CA2198704C

CA2198704C - Sprayable, film-forming system releasing active substances for use on plants

Info

Publication number: CA2198704C
Application number: CA002198704A
Authority: CA
Inventors: Hans-Rainer Hoffmann; Michael Roreger; Malgorzata Kloczko
Original assignee: LTS Lohmann Therapie Systeme AG
Current assignee: LTS Lohmann Therapie Systeme AG
Priority date: 1994-08-27
Filing date: 1995-08-12
Publication date: 2007-04-03
Anticipated expiration: 2015-08-12
Also published as: CA2198704A1

Abstract

A sprayable, film-forming active substance preparation for the application to plants is characterized by the fact that films which can be produced thereof are pressure-sensitive adhesive, water-insoluble, and at least partially biodegradable.

Description

Sprayable, film-forming system releasing active substances for use on plants SPECIFICATION
The present invention relates to a sprayable, film-forming prepara-tion, in particular for the systemic administration of biologically active substances to plant organisms.
Active substance formulations normally used for plants in practice are emulsion concentrates, suspension concentrates, or so-called wettable powders which are applied by means of different spray-ers, spargers, or nebulizing devices (e.g. spray bottles). However, these conventional preparations entail the disadvantage that active substance losses occurring during their application contribute to the contamination of the environmental sections (air, earth, wa-ter). This problem is caused by the spray flowing or dripping down the plant surfaces, by rain water washing the spray off, and by the spray drift during application. Their insufficient retention (adherence) and the poor wettability of plant surfaces are further disadvantages of these active substance formulations. These defi-ciencies frequently interfere with achieving the desired effect.
In the past, many attempts were made to minimize these draw-backs in order to optimize the use of spray agents:' According to the art, these attempts can be summarized as follows:
1. Application properties of sprays are improved by adding dif-ferent substances, such as surface-active agents, substances to prevent drying up, re-humidifying agents, hygroscopic addi-tives, foamers, and in particular adhesion promoters.

..- 2198104 2. Selective positioning to plant surfaces is considerably facili-tated by loading the spray electrostatically.

3. The retention and wetting properties can be improved by modifying the size of droplets, the spraying pressure, and the spraying distance.
However, none of these measures provide a satisfactory solution with respect to spray drift and environmental impact.
In order to overcome this disadvantage, improved active sub-stance release systems were developed which represent an alter-native to conventional sprays. These are depot formulations in the form of flat-shaped, patch-like, adherent or pressure-sensitive ad-hesive systems which are applied to the plant's shoot axis. These administration forms for active substances effectively overcome the problem of active substance losses and the resulting environ-mental pollution; however, their use involves a lot of other prob-lems mainly caused by their application. With this kind of devices it is extremely important to dimension the size of their contact surface to the plant such that it does not project any parts of the plant. In case of plants the growth of which limits the choices of application site, e.g. those completely covering the soil, their ap-plication is therefore very difficult. Also, the application of these systems to plants whose surfaces have spines or thorns must be regarded as critical.
In addition, there are problems with respect to using these sys-tems in plants excessively growing in thickness; if the carrier foil is insufficiently stretchable, the application around the stems in-volves the risk that the plant becomes strangled or that the sys-tem grows into the shoot axis, this may damage the underlying tissue layers.

21987u4 Finally, the use of such systems takes a relatively great deal of time and work not only with respect to the application, but also afterwards since they must be removed when the treatment is completed. Moreover, there is the cost-increasing problem of waste disposal.
According to this state of the art one can say in general terms that it has provided considerable progress with respect to the reduction of the required active substance expenditure, the frequency of application, and the undesired effects on other organisms, but that this is accomplished at the expense of other properties.
Film-forming formulations represent another kind of active sub-stance release systems. These are known in the art from the fol-lowing patents SU 1364267, DE 2804563, JP 66009674, and US
4923698.
The publication SU 1364267 relates to a film-forming formulation based on carboxymethylcellulose and used in the storage of agri-cultural products, in particular in the preservation of fruits and vegetables. To this end, the crop product to be stored is treated by spraying or dipping to form a thin film on the surface of the plant organs; owing to its physical properties, this film protects the plants from unnecessary losses of water and therefore im-proves their storage life. However, there is no indication in this publication that this preparation contains active substances.
German patent DE 2804563 discloses an active substance-con-taining, film-forming preparation. It describes a formulation that comprises bird repellents and is used as an agent against bud feeding in useful and flowering shrubs. This is an aqueous poly-mer dispersion that is stirred into water together with the active substance during the preparation of the plant spray; but it can also be formulated as an active substance-containing wettable powder.

