This invention relates to a preservative for treating of wood, wood based products or similar organic fibre products, which include one or more copper salts and perhaps zinc salts of weak organic acids, a stabilising chemical selected among the ammonium salt of a weak organic acid or a mixture of such an ammonium salt and an alkalimetal salt of a weak organic acid, nitrite plus perhaps further admixture - and/or aid chemicals. The treating solution has a pH-value of 5,2-6,2.

Treatment of wood and wood-based products to make it resistant against biological decomposition uses normally a preservative in the form of a chemical solution.

It has for a long time been known that copper - as well as zinc salts have protecting qualities and are very suitable for use- in preservatives.

Earlier using of preservatives in the form of acid solutions of chromium, copper and arsenic or ammoniacal solutions of copper- and arsenic salts was widespread.

Such preservatives are satisfactory concerning protection of the wood but are combined with the disadvantage, that they contain chromium and arsenic, which both are harmful to the environment and the health.

Concurrently with the growing attention to the consequence for the environment and the health by using such preservatives you have tried to find less poisonons alternatives. So, to day you know a serie of alternative preservatives based on different copper -and/or zinc salts. From JP-application number 25.363/81 you know a preservative containing 15-25 % boric acid, 30-40 % sodium chlorid, 5-12 % zinc formate or copper formate and 5-15 % zinc acetate or copper acetate possible in mixing with

- _ -

triethanoamine.

From EP number 58.142 you know a preservative for treating of wood in the form of an aqueous ammonacial solution containing copper and/or zinc plus quaternary ammonium compounds.

From US patent number 4.929.454 you know an aqueous, ammonacial arsenic-free preservative for treating of wood containing a quaternary ammonium compound and a metallic cation, selected among copper and zinc.

From US patent number 4.857.322 you know a preservative for wood based on a copper compound, an aliphatic carboxylic acid plus a polyamine. The copper compound is preferably copperoxid, copperhydroxid or copper carbonate, the alifatic carboxylic acid is preferably 2-ethylhexanoic acid or isooctanoic acid and the polyamine is preferably 1,3-diaminopropane.

Although the above mentioned preservatives give good protection of the wood, they all have to a more or less degree the dis¬ advantage, that you have a high degree of leaching of the metals from the treated wood, as the metals are not fixed to the wood, but exist in the wood as a precipitated metal salt.

DK application number 1432/87 corresponding to EP number 238.049 deals with a preservative in the form of an aqueous solution of a copper-II-compound in the form of a complex with ammonia, an amine, an organic hydroxycarboxylic acid or a mixture of this plus a compound with an anion, which in the wood transfers the copper compound to a precipitated, stable copper-I-compounds. As an example of such compounds with anions is mentioned thiocyanate and iodide. Moreover the preservative may contain a reduction chemical, which assists in the reduc¬ tion of the copper-II-compound to the copper-I-compound. As an example of such a reduction chemical is mentioned glucose. The preservative has a low copper content from about 7-11.5 % and

so it will have to be used in a high concentration. Further the preservative contains amines, which to day many peoples call in question from environmental reasons. Also in this preservative the copper is not fixed to the wood, but precipitated as a copper compound.

The authorities in the different countries have in the latest years intensified the demands on leaching from the treated wood. Thus, there is a need for preservatives, which will give a better fixation of the active ingredients and with this a decrease in leaching.

From WO number 91/11306 you know a copper based preservative, which for increasing the fixation of the copper ions contains a big amount of nitrit. In the application states that the fixation is best at a weak acid pH-value, but in spite of this it is stated that the pH-value shall be higher than 6.5 and preferably higher than 7.0, compare claim 1 and claim 2. This is explained by having in the preservative an increased tenden- cy to development of NO„,-emission the lower the pH-value is, and it is illustrated by a comparison test. In other words in the application is expressed a prejudice against to use nitrite containing preservati es at a pH-value lower than 6.5. To avoid precipitation of the cation as a water insoluble alcaline salt when the pH is higher than 6.5, WO 91/11306 states, that you per one mole of the catione have to use at least four moles of a complexing agent, it means minimum 80 per cent by weight calculated on the metal salt. As the complexing agent keeps the metal in a soluble form you have to use more nitrite to achieve the same degree of fixation as without the complexing agent, compare page 5-6 and page 18-19. Therefore, WO 91/11306 states as preferred amount 2.0 to 3.0 parts by weight of biocide cation, it is copper ion and perhaps other biocide cations or

- ^' - .

expressed as salts 1-1.5 parts by weight of sodium nitrite per 1 part by weight of copper acetate or 1.25-1.90 parts by weight of sodium nitrite per 1 part by weight of sodium sulfate anhydrous.

