JP2001234112A - Powder coating material for fluidized bed dip coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a powder coating material for fluidized bed dip coating capable of providing a coating film with a reduced number of pinholes in spite of being a thin film even on a substrate having a complicated shape. SOLUTION: This powder coating material for fluidized bed dip coating comprises a polyolefin based resin powder, an inorganic powder, and a metallic soap. In general, this polyolefin based resin powder has a medium particle diameter of 90-160 μm, a bulk density of 0.35-0.50 g/ml, and an angle of repose of 20-35 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a powder coating,
The present invention relates to a powder coating for fluid immersion coating.

[0002]

2. Description of the Related Art Powder coatings containing a polyolefin resin such as a polyethylene resin as a resin component are widely used as a coating material for base materials such as fences, kitchenware, automobile parts, gardening supplies and steel pipes. ing. This type of polyolefin resin powder coating is usually
It is applied to the above-mentioned various substrates by a fluid immersion coating method. Usually, in order to obtain a coating film without pinholes, the thickness of the coating is set to a relatively large range of about 500 to 700 μm. Is given to the material.

[0003] With the social demands for resource saving, energy saving, cost reduction, and the like, there has been a demand for a coating capable of realizing a coating film having no pinholes even though it is a thin film. Here, when the shape of the base material is a simple plate shape or the like,
When the substrate is immersed in a fluidized immersion tank, the powder coating easily flows uniformly over the entire surface of the substrate, so that even if the film thickness is set small, a coating film with few pinholes can be easily achieved. On the other hand, when the base material has a complicated shape such as a three-dimensional shape or includes a welded portion, for example, a base material such as a fence in which a wire is combined in a mesh or grid shape by welding, the welding is performed. Since the fluidity of the powder coating material tends to be non-uniform in parts and the like, setting a small film thickness of the coating film easily causes pinholes in the coating film applied to the welded portion.

[0004] An object of the present invention is to realize a powder coating for fluid immersion coating capable of applying a coating film having a small number of pinholes even though the substrate has a complicated shape.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, when an inorganic powder and a metal soap powder are added to a polyolefin resin powder, a base having a complicated shape is obtained. It has been found that a coating film having a small number of pinholes can be applied to the material while being a thin film, and the present invention has been completed.

That is, the powder coating for fluidized immersion coating of the present invention contains a polyolefin resin powder, an inorganic powder, and a metal soap powder. Here, the polyolefin resin powder usually has a median particle diameter of 90 to 160 μm, a bulk specific gravity of 0.35 to 0.50 g / ml, and an angle of repose of 20 to
35 degrees.

[0007] The inorganic powder usually has an average particle size of 0.1.
01-20 μm and polyolefin resin powder 1
0.01 to 0.50 part by weight is added to 00 parts by weight. The inorganic powder is, for example, a metal oxide powder.

Further, the metal soap powder usually has an average particle size of 5 to 30 μm and a polyolefin resin powder 1
0.05 to 2.0 parts by weight is added to 00 parts by weight. The metal soap powder is, for example, calcium stearate powder.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The powder coating for fluidized immersion coating of the present invention contains three kinds of powders: polyolefin resin powder, inorganic powder and metal soap powder.

[0010] The polyolefin resin powder used in the present invention is not particularly limited, and is not particularly limited, and may be various known polyolefin resin powders, for example, polyethylene resin, polypropylene resin, ethylene-acrylic acid copolymer resin. And powders of ethylene-vinyl acetate copolymer resin. In addition, two or more kinds of polyolefin-based resin powders may be appropriately mixed and used.

