Method for producing microcellular foam polypropylene thick board

摘要

Disclosed is a method for producing a microcellular foam polypropylene thick board, by foaming a polypropylene motherboard by a flat foaming equipment, wherein the polypropylene motherboard bears a core structure and a pore canal structure in the core of the foam polypropylene motherboard, shortening a diffusion path of supercritical carbon dioxide into a polypropylene matrix, thus reducing the saturation time required for diffusion equilibrium and significantly increasing the production efficiency. Also provided is a method for preparing the foam polypropylene motherboard bearing the pore canal structure in the core, by extrusion molding, from general polypropylene as the raw material. The method described in the present invention may be used to produce the microcellular foam board with small cell size, high cell density and high thickness.

主权项

1. A method for producing a microcellular foam polypropylene thick board by foaming a polypropylene motherboard with a special supercritical flat foaming equipment,
wherein the polypropylene motherboard bears a core structure, the polypropylene motherboard bearing the core structure is the polypropylene extruded board having one or more rows of pore canals in a center, the polypropylene extruded board has a thickness of 5-50 mm, the pore canals have a cross-section in a shape of a polygon with a number of sides of 3-8, a circle or an ellipse, the pore canals have a height of 0.1-10 mm, a width of 0.1-50 mm, and a pitch of 0:1-20 mm between the pore canals; wherein the supercritical flat foaming equipment comprises: a hydraulic system for supply clamping pressure, a temperature control system for supplying heat, a pressure gas delivery system for supplying supercritical fluid, a flat foaming mold, a flash blow-down system and a gas recovery system; and wherein the foaming process comprises the following steps: (1) the flat foaming mold is heated up to a foaming temperature by the temperature control system for supplying heat; (2) the polypropylene motherboard bearing the core structure is placed into the flat foaming mold, which is driven by the hydraulic system for closing; upon pressurizing up to 15-20 MPa by the hydraulic system, a high pressure and high temperature gas is introduced into the flat foaming mold by the pressure gas delivery system until the gas pressure is up to 5-25 MPa; (3) the high pressure and high temperature gas is diffused from the surface and core of the polypropylene motherboard into a polymeric matrix, with a saturation time required for diffusion being 30-200 minutes; and (4) upon dissolution in equilibrium, the high pressure and high temperature gas within the flat foaming mold is blown down by the flash blow-down system and is recovered by the gas recovery system; when the mold is opened, the polypropylene motherboard pops out of the mold and foams to give the microcellular foam polypropylene material.