US 5,412,035 A · Pressure-sensitive adhesives

Abstract

Pressure-sensitive adhesive (PSA) compositions containing a crystalline polymeric additive having an M.sub.w of less than 25,000 and a melting point (T.sub.a) greater than 23.degree. C., preferably 30.degree. to 60.degree. , and PSA composites of a backing, preferably a flexible backing, with such a PSA composition coated thereon. The presence of the additive causes the PSA to lose adhesive strength when heated to T.sub.a. The base resin of the PSA is preferably a polyacrylate or a styrene/butadiene copolymer. The additive, which is preferably present in amount 1 to 35%, e.g. 5 to 30%, is preferably a side chain crystallizable (SCC) polymer.

Claims98

Dependent claims

A pressure-sensitive adhesive (PSA) composition which comprises

(1) at least 50% by weight of a polymeric pressure-sensitive adhesive component, and
(2) a crystalline polymeric additive having a weight average molecular weight of less than 25,000 and a first order transition point T.sub.a in the composition greater than 23.degree. C.;
said composition, when tested for peel strength under selected test conditions as a PSA composite consisting of a selected backing and a layer of the PSA composition of selected thickness,
(i) at a selected temperature T.sub.1 which is less than T.sub.a and is from 20.degree. C. to 60.degree. C., having a PSA peel strength P.sub.1, and
(ii) at a selected temperature T.sub.2 which is higher than T.sub.a and is not greater than 100.degree. C., having a PSA peel strength P.sub.2 ;
a comparative composition which is the same as said composition except that it does not contain the additive, when tested for peel strength under the same test conditions, as a comparative PSA composite consisting of the same backing and a layer of the comparative PSA composition of the same thickness,
(i) at T.sub.1, having a PSA peel strength P.sub.1.sup.c or undergoing non-adhesive failure, and
(ii) at T.sub.2, having a PSA peel strength P.sub.2.sup.c or undergoing non-adhesive failure;
and at least one of the following conditions being fulfilled
(a) P.sub.1 -P.sub.2 is at least 25 g/cm,
(b) 100(P.sub.1 -P.sub.2)/P.sub.1 is at least 25,
(c) the comparative PSA composite undergoes non-adhesive failure at T.sub.1 or T.sub.2, and
(d) (P.sub.1 -P.sub.2)/P.sub.1 is greater than (P.sub.1.sup.c -P.sub.2.sup.c)/P.sub.1.sup.c.

10 more elements

A PSA composite which comprises

(A) a flexible backing, and
(B) adherent to the backing, a solvent-free layer of a pressure-sensitive adhesive (PSA) composition which comprises
(1) at least 50% by weight of a polymeric pressure-sensitive adhesive component, and
(1) at least 50% by weight of a polymeric pressure-sensitive adhesive component, and
a crystalline polymeric additive having a weight average molecular weight of less than 25,000 and a first order transition point T.sub.a in the composition greater than 23.degree. C.;
said PSA composite, when tested for peel strength by the method described in PSTC-1 using as the receptor a stainless steel plate as specified in Appendage B of PSTC-1 and after maintaining the assembly of the receptor and the PSA composite at a temperature of about 19.degree. C. for about 240 minutes,
(i) at a selected temperature T.sub.1 which is less than T.sub.a and is from 20.degree. C. to 60.degree. C., having a PSA peel strength P.sub.1, and
(ii) at a selected temperature T.sub.2 which is higher than T.sub.a and is not greater than 100.degree. C., having a PSA peel strength P.sub.2 ;
wherein P.sub.1 -P.sub.2 is at least 25 g/cm, or 100(P.sub.1 -P.sub.2)/P.sub.1 is at least 25, or both, and a comparative PSA composite which is the same as said composite except that the PSA composition does not contain the additive, when tested for peel strength under the same test conditions, having a PSA peel strength at T.sub.1.

