JPH11293158A - Pinhole preventing agent for powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pinhole preventing agent scarcely having an yellowing (yellowing phenomena) when baked at high temperatures or with time and capable of preventing pinholes by using a specific wax. SOLUTION: This preventing agent comprises (A) a fatty acid amide wax or (B) a fatty acid imide wax having 80-200 deg.C melting point and preferably (C) a substituted urea wax having 80-200 deg.C melting point. Furthermore, e.g. a monoamide synthesized by the dehydration of a fatty acid ammonium salt or ammonolysis of an oil and fat (ester) is preferably used as the component A and, e.g. a wax obtained by a condensation reaction of an acid anhydride with an amine or a dehydration reaction of a dibasic acid ammonium salt is preferably used as the component B. For example, a wax synthesized by an addition reaction of an amine with an isocyanate is preferably used as the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents pinholes generated during baking hardening of a powder coating by adding a small amount to a thermosetting powder coating composition of an epoxy, acrylic or polyester type. The present invention also relates to an additive for obtaining a smooth and beautiful coating film with less yellowing.

[0002]

2. Description of the Related Art As an additive for preventing pinholes generated during baking hardening of a powder coating, for example, Japanese Patent Publication No. 52-41769 discloses benzoin or a derivative thereof. Even if the effect of preventing holes is not sufficient, or even if pinholes can be prevented, there is a problem that yellowing of the coating film is observed during baking at a high temperature or over time.

[0003]

A powder coating using a thermosetting resin composition forms a coating film having particularly excellent weather resistance and contains no volatile solvent which is detrimental to the environment. Since it is not available, it has been widely used in recent years. However, resins used in powder coatings have relatively high molecular weights,
In addition, since no solvent component is contained at the time of coating, traces of air that escapes during the formation of the coating film or volatile components generated during the curing reaction of the resin tend to appear as pinholes. In particular, there is a disadvantage that the thicker the coating film, the stronger the tendency and the appearance of the coating film is remarkably deteriorated.

There have been few reports of additives useful for preventing pinholes generated during baking and curing of such powder coatings. As described above, benzoin, which is generally widely used, does not have a sufficient effect of preventing pinholes, or a phenomenon in which a coating film turns yellow during baking or over time even when the effect is observed (so-called benzoin). Yellowing), it is difficult to use in applications where emphasis is placed on aesthetics.

An object of the present invention is to provide an additive which can prevent pinholes generated during the formation of a coating film by adding a small amount to a thermosetting powder coating material. Another object of the present invention is to provide an additive capable of preventing yellowing during baking at a high temperature or over time and preventing pinholes.

[0006]

The inventors of the present invention have studied over the years, and as a result, have found that a melting point of 80 ° C. to 200 ° C., preferably 1 ° C.
Fatty acid amide wax or fatty acid imide wax having a melting point of 20 ° C to 180 ° C, or 80 ° C to 20 ° C
It has been found that the above objects of the present invention can be achieved by adding a small amount of a substituted urea wax having a melting point of 0 ° C, preferably from 120 ° C to 180 ° C, to a thermosetting powder coating composition.

As the fatty acid amide wax, for example,
Monoamides synthesized by dehydration of fatty acid ammonium salts or ammonolysis of fats and oils (esters); condensation reaction between fatty acid amide and formaldehyde, heat condensation reaction between monocarboxylic acid and diamine or heat condensation reaction between dibasic acid and monoamine Diamide (bisamide) synthesized by polycondensation of dibasic acid and diamine, polycondensation of diamine derivative and dibasic acid, polycondensation of diamine with dibasic acid derivative or dimer acid, or ring-opening polymerization of lactam Polyamides, and the like. Also,
Examples of the fatty acid imide wax include those obtained by a condensation reaction between an acid anhydride and an amine or a dehydration reaction of a dibasic acid ammonium salt. Note that, for example, as in the case of a reaction between a dibasic acid and an amine, depending on the combination of reaction raw materials, both an amide and an imide may be generated. The object of the present invention can be achieved as long as it has a melting point within the above range.

[0008] The substituted urea wax is synthesized by an addition reaction between an amine and an isocyanate.

