Curable powder coating composition comprising a mixture of an alkoxylated polyamide-aldehyde resin and a polyester resin

Abstract

Curable powder coating resin compositions comprise a small proportion of an alkoxylated polyamine-aldehyde resin and a polyester resin having an acid number below 20, a .[.melting.]. .Iadd.softening .Iaddend.point between 60° and 130° C., the acid component comprising a dibasic armoatic carboxylic acid and the alcohol component comprising diols such as 2,2-di(4-beta-hydroxyethyoxy-phenyl-) propane, certain glycidyl esters and certain dihydric aliphatic alcohols. The curable powder-coating composition is applied to a substrate by a powder-coating process and the coated substrate is heated to a temperature of from 120° to 220° C. for 10 to 60 minutes. .Iadd.

What is claimed is: 
     
       1. .[.A curable powder coating composition,.]. .Iadd.A fusible pulverulent solid mixture prepared by bringing together alkoxylated polyamine-aldehyde resin and polyester resin having a softening point in the range of 60° C. to 130° C., and mixing said resins sufficiently at a temperature above the softening point thereof to form a homogeneous mixture while retaining said mixture in a thermosettable state, said mixture .Iaddend.comprising .[.a mixture of.]. 3 percent to 15 percent by weight of .[.an.]. alkoxylated polyamine-aldehyde resin and 85 percent to 97 percent by weight of .[.a.]. polyester resin having an acid number below 20 .[.and a softening point falling within the range between 60° C. and 130° C..]., of which the acid component comprises a dibasic, aromatic carboxylic acid and of which the alcohol component comprises: a. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR4##  in which R 1  and R 2  represent alkylene groups having from two to four carbon atoms, R 2  represents a group selected from alkylidene groups having three or four carbon atoms, a cycloalkylidene group having six carbon atoms, a carbonyl group and a sulfone group, x and y are numerals each being at least one, the sum of x and y being not greater than six, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from one to six carbon atoms;   b. from 0 to 40 mole percent (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula. ##STR5##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from four to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus, and   c. from  .[.5.]. .Iadd.0 .Iaddend.to 1000 mole percent (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (a), (b) and (c) being 100 mole percent, said curable coating composition having a good powder stability.   
     
     
       2. A curable coating composition, as claimed in claim 1 in which the alcohol component (a) comprises from 0 to 100 mole percent (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR6## in which R 1  and R 2  represent alkylene groups having from two to three carbon atoms, R 1  represents an alkylidene group having three carbon atoms, x and y are numerals each being at least one, the sum of x and y being not greater than six and R 4  and R 3  represent hydrogen atoms. 
     
     
       3. A curable coating composition as claimed in claim 1 in which the alcohol component of the polyester comprises: a. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of a compound selected from the polyoxyethylene and polyoxypropylene ethers of 4,4-isopropylidene diphenol, wherein both phenolic groups are oxyalkenylated and the average number of oxyalkenyl groups is from two to six;   b. from 0 to 40 mole percent (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR7##  in which R is a branched chain saturated alkyl group having from four to .[.ten.]. .Iadd.twenty .Iaddend.carbon atoms, and   c. from  .[.5.]. .Iadd.0 .Iaddend.to 100 mole percent (based on the total alcohol component of the polyester) of 2,2-dimethylpropanediol-1,3.   
     
     
       4. A curable coating composition, as claimed in claim 1 in which the alkoxylated polyamine-aldehyde resin comprises methoxylated melamine-formaldehyde resin. 
     
     
       5. A curable coating composition, as claimed in claim 2 in which the alkoxylated polyamine-aldehyde resin comprises methoxylated melamine-formaldehyde resin. 
     
     
       6. A curable coating composition, as claimed in claim 3 in which the alkoxylated polyamine-aldehyde resin comprises methoxylated melamine-formaldehyde resin. 
     
