GB2025387A

GB2025387A - Liquid Methylene Urea Fertilizers

Info

Publication number: GB2025387A
Application number: GB7921166A
Authority: GB
Original assignee: Ashland Oil Inc
Current assignee: Ashland LLC
Priority date: 1978-06-19
Filing date: 1979-06-18
Publication date: 1980-01-23
Also published as: BE877100A; DE2924693A1; IT7923588A0; FR2429194A1; FR2429194B1; IT1121801B

Abstract

Liquid methylene urea fertilizers comprising aqueous mono-, di-, and trimethylene ureas which provide an efficient source of nitrogen for direct application to the foliage of commercial crops or lawn turfs without the hazard of foliage burn. Less than 25% of the total nitrogen is insoluble in hot water. Preparation is carried out in two stages. In the first stage, urea and formaldehyde are reacted at molar ratios less than 1, 85 to 105 DEG C and pH 4.7 to 5.2, to form low molecular weight methylene compounds containing relatively small amounts of nitrogen. The preparation is completed by reducing temperature to 55 to 75 DEG C, pH 3.5 and 4.5, adding urea to increase the urea to formaldehyde molar ratio to 1.4 to 3.0 and reacting for 30 to 90 minutes to produce substantially monomethylene diurea, dimethylene triurea and trimethylene tetraurea.

Description

SPECIFICATION Liquid Methylene Urea Fertilizers This invention relates to a new liquid fertilizer which provides a highly efficient nitrogen plant food in a substantially soluble form which may be used directly on the foliage of plants without the hazard of foliage injury and without the wasteful loss of nitrogen nutrients. More particularly, it relates to a liquid composition comprising mono-, di- and tri-methylene ureas in water solution and method for the effective preparation of this composition.

Liquid fertilizers have been used in commercial agriculture for many years to obtain the advantages of accurate application, and the ease and economy of handling and storing. Liquid fertilizers are normally aqueous solutions of inorganic chemicals such as ammonia, ammonium nitrate, urea, ammonium phosphate, potassium chloride and potassium nitrate. These fertilizers, when accurately used, give good results in conventional fertilization of the soil.

In recent years agronomic developments have shown that plant nutrients could be used with increased efficiency when applied directly to the foliage of the plant, rather than to the soil around the plant. Foliar feeding has been found to be effective for many types of plants including grasses, legumes, fruit trees, vegetables and ornamental plants.

Conventional inorganic liquid fertilizers cause foliar burn when applied in amounts sufficient to improve plant performance. Nitrogen is the main nutrient needed in the foliar feeds, amounting to at least three times the other ingredients proposed by workers in the area of foliar feeds.

Some workers indicate that nitrogen is the sole nutrient required in foliar feeds when the plant is in well fertilized soil. Thus, a foliar feed which will adequately supply nitrogen nutrient directly to the foliage without causing foliage burn or other damage has become the primary requirement for the development of large scale liquid feeding of foliage in field crops and on lawn turfs.

The aforementioned inorganic nitrogen compounds have caused foliage burn and destroyed lawns and crops when applied directly to the foliage. The burns are particularly devastating when applications are made in hot, dry, sunny weather.

The thrust of recent art has been the development of insoluble materials containing nitrogen in organic polymers which release contained nitrogen gradually for absorption by the plant. Urea-formaldehyde polymers have been mentioned most frequently in the art. Although the use of nitrogen in organic polymers does allow feeding of the foliage without damage, there are several serious drawbacks to the technique.

The nitrogen fertilizer is in finite polymer particles which may be lost from the desired location before decomposition to usable form, by rain washing, mechanical scrapping, shaking of the plant or wind action. Much of the nitrogen in ureaformaldehyde polymers does not become available in a growing season. The Official Methods of Analysis of the Association of Official Agricultural Chemists, tenth edition, defines this unavailable nitrogen in terms of insolubility in hot water and it is commonly called Hot Water Insoluble Nitrogen (HWIN). In United States Patent Specification No. 4 033 745 HWIN is used by forming the polymers into very finely divided particles and adding sugars to stimulate microbial degradation of the polymers to soluble compounds.

