Introduction

Very many inorganic salts are produced and marketed world wide. Salts are used, inter alia, as fertilizer and drying agent or as additive for foods, cleaning agents and the production of glass and porcelain.

Before it reaches its final use, inorganic salts often undergo a long-term storage and/or intercontinental transport. Therefore, granulate should not cake together, absorb moisture and/or form dust. In order to obtain robust granulates, small amounts of chemicals are added to the salts. A known example is prussiate of potash for sodium chloride (see e.g. US 3.174.825) .

Coatings

In the fertilizer industry, nearly always use is made of coatings based on a fatty amine (C12-C22) , which is dissolved in a mixture of oil and paraffins. These compositions, possibly in combination with talc, can prevent cake formation of salts (see e.g. US 4.150.965) and, after addition of alkyl phosphate esters, can also strongly reduce moisture absorption (see e.g. EP 0 113 687 and WO 03/006399). These mixtures are mostly applied on the fertilizer via a coating drum or via a spraying system at a conveyor belt. Because of this, a thin film layer is formed around the granulate, by which it is (partially) protected against external influences. Coatings on the basis of oil and paraffins have been examined very intensively and several compositions are claimed (see e.g. WO 03/006399 and references therein) . The power is that these coatings mostly give an excellent performance in very low

doses. Commonly used amounts are between 0.05 and 0.15 percent by weight, based on the weight of the treated fertilizer.

The legislation in Europe in the field of the treatment of salts, in particular fertilizer, becomes increasingly stringent. In Germany, for example, it is no longer allowed to process mineral oil as additive for fertilizer, soil auxiliary agents, agri-cultural substrates and plant auxiliary agents as of 4 December 2006 (Dϋngemittelverordnung - DuMV of 26 November 2003, published in Bundesgesetzblatt Jahrgang 2003 Teil I No. 57, 2373-2437) . It means that there is a need for environmentally friendly products that give plant auxiliary agents such a protection, that they can be stored and processed without problems.

Cake formation of ammonium nitrate-containing fertilizers can be reduced by using polyalkylene glycols as coating (GB 1.026.023). Most polyalkylene glycols are soluble in water, low-toxic and biodegradable. The optimum dose is between 0.3 and 1.0 percent by weight, based on the weight of the treated fertilizer. This is considerably higher than common with oil- paraffin-containing products.

Several water-soluble biodegradable polymers can be used, inter alia, as coating for the so-called "slow-release" fertilizers, i.e. that the plant nutrients are released slowly to the soil through slow decomposition of the coating (DE 198 20 297-A1) . The effect is only realized when relatively large amounts of coating (1-10% based on the weight of the treated fertilizer) are applied. Cake formation of the final product can be limited by adding inert powder, such as talc. Another process for obtaining "slow release" fertilizers has been reported in JP 8-277191. Herein, after applying to the granulate, initially water-soluble coatings are made insoluble by heating at 200 ⁰ C. Because of that, cross-linking of the polymers takes place (cross-linking) . Due to the required heating (and the subsequent cooling) , this process is not profitable for bulk processes.

Another approach for preventing lump formation of salts and fertilizer is the use of alkyl amine - alkyl naftalene sulfonate mixtures (US 4.374.039) and alkyl sulfates (US 4.772.308). Practice has proven that these products can

give a maximum reduction of cake formation of 50%. Moreover, fertilizers which have been treated with sulfonates or sulfates show cake and dust formation after long-term storage. Due to moisture absorption of the fertilizer, the strong sur'face active alkyl naftalene sulfonates or alkyl sulfates dissolve a part of the fertilizer, as a result of which the fertilizers can easily cake together and form dust particles.

The caking tendency of sodium chloride can be reduced strongly by treating it with metal complexes of hydroxyl poly carboxylic acids, preferably an iron complex of meso-tartaric acid (WO 00/59828) . These compounds prove not to satisfy as treating agent for granulate with a strong tendency of lump formation and/or moisture absorption, such as most kinds of fertilizer, for example NPK ¹ s, urea and ammonium nitrates. Another approach has been reported in WO 01/38263 and

WO 02/090295. In this case, a part of the paraffin and oil has been replaced by natural oils, such as rapeseed oil. The products are inherently biodegradable, but still contain mineral oil or derivatives thereof. Moreover, natural oils are sensitive to polymerization and oxidation, causing it to be only limitly imperishable.

