JPH0629381B2 - UV curable thick film paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an ultraviolet-curable thick film coating material excellent in adhesion to metals and the like and smoothness of a coated surface.

[Conventional technology]

Unsaturated polyester resin paints are generally known as one of the paints from which thick films can be easily obtained. However, the conventional unsaturated polyester resin has a large shrinkage strain at the time of curing because the curing reaction is fast, and the cured resin itself is rigid, so that the adhesion of the coating film to the coated object is essentially poor. There are drawbacks, and the following methods are known as attempts to improve this drawback.

(1) A method for forming a thick film pattern finish on a wall material by irradiating an energy ray with a coating composition consisting of a radical-polymerizable resin having a double bond and a hydroxyl group and an isocyanate compound (JP-A-2000-242). 53-112932
Issue).

(2) A method of coating resin such as unsaturated polyester resin, polyester urethane resin, acrylic resin, etc. on wood and irradiating it with ultraviolet rays and then infrared rays to cure the resin (Japanese Patent Laid-Open No. Sho 5)
0-111131).

(3) A resin composition for moldings comprising an ester compound of a urethane-modified epoxy compound, an organic acid, and a polymerizable monomer (Japanese Patent Publication No. 60-49644).

[Problems to be solved by the invention]

In the paints used in the methods (1) and (2) described in the previous section, the adhesion of the paint film to the object to be coated is improved, but the high degree of adhesion required for automobiles, motorcycles and household electric appliances is required. It was unsatisfactory as an undercoat paint for obtaining appearance.

Further, the resin composition for the molded product of (3) has excellent tensile strength and bending strength, but has the same drawbacks as (1) and (2) in applications requiring a high degree of appearance, Also, since it is a room temperature curable resin, it is unsuitable as an industrial coating resin.

An object of the present invention is to provide an ultraviolet-curable thick film coating having excellent adhesion to metals and the like, smoothness of the coated surface, high appearance without absorption of the top coating, and good coating workability. To provide.

[Means for solving problems]

The present invention is an ultraviolet curable coating composition containing the following components A to F as main components.

A Non-wax type unsaturated polyester resin having two or more unsaturated double bonds per molecule B B Polyester polyol having a hydroxyl value of 50 to 400 or a mixture of polyester polyol and polyether polyol C Non-yellowing polyisocyanate compound D Organic peroxide Oxide catalyst E Photopolymerization initiator F Fine powder barium sulfate having an average particle size of 0.5 μm or less (however, the weight ratio of A / B is 80/20 to 40/60,
The equivalent of isocyanate group of C is 0.5 to 1.5, and A, B and C are equivalent to 1 equivalent of total hydroxyl groups of A and B.
The weight ratio of F to the total weight of is 1 to 3. The non-wax type unsaturated polyester resin having two or more double bonds per molecule which is the component A of the present invention is a component which is cured mainly by ultraviolet irradiation and does not necessarily have a hydroxyl group in the molecule. It does not matter even if it has a hydroxyl group, in which case the hydroxyl group is the component C described below.
It also has an element that causes a curing reaction with the polyisocyanate compound.

Component A includes unsaturated dibasic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and tetrahydrophthalic acid, or their anhydrides, ethylene glycol, 1,2-propylene glycol, dipropylene glycol, and hydrogenation. Esterified with polyhydric alcohols such as bisphenol A, 2,2-bis (4-hydroxyethoxyphenyl) propane, 1,3-butylene glycol, 2,3-butylene glycol, glycerin, neopentyl glycol and trimethylolpropane Obtained. Further, as the component A of the present invention, a commercially available non-wax type non-wax-type epoxy resin obtained by esterifying the above-mentioned unsaturated dibasic acid or an anhydride thereof with allyl glycidyl ether, glycerin diallyl ether, pentaerythritol diallyl ether, etc. Saturated polyester resin (Gothax 400, 5
40 and 750-70: Both can be used as the trade name of Nippon Synthetic Compound Co., Ltd., Roskidar 530: the trade name of Sumitomo Bayer Urethane Co., Ltd.

The component B of the present invention, which is a polyester polyol having a seafood group value of 50 to 400 or a mixture of the polyester polyol and the polyether polyol, has a function of alleviating the shrinkage strain generated during curing of the unsaturated polyester resin which is the component A. Therefore, commercially available products such as Desmophen 651, 670 and 680 (all are trade names of Sumitomo Bayer Urethane Co., Ltd.), Nipporan 800 and 1100 (all are trade names of Nippon Polyurethane Industry Co., Ltd.) can be used.

