AU737838B2 - Film-coated fertilizer with controlled nutrient release - Google Patents

Description

S0050/47385 1 Film-coated fertilizer with controlled nutrient release The present invention relates to a film-coated fertilizer comprising individually coated volumes of a nutrient-containing substance, the film coating the nutrient-containing substance comprising a water-permeable polymer, a cellulosecontaining material, a textile material, a lignocellulose material or a combination of two or more thereof, and to a process for its preparation and to a fertilizing method in which the film-coated fertilizer according to the invention is used.

To improve the efficacy of fertilizers, it is generally known to employ, as fertilizers, fertilizer granules which are coated with a layer of a polymer. The increase in efficacy is caused by the fact that the coated fertilizer releases the substances which act as plant nutrients in a delayed manner so that it can be active over a prolonged period. Such slowrelease fertilizers are described, for example, in Ullmanns Enzyklopidie der Technischen Chemie, 5th Ed., 1987, Vol. Al0, pp. 363-369, and their advantages are compiled in Fert. Res., 1993, Vol. 35, pp. 1-12.

Such coat-core systems, which may also comprise fertilizers as active ingredient, are described, inter alia, in EP-A-0 523 098 and in EP-A-0 381 181. Other fertilizers which are coated with biodegradable polymers are disclosed, for example, in WO 95/03260.

The disadvantages of these granulated fertilizers which are provided with a coating are the additional costs in their preparation and the complications from storage due to stocking a large amount of different fertilizers. Moreover, different coat thicknesses, which are due to irregular particle surfaces and a broad particle size distribution within the fertilizers to be coated, entail a certain inaccuracy as regards the release of the nutrients.

005D/47385-2 2 A possibility of avoiding these disadvantages is to coat fertilizers, or nutrient-containing substances, with a film.

Thus, for example, US 4 224 048 describes a fertilizer in the form of a tube or tubing which consists of polyvinyl alcohol or a polymer which is swellable in water. Within this tube, or tubing, specific amounts of a nutrient-containing substance are located at regular intervals. The disadvantage of this system is the fact that the quantities of substance introduced during the preparation are not separate from each other so that they may move freely within the tubing, which may result in irregular distribution of the quantities of substance.

Moreover, once such a "tubing" has been introduced onto or into the soil, it represents a permanent hindrance when working the soil, since great care must be taken not to damage the "tubing".

DE-A 40 35 223 describes an article with active ingredient for fertilizing, soil conditioning or the like, which is characterized in that the constituents located in this article are embedded or distributed into a matrix of biodegradable polymer. The matrices described therein are merely waterimpermeable matrices, from which the constituent is only liberated when the former are subjected to biodegradation.

The result is that prior to beginning biodegradation no constituent is released, but once biodegradation has started, i.e. once the matrix shows sufficiently great perforations or openings, the constituent which is present within is liberated in a very short period, so that release is no longer controlled and the result may be in particular damage of the plants to be treated by unduly large quantities of active ingredient.

A very similar system in which, again, the active ingredient is released only when destruction has taken place is described in WO 91/01086.

US 4 845 888 describes a mulching film based on a watersoluble synthetic resin which equally comprises a nutrient or active ingredient. Again, such a film has the disadvantage that the film will first undergo incipient dissolution in a 3 water-containing medium and, once certain perforations or openings have been formed, the active ingredient or nutrient present will be released within a very short period.

With a view to the above prior art, it is an object of the present invention to provide a film-coated fertilizer which allows controlled release of the nutrient-containing substances over a prolonged period. The release of the nutrients starts immediately after application onto or into the soil or the substrate via diffusion or osmotic processes and is maintained over a defined period. The soil or the substrate is permanently supplied with a sufficiently high and correctly dosed amount of nutrient which is chosen so that it matches uptake by the plant in question.

Moreover, the preparation of such a film-coated fertilizer, in particular in comparison with fertilizers in the form of granules which are provided with a coat, has considerable advantages in terms of costs since complicated process steps for applying a coat of maximum uniformity to the granules are ntin-otiigsb 20 dispensed with or, when using the nutrient-containing substance in the form of, for example, a powder, no granulation of the nutrient-containing substance is necessary.

Furthermore, nutrient-containing substances which are normally incompatible, for example ammonium-nitrate-containing sub- 25 stances and urea, may be employed even in the form of gran- 25 ules, while normally their hygroscopicity would cause them to liquesce or liquefy.

Accordingly, it is an object of the present invention to provide a film-coated fertilizer including -one or more individually coated volumes of 20 cm 3 or less of at least one S 30 nutrient-containing substance, where the film which coats the volumes of at least one nutrient-containing substance includes a water-permeable polymer, a cellulose-containing material, a textile material, a lignocellulose material or a combination of two or more thereof. This water-permeable polymer is preferably biodegradable.

