JP2001098216A - Powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating that can be widely applied onto a general zinc-plated steel sheet or plate without causing the problems of primary adhesiveness and secondary one of a coating film of the conventional powder coating to a zinc-plated steel sheet or plate. SOLUTION: This powder coating composition contains a hydroxyl group- terminated polyester resin (a base resin) and a blocked isocyanate (a curing agent) and contains, as an additive resin in the powder coating, and 3-40 wt.%, preferably 5-20 wt.% one or more of an acrylic resin, a polyester urethane resin, a polyester resin, a styrene resin and a polyethylene resin each having a number average molecular weight of 8,000-100,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating composition coated on a galvanized steel sheet and having good adhesion between a zinc layer and the powder coating.

[0002]

2. Description of the Related Art Conventionally, when a powder coating is applied on a galvanized steel sheet, there are many problems that the powder coating peels off from a zinc layer of the galvanized steel sheet. Powder paints are solvent-free paints that have less pollution and are less harmful.Moreover, they have good workability.They have good performance, but the above problems may occur. there were.

[0003]

As described above, when the current powder coating is applied on a galvanized steel sheet, the primary adhesion,
There was a problem that a problem such as peeling occurred in the secondary adhesion.

[0004]

Accordingly, the present inventors have developed a powder coating that does not cause peeling even when coated on a galvanized steel sheet, and have added a powder coating that improves the adhesion to existing powder coatings. By adding a resin or adding a certain amount of extender pigment, we succeeded in developing a powder coating with good primary adhesion and secondary adhesion.

As a result, the coating of the powder coating on the galvanized steel sheet has been successfully prevented from peeling off from the galvanized steel sheet while maintaining the usual good performance and good workability of the powder coating.

That is, the present invention relates to a powder coating containing a hydroxyl group-terminated polyester resin (main resin) and a blocked isocyanate (curing agent), wherein an acrylic resin having a number average molecular weight of 8,000 to 100,000 as an additional resin is contained in the coating. Resin, polyester urethane resin, polyester resin, styrene resin, polyethylene resin
Species, or two or more species, 3 to 40% by weight, preferably 5 to 20%
It is a powder coating composition containing by weight.

[0007]

DETAILED DESCRIPTION OF THE INVENTION As described above, the powder coating composition of the present invention has a number average molecular weight of 8,000 to 1,000 as a hydroxyl group-terminated polyester resin, a curing agent, and an additive resin.
No. 00 contains an acrylic resin, a polyester resin, a polyester urethane resin, a styrene resin, a polyethylene resin, etc., but further contains an extender pigment as necessary.

The hydroxyl-terminated polyester resin used in the present invention is preferably a hydroxyl-terminated polyester resin used in ordinary powder coatings, and has a hydroxyl value of from 20 to 5
5 are used. Examples of the hydroxyl-terminated polyester resin include ER6610 / ER66 manufactured by Nippon Ester Co., Ltd.
20 ・ ER6570 ・ ER6800 ・ ER6640 ・ E
R6650 / ER7400 / ER7300 etc., M8050 / M8010 / M8100 manufactured by Dainippon Ink & Chemicals, Inc.
・ M8051 ・ M8020 ・ M8075 ・ M8021
GV120, GV150, GV70 manufactured by Yupika Japan
0 ・ GV740 ・ GV746 ・ GV500 ・ GV110
GV152, etc., and other hydroxyl-terminated polyester resins for powder coatings can also be used. As a curing agent for such a hydroxyl group-terminated polyester resin, a blocked isocyanate is used. As the isocyanate, an aliphatic or aromatic compound can be used, and a blocked product of IPDI, hydrogenated MDI, TDI, MDI, a non-blocked polyuretdione, or the like can be used. It can be used, for example, B1530 / BF15 manufactured by Huls.
40 ・ B1300 Alcure made by Maxwater
4400 ・ Alcure4430 ・ Alcure443
1. Alcure4450, Alcure4470 Bayer Corporation CrelanUI CleranVPLS2
151 CrelanVPLS2007 Crelan
VPLS2122 CrelanVPLS2147 VXL9935 / VXL9466 manufactured by Hoechst.

The ratio of the resin to the curing agent in the powder coating is preferably within a range of ± 10% of 1/1 of the equivalent of the resin and the equivalent of the curing agent. The number average molecular weight used in the present invention is 8000 to 10
As the added resin of 000, a usual resin can be used. For example, a polyester urethane resin such as Parsen U-100B manufactured by Nippon Polyurethane Co., Ltd., and a polyester resin such as Vestagon EP-P-10 manufactured by Huls Co., Ltd.
0 etc., acrylic resin made by Takeda Pharmaceutical Company
Lloyd AC-4030, AC-3832, AC-335
No. 5, Staphyloid GS-10 as a styrene resin
2R, staphyroid GM-0401S, etc., and a polyethylene resin such as Sumitomo Seika Chemical's Flowsen UF can be used. In addition, other materials having properties equivalent to these can be used. When the number average molecular weight is less than 8000, the adhesion is not sufficiently improved, and the number average molecular weight is 100,000.
If the ratio exceeds, dispersion and the like during powder coating production are difficult to perform, and it becomes difficult to produce powder coatings. On the other hand, if the addition amount is less than 3% by weight, the adhesion cannot be sufficiently improved, and if it exceeds 40% by weight, the curability of the powder coating becomes poor and the general performance becomes poor. Gets worse.

