MXPA99002978A - Use of an aqueous dispersion from a biodegradable polyester as a sheathing material for granulated fertilizer - Google Patents

Abstract

The present invention relates to a polyester dispersion containing water and a biodegradable copolyester encompassing structural units from (derivates from) a carboxylic acid, intended for use a sheathing material for granulated fertilizer. The invention also relates to the sheathed granulated fertilizer obtained from the polyester dispersion and the fertilizing method whereby said sheathed granulated fertilizer is applied.

Description

USE OF AN AQUEOUS DISPERSION OF A BIODEGRADABLE POLYESTER AS A COVERING MATERIAL FOR GRANULATED FERTILIZER The present invention relates to the use of a polyester dispersion containing water and a biodegradable copolyester, which contains structural units derived from aliphatic and aromatic carboxylic acids or their derivatives, and to coated fertilizer granules prepared using this polyester dispersion, and a process for its preparation. The present invention also relates to a method of fertilization in which the coated fertilizer granules according to the invention are used. In general, the use is known, such as fertilizers, granules of fertilizers that are coated with a polymer layer. The coating increases the effectiveness of these fertilizers because the coated fertilizer releases substances that act as plant nutrients in a delayed form and can thus show their action for a prolonged period. These slow-release fertilizers are described, for example in Ullmann's "Encyclopedia of Industrial Chemistry, 5th edition 1987, vol. A10, pp. 363-369, and the advantages are compiled in Fert. Res. 1993, vol. 35, pp.

A large amount of fertilizer granules coated with biodegradable polymers have been described in the past. Thus, WO 95/03260 refers to a fertilizer provided with a composite coating of two layers. This coated fertilizer, which can be used in arable agriculture and in hydroponics, consists of an inner layer that is biodegradable and constructed of an aliphatic polyester and / or polyurethane and an outer shell that is insoluble in water and consists of polymers that are slowly biodegradable, for example biodegradable cellulose derivatives, low molecular weight polyethylene, low molecular weight wax and low molecular weight paraffins or a light degradable resin. However, the polymers described herein, which are used as the outer layer, generally do not show any considerable thickness, which is a disadvantage when these coated fertilizers are used. The application of Japanese Patent JP 07-309 689 already described relates to a fertilizer which is provided with a coating composed mainly of a lactic acid polyester. It is stated that the main substance used is a copolymer of lactic acid lactic acid, a dicarboxylic acid and a diol, which preferably consists of lactic acid, an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid and a diol. It is stated in the description that the lactic acid content in the copolymer used therein represents at least 50% by weight. Other fertilizers that are coated with biodegradable polymers are described in the Japanese patent applications 08-2989, 07-315976, 08-26875, 07-33577 and 05-97561 described, aliphatic polyesters, poly (hydroxycarboxylic acids), cellulose and polymers that they have one of these components being the main component that is used as a coating. Coated fertilizer granules, which are coated with a carboxyl-containing ethylene copolymer, are described in the application of German Patent 195 21 502.8. However, the coated fertilizer granules must meet increasing specifications with respect to simple and economical preparation and technical properties in use, in particular, also since the application of fertilizer granules to the fields is carried with increasingly fast and powerful machines, which means that the requirements related to the mechanical strength of the coated fertilizer granules, in particular with respect to the coating, are especially high.

