ADDITIVES AGAINST CLUMPING AND THE HUMIDIFICATION OF NITROGEN FERTILIZERS
The present invention relates to new additives for preventing caking and humectation of nitrogenous fertilizers, based on compositions of materials containing hydrophobic substances and phosphoric acid esters. Spanish Patent Application ES-A-2121694, filed by the Applicant, describes anti-caking compositions for granular fertilizers based on the combined use of mineral oils, fatty amines and phosphoric acid alkyl esters. The description of said Spanish application includes an extensive exposition of the state of the art relating to anti-caking compositions for fertilizers, with specific reference made to relevant documents. Table II of example 1 of US patent 5,364,440 describes a composition that contains, expressed as % by weight, 50% of mineral paraffin oil, 40% of a paraffin wax and 10% of the magnesium salt of a phosphoric acid C16-C18 alkyl ester. Said composition is only described as an anti-caking agent for fertilizers, without any mention being made of aspects related to preventing humectation. Nitrogenous fertilizers, particularly those based on ammonium nitrate (AN) or ammonium and calcium nitrate (ACN), not only suffer from caking that restrict their handling and dosing, but present the drawback of absorbing humidity during their storage which, when stored or transported in large amounts as usually, often results in filtrations of highly moist material forming channels within the fertilizer mass, known as stalactites or candles, and which may even form deposits of liquefied fertilizer in the base of the pile due to its high degree of humectation. Patent Application EP-A-392468 proposes a solution to this problem by using compositions containing oily products and waxes together with compounds obtained by reacting an amine or an alcohol with an acid or a carboxylic anhydride containing a C20-C500 hydrocarbonated group, compounds that are known and available in the market under the commercial name GALORYL ATH 632M. The description of EP-A-692468 clearly states that it is not possible In said patent application it is also clearly admitted that the composition object of the patent, despite being effective against humectation, is much less effective against caking than classical anti-caking agents. (See table III and the following comment). Patent application EP-A-702999 proposes the use of mixed compositions containing as an anti-caking agent fatty amines and/or salts of fatty amines with arylalkyl sulphonic acids and/or salts of fatty amines with phosphoric acid esters, and as an anti-humectation agent compounds for inhibiting humectation described above in the aforementioned patent application EP-A-692468. Thus, in the patent application EP-A-702999 the problem to solve is obtaining additives for preventing both compacting and humectation of fertilizers, and the solution proposed consists in combining in a single composition specific compounds with already-known anti-caking properties, but lacking appreciable anti-humectation properties, and specific anti-humectation compounds which have no effective activity as anti-caking agents by themselves. It is thus clear that the problem of obtaining anti-caking and anti-humectation additives for nitrogenous fertilizers still requires new solutions that allow obtaining simpler and less expensive compositions, and with a greater effectiveness. The object of the present invention are new additives to prevent caking and humectation of nitrogenous fertilizers based on compositions of materials free of fatty amines or their salts that contain hydrophobic substances and phosphoric acid esters. Also part of the object of the invention is the use of said additives for the anti-caking and anti-humectation treatment of nitrogenous fertilizers, and a procedure for obtaining nitrogenous fertilizers .that are resistant to caking and humectation. The additives for preventing caking and humectation of nitrogenous fertilizers object of the invention are compositions of materials free of fatty acids or their salts, characterized in that they comprise: Macrocrystalline paraffins are petroleum derivatives that contain carbonated chains, mainly linear chains, with a molecular mass between 250 and 500 and, although solid at room temperature, with low melting points, generally between 40 and 70 °C. For the purposes of the present invention, macrocrystalline paraffins having a viscosity between 2 and 5 cSt, measured at 100°C in accordance with the considerations of standard ASTM D-455 (American Standard), are chosen. Macrocrystalline paraffins are commercially available and commercial products always have a certain portion of paraffin oil that is not constant and may