SU454215A1 - The method of obtaining polymers or copolymers of ethylene - Google Patents

Description

one

The invention relates to the production of polymers or copolymers of ethylene by free radical polymerization of monomers by the high pressure method.

A known method of producing polymers or copolymers of ethylene by free-radical polymerizing it or copolymerizing it with other monomers by treating the reaction mixture consisting of or containing ethylene at a temperature above 50 ° C and a pressure above 50 ag in the presence of compounds that decompose at freezing temperatures radicals (e.g. oxygen, organic peroxides, azo compounds), or by active irradiation.

Thus, azoisobutyronitrile, dilauroyl peroxide, dibenzoyl peroxide, dinonyl peroxide, trebutylperbenzoate, ditert-butyl peroxide, mesityl oxide peroxide, mesol hydroxide peroxide, oximes and hydrazines are used as polymerization initiators. However, these initiators must be added to the reaction mixture in a dilute solvent state either directly before introducing this mixture into the reactor, or directly into the reactor. Since the reaction pressure is usually higher than 1000 atm, special high-sensitivity is required.

Significant dosing devices. In addition, part of the solvent and decomposition products of the initiator or initiators remain in the polymer, which deteriorates its quality.

When using oxygen as an initiator for the polymerization and copolymerization of ethylene, it is generally added already in the low-pressure unit of the plant and therefore places particularly high demands on the ethylene feeder supply capacity. Fluctuations in feed rates affect the reaction temperature and polymer quality. The rate of polymerization can only be controlled due to a slowdown in time. However, here too oxygen compounds are introduced into polymers, which significantly reduce, for example, the thermal and ultraviolet stability of these polymers. When initiating a polymerization reaction by irradiation with X-rays, using high-frequency electromagnetic radiation to irradiate neutrons, the polymerization rate can be controlled by changing the irradiation intensity, but this is significant because of the radiation protection costs due to the thick walls. high pressure apparatus.

The aim of the invention is the initiation of free radical polymerization or copolymerization of ethylene, in which, without major equipment costs, the quality of the product does not deteriorate and the polymerization can be controlled without delay. The method is to obtain initiating radicals by decomposing the components involved in the reaction.

For the radical initiation of the polymerization of ethylene or the copolymerization of ethylene with other copolymerizable compounds, if necessary, in the presence of further co-reagents, at pressures above 50 atm and temperatures of the reaction mixture above 50 ° C, polymerization-induced radicals are obtained by thermal and / or catalytic decomposition of the components the reaction mixture of ethylene and / or copolymerizable compounds and / or further coagents, in the zone of local overheating of this mixture, created with the help of glow wire, The temperature in the local overheating zone is maintained at least at 50 ° C, preferably at 200-600 ° C, above the reaction temperature of the mixture.

For the manufacture of copolymers, propylene, vinyl esters, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, carbon monoxide, vinyl fluoride, inner chlorine nly allyl compounds can be used as copolymers.

Ethane, propane, sulfur dioxide, methanol, acetone, or hydrogen are used as further coagents.

The proposed method is carried out in such a way that the splitting energy, necessary for initiating the decomposition of the compounds, is transferred to the reaction mixture by creating a localized zone of the overheating of the reaction mixture using the glow wire. The polymerization in the reaction mixture proceeds with the aid of the radicals formed.

The rate of decomposition into radicals can be increased due to the presence of catalytically active substances. So, when polymerization in the presence of hydrogen in the reaction mixture, the temperature at which decomposition takes place can be greatly reduced without decreasing the rate of decomposition if electrically heated platinum spirals are introduced. Small amounts of stabilizers, such as 2,6-di-tregbutyl-g-cresol, can be added to the reaction mixture to trap radicals that are not able to initiate polymerization.

The advantage of the proposed method is that you can easily set the desired rate of decomposition by adjusting the electrical heating of the heat.

Further, it is possible to achieve different concentrations of radicals, and, consequently, different rates of polymerization by varying the productivity of the radiation-detecting device.

Thus, the adjustment of the energy supply allows simple adjustment of the polymerization process. The resulting polymers do not contain solvents and oxygen groups if no oxygen copolymerizable compounds or co-reagents have been added to the reaction mixture. Initiation can be carried out in a mixer-reactor or in a single-tube reactor. In the case of a single-tube reactor, initiation may occur at the entrance to the reactor and at various other places in the reactor.

Example 1. 900 tubes of ethylene with a temperature of 40 ° C under a pressure of 1130 bar are injected continuously into a tubular reactor with a coater (diameter 10 mm).

