JPH0240707B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a quick-drying urethane resin coating composition, and more particularly to a urethane resin coating composition that has excellent drying properties and provides a coating film with excellent weather resistance, solvent resistance, and flexibility. Conventionally, urethane resin coating compositions consisting of aliphatic polyisocyanate compounds and polyhydroxyl compounds have been used particularly in the paint field due to their excellent weather resistance, solvent resistance, and flexibility. It has the disadvantage of poor drying properties. On the other hand, urethane resin coating compositions using aromatic polyisocyanate compounds have excellent drying properties, but have the disadvantage of poor weather resistance. Further, although urethane resin coating compositions using alicyclic polyisocyanate compounds have good drying properties, they lack flexibility. As described above, it is difficult for urethane resin coating compositions to satisfy all properties from the viewpoint of polyisocyanate compounds, and therefore properties have been improved by adding polyhydroxyl compounds, catalysts, etc. However, it is still not completely satisfactory. Additionally, a method has been proposed in which hexamethylene diisocyanate derivatives and isophorone diisocyanate derivatives are mixed at a weight ratio of 50:50 to 10:90 (Japanese Patent Publication No. 19273/1983).
In this method, due to the difference in reactivity between hexamethylene diisocyanate derivatives and isophorone diisocyanate derivatives, it is thought that, for example, there are regions where the hexamethylene diisocyanate derivative portion is hardened and where the isophorone diisocyanate derivative portion is uncured. The resulting coating film has excellent solvent resistance, flexibility, weather resistance, etc.
You may not be completely satisfied. In view of these circumstances, the present inventors have conducted extensive research to develop a urethane resin coating composition that has excellent drying properties and excellent weather resistance, solvent resistance, and flexibility of the coating film. This objective is achieved with a composition consisting of a polyisocyanate compound having a specific viscosity range and a polyhydroxyl compound obtained by reacting a mixture of an aliphatic diisocyanate and an alicyclic diisocyanate with water or a polyhydric alcohol. Based on this knowledge, we have completed the present invention. That is, the present invention provides a mixture of (A) an aliphatic diisocyanate and an alicyclic diisocyanate, which is obtained by reacting water or a polyhydric alcohol, and which contains both an aliphatic isocyanate group and an alicyclic isocyanate group in one molecule. The present invention provides a quick-drying urethane resin coating composition comprising a polyisocyanate compound having a viscosity of 10 to 500 poise at a temperature of 25°C, and (B) a polyhydroxyl compound. Examples of the aliphatic diisocyanate used to form the polyisocyanate compound which is component (A) of the present invention include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and lysine diisocyanate. Among them, 1,6-hexamethylene diisocyanate is preferred. Examples of alicyclic diisocyanates include isophorone diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and cyclohexane-1,3-bis(isocyanatomethyl). is isophorone diisocyanate. In the composition of the present invention, the mixing ratio of the aliphatic diisocyanate and alicyclic diisocyanate is preferably within the range of 90:10 to 30:70 in terms of molar ratio. If the amount of aliphatic diisocyanate is more than this, there is no effect of improving drying properties, and if it is less than this, unfavorable results will be given in terms of flexibility and solvent resistance. The polyisocyanate compound as component (A) in the composition of the present invention can be obtained by reacting a mixture of the aliphatic diisocyanate and alicyclic diisocyanate with water or a polyhydric alcohol. This polyisocyanate compound has a biuret group when water is used, and a urethane group when a polyhydric alcohol is used. Examples of the polyhydric alcohol include trimethylolethane, trimethylolpropane, glycerin, tris-(2-hydroxyethyl)-isocyanuric acid, and pentaerythritol, among which trimethylolpropane is preferred. . The polyisocyanate compound used as component (A) in the composition of the present invention has both an aliphatic isocyanate group and an alicyclic isocyanate group in one molecule, and has a viscosity in the range of 10 to 500 poise at a temperature of 25°C. It is preferably in the range of 20 to 200 poise. If this viscosity is less than 10 poise, there will be no significant effect on improving the drying properties, which is the objective of the present invention, while if it exceeds 500 poise, the compatibility with the polyhydroxyl compound will deteriorate, resulting in unfavorable results. . A specific example of this polyisocyanate compound is 1,6-hexamethylene diisocyanate and isophorone diisocyanate in a molar ratio of 2:1.
Examples include those obtained by mixing at a ratio of 1 and reacting with water. This one is the following formula () It is thought to have the structure shown below, and since there are an aliphatic isocyanate group and an alicyclic isocyanate group in the same molecule, the characteristics possessed by aliphatic and alicyclic groups, such as flexibility, weather resistance, It is considered that the dryness is well balanced. Furthermore, the product obtained by mixing 1,6-hexamethylene diisocyanate and isophorone diisocyanate at a molar ratio of 1:2 and reacting with trimethylolpropane is expressed by the following formula () This polyisocyanate is thought to have the structure shown by the following formula, and like the one of formula (), this polyisocyanate has both an aliphatic isocyanate group and an alicyclic isocyanate group in the same molecule, so it has good flexibility and weather resistance. , provides a urethane resin with excellent drying properties. Examples of the polyhydroxyl compound used as component (B) in the composition of the present invention include acrylic polyols, polyester polyols, polyether polyols, etc. Among these, acrylic polyols are preferred in terms of drying properties and weather resistance. be. In the composition of the present invention, the molar ratio of the isocyanate groups in the polyisocyanate compound (A) to the hydroxyl groups in the polyhydroxyl compound (B) is within the range of 6:10 to 15:10. is desirable, and if the isocyanate group is less than 0.6 times the hydroxyl group on a molar basis, it will give unfavorable results in terms of weather resistance and solvent resistance.
On the other hand, if it exceeds 1.5 times, satisfactory results may not be obtained in terms of drying properties. If desired, various additives commonly used in the paint field, such as catalysts, plasticizers, leveling agents, pigments, dyes, thixotropic agents, pigment dispersants, etc., can also be added to the composition of the present invention. . The quick-drying urethane resin coating composition of the present invention has excellent drying properties and excellent weather resistance, solvent resistance, and flexibility of the coating film, and is particularly useful as a urethane resin coating for automobiles, railway vehicles, equipment, and structures. It is suitable for applications where workability, appearance, weather resistance, and coating performance are important, such as woodwork. Next, the present invention will be explained in more detail with reference to Examples. Reference example Polyisocyanate compound A shown in Table 1
~D were manufactured according to the following method. Adding water or polyhydric alcohol to a mixture of aliphatic diisocyanate and alicyclic diisocyanate,
140 in a mixed solvent of trimethyl phosphate and ethylene glycol monoethyl ether acetate.
The reaction was carried out at ℃ for 3 hours. Then 0.1mmHg,
Vacuum distillation was performed at 160° C. to recover unreacted aliphatic diisocyanate, alicyclic diisocyanate, and solvent, and polyisocyanate compounds A to D were obtained as residual liquid from the pot. Similarly, 1860 parts by weight of hexamethylene diisocyanate and 18 parts by weight of water were reacted in a mixed solvent of 1000 parts by weight of trimethyl phosphate and 1000 parts by weight of ethylene glycol monoethyl ether acetate, and then distilled to obtain polyisocyanate. Compound E was obtained. Next, 3330 parts by weight of isophorone diisocyanate and trimethylolpropane
134 parts by weight, 1500 parts by weight of trimethyl phosphate, ethylene glycol monoethyl ether acetate
After dissolving in 1500 parts by weight and reacting at 140°C for 5 hours, unreacted isophorone diisocyanate and solvent were recovered by vacuum distillation at 150°C at 0.1 mmHg to obtain polyisocyanate compound F. Polyisocyanate A~ obtained as above
The isocyanate content and viscosity at 25°C of F are shown in Table 1.

