WO2001038263A1

WO2001038263A1 - Agricultural composition and conditioning agent for reducing hygroscopicity, dust formation and caking of fertilizers

Info

Publication number: WO2001038263A1
Application number: PCT/NO2000/000398
Authority: WO
Inventors: Terje Wasvik; Espen Fridtjof Hansen; Susanne Gadman Snartland
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 1999-11-26
Filing date: 2000-11-24
Publication date: 2001-05-31
Anticipated expiration: 2002-05-26
Also published as: NO995833D0; NO995833L; AU1561801A; NO311424B1

Abstract

This invention relates to a new agricultural composition comprising a substrate being a nitrate-containing fertiliser and 0.08-2 weight % of a coating thereon for reducing hygroscopicity, dust formation and/or caking of the fertiliser. The invention further comprises a conditioning agent comprising wax, oil, resin and possibly a biodegradable polymer for obtaining coating on fertilisers. The conditioning agent applicable for coating the fertiliser comprises 1-60 weight % wax, 5-90 weight % natural occurring oils or oil compositions, 5-90 weight % fish oil distillate residue and 0-5 weight % biodegradable polymer.

Description

Agricultural composition and conditioning agent for reducing hygroscopicity, dust formation and caking of fertilizers

This invention relates to a new agricultural composition comprising a substrate being a nitrate-containing fertiliser and 0.08-2 weight% of a coating thereon for reducing hygroscopicity, dust formation and/or caking of the fertiliser. The invention further comprises a conditioning agent comprising wax, oil, resin and possibly a biodegradable polymer for obtaining coating on fertilisers.

It has been known for a long time to coat fertilisers to improve their handling and storing properties. Hygroscopic fertilisers like NP-fertilisers and especially nitrate of lime (NL) will cause problems when they are exposed to moisture. The absorbed moisture will result in caking of the particles, reduction of particle structure and dust formation during handling will also arise thereby. Handling of the product in bulk will accordingly be impossible unless this problem is solved. This problem can be solved by application of known conditioning agents like for instance those described in our European Patents Nos. 0320987 and 0768993. However, the degradation of the known conditioning agents do involve disadvantages for the environment. The previously known conditioning agents are not sufficiently biodegradable, they may contain carcinogenic polyaromatic hydrocarbons (PAH) and in addition they may be acute toxic towards water organisms. Thus, using the existing conditioning agents can involve environmental and health risks. It can be expected that in the near future various governments will introduce new legislation restricting the use of agricultural products not being inherently biodegradable and being toxic in water. Few of the existing conditioning agents applied to fertilisers satisfy the expected allowable degrees of biodegradability, content of PAH and toxicity towards water organisms for agricultural products.

The acceptable values for inherent biodegradability that could be reasonable to set is above 70% DOC according to the OECD302 method.

The acceptable values for toxicity that could be reasonable to set is below 2 dead animals according to the Toxicity towards Daphnia Magna (OECD 202 and EU no C.2.). If the test results give values between 2-10, it is recommended to perform tests on fish and algea in addition, in order to verify if there is a water toxicity or not.

The acceptable values for PAH that could be reasonable to set are below 1.5% at the I. P.346 analyse method. If the test results show values above 1.5%, identification of the actual organic components is necessary, in order to see whether they are carcinogenic, mutagenic or influence the reprotoxic nature or not.

As can be seen in Fig. 1 , none of the tested existing fertiliser coatings do satisfy both the expected demands set for biodegradability and toxicity. Fig. 1 is showing test results for several coatings from 8 different producers in Europe. Eight of the tested coatings are furthermore not satisfying the expected demands for content of PAH.

Dust reducing components used in coatings are very often polymers with low biodegradability, and also the carrier: technical white oil has low biodegradability because of their chemical nature (paraphenic and naphtenic substances). Most of the surfactants used today are oil soluble and show an acute toxicity towards water organisms.

Oil and waxes can contain polyaromatic hydrocarbons (PAH). Of course not all PAH can cause hazard assessment, but it is important to identify the specific substance to verify if it is carcinogenic or not.

The inventors of the present invention have developed a new conditioning agent for coating fertilisers that surprisingly does satisfy the above mentioned demands for biodegradability, water toxicity and content of PAH as well as reduces moisture absorption, caking and/or dust formation of the fertiliser and increases particle strength and spreadability of the fertiliser.

It is a main object of the invention to provide an agricultural composition comprising nitrate-containing fertilisers having reduced tendency for moisture absorption, caking and dust formation during handling and storage of fertiliser particles as well as being biodegradable and non-toxic.

Another object is to provide a conditioning agent being biodegradable and non- toxic.

A further object is to provide a conditioning agent being applicable in relatively large amounts without making the fertiliser particles sticky and thereby reduce their flowability.

Still another object is to provide a conditioning agent being flexible within the actual operating temperatures and being applicable to fertiliser particles by conventional coating or conditioning equipment.

