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.

1 - 29 . (canceled) 
     
     
         30 . A water-based adhesive composition comprising
 at least about 30 weight percent of water, based on the weight of the water-based adhesive composition;   an adhesive polymer comprising
 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, 
 wherein the adhesive polymer has a glass transition temperature that is less than about 0° C.; and 
   about 1 weight percent to about 3 weight percent of hollow, polymeric microspheres, based on the weight of the water-based adhesive composition, wherein the microspheres are coated with at least one barrier material.   
     
     
         31 . The water-based adhesive composition of  claim 30 , wherein the microspheres are coated with 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, or a mixture thereof. 
     
     
         32 . The water-based adhesive composition of  claim 30 , wherein the microspheres have a composite density of not greater than about 0.15 g/cm 3 , as measured including the outer coating. 
     
     
         33 . The water-based adhesive composition of  claim 30 , wherein the microspheres are thermally clad with the at least one barrier material. 
     
     
         34 . The water-based adhesive composition of  claim 30 , wherein the shells of the microspheres comprise at least one thermoplastic polymer. 
     
     
         35 . The water-based adhesive composition of  claim 30 , wherein the shells of the microspheres comprise a polymer that is a methyl methacrylate-acrylonitrile copolymer, a vinylidene chloride-acrylonitrile copolymer, or a vinylidene chloride-acrylonitrile-methyl methacrylate copolymer. 
     
     
         36 . The water-based adhesive composition of  claim 30 , wherein the microspheres are pre-expanded. 
     
     
         37 . The water-based adhesive composition of  claim 30 , wherein the adhesive polymer has a glass transition temperature that is less than about −20° C. 
     
     
         38 . The water-based adhesive composition of  claim 30 , further comprising at least one additive selected from the group consisting of an antioxidant, a defoamer, a wetting agent, a fungicide, a preservative, a biocide, a stabilizer, a tackifying resin, a filler, a processing oil, a corrosion inhibitor, a pigment, a plasticizer, an adhesion promoter, a viscosity modifier, an internal coagulant, a pH adjustment agent, a flame retardant, a rheology improver, or a mixture thereof. 
     
     
         39 . The water-based adhesive composition of  claim 30 , wherein the microspheres have an average diameter of about 20 microns to about 60 microns. 
     
     
         40 . The water-based adhesive composition of  claim 30 , wherein the water-based adhesive composition has a viscosity of less than about 300 Pa·s at a shear stress of 10 Pa. 
     
     
         41 . A process for bonding a first substrate to a second substrate comprising
 applying the water-based adhesive composition of  claim 30  on a surface of the first substrate;   drying, at least partially, the water-based adhesive composition to form an adhesive film layer on the surface of the first substrate; and   bonding the first substrate to the second substrate.   
     
     
         42 . The process of  claim 41 , wherein the bonding is by contacting the second substrate with the adhesive film layer on the surface of the first substrate. 
     
     
         43 . The process of  claim 41 , further comprising
 prior to the bonding step, applying the water-based adhesive composition of  claim 30  on a surface of the second substrate; and   drying, at least partially, the water-based adhesive composition to form an adhesive film layer on the surface of the second substrate;   wherein the bonding is by contacting the adhesive film layer on the surface of the second substrate with the adhesive film layer on the surface of the first substrate.   
     
     
         44 . The process of  claim 41 , wherein the application is by spraying. 
     
     
         45 . The process of  claim 42 , further comprising pressing the first and second substrates together. 
     
     
         46 . The process of  claim 42 , wherein the adhesive film layer is heated above ambient temperature prior to contacting the second substrate with the adhesive film layer on the surface of the first substrate. 
     
     
         47 . The process of  claim 41 , wherein the first and second substrates are plastic, wood, metal, rubber, glass, ceramic, paper, fabric, plasterboard, fiber, leather, concrete, rock, or sheet rock. 
     
     
         48 . The process of  claim 41 , wherein one or both of the first and second substrates are porous substrates. 
     
     
         49 . The process of  claim 44 , wherein the water-based adhesive composition is sprayed on the surface of the first substrate from a pressurized canister. 
     
     
         50 . An assembly produced according to the process of  claim 41 .