JP4619062B2 - Smoothing agent for powder coating - Google Patents

Description

  The present invention relates to a novel smoothing agent for powder coating, which is intended to impart smoothness to a coating film by adding a small amount to the powder coating.

  Powder coatings generally have poor smoothness compared to solvent-based coatings, and therefore tend to be difficult to use in applications that require a high appearance. However, in recent years, attempts have been made to use powder coatings instead of solvent-based coatings as a countermeasure against environmental pollution. For example, the use for top coats for automobiles is being studied. Accordingly, a smoother for powder coatings is required to have higher functionality, and various types are provided.

  For example, Patent Document 1 describes a method of using a copolymer of a long-chain alkyl acrylate and an N-containing olefin as a leveling agent for powder coatings. The leveling agent of Patent Document 1 is described as a copolymer of a long-chain alkyl acrylate having 16 to 34 carbon atoms in the alkyl group and an N-containing olefin.

  Patent document 2 describes the surface modifier for coating materials, and a coating composition. Patent document 2 aims at obtaining the surface modifier for coatings from which the coating film excellent in leveling property, stain resistance, and water repellency is obtained, and surface modifier is acrylic acid perfluoro octyl ethyl ester and acrylic acid. It is described as a copolymer obtained by copolymerizing a stearyl ester with lauryl mercaptan and azobisisobutyronitrile in turpentine.

  U.S. Patent No. 6,057,031 describes a thermosetting powder coating composition containing a flow modifier. Patent Document 3 aims to provide a method for providing a composite coating on a substrate, wherein the flow modifier is an alkyl acrylate or methacrylate having 6 to 12 carbon atoms in the alkyl group, And a copolymer of hydroxyalkyl acrylate or methacrylate.

  Patent Document 4 describes an acrylic polymer copolymer and a leveling agent for powder coatings containing the copolymer as a component. The leveling agent of Patent Document 4 has at least one structure selected from alkyl (meth) acrylates having 2 to 22 carbon atoms in the alkyl group and alkenyl (meth) acrylates having 2 to 22 carbon atoms in the alkenyl group. It is described as an acrylic polymer copolymer comprising a unit (A) and a structural unit (B) of an isocyanate-modified acrylic compound in which a monocarboxylic acid or a monoamine is bonded, and having a number average molecular weight of 4,000 to 100,000.

  Patent Document 5 describes a reactive flow control agent for powder coating and a powder coating. Patent Document 5 adjusts the fluidity of the powder coating when melted by reacting with the main resin by blending it with the acid curable powder coating, and thereby has excellent smoothness and excellent even in the case of a thin coating thickness. The flow modifier is a monobasic acid compound having an amide bond or an ester bond, and has a melting point. It is described as a compound having a solubility parameter in the range of 9.5 to 11 at 50 to 180 ° C.

  Patent Document 6 describes a leveling agent for powder coatings. The leveling agent of patent document 6 is described as polyvinylethyl ether, advantageously a homopolymer having a molecular weight distribution Mn = 800-10000, preferably 1000-5000.

Patent document 7 describes a leveling agent for surface coating. Patent document 7 aims to provide a completely leveling coating film, in particular a new leveling agent for obtaining powder coating, the leveling agent has a weight average molecular weight of 5,000 to 100,000, and is radical polymerization. Or a branched polymer having a base molecule polymerized by ion polymerization, wherein the base molecule has an ethylenically unsaturated bond at the end, and the weight average molecular weight is 1000 to 30000. The macromonomer unit is incorporated by radical copolymerization or ionic copolymerization, and the weight ratio of the macromonomer unit is from 1 to 2 based on the total weight of the branched polymer.
60% by weight.

Japanese Patent Laid-Open No. 2-102275 JP-A-6-240201 JP-A-8-325480 JP-A-10-158336 JP-A-8-34881 Japanese National Patent Publication No. 11-515052 JP 2002-179991 A

  However, it is difficult to say that conventional technology can provide sufficient smoothness in fields that require high appearance such as automotive applications that have been studied in recent years. Adverse effects such as whitening in hot water tests were often seen. Accordingly, an object of the present invention is to provide a smoothing agent that can be used for applications requiring a high appearance, which has not been obtained with conventional powder coating smoothing agents.

  According to the present invention, from a copolymer obtained by copolymerizing a dibasic acid ester (A) having a polymerizable unsaturated double bond and an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester (B). The copolymer is obtained by copolymerizing a monomer blend containing 2 to 65% by weight of (A) and 35 to 98% by weight of (B) in all monomers, and 1000 A smoothing agent having a number average molecular weight of ˜60000 is provided, and the above problem can be solved by blending it with a powder coating material.

  The smoothing agent of the present invention can impart excellent smoothness to the coating film when added to a powder coating.

