Pressure-sensitive adhesives high-tack formulation

Two important parameters in the formulation of pressure sensitive adhesives are tack and hold, which is the ability to resist creep under deadload. As noted, butyl and polyisobutylene are inherently tacky polymers. This tack can be enhanced with a wide variety of resins and other tackifiers. The hold or cohesive strength is low compared to some other pressure sensitive adhesive polymers, such as natural rubber, but can be increased if required by (1) incorporation of high molecular weight PIB or natural rubber, (2) the choice of the other ingredients, particularly resins and fillers, and (3) the partial or preferential curing techniques noted previously. The poly isobutylene polymers are primarily used in label pressure sensitive adhesives and in certain tapes where high cohesive strength is not necessary. 

The ever-increasing raw material choice available to the adhesive formulator is demonstrated with particular reference to Hercules resin dispersions for the modification of acrylic latex polymer systems used in pressure sensitive adhesive formulations. The requirements of a tackil g resin are examined and the advantages afforded by such products from Hercules as Tacolyn 1070, Tacolyn 3179 and Res A-2603 are discussed, in terms of their ability to offer balances of peel, tack and shear and consistently high levels of stability, it is claimed. 5 refs. 

The chemistry and structure of the tackifying terpene resins are developed by E. Ruckel al. These resins, produced commercially from pine turpentine, since the mid-Thirties, are formulated with natural rubber to produce pressure sensitive adhesives. More recently, the scope of their use has been broadened by formulation with elastomers and waxes for hot melt applications. Empirical application tests have developed a broad knowledge of utility but little science or predictability. By use of sophisticated high polymer techniques, polymerization mechanisms are used to explain how the minor structural differences between the beta-pinene and dipentene resins suit these resins respectively for pressure sensitive and hot melt adhesive usage. Again for use application the critical aspects of the formulation are its adhesive and cohesive properties as demonstrated by tack, shear and peel properties. 

In general, most labels are applied using pressure-sensitive adhesives formulated with water-borne acrylic adhesives, solvent-borne adhesives, or hot-melt adhesives. The adhesives used for these labels can also be formulated for variable adhesion performance, such as instant permanence, repositionability, peelability (removability), low temperature adhesion, high tack for rough surfaces, UV resistance, or plasticizer migration resistance. The adhesive s performance is linked to the base carrier material upon which it is applied. 

---