Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Reexamination Certificate
2000-09-12
2002-12-17
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
C428S035100, C428S412000, C428S423100, C428S424200, C428S424800, C427S372200, C427S385500, C427S393500, C427S524000, C427S507000, C427S531000, C427S525000, C427S123000, C427S455000
Reexamination Certificate
active
06495224
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to functionally enhanced shrink-wrap coverings and structures made therefrom with improved resistance to harsh conditions, such as environmental, chemical, physical, radioactive and thermal exposure. Specifically, the present invention relates to functionally enhanced shrink-wrap materials having protective coatings used to protect a wide range of consumer, industrial and military articles in addition to articles made entirely from shrink-wrap materials such as temporary buildings and structures.
BACKGROUND OF THE INVENTION
The constant exposure to naturally occurring and man-made sources of environmental stress ultimately leads to the decay and eventual decomposition of nearly any substance. The material's physical and chemical properties and the nature of the environmental stress will determine the length of the decay process. For example, silicate structures such as the Great Sphinx in the Valley of the Kings has withstood centuries of extreme environmental exposure. Yet, this seemingly impermeable structure of stone has decayed significantly from its original grandeur. Furthermore, the delicate materials used to fashion the Sphinx's ornate decorative facade have long since been destroyed by the sun, wind, rain and temperature extremes of the Upper Nile Valley.
Modern man-made devices and machines such as aircraft, boats, military and civilian vehicles, and consumer products including electronics (articles), just to name a few, are made from diverse materials having a wide range of durability. Moreover, the widely varying types of environmental exposure these devices must endure can adversely affect even the most robust materials. For example, delicate aircraft fuselages and other airframe structural components are often shipped from a manufacturing plant to an assembly facility thousands of miles away. In route to the assembly facility these delicate aircraft parts may be exposed to the freezing rains and snow of the North Western United States, the scorching heat and sandstorms of the Mojave Desert followed by the pelting briny spray, extreme heat and tortuous winds of the Pacific Ocean. In addition to surviving these dramatic environmental extremes, this valuable shipment of vulnerable aircraft parts must also withstand the abuse of countless freight handlers, deck hands and longshoreman. Therefore, it is essential that this precious cargo be protected from such sustained abuse in order to assure its safe arrival at the final destination.
One of the most successful techniques designed to protect precious cargo from the environmental damage and physical abuses associated with shipping and storage has been the development of shrink-wrapping. Shrink-wrapping, in general, is a process by which an article is first enclosed in a sealed plastic material that then heated causing the shrink-wrap, or shrink-film, to contract forming a tight fitting covering over the article. The shrink-wrap itself can be constructed of numerous materials and in a variety of ways. Shrink-wraps can be single or multi-layered and they may be reinforced with either metallic or non-metallic fabrics. However, regardless of the material used, it is the external surface of the shrink-wrap that must withstand the brunt of environmental exposure. Once this outer covering is damaged, the integrity of the article encapsulated therein is compromised.
One of the most daunting challenges facing the protective covering industry has been to produce a shrink-wrap material or system capable of withstanding long-term exposure to environmental and physical stress. When presently available shrink-wrap materials are properly applied, a protective covering sufficient to last approximately two years under most conditions can be achieved. However, if the shrink-wrap is exposed to environmental extremes such as wind, extreme heat and cold, moisture, or intense UV radiation, this two-year period may be significantly shortened. Moreover, other factors such as chemical contamination, biological agents, radiation, pollutants, physical stress and structural deformation can exacerbate environmental factors leading to an even more rapid decay process.
Consequently, once the shrink-wrap covering is damaged, the article must be either be removed from the original shrink-wrap and a new shrink-wrap covering applied, or another shrink-wrap covering must be applied over the damaged one. In either case, the application of a new shrink-wrap covering significantly increases the cost associated with long-term storage. Furthermore, if the original covering must be removed prior to applying a new one, there is an increased potential of damaging the protected item. Efforts have been made to increase the durability and life span of currently available shrink-wrap materials.
Moderate increases in the durability and life span of shrink-wrap materials can be achieved by modifying the base formula of the shrink-wrap material itself. For example, solar exposure induced brittleness of the shrink-wrap covering can be minimized by the addition of ultraviolet (UV) light absorbing compounds and UV light and heat reflecting pigments. Ethylene vinyl acetate can be added to increase the shrink-wrap's flexibility thus preventing cracking and tearing in low temperature environments. Dyes can be added to the base formula providing the shrink-wrap with additional resistance to UV exposure and radiation. However, these additives have not significantly increased the useful life of shrink-wrap materials beyond two years.
One modification to the base formula that has improved the durability of shrink-wrap material in some applications is the addition of carbon black. Carbon black is a highly toxic form of elemental carbon that is used to increase the hardness of rubber and other polymers. When added to the base formula of shrink-wrap materials the final product has an increased resistance to chemical attack and UV radiation. However, the addition of carbon black results in a shrink-wrap covering that absorbs and retains tremendous amounts of heat. If exposed to the sun for any significant period, the interior of the shrink-wrapped article can reach temperatures high enough to melt plastic and destroy delicate electrons including microprocessors. Consequently, carbon black has extremely limited usefulness in the formulation of shrink-wrap materials.
Another approach to increasing the durability of shrink-wraps involves various types of covering applied to the shrank surfaces. The most basic covering is a protective tarp draped over the article and secured against the shrink-wrap surface. However, this approach has met with limited success, and in some cases has proved detrimental accelerating the shrink-wrap's decay. Tarps which are merely placed over the shrank surface do not provide significant protection from humidity, airborne pollutants or chemical aerosols. Furthermore, the tarps will often continually shift during transport abrading the shrink-wrap's surface causing the shrink-wrap material to tear and pull away from the article it was designed to protect. Therefore, coverings such as tarps, which are not integrated into the shrink-wrap material itself, lack versatility and do not significantly extend the shrink-wrap's useful life.
Another approach to providing protective coverings to commercial shrink-film would be to apply conventional resin based paints. However, the application of these coatings is fraught with difficulties and would require extensive pretreatment of the shrink-wrap surface to ensure adherence of the topcoat. If the topcoat is applied to an untreated surface they may, peel and blister shortly after application affording little or no protection to the shrunken surface. Therefore, it would be necessary to pre-treat the surface of the plastic shrink-wrap to enhance its receptiveness to conventional coating compounds such as paint.
Generally, there are two categories of plastic surface pretreatment techniques: physical treatments and chemical methods. Physical
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