Among conventional copper based preservatives experts dis¬ tinguish between acid and alcaline preservatives as the charac¬ ter of the copper component is essentially different in the two fields. Thus, the copper in the acid preservatives usually will be soluble while you in the alcaline preservatives usually will need a complexing agent to soluble the copper compound. Thus in practice you have to add a complexing agent to the alkaline preservatives, for instance in the form of amines, which from an environmental point of view is seen as less desirable.

Experience-based you have an essential difference between the acid and alcaline preservatives. However the remaining com¬ pounds can have an essential influence so you cannot always say anything in general of the quality of this two types of preser¬ vatives. However, among the approved preservatives it is so, that the copper amount in the acid preservatives can be some¬ thing lower than in the alkaline preservatives, it is 3 kg copper per 1 m- sapwood when using acid preservatives against min. ^' kg copper per 1 m ³ sapwood when using alcaline preser¬ vatives, both for wood in ground contact.

From SE-appl ication number .09 you know a weak acid preset— vative for treating of wood, containing copper acetate and zinc acetate, with a content of copper acetate of at least 45 V. of the total amount of copper -and zinc acetate. The preservative may, for restraining of the corrosion on the treating plant, contain alkali- or ammonium nitrite or alkali- or ammonium acetatate in an amount up to 0.1 '/. by weight of the treating solution.

Acid copper salts is even in low concentrations, it means less than 2 '/., strong corrosive against iron and steel and for that reason it cannot be used in practice without addition of aid compounds, which neutralize the corrosive effect.

In spite of a low solubility in water of the mentioned copper- and perhaps zinc salts the leaching of the copper- and the zincions from the treated wood is considerable and, therefore, the use of these will from ecological and environmental reasons need better fixation. Thus it is desirable to add a suitable aid compound to such preservatives for improving the fixation.

Among experts it is considered as importent, that you have acid as well as alkaline preservatives available, so you have the possibility to solve different tasks. By solution of such tasks you have to consider many different things, for instance the species, the treating method, the use of the treated wood and especially the geographical variations in climate and soil.

When you choose between an acid and an alkaline preservative also the pratical conditions play a role as the different preservatives demand different treating plants. For instance, alkaline preservatives will frequently give corrosion in case of bronze fittings and acid preservatives especially chromium- free preservatives give heavy corrosion problems against iron and steel. In other words, you cannot just like that go to an other type of preservative in an existing plant. Thus, you still have a need for a weak acid water soluble preservative on the basis of non-toxix compounds with a low degree of leaching of the metals from the treated wood.

As mentioned earlier it is known, that preservatives on the basis of weak acid copper- and zinc salts with a sufficiently high copper content will give good protection of wood in ground contact. You will have a high copper content, when you use a copper salt of an organic acid with low molecular weight with

small amount of aid chemicals for stabilising of the copper salt solution.

The above mentioned copper salts have in an aqueous solution a more or less stark blue colour. After treating the wood-based products will have a colour, which vary from nearly invisible to a stark blue colour. Such an appearance us unacceptable. Thus you have to add one or mor compounds, which change the colour to a green nuance and at the same time give an identical and recognizable colour intensity.

It has been known for many years, that we have fungies, who are able to decompose treated wood with a high copper content. These fungies are called copper-tolerante fungies. To protect against decomposition caused by these fungies an unacceptable high copper loading in the wood is needed. Therefore, the preservative must in environments, where these fungis are found, be added a compound which ensures, that the wood is protected in these cases.

The present invention relates to a prservative for treating of wood, wood-based products or similar organic fibre products, which include one or more copper salts and perhaps zinc salts of weak organic acids, a stabilising chemical selected among the ammoniumsalt of a weak organic acid or a mixture of such an ammonium salt and an alkalimetal salt of a weak organic acid, nitrite plus perhaps further admixture - and/or aid chemicals characterised by containing 0.1-1.0 parts by weight of nitrite, calculated as sodium nitrite per 1.0 parts by weight of copper salt and perhaps zinc salts calculated as copper acetate. The preservative in the treating solution has a pH-value of 5.2-6.2 and the amount of nitrite calculated as sodium nitrite comes to at least 0.15 '/. by weight of the treating solution and the stabilizing chemical is found in an amount of at least 0.2 '/. by weight calculated as ammoniumacetat of the treating solution,

where the concentration of the ammonium salt calculated as ammoniumacetate must not exceed

0.07 x 1_ '/. by weight of the treating solution, a where a. is the concentration of nitrite calculated as sodium nitrite in per cent of the treating solution and where the nitrite exists in one packing unit divided from an other packing unit containing the remaining chemicals.