In addition to the art available on liquid fertilizers containing nitrogen with delayed release characteristics, there is patent art and appreciable commercial product of solid nitrogen fertilizers which release nitrogen slowly. United States Patent Specification No. 3 649 598 represents good, and probably the best, reaction of urea with formaldehyde to form solid fertilizers containing nitrogen which is soluble in hot water.

Yet, in the best example, cited in this art, 40% of the nitrogen reacted to urea formaldehyde polymers was insoluble in hot water and not available for supplying nutrient to the foliage of the plants.

Progress has been made in the area of liquid fertilizers which release their nitrogen slowly, so that nitrogen plant burn does not occur. There has been no disclosure of a substantially soluble liquid fertilizer which contains enough nitrogen to increase crop yields, in a form which is available for efficient metabolism by the plant without wasteful losses, but does not damage or burn the plant.

It is an object of this invention to provide a liquid fertilizer containing nitrogen in a substantially water soluble form which may be used as a plant food without hazard of burning or wasteful loss of nitrogen nutrient.

Therefore according to the invention there is provided a liquid methylene urea fertilizer composition, containing urea and formaldehyde in a molar ratio of from 1.4 to 3.0, the composition comprising a mixture of watersoluble methylene urea compounds containing one to three methylene moieties, in aqueous solution and having a concentration of watersoluble methylene ureas greater than the combined concentrations of unreacted urea and compounds containing Hot Water Insoluble Nitrogen.

The invention utilizes a methylene urea liquid fertilizer composition comprising aqueous mono-, di, and trimethylene ureas. The nitrogen in these methylene ureas is highly available as plant food, and substantially soluble in water, but does not cause foliage burn or plant damage even when applied directly as a foliar feed.

The liquid fertilizer of this invention is particularly effective for direct application to turf grasses, producing consistent, deep-green coloured turf, even through hot, dry weather without leaf-burning or yellowing. The liquid fertilizer is also effective as a foliar feed for commercial crops, such as soybeans, peas, apples, oranges and alfalfa.

The nitrogen contained in the new methylene urea liquid fertilizer is substantially available for effective metabolization by the plants. It thus avoids the hazards of loss from the foliage inherent with solids or slurries. The Association of Official Agricultural Chemists (AOAC) has published in their tenth edition of Official Methods of Analysis, a method for determination of water insoluble fertilizer nitrogen. Fertilizer Nitrogen Its Chemistry and Techology, by Sauchelli, 1964, states that nitrogen which is insoluble in hot water has little or no value as a plant nutrient.

Fertilizers, disclosed in the literature, which have non-burning characteristics, have contained appreciable amounts, usually 50% or more, of Hot Water Insoluble Nitrogen (HWIN). It was therefore surprising to discover that a liquid fertilizer composition could be formulated which provides water-soluble nitrogen nutrients for foliar feeding without hazard of foliage damage, yet allows little or no wasteful loss of nitrogen as HWIN.

The liquid fertilizer comprises aqueous solutions of methylene ureas, either as individual methylene urea compounds, or mixture of said compounds, containing one to three methylene moieties. Particularly effective compounds are monomethylene diurea, dimethylene triurea and trimethylene tetraurea. The liquid fertilizers of this invention may contain appreciable amounts of methylene ureas containing more than three methylene moieties so long as the methylene ureas are water-soluble. A small amount of HWIN may also be tolerated in the liquid fertilizer solutions but these compounds make no contribution to the fertilizer value of the liquids.

The physical properties of the methylene urea fertilizer liquids are adversely affected when more than 25% of the nitrogen is converted to HWIN.

Some methylol ureas and unreacted urea may be contained in the liquid fertilizers of this invention so long as about half or more of the total urea moieties are in the form of water soluble methylene ureas, and substantially all of the formaldehyde is present as methylene and methylol ureas. It was found that methylol ureas and unreacted urea both cause severe burns when placed directly on plant foliage, however, it was found, surprisingly, that these materials caused less foliar damage when used in a solution containing about half or more of the urea moieties in the form of water-soluble methylene ureas. Where less than 40% of the urea moieties were converted to methylene ureas, severe burning of the foliage occured even if the urea was substantially in the form of water-soluble methylol ureas.

