RU2711227C1 - Method of producing terpolymers of ethylene with vinyl acetate and butyl acrylate - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to a method of producing ternary copolymers of ethylene with vinyl acetate and butyl acrylate by radical copolymerization in bulk at high pressure. Reaction device used is a four-zone autoclave reactor equipped with a high-speed stirrer. Method involves feeding a reaction mixture of ethylene and vinyl acetate and organic peroxide in an organic solvent into all four zones of the reactor, wherein butyl acrylate is additionally added to the upper zone. Copolymerization process in the upper zone is carried out at temperature of 180–200 °C, and in all other zones at temperature of 200–240 °C. Depending on the given weight ratio of ethylene to vinyl acetate and butyl acrylate, redistribution of reaction streams fed to the second, third and fourth zones of the reactor is carried out, followed by separation of the obtained copolymer from the unreacted reaction mixture.EFFECT: method of the invention increases efficiency of the process of synthesis of the copolymer, reduces content of free ethers of acrylic acid in the copolymer, as well as increases its hydrolytic stability.4 cl, 1 dwg, 13 ex

Description

The invention relates to the field of chemical industry, in particular, to methods for producing ternary copolymers of ethylene with vinyl acetate and butyl acrylate by radical copolymerization in bulk at high pressure. Such terpolymers due to the possibility of varying the contents of ethylene, vinyl acetate and butyl acrylate are widely used in various segments of the industry, among which the main ones are:

- food packaging;

- multilayer food and agrofilms;

- sealing parts;

- cable insulation;

- impact modifier for a number of polymers;

- thermo and sound insulating materials.

A known method of producing polymer compositions by and.with. USSR No. 540876, which is carried out by polymerization of ethylenically unsaturated monomers by the high pressure method using a two-zone tubular reactor as a reaction device, initiating a copolymerization reaction by radical initiators, feeding a reaction mixture consisting of ethylene (or ethylene and vinyl acetate) and a more reactive monomer than ethylene and (or) vinyl acetate, in one of the two zones of the reactor, polymerization of this mixture at a temperature of 100-350 ° C and a pressure of 120-350 MPa, and in the other of the two zones of the reactor ethylene and vinyl acetate or a mixture of ethylene and a more reactive comonomer are polymerized, or if a mixture of ethylene with vinyl acetate is polymerized in the first zone, or a mixture of ethylene, vinyl acetate and a more reactive comonomer at a temperature of 150-400 ° C and a pressure of 115-345 MPa. The maximum reaction temperature in this zone is 1-100 ° C higher than in the previous one, the molar ratio of ethylene to vinyl acetate used in the corresponding zone is from 100: 1.5 to 100: 35, and the molar ratio of ethylene used in the corresponding zone to more reactive the comonomer ranges from 100: 0.004 to 100: 7. The copolymerization process can be carried out in the presence of chain growth regulators of the resulting polymers or copolymers; acrylic acid esters, for example, butyl acrylate, can be used as the third more reactive monomer. As the initiators of the reaction, compounds that form free radicals are used, for example, oxygen, azo compounds, tert-butyl peroxide, di-lauroyl peroxide, tert-butyl pivalate, etc. In this method, propane, butane, as well as ketones, aldehydes are mainly used to control the molecular weight of the copolymer or halogens, and ethylene production equipment is used to separate the resulting terpolymer from the unreacted reaction mixture, i.e. the copolymer is separated from the reaction mixture in high and low pressure recycle systems.

The advantage of this method is the fact that the preparation of copolymers (polymer compositions) can be carried out without significant technical changes in conventional tubular reactors used for the polymerization of ethylene under high pressure. In addition, the copolymers obtained by this method have a high degree of homogeneity, which allows them to be used in various fields of technology.

Among the disadvantages of this well-known should include the following:

1. High (~ 0.5 wt.%) The content of free esters of acrylic acid in terpolymer, which pollutes the air during its processing;

2. Low hydrolytic stability of terpolymer (degree of saponification of acetate groups α = 90 wt.%). Since terpolymers are capable of absorbing moisture, in the presence of reactive groups, moisture enters into chemical interaction with them with the formation of by-products, for example, acetic acid.