It is preferred that the copper salt is selected among copper formate, copper acetate and copper propionate or a mixture of these and that the zinc salt, if it is present, is selected among zinc formate, zinc acetate and zinc propionate or a mixture of these.

The content of nitrite in the preservative has two functions.

So, the content causes, that the leaching of the copperions and the zincions from the treated wood is reduced essentially. Further it reduces the corrosion on the treating plant from the treating solution.

The copper salt is as mentioned preferably selected among copper formate, copper acetate and copper propionate or mix¬ tures of these. In a preferred version the copper salt is copper acetate. The active ingredient in the preservative is as mentioned mainly the copper salt or a mixture of a coppersalt and a zinc salt, where the zinc salt comes to 25 '/. of this. The amount of the remaining chemicals such as nitrite is adjusted according to the amount of the active ingredient, it is the amount of copper salt and perhaps zinc salt plus the degree of fixation which is wanted. However, the content of nitrite calculated as sodium nitrite must for the sake of protection against corrotion at least comes to 0.15 V ^" by weight of the treating solution. The amounts in this case is calculated from the molecular equivalence which corresponds to the correspon- ding amount of copper acetate.

The nitrite is selected among the alcalimetal nitrites, it is potassium— and sodium nitrite, ammonium nitrite or a mixture of these. Sodium nitrite is preferred.

The amount of nitrite comes to at least 0.1 and particularly preferred is at least 0.15, especially at least 0.2 parts by weight, calculated as sodium nitrite per 1.0 part by weigth of copper salt and perhaps zinc salt calculated as copper acetate and preferably most 0.8 and particularly preferred most 0.7, more preferred most 0.65 and paricularly most 0.55 parts by weight calculated as sodium nitrite per 1.0 parts by weight of coppersalt and perhaps zinc salt calculated as copper acetate. At the same time you have to take care that the amount of nitrite calculated as sodiumnitrite must comes to at least 0.15 '/. by weight and freferably at least 0.20 '/. by weight of the treating solution to prevent corrosion of the treating plant.

The preservative according to the invention contains as mentio¬ ned a stabilising chemical selected among the ammonium salt of a weak organic acid or a mixture of such an ammonium salt and an alkalimetal salt of a weak organic acid in an amount of at least 0.2 '/. by weight calculated as ammonium acetate of the treating solution. As an example of usable weak organic acids you can mention formic acid, acetic acid and propionic acid or a mixture of these, preferably acetic acid. As alkali metal salt is preferably used sodium acetate.

The addition of the ammoniumsalt and in some cases also alkali- metal salt causes a stabilising of the treating solution by preventing precipitation of the usable chemicals and together with the nitrite it prevents corrosion of the treating plant. Further these added chemicals cause that the treated timber will have a more attractive and uniform colour. The ammonium salt is the most effective of the mentioned stabilising chemi-

cals and, therefore, it is preferably used. However, at a high content of nitrite the tendendy to decomposition of the ammo¬ nium salt is increased and as a consequence some nitrogen may 5 be generated. In these cases it is suitable to replace parts of the ammonium salt with the alkalimetal salt.

The concentration of the ammonium salt calculated as ammonium acetate must not exceed 10

0.07 x 1_ */. by weight of the treating solution, a

" ^~ ή where a_ is the concentration of nitrite calculated as sodium nitrite in per cent by weight of the treating solution. Thus the necessary amount of the stabilizing chemical must at high nitrite content be supplemented by addition of the alkalimetal salt so that the total amount of the stabilizing chemical 0 calculated as ammonium acetate comes to at least 0.2 */. by weight calculated on the treating solution.

Further, the preservative contains profitably boric acid in an amount until 30 '/. by weight, preferably until 15 */. by weight, 5 such as 1-10 ^• /. by weight calculated on the content of copper salt and perhaps zinc salt calculate as copper acetate.

The preservative has a pH-value of 5.2-6.2 preferably 5.5-6.1 and particularly preferred 5.8-6.1 which will increase the 0 biocidal effect of the copper and ensure a good fixation.

