SU1147717A1 - Method of obtaining polyethylene - Google Patents

Abstract

METHOD OF PREPARING POLYETCHNA by ethylene polymerization using the high pressure method in an autoclave reactor with a stirrer in the presence of radical initiators with feeding the initial ethylene into the reaction zone through several feeding holes and, in order to increase the conversion of ethylene , improving the homogeneity of the polymer and reducing the specific flow rate of the initiator, 25-50% of fresh ethylene is fed to the reaction zone in the axial direction, and the rest of the ethylene is fed in the radial direction through 1-3 nutrient x apertures located along the reactor height, with the temperature at lower ethylene § temperature (A applied in the axial direction.

Description

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The invention relates to a process for the production of polyethylene and can be used in chemical industry.

A known method of producing polyethylene by polymerizing ethylene under high pressure in a single-zone autoclave reactor equipped with a stirrer in the presence of radical type initiators. The presence of a mixer ensures the constancy of the initiator concentration in the reactor volume and the temperature gradient of the reaction medium over the height of the reactor no more than ClJ.

However, the known method is characterized by a relatively low conversion of ethylene per pass (up to 15%) and insufficiently high physicomechanical properties of the obtained product.

The closest to the technical essence of the invention is a method for producing polyethylene by polymerization of ethylene using the high pressure method in an autoclave reactor with a stirrer in the presence of radical initiators tc by feeding the initial ethylene into the reaction zone through several feeding openings. According to this method, the process is carried out in a vertical autoclave reactor, characterized by the ratio of height to diameter N / D 10-20, at least 80% of the initial ethylene, together with the initiator, is fed through a feeding hole located in the radial direction at a distance of 25 -60% of the height of the reaction eons from the top of the krppki, and the rest of the ethylene is fed in the axial direction. The average residence time of the reaction medium in the reactor is 20-90 with C23,

The disadvantages of this method are the low conversion of ethylene per pass and the uneven supply of the initiator, leading to a variation in the quality indicators of the polyethylene produced to a continuous consumption of the insulator,

The purpose of the invention is to increase the conversion of ethylene, to improve the homogeneity of the polymer and to reduce the specific consumption of the initiator.

The goal is achieved by the fact that according to the method of obtaining

polyethylene by polymerization of ethylene according to the high pressure method in an autoclave reactor with a stirring device in the presence of pa, cyclic impregnators feeding the initial ethylene into the reaction zone through several nutrient holes, 25-50% of fresh ethylene is fed into the reaction zone in axial direction, and the rest a portion of ethylene is fed in a radial direction through 1-3 feeding openings located at the height of the reactor, with a temperature lower than the temperature of ethylene fed in the axial direction.

The drawing shows the diagram of the autoslavnogo reactor.

Examples 1-6. In all examples given above, ethylene is fresh and the radical initiator solution is fed to an autoclave reactor, with a stirrer. Part of the original fresh ethylene is fed to the reaction zone in the longitudinal direction (stream E-1) with a certain temperature. The remainder of the gas is fed to the reaction zone by radial flow. through the feeding holes located in the reactor wall along its height (streams 3-2, e-3, e-4), the temperature of the gas in the flows entered radially by 10-30 ° С, lower than the temperature of the gas entering the zone reaction in the longitudinal direction. The specific conditions and results of the implementation of the proposed method are given in table. one.

Examples 7-12 (for c1 avneni), Experiments were performed in the same autoclave reactor, Condition 1M experiments and the results are shown in tabl, 2, In all comparative experiments the temperature of ethylene entering the reaction zone in the longitudinal direction is equal to the temperature of ethylene supplied radially through feeding holes in the reactor wall. In comparative example 7, considerable temperature fluctuations were observed in the lower zone of the reactor and an uneven supply of initiator, which in some cases led to the decomposition of ethylene and stopping the processing line and. In experiments 8 and 9 in the upper zone, the reactor was observed a periodic decrease in temperature below the permissible, which also necessitated the termination of the process 3 | for a short period of time. The basic object is the cnocoi of producing ethylene polymers in an autoclave reactor with the distribution of fresh ethylene in radial and longitudinal flows. The temperature of ethylene in both streams is the same. The results of the implementation of this method are given in examples 10 and 8. Thus, from the above examples, it is seen that the implementation 74 of polymerization of ethylene according to the proposed method allows one to increase the stability of the thermal regime, increase the conversion of ethylene per pass, reduce the variation of quality indicators of polyethylene and reduce the specific initiator flow. Increasing the plant capacity and reducing the initiator consumption ultimately leads to a decrease in the cost of polyethylene by approximately 5%,

Initiator A - ditretbutilil; B - lauryl peroxide; C - required perbenzoite

Table 2

3-1

Initiator

3-2

Initiator

E-3

Initiator

3tt.

Claims (1)

METHOD FOR PRODUCING POLYETHYLENE by high pressure polymerization of ethylene in an autoclave reactor with a mixing device in the presence of radical initiators with the feed of ethylene into the reaction zone through several feed holes, characterized in that, in order to increase the conversion of ethylene, improve polymer uniformity and reducing the specific consumption of the initiator, 25-50% of fresh ethylene is fed into the reaction zone in the axial direction, and the remaining part of ethylene is fed in the radial direction through 1-3 nutrient openings thium located along the height of the reactor, with a temperature of 10- ^ 30 ° C below the temperature of ethylene supplied in the axial direction. SU, _n , 1147717> Ί ί '11477