Thermoplastic adhesive compositions

DETAILED DESCRIPTION OF THE INVENTION It has now been discovered and forms a unique feature of this invention that novel adhesive compositions can be prepared by replacing all or a portion of the polyolefinic components of a conventional hot melt adhesive formulation with a grafted polymer in which the graft is a polar monomer preferably unsaturated acid or derivative thereof which has been graft polymerized to the backbone of a bare polymer.
The term "adhesive" as used herein is in its classical sense a substance which holds materials together because of surface attraction.
No one knows exactly what the theoretical basis is of adhesiveness.
However, all experts will concur that the overriding important characteristic of an adhesive is that the things which are bonded together, i.
e.
substrates, must be difficult to separate.
This probably comes about as a result of intimate contacting.
Thus when an adhesive is applied to a substance it must be fluid enough and surface-active enough to wet the substrate.
Then it must be capable of hardening or setting so that it develops high cohesive strength.
Preferably such cohesive strength is that comparable to what would be expected of a moldable thermoplastic or thermoset material.
Conventional hot melt adhesives are well known and comprise a wide variety of described systems and systems which are actually used in commerce.
Very generally a major component will be a carrier polymer which can be a structurally strong polyolefin such as polyethylene or polypropylene to impart the high cohesive strength when the adhesive sets up after cooling.
Other polymers used for their structural properties include nylons, vinyl acetate polymers, polyesters, polycarbonates, PVC, waxes, Saran and the like.
But other components are usually blended in.
Thus, hot melts can have an elastomeric component such as ethylene-propylene rubber, (EPR) ethylene-propylene diene monomer terpolymer (EPDM), polyisobutylene, (i.
e.
vistanex, butyl rubber) chlorinated polyethylenes, chlorinated butyl rubbers, and the like