Dual Composition Block Copolymers

Abstract

Dual composition block copolymers made from conjugated diene and monovinyl aromatic monomers in batch organolithium initiated polymerization show advantageous performance in the production of crosslinked microcellular rubber compounds and pressure sensitive hot melt adhesives. The block copolymers are partially coupled molecules with a coupling agent linking inner monovinyl aromatic blocks. An un-coupled low molecular weight fraction has greater monovinyl aromatic repeat unit content than a coupled high molecular weight fraction. Crosslinked microcellular rubber articles made from the block copolymers exhibit lower density, smaller and more homogeneous cell size, higher softness and higher resiliency than prior art block copolymers. Rubber compounding of formulations comprising the block copolymers proceed at slightly lower torque and slightly lower temperature than with prior art block copolymers. Pressure sensitive hot melt adhesives formulated with the block copolymers are very well suited for labels, exhibiting higher tack and higher softening temperature than those made from prior art block copolymers.

What is claimed is: 
     
         1 . A dual composition block copolymer made from conjugated diene and monovinyl aromatic monomers, comprising a block copolymer C, and a block copolymer U, wherein,
 (a) molecular weight distribution of the dual composition block copolymer exhibits at least two peaks, partially or totally resolved;   (b) block copolymer C constitutes the fraction with the peak at the highest molecular weight in the molecular weight distribution, and block copolymer U constitutes the remainder of the molecular weight distribution;   (c) block copolymer C accounts for from about 20 to about 80% of the molecular weight distribution;   (d) block copolymer C comprises a coupling agent residue linking inner monovinyl aromatic blocks, only;   (e) total monovinyl aromatic repeat unit content of the dual composition block copolymer is from about 20 to about 50 wt. %;   (f) monovinyl aromatic repeat unit content in block copolymer U is at least 10 wt. % higher than monovinyl aromatic repeat unit content in block copolymer C; and   (g) monovinyl aromatic repeat unit blockiness degree of the dual composition block copolymer is equal or greater than about 76 mole %, on a total monovinyl aromatic repeat unit basis.   
     
     
         2 . The dual composition block copolymer of  claim 1 , comprising C and U, wherein
 C comprises:
   [D-(D/A)-A 1 ] n -X; 
   [B-(B/A)-A 1 ] n -X; 
   [(B/A)-A 1 ] n -X; or 
   [B-A 1 ] n -X, or a mixture of the foregoing, and wherein 
   U comprises:
   D-(D/A)-A 2  or D-(D/A)-A 2  and D-(D/A)-A 1 , 
   B-(B/A)-A 2  or B-(B/A)-A 2  and B-(B/A)-A 1 , 
   (B/A)-A 2  or (B/A)-A 2  and (B/A)-A 1 ; 
   B-A 2  or B-A 2  and B-A 1 , or a mixture of the foregoing, wherein 
   B is a polymer block made from only conjugated diene monomer, wherein   (B/A) is a random polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein   D is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein conjugated diene repeat units are in a greater molar amount than monovinyl aromatic repeat units along the whole polymer block length, wherein   (D/A) is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein an end of the polymer block opposite to A 1  or A 2  is predominantly composed of conjugated diene repeat units, wherein the composition of the polymer block gradually changes along the length of the block until it becomes composed substantially of monovinyl aromatic repeat units at an end adjacent to A 1  or A 2 , wherein   A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only, wherein polymer block A 2  has a greater molecular weight than polymer block A 1 , wherein   X is the residue of a coupling agent, and wherein   n is an integer with a value from 2 to 30.   
     
     
         3 . The dual composition block copolymer of  claim 2 , wherein the monovinyl aromatic repeat unit content in U is at least 20 wt. % higher than in C. 
     
     
         4 . The dual composition block copolymer of  claim 2 , wherein the monovinyl aromatic repeat unit blockiness degree of the dual composition block copolymer is at least about 80 mole % on a total monovinyl aromatic repeat unit basis. 
     
     
         5 . The dual composition block copolymer of  claim 1 , further comprising from 0 to about 12 parts of oil per hundred weight parts of dual composition block copolymer. 
     
     
         6 . The dual composition block copolymer of  claim 5 , optionally oil extended, wherein the dynamic oscillatory shear test of the dual composition block copolymer, when sweeping oscillation frequency from 0.25 to 200 rad/s, at a temperature of 100° C., and a strain of 13.95%, only exhibits tan delta values of less than 0.95. 
     