Without addition of acid the pH-value of the treating solution is relatively constant and only to a low degree dependent on the concentration of the nitrite and the ammonium salt. In general the pH-value increases with increasing concentration of 5 the nitrite in the treating solution and with decreasing total concentration of the treating solution. On the other hand the pH-value decreases with increasing concentration of ammonium¬ salt and acid. If it is wanted you can add a weak organic

acid as acetic acid for adjusting of the pH-value and for stabilising the treating solution, preferably most in an amount until 0.1 */. by weight, calculated as acetic acid, of the treating solution.

Further the preservative can profitably contain a quaternary ammonium compound for instance in an amount of 15-25 '/. by weight calculated on the copper content. Quaternary ammonium compounds have a wide biocidal effect and thus it is able to support the effect of the copper and perhaps the zinc. The addition of the quaternary ammonium compound, for instance in an amount of 15-25 */. by weight calculated on the copper content in the preservative is relevant when treating wood products for use in environments where copper tolerant fungies is present. The quaternary ammonium compounds have a wide biocidal effect and thus they will support the effect of the copper and the zinc and more especially be effective against the copper to¬ lerant fungies. So, when you add a quaternary ammonium compound to the preservative you can use less preservative which from an environmental as well as on economic point of view is an advantage. As an example of very suitable compounds can be mentioned di-cocos-di-methy1-ammonium chloride.

In a preferred version the preservative according to the invention has the following composition:

30-80 '/. by weight of the copper salt, calculated as copper acetate,

0-20 */. by weight of the zinc salt, calculated as zinc acetate,

6-33 */. by weight of nitrite, calculated as sodium nitrite,

2—16 V. by weight of the acid ammonium salt, calculated as ammonium acetate, 0-20 '/. by weight of the alkalimetal salt, calculated as sodium acetate,

0—6 '/. by weight of the quaternary ammonium salt,

0-15 % by weight of boric acid, especially 1-10 '/. by weight of boric acid and

0-5 '/. by weight of a weak organic acid calculated as acetic acid.

The copper salt and perhaps the zinc salt plus the ammonium salt will exist in one from the nitrite separeted packing unit and shall be diluted with water and mixed just before use.

The preservative according to the invention can be based on the copper salt alone but if wanted it can contain up to 25 '/. by weight of zinc salt calculated on the total amount of copper salt and zinc salt.

The invention includes a treating solution which is charac¬ terised by containing 1-20 preferably 1-12 */. by weight of the preservative according to the invention and 80-99, preferably 88-99 '/. by weight of water.

Detailed description of the invention.

In general the coppersalt gives a good protection and it has a wide biocidal effect. Thus the preservative according to the invention can be used for many species and for many different purposes. Further, the copper salts have the advantage, that they fixe better to the wood compared to the zinc salts. However in some cases it is desirable to supplement the copper salt with other biocidal compounds as zinc salts and quaternary ammoniumcompounds.

It has appeared, that you, when adding a relatively small amount of nitrite, it is 0.1-1.0, preferably 0.15-0.80 parts by weight calculated as sodiumni rite per 1 part by weight of the copper salt calculated as copperacetate, essentially reduces the leaching of the copper from the timber compared to the leaching from corresponding weak acid copperbased preservatives without or with a very low content of nitrite, it is such

preservatives which is described in the mentioned SE number 466.094.

As it is wellknown among experts, the nitrite also has the advantage, that it restrains the corrosion. Thus, the preserva¬ tive is particulary usable in treating plants.

To improve the restraining effect against corrosion, stabili¬ sing the chemical and gives the treated timber a more attrac¬ tive colour, the preservative contains additional ammonium - and perhaps alkalimetal salts of weak organic acids in an amount of at least 0.2 '/. by weight, calculated as ammonium - acetate, of the treating solution.

The content of ammonium - and perhaps alkalimetal salts in the mentioned amount is essential as the content causes a transfor- mation of perhaps free copperions to cuprations at which the corrosive effect of the copperions to iron and steel disappear? at the same time as the solubility of the copper salt is essentially increased.

The amounts of the ammoniumsalt and perhaps the alkalimetal salt is calculated in every case from the molecular equivalent which corresponds to the corresponding amount of ammoniumaceta- te. If you use a mixture of for instance ammoniumacetate and sodiu acetate, it is not necessary to adjust in practice because of the small difference in molecular weight between these components when calculating the amount of sodiumacetate.

