In impregnating products
Impregnation of materials has been known for over a hundred years. The types of materials that are impregnated are textiles, leather, wood and other cellulose products. But also materials such as concrete can be impregnated. There are different reasons for the impregnation, one is to make the material water resistant or water repellent. Other reasons are to make the material flame proof or less susceptible to decay by rot or insects.
As there are several reasons for impregnation and also several different materials with different characteristics to be impregnated, there are a number of different aspects to take into account when performing the impregnation. Such are the type of compound for achieving the desired effect or how to avoid leaching of the compound. In order to make the impregnation compositions poisonous to rot fungi several compounds that also have been shown to have hazardous effects on the environment have been used.
These compounds can reach the environment in different ways. They can leach out in the water when clothing’s are washed. Compounds from impregnated wood can leach into the ground or water at heavy rain. The compositions containing these compounds have also been found in the soil at impregnation plants, especially plants for impregnation of wood. Due to the problems with forbidden impregnation compounds, such as creosote and arsenic, there is work going on to find compounds with the same effect but without being hazardous or that will alternatively bind firmly to the substrate of the product and not leak into the environment.
Except for poisonous compounds, other techniques have also been used since for long time for the protection of wood. It is well known to use resinous wood or slow grown wood as they are more resistant to deterioration than other types of wood. Another old way to make posts of fences resistant has been to burn the surface of the part of the post that is to be in contact with the soil.
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Some examples of proposed solutions to the problem in patent applications are given below.
Protection of wood with a composition containing crude tall oil or another oil free fatty acids and/or resin acids.
Concerns hydrophobised fibres. The natural fibre is modified by the reaction of the cellulose of the fibre with an aliphatic or aromatic anhydride, such as maleic or succinic anhydride.
Protection or preservation of rubber, polymers, leather or wood from degradation by wetting and penetrating the surface of the material with an emulsion of dimethylpolysiloxane.