Many methods have been proposed for synthesizing fatty acid amide waxes, fatty acid imide waxes and substituted urea waxes, and it is possible to synthesize them using various raw materials according to those methods. The present invention is an invention relating to the use of a fatty acid amide wax, a fatty acid imide wax or a substituted urea wax, and is not at all limited by the synthetic raw materials and the synthetic methods.

As the fatty acid monoamide, commercially available reagents and products can be used. The diamide wax is synthesized by a condensation reaction between a fatty acid amide and formaldehyde or a heat condensation reaction between a carboxylic acid and an amine. Fatty acid polyamide waxes are obtained by a heat polycondensation reaction between polyamines and dimer acids or polybasic carboxylic acids, or ring-opening polymerization of lactams. Among the polyamides, commercially available nylon-6 can be used. Fatty acid imide wax is synthesized by a reaction between an acid anhydride and an amine.

Examples of the fatty acid amide for synthesizing methylenediamide by a condensation reaction between the fatty acid amide and formaldehyde include caproic amide, caprylic amide, capric amide, lauric amide, myristic amide, palmitic amide, and the like. Stearamide, behenamide, palmitoleamide, oleamide, eicosenoamide, elaidic amide, trans-11-eicosenamide, trans-
13-docosenamide, erucamide (cis-13
-Docosenoic acid amide), linoleic acid amide, linolenic acid amide, ricinoleic acid amide.

Examples of other carboxylic acids for synthesizing diamide include caproic acid, capric acid, pelargonic acid, capric acid, undecylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and the like. Oleic acid, linoleic acid, linolenic acid, 2-
Aliphatic carboxylic acids such as ethylhexyl acid, hydrogenated castor oil fatty acid, etc .; monovalent aromatic carboxylic acids such as benzoic acid, toluic acid, naphthalic acid, etc .; succinic acid,
And polybasic carboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, and maleic acid; and mixtures thereof.

Examples of the amine include alcohol amines such as monoethanolamine, diethanolamine, isopropanolamine, aminoethylethanolamine, aminopropylethanolamine, etc .; butylamine, hexylamine, octylamine, laurylamine, stearylamine Monoamines such as ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, octamethylenediamine, and 1,10-decaamine. Methylenediamine, 1,11-undecamethylenediamine, 1,
Polyamines such as 12-dodecamethylenediamine, diethylenetriamine, triethylenetetramine, xylylenediamine, isophoronediamine, and the like; and mixtures thereof.

[0014] The dimer acid used in the synthesis of polyamide is obtained by dimerizing unsaturated fatty acids.

The acid anhydride for synthesizing the fatty acid imide wax includes, for example, benzoic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride and the like. Amines.

If the melting points of the fatty acid monoamide wax, fatty acid diamide wax, polyamide wax and fatty acid imide wax are lower than 80 ° C. or higher than 200 ° C., pinholes generated during the melting and baking of the target powder coating material are reduced. It is difficult to obtain the effect of prevention.

Examples of the isocyanate for synthesizing the substituted urea include monoisocyanates such as ethyl isocyanate, propyl isocyanate, butyl isocyanate, hexyl isocyanate, octyl isocyanate, lauryl isocyanate, stearyl isocyanate, phenyl isocyanate and the like, and trimethylene. Diisocyanates such as diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, dodecamethylene diisocyanate, toluylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and the like, and examples of the amine include the amines described above. .

When the substituted urea wax has a melting point lower than 80 ° C. or higher than 200 ° C., it is difficult to obtain the effect of preventing pinholes generated at the time of melting and baking the intended powder coating.

The form of the pinhole inhibitor for powder coatings of the present invention is not particularly limited. For example, flakes may be formed on a base such as a belt flaker after synthesis (the thickness of the flakes is not limited). Can be prepared and supplied, or the prepared flakes can be supplied in powder form using a pulverizer such as a pin mill. Further, it can be used as a powdery smoothing agent for powder coatings together with an acrylic polymer as shown in JP-B-61-21977.

