DE933891C - Process for bleaching wood affected by blue fungus - Google Patents

Description

Process for bleaching wood affected by blue stain For bleaching of the wood affected by blue stain fungi, various processes are known that are relatively appear weak and do not completely remove the color, or they do so after a while let come up again. As far as such disadvantages are avoided with other methods This happens because the mycellar structure of the wood is loosened by alkali will. Peroxide is used as the oxidizing agent. Here, however, is through the strong alkali can be expected to damage the wood surface. Also can with This process is very easy as a result of the too rapid drying of the surface of the impregnated The bleaching process will be impaired.

In the wood industry it is known to bleach wood in that it is treated with a hypochlorite solution containing soda. For an ordinary Bleaching may be such a procedure, but it is not possible with Solutions of the type of blue fungus used here discolored wood only to a certain extent to decolorize sufficiently. The hypochlorite concentration is known to decrease in such aqueous solutions very quickly and then completely loses its effect. Even repeated addition of alkali, which is suggested here, can be added to this do not change anything, because then the solution as a result of increasing the pH value one for the Mycellar structure tends to have an unfavorable effect.

According to the invention is used to decolorize wood from the blue fungus is infected, also uses a hypochlorite and an alkaline reacting salt. However, in order to achieve a p, 1 value that is favorable for loosening the mycellar structure and thus to create the prerequisites for perfect bleaching the means mentioned with the addition of an organic oxidation catalyst applied, the presence of which the bleaching process extending over a long period of time controls. For the correct course of the bleaching process, it is useful to turn this off the various compounds existing means to apply in paste form to the wood. In order to keep the degree of humidity as constant as possible during the decolorization process and restricting the moisture to the application site can also be a inert filler can be used. Diatomaceous earth, for example, can be used as such will. Finally, in special cases it may be desirable, the actual one To allow discoloration to precede a pre-bleaching of the wood. For this, an alkaline Persulfate solution, also used in conjunction with a catalyst will.

The operation of the method according to the invention is illustrated by the following Example explains that at the same time also other possibilities for implementation reveals such procedures.

On the surface of the wood is a water-poor, preferably pulpy Mixture of a hypochlorite, e.g. B. chlorinated lime, and an alkaline additive, e.g. B. Soda, applied in such a mixing ratio that one for loosening of the mycellar structure necessary, but if possible not exceeding the pH value is set. If he were to go beyond that, there would be the risk of that Structure is attacked more than it is for bleaching; or decolorization required is. A favorable pH value is achieved if the mixing ratio is, for example when using chlorinated lime and soda it is 5: i.

The organic oxidation catalyst is added in such a way that that this in the form of a solution before the actual decolorization process on the Wood is applied. This can either happen immediately beforehand or already some time before the decolorant was applied. The one containing the catalyst Solution is expediently adjusted so that its pH -a for- the deepest possible penetration of the catalyst necessary loosening of the mycellar structure he follows. For example, take soda per liter of the solution for 2o to suction will.

Any of the known oxidation catalysts, for example potassium iodide or the iron (2) -iron (3) system can be used. Particularly however, favorable results can be achieved with organic oxidation catalysts, and of these, best suited are those belonging to the prosthetic group of the Chloroplasts are built similarly. This condition is fulfilled, for example, by Hämin, which also contains iron in a complex bond. Such a catalyst a concentration of a few milligrams in r liter of the solution mentioned is sufficient. The catalyst is only used in traces and thus causes a real catalysis process in contrast to the well-known peroxide bleaching which is not a real catalytic process.

The composition of the funds described above is geared towards that the process can readily be carried out at room temperature. In in this case the exposure time is about 4 to 6 hours. As with all such chemical processes, the duration of the action is more or less dependent on the temperature.

Claims (4)

'PATENT CLAIMS: i. Process for bleaching those affected by blue stain Wood with chlorinated lime and an alkaline reacting salt, characterized that a mixture of hypochlorite and an alkaline reacting salt in porridge form with the addition of a bleaching process that controls the longer-term, preferably organic oxidation catalyst is applied. 2. Procedure according to Claim i, characterized in that, ß the mixing ratio of the to be applied Breies is adjusted so that one for the necessary loosening of the mycellar structure a favorable pH value is set, e.g. B. that when using chlorinated lime and soda a paste with a mixing ratio of 5: .1 is applied. 3. Procedure according to Claim i, characterized by the additional use of an inert filler. 4. The method according to claim i or 2, characterized by using .ein pre-bleaching by means of an alkaline persulfate solution using a catalyst .. References: French Patent No. 726 350; G m e 1 i n, "Handbook of Inorganic Chemistry", Vol. 6 (chlorine), 1927, pp.28o to 283, publisher Chemistry, Berlin.