Pressure sensitive adhesive tapes from cationic cure adhesives
View Patent ↗Pressure sensitive adhesive tapes produced by a process where cationic cure is conducted against a paper film substrate and an optional second film substrate, both having low moisture content. The low moisture content is maintained during cationic cure by putting the pressure sensitive adhesive tapes in an environment where moisture ingress is prevented. The maintenance of low moisture during cure provides enhanced SAFT values.
1. A pressure sensitive adhesive article prepared by a process comprising:
coating a cationic curable adhesive onto a paper film substrate having a moisture content of less than about 5%, initiating cure of the adhesive, optionally applying a second film substrate to said coated paper film substrate, said second film substrate having a moisture content of less than about 5%, and maintaining the moisture content of the paper film substrate and the optional second film substrate at a level of less than about 5% for a period of time, allowing the adhesive to substantially fully cure.
2. The adhesive article of claim 1 wherein cure of the adhesive is initiated by exposing the adhesive to radiation.
3. The adhesive article of claim 2 wherein cure of the adhesive is initiated by exposing the adhesive to UV radiation.
4. The adhesive article of claim 3 wherein the adhesive comprises an epoxidized block copolymer.
5. The adhesive article of claim 4 wherein the adhesive comprises from about 10 to about 60% by weight of at least one epoxidized block copolymer, from about 3 to about 60% of a compatible mono-ol such as rosin alcohol to control cure density, from 0 to about 30% by weight of at least one styrenic block copolymer, from about 20 to about 70% of at least one hydrocarbon resin, from 0 to about 30% of a mineral oil, and an effective amount of a cationic initiator.
6. The adhesive article of claim 1 where the moisture content of the paper film substrate and the optional second film substrate is and is maintained at a level of less than about 4%.
7. The adhesive article of claim 6 where the moisture content of the paper film substrate and the optional second film substrate is and is maintained at a level of less than about 2%.
8. The adhesive article of claim 1 which is a roll of tape, a label stock or a transfer film.
9. The adhesive article of claim 8 which is a label stock.
10. The adhesive article of claim 8 which is a roll of tape.
11. The adhesive article of claim 8 which is a transfer film.
12. The roll of tape, label stock or transfer film of claim 8 wherein the adhesive comprises from about 10 to about 60% by weight of at least one epoxidized block copolymer, from about 3 to about 60% of a compatible mono-ol such as rosin alcohol to control cure density, from 0 to about 30% by weight of at least one styrenic block copolymer, from about 20 to about 70% of at least one hydrocarbon resin, from 0 to about 30% of a mineral oil, and an effective amount of a cationic initiator.
13. The adhesive article of claim 1 wherein the moisture content of the paper film substrate and the optional second film substrate is maintained at said level by placing said article in a double bag of polyethylene film.
14. The adhesive article of claim 1 wherein the paper film substrate is a paper release liner or a paper backing.