NZ227167A - Thixotropic agricultural formulation containing water and alkaline earth metal alginate gel; methods of treatment - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £27167 2J2n\Gn Priority Date(s): ..

Complete Specification Filed: Class: Apj.^2^/o^.Co^.^/ QQy /sp/sfc: •*#«•*»•••••• Publication Date: ....2.9. P.O. Journal. No: ...... ...

NO DRAWINGS NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION A COMPOSITION FOR APPLYING TO A PLANT LOCUS ^pj We, HARVEST CHEMICAL (PROPRIETARY) LIMITED, a company registered according to the laws of the Republic of South Africa, of 4 Combrink Street, Alrode, Transvaal, SOUTH AFRICA hereby declare the invention for which^/ we pray that a patent may be granted to-^tfte/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 22 7 1 6 7 BACKGROUND OF THE INVENTION This invention relates to a composition for applying to a plant locus.

Agricultural chemicals such as herbicides, fertilisers, insecticides, fungicides and the like are applied in a variety of formulations and compositions. The compositions may take the form of dusting powders or granules, dispersible powders or granules, aqueous dispersions or emulsions and sprays and aerosol formulations. The active ingredients for such formulations are dispersed in a variety of mediums or carriers depending on the nature of the formulation.

Alginate gels are derived from seaweed and are used in various food products in a highly purified form, i.e. less than 0,1 percent by weight of + 10 micron insolubles. Alginate gels have not, to the best of the Applicant's knowledge, been used in any agricultural applications. 22 7 1 6 7 SUMMARY OF THE INVENTION According to the present invention, there is provided a thixotropic composition for application to a plant locus comprising a major amount of water and a minor amount of an alkaline earth metal alginate gel matrix uniformly dispersed through the water, the water being present in an amount of at least 90 percent by weight of the gel and the alginate gel matrix being present in an amount of up to 5 percent by weight of the gel and the gel containing at least 0,05 percent by weight of -70 micron insolubles. Water forms the continuous phase of the composition and the alginate gel matrix the dispersed phase.

DETAILED DESCRIPTION OF THE INVENTION It has been found that the composition adheres well to surfaces such as leaves and other foliage of plants. These adherent or sticking properties of the composition allow it to be used in a number of applications. For example, the composition contains a considerable amount of water and that water is retained on the surface to which the composition has been applied for a long period. This property may be used for fighting fires or preventing the spread of fires in forests and other agricultural areas. Active ingredients such as herbicides, fertilisers, insecticides, fungicides, and the like may be included in the composition. These active ingredients will be retained on the surface to which the composition has been applied.

The composition has particular application for sprays. The alginate gel makes the composition thixotropic which means that although it appears to be thick nd viscous, it will spray easily either from the ground or from the air at high concentrations. Due to the polymer structure of this gel, spray 22 7 1 6 7 particles of a uniform size are produced and "drift" i.e. sub-micron sized spray particles, is substantially reduced. The composition may be used for spraying herbicides, pesticides, fertilisers and foliar compositions.

The alginate gel matrix is an alkaline earth metal alginate gel matrix. The preferred alkaline earth metals are calcium, magnesium and mixtures thereof. The gel may be formed by bringing together a solution of a soluble alginate, for example, sodium alginate, and a dispersion of a finely divided, poorly soluble alkaline earth metal salt. It is important that in producing the gel there is a slow reaction of the alkaline earth metal salt with the soluble alginate for otherwise an insoluble fibrous alginate may well form. The amount of alkaline earth metal salt will generally be about 30 to 65 percent by weight of the soluble alginate. The preferred metal salt is dibasic calcium phosphate which will produce a calcium alginate gel.

The gel may also be produced by bringing together a soluble alginate such as sodium alginate, and a pre-swelled bentonite and allowing the alkaline earth metal ions of the bentonite to react with the soluble alginate and form an alkaline earth metal alginate gel. In this manner a calcium, magnesium or mixed calcium/magnesium alginate gel may be produced. This is the preferred method because bentonite is a good and economic slow release source of alkaline earth metal ions. Further the gel is a more stable gel than that produced using an alkaline earth metal salt. Bentonite is a montmorillonite which swells when wetted with water. The weight ratio of the soluble alginate to bentonite is preferably in the range 1:1 to 1:10. 22 7 167 The soluble alginate may be produced by boiling seaweed in an alkaline salt solution, such as a sodium carbonate solution, milling the thus treated seaweed, and then removing, e.g. by filtration, large, e.g. + 150 micron, insolubles.

The gel may be treated, e.g. by filtration, to remove + 70 micron insolubles. The resulting product is a coloured alginate gel containing at least 0,05 percent, generally at least 0,5 percent, by weight of -70 micron insolubles. These insolubles will be from the seaweed or the seaweed and the bentonite when bentonite is used in the manufacture of the gel. Such a gel, while suitable for agricultural applications, is totally unsuitable for food applications.

