Partially crosslinked microspheres

Abstract

An adhesive composition is provided comprising:(a) a plurality of polymeric, elastomeric microspheres wherein the microspheres are the reaction product of reactants comprising polymerizable starting materials comprising at least one C4-C14 alkyl (meth)acrylate monomer and optionally at least one comonomer and have a solvent soluble portion that is 30-98% of the microsphere.

We claim:  
     
       1. An adhesive composition comprising: 
       (a) a plurality of polymeric, elastomeric microspheres wherein the microspheres are the reaction product of polymerizable starting materials comprising at least one C 4 -C 14  alkyl (meth)acrylate monomer and optionally al least one comonomer;  
       (b) an initiator for the polymerizable monomer starting materials present in amounts ranging from 0.1 to approximately 2 parts per weight per 100 parts by weight of the polymerizable monomer starting materials;  
       (c) optionally, a polymeric stabilizer in an amount of between about 0.1 and about 3 parts by weight per 100 parts by weight of the microspheres;  
       (d) a surfactant in an amount of no greater than about 5 parts by weight per 100 parts by weight of the microspheres; and  
       (e) a chain transfer agent in an amount sufficient to produce 30-98% of a heptane soluble portion in the microspheres.  
     
     
       2. The adhesive according to  claim 1  wherein the polymeric stabilizer is present in an amount of about 0.1 to about 1.5 parts by weight per 100 parts by weight of the microspheres. 
     
     
       3. The adhesive according to  claim 1  wherein the surfactant is present in an amount of about no greater than 3 parts by weight per 100 parts by weight of the microspheres. 
     
     
       4. The adhesive according to  claim 1  wherein the chain transfer agent is selected from the group consisting of carbon tetrabromide, carbon tetrachloride, dodecanethiol, iso-octylthioglycolate, butyl mercaptan, and tertiarydodecyl mercaptan and is present in an amount of up to about 0.15%. 
     
     
       5. The adhesive according to  claim 1  wherein the chain transfer agent is a solvent and is present in an amount ranging from 1 to 30%. 
     
     
       6. The adhesive according to  claim 1  wherein the chain transfer agent is a tackifier or plasticizer and is present in an amount ranging from 1 to 30%. 
     
     
       7. A one step polymerization process for the microsphere adhesive according to  claim 1  comprising the steps of: 
       (a) stirring or agitating a mixture comprising polymerizable monomer starting materials comprising:  
       (i) at least one C 4 -C 14  alkyl (meth)acrylate monomer and optionally at least one comonomer;  
       (ii) an initiator for the polymerizable monomer starting materials present in amounts ranging from 0.1 to approximately 2 parts per weight per 100 parts by weight of the polymerizable monomer starting materials  
       (iii) optionally, a polymeric stabilizer in an amount in the range of 0.1 to about 3 parts by weight per 100 parts by weight of the polymerizable monomer starting materials;  
       (iv) a surfactant in an amount of no greater than about 5 parts by weight per 100 parts by weights of polymerizable monomer; and  
       (v) a chain transfer agent in an amount sufficient to provide 30-98% of a heptane soluble portion of the microspheres;  
       (b) polymerizing the (meth)acrylate monomer(s) and the comonomer(s).  
     
     
       8. The one-step polymerization process according to  claim 7  wherein the chain transfer agent is selected from the group consisting of carbon tetrabromide, carbon tetrachloride, dodecanethiol, iso-octylthioglycolate, butyl mercaptan, and tertiary-dodecyl mercaptan and is present in an amount of up to about 0.15%. 
     
     
       9. The adhesive according to  claim 7  wherein the chain transfer agent is a solvent and is present in an amount ranging from 1 to 30%. 
     
     
       10. The adhesive according to  claim 7  wherein the chain transfer agent is a tackifier or plasticizer and is present in an amount ranging from 1 to 30%. 
     
