Method for preparing long chain branched polyethylene

Abstract

The invention provides a method for preparing long chain branched polyethylene. The method comprises the following steps of: (1) irradiating a substrate polyethylene with high-energy electron beams or gamma-rays to obtain pre-irradiated polyethylene, wherein the irradiation dose is 1 to 20OkGy; (2) blending the pre-irradiated polyethylene obtained in the step (1) and the substrate polyethylene and uniformly stirring to obtain a premixture, wherein in the premixture, the pre-irradiated polyethylene accounts for 1 to 99 weight percent and the substrate polyethylene accounts for 99 to 1 weight percent; and (3) performing reaction extrusion on the premixture obtained in the step (2) to prepare the long chain branched polyethylene. The method is simple, feasible and low in cost; and the obtained long chain branched polyethylene has more sensitive shear thinning property and higher melt strength, is applied to multiple kinds of processing technology, has high processability and particularly has good application prospect in the fields of thin films and foaming.

Description

technical field [0001] The invention relates to a method for preparing long-chain branched polyethylene, in particular to a method for preparing long-chain branched polyethylene including pre-irradiation technology. technical background [0002] Commercial polyethylene resins have various excellent properties, but there are deficiencies in melt strength and processability. For example, even at temperatures above the melting point, linear polyethylene melts cannot produce strain hardening, so it is easy to appear during processing. The melt collapses and fractures. Another example is that linear low density polyethylene still has a high viscosity at high shear rates during the film blowing process, which makes the torque, melt temperature and die pressure during processing very large, causing the melt to flow at the die. The obvious relaxation of the film is not conducive to the formation of stable film bubbles when blowing the film. In addition, there are some other defect...

AI Technical Summary

Problems solved by technology

[0002] Commercial polyethylene resins have various excellent properties, but there are deficiencies in melt strength and processability. For example, even at temperatures above the melting point, linear polyethylene melts cannot produce strain hardening, so it is easy to appear during processing. melt collapse and fracture

The problems that this blended foaming material exists are: 1, need to adopt two kinds of polyethylene raw materials of different structures, have both increased the cost of material selection like this, also will carefully control the irradiation dose of linear polyethylene (10-40kGy) simultaneously , so as not to produce gel, which is not conducive to the blending process and product performance; 2. The blended material may also undergo phase separation during use, resulting in a decrease in product performance, so the content of the irradiated linear polyethylene component must be controlled at a low level Ratio (such as the highest content of irradiated linear low density polyethylene in the embodiment is 20wt%), so as to ensure the complete compatibility of the material and obtain a foamed product with better performance

However, in order to control the radiation crosslinking and other side reactions of polyethylene, on the one hand, it is necessary to reduce the irradiation dose and reduce the oxygen concentration in the irradiation environment; on the other hand, a post-treatment process is required to eliminate further reactions of residual free radicals, which increases the process complexity

Images