The methylene urea liquid fertilizer composition of this invention may be prepared by any convenient method. Blending one, or more, of the pure methylene ureas, such as dimethylene triurea, with water may be used. A more practical method of preparation consists of reaction of urea with formaldehyde in aqueous solution.

Regardless of the method of preparation, the composition must contain about 50% or more of the urea moieties as methylene ureas or mixtures thereof, and preferably less than 25% as compounds containing Hot Water Insoluble Nitrogen.

A particularly effective method for the preparation of methylene urea liquid fertilizer composition of this invention comprises a two step process in which a molecular ratio of urea to formaldehyde of less than 1, is reached in the first stage in a mildly acid aqueous solution of pH 4.7 to 5.2, at 85 to 1 050C to form low molecular weight methylene compounds. The exact nature of these intermediate compounds are not known, but they contain relatively small amounts of nitrogen and are completely water-soluble. The intermediate compounds are then reacted for 30 to 90 minutes with additional aqueous urea in a more acidic second stage at temperatures of 55 to 750C, pH 3.5 to 4.5, and an overal urea to formaldehyde molar ratio of 1.4 to 3.0, before neutralising with base and cooling to ambient temperature.The storage stability of the methylene urea liquid fertilizer is improved by addition of a small amount of alcohol or amide.

About 1% of formamide in the fertilizer solution of this invention stabilizes it so that the methylene ureas do not react further to form urea formaldehyde polymers, which are insoluble in hot water.

The exact mechanism by which the desired methylene ureas are formed is not clearly understood, but it was surprisingly found that a clear liquid solution having non-burning properties and containing as much as 26% nitrogen could be prepared only where a preliminary high temperature low acidity, reaction conditions were provided with the urea to formaldehyde molar ratio of less than 1, and preferably about 0.5 or less. High analysis products made with final urea to formaldehyde molar ratios of 1.5 or less, were clear until diluted appreciably with water. Some water insoluble methylene ureas were precipitated on water dilution of the high analysis product, but only a trace of the material precipitating was insoluble in hot water.

The methylene urea liquid fertilizer composition of this invention may be used directly as a foliar feed or soil fertilizer, or it may be diluted with water or other nutrients for use as a complete foliarfeed or fertilizer. Additives, such as attapulgite clay and emulsifiers, may be added to improve the physical properties and commercial utility of the liquid fertilizer compsotion without changing its nutdttonal value, non-burning, or the substantially complete availability of contained nitrogen nutrients.

The amount of the individual methylene urea compounds or the ratio between the individual compounds in the methylene urea liquid fertilizer composition of this invention is not criticai if all of the compounds are soluble in water. The methylene urea compounds, and their mixtures, containing one to three methylene moieties are preferred because they are water-soluble and still cause no foliage burn. Methylene urea compounds containing four or more methylene moieties have reduced water-solubilities and are less desirable than the lower molecular weight species. Higher molecular weight methylene urea combinations having higher molecular weight polymeric structures become insoluble in hot water and have little value for feeding foliage.

The lower molecular weight compounds in the methylene urea series of compounds have higher urea to formaldehyde molar ratios and therefore allow the preparation of economically desirable high nitrogen concentrations.

The invention will now be illustrated by the following Examples in which all parts and percentages are by weight unless otherwise specified.

Example 1 11 8.0 g of neutralised 50% aqueous formaldehyde solution and 47.0 g of crystal urea were added to a 500 ml capacity round bottom flask, equipped with reflux condenser, magnetic stirrer, electric Glas Col Heater, thermometer and fittings for ingredient addition. The solution was heated to 950C as clear solution at pH 6.6.

Formic acid in 20% aqueous solution was added dropwise to decrease the pH of the reaction mixture to 4.85, and the mixture was reacted for 20 minutes at 95 to 990C. The temperature of the mixture was reduced to 750C, and 60.0 g crystal urea was added. The reaction was continued to pH 4.7 and 750C for 10 minutes. Another 60 g crystal urea was added, pH was reduced to 4.6, and the reaction was continued at 750C until a dilution cloud point of 8/1 was obtained. The dilution cloud point was determined by adding water to a small sample of the reaction mixture at 250C until a cloud was precipitated. The cloud point reported was the ratio of diluting water to reaction mixture when a cloud first appeared in the mixture. The reaction mixture was then neutralised to a pH of 6.5 by the addition of triethanolamine and the reaction mixture was cooled to 300C in 10 minutes.Three grams of commercial grade formamide was added as a stabiiizer.