     
       11. A two-step polymerization process for the microsphere adhesive according to  claim 1  comprising the steps of: 
       (a) stirring or agitating a mixture comprising polymerizable monomer starting materials comprising:  
       (i) at least one C 4 -C 14  alkyl (meth)acrylate monomer;  
       (ii) an initiator for the monomer; a polymeric stabilizer in an amount of about 0.1 to about 3 parts by weight per 100 parts by weight of the polymerizable monomer starting materials;  
       (iii) a surfactant in an amount of no greater than about 5 parts by weight per 100 parts by weight of the polymerizable monomer starting materials;  
       (iv) a chain transfer agent in an amount sufficient to provide 30-98% of a heptane soluble portion of the microspheres; and  
       (v) water to form an oil in water suspension;  
       (b) partially polymerizing the polymerizable monomer starting materials;  
       (c) adding to the suspension at least one comonomer; and  
       (d) continuing the polymerization of the polymerizable monomer starting materials.  
     
     
       12. The two-step polymerization process according to  claim 11  wherein the modifier is a chain transfer agent is selected from the group consisting of carbon tetrabromide, carbon tetrachloride, dodecanethiol, iso-octylthioglycolate, butyl mercaptan, and tertiary-dodecyl mercaptan and is present in an amount of up to about 0.15%. 
     
     
       13. The adhesive according to  claim 11  wherein the chain transfer agent is a solvent and is present in an amount ranging from 1 to 30%. 
     
     
       14. The adhesive according to  claim 11  wherein the chain transfer agent is a tackifier or plasticizer and is present in an amount ranging from 1 to 30%. 
     
     
       15. An adhesive article comprising a backing and a coating the microsphere adhesive according to  claim 1  coated on at least a portion of at least one surface of the backing. 
     
     
       16. A process for preparing an adhesive composition comprising polymeric elastomeric microspheres, said process comprising: 
       ( a )  stirring or agitating an aqueous mixture comprising polymerizable monomer starting materials comprising:    
       ( i )  at least one C   4   -C   14    alkyl  ( meth ) acrylate monomer and optionally at least one comonomer;    
       ( ii )  an initiator for the polymerizable monomer starting materials present in amount ranging from  0 . 1  to approximately  2  parts by weight per  100  parts by weight of the polymerizable monomer starting materials;    
       ( iii )  optionally a polymeric stabilizer in an amount in the range of  0 . 1  to about  3  parts by weight per  100  parts by weight of the polymerizable monomer starting materials; and    
       ( iv )  a surfactant in an amount of no greater than about  5  parts by weight per  100  parts by weight of polymerizable monomer; and    
       ( v )  a chain transfer agent in an amount sufficient to provide  30 - 98   %  of a heptane soluble portion of the microspheres; and    
       ( b )  polymerizing the  ( meth ) acrylate monomer ( s )  and the comonomer ( s ). 
     
     
       17. A process for preparing an adhesive composition comprising polymeric elastomeric microspheres, said process comprising: 
       ( a )  stirring or agitating a mixture comprising polymerizable monomer starting materials comprising:    
       ( i )  at least one C   4   -C   14    alkyl  ( meth ) acrylate monomer;    
       ( ii )  an initiator for the monomer;    
       ( iii )  a polymeric stabilizer in an amount of about  0 . 1  to about  3  parts by weight per  100  parts by weight of the polymerizable monomer starting materials;    
       ( iv )  a surfactant in an amount of no greater than about  5  parts by weight per  100  parts by weight of the polymerizable monomer starting materials;    
       ( v )  a chain transfer agent in an amount sufficient to provide  30 - 98   %  of a heptane soluble portion of the microspheres; and    
       ( vi )  water to form an oil in water suspension;    
       ( b )  partially polymerizing the polymerizable monomer starting materials;    
       ( c )  adding to the suspension at least one comonomer; and    
       ( d )  continuing the polymerization of the polymerizable monomer starting materials.