Granulation additives

It is common knowledge that granulates are subject to crushing during production, storage and transport. High percentages of crushed granules result in dust problems with a strong tendency of caking, because the reactive surface is strongly enlarged. Several chemical compositions can be used as additive to improve the crushing strength, the tendency of caking and the resistance against moisture.

Formaldehyde, hexamethylene tetramine and formaldehyde/urea condensation products can be added as improvers of the crushing strength of urea. These additives must however be added in relatively large amounts, or the poisonous properties thereof make them difficult to handle. Moreover, formaldehyde derivatives are unsuitable when the urea is used for the production of melamine.

GB-A-I 217 106 describes a process for reducing of caking of urea by using a polyvinyl alcohol having a high molecular weight as an additive in order to prevent caking. More particularly, according to this process, an aqueous solution of the additive is mixed with an aqueous solution of urea. Preferably, an amount of additive of 0.005 to 5 % by weight, based on the weight of the urea, is admixed. The concentration of the aqueous urea solution is initially 80%, according to the example given; after admixing the solution of the additive, concentration to 95% takes place at increased temperature, after which one lets the urea crystallize through cooling. Practice has shown that the presence of polyvinyl alcohol in urea results in dust formation, probably due to internal moisture migration. WO 02/20471 mentions a process wherein a combination of a polyvinyl compound and inorganic salts are mixed with urea melt. The crushing strength as well as the impact resistance of the obtained granulate prove to be improved in comparison with untreated urea. Besides, the compressibility of the urea proved to be reduced considerably. This last observation could be an advantage because the urea granulates will be less sensitive to deformation in storage. However, adding inorganic salts, such as aluminium sulphate, in urea results in a strong decrease of the pH when dissolving the urea in water. This is a great disadvantage in the use of this urea in technical applications, such as the production of resins.

US 4,063,919 describes a fertilizer composition containing a polyvinyl alcohol and a plasticizer for the polyvinyl alcohol, wherein this plasticizer is preferably chosen from glycerol, sorbitol, glycol, polyglycols having A- 20 C-atoms, and mixtures thereof. Besides, mannitol and sucrose are mentioned as plasticizers in this publication. Although sorbitol, mannitol and sucrose are sugars, they are referred to as polyglycols in this publication. It is a disadvantage that sugars will colour at increased temperatures (> 100 ⁰ C), the so-called caramelizing. Also the presence of small polar substances can result in higher hygroscopicity of urea, as a result of which recrystallization can take place and consequently the dust formation will increase drastically.

Object of the invention

Due to the increasingly stringent legislation with respect to the treatment of salts, in particular plant auxiliary agents, such as fertilizer, there will be an increasing demand for a product that can be used as an additive in order to reduce the caking tendency, the moisture absorption of the granules, the dust formation (small particles which already float in case of small air turbulence) and/or the compressibility. This product should be added in a small amount, be cheap, free of paraffin, free of oil and environmentally friendly.

Therefore the object of the invention is to provide a free-flowing, mineral oil-free granulate of a plant auxiliary agent, as well as a process for manufacturing the same.

Another object of the invention is the use of residual flows of natural origin, preferably vegetable waste flows, such as corn and wheat residues, as additive for plant auxiliary agents, such as fertilizer. The products can be added in the melting phase of the granulation process or on the produced granules after the granulation.

Another object of the invention is the use of a particular polyoxy ethylene-containing organic component having an HLB value between 2 and 11 as additive for plant auxiliary agents, such as fertilizer.

