Main group 2 : Preservatives

In-can preservatives are biocidal-products used for the preservation of manufactured products, other than foodstuff or feedingstuff, in containers by the control of microbial deterioration to ensure their shelf life. In-can preservatives are used in virtually all water-based non-food products. In-can preservatives for medicine, toys, cosmetics and human hygiene products are not included, as these products are covered by other directives. The product type can based on application areas be organised into four application areas:

In-can preservatives for paints

In-can preservatives are generally used for preservation of all types of water-based paints.

In-can preservatives for inks, fountain water, adhesives and sealants

In-can preservatives are used in water-based inks, fountain water for offset printing, and water-based sealants and adhesives.

In-can preservatives for cleaning materials

In can preservatives are added to virtually all water containing cleaning materials except cleaning materials with a very high or low pH or cleaning materials which are preserved by the content of disinfectants (see Main Group 1).

In-can preservatives for other products

In-can preservatives are used for a large number of other product types, among others:

• Dyes and textile processing fluids
• Maintenance products (polishes, wax emulsions, car maintenance agents, etc.)
• Photographic process fluids
• Additives to concrete
• Lubricants and machine oils
• Water bed fluids
• Industrial fluids (e.g. enzyme solutions)

Film preservatives are used for the preservation of films or coatings by the control of microbial deterioration in order to protect the initial properties of the surface of materials or objects such as paint, plastic, sealants, adhesives, paper and art works. The product type can be organised into three subtypes:

Film preservatives for paints

Film preservatives are generally used for preservation of most types of topcoat paints used for outdoor applications by the control of microbial (mainly fungal) deterioration of the paint film. Biocides used in priming wood-care products, for which the main function is a protection of the wood against microbial deterioration, are included in product type 8: 'Wood preservatives'.

Film preservatives for plastics

Plastic products are in general not preserved against microbial degradation, but biocides may be added to plastics containing plasticisers to prevent microbial growth at the surface. During use of the plastic product, the plasticiser will diffuse to the surface and in moist environment, the plasticiser will be attached by micro-organisms, especially fungi, which use the plasticiser as carbon source. In some flooring products, the biocide is added for antiseptic reasons to prevent growth of undesirable bacteria at the surface. Plasticisers and other degradable additives may be added to different plastics, but soft PVC seems to account for the main part of preserved plastic.

Film preservatives for sealants, fillers and other products

Film preservatives may also be used in sealant, fillers, glues and adhesives. Fungicides are added as film preservatives to sealants and fillers for application in wet rooms. Film preservatives are in general not added to glues and adhesives. In some instances, however, they are added to prevent mould growth.

The product type includes products used for the preservation of wood or wood products by the control of wood-destroying or wood-disfiguring organisms. The product type includes both preventive and curative products. Treatment of wood before the sawmill stage is not covered by the Biocides Directive. The product type can be organised into two subtypes: vacuum preservatives and pressure preservatives, and preservatives for surface treatment. The first subtype includes preservatives used in industrial processes, whereas preservatives for surface treatment are used mainly by craftsmen and private persons. The product type does not include biocides for preservation of paints, where the effect of the biocide is to preserve the paint itself. These are included in product type 6 'In-can preservatives' and product type 7 'Film preservatives'. It should be noted that the term ‘wood preservatives’ is often used as synonym of all ‘wood-care products’. In this context, ‘wood preservatives’ only cover wood-care products for priming.

Vacuum preservatives and pressure preservatives

Pressure preservatives are used for wood for exterior use with a high risk of degradation, i.e. wood in contact with water or soil.

Preservatives for surface treatment

Preservatives for surface treatment are used for protection of wood constructions, which are only exposed to moistness at the surface and dry easily. The biocides used and the application areas are in many ways the same as for vacuum treatment, but surface application is cheaper and more suitable for larger constructions. The preservatives are most often used as primers and covered by one or more layers of wood grain fillers and topcoats. In-can preservatives and film preservatives in wood grain fillers and topcoats are included in product types 6 and 7. The methods of surface treatment can be divided into:

• Immersion of the wood products into preservative baths
• Application by machinery
• Brush painting
• Spray painting.

The group includes products used for the preservation of fibrous or polymerised materials, such as leather, rubber, paper and textiles by the control of microbiological deterioration of the material itself. The product type can be organised into the following subtypes:

Preservatives for textiles

Biocides may be used for preservation of textiles during storage, transport and use of the textiles. Liquids used during the production of the textiles (e.g. for sizing and finishing) and inks used for textile printing may also be preserved by biocides. The purpose of the use of these biocides is, however, to preserve the processing fluids or inks and not the finished textiles, and these agents are included in product type 6: In-can preservatives. The main application of preservatives for textiles is for preservation of textiles for outdoor applications. Preserved textiles are used for tents, tarpaulins, awnings, sunblinds, parasols, sails, waterproof clothing, etc. For in-door applications only shower curtains and in some instances mattress ticking are preserved. Most of the textiles are made of synthetic materials like acrylic, polyester and PVC or is coated with PVC. The boundary between this subtype and the subtype 'Film preservatives for plastics' is not clear-cut. For example bathroom curtains and tarpaulins are mainly made from reinforced soft PVC, whereas the function of the biocides is to prevent microbial growth on the surface. Clothing, especially for sport, may be preserved with biocides to prevent odour producing microbial growth on the sweat. One example is the use of tributyltin in some t-shirts.

