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1. WO2004007581 - COUPLED STYRENIC BLOCK COPOLYMERS AND PROCESS FOR PREPARING SAME

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

WHAT IS CLAIMED IS :

1. A radial styrenic block copolymer or a hydrogenated derivative thereof having a general formula:
(AB)nX
wherein:
(i) A is a styrenic block,
(ii) B is a dienic block,
(iii) X is a residue of a diester coupling agent,
(iv) n is the number styrenic block copolymer arms bonded to the residue of a diester coupling agent,
(v) the molecular weight of the styrenic block copolymer arm (AB) is from 2000 daltons to 300,000 daltons, and
(vi) the weight percentage of the polymer wherein n is at least 5 is less than 8 percent.

2. The radial styrenic block copolymer of claim 1 wherein the weight percentage of the polymer wherein n is at least 5 is less than 6 percent, preferably less than 5 percent, or wherein the weight percentage of the polymer wherein n is 2 is less than 5 percent, or wherein the weight percentage of the polymer wherein n is 2 and n is at least 5 is less than 12 percent.

3. The radial styrenic block copolymer of claim 1 or 2 wherein the styrenic block (A) is polystyrene and/or wherein the dienic block (B) is selected from polybutadiene, polyisoprene, and mixtures thereof.

4. The radial styrenic block copolymer of any one of claims 1 -4 wherein the residue of the diester coupling agent is a residue of a diester selected from dimethyl adipate, diethyl adipate, dimethyl terephthalate, diethyl terephthalate, and mixtures thereof.

5. A method for preparing a radial styrenic block copolymer of any one of claims 1 -4 comprising:
(a) contacting styrenic and dienic monomers with an anionic polymerization initiator which is an organo-substituted alkali metal compound in a suitable solvent to form a living polymer cement;
(b) adding from 0.01 to 1.5 equivalents of a metal alkyl compound per equivalent of living polymer chain ends to the cement, during or after polymerization, wherein the alkyl groups of the metal alkyl compound are chosen so that they will not exchange with the living polymer chain ends and the metal alkyl compound is selected from aluminum, zinc, and magnesium alkyls having from 1 to 20 carbon atoms per alkyl substituent; (c) adding a diester coupling agent to the cement under reaction conditions sufficient to couple the living polymer; and optionally
(d) hydrogenating the product obtained in step (c), preferably by using a selective hydrogenation process .

6. The method according to claim 5 wherein 0.9 to 1.1 equivalents of the metal alkyl compound per equivalent of living polymer chain ends is added to the cement.

7. The method according to claim 5 or 6 wherein the metal alkyl compound is a trialkyl aluminum compound, preferably triethyl aluminum.

8. The method according to any one of claims 5-7 wherein the metal alkyl compound is added in step (b) at or after 70%, preferably at or after 90% conversion of the monomers.

9. A modified bitumen comprising an admixture of the radial styrenic block copolymer of any one of claims 1 -4 or the product of the method of any one of claims 5-8 and bitumen.