PT96638A - PROCESS FOR THE TREATMENT OF A SUBSTRATE WITH A BIOCIDAL COMPOSITION CONTAINING IONS NITRITE - Google Patents

Description

(i.e.

Description of the invention of HICKSON INTERNATIONAL PLC, UK, industrial and commercial, headquartered at Wheldon Road, Castleford, West Yorkshire, W10 2JT, England (inventors: Judith Ann Cornfield and Christopher Waldie, resident in England) " PROCESS FOR THE PREPARATION OF PRESERVATIVE COMPOSITIONS UNDERSTANDING BIOCIDAL CATIIONS AND NITRILE IONS AND FOR THE TREATMENT OF SUBSTRATES WITH THESE COMPOSITIONS "

The present application relates to preservatives, and to a process for the preparation of a biocidal composition, and for the treatment of substrates. It is known that the degradation of wood by fungi and harmful insects can be avoided by treating the wood with aqueous solutions of six of, for example, copper and other metals which are toxic to these noxious organisms.

However, for effective treatment of the wood with these solutions it is essential that the wood absorb sufficient solution and that the solution rapidly penetrates the wood. European Patent Application No. 238413 and French Patent No. 1455359 describe aqueous preservative compositions of wood comprising inter alia copper and nitrite ions. All the compositions described in European patent application No. 238413 have a pH of 9.5 or higher and contain ammonia or a water soluble amine to complex the copper ion and the quaternary ammonium salt. The penetration of these compositions was known. in the wood is limited and thus the absorption of the preservative

ACL 1 is reduced. It is believed that this is due to the dilation of the cell walls and microfibrils which causes blockage of the pores through which the solution usually penetrates. The pH values of the compositions described in French Patent No. 1455359 are less than 5.75 which causes the nitrite ion to be in equilibrium with nitrogen oxides such as nitric oxide having only a limited solubility in water and thus leaving solution. These nitrogen oxides are highly corrosive to metals commonly used in the construction of wood treatment plants. They are also toxic and constitute a serious health risk if the compositions are used in the commercial treatment of building woods.

According to one aspect of this invention there is provided an aqueous preservative composition which includes biocidal cations (which may be in the form of free cations or may be present as part of a complex) and nitrite ions (which may be in the form of free or may be present as part of a complex), the composition having a pH of about 6.5 with the proviso that when the pH is greater than 9.25 and the composition contains ammonia or an amine, the composition can not contain a quaternary ammonium salt.

The compositions according to this invention have been found to penetrate the wood more extensively, and a higher absorption of the preservative is obtained than with the known alkaline compositions containing ammonia or amines and a quaternary ammonium salt. At the same time, the emission of nitrogen oxides occurring when using the more acidic nitrite and copper compositions of the prior art is eliminated.

The compositions according to this invention may be used to treat substrates such as wood other cellulosic materials (for example cotton, rope and cord), or other polymeric materials which may be natural or synthetic and which have functional groups susceptible to oxidation by the anion nitrite.

For convenience, this invention is described below with reference to the treatment of wood but it is to be noted that the above mentioned other materials can also be treated

analogously. The effect of the nitrite anion in the foregoing composition is to increase the degree to which the biocidal cation attaches to the cellulose compared to the degree of fixation obtained with, for example, a solution of the sulfate salt of the biocidal cation. The biocidal cation of cellulose thus becomes more resistant to levotization by water.

Without wishing to be bound by theory, it is believed that the mechanism by which the nitrite ion binds is as follows:

