JP2001234125A - Powder coating material for spray coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a powder coating material for spray coating which is hard to discolor even when exposed to high temperature flames in the coating process. SOLUTION: This powder coating material for spray coating comprises a thermoplastic resin, a hindered phenol antioxidant, and a phosphite antioxidant. In general, the powder coating material for spray coating has a medium particle diameter of 50-300 μm, a bulk density of >=0.30 g/ml, an angle of repose of <=35 deg. and comprises 0.05-2.0 pts.wt., based on 100 pts.wt. thermoplastic resin, hindered phenol antioxidant and phosphite antioxidant, respectively.

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 thermal spray coating.

[0002]

2. Description of the Related Art Powder coating using a thermoplastic resin powder coating is widely practiced to impart corrosion protection to a metal substrate. , An electrostatic coating method and a thermal spray coating method are employed. Here, the fluid immersion coating method and the electrostatic coating method require special coating equipment installed indoors, so that it is difficult to carry out the method outdoors, for example, at a building site of a steel structure such as a bridge because of the work. The site is limited. In contrast, the thermal spray coating method
The coating method uses a portable spray gun, so there are few restrictions on the work site, and it can flexibly cope with large-scale workpieces outdoors, such as steel construction sites. Have.

The above-mentioned spray gun used in the thermal spray coating method usually sprays a flame of a fuel gas obtained by mixing propane gas and air, and thereby melts the thermoplastic resin powder coating material to be coated. Unlike the fluid immersion coating method or the electrostatic coating method, the thermoplastic resin powder coating is 500
It will be exposed to high temperature flames above ℃. For this reason,
In the thermal spray coating method, the thermoplastic resin powder coating is discolored by receiving excessive heat in the coating process, and it is difficult to improve the coating film quality.

An object of the present invention is to realize a powder coating for thermal spray coating which is hardly discolored even when exposed to a high-temperature flame during a coating process.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a hindered phenol-based antioxidant and a phosphite-based antioxidant have been added to a thermoplastic resin as heat stabilizers. It has been found that, when a powder coating to which is added is used for thermal spray coating, a coating film with suppressed discoloration can be formed, and the present invention has been completed.

That is, the powder coating for thermal spray coating of the present invention contains a thermoplastic resin, a hindered phenol antioxidant, and a phosphite antioxidant. The powder coating for thermal spray coating usually has a median particle size of 5
0 to 300 μm, bulk specific gravity of 0.30 g / ml or more, angle of repose of 35 degrees or less, and usually 100 parts by weight of a thermoplastic resin, a hindered phenol-based antioxidant and a phosphite-based antioxidant From 0.05 to
Contains 2.0 parts by weight.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The powder coating for thermal spray coating of the present invention comprises:
It is a powder obtained by pulverizing a resin molded product containing a thermoplastic resin, a hindered phenol-based antioxidant and a phosphite-based antioxidant into powder.

[0008] The thermoplastic resin used in the present invention is a variety of known ones and is not particularly limited. Examples thereof include a polyethylene resin, a polypropylene resin, a nylon-11 resin, a nylon-12 resin, and ethylene-acetic acid. Examples thereof include a vinyl copolymer resin, an ethylene-acrylic acid copolymer resin, an ethylene-methacrylic acid copolymer resin, a modified polyethylene resin, and a modified polypropylene resin. These thermoplastic resins may be used as a mixture of two or more kinds as appropriate.

On the other hand, the hindered phenolic antioxidant used in the present invention is used as a heat stabilizer for the above-mentioned thermoplastic resin, and is represented by the following general formula (1).

[0010]

Embedded image

In the general formula (1), R ¹ and R ² each represent a methyl group, an ethyl group, a propyl group or a t-butyl group, and they may be the same or different. Good.

Specific examples of such hindered phenolic antioxidants include, for example, trade names “Irganox 1010”, “Irganox 1098”, and “Irganox 1330” (trade names) of Ciba Specialty Chemicals.
And "Irganox 3114". In the present invention, two or more hindered phenolic antioxidants may be used in combination.

