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Sprayable water-based adhesiveRelated Patent Categories: Stock Material Or Miscellaneous Articles, Structurally Defined Web Or Sheet (e.g., Overall Dimension, Etc.), Continuous And Nonuniform Or Irregular Surface On Layer Or Component (e.g., Roofing, Etc.), Particulate MatterSprayable water-based adhesive description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070224395, Sprayable water-based adhesive. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from U.S. Provisional Application No. 60/785,559, filed 24 Mar. 2006 and incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] This application relates to a sprayable water-based adhesive containing a plurality of barrier material-coated polymeric hollow microspheres, to its production and to its use. BACKGROUND OF THE INVENTION [0003] In the past, most commercially available contact adhesives have been solvent-based, i.e., adhesives containing one or more volatile organic solvents. "Contact adhesives" are adhesives which typically are applied to the surfaces of two substrates that are to be joined together and dried to form an adhesive coating layer on the substrate surfaces, with the adhesive coating layers then brought into contact with each other under pressure to form an immediate, durable bond. Such adhesives typically comprise an elastomeric polymer dissolved in solvent, perhaps in combination with certain other components. The elastomeric polymer provides the basis for forming an effective adhesive bond upon setting of the contact adhesive. [0004] It is usually desirable that the contact adhesive applied to the substrate surface quickly dries to form an adhesive film that is capable of providing sufficient bond strength shortly after the adhesive film layers are brought together under pressure such that the joined substrates are effectively held together and substantially resist separation during subsequent handling (e.g., after the contacting pressure is released). Fast drying (i.e., highly volatile) organic solvents have traditionally been used to formulate contact adhesives, particularly sprayable contact adhesives, since such solvents offer the advantage of short dry times, wherein the applied coating of adhesive is ready to be bonded to another coated substrate shortly after being applied so that assembly times for the bonded substrates and therefore production rates may be optimized. [0005] However, the use of organic solvent-based contact adhesives has come under increased scrutiny in recent years because of environmental and worker exposure concerns. In addition, many organic solvents are flammable. Due to the harm that at least certain organic solvents used in such adhesives may cause after being released into the atmosphere upon drying of the adhesive, regulations on these solvent-based contact adhesives have become stricter. Although in principle it is possible to control solvent losses and emissions through the installation of ventilation and recycling systems, such systems significantly add to the cost of employing such adhesives and in certain end-use applications (such as the construction industry) it is simply not practical to do so. As a result, there has been an increasing interest in developing alternative adhesives that avoid the use of volatile organic solvents altogether. Water-based contact adhesives represent one type of adhesive that can in principle be substituted for the traditional solvent-based contact adhesives and to date have typically been formulated to include a latex or emulsion of an elastomeric polymer in water. Polychloroprene is an example of a suitable elastomeric polymer for such formulations, as described in more detail in Gerlach, "Polychloroprene--An Evergreen Product for the Formulation of Water Based Contact Adhesives", Advances in Adhesives & Sealants Technology, Paper 14, 1994; and U.S. Pat. Nos. 6,086,997 and 6,440,259 (each of which is incorporated herein by reference in its entirety). [0006] However, the water-based contact adhesives developed to date have typically suffered from a number of deficiencies as compared to the conventional organic solvent-based contact adhesives. For example, the solvent-based contact adhesives have good storage and shelf stability, whereas the water-based contact adhesives have a tendency to coagulate over time. Such coagulation substantially interferes with the ease with which the adhesive can be applied to a substrate surface, especially by spraying. Although stabilizers (such as emulsifying agents) are commonly used to increase the stability of the elastomeric polymer emulsion, the water-based contact adhesives still tend to have a relatively short shelf life, particularly at elevated temperatures. Also, the water-based contact adhesives are more difficult to apply to substrate surfaces by spraying than the solvent-based contact adhesives, as the spray pattern observed is generally far inferior. The use of water as a contact adhesive carrier instead of an organic solvent additionally tends to greatly decrease both the drying rate and the degree of tack attained in the dried adhesive film. Such deficiencies have made it difficult for water-based contact adhesives to fully replace solvent-based contact adhesives, even though significant environmental, health and safety advantages could thereby be achieved. Further improvements in water-based contact adhesive formulations are therefore highly desired by the adhesive industry as well as the end users of such adhesives. [0007] U.S. Pat. No. 5,264,467 discloses aqueous high performance contact adhesives containing an adhesive polymer emulsion and thermoplastic hollow microspheres. The adhesive polymer can be a vinyl acetate-ethylene, acrylic, styrene-acrylic, styrene butadiene or neoprene polymer. However, there is no teaching or suggestion that microspheres having an outer coating of a barrier material could be utilized. In addition, U.S. Pat. No. 5,264,467 does not mention that such contact adhesives could be applied by spraying or could be provided in sprayable form within a pressurized container. BRIEF SUMMARY OF THE INVENTION [0008] It has now been surprisingly discovered that the incorporation of hollow polymeric microspheres having outer surfaces coated with at least one barrier material (such as finely divided calcium carbonate particles) into a water-based adhesive composition comprising an aqueous emulsion of at least one elastomeric adhesive polymer (e.g., a chloroprene polymer) provides significant benefits as compared to analogous formulations that do not contain such coated microspheres. In particular, the storage stability/shelf life, drying rate and tack are all improved. For example, contactability of the adhesive film during the bonding phase is enhanced. Additionally, the presence of the coated microspheres unexpectedly causes the spray pattern of the water-based adhesive to widen and soften, thereby making the adhesive much easier to apply in a satisfactory manner to a substrate surface by spraying. Another surprising effect of the coated microspheres is that the bonding attributes of a water-based contact adhesive are preserved or even enhanced at loadings of up to at least about 5 percent by weight of the coated microspheres, even though the density of the adhesive is significantly reduced. The coated microspheres preferably do not contain significant amounts of free volatile organic compounds and thus do not compromise the recognized environmental and worker exposure advantages of water-based contact adhesives. DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION [0009] The following are among the advantages provided by at least certain embodiments of the adhesives of the present invention: [0010] Density reduction [0011] Reduction in applied cost [0012] Increased storage stability (maintenance of homogeneity) [0013] Gap filling properties [0014] High build [0015] Enhanced application properties [0016] Sound deadening [0017] Reduced thermal transfer [0018] Increased modular strength [0019] Reduced bonding pressures Continue reading about Sprayable water-based adhesive... Full patent description for Sprayable water-based adhesive Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Sprayable water-based adhesive patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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