In the application to the wood, a part of the biocidal cations present undergo an ion exchange process with the cellulosic components of the wood. This involves the exchange of hydrogen ions by metal cations at polar sites along the chains of cellulose polymers such as carboxylic acid groups and hydroxy groups. This leads to the release of hydrogen ions which provides an effective lowering of the pH within the wood structure. In the lower pH environment, nitrite ions combine with the hydrogen ions to provide unstable and highly reactive nitroso acid. This, in turn, reacts with the lignin and the cellulosic components of the wood substrate to provide active sites in which the remaining biocidal cations may become firmly attached to the wood structure. Experience has now shown that maximum biocide cation fixation tends to occur within the treated wood with solutions having a slightly acidic characteristic at the same time as minimal emission of nitrogen oxides occurs from solutions which are neutral or preferably alkaline. The choice of the optimum pH of the compositions according to this invention thus generally involves the compromise between the need to maximize the fixation of the biocidal cations and minimize the emission of nitrogen oxides. The best refinements in timber penetration / preservative absorption and in the aspect of treated wood have been found to be low pH. It has been particularly noted that formulations containing ammonia or free amines having a pH greater than 9.25 limit the penetration of the preservative solution and give rise to surface deposits of the wood in the wood. These are other factors to take into account when selecting the optimum pH 3 and the alkalinizing agent of the compositions according to this invention.

Compositions having a pH of greater than 9.25 preferably contain no quaternary ammonium salt. This is because these high pH values of the compositions containing nitrite and quaternary ammonium salt must contain higher amounts of expensive surface active agents for the composition to be readily stable. Large quantities of these costly ingredients are unnecessary in the compositions according to this invention which do not contain high pH quaternary ammonium salts.

Compositions having a pH greater than 9.25 which does not contain ammonia or amines may have additional advantages, namely penetration and absorption of improved preservatives and improved surface appearance of the treated wood.

To minimize emissions of nitrogen oxides, the pH of the composition is preferably 7.0 or higher. There is greater resistance to the leaching of the biocidal cation in the wood treated with compositions according to this invention of pH 10 or less. The compositions according to this invention of pH 9.25 or less are especially advantageous since the penetration and absorption of the preservative are still better than with the more alkaline compositions according to this invention and the wood treated with these compositions presents higher resistance to lecithination of the biocidal cation.

Aqueous solutions of nitrite ion and biocidal cation are generally acidic and have a pH in the range of 3.5 to 5.5. The pH can be adjusted, if necessary, by addition of suitable alkalinizing reagents. The alkali metal hydroxides are particularly suitable for these purposes and of these, sodium, potassium or lithium hydroxides are preferred. Other soluble alkaline salts such as carbonates, bicarbonates or phosphates may be used. Ammonia and amines such as mono-ethanolamine may also be used to adjust the pH of the compositions except those containing quaternary ammonium salts in which the pH exceeds 9.25.

In some compositions according to this invention, a higher pH causes the precipitation of the biocidal cations as a water-insoluble basic salt. This problem can be avoided by using complexing agents which interact with the biocidal cations to form complexes and avoid the insolubilization of the cation at high pH.

Thus, by choosing a suitable complexing agent it is possible to prepare stable solutions containing biocidal cations and nitrite anions at neutral or alkaline pH.

Suitable complexing agents may be obtained from the following non-exhaustive list: polyphosphoric acids such as tri-polyphosphoric acid, hexamethaphosphoric acid or pyrophosphoric acid or mixtures thereof; amino-carbocylic acids such as glycine, glutamic acid, ethylene-di-amine tetraacetic acid, hydroxy-ethyl-di-amine-triacetic acid, nitrilotriacetic acid and N-dihydroxy- glycine; polymeric compounds which contain groups amenable to complexation with metal cations such as polyacrylic acids; hydroxy carboxylic acids such as tartaric acid, citric acid, malic acid, lactic acid, hydroxybutyric acid, polyhydroxy carboxylic acids such as glycolic acid and glucoheptonic acid; phosphonic acids such as nitrilo-tri-methylene-phosphonic acid, ethylene-di-amine-tetra- (methylene-phosphonic acid), hydroxy-ethylidene-diphosphonic acid; and azoles and their derivatives such as imizadol and N-methyl imidazole.

