US 4,219,627 AGranted

Process for the preparation of block copolymers

AssigneeThe Firestone Tire & Rubber Company

InventorsAdel F. Halasa, James E. Hall, Adolph Para

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Abstract

The process described herein involves the preparation of block copolymers of the S-B-S type wherein S represents a block of polystyrene and B represents a block of polybutadiene. In order to have the initial polystyrene block soluble in the polymerization medium, cyclohexane and aromatic hydrocarbons have been used as the diluent or solvent in these polymerizations. The present process permits the use of hexane as diluent by having dissolved therein prior to polymerization a small amount of the S-B-S type of block copolymer being produced in the polymerization. Advantageously this solution used as the polymerization medium is prepared merely by washing the reactor used in a previous polymerization for production of the same type of S-B-S block copolymer with hexane to dissolve solid residues of S-B-S block copolymer deposited on the wall or agitator of the reactor. This hexane solution is then retained in the reactor to serve as the medium for the next polymerization batch. The dissolved S-B-S copolymer serves as a suspension agent for dispersion of the initial polystyrene block.

Claims12

Dependent claims

In the process of preparing S-B-S block copolymers, wherein S represents a block of polystyrene and B represents a block of polybutadiene, by the steps of polymerizing the individual monomers to form the respective blocks, such polymerizations being initiated by a lithium compound, the improvement whereby:

(a) said polymerization is initiated by a hydrocarbyl lithium compound having up to 10 carbon atoms,
(b) said polymerization is conducted in a solution of the same S-B-S block copolymer dissolved in a solvent consisting essentially of hexane, the amount of said copolymer comprising 0.1-10 parts by weight per 100 parts of styrene to be incorporated in the first S block of the S-B-S polymer to be formed;
(c) sufficient styrene is added to the said solution of S-B-S block copolymer in hexane to give the desired molecular weight of the first S block and thereafter effecting polymerization of said styrene to give the product polystyrene-Li while still dispersed in said hexane;
(d) thereafter adding an appropriate amount of butadiene to the dispersed product of step (a) to form a desired size block of polybutadiene and effecting polymerization of said butadiene with said polystyrene-Li to give the product polystyrene-polybutadiene-Li while still dispersed in said hexane, and
(e) thereafter effecting the addition of a second block of polystyrene onto said polystyrene-polybutadiene-Li.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/776,047Filed 9 Mar 1977
Granted: 26 Aug 1980
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

C08F 297/044
Polymerising vinyl aromatic monomers and conjugated dienes: using a coupling agent
C08G 81/022
Block or graft polymers containing only sequences of polymers of C08C or C08F: containing sequences of polymers of conjugated dienes and of…
C08F
Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
C08G
Macromolecular compounds obtained otherwise than by reactions only involving unsaturated carbon-to-carbon bonds