  When the proportion of the monomer (A) in the total monomer blending is less than 2% by weight or more than 65% by weight, sufficient smoothness cannot be obtained. As long as the ratio of monomer (A) to monomer (B) is in the range of 2 to 65% by weight to 35 to 98% by weight, monomers other than monomer (A) and monomer (B) ( Sufficient smoothness can be obtained even when the proportion of C) is 45% by weight or less.

  When the number average molecular weight of the copolymer is smaller than 1000 or larger than 60000, sufficient smoothness cannot be obtained. A preferable range of the number average molecular weight is 1500 to 20000. A more preferred range is 2000 to 10,000.

  Examples of the monomer (A) include maleic acid di (mono) methyl ester, maleic acid di (mono) ethyl ester, maleic acid di (mono) normal propyl ester, maleic acid di (mono) isopropyl ester, maleic acid diester (Mono) normal butyl ester, maleic acid di (mono) isobutyl ester, maleic acid di (mono) normal octyl ester, maleic acid di (mono) 2-ethylhexyl ester, maleic acid di (mono) isononyl ester, maleic acid di (Mono) lauryl ester, maleic acid di (mono) stearyl ester, maleic acid di (mono) benzyl ester, fumaric acid di (mono) methyl ester, fumaric acid di (mono) ethyl ester, fumarate di (mono) normal propyl Esters, di (mono) isopropyl fumarate Tellurium, di (mono) normal butyl ester of fumaric acid, di (mono) isobutyl ester of fumaric acid, di (mono) normal octyl ester of fumaric acid, di (mono) 2-ethylhexyl fumarate, di (mono) isononyl fumarate Esters, fumaric acid di (mono) lauryl ester, fumaric acid di (mono) stearyl ester, fumaric acid di (mono) benzyl ester, itaconic acid di (mono) methyl ester, itaconic acid di (mono) ethyl ester, itaconic acid di (Mono) normal propyl ester, itaconic acid di (mono) isopropyl ester, itaconic acid di (mono) normal butyl ester, itaconic acid di (mono) isobutyl ester, itaconic acid di (mono) normal octyl ester, itaconic acid di (mono) ) 2-ethylhexyl ester, a Con di (mono) isononyl ester, itaconic di (mono) lauryl ester, itaconic di (mono) stearyl ester, itaconic di (mono) benzyl ester. These may be used alone or in combination of two or more.

  Examples of the monomer (B) include (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, (meth) acrylic acid normal propyl ester, (meth) acrylic acid isopropyl ester, and (meth) acrylic acid normal butyl ester. Ester, (meth) acrylic acid isobutyl ester, (meth) acrylic acid tertiary butyl ester, (meth) acrylic acid normal octyl ester, (meth) acrylic acid 2-ethylhexyl ester, (meth) acrylic acid isononyl ester, (meta ) Acrylic acid lauryl ester, (meth) acrylic acid stearyl ester, (meth) acrylic acid cyclohexyl ester, (meth) acrylic acid isobornyl ester, and the like.

  There is no restriction | limiting in a monomer (C), It can use individually or in combination of 2 or more types. Examples of the monomer (C) include (meth) acrylic acid 2-methoxyethyl ester, (meth) acrylic acid 2-ethoxyethyl ester, (meth) acrylic acid 2-butoxyethyl ester, (meth) acrylic acid 2-octoxy Ethyl ester, (meth) acrylic acid 2-lauroxyethyl ester, (meth) acrylic acid 3-methoxybutyl ester, (meth) acrylic acid 4-methoxybutyl ester, (meth) acrylic acid ethyl carbitol ester, (meth) Methoxypolyethylene glycol acrylate (ethylene glycol polymerization number 2 to 50) ester, (meth) acrylic acid methoxypolypropylene glycol (propylene glycol polymerization number 2 to 50) ester, (meth) acrylic acid methoxypoly (ethylene- Propylene) glyco (Ethylene glycol-propylene glycol polymerization number 2 to 50) ester, (meth) acrylic acid ester such as (meth) acrylic acid nonylphenoxypolyethylene glycol ester; acrylamide, N, N-dimethylacrylamide, N, N- Acrylamides such as diethylacrylamide, N-isopropylacrylamide, diacetoneacrylamide, acroylmorpholine; aromatic hydrocarbon vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, vinyltoluene; 3-methacryloxypropyltrimethyl Organosilicon compounds such as silane, 3-methacryloxypropyltris (trimethylsiloxy) silane, vinyltris (trimethylsiloxy) silane; vinyl acetate, vinyl propionate, diallyl Vinyl esters such as tarates and allyl compounds; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, normal propyl vinyl ether, isopropyl vinyl ether, normal butyl vinyl ether, isobutyl vinyl ether, tertiary butyl vinyl ether, normal octyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether; And other vinyl compounds such as vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, and fluoroolefin maleimide.