In general, it should be possible for the polymers used as coatings to be applied to the initial fertilizer granules without using organic solvents. The amount of polymer needed to coat the granules to achieve a sufficiently pronounced slow release effect should also be as small as possible. further, coated fertilizer granules should not have a tendency to adhere, particularly at temperatures such as those normally encountered during storage or transport, without special precautions. However, this means that the coated fertilizer granules must also show almost no stickiness at temperatures that are considerably above ambient temperature (25 ° C). On the other hand, the polymers used for the coating should not show undue toughness and fragility, since the coating would otherwise be damaged, or could still be peeling, when the coated fertilizer granules are exposed to mechanical stresses as is the case, example, during repacking, or in particular, during mechanical dispersion. The above-described fertilizer granules of the prior art have not yet been able to meet all of these requirements. Problems occur in particular with regard to stickiness (in particular in the case of polyurethanes) and insufficient mechanical properties (in particular in the case of aliphatic polyesters). The copolyesters which are used according to the invention also have good film-forming properties, which means that only small amounts of the copolyester are required to produce a stable layer, which is advantageous from an economic point of view. Organic solvents for dispersing copolyesters can be largely or totally omitted, so that it is possible (to a large extent) to avoid the problems associated with the use of organic solvents, such as toxicity, waste and explosion hazards, when the dispersions according to the invention are prepared. Accordingly, an object of the present invention is to provide coated fertilizer granules that meet the profile of the above requirements. We have found that this objective is achieved by the use of a polyester dispersion for coating fertilizer granules, whose polyester dispersion consists of: (A) 20 to 90% by weight of water, and (B) 10 to 80% by weight of a biodegradable copolyester (B) with structural units derived from aliphatic and aromatic carboxylic acids or their derivatives, which can be obtained by reaction of a mixture consisting of: (a) a mixture composed of: (all) 10 to 95 mol% of an aliphatic dicarboxylic acid or a cycloaliphatic dicarboxylic acid or of an ester-forming derivative thereof or of a mixture of two or more thereof. (al2) from 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, (al3) from 0 to 10 mol% of a compound containing sulfonate or a mixture of two or more thereof, the total of the individual mole percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio being ( al) a (a2) selected within a range from 0.4: 1 to 2.5: 1, (a3) from 0 to 10% by weight, based on the mixture (al), of a chain extender or a mixture of two or more thereof, and (a4) from 0 to 20% by weight, based on the mixture (a) of a compound having at least 3 groups capable of forming the ester or a mixture of two or more thereof , the recurring units derived from the aliphatic and aromatic carboxylic acid (cyclo) being distributed randomly or in alternating form, having the copolyester with a viscosity number in the range from 5 to 450 ml / g (measured in o-dichlorobenzene / phenol (weight ratio 50/50) at a concentration of 0.5% by weight of the copolyester, 25 ° C) and the amount of the components (al3) and (a4) not simultaneously being zero in each case. The biodegradable copolyesters containing recurring units which are obtained from aromatic carboxylic acids or their derivatives and from aliphatic carboxylic acids or their derivatives and which are used in the aqueous dispersion of the polyester used according to the invention are known per se and have been described 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's own company (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); However, the aqueous dispersions of a biodegradable copolyester, preferably used for the purposes of the present invention, will be described below. The term "biodegradable" as used for the purposes of the present invention "describes the fact that the films disintegrate after use according to the invention under environmental effects in an immeasurable suitable period of time. As a rule, the degradation takes place in hydrolytic and / or oxidative form, but mainly by the action of microorganisms such as bacteria, yeasts, fungi and algae. However, degradation can also be effected enzymatically, for example, as described in Y. To iwa 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 according to a preferred embodiment, to select an appropriate ratio between the recurring units from the aliphatic carboxylic acids and those derived from aromatic carboxylic acids to vary the rate of biodegradation, ie the point in the time by which the polyesters used according to the invention are practically completely degraded.A general rule is that, the higher the proportion of recurring units derived from aliphatic carboxylic acids, the higher the biodegradation rate of the copolyester. can be controlled by the number of layers and their thickness.The polyester dispersion used according to the invention consists of about 10 to about 90, preferably about 10 to about 65 and more preferably about 15 to about 40% by weight solids, ie, of the copolyester used in accordance with the invention. In general, the aliphatic dicarboxylic acids which can be used for the purposes of the present invention have from 2 to 10 carbon atoms, preferably from 4 to 6 carbon atoms. The cycloaliphatic dicarboxylic acids which can be used for the purposes of the present invention are those having from 7 to 10 carbon atoms, in particular those having 8 carbon atoms. In principle, however, it is also possible to use dicarboxylic acids with a greater 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, sebasic acid, fumaric acid, 2,2-dimethylglutaric acid, sucric acid, 1,3-cyclopentanedicarboxylic acid, acid 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid and 2,5-norbornanedicarboxylic acid, with adipic acid being preferred. The ester-forming derivatives of the aforementioned dicarboxylic acids which may be mentioned are, in particular, the Ci-Cß dialkyl esters, for example, dimethyl, diethyl, dipropyl, dibutyl, dipentyl, and dihexyl esters. The dicarboxylic acids or ester-forming derivatives thereof can be used individually or as a mixture of two or more of these. It is preferred to employ adipic acid or ester-forming derivatives thereof and sebasic acid or ester-forming derivatives thereof, in particular adipic acid or ester-forming derivatives thereof. In general, the aliphatic (cyclo) dicarboxylic acid or ester-forming derivatives thereof represent from about 10 to 95, preferably from about 20 to about 50, and in particular from about 25 to about 35 mol%, in each case based on the total amount of the components (all) a (al3). The aromatic dicarboxylic acid [sic] which may be mentioned are, in general, 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 1,5-naphthoic acid, and the ester-forming derivatives thereof. Particular mention may be made of the dialkyl Ci-Ce esters, for example, dimethyl, diethyl, dipropyl, dibutyl, dipentyl or dihexyl ester.

