Airless atomizing methods for making chemical mechanical planarization (cmp) polishing pads

Abstract

The present invention provides methods of making chemical mechanical planarization (CMP) polishing pads comprising introducing, separately, through a side liquid feed port into an internal chamber having a downstream open end a liquid polyol component stream comprising an amine curative at a temperature T 1 of from 40 to 90° C. and a liquid isocyanate component stream at a temperature T 2 of from 40 to 90° C., each of the two components under a set point pressure of from 13,000 to 24,000 kPa so that the two streams are pointed towards each other at 90 degrees to downstream flow, thereby impingement mixing the two components to form a reaction mixture, discharging a stream of the reaction mixture from the open end of the internal chamber under pressure through a narrow, preferably, round orifice and onto an open mold substrate having a urethane releasing surface, and curing the reaction mixture to form a porous polyurethane reaction product.

We claim: 
     
         1 . A method of making chemical mechanical planarization (CMP) polishing pads comprise introducing, separately, through a side liquid feed port into an internal chamber having a downstream open end a liquid polyol component stream at a temperature T 1  of from 40 to 90° C. and a liquid isocyanate component stream at a temperature T 2  of from 40 to 90° C., each of the two components under a set point pressure of from 13,000 to 24,000 kPa (2000 to 3400 psi) so that the two streams are pointed towards each other at 90 degrees to downstream flow, thereby impingement mixing the two components to form a reaction mixture, the liquid polyol component comprising one or more polyol and an amine curative; and the liquid isocyanate component comprising one or more polyisocyanate or isocyanate-terminated urethane prepolymer; at least one component containing a sufficient amount of up to 2.0 wt. %, based on the total solids weight of the reaction mixture, of a nonionic surfactant to facilitate the stabilization of pores, discharging a stream of the reaction mixture from the open end of the internal chamber under pressure through a narrow orifice and onto an open mold substrate having a urethane releasing surface, and curing the reaction mixture at from ambient temperature to 130° C. to form a porous polyurethane reaction product having a density ranging from 0.6 gm/cc to 1 gm/cc. 
     
     
         2 . The method as claimed in  claim 1 , wherein the liquid polyol component comprises as an amine curative an aromatic diamine. 
     
     
         3 . The method as claimed in  claim 1 , wherein the liquid isocyanate component comprises an aromatic polyisocyanate or aromatic isocyanate-terminated urethane prepolymer. 
     
     
         4 . The method as claimed in  claim 1 , wherein the reaction mixture contains no added blowing agents and no added pressurized gas. 
     
     
         5 . The method as claimed in  claim 1 , wherein the reaction mixture has a gel time of 2 to 300 seconds at the curing temperature. 
     
     
         6 . The method as claimed in  claim 1 , wherein the internal chamber is a closed end cylinder having a downstream open end, an axis of symmetry, at least two liquid feed ports that open into the internal cylindrical chamber, at least one liquid isocyanate component feed port that opens into the internal chamber and at least on liquid polyol component feed port that opens into the internal chamber, wherein the closed end and the open end are perpendicular to the axis of symmetry; and, wherein the at least one liquid polyol component feed port and the at least one liquid isocyanate component feed port are arranged along a circumference of the internal cylindrical chamber proximate the closed end. 
     
     
         7 . The method as claimed in  claim 1 , wherein the substrate is an open mold having a female topography that forms a desired groove pattern of a CMP polishing pad as the applied reaction mixture fills the mold. 
     
     
         8 . The method as claimed in  claim 1 , wherein upon introducing each of the liquid polyol component at temperature T 1  and the liquid isocyanate component at temperature T 2  to the internal chamber, each has a viscosity of from 10 to 1000 cPs. 
     
     
         9 . The method as claimed in  claim 1 , wherein the resulting CMP polishing pad has an average pore diameter of from 20 to 80 μm. 
     
     
         10 . The method as claimed in  claim 1 , wherein the reaction mixture and each of the liquid isocyanate component and the liquid polyol component are solvent free and substantially water free.