Solid polymer binders for thermosetting powder coating compositions, powder coating compositions containing these binders and metal objects coated with these coating compositions

Claim 2

A solid polymer binder for thermosetting powder coating compositions comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups and derived from polyisocyanates, hydroxycarboxylic acids and blocking agents different from oximes, containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, with (B) at least one compound selected from the group consisting of homo- and heterofunctional compounds either containing hydroxy groups or being capable of producing hydroxy groups, component (B) being present in an amount such that cross-linked products are formed under stoving conditions, in which the content of COOH-groups is not higher than 1.5% referred to the weight of components (A) and (B).

Claim 3

A solid polymer binder as claimed in claim 1, wherein the content of COOH-groups is not higher than 1.0 percent referred to the weight of components (A) and (B).

Claim 4

A solid polymer binder as claimed in claim 1, wherein the content of COOH-groups is not higher than 0.718% referred to the weight of components (A) and (B).

Claim 5

An article coated with a thermosetting powder coating composition comprising a homogeneous mixture of (I) a solid polymer binder comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups, formed by the following reaction X(M--H)+(OCN).sub.x --R.sup.1 --(NCO).sub.y +(HO).sub.y --R.sup.2 --(COOH).sub.n → (MCONH).sub.x --R.sup.1 --(NHCOO).sub.y --R.sup.2 --(COOH).sub.n wherein M--H is a blocking agent different from oximes and containing one active hydrogen atom which is capable of reacting with an isocyanate, R 1 and R 2 are aliphatic, cycloaliphatic or aromatic groups and x,y and n are equal or different integers being at least 1 and at most 15 and altogether at most 30 and containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, the residual amount of free isocyanate groups not exceeding 0.5% by weight of free NCO, with (B) at least one compound selected from the group consisting of homo- and hetero-functional compounds either containing hydroxy groups or being capable of producing hydroxy groups such that in the cross-linked products the content of COOH groups is not higher than 0.718% referred to the weight of component (A) and (B), with (II) at least one additive selected from the group consisting of dyes, pigments, fillers, flow agents thixotropic agents, additional cross linking agents, catalysts and oxidation inhibitors.

Claim 6

An article coated with a thermosetting powder coating composition comprising a homogeneous mixture of (I) a solid polymer binder comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups, formed by the following reaction X(M--H)+(OCN).sub.x --R.sup.1 --(NCO).sub.y +(HO).sub.y --R.sup.2 --(COOH).sub.n → (MCONH).sub.x --R.sup.1 --(NHCOO).sub.y --R.sup.2 --(COOH).sub.n wherein M--H is a blocking agent different from oximes and containing one active hydrogen atom which is capable of reacting with an isocyanate, R 1 and R 2 are aliphatic, cycloaliphatic or aromatic groups and x,y and n are equal or different integers being at least 1 and at most 15 and altogether at most 30 and containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, the residual amount of free isocyanate groups not exceeding 0.5% by weight of free NCO, with (B) at least one compound selected from the group consisting of homo- and hetero-functional compounds either containing hydroxy groups or being capable of producing hydroxy groups such that in the cross-linked products the content of COOH groups is not higher than 0.718% referred to the weight of component (A) and (B), with (II) at least one additive selected from the group consisting of dyes, pigments, fillers, flow agents thixotropic agents, additional cross linking agents, catalysts and oxidation inhibitors.

Claim 7

A process for the manufacturing of coatings on a substrate wherein a powder coating composition comprising a homogeneous mixture of (I) at least one solid polymer binder comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups, formed by the following reaction X(M--H)+(OCN).sub.x --R.sup.1 --(NCO).sub.y +(HO).sub.y --R.sup.2 --(COOH).sub.n →(MCONH).sub.x --R.sup.1 --(NHCOO).sub.y --R.sup.2 --(COOH).sub.n wherein M--H is a blocking agent different from oximes and containing one active hydrogen atom which is capable of reacting with an isocyanate, R 1 and R 2 are aliphatic, cycloaliphatic or aromatic groups and x,y and n are equal or different integers being at least one and at most 15 and altogether being at most 30 and containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, the residual amount of free isocyanate groups not exceeding 0.5% by weight of free NCO, with (B) at least one compound selected from the group consisting of homo- and hetero-functional compounds either containing hydroxy groups or being capable of producing hydroxy groups with (II) at least one additive selected from the group consisting of dyes, pigments, fillers, flow agents thixotropic agents, additional cross-linking agents, catalysts and oxidation inhibitors is applied to a substrate and then stoved at a temperature above 100° C. to yield a coating in which the content of COOH-groups is not higher than 0.718% referred to the weight of component (A) and (B).