  In the above description, maleic acid di (mono) methyl ester represents maleic acid dimethyl ester and maleic acid monomethyl ester (the same applies to others), and (meth) acrylic acid methyl ester represents acrylic acid methyl ester and methacrylic acid methyl ester ( Others are the same).

  As a method for synthesizing the copolymer used in the present invention, there are an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, and the like. In addition, as an initiator for polymerization, a commonly used azo polymerization is used. An initiator or a peroxide is used. Since the present invention relates to the function of the copolymer, it is not limited by the method for synthesizing the copolymer.

  The paint suitable for the powder coating smoothing agent obtained in the present invention is a powder paint that requires a high appearance, and a high appearance polyester powder mainly composed of an acrylic powder paint for automobile top coat and a PCM paint for home appliances. And body paints.

  The method of adding the smoothing agent for powder coatings according to the present invention to the coating is a method using a masterbatch with the resin to be used, or adding a powdered mixture with organic wax at the time of premixing the coating preparation. desirable.

  The addition amount of the powder coating smoothing agent according to the present invention varies depending on the type of coating resin, the composition of the pigment, etc., but is usually 0.01 to 5% by weight, preferably in terms of solid content, based on the coating vehicle, 0.1 to 2% by weight. If the amount added is less than 0.01% by weight, the smoothness cannot be sufficiently provided. Further, if it is added in an amount of more than 5% by weight, the possibility of adversely affecting the physical properties of the coating film increases, which is not preferable.

  Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the following, “parts” and “%” represent “parts by weight” and “% by weight”, respectively.

Production Example 1
A 1000 ml reaction vessel equipped with a stirrer, reflux condenser, dropping funnel, thermometer, and nitrogen gas inlet is charged with 150 parts of toluene, heated to 110 ° C. while introducing nitrogen gas, and shown below. The dropping solution (a-1) was dropped at a constant rate with a dropping funnel in 2 hours.
Dropping solution (a-1)
Acrylic acid normal butyl ester 188 parts Maleic acid dinormal butyl ester 112 parts Toluene 73 parts t-Ammylperoxy-2-ethylhexanoate 12.5 parts 1 hour after completion of dropwise addition of dropping solution (a-1) and 2 hours Later, 1.5 parts each of t-amylperoxy-2-ethylhexanoate was added, and the mixture was further reacted for 1.5 hours while maintaining at 110 ° C. After completion of the reaction, toluene was removed with a rotary evaporator to obtain an additive [A-1]. The number average molecular weight in terms of polystyrene by the gel permeation chromatograph of the synthesized copolymer was 2500.

Production Example 2
Additive [A-2] was obtained in the same manner as in Example 1 except that the following dropping solution (a-2) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (a-2)
Acrylic acid normal butyl ester 184 parts Itaconic acid di-normal butyl ester 116 parts Toluene 73 parts t-Ammylperoxy-2-ethylhexanoate 12.5 parts Number of polystyrene conversion by gel permeation chromatography of the synthesized copolymer The average molecular weight was 3000.

Production Example 3
Additive [A-3] was obtained in the same manner as in Example 1 except that the following dropping solution (a-3) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (a-3)
Acrylic acid isobutyl ester 207 parts Maleic acid diethyl ester 93 parts Toluene 73 parts t-Ammylperoxy-2-ethylhexanoate 12.5 parts The number average molecular weight in terms of polystyrene of the synthesized copolymer by gel permeation chromatography is 2700.

Production Example 4
Additive [A-4] was obtained in the same manner as in Example 1 except that the following dropping solution (a-4) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (a-4)
Acrylic acid isobutyl ester 207 parts Fumaric acid diethyl ester 93 parts Toluene 73 parts t-Ammylperoxy-2-ethylhexanoate 12.5 parts The number average molecular weight in terms of polystyrene by gel permeation chromatography of the synthesized copolymer is 2500.

Production Example 5
Additive [A-5] was obtained in the same manner as in Example 1 except that the following dropping solution (a-5) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (a-5)
Acrylic acid lauryl ester 180 parts Acrylic acid 2-ethylhexyl ester 60 parts Maleic acid normal octyl ester 175 parts Toluene 58 parts t-Ammylperoxy-2-ethylhexanoate 8 parts Gel permeation chromatograph of the synthesized copolymer The number average molecular weight in terms of polystyrene was 5400.

Production Comparative Example 1
Additive [N-1] was obtained in the same manner as in Example 1, except that the following dropping solution (n-1) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (n-1)
Acrylic acid isobutyl ester 300 parts Toluene 150 parts t-Amylperoxy-2-ethylhexanoate 15 parts The number average molecular weight in terms of polystyrene of the synthesized polymer by gel permeation chromatography was 6000.