     
         7 . The dual composition block copolymer of  claim 1 , wherein the dynamic oscillatory shear test of the dual composition block copolymer, when sweeping oscillation frequency from 0.25 to 200 rad/s, at a temperature of 100° C., and a strain of 13.95%, only exhibits tan delta values of less than 0.90. 
     
     
         8 . The dual composition block copolymer of  claim 2 , wherein the dynamic oscillatory shear test of the dual composition block copolymer, when sweeping oscillation frequency from 0.25 to 200 rad/s, at a temperature of 100° C., and a strain of 13.95%, only exhibits tan delta values of less than 0.85. 
     
     
         9 . The dual composition block copolymer of  claim 5 , optionally oil extended, wherein the Mooney viscosity (ML1+4 at 100° C.) of the dual composition block copolymer is from about 25 to about 90. 
     
     
         10 . The dual composition block copolymer of  claim 5 , optionally oil extended, wherein,
 the complex dynamic shear viscosity of the dual composition block copolymer, evaluated at a frequency of 0.99 rad/s, at a temperature of 100° C. and at a strain of 13.95%, is between about 50,000 Pa-s and about 350,000 Pa-s; and wherein   the complex dynamic shear viscosity of the dual composition block copolymer, evaluated at a frequency of 100 rad/s, at a temperature of 100° C. and at a strain of 13.95%, is between about 3,000 Pa-s and about 12,000 Pa-s.   
     
     
         11 . A dual composition block copolymer, comprising a block copolymer C and a block copolymer U, wherein C has the general formula:
   [D-(D/A)-A 1 ] n -X,   wherein U has the general formula:
   D-(D/A)-A 2    
   or 
   D-(D/A)-A 2  and D-(D/A)-A 1 , 
   wherein:   (a) D is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein conjugated diene repeat units are in greater molar amount than monovinyl aromatic repeat units along the whole polymer block length;   (b) (D/A) is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein polymer block end opposite to A 1  or A 2  is predominantly composed of conjugated diene repeat units and that gradually changes its composition until it becomes substantially composed of monovinyl aromatic repeat units at its end adjacent to A 1  or A 2 ;   (c) A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only;   (d) polymer block A 2  has greater molecular weight than polymer block A 1 ;   (e) X is the residue of a coupling agent, and n is an integer with a value from 2 to 30; and   (f) coupled block copolymer molecules of formula [D-(D/A)-A 1 ] n -X account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer;   (g) uncoupled block copolymer molecules of formula D-(D/A)-A 2  account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer; and   (h) uncoupled block copolymer molecules of formula D-(D/A)-A 1  account for from about 0 to about 20 wt % of the molecular weight distribution of the dual composition block copolymer;   (i) molecular weight distribution of the dual composition block copolymer exhibits at least two peaks, partially or totally resolved;   (j) block copolymer C constitutes the peak at the highest molecular weight range in the molecular weight distribution, and block copolymer U constitutes the remainder of the molecular weight distribution;   (k) monovinyl aromatic repeat unit content in block copolymer U is at least 10 wt. % higher than the monovinyl aromatic repeat unit content in block copolymer C.   
     
     
         12 . The dual composition block copolymer of  claim 1 , comprising a block copolymer C and a block copolymer U, wherein C has the general formula:
   [B-(B/A)-A 1 ] n -X,   wherein U has the general formula:
   B-(B/A)-A 2    
   or 
   B-(B/A)-A 2  and B-(B/A)-A 1 , 
   wherein:   (a) B is a polymer block made from conjugated diene monomer, only;   (b) (B/A) is a random polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer;   (c) A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only;   (d) polymer block A 2  has greater molecular weight than polymer block A 1 ;   (e) X is the residue of a coupling agent, and n is an integer with a value from 2 to 30;   (f) coupled block copolymer molecules of formula [B-(B/A)-A 1 ] n -X account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer;   (g) uncoupled block copolymer molecules of formula B-(B/A)-A 2  account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer; and   (h) uncoupled block copolymer molecules of formula B-(B/A)-A 1  account for from about 0 to about 20 wt % of the molecular weight distribution of the dual composition block copolymer; and   (i) dual composition block copolymer optionally comprises extender oil, in an amount from 0 to about 12 weight parts per hundred parts of dual composition block copolymer.   
     
