US 5,397,851 AGranted

Process for cis-1,4-polybutadiene production with reduced gel formation

AssigneePolysar Rubber Corporation

InventorsThomas F. Knauf, Akhtar Osman

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Abstract

A process for producing high cis-1,4-polybutadienes wherein there is reduced gel formation is provided which process comprises: polymerizing 1,3-butadiene in a polymerization medium comprising an inert hydrocarbon solvent and water at a temperature of from about -30.degree. C. to about 60.degree. C. in the presence of a catalyst system which is a mixture of (1) a substantially anhydrous divalent cobalt salt, (2) diethyl aluminum chloride or ethyl aluminum sesquichloride and (3) an organo aluminum compound of the formula R.sub.3 Al wherein R is an alkyl group having from 8 to 12 carbon atoms and, optionally triethylaluminum, the molar ratio of chloride in the diethyl aluminum chloride plus (3) being from about 0.7:1 to about 1 and the molar ratio of chloride in the ethyl aluminum sesquichloride plus (3) being from about 0.7:1 to about 1.4:1 and the ratio of the mols of the divalent cobalt salt to the total mols of diethyl aluminum chloride or ethyl aluminum sesquichloride plus (3) being from about 1:15 to about 1:30, the water being employed at a level of from about 0.1 to about 0.8 millimol for every millimol of diethyl aluminum chloride or ethyl aluminum sesquichloride used, to the desired conversion.

A process for producing a high molecular weight rubbery polybutadiene having more than 96 percent of the butadiene units present in the cis-1,4-structure with a reduction in gel formation, which process comprises the steps of (A) polymerizing monomeric 1,3-butadiene in a polymerization medium comprising an inert hydrocarbon solvent and water at a temperature of from about -30.degree. C. to about 60.degree. C. in the presence of a catalyst system dissolved in said polymerization medium, said catalyst system being a mixture of (1) a substantially anhydrous divalent cobalt salt of the formula CoA.sub.m wherein A represents a monovalent or divalent anion of the salt and m is 1 or 2;

(2) an alkyl aluminum chloride compound selected from the group consisting of diethyl aluminum chloride and ethyl aluminum sesquichloride;
and (3) an organo aluminum compound of the formula R.sub.3 Al wherein R is an alkyl group having from 8 to 12 carbon atoms and optionally triethyl aluminum, the molar ratio of chloride in the diethyl aluminum chloride to the total aluminum content in the diethyl aluminum chloride (2) plus the organo aluminum compound (3) being in the range of from about 0.7:1 to about 0.95:1 and the molar ratio of chloride in the ethyl aluminum sesquichloride to the total aluminum content in the ethyl aluminum sesquichloride (2) plus the organo aluminum compound and optionally the triethyl aluminum (3) being in the range of from about 0.7:1 to about 1.4:1 and the ratio of the mols of said divalent cobalt salt to the total mols of said alkyl aluminum chloride compound plus said organo aluminum compound and optionally triethyl aluminum being in the range of from about 1:15 to about 1:30, said water being employed at a level of from about 0.1 to about 0.8 millimol for every millimol of the alkyl aluminum chloride compound (2) used, (B) continuing the polymerization thus initiated to the monomer conversion desired, and (C) thereafter deactivating the polymerization and recovering the polybutadiene.

Abstract

Claims11