When the complexing agents are acidic they can be used as free acids or as their alkali metal or ammonium salts. The complexing agents may be used alone or in combination with each other. The affinity of a complexing agent for the biocidal cations is an important factor in the choice of a complexing agent. Complexing agents with too high affinity for the cation can reduce cation binding in the treated wood. This is believed to be due to the fact that the clearing agent prevents insurrection of the biocidal cation within the wood structure despite the completion of the reactions intended for this purpose. Complexing agents with too weak an affinity do not sufficiently solubilize the biocidal cations. The skilled artisan readily selects the appropriate complexing agents.

In general, for each mole of the biocidal cation, at least four moles of complexing agents are required. It is the case, in particular, that the complexing agent belongs to the class of compounds known as the polyhydrocarbocylic acids. 5

The skilled artisan can readily determine the optimum amount of complexing agent without routine experimentation. The cation may be, for example, any known fungicidal or insecticidal cation and is preferably a metal cation. Examples of suitable biocidal metal cations include copper, aluminum, manganese, iron, cobalt, nickel, zinc, silver, cadium, tin, antimony, mercury, lead and bismuth. Cations of the lanthanide elements may also be used. These include the series of elements from lanthanum (atomic number 57) to lutetium (atomic number 71). The particularly preferred active biocidal cation is the cupric ion.

To ensure that the formulations provide protection against the widest possible range of wood-destroying organisms, it is desirable to use more than one biocidal cation in the formula. Thus, for example, any of the biocidal cations shown above may be used in combination with each other to provide a broad spectrum of activity with respect to wood-destroying organisms. A preferred combination includes cupric and zinc ions.

Biocide cation sources which may be used to prepare compositions according to this invention are, for example, any suitable cation salt, such as salts of chlorides, sulfates, nitrates, formates, acetates, carbonates, borates or the like of the oxide. The salt chosen may be one that is sufficiently soluble to allow to prepare a solution of such a concentration that an effective amount of the active metal can be applied to the wood to be treated.

Examples of nitrite ion sources include salts such as lithium nitrite, sodium nitrite, potassium nitrite, magnesium nitrite, calcium nitrite, strontium nitrite, and barium nitrite: It may be convenient, in some cases, to use nitrite of the desired active biocidal cation as the source of the nitrite cation and the biocidal active cation. 6

required in the compositions varies with the cation used. There are a number of known toxic cations and the necessary concentration of the cation to treat the wood with an effective amount is obvious to the skilled person. When the biocidal cation is copper, it is preferred that the composition contains between 0.01 and 5% by weight of the solution. The optimum concentration of copper required in the composition depends on the degree of penetration desired in the wood treated by the cation. The presence and concentration of other active biocidal compounds in the composition may also affect the concentration of copper required in the composition. When complete penetration into the sapwood is required the composition preferably contains from 0.1% to 1%, more preferably from 0.2% to 0.7% copper by weight of the solution. When the wood is treated to obtain a preservative shell, for example, to a depth of 5 to 10 mm laterally and 25 to 75 mm axially, then the composition preferably contains 0.5 to 2% copper by weight of the solution. Similar levels can be used for brush-applied preservatives. In the case of mixtures containing other very active biocides the level of copper may be reduced to as low as 0.01% by weight of the solution. Concentrated solutions or pastes containing 3 to 10% copper by weight may be prepared. These may be diluted by adding an appropriate amount of water to prepare the solutions for treating the wood. The amount of nitrite anion used in the compositions according to this invention is preferably greater than 0.01, more preferably greater than 0.1% by weight of the solution. Expressed as a proportion of the weight of the biocidal cation present, the amounts are preferably between 0.7 and 7%, more preferably between 1.4 and 3.6, particularly between 2.0 and 3.0.

