WO2000006522A1

WO2000006522A1 - Method for making a nitrogenous fertilizer having a stabilized liquid form for releasing nitrogen for a long time

Info

Publication number: WO2000006522A1
Application number: PCT/IT1999/000191
Authority: WO
Inventors: Emo Chiellini; Sergio Miele; Enrica Bargiacchi; Gianluca Costa; Giuseppe Rizzi
Original assignee: Sadepan Chimica S.R.L.
Priority date: 1998-07-30
Filing date: 1999-06-28
Publication date: 2000-02-10
Also published as: ITMI981786A1; ITMI981786A0; IT1301970B1; AU4646999A; BR9912696A; EP1098863A1; CA2337831A1

Abstract

The present invention relates to a method for making a liquid nitrogenous fertilizer, designed for continuously releasing, for a long time, nitrogen having an optimum agrochemic efficiency index, which is not phytotoxic at the leave and root level, with very low negative environmental impacts.

Description

METHOD FOR MAKING A NITROGENOUS FERTILIZER HAVING A STABILIZED LIQUID FORM FOR RELEASING NITROGEN FOR A LONG TIME

BACKGROUND OF THE INVENTION

The present invention relates to a method for making a nitrogenous fertilizer, having a stabilized liquid form for releasing for a long time nitrogen.

More specifically, the invention provides a novel method for making a liquid nitrogenous fertilizer, in which the balance of ureic nitrogen in its monomeric form and in its oligomeric form is adapted to allow said fertilizer to be optimally used in several growth stages of vegetable products, without any phytotoxic and environmental impacts.

As is known, nitrogenous fertilizers based on an urea/formaldehyde condensate have been used for a long time in agronomic applications to provide a suitable nitrogen rate to the growing plants, without damaging the leave and/or root systems thereof, with an accompanying increasing of the efficiency parameters, comprising a reduced leaching loss through the soil, as well as reduced environmental negative effects, mainly related to the ureic nitrogen nitrification processes.

The above mentioned condensates, as they are prepared with a comparatively low free urea rate, include great amounts of high molecular weight products, ending to release nitrogen with a kinematic profile which cannot be easily preset for a safe and timely level of administration of the nitrogenous principles to the growing plants.

With respect to prior nitrogenous fertilizers based on urea/formaldehyde condensates, several attempts have been made for making liquid fertilizers, based either on a solution or on a dispersion of resins and urea/formaldehyde.

Thus, the documents U.S. 2,467,212 and U.S. RE 23,174, disclose that as urea is reacted with an excess amount of formaldehyde for a comparatively short reaction time, in the presence of bases at a moderate temperature, are obtained methylol ureas which constitute a basic material for the liquid nitrogenous fertilizers of the "UFC-85" type.

A further U.S.A. Patent, granted to GH G.H. JUSTICE et al at the number 3,462,256, discloses a method for making urea/formaldehyde resins, providing aqueous solutions which have stable storing properties of one to three weeks at temperatures of 0°C and 25°C, respectively.

Said resins are made by condensating in an alkaline environment, U/F mixtures having a molar ratio of 2:1 in the presence of an amount of 0.5-0.6% by weight of ammonia.

The presence in the end formulated compound of a comparatively high amount of methylol urea, causes the formation of precipitated materials by auto-condensating and/or cross-condensating processes with methylenurea.

W.P. Moore, in a patent assigned to Slow Release Inc. (U.S. 4,033,745) discloses the making of a complex liquid nitrogenous fertilizer, constituted by urea/formaldehyde resins having a high polymerizing degree, which are added with phosphoric acid, ammonia, polyphosphate ammonium, potassium chloride and a comparatively high amount of molasses. This high viscosity liquid fertilizer having a pH of 6.4, has been classified as a "NPK 15/5/3".

W.P. Moore, in a set of patents assigned to Coron Co. (U.S. 4,244,727, U.S. 4,304,588, U.S. 4,579,580, U.S. 4,781,749 and U.S. 5,549,394) discloses a method for making nitrogenous resins which can be prepared in a alkali environment with a buffered pH which sometimes is near to neutrality, having a low contents of ethylolurea and methylen- diurea, negatively affecting the stability of aqueous polymethylenurea solutions .

In all of the above mentioned formulations, ammonia is present in a rate varying up to a molar ratio of 1/3 and 1/2 with respect to urea and formaldehyde, respectively.

The U/F resins, as made according to the above mentioned patents and, more specifically, as claimed in the document U.S. 5,449,394 are useful for making liquid nitrogenous fertilizers of not polymeric nature and having a controlled fertilizing power as well as a low phytotoxicy due to the small amounts of ammonia, urea and formaldehyde which are present in the disclosed resins.

U.F. Hawkins discloses, in the document U.S. 4,544,005, a complex nitrogenous fertilizer, which is made by a condensating process using urea and formaldehyde mixtures, with two processing stages in a greatly alkaline environment.

On the other hand, the use of a comparatively high amount of urea brings to a product having high contents of movable nitrogen, the use of which is limited because of its high phy otoxicity.

The document JP 80-71689 in the name of

Allied Chemical Co. discloses a method for preparing a nitrogenous fertilizer in liquid form, by condensating urea and formaldehyde in an alkali environment, in the presence of a great amount of NH^OH.