The reaction pressure is set by means of a control valve located at the end of the reactor. Through the jacket of the reactor, water with a temperature of 220 ° C circulates. Ethylene residence time is 90 seconds. After ethylene stay for 20 seconds, a heating coil of BM 100 chromium-nickel alloy is installed in a tubular reactor, through which a current of 20 a is passed. The temperature of ethylene is after staying for 20 seconds at 110 ° C and rises after 60 seconds at maximum (240 ° C). After dilution of the reaction mixture, 36 parts of polyethylene are obtained in the separator, which corresponds to a conversion of 4%.

The product has a melt index of 4 g / 10 min (measured according to the American standard test method, test No. 1238-52 T), and the affinity of 0.916 g / cm.

Example 2. In described in example 1, the reactor is continuously served (at the entrance to the reactor) 500 hours of ethylene containing 5 parts of hydrogen, with a temperature of 60 ° C at a pressure of 1700 at. Water with a temperature of 180 ° C circulates through the jacket of the reactor. The residence time of the reaction mixture is 150 seconds. After the specified residence time of the reaction mixture, six heating coils of platinum wire are installed in the reactor, the first heating coil is placed after 10 seconds, the second after 30 seconds, the third after 50 seconds, the fourth after 70 seconds, and the fifth after 90 seconds, the sixth after 110 seconds.

Through heating spirals pass, as necessary, a current of 30 a. After 120 seconds of stay, the maximum temperature of the reaction mixture (230 ° C) is established. After dilution of the reaction mixture, 80 parts of polymer are obtained in the separator, which corresponds to a conversion of 16%, calculated as starting ethylene.

The polymer is a solid low molecular weight wax with a melting range of 105-115 ° C and a density of 0.938 g / cm. This high frequency wax is particularly resistant to UV

and therefore can be used as an anti-corrosion material.

Example 3. In the reactor described in Example 1, a gas mixture consisting of 650 parts of ethylene and 130 parts of vinyl acetate with a temperature of 50 ° C at a pressure of 2500 atm was continuously supplied (at the entrance to the reactor).

Water with a temperature of 200 ° C circulates through the jacket of the reactor. The residence time of the reaction mixture is 120 seconds. After the specified residence time of the reaction mixture, 5 heating coils of BM 100 chromium-nickel alloy are installed in the reactor. The first heating coil is put through: 8 seconds, the second after 25 seconds, the third after 40 seconds, the fourth after 56 seconds, and the fifth after 72 sec.

Through heating spirals pass, as necessary, a current of 18 a. After 90 seconds of residence of the reaction mixture, a maximum temperature of 260 ° C is established. After dilution of the reaction mixture, 135 parts of polymer are obtained in the separator, which corresponds to a conversion of 17%, calculated on the initial amount of monomer.

The polymer is plastic, contains 20 wt. % vinyl acetate. The density is 0.945 g / cm. The melt index is 6 g / 10 min. The product is particularly suitable for the manufacture of elastic sleeves, elastic toys and for use instead of soft polyvinyl chloride.

Example 4. In the mixer-reactor, diameter 80 mm, 600 hours of ethylene and 24 hours of ethane with a temperature of 40 ° C under a pressure of 1500 at. In the reactor there is a bachelor, rotating with a speed of 10 rpm. AT

The reactor jacket is placed symmetrically (in the upper third of it) three heating spirals, through which a current of 20 a is passed (for each spiral).

The temperature of the reaction mixture in the reactor is 240 ° C, the residence time of the reaction mixture is 120 seconds. After dilution of the reaction mixture, 96 parts of polyethylene are obtained in the separator, which corresponds to a conversion of 16%.

Polyethylene has a melt index of 8 g / 10 min and a density of 0.918 g / cm. In the absence of oxygen compounds in the product, it is also particularly resistant to atmospheric effects.

Subject invention

The method of producing polymers or copolymers of ethylene by free radical polymerization of it or by copolymerization with other monomers by treating the reaction mixture consisting of or containing ethylene at a temperature above 50 ° C and pressure

above 50 atm, characterized in that, in order to simplify the process and to regulate the process, the polymerization is initiated by radicals resulting from the thermal and / or catalytic breakdown of the components of the reaction mixture in the local overheating zone of this mixture, created by the help of the glow wire, and in the local zone overheating maintain temperature at least 50 ° C, preferably at

200-BOO C, above the temperature of the reaction mixture.