JPH0657209A - Paint composition - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the scratch resistance and indentation resistance of the coating film. [Structure] 1 mol of a trifunctional or higher functional epoxy compound,
An isocyanate prepolymer is added to an oligomer obtained by reacting a hydroxy acid having a skeleton portion of C ₃ or less and having a hydroxyl group or a methyl group in a side chain at a ratio of 0.5 to 1 mol.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating composition excellent in both scratch resistance and indentation resistance.

[0002]

2. Description of the Related Art In recent years, there is something to be looked at for improving the quality of paints. For example, the coating surface of an automobile that is finally formed by applying a clear coat is so beautiful that it captures a landscape in a state close to a mirror surface. It has become a thing. In addition, with the diversification of customer tastes, light white tones that were previously popular were now popular, but now dark colors such as black, dark blue, and dark green are becoming more popular.

By the way, when the color of an automobile becomes a dark color system,
Since scratches formed by physical rubbing are extremely conspicuous, a paint having excellent scratch resistance, which is not scratched even if the surface contacts something and is rubbed, is desired.

As a coating material having excellent scratch resistance, Japanese Patent Laid-Open No. 56-56
The one disclosed by Japanese Patent Laid-Open No. 103252 is known. What is disclosed in this publication is 40 to 80% by weight of a mixture of a polymer containing a hydroxyl group (hydroxyl group) and hexamethoxymethylolmelamine, 1 to 4% by weight of an acid catalyst, 2 to 16% by weight of a primary alcohol, and other than a primary alcohol. A coating composition comprising 0 to 57% by weight of an organic solvent. It is described that the pencil hardness of the coating film after baking and drying this coating material was H or F.

[0005]

However, the paints disclosed in the above publications have some excellent scratch resistance, but when the pressure is intensively applied to one location on the coating surface, Has a drawback that it is apt to have a so-called indentation scratch which is generated by being compressed.

The present invention has been made in order to solve the above problems of conventional coating compositions, and the coating film obtained is tough and has excellent scratch resistance and indentation scratch resistance. It is intended to provide a coating composition.

[0007]

The coating composition according to claim 1 of the present invention has a skeleton of C ₃ or less and a hydroxyl group or a methyl group in the side chain with respect to 1 mol of a trifunctional or higher functional epoxy compound. It is characterized in that an isocyanate prepolymer is added to an oligomer obtained by reacting the present hydroxy acid at a ratio of 0.5 to 1 mol.

The coating composition of the present invention will be described in more detail below. The epoxy compound mentioned here is an organic compound containing an epoxy ring (—CH (O) CH ₂ ). Such an organic compound containing an epoxy ring usually reacts with an organic compound having a hydroxyl group to condense to produce a so-called epoxy resin. When a curing agent such as polyamine is added to this epoxy resin, a predetermined reaction occurs to cure it. Those cured in this way have excellent adhesiveness, abrasion resistance and chemical resistance, and are used in large quantities as adhesives or paints.

Especially when it is used as a material for paints, it is often used by mixing with a melamine resin or a phenol resin.
It is said that an excellent coating film is formed by baking and drying before and after.

In the present invention, attention is paid to such an epoxy compound, and in order to form a tougher coating film, an epoxy compound containing three or more functional groups, that is, containing three or more of the above epoxy rings is used as a material for the coating composition. It is used.

As the trifunctional or higher functional epoxy compound, specifically, a trade name "PT-8" containing trisglycidyl isocyanurate manufactured by Ciba-Geigy Co., Ltd. as a main component is used.
10 ”, a trade name“ 725 ”manufactured by Dainippon Ink and Chemicals, and further, a compound obtained by reacting a prepolymer of isophorone diisocyanate or hexahydrodiisocyanate with glycidol and the like are used.

The structural formula of "PT-810" is shown in the following chemical formula 1.

[0013]

[Chemical 1]

The structural formula of the above "725" is shown in the following chemical formula 2.

[0015]

[Chemical 2]

Further, the structural formula of the compound obtained by reacting the prepolymer of isophorone diisocyanate or hexahydrodiisocyanate with glycidol is shown in Chemical formula 3.

