Process for producing polymer films from aqueous polymer compositions

A process for producing sheets of a pressure-sensitive adhesive composition, said process comprising:

• (A) providing an extruder comprising a plurality of interconnecting sections having at least one feed unit in one upstream section, at least one downstream unit comprising a homogenizer mixer, and at least one downstream section below at least one homogenizer mixer containing a water removal unit, said downstream water removal unit comprising a barrel section having a vent opening;
• (B) introducing an aqueous adhesive composition comprising water and a pressure-sensitive adhesive polymer into the feed unit or units of the extruder;
• (C) conveying the composition through the extruder;
• (D) maintaining the adhesive composition at a temperature which facilitates vaporization of at least a portion of the water as the composition is conveyed through the extruder;
• (E) reducing the pressure in the barrel section of the water removal units sufficiently to evaporate and remove at least a portion of the water in the adhesive composition conveyed through that unit to form a water-reduced pressure-sensitive adhesive composition;
• and
• (F) extruding the water-reduced pressure-sensitive adhesive composition through a sheet die to provide a sheet of the adhesive.

A process for coating a composition onto a support web, said process comprising the steps of:

• (A) introducing an aqueous composition comprising water and a polymer through at least one feed unit in one upstream section of an extruder comprising a plurality of interconnecting sections wherein at least one downstream section comprises a homogenizer mixer;
• (B) conveying the composition through the extruder;
• (C) maintaining the composition at a temperature which facilitates vaporization of at least a portion of the water as the composition is conveyed through the extruder;
• (D) reducing the pressure in at least one section of the extruder downstream of the feed unit sufficiently to evaporate at least a portion of the water in the composition conveyed through that section;
• (E) removing the evaporated water from the extruder through at least one vent in a downstream section to form a water-reduced composition;
• and
• (F) extruding the water-reduced composition onto a support web to thereby provide a uniform coating of polymer on the support web.

A process for producing a coating of a pressure-sensitive adhesive composition onto a support web, said process comprising:

• (A) providing an extruder comprising a plurality of interconnecting sections and having at least one upstream section containing a feed unit, at least one downstream section comprising a homogenizer mixer, and at least one downstream section below the homogenizer mixer containing a water removal unit, said downstream water removal unit comprising a barrel section having a vent opening, a vacuum pump, and a duct surrounding the vent opening and extending from the barrel section to the vacuum pump;
• (B) introducing into the feed unit or units of the extruder, an aqueous pressure-sensitive adhesive composition comprising water and a pressure-sensitive adhesive polymer, said water being present in an amount of from about 20% to about 60% by weight of the adhesive composition;
• (C) conveying the composition through the extruder;
• (D) maintaining the adhesive composition at a temperature which facilitates vaporization of at least a portion of the water as the composition is conveyed through the extruder;
• and
• (E) activating the vacuum pump to reduce the pressure in the barrel section of the water removal unit or units sufficiently to evaporate at least a portion of the water in the adhesive composition conveyed through that section to form a water-reduced adhesive composition;
• and
• (F) extruding the pressure-sensitive adhesive composition through a die onto a support web to provide a uniform coating of pressure-sensitive adhesive on the support web.