vary among the various batches purchased. For the purposes of the present invention, the oil content of the macrocrystalline paraffin must be less than 20% by weight as determined in accordance with standard ASTM D-721. The preferred macrocrystalline paraffins are Spindle-type paraffins with a viscosity between 2 and 3 cSt at 100°C and an oil content not greater than 12% by weight. Within this type of paraffins can be mentioned commercial references PARAFINA PRS and PARAFINA 1ST, both supplied by the company Repsol Derivados, S.A. Paraffinic oils are also commercially available petroleum derivatives that are rich in paraffinic components and have a low density and a variable viscosity. Their presence in the compositions of the invention is necessary, although the need to add them to said compositions and the amount to be added depends on the oil content of the macrocrystalline paraffin used. The total content of paraffinic oil in the compositions of the invention can be between 5% and 25% by weight, preferably between 7% and 20% by weight and more preferably between 9% and 15% by weight. Among current paraffinic oils suitable for the invention can be mentioned the oil corresponding to the commercial reference EXTENSOIL 200, supplied by Repsol Derivados, S.A. Microcrystalline paraffin is an optional component, albeit preferred, constituent of the compositions object of the invention. It is also derived from petroleum, and mainly contains saturated hydrocarbons in which predominate linear chains with short branches (isoparaffins). They generally have average molecular masses between 500 and 800 and are solid at room temperature, having melting points between 70°C and 100°C. Commercial products also generally contain a proportion of oil. Among the microcrystalline paraffins suitable for the invention can be mentioned the one commercially known as PARAFINA PRB (495-D) supplied by the company Repsol Derivados, S.A. Phosphoric acid esters suitable for the object of the invention are products well known to experts on tensioactives, and are obtained by reacting C2-C22 fatty alcohols or alkyl (C2-C12) phenols with phosphorus pentoxide, and optionally can be alkoxylated by reaction with 2-50 moles of an alkylene oxide, mainly ethylene and/or propylene oxide. The products obtained are a mixture of monoesters and diesters, and for the purposes of the present invention the preferred products are those in which the molar ratio of monoester to diester is between 70:30 and 30:70, and more preferably between 70:30 and 50:50, being particularly preferred those having a ratio of monoester to diester between 65:35 and 55:45. Unalkoxylated phosphoric acid esters of C2-C22 alkyl are preferred, and unalkoxylated phosphoric acid esters of C16-C18 alkyl with a molar ratio of monoester to diester of 60:40 are particularly preferred, such as those available under the commercial reference FOSFODET 80/50, supplied by the company KAO Corporation, S.A. Since phosphoric acid esters are obtained from a reaction with phosphorus pentoxide, they usually contain residues of (poly) phosphoric acids that can lead to undesirable brownish colours in the additives object of the invention. The authors of the present invention have found that the total or partial neutralization of the phosphoric acid esters with an amine selected from monoalkylamine, dialkylamine, trialkylamine, monohydroxyalkylamine, dihydroxyalkylamine or trihydroxyalkylamine, all of them C1-C4 amines such as monoethanolamine, allows to prevent or substantially diminish the appearance of said colouring in the additives of the present invention. This aspect, albeit optional, is also part of the invention. The amounts of short chain amine to be added shall depend on the type and quality of the phosphoric acid esters used, and on the degree of neutralization deemed necessary to reduce said undesired colouring. For example, when using FOSFODET 80/50 it may be enough to use monoethanolamine in amounts between 0.1 and 3.5 parts by weight with respect to the total composition, preferably between 0.5 and 2.0 parts by weight. Anti-caking and anti-humectation additives are preferred having compositions that are free of fatty amines or their salts and that they comprise: The additives object of the invention can be obtained by conventional methods of mixing the various constituents, well known to the expert. Thus, for example, the various constituents can be mixed in a molten state and after the mixture is homogenized, this is packaged and optionally cooled. The additives obtained in this way can be used to treat nitrogenous fertilizers, particularly AN and CAN fertilizers, providing them with an efficient resistance to caking and humectation; so that