JP2002069372A - Composition for polyamide foaming powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide foaming powder coating composition that causes no pinhole and has excellent heat insulation, sound absorbency, buffer action, feeling, appearance and the like. SOLUTION: This polyamide foaming powder coating composition comprises mainly powdery polyamide and characteristically includes at least one selected from the group consisting of azo compounds, nitroso compounds, hydrazine derivatives, bicarbonate salts as a foaming agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a polyamide foamable powder coating composition. An object of the present invention is to provide a composition for a polyamide-based foaming powder coating material having excellent heat insulating properties, sound absorbing properties, cushioning properties, texture, appearance, and the like.

[0002]

2. Description of the Related Art Surface coating has been practiced for a long time to prevent rust of metal materials and to improve appearance and characteristics of various materials. As the organic paint, esters, epoxies, or composites thereof, urethane, acrylic, polyamide, fluororesin, etc. are widely used, but these are generally used in a state of being dissolved or dispersed in an organic solvent for easy handling. ing. However, the use of organic solvents is not preferable in terms of living environment, work environment, etc., and is in the direction of being regulated legally. To solve this, water-soluble, water-dispersed, Alternatively, powder coatings have been developed and are already in practical use.

[0003] Depending on the application, these coated materials are improved in heat resistance, weather resistance, and the like, and are imparted with functionalities such as higher surface hardness. The present invention insulates the coating,
It is intended to provide functionality such as sound absorption and cushioning,
Achieving these by foaming the coatings is rarely done. In particular, in the case of coating with a powder coating, there is a problem of generation of pinholes, which is a cause of lowering the original rust prevention performance.

There are various types of blowing agents, such as inorganic compounds and organic compounds. To prevent the generation of pinholes, the decomposition temperature, decomposition rate, amount of gas generation, etc. of the blowing agent are carefully selected, and the amount of the resin to be compounded is further determined. It is important to select according to the type, processing conditions, use conditions, purpose, and the like.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a coating film having no pinholes and having a controlled expansion ratio. Found that it can be achieved.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a powder coating mainly composed of polyamide, which comprises an azo compound as a foaming agent;
A polyamide foamable powder coating composition comprising at least one selected from the group consisting of a nitroso compound, a hydrazine derivative, and a bicarbonate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, "polyamide" refers to a polyamide which is a polymer of a salt of an aminocarboxylic acid or lactam having 6 or more carbon atoms or a dicarboxylic acid with a diamine having 6 or more carbon atoms. Examples of the “salt of an aminocarboxylic acid having 6 or more carbon atoms or a lactam or a diamine having 6 or more carbon atoms and a dicarboxylic acid” include, for example, ω-aminocaproic acid, ω-aminoenanthic acid, ω-aminocaprylic acid, ω-aminoperargon. Acid, ω-aminocapric acid, aminocarboxylic acid such as 11-aminoundecanoic acid, 12-aminododecanoic acid; lactam such as caprolactam, enantholactam, caprylactam, laurolactam; hexamethylenediamine-adipate, hexamethylenediamine-sebacine And salts of hexamethylenediamine-isophthalate, undecamethylenediamine-adipate, 4,4'-diaminodicyclohexylmethane-dodecaneate, and the like. The polyamide may be a homopolymer or a copolymer. Further, a resin blended with another resin may be used. Also,
It may contain a catalyst, various stabilizers and the like. Of these, polyamide 11 and polyamide 12 are preferred.

[0008] In the present invention, "powder coating material" refers to a pigment, a dye, and various additives such as a heat stabilizer, a light stabilizer, a lubricant, a lubricant,
Plasticizers, antistatic agents, crystal nucleating agents, flame retardants, etc. are mixed or kneaded in a powder state, for example, and then powdered to be used for coating. A coating method such as a fluid immersion coating method, an electrostatic coating method, and a thermal spray coating method is not limited.

