Free-flowing pressure sensitive adhesives

Abstract

Hot melt adhesive consisting of a core of a pressure sensitive adhesive comprising at least one polymer selected from polyester, polyacrylate, polyolefin, polyurethane, ethylene vinyl acetate polymers, styrene blockcopolymers or mixtures, at least one tackifier and optionally additives, the core material has a softening point of 80 to 150° C. and a tacky surface at 25° C., the hot melt adhesive having the form of pellets, each pellet of adhesive has an outer shell of a film forming material, whereby i) the film forming material is a thermoplastic polymer with a melting point of less than 120° C., ii) each pellet being completely surrounded by the film material, iii) the film is applied as continuous film so that the pellets have a non-blocking surface and are free flowing at a temperature of less then 45° C. Such pellets can be used as feed for automated feeder devices for the supply hot melt application systems.

1 . A plurality of hot melt pressure sensitive adhesive pellets having a core of a pressure sensitive adhesive material surrounded by a continuous outer shell of a polymeric film;
 wherein the pressure sensitive adhesive material comprises, (i) a polyester, polyacrylate, polyolefin, polyurethane, ethylene vinyl acetate polymers, styrene block copolymers or mixtures thererof, and (ii) a tackifier; and the pressure sensitive adhesive material has a softening point of 80 to 150° C. and has a tacky surface at 25° C.; and   wherein the polymeric film comprises a thermoplastic polymer with a melting point of less than 120° C., and   wherein the pellets are free flowing at a temperature of less then 45° C.   
     
     
         2 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the pellets have a weight of less than 15 g each and/or a diameter of less then 25 mm in each direction. 
     
     
         3 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 2 , wherein the pellets have a cylindrical or a spherical shape. 
     
     
         4 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the polymeric film of the shell comprises less than 20 wt-% wax, based on the total weight of the polymeric film. 
     
     
         5 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the polymeric film is less than 12 wt-% of the pressure sensitive adhesive material. 
     
     
         6 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the pellets are non-tacky at a temperature of 25° C. to 45° C. 
     
     
         7 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the melting point of the polymeric film is equal to or lower than softening point of the core. 
     
     
         8 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the polymeric film comprises a polymer selected from (a) polyethylene, polypropylene, polyester, polyacrylate, ethylene vinyl acetate polymer, styrene block copolymers or blends and (b) optionally, up to 15 wt-% of an oil and/or a wax, based on the total weight of the core. 
     
     
         9 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the continuous outer shell of the polymeric film is manufactured by heating the polymeric film at a temperature above the melting point. 
     
     
         10 . The plurality of hot melt pressure sensitive adhesive pellets according to  claim 1 , wherein the pellets are manufactured by a co-extrusion process. 
     
     
         11 . A process to supply a melting device with a plurality of hot melt pressure sensitive adhesive pellets comprising:
 (a) preparing the plurality of hot melt pressure sensitive adhesive pellets of  claim 1 ; and   (b) transporting the pellets by a pressurized gas or by a vacuum feeder to a melting device.   
     
     
         12 . The A process according to  claim 11  whereby the pellets form a homogenous blend in the molten state. 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 . An article of manufacture comprising the plurality of hot melt pressure sensitive adhesive pellets of  claim 1 .