The weight ratio of A / B is 80/20 to 40/60. When component A is more than 80, shrinkage strain at the time of curing becomes large and the adhesion of the coating film to the object to be coated is deteriorated, and when it is less than 40, drying property of the coating film is deteriorated and problems occur.

The non-yellowing polyisocyanate compound which is the component C of the present invention mainly relaxes the shrinkage strain which occurs during curing of the unsaturated polyester resin together with the polyol which is the component B, and is a polymer of hexamethylene diisocyanate,
Polymers of isophorone diisocyanate or mixtures thereof are used. The amount of isocyanate group is 0.5 to 1 equivalent of hydroxyl group in the total amount of component B and component A.
Used in a ratio of 1.5 equivalents. If it is less than 0.5 equivalent, the curability and adhesion to the uncoated article become insufficient, and if it exceeds 1.5 equivalent, the performance is not so improved.

Examples of the organic peroxide catalyst which is the component D of the present invention include ketone peroxides, peroxyketals, hydroperoxides, peroxydicarbonates and peroxyesters.

As the photopolymerization initiator which is the component E of the present invention, 260 to
Benzoin or a derivative thereof, benzophenone or a derivative thereof, Michlerketone or a derivative thereof, benzyl or a derivative thereof, which has absorption in an ultraviolet region of 450 nm.
There are tetraalkyl thiuram monosulfides, thioxanes and the like, which are used alone or as a mixture.

The finely powdered barium sulfate which is the component F of the present invention is used as a filler in a coating composition, an anti-sagging agent, etc.,
The average particle size is 0.5 μm or less, preferably 0.05 μm or less. When the average particle size exceeds 0.5 μm, the top coating material is remarkably absorbed and a high degree of appearance cannot be obtained. The amount of fine barium sulfate used is 1 to 3 by weight relative to the total amount of components A, B and C. If it is less than 1, it is difficult to obtain a thick film because the flow and sagging are likely to occur in the painting of the vertical surface.
When it exceeds, the smoothness of the coated surface is deteriorated, which is not preferable.

In addition to these components A to F, a styrene monomer and a cissing inhibitor as a coating film forming component that also participates in the curing reaction as a diluent for adjusting the coating viscosity,
Known additives such as a fluidity modifier can be added as appropriate.

The coating method of the ultraviolet-curable thick film paint of the present invention is such that the paint of the present invention is diluted with a styrene monomer so that it is about 20 seconds in Ford Cup No. 4 (25 ° C.), and the coating film thickness after drying is 1
Spray coating or electrostatic coating on the object to be coated so as to have a thickness of 0 to 300 μm. After leaving the coated object at room temperature for 5 minutes,
Preheating is performed for 3 minutes with a heating device adjusted to 60 to 100 ° C., followed by irradiation with ultraviolet rays for several seconds, and then additional heating is performed for 10 minutes with a heating device adjusted to 160 ° C.

As a heating device used for preheating and follow-up heating, a far infrared furnace, an infrared lamp furnace, an electric heating furnace, and other furnaces used for drying general heat-drying type paints can be used.

A metal halide lamp, a mercury lamp, or the like can be used as the ultraviolet ray source for irradiation.

〔The invention's effect〕

The UV-curable thick film coating composition of the present invention has excellent adhesion to an object to be coated such as a steel plate, forms a smooth coating film by covering irregularities on the surface to be coated having a roughness of about 50 μm, and It has excellent workability that can form a thick film by painting.

〔Example〕

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Parts and% in the examples are by weight.

Examples 1 to 14 and Comparative Examples 1 to 17 (1) Preparation of coating material According to the coating material formulation shown in Table 1, first, the entire amount of the mill base composition was mixed and the particle size was adjusted to 5 μm or less by a sand mill (measured with a grind gauge). Each mill base was obtained by dispersing until. Next, each post-additive in each mill base was sequentially added and uniformly mixed to obtain each UV-curable thick film coating composition of Examples 1 to 14 and each coating composition of Comparative Examples 1 to 7.

(2) Preparation of test piece A styrene monomer was added to each coating material prepared in (1) and diluted so that the viscosity was 18 to 22 seconds in Ford cup No. 4 (25 ° C). As the coated plate, a 70 × 150 × 1 mm cold rolled steel plate was degreased and washed with xylene and dried at room temperature, and then cloth was polished to a surface roughness of 50 μm, and a zinc phosphate treatment agent was added. (Bondelight No.
144: the product treated with Nippon Parker Rising Co., Ltd.) was used.