In addition to the biocidal cations presented above, other compounds having activity in the formulation may be included to increase the activity of the main active components. By way of example only, these may include boric acid and other boron compounds with sufficient solubility in water and organic compounds having suitable activity

against fungi and insects that destroy the wood. Such organic compounds include carboxylic acids such as naphthenic acids and branched aliphatic acids and their salts of metals such as copper and zinc naphthanate, phenols and substituted phenols such as orthophenyl phenol and their alkali metal or ammonium salts; polyhalogenated phenols such as penta-chloro-phenol or tri-bromo-phenol and their alkali metal or ammonium salts; quaternary ammonium salts and salts of the third amines such as didecyl dimethyl ammonium chloride, octyl decyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, dodecyl-benzyl-trimethyl-ammonium chloride, dodecyl-dimethyl-amine chloride, didodecyl-methyl-amine chloride; isothiazolinone derivatives such as 4,5-dichloro-2- (n-octyl) -4-isothiazolin-3-one or 2-methyl-4-isothiazolin-3-one, 2n-octyl-4-isothiazolin- 3-one and mixtures thereof and other related compounds; sulphonamide derivatives such as N, N-dimethyl-N-phenyl- (N-fluoro-dichloromethylthio) -sulfonamide, N, N-dimethyl-N-tolyl-N- (di- fluoro-methylthio) sulfonamide; triazole derivatives such as 1- (2- (2,4-dichloro-phenyl) -1,3-dioxalan-2-yl) -methyl) -1H-1,2,4-triazole; TCMTP (2-thiocyanato-methyl-thio) -benzothiazole); MBT (methylene bisthiocyanate); IPBC (3-iodo-2-propynyl-butyl-carbamate) -carbenzidin and chlorothalonil; (- (2- (4-chlorophenyl) ethyl) - (1,1-dimethyl-ethyl) -1H-1,2,4-triazol-1-ethanol (tebuconazole) and N-nitroso- hydroxyl amines such as N-nitroso-phenyl-hydroxylamine, and N-nitroso-cyclohexylhydroxylamine, as the metal salts thereof or as metal chelates. Insecticides such as pyrethroids permetrine, cypermethrin and deltamethrin synthetic or chlorinated hydrocarbons such as lindane may also: be incorporated into the formulation.

These additional biocidal compounds may, where appropriate, be incorporated by dissolution in the aqueous solution or may be introduced in the form of oil-in-water emulsions or microemulsions when their solubility in water is too weak to form solutions with the requisite strength.

According to a further aspect of this invention there is provided a method of treating a substrate of the above-defined type which comprises applying to the substrate a composition as defined above.

The experts know the 8 t

various processes for treating substrates with aqueous solutions. For example, the compositions according to this invention may be applied to the wood by immersion, sprinkling, annealing, brushing and by vacuum and / or pressure impregnation. Other types of substrate may be treated by analogous processes.

In an alternative embodiment of this invention, instead of treating the substrate with a composition that includes nitrite and biocide cations, the substrate is first treated with a composition which includes nitrite ion and is subsequently treated with a solution of the biocidal cation. The effect of the initial treatment with the nitrite ion is to make the substrate more susceptible to fix the biocidal cation which is subsequently applied to the wood. Thus, according to a further aspect of the present invention, there is provided a method of treating a substrate of the above-defined type which comprises applying to the substrate an aqueous composition comprising nitrite ion (which may be in free anion form or may being present as part of a complex), the pH composition being greater than 6.5 (preferably 7.0 to 10.0), provided that when the pH of the composition is above 9.25 and the composition contains ammonia or an amine, the composition can not contain the quaternary ammonium salt, constitutes a further aspect of this invention. It is to be noted that for the nitrite composition used in this single step process or in a two-step process described above it is not necessary for the composition to contain a biocidal cation, but for other aspects these nitrite compositions may be analogous to the compositions described above which contain nitrite and biocide cations.

The following non-limiting examples illustrate the invention.

Examples

Preparations were prepared by mixing the following ingredients:

7.0

Sodium nitrite - 1.32 Copper sulphate 5H20 - 1.19 Sodium tri-polyphosphate - 2.55 Water -94.94

Example 2 Sodium nitrite - 1.32 Copper sulphate 5H20 - 1.19 Nitrile-triacetic acid - 1.12 Sodium hydroxide - 0.70 Water -95.67

Example 3

Sodium nitrite Copper sulphate 5H20 Ethylene-di-amine-tetra- (methylene-phosphonic) acid Potassium hydroxide Water Example 4 - 1.32 - 1.19 - 0.99 - 0.76 -95.74 7.0 7.5