     
         13 . The dual composition block copolymer of  claim 1 , comprising a block copolymer C and a block copolymer U, wherein C has the general formula:
   [(B/A)-A 1 ] n -X,   wherein U has the general formula:
   (B/A)-A 2    
   or 
   (B/A)-A 2  and (B/A)-A 1 , 
   wherein:   (a) (B/A) is a random polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer;   (b) A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only;   (c) polymer block A 2  has greater molecular weight than polymer block A 1 ;   (d) X is the residue of a coupling agent, and n is an integer with a value from 2 to 30;   (e) coupled block copolymer molecules of formula [(B/A)-A 1 ] n -X account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer;   (f) uncoupled block copolymer molecules of formula (B/A)-A 2  account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer; and   (g) uncoupled block copolymer molecules of formula (B/A)-A 1  account for from about 0 to about 20 wt % of the molecular weight distribution of the dual composition block copolymer;   (h) dual composition block copolymer optionally comprises extender oil, in an amount from 0 to about 12 weight parts per hundred parts of dual composition block copolymer.   
     
     
         14 . The dual composition block copolymer of  claim 1 , comprising a block copolymer C and a block copolymer U, wherein C has the general formula:
   [B-A 1 ] n -X,   wherein U has the general formula:
   B-A 2    
   or 
   B-A 2  and B-A 1 , 
   wherein:   (a) B is a polymer block made from conjugated diene monomer, only;   (b) A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only;   (c) polymer block A 2  has greater molecular weight than polymer block A 1 ;   (d) X is the residue of a coupling agent, and n is an integer with a value from 2 to 30;   (e) coupled block copolymer molecules of formula [B-A 1 ] n -X account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer;   (f) uncoupled block copolymer molecules of formula B-A 2  account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer; and   (g) uncoupled block copolymer molecules of formula B-A 1  account for from about 0 to about 20 wt % of the molecular weight distribution of the dual composition block copolymer;   (h) monovinyl aromatic repeat units blockiness degree is at least about 97 mole %;   (i) dual composition block copolymer optionally comprises extender oil, in an amount from 0 to about 12 weight parts per hundred parts of dual composition block copolymer.   
     
     
         15 . A process for making the dual composition block copolymer of  claim 11 , comprising the steps of:
 charging an aliphatic hydrocarbon solvent, a conjugated diene monomer and a monovinyl aromatic monomer to a reactor;   charging an organolithium initiator to the reactor;   allowing for full copolymerization of the monomers and forming polymeric anions;   charging a limited amount of a coupling agent to the reactor so as to couple only a fraction of the polymeric anions;   charging more and/or a different monovinyl aromatic monomer to the reactor;   allowing for full block copolymerization of the monovinyl aromatic monomer;   charging a proton donor or an electrophilic monofunctional compound for deactivating all remaining polymeric anions in the reactor; and   recovering a dual composition block copolymer.   
     
     
         16 . A process for making the dual composition block copolymer of  claim 12 , comprising the steps of:
 charging an aliphatic hydrocarbon solvent, a randomizer, and a conjugated diene monomer to a reactor;   charging an organolithium initiator to the reactor;   allowing for polymerization of conjugated diene monomer fed to the reactor to a conversion level from about 80% to about 95%;   charging a monovinyl aromatic monomer to the reactor;   allowing for full copolymerization of the remaining conjugated diene monomer and monovinyl aromatic monomer fed to the reactor, wherein polymeric anions are formed;   charging a limited amount of a coupling agent for partially coupling the polymeric anions;   charging more and/or a different monovinyl aromatic monomer to the reactor;   allowing for full block copolymerization of the monovinyl aromatic monomer;   charging a proton donor or an electrophilic monofunctional compound for deactivating all remaining polymeric anions; and   recovering a dual composition block copolymer.   
     
     
         17 . A process for making the dual composition block copolymer of  claim 14 , comprising the steps of:
 charging an aliphatic hydrocarbon solvent, a randomizer, and a conjugated diene monomer to a reactor;   charging an organolithium initiator to the reactor;   allowing for the complete polymerization of the conjugated diene monomer;   charging a monovinyl aromatic monomer to the reactor;   allowing for full copolymerization of the monovinyl aromatic monomer fed to the reactor, wherein polymeric anions are formed;   charging a limited amount of a coupling agent for partially coupling the polymeric anions;   charging more and/or a different monovinyl aromatic monomer to the reactor;   allowing for full copolymerization of the monovinyl aromatic monomer;   charging a proton donor or an electrophilic monofunctional compound so as to fully deactivate any remaining polymeric anions in the reactor; and   recovering a dual composition block copolymer.   
     