Description of the invention

The invention relates to free-flowing, mineral oil-free, granulate particles of a plant auxiliary agent, consisting of the reaction product of a nitrogen-, phosphor- and/or potassium-containing plant auxiliary agent and a nitrogen compound (s) -containing waste flow of natural material. The plant auxiliary agent is preferably a urea- or ammonium nitrate-containing fertilizer; whereas the waste flow preferably originates from the starch preparation from products such as corn, wheat, soy, barley and potatoes. If desired, the protein and/or amino acid content of the waste

stream to be used can be supplemented with a protein-rich or amino acid-rich source, such as soy protein, or chicken egg protein.

The invention also relates to the preparation of said granulate particles by treating the granules with a nitrogen- rich additive of natural origin at increased temperature. The additive (s) is (are) mixed in a polar solvent, if desired. If desired, this solvent, if present, can be removed after adding the additive solution according to a way known per se. It is noted that the treatment according to the invention can be applied for crystals, granules and prills; for simplification, the invention is explained by means of granules .

Preferably, the new additive is a natural waste flow of vegetable origin from the group of corn, potatoes, wheat, barley, soy, which preferably has a protein and amino acid content of more than 10% (w/w) , in particular granular corn derivatives. In a preferred embodiment, the nitrogen content can be raised, if desired, by means of adding extra protein, or (co) polymers on the basis of 1-alkenes having the general formula CHX=CHY, wherein X and Y, independently of each other, are part of the group consisting of NH ₂ , NH ₂ . HCl, (CH ₂ ) _n NHR (n = 1 to 5), (CH ₂ ) _n NH ₂ . HCl, (CH ₂ ) _n NH ₂ , NH-HC=O, NH-RC=O, while Y can further be H, wherein R consists of alkyl or alkenyl having 1 - 30 C-atoms . The (co) polymer is preferably synthesized of 2 to 2,000,000 units.

Coatings

If desired, the tendency of lump formation can be further reduced by adding (preferably) linear alkyl alcohols (ClO- C30), preferably C16-C22 alcohols to the granulate of a plant auxiliary agent.

To reduce the moisture absorption by the granulate, if desired, a biodegradable ethoxylated organic component can be added, which has a HLB value between 2 and 11.

The moisture absorption by granulate particles can be further reduced by adding a linear alkane having an alkyl

chain length between C16 and C40, which has a solidification range between 50 and 10 ⁰ C.

Although Applicant does not wish to be bound to any theory, it is assumed that the presence of a nitrogen- containing (in the form of amine and/or amide groups) natural product on the granulate particles of a plant auxiliary agent results in the formation of an adduct with these particles, causing (the outside of) the granulate to become less sensitive to interaction with surrounding granulate particles, as a result of which the tendency of caking is strongly reduced. Depending on the type of additive, also influence on the dissolving rate of the plant auxiliary agent in water has been observed.

Further preferred embodiments are reflected in the sub- claims.

Coatings on the basis of natural waste flows are known per se and are used for example in the paper industry (see US 2002/0121222) . Besides, corn products can serve as coating for tableware and cutlery (CN 1458189) . Vegetable waste flows are in some cases used as a fertilizer. In that way, maize gluten promote the growth of grass, but inhibit the formation of weed (US 5030268).

Some fertilizers can be treated with coatings on the basss of vegetable residues. Patent GB 8150829 claims an effect of a protein-rich polymer as a treating agent for fertilizer. In this embodiment, the fertilizer is first provided with an inorganic layer.

Patent GB 2110518 mentions the use of a water-soluble protein of natural origin and a metal salt as part of a hydrophilic, water-insoluble bioactive coating for the protection of plants and seeds.

The Japanese patent JP 6144981 describes a composition for an improved degradable coating for granular fertilizer, consisting of a biodegradable powder, such as starch, mixed with an auto oxidating organic compound having at least one double C=C bond, possibly supplemented with olefin (co) polymers and vinyl chloride (co) polymers .

Further, polyvinyl amine can be used as part of laminating films (EP 0 644 247) . Compositions with polyvinyl

amine-graft polymers are claimed as treating agent for textile (WO 02/095122) . Polyvinyl amine can even be added as polyelectrolyte to fertilizer in order to condition soil (GB 734 504). Polyallyl amine can be used as coating on e.g. textile in order to absorb harmful gases (WO 93/17760) . Resins on the basis of polyallyl amine or polyvinyl amine having an unsaturated C=C bond at the end of the chain can be used as protective films for all kinds of substrates, for example the inert materials glass and wood (EP 0 294 506) . Polyaspartic acid can serve as a surface coating for medicines and food (US 5.175.285). Besides, polyaspartic acid, in combination with fertilizer, can enhance the productivity of the plant (US 5,861,356).