However, in principle it is also possible to use aromatic dicarboxylic acids having a higher number of carbon atoms. The aromatic dicarboxylic acids or their ester-forming derivatives (al2) can be used individually or as a mixture of two or more thereof. In general, aromatic dicarboxylic acids or ester-forming derivatives thereof represent from about 5 to about 90, preferably from about 50 to about 80, and in particular from about 65 to about 75 mol%, in each case based on the total amount of the components (all) to (al3). The sulfonate (al3) -containing compound employed is generally an alkali metal salt or alkaline earth metal salt or a dicarboxylic acid containing sulfonate or its ester-forming derivatives, preferably the alkali metal salts of 5-sulfoisophthalic acid or mixtures thereof. of these, in particular the sodium salt. The sulfonate-containing compound (al3) represents from 0 to about 10, preferably from 0 to about 5 and in particular about 3 to about 5 mol%, in each case based on the total content of the components (all) a ( al3). The compounds containing sulfonate can be used individually or as a mixture of two or more thereof. Component (a2), according to the invention, is a dihydroxy compound or an amino alcohol or a mixture of two or more of these. In principle, all known diols or amino alcohols for the preparation of the esters can be used. in general, however, the alkanediols (a21) that • have from 2 to 10 carbon atoms, preferably from 4 to 6 carbon atoms, or cycloalkanediols having from 5 to 10 carbon atoms, polyether diols (a22), ie, dihydroxy compounds containing ether, and amino alcohols (a23) having 2 to 12 carbon atoms, preferably 2 to 4 carbon atoms, and amino cycloalcols having 5 to 10 carbon atoms are used. Examples which may be mentioned are ethylene glycol, 1,2-, 1,3-propanediol, 1,2-, 1, -butanediol, 1,5-pentanediol, 2,4-dimethyl-2-ethylhexan-1, 3 -diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 2,2,4-trimethyl -l, 6-hexanediol, in particular ethylene glycol, 1,3-propanediol, 1,4-butanediol and 2,2-dimethyl-1,3-propanediol (neopentyl glycol); cyclopentanediol, 1,4-cyclohexanediol, 1,2-, 1,3- and 1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-l, 3-cyclobutanediol; Diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol and polytetrahydrofuran, in particular diethylene glycol, triethylene glycol and polyethylene glycol, or mixtures thereof, or compounds having a variable number of ether units, for example, polyethylene glycol containing propylene units and which can be obtained, for example, by polymerization by methods known per se, first from ethylene oxide and subsequently from propylene oxide. The molecular weight (Mn) of the polyethylene glycols that can be used is, as a rule, about 250 to about 8000, preferably about 600 to about 3000 g / mol; 4-aminomethylcyclohexanemethanol, 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol; aminocyclopentanol and amino cyclohexanol; and mixtures of these. The dihydroxy compounds or amino alcohols can be used individually or as a mixture of two or more thereof. The molar ratio of (al) to (a2) is generally selected in a range from about 0.4: 1 to about 2.5: 1, preferably in a range of about 0.5: 1 to about 1.5: 1, more preferably to about 0.5. 1 to approximately 1.2: 2 in particular in a range from about 0.5: 1 to about 1: 1.

The molar ratios of (a) to (a2) in the isolated copolyester (if appropriate after the desired amount of the excess component (a2) has been removed) are about 0.4: 1 to about 1.5: 1., preferably about 0.5: 1 to about 1.2: 1, in particular about 0.5: 1 to about 1: 1. The chain extenders (a3) that can generally be used are all the chain extenders that are conventional for the preparation of the polyesters. If these are used, they represent about 0.01 to about 10, preferably about 0.05 to about 5, more preferably about 0.07 to about 3, in particular about 0.1 to about 1% by weight, in each case based on the mixture (at ). The following may be mentioned among the chain extenders employed: diisocyanates, for example toluene-2,4-diisocyanate, 2,6-toluene diisocyanate, 4,4'-diisocyanate and 2,4'-diphenylmethane, 1, 5 naphthylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and methylenebis (4-isocyanatocyclohexane), in particular hexamethylene diisocyanate; the trifunctional isocyanate compounds which may contain isocyanurate and / or biuret groups of a functionality of not less than 3; divinyl ethers, for example, 1,4-butanediol divinyl ether, 1,6-hexanedioldivinyl ether and 1,4-cyclohexanedimethanol divinyl ether; and 2, 2'-bis oxazolines of the general formula (I) The latter are usually obtained by the process described in Angew Chem Int. Edit., Vol. 11 (1972), pp. 287-28'8. Especially preferred bisoxazolines which may be mentioned are those in which R is a single bond, a (CH2) q-alkylene group where q = 2, 3 or 4, such as methylene, ethane-1,2-diyl, propan- 1,3-diyl, propan-1, 2-diyl, butan-1,4-diyl or a phenylene group. Particularly preferred are 2,2'-bis (2-oxazoline) bis (2-oxalzolinyl) methane, 1,2-bis (2-oxazolinyl) ethane, 1,3-bis (2-oxazolinyl) propane, 1,4- bis (2-oxazolinyl) butane, 1,4-bis (2-oxazolinyl) benzene, 1,2-bis (2-oxalinyl) benzene and 1,3-bis (2-oxazolinyl) benzene. Chain extenders (a3) can also be used as a mixture of two or more of these. In addition, it is possible to employ a compound having at least 3 groups capable of forming ester (a4) or a mixture of two or more of these, ie, if present, in an amount from about 0.01 to about 20, preferably from about 1 to about 10, especially preferably from about 3 to about 7, and in particular from about 3 to about 5% by weight, in each case based on the mixture (a). The compounds which are used as the compounds (a4) preferably contain 3 to 10 functional groups which are capable of formation of the ester bond. Especially preferred compounds (a4) have from 3 to 6 functional groups of this type in the molecule, in particular from 3 to 6 hydroxyl groups and / or carboxyl groups. The tri- and / or tetrafunctional dicarboxylic acids or derivatives thereof are particularly preferably used. Examples which may be mentioned are: tartaric acid, citric acid, alic acid, trimethylol propane, trimethylol ethane, pentaerythritol, polyether triloles, glycerol, trimesic acid, trimellitic acid, trimellitic anhydride, pyromellitic pyromellitic dianhydride and hydroxyisophthalic acid. By adding chain extenders (a3) and / or the compounds (a4) it is possible to modify, for example, the viscosity in the melt, the limiting viscosity number or the molecular weight in the desired form, ie, increase in correspondingly the number of limiting viscosity and molecular weight compared to polyesters to which none of the chain extenders (a3) and / or compounds (a4) have been added and thus vary the mechanical properties of the polyesters for adapt the specific use. It must be ensured that at least one of the compounds (al3) and / or (a4) must be present in accordance with the invention so that the copolyester has free acid groups available. In another embodiment, the present invention relates to the use, for coating granules of fertilizer, of a polyester dispersion comprising: (A) 20 to 90% by weight of water, and (B) from 10 to 80% by weight of a biodegradable copolyester (Bl) with structural units derived from aliphatic and aromatic dicarboxylic acids or their derivatives, which can be obtained by reaction of a mixture comprising: (a) a mixture composed of: (all) 10 to 95 mol% of an acid 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. (al2) from 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, (al3) from 0 to 10 mol% of a compound containing sulfonate or a mixture of two or more thereof, the total of the individual mole percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio being ( a) a (a2) selected within a range from 0.4: 1 to 2.5: 1, (a3) from 0 to 10% by weight, based on the mixture (a), of a chain extender or a mixture of two or more thereof, and (a4) from 0 to 20% by weight, based on the mixture (a) of a compound having at least 3 groups capable of forming the ester or a mixture of l. two or more thereof, (bl) from 0.01 to less than 50% "by weight, based on the mixture (a), of a hydrocarboxylic acid (bl) which is defined by the following formula lia or IIb.