In the present invention, examples of the "blowing agent" include azo compounds, nitroso compounds, hydrazine derivatives, bicarbonates and the like. Specifically, azo compounds include azodicarbonamide, azobisformamide, azobisisobutyronitrile, diazoaminobenzene, barium azodicarboxylate, and nitroso compounds include N, N'-dinitrosopentamethylenetetramine, N, N'-dimethyl-
N, N'-dinitrosoterephthalamide, hydrazine derivatives include 4,4'-oxybis (benzenesulfonylhydrazide), hydrazodicarbonamide, benzenesulfonylhydrazide, toluene-4-sulfonylhydrazide, benzene-1,3-disulfonyl Examples of hydrazide, diphenylsulfone-3, 3'-disulfonyl hydrazide, sulfone hydrazide and bicarbonate include sodium hydrogencarbonate.

When the decomposition temperature of the foaming agent is low, it is difficult to control foaming, and the decomposition temperature of the foaming agent is preferably higher than the melting point of the polyamide. However, if the decomposition temperature is too high, foaming during processing in the coating process becomes difficult. In view of the melting point of the polyamide as the base resin and the coating conditions, the foaming agent is particularly preferably azodicarbonamide, azobisformamide, and N, N'-dinitrosopentamethylenetetramine.

In the present invention, the form of the composition in which the foaming agent is blended with the polyamide resin is arbitrary. For example, a composition that is mechanically mixed in a powder state, a composition in which a blowing agent is attached to the surface of a polyamide powder, a composition in which the blowing agent is coated on the surface of a polyamide powder, and a foaming agent in a polyamide. A composition kneaded into the
Alternatively, a composition in which these forms are combined is exemplified.

In the composition of the present invention, the mixing ratio of the foaming agent to the polyamide is not particularly limited.
1% or more and 5% or less, preferably 0.05% or more and 3%
Or less, particularly preferably 0.1% or more and 2.5% or less. It is preferable to arbitrarily change the ratio when obtaining the texture.

In the present invention, a method for producing a composition containing the foaming agent is optional. For example, a method in which a foaming agent and polyamide powder are mechanically mixed with a stirring mixer to form a composition, after the foaming agent and polyamide powder are mixed, the foaming agent is further adhered to the surface of the polyamide particles by collision energy, shear energy, or the like. Alternatively, a method of welding to form a composition, a method of kneading a foaming agent into polyamide, and pulverizing the same to form a powdery composition are exemplified. Of course, it is needless to say that the present invention is not limited to these methods.

In the present invention, the method of powder coating using the polyamide powder containing the foaming agent is not limited, and a conventionally known fluid immersion method, electrostatic coating method, thermal spray coating method, mini coat coating method and the like can be employed. Of course, pretreatment such as degreasing, shot blasting, primer coating, or electrodeposition coating before coating is performed as necessary. Generally, in the case of the electrostatic coating method, it is preferable to use a foaming agent having a lower decomposition temperature than in the case of the fluid immersion method.

[0015]

The composition of the present invention has a foaming property as a powder coating and forms a foam film controlled by a heating step in a coating process, and has properties such as heat insulation, soundproofing, shock absorption, anti-slip, and texture. There is expected. Uses of the composition coated with the powder coating composition include: car, building undercarriage, walls, flooring, low- or high-temperature packaged goods (hot water piping, heat exchangers, etc.), handrails, etc. Demonstrate.

[0016]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but it goes without saying that the present invention is not limited to these examples. In Examples and Comparative Examples, coating and coating films were evaluated by the following methods.

(1) Decomposition temperature of foaming agent Using a thermal balance (TGA), the temperature at which weight loss starts when the temperature is increased at 20 C / min was taken as the decomposition temperature.

(2) Coating Spraying an epoxy-based primer on a 3.2 mm thick iron plate that has been rusted and degreased, the coating film thickness after drying is about 8-
It was applied so as to be 10 microns. 400C
Was heated for about 3 minutes and 40 seconds in an oven set at, and was taken out when the surface temperature of the iron plate reached 280C. On the other hand, it was applied to a predetermined thickness in a fluidized bed filled with a powder coating material containing a predetermined ratio of a foaming agent, and used as a sample for a coating film test.

