Solventless compounding and coating of non-thermoplastic hydrocarbon elastomers

Abstract

A solvent-free hot melt process, for preparing a non-thermosettable, pressure-sensitive adhesive from a tackified non-thermoplastic hydrocarbon elastomer. The process employs a continuous compounding device that has a sequence of alternating conveying and processing zones. The processing zones masticate and mix materials in them. Non-thermoplastic elastomers having high molecular weight may be readily compounded into adhesives in the process.

We claim: 
     
       1. A solventless hot melt process for preparing a non-thermosettable pressure sensitive adhesive from a tackified non-thermoplastic hydrocarbon elastomer, said process occurring in a continuous compounding device which has a sequence of alternating conveying and processing zones, said processing zones being capable of masticating and mixing, said process comprising the steps of: (a) feeding said non-thermoplastic hydrocarbon elastomer to a first conveying zone to transport said elastomer to a first processing zone;   (b) masticating said elastomer in the first processing zone for a time sufficient to render it capable of (i) receiving adjuvants, and (ii) being extruded;   (.Iadd.c) adding a tackifier to said device; .Iaddend.   .[.(c).]. (.Iadd.d) .Iaddend.transporting .Iadd.at least .Iaddend.said masticated elastomer from the first processing zone to .[.a second conveying zone, feeding tackifier to said masticated elastomer in the second conveying zone and transporting the combination of the masticated elastomer and tackifier to.]. a second processing zone;   .[.(d).]. (.Iadd.e) .Iaddend.forming a blend of said masticated elastomer and tackifier .[.in the second processing zone.].; and   .[.(e).]. (.Iadd.f) .Iaddend.discharging said blend from said continuous compounding device;   wherein said blend comprises a pressure sensitive adhesive which contains less than .[˜]. 8.5 percent by weight of a plasticizing aid.   
     
     
       2. A process according to claim 1 wherein the first said processing zone comprises at least two .Iadd.processing .Iaddend.sections separated from each other by a transporting section. 
     
     
       3. A process according to claim 2 wherein said elastomer is masticated in each of said separate sections. 
     
     
       4. A process according to claim 2 wherein a gas containing available oxygen is injected into said transporting section. 
     
     
       5. A process according to claim 1 wherein said blend is discharged onto a moving web to form a thin film thereof. 
     
     
       6. A solvent free hot melt process for the mastication of a non-thermoplastic hydrocarbon elastomer, the compounding of said elastomer into a non-thermosettable pressure-sensitive adhesive composition containing less than .[.10%.]. .Iadd.8.5% .Iaddend.by weight of a plasticizing aid, and the coating of said pressure-sensitive adhesive onto a sheet comprising the steps of: a) operating a continuous compounding device at a desired speed, said device having a twin screw therein which has a sequence of conveying and processing zones which alternate with one another.[.: and.]..Iadd.; .Iaddend.   b) feeding said elastomer to a first conveying zone of said device at a controlled rate so that said elastomer does not completely fill said first conveying zone; .[.and.].   c) transporting .Iadd.at least .Iaddend.said elastomer to a first processing zone of said device so that said elastomer essentially fills said first processing zone; .[.and.].   d) masticating said elastomer in said first processing zone .[.for a time sufficient to receive a subsequently added tackifier and form a blend thereof; said masticating occurring.]. in the absence of a quantify of a material which would prevent effective reduction of the molecular weight of said elastomer; .[.and.].   e) transporting .Iadd.at least .Iaddend.said masticated elastomer to a second conveying zone so that it does not completely fill said second conveying zone .[.and feeding said tackifier to said second conveying zone at a controlled rate to form a mixture of masticated elastomer and tackifier and passing said mixture.].; .[.and.].   f) .Iadd.adding a tackifier to said device to form a mixture;   g) .Iaddend.transporting said mixture to a second processing zone so as to essentially fill said second processing zone with said mixture and forming a blend of said mixture in said second processing zone; and   .Iadd.h) .Iaddend.discharging said blend from said device.   
     
     
       7. A process according to claim 6 wherein said blend is discharged from said continuous compounding device as a thin film onto a moving web and exposed to radiation.[.,.]..Iadd.. .Iaddend. 
     
     
       8. A process according to claim 7 wherein said radiation is selected from the group consisting of electron beam radiation and ultraviolet light. 
     
     
       9. A process according to claim 6 wherein said elastomer is selected from the group consisting of natural rubber, butyl rubber, synthetic polyisoprene, ethylene-propylene rubber, ethylene-propylene-diene monomer rubber, polybutadiene, polyisobutylene, poly(alpha-olefin), and styrene-butadiene rubber. 
     
     
       10. A process according to claim 6 wherein said tackifier is present in an amount of from 10 to 200 parts by weight per 100 parts by weight of said elastomer. 
     
     
       11. A process according to claim 6 wherein said tackifier is selected from the group consisting of rosin, rosin derivatives, hydrocarbon resins, aromatic hydrocarbon resins, aliphatic .Iadd.hydrocarbon resins, and terpene resins.Iaddend.. 
     