From patent DD No. 108999, a method is known for producing copolymers of ethylene with vinyl acetate and acrylic esters, in particular with butyl acrylate in bulk, using a single-zone autoclave reactor equipped with a high-speed stirrer as a reaction device, supplying a mixture of these monomers to the reactor, and conducting the process copolymerization at elevated pressure and temperature, initiating a synthesis reaction using free-radical-forming compounds fed to the reactor in an organic solution a reactor, separating the obtained polymer from the unreacted reaction mixture and then mixing the unreacted ethylene, vinyl acetate and acrylic esters with fresh ethylene, vinyl acetate and acrylic ester for subsequent feeding of the mixture into the reactor.

The disadvantages of this method are:

1. High (~ 0.5 wt.%) The content of free esters of acrylic acid in terpolymer, polluting the air during processing;

2. Low process performance. So, with a volume of the autoclave reactor of 0.8 l and the synthesis of ethylene terpolymer with vinyl acetate and butyl acrylate at a temperature of 220 ° C and a pressure of 140 MPa, the yield of terpolymer with a content of vinyl acetate units of 27 wt. %, butyl acrylate 49 wt. % terpolymer yield is 580 g / hr or 0.725 g / hr per liter of reactor volume;

3. The lack of hydrolytic stability of the product (the degree of saponification of the acetate groups α - 90 wt.%);

4. The lack of flexibility of the process to obtain a ternary copolymer with the desired consumer properties, due to the use of a single-zone autoclave reactor as a reaction device.

This known method for the combination of similar essential features and the achieved effect is selected as a prototype of the claimed invention.

The objective of the invention is:

1. The decrease in the content of free esters of acrylic acid in terpolymer;

2. Increase in process productivity;

3. Improving the consumer properties of the resulting polymer.

According to the invention, a method for producing ethylene terpolymers with vinyl acetate and butyl acrylate in bulk using a continuous autoclave reactor equipped with a high-speed stirrer as a reaction device, comprising feeding a mixture of these monomers into the reactor, conducting the copolymerization process at a pressure above 120 MPa and a temperature of 180-240 ° C, initiation of the copolymerization reaction with the help of free radical forming compounds fed to the reactor in an organic solvent, separation of the obtained polymer from n reacted reaction mixture and subsequent mixing of unreacted ethylene, vinyl acetate and butyl acrylate with fresh ethylene, vinyl acetate and butyl acrylate for subsequent feeding of the mixture into the reactor, characterized in that a four-zone autoclave reactor is used as a reaction device, the reaction mixture of ethylene with vinyl acetate is fed together with organic peroxide with a mixture of peroxides in all four zones of the reactor, while butyl acrylate and the copolymerization process are additionally introduced into the upper zone the zone is conducted at a temperature of 180-200 ° C, and in all other zones at a temperature of 200-240 ° C, and the consumer properties of the resulting product are optimized for a given mass ratio of ethylene, vinyl acetate and butyl acrylate by redistributing the reaction flows of ethylene with vinyl acetate and butyl acrylate, fed into the second, third and fourth zones of the reactor.

In addition, the claimed technical solution is characterized by the presence of a number of additional optional features, namely:

- as initiators of the copolymerization reaction can be used tert-butyl peroxypivalate, di-tert-butyl perbenzoate, di-tert-butyl peroxide, 2,2, di-tert-butyl peroxybutane and other peroxides, as well as mixtures thereof;

- as a peroxide solvent can be used hydrocarbons of normal and isostructure with the number of carbon atoms in the molecule from 10 to 20;

- chain transfer agents such as propane, propylene, propionaldehyde, acetone, etc. can be used to modify the consumer properties of the obtained copolymers.

The claimed combination of essential features ensures the achievement of a technical result, which consists in the fact that the use of a four-zone autoclave reactor as a reaction device allows for the same mass ratio of ethylene to vinyl acetate and butyl acrylate to redistribute the mass flows of the reaction mixture over the zones of the reactor, which leads to terpolymers with different molecular weight distribution and, therefore, with a variety of consumer properties. Another advantage of using a four-zone autoclave reactor is the ability to start the terpolymer synthesis reaction at a relatively low temperature of 180-200 ° C, which is very important in the case of using a more reactive compound than ethylene and vinyl acetate, in this case butyl acrylate.

As is known from US patent No. 6762254, the synthesis temperature of 180-200 ° C is optimal. In the case of the use of butyl acrylate, at this temperature ~ 95 wt. %, and the remaining 5 mass. % butyl acrylate polymerizes in other zones (or other reactors) at a higher temperature.