However, the preferred polyolefin resin powder has a median particle diameter of 90 μm or more and 160 μm or less (more preferably 100 μm or more and 150 μm or less);
Bulk specific gravity of 0.35 g / ml or more and 0.50 g / ml or less (more preferably 0.38 g / ml or more and 0.45 g / m
l) and the angle of repose is set in the range of 20 to 35 degrees (more preferably 23 to 33 degrees). When the median particle diameter and the like are out of these ranges, in the powder coating of the present invention, aggregation between the powder particles may be remarkable. As a result, when the powder coating of the present invention is applied to a substrate by fluid immersion coating, the fluidity of the powder deteriorates, and it becomes difficult to form a thin film, particularly, a coating film having a thickness of 400 μm or less. There is a possibility that even if such a coating film can be formed, pinholes may easily occur in the coating film. In addition, there is a possibility that it becomes difficult to form a coating film having good surface smoothness.

Such a polyolefin resin powder is
Pellets made of a polyolefin-based resin are produced, and the pellets are pulverized by a known pulverization method such as a mechanical pulverization method or a freeze pulverization method into a powder, and then appropriately classified using a sieve.

In the present invention, the median particle size is defined as
50 g of polyolefin resin powder is weighed,
After sieving using an S standard sieve, it is weighed for each sieve, and based on the result, the particle diameter at which the integrated weight becomes 50% is calculated by the following formula.

[0014]

(Equation 1)

In the formula, A is a value obtained by sequentially integrating the weights from the coarser particle size distribution, and the integrated value at a point where the integrated weight is less than 50% and closest to 50%. B is the sieve opening (μm) when the integrated value of A was obtained. C is the integrated value at the point where the weight is sequentially integrated from the coarser particle size distribution and the integrated weight is 50% or more and is closest to 50%. D is the sieve opening (μm) when the integrated value of C was obtained.

[0016] The bulk specific gravity is a glass rod of polyolefin resin powder, which is gently dropped from a container with 60 g of polyolefin resin powder into a cylindrical container having an inner volume of 100 ml and a diameter of 40 mm using a funnel. After dropping, the mass of the container containing the polyolefin-based resin powder is measured, and a value obtained by subtracting the mass of the container from the mass is divided by the internal volume of the container.

Further, the angle of repose means that 60 g of polyolefin-based resin powder is placed on a circular cylinder having a diameter of 10 cm horizontally arranged.
Refers to the angle formed by the generatrix of the conical sediment and the horizontal plane of the truncated cone when gently dropped by a funnel and deposited in a conical shape.

On the other hand, the inorganic powder used in the present invention is not particularly limited. For example, powders of oxides of metals such as silicon, aluminum, magnesium, zinc, calcium and titanium, more specifically, dioxide Silicon powder, aluminum oxide powder, magnesium oxide powder,
Examples include zinc oxide powder, calcium oxide powder, and titanium oxide powder. In addition, two or more kinds of inorganic powders may be appropriately used in combination.

The average particle size of the inorganic powder is not particularly limited, but is usually preferably 0.01 to 20 μm.
0.015 to 10 μm is more preferable. The average particle size is 0.
If it is less than 01 μm, the inorganic powder is liable to undergo secondary agglomeration and the like, and it may be difficult to uniformly mix the inorganic powder with the polyolefin resin powder and the like. As a result, the powder fluidity of the powder coating composition of the present invention is impaired,
There is a possibility that it is difficult to form a coating film having a thickness of 0 μm or less. Also, even if such a thin film coating could be formed,
Pinholes may occur in the coating. Conversely, if the average particle size exceeds 20 μm, uniform mixing with a polyolefin resin powder or the like is possible, but the powder fluidity of the powder coating of the present invention deteriorates, and similarly, May be difficult to form, or pinholes may occur in the coating film.

In the powder coating for fluid immersion coating of the present invention, when the inorganic powder having the above-mentioned average particle size is used, the content of the inorganic powder is set to 10
Usually, it is preferably set to 0.01 to 0.50 parts by weight, more preferably 0.05 to 0.30 parts by weight, based on 0 parts by weight. When the content of the inorganic powder is less than 0.01 part by weight, the coating film of the thin film, particularly, the film thickness is 400 μm
The formation of the following coating films may be difficult. vice versa,
If it exceeds 0.50 parts by weight, the meltability of the polyolefin-based resin powder may be reduced, and it may be difficult to form a coating film having good surface smoothness.