A further important property of the films used according to 0050/47385 4 the invention is that they allow the nutrient-containing substance to be released as required in a crop-specific manner.

In principle, all commercially available polymers which are water-permeable and capable of film formation may be used for the purposes of the present invention.

The term "water-permeable" used for the purposes of the present invention means that the films which can be used in this context and which comprise a water-permeable polymer (hereinbelow frequently termed "polymer films") have moisture vapor transmission values which exceed those of polyethylene.

The moisture vapor transmission value of films made of the polymers which can be used in accordance with the invention is preferably above 1 g/(m 2 -day), measured on a 100 gm film at 25 0 C and a humidity gradient of 90% to 0% relative humidity.

The upper limit of the moisture vapor transmission value of the polymer films which can be used in accordance with the invention is preferably approximately 100 g/(m 2 -day). Accordingly, polymer films which have a particularly pronounced moisture vapor transmission value or which are virtually water-soluble, for example starch, polysaccharides or else polyvinyl alcohol, may not be used for the purposes of the present invention since they would dissolve or decompose unduly rapidly in the surrounding medium and thus cannot guarantee controlled release for the purposes of the present invention, ie. longer-lasting delivery of the nutrients over a prolonged period [sic] which matches the plants' requirements.

For the purposes of the present inventions [sic], it is also possible to use laminate films or barrier films comprising two or more polymers which meet the above criteria.

The polymers which can be used for the purposes of the present invention include in particular the following: aliphatic polyesters, in particular those based on aliphatic dicarboxylic acids having 2 to 10 carbon atoms, preferably 4 to 6 carbon atoms, or cycloaliphatic dicarboxylic acids having S005'/47385 5 7 to 10 carbon atoms and preferably those having 8 carbon atoms, for example malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, 1,4-cyclohexanedicarboxylic acid, itaconic acid and maleic acid, as they are described, for example, in EP-A- 572 682; polyesters based on aromatic dicarboxylic acids, these generally having 8 to 12 carbon atoms, preferably 8 carbon atoms, for example terephthalic acid, isophthalic acid, 2,6-naphthoic acid and 1,5-naphthoic acid; copolyesters comprising structural units which are derived from both aliphatic and aromatic carboxylic acids or carboxylic acid derivatives, for example copolyesters based on adipic acid and terephthalic acid, copolyesters based on fumaric acid and terephthalic acid, and those based on succinic acid and terephthalic acid, as they are described, for example, in US 5 446 079 and in the parallel International Application WO 92/09654, in DE-A-44 32 161 and in a series of applications by the Applicant Company itself (P 44 40 858.7, P 44 40 850.1, P 44 40 837.4, P 44 40 836.6, 195 00 757.0, 195 00 756.5, 195 00 755.7, 195 00 754.9, 195 05 185.8 and 195 05 186.6); organic poly acids, for example polylactic acid, polyhydroxybutyric acid, polyamino acids and polymers of the hydroxycarboxylic acids mentioned further down as component (bl) within the scope of the description of the copolyesters (Bl) which can be used in accordance with the invention; polyamides, for example nylon 6, nylon 66, nylon 12 and nylons 610, 612, and also copolymers based on polyamides; polyvinyl compounds, for example polystyrene, polyvinyl chloride, polyvinylidene chloride, and copolymers of styrene and dienes, for example butadiene, or else styrene/acrylonitrile/butadiene copolymers; poly(meth)acrylates, for example polymethyl (meth)acrylate or polybutyl (meth)acrylate; polycarbonates; cellulose derivatives which have a moisture vapor transmission value within the above-defined range, for example cellulose acetate or cellulose acetobutyrate; and mixtures of two or more of these.

6 It is to be noted that the molecular weights of the polymers used in accordance with the invention must always be high enough to allow the formation of the films.

In a preferred embodiment, the above-defined polyesters based on (cyclo)aliphatic dicarboxylic acids and copolyesters including structural units derived from both aliphatic and aromatic carboxylic acids or carboxylic acid derivatives are used, the latter being especially preferred since these polyesters give good films, have a sufficiently high moisture vapor transmission value and are, moreover, biodegradable.

The term "biodegradable" as used for the purposes of the present Application describes the fact that the films disintegrate after use in accordance with the invention under environmental effects in an appropriate and measurable period of time. As a rule, degradation is effected hydrolytically and/or oxidatively, but mostly by the action of microorganisms such as bacteria, yeasts, fungi and algae. However, degradation may also be effected enzymatically, for example as described by Y. Tokiwa and T.Suzuki in "Nature", Vol. 270, pp.

76-78, 1977.

:For the purposes of the present invention it is possible, when using the copolyesters used in accordance with a preferred embodiment, by selecting a suitable ratio between recurring units derived from aliphatic carboxylic acids and those derived from aromatic carboxylic acids, to vary the biodegradation rate, ie. the point in time by which the polyesters used in accordance with the invention are essentially fully degraded. A rule of thumb says that, the higher the proportion of recurring units derived from aliphatic carboxylic acids, the higher the biodegradation rate of the copolyesters.