[0017]

[Chemical 3]

As shown in the above chemical formula 1, chemical formula 2 and chemical formula 3,
These epoxy compounds contain three epoxy rings per molecule, and these three epoxy rings react with a hydroxy acid to form a strong resin component having a network-like structure. In particular, in the above-mentioned "PT-810" of Chemical formula 1 and the compound of Chemical formula 3, the hexagonal melamine ring located in the center has radial branches in three directions, and an epoxy ring is arranged at the tip of this branch. Therefore, the mesh structure is further improved.

In the present invention, first, 0.5 mol of a hydroxy acid having a skeleton of C ₃ or less and a hydroxyl group or a methyl group in the side chain is added to 1 mol of the above-mentioned trifunctional or higher functional epoxy compound. The oligomer obtained by reacting at a ratio of ˜1 mol is formed. This oligomer is the so-called resin component of the coating composition.

The hydroxy acid having a skeleton of C ₃ or less and having a hydroxyl group or a methyl group in its side chain has a specific structure as shown in the following chemical formula 4, chemical formula 5 or chemical formula 6, for example. is there.

[0021]

[Chemical 4]

[0022]

[Chemical 5]

[0023]

[Chemical 6]

In the structural formulas of Chemical Formula 1, Chemical Formula 2 and Chemical Formula 3, V, W, X and Y are a hydro group (H) or a methyl group (CH ₃ ).

An isocyanate prepolymer is added to the oligomer thus produced to form a coating composition according to the present invention. Examples of the isocyanate prepolymer include prepolymers such as hexahydrodiisocyanate, isophorone diisocyanate, xylene diisocyanate, and hydrogenated xylene diisocyanate, which are called, for example, burette, isocyanurate, or agct type.

An organic solvent may be mixed in the mixture of the epoxy compound and the hydroxy acid as described above. As the organic solvent, for example, tetraglycidyl bisaminomethylcyclohexane shown in Chemical formula 7 is preferably used.

[0027]

[Chemical 7]

As a reaction catalyst between the epoxy compound and the carboxyl group contained in the hydroxy acid, an imidazole compound such as dimethylimidazole, a quaternary ammonium salt or a quaternary phosphonium salt is often used.

Further, as a reaction catalyst between the above isocyanate prepolymer and the hydroxyl group contained in the hydroxy acid, an acidic compound such as phosphoric acid ester or a tin compound such as dibutyltin dioctate or dibutyltin dimaleate may be used. Many.

[0030]

According to the coating composition of the above claim 1, a trifunctional or higher functional epoxy compound and a hydroxy acid having a skeleton of C ₃ or less and having a hydroxyl group or a methyl group in the side chain are firmly bonded. As a result, an oligomer as a network resin component is obtained. Then, since the isocyanate prepolymer having extremely high reactivity is added to this network-like oligomer to form the coating composition of the present invention, a predetermined temperature (100 to 150 ° C.) is reached after the coating composition is applied. When heated and dried at 1, the above oligomer reacts with the isocyanate prepolymer to form an extremely tough coating film. In particular, since a trifunctional or higher functional epoxy compound is used as a material for forming the oligomer, the oligomer itself has a mesh-like structure. An extremely reactive isocyanate prepolymer is added to this, and they react with each other to form a coating film, so that the formed coating film has a network structure and is extremely tough. It also has excellent scratch resistance and indentation resistance.

[0031]

【Example】

[Examples] (a) Synthesis of resin component First, a resin component of a coating composition as a clear coat according to the present invention was synthesized. Trisglycidyl isocyanate was used as the trifunctional or higher functional epoxy compound. Specifically, the product name "PT81" manufactured by Nippon Ciba Geigy
0 ”was used. In addition, hydroxypivalic acid was used as the hydroxy acid having a skeleton of C ₃ or less and having a hydroxyl group or a methyl group in the side chain.

Then, the trisglycidyl isocyanurate, the hydroxypivalic acid, and the 12-hydroxystearic acid were each injected into a four-necked flask at a preset ratio to prepare a mixed raw material.
Three four-necked flasks were prepared, and each flask had different mixing ratios of the above raw materials.