HO- í C (O) G O] pH (Ha) 0 Where p is an integer from 1 to 1500 and r is 1, 2, 3 or 4, and G is a phenylene group, a group CH2) n ~ / where n is an integer of 1, 3, 4 or 5, a group - C (R) H or a group -C (R) HCH2, where R is methyl or ethyl, or a mixture of two or more of these, the recurring units from the carboxylic acid (cyclo) aliphatic and aromatic being randomly distributed, the copolyester with a viscosity number in the range from 5 to 450 g / ml (measured in o-dichlorobenzene / phenol (50/50 weight ratio) at a concentration of 0.5% by weight of the copolyester at 25 ° C) and the amount of the components (al3) and (a4) not being simultaneously in each case zero. In the above formula, p is preferably 1 to about 1000; r is preferably 1 or 2; n is preferably 1 or 5. The content of hydroxycarboxylic acid (bl) in the reaction mixture preferably represents about 0.1 to 30% by weight, based on the mixture (al). The substances which are preferably used as hydroxycarboxylic acid (bl) are glycolic acid, D-, L-, D, L-lactic acid, 6-hydroxyhexanoic acid, cyclic derivatives thereof, such as glycolide (1,4-dioxan- 2, 5-dione), D-, L-, dilactide (3,6-dimethyl-l, -dioxan-2, 5-dione), p-hydroxybenzoic acid and oligomers and polymers thereof, such as acid 3 -polydroxybutyric acid, polyhydroxyvaleric acid, polylactide (for example, available under the name EcoPLA® (Cargill)), and a mixture of 3-polyhydroxybutyric acid and polyhydroxyvaleric acid (the latter available from Zeneca under the name Biopol®), the derivatives being used of low molecular weight and cyclics defined above. Of course, it is also possible to use mixtures of two or more of the aforementioned hydroxycarboxylic acids. Furthermore, the use of cyclic derivatives of the hydroxycarboxylic acids described above (bl) in the reaction with the biodegradable copolyester used according to the invention gives, in a manner known per se, by means of a so-called ring-opening polymerization reaction. "copolyesters of the type defined above containing block structures composed of the copolyester (b) used according to the invention which are joined to each other through in each case at least one hydroxycarboxylic acid unit (bl) (* polymerization reaction) with ring opening "see, Encyclopedia of Polymer Science and Engineering, Vol. 12, 2nd Ed., John Wiley &Sons, 1988, pp. 36-41). The copolyesters which are especially preferably used within the scope of the present invention have the following composition related to the components (all), (al2) and (a2), where 'it should be taken into consideration that these copolyesters can not only contain groups sulfo, but may also contain the chain extenders and / or compounds defined as components (a3) and (a4). The data in brackets that follows the components in question corresponds to the amount of these components in mol percent: 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 (5) - neopentyl glycol (100), The copolyesters used according to the invention are characterized by the following peculiarities: These have an index of viscosity in the range of about 5 to 450 g / ml, preferably about 50 to about 350 g / ml and, in particular, about 100 to about 350 g / ml, in each case measured in o-dichlorobenzene-phenol (weight ratio) 50/50) at a concentration of 0.5% by weight of the copolyester at a temperature of 25 ° C. In addition, the copolyester which is used according to the invention has not only terminal hydroxyl groups, but also terminal carboxyl groups. The hydroxyl number of the copolyesters used according to the invention is from 0 to about 30., preferably 0 to about 20 and in particular 0 to about 10. With regard to further details about the dicarboxylic (cyclo) aliphatic acids, aromatic dicarboxylic acids, diols and / or amino alcohols which may be used within the scope of the present invention and other components (a3), (a4) and (Bl), reference is made to the patent applications of the applicant's company mentioned at the beginning when the prior art is explained, and to US 5 446 079 and the parallel application WO 92 / 09654, the content with respect to the copolyesters described herein and their preparation are incorporated in the present application by reference. However, the following is proposed as a brief description of the preparation of the copolyesters used according to the invention. This preparation of polyesters is known in principle (Sorensen and Campbell, * Preparatory Methods of Polymer Chemistry, Interscience Publishers, Inc., New York, 1961, pp. 111-127; Encyclopedia of Polymer Science and Engineering, vol. 12, 2nd edition., John Wiley & Sons, 1988, p. 1-75; Kunststoffhandbuch, vol. 3/1, Cari Hanser Verlag, Munich, 1992, p. 15-23 (preparation of polyesters) and in the aforementioned patent applications). In this way, for example, the reaction of dimethyl esters of the dicarboxylic acids (all / al2) contained in (al) with the component (a2) (* transesterification ") and, if appropriate with the components (al3) and / or (bl) can be carried out from about 160 to about 230 ° C in the molten state under atmospheric pressure, preferably under an inert gas atmosphere.When the biodegradable copolyester used according to the invention is prepared, it is advantageous to use a molar excess of the component (a2) based on the dicarboxylic acids used, for example up to a maximum of approximately 2.5 times, preferably up to 1.5 times, the amounts The preparation of the aforementioned copolyester is normally carried out with the addition of Suitable catalysts that are known per se, such as metal compounds based on elements such as Ti, Ge, Zn, Fe, Mn, Co, Zr, V, Ir, La, Ce, Li and Ca, preferably compounds organometallics based on these metals, such as the salts of organic acids, alkoxides, acetyl acetonates and the like, in particular based on Zn, Sn and Ti. As a rule, the reaction of the components (al) m (a2) and, if appropriate (bl) is carried out under reduced pressure or in a stream of inert gas, for example in nitrogen, with further heating from 180 to 260 ° C until the desired molecular weight is reached, taking into consideration the desired molar ratio of the terminal carboxyl groups to the terminal hydroxyl groups. Then (a3) and / or (a4) can be added, as a rule, at atmospheric pressure from about 50 to about 200 ° C, and the reaction can be continuous. To avoid undesirable degradation and / or secondary reactions, it is possible to add stabilizers to this process step, if desired, but the content of these should be selected as low as possible and generally represents 0.1 to 200 ppm, based on the copolyester Examples of these stabilizers are phosphorus compounds, as described, for example, in EP-A 13 461, US 4 328 049 and the aforementioned patent applications of the applicant company. The preparation of the polyester dispersions is also known per se and is described, inter alia, in US 3 546 008, EP-A-0 332 870 and EP-A-0 498 156, whose contents in relation to the preparation of the Polyester dispersions described therein are incorporated in the present application as a reference. To prepare the aqueous dispersion of the polyester used according to the invention, the copolyester (B) or the copolyester (Bl) used according to the invention is first prepared as described above in detail, and the resulting copolyester is subsequently neutralized and dispersed in an aqueous medium using a suitable neutralizing agent. For this purpose, a process is generally followed in which the copolyester, as a rule still as the hot melt from about 150 to about 230 ° C, is treated with an aqueous solution or dispersion of a neutralizing agent. The viscosity of the melt is determined by the torque of the latter in solution. The amount of the neutralizing agent added is chosen in such a way that the latter is capable of neutralizing the acid groups from partial to complete, partial neutralization "in the context of the present invention means a degree of neutralization of at least 70% of the carboxyl groups in the polyester In general, the water is added in such an amount as an aqueous dispersion of the polyester with a polyester content of from about 10 to about 90% by weight, preferably about 10 to about 65% by weight, is the result. Although it is possible to add an excess of the neutralizing agent, this has no practical advantages. As already mentioned above, the mixture of water and neutralizing agent is added to the molten polyester at temperatures from about 150 to about 230 ° C, preferably from about 150 to about 200 ° C. However, it should not be carried out unless about 150 ° C since, otherwise there is a danger of not obtaining a finely dispersed distribution of the polyester in water. The aqueous dispersion of the polyester can also be prepared from the melt in such a way that up to about half of the necessary amount of water is first added slowly, then the neutralizing agent is added, and the remaining amount of water is only added to the final . When water or the mixture of water and the neutralizing agent is added to the melt, the temperature of the latter decreases. After the introduction of the neutralizing agent / water mixture has ended, the temperature of the resulting polyester dispersion is generally from about 70 to about 100 ° C. L =. The resulting polyester dispersion is stirred for another 2 to 12, preferably 4 to 5 hours, if suitable at an elevated temperature of up to 95 ° C, and subsequently cooled to room temperature. The neutralizing agents that can be used are generally all conventional neutralizing agents. Examples that may be mentioned are ammonia, triethylamine, triethanolamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, morpholine, N-methylmorpholine, 2-amino-2-methyl-1-propanol and mixtures of two or more thereof. The neutralizing agents which are preferably used are monoethanolamine, diethanolamine, N-methylmorpholine, methyl diethanolamine and ammonia. The alkali metal hydroxides such as sodium hydroxide or potassium hydroxide may also be used, but are less preferred. It is also possible to remove part of the water by distillation to obtain the highest possible solids content. It is also possible to first treat the melt obtained in the preparation of the copolyester with a suitable organic solvent, for example methyl ethyl ketone or tetrahydrofuran and dissolve the polyester therein, subsequently treat the mixture with a neutralizing agent and with water for the purpose of neutralization and dispersing, and then subjecting the mixture to vacuum distillation to remove the organic solvent, which must be miscible with water or at least dispersible with water, by distillation, if appropriate together with excess water. In general, this gives the aqueous polyester dispersions with a solids content of about 10 to about 90% by weight, preferably about 10 to about 65% by weight, more preferably about 15 to about 40% by weight, and particularly about 20 to about 30% by weight.

