Coating compositions containing a silane additive and structures coated therewith

#This invention relates to plastic films and containers, such as beverage containers, that include a barrier coating to reduce gas permeation therethrough, and more particularly to top coat materials for enhancing the performance properties of the barrier coating.

#Plastic containers comprise a large and growing segment of the food and beverage industry. Plastic containers offer a number of advantages over traditional metal and glass containers. They are lightweight, inexpensive, non-breakable, transparent, and easily manufactured and handled. Plastic containers have, however, at least one significant drawback that has limited their universal acceptance, especially in the more demanding food applications. That drawback is that all plastic containers are more or less permeable to water, oxygen, carbon dioxide, and other gases and vapors. In a number of applications, the permeation rates of affordable plastics are great enough to significantly limit the shelf life of the contained food or beverage, or prevent the use of plastic containers altogether.

#Plastic bottles have been constructed from various polymers, predominantly PET, for non-carbonated and particularly for carbonated beverages. All of these polymers, however, exhibit various degrees of permeability to gases and vapors, which have limited the shelf life of the beverages contained within them. For example, carbonated beverage bottles have a shelf life that is limited by loss of CO2. (Shelf life is typically defined as the time needed for a loss of seventeen percent of the initial carbonation of a beverage.) For non-carbonated beverages, similar limitations apply due to oxygen and/or water vapor diffusion. Diffusion means both ingress and egress (diffusion and infusion) to and from the bottle or container. It would be desirable to have a container with improved gas barrier properties.

#FIG. 1 is an elevation view of a packaged beverage including a container coated with a gas or vapor barrier top coat in accordance with an embodiment of this invention.

#FIG. 2 is a partial sectional view of the container in FIG. 1 illustrating the multilayer structure of the container.

#A coated, multilayer structure is provided which comprises a polymeric base layer, an inorganic oxide gas barrier layer on the surface of the polymeric base layer, and an improved top coat on the inorganic oxide gas barrier layer. The top coat comprises an organic compound capable of reducing the permeability of the multilayer structure to gas or vapor and a silane additive which crosslinks the organic compound with the inorganic oxide gas barrier layer, thereby providing a top coat with enhanced adhesion to the inorganic oxide layer and improved water resistance. The top coat is particularly suitable for blocking ingress or egress of oxygen and carbon dioxide through polymeric packaging containers.

#Composition for Forming the Top Coat

#The coating compositions used for forming the top coat layer described herein is preferably is provided as a solution or emulsion containing (i) an organic compound that provides a gas and vapor barrier, and (ii) a silane additive dispersed/dissolved therein which serves as a cross-linking agent and adhesion promoter. The solution or emulsion, which is preferably aqueous-based, must be capable of forming a continuous film upon drying. In a particularly preferred embodiment, the aqueous solution or emulsion is free of both volatile organic solvents and halogenated compounds.