The metal soap powder used in the present invention is a powder of a metal salt of a saturated fatty acid. For example, various metal salts such as stearic acid, lauric acid, palmitic acid and behenic acid, Salts, zinc salts, magnesium salts and the like can be mentioned. Of these, calcium stearate powder is particularly preferred in that it has excellent thermal stability during coating. In addition, two or more kinds of metal soap powders may be appropriately used in combination.

The average particle size of the metal soap powder is not particularly limited, but is usually preferably 5 to 30 μm, and preferably 1 to 30 μm.
0-20 μm is more preferred. If the average particle size is less than 5 μm, the metal soap powder is likely to be blocked, and the fluidity of the powder coating may be impaired. Conversely, if the average particle size exceeds 30 μm, the surface smoothness of a coating film formed using the powder coating of the present invention may be impaired.

In the powder coating composition for fluid immersion coating of the present invention, when the metal soap powder having the above-mentioned average particle size is used, its content is usually based on 100 parts by weight of the polyolefin resin powder. , 0.05 to 2.0 parts by weight, and more preferably 0.1 to 1.0 part by weight. Metal soap powder content is 0.
When the amount is less than 05 parts by weight, when the powder coating of the present invention is applied to a substrate, the slip properties of the powder coating on the substrate become insufficient, so that the coating is unnecessarily necessary for the substrate. Powder coatings are easily adhered, and coating films having a small film thickness, particularly, a film thickness of 4
There is a possibility that it may be difficult to form a thin film coating having a thickness of 00 μm or less. On the other hand, if it exceeds 2.0 parts by weight, the meltability of the polyolefin-based resin powder may be reduced, and it may be difficult to form a coating film having good surface smoothness.

The powder coating for fluidized immersion coating of the present invention may contain, in addition to the above essential components, other powdery components such as a lubricant, an antioxidant, a UV absorber, a pigment, A powder such as an antistatic agent may be added and mixed as needed.

The powder coating for fluid immersion coating of the present invention is usually prepared by preparing the above-mentioned polyolefin-based resin powder, inorganic powder, metal soap powder and other powdery components as required, respectively. By mixing them sufficiently uniformly. Incidentally, as a mixing method, a dry mixing method using a Henschel mixer or the like can be adopted.

Since the powder coating for fluid immersion coating of the present invention is obtained by adding an inorganic powder and a metal soap powder to a polyolefin resin powder, the powder coating for fluid immersion coating has a higher fluidity than the conventional powder coating for fluid immersion coating. Is significantly improved. For this reason, the powder coating of the present invention has a thinner coating film on the substrate by the fluid immersion coating method than the conventional powder coating.
It is possible to form a dense coating film having a thickness of not more than 00 μm and having few pinholes. Further, the powder coating of the present invention has a medium particle diameter of polyolefin resin powder,
When the bulk specific gravity and the angle of repose are set in the above ranges, a coating film having better surface smoothness can be formed.

The powder coating composition for fluidized immersion coating of the present invention is preferably made of a metal, for example, iron, iron alloy, zinc or a plated product thereof, particularly a complex shape having a three-dimensional shape or a welded portion. This is particularly effective when a thin film coating is applied to the substrate.

[0028]

EXAMPLES Examples 1 and 2 Low density polyethylene resin (trade name “G801” of Sumitomo Chemical Co., Ltd .: density = 0.918 g / cm ³ , MFR =
(20 g / 10 min) was pulverized into a powder at room temperature using a high-speed rotary pulverizer and classified by a classifier. Thus, a resin powder having a median particle diameter of 110 μm, a bulk specific gravity of 0.45 g / ml, and a repose angle of 25 ° was obtained.