The end product has been found to have overall nitrogen contents of 31%, and, more specifically, corresponding to 15% of ureic nitrogen,

20% methylolureic nitrogen, 60% methylenureic nitrogen and 5% ammoniaσal nitrogen.

The high rate of ureic nitrogen negatively affects the stability properties of the aqueous solutions, even if the presence of NH^OH, which is not specifically quantified in determining the total nitrogen amount, seems to positively affect the stability of said solutions.

By a single-stage condensating method, in a basic environment, and operating on formaldehyde, urea and hesamethylentetramine, A. Bodo et al, in the patent DDR 149,209, provides a liquid nitrogenous fertilizer, having a two-month period of stability, which fertilizer has a very high viscosity and, more specifically, a dynamic viscosity of 1630 mPA.s, and adapted to be diluted in water at any rates. This fertilizer has contents of methylolureic groups corresponding to 15%.

R.M. Coury, in the U.S. 4,318,729 patent to Chem-Lawn Co., discloses a method for making a fertilizer NPK 19:1:1 in a liquid form and having a long time stability greater than six months, by using an urea-formaldehyde resin made by an alkali condensating process with nitrogen contents of 15-35% and high methylolurea contents of 30%.

Further nitrogenous fertilizers provided for continuously slowly releasing nitrogen, in the form either of suspensions or dispersions, and stabilized by adding natural or synthetic surface active materials, have been claimed in a lot of patents.

The base matrix arrangements are prepared by condensating urea and formaldehyde and like aldehydes, in an alkaline environment, as well as in an acid environment having a pH from 3 to 6, such as, for example, in the U.S. patents 4,298,512, 4,332,610, 4,474,925 and 4,578,1045.

SUMMARY OF THE INVENTION The aim of the present invention is to provide a method for making a nitrogenous fertilizer having a stable liquid form and specifically designed for continuously releasing, for a long time, nitrogen, allowing to provide a high agronomic efficiency, as well as a small nitrogen leaching loss in a first period of the plant growth.

Within the scope of the above mentioned aim, a main object of the present invention is to provide such a method allowing to easily make a fertilizer having a very small apparent phytotoxicy for the leave and root systems of the plants, both of the graminaceous and dicotyledonous type due to possible treatments carried out in a post-emergency condition thereon.

Within the scope of the above mentioned aim, a main object of the present invention is to provide such a method allowing to easily make a fertilizer having good storage properties, together with a long controllable operating efficiency.

According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a method for making a nitrogenous fertilizer, having a stable liquid form, specifically designed for continuously releasing nitrogen for a long time, characterized in that said method comprises a preliminarily stage, a first stage and a second stage, said preliminarily stage comprising the step of controllably condensating an urea/formaldehyde precondensate with urea, the molar ratio corresponding to U/F l:(l-6).

BRIEF DESCRIPTION OF THE DRAWING Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed disclosure of some preferred, though not exclusive, embodiments of said method, which will be disclosed with reference to the accompanying drawing, the sole figure of which illustrates the evolvement of the leaching nitrogen loss in a first growth period of a plant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the number references of the above mentioned figure, the method for making a nitrogenous fertilizer, having a stable liquid form, specifically designed for continuously releasing for a long time nitrogen, according to the present invention, has the main feature that it can be carried out in a preliminarily stage, a first stage and a second stage or, possibly, a first stage and a second stage which is the same for both cases.

The method according to the present invention for making a liquid form nitrogenous fertilizer having low contents of movable nitrogen (ureic nitrogen (ureic nitrogen ≤ 8%) on total contents of nitrogen varying from 20% to 35%, which is stable to the storing at an environmental temperature for a long time (from 1 to 2 months), is based on a process which can be carried out in the above disclosed manner.

In the first case, the preliminarily stage comprises a controlled condensation performed between an urea/formaldehyde precondensate with a molar ration

U/F 1:5 (formurea 80) or 1:6 (formurea 70), with urea.

The condensation is carried out at a pH smaller than 7, preferably from 3 to 5, in the presence of acid catalyzers comprising either mineral acids or inorganic acids (such as formic and acetic acids) or salts thereof with ammonia which, under the used conditions, will provide an acid reaction.

The temperatures of the above mentioned preliminarily stage are stabilized within a range of 70°C to 105°C for a variable reaction time which depends on the achieving of preset dynamic viscosity values, included in the range of 50 Pa.s to 2,000 mPa.s at 20°C.

As the maximum temperature limit is achieved, the catalyzer is added with a rate adapted to provide a very small temperature variation through the reaction mass.

The preliminarily stage operation is stopped by adding an organic base of an ethanolamine type or an inorganic base, so as to provide a pH value from 6 to 7, or slightly greater than 7. The preliminarily stage is followed by a first stage in which an urea portion having a pH of 6- 7 is added in an amount comparable to that used in the first stage.

The reaction time is adjusted based on the achieving of a preset viscosity value.

According to a different embodiment of the subject method, it is possible to carry out said method in a first stage and in a second stage.

In this case, the first stage comprises the steps of condensating urea and formaldehyde mixtures, or an urea-formaldehyde precondensate with an end molar ratio U/F from 1:1 to 1:3.

Even in this case, the condensation reaction is performed at a pH smaller than 7, preferably from 3 to 5, in the presence of acid catalyzers comprising mineral acids or organic acids or salts thereof with ammonia which, under the assumed conditions, will provide an acid reaction.

