Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Statutory Invention Registration
1998-06-08
2001-04-03
Jordan, Charles T. (Department: 3641)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S339000
Statutory Invention Registration
active
H0001956
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the manufacture of hydrogenated block copolymers of conjugated dienes and/or vinyl aromatic hydrocarbons by anionic polymerization of these monomers in a hydrocarbon solvent. More particularly, this invention relates to an improvement in such a process whereby efficiency of the hydrogenation catalyst removal step is enhanced by reducing the viscosity of the polymer cement (the solution/slurry/suspension of the anionic polymer in the hydrocarbon solvent).
BACKGROUND OF THE INVENTION
Polymers of conjugated dienes and/or vinyl aromatic hydrocarbons have been produced by numerous methods. However, anionic polymerization of such dienes in the presence of an anionic polymerization initiator is the most widely used commercial process. The polymerization is carried out in an inert solvent such as hexane, cyclohexane, or toluene and the polymerization initiator is commonly an organo alkali metal compound, especially alkyl lithium compounds. The solvent used is almost always a non-polar hydrocarbon because such solvents are much better solvents for the conjugated diene which usually form the largest part of the block copolymers.
As the polymer is created from the monomers, a solution/slurry/suspension of the polymer forms in the inert hydrocarbon solvent. This solution/slurry/suspension is called the polymer cement. These polymerizations may be carried out at a variety of solids contents and it is reasonably obvious that if the process can be run at high solids content, the manufacturing cost will be decreased because more polymer can be produced in a given amount of time.
Unfortunately, with polymer cements of these block copolymers, one of the most significant rate limiting aspects is the viscosity of the polymer cement. For instance, in order to achieve a reasonable efficiency in the removal of hydrogenation catalyst residue from the polymer cement, the viscosity of the polymer cement must not be more than 1000 cp at 80° C. Some of the desired hydrogenated block copolymers can achieve this viscosity requirement so hydrogenation catalyst residue can be efficiently removed at 20% solids, some at 15% solids, but there are other block copolymers that can only achieve the viscosity requirement in polymer cements at close to 10% solids. The manufacturing cost of such hydrogenated block copolymers is therefore much higher. It can be seen that there would be a significant advantage achieved if a way could be found to utilize the current manufacturing technology but decrease the polymer cement viscosity for enhanced catalyst residue removal at higher solids contents so more polymer can be produced in a given amount of time.
It would be desirable to operate the process at a higher solids content in the cement if the same amount of catalyst removal could be achieved in the same amount of time. More polymer would be produced then in a given amount of time. Alternatively, it would be advantageous to be able to decrease the time it takes to remove the desired amount of catalyst residue while operating at the same solids content. The total throughput time would thus be decreased. Another result which would be highly advantageous would be to operate at the same conditions as are presently used (time, solids content, etc.) and thus remove more of the residual hydrogenation catalyst. The present invention provides a method for achieving these goals.
SUMMARY OF THE INVENTION
This invention is an improvement upon the current process for the production of block copolymers, especially hydrogenated block copolymers, of conjugated dienes and/or vinyl aromatic hydrocarbons which comprises anionically polymerizing the monomers in an inert hydrocarbon solvent in the presence of an alkali metal initiator whereby a polymer cement is produced, contacting the cement with hydrogen under hydrogenation conditions in the presence of a hydrogenation catalyst, and then removing the hydrogenation catalyst residue by washing the polymer cement with water or, preferably, an aqueous acid. This invention and the improvement to the foregoing process comprises reducing the viscosity of the polymer cement by polymerizing the block copolymer under conditions such that the vinyl content of the polymer produced is from 45 to 80 percent by weight (% wt).
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Yih-Chau Lin, Raymond Chien-Chao Tsiang, “Using Heavy Ethers as Structure Modifiers in the Synthesis of SBS Block Copolymers in Cyclohexane,”Journal of Applied Polymer Science, vol. 64, No. 13, Jun. 27, 1997, pp. 2543-2560.
de Groot Eleanor Meyer
Modic Michael John
Schisla David Karl
Baker Aileen J.
Haas Donald F.
Jordan Charles T.
Shell Oil Company
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