Furthermore, the higher the proportion of. sections with alternating sequence of recurring units derived from aliphatic and aromatic carboxylic acids or carboxylic acid derivatives, the higher the biodegradation rate of the copolyesters.

Films which are used in particular for the purposes of the present invention are those including a biodegradable copolyester which has structural units derived from both ali- 0050/47385 7 phatic and aromatic carboxylic acids or carboxylic acid derivatives and which is obtainable by reacting a mixture composed of: (al) a mixture composed of (all) 10 to 95 mol of an aliphatic dicarboxylic acid or of a cycloaliphatic dicarboxylic acid or of an ester-forming derivative thereof or of a mixture of two or more thereof, (a12) 5 to 90 mol of an aromatic dicarboxylic acid or of an ester-forming derivative thereof or of a mixture of two or more thereof, (a13) 0 to 10 mol of a sulfonate-containing compound or of a mixture of two or more thereof, the total of the individual mol percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio of (al) to (a2) being selected within a range of from 0.4:1 to 2.5:1, (a3) 0 to 10% by weight, based on the mixture of a chain extender or a mixture of two or more thereof, and (a4) 0 to 20% by weight, based on the mixture of a compound having at least three groups capable of ester formation or a mixture of two or more thereof, the recurring units derived from the (cyclo)aliphatic and aromatic carboxylic acid being randomly distributed, and the copolyester having a viscosity number in the range of from to 450 g/ml (measured in o-dichlorobenzene/phenol (weight ratio 50/50) at a concentration of 0.5% by weight of copolyester at a temperature of 25 0

C).

In general, the aliphatic dicarboxylic acids which can be used for the preparation of the above copolyester have 2 to carbon atoms, preferably 4 to 6 carbon atoms. The cycloaliphatic dicarboxylic acids which can be used for the same 0050/47385 8 purpose are those having 7 to 10 carbon atoms, in particular those having 8 carbon atoms. In principle, however, it is also possible to employ dicarboxylic acids having a larger number of carbon atoms, ie. having up to 30 carbon atoms.

Examples which may be mentioned are: malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and dicarboxylic acid, with adipic acid being preferred.

Ester-forming derivatives of the abovementioned dicarboxylic acids which may be mentioned are, in particular, the di-C 1 alkyl esters, for example dimethyl, diethyl, dipropyl, dibutyl, dipentyl and dihexyl ester.

The dicarboxylic acids or ester-forming derivatives thereof can be employed singly or as a mixture of two or more thereof.

It is preferred to employ adipic acid or ester-forming derivatives thereof and sebacic acid or ester-forming derivatives thereof, in particular adipic acid or ester-forming derivatives thereof.

In general, the (cyclo)aliphatic dicarboxylic acid or esterforming derivatives thereof amount to approximately 10 to preferably approximately 20 to approximately 50 and in particular approximately 25 to approximately 35 mol in each case based on the total amount of components (all) to (a13).

Aromatic dicarboxylic acids which may be mentioned are generally those having 8 to 12 carbon atoms, preferably those having 8 carbon atoms. Examples which may be mentioned are terephthalic acid, isophthalic acid, 2,6-naphthoic acid and acid, and ester-forming derivatives thereof.

Particular mention may be made of the di-Cl-C 6 -alkyl esters, for example dimethyl, diethyl, dipropyl, dibutyl, dipentyl or dihexyl ester.

0050/47385 9 In principle, however, it is also possible to employ aromatic dicarboxylic acids which have a higher number of carbon atoms.

The aromatic dicarboxylic acids or their ester-forming derivatives (a12) can be employed singly or as a mixture of two or more thereof.

In general, the aromatic dicarboxylic acids or ester-forming derivatives thereof amount to approximately 5 to approximately preferably approximately 50 to approximately 80 and in particular approximately 65 to approximately 75 mol in each case based on the total amount of components (all) to (a13).

The sulfonate-containing compound (a13) employed is generally an alkali metal salt or alkaline earth metal salt of a sulfonate-containing dicarboxylic acid or of its ester-forming derivatives, preferably alkali metal salts of phthalic acid or mixtures of these, in particular the sodium salt. The sulfonate-containing compound (a13) amounts to 0 to approximately 10, preferably 0 to approximately 5 and in particular approximately 3 to approximately 5 mol in each case based on the total content of components (all) to (a13).

The sulfonate-containing compounds can be employed singly or as a mixture of two or more thereof.

According to the invention the component (a2) employed is a dihydroxy compound or an amino alcohol or a mixture of two or more thereof. In principle, all diols or amino alcohols known for the preparation of esters can be employed.

