A METHOD FOR PACKAGING A PRODUCT FOR STERILIZATION AND A STERILIZED PACKAGE MANUFACTURED BY THE METHOD

Abstract: The invention relates to a method for packaging a product for sterilization effected by irradiation and a sterilized package, wherein the product (1) is enclosed in a substantially gas impermeable package (2). The invention is characterized in that the product (1) is placed in the package (2), the package is deaerated and filled with a protective gas, whereafter the package is sealed for sterilization by irradiation.

Description: A method for packaging a product for sterilization and a sterilized package manufactured by the method The invention relates to a method for packaging a product for sterilization effected by irradiation, wherein the product is enclosed in a substantially gas impermeable package. The invention also relates to a sterilized package manufactured by the method. Sterile packages, such as packages for hospital equipment, are often bag-like, airproof, or air per¬ meable but bacterium impermeable packages in which the equipment to be packaged is placed before the packages are sealed. Sterilization is effected by irradiating the package by ionizing radiation, such as gamma radiation, ultraviolet light or by some other means. The products to be packaged may be surgical textiles, surgical instruments, various tubes, syringes, cannulae, etc. The problem with packages of this type is that when opened, they give off a strong odour. Radiation causes the oxygen within the package to be converted into ozone, which reacts with the molecular chain of the product, which is usually plastic-based, to form bad- smelling compounds, such as acetic acid and butanal. Moreover, an oxidizing environment reduces the mechan- ical strength of the plastic products placed in the packages. This problem has been discussed e.g. in European Patent No. 218 003. The package disclosed in this reference comprises a deoxidizer, such as activated iron oxide, for the elimination of odour. The solution requires, however, a two-layer package: a breathing inner layer and a tight outer layer, between which the deoxidizing - and thus deodorizing - agent is posi¬ tioned. The disadvantages of such a package are that it is complicated and that iron oxide must be separately added thereto. The object of the present invention is to provide such a method for sterilizing a package, and a sterilized package manufactured by the method, by means of which the product can be easily and securely packaged for sterilization, and in which the problem of odour caused by radiation in the corresponding known products has been minimized. To achieve this, the method accord¬ ing to the invention is characterized in that the product is placed in the package, the package is de- aerated and filled with a protective gas, whereafter the package is sealed for sterilization by irradiation. The invention has the advantages that, in addi¬ tion to being odourless, the package is uncomplicated, and the different steps of manufacture can be rapidly taken. The same nozzle can be used both for removing air and for adding a protective gas. The package may be a simple plastic package, wherefore it is also inexpens¬ ive. The other preferred embodiments of the method according to the invention and the package according to the invention are characterized by what is disclosed in the appended claims. In the following, the invention will be described in greater detail with reference to the accompanying drawings, in which Figures 1 to 4 show the package of the inven¬ tion during the different steps of manufacture, Figures 5 to 8 show gas chromatograms of the contents of packages according to the invention and those of reference packages. A sterile package according to the invention, containing a product (e.g. a surgical gown) to be sterilized, is manufactured by disposing a product 1 in a plastic package 2 (Figure 1 ), whereafter the package is deaerated e.g. by a vacuum pump (not shown) through a hose 3 (Figure 2). A protective gas, such as nitrogen or carbon dioxide, is then added to the package 2 (Figure 3) . The package is sealed and sterilized by gamma radiation (Figure 4), whereafter it is ready for use. Practical experiments have shown that when the packaging method of the invention is used, the unpleas¬ ant odour which a package sterilized by irradiation emits when opened almost completely disappears. Table 1 shows results based on sensory evalua¬ tion of odour (scale from 0 to 3 ) . Sample A is a gamma sterilized package without a protective gas, sample B is a corresponding package where the protective gas is nitrogen, and sample C is a corresponding package where the protective gas is carbon dioxide. As appears from the table, most of the assessors 1-7 sense that the odour of sample A is strong (average ca 1.8), whereas the odour of samples B and C is typically hardly dis¬ cernible (average ca 1 ) . In samples B and C the oxygen TABLE 1 content of the packages was below 1%, in sample A it was the normal oxygen content of air (21%). Depending e.g. on the size of the product to be sterilized, a suitable oxygen content in the package is estimated to be 0.5 to 5%. The reason for the lack of odour or the con¬ siderable decrease in it has been studied at the University of JyvSskylS by gas chromatography and mass spectrometer measurements (Figures 5 to 8) . Figure 5 shows a gas chromatogram of a package which contains air and which has not been irradiated. It can be seen that various compounds are present only in relatively low contents. Figure 6 shows the effect of irradiation when the package containing air (cf. Figure 5) is irradiated by gamma radiation. From the gas chromatogram it can be seen that, in addition to the increase in the amount of the compounds already present, two new compounds are formed in considerable amounts. These compounds are butanal and acetic acid, which are both known to have a very strong odour. Butanal and acetic acid are probably formed as a result of the reactions of ozone with the plastic materials in the package due to gamma radiation. Reactive ozone reacts with plastic polymers, causing oxidation reactions, whereby bad-smelling com- pounds, for example, are produced. Figures 7 and 8 show gas chromatograms of cor¬ responding packages which have first been deaerated in accordance with the invention and then filled with a protective gas: nitrogen (Figure 7) or carbon dioxide (Figure 8) . It can be seen that the butanal and acetic acid peaks have disappeared completely or almost com¬ pletely. Thus it seems that the sensed lack of odour or the considerable decrease in it is a result of the fact that in packages filled with a protective gas there are hardly any signs of two compounds with a strong odour - butanal and acetic acid - which are present in an irradiated package containing air (Figure 6). In addi¬ tion to the above-mentioned protective gases, it is also possible to use other gases for the same purpose. On account of the insignificant formation of ozone or the lack of it during irradiation (cf. EP 218 003), which is due to the low content of oxygen, the pungent odour emitted by known packages (sample A in table I) has been eliminated in the packages manu- factured according to the invention (samples B and C in table I). It will be clear to one skilled in the art that the different embodiments of the invention are not restricted to the examples described above but can be modified within the scope of the appended claims.