The operating temperatures are included, as in the previous case, in the 70°C - 105°C range, and the operation of the first stage is stopped by adding an organic base of an ethanolamine type or an inorganic base, to provide a pH value from 6 to 7 or slightly larger than 7.

The reaction of the second stage, in both the above disclosed applications, comprises, at the start, the adding of such an amount of water to achieve a set temperature from 50°C to 70°C.

By holding the temperature at a set value within the above indicated range, the mixture is added with an amount of urea of 4/5 greater than that generally previously used.

The addition can be carried out in a continuous manner or, preferably, at time intervals varying from 30 to 45 minuted.

The reaction is ended by adding either an organic or an inorganic base, or a combination thereof, to provide a homogeneous mixture having well defined pH values, within the value range of 7 to 10.

The product, as cooled to 20°C, after having added to it, if necessary, small amounts of low or high molecular weight polyols or other stabilizers, will be ready for storing and use.

The above disclosed method provides a product allowing to make an urea/formaldehyde resin solutions which can be used as a fertilizer in a liquid form and adapted to continuously release, for a long time, nitrogen therefrom.

The fertilizer and the method for making it will be hereinbelow illustrated by the following examples .

EXAMPLES

The following Examples will clearly illustrate the invention, in an exemplary and not limitative manner.

In the Examples reference will be made to a reference formulation of 1000 kg of finished or end product (i.e. a slow release nitrogenous fertilizer).

The starting materials and intermediate compounds used in the subject method are:

Formaldehyde 43: An aqueous solution containing 43% formaldehyde.

Formurea 70:

An urea-formaldehyde precondensate having a molar ratio expressed as urea:formaldehyde, usually from 1:5.7 and 1:6.3, and a theoretical dry contents, expressed as a % sum of urea and formaldehyde, usually from 69 to 71. It comprises formaldehyde (-53%) and urea (-17%).

Formurea 80:

An urea-formaldehyde precondensate having a molar ratio, expressed as urea: formaldehyde, of 1:4.95 and a theoretical dry contents, expressed as a % sum of urea and formaldehyde, of 80. It comprises formaldehyde (57%) and urea (23%).

Urea in pearl forms:

An industrial use type of urea.

Water:

A deferizated water, preferably softened. Catalyzers :

10% sulphuric acid (H2SO4), 50% sulphamic acid (NH₂S0₃H), 50% ammonium nitrate (NH₄N0₃), 30% ammonium sulphate [ (NH₄)₂Sθ4 ) ] , 20% ammonium chloride (NH4CL), 25% mono-ammonium phosphate (NH4H2PO4), 20% formic acid (HCOOH), 33% ammonium acetate (CH3COONH4), 17% hydrochloric acid (HC1), 30% nitric acid (HNO3), 55% phosphoric acid (H3PO4), 55% glacial acetic acid

Alkalizing:

Sodium hydroxide in a 30% aqueous solution

(NaOH), 25% potassium hydroxide (potash), triethanolamine in a 50% aqueous solution (TEA), monoethanolamine in a 50% aqueous solution (MEA), diethanolamine in a 50% aqueous solution (DEA).

Hexamine:

Hesamethylentetramine in a crystal form for an industrial use (EMTA).

Stabilizing agents:

Polyols of a low and high molecular weight, aliphatic and aromatic non-ionic surface active agents, decahydrated sodium borate, hesamethylentetramine, diciandiamide, potassium carbonate, sodium carbonate and sodium sulphite.

Example No. 1 Under stirring into an autoclave at an atmospheric pressure and environment temperature, the following starting materials, in the hereinbelow indicated order, are loaded:

Formaldehyde 43 kg 372.00 (5,332.0 moles)

Neutralized with 30% soda

Urea kg 128.00 (2,133.3 moles) Molar ratio CH₂0/CH₄N₂O = 2.5:1

Then, the mixture is heated to 80°C, and 2.00 kg 10% sulphuric acid are added.

The reaction pH varies from 3.0 to 3.5.

The reaction, being monitored at even intervals through dynamic viscosity at 20°C measurements, is stopped as a viscosity value of 100 mPa's is achieved.

The condensation is stopped by adding 0.60 kg of 30% soda.

After the stopping, the pH value has a stable value of 7.5.

Then, there are loaded, in the indicated order:

Water kg 24.20

Urea kg 471.70 (7,861.7 moles) in three weight-like weight portions. Total urea kg 599.70 (9,995.0 moles)

Total molar ratio CH₂0/CH₄N₂0 = 0.53:1

By adding water, temperature is decreased to 60°C

70°C. The three urea portions must be added at a half- hour interval from one another, by holding during all this step the temperature at about 60°C.

Finally, at the same temperature, 1.50 kg of decahydrate sodium borax are added.

The end pH is included in the range from 8.0 to 9.0.

Then, it is cooled to 20°C, and the product is ready for use. Example No . 2

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formaldehyde 43 kg 372.00 (5,332.0 moles)

Neutralized with 30% soda

Urea kg 128.00 (2,133.3 moles)

Molar ratio CH₂0/CH₄N₂O = 2.5:1

It is added to 90°C, and 0.50 kg 50% sulphamic acid are added.

The reaction pH is included in the range of 4.0 to

5.0.

The reaction, monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 120 mPa's is achieved.

The condensation is stopped by adding 0.50 kg 30% soda.

