Method for synthesizing polyethylene

Abstract

The invention relates to a method for synthesizing polyethylene, which comprises the following steps: (1) setting the temperature of a reaction system to be 20-30% lower than the reaction temperature; (2) the catalyst is conveyed to the reaction system in the form of nitrogen flow, the feeding rate of the catalyst is 0.5-2.0 g / h, and the heating rate of the reaction system is 0.5-1.5 DEG C / h; (3) when the inlet temperature of the reactor is increased to 90%-95% of the reaction temperature and the bed pressure difference of the reactor meets the requirement, setting the feeding rate of the catalyst to be 1.0-2.5 g / h and the heating rate of the reaction system to be 1.0-5.0 DEG C / h; and (4) after the activity of the catalyst meets the design requirement and the reaction system enters steady-state operation, the setting of process parameters of the reaction system is related to the change of the vicat softening point of a polymerization reaction product.

Description

technical field [0001] The invention relates to the field of polyethylene synthesis, in particular to a method for synthesizing polyethylene, and the method for synthesizing polyethylene is especially suitable for a gas-phase fluidized bed. Background technique [0002] Polyolefin production processes include slurry process, solution process, and gas phase process. With the advancement and development of technology, the advantages and disadvantages of each major production process are gradually emerging. Slurry method polyethylene, dispersed in a solvent to form a slurry, this production method solves the viscosity problem of the polymer solution, there is no limit to the MFR of the product, but there is a strict limit on the lower limit of the product density, generally at 0.935g / cm 3 About; the solution method is restricted by the viscosity of the solution, and has a certain limit on the lower limit of the product MFR, but there is no limit on the density; the gas phase ...

AI Technical Summary

Problems solved by technology

However, the production process control of high-end grades by major domestic production companies is not very mature, especially for the production of polyethylene products with high content of high-grade α-olefin comonomers (carbon chain length > 6). In the control of process parameters such as the comonomer addition ratio, a single control parameter is still used to set the process operation unit, and there is a lack of process technology associated with other parameters, which results in higher α-olefins such as hexene in the gas phase process polymerization system. , it is very easy to cause high viscosity of the polymerization system, flaking and blockage of the reactor, causing the shutdown of the device; at the same time, frequent switching of grades also has a certain impact on the stability of the resin performance, resulting in an increase in the complaint rate of downstream users

Therefore, in the development of high-end new products in China, there are shortcomings such as short device operation period and unstable performance of special materials, resulting in frequent shutdown of devices and excessive transition materials, which greatly affects the benefits of enterprises and restricts the process of domestic new product development.

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