The essence of the proposed technical solution is illustrated by the drawing, which shows the technological scheme of a pilot plant that implements the claimed method.

The positions on the block diagram indicate: 1 - compressor of the first stage, 2 - mixer, 3 - compressor of the second stage, 4 - four-zone autoclave reactor, 5, 6 - pumps, 7 - high pressure separator, 8 - high pressure recycling system, 9 - auger receiver, 10 - water bath, 11 - low pressure recycling system.

The claimed method is implemented as follows.

Example 1

Ethylene from cylinders with a pure 99.9 mass. % was supplied to the compressor inlet of the first stage 1, where it was compressed to a pressure of 23 MPa. The performance of compressor 1 in the experiment was 3 kg of ethylene per hour. Ethylene from compressor 1 was fed to mixer 2, where it was mixed with a return mixture of ethylene with vinyl acetate and butyl acrylate separated from separators 5 and 6. Fresh mixer was fed into mixer 2 with pump 5 in an amount of 0.3 kg / h. From mixer 2, a mixture of ethylene with vinyl acetate was fed to the compressor inlet of the second stage 3, where it was compressed to a pressure of 140 MPa. The productivity of compressor 3 was 30 kg / h. Then, by compressor 3, the mixture was fed into a four-zone continuous autoclave reactor 4 with a volume of 3 L, the reaction space of which was divided into four zones of equal volume. The reactor is equipped with a high-speed mixer, the rotation speed of which is 1000 rpm. Thermocouples are installed in each zone of the reactor to measure the reaction temperature. The temperature of the outer wall of the reactor was maintained using a coolant supplied to the jacket of the reactor. The temperature of the coolant was 170 ° C. A mixture of ethylene with vinyl acetate in an amount of 30 kg / h was fed into the reactor in four streams. Additionally, butyl acrylate in an amount of 0.3 kg / h was supplied to the pipeline for supplying a mixture of ethylene with vinyl acetate to the upper zone of the reactor with a pump 6. To initiate the polymerization reaction, tert-butyl peroxypivalate peroxide was introduced into the upper zone of the reactor in an acyclic solvent, isododecane. The concentration of tert-butyl peroxypivalate in a solvent of 6 mass. % The synthesis temperature in the upper zone of the reactor is 190 ° C. The synthesis reaction was initiated in the remaining zones of the reactor using di-tert-butyl peroxide, the synthesis temperature of 230 ° C. The total concentration of initiator in the reactor of 0.003 mass. % The terpolymer obtained, together with unreacted ethylene and vinyl acetate and butyl acrylate residues, was sent through a throttling valve to the high-pressure separator 7, where the mixture was divided into two phases: liquid, mainly consisting of a high molecular weight polymer with unreacted monomers dissolved in it, and gas, consisting of monomers and the low molecular weight copolymer dissolved in them (NMHS). From the high-pressure separator 7, the gas mixture under pressure of 19 MPa was sent to the high-pressure recycle system (item 8), where it was cooled and purified from the low molecular weight terpolymer (NCSP) and then passed to the mixer 2, where it was mixed with ethylene and vinyl acetate. The terpolymer melt with a temperature of 210 ° C from the high-pressure separator was fed through a throttling valve into the screw receiver 9 and then in the form of bundles into the water bath 10. The remaining reaction mixture and NCSP released in the screw receiver were sent to the low-pressure recycling system 11, where the gas mixture was cooled, refined and mixed with fresh ethylene and then compressor 1 with a fresh ethylene-vinyl acetate mixture. Analysis of the reaction mixture after exiting reactor 4 shows a content of butyl acrylate of 0.23 mass. %

In US Pat. No. 6,672,254, when using a hybrid reactor consisting of an autoclave reactor and a tubular reactor installed thereafter, the residual content of butyl acrylate in the terpolymer was at least 0.3 mass. % The yield of terpolymer according to the proposed method is 3.1 kg / h or 1.033 per 1 liter of reactor. The content of vinyl acetate in the polymer is 9.8 mass. % The content of butyl acrylate 11.7 mass. %, the degree of saponification of acetate groups α = 51 mass. %

The degree of saponification of the acetate groups was determined according to the method described in the USSR author's sidekeeping No. 979382. In addition to these quality indicators, the water absorption of terpolymer was determined, i.e. the amount of water that terpolymer absorbs after 24 hours in water at 20 ° C. This indicator is 0.4 mass. %

The resulting terpolymer is preferably used for extrusion into pipes, hoses, fittings, etc. Manufactured products have increased strength and thermal stability.