Preservatives for leather

Biocides are applied to leather during the tanning process for life-time preservation of the leather.

Preservatives for rubber and other polymerised materials

Preservatives may be used for rubber products for two reasons:

• Preservation of liquid latex raw materials
• Preservation of the finished rubber products

Liquid latex is preserved for control of microbial growth in the liquid before polymerisation of the latex. The preservatives used for this application may instead be considered ‘In-can preservatives’. Rubber products are in general not explicitly preserved against microbial degradation, but many of the chemicals used for manufacturing of rubber products may, however, have a biocidal effect as well.

Preservatives for insulating materials of organic fibre

Insulating materials of organic fibre materials like paper, cellulose, wool and flax (Linum) contain preservatives for control of microbial degradation of the fibres during use. The preservatives are mixed up with the fibre materials before the insulation material is blown into the walls of the houses or placed above the ceiling. The used agents have both a biocidal effect and a flame retarding effect.

Preservatives for paper (exclusive insulating materials) and other fibre materials

‘Paper and other materials’ include:

• Paper and cardboard (other than insulating materials)
• Art and archaeological artefacts

Biocides used for prevention of slime formation during production of paper and cardboards are included in product type 12: 'Slimicides'. Besides these preservatives may be used during the production process to control microbial growth in the wet paper, if it is stored before drying. Paper for applications where the paper can be exposed to moisture may be preserved. One example of use of preservatives for paper is preservation of library books that have been stored under moist conditions.

Products of this product type are used for the preservation of water or other liquids used in cooling, heating or processing systems by the control of harmful organisms such as microbes, algae and mussels. District heating systems are neither liquid-cooling systems nor processing systems, but are included here, as they do not fit into any other product type. The product type does not include slimicides (product type 12) and products used for the disinfection of drinking water (product type 5), drinking water drain work (product type 4), preservation of metalworking-fluids (product type 13) and moisteners used in the printing process (product type 6). Biocides are applied to the systems either to preserve the liquids (control of micro-organisms) or to disinfect the systems (kill the micro-organisms). Biocides used for preservation of the liquid cooling system or air-conditioning systems are included here although the biocides in semi-open systems may serve as both preservatives and disinfectants. Microbial growth in the systems leads to biofilm mediated corrosion, and the formation of biofilms increases the heat exchange resistance of the systems. The liquid systems can be organised into three types:

• Once-through cooling systems
• Open recirculation systems
• Closed recirculation systems

Once-through systems can be used when plenty of cheap cool water is available and adequate facilities for disposal of warm water are available. Once-through cooling systems may be used for power plants and industrial installations. Open recirculation systems are mainly used for cooling water in the food-processing and pharmaceutical industry and in large air-conditioning systems. The water in these systems is cooled down in open cooling towers. In these systems, the biocides are applied by shock dosage at a frequency of usually once or twice a week. The water in the semi-open systems is changed continuously, and the average residence time of the water may be down to a few hours. Closed systems include first of all district heating systems, but also liquid systems of air-conditioning systems. The biocides are added continuously. Open processing systems are used for pressure founding and wash of semi-manufactures and tolls. Microbial growth may as well be a problem in these systems, but the use of biocides for control of the growth in these systems is not as widespread as in the food-processing and pharmaceutical industry. In air-conditioning systems with open recirculating cooling water, the biocides may as well be applied for control of pathogenic bacteria; especially some species of Legionella. Some of the applied biocides are particularly efficient in the control of these organisms and are often used in air-conditioning systems of hospitals. The bacteria in the cooling water may be released with aerosols from the cooling towers and expose patients via e.g. windows. The content of Legionella in the cooling water is not a hospital specific phenomenon, but patients may be more liable to infection than the main population.

Slimicides are used for the prevention or control of slime growth on materials, equipment and structures used in industrial processes. The product type can be organised into two subtypes:

Slimicides for wood and paper pulp

Slimicides are added to paper pulp to prevent the formation of slime during the pulping process by biocidal control of bacteria in the pulp. The slime formation may also be controlled by other agents as enzymes.

Slimicides used by oil extraction and fuel storage

Biocides are used at oil extraction for three purposes:

• Control of slime forming micro-organisms in water-based drilling mud during storage (when necessary)
• Control of hydrogen sulphide formation by sulphate reducing bacteria by oil extraction
• Control of microbial growth and hydrogen sulphide formation in oil pipe-lines

The biocides are added to flows pumped into the reservoir (drilling processes, injection and reinjection water) and to the transportation flow of produced oil and gas before transportation by either pipeline or tanker to shore. During storage of fuels, especially diesel and fuel oil, slime formation by micro-organisms may take place if water finds it ways into the tanks. Beside this, biocides may be used in antifouling paint for oilrigs.