Importance

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Abstract

A viscoelastic hot melt pressure-sensitive adhesive consisting essentially of: (a) about 35 to about 55% by weight of a rubbery block copolymer which comprises a rubbery polyisoprene midblock portion and a plurality of end blocks comprising a crystalline poly(vinylarene); (b) about 25 to 45% by weight of a terpene tackifying resin generally compatible with and generally associated with said midblock portion; (c) about 10 to about 30% by weight of an aromatic, essentially hydrocarbon resin having a glass transition temperature and a softening point above about 115.degree. C., said essentially hydrocarbon resin being generally compatible with said end blocks of said rubbery block copolymer; the proportions of said components (a), (b), and (c) being selected to provide the following pressure-sensitive adhesive and rheological properties: (i) a tensile strength at 500% elongation, determined at 20.degree.-25.degree. C., of at least 50 pounds per square inch; (ii) a 180.degree. peel resistance, according to PSTC-1, determined at 20.degree.-25.degree. C. 24 hours after formation of the pressure-sensitive adhesive bond, of at least about 1500 grams per 25.4 mm-width; (iii) a dead load deformation, tested at room temperature, 37.8.degree. C., 43.3.degree. C., and 48.9.degree. C. for 3 hours under 1500 g/cm.sup.2, of less than 100%, where dead load deformation=the increased length minus the original length divided by the original length of a sample at least 25 mm in length; (iv) the following loss modulus, storage modulus, and loss tangent values at 0.01 and 0.25 Hz throughout the temperature range of 25.degree.-50.degree. C.:

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First Claim