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.

Description

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, p...

AI Technical Summary

Benefits of technology

[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.

Problems solved by technology

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.

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.

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.

However, there is no teaching or suggestion that microspheres having an outer coating of a barrier material could be utilized.