SU433683A3 - METHOD OF OBTAINING IOLIIZOPREN - Google Patents

Description

; The invention relates to the production of synthetic rubber, in particular to the production of polyisoprene by the catalytic polymerization of isoprene. A known method of producing polyisoprene by catalytic polymerization of isoprene at 0-70C in an aliphatic or cycloaliphatic mass or medium containing 5-8 carbon atoms of hydrocarbon solvents, the boiling point of which under normal pressure is higher than the polymerization temperature, when carrying out the process in one or several series-connected reactors, The process is carried out under normal or elevated pressure in an inert gas atmosphere with removal of the reaction heat using indirect heat exchange. The aim of the invention is to increase the yield of polyisone and the rate of polymerization, as well as increase the efficiency of removal of the reaction heat. This goal is achieved by carrying out an I process under reduced pressure in the mode and boiling of the reaction mass with removal of i 6 x vapor. Preferably the polymerization is carried out in the presence of solvents, with cyclic or acyclic, straight chain or branched saturated aliphatic hydrocarbons with 5-8 carbon atoms, in particular n-pentane, n-hexane, iso-octanes, methylcyclopentane, cyclohexane being used as solvents. or a mixture of these. x solvents. The polymerization temperature is preferably 5-35 ° C. The negative pressure required at this temperature for boiling the reaction mass is obtained with the aid of a vacuum pump. The vacuum established at the given polymerization temperatures depends not only on the solvent, but also on the conversion of the monomer. If at temperatures of polymerization, for example, 5–30 ° C, the mixture of solvents of the composition, wt. %: Nzo-Nentane 0, O46 n-Pengy0,2 j 2,2-Dimethylbutane0,10 2-Methylpentane1 h RO 2,3-Dimethylbutane 3-Methylpentane. 14.40 n-Hexane 48.4 O Methyl cyclopentane 12.90 Benzene 0.22 Cyclohexane 8.60 iso-Heptane1.18 n-Heptane 0.11 Methylcyclohexane, 0.016 Boiling pressure approx. 8 O-36 O When n-pentane is used as solvent, boiling pressure area is 1 h. approximately 240-65 O torr. Using the proposed method, it became possible to reduce the amount of catalyst required by the desired reaction rate by at least 2% compared with the known process. This is due to the removal of extraneous gases dissolved in the monomer and B solvent, which negatively affect the activity of the polymerization catalyst. It is preferable to carry out the polymerization in several, for example, ice polymerization reactors (autoclaves), and the temperature and transformation in successive autoclave I are maintained at different levels . In autoclaves, it is preferable to consistently increase the temperature from the autoclave to the autoclave, respectively, and gradually increase the polymerisation in succession; | Moo1-engraved 1% immersion process - without cooling by evaporation at no (maximal pressure or slightly increased pressure to release) the heat of polymerization should be used to increase the nojaiMepH3aunH temperature for the conversion of the monomer.It is advisable to use autoclaves with volumes of at least 4O m, preferably titol; tiO-25O m, in particular 100 1-200 m. It is depicted scientifically, the length of the curve being shown is i; nat; o6; i installation. Three boilers 1,2 and 3, Hci bottom of which is a pair of propeller mixers 4, successively connected. Boilers 1 and 2 are equipped with condensers 5, which condense the 6-horicles blown down by blowers into |) s and let them flow back. 1c13 | n; zh1111e in boilers are supported by vacuum. mind-H (1-pump 7, which as necessary sucks CciTupii gases non-condensable after the condensations. Pressure is regulated by valves 8. The heat sink can be regulated by valves 9, Boilers can be fed with pressure through inlets O. The solvent, monomer and catalysts are continuously injected boiler 1 with a regulated level height. By means of a displacement pump 11, which it is advisable to place so deep under the surface of the liquid so that there is a slight increase in pressure, the polymer solution is transported from boiler 1 to bodies 2 also with a regulated level height. Boiler 2 is similar to boiler 1. Pump 12 maintains the height of level in boiler 2 and delivers the polymer solution to boiler 3. Ko, body 3 does not cool, residual heat. I polymerization contributes to the desired I temperature increase in it. Solution of polymers can be removed from boiler 3 without separate filling, this boiler 3 is fully or partially filled. Only partial discharge by filling polymer solution of boiler 3 with pressure in the gas space} This type of boiler is set so that the polymer solution is supplied for processing. In the examples, all the percentages are by weight. Example 1. In a boiler 1 of a polymerization unit, consisting of three boilers (capacity 200 vol. H each), non-. A 1O% isoprene solution in a hexane mixture (the composition is indicated earlier) and also formed from 0.17 wt. % etherate c1 / 1K) g.1Initriethyl and 0.24% by weight of titanium tetrachloride (both substances are dissolved in hex; ane) mixed jamajiTop. The indicated amounts of catalyst refer to the isoprene used. The temperature inside the boiler is maintained by cooling with a reverse holocil at a pressure of 97 Torr and 10 ° C; Low pressure, puluchschzt using a vacuum pump. The rotation in this kit is about 1% to about 5%. The polymerization solution p (; and the pump of the pressure pump is fed to the boiler 1 to the boiler 2, in which the polymerization process reaches a conversion of approximately 8O% when cooled by the reverse cooler at a pressure of 146 Torr and a temperature of 20 ° C. The solution of the immersion solution is pumped from the boiler 2 through the full boiler 3 to the plant for processing. Without further cooling in the boiler 3, a temperature of 33 s and a conversion of 97% are reached, the pressure in the boiler 3 has no effect on the polymerization. The residence time of the polymerization solution in a three-stage poliri atsioppoy installation is 4 hours.