The pH, after stopping the condensation, is settled at

7.0. Then, the following substances are loaded, in the indicated order:

Water kg 25.20

Urea kg 471.70 (7,861.7 moles) in three weight-like portions . Total urea kg 599.70 (9,995.0 moles)

Total molar ratio CH₂0/CH₄N₂0 = 0.53:1

By adding water, temperature is decreased to 60°C-

70°C.

The three urea portions are added with a spacing of a half-hour from one another, while holding, during all this adding step, the temperature at about 60°C.

Finally, at the same temperature, 1.50 kg decahydrated sodium borax are added.

The end pH is included in the range from 8.0 to 9.0. Then it is cooled to 20°C, and the product is ready for use.

Example No. 3

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formurea 70 kg 351.80

Urea kg 66.80 (1,133.3 moles)

It is heated to 90°C, and 0.40 kg 50% NH₄N0₃ are added.

The reaction pH is included in the range from 4.5 to 5.0.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1000 mPa's is achieved. The condensation is stopped by adding 0.70 kg of 30% soda.

The pH, after stopping the condensation, is settled at

7.5.

Then, the following materials are loaded, in the indicated order: Water kg 106.40

Urea kg 473.40 (7,890.0 moles) in three weight-like portions . Total urea kg 540.20 (9,023.30 moles) By adding water, the temperature is decreased to 60°C- 70°C. The three urea portions are added at a spacing of a half hour from one another, by holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 0.50 kg sodium sulphite are added.

The end pH is included in the range from 9.0 to 10.0. Then, it is cooled to 20°C, and the product is ready for use.

Example No. 4

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order:

Formurea 70 kg 351.80

Urea kg 66.80 (1,133.3 moles)

It is heated to 100°C, and 0.90 kg of 20% NH₄C1 are added. The reaction pH is included within the range from 4.5 to 5.0.

The reaction is monitored at even intervals by dynamic viscosity measurements at 20°C, and is stopped as a viscosity value of 1000 mPa's is achieved. The condensation is stopped by adding 0.70 kg of 30% soda.

The pH, after stopping the condensation, is settled at

7.5.

Then, the following materials are loaded, in the indicated order:

Water kg 105.70

Urea kg 473.40 (7,890.0 moles) in three weight-like portions.

Total urea kg 540.20 (9,023.3 moles) By adding water, temperature is decreased to 60°C-

70°C. The three urea portions are added, at a spacing of a half hour from one another, by holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 0.50 kg sodium sulphite are added.

Example No. 5

Formurea 80 kg 386.00

Water kg 26.00

Urea kg 36.90 (615.0 moles) It is heated to 102°C, and 2.00 kg of 25% NH₄H₂P0₄ are added.

The reaction pH is included within the range from 5.0 to 5.5.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1400 mPa's is achieved.

The condensation is stopped by adding 0.65 kg of 50%

TEA.

The pH, after stopping the condensation, is settled at 7.0.

Then, the following materials are loaded, in the indicated order:

Water kg 72.95

Urea kg 474.50 (7,908.3 moles) in three weight-like portions.

Total urea kg 511.40 (8,523.3 moles)

By adding water, temperature is decreased to 60°C- 70°C. The three urea portions are added, at a spacing of a half hour from one another, while holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 1.00 kg decahydrated ^ sodium borax are added.

The end pH is included in the range from 8.5 to 9.5. Then, it is cooled to 20°C, and the product is ready for use.

° Example No. 6

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formurea 80 kg 386.00 5 Water kg 26.00

Urea kg 36.90 (615.0 moles)

Dicyandiamide kg 10.00 (119.0 moles) It is heated to 105°C, and 3.00 kg of 25% NH₄H₂P0₄ are added. 0 T e reaction pH is included within the range from 6.0 to 6.5.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1500 mPa's is achieved. 5 The condensation is stopped by adding 0.80 kg 50% TEA. The pH, after stopping the condensation, is settled at 7.0.

Then, the following materials are loaded, in the indicated order: Water kg 76.20

Urea kg 460.30 (7,671.7 moles) in three weight-like portions. Total urea kg 497.20 (8,286.7 moles) By adding water, temperature is decreased to 60°C- 70°C. The three urea portions are added, at a spacing of a half-hour from one another, while holding, during all this step, the temperature at about 60°C.

Finally, at the same temperature, 0.80 kg decahydrated sodium borax are added.

The end pH is included within the range from 8.0 to 9.0. Then, it is cooled to 20°C, and the product is ready for use.

Example No. 7

Formurea 80 kg 274.00

Water kg 20.30

Urea kg 42.04 (700.7 moles) It is then heated to achieve the desired temperature

(90°C), and then 0.24 kg of 30% ammoniumsulphate are added to provide a pH in the range of 4.5 to 4.8.

The reaction temperature is brought to 90°C, and the condensation step is carried out. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1400 mPa's is achieved.

The condensation is stopped by adding 0.43 kg 30% sodium hydroxide. After the stopping of the condensation, the pH is settled at about 7.0.

Then, the following materials are loaded, in the indicated order:

Water kg 152.59

Urea kg 80.00 (1,333.3 moles)

Urea kg 222.00 (3,700.0 moles)

Urea kg 192.00 (3,200.0 moles)

2° stage ^■total urea kg 494.00 (8,233.3 moles)

Total urea kg 536.04 (8,934.0 moles)

By adding water, temperature is decreased to 60°C- 70°C. The three urea portions are added, at a spacing of a half-hour from one another, while holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, to the mixture 15.00 kg hexamine are added and, after a further half- hour, 1.40 kg decahydrated sodium borax are further added. The end pH is included in the range from 8.5 to 9.5. Then, it is cooled to 20°C, and the product is ready for use.