In addition, the present invention also relates to granules of fertilizer coated with a coating consisting of a copolyester as defined above or a mixture of two or more thereof In another embodiment, the present invention relates to granules. of fertilizer with a multilayer coating consisting of at least one inner layer and one outer layer, the outer layer of which contains the copolyester already described above in detail, or a mixture of two or more thereof. for the internal layer (s), in principle, all those that can be used to coat fertilizers and which differ from the copolyester used according to the invention, the at least one inner layer of the coating preferably consists again at least one biodegradable substance which, however, differs from the copolyester in the outer layer, or the mixture of two or more thereof. The embodiment of the present invention comprises the developments of the coating consisting of two or more layers of different biodegradable copolyesters, each of which comes under the definition of the copolyesters used according to the invention, or even of the coating comprising an outer layer which consists of the copolyester used according to the invention and one or more internal layers consisting of, preferably also bidectable, substances that do not fall within the definition of the copolyester. The following may be mentioned as especially suitable biodegradable substances which do not fall within the definition of the copolyester: Aliphatic polyesters, for example, polyester butanediol of adipic acid, polyester butanediol of succinic acid, polyester neopentyl glycol of adipic acid, polyester ethylene glycol of acid adipic, biodegradable cellulose derivatives, for example microcellulose, ethylcellulose and triacetyl cellulose, poly (hydroxycarboxylic acids) as homopolymers or copolymers of the hydroxycarboxylic acids described as component (bl) within the scope of the present invention, polyvinyl alcohols and the like. Substances that contain the nutrient that are suitable for coating may also be used as the inner layer of the coating. Suitable fertilizer granules for coating are generally the known granules of organic and mineral fertilizers such as those described, for example, in Ullmans Encyclopedia of Industrial Chemistry, 5th Ed. 1987, Vol. 323-431 (see, in particular, chapters 2.1 and 4). Suitable substances are, for example, pure fertilizers and compounds, which contain, individually 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, pure nitrogen-containing fertilizers such as ammonium nitrate-lime, ammonium sulfate, ammonium nitrate sulfate and urea, and also slow-release fertilizers, particularly urea-based fertilizers, for example, isobutylideneurea, crotonylidene diurea and the urea / formaldehyde condensate. It is also possible to use initial fertilizer granules which, in addition to the main components mentioned above, also comprise the Mg, Fe, Mn, Cu, Zn, Mo and / B salts in smaller amounts, that is, normally in amounts of about 0.01. to about 5% by weight. The largest average diameter of the initial granules of the fertilizer is generally from about 0.5 to about 10, preferably about 0.7 to about 5 mm. Its density is density. it is normally from about 0.5 to about 1.5 kg / 1.

