CA1093761A - Fungicidal cuprammonium complex composition and method - Google Patents

Abstract

ABSTRACT OF DISCLOSURE
This invention relates to aqueous solutions of cuprammonium carboxylate complexes and the use of such solutions as a fungicide for treating wood, painted surfaces, fabric and to inhibit algal growth. The novelty of the invention resides in the compositions containing a relatively higher concentration of effective copper of between 4 and 10% for a considerably smaller concentration of water therein. Aqueous solutions of such compounds have always been desirable because they are easier to apply on the substrate than solids and the production of these compositions in concentrated form has mitigated the problem of bulk handling.

Description

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The present invention relates to compositions containing cuprammonium complexes of carboxylic acids and a method of preparing such compositions~
Copper salts have long been used ln fungicidal compositions.
Furthermore, the toxicity of soluble copper salts is also well recognised. Whilst it is possible to produce solid copper compounds of moderate and acceptable to~icity levels, the use of such solid compounds even in very fine form is limited to a considerable extent due to the difficulties in applying such solids uniformly on a substrate surface to achieve maximum surface cover for effective protection per unit weight of the compound. Even in cases where such copper compounds have been produced in soluble form, such solutions have been very dilute solutions containing more than 60%
by weight of the solvent or about 8% of effective copper content.
Such compositions in the context of cuprammonium carboxylate have been claimed and described in US patent Nos. 3900504 and 4020180.
Such solutions present a different kind of problem, i.e. that o bulk handling which makes them commercially unviable and furthermore, the limited solubility of these complexes generate additional problems due to precipitation and sedimentation in the containers used for transportation~ In commercial operations, such precipi-tation can also Iead to blockages in pumping and spraying equipment.
It has now been found that homogeneous aqueous solutions of cuprammonium complexes may be produced which not only contain relatively~smaller amounts of the solvent but also have a higher effective copper content than produced hitherto.
Aecordingly,~the present invention is a homogeneous liquid composition ccmprislng~a cuprammonium complex of one or more Cl to C4~monocarboxylic acids containing between 4 and 10% by welght of 30 ~ ~dissolved copper and up to 40% by weiyht of water.

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According to a further embodiment, the present invention is also a method of preparing a homogeneous liquid composition comprising a cuprammonium complex of one or more Cl to C4 mono-carboxylic acids containing between 4 and 10% by weight of dissolved copper and up to 40% by weight of water, said method comprising reacting an acid a~nonium salt of the monocar~oxylic acid with a copper compound selected from cuprous oxide and cupric oxide in the presence of aqueous ammonia.
The monocarboxylic a dd moieties in the salt may be derived from saturated or unsaturated monocarboxylic acids. Examples of such acids include fo =ic acid, acetic acid, propionic acid, the isomeric butyric acids, acrylic acid and methacrylic acid. By the expression "acid ammonium salt" as used here and throughout the specification is meant salts in which two moles of the acid moiety are present per mole of the ammonium ion on a chemical equivalent basis. mus~ the acid ammonium salts are preferably one or more of ammonium di-formate, ammonium di-acetate and ammonium di-propionate.
The product of the reaction between the acid ammonium salt and the copper oxide in the presence of aq~leous ammonia is a dark blue aqueous solution cor~aining the cupram~nonium complex in a concen-tration within the specified range, The llquid compositions of the present invention possess fungicidal activity due to the presence of copper. These compo-sitions therefore find several uses, for example as paint biocides, as wood preservatives, as fungicides to prevent mildew on fabrics and to counteract growth of alg`ae and marine fouling. Particularly, these composltions inhibit the growth of fungi such as herbarum which are responsible for the spoilage of paints, and Co~ which causes wood decay.

For any o~ the above uses9 the compositions may be used as such ;~

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--3'76.1 in the form of their aqueous solution. me aqueous solution may however contain other conventiollal additives capable of supple-menting their activity such as free formic acidl propionic acid, formalin and bisulphites. The aqueous solutions may additionally contain wetting, spreading or sticking agents or may be emulsified with mineral oils where necessarya The concentration of the cuprammonium complex applied to a substrate will depend not only upon the substrate and its end use but also on the nature of the attack to be treated or prevented~
10 m ese can however be easily ascertained by those skilled in the art. For example, for the preservation o* wood, treatment rate equivalent to concentrations of copper in the range On4 to 1.0%
may be used.
Where it is desirable to dilute the cuprammonium complex solution for high volume application, as for instance in the case of preservation of wood referred to above, the dilution is preferably carried out using a 1~3% aqueous ammonia solution to prevent precipitation of the comple~. I water alone is used as diluent, for example at dilutions o about 100:1, a flocculent 20 gelatinous blue precipikate may separate.
The cuprammonium complexes of the present invention have greater solubility in water than the conventional copper salts such as copper formate and copper propionate, and when prepared, have a pH of between 7 and 9~ Their improved solubility allows a freerflow and more even spread of the composition onto the substrate, particularly when used as epraysO As can be seen from the table, compared to copper propionate and copper formate, the cuprammonium complexés are ~ore water soluble which facilitates application by spraying. The differences in copper solubility (at ambient temperature~
are presented below:

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____ _ %Cu in a saturated Compound aqueous solution ~ _ Copper Propionate2.2 Cuprammonium 5 - 10 0 Propionate Complex .
Copper Formate 2O9 Cupramntonit~ 4 5 Forma~e Complex .
~_ The invention is furbher illustrated with reference to the following ~xamples.
10 XXA~PI,155 A. PREPARATION OF COMPLEXES
The comple~ can be prepared by reaction of the acid ammonium salt ~70% w/w aqueous solution) with either cupric or cuprous oxide and aqteous ammonia. Some preparations are described below.