Sodium nitrite Copper sulphate 5H20 Boric acid Sodium glucohepnotate Sodium hydroxide Water Example 5 Sodium nitrite Copper sulphate 5H20 Boric acid Sodium gluconate - 1.32 - 1.19 - 0.79 - 0.625 - 0.30 -95.78 7.5 - 1.320 - 1.190 - 0.790 - 0.625 7.5 10

PH

Sodium hydroxide - 0.625 Water -95.689 Example 6 Sodium nitrite - 1.32 Copper sulphate 5H20 - 1.19 Boric acid - 0.79 Sodium heptonate 4,5-dichloro-2- (N-octyl) -6,5,5,5- isotiazoline-3-one-o.ll Mixture of nonionic / anionic surfactant - 0.10 Water -95.565 Example 7 Sodium nitrite - 1.32 Copper sulphate 5h20 - 1.19 Boric acid - 0.79 7.0 Citric acid - 1.29 Water -95.41 Sodium hydroxide - QB to give pH 7.0 Example 8 Sodium nitrite - 1.32 Basic copper carbonate - 0.54 Boric acid - 0.79 7.0 Lactic acid (88%) - 2.42 Water -94.28 Sodium hydroxide - QB to give pH 7.0 Example 9 Solution A: Sodium nitrite -2.62 7.5 Water -97.38 11

Copper Acetate Water - 1.89 4.0 -98.11

Solution B (2): Basic copper carbonate Mono-ethanol-amine Water - 1.09 - 2.31 10.1 -96.60 Solution A may be applied to the material to be treated which is then stored under conditions which avoid evaporation of the water for 48 hours. hours or more. it can then be dried by natural evaporation or by application of heat. This is then treated with solution B (1) or B (2) and allowed to dry again. Solutions B (1) or B (2) may be applied to the still wet material of treatment with solution A immediately or after a certain elapsed time.

Example 10

pH

Sodium Nitrite Copper Sulphate 5H20 Lactic Acid 88% 35% Ammonia Solution Water - 1.30 - 1.18 - 1.60 - 1.29 -94.63 7.5

Example 11 Sodium nitrite Copper sulphate 5h20 Boric acid Sulfo-salicylic acid Water - 1.32 - 1.19 7.5 - 0.79 - 2.40 -94.30

The pH was adjusted to 7.5 by addition of sodium hydroxide.

Example 12 Sodium Nitrite - 1.32 11

Copper sulphate 5H20 Boric acid Imidazole Water - 1.19 - 0.79 6.7 - 0.97 -95.73

Example 13

Sodium nitrite Copper sulphate 5H20 Boric acid

- 1.32 - 1.19 - 0.79 - 2.80 -93.90 6.5

MWT 2000 neutralized polyacrylic acid

Water

Example 14 Sodium nitrite - 1320 Copper sulphate 5H20 - 1,190 Boric acid - 0.400 Sodium heptonate - 0.625 Sodium hydroxide - 0.390 Tebuconazole - 0.012 Mixture of surfactants in xylene - 0.391 Water -95.762 7.5 - 8.0

Example 15

Sodium nitrite Copper sulphate 5HZ0 boric acid

Sodium glucoheptonate

Di-decyl-octyl-dimethyl ammonium chloride

Nonionic surfactant

Sodium hydroxide

Water - 1.32 - 1.19 - 0.79 - 0.63 7.5 - 8.0 - 0.31 - 0.15 - 0.39 -95.22 13

Example 16

Sodium nitrite Copper sulphate 5H20 Boric acid

Sodium glucoheptonate

Di-decyl-octyl-dimethyl ammonium chloride

Non-ionic surfactant

Sodium hydroxide Water

Example 17

Sodium nitrite Copper sulphate 5H20 Boric acid

Sodium glucoheptonate

N-cyclohexyl-di-azene dioxide

Sodium hydroxide

Nonionic surfactant

Water

Example 18

Sodium Nitrite Zinc Sulphate 7H20 Boric Acid Sodium Heptonate Sodium Hydroxide at pH 7.5 - 1.32 - 1.19 - 0.79 - 0.63 7.5 - 8.0 - 0.10 - 0.05 - 0.39 -95.53 - 1.32 - 1.19 - 0.79 7.5 - 8.0 - 0.63 -1.54 - 0.39 - 0.14 -94.00 -13.10 -13.19 7.5 - 6.00 -10.00