Example No. 8 Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formurea 80 kg 329.80 Water kg 52.60 Hexamine kg 23.48 (167.1 moles) Urea kg 67.30 (1,121.7 moles)

It is heated to the desired temperature (95°C), and then 0.56 kg 30% a moniumsulphate are added. The pH is gradually decreased to achieve a value included in a range of 4.5 to 5.0. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 150 Pa's is achieved.

The condensation is stopped by adding 0.61 kg of 50% triethanolamine.

After stopping of the condensation, the pH is settled at about 6.0, with variations from 5.8 to 6.4.

Then, are further added:

Urea kg 34.15 (569.2 moles)

Upon achieving a dynamic viscosity value of 400 mPa's, the reaction is stopped by adding 0.42 kg triethanolamine.

After this step, the pH is settled at about 7.0.

Then, the following materials are loaded, in the indicated order:

W Waatteerr kg 69.69

U Urreeaa kg 90.00 (1,500.0 moles)

T TEEAA kg 0.19 (1.27 moles)

U Urreeaa kg 160.00 (2,666.7 moles)

U Urreeaa kg 169.20 (2,820.0 moles)

3 3 °° ssttaaggee ttoottaall uu:rea kg 419.20 (6,986.7 moles)

T Toottaall uurreeaa kg 520.65 (8,677.6 moles)

By adding water, temperature is decreased to 60°C-

70°C. The three urea portions are added at a spacing of a half-hour from one another, while holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 1.00 kg hesamethylentratramine and 1.00 kg decahydrated sodium borax are added.

The end pH is included within the range from 8.5 to

9.5. Then, it is cooled to 20°C, and the product is ready for use. Example No. 9

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formaldehyde 43 kg 300.00 (4,300.0 moles) Neutralized by 30% soda Water kg 20.00

Urea kg 100.00 (1,666.7 moles)

Molar ratio CH₂0/C₂H₄NO = 2.58:1 The mixture is added to 100°C, and then 0.10 kg of 20% formic acid are added.

The reaction pH is included within the range from 4.0 to 5.0. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 300 mPa's is achieved.

The condensation is stopped by adding 0.50 kg of 50% triethanolamine.

After the stopping of the condensation, the pH is settled at about 7.0. Then, the following materials are loaded, in the indicated order:

Water kg 75.80

Urea kg 487.40 (8,123.3 moles) in three weight-like portions T Toottaall UUrreeaa kkgg 587.40 (9,790.0 moles)

By adding water, temperature is decreased to 60°C- 70°C. The three urea portions are added, at a spacing of a half-hour from one another, while holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 15.00 kg hesamethylentetramine is added and then (after a further half hour) 1.20 kg decahydrated sodium borax are added .

The end pH is included within the range from 8.0 to 10.0.

It is then cooled to 20°C and the product is ready for use.

Example No. 10

Formaldehyde 43 kg 249.23 (3,572.3 moles) neutralized by the required 30% soda amount,

Water kg 31.06

Urea kg 214.34 (3,572.3 moles) Molar ratio CH₂0/C₂H₄N₂0 = 1:1

The mixture is heated to 80°C and then 0.50 kg 20% formic acid are added.

The reaction pH is included within the range from 4.0 to 4.5. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 60 mPa's is achieved.

The condensation is stopped by adding 0.35 kg 30% soda. After stopping the condensation, the pH is settled at about 7.5.

Then, the following materials are loaded, in the indicated order:

Water kg 288.88 Urea kg 214.34 (3,572.3 moles)

Total urea kg 428.68 (7,144.6 moles)

By adding water, temperature is decreased to 50°C- 60°C. The remaining urea portion is added in a continuous manner, while holding the temperature at about 55°C.

Finally, at the same temperature, 1.30 kg decahydrated sodium borax are added.

The end pH is included within the range from 8.5 to 9.0. Then, it is cooled to 20°C, and the product is ready for use.

Example No. 11

Formaldehyde 43 kg 249.23 (3,572.3 moles) neutralized by the required 30% soda amount.

Water kg 24.65

Urea kg 142.89 (2,381.5 moles)

Molar ratio CH₂0/C₂H₄N₂0 = 1:1.5.

The mixture is headed to 90°C and then 0.50 kg of 17% hydrochloric acid are added.

The reaction pH is included within the range from 3.5 to 4.0.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 75 mPa's is achieved.

The condensation is stopped by adding 0.35 kg of 30% soda.

After stopping the condensation, the pH is settled at about 7.0. Then, the following materials are loaded, in the indicated order:

Water kg 295.59 Urea kg 285.79 (4,763.2 moles)

Total urea kg 428.68 (7,144.7 moles)

By adding water, temperature is decreased to 60°C, and is held at about this value during all the urea adding step, in a continuous manner.

Finally, at the same temperature, 1.00 kg sodium carbonate are added.

The end pH is included within the range from 9.0 to 9.5. Then, it is cooled to 20°C, and the obtained product is ready for use.

Example No. 12

Under stirring, the following raw materials are loaded into an autoclave at an atmospheric pressure and environment temperature, in the indicated order:

Formurea 70 kg 379.06

Water kg 58.48

Urea kg 136.46 (2,274.3 moles) The mixture is heated to 90°C, and then 0.40 kg of 30% nitric acid are added.