These and other objects of the invention are achieved by the attached claims. Similar to the known conditioning agents referred to in EP-0320987 and EP-0768993, the invented conditioning agent comprises oil, wax and resin. In addition the invented conditioning agent might comprise a biodegradable polymer.

The oil comprises all kinds of natural occurring oils like vegetable oils, animal oils and marine oils or products made from these.

Vegetable oils might be corn oil, canola oil, sunflower oil, soya oil, linseed oil, rapseed oil or mixtures thereof.

A preferred oil composition is a fish oil ester.

It was found that the wax component was not very critical though careful selection of this component would give optimal effects. Useful types of wax in the new conditioning agent is:

Intermediary waxes, paraffin waxes, microcrystalline waxes, carnuba wax, marine wax and vegetable waxes. Mixtures of two or more of these waxes will be an actual wax component.

Paraffin waxes can be defined as predominantly straight-chain saturated hydrocarbons with smaller proportions of branched-chain and cycloparaffinic compounds.

Intermediary waxes are mixtures of straight-chain, branched-chain and cycloparaffinic compounds, intermediate in character between those of paraffin and microcrystalline waxes.

Microcrystalline waxes are hydrocarbons of higher average molecular weight than those of paraffin waxes with a wider range of components containing a high portion of branched-chain and cycloparaffinic hydrocarbons. In order to obtain lowest possible congealing point, intermediary waxes are preferred. These will give congealing point of about 37°C compared to congealing point of about 43°C for a mixture of paraffinic and microcrystalline wax.

The resin used in the new conditioning agent is a mixture comprising fatty acids, fish oil and/or herring oil and distillation residue.

A preferred resin according to this invention is a fish oil distillation residue.

When the new conditioning agent comprising a fish oil distillation residue is applied to NPK-fertiliser, the fish oil distillation residue acts like a surfactant for the fertiliser. It modifies the crystals being built between the fertiliser particles during a caking process. Instead of strong breadth bridges, fine crystal needles are being made, making the caking less severe. The negative effect of a caking is because of this invention reduced dramatically.

In order to reduce the dust formation even more, a biodegradable polymer like polyisobutylene could be added to the conditioning agent.

The fertilisers according to this invention are particulated fertilisers like NPK (complex nitrogen-, phosphorus- and potassium fertiliser), NK (nitrogen- and potassium type fertiliser), NP (nitrogen- and phosphorus type fertiliser), AN (ammonium nitrate), CN (calcium nitrate), NL (nitrate of lime; i.e. CN or CN +AN) and urea.

It was found that the relative amounts in weight% of the components of the conditioning agent should be:

Wax: 1 -60, preferably 20-60

Oil: 5-90, preferably 20-40

Resin: 5-90, preferably 25-45

Polymer: 0-5 The invention is further explained below by examples and attached figures.

Fig. 1 shows values for biodegradability and toxicity for 16 conventional fertiliser coatings from 8 different producers in Europe. PAH is below 1.5% in 8 of the tested 16 coatings.

Fig. 2 shows water absorption tendency for a CN-fertiliser coated with the invented conditioning agent compared to CN-fertilisers coated with conditioning agents disclosed in EP-0320987 and EP-0768993.

Fig. 3 shows caking tendency for a NPK-fertiliser coated with the invented conditioning agent compared to uncoated NPK-fertiliser.

Fig. 4 shows the dust reducing effect of the invented coating compared to a fertiliser sample without coating.

Fig. 5 shows values for biodegradability and toxicity for a conditioning agent (coating) according to the present invention compared to conventional coatings.

Fig. 6 shows the dust reducing effect of the invented coating when a polymer is added.

Example 1

This example shows moisture absorption of CN granules at 75% relative humidity and 25°C. The results of this experiment are shown in Fig. 2 as water absorbed in weight percent as function of time in hours. Curve 1 refers to uncoated particles, curve 2 refers to 0.3 weight.% of reference 1 (EP-0320987), curve 3 refers to 0.5 weight% of reference 1 , curve 4 refers to 0.3 weight.% of a coating according to the invention, curve 5 refers to 0.7 weight% of reference 2 (EP-0768993) and curve 6 refers to 0.7 weight.% of a coating according to the invention. The condition agent according to the invention applied on the particles had the following composition:

31 weight.% intermediary wax

31 weight% fish oil ester

38 weight% fish oil distillation residue

As can be seen from Fig. 2, particles with 0.3 and 0.7 weight% of the coating according to the invention applied, absorbed water to a far less degree than particles having 0.3 or 0.5 weight.% of reference 1. Particles with 0.5 weight.% of the coating according to the invention also absorbed less water than 0.7 weight% of reference 2.

CN will become a liquid solution when 2.5-3% water is absorbed. As can be seen from Fig. 2 this will be the case when reference 1 is used, but not for the product according to the present invention.

Example 2

This example shows caking tendency of NPK fertiliser particles at 60% relative humidity and 25°C. The results are shown in Fig. 3 where the bars indicate the fertiliser's tendency to cake, explained by a caking index.

