Process for forming solid pressure sensitive adhesive polymer microspheres

a polymer microsphere and pressure-sensitive technology, applied in the direction of acid polymer adhesives, adhesive types, adhesive types, etc., can solve the problems of unreacted residual ionic monomer, hazardous to humans, odorous and corrosive, etc., to improve the transfer performance characteristics and reduce the residual ionic monomer

Inactive Publication Date: 2005-06-16
GUO JONG SHING +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The process significantly reduces residual unconverted monomer levels and enhances the adhesive transfer performance of the microspheres, minimizing microsphere transfer and maintaining the carrier's adhesion capability, while ensuring safety by reducing hazardous monomer presence.

Problems solved by technology

High levels of unreacted residual monomer are undesirable and, depending on monomer identity, can lead to downstream handling problems.
For example, ionic acrylic acid (e.g. NH4acrylate) is hazardous to humans and quite odorous and corrosive.
When microspheres are pulled away from the carrier or backing layer, this is recognized as a post synthesis application problem in the art.

Method used

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  • Process for forming solid pressure sensitive adhesive polymer microspheres
  • Process for forming solid pressure sensitive adhesive polymer microspheres

Examples

Experimental program
Comparison scheme
Effect test

example 1

Control

[0064] A two liter resin reactor equipped with a mechanical stirrer, a condenser, a thermocouple probe and a gas inlet port was charged with a solution of 740 grams of deionized water and 5 grams of acrylic acid (AA) neutralized with 5 grams of ammonium hydroxide (28%) to pH 8.5. In a separate container, 1.0 gram of benzoyl peroxide (BPO) was dissolved in 245 grams of 2-ethyl hexyl acrylate (2-EHA) and then added to the reactor. The agitation was set at 320 rpm. The solution was purged with nitrogen for fifteen minutes after which the nitrogen line was repositioned above the fluid for the remainder of the reaction. Finally, 22.7 grams of SDBS were added to the reactor. After 15 minutes of mixing, the reaction mixture was heated to 65° C. and held for the first hour. At a heating rate of approximately 2.2° C. per minute, the reaction became exothermic after 20 minutes and subsided after approximately another 20 minutes. The reaction mixture was then heated to 77° C. and held ...

examples 2-4

Controls

[0066] Example 1 was duplicated using the following monomers, catalysts and surfactants with similar results. The reagents and results are summarized in Tables 1 and 2.

example 5

Control

U.S. Pat. No. 5,578,650

[0067] A two liter resin reactor equipped with a mechanical stirrer, a condenser, a thermocouple probe and a gas inlet port was charged with 750 grams of deionized water and 10 grams of ADS. The aqueous solution was stirred at 350 rpm and heated to 65° C. In a separate container, 1.1 grams of BPO was dissolved in 245 grams 2-EHA and 5 grams of acetic acid. The mixture was added to the hot aqueous solution while stirring at 350 rpm. The pH was determined to be 2.9. The temperature of the reactor was reduced to a polymerization temperature of 60° C. and the reactor was degassed with nitrogen. After 8 hours at 60° C., the reaction was cooled to 25° C. and filtered through a 400 micron nylon mesh filter. Very little coagulum was found to be present. The twenty minute peel performance (PL20) on 60# Kromekote paper was 0.38 lbs. / in. with 100% bead transfer. The reagents and results are summarized in Tables 1 and 2.

TABLE 1ExampleMonomersCatalystSurfactant1...

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Abstract

In forming pressure sensitive adhesive microspheres by copolymerizing a non-ionic monomer of an alkyl acrylate or alkyl methacrylate ester of a non-tertiary alcohol and an ionic monomer copolymerizable with said non-ionic monomer, non-free radically polymerizable acid is present during the polymerization to promote formation of solid rather than hollow microspheres and to reduce residual unconverted ionic monomer. These microspheres exhibit reduced adhesive transfer in downstream use as a repositionable pressure sensitive adhesive. A water soluble initiator is optionally added to the polymerization mixture after achieving about 90% conversion of the non-ionic monomer to further reduce residual unconverted ionic monomer.

Description

RELATED APPLICATION [0001] This application is a non-provisional application which claims the priority of prior provisional application serial No. 60 / 213,851, entitled “Process For Forming Solid Pressure Sensitive Adhesive Polymer Microspheres”, filed Jun. 23, 2000, which is hereby incorporated by reference into this application.BACKGROUND OF THE INVENTION [0002] This invention relates to a process for forming pressure sensitive polymeric microspheres, and to the solid microspheres so formed as well as their use as repositionable pressure sensitive adhesives. [0003] Solid and hollow inherently tacky acrylate polymer microspheres are known in the art for use in repositionable pressure sensitive adhesive applications. The term “repositionable” refers to the ability to be repeatedly adhered to and removed from a substrate without substantial loss of adhesion capability. [0004] U.S. Pat. No. 3,691,140 to Silver teaches preparation of such microspheres utilizing water soluble, substantia...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C08F2/00C08F2/24C08F220/00C08F220/18C09J133/02C09J133/08
CPCC08F220/18C08L2205/18C09J2201/606C09J133/08C09J133/02C09J2301/302C08F220/1808
InventorGUO, JONG-SHINGTREMBLEY, SHARON D.
OwnerGUO JONG SHING