Claims: Claims 1. A method for packaging a product for steril¬ ization effected by irradiation, wherein the product (1) is enclosed in a substantially gas impermeable package (2), c h a r a c t e r i z e d in that the product (1) is placed in the package (2), the package is deaerated and filled with a protective gas, whereafter the package is sealed for sterilization by irradiation. 2. A method according to claim 1, c h a r a c ¬ t e r i z e d in that the protective gas is nitrogen. 3. A method according to claim 1, c h a r a c ¬ t e r i z e d in that the protective gas is carbon dioxide. 4. A method according to claim 1, 2 or 3, c h a r a c t e r i z e d in that the package is de¬ aerated in such a manner that the amount of residual oxygen does not exceed 1% of the amount of gas contained in the package after the addition of the protective gas. 5. A substantially gas impermeable package (2) sterilized by irradiation, c h a r a c t e r i z e d in that it comprises a package containing a product (1), the package (2) being substantially deaerated and filled with a protective gas for sterilization by irradiation. 6. A package according to claim 4, c h a r ¬ a c t e r i z e d in that the protective gas contained in the package is nitrogen. 7. A package according to claim 4, c h a r ¬ a c t e r i z e d in that the protective gas contained in the package is carbon dioxide.

Inventors: HIMOTTU MARJA, KARHAPAEAE ESA, MYKKAENEN ANNE, PIRKKANEN JOUKO, HIMOTTU, MARJA, KARHAPAEAE, ESA, MYKKAENEN, ANNE, PIRKKANEN, JOUKO
Applicants: HIMOTTU MARJA, KARHAPAEAE ESA, KOLMI SET OY, MYKKAENEN ANNE, PIRKKANEN JOUKO, HIMOTTU, MARJA, KARHAPAEAE, ESA, KOLMI-SET OY, MYKKAENEN, ANNE, PIRKKANEN, JOUKO
Application year: 1993
Main classification: B65B55
IPC codes: B65B55