Bar 1 refers to 0.15 weight% of a coating according to the invention and 0.35 weight% of a conditioning powder (talcum), and bar 2 refers to uncoated particles.

The condition agent according to the invention applied on the particles had the following composition:

8 weight.% intermediary wax 40 weight% fish oil ester 60 weight% fish oil distillation residue As can be seen from Fig. 3, particles coated with 0.15% of the coating according to the invention decrease the caking tendency compared to uncoated fertiliser. This shows that the conditioning agent according to the invention also is applicable on NPK-fertilisers.

Example 3

This example shows potential dust in CN granules. The results are shown in Fig. 4 where the bars indicate the fertiliser's potential dust in mg/kg. Bar 1 refers to 0.50 weight% of a coating according to the invention and bar 2 refers to uncoated CN particles.

31 weight.% intermediary wax

31 weight% fish oil ester

38 weight% fish oil distillation residue

As can be seen from Fig. 4, CN with condition agent according to the invention reduces the potential dust with more than 80% compared to uncoated particles.

Example 4

The invented coating with composition as mentioned in Example 1 , has been tested for biodegradability in accordance with OECD 302, toxicity towards water organisms in accordance with OECD 202, EU no.C2 (Daphnia Magna) and concentrations of PAH in accordance with method IP 346. The coating has passed all the test limits stated earlier in this specification. None of the other 16 tested coatings on the market today pass all three criteria at the same time. These results are shown in Fig. 5. Example 5

This example shows the dust tendency of CN granules with a coating according to the present invention and where a biodegradable polymer like polyisobutylene (PIB) is added. The condition agent according to the present invention applied on the particles had the following composition:

39.4 weight% intermediary wax 34.6 weight% fish oil ester 22.0 weight% fish oil distillation residue 4 weight% polyisobutylene

The result from the measurement of dust is visualised in Fig. 6. The figure shows that by adding polyisobutylene to the conditioning agent the dust formation is further reduced.

In addition the separated components of the invented coating according to Example 1 have been tested by gas chromatograhpy and mass selective detection (GC/MS) where the aromatic components are specified and quantified down to ppm concentrations. None of the identified aromats are classified as carcinogenic (in accordance with "Stortingsmelding" 58).

This invention shows that it is possible to use components in coatings which have a good environmental profile, with high efficiency as a coating on fertiliser and being economically feasible at the same time.

By the present invention the inventors have succeeded in arriving at nitrate- containing fertilisers that can be handled, stored and applied without giving problems with regard to moisture absorption and caking of the particles and dust formation during handling. The new coating agent achieved is easy to apply during the coating of the fertiliser particles. The resulting coating on the particles makes them free-flowing and non-sticky which is favourable with regard to spreadability.

The coating according to the invention satisfies expected restrictions concerning biodegradability, toxicity and PAH-content. None of the existing coatings do satisfy all these restrictions at the same time.

Claims

1. An agricultural composition comprising a substrate being a nitrate- containing fertiliser and 0.08-2.0 weight.% of a coating comprising wax, oil and resin, characterized in that the coating contains 1-60 weight% wax, 5-90 weight% oil, 5-90 weight% resin being a mixture comprising fatty acids, herring-oil and distillation residue and 0-5 weight% of a biodegradable polymer.

2. Agricultural composition according to claim 1 , characterized in that the substrate is NP-, NK- or NPK-fertilisers, CN-, AN- or NL-fertilisers or urea and that the wax component comprises 20-60 weight.% of the coating, that the oil component of the coating comprises natural occurring oils in amounts of 20-40 weight.%, the resin component 25-45 weight% of the coating and the polymer component 0-5 weight.% of the coating.

3. Agricultural composition according to claim 1 or 2, characterized in that the oil component of the coating comprises vegetable oils, animal oils, marine oils or preparations of these.

4. Agricultural composition according to claim 3, characterized in that the oil component of the coating comprises fish oil ester.

5. Agricultural composition according to claim 1 or 2, characterized in that the resin component of the coating comprises fish oil distillation residue.

6. Agricultural composition according to claim 1 or 2, characterized in that the wax component of the coating comprises intermediary wax.

7. Agricultural composition according to claim 1 or 2, characterized in that the polymer component of the coating comprises polyisobutylene.

8. Conditioning agent for reducing hygroscoposity, dust formation and caking of fertilisers, comprising wax, oil and resin, characterized in that it comprises 1-60 weight.% wax, 5-90 weight% oil, 5-90 weight% resin being a mixture comprising fatty acids, herring-oil and distillation residue and 0-5 weight% of a biodegradable polymer.

9. Conditioning agent according to claim 8, characterized in that it comprises 20-60 weight.% wax, 20-40 weight% natural occurring oils, 25-45 weight% resin and 0-5 weight% biodegradable polymer.

10. Conditioning agent according to claim 8 or 9, characterized in that the wax component comprises intermediary waxes, the oil component comprises vegetable oils, animal oils, marine oils, oil preparations of these and/or fish oil esters, the resin component comprises residue from fish oil production and the polymer component comprises polyisobutylene.