| abstract |
A process for the manufacture of resilient rollers by coating a central shaft with a polyurethane manufactured from a polyester and a polyisocyanate is characterised in that the polyester has an acid value below 3 mg. KOH per gm. and a viscosity of 50 to 150, preferably 85 to 100 poises at 25 DEG C. In addition to dicarboxylic acids and glycols, there may also be incorporated in the reaction mixture for the initial polyesters branching components, (preferably 2 to 18 molar per cent of the total dicarboxylic acid), such as glycerol, pentaerythritol, sorbitol, mannitol, hexcanetriol, polyallyl alcohol and triethanolamine; tricarballylic acid and pyromellitic acid; compounds containing mixed groups such as diethanolamine and dihydroxy-stearic acid. Mixed linear and branched polyesters can also be used. In one method the polyester is dehydrated by heating at reduced pressure and mixed at 70 DEG C. with diisocyanate. The mixture is degassed, poured into a mould containing the shaft to be coated and cured at 110 DEG C. In the reaction mixture there may also be present pigments, such catalysts as bis(diethyl-aminoethyl) adipate, diethylamino propionamide, and dimethylcylohexylamine and silicones and plasticisers. Specifications 749,541 and 756,679 are referred to. |