METHOD AND APPARATUS FOR CONTROLLING THE GAS CONTENT OF DISPENSED HOT MELT THERMOPLASTIC ADHESIVE FOAM

摘要

METHOD AND APPARATUS FOR CONTROLLING THE GAS CONTENT OF DISPENSED HOT MELT THERMOPLASTIC ADHESIVE FOAM A method and apparatus for controlling the gas content of dispensed hot melt thermoplastic adhesive foam. Air or another relatively inert gas is mixed with molten thermoplastic adhesive, and the mixture is pressurized to form a gas and molten adhesive "solution". When the molten adhesive and gas "solution" is dispensed at atmospheric pressure, the gas is released from "solution" and becomes entrapped in the adhesive in order to form a homogeneous closed cellular adhesive foam. In order to control the gas content of the dispensed adhesive and gas "solution", the pressure drop across a restriction in the flow path of the solution is sensed, and a control circuit controls the addition of gas to the adhesive to maintain the sensed pressure drop at a desired level.