these fertilizers, even after their period of storage and transport, show excellent disintegrating properties and do not form the known stalactites or candles due to a high humectation degree, nor liquefied deposits in the base of the piles of stored product. This use is also part of the present invention. Also part of the present invention is a procedure for obtaining nitrogenous fertilizers resistant to caking and humectation that consists in applying on the surface of the fertilizer granules a coating of the aforementioned additives. The procedures for applying said coating are well known to the expert and consist, for example, in applying the additive in a molten state by spraying techniques, on the surface of the fertilizer granules after said additive is manufactured. The amount of additive to apply on the fertilizer will depend in each case on the humidity conditions, time of storage and temperature expected for storage of the fertilizer, although good results can be obtained when the additives are applied to the fertilizer in proportions from 500 to 2000 ppm with respect to fertilizer weight. The examples that follow intend to provide an expert on the field with a sufficiently clear and thorough explanation of the present invention, but should not be understood as a limitation of the essential aspects of the object of the invention, as described in the previous sections of this description. In a container provided with stirring, the macrocrystalline paraffin is loaded in a molten state and then the microcrystalline paraffin and the paraffinic oil are added under stirring and at a temperature between 80° and 90° C. The mass is kept stirred and the phosphoric acid ester added in flakes or molten, maintaining the same temperature. Once the mass has been homogenised, monoethanolamine with at least 99% of purity is optionally added. The molten mass is left stirred for 30 minutes at the same temperature. Afterwards it is unloaded and packaged. According to the general method, the compositions A, B, C and D described in Table 1 are prepared, in which the amounts of the constituents shown are expressed as parts by weight of each component added to each composition. The names of the constituents used in the table correspond to the commercial references described in the section corresponding to the description of the invention. 70 to 100 g of granular fertilizer are introduced in cylindrical perforated metal test tubes 60mm high and 45mm diameter, which can be longitudinally opened for extracting samples, using 3 test tubes for each fertilizer sample. The samples are subjected to a pressure of 1.26 Kg/cm2 in an INSTRON dynamometer, model 1011, in one of the two following climate conditions: The results are assessed by opening the test tubes carefully and depositing the sample on an unshaken sieve with 6.3mm mesh size, previously weighed, then weighing the amount of sample retained. The amount of sample retained is expressed as a % of the total weight and the result indicates the average % of caking before break-up. If the sample were fully clumped it is then broken up in the aforementioned dynamometer at a rate of 10 mm/min. The result is expressed as an average Resistance to break-up in Kg. The test carried out is based on the method described in the "Manual for Determining Physical Properties of Fertilizer", 2nd Edition, 1993, by David, W. Ritland (ISBN 0-88090-101-2) in the section IFDC S-100 "Laboratory Absorption-Penetration test". The following changes are made with respect to said method: The climate conditions are: 20°C and between 75%-85% RH. A HERAEUS model HC 2057 climate chamber is used. The cylindrical glass test tube has a diameter of 57mm and the height of fertilizer is between 37 and 48 mm, depending on the fertilizer grain size. The weight of the granular fertilizer is 100g in each test tube, and controls are made, depending on each case, at 6, 24, 48 and 72 hours. The results are expressed as mg/cm2 of humidity absorption with respect to the top surface of the test tube, and as mm of penetration, and the visual appearance is described, including the formation of channels and the possible presence of water on the bottom. A granular ammonium nitrate with 33.5% nitrogen, with a retained granule size of between 2.36 and 4.00 mm mesh size)" and a pH of 6.2 in water (4% by weight), was treated according to the "Manual for Determining Physical Properties of Fertilizer", 2nd Edition, 1993, by David, W. Ritland (ISBN 0-88090-101-2) in the section IFDC S-107 "Size Analysis (Sieve Method, by spraying on the fertilizer the molten additives being tested in a rotary mixer, in a dose of 1200 ppm with respect to fertilizer weight. The following additives were tested: