Packaging Method for Hot Melt Adhesive II
The method of the present invention is adaptable to the packaging of virtually any type of hot melt polyurethane composition. It is especially adapted to the packaging of thermoplastic or thermosetting pressure sensitive adhesives where the handling problems are most severe. As examples, the method disclosed herein may be used to package hot melt adhesives prepared from polymers and copolymers of synthetic resins, rubbers, polyethylene, polypropylene, polyurethane, acrylics, vinyl acetate, ethylene vinyl acetate, polyvinyl alcohol, and so on.
Most often, such adhesives are formulated with tackifying resins in order to improve adhesion and introduce tack into the adhesive. Such resin include natural and modified resins, polyterpene resins, phenolic modified hydrocarbon resins, coumarone-indene resins, aliphatic and aromatic petroleum hydrocarbon resins, phthalate esters and hydrogenated hydrocarbons, hydrogenated rosins, and hydrogenated rosin esters.
Desirable optional ingredients include diluents, like liquid polybutene or polypropylene, petroleum waxes such as paraffin and microcrystalline waxes, polyethylene greases, hydrogenated animal, fish and vegetable fats, mineral oil and synthetic waxes as well as hydrocarbon oils such as naphthionic or paraffinic mineral oils.
Other optional additives may include stabilizers, antioxidants, colorants and fillers. The selection of components and amounts as well as the preparation thereof are well known in the art and described in the literature.
The thermoplastic film into which the molten adhesive is poured may be any film which is melted together with the adhesive composition and blended into molten adhesive and which will not affect the properties of the adhesive composition when blended therewith.
The films may, if desired, contain antioxidants for enhanced stability as well as other optional components such as fatty amides or other processing aids, anti-stats, stabilizers, plasticizers, dyes, perfumes, fillers and the like.
The specific thermoplastic film utilized will depend, in large part, on the composition and melting point of the hot melt adhesive being packaged, with the softening point of the film generally being less than about 125°C.
Particularly preferred for most hot melt adhesives are thermoplastic films of low density polyethylene or polyethylene vinyl acetate wherein the amount of vinyl acetate is 0 to 10%, preferably 3 to 5%, by weight.
The thickness of the film utilized generally varies between about 0.1 mil to 5 mil, preferably 0.5 mil to 4 mil. It is further preferred that the thermoplastic film comprise not more than about 1.5% by weight of the total adhesive mass and that it optimally vary from 0.2 to 1.0% by weight of the mass in order to prevent undue dilution of the adhesive properties.
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