The reaction pH is included within the range from 4.0 to 4.5.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 800 mPa's is achieved.

The condensation is stopped by adding 0.25 kg 30% soda.

After stopping the condensation, the pH is settled at about 7.0.

Then, the following materials are loaded, in the indicated order: Water kg 89.40

Urea kg 150.00 (2,500.0 moles)

Urea kg 184.95 (3,082.5 moles)

2° stage total urea kg 334.95 (5,582.5 moles) Total urea kg 471.40 (7,856.7 moles)

By adding water, temperature is decreased to 50°C- 60°C. The two urea portions are added at a spacing of a half-hour from one another while holding, during all this step, the temperature at 60°C. Finally, at the same temperature, 1.00 kg potassium carbonate are added.

The end pH is included within the range from 9.0 to 10.0. It is then cooled to 20°C, thereby providing a ready for use product.

Example No. 13

Formurea 80 kg 352.45

Water kg 50.05

Urea kg 79.65 (1,327.5 moles)

The mixture is heated to 100°C, and then 0.40 kg 55% phosphoric acid are added.

The reaction pH is included within the range from 5.0 to 5.5.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1000 rnPa's is achieved.

The condensation is stopped by adding 0.30 kg 30% soda. After stopping the condensation, the pH is settled at about 7.5.

Then, the following materials are loaded, in the indicated order: Water kg 140.82

Urea kg 357.02 (6,250.3 moles)

Total urea kg 454.67 (7,577.8 moles)

By adding water, temperature is decreased to 50°C-

60°C. During all the urea adding step, the temperature is held at about 55°C. Then, at the same temperature,

1.30 kg sodium borax are added.

The end pH is included within the range from 8.5 to

9.0.

Then, it is cooled to 20°C, and the product is ready for use.

Example No. 14

Formurea 80 kg 170.53

Water kg 24.21

Urea kg 38.54 (642.3 moles)

The mixture is heated to 100°C, and then 0.50 kg 55% phosphoric acid are added.

The reaction pH is included within the range from 4.3 to 4.8.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 900 mPa's is achieved.

The condensation is stopped by adding 0.10 kg 30% soda. After stopping the condensation, the pH is settled at about 6.0.

Then:

Urea kg 51.84 (864.0 moles) is loaded, and the second reaction to achieve a viscosity value of 900 mPa's is carried out.

The condensation is stopped definitely by adding 0.25 kg 30% soda.

W Waatteerr kkιg 192.11

U Urreeaa kk<g 150.00 (2,500.0 moles)

U Urreeaa kk<g 200.00 (3,333.3 moles)

U Urreeaa kk<g 120.92 (2,015.3 moles)

3 3°° ssttaaggee ttoottaall uurreeaa kk<g 470.92 (7,848.7 moles)

T Toottaall uurreeaa kk«g 561.30 (9,355.0 moles)

By adding water, temperature decreases to 60°C. The three urea portions are added at a spacing of a half- hour from one another, while holding, during all this step, the temperature at about 60°C. Finally, at the same temperature, 50.00 kg hexamine and, after a further half-hour, 1.00 kg potassium carbonate are added. The end pH is included within the range from 9.0 to

9.5.

Then it is cooled to 20°C, and the product is ready for use.

Example No. 15

Formurea 80 kg 170.53

Water kg 20.73

Urea kg 57.98 (966.3 moles) The mixture is heated to 105°C, and then 0.20 kg 50% acetic acid are added.

The reaction pH is included within the range from 5.5 to 5.8.

The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 1600 mPa's is achieved.

The condensation is stopped by adding 1.30 kg 50% TEA.

After stopping the condensation, the pH is settled at about 8.0. Then, the following materials are loaded, in the indicated order:

Water kg 194.94

Urea kg 150.00 (2,500.0 moles)

Urea kg 250.00 (4,166.7 moles)

Urea kg 103.32 (1,722.0 moles)

2nd stage total urea kg 503.32 (8,388.7 moles)

Total urea I kg 561.30 (9,355.0 moles)

By adding water, temperature decreases to 60°C. The three urea portions are added at a spacing of a half- hour from one another, while holding, during all this step, the temperature at about 60°C.

Finally, at the same temperature, 50.00 kg hexamine and, a further half-hour, 1.00 kg 50% MEA are added. The end pH is included within the range from 8.5 to 9-0.

Then it is cooled to 20°C, and the product is ready for use. Example No. 16

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formurea 80 kg 170.53 Water kg 28.89

Urea kg 25.58 (426.3 moles)

The mixture is heated to 105°C, and then 0.80 kg 33% CH₃C00NH₄ AL are added. The pH, at the start, is nearly neutral, but it is decreased quickly to settle at a value of about 5-6. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 600 mPa's is achieved. The condensation is stopped by adding 1.70 kg of 50% TEA.

After stopping the condensation, the pH is settled at about 7.5. Then, the following materials are loaded, in the indicated order:

Water kg 185.78

Urea kg 180.00 (3,000.0 moles)

Urea kg 220.00 (3,666.7 moles)

Urea kg 135.72 (2,262.0 moles)

2° stage total urea kg 535.72 (8,928.7 moles)

Total urea kg 561.30 (9,355.0 moles)

By adding water, temperature decreases to 60°C. The three urea portions are added at a spacing of a half- hours from one another, while holding, during all this step, the temperature at about 60°C.