6 more elements

A PSA composite which comprises

(A) a flexible backing;
and
(B) adherent to the backing, a layer of a composition which is a pressure-sensitive adhesive at 20.degree. C. and which comprises
(1) at least 65% by weight of a polymeric pressure-sensitive adhesive component which, on its own, is a pressure-sensitive adhesive at 20.degree. C., and
(2) a crystalline polymeric additive which has a weight average molecular weight of less than 25,000 and a first order transition point T.sub.a in the composition of 25.degree. to 100.degree. C. and which comprises repeating units of the general formula ##STR4## where Y is an organic radical forming part of a polymer backbone and Cy comprises a crystallizable moiety, the total weight of the Cy moieties being at least twice the weight of the remainder of the crystalline polymeric additive;
said PSA composite being a pressure-sensitive adhesive at T.sub.a, but having a lower peel strength at T.sub.a than at 20.degree. C.

3 more elements

A pressure-sensitive adhesive composition which is a pressure-sensitive adhesive at at least one temperature in the range 20.degree. to 40.degree. C., and which comprises:

(1) p% by weight, based on solids, of a polymeric pressure-sensitive adhesive component;
and
(2) q% by weight, based on solids, of a crystalline polymer additive which
(a) has a heat of fusion of at least 20 Joules/g,
(b) is intimately admixed with the polymeric pressure-sensitive adhesive component,
(c) has a first order transition point T.sub.m .degree. C. when measured on its own,
(d) has a first order transition point T.sub.a .degree. C. when measured in the composition, where T.sub.a is less than T.sub.m, and
(e) has a weight average molecular weight less than about 25,000 Daltons;
p being at least 50, and q being greater than 0 and less than 50 and such that said composition, when tested by an IMTI procedure using a backing which is a 1.75 mil thick film of a polyester thermoplastic elastomer (Hytrel 4056) and a test surface which is human skin, or by an ISPT procedure using a backing which is a 1.5 mil thick film of polyethylene terephthalate (Mylar) and a test surface which is stainless steel as specified in Appendage B of PSTC-1
(i) at a temperature T.sub.1 which is between (T.sub.a -10).degree. C. and (T.sub.a -4).degree. C., having a PSA peel strength P.sub.1 g/cm, and
(ii) at a temperature T.sub.2 which is between (T.sub.a +4).degree. C. and (T.sub.a +10).degree. C. having a PSA peel strength P.sub.2 g/cm, where 100(P.sub.1 -P.sub.2 /P.sub.1) is at least 50;
and said polymeric pressure-sensitive adhesive component, when tested on its own by said IMTI or ISPT procedure, being a pressure-sensitive adhesive at said temperature T.sub.1.

9 more elements

A PSA composite which comprises

(A) a flexible backing, and
(B) coated on the backing, a solvent-free layer of a pressure-sensitive adhesive composition which is a pressure-sensitive adhesive at at least one temperature in the range 20.degree. to 40.degree. C., and which comprises:
(1) p% by weight of a polymeric pressure-sensitive adhesive component;
and
(2) q% by weight of a crystalline polymer additive which
(a) has a heat of fusion of at least 20 Joules/g,
(b) is intimately admixed with the polymeric pressure-sensitive adhesive component,
(c) has a first order transition point T.sub.m .degree. C. when measured on its own,
(d) has a first order transition point T.sub.a .degree. C. when measured in the composition, where T.sub.a is less than T.sub.m, and
(e) has a weight average molecular weight less than about 25,000 Daltons;
p being at least 50, and q being greater than 0 and less than 50 and such that said composite, when tested by an IMTI procedure using a test surface which is human skin, or by an ISPT procedure using a test surface which is stainless steel as specified in Appendage B of PSTC-1
(i) at a temperature T.sub.1 which is between (T.sub.a -10).degree. C. and (T.sub.a -4).degree. C., having a PSA peel strength P.sub.1 g/cm, and
(ii) at a temperature T.sub.2 which is between (T.sub.a +4).degree. C. and (T.sub.a +10).degree. C. having a PSA peel strength P.sub.2 g/cm, where 100(P.sub.1 -P.sub.2 /P.sub.1) is at least 50;
and said polymeric pressure-sensitive adhesive component, when tested on its own by an IMTI procedure using a backing which is a 1.75 mil thick film of a polyester thermoplastic elastomer (Hytrel 4056) and a test surface which is human skin, or by an ISPT procedure using a backing which is a 1.5 mil thick film of polyethylene terephthalate (Mylar) and a test surface which is stainless steel as specified in Appendage B of PSTC-1, being a pressure-sensitive adhesive at said temperature T.sub.1.

