Field of the Invention

The present invention relates to the field of containers, generally, and specifically

to waste, storage and shipping containers designed to reduce the risk of fire More particularly, the invention relates to waste disposal, storage, and shipping containers, or liners therefor, made at least in part of a material that shrinks upon exposure to heat, forming a barrier that deprives the fire of oxygen and extinguishes the fire inside of the

container

Background

According to the National Fire Protection Association, millions of dollars and

many lives are lost each year to fires that originate in waste containers in high rise office

buildings, hotels, and family dwellings, alone A cigarette, a match, a smoldering cloth, or another ignition source dropped into a waste container or accidentally dropped on or into a storage container may ignite the contents of the container and result in a raging, highly

destructive fire O S H A has issued regulations under which all containers in factories must be provided with either a cover or a device which will extinguish a blaze

Unfortunately, the O S H A regulations do not extend to all buildings, and the products that have been developed to date for factories have not adequately reduced the risk of fire

One of the proposed solutions has been to provide waste containers with a lid or cover that automatically closes the container upon exposure to fire. The lid or cover

theoretically should deprive the fire of oxygen and thereby extinguish the fire. However, the devices used to date either do not adequately shut off the supply of oxygen to the fire

or are relatively complicated in construction and/or expensive to use.

A relatively uncomplicated and inexpensive container or liner that would

effectively cut off the supply of oxygen to a fire contained within the container would be very desirable. Summary of the Invention

The present invention provides a container at least in part made of shrink wrap

material defining an enclosed area having a first diameter. The container is configured

so that, when a potential fire source is in the enclosed area, the shrink wrap material

shrinks to a second, smaller diameter, reducing oxygen supply to the potential fire

source.

Detailed Description of the Invention

Shrink wrap film or packaging is a film made of thermoplastic polymers that shrinks in a biaxial mode between about 20-60%, even up to about 65%, when exposed to

sufficient heat. Typically, the film is folded and the product to be sealed is inserted The

film then is heat-sealed around the edges. The product, loosely wrapped by the film, is

exposed to hot air so that the film shrinks around the product Shrink wrap films currently

are used to provide sanitary packaging for various food products and to provide an air tight seal for packaging electronic components, such as PC cards and chips.

Substantially any material that shrinks but otherwise maintains substantial integrity upon exposure to heat should function in the present invention, and the invention is not limited to the shrink wrap materials that are currently known. Currently known shrink

wrap materials are polyvinyl chloride, polyolefins and copolyolefins, primarily containing

polyethylene, polypropylene, or mixtures thereof, and copolymers of said polyolefins with

ethylene vinyl acetate (EVA), such as low density polyethylene (LDPE)/EVA copolymers

and/or LLDPE/EVA copolymers. Shrink wrap films are non-toxic at ambient temperatures. When heated or burned, shrink wrap films are no more toxic than existing plastic/polymer bags. Currently, shrink

wrap films are produced in film thicknesses of 60-165 gage; however, shrink wrap

material having a greater or lesser thickness would be useful in the present invention. All

properties of shrink wrap material (e.g., activation temperature, shrink rate, shrink force, thermal capacitance, infrared thermal emissivity, etc.) can be tailored for a specific product application using methods known to persons of ordinary skill in the art.

Substantially any shrink wrap material will function in the present invention.

Typical shrink wrap materials are made of polyvinyl chloride or polyolefins, such as

polypropylene, polyethylene, etc. Suitable shrink wrap materials are available from numerous commercial sources and include, but are not necessarily limited to: CLYSAR,

which is available from E. I DuPont de NeMours Int'l SA, DuPont Packaging and

industrial Polymers, Wilmington DE; CRYOVAC, available from W.R. Grace & Co., P. O. Box 464, Duncan, SC 29334; FILM SOTERM C-3, available from Tantraco Enterprise PTE, Ltd., Block 5071, Ang Mo Kio Industrial Park, #04156, Singapore, China 2056;

shrink film available from Huntsman Chemical, 3575 Forest Lake Drive, Uniontown, Ohio

44685; and, electronic shrink wrap bags made of polyvinyl chloride, available from

National Bag Company, Inc., 2233 Old Mill Road, Hudson, Ohio 44236. A variety of shrink wrap film products, which currently are designed to provide sanitary packaging for

food products or to provide an air tight seal for packaging electronic components, are

available from National Bag Company, Inc., and Traco Mfg., Inc., 443 S. Commerce

Road, Orem, Utah. A preferred shrink wrap material is the electronic shrink wrap bag

material available from National Bag Company, Inc. (polyvinyl chloride).

