DETAILED DESCRIPTION OF THE INVENTION The pressure sensitive adhesive useful to prepare the composition of this invention may be selected from a number of generic formulas.
Most of them are available commercially: Silicones (mostly polydimethylsiloxane).
In the electronic industry they are often referred to as silicone gels.
Acrylics (mostly homo-or copolymers of otylacrylate and butyl acrylate with minor amounts of vinyl acetate and other acrylate) Vinyl ether polymers (made mostly with methyl, ethyl or isobutyl vinyl ether) Polyurethanes Polychloroprene All these adhesives may contain various additives, such as tackifiers, plasticizers, fillers, stabilizers, colorants and other additives.
Another type of pressure sensitive adhesive contains at least the following 2 ingredients: a hydrocarbon rubber and a tackifier.
The rubber could be natural rubber, polyisoprene, styrene butadiene rubber, butyl rubber, polyisobutylene, styrene isoprene block copolymers, styrene butadiene block copolymers and others.
Well known tackifiers include rosin, rosin derivatives, hydrocarbon tackifiers and others.
An excellent treatise on pressure sensitive adhesives is: D.
Satas: "Handbook of Pressure Sensitive Adhesive Technology" Van Nostrand Reinhold, 1982.
A great number of desiccants or drying agents useful for drying gases are available.
They may be solids or liquids.
Generically they may be silicates, oxides, hydroxides, halides, sulphates, perchlorates, carbonates, activated carbon, sulfuric acid, glycols and other compositions.
The mechanism of dehydration may be physical absorption, chemical reaction to form hydrates and chemical reaction to form a new compound.
Some may absorb or react with moisture at room temperature but liberate it at higher temperatures.
The desiccant useful to prepare the getter composition of this invention is a solid particulate material.
Its average particle size is usually 0.
2-100 micrometer, preferably 0.
5-10 micrometer.
It should be capable of gettering substantial amounts of water vapor, in some cases even at relatively high temperatures, since some devices have high operating temperatures and they are heated to 100
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