Pressure sensitive adhesive labels and method of making

• US 3,914,484 A
• Filed: 02/24/1971
• Issued: 10/21/1975
• Est. Priority Date: 02/24/1971
• Status: Expired due to Term

• Current Assignee: Daniel J. White, Robert M. Creegan
• Original Assignee: Daniel J. White, Robert M. Creegan
• Inventors: Creegan, Robert M., White, Daniel J.
• Primary Examiner(s): Ansher, Harold
• Application Number:
  US05/118,573
• Time in Patent Office: 1,700 Days
• Field of Search: 260/858,859,859R 117/122PA,122PB,122P 161/190,406,39-40,167
• US Class Current: 428/41.5
• CPC Class Codes: C08L 15/00 Compositions of rubber derivatives C08L11/00, C08L13/00 take precedence
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 75/04 Polyurethanes
• CPC Class Codes: C08L 87/00 Compositions of unspecified macromolecular compounds, obtained otherwise than by polymerisation reactions only involving unsaturated carbon-to-carbon bonds
• CPC Class Codes: C09J 175/04 Polyurethanes
• CPC Class Codes: C09J 7/21 Paper; Textile fabrics
• CPC Class Codes: C09J 7/38 Pressure-sensitive adhesives [PSA]
• CPC Class Codes: Y10S 525/942 Polymer derived from nitrile, conjugated diene and aromatic co-monomers
• CPC Class Codes: Y10T 428/1462 Polymer derived from material having at least one acrylic or alkacrylic group or the nitrile or amide derivative thereof [e.g., acrylamide, acrylate ester, etc.]
• CPC Class Codes: Y10T 428/2887 including nitrogen containing polymer [e.g., polyacrylonitrile, polymethacrylonitrile, etc.]
• CPC Class Codes: Y10T 428/2896 including nitrogen containing condensation polymer [e.g., polyurethane, polyisocyanate, etc.]

Abstract

In a pressure sensitive adhesive label sheet stock in which the pressure sensitive adhesive layer (applied to a paper substrate) employs a normally non-tacky elastomer, such as natural or artificial rubber, and a normally tacky resin, such as an hydrogenated rosin ester, the improvement of replacing part but not all of the elastomer with a polyurethane elastomer, which has been cured on the substrate, as part of the elastomer system. The polyurethane elastomer is formed from an organic polyol and an organic diisocyanate, which are present, as such, in the pressure sensitive adhesive coating composition when it is applied to the paper substrate. The polyol and diisocyanate are cured by heat while applied to the substrate during drying of the coating composition.

Claims

1. PRESSURE SENSITIVE ADHESIVE LABEL SHEET STOCK COMPRISING A LAYER OF PRESSURE SENSITIVE ADHESIVE ADHERED TO A SUBSTRATE, SAID PRESSURE SENSITIVE ADHESIVE COMPRISING AN ELASTOMER BASE AND A TACKIFYING RESIN, SAID ELASTOMER BASE CONSISTING ESSENTIALLY OF A BLEND OF A SOLID POLYRUETHANE ELASTOMER CURED ON THE SUBSTRATE AND ONE OR MORE NORMALLY NON-TACKY ELASTOMERS OTHER THAN POLYURETHANE ELASTOMER, SAID POLYURETHANE ELASTOMER BEING A COPOLYMER OF A POLYOL AND AN ISOCYANATE WHICH HAVE BEEN APPLIED TO SAID SUBSTRATE IN ADMIXTURE WITH SAID TACKIFYING RESIN AND SAID ONE OR MORE NON-TACKY ELASTOMERS WITHOUT FIRST SUBJECTING THEM TO PREPOLYMERIZING TEMPERATURES TO SUBSTANTIALLY PREPOLYMERIZE THEM AND WHICH HAVE BEEN CURED IN SITU ON SAID SUBSTRATE IN THE PRESENCE OF SAID TACKIFYING RESIN AND SAID ONE OR MORE NORMALLY NON-TACKY ELASTOMERS, SAID ONE OR MORE NON-TACKY ELESTOMERS BEING SELECTED FROM THE GROUP CONSISTING OR NATURAL AND SYNTHETIC RUBBERS.

2. Pressure sensitive adhesive label sheet stock according to claim 1, said polyurethane and said one or more elastomer components together comprising between 30% and 70% by weight of the pressure sensitive adhesive, said tackifying resin comprising between 30% and 70% by weight of the pressure sensitive adhesive and said polyurethane comprising between 10% and 90% by weight of the elastomer base.

3. Pressure sensitive adhesive label sheet stock according to claim 1, said synthetic rubber being selected from the group consisting of styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, butadiene-styrene-acrylonitrile copolymer, polyisoprene, isopolybutadiene, polyisobutylene, ethylene-propylene terpolymer, acrylic resin, poly-vinyl ethers, and butyl rubber.

4. Pressure sensitive adhesive label sheet stock according to claim 1, said tackifying resin being selected from the group consisting of hydrogenated rosin esters, coumarone-indene resins, unsaturated aliphatic hydrocarbons, polyterpene, polyisobutylene, phenylated terpene and petroleum resins.

