GB2179002A - Package structure - Google Patents

Abstract

A package structure for holding an article in a rust-proof manner, the package structure comprising a composite sheet comprising a core sheet e.g. aluminium, in the center, a first layer of polyolefin resin containing a vaporisable anti-rust substance, and a second layer having air-barrier properties; wherein the composite sheet is folded with the first layer facing inwards, and wherein the periphery of the folded composite sheet is thermally sealed with an article contained therein.

Description

SPECIFICATION Package structure The present invention relates to a package structure for storing an article in a rust-proof manner, and has been particularly developed for packaging and sealing cutting blades such as razor blades and blades for surgical instruments such as scalpels.

Surgical scalpel blades are generally made of carbon steel, and normally they are individually wrapped in rust-preventing paper, which is available as a water-proof wrapper. Several sealed blades are jointly packaged in a plastics film. Aluminum foil is sometimes used as a packaging material. Every precaution is taken to prevent moisture from corroding the blades.

Nevertheless it is very difficult to avoid the problem of corrosion with articles such as scalpel blades, which require a high degree of moisture exclusion. This is partly due to the carbon steel construction of the blade. As mentioned above metal foil such as aluminum foil may be used to provide an air-tight package, but the problems cannot be completely solved in this way. Therefore extra processes are required to secure the rust-preventing packaging. This leads to time and labor-consuming packaging operations, thereby resulting in increased production costs.

A proposal has been made for avoiding such problems, according to which a rust-preventing film containing a vaporisable anti-rust agent is used. However a new problem has arisen in that the agent is decomposed when a germ-killing treatment is applied to the packaged article thermally or by radiation e.g. with gamma rays. As a result of such decomposition an unexpected gas is generated which tends to corrode the articles in the packages. For example when the agent contains ethylene vinylacetate, acetic acid is generated and corrodes the article contained in the package. In addition the plastic constituent of the packaging material may be decomposed so as to generate acetic acid.

According to the present invention there is provided a package structure for storing an article in a rust-proof manner, the package structure comprising: a composite sheet comprising a core sheet in the center, a first layer comprising or coated with polyolefin resin containing a gasifiable anti-rust substance and a second layer comprising or coated with anti-oxidizing substance; wherein the composite sheet is folded with the first layer facing inwards, and wherein the periphery of the folded composite sheet is sealed with an article contained therein.

The invention also provides a packaging material for storing an article in a rust-proof manner, the material comprising: a composite sheet comprising a core sheet in the center; a first layer coated with polyolefin resin containing a gasifiable anti-rust substance and a second layer coated with anti-oxidizing substance; and wherein the composite sheet is foldable with the first layer facing inwards.

Embodiments of the invention will now be described by way of example with reference to the drawings, in which: Figure I is a vertical cross-section through a composite sheet used in carrying out the present invention; Figure 2 is a perspective view showing a package structure embodying the present invention; Figure 3 is a perspective view showing a modification to the package structure shown in Figure 2; Figures 4 to 6 inclusive show an example of a scalpel for surgical use; and Figures 7 and 8 inclusive are diagrammatic views showing a method of conducting an experiment.

As shown in Figure 1 a packaging composite sheet 4 comprises a first layer 2 and a second layer 3 with a core layer 1 interposed therebetween, the layer 1 being an aluminum foil having a thickness of 40 microns. The layers 1, 2 and 3 are securely bonded together. The layer 2 is a film having a thickness of 3 microns, which is made of a mixture of polyethylene resin, which contains 3% by weight of dicyclohexyl aminonitrite, and ethylene ionomer resin. The layer 3 is a film coated with or comprising nitrocellulose resin. The layer 2 is intended for anti-rust and thermal sealing, and the layer 3 has anti-oxidizing properties. As shown in Figure 2 the sheet 4 is folded so as to accommodate an article 5, such as a scalpel blade, therein.In this case the layer 2 faces inwards, that is, towards the article 5, and the open edges of the folded sheet 4 are thermally sealed as shown in Figure 2. Alternatively, all the periphery can be thermally sealed as shown in Figure 3.