Finally, at the same temperature, 50.00 kg hexamine and, after a further half-hour, 1.00 kg 50% DEA are added .

The end pH is included within the range from 8.5 to 9.0.

It is then cooled to 20°C, and the product is ready for use.

Example No. 17

Formurea 80 kg 7.54

Water kg 1.56

Urea kg 1.12 (18.7 moles)

The mixture is heated to 100°C, and then 0.03 kg glacial acetic acid are further added.

The reaction pH is included within the range from 5.6 to 5.9.

The condensation is stopped by adding 0.04 kg 30% soda.

After stopping the condensation, the pH is settled at about 6.5. Then,

Urea kg 5.74 (95.7 moles) is loaded, and the second reaction is continued to achieve the viscosity value of 850 Pa's.

The condensation is then definitely stopped by adding 0.05 kg 50% TEA.

After stopping the condensation, the pH is settled at about 7.5. Then, the following materials are loaded in the indicated order:

Water kg 226.31

Urea kg 250.00 (4,166.7 moles)

Urea kg 300.00 (5,000.0 moles)

Urea kg 106.61 (1,766.8 moles)

3° stage total urea kg 656.61 (10,943.5 moles)

Total urea kg 663.47 (11,057.8 moles)

By adding water, temperature decreases to 60°C. The three urea portions are added at a spacing of 45 minutes from one another while holding, during all this step, the temperature at about 70°C.

Finally, at the same temperature, after further 45 minutes, 100.00 kg hexamine and, after a further half- hour, 1.00 kg 50% TEA are added.

The end pH is included within the range from 9.0 to

9.5.

Then, it is cooled to 20°C, and the product is ready for use.

E empt_* NO. 18

Under stirring, the following raw materials are loaded into an autoclave at atmospheric pressure and environment temperature, in the indicated order: Formurea 80 kg 7.54 Water kg 1.56

Urea kg 1.12 (18.67 moles)

The mixture is heated to 105°C, and then 0.10 kg 33% CH₃C00NH are added. The pH, at the starting of the reaction, is of about 7, but it tends to quickly decrease with the reaction to settle at a value of about of 5.5. The reaction, as monitored at even intervals by dynamic viscosity measurements at 20°C, is stopped as a viscosity value of 500 mPa's is achieved.

The condensation is stopped by adding 0.02 kg 30% soda. After stopping the condensation, the pH is settled at about 6.5.

Then:

Urea kg 2.88 (48.0 moles) is loaded and the second reaction is carried out to achieve a viscosity value of 900 mPa's.

The condensation is definitely stopped by adding 0.07 kg 50 TEA.

After stopping the condensation, the pH is settled at about 7.0. Then, the following materials are loaded in the indicated order:

W Waatteerr kg 226.24

U Urreeaa kg 250.00 (4,166.7 moles)

U Urreeaa kg 300.00 (5,000.0 moles)

U Urreeaa kg 109.47 (1,824.5 moles)

3 3°° ssttaaggee ttoottaall uu:rea kg 659.47 (10,991.2 moles)

T Toottaall uurreeaa kg 663.47 (11,057.8 moles)

By adding water, temperature decreases to 60°C. The three urea portions are added at a spacing of 45 minutes from one another, while holding, during all this step, the temperature at about 70°C.

Finally, at the same temperature, after further 45 minutes, 100.00 kg examine and, after a further half- hour, 1.00 kg 50% TEA are added. The end pH is included within the range from 8.5 to

9.5.

Then, it is cooled to 20°C, and the product is ready for use.

From the above it should be apparent that the invention fully achieves the intended aim and objects. In particular, it should be pointed out that the subject method and the fertilizing made thereby provides great advantages with respect to the prior art, in particular with respect to the very high agronomic efficiency due to the small nitrogen losses by leaching in the first plant growing period.

Moreover, the subject fertilizer does not have any dangerous phytotoxicity for the leave system of the plant, in particular both for graminaceous and cotyledons plants, following post-emergency treatments .

The invention as disclosed is susceptible to several modifications and variations, all of which will come within the scope of the invention.

Moreover, all of the details can be replaced by other technically equivalent elements.

Claims

1. A method for making a nitrogenous fertilizer having a stable liquid form, for releasing nitrogen during a long time, characterized in that said method comprises a preliminary stage, a first stage and a second stage, said preliminarily stage comprising a controlled condensation between an urea/formaldehyde precondensate, with urea, the molar ratio corresponding to U/F 1 : ( 1 : 3 ) .

2. A method, according to the preceding claim, characterized in that said condensation of said preliminarily stage is carried out at a pH less than 7, preferably of 3-5; said preliminarily stage being stopped by adding a base to achieve a pH from 6 to 7, said first stage comprising adding urea with a pH from 6 to 7.

3. A method for making a nitrogenous fertilizer having a stable liquid form, for releasing nitrogen during a long time, characterized in that said method comprises a first stage and a second stage, said first stage starting with a controlled condensation of urea-formaldehyde mixtures or an urea- formaldehyde precondensate in an end molar ratio from 1:1 to 1:3.