Advantages of polyalkenyl amines and polyaspartic acid are the good biodegradability, relatively low toxicity and good irascibility with water. Use of these products as additive for salts will therefore result in a much lower burden for the environment relative to the current situation: badly water- soluble, toxic fatty amines in oil and/or paraffins. Coating products on the basis of (modified) polyalkylene alcohols are known per se. In this context, GB 1 383 444 describes the use of mixtures of polyalkylene alcohols and a surface active substance as coating for fertilizer for reducing lump and dust formation during storage and handling. For the protection against moisture absorption by the present granulate particles, preferably a biodegradable ethoxylated organic component is added, which has a HLB value between 2 and 11.

The use of polyoxy ethylenes on fertilizer has been reported (DE 2330847) per se. However, these compounds are mixed with mineral oil, of which the use can however be overcome by the present invention. Polyoxy ethylenes are also used as a part of compositions for coatings, which can establish controlled release of particular agrochemicals in fertilizers (see e.g. JP 2003081705).

The moisture absorption of inorganic salts can be further reduced by coating the granules with a mixture consisting of residue flows of natural origin and linear alkanes. Adding linear alkanes to salt granulate is known per se

(WO03/006399) , but then it relates to a fully apolar medium, consisting of paraffin and oil. However, no combinations with natural residue products are claimed.

Granulation additives

Furthermore, Applicant surprisingly found that adding a waste material of natural origin to the molten plant auxiliary agent results in a significant decrease of the compressibility and the tendency of caking of the granulate being formed thereafter. Moreover, the granulate is not sensitive to recrystallization by moisture absorption during storage and handling. The natural waste materials can be added to the molten plant auxiliary agent either separately or together with the polyalkenyl compound, whether or not as an aqueous mixture or solution. According to a preferred embodiment, the total added amount of the natural waste material is at most 10% b.w., based on the total amount of plant auxiliary agent. It is noted that the treatment according to the invention can be applied to all kinds of grains, such as crystals, granules or prills.

Preferably, the new additive is a waste flow of natural origin, particularly of vegetable origin, such as maize, potatoes, wheat, barley, soy, which preferably has a protein and/or amino acid content of more than 10% (w/w) , in particular granular maize derivatives. In a preferred embodiment, the granulate properties can be optimized, if desired, by means of adding (co) polymers on the basis of 1- alkenes having the general formula of CHX=CHY, wherein X and Y, independently of each other, are part of the group consisting of OH, 0(RC=O), COOH, NH ₂ , NH ₂ -HCl, (CH ₂ ) _n NHR, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n NH ₂ . HCl, NH-HC=O, NH-RC=O, while Y can further be H, wherein R consists of alkyl or alkenyl having 1-30 C- atoms and n = 1 to 5. The (co) polymer is preferably synthesized of 2 to 2,000,000 units.

Preferably, use is made of polyvinyl alcohol and/or polyvinyl amine and/or polyaspartic acid.

Further preferred embodiments are reflected in the sub- claims .

It has been reported in the PCT publication WO 02/20471 that polyaspartic acid does not offer a considerable improvement to the hardness of urea. Adding polyaspartic acid to urea is interesting, because this biopolymer can enhance the productivity of plants (see US 5,861,356). It has however been found that polyaspartic acid in combination with vegetable residues can act indeed as good granulation additive for urea.

Advantages of the use of natural residues are recycling of raw materials, the good biodegradability, low toxicity, ample availability and the very favourable price. Use of these products as granulation additive for plant auxiliary agents will result in a much lower burden for the environment relative to the current situation, which gives toxic formaldehyde products.

The invention therefore relates to a urea composition as defined in the accompanying claims which has a reduced compressibility, tendency of cake formation and dust formation through recrystallization, compared with a common urea composition.