Example 19 The following is a dilutable concentrate: -13.20

Sodium nitrite

PH

Copper sulphate 5H20 -11.90 Boric acid - 7.90 Sodium heptonate - 6.25 Sodium hydroxide - 3.90 Water -56.85

Example 20

Sodium Nitrite - 1.32 Copper Acetate 1H20 - 0.94 Boric Acid - 0.79 Sodium Glycoheptonate - 0.63 Sodium Hydroxide - 0.64 Water -95.68 9.5

Example 21 Sodium nitrite - 1.40 Basic copper carbonate - 0.58 Boric acid - 1.25 Ammonia 35% - 1.97 Water -94.480 9.4

Example 22

Sodium nitrite - 2.62 Basic copper carbonate - 1.09 Mono-ethanol-amine - 2.31 Water -93.98 10.0

Example 23

Sodium nitrite - 0.36 N-cyclohexyl-di-azene-dioxy-copper complex (16.47% Cu) - 0.50 Mono-ethanol-amine -0.50 Boric acid - 0.25 Water -98.39 9.6 15

Sodium nitrite - 1.32

Copper sulphate 5H20 - 1.19

Boric acid - 0.4 7.5 - 8.0

Sodium heptonate - 0.625

Sodium hydroxide - 0.39

Permetrine -0.1

Mixture of surfactants -0.39

Water -95.5

Example 25

Sodium nitrite - 0.36

N-cyclohexyl-di-azeno dioxy-copper complex (16.47% Cu) - 0.50

Tri-ethylene tetramine - 0.50 Boric acid - 0.25

Water -98.39

The following experiments show the release of nitrogen oxide (Ν0χ) from solutions with different pH.

Solutions containing 4% by weight of copper as Cu2 + were prepared from the base formulation:

% P / P

Sodium nitrite 17.43 Copper sulphate 5HZ0 15.71 Boric acid 10.43 Sodium glucoheptonate 8.32 Sodium hydroxide QB Water at 100%

The pH was adjusted by varying the amount. of sodium hydroxide in order to obtain compositions of pH 6.0; j 7.0; 8.0 and 9.0 respectively. 16

The solutions were stored in sealed bottles, which caps were perforated to allow air to be withdrawn from the solutions for analysis. These holes were temporarily sealed and the containers stored for 24 hours at a temperature of 20 to 25 ° C.

The NO level in the x-air above the solutions was then measured using Dragen's air sampling tubes.

Results: Solution pH 6.0 7.08.0 9.0 N0 ppm x 22.510,0 0.55 less than 0.5

This illustrates how N0 emissions can be reduced to acceptable levels by increasing the pH. x

The following laboratory experiments illustrate the effect that the choice of the complexing agent has on the fixing of copper within the wood.

Small pinus sylvestris sapwood flakes of approximately 2mm2x50mm were treated by vacuum impregnation with 3.5% w / w aqueous solutions of the following formulations (amounts are expressed as weight ratios): FGH NaNo2 1.32 1.32 1.32 CuSO4 Sodium tri-polyphosphate 2.55 - - Sodium nitrile-triacetate - 1.50 - Sodium glucoheptonate - - 0.75 Water 94.94 95.99 95.96 The solutions were adjusted at pH 7.0 by addition of sodium hydroxide before being used to treat the wood chips.