Next, silica powder (trade name “Aerosil R972” of Nippon Aerosil Co., Ltd .: average particle diameter = 0.0) was used as an inorganic powder with respect to 100 parts by weight of the obtained resin powder.
16 μm) and calcium stearate powder (produced by Kawaken Fine Chemical Co., Ltd .: average particle size = 16 μm) as metal soap powders were added at the ratios shown in Table 1, and mixed for 1 minute using a Henschel mixer for fluid immersion coating. A powder coating for use was prepared.

Example 3 Aluminum oxide powder (trade name "Aluminum oxide C" of Nippon Aerosil Co., Ltd.) was used as an inorganic powder with respect to 100 parts by weight of the resin powder obtained in the process of Example 1.
(Average particle size = 0.020 μm) and calcium stearate powder (produced by Kawaken Fine Chemical Co., Ltd .: average particle size = 16 μm) as a metal soap powder were added at the ratios shown in Table 1, respectively, and the mixture was added using a Henschel mixer for 1 minute By mixing, a powder coating for fluid immersion coating was prepared.

Example 4 Low-density polyethylene resin (trade name “G801” of Sumitomo Chemical Co., Ltd .: density = 0.918 g / cm ³ , MFR =
(20 g / 10 min) was pulverized into a powder at room temperature using a high-speed rotary pulverizer and classified by a classifier. Thereby, a resin powder having a median particle diameter of 140 μm, a bulk specific gravity of 0.40 g / ml, and a repose angle of 33 ° was obtained.

For 100 parts by weight of the obtained resin powder, silica powder (Aerosil R972, trade name of Nippon Aerosil Co., Ltd .: average particle size = 0.016 μm) was used as an inorganic powder.
m) and calcium stearate powder as metal soap powder (manufactured by Kawaken Fine Chemical Co., Ltd .: average particle size = 16)
μm) at the ratios shown in Table 1 and mixed for 1 minute using a Henschel mixer to prepare a powder coating for fluidized immersion coating.

Example 5 Ethylene-acrylic acid copolymer resin (trade name "Novatec A220S", manufactured by Mitsubishi Chemical Corporation: density = 0.935)
g / cm ³ , MFR = 17 g / 10 minutes) was pulverized at room temperature using a high-speed rotary pulverizer and classified by a classifier. Thereby, a resin powder having a median particle diameter of 120 μm, a bulk specific gravity of 0.42 g / ml, and a repose angle of 31 ° was obtained.

With respect to 100 parts by weight of the obtained resin powder, silica powder (trade name “Aerosil R972” of Nippon Aerosil Co., Ltd .: average particle size = 0.016 μm) was used as an inorganic powder.
m) and calcium stearate powder as metal soap powder (manufactured by Kawaken Fine Chemical Co., Ltd .: average particle size = 16)
μm) at the ratios shown in Table 1 and mixed for 1 minute using a Henschel mixer to prepare a powder coating for fluidized immersion coating.

EXAMPLE 6 Polypropylene resin (trade name "Noblen Z131" of Sumitomo Chemical Co., Ltd.), which is a random copolymer resin of 95% by weight of propylene and 5% by weight of ethylene, was powdered using liquid nitrogen. The mixture was freeze-pulverized and classified by a classifier. Thereby, a resin powder having a median particle diameter of 130 μm, a bulk specific gravity of 0.45 g / ml, and a repose angle of 29 ° was obtained.

With respect to 100 parts by weight of the obtained resin powder, silica powder (trade name “Aerosil R972” of Nippon Aerosil Co., Ltd .: average particle size = 0.016 μm) was used as an inorganic powder.
m) and calcium stearate powder as metal soap powder (manufactured by Kawaken Fine Chemical Co., Ltd .: average particle size = 16)
μm) at the ratios shown in Table 1 and mixed for 1 minute using a Henschel mixer to prepare a powder coating for fluidized immersion coating.

