Removal of hydrogenation catalyst from polymer solutions by trialkyl aluminum precipitation

DETAILED DESCRIPTION OF THE INVENTION The aluminum compound of the present invention may be triethyl aluminum or another lower alkyl aluminum compound such as trimethyl aluminum or triisobutyl aluminum.
There should be three alkyl groups and none of them should have more than 6 carbon atoms.
The preferred aluminum compound is triethyl aluminum because of its cost, availability, effectiveness and relative ease of handling.
Sufficient trialkyl aluminum compound must be used in order to react with the Group VIII metal present in the catalyst residue so that catalyst residue particles of increased size will be formed.
The larger catalyst residue particles then will precipitate out of the polymer solution.
In order to accomplish this, the molar ratio of aluminum alkyl to Group VIII metal should be from 20 to 160.
Preferably, the molar ratio should be from 20 to 40 because excessive alkyl aluminum is unnecessary and reduces the aluminum removal efficiency.
The addition of water is also necessary to carry out the process of the present invention and achieve the desired advantages, i.
e.
removal of the Group VIII metal residue from the polymer solution, preferably to a level of less than five parts per million.
The water should be used in an amount from 0.
05 to 0.
50% by weight, preferably 0.
10 to 0.
30% by weight.
The polymer solutions of the present invention preferably comprise from 1 to about 40 percent by weight of a polymer, and more preferably comprise from about 2 to about 20 percent by weight of polymer based on the total amount of solution.
The polymer is a partially, selectively, or totally hydrogenated polymer.
The present invention does not depend upon the type of nature of the polymer .
The polymer may therefore be a thermoplastic polymer, or an elastomeric polymer and may have a molecular weight which varies between wide limits.
Most typically, polymers which are benefitted by hydrogenation are those comprising polymerized conjugated diolefins.
These conjugated diolefin containing polymers are therefore preferred for the practice of the present invention