Protective Covers

Field of the Invention

This invention relates to degradable protective covers. More particularly, but not exclusively, it relates to degradeable covers for short life consumer products such as cell phones, pagers, I pods, two way radios and metal kegs for transportation and storage of liquid food products and other materials.

Background to the Invention

Portable communication devices such as two way radios, transmitter and cell phones are rapidly becoming a disposable item. Whilst the internal electronic components have high durability, the facilities provided to the users are changing continuously thus encouraging for continuous upgrades in the services offered by the cell phone. Moreover, there is a demographic section of the cell phone users who demand a continuous change in the physical appearance of the cell phone housing. This is predominantly a cosmetic effect to match clothing accessories or to be attuned to the current promotional culture. There is a need which already exists to provide replace cell phone housing or cell phone covers in various cosmetic designs. These covers are currently produced by injection molding with conventional petroleum based thermoplastic compounds and then decorated with a surface finish, the surface finish being applied as an insert in the injection molding process or post the molding operation. Because of the nature of the molding operations and complexity of the shape, the cell phone housings are relatively thick.

Further, the coated cell phone housing cannot be easily recycled and are typically disposed of via incineration or landfill.

There are numerous other short life products which could benefit from a sacrificial protective cover to minimize abrasion and impact damage. For example, two way radios, pagers etc used on construction sites or by the military in the field often are exposed to have mechanical abuse which subsequently leads to mechanical damage of the housing and failure of the internal electrical components. The ability to have a thin disposable protective cover for these units will both increase the durability.

Similarly, liquid refreshments such as beer, wine and fruit concentrates, cooking oils etc are typically transported in the retail trade in metal or wooden kegs or drums having a capacity from 25 litres to around 250 litres. The liquid medium being introduced into the keg through a bung hole that is then sealed with a metal screw threaded closure. There is considerable concern, especially for food products, that during transport the container could be opened and foreign materials introduced. Metal and plastic "tamper proof outer caps are often used to protect against this problem. The geometry of the parts is fairly complex to provide the fitting and removal requirements which results in complex and expensive manufacturing processes. Also, when removed the closure provides a waste disposal problem which is environmentally undesirable as a metal closure must be disposed of.

US patent specifications 5,176,279, 4,784,296, 4,779,750, Design 327,849 and Design 311 ,868 describe a variety of geometries for keg cap design but make no reference to the nature of the materials used in construction or disposal of the cap after use.

Summary of the Invention

The present invention is formed articles that can act as a protective cover for the required service life and then rapidly degrades or can be recycled after the intended life use.

The products have sufficient durability and strength to withstand normal wear during the expected life cycle of the product during use and then rapidly degrade with no adverse impact on the environment. A further embodiment of the invention is where the protective cover is biodegradable.

The nature of the protective cover is that it is of lower mass than the current housing construction, offering additional weight and hence cost savings.

A further embodiment of the present invention is for a protective cover for mobile electrical devices such as portable communication devices, cell phones, disc players, I pods, calculators etc which protect the device from excessive scratching or mechanical damage but do not inhibit the function of the device during use. The protective cover can easily be attached to the device, usually by friction fit of mechanical clip lugs, and easily removed for disposal.

A further embodiment of the present invention is for tamper proof protective cap for drums that can be used to mechanically protect the bung from unauthorised access. The cap cannot be removed without obviously visual indication that unauthorised access has been attempted. However, when required, the cap is easily removed and biodegrades with no adverse impact on the environment.

A preferred embodiment of the present invention relates to a thermoformed article that can act as a protective cover for the required service life and then rapidly degrade after the intended life use. The nature of the protective cover is that it is lower mass than the current housing construction, offering additional weight and hence cost savings against current molded products. The preferable average thickness of the cover is less than 1m, more preferably less than 0.5mm and most preferably less than 0.25mm.

In one embodiment of the invention, the protective cover is produced from a thermoplastic polymeric system which is degradable.

More preferably the cover is degradable by exposure to sunlight, solar heating or both. The composition of the cover is preferably a polyolefin base which can degrade through an oxidative mechanism initiated by heat or UV radiation. More preferably the polyolefin system is based on polypropylene homopolymer or copolymer containing a metal catalyst additive that promotes the degradation process after some acceptable time delay. Typical metal catalysts are those that have two stable oxidative states. More preferably the metals are selected from iron, chromium, cobalt and titanium. Most preferably the metal is an iron salt such as iron stearate or an iron thioester, dithioester, thioether or dithioether.