The method of applying the present invention to powder coatings is not different from the case of ordinary powder coating additives and is not subject to any particular restrictions, but the product of the present invention is supplied in powdered state. Therefore, it can be said that the simplest application method is to mix the powder coating composition with other compositions at the time of dry kneading before melt-kneading.

When the product of the present invention is used as an anti-pinhole agent, the amount added depends on various factors such as the properties of the powder coating system, the manufacturing conditions of the powder coating, and the coating conditions.
Without limitation, it is usually in the range of 0.1 to 10%, preferably 0.25, based on the weight of the powder coating composition.
To 3%.

[0022]

Next, the present invention will be described in more detail with reference to examples. In the following, "part" and "%"
"Parts by weight" and "% by weight" are indicated.

Production Example 1 Production of Pinhole Preventing Agent Using Fatty Acid Amide Wax or Fatty Acid Imide Wax There are various methods for synthesizing fatty acid amide wax depending on structural differences such as fatty acid monoamide, fatty acid diamide and fatty acid polyamide.

Production Examples SA-01 to SA-06 As fatty acid monoamides, commercially available reagents and industrial products were used as they were (Table 1 SA-01 to SA-06). The melting points shown in the table were measured using a differential scanning calorimeter (DSC-22C, manufactured by Seiko Instruments Inc.). Production Example SA-07 (Synthesis of methylenebisstearic acid amide)
While blowing nitrogen gas into a 2000 ml reaction vessel equipped with a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, 850 parts of a 1% sulfuric acid solution and 106 parts of stearamide were charged, and the mixture was stirred while stirring. 16.7 parts of a 1% aqueous formalin solution were slowly added dropwise. After completion of the dropwise addition, the mixture was heated to 100 ° C. and reacted for 3 hours.
00 parts were obtained. Next, 100 parts of the obtained crude product was charged into a 2000 ml reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas inlet while blowing nitrogen gas, and 1000 parts of toluene was added thereto, followed by heating. After the solid was dissolved under reflux, it was cooled to room temperature and precipitated. The precipitate was filtered using a suction filter to obtain a reaction product on filter paper. After washing with toluene three times and drying,
A fatty acid bisamide wax having a melting point of 146 ° C. shown in Table 2 SA-07 was obtained.

Production Examples SA-08 to SA-10 In Table 2, fatty acid bisamide waxes of Tables SA-08 to SA-10 were synthesized in the same manner.

Production Example SA-11 (Synthesis of hexamethylene bisstearic acid amide) Stearic acid was blown into a 2000 ml reaction vessel equipped with a stirrer, a water separator, a thermometer and a nitrogen gas inlet. 852 parts and hexamethylene diamine 1
74 parts and 100 parts of xylene as a dehydration aid were charged, and a reaction was carried out for 10 hours in a nitrogen gas stream at a temperature of 170 ° C. while removing generated water together with xylene. Of a fatty acid bisamide wax having a melting point of 145 ° C.

Production Examples In the same manner as in SA-12 to SA-24, fatty acid amide waxes in Tables SA-12 to SA-24 were synthesized.

[0028]Production Example SA-25 (Synthesis of polyamide) Stirrer, thermometer, dropping funnel,
1000 ml reaction vessel equipped with water separator and nitrogen inlet tube
While blowing in nitrogen gas, stearic acid 170.
Charge 4 parts, 56.5 parts of azelaic acid and 50 parts of xylene
And heat and dissolve at 80 ° C. Next, isophorone diamine
102.2 parts were slowly added dropwise. 175 ° C after dropping
Warm up and remove the generated water together with xylene
The dehydration condensation reaction was carried out for 5 hours while performing Table 4
A polyamide wax having a melting point of 148 ° C. as shown in No. 5 was obtained. Production Example SA-26 (Synthesis of N-stearylphthalimide)
1000 ml with flow cooler, thermometer and nitrogen inlet tube
While blowing nitrogen gas into the reaction vessel
118 parts of acid, 216 parts of stearylamine, and xylene
50 parts were charged, and at a temperature of 170 ° C. in a nitrogen gas stream, 5
The reaction was carried out for 12 hours, and the melting point was 12 as shown in Table 5 SA-26.
An imide wax at 5 ° C. was synthesized.