2198 l04 In both cases the incorporated base polymers, such as homopoly-mers and copolymers of vinyl acetate or acrylic ester, serve as adhesives.
Japanese patent publication JP 6445100 describes another active substance-containing, film-forming formulation. This is a prepara-tion of rodent repellents based on an inorganic active substance absorber (e.g., kaolin, talc). The addition of polymeric adhesion pramters such as methyl or carboxymethylcellulose, polyvinyl alcohol, or urea, results in the formation of a water-insoluble film layer adher-ing to the plants' surfaces and providing protection against ro-dents owing to its content of repellents.
US 4923698 relates to film-forming, nonpolymeric preparations of insecticides or insect repellents. In this case a formulation based on a water-in-oil emulsion is proposed which comprises lubricants in addition to the bioactive substances. These lubricants ensure that the film formed by evaporation of the predominant portion of the oil and water phase has a property rendering the movement of running insects on its surface impossible. In addition, the active substances contained in the film can considerably increase the outcome of pest control because of their direct influence on pests.
In connection with film-forming, sprayable active substance prepa-rations it is finally referred to the articles in the technical journals Hort science (20,50 : 879-881 ) and Plant Disease (67 : 212-214), which describe the experimental use of such developments in plants to control leaf diseases.
These known active substance-containing sprayable formulations which are capable of forming films have the severe disadvantage in common that the films resulting after their application cover the plant surface only for a relatively short time; this is to be ascribed to their hydrophilic character. These formulations are not suitable .. 2198 704 for the systemic release of active substances to the plant organ-ism because they lack the capability of adhering permanently. The active substances must be present on the plant surface for a suf-ficiently long time in order to supply the plant organism with the active substance in a concentration sufficient to develop persistent systemic action.
Moreover, it is not the main function of these formulations to ad-minister active substances to the plant, but to provide an external protection of the plant against pests. For this reason the known application systems do not offer a satisfactory solution of the above-mentioned problem with respect to the administration of biologically active substances to plant organisms.
Thus, the horticultural wish for ecologically beneficial active sub-stance depot preparations for plants which are easy to handle is still left open by the art.
It is the object of the present invention to propose a sprayable, active substance-containing, film-forming, pressure-sensitive ad-hesive, water-insoluble, and at least partially biodegradable prepa-ration that preferably does not pollute the environment and which provides active substance release systems combining the advan-tages of conventional spraying systems and those of the so-called controlled-release-formulations without having to accept their drawbacks.
Most surprisingly, this object is achieved with an active substance formulation according to the characterizing features of the main claim; this fully meets the above-mentioned requirements. Addi-tional essential embodiments of the active substance formulation are provided in the subclaims.

The term "sprayable, film-forming preparation/formulation" is used to mean preparations which form a film on the surface of a sub-strate after application on said substrate by means of spraying.
The film's state of distribution may differ; it may be a con-tinuous film, or a discrete film distributed in lumps, and also inter-mediary transient stages.
Films made of the active substance formulations according to the present invention advantageously are pressure-sensitive adhesive, insoluble in water, and at least partially biodegradable.
Polymers performing both the function of film formers and that of active substance carriers are essential components of formulations according to the present invention. Such film-forming, sprayable polymer solutions are known from human medicine. They are used as wound dressings instead of textile dressing materials and ad-hesive dressings and are called "spray plaster" in colloquial lan-guage.
Homopolymers or copolymers of esters of acrylic acid and/or methacrylic acid, e.g., methyl acrylate, ethyl acrylate, acrylic acid-n-butyl-ester, and methacrylic methyl ester, are used as film-forming substances for the production of formulations according to the present invention. Moreover, other suitable polymers are ethylcellulose, cellulose butyrate or cellulose acetate, as well as polyhydroxy butyrate and polyhydroxy valerate.
The preparations according to the present invention are physical active substance/polymer-combinations which are present as solu-tion or emulsion. They are sprayed on a plant surface as aerosols and form thin, coherent, active substance-containing, and water-insoluble films after evaporation of the solvents or emulsifiers.

