea compound. Of these decomposition aids, those having coloring properties affect the color of the coating film, and are therefore not preferred for light-colored powder coatings, but there is no problem for dark-colored powder coatings. The blending amount of the foaming agent is 0.1 to 1.0 part by weight, preferably 0.1 to 0.3 part by weight, based on 100 parts by weight of the resin used as the binder in the coating composition. The reason for limiting the blending amount in this way is that if the blending amount is less than the above range, there is little foaming of the paint pellets, and improvement in pulverization efficiency cannot be expected. Remains, and a foamed coating film is formed during coating film formation, which is not preferable.

Incidentally, for example, JP-A 1-245070, JP-A-2-43273, JP-A-3-93865, and JP-A-4-4507.
117467, JP-A-4-161277, and JP-A-4-35
As described in Japanese Patent No. 6566 and the like, it has been known to mix a foaming agent into a powder coating material to obtain an expandable powder coating material and a foamed coating film. In the manufacturing process of these powder coating materials, it is necessary to prevent the foaming in the melt-kneading step and to manufacture the powder coating material that foams during the baking treatment of the coating film. It does not facilitate the crushing process of powder coatings by preparing a solid pellet. However, the expandable powder coating material can also be manufactured by the manufacturing method of the present invention. That is, in the present invention, if a fine pelletizing treatment is carried out by producing porous pellets, a desired fine particle powder coating material can be obtained easily and economically. Therefore, after the powder coating material composition is foamed by melting, By further adding a foaming agent, adding an excess amount of a foaming agent, or adding a combination of a low temperature foaming agent and a high temperature foaming agent, and leaving the high temperature foaming agent unfoamed in the melt-kneading step, It is possible to obtain an expandable powder coating material.

In this case, the blending amount of the foaming agent is 0.1 to 5.0 parts, preferably 0.2 to 3.0 parts, relative to 100 parts by weight of the resin. The reason for limiting in this way is that if the content is less than the above-mentioned amount, foaming occurs during kneading to eliminate the foaming agent, and foaming does not occur during formation of the foamed coating film. Further, when the compounding amount is larger than this, the gas amount at the time of forming the foamed layer is too large and the cell structure of the foamed coating film becomes large, so that a good foamed state cannot be obtained. When a foaming agent is combined, it is preferable to combine one having a decomposition temperature of 170 ° C. or less and one having a decomposition temperature of 170 ° C. or more. 0.1 to 0.3 parts by weight, 0.2 to 4.0 parts by weight at 170 ° C or higher, preferably
It is preferable to add 0.4 to 2.0 parts by weight. The powder coating composition of the present invention is produced by mixing the powder coating composition with various pigments and additives as necessary, and at a temperature at which the resin used as the binder and the curing agent do not cause a crosslinking reaction. It is obtained by melt-kneading using an extruder, a heat roll, a kneader, etc., cooling, pulverizing and then classifying.

The obtained pellets are pulverized using a pin mill, bantam mill, jet mill, centrifugal pulverizer, etc.
Adjust to the desired particle size using a sieve and an air handling machine. The melt-kneading of the powder coating composition is usually carried out at a temperature in the range where the foaming agent does not remain. Therefore, although the melting temperature varies depending on the properties of the blowing agent used, it is usually 90 ° C to 160 ° C.
C., preferably 120 to 130.degree. C., for 10 to 30 seconds. The powder coating material of the present invention is applied to an object to be coated by a conventional method such as an electrostatic spray method or a fluidized-bed method, and is baked in a hot air oven, an infrared oven, an induction heating oven or the like to form a cured coating film. You can

[0011]

According to the method for producing a powder coating material of the present invention, a powder coating material having a small particle size can be easily produced from a melt-kneaded resin composition for powder coating material. That is, a powder coating having a smaller diameter can be obtained with the same grinding energy. Further, it is possible to reduce the heat history of the coating due to wear of equipment, metal contamination, and generation of heat when a powder coating having the same particle size is obtained.

[0012]

The present invention will be described in more detail with reference to the following examples. In the examples, "parts" and "%" are based on weight. (Production Example 1) 50 parts of thermosetting polyester resin (Note 1) having a hydroxyl value of 46 mgKOH / g, 10 parts of polyisocyanate resin of isophorone diisocyanate (IPDI) ε-caprolactam block (Note 2), and acrylic oligomer as an additive (Note 3) 1 part, as a foaming agent, 4,4'-oxybisbenzenesulfonyl hydrazide type foaming agent (Note 4) 0.
2 parts and 35 parts of titanium oxide were kneaded to prepare pellet A for powder coating. (Production Example 2) 80 parts of a thermosetting acrylic resin (Note 5) having an epoxy equivalent of 460 g / eq and 0.5 parts of dodecane diacid (DDA).
Part, 0.5 part of an acrylic oligomer (Note 6) as an additive,
Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate-based light stabilizer (Note 7) 3 parts, azobisisobutyronitrile-based foaming agent (Note 8) 0.3 part as a foaming agent Was kneaded to prepare a pellet B for powder coating.