The invention will be explained hereafter by means of a number of examples, by using methods which are representative for the production and testing of the quality of the obtained granulates. These examples exclusively serve to explain and not to limit the claimed protective scope of the present invention.

Process for applying the coating

Before applying the coating, the granulate (1.0 kilogram per sample) is kept in sealed plastic jars in an oven at 35 ⁰ C for 16 hours. The treatment takes place as follows: the granulate is brought into a rotating coating drum, which has a temperature of about 5O ⁰ C. Thereafter, 0-5000 ppm of a coating is dripped onto the granulate, followed by rotating the drum for yet another 5 minutes. The thus treated granulate is dumped into a broad plastic tank, where the granulate can "evaporate" for 5 minutes. Subsequently, the treated granulate

is transferred into a plastic jar. After sealing the jar, the grains are allowed to cool to room temperature over a period of 24 hours.

Preparation method of an intimate mixture through the melt

An aqueous solution of the additive (having the concentrations indicated in the examples) is added to a urea melt (T = approx. 133 ⁰ C) consisting of 99.7 % w/w urea p. a. and 0.3 % w/w water. Thereafter, urea pellets were formed by dropping the molten urea drops separately from a height of 1 cm onto a glass plate. After solidification, the pellets were scraped off the glass plate and the fine dust was removed by means of a sieve. The pellets were collected and kept in an air tight flask until the compressibility and tendency of cake formation were measured.

Process for determining the compressibility and cake formation

A transparent round tube with an internal diameter of 3 cm was filled with 40 g urea pellets. On top of that a plunger was arranged, which caused a pressure of about 600 kPa to be exerted on the sample. Directly after applying the gauge pressure and again after 24 hours, the height of the urea column was measured. The relative difference in height, which is a measure for the compressibility, was calculated from these two values (Δ height (%) ) .

The degree of cake formation can be determined by measuring the breaking strength (expressed in kilograms) of the compressed urea sample.

Process for determining the tendency of baking

A representative test for simulating caking of granulate was performed as follows. Polyethylene tube foil was closed on one side by means of sealing (70 mm wide, 300 mm long) . At the bottom of the formed pouch, a plastic chip (48 mm diameter) was brought. The pouch was filled with 125 gram granulate. Subsequently, another plastic chip was put on the granulate.

The pouch was evacuated and closed by a seal. The obtained pouch was suspended from a metal pin. This procedure was repeated twice for the same sample. All sealed pouches with granulate were subsequently placed in an autoclave. The samples were kept for a week at 2 bar gauge pressure at a temperature of 35 or 50 ⁰ C. Subsequently the pouches were carefully cut open. The hardness of the baked sample was measured in a breaking apparatus. The force required to break the sample was read electronically. The obtained values (expressed in kilograms) were the average of at least three samples

Process for determining the moisture absorption

Two plastic beakers of 200 ml were filled with 160 gram (blank or treated) fertilizer. The weights of the beakers as well as the fertilizer are measured with an analytical balance. The total weight is calculated (m _to t) • The beakers are placed in a climate chamber with the following conditions: 80% relative air humidity and a temperature of 2O ⁰ C. After 72 hours, the samples are removed from this climate chamber and subsequently the weight is determined (m _na ) and the appearance is examined. Thereafter, the moisture absorption can be calculated as follows :

Moisture absorption = m _na ~ mtot

Process for determining the degree of recrystallization by moisture absorption

A Petri dish with a diameter of approximately 8.5 cm was filled with 15.0 gram urea pellets. This was subsequently placed in a climate chamber with a relative air humidity of 80% and a temperature of 20 ⁰ C. After 24 hours, the increase in weight as a result of moisture absorption by the granulate was measured, after which the Petri dish was closed with the corresponding cover. The dish was put aside in the dark at room temperature. After two weeks, the content of the dish was examined by looking at the granulate under a loupe.

The abbreviation ghk stands for no recrystallization, whereas hk stands for recrystallization after moisture absorption and drying.

