Chemical degradation method of polypropylene

Abstract

A chemical degradation method of polypropylene comprises the degradation by adding 0.01 weight percent to 0.2 weight percent of organic peroxide and 0.1 weight percent to 1.0 weight percent of nucleating agent into the polypropylene. The method can effectively improve the efficiency of degradation, increase the melt index of degraded polypropylene, improve the molecular weight distribution of polypropylene, and maintain the good mechanical performances at the same time.

Description

Technical field [0001] The present invention is a method for controlling degradation of polypropylene, specifically, a method for chemical degradation of polypropylene. Background technique [0002] During the processing of polypropylene, it is often necessary to control the degradation of polypropylene to meet the needs of improving production efficiency and processing technology. The United States EXXON Chemical Company first realized the controlled degradation of homopolypropylene in 1971. The methods reported in US3,551,943, US3,563,972, US3,608,001, and US3,593,011 mainly adopted the introduction of air during the polypropylene extrusion process. The hot air of polypropylene degrades to form free radicals, which triggers the β chain scission of polypropylene to achieve controlled degradation. During the implementation of the above patent, the temperature of the extruder barrel is as high as 371-427°C, and the temperature distribution mode adopted is reverse distribution, th...

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Problems solved by technology

However, the relative price of this initiator is relatively high, and the residual groups in the system after initiating the degradation of polypropylene are relatively large, which has become a negative factor of concern.

In addition, since it is difficult to completely isolate the whole process from the air during the synthesis and granulation of polypropylene, it is inevitable that some polypropylene molecules will be oxidized into trace acid groups, and the catalyst used in the polymerization process will also generate trace acid groups groups, while organic peroxides without acid groups are sensitive to acids

At the same time, in order to ensure the service life of polypropylene, it is also necessary to add antioxidants containing active hydrogen atoms when granulating polypropylene. These additives will also preferentially consume active free radicals and affect the formation of macromolecular free radicals.

The above factors will affect the effectiveness of the initiator to varying degrees.

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