The product was a clear liquid until cooled. On storage the product developed a cloudy appearance but no solids settled to the bottom of the storage container and the amount of solids recovered by filtration was less than 1% of the solution. When the reaction product was diluted with 5 parts of water much of the ureaformaldehyde product precipitated from solution as finely divided solids. The urea-formaldehyde product was quite soluble in the fertilizer but only partially soluble in cold water. The molar ratio of urea to formaldehyde was 1.41.

Analysis of the reaction product by liquid chromatograph gave the following results: Components Wt. % Monomethylene Diurea 1.5 Dimethylene Triurea 10.0 Trimethylene Tetraurea 21.5 Heavier Methylene Ureas 1 2.9 Methylol Ureas, as monomethylol urea 17.1 Urea 12.6 Water (by difference) 24.4 Total nitrogen content of the reaction product was analysed to be 26.8% and hot water insoluble nitrogen was determined to be 0.1%.

Conversion of formaldehyde was substantially complete. Conversion of urea to water soluble methylene ureas was calculated to be 67.2%, while the amount of urea converted to unavailable hot water insoluble nitrogen amounted to only 0.4% of the total nitrogen recovered in the product.

Example 2 The substantially clear product from Example 1 was treated with potassium polyphosphate solution, analysing 0--1 5--1 5 and water to bring the analysis to 10-3-3. When the water was added at 250C, 28% of the total nitrogen content precipitated from solution. Agitation of the mixture kept the solids in homogeneous suspension.

Kentucky 31 tall fescue grass turf was placed in 10 separate, drained, 10 inches square, 2+ inches deep, aluminium flats. When the height of the grass was cut evenly to 3", the following materials were applied: Flats 1 and 2 received no fertilizer; flats 3 and 4 received the 10-3-3 fertilizer amounting to 1.25 pounds of nitrogen per 1000 square feet; flats 5 and 6 received the 10-3-3 fertilizer amounting to 2.5 pounds of nitrogen per 1000 square feet; flats 7 and 8 received a clear liquid fertilizer, containing ureaammonium nitrate solution, and potassium phosphate solution analysing 1 3-3, amounting to 1.25 pounds of nitrogen per 1000 square feet; and flats 9 and 10 received the same fertilizer as flats 7 and 8 amounting to 2.5 pounds of nitrogen per 1000 square feet of turf.All flats were placed outside in direct sun during the months of April and May in Virginia, and adequate moisture was maintained in all flats.

No burning was found in flats 1,2, 3, 4, 5 and 6. Burning of the foliage was found inflates 7, 8, 9 and 10, with the burning more severe in flats 9 and 10 than in 7 and 8. The flats 1 and 2 receiving no fertilizer were pale green in colour and growth rate was slow. Flats 3 and 4 showed a healthy green colour and a good growth rate.

Flats 5 and 6 had a deep green colour and the growth rate was the highest of all the flats tested.

Example 3 4668 pounds of neutralized 50% aqueous formaldehyde 13000 pounds of water, and 3200 pounds of prilled urea, containing 46% nitrogen were added to a well agitated, jacketed 5000 gallon capacity stainless steel reactor equipped with coils for heating and cooling. The solution was heated to 500C and pH was decreased to 4.7 by careful addition of 20% formic acid in water while the reaction mixture was vigorously agitated. The heat from the reaction was allowed to increase the temperature to 95 0C, where the temperature was maintained for 20 minutes. An additional 3000 pounds of urea was then added and the reaction was continued at 950C, and pH 4.7 until a dilution cloud point of 8 to 1 was observed. The time required to reach the cloud point was an additional 25 minutes.Then 5670 pounds of urea prills and 14,140 pounds of water was added and the temperature was decreased to 600C. Dilute phosphoric acid was added to decrease the pH of the mixture to 4.1. The reaction was continued for an additional 20 minutes. The reaction mixture was then neutralized to a pH of 6.5 by the addition of triethanolamine, and cooled to 250C. Formamide, amounting to 250 pounds was added to the agitated reaction product as a stabilizer. During the high temperature acid cook to produce a high concentration of methylene groups, the reaction mixture remained clear. When the final urea addition and pH adjustment was made, precipitation of urea to formaldehyde solids occured.