Process for determining the dust content

The relative amount of dust particles of the granulates, mentioned in this document was determined as follows. 40 grams (accurately weighed) of fertilizer was brought into a three- neck round-bottom flask of 500 ml. The flask was provided with a glass column and a gas capillary, connected with a compressed air cylinder. The end of the gas capillary was placed in the granulate. Air (2 bar gauge pressure) was blown through the granulate for 75 seconds, by which a fluidised bed system was created. The weight of the remaining granulate was determined accurately on an analytical balance. The loss in weight is a measure for the amount of free dust particles and the dust particles created by friction. The determinations were at least performed twice.

Coatings

Example 1

A number of residues of natural origin is applied as coating to Calcium Ammonium Nitrate granules (CAN, 27% N) . The baking tendency of the thus coated material is determined. The different natural residue products are shown in Table 1. The protein and amino acid contents relate to the dry matter. The obtained results are presented in Table 2.

Table 1

It is noted that the used grain maize residue consists of the steep liquid resulting from the extraction of starch from grain maize, possibly after concentration of the slurry for restricting the added amount of liquid.

Table 2

The above example proves that waste flows from natural origin can considerably reduce the baking tendency of granulate, such as CAN.

Example 2

It can be deduced from example 1 that natural proteins provide the decrease of caking. In order to further substantiate this, the protein concentration of the grain maize residue has been increased by adding 5 to 15% w/w very fine (< 60 micron) soy protein powder. The obtained mixtures were applied as coating to Calcium Ammonium Nitrate granules (CAN, 27% N) . The baking tendency of the thus coated material has been determined (Table 3) .

Table 3

The above example shows that adding extra protein to natural residue products results in a good coating for preventing lump formation of plant auxiliary agents.

Example 3

Another plant auxiliary agent often used is urea, which can as such be sensitive to caking. Waste materials of natural origin could reduce that baking tendency. In order to test this, a number of products of natural origin was applied as a coating to urea prills (46% N, without internal additive) . The baking tendency of the coated material has been determined. The results are mentioned in Table 4.

Table 4

ixture as described in US 4,812,158, consisting of 67% (w w) water, 11% (w/w) polyvinyl acetate and 22% (w/w) alkyl sulphate.

It proves from the experiment that residue products of natural origin can act as additive for preventing lump formation of urea grains .

Example 4

The natural residue products mentioned in Example 1, were tested as suspension in water. Since the presence of water in case of hygroscopic granulate often causes accellerated cake formation, it has been checked whether the use of other solvents resulted in improvement of the anti-baking properties. In order to investigate this, 20% w/w very fine (< 60 micron) soy protein powder was mixed with several polar solvents. The obtained slurries were applied to calcium ammonium nitrate, CAN (27% N) via the coating process.

Subsequently, the baking tendency of the treated grains was determined.

Table 5

It proves from this experiment that, in a coating on the basis of natural residue products, replacing water by another polar solvent results in an improved functioning with respect to the tendency of lump formation of plant auxiliary agents.

Example 5

For a stronger reduction of the caking of granulate, 2% (w/w) polyvinyl amine (molecular mass 10,000 g/mol,

hydrolysis degree > 90%) was added to the natural waste material. The obtained mixtures were coated onto calcium ammonium nitrate, CAN (27% N) , by means of spraying. As reference, a paraffin product A has been taken in the test. It had the following properties: solidification point 45°C, viscosity 7 mPa . s (8O ⁰ C). The composition is as follows: tallow fat amine content 7.0% w/w, mineral oil 20% w/w and 73% w/w low-melting paraffin wax.

Table 6

The above example proves that adding a small amount of polyvinyl amine to vegetable waste flows results in a performance as coating which is similar to classic paraffin products .

Example 6

Another process for reducing the caking of granulate is adding a fatty alcohol (C10-C30) to the vegetable waste material. In this experiment, 5% (w/w) has been mixed with grain maize residue at a temperature of approx. 60 ⁰ C. The obtained mixtures were coated onto calcium ammonium nitrate granules (27% N) . As reference, paraffin-containing product A has been taken in the test. In this experiment, also the dust- binding properties of the formulations have been observed.