Preparation of Pinhole Preventing Agent The amide wax and the imide wax of SA-01 to SA-26 were each poured in a molten state onto a cooled stainless steel plate to form a flake having a thickness of about 2 mm. After sufficiently cooling this flake, it is pulverized with a pin mill and
The powder obtained by passing through a 2-mesh sieve was used as a pinhole inhibitor for powder coatings.

[Production Comparative Example 1] Production Comparative Examples NA1-01 to NA-03 Purchased waxes having melting points such as monoamides shown in Table 6 NA-01 and NA-02 and polyamide (nylon) shown in NA-03. Then, it was pulverized to 32 mesh or less in the same manner as in Production Example 1 to obtain a comparative sample.

[Production Example 2] Production example of pinhole inhibitor using substituted urea wax SU-01 (Synthesis of toluylene bisstearyl urea) Stirrer, reflux condenser, dropping funnel, thermometer and nitrogen gas injection 16.8 parts of toluylene diisocyanate and 635 parts of acetone were charged into a 2000 ml reaction vessel equipped with a mouth while blowing nitrogen gas, and 53.8 parts of stearylamine was added to the reaction vessel while stirring in an ice bath. It was added dropwise over 1 hour. After completion of the dropwise addition, stirring was continued for 3 hours to terminate the reaction. This reaction product was filtered using a suction filter to obtain a reaction product on filter paper. After washing with acetone three times and drying, a substituted urea wax having a melting point of 172 ° C. shown in Table 7 SU-01 was obtained.

Preparation Examples SU-02 to SU-06 Substituted urea waxes of SU-02 to SU-06 in Table 7 were synthesized in the same manner as in Preparation Example SU-01.

Preparation of Pinhole Preventing Agent The obtained substituted urea wax was poured in a molten state onto a cooled stainless steel plate to prepare flakes having a thickness of about 2 mm. After sufficiently cooling this flake, it was pulverized with a pin mill, and the powder obtained by passing through a 32 mesh sieve was used as a pinhole inhibitor for powder coatings.

[Production Comparative Example 2] Table 8 NU-01 and N in the same manner as in Production Comparative Example NU-01 and NU-02 Production Example SU-01
A substituted urea wax having a melting point as shown in U-02 was obtained.
The obtained substituted urea wax was treated in the same manner as in Production Example 1 to give 3
It was pulverized to 2 mesh or less to obtain a comparative sample.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

Both NA-01 and NA-02 are products of Nippon Kasei Co., Ltd.

NA-03 is a product of Toray Industries, Inc.

[0043]

[Table 7]

[0044]

[Table 8]

Example 1 Test with Polyester Powder Coating (Preparation of Masterbatch) A polyester resin (M-8050) to be used was melted at 180 ° C., and 10%
PCL-40 (a leveling agent for acrylic powder coatings manufactured by Kusumoto Kasei Co., Ltd.) was uniformly dispersed with a disper while stirring at a high speed so as to obtain a concentration. After cooling, the mixture was pulverized with a pin mill and passed through a 32 mesh sieve to obtain a 10% polyester resin master batch composition.

(Preparation of Polyester Powder Coating) Production Example 1
Then, the compounds shown in Tables 1 to 8 powdered by the operation of Production Example 2 were added to a standard polyester-based powder paint having the composition shown in Table 9 and dry-mixed. 11
The mixture was melted and kneaded with an extruder kept at 5 ° C. After cooling, the mixture was pulverized with a pin mill and passed through a 150-mesh sieve to obtain a white powdery powder coating composition.

[0047]

[Table 9]

The polyester resin and the epoxy resin are products of Dainippon Ink and Chemicals, Inc.

Cleran UI is a product of Sumitomo Bayer Urethane Co., Ltd.

R-930 is a product of Ishihara Sangyo Co., Ltd.

RCL-40 is a leveling agent for acrylic powder coatings manufactured by Kusumoto Kasei Co., Ltd.