[0013] The content of the hindered phenolic antioxidant in the powder coating for thermal spray coating of the present invention is preferably set to 0.05 to 2.0 parts by weight based on 100 parts by weight of the thermoplastic resin. , 0.1 to 1.0 part by weight. When the content is less than 0.05 part by weight, the discoloration of the coating film may not be effectively suppressed when the powder coating for thermal spray coating is spray-coated. Conversely, 2.
When the amount exceeds 0 parts by weight, although discoloration of the coating film due to thermal spray coating can be effectively suppressed, bleed-out of the hindered phenolic antioxidant easily occurs in the coating film, so-called powder blowing can occur on the coating film surface. Thus, the commercial value of the coating film may be reduced.

The phosphite antioxidant used in the present invention is a compound represented by the following general formula (2) or (3).

[0015]

Embedded image

In the general formulas (2) and (3), R ¹ and R ² each represent a methyl group, an ethyl group, a propyl group or a t-butyl group, and both may be the same, It may be different.

Specific examples of such a phosphite-based antioxidant include those represented by the general formula (2):
For example, the product name “ADK STAB P
EP-36 "and the like, and examples of the compound represented by the general formula (3) include" Irgafos 168 "(trade name of Ciba Specialty Chemicals). In the present invention, Two or more phosphite-based antioxidants may be used in combination.

The content of the phosphite-based antioxidant in the powder coating for thermal spray coating of the present invention is as follows.
It is preferably set to 0.05 to 2.0 parts by weight, more preferably 0.1 to 1.0 part by weight, per 100 parts by weight. When the content is less than 0.05 part by weight, the discoloration of the coating film may not be effectively suppressed when the powder coating for thermal spray coating is spray-coated. Conversely, when the amount exceeds 2.0 parts by weight, although discoloration of the coating film due to thermal spray coating can be effectively suppressed, bleed-out of the phosphite antioxidant tends to occur in the coating film, and so-called powder Spraying may cause a decrease in the commercial value of the coating film.

The powder coating for thermal spray coating of the present invention comprises, in addition to the above essential components, other fillers and additives such as an ultraviolet absorber, a radical scavenger, a flame retardant,
An antistatic agent, a lubricant, a nucleating agent, a coloring agent, and the like may be appropriately contained.

In producing the powder coating for thermal spray coating of the present invention, for example, first, the above-mentioned thermoplastic resin, hindered phenol-based antioxidant, phosphite-based antioxidant and, if necessary, other fillers are used. The agents and additives are sufficiently mixed at a predetermined ratio using a Henschel mixer, a tumbler mixer or the like to prepare a mixture. Next, the obtained mixture is uniformly melt-mixed using a kneader such as a single-screw extruder, a twin-screw extruder, a kneader or a Banbury mixer, and formed into pellets. When the pellets are pulverized into powder by a known pulverization method such as a mechanical pulverization method or a freeze pulverization method, the powder coating for thermal spray coating of the present invention is obtained. The fluidity of the powder coating for thermal spray coating of the present invention thus produced may be adjusted by appropriately adding a flow modifier such as fine-particle silica.

The powder coating for thermal spray coating of the present invention produced as described above is usually classified with a sieve or the like to obtain a coating having a smooth surface. It is preferable to adjust the angle of repose appropriately. Here, the median particle diameter is preferably set to 50 to 300 μm,
More preferably, it is set to 250 μm. When the median particle diameter is less than 50 μm, the powder of the present invention is stably sprayed from a spray gun during thermal spraying because the powder of the powder coating of the present invention becomes too fine and easily aggregates. , And uneven coating may occur, making it difficult to obtain a smooth coating film. Conversely, the median particle size is 300μ
If it exceeds m, the powder of the powder coating material of the present invention becomes too coarse, so that it may be difficult to form a coating film having good surface smoothness.

In the present invention, the median particle size is defined as
50 g of the powder coating of the present invention was weighed, sieved using a JIS standard sieve, weighed for each sieve, and based on the result, the particle diameter at which the integrated weight became 50% was calculated by the following equation. A thing.

[0023]

(Equation 1)

In the formula, A is a value obtained by sequentially integrating 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.