(Production Example 3) 60 parts of an epoxy resin (Note 9) having an epoxy equivalent of 915 g / eq, 5 parts of adipic acid dihydrazide (ADH) as a curing agent, 1 part of an acrylic oligomer (Note 3) as an additive, and a catalyst. As a foaming agent, a compound obtained by adding a urea compound to 2-phenylimidazole (0.3 parts), precipitating barium sulfate (30 parts), titanium oxide (4 parts), carbon black (0.1 part), and a dinitrosopentamethylenetetramine-based foaming agent (Note 10). ) 0.3 parts were kneaded to prepare powder coating pellets C. (Production Example 4) 50 parts of thermosetting polyester resin (Note 1) having a hydroxyl value of 46 mgKOH / g, 10 parts of polyisocyanate resin of isophorone diisocyanate (IPDI) ε-caprolactam block (Note 2), and acrylic oligomer as an additive (Note 3) Powder coating pellets D were prepared by kneading 1 part, 1.5 parts of 4,4'-oxybisbenzenesulfonylhydrazide type foaming agent as a foaming agent and 35 parts of titanium oxide.

(Production Example 5) 50 parts of a thermosetting polyester resin (note 1) having a hydroxyl value of 46 mgKOH / g, 10 parts of polyisocyanate resin (note 2) of isophorone diisocyanate (IPDI) ε-caprolactam block, as an additive Acrylic oligomer (Note 3) 1 part, titanium oxide 35
The parts were kneaded to prepare a powder coating pellet E. (Production Example 6) 50 parts of a thermosetting polyester resin (Note 1) having a hydroxyl value of 46 mgKOH / g, 10 parts of a polyisocyanate resin of isophorone diisocyanate (IPDI) ε-caprolactam block (Note 2), and an acrylic oligomer ( Note 3) Powder coating pellets F were prepared by kneading 1 part, 0.3 part of an azodicarbazoamide type foaming agent (note 11) as a foaming agent, and 35 parts of titanium oxide.

(Production Example 7) 50 parts of a thermosetting polyester resin having a hydroxyl value of 46 mgKOH / g, 10 parts of a polyisocyanate resin of isophorone diisocyanate (IPDI) ε-caprolactam block, and 1 part of an acrylic oligomer (Note 3) as an additive. As a foaming agent, 0.2 part of 4,4'-oxybisbenzenesulfonylhydrazide type foaming agent and 35 parts of titanium oxide were kneaded to prepare powder coating pellets G. (Production Example 8) 80 parts of a thermosetting acrylic resin having an epoxy equivalent of 460 g / eq, 0.5 part of dodecane diacid (DDA), 0.5 part of an acrylic oligomer (Note 5) as an additive, bis (1,
Powder coating pellets H were prepared by kneading 3 parts of 2,2,6,6-pentamethyl-4-piperidyl) sebacate-based light stabilizer. (Production Example 9) To 60 parts of an epoxy resin having an epoxy equivalent of 915 g / eq, adipic acid dihydrazide (AD
H) (Note) 5 parts, acrylic oligomer (Note 3) 1 part as an additive, 2-phenylimidazole 0.3 as a catalyst
Parts, 30 parts of precipitated barium sulfate, 4 parts of titanium oxide, and 0.1 part of carbon black were kneaded to prepare powder paint pellets I.

(Note 1) Yupica Coat GV110 (trade name of Japan Yupica) (Note 2) B-1530 (trade name of Huls) (Note 3) Modaflow Powder III (trade name of Monsanto) (Note 4) Neocerbon # 5000 (trade name, manufactured by Eiwa Chemical Industry Co., Ltd.) [decomposition temperature: 159 ° C] (Note 5) ALMATEX PD7690 (trade name, manufactured by Mitsui Toatsu Chemicals, Inc.) (Note 6) ACRONAL 4F (trade name, manufactured by BASF) (Note) 7) SANOL LS-292 (trade name manufactured by Sankyo Co., Ltd.) (Note 8) VINYALL AZ-S (trade name manufactured by Eiwa Chemical Industry Co., Ltd.) [decomposition temperature 100 ° C.] (Note 9) Epicoat 1004 (produced by Yuka Shell Epoxy Co., Ltd.) (Product name) (Note 10) Cellular GX (Methylenetetramine-based foaming agent, product name manufactured by Eiwa Chemical Industry Co., Ltd.) [Decomposition temperature 120 ° C] (Note 11) Vinyl Hall AC # 3 (Eiwa Chemical Industry Co., Ltd.) Company brand name) [decomposition temperature 208 ° C]