After the treatment the chips were stored in bottles sealed at 40 ° C for 48 hours after which 50 ml of distilled water were added to each bottle. This was repeated after 24 hours, after a week and finally after 2 weeks. The copper loss of the chips during the 14-day leaching period was: Solution F loss of 51.60% Solution G loss of 45.01% Solution H loss of 26.16% To illustrate the effect that the concentration of a certain chelating agent has copper fixation the following solutions were tested: IJK NaNo2 1.32 1.32 1.32 CuSO4 5H0 4 2 1.19 1.19 1.19 b (oh) 3 0.79 0.79 0.79 Sodium glucohepta 1.00 1.00 0.75 0.625 Water 95.70 95.95 96.075 The pH of the solutions was adjusted to 7.0 by the addition of sodium hydroxide: The loss of copper from the wood chips during the 14 day leaching period was found to be: 49% Solution J loss of 26.16% Solution K loss of 18.16%

As an illustration of the effect that the pH of the solution can have on the degree of copper fixation the solution K was prepared and its pH adjusted with 7.5: 8.5 sodium hydroxide; 9.5 and 10.5. 18

Pine sapwood blocks having the dimensions of 5.0 x 2.5 x 1.5 cm were impregnated with the solutions and allowed to dry by the method described in EN113. They were leached with cold water according to EN84 and the following copper loss results were obtained:

pH 7.5 loss of 18.5 � pH 8.5 loss of 21.0% pH 9.5 loss of 22.2% pH 10.5 loss of 38.5% Penetration and absorption assay of the preservative Assay AA next experiment compares the absorption of the preservative obtained when uses a preferred composition in accordance with this invention as obtained with a composition according to this invention having a pH greater than 9.25 and containing amine. The following formulations were used in a preservative penetration experiment on Pinus Silvestris. Formulation 1: (preferred composition according to this invention)% w / w CuS0..5H_0 4 1.18 = 0.30% w / w Na Cu Heptonate 0.625 H3B ° 3 0.79 pH = 8.0 NaOH pH 8.0 NaNO 2 1.31 Water 100g (the complexing agent, heptonate, is necessary to avoid precipitation of copper when adjusting the pH to 8).

Formulation 2: (Example of a composition according to this invention having a pH greater than 9.25 and containing an amine)

CuSO. , 5H "0 4 2 1.18 = 0.30% w / w Cu H3B ° 3 0.79 Monoethanol amine 1.16 pH = 9.4 NaNO2 1.31 Water 100g

Two equal groups of 10 samples of Pinus silvestris of nominal cross-sectional area of 9.7 x 7.7 cm and 15.5 cm in length were sealed at the end before treatment using the following scheme: Initial Vacuum 635 mm Hg 30 mins Pressure 12 , 5 kg / cm2 90 mins Final vacuum 635 mm Hg 20 mins

The resulting weights for the two formulations were determined which allowed conservative absorptions to be calculated as follows:

Absorption 1 / m3

Formulation 1 Formulation 2 363.65 326.09 290.06 261.45 324.05 245.38 351.46 348.01 400.59 332.94 292.22 247.74 470.85 457.87 295.43 193.36 304.02 277.53 Average 257.11 187.88 334.94 287.85 The difference in mean absorbances is significant at the 99.5% confidence level. Percentage of sapwood penetrated was recorded and the results are presented below: Mean

Formulation 1 100 100 100 100 100 100 100 100 100 98 100

% of sapwood penetrated

Formulation 2 64 81 60 96 73 94 50 62 98 60 Medium 73.8 It is evident that the penetration of wood is better with formulation 1. It is also to be noted that the appearance of the wood treated with formulation 1 was better than that of the treated wood with formulation 2.

Assay B

The following experiment compares the absorption obtained when using a preferred composition according to this invention (formulation 1, as used in Run A), a composition according to this invention having a pH greater than 9.25 and containing an amine (formulation 2 as used in Test A) and a composition having a pH greater than 9.25 and containing an amine and a quaternary ammonium compound (Formulation 3), i.e., a composition that falls outside the scope of this invention.