5. Pressure sensitive label sheet stock according to claim 1, said polyurethane being the polyurethane of a polyisocyanate and an organic polyol polymer having an elastomeric-imparting, repeating backbone structure derived from olefinic polymerization.

6. Pressure sensitive adhesive label sheet stock according to claim 5, said polyol polymer being a hydroxy-terminated diene polymer.

7. Pressure sensitive adhesive label sheet stock according to claim 6, said hydroxy-terminated diene polymer being selected from the group consisting of butadiene homopolymer, butadiene-acrylonitrile copolymer, butadiene-styrene copolymer, butadiene-styrene-acrylonitrile copolymer and mixtures thereof.

8. Pressure sensitive adhesive label sheet stock according to claim 1, said polyurethane being the polyurethane of a diisocyanate and an organic polyol polymer having an elastomeric-imparting, repeating backbone structure which is substantially the same as the elastomeric-imparting, repeating backbone structure of at least one of said one or more elastomers.

9. Pressure sensitive adhesive label sheet stock according to claim 8, said polyol polymer being a polyol butadiene polymer and said one or more elastomers including a butadiene polymer.

10. Pressure sensitive adhesive label sheet stock according to claim 1, said polyurethane being a polyurethane of a diisocyanate and a polyol butadiene polymer and another modifying polyol selected from the group consisting of a non-polymeric diol and a triol to promote hydrogen bonding.

11. Pressure sensitive adhesive label sheet stock according to claim 1, having a release sheet releasably adhered to the exposed layer of pressure sensitive adhesive to protect it, the ratio of polyurethane elastomer to non-polyurethane elastomer being less than 1:

1.

12. Pressure sensitive adhesive label sheet stock according to claim 1, said polyurethane being an incompletely polymerized polyurethane.

13. Pressure sensitive adhesive label sheet stock according to claim 1, said polyurethane being a polyurethane of a polyol and a polyisocyanate, the amount of polyol being greater than the stoichiometric amount for complete polymerization with said polyisocyanate.

14. A plurality of individual pressure sensitive adhesive labels, each comprising a layer of pressure sensitive adhesive adhered to a substrate, said plurality of labels being releasably mounted by their pressure sensitive layers on a release sheet in spaced relation with respect to each other, said pressure sensitive adhesive comprising an elastomer base and a tackifying resin, said elastomer base consisting essentially of a blend of a polyurethane elastomer and one or more normally non-tacky elastomers other than polyurethane, said polyurethane elastomer being a copolymer of a polyol and an isocyanate which have been applied to said substrate in admixture with said tackifying resin and said one or more non-tacky elastomers without first subjecting them to prepolymerizing temperatures to substantially prepolymerize them and which have been cured in situ on said substrate in the presence of said tackifying resin and said one or more normally non-tacky elastomers, said one or more non-tacky elastomers being selected from the group consisting of natural and synthetic rubbers.

15. A plurality of labels according to claim 14, said polyurethane being a polyurethane of a non-volatile diisocyanate and a hydroxy terminated butadiene polymer, the ratio of said polyurethane to said one or more elastomeric components other than polyurethane being between 2:

3 and 1;

3 and the ratio of tackifying resin to elastomer base being between 1;

2 and 2;

1.

16. Pressure sensitive adhesive label sheet stock comprising a paper substrate having adhered thereto a coating of pressure sensitive adhesive comprising an elastomeric base and a tackifying resin, said elastomeric base consisting essentially of a blend of solid polyurethane elastomer, formed from a polyisocyanate and a polyol, and one or more normally non-tacky elastomers other than polyurethane elastomer, said polyurethane being chemically bonded to said substrate to thereby firmly anchor said pressure sensitive adhesive coating to said substrate by curing said polyisocyanate and polyol in situ on said substrate from a substantially non-prepolymerized state and in the presence of said tackifying resin and said one or more non-tacky elastomers other than polyurethane, said one or more non-tacky elastomers being selected from the group consisting of natural and synthetic rubber.

17. Pressure senSitive adhesive label sheet stock according to claim 16, said one or more elastomers being chemically bonded to said polyurethane by curing said polyisocyanate and polyol in situ on said substrate from a substantially non-prepolymerized state.

18. Pressure sensitive adhesive label sheet stock according to claim 16, said polyol being a hydroxy-terminated polydiene.

19. A method of making pressure sensitive adhesive label stock comprising coating on a substrate a pressure sensitive adhesive coating composition composed of a liquid solution of a tackifying resin and an elastomer other than a polyurethane elastomer and containing organic polyol and isocyanate which have not been previously subjected to prepolymerizing temperatures but which are polymerizable to an elastomeric polyurethane, drying said applied coating and curing said polyol and diisocyanate to said elastomeric polyurethane while applied to said substrate and in the presence of said tackifying resin and said elastomer other than polyurethane elastomer.

20. A method according to claim 19, said polyurethane being incompletely polymerized.

21. A method according to claim 19, the amount of polyol being greater than the stoichiometric amount for complete polymerization with said polyisocyanate.

22. A method according to claim 19, said polyurethane and said elastomer other than polyurethane both having substantially the same elastomeric-imparting repeating backbone structure.

23. A method according to claim 19, said polyol being a hydroxy-terminated diene polymer.

24. A method according to claim 23, said elastomer other than polyurethane including a diene polymer.