The fertilizer granules or the coating may also contain other customary additives, for example nitrification inhibitors, for example as described in DE-A 41 28 828, DE 195 03 827.4 and DE 196 31 764.9 and in the prior art mentioned in the present, in particular pyrazoles, pyrazole derivatives, growth regulators and active ingredients used in the protection of crops, for example herbicides, fungicides and insecticides. The present invention also relates to the process for the preparation of the coated fertilizer granules according to the invention in which an aqueous polyester dispersion as defined above is applied to the fertilizer granules. To prepare fertilizer granules coated with a multilayer coating, at least one dispersion of at least one other substance that differs from the copolyester in the outer coating, or the mixture of two or more of these, is additionally applied before applying the aqueous dispersion of polyester as already defined. The aqueous dispersions preferably contain about 10 to about 65, more preferably about 15 to about 40% by weight of the copolyester or of another substance other than the copolyester. In addition, the substances that control the release of fertilizers can be added to the solutions or dispersions. These are mainly substances such as lignin, starch and cellulose. These generally represent about 0.1 to about 5% by weight, about 0.1 to 3% by weight, based on the total amount of the coating substance. The solutions or dispersions of the (co) polymers forming the coating are conveniently applied by spraying from about 10 to about 110 ° C, preferably about 30 to about 70 ° C. To avoid incipient dissolution of the initial granules of the fertilizer when a dispersion or aqueous solution is used and applied, only a limited amount of the solution or dispersion is applied per unit time and the rapid evaporation of the water must be considered. This is conveniently achieved by spraying in a fluidized bed which is produced by fluidizing the initial granules of the fertilizer or with a fluidizing gas with the solutions or dispersions at about 10 to about 110 ° C, preferably about 30 to about 70 ° C. After the solutions or dispersions have been sprayed, the fluidized bed is generally maintained for some time until the solvent or the dispersing medium has evaporated. Accordingly, the present invention also relates to a process for the preparation of coated fertilizer granules in which a fluidized bed produced by fluidizing the initial fertilizer granules with a fluidizing gas is sprayed, from 10 to 110 ° C, with a dispersion polyester water as defined above, or first sprayed with at least one dispersion being at least one, biodegradable that differs from the copolyester substance in the outer layer, and subsequently the resulting granules are sprayed with an aqueous polyester dispersion as before. it defined itself. These fluidized bed application processes are generally known and described for the preparation of fertilizer granules coated in US-A-5 911 985. These processes allow to generate particularly uniform and thin coatings which generally have a thickness of about 10 to about 150. μ, preferably about 10 to about 100 and, in particular, about 20 to about 80 μ. To further reduce the tendency of the coated fertilizer granules to cake adhesion and formation, it may be advantageous to apply powdery solids such as talcum, SiO2, A1203 or TiO2 after the granules have been coated with the substances described herein. Coated fertilizer granules, if appropriate together with nitrification inhibitors or growth regulators, are applied to the soil by customary methods, and in this they release the nutrients over a prolonged period. The granules of fertilizers are distinguished, in particular by the fact that they have a relatively low tendency to adhesion and cake formation, even at high temperatures and that their coating is resistant to mechanical stresses such as those that commonly occur when they are transferred and transported and, in particular, when they are applied by means of modern machinery that operates quickly. The invention further relates to the coated fertilizer granules which are prepared with the process according to the invention and to a fertilization method in which the fertilizer granules coated according to the invention are applied to the soil, are mixed with the floor or are incorporated into the ground. Next, the present invention is illustrated using some examples, together with the diagrams contained in this application. Figure 1 shows a schematic representation of the measuring apparatus for determining the quality of the coating. Figure 2 shows the release of nitrogen from NPK fertilizers coated with a polyester used according to the invention. Figure 3 shows the corresponding nitrogen release using a coating based on Osmocote® plus 3-4 M.