To the neutralized reaction mixture was added 3 pounds of tetrasodium tripolyphosphate wetting agent and 220 pounds of Minugel (fine attapulgite clay). Viscosity of the final product was 240 centipoise. Overall molar ratio of urea to formaldehyde was 1.95. The urea to formaldehyde molar ratio during the initial methylene cook was 0.64.

Liquid chromatographic analyses of the product gave the following results: Components wt. % Monomethylene Diurea 9.7 Dimethylene Triurea 3.2 Trimethylene Tetraurea 3.0 Heavier Methylene Ureas 7.7 Methylol Ureas, as monomethylol urea 0.0 Urea 6.6 Water (by difference) 69.8 Total nitrogen content of the reaction product was analyzed to be 12.2%. Conversion of urea to water soluble methylene ureas was calculated to be 56.9%, and urea conversion to hot water insoluble nitrogen polymers was 18.0%.

Example 4 To the suspension product of Example 3 was added with agitation, potassium polyphosphate solution (0-1 6-1 6) to produce a liquid foliar feed analyzing 10% N3% P205-3% K2O. This foliar feed was sprayed onto the foliage of a field of English Peas in Virginia at the later flowering stage of the crop. A single application was made with a motorized Stihl atomizer-blower as a fine spray of droplets at a rate of 200 pounds per acre.

No burns or foliage damage occured. A check plot in the same field was not treated with any foliar feed but received the same starter fertilizer and the same cultural practices. A count of viable pea pods was made in the treated and untreated field plots. The plot receiving the foliar feed averaged 28% more viable pea pods than the untreated plot.

Example 5 Using the same procedures, reaction conditions, and equipment of Example 3, the total amounts of raw materials charged to the reaction were as follows: Ingredients Pounds Formaldehyde (50% Aqueous) 3730 Water 20500 Urea (46% N) 11210 The initial cook at 950C and pH 4.7 to produce methylene ureas was done with the total amount of formaldehyde ingredient and with a molar ratio of urea to formaldehyde of 0.40 for 20 minutes.

The second cook period at 950C and pH 4.6 was done with a urea to formaldehyde ratio of 1.24 for 20 minutes. The final cook containing the remaining urea and water was at 600C and pH 4.2 for 20 minutes, before neutralization to pH 6.5 and cooling to 27 0C. Formamide amounting to 250 pounds was added to the reactor. Wetting agent and 200 pounds of Minugel (fine attapulgite clay) was added. Viscosity of the final product was 220 centipoise. Overall molar ratio of urea to formaldehyde was 3.0 and total amount of product recovered was 35750 pounds. The composition of the product was as follows: Component Wt. % Monomethylene Diurea 7.7 Dimethylene Triurea 3.5 Trimethylene Tetraurea 1.6 Heavier Methylene Ureas 6.8 Methylol Ureas 0.0 Urea 15.1 Water (by difference) 65.3 Total nitrogen content of the reaction product was found to be 14.4% and hot water insoluble nitrogen content was 0.14%. Conversion of formaldehyde to methylene compounds was substantially complete and conversion of urea to water soluble methylene ureas was calculated to be 51.5% with only 0.1% of the urea converted to water insoluble nitrogen compounds.

Example 6 Using the procedure of Example 2, the product from Example 5 was applied to Kentucky31 tall fescue grass turf at rates of 1.0 and 2.0 pounds of nitrogen per 1000 square feed of turf surface.

There was a rapid deepening in the colour of the grass and an increase in the growth rate. There was no foliage damage or burning.

Example 7 To the same well agitated reactor, used in Examples 3 and 5, 4668 pounds of neutralized aqueous formaldehyde, 27,140 pounds of water, and 11 670 pounds of prilled urea were added.

The reaction mixture was heated to 950C and pH was maintained between 7.0 and 8.0 during a 75 minute reaction period. At the end of this period the pH was adjusted to 6.5 and the reaction product was cooled to 240C. Total weight of the neutralized reaction product was 44,800 pounds.