The extender used in the present invention is not particularly limited as long as it is an extender usually used in paints.
Barium sulfate, calcium carbonate and the like are preferred. The extender is 0 to 30% by weight, preferably 0 to 15% by weight.
contains. If the extender exceeds 30% by weight, general physical properties become poor and workability deteriorates.

The powder coating composition of the present invention comprises, in addition to the above components, a coloring pigment used in a general powder coating,
It may contain a fluidity adjusting agent, an anti-blocking agent, an ultraviolet absorber, an ultraviolet stabilizer, a surface adjusting agent, an anti-bake agent, a charge controlling agent, a curing accelerator, an epoxy resin and the like.

The method for producing the powder coating composition of the present invention is the same as the method for producing a normal powder coating composition, in which a resin, a curing agent, a pigment, additives and the like are pre-blended by a mixer or the like, and then mixed. After melt blending by passing through a kneader,
After cooling, coarse pulverization and fine pulverization, those that need to be added later can be adjusted by performing post addition and filtering.

The coating can be performed by a known electrostatic powder coating method. For example, the coating can be performed on an object to be coated by a corona charging method, a friction charging method or the like. The amount of charge of the corona charging method is set according to each painted object. In addition, the coating gun of the triboelectric charging system can be set according to each object to be coated. The coating film forming (baking) method is set in accordance with the baking temperature and the baking time suitable for each paint, as in the baking of ordinary powder paint. The coating thickness is 40 ~
A range of 90 μm is preferred.

[0014]

The present invention will be described below based on examples and comparative examples. The powder coatings of Examples 1 to 8 and Comparative Examples 1 to 4 having the composition shown in Tables 1 to 3 were produced by the above-described production method, and were subjected to the coating method and the coating film formation (baking) method described above. (Zinc basis weight 270 g / m ³ ) to form a coating film. The results of the performance test of the coating film obtained by these methods,
As shown in Tables 1 to 3, the powder coatings of the examples had no problem with the primary adhesion, the adhesion after 240 hours of the constitution test, and the adhesion after 1 hour and 3 hours of the boiling water test. . The powder coating shown in the comparative example has good primary adhesion and physical properties,
There were problems with the adhesion after 240 hours of the moisture resistance test and the adhesion after 1 hour and 3 hours of the boiling test. The results of other performance tests also showed that the paints of the examples tended to be better than the current paints.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

All baking was performed at 180 ° C. × 20 minutes while holding the substrate. All performance tests used galvanized steel sheets with a basis weight of 275 g / m ³ . * 1 Hydroxyl-terminated polyester resin manufactured by Dainippon Ink Co., Ltd. M8100 hydroxyl value = 30 M8021 hydroxyl value = 30 * 2 Hydroxyl-terminated polyester resin manufactured by Nippon Yupika GV701 hydroxyl value = 30 GV540 hydroxyl value = 33 * 3 Hydroxyl-terminated polyester resin manufactured by Nippon Ester Co., Ltd. Resin ER6640 hydroxyl value = 30 ER6700 hydroxyl value =
40 * 4 Hydroxyl-terminated polyester resin manufactured by McWHORTER, Inc. Albester 120 hydroxyl value = 50 * 5 Epoxy resin manufactured by Toto Kasei * 6 Blocked isocyanate hardener manufactured by Huls * 7 Resin manufactured by Nippon Polyurethane * 8 Added resin manufactured by Huls * 9 Takeda Additive resin manufactured by Yakuhin Kogyo Co., Ltd. * 10 Flow agent manufactured by Monsanton Co., Ltd. * 11 Benzoin may be used * 12 Tin catalyst manufactured by Takeda Yakuhin Co., Ltd. 15 Sumitomo Seika Chemical's polyethylene resin * 16 McWHORTER's block isocyanate curing agent

* 1. Numerical values in the composition represent parts by weight. * 2. Explanation of the test method The number of pieces remaining by the method of the cross cut test K5400 8.5 is displayed. Judgment was passed when 100 of the 100 remained. Fail if any peeled off. * 3. ◎ of physical property judgment is 5 at impact 500g 1 / 2φ
0cm Erichsen 6mm <Bending 10φ passed △: Impact of 500g 1 / 2φ 40cm Erichsen 4mm bending 10φ passed Overall judgment of ◎ indicates that physical properties and adhesion were acceptable. × is
When one or both of physical properties and each adhesion are rejected.

[0020]

When the powder coating composition of the present invention is applied to a galvanized steel sheet, the conventional powder coating compositions have problems with the primary adhesion and the secondary adhesion properties. It can be widely applied on general galvanized steel sheet without generation.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayasu Masayasu 6-10-73 Minamitsukaguchi-cho, Amagasaki City, Hyogo Prefecture Shinto Paint Co., Ltd. F-term (reference) 4D075 AA09 BB26Z BB92Z CA13 DB05 EA02 EB13 EB22 EB35 EB38 EC11 EC13 EC37 4J038 CB022 CC032 CG142 DD002 DG111 DG112 DG301 HA286 HA376 KA08 MA02 MA14 NA12

Claims (2)

[Claims] 1. A powder coating containing a hydroxyl group-terminated polyester resin (main resin) and a blocked isocyanate (curing agent), wherein an acrylic resin having a number average molecular weight of 8,000 to 100,000 as an additional resin in the coating. One or more of polyester urethane resin, polyester resin, styrene resin and polyethylene resin
A powder coating composition containing up to 40% by weight, preferably 5 to 20% by weight. 2. The powder coating composition according to claim 1, wherein the content of the extender pigment is 0 to 30% by weight, preferably 0 to 15% by weight.