The ammonium salt is the most preferred stabilising chemical but at an increasing concentra ion of nitrite in the treating solution you will have a tendency to generate nitrogen because of a decomposition of the ammonium. Thus, at a high content of nitrite in the treating solution it is suitable to replace a part of the ammonium salt with an alkalimetal salt. So the con¬ centration of the ammonium salt calculated as ammonium acetate

must not exceed

0.07 x 1_ V. by weight a

10 in the treating solution where a. is the concentration of nitrite, calculated as sodium nitrite in per cent by weight of the treating solution. The factor 0.07 is calculated on danish climate conditions and when used in more hot climates it may in practice be necessary to keep the amount lower than this

15 maximum value as the tendency to generation of gas is increased with increasing temperature. A corresponding phenomenon but with an opposite sign may be present when used in a more cold climate. In practice it is usual in the treating solution to use a concentration of ammonium salt calculated as per cent by

20 weight of ammoniumacetate on

0.05 κ 1_ '/. by weight to 0.07 κ 1_ per cent by weight, a a

25 where a_ is the concentration of nitrite, calculated as per cent by weight of sodium nitrite in the treating solution. If necessary an alkalimetal salt is added, so the total amount of the stabilising chemicals calculated as ammoniumacetate at

-0 least comes up to 0.2 per cent by weight of the treation solution.

Tests have shown the following in practice usuable minimum - and maximum limits for the content of the ammonium salt cal- 35 culated as ammonium acetate at different concentrations of nitrite calculated as sodiumni rite.

40

Further the preservative according to the invention can in many cases with advantage contain a quaternary ammonium compound, for instance in an amount of 15-25 per cent by weight cal¬ culated on the copperions. The quaternary ammoniumcompounds have a wide biocidal effect and therefore it will support the effect of the copper and the zinc and will especially be effective against the copper tolerant fungies. The addition of quaternary ammonium compounds is especially relevant when treating wood-products for use in environments where the copper tolerant fungies exist. The addition of a quaternary ammonium- compound make it possible to use less amount of preservative than else would be necessary. This is an advantage from an environmental as well as an economic point of view. As an example of suitable quaternary ammonium compounds can be mentioned di-coco-di-methy1-ammonium chloride and coco-tri- methy1-ammonium chloride.

Boric acid can profitably enter the preservative according to

the invention. The boric acid can assist the fixation of the copper - and the zinc ions. Besides it contributes to protec- tion of the wood against mould, copper tolerant fungies and insects, including termittes.

Moreover the preservative can contain further conventional admixture — and/or aid chemicals. As an example can be mentio- ned chemicals for inhibition of corrosion and for stabilizing plus further fungicides and insecticides, dies, pigments and trace chemicals.

When treating timber is it advantageous that the timber after treatment has a greenish colour. Further this colouring can serve as a security that the active ingredients in the preset— vative have totally penetrated the wood. Thus it is important for the acceptance of the users of the treated timber, that the product can be recognized as a product with a reliable and effective treatment. Especially for wood for use as claddings, as carports, fencings etc. it is of importance, that the greenish colour can be achived. It is an advantage, too, that you can practically have the same colour when mixing wood producs from the new chromiumfree treating with older chromium coloured products. Secondly, this colouring secures against a wrong use of untreated wood products for objects where use of treated timber is necessary if you will avoid occurrence of damages, for instance expensive damages of buildings.

In an essential part of the field for the nitrite content in the preservative according to the invention you will have the desired greenish colour despite that the preservative is chromium-free. In the remaining field it can be advantageous to add a supplementary dye. Usuable dies are "Unisperse/Irgasperse Green" and "Unisperse/Ingasperse Black" from Ciba Geigy,

Schwitzerland . The amount of dye in the treating solution will typical be around 0.1 per thousand.

The application of the preservative according to the invention

can be done in the well-known ways, for instance coating, spraying, immersion, double vacuum, double vacuum-pressure or pressure processes as "Lowry" (empty- cell), "Bethel" (full- cell) and "Reuping". Among these processes immersion and pressure processes, especially "Lowry" and "Bethel" are prefei— red.

The concentration of the copper salt in the treating solution can vary depending on the process and the use of the timber but generally the treating solution contains 0.2 - 5 per cent by weight of copper calculated as copperacetate.

The content of nitrite calculated as sodium nitrite in the treating solution comes to at least 0.15 per cent by weight as mentioned above and is generally kept on 0.2-1.3 per cent by weight preferably 0.2-1.0 per cent by weight and mainly prefet— red is 0.26-0.70 per cent by weight.

To prevent biological decomposition from fungies and insects the preservative according to the invention can be used in a serie of other biodegradable organic materials, for instance textiles, ropes, racks, papers and boards plus bather, in which cases it must be applicated by means of known methods far treating of such materials.

The preservative according to the invention is effective regarding both to prevent growth of wood-destroying fungies as well as to remain in the wood. The addition of nitrite reduces essentially the leaching of the copper and the zinc from the wood.

