CS239520B1 - A method for producing butadiene styrene rubber by emulsion copolymerization - Google Patents

Abstract

The purpose of the invention was to increase the capacity of extractive distillation of butadiene. This is achieved by using a mixture of pure butadiene containing at least 99.7% by weight of 1,5-butadiene and crude butadiene free from methylacetylene containing at least 96% by weight of 1,5-butadiene in a ratio of 8:1 to 50:1 for the copolymerization of butadiene and styrene.

Description

The invention relates to a method for producing butadiene-styrene rubber by emulsion copolymerization.

For the production of butadiene-styrene rubber by emulsion copolymerization, pure 1,3-butadiene (hereinafter butadiene) with a concentration of at least 99.6% by weight is supplied, produced in a butadiene production plant by separating it from the so-called fraction (i.e. from a mixture of hydrocarbons with 4 carbons such as 1,3-butadiene, 1-butene, 2-butene, and others), recycled butadiene containing at least 96% by weight of 1,3-butadiene and styrene, and finally recycled styrene. Part of the recycled butadiene (25%) is discharged as so-called returnable butadiene to the butadiene production plant from the fraction, where styrene, cis-2-butadiene, and butadiene dimer are removed from it.

The need to purify the returnable butadiene limits the capacity of the butadiene production plant, especially the rectification part of the raw butadiene.

239,920

The method of producing butadiene-styrene rubber by emulsion copolymerization of butadiene and styrene according to the present invention appears to be more preferable, the essence of which is that a mixture of pure butadiene with a content of at least

99.7% by weight of 1,3-butadiene and crude butadiene free from methylacetylene with a content of at least 96% by weight of 1,3-butadiene in a ratio of 8:1 to 50:1.

The advantage of the new emulsion copolymerization method is an increase in the fraction throughput in the butadiene production plant, an increase in the production and quality of pure butadiene, energy savings in the final rectification of butadiene, and an increase in the production of the butane-butene fraction.

The invention is based on branching off a portion of raw butadiene with a concentration of at least 96% by weight of butadiene from a butadiene production plant and introducing this stream into the copolymerization, i.e. e.g. into a recycled butadiene tank for butadiene copolymerization. The ratio of pure butadiene to raw butadiene can be selected such that the concentration of butadiene at the inlet to the copolymerization does not change or is reduced compared to the current state. For a reduced concentration of butadiene at the inlet to the copolymerization, it is possible to increase, e.g., the volume of the reaction mixture or the concentration of the copolymerization initiator so that the copolymerization efficiency remains maintained. An increase in the volume of the reaction mixture can be achieved in the copolymerization, e.g., by increasing the use of copolymerization lines. The concentration of butadiene at the inlet to the copolymerization can be regulated, e.g., by changing the ratio of the inflow of pure and raw butadiene to the copolymerization. Since frequent changes in the concentration of butadiene at the inlet to the copolymerization are detrimental to the copolymerization,

239 S20 these reactors more than operating the copolymerization with a lower but uniform concentration of butadiene, the new copolymerization method brings an additional advantage in that the concentration of butadiene at the inlet to the copolymerization reactors is uniform and thus stabilizes the copolymerization rate and the quality of the latex. Reducing the concentration of butadiene at the inlet to the copolymerization does not negatively affect the quality of the resulting latex. The amount of butadiene returned to the butadiene plant is adjusted so as to avoid the accumulation of butenes and butadiene dimers in the copolymerization plant.

The attached figure schematically shows a scheme for the production of butadiene styrene rubber and pure butadiene in conjunction according to the present invention, which is described below together with an explanation of the function.

The fraction is fed by stream 8 to the extractive distillation section, where it is mainly freed from butenes and butanes by stream 10 and from some acetylenes by stream 13. From the extractive distillation section 14, crude butadiene is fed by stream 17 to the rectification section 15, where methylacetylene residues are removed by stream 11. The crude butadiene freed from methylacetylene is mostly fed by stream Jjj· to the final rectification section 16, the remainder by stream J; to the copolymerization section 18. Pure butadiene, freed from butene residues in the final rectification section 16 by stream 12, is fed by stream 1 to the copolymerization section 18, and the unused excess is fed by stream % outside the production plant.

For copolymerization, ge uses, among other components, pure butadiene from stream 1, crude butadiene from stream 4 ^and recycled butadiene from stream 2. The product in the form of butadiene-styrene latex in stream J is discharged from copolymerization section 18, while the unreacted butadiene leaving stream £ is further divided into a recycled portion in stream 2 and a return butadiene led back to extractive distillation section 1£.

The following table presents the numerical results of the mass balance of three experiments according to the invention No. 1 to 3 and one in the embodiment according to the known state, i.e. current £ = 0, experiment No. 4.

Current sz c. 1 2 3 4 7 8 9 10 Attempt No. 1 t/h 5.2 1.5 5.0 0.3 0.5 22.01 3.44 12.67 % wt. BTD 99.7 95.08 100 97.0 95.08 40.0 99.7 0.1 Attempt No. 2 t/h 5.2 2.1 5.0 0.5 0.7 21.37 3.81 11.69 # wt. BTD 99.7 95.72 100 97.0 95.72 43.0 99.7 0.1 Attempt No. 3 t/h 5.4 1.5 5.0 .0.1 0.5 20.43 3.43 11.18 % wt. BTD 99.7 96.28 100 97.0 96.28 43.0 99.7 0.1 Attempt Μ A c. 4 t/h 5.5 1.5 5.0 0 0.5 21.25 3.15 12.24 % wt. BTD 99.7 96.7 100 97.0 96.7 40.0 99.7 0.1

From the comparison of the mass balance data of the method according to the invention with the known method, it follows that while maintaining the amount of produced butadiene-styrene copolymers (streams), specifically 5 t/h, it is possible to influence the amount of processed butadiene-styrene copolymers by the size of the stream £.

239 S20 fraction (stream 8) and thus the amount of pure butadiene led out of the production plant (stream £) with relatively £ small changes in polymerization conditions (concentration of 1,3-butadiene in stream 2, resp.

1)· A comparison of examples 1 and 4 shows that by changing the stream £ from zero flow to a flow of 0.3 t/h, the amount of butadiene production distributed by stream % outside the production plant can be increased by 0.29 t/h, i.e. by about 9.2%, and the fraction free of butadiene (stream 10) by 0.43 t/h, i.e. by 3.5%, while reducing the butadiene concentration in the reaction mixture (stream 2 or J) by about 1.6% by weight. From examples .

and 3 then it follows that when the flow rate in stream 4 is increased from 0.1 to 0.5 t/h, i.e. fivefold, the concentration of butadiene in the reaction mixture changes from 96.28 to 95.72% by weight, i.e. the deterioration represents only 0.56%, if the withdrawal of the unreacted mixture by stream 2 (return butadiene) is also increased.

Claims (1)

Process for producing butadiene-styrene rubber emulating copolymers by measuring butadiene and styrene, characterized in that a mixture of pure butadiene containing at least 99.7% by weight is used for the reaction. 1,3-butadiene and methylacetylene-free crude butadiene containing at least 96 wt. 1,3-butadiene in a ratio of 8; 1 to 50: 1.