JPH0794638B2 - Anti-chipping coating composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a chipping-resistant coating composition suitable for coating, for example, vehicles, chemical plants and building materials.

[Prior Art] The body of an automobile is coated to prevent corrosion of the substrate. The coating generally has a multilayer structure including at least an electrodeposition coating layer, an intermediate coating and an overcoat layer. Particularly, the overcoat layer is required to have beautiful gloss in addition to weather resistance.

Japanese Patent Publication No. 60-11989 discloses a paint using benzoin as an additive, and Japanese Patent Laid-Open Publication No. 56-58564 discloses a method for forming a coating film in which a baking process is set in two stages. These coating layers, weather resistance, and workability of coating almost meet various characteristics, but there are many unsolved problems regarding chipping resistance. That is, if a pebbles on the road bounce up and collide with the painted surface of the body when the vehicle is moving, the paint peels off due to the impact. Even if peeling of the coating remains on the topcoat layer, the scratches (chipping) that occur are deep because each coating layer is hard, and the steel sheet substrate is penetrated from the topcoat layer to the intermediate coating layer and the electrodeposition coating layer. Reach. When water enters from there, rust is generated, which is very inconvenient. Further, Japanese Patent Application Laid-Open No. 56-57855 discloses a high film thickness type coating in which the kind, amount and particle size distribution of the pigment are specified. However, although this paint also has a good finished appearance and workability, it does not have sufficient chipping resistance as the above-mentioned paint.

[Problems to be solved by the invention]

The present invention has been made in order to eliminate the above-mentioned inconvenience, and an object of the present invention is to provide a chipping-resistant coating composition having excellent chipping resistance and suppressing the generation of rust on the substrate.

[Means for solving problems]

The chipping resistant coating composition to which the present invention is applied for achieving the above-mentioned object is a mixture of a resin component, a curing agent and a solvent. The resin component of the coating composition has a weight average molecular weight of 1000.
100 parts by weight of a polyester resin of 0 to 17,000 and 10 to 30 parts by weight of an aliphatic polyester resin having a cyclohexane ring in the molecular skeleton and a weight average molecular weight of 400 to 1000. The curing agent is 20 to 60 parts by weight of melamine having a methyl group and a butyl group and a weight average molecular weight of 100 to 600. The solvent is a mixed solvent consisting of trimethylbenzene, dimethylbenzene and tetramethylbenzene.

In the present invention, the weight average molecular weight of the resin component is 10
000-17,000 polyester resin has a hydroxyl value of 30-200
So, for example, Beckolite M manufactured by Dainippon Ink and Chemicals
-6205 can be used.

Similarly constituting the resin component, the aliphatic polyester resin having a weight average molecular weight of 400 to 1000 having a cyclohexane ring in the molecular skeleton has a hydroxyl value of 100 to 500, for example, manufactured by King Co.
FLEXOREZ 188 can be used.

As the melamine having both a methyl group function and a butyl group function and having a weight average molecular weight of 100 to 600 used as a curing agent, for example, Cymel 166 manufactured by Mitsui Toatsu Chemicals, Inc. can be used.

As the solvent, use a mixed solvent in which trimethylbenzene / dimethylbenzene / tetramethylbenzene are mixed in 1/2/7 (volume ratio).

The weight average molecular weight of the polyester resin is preferably 10,000 to 17,000. If it is less than 10,000, the coating film tends to be brittle, and if it is more than 1700, the armpit limit film thickness is reduced.

The aliphatic polyester resin having a cyclohexane ring in its molecular skeleton preferably has a weight average molecular weight of 400 to 1,000. If it is less than 400 or more than 1000, the coating becomes brittle.

Melamine having a weight average molecular weight of 100 to 600 is used. When it is less than 100 and more than 600, it is not possible to impart sufficient flexibility to the coating film.

The weight ratio of the polyester resin having a weight-average molecular weight of 10,000 to 17,000 and the aliphatic polyester resin having a cyclohexane ring in the molecular skeleton is 100 parts by weight for the former and 10 to 30 for the latter.
It is preferable to use parts by weight. When the latter is less than 10 parts by weight, the coating film after baking is hard, and when it is more than 30 parts by weight, sufficient strength cannot be obtained.

Similarly, the weight ratio of the polyester resin having a weight average molecular weight of 10,000 to 17,000 and melamine is preferably 20 to 60 parts by weight of melamine with respect to 100 parts by weight of the polyester resin.
When the amount of melamine is less than 20 parts by weight, the strength of the coating film after baking is insufficient, and when it exceeds 60 parts by weight, the flexibility of the coating film is lost.

In addition to the above components, additives such as pigments, defoamers, and curing catalysts are included.

[Action]

By baking the coating film, polyester and melamine are crosslinked and cured. The conventional polyester-melamine resin has a high crosslink density and the coating film is hard. On the other hand, in the case of the coating composition of the present invention, the polyester resin having a weight average molecular weight of 10,000 to 17,000 and melamine form a hard coating film, but the aliphatic polyester resin having a cyclohexane ring in the molecular skeleton and the melamine have a flexible reticulated structure. Form a structure. Therefore, the coating film is softer than before, and the impact of flying stones is elastically absorbed to prevent the coating from peeling off.