The composition of the invention may also contain a wetting agent. The wetting agent assists in improving the spreadability of the composition on the surface to which it is applied. The preferred wetting agent is an anionic surfactant. Non-ionic surfactants may also be used. Examples of suitable non-ionic surfactants are linear primary alcohol ethoxylates, polyoxyethylene dodecyl phenol, polyoxyalkylene nonyl phenol, polyoxyethylene octyl phenol, ethoxylated castor oil, polyoxyethylated sorbitol, polyoxyethylene stearate, sorbitan monolaurate, sorbitan monostearate and sorbitan monooleate. Examples of anionic surfactants are alkylaryl sulfonates, lauryl polyoxyethylene salts, dioctyl sodium sulfosuccinate, salts of lignosulfonic acids, salts of sulfate ester of nonylphenoxypoly (ethylenoxy) ethanol, polyoxyethylene nonylphenol phosphate esters, tall oil and salts of alkyl sulfates.

The composition of the invention may also include an active ingredient such as a herbicide, pesticide, fertiliser, fungicide or the like. The amount of active ingredient present will vary 22 7 1 67 according to the nature of the active ingredient and the application to which the composition is to be put. Examples of active ingredients are mancozeb, paraquat, fenthion, malathion, and the like.

The composition of the invention will typically be applied to a plant locus by spraying. To this end, the composition will generally be diluted with water to the desired concentration. The dilution will vary according to the application.

In one particular form of the invention, the composition includes a thripsicide such as a salt of an antimony carboxylic acid having an alpha monohydroxy group or nicotine sulphate. The preferred thripsicide is tartar emetic which has the chemical name potassium antimony tartrate. The composition is applied to citrus fruit where thrips, also known as Scirtothrips Aurantii Sauri, causes considerable damage to citrus fruit by eating the tissue around the calyx when the fruit is still young and small. This damage then heals as a scar which stretches as the fruit grows and causes unsightly discolouration to the skin around the calyx. In many cases these fruits are unsaleable. The composition containing the thripsicide is applied to the citrus trees. The alginate gel provides a non-phytotoxic protective coating for the thripsicide active ingredient which nevertheless allows the thripsicide to function effectively.

The composition of the invention has been found to be particularly effective, when diluted with water, for fire fighting, particularly for the control and extinguishing of forest fires. The composition may be applied to the burning trees or ahead of the burning trees to prevent spread of the fire. The water containing the composition 22 7 1 will generally be dropped from an aeroplane or helicopter on the desired area as a single mass or "bomb". As it drops the water disperses into fine droplets and strikes the area in this form.

The composition will preferably contain the alginate gel, a foaming agent and optionally also a wetting agent. The foaming agent may be an agent such as a lauryl ether sulphate, e.g. sodium lauryl ether sulphate, and the wetting agent may be any of the wetting agents described above. The preferred amounts of each component added to 2000 litres of water are: Alginate gel - 25 to 200 litres, preferably 40 to 70 litres. Foaming agent - at least 500 grams, typically 1kg to 5kg.

Wetting agent - 300 to 700 grams.

Typical uses and compositions of the invention are set out in Table 1. 12 7 1 67 TABLE 1 Composition Dilution Use Alginate Gel (% by weight) Wetting Agent (% by weight) In Use (Amount of Composition Added to 100-6 Water) Active Ingredient Thripsicide 100 0 250 to 1000ml Tartar emetic 400g plus sugar 400g Red Spider 1 : j Remedy 40 to 75 0.5 to 1 1 to 5^ Organo- phosphate (optional) j Forest Fire ; Fighting 88 to 98,5 0,5 to 2 1,25* to 10€ Foaming Agent 1 Wetter/ Sticker ! Adjuvant | for Sprays to 60 to 30 50 to 250 Trace Elements Fungicide, Pesticide or Herbicide 22 7 1 67 COMMENTS 1. The sugar which is added to the thripsicide is present as a bait. 2. For the red spider remedy, the composition when diluted is applied to an infested locus and in effect acts to drown the pest. Thus, the organophosphate or other active ingredient is optional.

The invention will be illustrated further by the following specific examples.

EXAMPLE 1 A mixed calcium and magnesium alginate gel was made in the following manner. Seaweed of the Laminaria type was brought to the boil with sodium carbonate solution and then milled in a high shear mixer to produce a slurry containing the milled seaweed. The slurry contained approximately one percent by weight sodium alginate. The slurry was filtered to remove + 150 micron insoluble weed body. To the filtered slurry was added finely particulate bentonite which had been pre-swelled with water to give a/composition containing about 8 percent by weight bentonite. The bentonite had the following composition: 22 7 J 87 Si02 60,99% A1203 20,30 Fe203 6,16 Ti02 0,35 CaO MgO 7,43 Na20 K20 3,73 MOISTURE 9,9.

Ion exchange occurred over a period of about 30 minutes producing a mixed calcium and magnesium alginate gel of good gel strength. The thus produced gel was filtered again to remove + 70 micron insolubles. The final composition was as follows: Component Amount (per 250-6) Alginate (predominantly calcium) 1,3 kg Bentonite 6,0 kg Water 241 £ Other seaweed solubles & insolubles 2,0 kg - 70 micron insolubles 0,2 kg EXAMPLE 2 A mixed calcium and magnesium alginate gel in a water base was made in the manner set out in Example 1 except the seaweed used was of the Ecklonia Max. type. 22 7 1 0 7 - li - EXAMPLE 3 The composition of Example 1 had added to it sodium dioctyl sulfosuccinate (a wetting agent), silicon 1520 (a de-foamer from Dow Corning) and acetic acid. The final composition had the following constituents: Ingredient Percent by Weight Sodium Dioctyl Sulfosuccinate 10 Alginate Gel 20 Silicon 1520 0,4 Acetic Acid to pH 1,2 Water balance This composition was an excellent wetter/sticker adjuvant for various spray applications and can be used in the manner set out in Table 1 above.

