Additive for Coating Compositions

This invention relates to an additive for coating compositions which imparts flexibility to finishes formed from coating composition containing the additive.

For painting and refinishing of automobiles and trucks, the following paints are sold: acrylic lacquers as described in Meyer U.S. Pat. No. 4,168,249 issued Sept. 18, 1979, nitrocellulose lacquers, acrylic alkyd enamels as described in Miller U.S. Pat. No. 3,844,993 issued Oct. 29, 1974 and acrylic polyurethane enamels as described in Vasta U.S. Pat. No. 3,558,564 issued Jan. 26, 1971. The lacquers and enamels have a low level of flexibility and are primarily designed for application over rigid metal parts of automobiles and trucks. However, there are a number of parts of automobile and truck bodies that use flexible materials such as the flexible material covering the area between the bumper and the body of an automobile. When the aforementioned enamels or lacquers are applied over this flexible material, upon flexing, they crack, chip and peel off. A universal additive is needed that would form flexible finishes of these enamels and lacquers but would not degrade other important properties such as adhesion, weatherability, gasoline resistance, gloss and distinctness of image.

An additive for coating compositions which is a mixture of about

(A) 20-50% by weight of a polyisocyanate of the formula ##STR2## where R.sup.1 is (CH.sub.2).sub.6, (B) 1-15% by weight of an ester selected from the group of a polyalkylene glycol alkyl alkylate, an alkyl phthalate or an alkyl aromatic phthalate,

(C) 1-10% by weight of a blend of ultraviolet light stabilizers and

(D) 25-78% by weight of an organic solvent.

The additive of this invention can be blended with the following coating compositions: acrylic lacquers, nitrocellulose lacquers, acrylic alkyd enamels and acrylic polyurethane enamels and provides finishes with excellent flexibility. The additive does not degrade other properties of these finishes such as gloss, adhesion, weatherability and gasoline resistance. Typically useful lacquer and enamel coating compositions are described in the aforementioned patents to Meyer, Miller and Vasta and the disclosure of these patents is hereby incorporated by reference.

Usually about 10-100% by weight, based on the weight of the coating composition, of the additive is blended with the coating composition. Preferably, about 20 to 70% by weight of the additive is used. Generally, about 2 parts by weight of acrylic or nitrocellulose lacquer are used per 1 part additive, 8 parts by weight acrylic alkyd enamel per 1 part of additive are used and 4 parts by weight of acrylic polyurethane enamel per 1 part additive are used.

The addition of the additive decreases the "pot" life of the coating composition. Generally, the aforementioned lacquers containing the additive must be used within about 4 hours after addition of the additive before the lacquer increases in viscosity or gels. The above enamels have a "pot" life of about 8 hours after addition of the additive.

The additive contains about 20-50% by weight, based on the weight of the additive, of a polyisocyanate of the formula ##STR3## where R.sup.1 is (CH.sub.2).sub.6, Preferably, about 25 to 40% by weight of the polyisocyanate is used.

The additive contains 1-15% by weight, based on the weight of the additive of a polyalkylene glycol alkyl acrylate, an alkyl phthalate or an alkyl aromatic phthalate. Preferably, about 4 to 10% by weight of the polyalkylene glycol alkyl acrylate are used. Typically, polyethylene glycol di(2-ethylhexoate) is used. A typical alkyl phthalate that can be used is dioctyl phthalate and a typical alkyl aromatic phthalate is butyl benzyl phthalate.

The additive contains about 1-10% by weight based on the weight of the additive, of ultraviolet light stabilizers. Preferably, 5 to 10% by weight of ultraviolet light stabilizers are used.

Typical ultraviolet light stabilizers that are useful in the additive are as follows:

Benzophenones such as hydroxydodecycl benzophenone, 2,4-dihydroxybenzophenone, hydroxybenzophenones containing sulfonic acid groups, 2,4-dihydroxy-3',5'-di-t-butylbenzophenone, 2,2',4'-trihydroxybenzophenone esters of dicarboxylic acids, 2-hydroxy-4-acryloxyethoxybenzophenone, aliphatic mono-esters of 2,2',4-trihydroxy-4'-alkoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone;

Triazoles such as 2-phenyl-4-(2'-4'-dihydroxybenzoyl)triazoles, substituted benzotriazoles such as hydroxyphenyltriazoles such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-octylphenyl)naphthotriazole;

Triazines such as 3,5-dialkyl-4-hydroxyphenyl derivatives of triazine, sulfur-containing derivatives of dialkyl-4-hydroxyphenyltriazines, hydroxyphenyl-1,3,5-triazines and such triazines containing sulfonic acid groups, aryl-1,3,5-triazines, orthohydroxyaryl-s-triazine;

Benzoates such as dibenzoate of diphenylolpropane, t-butyl benzoate of diphenylolpropane, nonyl phenyl benzoate, octyl phenyl benzoate, resorcinol dibenzoate.