In general, however, (a21) alkanediols having 2 to 12 carbon atoms, preferably 4 to 6 carbon atoms, or cycloalkanediols having 5 to 10 carbon atoms, (a22) polyetherdiols, ie. ethercontaining dihydroxy compounds, and (a23) amino alcohols having 2 to 12 carbon atoms, preferably 2 to 4 carbon atoms, and amino cycloalcohols having 5 to 10 carbon atoms are employed.

Examples which may be mentioned are ethylene glycol, 1,2-, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,4- 0050/47385 10 dimethyl-2-ethylhexane-l,3-diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-l,3propanediol, 2,2,4-trimethyl-1,6-hexanediol, in particular ethylene glycol, 1,3-propanediol, 1,4-butanediol and 2,2dimethyl-1,3-propanediol (neopentyl glycol); cyclopentanediol, 1,4-cylcohexanediol, 1,3- and 1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; Diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol and polytetrahydrofuran, in particular diethylene glycol, triethylene glycol and polyethylene glycol, or mixtures of these, or compounds which have a varying number of ether units, for example polyethylene glycol which contains propylene units and which can be obtained for example by polymerization of first ethylene oxide and subsequently propylene oxide, following methods known per se. The molecular weight (Mn) of the polyethylene glycols which can be employed is, as a rule, approximately 250 to approximately 8,000, preferably approximately 600 to approximately 3,000 g/mol; 4-Aminomethylcyclohexanemethanol, 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol; aminocyclopentanol and aminocyclohexanol; and mixtures of these.

The dihydroxy compounds or amino alcohols can be employed singly or as a mixture of two or more thereof.

The molar ratio of (al) to (a2) is generally selected in a range of from approximately 0.4:1 to approximately 2.5:1, preferably in a range of approximately 0.5:1 to approximately 1.5:1, more preferably at approximately 0.5:1 to approximately 1.2:1, in particular in a range of from approximately 0.5:1 to approximately 1:1.

The molar ratios of (al) to (a2) in the isolated copolyester (if appropriate after the desired amount of excess component (a2) has been removed) are approximately 0.4:1 to approximately 1.5:1, preferably approximately 0.5:1 to approximately 1.2:1, in particular approximately 0.5:1 to approximately 1:1.

0050/47385 11 Chain extenders (a3) which can generally be employed are all chain extenders which are conventional for the preparation of polyesters. If these are used, they amount to approximately 0.01 to approximately 10, preferably approximately 0.05 to approximately 5, more preferably approximately 0.07 to approximately 3, in particular approximately 0.1 to approximately 1% by weight, in each case based on the mixture (al).

The following may be mentioned among the chain extenders employed: diisocyanates, eg. tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, and 2,4'-diphenylmethane diisocyanate, naphthylene 1,5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate andmethylenebis (4-isocyanatocyclohexane) in particular hexamethylene diisocyanate; trifunctional isocyanate compounds which may contain isocyanurate and/or biuret groups of a functionality of not less than 3; divinyl ethers, eg. 1,4butanediol divinyl ether, 1,6-hexanediol divinyl ether and 1,4-cyclohexanedimethanol divinyl ether; and 2,2'-bisoxazolines of the general formula (I)

NN

S

(I)

0 0 The latter are generally obtainable by the process described in Angew. Chem. Int. Edit., Vol. 11 (1972), pp. 287-288.

Especially preferred bisoxazolines to be mentioned are those where R 1 is a single bond, a (CH,),-alkylene group where q 2, 3 or 4, such as methylene, ethane-l,2-diyl, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl or a phenylene group.

Particularly preferred are 2,2'-bis(2-oxazoline), bis(2oxazolinyl)methane, 1,2-bis(2-oxazolinyl)ethane, 1,3-bis(2oxazolinyl)propane, 1, 4 -bis(2-oxazolinyl)butane, 1,4-bis(2oxazolinyl)benzene, 1, 2 -bis(2-oxazolinyl)benzene and 1,3bis(2-oxazolinyl)benzene.

0 so/47385 12 The chain extenders (a3) may also be employed as a mixture of two or more of these.

Furthermore, it is possible to employ a compound having at least three groups capable of ester formation (a4) or a mixture of two or more of these, viz., if present, in an amount of from approximately 0.01 to approximately 20, preferably from approximately 1 to approximately 10, especially preferably from approximately 3 to approximately 7, and in particular from approximately 3 to approximately 5% by weight, in each case based on the mixture (al).

The compounds employed as compounds (a4) preferably comprise 3 to 10 functional groups which are capable of ester bond formation. Especially preferred compounds (a4) have 3 to 6 functional groups of this type in the molecule, in particular 3 to 6 hydroxyl groups and/or carboxyl groups. Tri- and/or tetrafunctional carboxylic acids or derivatives thereof are particularly preferably employed. Examples which may be mentioned are: tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triols, glycerol, trimesic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic dianhydride and hydroxyisophthalic acid.

