Pressure sensitive adhesive compositions

#This invention relates to pressure sensitive adhesive compositions which includes a hydrogenated block copolymer such as Kraton G, about 25 to about 250 parts by weight of a hydrocarbon resin of a petroleum or coal tar distillate, aliphatic dienes and mono- and diolefins, cyclic olefins of 5 or 6 carbon atoms and hydrogenated polycyclics per 100 parts by weight of the hydrogenated block copolymer, and about 25 to 200 parts by weight of a polybutene or polyisobutylene per 100 parts of the hydrogenated block copolymer, wherein said mixture of Kraton G, said hydrocarbon resin and said polybutene or polyisobutylene are dissolved in a non-reactive solvent at a concentration level of about 5 to about 25 grams per 100 ml. of non-reactive solvent.

#Broadly speaking, synthetic adhesives used in packaging can be classified into four categories: water based, solvent based, reactive and hot melt adhesives. Of these four, currently, the water based are used most extensively. Usually the water based adhesives are based on emulsion polymers and are applied to porous cellulosic substrates. Energy from the outside, in some fashion, is applied to the system to evaporate the water in order that a strong bond may be formed. Beside this energy requirement for the formation of the bond, there is another complication with the use of water based adhesive. For a uniform coating, a good uniform wetting of the substrate surface is desired, which is not easily achieved.

#The key requirements for pressure sensitive adhesives are that they should have good cohesive and tackifying properties at ambient conditions. These adhesives should also have good flow characteristics if they are to be used in the bulk state, otherwise they should possess sufficient consistency when dissolved in suitable solvents so that they can be coated or sprayed on the surfaces to be bonded.

#The advantages of both the physical properties and adhesive characteristics of the compositions of the present invention can be more readily appreciated by references to the following Examples and Tables. Unless otherwise defined, the measurements of the compositions are in parts per hundred by weight.

#TABLE II ______________________________________ Vis- % % cosity % Aro- Sat- Type Oil Oil Code # ssu Mn Polars matic urate ______________________________________ Paraffinic Sunpar 115 155 400 0.3 12.7 87.0 Paraffinic Sunpar 180 750 570 0.7 17.0 82.3 Paraffinic Sunpar 2280 2907 720 1.5 22.0 76.5 Aromatic Flexon 340 120 -- 1.3 70.3 28.4 Naphthenic Flexon 765 505 -- 0.9 20.8 78.3 ______________________________________

#The binary blends of Kraton G polymer and tackifying resins failed to show any respectable degree of tackiness; attempts were made to make tertiary blends of Kraton G, tackifying resins and polybutenes.