EXAMPLE 4 250ml of a composition as produced in Example 1 was added to 100£ water. Also added to the water was tartar emetic and sucrose each in an amount of 400g- The diluted composition was thoroughly mixed. The composition was then delivered to a spray nozzle for application to a citrus crop. It was found that an excellent application of the composition to the citrus crop was achieved with the composition being firmly adhered to the leaves and fruit of the trees. Further, good control of the thrips was achieved. It was noted that the composition was not removed by rain from the trees. 227167 EXAMPLE 5 A solution was made of sodium alginate, sucrose and tartar emetic by dissolving the various components in water. Each of the components was provided in an amount of 400g per 100€. 200g of finely divided dibasic calcium phosphate was dispersed in 1€ of water. The dispersion was added to the solution and the mixture delivered to a spray nozzle for application to a citrus crop. On delivery of the mixture to the spray nozzle the gel began to form. However, by the time the mixture was sprayed on to the crop, gelling had not occurred to an extent whereby the nozzle became blocked. The formation of a calcium alginate gel was completed soon after application to the crop. The coating for the crop which was obtained consisted of a calcium alginate gel which was non-phytotoxic and substantially water-insoluble and included the tartar emetic and the sucrose. The gel did not in any way affect the efficacy of the tartar emetic in controlling the thrips.

EXAMPLE 6 A composition useful, when added to water, in fire fighting consists of the following: 4- Alginate gel - 48 litres. The alginate gel was as produced in Example 1.

. Sodium lauryl ether sulphate - 1kg. 6. Sodium dioctyl sulfosuccinate - 0,5kg.

This composition had a volume of about 50 litres and was added to 2000 litres of water. The water, with the composition added to it, was dropped from an aeroplane on to an area of burning pine trees. The falling water formed droplets which were found to be large and 117167 have a size distribution within a narrow band, thus allowing the water to be concentrated on the area of the burning trees. The fire was effectively extinguished and did not start again. In contrast, a similar area of burning pine trees was only partially extinguished with the same amount of water, also containing the foaming and wetting agents, but not the alginate gel, and started again soon after spraying.

Due to the thixotropy of the composition, it appears to cling to the target which gives the water a better chance of dousing the ember. It has also been found that there are less mist particles and this could account for the greater efficiency in fire-fighting due to the reduction of evaporation loss and the reduction of drift.

The composition was used to extinguish a fire which had started in a narrow valley inaccessible by land. The only way of combatting the fire was from the air. One conventional method from the air is to fly low over the fire and drop water at a height of 3 to 4 metres above the ground. The fire was, however, in a terrain which did not allow this method to be used. Water alone dropped from a higher altitude would have been ineffective due to the high evaporation losses and dispersion. Two drops of 2000 litres each of the above composition from an altitude of several hundred metres completely extinguished the fire. 227167

Claims (12)

WHAT WE CLAIM IS:

1. A thixotropic composition for application to a plant locus, which comprises a major amount of water and a minor amount of an alkaline earth metal alginate gel matrix and bentonite uniformly- dispersed through the water, the water'being present in an amount of at least . 90 percent by weight of the composition and the alginate gel matrix being present in an amount of up to 5 percent by weight of the composition, the composition containing at least 0.05 percent by weight of - 70 micron insolubles, and the weight ratio of the alginate gel matrix to bentonite being in the range 1:1 to 1:10.

2. A composition according to claim 1, in which the alkaline earth metal is calcium or magnesium or a mixture thereof.

3. A composition according to claim 1 or 2, which contains at least 0.5 percent by weight - 70 micron insolubles.

4. A composition according to any of claims 1 to 3, which also comprises a wetting agent.

5. A composition according to claim 4, in which the wetting agent is an anionic surfactant.

6. "" A composition according to any of claims 1 to 5, which also comprises a herbicide, pesticide, fertiliser, or fungicide. - 15 - 227167

7. A composition according to any of claims 1 to 6, which also comprises a foaming agent.

8. A method of applying a herbicide, pesticide, fertiliser, or fungicide to a plant locus which comprises the step of applying to that locus a composition according to claim 6.

9. A method according to claim 8, in which the application is by spraying.

10. A method of treating a burning plant locus, which comprises the step of applying to that locus a composition according to claim 7.

11. A thixotropic composition as defined in claim 1 substantially as herein described with reference to any example thereof.

12. A method as defined in claim 8 of applying a herbicide pesticide, fertiliser, or fungicide to a plant locus substantially as herein described with reference to any example thereof. CHenniCALS By Mis/Their authorised Agent A.,1. PARK ?■ SOM