NO156489B - SYNTHETIC SPACEBOARD RISK MAGNETITT - Google Patents

Description

Wood preservative.

Known wood preservatives, which are particularly suitable for use in wooden constructions outdoors and have the property of being fixed in the wood, consist of alkali fluorides, alkali chromates and/or alkali arsenates or the corresponding ammonium salts.

In addition to their good properties for the various impregnation methods (boiler pressure impregnation, trough rewetting, etc.), a special advantage of such alkali fluoride-containing wood preservatives is that the total fluoride is not fixed in the wood, but that part of the fluoride during the service life of the impregnated wood remains diffusible and is thereby capable of — especially after the entry of water — penetrating into the wood zone, which was not covered by the impregnation process itself. The effect of these agents against wood-damaging fungi and insects is good; only in the case of certain lower fungal species, which are known to cause decay, are relatively high dosages necessary.

It has now been found that the wood protection effect of the per se known mixtures based on water-soluble 6-valent chromium oxygen compounds, alkali fluorides and alkali arsenates resp. alkali metaarsenates can be improved considerably when, in the above-mentioned mixtures, the alkali fluorides are at least partially replaced by water-soluble fluorides of cobalt or nickel.

The new cobalt- and/or nickel-fluoride-hydrated wood protection mixture has a particularly good effect against the cause of decay, since, in contrast to the previously known agents, no higher dosage is necessary. The wood preservatives according to the invention therefore stand out in addition to their good effect also because of their economy.

The solubility of these fluoride hydrates of cobalt and/or nickel in the impregnation solutions can possibly be increased by adding hydrofluoric acid. The hydrofluoric acid can be added in the form of acidic fluorides and/or freed from fluorides by the addition of acids such as chromic acid or alkali bisulphate.

The presence of nickel and/or cobalt fluoride hydrates in the impregnation solutions can also be achieved by allowing their formation to take place in aqueous solution, e.g. proceeds from other nickel resp. cobalt salts (e.g. sulphates, chlorides, nitrates or carbonates) and at the same time add alkali fluorides.

As water-soluble chromium oxygen compounds, the alkali compounds of chromic acid and polychromic acid are used, especially sodium chromate, potassium chromate, ammonium chromate, sodium dichromate, potassium dichromate and ammonium dichromate. Thus, mixtures of these compounds can also be used, possibly also in a mixture with anhydrite of chromic acid Cr03. The wood protection mixtures must contain 20 to 80% by weight of the chromate, preferably 30 to 50% by weight calculated on the overall mixture.

Alongside the neutral and acidic fluorides of the alkali ions, as the term alkali here includes ammonium, boron fluorides can be used as well as water-soluble silicofluorides (e.g. ammonium, magnesium, zinc silicofluorides, etc.) resp. mixtures of these fluorides, with a total content of fluorides in wood preservatives from 20 to 80% by weight, preferably 25 to 60% by weight, the characteristic being that at least part of the mentioned fluorides are replaced by fluoride hydrates of cobalt and/or nickel. Generally, the content of nickel or cobalt fluoride hydrates constitute 2 to 20 percent by weight, preferably 3 to 10 percent by weight, calculated on the wood protection mixture. Alkali arsenates or alkali metaarsenates can be present in amounts from 0 to 40% by weight, preferably in amounts from 15 to 30% by weight.

The application concentrations of the wood preservative according to the invention are based on the absorbency of the wood to be impregnated, resp. according to the impregnation method.

For use with boiler pressure humidification, e.g. aqueous solutions with a content of between 1 and 6% by weight of the wood preservative. For impregnation by artisanal methods (e.g. ironing, spraying, etc.), concentrations between 10 and 25% by weight are used.

The fixation of nickel and/or cobalt within the framework of the salt mixtures composed according to the invention in the wood is practically complete. The effect of these substances is then also retained when the wood is subjected to weathering or running water, e.g. in cooling towers.

Example 1.

It mixes

40 parts potassium bichromate,

15 parts sodium fluoride

and 40 parts potassium bifluoride with 5 parts nickel fluoride hydrate (Ni<F>2.4H20).

With a 4% solution of this salt mixture, the pine sapwood is fully moistened according to DIN 52.176, sheet 2, and the leachability is determined. The nickel is practically fixed at 100 per cent.

Example 2.

40 parts potassium bichromate,

7 parts chromic acid,

15 parts disodium arsenate

and 31.6 parts of ammonium bifluoride are mixed with 5 ; parts nickel sulfate and 1.4 parts potassium bifluoride.

The wetting and leaching test according to DIN 52.176, sheet 2, on a 40% solution moistened wood likewise shows a practically complete fixation of the nickel.

Example 3.

35 parts potassium bichromate

10 parts sodium fluoride

35 parts potassium bifluoride

20 parts nickel fluoride hydrate (NiF2.4H20).

With a 4% solution of this salt mixture, the pine sapwood is fully moistened according to DIN 52.176, sheet 2, and the leachability is determined. Nickel is practically fixed at 100 per cent,<1>

Example 4.

a) It:' is mixed

40 ciels of potassium bichromate

15 parts sodium fluoride and

40 parts potassium bifluoride with

5 parts nickel fluoride hydrate, (NiF2.4 H20)

b) 40 parts of potassium bichromate are mixed

15 [divides sodium fluoride and

40 'divides potassium bifluoride with

5 parts cobalt fluoride hydrate (CoF2.4H20).

With a 4% solution of these salt mixtures, the pine plinth wood is fully moistened according to DIN 52.176, sheet 2, and the leachability is determined. The nickel or the co-bolt is practically fixed 100 percent.

While the limit value for the fluorine-chromium salt against rust is 40 kg salt/m.3 wood, the addition of cobalt or nickel fluoride hydrates, the addition is lowered to 20 kg/m3.

In the case of fluorine-chromium-arsenic salts, the limit value against ground rot is 60 kg/m3.

Example 5.

It mixes

40 parts potassium bichromate

7 parts chromic acid

15 parts disodium arsenate and

31.6 shares ammonium bifluoride with

;5 parts nickel sulphate and 1.4 parts potassium fluoride

and the limit value against the producer of root rot is determined. For the above-mentioned mixture, limit values of 40 kg/m3 were determined.

Example 6.

It mixes

40 parts potassium dichromate 7 parts chromic acid 15 parts disodium arsenate and 31.6 parts ammonium bifluoride with 5 parts cobalt sulfate and 1.4 parts potassium bifluoride

and the limit value against the producer of root rot is determined. In the case of the above-mentioned mixture, the limit value for the addition of cobalt salt was determined to be 15-20 kg/m3.

Claims (2)

1. Wood preservative against plant and animal harmful organisms with a content of alkali dichromates and/or chromates and/or chromic acids in amounts from 20 to 80 percent by weight, alkali arsenates and/or alkali metaarsenates in amounts from 0 to 40 percent by weight and water-soluble fluorides in amounts from 20 to 80, preferably 25 to 60, weight percent, the term alkali also includes ammonium, characterized in that part of the water-soluble fluorides are present in the form of the fluoride hydrates of cobalt and/or nickel. 2. Wood preservative according to claim 1, with a content of fluoride hydrates of cobalt and/or nickel in amounts from 2 to 20, preferably from 3 to 10, percent by weight.