The sealed unit is indicated by the reference numeral 7, hereinafter referred to as the package. The package 7 is subjected to sterilizing treatment by the use of cobalt-60 rays. Experiments have demonstrated that the sealing strength is not affected by the gamma rays.

Figures 4 to 6 show a surgical scalpel having replacement blades which may be packaged according to the invention.

A surgical scalpel 101 has a shank 102 and a disposable blade 103. The shank includes grooves 104 at its tip portion for releasably fixing the blade 103 to the shank. The sides of a slot 106 in the blade 103 are slid into the grooves 104 while the blade is transversely resiliently bent, the wider opening 105 permitting the sliding movement to be started and accommodating the rear part of the tip portion when the blade has been fully slid into position. The blade is removed by the reverse series of operations i.e. bending its rear portion upwards and sliding it out of the grooves 104.

To ascertain the effect of rust prevention using the present invention the experiment shown in Figure 7 and 8 was conducted: The package 7a comprises a film 11 of polyester resin having a thickness of 50 micron, the film having a coating layer 12 of polyethylene resin to a thickness of 15 micron. The film 11 was further coated with polyolefin emulsion to a thickness of 3 micron, the coating film being indicated by the reference numeral 1 3a. Another package 7b was similar to package 7a but film 1 3a was replaced by film 1 3b which was made of polyolefin emulsion containing 1.0% by weight of dicyclohexyl aminonitrite. Each wrapped package was 50 mm x 70 mm, and the width of the thermal seal was 10 mm.The two wrapped packages 7a and 7b were half immersed in a 3% sodium chloride solution in a container 10 as shown in Figure 8, the solution being heated to 40"C. The changes were observed, and the results are shown in Table 1: TABLE I 1st Week 2nd Week 3rd Week 4th Week wrapped package 7a tip overall",, - wrapped package 7b - - - no change Corrosion occurred in the tip portion alone of the blade.

Corrosion occurred on all surfaces of the blade.

For the vaporisable substances mentioned above, the known substances can be used; for example, dicyclohexyl aminonitrite, cyclohexyl aminocarbonate, amylamino benzoate, diisopropyl amino nitrite, methylcyclohexyl aminocarbonate or octadecyl amine.

For the thermal sealing plastics ethylene ionomers or ethylene ionomers or polypropylene can be used. The ratios of the first-mentioned substance to the second-mentioned substance are in the range of 99.9-to-0.1 to 90.0-to-10.0. The thicknesses of the first layer and the second layer are in the range of 1 to 20 microns. If the amount of the anti-rust substance exceeds 10% by weight the thermal sealing ability is reduced. For the metal foil, aluminum foil is preferably used.

As is evident from the foregoing description, the package structure described ensures that no change occurs in the packaging material even under heat or radiation treatment, such as germ-killing treatment by radiation, is applied thereto. The package structure ensures that the article wrapped therein is kept safe from moisture over a long period of time. The confined vaporisable agent effectively vaporizes in the package, thereby protecting the article against becoming rusty. The outer (second) layer is effective to prevent air from entering the package. The necessity of wrapping each article by hand has been avoided thereby leading to labor-saving packing performance, and the surgical blades can be safely packaged, thereby making it possible to export them over a long distance and to humid areas.

Claims (4)

1. A package structure for storing an article in a rust-proof manner, the package structure comprising: a composite sheet comprising a core sheet in the center, a first layer coated with polyolefin resin containing a vaporisable anti-rust substance and a second layer coated with anti-oxidizing substance; wherein the composite sheet is folded with the first layer facing inwards; and wherein the periphery of the folded composite sheet is thermally sealed with an article contained therein.

2. A packaging material for storing an article in a rust-proof manner, the material comprising: a composite sheet comprising a core sheet in the center; a first layer coated with polyolefin resin containing a vaporisable anti-rust substance and a second layer coated with anti-oxidizing substance; and wherein the composite sheet is foldable with the first layer facing inwards.

3. A structure according to claim 1, which contains a surgical blade.

4. A structure according to claim 1, substantially as described with reference to Figures 1 and 2 or 3 of the drawings.