JP2000129166A - Polyolefin-based powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of stably forming a specific special pattern having rough feeling with one time of coating and useful for increasing beautifulness of a metal, etc., by using a plurality of different polyolefin-based powder resins. SOLUTION: This polyolefin-based powder coating composition contains (A) total 100 pts.wt. of two kinds of polyolefin-based powder resins having different color tones and crystallization temperatures and (B) 0.1-10 pts.wt. of an organic-based foaming agent. Preferably, in the component A, a weight ratio of (a resin having high crystallization temperature to a resin having low crystallization temperature) is (10/90)-(80/20) and a difference of the crystallization temperatures is 5-70 deg.C, and further in the component B, an average particle diameter is 0.1-50 μm, concretely azodicarbonamide is used, and further, an antioxidant, an ultraviolet absorber, a free radical scavenger, etc., may suitably be mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyolefin-based powder coating composition. More specifically, it relates to a polyolefin-based powder coating composition capable of stably forming a certain special pattern with a single coating.

[0002]

2. Description of the Related Art Conventionally, powder coatings have been used for the purpose of forming a coating film by coating the surface of a metal or the like and enhancing the aesthetic appearance of the metal or the like, an effect of preventing rust, and the like. However, in recent years, the development of powder coating compositions capable of imparting various patterns to a surface coating film has been desired from the expansion of uses of powder coatings and diversification of needs. The powder coating composition capable of imparting various patterns to the coating film surface is composed of at least two types of powder resins having significantly different melt viscosities. A powder coating composition capable of giving a natural stone-like texture, a stipple-like pattern, a crepe pattern or the like to a coating film surface by selecting a baking temperature and a baking time is disclosed (JP-B-48-7492). No.).

However, in the above powder coating composition,
Because the special pattern formed on the coating film changes each time it is painted,
A certain special pattern cannot be obtained. Therefore, when applied to a large-sized molded product, there is a problem that a target special pattern cannot be stably obtained. Further, since the surface of the obtained coating film becomes smooth, it is not possible to obtain a coating film having an uneven shape and a rough feeling.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyolefin-based powder coating composition which can stably form a certain special pattern having a rough feeling with a single coating. .

[0005]

The gist of the present invention is that a total amount of 100 parts by weight of two kinds of polyolefin-based powder resins having different color tones and crystallization temperatures and an organic foaming agent of 0.1 to 10 parts.
The present invention relates to a polyolefin-based powder coating composition containing parts by weight.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The polyolefin-based powder resin in the present invention is not particularly limited, but is usually polyethylene, polypropylene, ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer used in a powder coating method. Coalescence and the like are preferred.

The two types of polyolefin powder resins used in the present invention have different crystallization temperatures.
The difference in crystallization temperature between the two types of polyolefin-based powder resins is preferably 5 to 70 ° C, more preferably 5 to 60 ° C.
° C, particularly preferably 5 to 45 ° C. If the difference in crystallization temperature is less than 5 ° C., it is difficult to form the intended special pattern having a rough feeling, and if it exceeds 70 ° C., the compatibility of the resins with each other is deteriorated. It is hard to be. According to the present invention, when a coating film is formed using a powder coating composition containing two types of polyolefin-based powder resins having different crystallization temperatures, the color of the polyolefin-based resin having a low crystallization temperature is used as a base. A coating film having a special pattern in which irregular spots derived from the color of the polyolefin resin having a high crystallization temperature are scattered can be formed on the coating film to be formed.

The two kinds of polyolefin powder resins used in the present invention have different color tones.
That is, the two types of polyolefin-based powder resins are:
Each contains a colorant having a different color tone, and there is no particular limitation on the combination of colorants used for each polyolefin-based powder resin, and any colorant may be used depending on the application. . In the present invention, a base colorant is used for a polyolefin resin having a low crystallization temperature, and an irregular spot color is used for a polyolefin resin having a high crystallization temperature. As the colorant, an organic pigment, an inorganic pigment, a dye, or the like is used.

The mixing ratio of the two kinds of polyolefin-based powder resins is as follows: a resin having a high crystallization temperature / a resin having a low crystallization temperature, preferably 10/90 to 80/20 (weight ratio), more preferably 20/80. / 80 to 70/30 (weight ratio). 10% by weight of resin with high crystallization temperature
If it is less than 80%, a special pattern is unlikely to appear, and if it exceeds 80% by weight, it becomes difficult to form a spot-like pattern, and it is difficult to obtain a target coating film.

