Chemistry: fertilizers – Processes and products – Forms or conditioning
Reexamination Certificate
1998-07-29
2001-09-11
Michl, Paul R. (Department: 1714)
Chemistry: fertilizers
Processes and products
Forms or conditioning
Reexamination Certificate
active
06287359
ABSTRACT:
The present invention relates to granule mixtures composed of
a) 5 to 45% by weight of coated fertilizer granules (granules a), composed of
a1) a core, comprising a customary fertilizer, and
a2) a coat, comprising a coat polymer, and
b) 55 to 95% by weight of non-coated fertilizer granules, comprising a customary fertilizer (granules b)
and to fertilization methods in which the granule mixtures are used.
Fertilizer granules which are not coated are generally known and described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition 1987, Volume A10, pages 363 to 369. The disadvantage of these fertilizer granules is the fact that the fertilizing agents, which are normally salts, are rapidly released from these granules, which results in a high nutrient concentration in the soil over a short period. Frequently, such high amounts cannot be taken up by the plants immediately. In this case, there is a danger of the nutrients being fixed in the soil, in which case they are no longer available to the plants or are leached out and reach the ground water, which is to be avoided for water conservation reasons. Moreover, the high salt concentrations, which are observed temporarily, may damage the plants and cause, for example, stunted growth.
Even when large amounts of fertilizer are applied, the concentration of fertilizing agent in a form that can be utilized by the plants drops so rapidly in this type of fertilization that it is too low even a short time after fertilization, ie. suboptimal for plant growth, and fertilization has to be carried out repeatedly within a comparison period. Not only does this mean more work, but one is also faced with the problem of the fertilizer particles adhering to the leaf axils, where they result in chemical burns.
To overcome these disadvantages, “slow-release” fertilizers were developed, which release the fertilizing agent in a form which is tolerated by plants over a prolonged period, for example over an entire vegetation period, in an amount which is better adapted to the nutrient requirements of the plant in the course of time.
These slow-release fertilizers are, for example, fertilizer granules which are coated with a polymer coat. Such fertilizers are known, for example, from Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition 1987, Volume A10, pages 367 to 369.
Until now, it has been assumed that the rate at which the fertilizing agents are released is adapted satisfactorily to the changing nutrient requirements of the plants only when the majority of the granule particles are coated, and this is why the German Düngemittelverordnung [German Fertilizer Regulation] in its version of Jul. 9, 1991, § 2, in conjunction with Table 3 (cf. Das Düngemittelrecht [Fertilizer Law], edition 1992, by Günter Kluge and Georg Embert, Landwirtschaftsverlag GmbH, Münster-Hiltrup, 1992, pages 21 and 62) and the Verordnung zur Änderung düngemittelrechtlicher Vorschriften [Regulation for the Amendment of Provisions concerning Fertilizer Law] of Aug. 22, 1995 (Bundesgesetzesblatt [Federal Law Gazette], Year 1995, Part I, pages 1060 to 1071) provides that only those non-coated NPK fertilizers may be labelled as “EEC fertilizers” (and hence do not require separate licensing) where the fertilizer-coated granules amount to at least 50%.
The disadvantage of the granule mixtures with a high proportion of coated granules is the high price, due to the relatively complicated production of the coated granules (in general, the starting material for the production of the coated granules are non-coated customary fertilizer granules, which are coated with solution or dispersion of the coat polymer).
It is an object of the present invention to develop controlled-release fertilizers which are less expensive than the known ones and whose release rate is adapted with a view to the nutrient requirements of the plants in the course of time.
We have found that this object is achieved by the granule mixtures defined at the outset.
The granule mixtures according to the invention comprise
a) 5 to 45, preferably 15 to 40, % by weight of polymer-coated fertilizer granules (granules a) composed of
a1) a core, comprising a customary fertilizer agent, and
a2) a coat, comprising a coat polymer, and
b) 55 to 95, preferably 60 to 85, % by weight of non-coated fertilizer granules, comprising a customary fertilizer agent (granules b).
Granules (a) are generally known and described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition 1987, Volume A10, pages 367 to 368.
Customary fertilizers which generally essentially constitute the core (al) are, for example, single-constituent or else compound fertilizers which comprise nutrients such as nitrogen, potassium or phosphorus in the form of their salts, either individually or, if desired, in combination. Examples are NP, NK, PK and NPK fertilizers, such as nitrochalk, ammonium sulfate, ammonia sulfur-nitrate and urea.
Furthermore, the core (a1) may comprise, besides the abovementioned main constituents, secondary nutrients, such as Ca, B and/or Mg, trace elements, such as Fe, Mn, Cu, Zn and/or Mo in minor quantities, ie. usually in amounts of from 0.5 to 5% by weight, and other additives, such as crop protection agents, eg. insecticides or fungicides, growth regulators or nitrification inhibitors.
The coat (a2) is generally essentially composed of customary coat polymers, such as polyethylene, polypropylene, PVC, polyvinylidene chloride, vinyl chloride/vinylidene chloride block copolymers, (aliphatic and/or aromatic) polurethane [sic], polyvinyl acetate, polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, urea/formaldehyde and melamine/formaldehyde resins, polyethylene oxide and polyethyleneimine, maleic anhydride/styrene block copolymers, ethylene/vinyl acetate/Co [sic] block copolymers, terpolymers based on ethylene/vinyl chloride and, for example, acrylic acid, linseed oil and soya oil block copolymers crosslinked with cyclopentadiene or butadiene, ethylene/acrylic acid block copolymers, polylactic acid, poly-caprolactone, polyesters, polyhydroxybutyric acid, hydroxypropylcellulose, polyglycolic acid, polyhydroxyvaleric acid, polyas-partic acid and paraffin waxes, phthalic esters of fatty alcohols, rosin, and metal salts of fatty acids.
Mainly suitable as coat polymers are carboxyl-carrying ethylene block copolymers where the carboxyl groups may also be present in the form of their salts, the carboxyl-carrying ethylene block copolymer being composed of
a2.1) 75 to 90% by weight, preferably 15 to 25% by weight, of ethylene and
a2.2) 10 to 25% by weight, preferably 15 to 25% by weight, of an &agr;-olefinically unsaturated C
3
- to C
8
-carboxylic acid.
Suitable monomers (a2.2) are, in particular, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid and mixtures of these.
The carboxyl-carrying ethylene block copolymers preferably have a Melt Flow Index (MFI) of from 1 to 25, particularly preferably 5, from 8 to 15 (measured at 160° C. and 325 Kp). The MFI indicates the amount of polymer melt in grams which can be forced through a nozzle of specific dimensions with a specific expenditure of force (load) at a specific temperature and time. The Melt Flow Indices (MFI units) are determined in accordance with the standard protocols ASTM D 1238-65 T, ISO R 1133-1696 (E) or DIN 53 735 (1970), which are identical with regard to each other.
The carboxyl-carrying ethylene block copolymers preferably have a melting range whose melting end (T
SE
) is above 80° C., preferably above 110° C. In general, the T
SE
does not exceed 200° C. The T
SE
can be determined for example by the differential scanning calorimetry (DSC) method, the procedure usually being carried out in accordance with the protocol of DIN53765.
The carboxyl-carrying ethylene block copolymers furthermore preferably have a glass temperature (T
G
) of below 50° C., preferably from −20 to +20
Dressel Jurgen
Erhardt Klaus
Hähndel Reinhardt
Lang Hans
von Locquenghien Klaus Horchler
K+S Aktiengesellschaft
Michl Paul R.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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