Also tested is a blank, which is a sample of fertilizer without additives. The tendency towards caking of each treated sample and the untreated fertilizer are assessed in the environmental conditions defined in point (b) of section 2.1 of Example 2, using 90 grams of fertilizer per test tube in a period of 6 days. The results obtained are shown in table 2. From the results obtained it can be seen that compositions A and B of the invention provide good results as anti-caking agents, even somewhat better than the conventional anti-caking agents. In addition, the absorption and penetration of humidity in the treated samples and the untreated fertilizer (blank) were tested according to the method described in section 2.2 of Example 2, using 100 g of ammonium nitrate per test tube at 82% RH. The results obtained are shown in table 3. The untreated sample does not show the formation of channels since the water absorption is very high and uniform throughout the mass. The results clearly show the high anti-humectation efficiency of the additives of the invention, and the inefficiency in this respect of the conventional anti-caking additives based on fatty amines. With the same fertilizer used in Example 3 and in similar conditions, the water absorption of the following additives was tested: In addition a blank, which consisted of a sample of untreated fertilizer, was tested. The results are shown in table 4. The results obtained shown the superior efficiency of the additives of the invention compared to the anti-caking additive GALORYL ATH-626M, both regarding water absorption and formation of channels. A granular ammonium nitrate with 33.5% nitrogen, obtained from the factory in Rouen (France) of Grande Paroise S.A. company, was treated by spraying on the fertilizer the molten additives tested in a rotary mixer at a dose of 1200 ppm with respect to fertilizer weight. The following additives were tested: In addition a blank was tested, which consists of a sample of fertilizer without additives. The tendency towards caking of the treated samples and the untreated fertilizer was tested in the environmental conditions defined in point (b) of section 2.1 of Example 2, using 80g of fertilizer per test tube for a period of 6 days. The results obtained are shown in Table 5. The results obtained show that composition B of the invention gives good result as an anti-caking additive, on the same order as that obtained with conventional anti-caking additives. In addition, the humidity absorption and penetration of the treated samples and the untreated fertilizer (blank) were tested following the method described in section 2.2 of Example 2, using 100 grams of ammonium nitrate per test tube at 80% RH. The results obtained are shown in Table 6. The results show the high anti-humectation efficiency of the additive of the invention and the inefficiency for this purpose of the conventional anti-caking additives based on fatty amines. With the same fertilizer used in example 5, but in a dose of 1100 ppm, the aforementioned additives SK FERT FW18M, SK FERT FW5AG and SK FERT F85 and the compositions C and D of Example 1 were tested. In addition, a blank is tested which consists of a sample of fertilizer without additives. The tendency towards caking of the treated samples and the untreated fertilizer was then tested in the two environmental conditions defined in section 2.1, (a) and (b) of Example 2. The results obtained are shown in Table 7. The results of Table 4 show that the additives of the invention show a considerable anti-caking efficiency, comparable to that of the conventional anti-caking additives tested. In addition, the humidity absorption and penetration were assessed for the treated samples and the untreated fertilizer (blank), following the method described in section 2.2. of Example 2, using 100 grams of ammonium nitrate per test tube at 75% RH. The results obtained are shown in Table 8. The results show the high anti-humectation efficiency of the additives C and D of the invention compared to the low efficiency in this sense of the conventional anti-caking additives. Although the present invention has been explained with reference to the described embodiments and the accompanying examples, those expert on the art may introduce multiple variations thereof, which will remain within the scope of the invention, which are solely limited by the appending claims. Anything that does not alter, change or modify the essence of the described additives may be variable for the purposes of the present invention. The present invention relates to new additives for preventing caking and humectation of nitrogenous fertilizers having a material composition which is free of fatty amines or their