Cyclohexanone as a solvent was added thereto in an amount of 30% by weight, and the mixture was heated and stirred for about 2 hours. Then, 0.1% by weight of dimethylimidazole as a reaction accelerator
Was added, and the mixture was further heated and stirred for 1 hour to obtain a resin component having a solid content of about 70%.

The composition ratios of the above resin components (resin 1, resin 2 and resin 3) are shown in Table 1.

[0035]

[Table 1]

(B) Preparation of coating composition Next, hexahydrodiisocyanate as an isocyanate prepolymer, specifically, a trade name "TPA-100" manufactured by Asahi Kasei Co. was mixed with the above-synthesized resin component. A coating composition was prepared. A predetermined amount of an ultraviolet absorber (specifically, "Tinuvin 900" manufactured by Ciba Geigy), a light stabilizer (specifically, "Sanol LS770" manufactured by Ciba Geigy), and a surface preparation (specific BIC Chemie's "BYK307") is added to
Finally, xylene as a solvent is mixed.

The composition ratio of the prepared coating composition is shown in Table 2 below.

[0038]

[Table 2]

Comparative Example (a) Synthesis of Resin Component A resin component of a coating composition as a comparative example was synthesized. As the trifunctional or higher functional epoxy compound, the resin 1 of the above-mentioned example is used.
Product name "PT81" manufactured by Japan Ciba-Geigy
0 ”was used. As the hydroxy acid to be mixed with this, 12 hydroxystearic acid was frequently used instead of the hydroxypivalic acid of the examples.

The above-mentioned epoxy compound was poured into two four-necked flasks, and a predetermined amount of hydroxypivalic acid, 12-hydroxystearic acid, and cyclohexanone as a solvent were added to each, and the mixture was heated and stirred for about 2 hours. .
Then, 0.1% by weight of dimethylimidazole as a reaction accelerator was added, and the mixture was further heated and stirred for 1 hour to obtain a resin component having a solid content of about 70%.

The composition ratios of the resin components (resin 4 and resin 5) of this comparative example are as shown in Table 3 below.

[0042]

[Table 3]

(B) Preparation of coating composition Next, a hexahydrodiisocyanate (above "TPA-100") as an isocyanate prepolymer is mixed into the above-synthesized resin components (resin 4 and resin 5) to obtain a coating composition. A composition was prepared. In addition, a predetermined amount of an ultraviolet absorber (“Tinuvin 900” above), a light stabilizer (“Sanol LS770” above) and a surface preparation agent (“BYK307” above) were added as additives, and finally xylene as a solvent was added. The paints (paint 4 and paint 5) were mixed and sufficiently stirred to prepare paints.

The composition ratio of the prepared coating composition is shown in Table 4.

[0045]

[Table 4]

[Comparison between Examples and Comparative Examples] (a) Preparation of Base Coat Composition In order to compare the performances of the coating composition of the above-mentioned example and the coating composition of the comparative example, they were first used as an undercoat. A base coat was prepared as follows.

That is, xylene 20 was added to the four-necked flask.
Wt% and butyl isoacetate 10% by weight at 130 ° C
And stirring with 20 wt% butyl acrylate,
2-hydroxyethyl methacrylate 10% by weight, methyl methacrylate 20% by weight, butyl methacrylate 10
% By weight, perbutyl O 0.05% by weight, perbutyl A
A mixture of 0.05 wt% was stirred for 3 hours while dropping.

Thereafter, the mixture was heated and mixed for another hour, and after 1 hour, 0.05% by weight of perbutyl A was added to the mixture.
After stirring for 2 hours, 10% by weight of xylene was added to obtain a resin component for base coating having a solid content of 60%.

Then, to 50% by weight of the resin component obtained as described above, 5% by weight of aluminum paste (commercial name "CR-601S" manufactured by Asahi Kasei) and "Uban" manufactured by Mitsui Toatsu Co., Ltd. 122 "21.5% by weight, xylene 15% by weight, butyl acetate 15% by weight, product name" BYK307 "manufactured by BIC Chemie Co., Ltd. 0.1% by weight, product name" CAB531-1 "manufactured by Eastman Co. 5% by weight and Toluene 2
A base coat was prepared by adding and mixing 0% by weight.