1. A 70% aqueous solution of ammonium dipropionate (212 g) was added to cupric oxide ~30 g), and the mixture heated tmder reflux for 30 minutes. A~ter cooliny 88 g of aqueous amntonia (33.3% w/w 20 NH3) was added, and the mixture filtered to give a dark blue solution containing 13.5% w~w MH3, 39~% w/w propionate, 7.~% w/w copperj and 39.7% w/w water (pH = 8.0).
2. A 70% aqueous solution of ammonium dipropionate (106 g) was added to cupric oxide (30 g), and the mixture heated urtder reflux for 30 minutes. After cooling 44 g of aqueous ammonium (33O3% NH3) was added, the solution recooled, and filtered to rentove unxeacted cupric oxide ~6.6 g). l~te final solution contained 13.0% w/w NH39 38.2% w/w propionate~ 10% w/w copper, and 38.8% w/w water (pH -- 8~0).
30 ;3. ~ 70~ aqueous solution of amntoniu~ dipropionate (212 g) was added - S-'7~:~

to 30 g of cuprous oxide and heated under reflux for 1 hour.
After cooling, 88 g of aqueous ammonia ~33.3%) was added, the solution cooled, and filtered to remove excess copper metal (12 g).
The final solution contained 14.0% w~w NH3, 41~3% w/w propionate,

5~0% w/w copper9 and 39~7% w/w water tpH = 7.6).

This complex was prepared by reacting cupric oxide with aqueous am~onia and 70% aqueous ammonium diformate. The final solution contained 4.5% by weight copper, 40% by weight formate, and 39.0% by weight water.
B~ ACTIVITY u~ ~IDR~MM0~lUM C[M L~3S
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5. The complex in solution at various dilutions was run onto wooden blocks o Scots pine sapwood o the species as follows: ~
The blocks were oven dried, weighed and vacuum impregnated with a solution of cuprammon ~ propionate. Twelve (12) blocks were treated at each of the ~ollowing concentration of the complex in solution as % copper: 1.0, 0.637 0.40, 0~25, 0.16, 0`.10 and 0.063~
The blocks thus treated along with untreated blocks were exposed to a culture of Cc~ r~ell~ organism in bottles containing soil for a period of six (6) weeks.
After this period the test blocks were removed from the culture, weighed, oven dried and reweighed~ The inal oven dried mass was ` compared with the initial dry mass to calculate the loss in mass due to decay by the organism~ Two blocks treated at each concen-tration and not exposed to the o~ganism were also oven dried and weighed to~correct for the uptake of the preservative complex.
On the basis of weight loss, the toxic limit, i.e. the interval ;
~ 30 between that concentration which just permits decay and the concentration .
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next highest in the series which inhibits all decay was 0.25 -0.40% copper in the treating solution. The loading in the wood expressed as copper for this toxic limit was 1.9 - 3.2 Kg/m of wood.
As a further comparison one of the most widely used waterborne preservativ~ based on copper sulphate, potassium dichromate and arsenic pentoxide known as 'CCA preservative' was tested as before using blocks of the sa~e wood and the same organism, This gave a toxic limit of 1.8 - 3~0 Kg/m in terms of metal content. Thus for a metal loading similar to that of CCA, the present invention enables the use of the more acceptable copper complexes~
Paint Biocide Activity

6, The activity of copper ammonium propionate as a paint biocide was evaluated as follows:
Copper = cnium propionate (500 ppm) was added to a molten medium (50C) consisting of Czapek Dox agar (Oxid CM 97) and poured lnto 100 mm Petri dishes and the mixture allowed to harden. Surface moisture was removed from the growth media by drying at 50,C. The agar plates were inoculated with suspensions of the test organisms using a multipoint inoculator, and incubated for seven (7) days at ; 25C. A corresponding control medium without addition of the complex was prepared, inoculated and incubated under identical conditions.
The following spore ger~ination results were obtained. In all cases even the slightest growth or spore germination was considered to constitute a failure of the preservative to inhibit the organisms~

_ - ~ , Test Organisms Cladosporium Fusarium Penicillium Pestalotia herbarum species expansum macrotricha ~ ~ ~ , Cuprammonium No No No No propionate germination germination germination germination (500 ppm) ~_ ~ ~ ~

- Control Positi~e Positive Positive Positive _ germination germination germination germination _ ___ __ _.................... ,.... ~ ~,

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Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-We claim:

1. A homogeneous liquid composition comprising a cuprammonium complex of one or more C1 - C4 monocarboxylic acids containing between 4 and 10% by weight of dissolved copper and up to 40% by weight of water.

2. A process for preparing a homogeneous liquid composition comprising a cuprammonium complex of one or more C1 - C4 monocarboxylic acids containing between 4 and 10% by weight of dissolved copper and up to 40% by weight of water, said process comprising reacting an acid ammonium salt of the monocarboxylic acid with a copper compound selected from cupric oxide and cuprous oxide in the presence of aqueous ammonia.

3. A process for preparing cuprammonium complex according to Claim 2 wherein the acid ammonium salt is selected from ammonium diformate, ammonium diacetate and ammonium dipropionate.

4. A process for protecting substrates selected from wood, painted surfaces, fabrics and marine structures against fungal attacks comprising treating said substrate with an aqueous solution of a cuprammonium complex of C1 - C4 monocarboxylic acid.