Examp l e 1

A preservative with the following composition was prepared:

Zinc acetate, 2H _S 0 17 kg

Copper acetate, H _e O 57 kg Ammonium acetate 7 kg

Sodium acetate 2 kg

Boric acid 3 kg

Sodium nitritrite 14 kg

The preservative was dissolved in water to a concentration of 2.2-2.5 per cent by weight and can be classed with the Nordic class A ⁽ Danish Standard DS 2122). The treating solution had a pH-value of 5.8

Example 2

A preservative with the following composition was prepared:

Zinc acetate, 2H _Ξ 0 16 kg Copper acetate, H _s 0 49 kg

Ammonium acetate 14 kg

Boric acid 3 kg

Sodium nitrite 17 kg

Di-decy1-di-methylammoniumchloride 1 kg

The preservative was dissolve to a concentration of 1.5-1.7 per cent by weight and can be classed with the Nordic class AB (Danish Standard DS 2122). The treating solution had a pH-value of 5.9.

Examp l e 3

A preservative with the following composition was prepared:

Zinc acetate, 2H _S 0 14 kg Copper acetate, H _a 0 44 kg

Acetic acid 2 kg

Ammonium acetate 2 kg

Sodium acetate 5 kg

Boric acid 10 kg Sodium nitrite 23 kg

The preservative was dissolved in water to a concentration of 3.5 per cent by weight and is well qualified for use in terri¬ tory with probability for attack from termites. The treating solution had a pH-value of 6.0.

Example 4

A preservative with the following composition was prepared:

Zinc acetate, 2H _S 0 16 kg

Copper acetate, H _Ξ 0 53 kg

Acetic acid 1 kg

Ammonium acetate 6 kg Sodium acetate 2 kg

Boric acid 8 kg

Sodium nitrite 14 kg

The preservative was dissolved in water to a concentra ion of 2.7 per cent by weight and can be classed with the DIN-Norm class 4. The treating solution had a pH-value of 5.9.

Examp le 5

A preservative with the following composition was prepared:

Zinc acetate, 2H _a 0 14 kg Copper acetate, H _Ξ 0 45 kg Ammonium acetate 11 kg Sodium acetate 1 kg Boric acid 8 kg Sodium nitrite 18 kg

Di-decyl-di-methyl-ammoniumchloride3 kg

The preservative was dissolved to a concentration of 1.8 per cent by weight and can be classed with the DIN-NDRM Class 3. The treating solution had a pH-value of 6.1.

Example 6

For use in class A and class AB in Scandinavia the following 3 packing units was prepared:

Packing A Packing AB

Copper acetate, H _Ξ 0 24.0 kg 18.4 kg Zinc acetate, 2H_,0 7.5 kg 6.0 kg Ammonium acetate 3.0 kg 5.3 kg Sodium acetate 0.4 kg Boric acid 1.3 kg 1.1 kg Di-decyl-di-methyl- ammoniumchlorid, 50 '/. 0.75 kg Water 67 kg 67 kg

Packing C:

Sodium nitrite 6.1 kg Water 10 kg

The treating solution for class A is prepared when you dissolve in 4800 Itr. of water 3 units of packing A and then add 3 units of packing C.

The treating solution for class AB is prepared when you dis¬ solve in 4850 Itr. of water 2 units of packing AB and then add 2 units of packing C.

Example 7

A preservative with the following composition was prepared:

Copper acetate, H _Ξ 0 63 kg

Ammonium acetate 4 kg

Sodium acetate 6 kg

Boric acid 2 kg

Sodium nitrite 25 kg

The preservative was dissolved in water to a concentration of 2.1-2.6 per cent by weight and can be classed with the Nordic class A according to DS 2122 for wood in ground contact. The treating solution had a pH-value of 5.9.

Example 8

A preservative with the following coposition was preparared:

Copper acetate, H _ε 0 59 kg

Ammonium acetate 11 kg

Sodium acetate 4 kg

Sodium nitrite 22 kg

Di-coco-di-methyl-ammoniumchlαride 4 kg

The preservative was dissolved to a concentration of 1.5-1.7 per cent by weight and can be clased to class AB according to DS 2122 for wood out of ground contact. The treating solution had a pH-value of 6.0.

Example 9

A preservative with the following composition was prepared:

Copper acetate, H _S D 54 kg

Ammonium acetate 2 kg

Sodium acetate 8 kg

Boric acid 5 kg

Acetic acid 1 kg

Sodium nitrite 30 kg

The preservative was dissolved to a concentration of 3.2 per cent by weight and is well qualified for treating of timber for use in territory with probability for attack from termites. The treating solution had a pH-value of 5.9.