     
       12. A solvent free hot melt process for the mastication of a high molecular weight non-thermoplastic hydrocarbon elastomer and the compounding of said elastomer into a non-thermosettable pressure-sensitive adhesive, which process employs less than .[.10%.]. .Iadd.8.5% .Iaddend.by weight of said elastomer of a plasticizing aid comprising the steps of: a) providing a continuous compounding device having a twin screw therein which has a sequence of conveying and processing zones which alternate with one another; .[.and.].   b) feeding said high molecular weight elastomer to a first conveying zone of said device at a controlled rate so that said elastomer does not completely fill said first conveying zone; .[.and.].   c) transporting said elastomer to a first processing zone of said device so that said elastomer essentially fills said first processing zone; .[.and.].   d) masticating said elastomer in said first processing zone in the absence of any significant amount of plasticizing aid .[.for a time sufficient to receive a subsequently added tackifier and form a blend thereof.].; and   e) .Iadd.adding a tackifier to said device; .Iaddend.   .[.e).]. .Iadd.f) .Iaddend.transporting .Iadd.at least .Iaddend.said masticated elastomer to a second conveying zone so that it does not completely fill said second conveying zone .[.and feeding said tackifier to said second conveying zone at a controlled rate to form a mixture of masticated elastomer and tackifier and passing said mixture.].; .[.and.].   .[.f).]. .Iadd.g) .Iaddend.transporting said .[.mixture.]. .Iadd.masticated elastomer and said tackifier .Iaddend.to a second processing zone so as to essentially fill said second processing zone with said .Iadd.masticated elastomer and said tackifier to form a .Iaddend.mixture .Iadd.thereof .Iaddend.and forming a blend of said mixture in said second processing zone; and   .[.g).]. .Iadd.h) .Iaddend.discharging said blend from said device.   
     
     
       13. A process according to claim 12 wherein said blend is discharged from said device onto a moving web to form a layer of a pressure sensitive adhesive on said moving web. 
     
     
       14. The process of claim 13 wherein the adhesive layer on said moving web is exposed to radiation. 
     
     
       15. A process according to claim 14 wherein said radiation is selected from the group consisting of electron beam radiation and ultraviolet light. 
     
     
       16. A process according to claim 13 comprising the further step of applying a release material to the surface of said web opposite the surface ultimately bearing said adhesive film. 
     
     
       17. A process according to claim 12 comprising the further step of adding adjuvants to said elastomer. 
     
     
       18. A process according to claim 17 wherein said adjuvants are added after said elastomer has been masticated. 
     
     
       19. A process according to claim 18 wherein said adjuvants are added after said blend has been formed. 
     
     
       20. A process according to claim 17 wherein said adjuvants are added before said elastomer is masticated. 
     
     
       21. A process according to claim 20 wherein said adjuvants are selected from the group consisting of antioxidants, inorganic fillers, pigments, odorants, and radiation enhancers. 
     
     
       22. The process of claim 12 wherein said first processing zone has a first processing section, a second processing section and a transporting section between the two. 
     
     
       23. The process of claim 22 wherein air is injected into said transporting section. 
     
     
       24. A process according to claim 12 which employs a combination of at least two of said elastomers. 
     
     
       25. A non-thermosettable pressure sensitive adhesive tape comprising (i) a tackified non-thermoplastic elastomer and (ii) less than .[.10%.]. .Iadd.8.5% .Iaddend.by weight of a plasticizing aid; wherein said tape has been prepared by a solventless hot melt process in a continuous compounding device which has a sequence of alternating conveying and processing zones, said processing zones being capable of masticating and mixing, which process comprises: (a) feeding said non-thermoplastic hydrocarbon elastomer to a first conveying zone to transport said elastomer to a fist processing zone;   (b) masticating said elastomer without the presence of any significant amount of a plasticizing aid in the first processing zone for a time sufficient to render it capable of (i) receiving adjuvants, and (ii) being extruded;   (.Iadd.c) adding a tackifier to said device; .Iaddend.   .[.(c).]. (.Iadd.d) .Iaddend.transporting .Iadd.at least .Iaddend.said masticated elastomer from the first processing zone to a second conveying zone.[., feeding tackifier to said masticated elastomer in the second conveying zone and transporting the combination of the masticated elastomer and tackifier to a second processing zone.].;   .[.(d).]. (.Iadd.e) .Iaddend.forming a blend of said masticated elastomer and tackifier .[.in the second processing zone.].; and   .[.(e).]. (.Iadd.f) .Iaddend.discharging said blend onto a moving web to form said tape.   
     