Dry coating thickness of each coating diluted to 130-170
Spray coating was performed so as to have a thickness of μm, the mixture was allowed to stand at room temperature for 5 minutes, and then preheated (heated with a hot air dryer adjusted to 100 ° C. for 10 minutes). However, only in Comparative Example 7, preheating was omitted. High pressure mercury lamp (manufactured by Nippon Battery Co., Ltd., high cure lamp, length 20 cm, 3 bulbs 4.9)
KW) was uniformly irradiated on the surface of the coated plate from a distance of about 20 cm for 3 seconds, and further followed by heating (heating with a hot air dryer adjusted to 160 ° C. for 10 minutes) to obtain each test piece.

Each paint and each test piece are described below. The test was conducted by the method, and the results are shown in Table 2.

(3) Test method and evaluation method Appearance of coating film: Top coating material (water-soluble acrylic resin coating: manufactured by NOF CORPORATION, Aqua No. 7100 Black) on the coated surface of the test pieces prepared in Examples and Comparative Examples. ) Was sprayed and overcoated so that the dry coating film thickness was 25 μm, and then allowed to stand for 10 minutes at room temperature. Then, after heating and drying for 20 minutes with a hot air dryer adjusted to 150 ° C, the temperature is allowed to cool to room temperature and the sharpness of the coated surface is measured with a portable sharpness gloss meter PGD-IV manufactured by Tokyo Koden Co., Ltd. It was measured. When the image clarity was 0.6 or more, it was determined to be acceptable.

Gravel resistance: When the coated surface of each test piece is observed with the naked eye, ○ (pass) when no grain is observed, x when recognized
(Failed)

Adhesion: Tested by the method of JIS K 5400-6.15 (cross-cut test). When it was 100, it passed, and when it was 99 or less, it failed.

Hardness: Tested by the method of JIS K 5400-6.14 (pencil scratch test). The case of HB to 2H was regarded as passing.

Sagging limit film thickness (μm): A cold-rolled steel plate (height 3 × width 10 × thickness 0.1 cm) that had been degreased and washed with xylene and then dried at room temperature was used as a coated plate. Ford cup No. 4 (25 ° C) sprayed with a paint diluted to 18 to 22 seconds was sprayed onto this vertically fixed coated plate so that the dry coating film thickness would be zero at the coated plate edge and 300 μm at the lower edge. The coating film was continuously coated with the coating thickness varied, and dried by the drying method described in (2). The maximum thickness of the coating film without sagging was determined by observing the presence or absence of sagging on the coated surface and measuring the coating film thickness. 1
A pass of 80 μm or more was determined.

As is clear from the test results in Table 2, the paints of Examples 1 to 14 according to the present invention show good results, but paints outside the scope of the present invention are unsatisfactory in the test results.

In Comparative Example 1 containing a large amount of the component F of the present invention, the smoothness of the coating surface is not good, and therefore the top coating material is sucked in, and the adhesion to the article to be coated is poor. Comparative Example 2 in which the component F of the present invention is small and Comparative Example 4 in which titanium oxide is used instead of the component F of the present invention,
In both cases, the sagging limit film thickness is unsatisfactory, and therefore, the grain cover cannot be covered, and the coating appearance is inferior. Comparative Example 3 containing less component C of the present invention fails in hardness and adhesion. Comparative Example 5 containing a large amount of Component A of the present invention has poor adhesion to the article to be coated, and Comparative Example 6 containing a small amount of Component A of the present invention is unsatisfactory in hardness and sag limit film thickness.

Further, in Comparative Example 7 in which preheating was omitted in the drying step of the ultraviolet curable thick film coating material of the present invention, the original adhesiveness was not exhibited.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09D 5/00 167/06 PEH 8933-4J

Claims (1)

[Claims] 1. An ultraviolet-curable coating material containing the following components A to F as main components. A Non-wax type unsaturated polyester resin having two or more unsaturated double bonds per molecule B B Polyester polyol having a hydroxyl value of 50 to 400 or a mixture of polyester polyol and polyether polyol C Non-yellowing polyisocyanate compound D Organic peroxide Oxide catalyst E Photopolymerization initiator F Fine powder barium sulfate having an average particle size of 0.5 μm or less (however, the weight ratio of A / B is 80/20 to 40/60,
The equivalent of isocyanate group of C is 0.5 to 1.5, and A, B and C are equivalent to 1 equivalent of total hydroxyl groups of A and B.
The weight ratio of F to the total weight of is 1 to 3. )