Claims
- 1. A process for preparing polyurethane powder enamles free of cleavage products selected from monoalcohols, primary or secondary amines, having good storage stability, which are curable above 120.degree. C., and which are linear polyisocyanate addition products which are irreversibly, partially or completely, blocked and which contain uretidinedione groups, characterized in that,
- a. linear isophorone diisocyanate-diol polyaddition adducts which are irreversibly, partially or completely, blocked with terminal monoalcohols or monoamines and which contain uretidinedione groups, whose uretidinedione groups are essentially free from isocyanurate groups and are derived from isophorone diisocyanate which can be more than 98% decomposed back into isophorone diisocyanate by heating, having the following formula: ##STR7## wherein R= ##STR8## X= ##STR9## R'=a divalent aliphatic, cycloaliphatic, aromatic or araliphatic hydrocarbon radical of a diol, n>1,
- R"=a monoalcohol radical or primary or secondary monoamine radical having 1-30 C-atoms, having an NCO/OH ratio or uretidinedione dimer of isophorone diisocyanate to diol of 1:0.5 to 1:0.9, preferably 1:0.6 to 1:0.8, a uretidinedione/diol molar ratio between 2:1 and 6:5, preferably 3:2 to 5:4, a molecular weight between 550 and 4300, preferably between 1500 and 2000, and a melting point of .gtoreq.70.degree. C. to .ltoreq.130.degree. C., preferably 80.degree. C. to 120.degree. C.,
- b. polyhydroxy compounds having an OH functionality of .gtoreq.3.4 to .ltoreq.7, preferably 3.7 to 4.5, an average molecular weight of 2000 to 5000, preferably 2500 to 4500, a hydroxyl number between 30 and 100 mg KOH/g, preferably between 40 and 80 mg KOH/g, a viscosity of <100,000 mPa s preferably <40,000 mPa s at 160.degree. C. and a melting point of .ltoreq.70.degree. C. to .ltoreq.120.degree. C., preferably 75.degree. C. to 100.degree. C., and
- c. the additives customary in polyurethane chemistry, are reacted, wherein the molar ratio of a. and b. is selected so that the NCO/OH ratio is 0.8:1 to 1.2:1.
- 2. Polyurethane powder enamels prepared according to claim 1.
- 3. A polyurethane powder enamel free of volatile cleaverage products selected from monoalcohols or primary or secondary amines comprising:
- a. a partially or completely blocked adduct of the uretidinedione dimer of isophorone diisocyanate, essentially free from isocyanurate groups, with a diol, wherein said adduct has the formula: ##STR10## wherein R= ##STR11## X=NCO or ##STR12## R'=a divalent aliphatic cycloaliphatic, aromatic or araliphatic hydrocarbon radical of a diol, n>1, and
- R"-a monoalcohol radical or primary or secondary monoamine radical with 1-30 C-atoms, the NCO/OH ratio of said dimer to said diol is from 1:0.5 to 1:0.9, the dimer-diol molar ratio is from 2:1 to 6:5, the average molecular weight is between 550 and 4300, and the melting point is .gtoreq.70.degree. C. and .ltoreq.130.degree. C., and wherein the uretidinedione groups present in said adduct are cleavable with heat into .gtoreq.98% --NCO groups, and
- b. a polyol having an OH functionality >3.4 to <7, an average molecular weight of 2000 to 5000, an OH number between 30 and 100 mg KOH/g, a viscosity of <100,000 mPa s at 160.degree. C., and a melting point .gtoreq.70.degree. C. and .ltoreq.120.degree. C.,
- c. the additives customary in polyurethane chemistry, wherein the mole ratio of said adduct to said polyol is chosen so that the ratio of NCO groups in said adduct to OH groups in said polyol is from 0.8:1 to 1.2:1.
- 4. The powder enamel of claim 3, wherein the NCO/OH ratio of said dimer to said diol is from 1:0.6 to 1:0.8.
- 5. The powder enamel of claim 3, wherein the dimer/diol molar ratio is ferom 3:2 to 5:4.
- 6. The powder enamel of claim 3, wherein the melting point of said adduct is from 85.degree. C. to 120.degree. C.
- 7. The powder enamel of claim 3, wherein the OH functionality of said polyol is from 3.7 to 4.5.
- 8. The powder enamel of claim 3, wherein the average molecular weight of said polyol is from 2500 to 4500.
- 9. The powder enamel of claim 3, wherein said OH number is between 40 and 80 mg KOH/g.
- 10. The powder enamel of claim 3, wherein said viscosity is <40,000 mPas.s at 160.degree. C.
- 11. The powder enamel of claim 3, wherein the melting point of said polyol is from 75.degree. C. to 100.degree. C.
- 12. The powder enamel of claim 3, wherein said powder enamel additionally comprises an additive common to polyurethane chemistry.
- 13. The powder enamel of claim 3, wherein said additive is a pigment, a spreading agent, a softener, or a catalyst.
- 14. A polyurethane enamel coating produced from the powder enamel of claim 3.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3030539 |
Aug 1980 |
DEX |
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Parent Case Info
This is a continuation of application Ser. No. 292,712, filed Aug. 13, 1981 and now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
3998794 |
Muller et al. |
Dec 1976 |
|
Foreign Referenced Citations (2)
Number |
Date |
Country |
2420475 |
Nov 1975 |
DEX |
2502934 |
Jul 1976 |
DEX |
Non-Patent Literature Citations (2)
Entry |
Chem. Abstr., vol. 85, 144945q, 1976, p. 109. |
Chem. Abstr., vol. 84, 91789n, 1976. |
Continuations (1)
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Number |
Date |
Country |
Parent |
292712 |
Aug 1981 |
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