     
       26. A porous pressure sensitive adhesive tape according to claim 25. 
     
     
       27. A process according to claim 1 wherein said elastomer is masticated in the absence of said plasticizing aid. 
     
     
       28. A process according to claim 6 wherein said elastomer is masticated in the absence of said plasticizing aid. 
     
     
       29. A process according to claim 12 wherein said elastomer is masticated in the absence of said plasticizing aid. 
     
     
       30. A solvent free hot melt process for the mastication of a non-thermoplastic hydrocarbon elastomer, the compounding of said elastomer into a non-thermosettable tackified pressure-sensitive adhesive composition, and the coating of said pressure-sensitive adhesive as a film comprising the steps of: a) operating a continuous compounding device at a desired speed, said device having a sequence of conveying and processing zones which alternate with one another, .[.and.].   b) feeding said elastomer to a first conveying zone of said device at a controlled rate so that said elastomer does not completely fill said first conveying zone; .[.and.].   c) transporting said elastomer to a first processing zone of said device so that said elastomer especially fills said first processing zone; .[.and.].   d) masticating said elastomer in said first processing zone .[.for a time sufficient to receive a subsequently added tackifier and form a blend thereof.].; .[.and.].   .Iadd.e) adding a tackifier to said device; .Iaddend.   .[.e).]. .Iadd.f) .Iaddend.transporting .Iadd.at least .Iaddend.said masticated elastomer to a second conveying zone so that it does not completely fill said second conveyor zone .[.and feeding said tackifier to said second conveying zone at a controlled rate to form a mixture of masticated elastomer and tackifier and passing said mixture.].; .[.and.].   .[.f).]. .Iadd.g) .Iaddend.transporting said .[.mixture.]. .Iadd.masticated elastomer and said tackifier .Iaddend.to a second processing zone so as to essentially fill said second processing zone with .[.said.]. .Iadd.a .Iaddend.mixture .Iadd.thereof .Iaddend.and forming a blend of said mixture in said second processing zone; and   .[.g).]. .Iadd.h) .Iaddend.discharging said blend from said device as a pressure sensitive adhesive film containing less than .[.10%.]. .Iadd.8.5% .Iaddend.by weight of a plasticizing aid. .Iadd.31. A solventless hot melt process for preparing a non-thermosettable pressure sensitive adhesive from a tackified non-thermoplastic hydrocarbon elastomer, the process comprising the steps of:   a) feeding the non-thermoplastic hydrocarbon elastomer to a continuous compounding device which has a sequence of alternating conveying and processing zones, the processing zones being capable of masticating and mixing, and masticating the elastomer in the first processing zone for a time sufficient to render it capable of (i) receiving adjuvants, and (ii) being extruded;   b) feeding a tackifier for the non-thermoplastic hydrocarbon elastomer to the continuous compounding device and mixing to form a blend of the ingredients; and   c) discharging the blend from the continuous compounding device in the form of a pressure sensitive adhesive, wherein the adhesive is compounded in the presence of from 0 to less than 8.5% by weight of plasticizing aid with respect to adhesive. .Iaddend..Iadd.32. A process according to claim 31, wherein the compounding device comprises a first processing zone having at least two sections separated from each other by a transporting section. .Iaddend..Iadd.33. A process according to claim 32 wherein a gas containing available oxygen is injected into the transporting section. .Iaddend..Iadd.34. A process according to claim 31 wherein the blend is discharged from the continuous compounding device as a thin film onto a moving web and exposed to ionizing radiation. .Iaddend..Iadd.35. A process according to claim 31 comprising the steps of:     a) providing a continuous compounding device having a twin screw therein which has a sequence of conveying and processing zones which alternate with one another;   b) feeding the elastomer to a first conveying zone of the device at a controlled rate so that the elastomer does not completely fill the first conveying zone;   c) transporting the elastomer to a first processing zone of the device so that the elastomer essentially fills the first processing zone;   d) masticating the elastomer in the first processing zone in the absence of any significant amount of plasticizing aid for a time sufficient to receive a subsequently added tackifier and from a blend thereof;   e) transporting the masticated elastomer to a second conveying zone so that it does not completely fill the second conveying zone and feeding the tackifier to the second conveying zone a controlled rate to from a mixture of masticated elastomer and tackifier; and   
     
     
       f) discharging the blend from the device. .Iaddend..Iadd.36.  A process according to claim 31 wherein said non-thermoplastic hydrocarbon elastomer has a viscosity average molecular weight of at least 250,000. .Iaddend..Iadd.37. A process according to claim 31 wherein the mastication of the non-thermoplastic hydrocarbon elastomer in the first processing zone occurs in the absence of a quantity of material that would prevent the effective reduction of the molecular weight of the elastomer. .Iaddend..Iadd.38. A process according to claim 34 comprising the further step of applying a release material to the surface of the web opposite the surface ultimately bearing the adhesive film. .Iaddend..Iadd.39. A process according to claim 31 employing a combination of at least two non-thermoplastic hydrocarbon elastomers. .Iaddend..Iadd.40. A process according to claim 31 wherein the elastomer is masticated in the absence of a plasticizing aid. .Iaddend.