     
       7. A process for the preparation of coated substrates, in which a coating composition, comprising the curable coating composition as claimed in claim 1 is applied to a substrate by a powder-coating process and the coated substrate is heated to a temperature of from 120° to 220° C. for 10 to 60 minutes. 
     
     
       8. A process for the preparation of coated substrates, in which a coating composition, comprising the curable coating composition as claimed in claim 2 is applied to a substrate by a powder-coating process and the coated substrate is heated to a temperature of from 120° to 220° C. for 10 to 60 minutes. 
     
     
       9. A process for the preparation of coated substrates, in which a coating composition, comprising the curable coating composition as claimed in claim 3 is applied to a substrate by a powder-coating process and the coated substrate is heated to a temperature of from 120° C. for 220° C. for 10 to 60 minutes. .Iadd. 10. The coating composition of claim 1 wherein said mixture has a softening point between about 60° C. and about 120° C. .Iaddend..Iadd. 11. The coating composition of claim 1 wherein said mixture has a softening point between about 80° C. and about 110° C. .Iaddend..Iadd. 12. The coating composition of claim 1 wherein said mixture is a free-flowing powder having a particle size range of approximately 20-150 microns. .Iaddend..Iadd. 13. The coating composition of claim 1 wherein said dibasic aromatic carboxylic acid is ortho-phthalic acid, terephthalic acid, isophthalic acid, hexachlorophthalic acid, hexachlorophthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, endomethylene-tetrahydrophthalic acid, endomethylene-tetrahydrophthalic anhydride, hexachloroendomethylene-tetrahydrophthalic acid, hexachloroendomethylene-orthophthalic anhydride, methanol esters of the above, or ethanol esters of the above. .Iaddend..Iadd. 14. The coating composition of claim 1 wherein the alcohol component (b) of the polyester is a glycidyl ester of saturated aliphatic monocarboxylic acids having 9 to 11 carbon atoms and having tertiary or quaternary carbon atoms in alpha-position to the carboxyl group. .Iaddend..Iadd. 15. The coating composition of claim 1 wherein the alcohol component (c) of the polyester is 2,2-dimethylpropanediol-1,3. .Iaddend..Iadd. 16. The coating composition of claim 1 wherein the polyester contains up to 10 mole percent (based on the total alcohol component) of an aliphatic trihydric or polyhydric alcohol. .Iaddend..Iadd. 17. The coating composition of claim 1 wherein the alkoxylated polyamine-aldehyde resin is a polyamine-aldehyde resin alkoxylated with one or more aliphatic alcohols having one to six carbon atoms. .Iadd. 18. A fusible pulverulent solid mixture prepared by bringing together alkoxylated polyamine-aldehyde resin and polyester resin having a softening point in the range of 60° C. to 130° C., and mixing said resins sufficiently at a temperature above the softening point thereof to form a homogeneous mixture while retaining said mixture in a thermosettable state, said mixture comprising 3 percent to 15 percent by weight of alkoxylated polyamine-aldehyde resin and 85 percent to 97 percent by weight of polyester resin having an acid number below 20 (A) of which the acid is a dibasic, aromatic carboxylic acid or a combination of said dibasic, aromatic carboxylic acid and up to 10 mole percent (based on the total dibasic aromatic carboxylic acid) of a polybasic aliphatic carboxylic acid or an at least tribasic aromatic carboxylic acid and (B) of which the alcohol is (1) an alcohol component comprising (a) from 0 to 100 mole % (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR8##.Iaddend.  in which R 1  and R 2  represent alkylene groups having from 2 to 4 carbon atoms, R 3  represents a group selected from alkylidene groups having 3 or 4 carbon atoms, a cycloalkylidene group having 6 carbon atoms, a carbonyl group and a sulphone group, x and y are numerals each being at least one, the sums of x and y being not greater than 6, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from 1 to 6 carbon atoms;   (b) from 0 to 40 mole % (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR9##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from 4 to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus, and   (c) from 0 to 100 mole % (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (a), (b), and (c) being 100 mole % (based on the total alcohol component of the polyester); or     (2) a combination of said alcohol component and up to 10 mole percent (based on the total alcohol component of the polyester) of aliphatic trihydric or polyhydric alcohol, said curable coating composition having a   
     
