Process for forming rubber latex from branched polymers
The disclosure relates to rubber latex formed from any of: branched block copolymers derived from alkenyl aromatic hydrocarbon—1,3-diene monomer system, and branched polyisoprene homopolymers derived from isoprene. The polymers in embodiments are obtained by polymerization in the presence of an anionic initiator; at a temperature from 0° C. to 100° C.; followed by coupling with a multifunctional coupling agent of formula (R 1 O) 3 Si—Y—Si(OR 2 ) 3 , wherein R 1 and R 2 are independently C 1 -C 6 alkyl groups; and Y is a C 2 -C 8 alkylene group. The polymers are obtained as rubber cements having high solids content and low zero shear viscosities. The rubber cements are valuable for making latices for further applications.
1. A process for forming a rubber latex, comprising:
providing a rubber cement comprising a branched block copolymer having coupling efficiency (CE) of at least 40%, the branched block copolymer comprising one or more polymer blocks A and one or more polymer blocks B and having a formula (A-B) m (R 1 O) 3-m Si—Y—Si(R 2 O) 3-n (B-A) n , wherein
each A block independently comprises at least 90 mole percent of an alkenyl aromatic hydrocarbon; wherein the one or more A blocks form 8-13 weight percent of the total weight of the block copolymer;
each B block is independently a poly(1,3-diene) block comprising at least 90 mole percent of one or more 1,3-dienes;
each A block independently has a weight average molecular weight from 9-15 kg/mol, and each B block independently has a weight average molecular weight from 75-150 kg/mol;
R 1 and R 2 are independently H, or C 1 -C 6 alkyl groups;
Y is a C 2 -C 8 alkylene group;
m and n are integers independently having values from 1-3; and
emulsifing the rubber cement to form a rubber latex;
wherein the rubber cement has a zero shear viscosity of less than 25,000 mPas in a solids content range from 15 wt. % to 25 wt. %.
2. The process of claim 1 , wherein (m+n) in the branched block copolymer in the rubber cement has a value from 3-6.
3. The process of claim 1 , wherein Y in the branched block copolymer in the rubber cement is —CH 2 CH 2 —, and R 1 and R 2 are hydrogen, methyl groups or ethyl groups.
4. The process of claim 1 , wherein the 1,3-diene in the branched block copolymer in the rubber cement is isoprene, and the alkenyl aromatic hydrocarbon in the branched block copolymer is styrene.
5. A latex formed by the process of claim 1 .
6. A process for forming a rubber latex, comprising:
providing a rubber cement comprising a branched polyisoprene homopolymer having a coupling efficiency (CE) of at least 40%, having a formula (C) m (R 1 O) 3-m Si—Y—Si(R 2 O) 3-n (C) n , wherein
each C block is independently a polyisoprene block having a weight average molecular weight from 400-1000 kg/mol;
R 1 and R 2 are independently H, or C 1 -C 6 alkyl groups;
Y is a C 2 -C 8 alkylene group;
m and n are integers independently having values from 1-3; and
emulsifing the rubber cement to form a rubber latex.
7. The process of claim 6 , wherein (m+n) in the branched polyisoprene homopolymer has a value from 3-6.
8. The process of claim 6 , wherein Y in the branched polyisoprene homopolymer is —CH 2 CH 2 —, and R 1 and R 2 are hydrogen, methyl groups or ethyl groups.
9. The process of claim 6 , wherein the C block in the branched polyisoprene homopolymer has a weight average molecular weight from 500-700 kg/mol.
10. The process of claim 6 , wherein the rubber cement has a zero shear viscosity of less than 80,000 mPas at a solids content range from 15 wt. % to 25 wt. %.
11. The process of claim 6 , wherein the rubber cement has a solids content from 5 wt. % to 25 wt. %.
12. The process of claim 6 , wherein the rubber cement has a zero shear viscosity of less than 80,000 mPas in a solids content range from 15 wt. % to 25 wt. %;
a cis content from 70% to 95%; and
a weight average molecular weight from 1,000 to 3500 kg/mol.
13. A process for forming a rubber latex, comprising:
providing a rubber cement comprising a branched polyisoprene homopolymer having a coupling efficiency (CE) of at least 40%, having a formula (C) m (R 1 O) 3-m Si—Y—Si(R 2 O) 3-n (C) n , wherein
each C block is independently a polyisoprene block having a weight average molecular weight from 400-1000 kg/mol;
R 1 and R 2 are independently H, or C 1 -C 6 alkyl groups;
Y is a C 2 -C 8 alkylene group; and
m and n are integers independently having values from 1-3; and
emulsifing the rubber cement to form a rubber latex;
wherein the rubber cement has a zero shear viscosity of less than 80,000 mPas at a solids content range from 15 wt. % to 25 wt. %.