salts and characterized in that it comprises: (i) between 50 and 90 parts by weight of a macrocrystalline paraffin having a viscosity at 100 ·C between 2 and 5 cSt (ASTM D-455), with a paraffin oil content under 20% by weight (ASTM D-721); (ii) between 0 and 20 parts by weight of a paraffinic oil having a viscosity at 100 ·C between 3 and 40 cSt (ASTM D-455); (iii) between 0 and 10 parts by weight of a microcrystalline paraffin having a viscosity at 100 ·C between 10 and 25 cSt (ASTM D-455) with a paraffin oil content not greater than 15% by weight (ASTM D-721); (iv) between 10 and 50 parts by weight of phosphoric acid monoesters and/or diesters of C2-C22 alkyl or C2-C12 arylalkyl, optionally alkoxylated; so that the total paraffin oil content of the composition is greater than 1% by weight. An additive for preventing caking and humectation of nitrogenous fertilizers, having a material composition which is free of fatty amines or their salts,characterized in that it comprises: (i) between 50 and 90 parts by weight of a macrocrystalline paraffin having a viscosity at 100°C between 2 and 5 cSt (ASTM D-455), with a paraffin oil content under 20% by weight (ASTM D-721); (ii) between 0 and 20 parts by weight of a paraffinic oil having a viscosity at 100°C between 3 and 40 cSt (ASTM D-455) ; (iii)between 0 and 10 parts by weight of a microcrystalline paraffin having a viscosity at 100°C between 10 and 25 cSt (ASTM D-455) with a paraffin oil content not greater than 15% by weight (ASTM D-721); (iv) between 10 and 50 parts by weight of phosphoric acid monoesters and/or diesters of C2-C22 alkyl or C2-C12 arylalkyl, optionally alkoxylated; An additive according to claim 1, characterized in that the total paraffin oil content is between 5% and 25% by weight. An additive according to claim 1 or claim 2,characterized in that it comprises: (i) between 60 and 80 parts by weight of macrocrystalline paraffin; (ii) between 2 and 12 parts by weight of paraffinic oil; (iii)between 2 and 7 parts by weight of microcrystalline paraffin; (iv) between 12 and 20 parts by weight of phosphoric acid monoesters and/or diesters; An additive according to any of claims 1 to 3,characterized in that the macrocrystalline paraffin is a Spindle-type paraffin, with a viscosity between 2 and 3 cSt at 100°C and an oil content not greater than 12% by weight. An additive according to any of previous claims,characterized in that the molar ratio of monoester to diester in the phosphoric acid esters lies between 70:30 and 30:70. An additive according to claim 5, characterized in that the molar ratio of monoester to diester in the phosphoric acid esters lies between 70:30 and 50:50. An additive according to claim 6, characterized in that the molar ratio of monoester to diester in the phosphoric acid esters lies between 65:35 and 55:45. An additive according to any of previous claims,characterized in that phosphoric acid esters are chosen from unalkoxylated phosphoric acid esters of C2-C22 alkyl. An additive according to claim 8, characterized in that phosphoric acid esters are chosen from unalkoxylated phosphoric acid esters of C16-C18 alkyl, with a monoester to diester molar ratio of 60:40. An additive according to any of previous claims,characterized in that the phosphoric acid esters have been partially or fully neutralized with a C1-C4 amine selected from monoalkylamine, dialkylamine, trialkylamine, monohydroxyalkylamine, dihydroxyalkylamine or trihydroxyalkylamine. An additive according to claim 10, characterized in that the phosphoric acid esters are partially or fully neutralized with monoethanolamine. The use of the additive according to claims 1 to 11 to prevent caking and humectation of nitrogenous fertilizers. A method for obtaining nitrogenous fertilizers that are resistant to caking and humectation,characterised in that a coating of the additive of claims 1 to 11 is applied on the surface of the fertilizer granules. A method according to claim 13, characterized in that the additive is applied on the fertilizer in a proportion between 500 and 2000 ppm with respect to the fertilizer weight.FIELD OF THE INVENTION
PRIOR STATE OF THE ART
OBJECT OF THE INVENTION
DESCRIPTION OF THE INVENTION
so that the total paraffin oil content of the composition is greater than 1% by weight.
so that the total oil content in the prepared composition is between 7% and 20% by weight.ExamplesExample 1. Preparation of the additives of the invention.1.1. General Method
1.2 Prepared compositions
Example 2. Assessment methods2.1 Accelerated caking test
2.2 Humidity absorption and penetration test
Example 3. Comparative tests (1)
Example 4. Comparative tests (2)
Example 5. Comparative Tests (3)
Example 6. Comparative tests (4)