Production Comparative Example 2
Additive [N-2] was obtained in the same manner as in Example 1, except that the following dropping solution (n-2) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (n-2)
Acrylic acid normal butyl ester 40 parts Itaconic acid di-normal butyl ester 110 parts Toluene 100 parts t-Ammylperoxy-2-ethylhexanoate 7.5 parts Number of polystyrene conversion by gel permeation chromatography of the synthesized copolymer The average molecular weight was 3400.

Production Comparative Example 3
Additive [N-3] was obtained in the same manner as in Example 1, except that the following dropping solution (n-3) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (n-3)
Acrylic acid normal butyl ester 90 parts Maleic acid di-normal butyl ester 55 parts Toluene 250 parts t-Ammylperoxy-2-ethylhexanoate 12.5 parts Number of polystyrene conversion by gel permeation chromatography of the synthesized copolymer The average molecular weight was 800.

Production Comparative Example 4
Additive [N-4] was obtained in the same manner as in Example 1, except that the following dropping solution (n-4) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (n-4)
Acrylic acid normal butyl ester 188 parts Maleic acid normal butyl ester 112 parts Toluene 25 parts t-Ammylperoxy-2-ethylhexanoate 0.2 parts The number of polystyrene conversion by gel permeation chromatography of the synthesized copolymer The average molecular weight was 75000.

Production Comparative Example 5
Additive [N-5] was obtained in the same manner as in Example 1, except that the following dropping solution (n-5) was used instead of the dropping solution (a-1) in Production Example 1.
Drop solution (n-5)
150 parts normal butyl vinyl ether 150 parts normal butyl vinyl ether 150 parts toluene 73 parts t-amylperoxy-2-ethylhexanoate 12.5 parts Polystyrene conversion by gel permeation chromatography of the synthesized copolymer The number average molecular weight was 4000.

Production Comparative Example 6
BYK354 (manufactured by BYK-Chemical Co., Ltd.) was used as a smoothing agent for the acrylic polymer. This was designated as additive [N-6].

Production Comparative Example 7
KP322 (manufactured by Shin-Etsu Silicon Co., Ltd.) was used as a silicone leveling agent. This was designated as an additive [N-7].

Paint test example 1 (Smoothness test with clear powder paint)
A smoothness test was conducted on the acrylic clear powder coating composition having the composition shown in Table 3.

(Create master batch)
The acrylic resin (PD-3402) to be used was melted at 170 ° C., and the leveling agents shown in Tables 1 and 2 were uniformly dispersed therein while stirring at high speed with a disper so that the solid content would be 10%. After cooling, it was pulverized with a pin mill and passed through a 32 mesh sieve to obtain a 10% acrylic resin master batch composition.

(Create acrylic powder paint)
The acrylic powder coating material having the composition shown in Table 3 containing the masterbatch composition prepared by the above method was dry-mixed and then melt-kneaded with an extruder maintained at 90 to 100 ° C. After cooling, the mixture was pulverized with a pin mill and passed through a 150-mesh sieve to obtain a white powdery clear powder coating composition.

(Acrylic powder coating)
Two heat-resistant stainless steel plates (0.5 × 70 × 100 mm) were prepared for each additive, and the prepared powder coating powder was sprayed by an electrostatic powder coating method so that the cured film thickness was 60 μm. . Next, this coated plate was baked at 150 ° C. for 20 minutes.

(Evaluation of smoothness of acrylic powder coating)
For the evaluation of smoothness, the appearance of the skin was visually evaluated in five stages from “best” (5) to “worst” (1). In addition, SW values (Short Wave) and LW values (Long Wave) by wave scan (manufactured by Big Chemie) were also digitized. This is a numerical value indicating whether the smoothness is good or bad. The lower the value, the better the smoothness. In addition, the number of repellents and craters seen in the coating film was visually counted and evaluated in five stages from “best” (5) to “worst” (1).

Paint test example 2 (Evaluation of water whitening resistance)
The coated plate prepared in Paint Test Example 1 was immersed in warm water at 80 ° C. for 1 hour and allowed to cool naturally while immersed. After standing to cool, the coating film was dried at room temperature, and the whitening was visually evaluated in five stages from “best” (5) to “worst” (1).

Table 4 shows the results of the above test.

Claims (2)

  Comprising a copolymer obtained by copolymerizing a dibasic acid ester (A) having a polymerizable unsaturated double bond and an alkyl acrylate ester and / or an alkyl methacrylate ester (B), the copolymer Is obtained by copolymerizing a monomer blend containing 2 to 65% by weight of (A) and 35 to 98% by weight of (B) in all monomers, and has a number average molecular weight of 1000 to 60000 A smoothing agent for powder coatings, comprising:   The smoothing agent for powder coatings according to claim 1, wherein (A) is maleic acid diester, maleic acid monoester, fumaric acid diester, fumaric acid monoester, itaconic acid diester or itaconic acid monoester.