Example 2

The process of obtaining terpolymer was carried out under the conditions of example 1, but the amount of vinyl acetate supplied to the mixer 2 was 0.35 kg / h, butyl acrylate was 0.09 kg / h. In the resulting terpolymer, the content of vinyl acetate is 35 mass. %, butyl acrylate - 15 mass. %, the content of free butyl acrylate in the polymer is 0.25 mass. % The degree of saponification of acetate groups in the product 55 mass. %, water absorption - 0.45 mass. % The yield of terpolymer in the experiment was 3.3 kg per hour or 1.1 kg per 1 liter of reactor.

The resulting polymer is preferably used in the production of pipelines as an adhesive material, for the production of heat and sound insulating materials, as an impact modifier for a number of polymers.

Example 3

The process of obtaining terpolymer was carried out under the conditions of example 1, but the amount of vinyl acetate supplied to the mixer 2 was 0.1 kg / h, the amount of butyl acrylate was 0.2 kg / h. The yield of terpolymer in the experiment is 3.0 kg / h, or 1.0 kg from one liter of reactor. The content of vinyl acetate in the product is 3.1 mass. %, butyl acrylate - 6 mass. %, the content of free butyl acrylate in terpolymer - 0.24 mass. % The degree of saponification of acetate groups α = 42 mass. %, water absorption - 0.49 mass. %

Example 4

The process of obtaining terpolymer was carried out under the conditions of example 1, but the temperature in all zones of the reactor (except the first) was 250 ° C. In the first zone, the synthesis temperature is 190 ° C. The yield of terpolymer in the experiment is 3.6 kg / h or 1.20 kg from one liter of reactor. The content of vinyl acetate in the product is 8.9 mass. %, butyl acrylate - 11.2 wt. % The degree of saponification of acetate groups α = 0.49 mass. %, water absorption - 0.45 mass. % The content of free butyl acrylate in the terpolymer is 0.22 mass. %

It is advisable to use the resulting product for processing by extrusion into pipes, hoses, fittings, etc. with increased strength and thermal stability.

Example 5

The process of obtaining terpolymer was carried out under the conditions of example 1, but the synthesis temperature in the first zone of the reactor was 180 ° C, in all other zones - 230 ° C. The yield of terpolymer is 3.05 kg / h or 1.01 kg / h from one liter of reactor. Qualitative indicators of terpolymer are similar to the properties of the product of example 1, with the exception of the degree of saponification of the acetate groups α = 45 mass. % Application areas of the product are the same as in example 1.

Example 6

The experiment was carried out under the conditions of example 1, but the synthesis temperature in the first zone of the reactor was 200 ° C. The yield of terpolymer is 3.08 kg / h or 1.03 kg / h from one liter of reactor. Qualitative indicators of the product are similar to those of the product obtained in example 1. The content of free butyl acrylate in the product of 0.21 mass. % The areas of application of the product are the same as for the terpolymer obtained in example 1.

Example 7

The experiment was carried out under the conditions of example 1, but the temperature in the second zone of the reactor was 210 ° C. The yield of terpolymer is 3.02 kg / h or 1.00 kg / h per liter of reactor. Qualitative indicators of the product are similar to those of the product obtained in example 1. The resulting copolymer is preferably used for the production of hollow and other injection molded products.

Example 8

The experiment was carried out under the conditions of example 1, but the temperature in the third zone of the reactor was 210 ° C. The yield of terpolymer is 3.05 kg / h or 1.01 kg / h from one liter of reactor.

Qualitative indicators of the obtained terpolymer are similar to those of Example 1. The main fields of application of this terpolymer are the production of multilayer food and agrofilms, as well as in production as an impact modifier.

Example 9

The experiment was carried out under the conditions of example 1, but the temperature in the second zone of the reactor was 210 ° C. The yield of terpolymer in the experiment was 2.70 kg / hr or 0.90 kg / hr per liter of reactor volume. Qualitative indicators of the product are similar to those of Example 1. The resulting terpolymer is expediently used in the production of packaging materials for food products.

