Sprayable water-based adhesive

Abstract

Water-based adhesive compositions are improved by the incorporation of hollow polymeric microspheres having outer surfaces coated with one or more barrier materials such as calcium carbonate particles. The adhesive compositions exhibit enhanced rheology, sprayability, drying time, tack and storage stability as compared to analogous adhesives that are not modified with coated hollow polymeric microspheres. Such compositions are useful as both contact adhesives as well as wet bonding one-way adhesives.

What is claimed is: 
     
         1 . An assembly comprising at least a first substrate and a second substrate, wherein said first substrate and said second substrate are joined by an adhesive layer obtained from a water- based adhesive composition comprising:
 a) an aqueous emulsion of at least one elastomeric adhesive polymer; and   b) hollow polymeric microspheres having outer surfaces coated with at least one barrier material.   
     
     
         2 . The assembly of  claim 1 , wherein said water-based adhesive composition is comprised of from about 0.2 to about 10 weight percent hollow polymeric microspheres. 
     
     
         3 . The assembly of  claim 1 , wherein said water-based adhesive composition is comprised of from about 0.5 to about 6 weight percent hollow polymeric microspheres. 
     
     
         4 . The assembly of  claim 1 , wherein said water-based adhesive composition is comprised of from about 1 to about 3 weight percent hollow polymeric microspheres. 
     
     
         5 . The assembly of  claim 1 , wherein said hollow polymeric microspheres have shells comprised of thermoplastic polymer. 
     
     
         6 . The assembly of  claim 1 , wherein said hollow polymeric microspheres are thermally clad with said at least one barrier material. 
     
     
         7 . The assembly of  claim 1 , wherein said hollow polymeric microspheres have a composite density of not greater than about 0.15 g/cm 3 , as measured including the outer coating. 
     
     
         8 . The assembly of  claim 1 , wherein said hollow polymeric microspheres have a density of not less than about 0.06 g/cm 3 , as measured including the outer coating. 
     
     
         9 . The assembly of  claim 1 , wherein said hollow polymeric microspheres have an outer coating comprised of finely divided particles of at least one barrier material selected from the group consisting of talc, calcium carbonate, barium sulfate, alumina, silica, carbon, titanium dioxide, zinc oxide, ceramic beads, quartz beads, glass beads, poly (tetrafluoroethylene) beads, glass fibers, cotton fibers, polyamide fibers, carbon fibers, ceramic fibers, and mixtures thereof. 
     
     
         10 . The assembly of  claim 1 , wherein said hollow polymeric microspheres are comprised of a polymeric shell and an outer coating comprised of a free-flowing solid barrier material having a softening or melting point at a temperature above that of the polymeric shell. 
     
     
         11 . The assembly of  claim 1 , wherein said hollow polymeric microspheres have an average particle size of from about 5 to about 500 microns. 
     
     
         12 . The assembly of  claim 1 , wherein said hollow polymeric microspheres are non-expandable. 
     
     
         13 . The assembly of  claim 1 ; wherein said hollow polymeric microspheres have shells comprised of a polymer selected from the group consisting of methyl methacrylate- acrylonitrile copolymers, vinylidene chloride-acrylonitrile copolymers and vinylidene chloride-acrylonitrile-methyl methacrylate copolymers. 
     
     
         14 . The assembly of  claim 1 , wherein said hollow polymeric microspheres are comprised of a polymer obtained by polymerization of one or more acrylic monomers, optionally in combination with one or more non-acrylic monomers. 
     
     
         15 . The assembly of  claim 1 , wherein said aqueous emulsion is comprised of at least one homopolymer or copolymer of chloroprene or a blend of at least one homopolymer or copolymer of chloroprene and at least one acrylic copolymer. 
     
     
         16 . The assembly of  claim 1 , wherein said water-based adhesive composition is additionally comprised of at least one additive selected from the group consisting of antioxidants, defoamers, wetting agents, fungicides, preservatives, biocides, stabilizers, tackifying resins, fillers, processing oils, corrosion inhibitors, pigments, plasticizers, adhesion promoters, viscosity modifiers, internal coagulants, pH adjustment agents, flame retardants, rheology improvers and mixtures thereof. 
     