The bulk specific gravity is preferably set to 0.30 g / ml or more. More specifically, 0.30 g /
It is preferably set in the range of not less than ml and not more than 0.60 g / ml, more preferably in the range of not less than 0.33 g / ml and not more than 0.50 g / ml. Bulk specific gravity is 0.30
In the case of less than g / ml, the flow state of the powder coating of the present invention becomes non-uniform in the hopper for storing the powder coating of the present invention to be supplied to the spray gun, and the present invention stably controls the spray coating from the spray gun. In some cases, it may be difficult to inject the powder coating material, and it may be difficult to obtain a coating film having good surface smoothness. On the other hand, when the bulk specific gravity exceeds 0.60 g / ml, it becomes difficult to stably transport the powder coating material of the present invention from the hopper to the spraying gun or to stably spray the powder coating from the spraying gun. May occur.

In the present invention, the bulk specific gravity is defined as the volume of the present invention in which 60 g of the powder coating material of the present invention is gently dropped using a funnel into a cylindrical container having an inner volume of 100 ml and a diameter of 40 mm. After rubbing off the powder paint with a glass rod, measure the mass of the container containing the powder paint,
The value obtained by subtracting the mass of the container from this mass is divided by the internal volume of the container.

Further, the angle of repose is preferably set to be 35 degrees or less. More specifically, 15 degrees or more 3
The angle is preferably set to 5 degrees or less, more preferably 20 degrees to 33 degrees. When the angle of repose exceeds 35 degrees, the flow state of the powder coating of the present invention becomes non-uniform in the hopper for storing the powder coating of the present invention supplied to the spray gun, and the powder coating is stably supplied from the spray gun. Since it may be difficult to spray the powder coating of the present invention, a coating film having good surface smoothness may not be easily formed. On the other hand, when the angle of repose is less than 15 degrees, it becomes difficult to stably transport the powder coating material of the present invention from the hopper to the spray gun or to stably jet the powder coating from the spray gun, which may cause uneven coating. There is.

In the present invention, the angle of repose is defined as the case where 60 g of the powder coating material of the present invention is gently dropped using a funnel onto a horizontally placed circular trellis having a diameter of 10 cm and deposited in a conical shape. Means the angle formed by the generatrix of the conical deposit and the horizontal plane of the truncated circle.

Since the powder coating for thermal spray coating of the present invention contains a hindered phenolic antioxidant and a phosphite antioxidant in addition to the thermoplastic resin, it can be used as a conventional powder coating for thermal spray coating. In comparison, heat resistance can be significantly improved.
Therefore, the powder coating of the present invention suppresses discoloration even when exposed to a high-temperature gas flame ejected from a thermal spray gun during thermal spray coating, and can form a high-quality coating film with little discoloration. Further, when the median particle diameter, bulk specific gravity and angle of repose are set in the above ranges, the powder coating of the present invention not only has little discoloration during thermal spray coating, but also has good surface smoothness. A film can be formed.

The powder coating for thermal spray coating of the present invention, like the powder coating for thermal spray coating so far, comprises a base material made of metal, for example, iron, iron alloy, zinc or their plating, ceramic, It can be used when painting concrete, FRP or gypsum board.

[0031]

EXAMPLES Examples 1 to 4 Low-density polyethylene resin (trade name "Sumikacene G801" of Sumitomo Chemical Co., Ltd .: MFR = 20 g / 10 min)
For 100 parts by weight, a trade name "Irganox 1010" of Ciba Specialty Chemicals, a hindered phenolic antioxidant, and a trade name of "ADEKA STAB P" of Asahi Denka Kogyo Co., Ltd., a phosphite antioxidant
EP-36 "was mixed at a ratio shown in Table 1. The mixture was melt-kneaded using a single screw extruder to obtain pellets. The pellets were powdered at room temperature using a high-speed rotary pulverizer. And the obtained powder was classified by a classifier.
As a result, a powder resin (powder coating of the present invention) in which the median particle diameter, bulk specific gravity and angle of repose were set as shown in Table 1 was obtained.

Example 5 A polypropylene copolymer resin (trade name “Noblen Z131” of Sumitomo Chemical Co., Ltd.) as a random copolymer of 95% by weight of propylene and 5% by weight of ethylene 100
The hindered phenolic antioxidant, Ciba Specialty Chemicals' trade name "Irganox 1330", and the phosphite-based antioxidant Ciba Specialty Chemicals, trade name "Irgafos 168" are shown in parts by weight. The components were mixed at the ratio shown in FIG. This mixture was melt-kneaded using a single screw extruder to obtain pellets. The pellets were frozen and pulverized into a powder using liquid nitrogen, and the obtained powder was classified by a classifier. As a result, a powder resin (powder coating of the present invention) in which the median particle diameter, bulk specific gravity and angle of repose were set as shown in Table 1 was obtained.