(3) Foaming Ratio of Coating Film It was represented by the ratio of the film thickness when coated under the same conditions to the coating film thickness without the foaming agent.

(4) Performance Evaluation of Coating Film The appearance of the coating film was carefully observed, and the edge coverage, discoloration, etc. were visually evaluated. In addition, about the pinhole, the presence or absence of a spark was judged by the presence or absence of spark using the pinhole detector made by Sanko Electronics Research Laboratory.

[0021]

Examples 1-6, Comparative Examples 1 and 2 A powder coating composed of polyamide 11 (Rilsan Fine Powder manufactured by Atofina) W1482 (Comparative Example 1), and W, 1482 was N, N'-dinitrosopentamethylenetetramine (decomposed) Temperature 205C)
0.5, 1.0, 2.0 and 6.0% by weight (compositions 1, 2, 3, 4, but 4
Are comparative examples), azodicarbonamide (decomposition temperature 208
C) 1% by weight (composition 5), 1% by weight of azobisformamide (decomposition temperature 198C) (composition 6), and a azodicarbonamide / N, N'-dinitrosopentamethylenetetramine 1/1 mixture ( Decomposition temperature 205C) 0.8% by weight
(Composition 7) was mixed and stirred and mixed with a Henschel mixer to obtain a powdery composition. This was coated on an iron plate by a fluid immersion method. The thickness of the coating film (comparative example) that did not contain the foaming agent was
400 microns. The coating thicknesses from compositions 1, 2, 3, and 4 were 780, 1040, 1780, and 2010 microns, respectively, and the expansion ratios were 1.95, 2.60, 4.45, and 5.25. Evaluation was discontinued because the coating from Composition 4 turned light brown and the coating was incomplete without being subjected to an upper pinhole detector with poor appearance. The coating film from composition 3 was slightly discolored and had some difficulty in edge covering properties, but the other coating films (1 and 2) had no discoloration and good appearance and edge covering properties. In addition, coating films 1, 2 and 3 were all pinhole detectors and no coating film defects were found. Coatings from compositions 5, 6, 7 have an expansion ratio of 3.8
3, 3.63, 3.00 and compositions 5, 6 slightly discolored,
Other than that, there were no particular problems in appearance and edge cover properties.
When all of these coating films were subjected to a pinhole tester, no spark was generated, and it was found that there was no pinhole in each case.

[0022]

Comparative Example 3 In Example 1, the composition (8) containing 0.8% by weight of diazoaminobenzene (decomposition temperature: 103C) as a foaming agent was difficult to control foaming, and the coating film produced a spark during a pinhole test. Then, the existence of the pinhole was found.

[0023]

As described above, the composition of the present invention gives a foamable coating film which is controlled in the step of applying a powder coating by heating.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naohiko Tabino 3-23 Kioicho, Chiyoda-ku, Tokyo Atfina Japan Co., Ltd. F-term (reference) 4J038 DH001 DH011 JB16 JB17 MA02 NA01

Claims (6)

[Claims] 1. A polyamide-based foaming material characterized in that, in a powder coating mainly composed of polyamide, at least one selected from the group consisting of an azo compound, a nitroso compound, a hydrazine derivative and a bicarbonate is blended as a foaming agent. Composition for powder coating. 2. The composition according to claim 1, wherein the polyamide is polyamide 11 or polyamide 12. 3. The composition according to claim 1, wherein the decomposition temperature of the foaming agent is equal to or higher than the melting point of the polyamide. 4. The composition according to claim 1, wherein the azo compound of the foaming agent is azodicarbonamide. 5. The composition according to claim 1, wherein the nitroso compound as a foaming agent is N, N′-dinitrosopentamethylenetetramine. 6. The polyamide foamable powder coating composition according to claim 1, wherein the compounding amount of the foaming agent is 0.01% or more and 5% or less based on the whole composition.