Chemistry: fertilizers – Processes and products – Forms or conditioning
Reexamination Certificate
1997-12-15
2001-02-13
Langel, Wayne (Department: 1754)
Chemistry: fertilizers
Processes and products
Forms or conditioning
C071S064110
Reexamination Certificate
active
06187074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to novel coated fertilizer granules which are coated with a carboxyl-carrying ethylene copolymer in which the carboxyl groups may also be in the form of their alkali metal, alkaline earth metal or ammonium salts, the carboxyl-carrying ethylene copolymer being composed of
a) from 75 to 90% by weight of ethylene and
b) from 10 to 25% by weight of an &agr;-olefinically unsaturated C
3
-C
8
-alkanecarboxylic acid, and those coated fertilizer granules which contain an active ingredient for crop protection being excepted. The present invention furthermore relates to a process for their preparation and to fertilizer application methods in which the novel coated fertilizer granules are used.
2. Description of the Background
It is generally known that fertilizer granules which are coated with a water-impermeable layer of a polymer can be used as fertilizer. As a result of the coating, the efficiency of these fertilizers is increased because the coated fertilizer releases in a sustained manner the substances serving as plant nutrients and can thus display its action over a long period. Such slow-release fertilizers are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition 1987, volume A 10, pages 363 to 369, and their advantages are summarized in Fert. Res. 35 (1993), 1-12.
U.S. Pat. No. 4,851,027 discloses the use of aqueous dispersions which contain a polymer having a glass transition temperature of 60° C. or more for coating fertilizer granules. A large number of monomers, including ethylene and unsaturated carboxylic acids, such as acrylic acid and methacrylic acid, are specified as monomers which are suitable for the preparation of these polymers.
No specific information about the use of copolymers of ethylene and olefinically unsaturated carboxylic acids as coating polymers is given. EP-A-337 298 recommends the use of copolymers of ethylene, vinyl chloride and at least one monomer selected from the group consisting of acrylamide, methacrylamide, N-methylolacrylamide, N-butoxymethacrylamides, acrylic acid, glycidyl methacrylate and hydroxyethyl acrylate as coating polymers for coating fertilizer granules.
Japanese Preliminary Published Application 71 698/87 discloses coated fertilizer granules which are prepared by applying a solution or a dispersion of an ethylene/acrylic acid copolymer in which the solvent or the continuous phase is an organic solvent, for example a hydrocarbon.
The coated fertilizer granules have to meet a variety of requirements with regard to simple and economical preparation and their performance characteristics.
The polymers should be capable of being applied to the fertilizer granules without the use of organic solvents. Furthermore, the amount of polymer required for coating the granules should be very small in order to achieve an adequate slow-release effect.
In addition, the coated fertilizer granules should show no tendency to stick together, in particular at temperatures as usually occur during their storage or during transport, without special measures being necessary in this respect. On the other hand, the coating polymers must not be excessively hard and brittle, since the coats would otherwise be damaged or even flake off when the coated fertilizer granules are subjected to mechanical stress as occurs, for example, during transfer or broadcasting on the arable land.
Coated fertilizer granules which meet these complex requirements have not been disclosed to date. Only the non-prior-published German Patent Applications with the file reference P 43 43 176.2 describe coated fertilizer granules which contain a crop protection agent and whose coat consists of a polymer which is composed of from 75 to 90% by weight of ethylene and from 10 to 35 25% by weight of an &agr;-olefinically unsaturated mono- or dicarboxylic acid.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide coated fertilizer granules which meet the abovementioned requirements.
We have found that this object is achieved by the coated fertilizers defined at the outset. We have also found a process for their preparation and fertilizer application methods in which these coated fertilizers are used.
DETAILED DESCRIPTION OF THE INVENTION
Starting fertilizer granules which are suitable for coating are generally known granules of organic or mineral fertilizers, as described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition 1987, volume A 10, pages 323 to 431 (cf. in particular sections 2.1 and 4).
For example, single-nutrient and multinutrient fertilizers which contain nutrients such as nitrogen, potassium or phosphorus in the form of their salts, individually or, if required, in combination, are suitable. Examples of these are NP, NK, PK and NPK fertilizers, such as calcium ammonium nitrate, ammonium sulfate, ammonium nitrate sulfate and urea.
It is also possible to use starting fertilizer granules which contain salts of Mg, Fe, Mn, Cu, Zu, Mo and/or B in minor amounts, ie. usually in amounts of from 0.5 to 5% by weight, in addition to the stated main components.
The longest average diameter of the starting fertilizer granules is in general from 0.5 to 10, preferably from 0.7 to 5, mm. Their bulk density is usually from 0.5 to 1.3 kg/l. The coating consists of a carboxyl-carrying ethylene copolymer in which some or all of the carboxyl groups may also be in the form of their salts, preferably the zinc, alkali metal, alkaline earth metal or ammonium salts, the sodium or ammonium salts being particularly preferred.
Particularly suitable ammonium salts are those which are derived from ammonia, a mona-, di- or trialkanolamine, each having 2 to 18, preferably 2 to 6 carbon atoms in the hydroxyalkyl radical, or mixtures of the stated alkanolamines, or a dialkylmonoalkanolamine having 2 to 8 carbon atoms in the alkyl radical and 2 to 8 carbon atoms in the hydroxyalkyl radical, or mixtures thereof. Examples of these are diethanolamine, triethanolamine, 2-amino-2-methylpropan-1-ol and dimethylethanolamine.
Preferably from 40 to 100, particularly preferably from 70 to 90, % of the carboxyl groups are in the form of their salts.
The carboxyl-carrying ethylene copolymer is composed of
a) from 70 to 90, preferably from 75 to 85, % by weight of ethylene and
b) from 10 to 30, preferably from 15 to 25, % by weight of an &agr;-olefinically unsaturated C
3
-C
8
-alkanecarboxylic acid.
Particularly suitable monomers (b) are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid and mixtures of these acids.
The carboxyl-carrying ethylene copolymers preferably have a melt flow index (MFI) of from 1 to 25, particularly preferably 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, at a certain temperature and in a certain time, through a nozzle of certain dimensions when a certain force (load) is applied. The melt flow indices (MFI units) are determined similarly to the standards ASTM D 1238-65 T, ISO R 1133-1696 (E) or DIN 53 735 (1970), which are identical to one another.
The carboxyl-carrying ethylene copolymers preferably have a melting range whose final melting point (T
FM
) is above 80° C., preferably above 110° C. The T
FM
is in general not higher than 200° C. The T
FM
can be determined, for example, by the differential scanning calorimetry (DSC) method, the procedure of DIN 53765 usually being employed.
The carboxyl-carrying ethylene copolymers furthermore preferably have a glass transition temperature (T
G
) of less than 50° C., preferably from −20 to +20° C., and no glass transition temperature above 50° C. The T
G
is likewise usually determined by the DSC method according to DIN 53765.
The proportion of carboxyl-carrying ethylene copolymer in the total amount of the coated fertilizer granules is in general from 0.5 to 15, preferably from 2 to 10, % by weight.
The novel coated fertilizer granules are generally pr
Engelhardt Karl
Kleinbach Eberhard
Muller Michael Wolfgang
von Locquenghien Klaus Horchler
K + S Aktiengesellschaft
Langel Wayne
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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