Most preferably the cover is biodegradable. Whilst not being exclusive these can include polylactic acid, polyglycolic acid, polycaprolactone, polyalkylene carbonates, polyhydroxyalkanoates, polyvinyl alcohol, natural or chemically modified starches, soy proteins, tall oil and/or wood resins, tall oil and/or wood esters, tall oil and/or wood resin derivatives, urea

formaldehyde resins, melamine formaldehyde resins, alkyd resins, polymerized vegetable oils, polyurethanes derived from soy and other vegetable based polyols, polyurethanes derived from castor oil based derivatives, synthetic aliphatic and aromatic copolysters compromising monomers selected from 1 , 4 butane diol, 1 ,3 propane diol, ethylene glycol, adipic acid, succinic acid, succinic anhydride, terephthalic acid, lactic acid, colophony, natural rubber, gum arabic, cellulose acetate, cellulose butyrate, cellulose proprionate.

The covers can be produced by single layer extrusion, multilayer coextrusion or multilayer lamination of a flat sheet 1.5mm to 0.25mm thick which can be converted into the desired shape by a thermoforming and/or stamping operation.

In one preferred embodiment of the present invention a cap is formed for use as a tamper proof protective cover for kegs used in the transportation of liquid products.

In another embodiment of the invention the keg cap is heat crimped into position around the bung hole providing a mechanical fit which cannot be removed without damage to the keg cap. The crimped cap is easily removed by tearing to provide access to the bung hole but cannot be reused.

In another embodiment of the present invention the protective cover is for use with portable electronic equipment such as radio transmitters, telephones, cell phones, I pods, CD players, calculators etc. The cover provides both protection from mechanical damage e.g. abrasion and impact but also provides the ability to encase the object in a more decorative pattern cover.

The decorative pattern can be applied to the protective cover before, during or after the forming process. More preferable for injection of compression molding the decorative finish is applied as a film which is inserted into the mold prior to the molding operation.

More preferably for thermoforming operations the sheet is preprinted prior to the thermoforming operation and may consist of a multiple laminate sheet of which one of the layers provides the outer decorative or abrasion resistant layer.

Brief Description Of The Drawings

Figure 1 is an embodiment of a cover according to an aspect of the present invention suitable for use with a small electrical appliance; and

Figure 2 is an embodiment of a keg seal according to an aspect of the present invention.

A cover 100 comprises a sheet 102 formed of a plurality of layers 104a-c of thermoformed polymeric material. The sheet 102 is typically 0.25mm to 1.5mm thick.

The layers 104a-c are formed into the sheet 102, typically by co-extrusion or lamination, prior to thermoforming the sheet 102 into the configuration of the cover 100.

An upper layer 104a of the sheet 102 will typically exhibit a high abrasion resistance in excess of that of the other layers 104b,c or the external casing of the appliance around which the cover is arranged to fit.

One of the lower layers 104b,c incorporates an decorative pattern or design 105 so as to improve the aesthetic appeal of the cover 100 to a user of a mobile telephone to which the cover 100 is attached.

In the present embodiment the cover 100 is dimensioned so as to fit closely over the mobile telephone 106 and to engage with the external casing of the telephone 106 such that a friction fit is achieved. The cover 100 may be arranged to snap fit over the mobile telephone. Alternatively, there may be complimentary projections and recesses on the cover 100 and telephone 106 to retain the cover 100 in place.

In one embodiment the cover 100 is typically made from a polyolefin polymer that is impregnated with particles of a transition metal catalyst 108. The catalyst is typically either a compound of, or elemental iron, titanium, cobalt, chromium.

The catalyst 108 acts to initiate the degradation of the cover 100 in ultraviolet light, for example in sunlight. The amount of catalyst can be varied in order to tailor the expected lifetime of the cover 100 to correspond to the expected lifetime of the consumer item to which it is applied, in the present example the mobile telephone 106.

In a second embodiment the cover 100 is biodegradeable and will degrade over time. A suitable material can be chosen such that the expected lifetime of the cover 100 corresponds to the expected lifetime of the consumer item to which it is applied, in the present example the mobile telephone 106.

In the present embodiment the cover 100 is shown as a mobile phone cover. However, it will be appreciated that the present invention is not to be limited to mobile telephone covers but any suitable electronic device, for example a PDA, an iPOD™, a portable compact disc player or a calculator may benefit from such a cover.

It will be further appreciated that the material of the cover is not limited to polyolefin polymers, either with or without transition metal particles, but is intended to encompass any suitable degradable material as exemplified in the lists hereinbefore.

Although shown as a multilayer sheet the sheet 102 may comprise a single layer extrusion.

Referring now to Figure 2, a keg seal 200 comprises a sheet 202 formed of a plurality of layers 204a-c of thermoformed polymeric material. Typically, the layers 204a-c are formed into the sheet 202, typically by co- extrusion or lamination.

The sheet 202 is placed over an outlet 206, typically a bung hole or a siphon outlet, of a keg 208 and crimped into over the outlet 206 using a conventional crimping tool (not shown). The sheet 202 is thermoformed over the outlet 206 to provide a keg cap. The keg cap formed from the sheet 202 engages with the outlet 206 such that the keg cap is readily removed by tearing the sheet 202. The requirement to tear the sheet 202 in order to remove the keg cap gives a ready indication of whether the keg cap has been tampered with.