Open-loop method for producing a controlled blend of polyol and blowing agent for use in the manufacture of polyurethane foam

摘要

A novel methodology and apparatus have been discovered which is of value in the production of polyurethane foam. This invention relates to a one-pass, on-demand process and apparatus for producing a controlled, homogeneous blend of the polyol-blowing agent mixture used in the manufacture of polyurethane foam using either a low-boiling point or high-boiling point blowing agent. A method is provided to control the amount of each material in the mixture, ensure homogeneous blending of the two materials after mixing, a pressure control means to maintain blowing agents in their liquid state (where necessary), and a monitoring means which allows rapid verification of the operating status of the entire system. The process is comprised of: (a) using variable flow rate displacement pumps for both materials; (b) using mass flow meters to determine the mass flow rates of both materials; (c) using electronic controllers to control the output of the pumps based on preselected input values, and thereby controlling the ratio of the mixture formed by the combination of the two materials; (d) feeding the mixture of materials into a blending zone; (e) application of kinetic blending energy to produce a homogeneous mixture; (f) the use of a back pressure control device to ensure that the processing of the materials is carried out at a pressure above the vapor pressure of the blowing agent; and (g) passing the blended material through a mass flow meter to ensure the accuracy of the mixture, that is, the sum of mass flow rates of the ingredient materials should equal the total mass flow rate of the blended materials.