Development of a disinfecting CO2 cleaning process for safety shoes from hygiene demanding areas with regard to protective properties of personal protective equipment (PPE)
IGF 15910 N
In many industrial branches, including food stuffs, pharmaceutical and cosmetic industry, hygiene demands are increasing. Personal protective equipment (PPE) includes textiles but also footwear, which has to be cleaned and disinfected, respectively. Classical, water-based cleaning methods cause serious damages to the footwear or do not yield in adequate disinfection. Analysis showed remarkable hygiene deficits due to lack of processing possibilities. With the implementation of European food hygiene regulations and directives in national legislation, e.g. through the Ordinance of Food Hygiene in Germany, the HACCP concept as well as demands on personal hygiene and work wear including footwear have become legally binding. The main focus of this research project was the maintenance of protective and safety functions against mechanical forces and a development of a disinfecting cleaning process for safety shoes with liquid CO2. The advantages of liquid CO2 are, that it is not toxic and there is no need for drying after reprocessing. The processing of the shoes and shoe components was performed in a 4-bath-cleaning-procedure in a pilot plant. The cleaning of materials in liquid CO2 was investigated with several different additives. After a fixed maximum of 25 reprocessing cycles some materials e.g. a few leathers did not fulfil the safety requirements according to DIN EN ISO 20344 ff. Breaking, loss of tensile strength or partially decrease of breathability were the most detected deficits. However, some leathers and artificial leathers were not altered due to the CO2-process and fulfilled the safety-requirements also after reprocessing. These materials could be used e.g. for PPE-shoes. Several toe-caps consisting of steel or aluminium showed moderate corrosion but still guaranteed the safety parameters. Plastic toe-caps fulfilled all safety requirements. As well, additional relevant materials like for example some lining materials showed no or very low impairment due to liquid CO2-treatment. The application of dirt absorber materials and spherical brushes improved the cleaning effect of even and low textured materials enormously. Upper material has been soiled with fatty, carbohydrate-containing and proteinaceous soils. Fatty and carbohydrate-containing soils could be cleaned with the help of dirt absorber and spherical brushes which were included for improving the mechanical forces. The cleaning of blood was not satisfying. In order to assess the disinfecting action, test items were contaminated with relevant microorganisms (bacteria, yeasts and moulds), either directly or mixed with the above-mentioned soiling. Inactivation of microbes in liquid CO2 depends upon the species, the time of action, and the effect of certain additives. Particularly in the presence of blood, reduction of the population of certain microorganisms was found to be especially difficult. The rate of germ reduction could be increased by the use of various additives. Hence it is possible to develop a shoe which still shows the essentially safety requirements after hygienic cleaning in liquid CO2. A catalogue of requirements for the production of protective and safety footwear has been developed.
The IGF-project 15910 N of the research association Europäische Forschungsgemeinschaft Reinigungs- und Hygienetechnologie e.V., Campus Fichtenhain 11, D-47807 Krefeld, was supported via the AiF within the funding programme „Industrielle Gemeinschaftsforschung und –entwicklung (IGF)“ by the Federal Ministry of Economic Affairs and Technology (BMWi) due to a decision of the German Parliament.
The research report is available on request from FRT.