EXAMPLES The aromatic and aliphatic dicarboxylic acids and the dihydroxy compounds that are; shown in Table 1 were entered in the quantities that are also shown in Table 1 together with 100 ppm of terbutyl orthotitanate (TBOT) (added as a 10% solution in toluene) in a four-necked flask and heated to 170-190 ° C and reacted at this temperature for 3 to 4 hours. The temperature was subsequently raised to 240 ° C, and the excess of neopentyl glycol was distilled in vacuo. The OH number of the polyester was measured and brought to 24 by adding neopentyl glycol.

Preparation of the dispersions Copolyesters PE 1 to 3 (as shown in Examples 1 to 3) were melted in a reactor at 110 ° C. The amounts of pyromellitic dianhydride (PMDA) shown in Table 1 were added to the resulting molten polyester, and the mixture was stirred at 50 rpm. The temperature was slowly raised to 180 ° C, and hexamethylene diisocyanate (HDI) was added in 0.5 ml portions until the HDI content shown in Table 1 was reached. During this addition, the torque was measured simultaneously, and when a torque of 50% (measured with a laboratory meter RE162 or Janke &Kunkel) had been reached, 300 ml of methyl ethyl ketone were added, during which the copolyester in question dissolved. After the polyester solution had cooled to 40 ° C, the acid groups of the copolyester were neutralized with a stoichiometric amount of ethanolamine. Then, one liter of water was poured into the solution and the mixture was kept under vigorous stirring. 200 ml of acetone were added to the dispersion formed. The acetone bound with MEK was then distilled under vacuum at 60 ° C.

In the table, TA = terephthalic acid AA = adipic acid MPG = neopentyl glycol DEG = diethylene glycol CHDM = cyclohexane dimethanol In a commercially available fluidized bed coater, the initial granules of the fertilizer Nitrophoska® Perfekt (15 + 5 + 20 + 2) were fluidized using preheated air and heated to the desired temperature. The aqueous dispersions of the polyester in question were sprayed through suitable nozzles, thus coating the initial granules of the fertilizer with a copolyester coating. The spray speed was chosen so as to avoid the incipient dissolution of the fertilizer. After the spraying process had ended, the resulting coated fertilizer granules were dried for a few more minutes in the fluidized bed. This provided coated fertilizer granules with good processability that were not tacky at room temperature. To characterize the release of nutrients, the granules of coated fertilizers were subjected to a leaching test. For this purpose, a sample of the coated fertilizer granules (1) to be tested (10 g) were introduced into the apparatus that is schematized in figure 1, and the apparatus was subsequently flooded with 1 ml / minute of distilled water (2) at 25 ° C. The collected washing liquid (3) was tested daily for its nutrient content (mainly nitrogen), and the result was expressed as a percentage relative to the amount of nutrient in the initial granules of the fertilizer. The results of the tests carried out over several days are compiled in the attached leach curves as shown in Figure 2. Figure 3 shows the results in relation to the release of nitrogen, which were obtained using a product available in trade with a non-degradable coating based on cross-linked vegetable oils (Osmocote® Plus 3-4M, from Scotts). It should be noted that the fertilizer granules coated according to the invention are the same as the coatings that are available to date and that were satisfactory with respect to their release of nitrogen, but also have the advantageous characteristic of being biodegradable and In this way they do not form residues in the soil.