4. A method, according to one or more of the preceding claims, characterized in that said preliminarily stage is carried out at a pH less than 7 in the presence of mineral and organic acid or salts thereof with ammonia at a temperature of 70°C - 105°C and preferably 90°C - 100°C; the operative duration of said stage depending on the dynamic viscosity of the solution from 50 to 2,000 mPa's and preferably from 100 to 900 mPa-s at 20°C.

5. A method, according to one or more of the preceding claims, wherein the first stage is carried out at a pH from 6 to 7 at temperatures varying from 90°C to 105°C, to achieve a dynamic viscosity value preferably from 300 to 1,100 mPa's at 20°C.

6. A method, according to one or more of the preceding claims, characterized in that said first stage is stopped at a pH greater than 7 by adding organic or inorganic basis in an aqueous solution or mixtures thereof, and wherein in said first stage aqueous 30% sodium hydroxide and aqueous 50% triethanolamina are used.

7. A method, according to one or more of the preceding claims, characterized in that the reaction for preparing the end urea/formaldehyde resin is carried out in an alkaline environment with a pH from 7 to 10 and preferably from to 7.5 to 9, with an excess urea with respect to the used formaldehyde, used as such or in a form of a precondensate material at a temperature from 50°C to 70°C, preferably of 60°C.

8. A method, according to one or more of the preceding claims, characterized in that said method comprises the step of adding urea in three weight-like portions at intervals of 30 or 45 minutes, with a spacing of 30 or 45 minutes from the addition of the last portion, the end solution being added with stabilizers of the polyol types, of high or low molecular weight, or hexamine and/or sodium borax, in a rate from 0.1 - 10.0% based on the ready for use end solution.

9. An urea/formaldehyde resin solution, according to one or more of the preceding claims, characterized in that said solution is adapted to be used as a liquid fertilizer releasing in a long time c the nitrogen contained therein.

10. A fertilizer, made by a method according to one or more of the preceding claims, characterized in that said fertilizer has a liquid form obtained by a liquid and opalescent solution having an end dynamic _Q viscosity varying from 10 to 500 mPa's, preferably from 20 to 60 mPa's at 20°C.

11. A fertilizer, according to the preceding claims, characterized in that said fertilizer has a storing stability at a temperature from 0°C to 50°C, 5 preferably from 5°C to 30°C, not less than 5 weeks.

12. A fertilizer, according to one or more preceding claims, characterized in that said fertilizer has a total nitrogen contents from 20% to 35% and preferably from 25% to 30%. 0

13. A fertilizer, according to one or more of the preceding claims, characterized in that said fertilizer has a movable nitrogen contents less than 8%.

14. A fertilizer, according to one or more 5 of the preceding claims, characterized in that said stabilizers are selected from natural and synthetic polyols of high and low molecular weight, inorganic basic salts or lower inorganic basis and varying from 0.1 to 10.0% based on the total of the mixture. 0

15. A fertilizer, according to one or more of the preceding claims, characterized in that said stabilizers are selected from the group of the polyoxydrilated derivatives of β-cyclodestrine, monomeric polyols (xilitol, sorbitol, mannitol), polyvinyl alcohol having a numerical average molecular weight (Mn) from 1,000 to 250,000, preferably from 5,000 to 50,000.

16. A fertilizer, according to one or more of te preceding claims, characterized in that said basic nature stabilizer preferably comprise hesamethyltetramine and decahydrated sodium borax or mixtures thereof.

17. A method for making a nitrogenous fertilizer having a stable liquid form, for releasing nitrogen in a long time, and a fertilizer obtained thereby, according to one or more of the preceding claims, as substantially as broadly disclosed and illustrated and for the intended objects.

AMENDED CLAIMS

[received by the International Bureau on 29 November 1999 (29.11.99); original claim 17 cancelled; original claims 1,3 and 16 amended; remaining claims unchanged (2 pages)]

1. A method for making a nitrogenous fertilizer having a stable liquid form, for releasing nitrogen during a long time, comprising a first stage and a second stage in which said first stage starts with a controlled condensation of urea-formaldehyde mixtures or an urea-formaldehyde precondensate in an end molar ratio from 1:1 to 1:3, and optionally a preliminary stage which comprises a controlled condensation between an urea/formaldehyde precondensate, with urea, the molar ratio corresponding to U/F 1: (1 : 3).

2. A method, according to the preceding claim, characterized in that said condensation of said preliminary stage is carried out at a pH less than 7, preferably of 3-5; said preliminary stage being stopped by adding a base to achieve a pH from 6 to 7, said first stage comprising adding urea with a pH from 6 to 7. 3. A method, according to one or more of the preceding claims, characterized in that said second stage comprises, at the start, the adding of such an amount of water to achieve a set temperature from 50 °C to 70°C. 4. A method, according to one or more of the preceding claims, characterized in that said preliminary stage is carried out at a pH less than 7 in the presence of mineral and organic acid or salts thereof with ammonia at a temperature of 70°C - 105°C and preferably 90°C - 100°C; the operative duration of said stage depending on the dynamic viscosity of the solution from 50 to 2,000 mPa . s and preferably from polyoxydrilated derivatives of β-cyclodestrine, monomeric polyols (xilitol, sorbitol, mannitol) , polyvinyl alcohol having a numerical average molecular weight (Mn) from 1,000 to 250,000, preferably from 5,000 to 50,000.

16. A fertilizer, according to one or more of the preceding claims, characterized in that said basic nature stabilizer preferably comprises hesamethyltetrame and decahydrated sodium borax or mixtures thereof.