Other ultraviolet light stabilizers that can be used include lower alkyl thiomethylene-containing phenols, substituted benzenes such as 1,3-bis(2'-hydroxybenzoyl)benzene, metal derivatives of 3,5,-di-t-butyl-4-hydroxyphenylpropionic acid, asymmetrical oxalic acid diarylamides, alkylhydroxyphenylthioalkanoic acid esters, dialkylhydroxyphenylalkanoic acid esters of di- and tri-pentaerythritol, phenyl- and naphthlene-substituted oxalic acid diamides, methyl-.beta.-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, .alpha.,.alpha.'-bis(2-hydroxyphenyl)diisopropylbenzene, 3,5'-dibromo-2'-hydroxyacetophenone, ester derivatives of 4,4-bis(4'-hydroxyphenyl)pentanoic acid wherein there is at least one unsubstituted position ortho to the aromatic hydroxyl groups, organophosphorus sulfides such as bis(diphenylphosphinothioyl)monosulfide and bis(diphenylphosphinothioyl)disulfide, 4-benzoyl-6-(dialkylhydroxybenzyl)resorcinol, bis(3-hydroxy-4-benzoylphenoxy)diphenylsilane, bis(3-hydroxy-4-benzoylphenoxy)dialkylsilane, 1,8-naphthalimides, .alpha.-cyano-.beta.,.beta.-diphenylacrylic acid derivatives, bis(2-benzoxazolyl)alkanes, bis(2-napthoxazolyl)alkanes, methylene malonitriles containing aryl and heterocyclic substitutes, alkylenebis(dithio)carbamate, 4-benzoyl-3-hydroxyphenoxyethyl acrylate, 4-benzoyl-3-hydroxyphenoxyethyl methacrylate, aryl- or alkyl-substituted acrylonitriles, 3-methyl-5-isopropylphenyl-6-hydroxycoumarone.

Particularly useful ultraviolet light stabilizers that can be used are hindered amines of piperidyl derivatives such as those disclosed in Murayama et al., U.S. Pat. No. 4,061,616, issued Dec. 6, 1977, column 2, line 65, through column 4, line 2, and nickel compounds such as [1-phenyl-3-methyl-4-decanoylpyrazolate(5)]-Ni, bis[phenyldithiocarbamato]-Ni(II), and others listed in the above patent, column 8, line 44 through line 55.

The following blend of ultraviolet light stabilizers is particularly preferred 2-[2'-hydroxy-3',5'-1(1-1-dimethyl-propyl)phenyl]benzotriazole and di-[4-(2,2,6,6,-tetramethylpiperidyl)]sebecate. The stabilizers can be used in any ratio however, a 2:1 ratio of benzotriazole to sebecate is preferred.

The additive contains about 25-78% by weight, based on the weight of the additive of organic solvents. Preferably, about 40 to 66% by weight of organic solvents are used. Typically useful solvents are toluene, xylene, ethyl acetate and other organic solvents that do not contain hydroxyl groups or carboxyl groups.

After the additive is blended with a coating composition, the resulting blend is applied by conventional technique such as spraying, electrostatic spraying, brushing, dipping and the like to a substrate and dried at ambient temperatures. Typical flexible substrates to which these compositions can be applied are flexible thermoplastic polyurethane and injection molded polyurethanes. Low baking temperatures of 50.degree.-125.degree. C. can also be used to force dry the composition. The resulting finishes have good flexibility and retain the other good properties of the composition to which they were added.

The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated.

The following constituents were blended together to form the additive of this invention:

A white acrylic lacquer was prepared by blending together the following ingredients:

About 67 parts of the above white acrylic lacquer and 33 parts of the above additive were blended together to form Paint 1 and sprayed onto a thermoplastic polyurethane flexible substrate and dried tack free at ambient temperature in 15 minutes. The gloss, distinctness of image, flexibility at room temperature and at -28.degree. C. and gasoline resistance was measured and the panel was then exposed to outdoor weathering in Florida for 6 months and the gloss at 60.degree. was measured and % gloss retention was determined. The results of these tests are recorded in the Table.

The following paints were formulated using commercial products which are used to improve flexibility of finishes.

Each of the above paints A-D were each applied to a separate flexible substrate described above as the paint made with the additive of this invention and dried tack free at ambient temperature and gloss, distinctness of image, flexibility at room temperature at -28.degree. C. and gasoline resistance for each was measured and 60.degree. gloss retention was determined after 6 months outdoor weather in Florida. The results are shown in the Table.

The gloss and distinctness of image (DOI) of all the paints was about equivalent. The flexibility of Paint 1 containing the additive of the invention was better than Paint A and about equivalent to the other paints and the flexibility of Paint 1 at -28.degree. C. was equal to Paint D and better than the other paints. The gasoline resistance of Paint 1 was better than the other paints. The outstanding feature is that Paint 1 has substantially better gloss retention after exposed to outdoor weathering in Florida for 6 months in comparison to the Paints A-D.

A black nitrocellulose lacquer was prepared by blending together the following constituents:

About 264.5 parts of the additive of this invention, prepared in Example 1, were blended with the above black lacquer and the resulting composition was sprayed onto a thermoplastic polyurethane flexible substrate and dried in 15 minutes to a tack free state at ambient temperatures. The gloss at 20.degree. was 64, at 60.degree. 91 and the distinctness of image was 40. The flexibility at room temperature was 9 and at -28.degree. C. was 8. Gasoline resistance was 4. 60.degree. gloss retention after 6 months weathering in Florida was 90%. The same tests and ratings were used in Example 1.

A white alkyd-acrylic resin paint was formulated by blending the following constituents:

About 160 parts of the additive of this invention, prepared in Example 1, were blended with the above with alkyd acrylic resin paint and the resulting composition was sprayed onto a thermoplastic polyurethane flexible substrate and dried in 30 minutes to a tack free state at ambient temperatures. The gloss at 20.degree. was 80, at 60.degree. 90, flexibility at room temperature was 10 and at -28.degree. C. was 8. Gasoline resistance was 4. 60.degree. Gloss retention after 6 months weathering in Florida was 84%. The same tests and ratings were used as in Example 1.