Abrasive material and process for manufacturing the same

Claim 1

A process for the manufacture of an abrasive material which comprises the steps (i) applying a basic binder layer to a substantially flat flexible support; (ii) scattering abrasive particles onto the said basic binder layer; (iii) drying the product of step (ii) in a horizontal drying unit having an air temperature of from 100° to 140° C. and subsequently cooling the product in an air stream having a temperature of not more than 40° C., the drying process being effected for a time sufficient to allow the said basic binder layer to attain sufficient adhesive strength to prevent displacement of the abrasive particles disposed therein when the product is cooled; (iv) applying a second binder layer as sizer to the cooled product of step (iii); (v) drying the sizer in a horizontal drying unit having an air temperature of from 100° to 140° C. and subsequently cooling the product in an air stream having a temperature of not more than 40° C., the drying process being effected for a time sufficient to allow the said sizer to become imprint resistant; (vi) loosely rolling up the product of step (v); and (vii) curing the product of step (vi) by gradual heating to 110° to 140° C. followed by gradual cooling to a temperature of about 50° C., wherein the gradual heating and gradual cooling is effected by passing a heating or cooling air stream, as required, substantially axially through the rolled-up product; wherein the said basic and second binder layers each comprise an aqueous mixture with solids content of at least 55% by weight, based on the total composition, and a viscosity of no more than 5,000 mPa.s of (A) at least one predominantly ortho-structured resol having a molar ratio of phenolic component to formaldehyde of from 1:(1.1 to 2.5), and (B) at least one polyvinyl alcohol in an amount of from 5 to 30% by weight, based on the weight of solid phenolic resin.