Silicone pressure-sensitive adhesives with control removal property

• US 5,248,716 A
• Filed: 01/30/1992
• Issued: 09/28/1993
• Est. Priority Date: 01/30/1992
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kerr, Stuart R. III, Lin, Shaow B.
• Primary Examiner(s): Marquis, Melvyn I.
• Assistant Examiner(s): MOORE, MARGARET G
• Application Number:
  US07/828,437
• Time in Patent Office: 607 Days
• Field of Search: 524/267, 524/268, 525/478, 525/477
• US Class Current: 524/268
• CPC Class Codes: C08L 83/00 Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
• CPC Class Codes: C09J 183/04 Polysiloxanes

Abstract

Distortion and haze of pressure sensitive tapes upon removal can be minimized by incorporating a small amount of chemically compatible, high molecular weight silicone polymer release modifier to the curable PSA compositions. Organopolysiloxanes of the general formula:

RR.sup.1.sub.2 SiO(R.sup.1.sub.2 SiO).sub.x (RR.sup.2 SiO).sub.y

SiR¹₂ R

are used as the release modifier, wherein each R¹ and R² is independently an aryl or alkyl group having from 1 to about 10 carbon atoms, each R is independently chosen from the following groups: R¹, R², alkenyl having from 1 to about 10 carbon atoms, hydrogen, alkoxy (such as methoxy, ethoxy, propoxy, etc.) hydroxy, epoxy, amino, and fluoroalkyl having up to 10 carbon atoms; x and y are each an integer such that the value of (x+y) is sufficient to yield a composition having a viscosity of from at least 1500 cps at room temperature to as high as the viscosity of silicone gums. When compared to similar compositions without the release modifier, a cured silicone PSA with much less distortion, a smoother surface, and clearer optics is obtained upon removal or dispensing.

Claims

1. A pressure sensitive adhesive, having improved control removal properties, said adhesive comprising a resin/organopolysiloxane composition curable to produce a pressure sensitive adhesive said organopolysiloxane composition curable to produce a pressure sensitive adhesive comprising about 50 to about 75 parts by weight of a benzene toluene-soluble siloxane resin, about 25 to about 50 parts by weight of vinyl-and hydride-containing organopolysiloxanes, a Pt catalyst, and from 0 to about 40 weight percent organic solvent and from about 0.5 to about 15 weight percent based upon the resin/organopolysiloxane composition of a chemically compatible high molecular weight organopolysiloxane having the general formula:

space="preserve" listing-type="equation">RR.sup.1.sub.x SiO(R.sup.1.sub.2 SiO).sub.x (RR.sup.2 SiO).sub.y SiR.sup.1.sub.2 R (1)

wherein each R¹ is independently an alkyl or aryl group having from 1 to about 10 carbon atoms, each R² is independently an alkyl or aryl group having from 1 to about 10 carbon atoms, each R is independently chosen from R¹ or R², x is an integer, and y is an integer, x and y having values such that the chain-length dependent viscosity of the chemically compatible high molecular weight polyorganosiloxane is at least 1500 cps at 25°

C.

2. A pressure sensitive adhesive as in claim 1, wherein said chemically compatible high molecular weight organopolysiloxane is present in an amount of between 2 and 10 weight percent.

3. A pressure sensitive adhesive as in claim 1, wherein x and y are such that the chain-length dependent viscosity of said chemically compatible high molecular weight organopolysiloxane is at least 7600 cps at 25°

C.

4. A pressure sensitive adhesive as in claim 1, wherein x and y are such that the chain-length dependent viscosity of said chemically compatible high molecular weight organopolysiloxane is at least 10,000 cps at 25°

C.

5. A pressure sensitive adhesive as in claim 1, wherein x and y are such that the chain-length dependent viscosity of said chemically compatible high molecular weight organopolysiloxane is at least about 85,000 cps at 25°

C.

6. A pressure sensitive adhesive as in claim 1, wherein said chemically compatible high molecular weight organopolysiloxane comprises an alkyl-terminated silicone polymer.

7. A pressure sensitive adhesive as in claim 6, wherein said chemically compatible high molecular weight organopolysiloxane comprises a polydimethylsiloxane.

8. A pressure sensitive adhesive as in claim 7, wherein said polydimethylsiloxane has a viscosity of from about 7600 cps to about 8,600,000 cps at room temperature.

9. A pressure sensitive adhesive as in claim 6, wherein said alkyl-terminated silicone polymer is present in an amount of between 2 parts by weight and 10 parts by weight based on 100 parts by weight of the organopolysiloxane composition curable to produce a pressure sensitive adhesive.