Patent ID: 7399437

Claim:
A method of forming a chemical mechanical polishing pad, comprising: providing a tank with polymeric materials; providing a storage silo with polymeric microspheres; providing an isocyanate storage tank with isocyanates; providing a premix prep tank for forming a pre-mixture of the polymeric materials and the polymeric microspheres; providing a recirculation loop on the premix prep tank for controlling a bulk density of the pre-mixture in the premix prep tank; providing an in-line densitometer in the recirculation loop for measuring the bulk density of the pre-mixture; providing a premix run tank for storing the pre-mixture; providing a mixer for blending the pre-mixture from the premix run tank and the isocyanates; providing a reaction injection molding mold; providing a vacuum; delivering the polymeric materials and the polymeric microspheres to the premix prep tank forming a pre-mixture of the polymeric materials and the polymeric microspheres; recirculating the pre-mixture through the recirculation loop on the premix prep tank and adding polymeric materials or polymeric microspheres to obtain a desired bulk density; delivering the pre-mixture having the desired bulk density to the premix run tank; delivering the pre-mixture having the desired bulk density from the premix run tank and the isocyanates to the mixer forming a mixture of the pre-mixture and the isocyanates; injecting the mixture into a reaction injection molding mold; and, curing the mixture to form a polishing pad in the reaction injection molding mold; wherein the vacuum is used to degas at least one of the tank with polymeric materials, the isocyanate storage tank and the reaction injection molding mold.