Table 7

The above example proves that adding a small amount of fatty alcohol (C10-C30) to vegetable waste flows results in a performance as coating, which is similar to classic paraffin products, both in the field of cake formation and binding of dust particles .

Example 7

Several salts, including fertilizers, can be sensitive to moisture absorption. Excessive moisture absorption by salts can result in undesired phenomena such as dust formation and caking. The natural residue substances show per se a low hydrophobic effect. In order to reduce the moisture absorption by salts, a number of moisture resistant substances are added to the formulations, with a baking tendency reducing effect. The examined moisture resistant compounds are shown in Table 8. These compounds are well biodegradable.

Table 8

The formulations in Table 9 consist of 95% grain maize residue and 5% moisture resistant active compound. These formulations (temperature approx. 6O ⁰ C) were applied to calcium ammonium nitrate (CAN, 27% N) .

Table 9

The above experiment proves that applying coatings on vegetable basis, which are provided with ethoxylated alkyl compounds, results in a decrease of the moisture absorption of the treated fertilizer. Moreover, the tendency of caking remains low. A performance can be realized which is equivalent to or better than coatings on paraffin basis.

Example 8

The protection against moisture absorption has been further examined on very moisture-sensitive ammonium nitrate (33.5% N, stabilized with dolomite and magnesium nitrate). A

formulation B has been made, having the following composition: 85% (w/w) aqueous grain maize residue, 10% (w/w) polyoxyethylene (2) stearyl ether and 5% (w/w) tallow fat alcohol. This mixture has been applied as coating in different doses. As reference, a moisture resistant coating C has been taken, in accordance with WO 03/006399 (7.5% (w/w) tallow fat amine (C16-C18), 7.5% (w/w) 2-ethyl hexyl phosphate acid ester, 85% (w/w) paraffin wax (> 50% linear alkane) , melting point 45°C) . The results are mentioned in Table 10.

Table 10

It has proven from this experiment that already with a dose of 300 ppm of a coating in accordance with the invention, a good protection against moisture action on very hydroscopic salts can be established.

Example 9

The reduction of moisture absorption by inorganic salts with coatings on the basis of residues of natural origin can also be established by adding linear alkanes. In order to examine this, a number of mixtures (temperature approx. 60°C) has been made on the basis of aqueous grain maize residue and a linear alkane mixture. This product was obtained through a Fischer-Tropsch process (solidification range 45-2O ⁰ C, C16-C40 alkanes). The coatings were tested on calcium ammonium nitrate

(27% N) . As reference, coating C was used. The results are mentioned in Table 11.

Table 11

The protection against moisture absorption of moisture- sensitive inorganic salts can therefore also be established by applying mixtures on the basis of natural residue products and linear alkanes.

The following examples relate to the use of vegetable waste flows as granulation additive, to the urea melt.

Example 10

Furthermore, a number of aqueous waste flows of natural origin has also been tested as granulation additive for urea. In this case, the additive is added to urea in molten state (T = approx. 133 ⁰ C), after which granulation takes place by means of the formation of pellets. The compressibility and the baking tendency of the thus obtained material has been determined after compression. Moreover, the appearance of the granulate after moisture absorption (24 hours, 2O ⁰ C, 80% RH) has been examined. As references, a blank as well as a urea- formaldehyde and polyvinyl alcohol were taken. The obtained results are mentioned in Table 12.

Table 12

ghk = no recrystallization after moisture absorption and drying hk = recrystallization after moisture absorption and drying

The above example proves that waste flows of natural origin have a positive influence on decreasing the compressibility and the cake formation. The grain maize residue gives a performance which is at least equivalent to urea treated with urea-formaldehyde in all measured properties .

Example 11

Subsequently, several mixtures were composed on the basis of the grain maize residue and a number of polymers. One started from a mixture consisting of 80% w/w grain maize residue and 20% w/w polymer. The examined polymers are shown in Table 13. The results are mentioned in Table 14.

Table 13

Table 14

It can be concluded from the results that adding polymers provided with polar groups to a natural residue flow as urea additive can result in the production of very high-quality urea granulate.