11 more elements

A process for affixing a flexible backing to a receptor, which process comprises

(A) interposing between said flexible backing and said receptor a solvent-free pressure-sensitive adhesive composition which is a pressure-sensitive adhesive at at least one temperature in the range 20.degree. to 40.degree. C., and which comprises:
(1) p% by weight of a polymeric pressure-sensitive adhesive component;
and
(2) q% by weight of a crystalline polymer additive which
(a) has a heat of fusion of at least 20 Joules/g,
(b) is intimately admixed with the polymeric pressure-sensitive adhesive component,
(c) has a first order transition point T.sub.m .degree. C. when measured on its own,
(d) has a first order transition point T.sub.a .degree. C. when measured in the composition, where T.sub.a is less than T.sub.m, and
(e) has a weight average molecular weight of less than about 25,000 Daltons;
p being at least 50, and q being greater than 0 and less than 50 and such that said composition, when the receptor is human skin, when tested by an IMTI procedure using said flexible backing and a test surface which is human skin, and, when the receptor is any other surface, when tested by an ISPT procedure using said flexible backing and a test surface which is said receptor
(i) at a temperature T.sub.1 which is between (T.sub.a -10).degree. C. and (T.sub.a -4).degree. C., having a PSA peal strength P.sub.1 g/cm, and
(ii) at a temperature T.sub.2 which is between (T.sub.a +4).degree. C. and (T.sub.a +10).degree. C. having a PSA peel strength P.sub.2 g/cm, where 100(P.sub.1 -P.sub.2 /P.sub.1) is at least 50;
and said polymeric pressure-sensitive adhesive component, when tested on its own by said IMTI or ISPT procedure, being a pressure-sensitive adhesive at said temperature T.sub.1 ;
and
(B) pressing the backing against the receptor, with the pressure-sensitive adhesive composition between them, while the adhesive composition is at a temperature which is below T.sub.a and at which the composition is tacky.

12 more elements

An assembly which comprises a receptor and PSA composite which is adherent to the receptor and which comprises

(A) a flexible backing;
and
(B) coated on the backing, a solvent-free layer of a pressure-sensitive adhesive composition which is a pressure-sensitive adhesive at at least one temperature in the range 20.degree. to 40.degree. C., and which is adherent to the receptor and which comprises
(1) p% by weight of a polymeric pressure-sensitive adhesive component, and
(2) q% by weight of a crystalline polymer additive which
(a) has a heat of fusion of at least 20 Joules/g,
(b) is intimately admixed with the polymeric pressure-sensitive adhesive component,
(c) has a first order transition point T.sub.m .degree. C. when measured on its own,
(d) has a first order transition point T.sub.a .degree. C. when measured in the composition, where T.sub.a is less than T.sub.m, and
(e) has a weight average molecular weight less than about 25,000 Daltons;
p being at least 50, and q being greater than 0 and less than 50 and such that said PSA composite, when peeled away from the receptor at an angle of about 180.degree. and at a rate of about 12 inch/minute
(i) at a temperature T.sub.1 which is between (T.sub.a -10).degree. C. and (T.sub.a -4).degree. C., having a PSA peel strength P.sub.1 g/cm, and
(ii) at a temperature T.sub.2 which is between (T.sub.a +4).degree. C. and (T.sub.a +10).degree. C. having a PSA peel strength P.sub.2 g/cm, where 100(P.sub.1 -P.sub.2 /P.sub.1) is at least 50;
and said polymeric pressure-sensitive adhesive component, when tested on its own by an IMTI procedure using a backing which is a 1.75 mil thick film of a polyester thermoplastic elastomer (Hytrel 4056) and a test surface which is human skin, or by an ISPT procedure using a backing which is a 1.5 mil thick film of polyethylene terephthalate (Mylar) and a test surface which is stainless steel as specified in Appendage B of PSTC-1, being a pressure-sensitive adhesive at said temperature T.sub.1.

11 more elements

Dependencies are inferred from the claim text.

Pressure-sensitive adhesives

Life of this patent

Pressure-sensitive adhesives

Life of this patent

Abstract

Claims98