Further, the powder coating composition of the present invention contains a predetermined amount of an organic foaming agent in addition to the two kinds of polyolefin-based powder resins. When a coating film is formed using the powder coating composition of the present invention containing an organic foaming agent, a coating film having a rough surface can be formed.

The organic foaming agent used in the present invention includes, for example, nitroso foaming agents, sulfohydrazide foaming agents, and azo foaming agents. Among them, azodicarbonamide, which is an azo foaming agent, is preferable from the viewpoint of obtaining stable foaming.

From the viewpoint of obtaining uniform fine bubbles, the foaming temperature of the organic foaming agent is determined based on the melting point of the higher crystallization temperature of the two types of polyolefin resins.
It is preferably between the lower crystallization temperature and the decomposition temperature of the resin. In the present invention, the crystallization temperature and the decomposition temperature of the resin can be measured by differential scanning calorimetry (DSC).

The average particle size of the organic foaming agent is preferably 0.1 to 50 μm, more preferably 5 to 40 μm, and particularly preferably 5 to 30 μm. Average particle size is 0.1μ
If less than 50 m, dust is generated and workability is inferior.
If the ratio exceeds the above range, large voids may be generated inside the coating film due to foaming, and the strength of the coating film may be reduced. Here, the average particle size refers to the integrated distribution 5 in the particle size distribution curve.
The particle size corresponds to 0%.

The compounding amount of the organic foaming agent is 0.1 to 10 parts by weight, preferably 1 to 7 parts by weight, based on 100 parts by weight of the total amount of the two kinds of polyolefinic powder resins. When the amount of the organic foaming agent is less than 0.1 part by weight,
Insufficient foaming causes the coating film to be smooth, and the surface of the obtained coating film lacks roughness. When the amount of the organic foaming agent exceeds 10 parts by weight, foaming is increased, defoaming marks are observed on the surface of the obtained coating film, and pinholes are generated.

Further, the powder coating composition of the present invention may optionally contain, if necessary, an antioxidant, an ultraviolet absorber, a radical scavenger, a lubricant, a grinding aid, and the like.

The method for producing the powder coating composition of the present invention is not particularly limited. For example, two kinds of polyolefin resins are mixed with a coloring agent having a different color tone, a kneading extruder, a heating roll, a Banbury mixer, Using a kneader such as a kneader, melt kneading, after preparing pellets,
The obtained pellets are pulverized and classified by a mechanical pulverization method, a freeze pulverization method, or the like, and the particle size is adjusted.
And polyolefin powder resin. In this case, the colorant of the base color is kneaded with a polyolefin resin having a low crystallization temperature, and the colorant of the color that forms irregular spots is kneaded with the polyolefin resin having a high crystallization temperature.
Thereafter, the obtained two kinds of polyolefin-based powder resins and the organic-based blowing agent are mixed at a predetermined ratio by a mixer such as a Henschel mixer to obtain a powder coating composition of the present invention.

The powder coating composition of the present invention can be applied to an object to be coated by a known method such as a flow immersion method and an electrostatic coating method to form a coating film.

When a coating film is formed using the above-described polyolefin-based powder coating composition of the present invention, the surface has a rough feeling, and the undercoat layer is formed on the surface of the color used as the undercoat layer of the coating film. It is possible to form a coating film having a special pattern in which irregular spots of a color different from a certain color are scattered. The powder coating composition of the present invention is suitably used for coating metals, mainly steel products.

[0019]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Ethylene-methacrylic acid copolymer [trade name: Nucrel N1525 (manufactured by Mitsui DuPont), crystallization temperature: 7]
5 ° C., melting point: 95 ° C., decomposition temperature: 205 ° C.) and a black pigment were kneaded, the resin was colored black, pulverized mechanically, and then classified to obtain a powder resin (powder resin A). Similarly, low density polyethylene [trade name: Sumikasen G801 (manufactured by Sumitomo Chemical Co., Ltd.), crystallization temperature: 95 ° C., melting point: 108
° C, decomposition temperature: 215 ° C] and a green pigment, and the resin was colored green, pulverized mechanically and classified to obtain a powder resin (powder resin B).