〔Example〕

 Hereinafter, examples of the present invention will be described in detail.

The chipping resistant coating composition is prepared by mixing the following substances.

Resin component (see Table 1 for composition ratio) Polyester resin having a weight average molecular weight of 10,000 to 17,000 (first
In the table, it is described as "high molecular polyester"): Dainippon Ink and Chemicals, Inc., Beckolite M-6205 Weight average molecular weight 40 having cyclohexane ring in the molecular skeleton
0 to 1000 aliphatic polyester resin (referred to as "low molecular weight polyester" in Table 1): PE-A King, FLEXOREZ188 PE-B King, FLEXOREZ171-90 PE-C Asahi Denka Kogyo ( Co., Ltd., P-400 (low molecular weight polyester is selected from the above PE-A and PE-B PE-C for each example and comparative example.) Curing agent (see Table 1 for composition ratio) Melamine having a methyl group and a weight average molecular weight of 100 to 600: ME-A manufactured by Mitsui Toatsu Chemical Co., Ltd., Cymel 1116 ME-B manufactured by Mitsui Toatsu Chemical Co., Ltd., Uban 20SE (melamine is used in each Example and Comparative Example). The above ME-A,
Select one type from ME-B. ) Solvent trimethylbenzene / dimethylbenzene / tetramethylbenzene = 1/2/7 (volume ratio) mixed solvent 25 parts by weight methoxybutyl acetate 10 parts by weight The following substances are used as pigments for high-thickness paints.

Silica (Marueju Co., Ltd., Toneya silica stone) 100 parts by weight Titanium oxide (Ishihara Sangyo Co., Ltd., Taipaque R-680) 1
0 parts by weight Calcium carbonate (Maruo Calcium Co., Ltd., MC-S II)
7 parts by weight The following are used as additives.

Defoaming agent (Big Marin Rod, BYK-052) 1 part by weight Curing catalyst (King, Necure # 3525) 1 part by weight The above chipping resistant coating composition, pigment and additives are mixed with a disper for 15 minutes. Stir then disperse using a sand grinder for 20 minutes. After adjusting the viscosity, defoaming is performed under a reduced pressure of about 70 cmHg for 10 minutes to obtain a high film thickness type coating material.

Evaluation of coating film Armpit (foaming) film thickness test Hold the electrodeposition-coated test panel vertically so that the resulting high film thickness paint has various dry film thicknesses of 500-1000 μm. And apply airless coating. After setting for 2 minutes, pre-dry at 110 ° C for 10 minutes.
Next, an intermediate coating (oil-free alkyd resin coating manufactured by Kansai Paint Co., Ltd.) is applied so that the dry film thickness is about 40 μm, set for 10 minutes, and then baked at 140 ° C. for 30 minutes. After cooling, the coated surface is visually observed, and the maximum film thickness at which no cracking occurs is defined as the cracking film thickness.

Sagging film thickness test The same test panel as that used for the sagging film thickness test is used. After cooling, visually observe the coated surface,
The maximum film thickness without sagging is defined as the sagging film thickness.

Peeling diameter test Other than airless coating of high film thickness paint to a dry film thickness of 100 μm, an intermediate paint was applied in the same manner as the test panel using the sagging film thickness test, and the same as the intermediate paint. After applying the top coat, baking is performed. Diameter 8 ~ 11
Perform a gravel stepping stone test by hitting 500 g of mm of mikage stone perpendicularly to the coating film (70 mm x 150 mm) from a distance of 30 cm at an air pressure of 3 Kg / cm2. Measure the diameter of the part where the top coat has peeled off,
The average value of 10 peeled diameters is calculated as the peeled diameter.

Impact resistance test The same test panel as that used in the above peeling diameter test is used. Drop a weight of 500 g on the painted surface of the test panel and measure the maximum height at which the paint film does not crack.

Table 1 shows the compositions of Examples 1 to 4 and Comparative Examples 1 to 4 and the test results.

The high-film-thickness type coating materials of Examples 1 to 4 using the chipping-resistant coating material have a smaller peeling diameter and a higher impact resistance than the comparative examples. Further, the film has a flat film thickness and a sag film thickness that are equivalent to those of the comparative example.

〔The invention's effect〕

As described in detail above, the high-thickness coating composition containing the anti-chipping coating composition of the present invention elastically absorbs the impact of flying stones and the like, so that the coating film is less likely to peel off. Further, even if the coating film has a crack, the crack is absorbed by the layer of the high-thickness coating material and hardly reaches the base steel sheet, and rust can be prevented from occurring. Therefore, the life of the body of the vehicle is extended,
This has the effect of improving reliability.

Claims (1)

[Claims] 1. A resin component comprising 100 parts by weight of a polyester resin having a weight average molecular weight of 10,000 to 17,000 and 10 to 30 parts by weight of an aliphatic polyester resin having a cyclohexane ring in a molecular skeleton and having a weight average molecular weight of 400 to 1000, Chipping resistance, characterized by comprising a curing agent comprising 20 to 60 parts by weight of a melamine having a weight average molecular weight of 100 to 600 having a methyl group and a butyl group, and a mixed solvent comprising trimethylbenzene, dimethylbenzene and tetramethylbenzene. Coating composition.