Example 10

A preservative with the following composition was prepared:

Copper acetate, H _a 0 63 kg

Ammonium acetate 8 kg

Sodium acetate 2 kg Boric acid 9 kg

Acetic acid 1 kg

Sodium nitrite 17 kg

The preservative was dissolved in water to a concentration of 2.2 per cent by weight and can be classed to class 4 in the DIN-norm for treated wood in ground contact. The treating solution had a pH-value of 5.9.

Examp l e 1 1

A preservative with the following composition was prepared:

Copper acetate, H _a 0 56 kg

Ammonium acetate 14 kg Boric acid 9 kg

Sodium nitrite 18 kg

Di-coco-dimethyl-ammoniumchloride 3 kg

The preservative was dissolved to a concentration of at least 1.5 per cent by weight and can be classed to class 3 in the DIN-norm for treated wood for use out of ground contact. The treating solution had a pH-value of 6.0.

Example 12

For use in class A and class AB in Scandinavia the following 3 packing units was prepared:

Packing A Packing AB

Copper acetate, H _s 0 14.8 kg 15.7 kg Ammonium acetate 0.9 kg 2.9 kg

Sodium acetatate 1.4 kg 1.1 kg

Boric acid 0.5 kg -

Di-decyl-di-methyl- - 2.2 kg ammoniumchloride, 50 '/. Water 50 kg 50 kg

Packing C

Sodium nitrite 5,85 kg Water 10 kg

The treating solution for class AB was prepared when you dis-

solve in 4700 Itr. of water 5 units of packing A and then add 5 units of packing C. The treating solution for class AB was prepared when you dissolve in 4800 Itr. of water 3 units of packing AB and then add 3 units of packing C.

Example 13

A preservative with the following composition was prepared:

Zinc acetate, 2H _a 0 16 kg

Copper acetate, H _s 0 48 kg

Ammonium acetate 3 kg

Sodium acetate 5 kg

Acetic acid 1 kg

Boric acid 5 kg

Sodium nitrite 22 kg

The preservative was dissolved in water to a concentration of 2.7-3.1 per cent by weight and can be classed to class A (DS 2122) . The treating solution had a pH-value of 6.0.

Example 14

A preservative with the following composition was prepared:

Zinc acetate, 2H _a 0 14 kg Copper acetate, H _a Q 45 kg

Ammonium acetate 12 kg

Boric acid 8 kg

Sodium nitrite 18 kg Di-decyl-di-methyl-ammαniumchloride3 kg

The preservative was dissolved to a concentration of 1.7-1.8 per cent by weight and can be classed to class AB (DS 2122). The treating solution had a pH-value of 6.1

Examp l e 15

A preservative with the following composition was prepared:

Zinc acetate, 2H _S 0 14 kg

Copper acetate, H _a O 43 kg

Ammonium acetate 2 kg Sodium acetate 9 kg

Boric acid 2 kg

Sodium nitrite 30 kg

The preservative was dissolved in water to a concentration of 3.3 per cent by weight and can be classed to class 4 in the DIN-norm. The treating solution had a pH-value of 6.1.

Example 16

A preservative with the following composition was prepared:

Zinc acetate, 2H _a 0 13 kg

Copper acetate, H _a 0 42 kg

Ammonium acetate 8 kg Sodium acetate 5 kg

Boric acid 9 kg

Sodium nitrite 23 kg

The preservative was dissolved in water to a concentration of 1.9 per cent by weight and can be classed to class 3 in the DIN-norm. The treating solution had a pH-value of 6.1.

Example 17

For use in class A and class AB in Scandinavia the following 3 packing units was prepared:

Packing A Packing AB

Zinc acetate, 2H _Ξ 0 4.5 kg 4.1 kg Copper acetate, H _Ξ 0 13.8 kg 13.1 kg Ammonium acetate 0.9 kg 3.5 kg Sodium acetate 1.5 kg Acetic acid 0.3 kg Boric acid 1.5 kg 2.3 kg Di-decyl-di-methyl ammonium chloride, 50 */. 1.8 kg Water 50 kg 50 kq

Packing C

Sodium nitrite 7.70 kg Water 10 kq

The treating solution for class A was prepared when you dis¬ solve in 4700 Itr. of water 5 units of packing A and then add 5 units of packing C. The treating solution for class AB was prepared when you dissolve in 4800 Itr. of water 3 units of packing AB and then add 3 units of packing C.