By adding the chain extenders (a3) and/or the compounds (a4) it is possible to alter, for example, the fusion viscosity, the limiting viscosity number or the molecular weight in the desired manner, ie. accordingly increase the limiting viscosity number and the molecular weight in comparison with polyesters to which none of the chain extenders (a3) and/or compounds (a4) have been added and thus to vary the mechanical properties of the polyesters to suit the specific use.

In an embodiment, films are used which comprise a biodegradable copolyester (Bl) which has structural units derived from both aliphatic and aromatic carboxylic acids and carboxylic acid derivatives, obtainable by reacting a mixture composed of: (al) a mixture composed of (all) 10 to 95 mol of an aliphatic dicarboxylic 0050/47385 13 acid or of a cycloaliphatic dicarboxylic acid or of an ester-forming derivative thereof or of a mixture of two or more thereof, (a12) 5 to 90 mol of an aromatic dicarboxylic acid or of an ester-forming derivative thereof or of a mixture of two or more thereof, (a13) 0 to 10 mol of a sulfonate-containing compound or of a mixture of two or more thereof, the total of the individual mol percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio of (al) to (a2) being selected within a range of from 0.4:1 to 2.5:1, (a3) 0 to 10% by weight, based on the mixture of a chain extender or a mixture of two or more thereof, (a4) 0 to 20% by weight, based on the mixture of a compound having at least three groups capable of ester formation or a mixture of two or more thereof, (bl) 0.01 to less than 50% by weight, based on the mixture of a hydroxycarboxylic acid (bl) which is defined by the following formula IIa or IIb HO- G -0 pH (Ia) (b) where p is an integer from 1 to 1,500 and r is 1, 2, 3 or 4, and G is a phenylene group, -CH 2 0050/47385 14 group, n being an integer of 1, 2, 3, 4 or 5, a group or a -C(R)HCH 2 group, R being methyl or ethyl, or a mixture of two or more of these, the recurring units derived from the (cyclo)aliphatic and aromatic carboxylic acid being randomly distributed, the copolyester having a viscosity number in the range of from 5 to 450 g/ml (measured in o-dichlorobenzene/phenol (weight ratio 50/50) at a concentration of 0.5% by weight of copolyester at 25 0

C).

In the above formula, p is preferably 1 to approximately 1000; r is preferably 1 or 2; n is preferably 1 or The hydroxycarboxylic acid content (bl) in the mixture reacted preferably amounts to approximately 0.1 to 30% by weight, based on the mixture (al).

Substances which are preferably employed as hydroxycarboxylic acid (bl) are glycolic acid, D,L-lactic acid, 6hydroxyhexanoic acid, its cyclic derivatives, such as glycolide (1,4-dioxane-2,5-dione), L-dilactide (3,6-dimethyl- 1,4-dioxane-2,5-dione), p-hydroxybenzoic acid and oligomers and polymers thereof, such as 3-polyhydroxybutyric acid, polyhydroxyvaleric acid, polylactide (eg. available under the name EcoPLA* (Cargill)), and a mixture of 3-polyhydroxybutyric acid and polyhydroxyvaleric acid (the latter is available from Zeneca under the name Biopol"), the above-defined low-molecular-weight and cyclic derivatives being employed.

Naturally, mixtures of two or more of the above-defined hydroxycarboxylic acids may also be employed.

Furthermore, using the cyclic derivatives of the abovedescribed hydroxycarboxylic acids (bl) in the reaction with the biodegradable copolyester used in accordance with the invention gives, in a manner known per se, by means of a socalled "ring-opening polymerization reaction" copolyesters of the above-defined type which contain block structures composed of the copolyester used in accordance with the invention which are linked to each other via in each case at least one 0050/47385 15 hydroxycarboxylic acid unit (bl) (re "ring-opening polymerization reaction" see Encyclopedia of Polymer Science and Engineering, Vol. 12, 2nd Ed., John Wiley Sons, 1988, pp.

36-41).

Copolyesters which are especially preferably used within the scope of the present invention have the following composition regarding components (all), (a12) and where it has to be taken into consideration that these copolyesters can not only contain sulfo groups, but can also contain the chain extenders and/or compounds defined as components (a3) and The data in brackets following the components in question correspond to the amount of these components in mol Terephthalic acid (75) adipic acid (25) neopentyl glycol (100), terephthalic acid (70) adipic acid (30) butanediol (100), terephthalic acid (70) adipic acid (25) isophthalic acid neopentyl glycol (100), terephthalic acid (60) adipic acid (40) butanediol (100).

The copolyesters used in accordance with the invention are characterized by the following features: They have a viscosity number in the range of from approximately 5 to 450 g/ml, preferably approximately 100 to approximately 350 g/ml and in particular approximately 200 to approximately 350 g/ml, in each case measured in o-dichlorobenzene/ phenol (weight ratio 50/50) at a concentration of 0.5% by weight of copolyester at a temperature of 25 0

C.

