Patent ID: 7144532

Claim:
A method of introducing blowing agent into polymeric material comprising: accumulating a first dose of blowing agent in an accumulator; controlling pressure of the first dose of blowing agent in the accumulator to a value between about 50 psi and about 1000 psi greater than pressure of polymeric material in the vicinity of a blowing agent port of a polymer processing apparatus; introducing a first dose of blowing agent from the accumulator through the blowing-agent port into the polymeric material in the polymer processing apparatus; accumulating a second dose of blowing agent in an accumulator; controlling pressure of the second dose of blowing agent in the accumulator to a value between about 50 psi and about 1000 psi greater than pressure of polymeric material in the vicinity of a blowing agent port of a polymer processing apparatus; and introducing the second dose of blowing agent from the accumulator through the blowing agent port into the polymeric material in the polymer processing apparatus.