Method for preparing thermoplastic polymer foamed beads

Abstract

The invention discloses a method for preparing thermoplastic polymer foamed beads. The method comprises the following steps: 1) putting polymer particles into a sealed container heated to a foaming temperature, and putting the sealed container in a vacuum environment; 2) introducing supercritical fluid into the sealed container, and performing swelling diffusion; 3) after swelling diffusion of the supercritical fluid lasts for 5-60 minutes, releasing the pressure of the sealed container to discharge out the supercritical fluid, and controlling the pressure release velocity to induce nucleation and growth of foam pores so as to enable the polymer particles to swell and grow; 4) leading the polymer particles inside the sealed container into the vacuum environment to further swell and grow, thereby obtaining the polymer foamed beads with a high foaming ratio, wherein the foaming temperature in the step 1) is a temperature that the polymer particles can generate plastic deformation but cannot flow yet, the forming temperature is within Tg-Tg+40 DEG C for an amorphous polymer, and Tg is a glass-transition temperature of the amorphous polymer; for a crystallized polymer, the foaming temperature is within Tm-20 DEG C and Tm, and Tm is a melting point of the crystallized polymer.

Description

technical field [0001] The invention relates to a method for preparing thermoplastic polymer foaming materials, in particular to a method for preparing high-magnification thermoplastic polymer foaming beads by supercritical fluid technology. Background technique [0002] Using foaming technology to form a large number of bubbles inside the polymer material to form a polymer foam material with a porous structure is an effective means to achieve lightweight products and save materials. The existence of a large number of cells also endows the material with excellent thermal insulation, damping and buffering, noise reduction and sound absorption and other characteristics. Generally speaking, the higher the expansion ratio of the polymer foam material, the lighter the weight of the product, the more material is saved, and the better the performance of heat insulation and cushioning. Compared with non-recyclable thermosetting foam materials that are easy to cause environmental po...

AI Technical Summary

Problems solved by technology

In autoclave foaming, the polymer particles are dispersed in water, and the blowing agent gas dissolves and diffuses into the polymer particles under high temperature and high pressure, and then through rapid pressure relief, the nucleation and growth of bubbles are triggered to form foamed beads. The water suspension used consumes a lot of heat, and the heating process also results in a longer production cycle

Furthermore, the foamed beads obtained by this method have to be washed with water to remove various additives adhering to the surface from the water suspension, so as to prevent the subsequent welding molding from being affected, causing waste of water resources and cost again. Increase

In addition, a variety of easily degradable polymers, such as thermoplastic polyurethane (TPU), polylactic acid (PLA), etc., are not suitable for cooking at high temperature for a long time

Continuous extrusion foaming is also used to manufacture polymer foaming beads. During the extrusion foaming process, because the polymer is in a molten state, it is easy to cause a high opening rate of the bubbles, resulting in easy shrinkage and deformation of the foamed bead product, which affects Subsequent welding process

[0005] Foaming agent gas is unsafe and environmentally friendly; the process consumes more energy and the product cost is higher; the process is complicated and the production efficiency is low, which is an urgent problem to be solved in the polymer bead foaming industry

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