As regards further details on the (cyclo)aliphatic dicarboxylic acids, aromatic dicarboxylic acids, diols and/or amino alcohols which can be used within the scope of the present invention and further components (a4) and reference is made to the patent applications of the Applicant Company mentioned at the outset when discussing the prior art, and to US 5 446 079 and the parallel application WO 92/09654, the contents as regards the copolyesters described therein and their preparation being incorporated in the present application by way of reference.

0050/47385 16 It is furthermore possible, if appropriate, to use a cellulose-containing material, a textile material or a lignocellulose material as film material in combination with the water-permeable polymer described in detail above. The cellulose-containing materials usable as films in accordance with the invention include paper celluloses and man-made fiber celluloses, where the raw materials for the paper celluloses may be obtained from woods, straw, reed, bamboo and bagasse.

Man-made fiber celluloses which can be used are those based on man-made cellulose fibers, or man-made cellulose ether and ester fibers. More details with respect to the cellulosecontaining materials which can be used in accordance with the invention are described in Ullmans Encyklopidie der technischen Chemie, 4th edition, vol. 17 (1979), pp. 531-631, under the entry "Papier", the content of which is, with regard to the cellulose-containing materials described therein, incorporated in its entirety into the context of the present application.

It is furthermore possible to use a textile material as film according to the invention. The term "textile material" as used for the purpose of the present application includes all materials in the form of a web which are based on textile fibers in the form of felts, fabrics and mats. The textile fiber materials which can be used in accordance with the invention for preparing the textile material which can be used in accordance with the invention are both natural fibers, such as, for example, cotton and kapok, and in particular man-made fibers, such as, for example, fibers made of regenerated cellulose, cellulose acetates, alginates and polyisoprenes, synthetic fibers, such as, for example, those made of the water-soluble polymers defined above, but also fibers of polymers which are non-water-impermeable in accordance with the definition of the present invention, such as, for example, polyethylene and polypropylene.

It is furthermore possible to use a lignocellulose material.

The rate at which the nutrients are released from the filmcoated fertilizers according to the invention can be controlled not only by selecting the film material employed, but 0050/47385 17 also by the thickness of the films, which is generally approximately 500 Am or less, preferably approximately 200 [lacuna] or less and, in particular, approximately 10 to approximately 100 Am.

Depending on the intended purpose, the crop and the vegetation time, it is furthermore essential in accordance with the invention that the volume of the nutrient-containing substance contained in the film-coated fertilizer amounts to approximately 20 cm 3 or less, preferably approximately 10 cm 3 or less, more preferably approximately 5 cm 3 or less, in particular approximately 3 cm 3 or less, and particularly preferably approximately 0.05 cm 3 to approximately 2 cm 3 since the provision of such minute amounts of nutrient-containing substance guarantees the controlled release of the nutrientcontaining substance in such amounts that no unduly high charge or load of the substrates and associated damages result. The lower limit for the volumes coated in accordance with the invention is approximately 0.01 cm 3 preferably approximately 0.05 cm 3 The nutrient-containing substances which are present in the film-coated fertilizer according to the invention can be present in the form of a powder, granules, a paste or a liquid.

Suitable nutrient-containing substances which can be used within the scope of the present invention are, in particular, organic or mineral fertilizers as they are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Ed. 1987, Vol. A10, pp. 323-431 (see, in particular, Chapters 2.1 and 4).

Suitable fertilizers are, for example, straights and compound fertilizers, which comprise, either singly or, if appropriate, in combination, nutrients such as nitrogen, potassium or phosphorus, if appropriate in the form of their salts.

Examples are NP, NK, PK and NPK fertilizers, nitrogencontaining straights such as nitrochalk, ammonium sulfate, ammonium nitrate sulfate and urea, and also slow-release fertilizers, in particular based on urea, eg. isobutylidene- 18 diurea, crotonylidenediurea and urea/formaldehyde condensate.

It is furthermore possible to employ further plant nutrients and also trace elements which, in addition to the abovementioned main components, including minor amounts of compounds including Mg, Ca, S, Fe, Mn, Cu, Zn, Co, Mo and/or B, ie. Normally in minor amounts as specified by the Srequirements of the relevant legislation such as the German Fertilizers Act.

The nutrient-containing substances can be employed singly or as a mixture of two or more thereof.

In addition to the nutrient-containing substance or the mixture of two or more thereof, the product may furthermore include other additives, for example nitrification inhibitors as they are described, for example, in DE-A 41 28 828, DE 195 03 827.4 and DE 196 31 764.9 and in the prior art cited in these publications, in particular pyrazoles or pyrazole derivatives, growth regulators and active ingredients used in .crop protection, for example fungicides, insecticides and om herbicides.