The nontoxic organic solvents contained in these preparations are highly volatile. In general, they have a boiling range of +50°C to 180°C. If possible, their boiling point should not exceed 150°C
to prevent unnecessarily long drying periods of the formed film. Suit-able solvents include ethyl acetate, chloroform, acetone, ethanol, or their mixtures. The amount of the solvent or solvent mixture must be chosen such that the total preparation has a relatively low viscosity ensuring perfect spraying without formation of ropes.
In addition, the preparations according to the present invention must be perfectly aerosolizable and stable during storage in aero-sol containers. Suitable propellants include light hydrocarbons, such as propane, butane, isobutane, and their mixtures in the form of a liquefiable gas. The halogenated hydrocarbons frequently used as propellant in the past shall not be used any longer because of their high ozone-destructive potential. Nitrogen, carbon dioxide, or dinitrogen monoxide may be used as blowing gases instead of light hydrocarbons.
The total amount of the solids mixture used as film former and active substance carrier system shall amount to 0.5 to 10~-wt., preferably 4 to 6~-wt., relative to the total preparation in-__.~~
cluding propellant.
An important advantage of the active substance formulation ac-cording to the present invention is the fact that the formed films are pressure-sensitive adhesive. This efficiently counteracts the serious disadvantage of conventional techniques, i.e., the insuffi-cient retention. The active substance-containing films resulting from these formulations preferably exhibit permanent adhesive-ness. They immediately and permanently adhere to plant surfaces and thus ensure intimate contact to the terminal tissue of the plant; this contact is absolutely necessary for an optimum active substance release. In particular if a long-term, sustained active lJ l substance supply is required, this property gains special impor-tance. The high adhesive capacity is relatively temperature-inde-pendent in the application area. The stability of the films is also ensured in this area. For this reason, they are suitable both for the application to plants in the interior and for outdoor uses.
The pressure-sensitive adhesive properties of the film bring about additional advantages with respect to application, in particular in plant protection. Owing to the immediate adhesive power these films may serve as mechanical barrier or trap for numerous de-structive insects which adhere to the film surface at the slightest touch. Since the films comprise active substances pests (e.g., fungus spores or insects) immediately come into contact with the active substance so that a harmful action is prevented.
Pressure-sensitive adhesive properties may be achieved by using suitable polymers as active substance carrier. These mainly include mixed copolymers of acrylic acid and acrylic esters, in particular alkyl acrylate having 4 to 12 carbon atoms in the alkyl group, for example, 2-ethylhexyl acrylate, n-butyl acrylate, and isooctyl acrylate.
If polymers are used which are not pressure-sensitive adhesive, suitable auxiliaries must be added to obtain the desired properties.
Resin-like substances, such as modified natural resins, above all colophony and its derivatives, polyterpene resins, hydrocarbon resins, and coumarone-indene resins mainly serve this purpose.
Particularly suitable are colophony esters (such as Fora~~ 85 and Staybelite~Fster 10) since these are excellently compatible with polyacrylates. The amount of resin to be added depends on the desired adhesive properties and has an upper limit because the cohesion of the formed films is too low where the resin proportion is excessively high. The amount may vary fxom 1.0 to 20~-wt., normally __. 2198 70~+