Comparative Examples 1-4 Low density polyethylene resin (trade name "G801" of Sumitomo Chemical Co., Ltd .: density = 0.918 g / cm ³ , MFR =
(20 g / 10 min) was pulverized into a powder at room temperature using a high-speed rotary pulverizer and classified by a classifier. As a result, a resin powder (powder coating for fluid immersion coating) in which the median particle diameter, bulk specific gravity and angle of repose were set as shown in Table 1 was obtained.

The powder coating for fluidized immersion coating obtained in each of Examples and Comparative Examples was fluidized immersion coated on the evaluation substrate. The base material used here was, as shown in FIG. 1, three types of wire rods A having different diameters.
(Diameter = 3 mm), B (diameter = 4 mm), and C (diameter = 5 mm) are combined in a grid pattern and the intersections are spot-welded. In addition, in the fluid immersion coating, the base material is 38
After the pre-heating treatment at 0 ° C. for 6 minutes, the immersion time was set at 6 seconds, and then the substrate was subjected to a post-heating treatment at 200 ° C. for 2 minutes. With respect to the coating film applied to the base material, the presence or absence of pinholes and the film thickness at a spot weld at the intersection of the wires were examined. The occurrence of pinholes was visually observed, and the film thickness was measured with calipers. Table 1 shows the results.

[0039]

[Table 1]

[0040]

The powder coating for fluid immersion coating of the present invention is obtained by mixing an inorganic powder and a metal soap powder with respect to a polyolefin resin powder, so that it can be applied to a substrate having a complicated shape. It is possible to provide a coating film having few pinholes while being a thin film.

[Brief description of the drawings]

FIG. 1 is a view showing a substrate used for evaluation of powder coatings for fluidized immersion coating prepared in Examples and Comparative Examples.

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[Procedure amendment]

[Submission date] October 26, 2000 (2000.10.
26)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

(Equation 1)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

In the formula, A is the integrated value (g) at the point where the integrated weight is less than 50% and is closest to 50% when the weight is sequentially integrated from the coarser particle size distribution. B is the sieve opening (μm) when the integrated value of A was obtained. C is a cumulative value (g) at a point where the cumulative weight is 50% or more and is closest to 50% by sequentially integrating the weights from the coarser particle size distribution.
D is the sieve opening (μm) when the integrated value of C was obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Goto 1384-1, Uetakano, Yachiyo-shi, Chiba Sumitomo Seika Co., Ltd. Functional Plastics Research Laboratories (72) Inventor Takashi Masuda 1384-1, 1384 Uetakano, Yachiyo-shi, Chiba Sumitomo Seika Co., Ltd. Chiba Plant (72) Inventor Tatsuro Okano 1384-1, Uetakano, Yachiyo-shi, Chiba F-term in Functional Resin Research Laboratories Sumitomo Seika Co., Ltd. 4J038 CB001 HA216 JA44 KA20 MA02 MA14

Claims (6)

[Claims] 1. A powder coating for fluid immersion coating, comprising a polyolefin resin powder, an inorganic powder, and a metal soap powder. 2. The polyolefin resin powder has a median particle diameter of 90 to 160 μm and a bulk specific gravity of 0.35 to 0.50.
The g / ml and angle of repose is 20-35 degrees.
Powder coating for fluidized immersion coating according to the above. 3. The inorganic powder has an average particle size of 0.01 to 2
0 μm and the polyolefin resin powder 100
The powder coating for fluidized immersion coating according to claim 1, wherein the powder coating is added in an amount of 0.01 to 0.50 parts by weight based on parts by weight. 4. The method according to claim 1, wherein the inorganic powder is a metal oxide powder.
The powder coating for fluidized immersion coating according to claim 1, 2 or 3. 5. The metal soap powder has an average particle size of 5 to 30.
μm and 0.05 to 2.0 parts by weight are added to 100 parts by weight of the polyolefin resin powder,
The powder coating for fluidized immersion coating according to claim 1, 2, 3, or 4. 6. The powder coating for fluidized immersion coating according to claim 1, wherein the metal soap powder is a powder of calcium stearate.