The present invention furthermore relates to a film-coated 20 fertilizer, the latter being in the form of a plurality of individually coated volumes of 20 cm 3 or less of at least one nutrient-containing substance which are arranged in succession in one or more parallel rows. This means that the film-coated "fertilizer according to the invention may be, for example, in b "i 25 the form of a "string of beads", a plurality of such "strings of beads" arranged beside each other, but also individually, after the above-described structures have been cut in the

S

interstices which are located between the volumes, using suitable cutting devices.

The present invention furthermore relates to a process for the preparation of the film-coated fertilizer according to the invention which includes the following steps: a) feeding, into an application device, at least one first and at least one second film including .a water-permeable polymer as defined above; S 0050/47385 19 b) applying, by means of the application device, a plurality of volumes of 20 cm 3 or less of at least one nutrientcontaining substance to the at least one first film in such a way that the volumes are separated by interstices; c) joining the at least one first and the at least one second film in the interstices located between the volumes in such a way that each of the volumes is coated individually, whereby a film-coated fertilizer is obtained.

For the purposes of the process according to the invention, the films are fed to the application device by means of a conventional feeding device, for example a roller.

As soon as the film of the water-permeable polymer is located in the application device for applying the nutrient-containing substance, a suitable amount of this substance is applied to the at least one first film, it being essential that the volumes applied are in each case spaced by interstices.

In one embodiment, the surface(s) within the application device, in general one or more preferably heatable metal surface(s), to which the at least one first film, the at least one second film or the at least one first and the at least one second film is, or are, fed and on which the respective film(s) inside the application device is, or are, located during the application process, is/are designed in such a way that it is, or they are, provided with recesses. In general, the areas of the fed-in film(s) which cover the recesses are then moulded into these recesses by means of a pressure source, ie. a source for superatmospheric pressure or a vacuum source, preferably a vacuum source. The recesses of the abovementioned surface(s) have preferably at least one volume which corresponds to half the volume of the nutrient-containing substance to be applied. If the volume of the recesses with which the first film is provided corresponds to half the volume of nutrient-containing substance, the at least one second film is preferably also fed to a surface inside the application device, or is located, during the application process on such a surface which is provided with recesses whose volumes correspond to at least half of the volume of the 0050/47385 20 nutrient-containing substance.

Naturally, the process according to the present invention can also be carried out in such a way that the surfaces on which there are located the at least one first film, the at least one second film or the at least one first and the at least one second film inside the application device is [sic] provided with recesses whose volumes are greater than half the volume of the nutrient-containing substance to be applied and correspond, for example, to the volume of the nutrientcontaining substance to be applied, in which case the second film may be provided with proportionally smaller or without additional recesses when applied to the first film.

It is thus only essential that the films described here which coat the fertilizer form a total volume in which the amount of fertilizer fed can be accommodated.

After the feeding and application processes have ended, the above-defined films are joined to each other at the interstices located between the volumes, which is generally carried out by adhesive bonding or by welding the films by customary methods. Furthermore, the two films may also be joined together by applying a vacuum, or by an electrostatic charge.

In a further embodiment of the present invention, the at least one first and the at least one second film are each fed to a roller whose surfaces are provided with recesses. The volume of each of the recesses corresponds to half of the volume of nutrient-containing substance applied.

Devices which are preferably used are calenders, ie. machines with a plurality of cylinders, as defined above, which are optionally provided with heatable recesses which are typically arranged one above the other, or side by side.

In general, the procedure is as follows: In each case at least one first and at least one second film are fed from two sides to the cylinder whose surface is provided with suitable recesses. The films are then introduced into the recesses by means of a suitable device, for example 21 a vacuum source. Prior to charging with the nutrientcontaining substance, the films are brought into contact with each other at one point of the device used and joined to each other on one side. A suitable amount (volume) of the nutrient-containing substance is then fed, the two films are again brought into contact with each other once the addition of the nutrient-containing substance has ended and again joined to each other for example by adhesive bonding, by welding, by applying a vacuum or by applying an electrostatic charge.

Furthermore, the invention relates to a process for the preparation of a film-coated fertilizer as defined above which includes the following steps: a) feeding, into an introduction device, at least one film which is in the form of a tube and which includes a water-permeable polymer; b) introducing, by means of the introduction device, a plurality of volumes of 20 cm 3 or less of at least one nutrient-containing substance into the at least one film in the form of a tube in such a way that the volumes are separated by interstices; closing, preferably sealing or welding, the at least *o one film in the form of a tube in the interstices located between the volumes in such a way that each of the volumes is coated individually, whereby a film-coated fertilizer is obtained.

oe If it is desired to apply the film-coated fertilizer in the form of individual coated volumes of the nutrient-containing substance, the film-coated fertilizer obtained in step c) of 30 the processes in question can be separated by either cutting or perforating the fertilizer in the interstices located between the volumes by means of a cutting or perforating device to give individual film-coated fertilizers, each of which includes a volume of approximately 20 cm 3 or less of the nutrient-containing substance; in the case of perforation, the separation of the coated fertilizer units is effected when the fertilizer is applied.

