Patent ID: 6040414
Filing Date: 2000-03-21
Classification: C08G,C09D,Y10T

Abstract:
A process for coating coils with crosslinkable compositions comprising blocked isocyanates and (per)fluoropolyetheral polymers having an average number molecular weight of between 500 and 5000 and hydroxyl bifunctional termination and having improved stain release properties, no dirt pick-up and resistance to pressure marking and to hostile environments, said (per)fluoropolyetheral polymers comprising repeating units selected from the group consisting of:a) --(C.sub.3 F.sub.6 O).sub.m (CFYO).sub.n -- wherein the unit (C.sub.3 F.sub.6 O) and (CFYO) are perfluorooxyalkylenic units statistically distributed along the chain; m' and n' are integers such as to give the molecular weight indicated above, and the ratio m'/n' between 5 and 40, when n' is different from 0; Y is equal to F or CF.sub.3 ; n' can also be 0; said units can be linked to each other by a bridge bond --O--R'.sub.f --O--, wherein R'.sub.f has the meaning defined in c) hereunder;b) --(C.sub.2 F.sub.4 O).sub.p' (CFYO).sub.q' (C.sub.3 F.sub.6 O).sub.t' -- wherein p' and q' are integers such that p'/q' ranges between 5 and 0.3, and such that the molecular weight is that indicated above; t' being an integer with the meaning of m', Y=F or CF.sub.3 ; t' can be 0 and q'/q'+p'+t' lower than or equal to 1/10 and the t'/p' ratio is from 0.2 to 6;c) --CR.sub.4 R.sub.5 CF.sub.2 CF.sub.2 O-- wherein R.sub.4 and R.sub.5 are equal to or different from each other and chosen from H, Cl, F or perfluoroalkyl 1-4 C atoms, the molecular weight being that indicated above, said unit inside the fluoropolyoxyalkylenic chain being linked to each other as follows:--(OCR.sub.4 R.sub.5 CF.sub.2 CF.sub.2).sub.p --O--R'.sub.f --O--(CR.sub.4 R.sub.5 CF.sub.2 CF.sub.2 O).sub.q --wherein R'.sub.f is a fluoroalkylenic group from 1 to 4 C, and p+q is at least 1 and such that the molecular weight is that indicated above,d) --(CF(CF.sub.3)CF.sub.2 O-- said units being linked each other inside the fluoropolyoxyalkylenic chain as follows:--(OCF.sub.2 CF(CF.sub.3)).sub.a O--CF.sub.2 (R'.sub.f).sub.x CF.sub.2 --O--(CF(CF.sub.3)CF.sub.2 O).sub.b --wherein R'.sub.f has the meaning indicated above, x is 0 or 1, a and b are integers and a+b is at least 1 and such that the molecular weight is that indicated above, ande) --(C.sub.2 F.sub.4 O).sub.a' (CFYO).sub.b' -- wherein a' and b' are integers such that the molecular weight is within the range indicated, a'/b' ranges between 5 and 0.3, Y has the meaning indicated above, having hydroxyl bifunctional termination;said process comprising coating coils with said composition, and crosslinking said polymers, said crosslinking being carried out with the blocked isocyanates having at least three NCO groups.