(Examples 1 to 3 and Comparative Examples 1 to 6) The powder paint pellets obtained in Production Examples 1 to 9 were crushed using a pin mill, and then crushed by a crusher to a 2 mm mesh all-through. , Rotation speed 20000 rp in a room kept at 20 ° C. using a pulverizer (Nippon Seiki Centrifugal Crusher ZM-1 type)
m, pulverized at a supply rate of 100 g / min to obtain pellet A,
For C, D, E, F, G and I, classification is performed with 150 mesh to obtain powder coatings A ', C', D ', E', F ',
G'and I'were prepared and various tests were conducted. The powder coating pellets B and H were pulverized to a 270 mesh passing ratio of 70% to prepare powder coatings B'and H '. The obtained powder coating material was evaluated by the following test methods. Also, electrostatic powder coating gun is used for powder coating A ', C', E ', F', G ', I'.
And was dried in a hot air drying oven at 180 ° C. for 20 minutes to obtain a coating film having an average film thickness of 80 μm. Also, powder coatings B'and H'are coated with an electrostatic powder coating gun at 150 ° C x 20.
It was dried in a hot air drying oven for a minute to obtain a coating film having an average film thickness of 25 μm.
The results are shown in Table 1.

(Note 12): Measured with a laser diffraction type particle size distribution measuring device 50% average particle diameter (Note 13): visually determined ◯: good ×: with foaming marks (Note 14): measured by cure plate method ( Test paints C ', I') (Note 15): Clear powder paint B ', H'on a white coated plate
Is applied to have an average film thickness of 25 μ, and L values are compared with a color difference meter. (L value of white coated plate = 93.8)

[0019]

[Table 1] Table 1 ─────────────────────────────────── Actual Example Ratio Comparative Example 1 2 3 1 2 3 4 5 6 Coating name A ′ B ′ C ′ D ′ E ′ F ′ G ′ H ′ I ′ Thermosetting polyester resin Note 1) 50 50 50 50 50 Thermosetting acrylic resin Note 5) 80 80 Epoxy resin Note 9) 60 60 Polyisocyanate resin Note 2) 10 10 10 10 10 Dodecane diacid 16 16 Adipic acid dihydrazide 5 5 Acrylic oligomer Note 3) 1 1 1 1 1 1 1 1 Acrylic oligomer Note 6) 0.5 0.5 2-phenyl Imidazole 0.3 0.3 Light stabilizer Note 7) 3 3 Titanium oxide 35 4 35 35 35 35 4 Precipitable barium sulfate 30 30 Carbon black 0.1 0.1 Foaming agent Note 4) Decomposition temperature 159 ° C 0.2 7.0 0.05 Foaming agent Note 8) Decomposition temperature 100 ℃ 0.3 Foaming agent Note 10) Decomposition temperature 120 ℃ 0.3 Foaming agent Note 11) Decomposition temperature 208 ℃ 0.3

[0020]

[Table 2]Table 2 ──────────────────────────────────── Example comparison 1 2 3 1 2 3 4 5 6 Coating name A ′ B ′ C ′ D ′ E ′ F ′ G ′ H ′ I ′ Particle size distribution (μ) Note 12) 37 17 34 36 45 45 45 18 41 Appearance of coating film Note 13) 〇 〇 〇 × 〇 × 〇 〇 〇 Gel time (sec) Note 14) − − 120 − − − − − 100Metal contamination Note 15) −92.5 − − − − − 91.4 −

As is clear from the results shown in Table 1, Comparative Example 1 containing 5.0 parts by weight or more of the foaming agent had a poor coating film appearance. Comparative Example 2 containing no foaming agent, a foaming agent of 0.
It can be seen that in Comparative Example 4 containing less than 1 part by weight, the particle size distribution of the obtained powder coating material is larger than that in Example 1, and the effect of improving pulverizability is not obtained. Further, Comparative Example 3 containing a foaming agent having a decomposition temperature of 160 ° C. or higher had a poor coating film appearance. In Comparative Example 5, the L value of the coating film was smaller than that in Example 2 due to metal contamination during pulverization, and it can be seen that the FLIR coating film was clouded by the metal particles. In Comparative Example 6, thermal history is generated due to pulverization, and shortening of gel time is observed as compared with Example 3.

Claims (2)

[Claims] 1. A resin composition for powder coating is melt-kneaded,
A method for producing a powder coating material which comprises pulverizing after cooling, wherein a foaming agent of 0.
After adding 1 to 5.0 parts by weight to prepare a porous pellet,
A method for producing a powder coating material, which comprises pulverizing. 2. The production method according to claim 1, wherein the decomposition temperature of the foaming agent is 170 ° C. or lower.