70 parts by weight of the obtained powder resin A, 30 parts by weight of powder resin B and an organic foaming agent [azodicarbonamide, trade name: CellMike CAP500 (Sankyo Chemical Co., Ltd.)
), Average particle size: 10 µm, foaming temperature: 150 ° C], and 2 parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

The obtained powder coating composition was placed in a fluidized immersion tank, and air was fed from the bottom of the tank to maintain a stable fluidized state. A 70 mm × 150 mm × 2 mm steel plate pre-heated in a 360 ° C. oven for 4 minutes was immersed therein for 5 seconds. Thereafter, post-heating was performed in an oven at 180 ° C. for 2 minutes, and the product was cooled at room temperature to obtain a fluidized dip-coated product. The coating film of the obtained coated article had a pattern in which green irregular spots were sparsely scattered on a black base, and the surface had a rough feeling.

Example 2 In Example 1, the amount of the obtained powder resin A was changed to 40
A powder coating composition was obtained in the same manner as in Example 1 except that the used amount of the powder resin B was changed to 60 parts by weight, and the used amount of the organic foaming agent was changed to 6 parts by weight.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated product had a pattern in which a number of green irregular spots were scattered on a black base, and the surface had a rough feeling.

Example 3 Ethylene-acrylic acid copolymer [brand name: Novatec A]
220S (manufactured by Nippon Polychem Co., Ltd.), crystallization temperature: 89
C., melting point: 100.degree. C., decomposition temperature: 205.degree. C.] and a black pigment, and the resin was colored black, pulverized mechanically, and then classified to obtain a powder resin (powder resin C). Similarly, low density polyethylene [trade name: Sumikasen G801 (manufactured by Sumitomo Chemical Co., Ltd.), crystallization temperature: 95 ° C., melting point: 108
C., decomposition temperature: 215.degree. C.] and a yellow pigment, and the resin was colored yellow, pulverized mechanically and classified to obtain a powder resin (powder resin D).

The obtained powder resin C (60 parts by weight), powder resin D (40 parts by weight) and an organic foaming agent [azodicarbonamide, trade name: Cellmic AN (manufactured by Sankyo Chemical Co., Ltd.), average particle size: 25 μm, (Foaming temperature: 130 ° C.) 2 parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated product had a pattern in which yellow irregular spots were sparsely scattered on a black base, and the surface had a rough feeling.

Example 4 Low-density polyethylene [trade name: Sumikasen G801 (manufactured by Sumitomo Chemical Co., Ltd.), crystallization temperature: 95 ° C., melting point: 1]
08 ° C., decomposition temperature: 215 ° C.] and a red pigment.
The resin was colored red, pulverized mechanically, and classified to obtain a powder resin (powder resin E). Similarly, linear low-density polyethylene [trade name: Ultoxex 25100 (manufactured by Mitsui Chemicals, Inc.), crystallization temperature: 114 ° C, melting point: 120 ° C,
(Decomposition temperature: 240 ° C.) and a white pigment, and the resin was colored white, pulverized mechanically, and then classified to obtain a powder resin (powder resin F).

30 parts by weight of the obtained powder resin E, 70 parts by weight of powder resin F and an organic foaming agent [azodicarbonamide, trade name: CellMic AN (manufactured by Sankyo Kasei Co., Ltd.), average particle size: 25 μm, (Foaming temperature: 130 ° C.) 6 parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated product had a pattern in which a number of white irregular spots were scattered on a red base, and the surface had a rough feeling.

Example 5 Ethylene-methacrylic acid copolymer [trade name: Nucrel N1525 (manufactured by Mitsui DuPont), crystallization temperature: 7]
5 ° C., melting point: 95 ° C., decomposition temperature: 205 ° C.] and the white pigment were kneaded, the resin was colored white, pulverized mechanically, and then classified to obtain a powder resin (powder resin G). Similarly, a linear low-density polyethylene [trade name: Ultzex 2510]
0 (manufactured by Mitsui Chemicals, Inc.), crystallization temperature: 114 ° C., melting point: 120 ° C., decomposition temperature: 240 ° C.) and a brown pigment, and the resin is colored brown, mechanically pulverized, and classified. Thus, a powder resin was obtained (powder resin H).

The obtained powder resin G (40 parts by weight), powder resin H (60 parts by weight) and an organic blowing agent [azodicarbonamide, trade name: CellMike CAP500 (Sankyo Chemical Co., Ltd.)
), Average particle size: 10 µm, foaming temperature: 150 ° C], and 4 parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated product had a pattern in which a number of brown irregular spots were scattered on a white base, and the surface had a rough feeling.