     
         18 . A process for making the dual composition block copolymer of  claim 13 , comprising the steps of:
 charging an aliphatic hydrocarbon solvent, a randomizer, a conjugated diene monomer and a monovinyl aromatic monomer to a reactor;   charging an organolithium initiator to the reactor;   allowing for complete copolymerization of the conjugated diene monomer and the monovinyl aromatic monomer;   charging more and/or a different monovinyl aromatic monomer to the reactor;   allowing for full copolymerization of the monovinyl aromatic monomer fed to the reactor, wherein polymeric anions are formed;   charging a limited amount of a coupling agent so as to couple only a fraction of the polymeric anions;   charging more and/or another monovinyl aromatic monomer to the reactor;   allowing for full copolymerization of the monovinyl aromatic monomer;   charging a proton donor or an electrophilic monofunctional compound to fully deactivate any remaining polymeric anions; and   recovering a dual composition block copolymer.   
     
     
         19 . A dual composition block copolymer made from conjugated diene and monovinyl aromatic monomers, comprising a block copolymer C, and a block copolymer U, wherein,
 (a) molecular weight distribution of the dual composition block copolymer exhibits at least two peaks, partially or totally resolved;   (b) block copolymer C constitutes the fraction with the peak at the highest molecular weight in the molecular weight distribution, and block copolymer U constitutes the remainder of the molecular weight distribution;   (c) block copolymer C accounts for from about 20 to about 80% of the molecular weight distribution;   (d) total monovinyl aromatic repeat unit content of the dual composition block copolymer is from about 20 to about 50 wt. %;   (e) monovinyl aromatic repeat unit content in block copolymer U is at least 10 wt. % higher than monovinyl aromatic repeat unit content in block copolymer C;   (f) monovinyl aromatic repeat unit blockiness degree of the dual composition block copolymer is equal or greater than about 77 mole % on a total monovinyl aromatic repeat unit basis;   (g) Mooney viscosity (ML1+4 at 100° C.) of the dual composition block copolymer is from about 25 to about 70;   (h) complex dynamic shear viscosity of the dual composition block copolymer, evaluated at a frequency of 0.99 rad/s, at a temperature of 100° C. and at a strain of 13.95%, is greater than about 50000 Pa-s and smaller than about 150000 Pa-s;   (i) complex dynamic shear viscosity of the dual composition block copolymer, evaluated at a frequency of 100 rad/s, at a temperature of 100° C. and at a strain of 13.95%, is greater than about 3000 Pa-s and smaller than about 7000 Pa-s; and   (j) dynamic oscillatory shear test of the dual composition block copolymer, when sweeping oscillation frequency from 0.25 to 200 rad/s, at a temperature of 100° C., and a strain of 13.95%, exhibits tan delta values only smaller than 0.95.   
     
     
         20 . The dual composition block copolymer of  claim 19 , comprising a block copolymer C with the general formula:
   [D-(D/A)-A 1 ] n -X   and a block copolymer U, with the general formula:
   D-(D/A)-A 2    
   or 
   D-(D/A)-A 2  and D-(D/A)-A 1 , 
   wherein,   (a) D is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein conjugated diene repeat units are in greater molar amount than monovinyl aromatic repeat units along the whole polymer block length;   (b) (D/A) is a polymer block made from at least a conjugated diene monomer and at least a monovinyl aromatic monomer, wherein polymer block end opposite to A 1  or A 2  is predominantly composed of conjugated diene repeat units and that gradually changes its composition until it becomes substantially composed of monovinyl aromatic repeat units at its end adjacent to A 1  or A 2 ;   (c) A 1  and A 2  are polymer blocks made from monovinyl aromatic monomer only;   (d) polymer block A 2  has greater molecular weight than polymer block A 1 ;   (e) X is the residue of a coupling agent, and n is an integer with a value from 2 to 30; and   (f) coupled block copolymer molecules of formula [D-(D/A)-A 1 ] n -X account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer;   (g) uncoupled block copolymer molecules of formula D-(D/A)-A 2  account for from about 20 wt. % to about 80 wt. % of the molecular weight distribution of the dual composition block copolymer; and   (h) uncoupled block copolymer molecules of formula D-(D/A)-A 1  account for from about 0 to about 20 wt % of the molecular weight distribution of the dual composition block copolymer.