Example 2. If the method of polymerization of isoprene described in example 1 is carried out in n-pentane as a solvent, only the pressures in boilers 1 and 2 change. At polymerization temperature g

U C in the boiler 1 pressure of 286 Torr, in the boiler 2 is polymerized, as in example 1, at a temperature of 20 C, and the pressure is 440 Torr.

Example 3.0 Nitrogen Filled

and an anhydrous 5OO l polymerization reactor with reflux condenser and impeller connected to a vacuum pump, is fed a 16% isoprene solution into a hexano-jg false mixture (the composition is indicated earlier). Bringing the pressure to BUT torr, the mixture of nag solvent and monomer is cooled to 10 ° C and at the same time free from dissolved extraneous gases. Polymerization begins with the addition of a mixture of 0.35% by weight of aluminum triethyl etherate and 0.49% by weight of itan tetrachloride (relative to isoprene) of a mixed catalyst (dissolved hexane). After the DL has elapsed, 25 conversions reach about 55%, and the temperature of the reaction mixture rises to 14 ° C at a constant pressure of 110 Torr. Over the next 60 minutes, the pressure is constantly n-i but increased to 18 O tprr, and as a result of a 30-second polymerization temperature rises to 25 ° C. The conversion achieved is then approximately 90%. By introducing nitrogen, the pressure is increased to normal, as a result of which the temperature rises 35 to 27 ° C. Upon expiration of further AOR min, a conversion of 97% is achieved. The total polymerization time is 2 hours.

The Mooney viscosity of a polyisoprene recovered in a known manner is 40 ML.

Example 4. Example 3 is repeated with a reduced amount of catalyst. The aluminum triethyl etherate is only O, 27% by weight, and tetra.chloride of titanium is 0.39% by weight with respect to isoprene. The polymerization time before conversion of 97% is increased to 4 hours. The in-viscosity of the isolated and dried polyisopre-i is not ML. -4 89.

Example 5 (for comparison). In a nitrogen-filled and anhydrous polymerization reactor with a volume of 500 l, equipped with a gg cooling jacket and impeller (stirrer), 16% isoprene solution in a hexane mixture is fed (the composition is indicated earlier). The contents of the boiler are cooled with a shirt up to 10 ° C. GQ polymerization

Begin by adding ns 0.35 j% by weight of aluminum triethyl etherate and 0.49% by weight of titanium tetrachloride (relative to isoprene) mixed catalyst (both substances are dissolved in hexane). The cooling is carried out so as to maintain the polymerization temperature of 10-15 ° C to

obtaining a conversion of about 50%, which is reached after 1 hour. Then cooling with a shirt

10 is reduced to a polymerization temperature of about 20-25 ° C. After reaching a conversion of about 80% after approximately 3 hours of polymerization, the cooling is stopped. Theme

The temperature of the polymerization solution increases to 30 ° C, the conversion increases to 94-98% over the next 6O minutes. According to this method, the minimum polymerization time is

, 4 hours

The polymer solution is processed in a known manner. Dried polyisoprene has a Mooney viscosity MLi-4 of 74.

Example 6. (for comparison). Example 5 is repeated with a reduction of the amount of catalyst. The proportion of aluminum triethyl etherate is 0.27% by weight, and titanium tetrachloride 0.39% by weight relative to isoprene. The polymerization rate is greatly reduced: after 4 hours at a polymerization temperature of 10-15 ° C, a conversion of 50% is achieved, after a further 4 hours at 10-25 ° C, the conversion reaches 80%. The polymerization is terminated at 30 ° C, the conversion is 9 O%. OGiuee time is about 12 hours. Mooney viscosity polyisoprene ML,.

When comparing examples 3 and 4 with examples 5 and 6, the following advantages of the proposed method are seen:

higher polymerization rate; lower catalyst consumption with the same polymerization time;

higher molecular weight, higher Mooney viscosity.

Subject invention

1. A method of producing polyisoprene by catalytic polymerization of isoprene at 0-7 ° C in the mass or medium of aliphatic or cycloaliphatic C-C -hydrocarbon solvents, the boiling point of which under normal pressure is higher than the nepaiypbi polymerization, during the first process in one or several series-connected reactors By the fact that, in order to increase the yield of polyisoprene and the speed of the process, the latter is carried out at a reduced pressure in the boiling mode of the reaction mass with removal of the resulting vapors. 2. The method according to l. 1, that is, the fact that during the process B of several reactors the pressure in them is consistently increased.