Analyses of the reaction product was made with results as follows: Component Wt. % Monomethylene Diurea 7.5 Dimethylene Triurea 1.3 Trimethylene Tetraurea 0.1 Heavier Methylene Ureas 0.0 Monomethylol Urea 6.5 Dimethylol Urea 4.3 Urea 10.0 Water (by difference) 69.4 Total nitrogen content of the reaction product was analyzed to be 12.0%, and hot and cold water insoluble nitrogen was 0.0%. Total conversion of formaldehyde to methylene compounds was 32.9% and conversion of urea to methylene compounds totalled 31.9%.

Conversion of formaldehyde to methylol ureas was calculated to be 67.0%, and conversion of urea to methylol ureas totalled 25.7%.

Example 8 Using the same procedure as in Examples 2 and 6, the product from Example 7 was applied to Kentucky-31 tall fescue at rates of 1.0 and 2.0 pounds of nitrogen per 1 000 square feet of turf surface. Yellowing of the foliage, particularly at the tips of the grass blades, occurred with the 1.0 pound rate and severe burning occurred on the turf treated with the 2.0 pound per square feet rate.

Example 9 Using the equipment of Example 3 and the same raw material sources, urea and formaldehyde were reacted in a molar ratio of 1.75 at 720C, for 60 minutes at pH 4.3 to make a product containing 12.19/0 total nitrogen. After neutralization and cooling, analysis of the product showed that the total conversion of urea to water soluble methylene ureas was 20% and conversion to water insoluble nitrogen compounds was 80%.

Example 10 Using the procedure of Example 2, the product of Example 9 was applied to Kentucky-31 tall fescue grass at the rate of 1.0 and 2.0 pounds nitrogen per 1000 square feet of turf, and compared at equal application rates to the product made in Example 5. None of the treatments caused burning or foliar damage. The foliage growth rate and the deepness of foliage colour of the treatment with Example 5 at the 1.0 pound feed rate was superior to the treatment with a 2.0 pound rate of product from Example 9, and 2.0 pound feed rate of Example 5 product gave performance for exceeding that with Example 9 product.

Claims

1. A liquid methylene urea fertilizer composition, containing urea and formaldehyde in a molar ratio of from 1.4 to 3.0, the composition comprising a mixture of water-soluble methylene urea compounds containing one to three methylene moieties, in aqueous solution and having a concentration of water-soluble methylene ureas greater than the combined concentrations of unreacted urea and compounds containing Hot Water Insoluble Nitrogen.

2. A composition as claimed in Claim 1 which contains no unreacted formaldehyde and comprises an aqueous mixture of monomethylene diurea, dimethylene triurea, trimethylene tetraurea and compounds containing Hot Water Insoluble Nitrogen, the Hot Water Insoluble Nitrogen content amounting to less than 25 per cent of the total nitrogen content of the composition, the composition having a near neutral pH of from 6.0 to 7.5, and a total nitrogen content of from 10 to 30 per cent.

3. A composition as claimed in Claim 2 in which at least 50 per cent of the urea moieties are present as methylene urea compounds and less than 25% of the urea moieties are present as compounds containing Hot Water Insoluble Nitrogen.

4. A composition as claimed in any preceding claim which additionally comprises from 2 to 8 per cent of phosphorous pentoxide and from 2 to 8 percent potassium oxide, in the form of water soluble potassium and phosphate salts.

5. A liquid methylene urea fertilizer composition substantially as herein described with reference to any one of the Examples.

6. A two-stage method for the preparation of a non-burning liquid methylene urea fertilizer comprising: the first stage comprising reacting urea and formaldehyde in a molar ratio lower than 1.0, in an aqueous solution of pH 4.7 to 5.2 at a temperature of 85 to 1050C to form low molecular weight methylene intermediate compounds, and the second stage comprising reacting the intermediate compounds at pH of 3.5 to 4.5 at a temperature of 55 to 750C for 30 to 90 minutes with aqueous urea to bring the final urea to formaldehyde molar ratio of 1.4 to 3.0 and neutralizing by addition of base to a pH of 6.3 to 6.7.

7. A two-stage process for the preparation of non-burning liquid methylene urea fertilizer substantially as herein described with reference to any one of Examples 1, 3, 5, 7 and 9.