Thermosetting powder coating compositions having lower chalk-free temperature

A thermosetting powder coating composition comprising the following components A to E:

• A:
• one or more unsaturated resins comprising ethylenic unsaturations (UR) selected from the group consisting of polyester resins, polyurethanes, epoxy resins, polyamides, polyesteramides, polycarbonates, polyureas and mixtures thereof, and
• B:
• one or more curing agents selected from the group consisting of vinyl urethanes, vinyl functionalized urethane resins and mixtures thereof, wherein at least one of the one or more curing agents is curing agent A which is selected from the group consisting of i), ii) and iii):
• i) one or more crystalline VU-c each of which is a crystalline vinyl urethane having a melting enthalpy ΔHm≥35 J/g, and
• ii) one or more crystalline VFUR-c each of which is a crystalline vinyl functionalized urethane resin having a melting enthalpy ΔHm≥35 J/g, and
• iii) mixtures of the one or more crystalline VU-c and the one or more crystalline VFUR-c, wherein
• the ΔHm is each measured via Differential Scanning Calorimetry (DSC) according to the description, and
• a ratio K of the total mol of the ethylenic unsaturations in B divided by the total mol of the ethylenic unsaturations in A is at least 0.9 and at most 7,
• C:
• one or more thermal radical initiators selected from the group consisting of organic peroxides, azo compounds, and mixtures thereof, wherein the total amount of component C is at least 25 and at most 300 mmol/Kg A and B, and
• D:
• one or more co-initiators selected from the group consisting of onium compounds, sulpho-compounds, and mixtures thereof, wherein
• (D1) the onium compound is selected from the group consisting of compounds represented by formulae I-X through IX-X below:
• wherein
• A− is a halide anion;
• R1′″ is a C1-C12 saturated hydrocarbyl,
• R2′″ is a C1-C12 saturated hydrocarbyl;
• R3′″ is H or a C1-C12 hydrocarbyl,
• R4′″ is a C1-C12 hydrocarbyl;
• R5′″ is H or a C1-C12 hydrocarbyl,
• R6′″ is a C1-C12 hydrocarbyl;
• R7′″ is H or a C1-C12 hydrocarbyl,
• R8′″ is H or a C1-C12 hydrocarbyl;
• R9′″ is H or a C1-C12 hydrocarbyl,
• R10′″ is H or a C1-C12 hydrocarbyl,
• R11′″ is H or a C1-C12 hydrocarbyl, and
• R12′″ is H or a C1-C12 hydrocarbyl, and wherein
• (D2) the sulpho-compound is selected from the group consisting of sulpho-compounds-1, sulpho-compounds-2, sulpho-compounds-3, sulpho-compounds-4, sulpho-compounds-5, and mixtures thereof, wherein
• the sulpho-compound-1 is a compound represented by the following formula L1:
• wherein R1′ is a C1-C10 hydrocarbyl, and R2′ is a C1-C10 hydrocarbyl, and wherein
• the sulpho-compound-2 is a compound represented by the following formula L2:
• wherein R3′ is a C1-C12 hydrocarbyl, and R4′ is a C1-C12 hydrocarbyl, and wherein
• the sulpho-compound-3 is a compound represented by the following formula L3:
• wherein R5′ is a C1-C12 hydrocarbyl, and R6′ is a C1-C12 hydrocarbyl and R7′ is a C1-C12 saturated hydrocarbyl, and R8′ is a C1-C12 saturated hydrocarbyl, and wherein
• the sulpho-compound-4 is a compound represented by the following formula L4:
• wherein R9′ is a C1-C12 hydrocarbyl, and R10′ is a C1-C12 hydrocarbyl and R11′ is a C1-C12 hydrocarbyl, and wherein
• the sulpho-compound-5 is a compound represented by the following formula L5:
• wherein R12′ is a C1-C12 hydrocarbyl or a substituted hydrocarbyl, and R13′ is a C1-C12 hydrocarbylene, and wherein
• the total amount of component D is at least 10 and at most 150 mmol/Kg A and B, and
• E:
• one or more inhibitors selected from the group consisting of phenolic compounds, stable radicals, catechols, phenothiazines, hydroquinones, benzoquinones and mixtures thereof, and wherein the component E is present in a total amount which is at least 20 and at most 2000 mg/Kg of the components A and B.