Claim 8

A process for the manufacturing of coatings on a substrate wherein a powder coating composition comprising a homogeneous mixture of (I) at least one solid polymer binder comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups, formed by the following reaction X(M--H)+(OCN).sub.x --R.sup.1 --(NCO).sub.y +(HO).sub.y --R.sup.2 --(COOH).sub.n →(MCONH).sub.x --R.sup.1 --(NHCOO).sub.y --R.sup.2 --(COOH).sub.n wherein M--H is a blocking agent different from oximes and containing one active hydrogen atom which is capable of reacting with an isocyanate, R 1 and R 2 are aliphatic, cycloaliphatic or aromatic groups and x,y and n are equal or different integers being at least one and at most 15 and altogether being at most 30 and containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, the residual amount of free isocyanate groups not exceeding 0.5% by weight of free NCO, with (B) at least one compound selected from the group consisting of homo- and hetero-functional compounds either containing hydroxy groups or being capable of producing hydroxy groups with (II) at least one additive selected from the group consisting of dyes, pigments, fillers, flow agents thixotropic agents, additional cross-linking agents, catalysts and oxidation inhibitors is applied to a substrate and then stoved at a temperature above 100° C. to yield a coating in which the content of COOH-groups is not higher than 0.718% referred to the weight of component (A) and (B).

Claim 9

An article as claimed in claim 4, wherein the prepolymer (A) contains from 7 to 20% by weight of blocked isocyanate groups.

Claim 10

An article as claimed in claim 4, wherein the prepolymer (A) has an acid number in the range from 5 to 80.

Claim 11

An article as claimed in claim 4, wherein x, y and n are equal or different integers being at least 1 and at most 10 and altogether being at most 15.

Claim 12

An article as claimed in claim 4, wherein prepolymer (A) has been produced in a manner such that those isocyanate groups of the polyisocyanate component which are not blocked, are substantially compensated by hydroxy groups such that an at least oligomeric product is formed.

Claim 13

An article as claimed in claim 9, wherein the residual amount of free isocyanate groups in component (A) does not exceed 0.5% by weight of free NCO.

Claim 14

An article as claimed in claim 4, wherein component (B) contains groups capable of reacting with carboxyl groups without formation of volatile compounds.

Claim 15

An article as claimed in claim 4, wherein as an additive an aromatic diketone is present in an amount of from 0.1 to 3% referred to the weight of the binder.

Claim 16

An article as claimed in claim 4, wherein the substrate is a metal.

Claim 17

A process as claimed in claim 5, wherein a powder composition comprising a homogeneous mixture of (I) at least one binder with (II) at least one additive selected from the group consisting of fillers, flow agents and oxidation inhibitors is applied to a metal substrate by the whirl sintering method or electrostatic powder spraying and then stoved at a temperature above 100° C.

Claim 18

A solid polymer binder for thermosetting powder coating compositions as claimed in claim 3 comprising a combination of (A) a polyurethane prepolymer containing carboxyl groups, formed by the following reaction X(M--H)+(OCN).sub.x --R.sup.1 --(NCO).sub.y +(HO).sub.y --R.sup.2 --(COOH).sub.n →(MCONH).sub.x --R.sup.1 --(NHCOO).sub.y --R.sup.2 --(COOH).sub.n wherein M--H is a blocking agent different from oximes and containing one active hydrogen atom which is capable of reacting with an isocyanate, R 1 and R 2 are aliphatic, cycloaliphatic or aromatic groups and x,y and n are equal or different integers being at least 1 and at most 15 and altogether being at most 30 and containing from 1 to 40% by weight of blocked isocyanate groups and having an acid number in the range from 1 to 80, the residual amount of free isocyanate groups not exceeding 0.5% by weight of free NCO, with (B) at least one compound selected from the group consisting of homo- and hetero-functional compounds either containing hydroxy groups or being capable of producing hydroxy groups, component (B) being present in an amount such that cross-linked products are formed under stoving conditions, in which the content of COOH-groups is not higher than 0.718% referred to the weight of components (A) and (B).