Comparative Example 1 Low-density polyethylene [trade name: Sumikasen G801 (manufactured by Sumitomo Chemical Co., Ltd.), crystallization temperature: 95 ° C., melting point: 1
08 ° C, decomposition temperature: 215 ° C] and a black pigment.
The resin was colored black, pulverized mechanically, and classified to obtain a powder resin (powder resin I). Similarly, low-density polyethylene [trade name: Sumikasen G801 (Sumitomo Chemical Co., Ltd.)
Crystallization temperature: 95 ° C., melting point: 108 ° C., decomposition temperature: 215 ° C.) and a yellow pigment to color the resin yellow, pulverize mechanically, and classify to obtain a powdered resin. (Powder resin J).

40 parts by weight of the obtained powder resin I, 60 parts by weight of powder resin J and an organic blowing agent [azodicarbonamide, trade name: CellMike CAP500 (Sankyo Chemical Co., Ltd.)
), Average particle size: 10 µm, foaming temperature: 150 ° C], and 2 parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

Example 1 was prepared using the obtained powder coating composition.
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated product had a black and yellow marble-like pattern, and the surface had a rough feeling.

Comparative Example 2 A powder coating composition was obtained in the same manner as in Example 1 except that the powder coating A and the powder coating B were not mixed with an organic foaming agent.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated article had a pattern in which green irregular spots were scattered on a black base, but the surface was smooth.

Comparative Example 3 Ethylene-acrylic acid copolymer [trade name: Novatec A
220S (manufactured by Nippon Polychem Co., Ltd.), crystallization temperature: 89
C., melting point: 100.degree. C., decomposition temperature: 205.degree. C.] and a white pigment, and the resin was colored white, pulverized mechanically, and then classified to obtain a powder resin (powder resin K). Similarly, a linear low-density polyethylene [trade name: Ultzex 2510]
0 (manufactured by Mitsui Chemicals, Inc.), crystallization temperature: 114 ° C., melting point: 120 ° C., decomposition temperature: 240 ° C.) and a red pigment, and the resin is colored red. Thus, a powder resin was obtained (powder resin L).

70 parts by weight of the obtained powder resin K, 30 parts by weight of powder resin L and an organic foaming agent [azodicarbonamide, trade name: CellMike CAP500 (Sankyo Chemical Co., Ltd.)
), Average particle size: 10 µm, foaming temperature: 150 ° C] 15
Parts by weight were uniformly mixed with a Henschel mixer to obtain a powder coating composition.

Using the obtained powder coating composition, Example 1
In the same manner as in the above, a fluid immersion coated product was obtained. The coating film of the obtained coated article had a pattern in which red irregular spots were scattered on a white base, and pinholes were observed on the surface.

From the above results, in comparison with the case where the powder coating compositions of Comparative Examples 1 to 3 were used, when the powder coating compositions of Examples 1 to 5 were used, the undercoat It can be seen that an irregular spot of a color different from the base color is scattered on the surface of the base color and a coating film having a pattern with a rough feeling on the surface of the coating film can be easily formed. .

[0043]

According to the polyolefin-based powder coating composition of the present invention, it is possible to stably form a coating film having a certain special pattern with a rough feeling by one coating.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tatsuro Okano 1384-1 Uetakano, Yachiyo-shi, Chiba F-term in the 2nd research institute of Sumitomo Seika Co., Ltd. 4J038 MA02 PA05

Claims (5)

[Claims] 1. A polyolefin-based powder coating composition comprising 100 parts by weight of a total of two kinds of polyolefin-based powder resins having different color tones and crystallization temperatures and 0.1 to 10 parts by weight of an organic blowing agent. 2. The compounding ratio of the two kinds of polyolefin-based powder resins is as follows: resin having a high crystallization temperature / resin having a low crystallization temperature = 10/90 to 80/20 (weight ratio).
The polyolefin-based powder coating composition according to the above. 3. The polyolefin powder coating composition according to claim 1, wherein the difference in crystallization temperature between the two polyolefin powder resins is 5 to 70 ° C. 4. An organic foaming agent having an average particle size of 0.1 to 5
The polyolefin-based powder coating composition according to any one of claims 1 to 3, which is 0 µm. 5. The polyolefin powder coating composition according to claim 1, wherein the organic blowing agent is azodicarbonamide.