In one embodiment of the present invention, shrink wrap material is applied around the top portion, and only the top portion, of a typical inflammable waste container

liner When a fire occurs in the lower portion of the bag and progresses, the fire cannot

burn through the lower portion of the bag. As the exiting heat/flame passes by the shrink

wrap material section at the top of the bag, the shrink wrap material shrinks, thereby effectively closing off the top portion of the bag to an air/oxygen supply which results in

smothering the fire.

In another embodiment, the shrink wrap material is incorporated into a multi-

layered container in which each layer is custom tailored to provide desired shrink vs. temperature vs. time performance The entire waste or storage container also could be

fabricated of a thick version of shrink wrap material to produce a passive/active fire

protection system.

In still another embodiment, the shrink wrap material could be configured as a more permanent waste container liner. This more permanent waste container liner could be placed inside of a waste container, and then a regular plastic waste container liner could

be placed inside of the permanent liner. If a fire occurred, the fire would quickly burn

through the regular liner, thereby exposing the more permanent shrink wrap liner to

thermal insult. The shrink wrap liner then would forcibly collapse around the fire

source and passively extinguish the fire by depriving it if air/oxygen. The regular

plastic waste container would be changed regularly. The shrink wrap bag could be

changed once a month, or as frequently as necessary depending upon the circumstances

of use. This embodiment would add an extra degree of safety without substantially

disrupting normal custodial procedures.

The shrink characteristics of the shrink wrap material can be optimized using

known procedures. Basically, where the container is a waste/trash container, the typical

waste/trash combustion properties should be determined. This would include a

determination of the radiant and convective heat flux produced by combustion with

respect to various distances from the source of fire. A cylindrical coordinate system

would be used to map the various thermal insults. Of particular importance is the

temperature vs. vertical distance from the fire source at various radii from the central

axis. Based on the foregoing thermal characterization, the transient heat conduction

characteristics of a proposed waste/trash can at a specific thickness/diameter and of

various axial heights would be determined. Also, the thermal emissivity of the inside

surface (i.e. , the surface facing the fire source) should be modified to increase the

radiant thermal absorption to an appropriate level. A five dimensional array of these

parameters should be defined to identify the optimal thickness and height of the

proposed trash/waste can which will shrink to an adequate percentage to close off the

oxygen supply to the fire source. Based on the above information, it should be

determined whether the polymer material at the specified thickness will ignite/burn as a function of exposure time. If it will not ignite/burn, then the thickness can continue to

be increased until its thermal mass capacitance is too great to properly shrink to a point

that it restricts the oxygen supply to the fire source. This process will not only

optimize the SWF trash/waste can to function properly, but will introduce a factor of

added safety to avoid premature burn through. If the material does not fulfill the

thermal requirements in its virgin form, chemical additives can be used to enhance or

retard the thermal response and to custom tailor the materials to the specific

application. In most cases, a fast response at relatively low temperatures (i.e. , early

event temperatures achieved as the fire source builds to its maximum level)

accompanied by a high shrink rate will be desirable.

Shrink wrap material would be useful to manufacture containers that are used to

ship and store flammable materials. The parameters of the container can be custom

tailored to fit the particular material being shipped and the particular size and shape of the container.

Alternately, shrink wrap material could be used to reduce or terminate the flow of

fluid through a piping system. The pipe, or section of pipe, could be configured such that-

-upon internal or external exposure to a predetermined thermal level (i.e., at an upper thermal threshold), the pipe would forcibly shrink/collapse to reduce or stop the flow of the fluid, thereby protecting the piping system from thermal damage and/or limiting the

flow of a hot fluid/gas in compliance with a chemical process. Knowing the system into

which the invention was to be incorporated, persons of ordinary skill in the art could

calculate the appropriate thermal level at which the pipe should shrink or collaps, and could tailor the shrink characteristics of the pipe accordingly using known procedures

(described generally above). This concept could be extended to a passive/active thermomechanical fluid switch which activates by itself or on another device which stops

fluid flow.

Example 1

At least fifteen electronic shrink wrap bags made of polyvinyl chloride having a

thickness of 80 gage and a size of one square foot were obtained from National Bag

Company, Inc The bags were used to line a simulated waste can. Waste paper was

placed inside of the bags, and a burning piece of waste paper was tossed into the bag.

This procedure was repeated fifteen times using fifteen bags. Each time, when the burning

piece of waste paper was tossed into the bag, the bag collapsed and smothered the fire.

Persons of ordinary skill in the art will appreciate that many modifications may

be made to the embodiments described herein without departing from the spirit of the

present invention. Accordingly, the embodiments described herein are illustrative only

and are not intended to limit the scope of the present invention.