Example 6 Nylon (polyamide) resin (EMS-CHEMIE)
AG brand name "Grilamide") 100 parts by weight, hindered phenolic antioxidant Ciba Specialty Chemicals Corporation brand name "Irganox 10
98 "and phosphite-based antioxidant, trade name" ADEKA STAB PEP-36 "of Asahi Denka Kogyo Co., Ltd. were mixed in the ratio shown in Table 1. This mixture was melt-blended using a single screw extruder. The pellets were frozen and pulverized into a powder form using liquid nitrogen, and the obtained powder was classified by a classifier, whereby the median particle diameter, bulk specific gravity and angle of repose were as shown in Table 1. A powder resin (powder coating material of the present invention) set as shown in (1) was obtained.

Comparative Example Low-density polyethylene resin (trade name "Sumikacene G801" of Sumitomo Chemical Co., Ltd .: MFR = 20 g / 10 min)
Only the mixture was melt-kneaded using a single screw extruder to obtain pellets. The pellet was pulverized into a powder at room temperature using a high-speed rotary pulverizer, and the obtained powder was classified by a classifier. As a result, a powder resin having a median particle diameter, bulk specific gravity, and angle of repose set as shown in Table 1 was obtained.

Using a thermal spray coating machine (manufactured by PFS Thermoplastic Powder Coatings) equipped with an evaluation thermal spray gun, the powder resin obtained in each of the Examples and Comparative Examples was 70 × 150 × 2 m.
spraying painted steel plate of m ^t, it was evaluated by visual observation of the color change and surface smoothness of the formed thereby coating. Here, in the thermal spray gun, the propane gas pressure is 118 kP.
a, The mixed fuel gas whose air pressure was adjusted to 686 kPa was ejected while burning, the discharge amount of the powder resin was set to 100 g / min, and the distance between the spray gun and the steel plate was set to 400 mm. Table 1 shows the results.

[0036]

[Table 1]

[0037]

The powder coating for thermal spray coating according to the present invention is a powder obtained by mixing a hindered phenol antioxidant and a phosphite antioxidant with a thermoplastic resin. And hardly discolors even when exposed to high-temperature flame. In particular, the powder coating for thermal spray coating has a medium particle diameter, a bulk specific gravity and an angle of repose set in the above ranges, and not only does it not easily discolor during the thermal spray coating process, but also has a surface smoothness. A good thermal spray coating can be formed.

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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] 0023

[Correction method] Change

[Correction contents]

[0023]

(Equation 1)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

In the formula, A is the integrated value (g) at the point where the weight is sequentially integrated from the coarser particle size distribution and the integrated weight is less than 50% and is closest to 50%. 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 Kamikono, Yachiyo-shi, Chiba Sumitomo Seika Co., Ltd. Functional resin research institute (72) Inventor Tatsuro Okano 1384-1 Kamikono, Yachiyo-shi, Chiba Sumitomo Seika Co., Ltd. Functional Resin Laboratory F-term (reference) 4J038 CB021 CB051 CB061 CB081 CF031 CG031 DH011 JA64 JC20 KA12 MA02 MA14 NA14 PA02 PB05 PC02 PC03 PC04

Claims (3)

[Claims] 1. A composition comprising a thermoplastic resin, a hindered phenol-based antioxidant, and a phosphite-based antioxidant.
Powder coating for thermal spray coating. 2. The powder coating for thermal spray coating according to claim 1, which has a median particle size of 50 to 300 μm, a bulk specific gravity of 0.30 g / ml or more, and a repose angle of 35 ° or less. 3. The method according to claim 1, wherein the hindered phenol-based antioxidant and the phosphite-based antioxidant are each contained in an amount of 0.05 to 2.0 parts by weight based on 100 parts by weight of the thermoplastic resin. A powder coating for thermal spray coating according to the above.