# US 6,293,037 B1 · Pressure-sensitive adhesives and self-adhesive postage stamps made therewith

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- Number: US 6,293,037 B1
- Document ID: US6293037B1
- Status: Granted
- Kind: B1
- Application number: 09/319,295
- Filed: 1999-09-22
- Granted: 2001-09-25
- Earliest claimed: 1996-12-04
- Assignees: Avery Dennison Corporation
- Inventors: Lon T. Spada; Carol A. Koch; Kathleen M. Alpaugh
- Web page: https://patentgrep.com/patent/US6293037B1

## CPC

- C09J 133/08: Homopolymers or copolymers of acrylic acid esters
- C09J 4/00: Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond {; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16}
- Y10T 428/31797: Next to addition polymer from unsaturated monomers
- Y10T 428/31895: Paper or wood
- Y10T 428/31917: Next to polyene polymer
- C09J: ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES (preparation of glue or gelatine C09H)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Acrylic, self-adhesive postage stamps are provided and include a flexible facestock bearing an acrylic pressure-sensitive adhesive (PSA), protected by a release liner. The acrylic PSA is a tackified or inherently tacky polymer formed from a plurality of monomers comprising, based on the total weight of monomeric composition, essentially of (i) 9 to 40% isobornyl acrylate and (ii) 50 to 91% of one or more alkyl acrylates.

## Claims

### Claim 1

A self-adhesive postage stamp, comprising:
(a) a flexible face stock having opposed first and second faces, at least one of which is imprinted with postage indicia; and
(b) a pressure-sensitive adhesive applied to one face of the flexible face stock, said pressure-sensitive adhesive comprising an acrylic copolymer made from a mixture of monomers, comprising, based on the total weight of monomers,
(i) from about 9 to about 40% of an ethylenically unsaturated monomer having an isobornyl group, and
(ii) from about 50 to about 91% of at least one alkyl acrylate having an alkyl group with about 4 to about 8 carbon atoms.

### Claim 2 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the monomer having an isobornyl group is isobornyl acrylate.

### Claim 3 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the isobornyl acrylate is present in an amount of from about 20 to about 30% by weight, based on the total weight of monomers.

### Claim 4 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the mixture of monomers further comprises up to about 20% by weight of 1 or more additional monomers selected from the group consisting of polar monomers, short chain alkyl acrylates and methyl methacrylates having alkyl groups with up to 3 carbon atoms, and monohydric alkyl acrylates and methacrylates having alkyl groups with about 2 to about 8 carbon atoms.

### Claim 5 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the acrylic copolymer is an emulsion polymer.

### Claim 6 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the acrylic copolymer is a bulk polymer.

### Claim 7 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the acrylic copolymer is applied as a hot melt.

### Claim 8 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the acrylic copolymer is applied as a solvent-borne coating.

### Claim 9 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the flexible face stock is selected from the group consisting of paper and polymeric face stocks.

### Claim 10 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the flexible face stock meets United States Postal Service facestock requirements classified as “required” in USPS-P-1238C.

### Claim 11 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the flexible face stock meets the United States Postal Service facestock requirements classified as “target” in USPS-P-1238C.

### Claim 12 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, further comprising a removable release liner protecting the pressure-sensitive adhesive.

### Claim 13

A self-adhesive postage stamp, comprising:
(a) a flexible face stock having opposed first and second faces, at least one of which is imprinted with postage indicia; and
(b) a pressure-sensitive adhesive applied to one face of the flexible face stock, said pressure-sensitive adhesive comprising an acrylic copolymer made from a mixture of monomers comprising, based on the total weight of monomers,
(i) from about 20 to about 30% isobornyl acrylate,
(ii) about 50 to about 80% of one or more alkyl acrylates having alkyl groups with about 4 to about 8 atoms,
(iii) about 1 to about 20% methyl methacrylate,
(iv) about 1 to about 6% acrylic acid, and
(v) about 0.5 to about 6% hydroxyethyl acrylate.

### Claim 14 (depends on 13)

A self-adhesive postage stamp as recited in claim 13 wherein the flexible face stock meets the United States Postal Service facestock requirements classified as “required” in USPS-P-1238C.

### Claim 15 (depends on 13)

A self-adhesive postage stamp as recited in claim 13, further comprising a release liner.

### Claim 16 (depends on 1)

A self-adhesive postage stamp as recited in claim 1, wherein the stamp exhibits more than a slight fiber pick when removed from an envelope after a dwell time of at least about five minutes.