Formulation 3 (Comparative Example)% wt / wt 1.18 0.79 1.42

Copper sulphate 5H 0 Boric acid Mono-ethanol-amine 21

pH 9.4 0.62 0.62 94.06

Sodium nitrite Benzalkonium chloride (quaternary ammonium salt) 50% aqueous solution Nonionic surfactant Water 0 " benzalkonium chloride " in formulation 3 is a mixture of compounds of formula (A)

wherein R represents a branched or straight chain alkyl group. In most of the compounds of formula A, the R group contains from 8 to 18 carbon atoms.

Three equal groups of 10 samples of Pinus silvestris of nominal cross-sectional area of 9.7 x 7, 1cm and 15.5cm in length were sealed at the extremity prior to treatment with the 3 formulations according to the scheme presented in the test THE.

The resulting weights for the three formulations were determined which allowed calculation of the absorptions of preservative as follows:

Absorption 1 / m3

Formulation 1

Formulation 2 159.5 193.5 219.7 279.8 193.0 221.6 153.6 170.2 137.9 150.7 217.3 137.1 230.8 228.2 148.6 122.3

Formulation 3 (Comparative example) 120.8 135.1 163.9 134.7 117.8121.1 115.8121.6 22

Claims (1)

179.3 180.4 115.3 165.5 193.9 100.3 Mean 193 175 124 (the mean absorbances for formulations 1 and 2 were higher in test A than in test B because the wood used in test A contained a higher proportion of rubber than in test B). The data confirm the results of test A as they show that with formulation 1, a better absorption of preservative is obtained than with the more alkaline amine-containing formulation 2. The absorption of preservative with formulation 2 however shows to be better than that obtained with formulation 3 which includes the quaternary ammonium salt and which is outside the scope of the present invention. A process for the preparation of an aqueous preservative composition which comprises a biocidal cation, which may be a free cation or be present as part of a complex and a nitrile ion, which may be a free anion or present as part of a complex, the composition having a pH greater than 6.5 with the proviso that when the pH is greater than 9.25 and the composition contains ammonia or an amine, the composition may not contain a quaternary ammonium salt, characterized by adding by mixing the constituents of the aforementioned composition. A process according to claim 1, characterized in that a composition having a pH of 7.0 or higher is obtained. A process according to claim 1 or 2, characterized in that a composition having a pH of 10.0 is obtained. A process according to claim 3, characterized in that a composition having a pH of 9.25 or less is obtained. A process according to any of the preceding claims, characterized in that a composition is obtained in which the biocidal cation is the cupric ion. Process according to claim 5, characterized in that a composition containing additionally zinc ions is obtained. A process according to claim 5 or 6, characterized in that a composition containing from 0.01 to 5% cupric ion by weight of solution is obtained. 8. A process according to any preceding claim, wherein the weight of the nitrite ion in the composition obtained is between 0.7 and 7.0 times the weight of the biocidal cation. A process for treating a substrate of the type defined in the disclosure characterized in that a composition when prepared according to any of the preceding claims is applied to the substrate. A method for treating a substrate of the type defined in the description, characterized in that an aqueous composition comprising a nitrite ion, which may be a free anion or is present as part of a complex, is applied to the substrate and subsequently applied to the substrate biocidal cation, which may be a free cation or may be present as part of a complex. A process for treating a substrate of the type defined in the disclosure characterized in that an aqueous composition comprising nitrite ions (which may be free anions or present as part of a complex) is applied to the substrate, the composition having a pH of greater than 6 , With the proviso that when the pH of the composition is above 9.25 and the composition contains ammonia or an amine, the composition may not contain a quaternary ammonium salt. 12- Method according to any of claims 9 to 11, characterized in that the treated substrate is wood. Process according to any one of claims 9 to 12, characterized in that the substrate is treated by vacuum impregnation and / or under pressure. Process for the preparation of an aqueous preservative composition according to any of claims 1 to 8, characterized in that a concentrate of the composition is diluted. 15- A process according to claim 14, characterized in that the concentrate contains 3 to 10% by weight of copper. The applicant claims the priorities of the British patent applications filed on 2 February 1990, 3 August 1990 and 30 November 1990, Nos 9002367.2, 9017111.7 and 9026091.0 respectively. Lisbon, February 1, 1991 25