The process according to the invention can be carried out 22 either continuously or batchwise.

The present invention furthermore also relates to a filmcoated fertilizer which can be prepared by a process including the following steps: a) feeding, into an application device, at least one first and at least one second film including a water-permeable polymer; b) applying, by means of the application device, a plurality of volumes of 20 cm 3 or less of at least one nutrientcontaining substance to the at least one first film in such a way that the volumes are separated by interstices; c) joining the at least one first and the at least one second film in the interstices located between the volumes in such a way that the volumes are coated individually, and to a film-coated fertilizer'which can be prepared by a process which includes the following steps: a) feeding, into an introduction device, at least one film which is in the form of a tube and which S 20 includes a water-permeable polymer; S" b) introducing, by means of the introduction device, a e plurality of volumes of 20 cm 3 or less of at least one

S..

nutrient-containing substance into the at least one film in the form of a tube in such a way that the volumes are separated by interstices; c) closing the at least one film in the form of a tube in the interstices located between the volumes in such a way that each of the volumes is coated individually, whereby a film-coated fertilizer is 30 obtained.

The present invention furthermore relates to a fertilization eoe S" method in which the film-coated fertilizer according to the present invention or a film-coated fertilizer prepared in accordance with the present invention is applied to, mixed with or worked into, the soil or the substrate.

"Comprises/comprising" when used in this specification is taken to specify the presence of state features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims (9)

1. A film-coated fertilizer including one or more individually coated volumes of 20 cm 3 or less of at least one nutrient-containing substance in the form of a powder, a paste or a liquid, the film coating volumes of at least one nutrient-containing substance including a water-permeable polymer.

2. A film-coated fertilizer as claimed in claim 1, wherein the water- permeable polymer is biodegradable.

3. A film-coated fertilizer as claimed in claim 1 or 2, wherein the film- coated fertilizer is in the form of a plurality of individually coated volumes of cm 3 or less of at least one nutrient-containing substance which are S-arranged in succession in one or more parallel rows.

4. A process for the preparation of a film-coated fertilizer as claimed in any of the preceding claims, which includes the following steps: a) feeding, into an application device, at least one first and at least one second film, as defined in claim 1 or 2; b) applying, by means of the application device, a plurality of volumes of 20 cm 3 or less of at least one nutrient-containing substance to the at least one first film in such a way that the volumes are separated by interstices; c) joining the at least one first and the at least one second film in the interstices between the volumes in such a way that each volume is coated individually, whereby a film-coated fertilizer is obtained.

A process as claimed in claim 4, wherein the at least one first film, the at least one second film or the at least one first and the at least one second film are fed in each case to at least one surface arranged within 24 the application device and provided with recesses and wherein the areas which cover the recesses, of the at least one first film, of the at least one second film or of the at least on first and the at least one second film, are moulded into the recesses by means of a pressure source.

6. A process as claimed in claim 4 or 5, wherein the at least one first and the at least one second film are each fed to a cylinder whose surfaces are provided with recesses.

7. A process as claimed in any of claims 4 to 6, wherein the at least one first and the at least one second film, after having been charged with the at least one nutrient-containing substance, are joined to each other by applying a vacuum, by applying an electrostatic charge, by adhesive bonding or by welding the films in the interstices located between the volumes. iooo

8. A process for the preparation of a film-coated fertilizer as claimed in 4 any of claims 1 to 3 which includes the following steps: a) feeding, into an introduction device, at least one film which is in the form of a tube, as defined in claim 1 or 2; b) introducing, by means of the introduction device, a plurality of volumes of 20 cm 3 or less of at least one nutrient-containing substance into the at least one film in the form of a tube in o ~such a way that the volumes are separated by interstices; c) closing the at least one film in the form of a tube in the interstices located between the volumes in such a way that each of the volumes is coated individually, whereby a film- coated fertilizer is obtained.

9. A process as claimed in any of claims 4 to 8 which additionally includes the following step d): d) cutting or perforating the film-coated fertilizer in the interstices located between the volumes by means of a cutting or perforating device. A fertilization method wherein a film-coated fertilizer as claimed in any of claims 1 to 3, or a film-coated fertilizer prepared by means of a process as claimed in any of claims 4 to 9, is applied to, mixed with or worked into, the soil or a substrate. DATED this 16"h day of November 1999 BASF AKTIENGESELLSCHAFT C WATERMARK PATENT AND TRADEMARK ATTORNEYS S.. 290 BURWOOD ROAD HAWTHORN 3122 AUSTRALIA P8486AU .DOC LCG:CLR:VRH P8486AUOO.DOC