Micro-foaming polypropylene material and preparation method thereof

Abstract

The invention relates to the field of macromolecules, and particularly relates to a micro-foaming polypropylene material and a preparation method thereof. The invention provides the micro-foaming polypropylene material with low density and high foaming rate and the preparation method thereof, wherein pores have uniform pore diameters and are mainly centralized in the material, no marks are formedon the surface and appearance is excellent. The preparation method comprises the following steps: preparing foaming agent composite powder with a particle size distribution D50 value of 1-10 microns through matrix particles and a composite foaming agent, uniformly loading the foaming agent on the matrix particles, carrying out mixing and extruding granulation on the foaming agent composite powderwith polypropylene resin, and carrying out injection molding to obtain the micro-foaming polypropylene material. Compared with a conventional micro-foaming mode, the method provided by the invention has lower cost and fewer requirements on special equipment, and excellent characteristics of pure polypropylene can be retained to the largest extent.

Description

technical field [0001] The invention relates to the field of macromolecules, in particular to a microfoaming polypropylene material and a preparation method thereof. Background technique [0002] Compared with ordinary plastics, because of its low density, good heat-gathering performance, high thermal stability, and good mechanical properties, such as impact strength, toughness, and fatigue resistance, foamed resin is widely used in packaging materials, auto parts, and adsorbents. , Mechanical support equipment and other places have many applications. Among them, polypropylene, due to its low cost, high melting point, high tensile modulus, low density, and good chemical stability, is widely used in the foaming resin industry. According to the difference of foam pore size, foamed polypropylene can be divided into ordinary foamed PP and micro-foamed PP. Ordinary expanded polypropylene usually has cells visible to the naked eye, and the cell diameter is higher than 100 micron...

AI Technical Summary

Problems solved by technology

However, there are two major difficulties in the preparation of micro-foamed polypropylene. The first difficulty is the control of the foam size, because compared with polyurethane, polystyrene and other materials, the melt strength of polypropylene is low, making foam molding very difficult. Difficult, prone to problems such as bubble fusion and rupture, resulting in irregularly distributed large bubbles. The second major difficulty is that it is difficult to control the uniformity of foam size. In addition to being affected by the melt strength of polypropylene itself, the size of polypropylene foam There are mainly two reasons why the uniformity control is difficult. The first reason is that polypropylene itself is a semi-crystalline polymer. During the process of forming spherulites, the internal physical structure of the entire polymer is no longer uniform, resulting in problems with the uniformity of foam formation. The second reason is that the mixing of foaming agent, microfoam nucleating agent and polypropylene resin is not uniform enough, resulting in differences in foam size

There are also two problems in the mixing of foaming agent, microfoam nucleating agent and polypropylene resin. One is the agglomeration of foaming agent itself, and the other is the mixing of inorganic particles such as foaming agent and microfoam nucleating agent with polypropylene. mixing between resins

[0003] At present, in view of the difficulty in foaming molding above the melting point of polypropylene and the poor uniformity of foam size distribution, the main technical route is to improve the melt strength of polypropylene, modify the polarity of polypropylene, or use physical ultra- Prepared by critical foaming method

In order to improve the melt strength of polypropylene, the first common way is to use high melt strength polypropylene HMSPP, such as using a new catalyst or introducing a small amount of long-chain branched polypropylene into the reactor, but the preparation cost is usually very high; the second The way why other high melt strength polyolefins (such as polyethylene) are blended, but adding other polyolefins will reduce the advantages of polypropylene itself such as heat resistance and good mechanical properties; the third way is to introduce a certain amount of cross-linking Linked structure, such as cross-linking some polypropylene by radiation cross-linking or chemical cross-linking agent, but it is difficult to control the degree of cross-linking, and there are easy chemical residues, the preparation process is difficult to control, and there may even be a certain risk of explosion

In order to improve the mixing of polypropylene and inorganic fillers, a common way is to use maleic anhydride to modify polypropylene to improve the compatibility between it and inorganic fillers, but the cost of maleic anhydride is high, and the control of cell size is also difficult. not ideal

In addition, the preparation by physical supercritical foaming method is to use the polymer-gas homogeneous system in the form of supercritical fluid, and use the method of rapid temperature change to make the solubility of gas in the polymer change sharply to prepare microbubbles. However, the supercritical fluid method usually requires special equipment, the process is complicated, the product quality control is difficult, and the cost is high

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