Claims
- 1. Branched block copolymers of from 60 to 95 percent by weight of a monovinyl-aromatic compound and from 40 to 5 percent by weight of a conjugated diene of 4 to 8 carbon atoms, which have an average structure of the general formula
- (A.sup.1 --A.sup.2 --B.fwdarw.A.sup.3).sub.n --X--(A.sup.3 .rarw.B--A.sup.2).sub.m
- where A.sup.1, A.sup.2 and A.sup.3 are non-elastomeric polymer segments based on the monovinyl-aromatic compound and the B's are elastomeric polymer segments based on the conjugated diene, m and n are numbers, m being equal to or greater than n and the sum of m and n being at least 3, and X is the radical of a polyfunctional coupling agent by means of which the linear polymer blocks (A.sup.1 --A.sup.2 --B.fwdarw.A.sup.3) and (A.sup.2 --B.fwdarw.A.sup.3), which form the branches, are chemically bonded to one another at the polymer segments A.sup.3, with the provisos that the polymer segment or segments A.sup.1 contains or contain from 50 to 80 percent by weight, the polymer segments A.sup.2 from 1 to 30 percent by weight, but the polymer segments A.sup.1 and A.sup.2 together not more than 90 percent by weight, of the total monovinyl-aromatic compound of the branched block copolymer, as copolymerized units, the transition between the polymer segments A.sup.2 and B is sharp and the transition between the polymer segments B and A.sup.3 is gradual.
- 2. Branched block copolymers as set forth in claim 1, which have a weight-average molecular weight of from 100,000 to 1,000,000.
- 3. Branched block copolymers as set forth in claim 1, which are partially or completely hydrogenated.
- 4. A process for the manufacture of branched block copolymers of claim 1 which comprises: polymerizing in a first stage of the process, from 50 to 80 percent by weight of the total amount of monovinyl-aromatic compound in an inert solvent, in the presence of a relatively small amount of a monolithium-hydrocarbon as the initiator, until conversion is virtually complete, thereafter, in a second stage of the process, adding to the reaction solution a further amount of monolithium-hydrocarbons, which is equal to or greater than the amount of initiator originally employed, followed by the addition of a further 1 to 30 percent by weight of the total amount of the monovinyl-aromatic compound, the sum of the amount of monovinyl-aromatic compound added in the first and second stage of the process being at most 90 percent by weight of the total amount of monovinyl-aromatic compound employed overall for the manufacture of the branched block copolymers, and polymerizing the monovinyl-aromatic compounds added in the second stage of the process until conversion is virtually complete, thereafter, in a third stage of the process, adding to the reaction solution a mixture of the remaining monovinyl-aromatic compound and the whole of the conjugated diene and polymerizing said mixture, and when the monomers have been virtually completely converted, subjecting the mixture of the resulting linear block copolymers with active terminal lithium-carbon bonds to a coupling reaction, by adding the polyfunctional coupling agent, to form a branched block copolymer and finally isolating the branched block copolymer from the reaction solution.
- 5. A branched block copolymer as set forth in claim 1, wherein the monovinyl-aromatic compound is styrene, styrene alkylated in the side chain and nuclear substituted styrene.
- 6. A branched block copolymer as set forth in claim 1, wherein the conjugated diene is butadiene, isoprene and 2,3-dimethylbutadiene.
- 7. A branched block copolymer as set forth in claim 1, wherein the polyfunctional coupling agent is a polyepoxide, polyisocyanate, polyketone, polyanhydride, polyhalide, dicarboxylic acid ester, silicon halide or polyvinyl-aromatic.
- 8. A branched block copolymer as set forth in claim 1, wherein the sum of n+m is from 3 to 10.
- 9. A branched block copolymer as set forth in claim 1, wherein the molecular weight of the polymer block (A.sup.1 --A.sup.2 --B.fwdarw.A.sup.3) is from 100,000 to 500,000.
- 10. A branched block copolymer as set forth in claim 1, wherein the molecular weight of the polymer block (A.sup.2 --B.fwdarw.A.sup.3) is from 10,000 to 100,000.
- 11. A process as set forth in claim 4, wherein the amount of initiator in the first stage is from 0.1 to 10 moles per mole of monovinyl-aromatic compound.
- 12. A process as set forth in claim 4, wherein the amount of initiator in the second stage is from 1 to 15 times the amount of initiator in the first stage.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2550227 |
Nov 1975 |
DEX |
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Parent Case Info
This is a continuation of application Ser. No. 732,900 filed Oct. 15, 1976 now abandoned.
US Referenced Citations (3)
Continuations (1)
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Number |
Date |
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Parent |
732900 |
Oct 1976 |
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