Example 18

The present example indicates the leaching tests for determina¬ tion of the degree of leaching of the zinc- and the copperions from wood treated with different preservatives according to the invention with varied content of sodium nitrite at pH 5.8-6.1.

The tests was carried out on Scotch Pine (Pinus Silvestris), treated according to the full-cell process. After fixation the degree of leaching was determined be immersion in distilled water for 72 hours.

To ensure totally immersion of the wood samples, the air in the wood was disappeared in vacuum before immersion. The fixation in the following table 1, expressed as per cent, is determined from an analyse of the copper- and zinc content in the wood samples before the immersion and an analyse of the copper- and zinc content in the water extract.

You will find the results from the present test in the follo¬ wing table 1:

Footnote

* Not according to the invention - formulation for comparison.

From the table you see, that the addition of nitrite in an amount of 75 */. of the total amount of copper- and zinc acetate increases the fixation of copper from 55 '/. to 82 V. and the fixation of zinc from 27 '/. to 48 */..

Examp l e 19

The present example illustrates a test to determinate the generation of gas from a serie of different treating solutions according to the invention.

The determination was carried out on solutions in a closed system at a temperature of minimum 18° C for at least 3 mounths by measuring a possible increase in pressure. The concentration of copper- and zincacetate was totally 1.72-1.92 ^• /. and the concentration of boric acid was 0.22 */..

Table 2.

Acetic Ammonium Sodium Sodium Generation acid acetate acetate n trite of gas

0.10 0.10 0.20 no 0.20 0.20 no 0.20 0.20 O.40 no 0.20 0.40 yes/no

0.04 0.20 0.40 yes/no 0.08 0.20 0.40 yes 0.24 0.48 yes 0.16 0.10 0.60 no 0.10 0.16 0.68 no 0.20 0.56 0.72 no 0.20 0.20 0.72 yes 0.20 0.60 0.76 no 0.08 0.16 0.76 no 0.12 0.24 0.76 yes/no 0.20 0.40 0.76 yes 0.20 0.20 0.76 yes 0.16 0.08 0.76 yes

0.10 0.20 0.40 0.76 yes 0.24 0.16 0.76 yes 0.40 0.40 0.76 yes 0.24 0.76 yes 0.36 0.76 yes 0.08 0.16 0.80 no 0.10 0.20 0.80 no

0.04 0.08 0.16 0.80 no

In the table you see, that contemporary high concentrations of sodium nitrite and ammonium acetate increases the generation of gas but if at the same time sodium acetate is added, the tendency to the generation is reduced. Acetic acid in return increases the generation. When adjusting the amount of the different components, the generation of gas is eliminated.

Example 20

The present example illustrates a test to determinate the generation of gas from 2 treating solutions according to the invention.

The possible generated type of air consists nearly totally of unpoisonous nitrogen because of the content of ammoniumions in the solution, compare the following chemical reaction:

NH, + NO. ^• > N__, + 2HJD

A possible generation of gas is directly proportional with a corresponding decrease in the concentra ion of nitrite ions.

The solution was prepared in that way that the sodium nitrite was dissolved alone as a 10 */• solution. The remaining compo¬ nents were dissolved in the remaining water and at least the 2 solutions were mixed. The treating solutions were kept at 18-20° C.

The solutions had the following compositions:

Per cent by weight

B

Cupri acetate, H _a 0 1.46 0.72

Zinc acetate, 2H _a 0 0.46 0.23

Boric acid 0.07 0.04

Ammonium acetate 0.17 0.20

Sodium nitrite 0.37 0.25

Sodium acetate 0.03

Quaternary ammonium- 0.04 chloride, 50 '/.

You will find the results in the following table 3.

Hours after NO _j in μg/ml pH-value produc¬ tion A B B

0 2513 1740

24 2440 1718

168 2414 1644

720 2532 1723

Average 2475 1706

Dispersion 55 60

Calculated 2474 1667 concentra¬ tion

As you see from the table the concentration of nitrite ions are the same even at 720 h after the production. From this it can be concluded that no generation of nitrogen containing gases will take place. The above mentioned reaction is consequently

totally stopped at the concentrations, which are used in this application for a patent. The effect of an increase of the concentration or an increase of the temperature can besides be compensated of a small addition of a mixture consisting of 3 parts of acetic acid plus 97 parts of sodium acetate, which a the same time will keep the pH-value on about.5.9, by which a maximum utilization of the nitrite ions is achieved.