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, perhaps ...

AI Technical Summary

Benefits of technology

The patent text describes a new discovery that adding hollow polymer microspheres coated with a barrier material like calcium carbonate to a water-based adhesive improves its stability, drying time, and tack. This makes it easier to apply to surfaces. The coated microspheres also cause the adhesive to spread wider and softer when sprayed. Surprisingly, the bonding properties of the adhesive are not negatively impacted when the microspheres are added in high quantities. This coated adhesive is also more stable and easier to use with no harmful chemicals.

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.