it is of the order of 5 to 10%-wt., relative to the solids content of the preparation.
Another advantage of the preparations according to the present invention lies in the fact that the formed films are insoluble in wa-ter. This is of particular importance because the films adhere to the plant surfaces even during high-rainfall periods. For this reason the adhesive strength of the films does not change over a desired treatment period.
The water resistance results from hydrophobic properties of the film-forming substance. In addition to polyacrylates, polyhydroxy butyrate and hydroxy butyrate-hydroxyvalerate-copolymers, as well as ethylcellulose and cellulose butyrate and cellulose acetate may be used as suitable film-forming components of the prepara-tions according to the present invention. Moreover, they stand out for biodegradability, rendering them particularly suitable for use in the production of the preparations according to the present inven-tion.
Films formed on plant surfaces from preparations according to the present invention must preferably be biodegradable. This means that they are partially or completely decomposed by the action of a biologically active environment (microorganisms). This property is particularly advantageous since the films, owing to their good pressure-sensitive adhesiveness, may remain on the plants as ac-tive substance depots for longer periods of time (e.g., one vegeta-tion period) without having to be removed later. The degree of biodegradability can be controlled by the choice of polymer. The user of these formulations can therefore save a great deal of time and work and simultaneously has the advantage of a persistent active substance supply. This combination of the above-mentioned properties renders the preparations according to the present ... 2198104 invention clearly superior to active substance release systems de-scribed in the art.
The active substances contained in the films according to the present invention are released in a controlled manner, the release taking place by diffusion.
Active substances which can be released to plants by means of the preparations according to the present invention are those in-fluencing processes in the animal or plant organism. Insecticides, fungicides, acaricides, bactericides, and growth regulators are to be mentioned as systemically active plant protection agents in the first place.
Systemic insecticides include, for example, butocaroxim, di-methoate, fenoxycarb, methamyl, oxamyl, oxydemeton-methyl, pirimicarb, or propoxur.
Systemic fungicides include, for example, benomyl, bromucona-zole, bitertanole, etaconazole, flusilazol, furalaxyl, fosetyl-Al, imazalil, metalaxyl, penconazole, propiconazole, thiabendazol, triadimefon, triadimenol, or triforine.
Systemic acaricides include, for example, clofentizine, fenbutatin oxide, and hexythiazox.
Systemic growth regulators include, for example, ethephon and j3-indolylacetic acid (IAA).
Flumequine, for example, is to be mentioned among the systemic bactericides.
Moreover, the preparations according to the present invention may comprise active substances which do not act systemically in the plant but remain on the plant surface and therefore have a contact action on pests. It is possible, for example, to incorporate contact fungicides belonging to the family of dithiocarbamates, such as maneb, zineb, or mancozeb, into the preparations according to the present invention in order to protect plant surfaces from local fungus infections (fungi causing false mildew, organisms causing spot-ting on leaves, various rust diseases).
Bird and insect repellents represent another application example of bioactive substances which do not develop their action via the plant. These may also be applied on plant surfaces by means of the preparations according to the present invention and can thus develop their action on the respective pest.
Active substances may be present in preparations according to the invention either individually or in a mixture. They may be dissolved or dispersed in the polymer matrix. A preferred embodiment of formulations according to the present invention has the following ingredients:
a) 1.0 to 10.0%-wt. of solids, the solids comprising 0.5 to 8.0%-wt. of at least one polymer 0.5 to 5.0 of at least one active substance 0.0 to 2.0%-wt. of formulation auxiliaries, relative to the total weight of the preparation, b) 0.5 to 80%-wt. of at least one volatile organic solvent c) 0.5 to 80%-wt. of at least one liquefied gas propellant.
Preparations according to the present invention may comprise as auxiliary agents penetration enhancers, tackifiers, emulsifiers, and plasticizers. The function of these auxiliary agents is, on the one hand, to offer the active substance to the plant in a suitable physical-chemical form and, on the other hand, to produce the optimum effect of the potency inherent in an active substance Penetration enhancers intensify the diffusion of a bioactive substance into the conducting system of the plant. For this purpose, the following substances may be added: alkylsulfates, alkyl sulfonates, fatty acids, fatty acid salts of multivalent metals, fatty acid esters, amine oxides, mono-, di- or triglycerides, long-chain alcohols, salicylic acid, 2-pyrrolidone derivatives, or urea.
Adhesive resins are suitable tackifiers. Colophony esters (Staybelite ~ Ester 10) and synthetic hydrocarbons (such as Escorez~ 1102 F) are particularly suitable.
Suitable emulsifiers include, for example, higher fatty alcohols, partial fatty acid esters, polyvalent alcohols, partial fatty acid esters of sugars, polyethyleneglycol fatty acid esters, polyethyleneglycol sorbitan-fatty acid esters, as well as phospholipides, quaternary ammonium compounds, and pyridinium compounds.
Suitable plasticizers include low-molecular polyethylene alcohols, glycerol esters, mono- and polyvalent alcohols, fats, or waxes.
The formulations according to the present invention may serve to administer bioactive substances to plants, which have both a systemic and a local action.
Plant protection is a preferred field of application of the preparations according to the present invention. In an embodiment of the present invention, the formulations of the present invention can be used as a protective film covering plant surfaces for prevention of fungus infections, and/or suction and voracity by pests. The following examples are given to illustrate the present invention. Any indications as to quantities, proportions, and percentages relate to the total weight of the preparation (including propellant), unless otherwise stated.
21504180.2 Example 1:
4.5 parts by weight of a 2-ethylhexyl acrylate/acrylic acid-copoly-mer having a molar mass of 750,000 dalton are dissolved in a pressure vessel under heating and stirring in 44 parts by weight of ethyl acetate. After addition of 0.9 parts by weight of colophony resin (Fora1~85) used as tackifier, 0.6 parts by weight of the active substance triticonazole are dispersed in the mass thus obtained.
This active substance-containing polymer solution, whose relative viscosity at 25°C amounts to 0.58 Pa.s (according to Brookfield LVF/measuring body), can be filled into an aerosol container under addition of 50 parts by weight of same portions of butane, pro-pane, and isobutane.
Example 2:
parts by weight of the active substance fenarimole together with 0.5 parts by weight of N-methyl-2-pyrrolidone are added to 29.5 parts by weight of a conventionally obtained mixed polymer consisting of 75%-wt. of poly-2-ethylhexyl acrylate, 15%-wt. of polyacrylic acid, and 10%-wt. of polymethyl methacrylate, and which is present as a 48%-wt.-polymer solution in a solvent mixture consisting of equal parts by weight of ethyl acetate and ethanol. The added active substance is homogeneously distributed in the mass under constant stirring. After addition of 65 weight percentage of liquefied butane, the active substance-containing polymer solution is filled into an aerosol container.