     
         17 . A process for making the assembly of  claim 1 , said process comprising applying the water-based adhesive composition to a surface of said first substrate, applyingthe water-based adhesive composition to a surface of said second substrate, drying the adhesive composition that has been applied to said surfaces of said first substrate and said second substrate, contacting said surfaces of said first substrate and said second substrate having the adhesive composition in a dried state applied thereon to form said adhesive bond. 
     
     
         18 . The process of  claim 17  wherein said water-based adhesive composition is applied to said surfaces of said first substrate and said second substrate by spraying. 
     
     
         19 . The process of  claim 17  wherein said adhesive composition is initially contained in a pressurized canister and is transferred from the pressurized canister to said surfaces of said first substrate and said second substrate by spraying. 
     
     
         20 . An adhesive application system comprising a) a water-based adhesive comprising i) an aqueous emulsion of at least one elastomeric adhesive polymer and ii) hollow polymeric microspheres having outer surfaces coated with at least one barrier material, b) a propellant, c) a pressure container for containing said water-based adhesive and said propellant under pressure, and d) a valve system capable of regulating the flow of said water-based adhesive and said propellant out of said pressure container. 
     
     
         21 . A water-based adhesive comprising water and: 
       
         
           
                 
                 
               
                   Chloroprene Homopolymer(s) and/or Copolymer(s) 
                   25-40 wt.% 
                 
                   Antioxidant(s) 
                   0.5-5 wt.% 
                 
                   Acid Acceptor(s) 
                   0.5-5 wt.% 
                 
                   Plasticizer(s) 
                   1-6 wt % 
                 
                   Tackifier(s) 
                   10-20 wt.% 
                 
                   Pigment(s) 
                   0-1 wt.% 
                 
                   Barrier Material-Coated Microspheres 
                   0.5-6 wt.% 
                 
             
                
                
                
                
                
                
                
               
            
           
         
       
       . 
     
     
         22 . A water-based adhesive comprising water and: 
       
         
           
                 
                 
               
                   Polychloroprene 
                   30-35 wt.% 
                 
                   Antioxidant(s) 
                   1-3 wt.% 
                 
                   Acid Acceptor(s) 
                   1-3 wt.% 
                 
                   Plasticizer(s) 
                   2-4 wt % 
                 
                   Tackifier(s) 
                   12-18 wt.% 
                 
                   Pigment(s) 
                   0.01-0.5 wt.% 
                 
                   Calcium Carbonate-Coated Microspheres 
                   1-3 wt.% 
                 
             
                
                
                
                
                
                
                
               
            
           
         
       
       . 
     
     
         23 . A process for making the assembly of  claim 1 , said process comprising applying the water- based adhesive composition to a surface of said first substrate, drying the adhesive composition that has been applied to said surface of said first substrate, contacting said surface of said first substrate having the adhesive composition in a dried state applied thereon with a surface of said second substrate to form said adhesive bond. 
     
     
         24 . The process of  claim 23  wherein said water-based adhesive composition is applied to said surfaces of said first substrate by spraying. 
     
     
         25 . The process of  claim 23  wherein said adhesive composition is initially contained in a pressurized canister and is transferred from the pressurized canister to said surface of said first substrate by spraying. 
     
     
         26 . The process of  claim 23  wherein said first substrate is a porous substrate. 
     
     
         27 . The process of  claim 23  wherein said first substrate is a flexible open-cell foam. 
     
     
         28 . The process of  claim 23  wherein said water-based adhesive composition comprises a) an aqueous emulsion comprised of at least one chloroprene homopolymer or copolymer and at least one acrylic homopolymer or copolymer, b) hollow polymeric microspheres having outer surfaces coated with at least one barrier material, and c) at least one surfactant stabilizer. 
     
     
         29 . A water-based adhesive comprising water and: 
       
         
           
                 
                 
               
                   Chloroprene Homopolymer(s) and/or Copolymer(s) 
                   30-35 wt.% 
                 
                   Acrylic Homopolymer(s) and/or Copolymer(s) 
                   7.5-10 wt.% 
                 
                   Acid Acceptor(s) 
                   1-5 wt.% 
                 
                   Plasticizer(s) 
                   0.5-5 wt% 
                 
                   Defoamer(s) 
                   0.001-1 wt % 
                 
                   Surfacant Stabilizer(s) 
                   0.001-1 wt.% 
                 
                   Barrier Material-Coated Microspheres 
                   0.001-5 wt.% 
                 
             
                
                
                
                
                
                
                
               
            
           
         
       
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