Claims (10)

REI INDICATIONS

1. The use, to coat granules of fertilizer, of a polyester dipsersion consisting of: (A) 20 to 90% by weight of water, and (B) 10 to 80% by weight of a biodegradable copolyester (B) with structural units from aliphatic and aromatic carboxylic acids or their derivatives, which may be obtained by reaction of a mixture consisting of: (a) a mixture composed of: (a) 10 to 95 mol% of an aliphatic dicarboxylic acid or a dicarboxylic acid cycloaliphatic or of an ester-forming derivative thereof or of a mixture of two or more thereof. (al2) from 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, (al3) from 0 to 10 mol% of a compound containing sulfonate or a mixture of two or more thereof, the total of the individual mole percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio being ( al) a (a2) selected within a range from 0.4: 1 to 2.5: 1, (a3) from 0 to 10% by weight, based on the mixture (al), of a chain extender or a mixture of two or more thereof, and (a4) from 0 to 20% by weight, based on the mixture (a) of a compound having at least 3 groups capable of forming the ester or a mixture of two or more thereof , the recurring units derived from the aliphatic and aromatic carboxylic acid (cyclo) being distributed randomly or in alternating form, having the copolyester with a visco number sity in the range from 5 to 450 ml / g (measured in o-dichlorobenzene / phenol (50/50 weight ratio) at a concentration of 0.5% by weight of the copolyester, 25 ° C) and the amount of the components (al3) ) and (a4) not simultaneously being zero in each case. 2. The use, for coating fertilizer granules, of a polyester dispersion according to claim 1, which contains: (A) 20 to 90% by weight of water, and (B) from 10 to 80% by weight of a biodegradable copolyester (Bl) with structural units derived from aliphatic and aromatic dicarboxylic acids or their derivatives, which can be obtained by reaction of a mixture comprising: (a) a mixture composed of: (all) 10 to 95 mol% of an acid 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. (al2) from 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, (al3) from 0 to 10 mol% of a compound containing sulfonate or a mixture of two or more thereof, the total of the individual mole percentages being 100, (a2) a dihydroxy compound or an amino alcohol or a mixture of two or more thereof, the molar ratio being ( al) a (a2) selected within a range from 0.4: 1 to 2.5: 1, (a3) from 0 to 10% by weight, based on the mixture (al), of a chain extender or a mixture of two or more thereof, and (a4) from 0 to 20% by weight, based on the mixture (a) of a compound having at least 3 groups capable of forming the ester or a mixture of two or more thereof , (bi; from 0.01 to less than 50% by weight, based on the mixture (al), of a hydrocarboxylic acid (bl) which is defined by the following formula lia or Ilb.

HO- [C (O) -] H Ola) where p is an integer from 1 to 1500 and r is 1,2,3 or 4, and G is a phenylene group, a group CH2) n ~ where n is an integer of 1, 3, 4 or 5, a group -C ( R) H or a group -C (R) HCH2, where R is methyl or ethyl, or a mixture of two or more of these, the recurring units from the carboxylic acid (cyclo) aliphatic and aromatic being randomly distributed, the copolyester with a viscosity number in the range from 5 to 450 g / ml (measured in o-dichlorobenzene / phenol (weight ratio 50/50) at a concentration of 0.5% by weight of the copolyester at 25 ° C) and the amount of the components (al3) and (a4) not being simultaneously in each case zero.

3. The granules of fertilizer that are coated with a coating consisting of a copolyester as defined in claim 1 or 2, or a mixture of two or more thereof.

4. Granules of fertilizer with a multilayer coating consisting of at least one inner layer and one outer layer, the outer layer of which comprises a copolyester as defined in claim 1 or 2, or a mixture of two or more thereof.

5. The fertilizer granules as recited in claim 4, wherein at least one inner layer of the multilayer coating consists of at least one biodegradable substance which differs from the copolyester in the outer layer or a mixture of two or more of the same.

6. A process for the preparation of coated fertilizer granules in which an aqueous polyester dispersion, as defined in claim 1 or 2, is applied to the initial granules of the fertilizer.

7. A process for the preparation of fertilizer granules coated with a multilayer coating, wherein before applying the aqueous polyester dispersion as defined in claim 1 or 2, at least one dispersion consisting of at least a biodegradable substance that differs from the copolyester in the outer layer or the mixture of two or more thereof.

8. The process as recited in claim 6 or 7, wherein a fluidized bed, produced by fluidizing the initial fertilizer granules with a fluidizing gas, is sprayed with an aqueous polyester dispersion as defined in claim 1 or 2, of 10 to 110 ° C, or first sprayed with at least one dispersion consisting of at least one biodegradable substance that differs from the copolyester of the outer layer, and subsequently the resulting granules are sprayed with an aqueous dispersion of polyester as defined in claim 1 or 2.

9. Coated fertilizer granules obtainable by means of a process as mentioned in any of claims 6 to 8.

10. A method of fertilization in which the fertilized granules coated as mentioned in any of claims 3 to 6 and 9 are applied to the soil, mixed with the soil or incorporated with the soil.