(B) Formation of coating film for comparison On a metal flat plate which was electrodeposited with an undercoat paint different from the above, 50% by weight of xylene and 50% by weight of butyl acetate were used.
The above base coat diluted with FC # 4 for 12 seconds (25 ° C) with a mixed solution of and is left for 10 minutes and then 140 ° C.
And dried for 15 minutes to prepare a coated plate for applying the coating composition to be the subject of the comparative test.

The coating compositions to be subjected to the comparative test were 40% by weight of xylene and 60% by weight of cyclohexanone, respectively.
FC # 4 was diluted with mixed solvent water for 18 seconds (25 ° C.), and these diluted coating compositions were applied to the surface of the coated plate on which the above base coat was formed. And
The coating composition was left to stand for 10 minutes and then dried at 140 ° C. for 30 minutes to form a finish coating film on a coated plate for comparison.

(C) Comparison and Evaluation The coated plate on which a coating film finished with the coating composition was formed as described above was fixed to the outer ceiling surface of the automobile, washed with a car washing machine, and then applied by rubbing a car wash brush. The scratches formed on the film were visually observed, and the scratch resistance was evaluated according to the state of the scratches. The number of car washes was 20 each.

As for the indentation resistance, JISK5
The pencil hardness test method specified in 401 was applied correspondingly, and the indentation resistance was evaluated based on the test results.

The evaluation results are shown in Table 5.

[0055]

[Table 5]

As can be seen from this table, no scratches were observed when the coating composition according to this example was used. The indentation resistance was also very good, and the pencil hardness was F or HB.

On the other hand, the coating composition of the comparative example was slightly scratched. The indentation resistance was not so good, and the pencil hardness was B or less in all cases.

It should be noted that the comparative examples themselves are those very close to those of the examples, and if a conventional ordinary coating composition far from the examples is subjected to the same evaluation test, very noticeable scratches are produced. Although it was generated and the indentation hardness was inferior to that of the comparative example, such a sample was intentionally not adopted in this evaluation test.

From the above, it can be seen that the coating composition according to this example is extremely excellent in scratch resistance and indentation resistance, and is very excellent in keeping the coating film beautifully. .

[0060]

As described above, the coating composition of the present invention is a hydroxy compound having a skeleton of C ₃ or less and a hydroxyl group or a methyl group in the side chain with respect to 1 mol of a trifunctional or higher functional epoxy compound. Since the isocyanate prepolymer is added to the oligomer obtained by reacting the acid at a ratio of 0.5 to 1 mol, the trifunctional or higher functional epoxy compound and the skeleton are C ₃ or lower and It is convenient because a hydroxy acid having a hydroxyl group or a methyl group in the side chain is firmly bonded to obtain a network-like oligomer as a resin component.

The coating composition of the present invention is formed by adding an isocyanate prepolymer having extremely high reactivity to the network oligomer. Therefore, when the coating composition is completely dried by heating at a predetermined temperature (100 to 150 ° C.), the oligomer and the isocyanate prepolymer react with each other to form an extremely tough coating film. Since a trifunctional or higher functional epoxy compound is used as a material for forming the oligomer, the oligomer itself has a network-like structure. To this, an extremely reactive isocyanate prepolymer was added,
Since they react with each other to form a coating film, the coating film formed is extremely tough with a network structure and has excellent scratch resistance and indentation resistance. It will be a good thing.

As described above, the coating film formed from the coating composition of the present invention is extremely excellent in quality because scratches are unlikely to occur and pressing scratches are unlikely to occur. Excellent for painting automobiles.

Claims (1)

[Claims] 1. A hydroxy acid having a skeleton of C ₃ or less and having a hydroxyl group or a methyl group in a side chain is reacted with 1 mol of a trifunctional or higher functional epoxy compound at a ratio of 0.5 to 1 mol. A coating composition comprising an isocyanate prepolymer added to the thus obtained oligomer.