Example 10

The experiment was carried out under the conditions of example 1, but the pressure in the reactor was 180 MPa. The yield of terpolymer in the experiment is 3.3 kg / h or 1.1 kg / h per liter of reactor. The resulting terpolymer is preferably used for extrusion into pipes, hoses, fittings, etc. with increased strength and thermal stability.

Example 11 (control)

The experiment was carried out under the conditions of example 1, but the synthesis temperature in the first zone of the reactor was 170 ° C. The quality indicators of the resulting terpolymer are similar to those of the product of example 1. The yield of terpolymer is 2.90 kg / h or 0.9 kg / h per liter of reactor volume.

Example 12 (control)

The experiment was carried out under the conditions of example 1, but the synthesis temperature in the first zone of the reactor was 210 ° C. The yield of terpolymer in the experiment is 3.11 kg / h or 1.04 kg / h from one liter of reactor. Qualitative indicators of the product are similar to the corresponding indicators of example 1, with the exception of the degree of saponification of the acetate groups α = 0.61 mass. %, water absorption - 0.73 mass. %

Example 13 (control)

The experiment was carried out under the conditions of example 1, but the synthesis temperature in the second, third and fourth zones of the reactor was 260 ° C.

The yield of terpolymer in the experiment was 3.7 kg / h or 1.23 kg per hour per liter of reactor. The resulting product contained free butyl acrylate 0.23 mass. % and had a degree of saponification of acetate groups α = 70 mass. % and water absorption of 0.5 wt. %

Thus, the proposed method for the preparation of ethylene terpolymers with vinyl acetate and butyl acrylate in comparison with the prototype has the following advantages:

1. Obtaining terpolymers with a reduced content of free butyl acrylate in terpolymer (0.23 wt.% According to the proposed method and 0.5 wt.% According to the prototype), which is important in the processing of terpolymer, since it significantly improves working conditions;

2. The increase in the productivity of the process of synthesis of terpolymer (from 0.725 kg / hour from one liter of the reactor according to the prototype to a value of not less than 1 kg / hour from one liter of the reactor according to the proposed method);

3. Increasing the hydrolytic stability of terpolymer (the degree of saponification of acetate groups according to the prototype α = 90 wt.%, According to the proposed method α - not more than 55 wt.%, While water absorption is not more than 0.5 wt.%);

4. The ability to obtain terpolymers with the desired consumer properties by changing the temperature in the second, third and fourth zones of the reactor.

The copolymers obtained in accordance with the proposed method can be used for food packaging, as sealing parts, in the production of cable insulation, heat and sound insulation materials, and other industries.

Claims (4)

1. The method of obtaining ethylene terpolymers with vinyl acetate and butyl acrylate in bulk using a continuous autoclave reactor equipped with a high-speed stirrer as a reaction device, comprising feeding a mixture of these monomers into the reactor, conducting the copolymerization process at a pressure above 120 MPa and a temperature of 180-240 ° C, initiation of the copolymerization reaction using free radical forming compounds fed to the reactor in an organic solvent, separating the obtained polymer from unreacted p reaction mixture and subsequent mixing of unreacted ethylene, vinyl acetate and butyl acrylate with fresh ethylene, vinyl acetate and butyl acrylate for subsequent feeding of the mixture into the reactor, characterized in that a four-zone autoclave reactor is used as the reaction device, the reaction mixture of ethylene with vinyl acetate is fed together with an organic peroxide or mixture peroxides in all four zones of the reactor, while butyl acrylate is additionally introduced into the upper zone and the copolymerization process in the upper zone is a temperature of 180-200 ° C, and in all other zones at a temperature of 200-240 ° C, moreover, they optimize the consumer properties of the resulting product at a given mass ratio of ethylene, vinyl acetate and butyl acrylate by redistributing the reaction flows of ethylene with vinyl acetate and butyl acrylate, supplied to the second, the third and fourth zones of the reactor. 2. The method according to p. 1, characterized in that tert-butyl peroxypivalate, di-tert-butyl perbenzoate, di-tert-butyl peroxide, 2,2, di-tert-butyl peroxybutane and other peroxides, as well as their mixtures. 3. The method according to p. 1, characterized in that as a solvent of peroxides, normal and isostructural hydrocarbons are used with the number of carbon atoms in the molecule from 10 to 20. 4. The method according to p. 1, characterized in that for the modification of consumer properties of the obtained copolymers using chain transfer agents, such as propane, propylene, propionaldehyde, acetone, etc.

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