     
        good powder stability. .Iadd. 19.  The coating composition of claim 18 wherein said mixture has a softening point between about 60° C. and about 120° C. .Iaddend..Iadd. 20. The coating composition of claim 18 wherein said mixture has a softening point between about 80° C. and about 110° C. .Iaddend. .Iadd. 21. The coating composition of claim 18 wherein said mixture is a free-flowing powder having a particle size range of approximtely 20-150 microns. .Iaddend..Iadd. 22. The coating composition of claim 18 wherein said dibasic aromatic carboxylic acid is ortho-phthalic acid, terephthalic acid, isophthalic acid, hexachlorophthalic acid, hexachlorophthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, endomethylene-tetrahydrophthalic acid, endomethylene-tetrahydrophthalic anhydride, hexachloroendomethylene-tetrahydrophthalic acid, hexachloroendomethylene ortho-phthalic anhydride, methanol esters of the above, or ethanol esters of the above. .Iaddend..Iadd. 23. The coating composition of claim 18 wherein the alcohol component (b) of the polyester is a glycidyl ester of saturated aliphatic monocarboxylic acids having 9-11 carbon atoms and having tertiary or quaternary carbon atoms in alpha-position to the carboxyl group. .Iaddend..Iadd. 24. The coating composition of claim 18 wherein the alcohol component (c) of the polyester is 2,2-dimethylpropanediol-1,3. .Iaddend. .Iadd. 25. The coating composition of claim 18 wherein the alkoxylated polyamine-aldehyde resin is a polyamine-aldehyde resin alkoxylated with aliphatic alcohols having one to six carbon atoms. .Iaddend..Iadd. 26. The composition of claim 18 wherein the alkoxylated polyamine-aldehyde resin is methoxylated melamine formaldehyde resin. .Iaddend..Iadd. 27. A fusible pulverulent solid mixture prepared by bringing together methoxylated melamine formaldehyde resin and polyester resin having a softening point in the range of 60° C. to 130° C., and mixing said resins sufficiently at a temperature above the softening point thereof to form a homogeneous mixture while retaining said mixture in a thermosettable state, said mixture comprising methoxylated melamine formaldehyde resin and polyester in a weight ratio of polyester to polyamine-aldehyde between 90:10 and 95:5, and wherein said polyester has an acid number below 20 and a softening point falling within the range between 60° C. and 130° C., of which the acid component comprises a dibasic, aromatic carboxylic acid and of which the alcohol component comprises: a. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR10##.Iaddend.  in which R 1  and R 2  represent alkylene groups having from two to four carbon atoms, R 3  represents a group selected from alkylidene groups having three or four carbon atoms, a cycloalkylidene group having six carbon atoms, a carbonyl group and a sulfone group x and y are numerals each being at least one, the sum of x and y being not greater than six, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from one to six carbon atoms;   b. from 0 to 40 mole percent (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR11##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from four to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus, and   c. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (a), (b) and (c) being 100 mole percent, said curable   
     