(Evaluation and Application of Polyester Powder Coating) Then, the obtained powder was cured to a film thickness of 200 μm or 50 μm.
Sprayed on a heat-resistant stainless steel plate (0.5 × 70 × 100 mm) by an electrostatic powder coating method, then baked a 200 μm coated plate at 180 ° C. for 30 minutes, and then pinhole and leveling the coating surface The 50 μm coated plate was baked at 180 ° C. for 2 hours and then evaluated for yellowing. Table 10 shows the results.

[0053]

[Table 10]

Pinholes: number 0 (value 5) to number 20
Five-level evaluation of the above (value 1) Leveling: Five standard coating plates were prepared from extremely good (value 5) to extremely uneven coating (value 1) and evaluated. Yellowing property: No addition was value 5 (good yellowing) 5) Standard coating plates were prepared and evaluated for the worst yellowing (value 1). [Example 2] Test with acrylic powder coating (Preparation of acrylic powder coating) First, PCL was prepared in the same manner as in Example 1. A -40 10% acrylic resin (Fine Dick A-223S) master batch was prepared. Next, the compounds shown in Tables 1 to 8 which were powdered by the operations of Production Examples 1 and 2 were added to a standard acrylic powder paint having the composition shown in Table 11 and then dry-mixed. And melt-kneading with an extruder kept at 95 ° C to 105 ° C.
After cooling, the mixture was pulverized with a pin mill and passed through a 150-mesh sieve to obtain a white powdery powder coating composition.

[0055]

[Table 11]

The acrylic resin and the epoxy resin are products of Dainippon Ink and Chemicals, Inc. Dodecanedicarboxylic acid is a product of Ube Industries, Ltd.

(Coating and Evaluation of Acrylic Powder Coating)
The obtained powder is heat-resistant stainless steel sheet 0.5 × 7 by electrostatic powder coating so that the cured film thickness becomes 200 μm.
(0 × 100 mm) and then baked at 180 ° C. for 20 minutes, and the pinhole and leveling properties of the coating film surface were evaluated. Table 12 shows the results.

[0058]

[Table 12]

The evaluation criteria are the same as in Table 10.

Example 3 Test with Epoxy Powder Coating (Preparation of Epoxy Powder Coating) First, a 10% epoxy state of PCL-40 (GT-700) was prepared in the same manner as in Example 1.
4) A master batch was created. Next, the compounds shown in Tables 1 to 8 powdered by the operations of Production Example 1 and Production Example 2 were added to a standard epoxy-based powder paint having the composition shown in Table 13 and dry-mixed. And melt kneading with an extruder maintained at 105 ° C to 115 ° C. After cooling, pulverize with a pin mill, pass through a 150 mesh sieve,
A white powdery powder coating composition was obtained.

[0061]

[Table 13]

GT-7004 is a product of Dainippon Ink and Chemicals, Inc.

HT-2844 is a product of Nippon Ciba Geigy Co., Ltd.

(Coating and Evaluation of Epoxy Powder Coating)
The obtained powder is heat-resistant stainless steel sheet (0.5 ×) by electrostatic powder coating so that the cured film thickness becomes 200 μm.
70 × 100 mm) and then at 180 ° C. for 15
After baking for minutes, the pinholes on the surface of the coating film and the leveling property were evaluated. Table 14 shows the results.

[0065]

[Table 14]

The evaluation criteria are the same as in Table 10.

[0067]

From the results of Tables 10, 12 and 14, it is clear that all of the fatty acid amide wax, the fatty acid imide wax and the substituted urea wax are added in small amounts to the thermosetting powder coating composition. As a result, it is understood that the effect of preventing pinholes is brought about. Also, from the results in Table 10, it can be seen that these waxes have less yellowing at the time of high-temperature baking than benzoin.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Horiguchi 1525 Hikawacho, Soka City, Saitama Prefecture Cowbell 105 (72) Inventor Shigehiro Kawahito 536-1 Kiyomoncho, Soka City, Saitama Prefecture

Claims (2)

[Claims] 1. A fatty acid amide wax or fatty acid imide wax having a melting point of 80 ° C. to 200 ° C.,
Pinhole inhibitor for powder coatings. 2. A pinhole inhibitor for powder coatings comprising a substituted urea wax having a melting point of 80 ° C. to 200 ° C.