Claims

The Embodiments Of The Invention In Which An Exclusive Property Or Privilege Is Claimed Are Defined As Follows:

1 A spray preparation for application of an active substance to plants, the preparation comprising an active substance and a polymer material that forms an active substance-containing film which is pressure-sensitive adhesive, water-insoluble and at least partially biodegradable, wherein the polymer material is selected from the group of film-forming polymers consisting of cellulose derivatives with a degree of substitution of s 2, polyhydroxybutyrate, polyhydroxyvalerate and hydroxybutyrate-hydroxyvalerate copolymers.

2. The spray preparation according to claim 1, characterized in that the cellulose derivative with a degree of substitution of <= 2 is selected from the group consisting of cellulose ethers, cellulose esters and cellulose-acetate-butyrate mixed esters.

3. The spray preparation according to claim 2, characterized in that the cellulose ether is ethyl cellulose.

4. The spray preparation according to claim 2, characterized in that the cellulose ester is selected from the group consisting of cellulose acetate and cellulose butyrate.

5. The spray preparation according to claim 1, characterized in that it comprises at least one auxiliary agent selected from the group consisting of penetration enhancers, tackifiers, emulsifiers and plasticizers.

6. The spray preparation according to claim 1, characterized in that the active substance to be supplied to plants is selected from the group consisting of insecticides, fungicides, bactericides, acaricides and plant growth regulators;
wherein the insecticides are selected from the group consisting of butoceroxim, dimethoate, fenoxycarb, methamyl, oxamyl, oxydemeton-methyl, pimicarb and propoxur;
the fungicides are selected from the group consisting of benomyl, bromuconazole, bitertanole, etaconazole, flusilazol, furalaxyl, fosetyl-A1, imazalil, metalaxyl, penconazole, propiconazole, thiabendazol, triadimefon, triadimendol and triforine;
the bactericides are flumequine;
the acaricides are selected from the group consisting of clofentizine, fenbutatin oxide and hexythlazox; and the plantgrowth regulaters are selected from the group consisting of ethephon and .beta.-indolylacetic acid (IAA).

7. The spray preparation according to claim 1, characterized in that the active substance is a substance having contact action and is selected from the group consisting of fungicides and insect repellents, wherein the fungicides having contact action are selected from the group consisting of dithiocarbamates, ziram, zineb, nabam, marcozeb and thiram;
and the insect repellents having contact action are selected from the group consisting of dimethylphthalate, indalone or N,N-diethyl-meta-toluamide.

8. The spray preparation according to any one of claims 1 to 7, characterized by a controlled active substance release.

9. Use of the spray preparation as defined in any one of claims 1 to 8 for administration of active substances to plants.

10. Use of the spray preparation as defined in any one of claims 1 to 8 for formation of thin layers on plant surfaces.

11. Use of the spray preparation as defined in any one of claims 1 to 8 as a protective film covering plant surfaces for prevention of fungus infections, or suction and voracity by pests.

12. Use of the spray preparation as defined in any one of claims 1 to 8 as a protective film covering plant surfaces for prevention of fungus infections, and suction and voracity by pests.