     
        coating composition having a good powder stability. .Iadd. 28.  The coating composition of claim 27 wherein said mixture has a softening point between about 60° C. and about 120° C. .Iaddend..Iadd. 29. A fusible pulverulent solid mixture prepared by bringing together alkoxylated polyamine-aldehyde resin and polyester resin having a softening point in the range of 60° C. to 130° C., and mixing said resins sufficiently at a temperature above the softening point thereof to form a homogeneous mixture while retaining said mixture in a thermosettable state, said mixture comprising alkoxylated polyamine-aldehyde and polyester in a weight ratio of polyester to polyamine-aldehyde between 90:10 and 95:5, and wherein said polyester has an acid number below 20 (A) of which the acid is dibasic aromatic carboxylic acid or a combination of said dibasic aromatic carboxylic acid and up to 10 mole percent (based on the total dibasic aromatic carboxylic acid) of a polybasic aliphatic carboxylic acid or an at least tribasic aromatic carboxylic acid and   (B) of which the alcohol is:   (1) an alcohol component comprising: a. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR12##.Iaddend.  in which R 1  and R 2  represent alkylene groups having from two to four carbon atoms, R 3  represents a group selected from a cycloalklidene group having six carbon atoms, a carbonyl group and a sulfone group, x and y are numerals each being at least one, the sum of x and y being not greater than six, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from one to six carbon atoms;   b. from 0 to 40 mole percent (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR13##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from four to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus, and   c. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (a), (b) and (c) being 100 mole percent, (based on the total alcohol component of the polyester) or     (2) a combination of said alcohol component and up to 10 mole percent (based on the total alcohol component of the polyester) of aliphatic trihydric or polyhydric alcohol, said curable coating composition having a   
     
     
        good powder stability. .Iadd. 30.  The coating composition of claim 29 wherein the alkoxylated polyamine-aldehyde resin is methoxylated melamine-formaldehyde resin. .Iaddend. .Iadd. 31. A fusible pulverulent solid mixture prepared by bringing together methoxylated polyamine-aldehyde resin and polyester resin having a softening point in the range of 67° C. to 110° C., and mixing said resins sufficiently at a temperature above the softening point thereof to form a homogeneous mixture while retaining said mixture in a thermosettable state, said mixture being suitable for application by electrostatic spray coating or fluidized bed coating and comprising methoxylated polyamine-aldehyde resin and polyester resin in a weight ratio of polyester to methoxylated polyamine aldehyde resin in the range of 97:3 to 85:15; said polyester resin having an acid number below 20 and being the esterification reaction product of acid comprising dibasic aromatic carboxylic acid and of alcohol which is: a. up to 100 mole percent (based on the total alcohol in the polyester) of an alcohol having the general formula: ##STR14##.Iaddend.  in which R 1  and R 2  represent alkylene groups having from two to four carbon atoms, R 3  represents a group selected from alkylidene groups having three or four carbon atoms, a cycloalkylidene group having six carbon atoms, a carbonyl group and a sulfone group, x and y are numerals each being at least one, the sum of x and y being not greater than six, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from one to six carbon atoms; and   b. from 0 to 40 mole percent (based on the total alcohol in the polyester) of a glycidyl ester of lauric acid or glycidyl ester of branched chain monocarboxylic acids having 9 to 11 carbon atoms; the sum of the moles of alcohol (a) and (b) representing 100 mole percent     
     
     
        of all alcohol in the polyester.  .Iadd. 32.  A process for the preparation of coated substrates which comprises: (I) applying to a substrate by powder-coating process a curable powder coating composition comprising a mixture of 3% to 15% by weight of an alkoxylated polyamine-aldehyde resin and 85% to 97% by weight of a polyester resin having an acid number below 20 and a softening point falling within the range between 60° C. and 130° C.,   (a) of which the acid is a dibasic, aromatic carboxylic acid and up to 10 mole percent (based on the total dibasic aromatic carboxylic acid) of a polybasic aliphatic carboxylic acid or an at least tribasic aromatic carboxylic acid and   (B) of which the alcohol is (1) an alcohol component comprising (a) from 0 to 100 mole % (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR15##.Iaddend.  in in which R 1  and R 2  represent alkylene groups having from 2 to 4 carbon atoms, R 3  represents a group selected from alkylidene groups having 3 or 4 carbon atoms, a cycloalkylidene group having 6 carbon atoms, a carbonyl group and a sulphone group, x and y are numerals each being at least one, the sums of x and y being not greater than 6, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from 1 to 6 carbon atoms;   (b) from 0 to 40 mole % (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR16##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from 4 to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus, and   (c) from 0 to 100 mole % (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (a), (b), and (c) being 100 mole % (based on the total alcohol component of the polyester); or     (2) a combination of said alcohol component and up to 10 mole percent (based on the total alcohol component of the polyester) of aliphatic trihydric or polyhydric alcohol, said curable coating composition having a good powder stability;     (II) heating the coated substrate to a temperature of from 120° to   
     