【table】

[Table] Examples 1 to 4 Polyisocyanate compounds A to D obtained in reference examples
and polyhydroxyl compounds (Dainippon Ink Industries, Ltd.)
Manufactured by Akridik A801, hydroxyl value 50, solid content
50% by weight) as shown in Table 2, dissolved in toluene/n-butyl acetate mixed solvent (1/1 weight ratio), applied to an iron plate, and immediately left in an atmosphere at 5°C for 20 minutes. After that, a drying test was conducted.
In addition, a solvent resistance test and an impact test were conducted on the coating film which was left at 20°C for 7 days. The results obtained are shown in Table 2. Comparative Examples 1 to 3 Polyisocyanate compounds E and F obtained in Reference Examples
and Acridik A801 and toluene/acetic acid n-
The same characteristic tests as in Examples 1 to 4 were conducted on products containing a butyl mixed solvent in the amounts shown in Table 2. The results obtained are shown in Table 2.

[Table] Example 5 When the coating film of Example 1 was subjected to an accelerated weather resistance test for 1000 hours under the conditions of a weather meter in accordance with JIS D-0205, there was no yellowing and the gloss retention rate was 100%. Comparative Example 4 When the coating film of Comparative Example 2 was subjected to a 1000 hour accelerated weather resistance test under the conditions of a weather meter in accordance with JIS D-0205, the gloss retention rate was 87%.

Claims (1)

[Claims] 1 (A) A mixture of an aliphatic diisocyanate and an alicyclic diisocyanate that is obtained by reacting water or a polyhydric alcohol and has both an aliphatic isocyanate group and an alicyclic isocyanate group in one molecule, and A quick-drying urethane resin coating composition with excellent weather resistance, comprising a polyisocyanate compound having a viscosity of 10 to 500 poise at a temperature of 25°C and (B) a polyhydroxyl compound.