DUAL-PATH GAS INJECTION SYSTEM USED FOR PHYSICAL FOAMING PROCESS, AND GAS INJECTION METHOD FOR DUAL-PATH GAS INJECTION SYSTEM

摘要

The present invention relates to a dual-path gas injection system applied to a physical foaming and insulating process, and a gas injection method for the dual-path gas injection system. The degree of foaming of a leaky cable is increased, and a high degree of foaming is achieved while the stability and uniformity of a foaming process are ensured, improving product performance and reducing product costs. The present invention is particularly suitable for a polyethylene insulation material physical foaming process. The dual-path gas injection system used for a physical foaming process comprises a carbon dioxide gas injection device portion and an octafluorocyclobutane gas injection device portion. The carbon dioxide gas injection device comprises a quantitative gas injection needle, a gas path, a gas injection machine and a gas cylinder. The gas cylinder is connected to a gas pipe and then connected to the gas injection machine, the gas injection machine stores gas to a set pressure then injects a gas at a set pressure into an extrusion machine via the quantitative gas injection needle connected by a gas pipe, and the gas is dissolved in a molten polyethylene foaming material, forming a fine cell structure. The octafluorocyclobutane gas injection device comprises a nitrogen gas cylinder, an octafluorocyclobutane gas cylinder, a gas pipe, a variable-frequency drive, a quantitative pump, a pressure relief valve, a gas path and a quantitative gas injection needle. Nitrogen in the nitrogen gas cylinder enters the octafluorocyclobutane gas cylinder via the gas pipe, and provides pressure for liquid-state octafluorocyclobutane for flowing into the gas path. The octafluorocyclobutane cylinder is connected to the quantitative pump by the gas path, after the liquid-state gas has entered the gas path, a motor is controlled by the variable-frequency drive to enable the quantitative pump to operate, the octafluorocyclobutane liquid enters the gas path after exiting the quantitative pump, the pressure within the gas path is controlled by the pressure relief valve, and when the gas pump discharge pressure exceeds a pressure relief valve set pressure, the pressure relief valve automatically ejects the liquid-state gas. The gas remains in a liquid state within the gas path, and is only converted from the liquid state to a gaseous state when passing through a final pipe. The gas is then injected into the extrusion machine via the quantitative gas injection needle, and similarly dissolved in the molten polyethylene foaming material, forming a fine cell structure.