     
        220° C. for 10 to 60 minutes. .Iadd. 33.  The process of claim 32 wherein said coating process is an electrostatic powder spray-coating process and said coating composition has a particle size range of approximately 20-150 microns. .Iaddend..Iadd. 34. A process for the preparation of coated substrates which comprises (A) applying to a substrate by an electrostatic powder spray process a curable powder coating composition comprising a mixture of 3 percent to 15 percent by weight of an alkoxylated polyamine-aldehyde resin and 85 percent to 97 percent by weight of a polyester resin having an acid number below 20 and a softening point falling within the range between 60° C. and 130° C. of which the acid component comprises a dibasic aromatic carboxylic acid and of which the alcohol component comprises: a. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR17##.Iaddend.  in which R 1  and R 2  represent alkylene groups having from two to four carbon atoms; R 3  represents a group selected from alkylidene groups having three or four carbon atoms, a cycloalkylidene group having six carbon atoms, a carbonyl group and a sulfone group, x and y are numerals each being at least one, the sum of x and y being not greater than six, R 4  and R 5  represent a group selected from hydrogen atoms and alkyl radicals having from one to six carbon atoms;   b. from 0 to 40 mole percent (based on the total alcohol component of the polyester) of a glycidyl ester having the general formula: ##STR18##  in which R represents a group selected from straight and branched chain, saturated and unsaturated alkyl groups having from four to 20 carbon atoms, a substituted benzene nucleus and an unsubstituted benzene nucleus,   c. from 0 to 100 mole percent (based on the total alcohol component of the polyester) of at least one dihydric aliphatic alcohol, the sum of the alcohol components (a), (b) and (c) being 100 mole percent, said curable coating composition having a good powder stability; and having a particle-size range of approximately 20-150 microns; and     (B) heating the coated substrate to a temperature of from 120° to   
     
     
        220° C. for 10 to 60 minutes.  .Iadd. 35.  A method of forming a heat-single layer of coating material on a substrate comprising applying to said substrate by electrostatic powder spray coating or fluidized bed powder coating, a powdery resin composition including polyester resin and methoxylated polyamine aldehyde resin in admixture in a weight ratio in the range of 97:3 to 85:15 and having a softening point in the range of 70°-104° C., said polyester having a softening point in the range of 67°-110° C. and an acid number of less than 20, and comprising the polyesterification product of aromatic dicarboxylic acid and at least one alcohol having two hydroxyl groups, said mixture having the property of flowing on melting to form a uniform film; melting said powder, forming a film and curing said film by heating to a temperature in the range of 120° C. to 220° C. for 10 to 60 minutes; said coating material being sufficiently flexible so that a 50 micron thick layer thereof which has been cured for 30 minutes at 180° C. on a 1 millimeter thick steel test panel will not fail when bent 180° over a 3/4 inch mandrel; and said coating material also having a shock resistance of at least 2-3 mm as determined by German test specification DIN 53,156 using a coating and test panel prepared as described in connection with the foregoing flexibility test. .Iaddend..Iadd. 36. A method in accordance with claim 35 wherein the methoxylated polyamine aldehyde resin is methoxylated melamine formaldehyde resin. .Iaddend..Iadd. 37. A method in accordance with claim 35 wherein the polyester and methoxylated polyamine aldehyde resin are present in a weight ratio in the range of 95:5 to 90:10. .Iaddend.