Seal-coated plastic container for dispensing a pressurized product

Abstract

A seal coated plastic container for dispensing a pressurized product such as an aerosol or pressurized liquid, gel, or foam. The seal coating is applied to the exterior surface of the plastic container and effectively inhibits migration of non-liquefiable gas propellants and oxygen through the walls of the container. The plastic bottle is composed of a gas permeable polymeric material such as a polyolefin, polyester, or nylon or polycarbonate, and the seal coating is composed of at least one layer of a barrier material which has a low permeability to the non-liquefiable gas used as the propellant, i.e. the seal coating exhibits a high resistance to the passage of the non-liquefiable gas therethrough. The preferred polymeric material for the plastic bottle is polyethylene terephthalate, and the preferred seal coating is an epoxy-amine. The seal coating provides a coating of the barrier material that is about 0.005 to about 0.025 mm thick, but yet can greatly extend the shelf life of pressurized products such as an aerosol.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to containers for dispensing pressurized products such as aerosols, and more particularly to a seal coated plastic container for dispensing a pressurized product such as an aerosol that effectively inhibits migration of carbon dioxide or similar propellants through the walls of the container. [0002] The term “pressurized products” or “pressurized compositions” will be understood herein to encompass both aerosols, literally, as well as other liquid or flowable products that can be dispensed from pressurized containers in a manner comparable to aerosolized products and, unless a narrower meaning is clearly imposed by the context, “aerosol” herein shall be understood to include such other forms of “pressurized products.” Such pressurized products include but are not limited to foamed or gel preparations or to liquid products delivered in a non-aerosol stream. Typical examples of such pressurized products are insecticides,...

AI Technical Summary

Benefits of technology

[0006] The present invention is directed toward a seal coated plastic bottle or container for dispensing a pressurized product such as an aerosol. The seal coating is applied to the exterior surface of the plastic bottle and effectively inhibits migration of carbon dioxide and other non-liquefiable propellant gasses through the walls from the interior to the exterior of the bottle. The seal coating also effectively inhibits migration of oxygen in the surrounding atmosphere through the walls into the bottle, which could affect the product if the product is oxygen sensitive. Thus, the plastic bottle is comprised of a relatively gas permeable polymeric material such as a polyolefin, a polyester, polyvinylchloride (PVC), copolymer PVC, a nylon, or a polycarbonate, and the seal coating disposed on the exterior surface of the bottle comprises at least one layer of a barrier material which has no or at least a low permeability to non-liquefiable gasses such as carbon dioxide and oxygen, i.e. the seal coating exhibits a high resistance to the passage therethrough of carbon dioxide or other non-liquefiable gas being used as a propellant or of oxygen. “Relatively gas permeable” materials are defined herein as materials that are permeable to carbon dioxide to at least about the same extent as are polyolefins such as polyethylene (PE) or polypropylene (PP), as polyvinylchloride (PVC) or copolymer PVC, or as polyesters such as polyethylene terephthalate (PET), nylons and polycarbonates. The preferred polymeric material for the plastic bottle is polyethylene terephthalate, and the preferred seal coating is an epoxy-amine, although other coatings, such as saran-based coatings, are also possible. Although the seal coating provides only about a thin coating of the barrier material, coating thicknesses ranging from 0.005 to 0.025 mm can greatly extend the shelf life of pressurized products such as an aerosol.

[0008] The principal advantage of plastic bottles or containers utilizing a seal coating in accordance with the present invention is the overall reduction in the migration of carbon dioxide or other non-liquefiable propellant gas through the container walls which results in a major increase in shelf life of the product. To achieve this advantage, however, it is not necessary that the entire surface area of the bottle be coated with the barrier material, and significant reductions in the loss of carbon dioxide propellant may be achieved with only about 50% or less of the bottle's outer surface covered by the seal coating. Coating the entire outer surface of the plastic bottle is most advantageous, but under some circumstances, coating only a portion of the outer surface area is advantageous in that the coating process may be simplified and may be more economic to manufacture if the seal coating is applied only onto areas of the bottle that are relatively easy to coat, such as the sidewalls of the bottle. Thus, sufficient reduction in carbon dioxide and / or oxygen migration may result with both total as well as partial coatings, depending upon the pressurized product being contained as well as the desired shelf life for the product.

[0009] In one particularly preferred embodiment, the present invention is directed toward a pressure resistant plastic bottle for containing and dispensing a pressurized product, such as an aerosol composition, wherein the plastic bottle is seal coated with the barrier material. In this embodiment, the plastic bottle is comprised of a hollow elongate body having a longitudinal axis and an outer wall. The outer wall is seal coated with a carbon dioxide barrier material over at least 50% of its exterior surface area, and defines a central portion, a top portion and an opposite bottom portion. The central portion has a circular cross-sectional configuration taken through a plane perpendicular to the longitudinal axis and has an inwardly projecting concave configuration extending along its longitudinal direction. Preferably, the central portion of the bottle has a hyperboloid configuration. The bottom portion of the elongate body is integral with the central portion and defines an outwardly projecting convexly shaped configuration extending along a direction transverse to said longitudinal axis. Preferably, the convexly shaped configuration comprises a base portion having a spherical end configuration and a side portion having a spherical segment configuration. The seal coating effectively reduces the migration of carbon dioxide and / or oxygen through the walls of the bottle to yield a major increase in the shelf life of the pressurized product. In addition, the seal coating protects the bottle and its contents from ultraviolet (UV) light degradation. Also, the design of the central portion and bottom portion of the plastic bottle effectively resists the internal pressures generated by an aerosol to minimize any deformation. Further, any deformation that may occur results in a substantially uniform change which can be accommodated by the top portion of the plastic bottle.

Problems solved by technology

Despite the desirability of using plastic containers, there are some disadvantages to utilizing plastic materials to contain pressurized products.

In other words, gasses such as carbon dioxide utilized as a propellant in pressurized products can migrate through the polymeric materials at an unacceptable rate thus substantially reducing the shelf life of the product.

This especially is a problem with propellant gasses that are not liquid at common room temperatures and typical aerosol pressures (referred to herein as “non-liquefiable” gasses).

However, when a propellant is a gas that is non-liquid at those temperatures and pressures, only the container's original charge of pressurized gas is available for use, with no reservoir to restore pressure after product is discharged, except perhaps for such small amounts of gas as may be dissolved in any remaining product.

As a result of the gas permeability problem, polymeric materials such as polyolefins, polyesters, nylons and polycarbonates have in the past had limited use for packaging of pressurized products that may be subjected to extended storage.

While such barrier coatings have been moderately successful in the beverage industry in connection with soft drinks and beer, such coatings have not heretofore been utilized in connection with dispensers for pressurized products such as aerosols which are generally delivered from a pressurized container through a valve and actuator at higher pressures than soft drinks and / or beer and require significantly longer shelf life.

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