PROCESS IN CONTINUOUS FOR THE PREPARATION OF RANDOM CONJUGATED DIENE/VINYL ARENE COPOLYMERS

Abstract

Process in continuous carried out in the presence of at least two reactors in series, for the preparation of statistical vinyl arene/conjugated diene copolymers, the vinyl arene content ranging from 15 to 50% by weight, by means of the copolymerization under isothermal conditions in a hydrocarbon solvent, at a temperature ranging from 30 to 120° C., of vinyl arene/conjugated diene monomers, in the presence of at least one initiator and a 2-methoxy ethyl tetra-hydrofuran (THFA-ethyl) modifier.

Description

Claims

1. Process in continuous effected in the presence of at least two reactors in series, for the preparation of statistical vinyl arene/conjugated diene copolymers, the vinyl arene content ranging from 15 to 50% by weight, by means of the copolymerization under isothermal conditions in a hydrocarbon solvent, at a temperature ranging from 30 to 120° C., of vinyl arene/conjugated diene monomers, the above process being carried out in the presence of at least one initiator selected from organo-lithium derivatives and a modifier, characterized in that the modifier is 2-methoxy ethyl tetra-hydrofuran (THFA-ethyl).

2. The process according to claim 1, wherein the reactors in series are of the CSTR type.

3. The process according to claim 1, wherein the vinyl arene is styrene.

4. The process according to claim 1, wherein the conjugated diene is 1,3-butadiene.

5. The process according to claim 1, wherein the vinyl arene content ranges from 20 to 45% by weight.

6. The process according to claim 1, wherein the temperature ranges from 50 to 110° C., preferably from 80 to 110° C.

7. The process according to claim 1, wherein the organolithium derivatives are selected from lithium alkyls, the latter being present in quantities ranging from 1 to 20 mmoles, preferably from 4 to 10 mmoles per 1,000 g of the blend of monomers.

8. The process according to claim 1, wherein the molar ratio between THFA-ethyl and the organo-lithium derivative ranges from 0.5 to 15, preferably from 2 to 10.

9. The process according to claim 1, wherein the hydrocarbon solvent consists of one or more hydrocarbons selected from hydrocarbons of the aliphatic and cycloaliphatic series or mixtures thereof.

10. The process according to claim 1, wherein the statistical styrene/butadiene copolymer has a weight average molecular weight (Mw) of between 200,000 and 800,000 and a Mw/Mn ratio of between 1.6 and 2.5.

11. The process according to claim 1, wherein the continuous process is carried out with a residence time ranging from 30 to 120 minutes.

12. The process according to claim 1, wherein the concentration of monomers in the reaction medium is from 5 to 20% by weight.

13. The process according to claim 1, wherein an oil extender, mainly aromatic, is added to the statistical styrene/butadiene copolymer formed at the end of the process.

14. The process according to claim 1, wherein the statistical styrene/butadiene copolymer has a content of vinyl units lower than 30% with respect to the diene portion only.

15. The process according to claim 1, wherein the statistical styrene/butadiene copolymer has a content of vinyl units higher than 60% with respect to the diene portion only.

16. Statistical styrene/butadiene copolymers having a styrene content of 25±3% and a content of vinyl units of 25±3%, prepared according to claim 1 at a temperature ranging from 90 to 95° C. and a THFA-ethyl/lithium molar ratio from 2 to 3.

17. Statistical styrene/butadiene copolymers having a styrene content of 40±3% and a content of vinyl units of 40±3%, prepared according to claim 1 at a temperature ranging from 90 to 95° C. and a THFA-ethyl/lithium molar ratio ranging from 6.0 to 7.5.