Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1997-03-14
2001-05-01
Lund, Jeffrie R (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230AN, C118S718000, C118S719000, C118S729000
Reexamination Certificate
active
06223683
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to pressurized plastic containers that have enhanced barrier performance and methods to provide said containers and to the coatings. The enhanced barrier performance is obtained by application of inorganic coatings to the external surface of the container. The coatings exhibit enhanced adhesion relative to prior art coatings.
DESCRIPTION OF THE BACKGROUND ART
Plastic containers currently 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, nonbreakable, transparent and easily manufactured and handled. However, plastic containers have 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. Shelf-life is the time needed for a loss of seventeen percent of the initial carbonation of a beverage.
It has been recognized for some time that a container structure that combines the best features of plastic containers and more traditional containers could be obtained by applying a glass-like or metal-like layer to a plastic container, and metallized plastic containers. For example, metallized potato chip bags have been commercially available for some time. However, in a number of applications, the clarity of the package is of significant importance, and for those applications metallized coatings are not acceptable. obtaining durable glass-like coatings on plastic containers without changing the appearance of the container has proven to be much more difficult.
A number of processes have been developed for the purpose of applying glass-like coatings onto plastic films, where the films are then subsequently formed into flexible plastic containers. However, relatively few processes have been developed that allow the application of a glass-like coating onto a preformed, relatively rigid plastic container such as the PET bottles commonly used in the U.S. for carbonated beverages, and heretofore no process has been developed that allows the application of a glass-like coating onto the external surface of a plastic container that is sufficiently durable to withstand the effect of pressurization of the container, retain an enhanced barrier to gases and vapors subsequent to said pressurization, and not affect the recyclability of the containers. Pressurized beverage containers currently comprise a very large market world-wide, and currently affordable plastics have sufficiently high permeation rates to limit the use of plastic containers in a number of the markets served.
Such pressurized containers include plastic bottles for both carbonated and non-carbonated beverages. Plastic bottles have been constructed from various polymers, predominant among them being polyethylene terephthalate (PET), particularly for carbonated beverages, but all of these polymers have exhibited various degrees of permeability to gases and vapors which have limited the shelf life of the beverages placed within them. For example, carbonated beverage bottles have a shelf-life which is limited by loss of CO
2
. While this limitation becomes increasingly important as the size of the bottle is reduced, because of the increasing surface to volume ratio, small containers are needed for many market applications, and this severely limits the use of plastic bottles in such cases. Generally, based upon this surface to volume ratio, as a bottle becomes smaller, carbonation retention in the beverage becomes more difficult.
For non-carbonated beverages, similar limitations apply, again with increasing importance as the bottle size is reduced, on account of oxygen and/or water-vapor diffusion. It should be appreciated that diffusion means both ingress and egress (diffusion and infusion) to and from the bottle or container. The degree of impermeability (described herein as “gas barrier”) to CO
2
diffusion and to the diffusion of oxygen, water vapor and other gases, grows in importance in conditions of high ambient temperature. An outer coating with high gas barrier can improve the quality of beverages packed in plastic bottles and increase the shelf life of such bottles, making small bottles feasible, and this in turn presents many advantages in reduced distribution costs and a more flexible marketing mix.
Some polymers, for example PET, are also susceptible to stress cracking when they come in contact with bottle-conveyor lubricants used in bottle filling plants, or detergents, solvents and other materials. Such cracking is often described as “environmental stress cracking” and can limit the life of the bottle by causing leaks and prevent damage to adjacent property. An impermeable outer surface for plastic bottles, and prevent damage to adjacent property which resists stress-cracking-inducing chemicals, will extend the shelf life of plastic bottles in some markets.
Another limitation to shelf life and beverage quality is often UV radiation which can affect the taste, color and other beverage properties. This is particularly important in conditions of prolonged sunshine. An outer coating with UV absorbing properties can improve the quality of such beverages and make plastic bottles much more useable under such conditions.
Additional functionality can be incorporated into the inorganic coating by incorporating visible light absorbing species, rendering the plastic container cosmetically more appealing.
An additional benefit of the present invention is ease of recycling. Prior art barrier enhancing coatings generally are organic in nature and are much thicker than the coating of the present invention. Consequently, when post-consumer scrap containing containers coated with prior art organic coatings are recycled, significant deterioration in the appearance and properties of the plastic occur. In contrast, because of the inert nature and thinness of the coatings of the present invention, the coated containers can be processed in any conventional recycling system without modification of the process.
Moreover, haziness in recycled articles can occur when large sized particles are used in a coating. However, such a haze is avoided in the present invention because relatively small particles are used as will be described. Moreover, the coating is acceptable for food contact and therefore will not adversely affect the recycling effort when ground or depolymorized in the recycling process.
Along the lines of recycling, the present invention provides for a method of recycling coated plastic which has results heretofore unattainable. In particular, separation of coated and uncoated plastics is unnecessary whereby modifications to existing recycling systems are unnecessary or whereby extra process steps (separating coated bottles from uncoated bottles) can be avoided. Moreover, it is possible to produce a transparent plastic from coated plastic while avoiding the above-noted problem of haziness in the final recycled product. While the present invention can be used in recycling many types of plastic, it is contemplated that this invention can be used with plastic articles, such as containers or bottles and more particularly, with plastic beverage bottles. Bottle-to-bottle recycling remains unaffected with the present invention.
Recycling in the instant invention can be carried out in both a chemical process and a physical process. The plastic subjected to recycling processes can be molded or extruded. Even if a coated plastic is initially introduced in the recycling process, the coating of the present invention will not interfere with the downstream injection molding or blow molding.
Finally, the cost of applying a coating to the outside
Ehrich Horst
Plester George
Rule Mark
Lund Jeffrie R
Sutherland Asbill & Brennan
The Coca-Cola Company
LandOfFree
Hollow plastic containers with an external very thin coating... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hollow plastic containers with an external very thin coating..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hollow plastic containers with an external very thin coating... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2572133