SU418480A1 - - Google Patents

Description

one

The invention relates to the production of synthetic elastomers and thermoplastic elastomers, and in particular to a method for separating these polymers from hydrocarbon solutions.

There is a method for separating synthetic elastomers and thermoplastic elastomers from their hydrocarbon solutions by evaporation of the solvent B with a stream of water vapor when the solution is heated with steam or hot water. However, the solvent is removed as a mixture with water vapor and for re-use the solvent requires drying, in addition, wastewater appears, the polymer is contaminated during the isolation and drying stages.

The aim of the invention is to develop a method devoid of such disadvantages.

This goal is achieved by pre-concentrating the polymer solution with vigorous stirring and then finally removing the solvent while applying heat to a thin layer of polymerizate through the wall without mechanical impact on the polymer. This release mode can be achieved using heated rolls.

The drawing shows a diagram, based on the proposed method.

The solution of the polymerization initiator from the apparatus 1 is mixed in a stream with a solvent and a monomer or with a mixture of polymerization monomers of purity coming from the apparatus 2, and fed into the polymerization units 3, 4, 5. During the polymerization process, additional quantities of monomers can be introduced into the reaction mixture, the initiator or modifier from the apparatus 6, 7 through the mixers 8, 9. After the process is over, the polymerizate is charged with the stabilizer solution from the apparatus 10 through the mixer 11, averaged in the apparatus 12 and sent through the filter 13 and polymer selection. Removal of the solvent from the polymer is carried out on heated rollers 14 (anhydrous degassing unit).

The polymer from the degasser comes out in the form of a tape, which is subjected to a bundle. The polymer tow is granulated in granulator 15 and packaged by machine 16.

Solvent vapors are condensed in condenser 17, and then subjected to azeotropic drying on column 18 to remove traces of water and rectification on column 19. Purified return solvent is collected

in a 20 n vessel, it is directed again to the polymerization process.

To increase the efficiency of the extraction unit, it is possible to increase the polymer content in the solution by pre-concentrating it in a special apparatus. At the same time, the concentration of the polymer in the solution can be increased up to 50% as compared with the usually used contextual 10-30%.

As an initiator of polymerization, organic derivatives of lithium, sodium, potassium, aluminum, zinc, cadmium, their mixtures or mixtures with their alkoxides, ethers, amines can be used. As monomers, mono- and diolefins such as prolylene, butene, isoOprene, butadiene, piperylene, 2,3-dimethylbutadiene, vinylaromatic compounds, for example styrene, alphamethylstyrene, alpha phenylstyrene, divinylbenzene can be used.

The solvent can serve as individual hydrocarbons starting with C4 and above, their mixtures or mixtures with ethers or amines. It is most advisable to use mixtures of cyclohexane with paraffin, isoparaffin and aromatic hydrocarbons with a predominant content of cyclohexane. This mixture provides the highest solubility of vinyl aromatic compounds based on polymers and, in contrast to cyclohexane, has a relatively low freezing point (-30) - (-20) ° C.

The polymerization is carried out both periodically and in a continuous manner in devices of ideal displacement, ideal mixing, or in a system consisting of a combination of these devices, depending on the tin of monomers and the required amount of polymer, at a temperature of (-70) to (- | -150 ) ° C and pressure, ensuring the presence of the reaction medium in the liquid phase.

The unit for anhydrous degassing consists of two hollow heated work rolls, two expansion rolls and two chambers. Removal of the solvent from a thin film of polymer is performed on the hot surface of the work rolls. The pressure in the chambers should be in the range of 1.001 -1.1 MPa. The chambers of the aggregate are sealed by the elastic properties of the product after degassing.

According to the proposed method, unlike the opposed one, the use of water and acute water vapor as a medium for separating the polymer from the solution is excluded. This completely eliminates the presence in the production of chemically polluted wastewater requiring special treatment before dumping them into reservoirs; eliminates the need for dehydration of the solvent polymerization, which significantly simplifies and reduces the cost of the refining solvent purification flowchart, allows for the production of cleaner polymers by eliminating the need to use anti-agglomerators (used in the opposed way) and other contamination products present in the water ( inorganic salts).

The proposed method allows the use of non-darker antioxidants, which cannot be used but against the opposed method due to their solubility in water and entrainment with water vapor during drying; makes it possible to exclude a number of large-sized and metal-intensive equipment — a water degasser, a vibrating screen, an annarat for preliminary dewatering of rubber crumbs,

dryers and so on., - significantly reduce the production area, which significantly reduces the cost of production.

Example. A mixture of cyclohexanate (i80%) and gasoline (20%) is continuously fed to the reactor,

previously subjected to azeotropic drying and rectification. A mixture of butadiene and styrene in a ratio of 75: 25 is introduced into this stream. The total content of monomers in the mixture is 15%. Into the reactor continuously

Add a solution of dilithium polyvinyl at a rate that cleans the active lithium content in the reaction medium, 0.01 mol / l. The reaction mixture is vigorously stirred with a stirrer and circulated by the pump. Heat

Nimerization is removed through a shirt. The residence time in the reactor is about 4 hours.

The polymer is continuously withdrawn from the reactor and set to stabilize. Stabilization is carried out by mixing the polymerizate with the ionol solution. The polymer is separated from the solution on a sealed two-roll unit with a temperature of rollers up to 200 ° С, the residence time of the polymer on the rollers is not

more than 1 min The solvent content in the polymer is 0.1-0.2 wt.%.

After azeotropic drying and rectification, the solvent is again infused into the preparation of the polymerization mixture.

Characteristics of the obtained polymer: Defoe hardness, g800

Molecular weight distribution

 .1,1

Mp

The content of block styrene, Characteristics of carbon black vulcanizates (30% by weight. Soot):

Breaking strength, kgf / cm 300

Relative lengthening,% 600

Residual elongation,% 20

Subject invention

The method of separating synthetic elastomers and thermoplastic elastomers from their hydrocarbon solutions by evaporating the solvent by heating the solution of the polymer, characterized in that, to eliminate wastewater, eliminate thermal decomposition of the polymer and increase the degassing completeness, the polymer solution is first subjected to preliminary concentration with intensive

stirring and then finally removing the solvent with Heat

to a thin layer of polymer through the wall without mechanical impact on the polymer.

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