Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
2000-01-11
2002-06-25
Levy, Neil S. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C424S405000, C424S408000, C424S409000, C424S417000, C424S421000, C424S705000, C504S101000, C514S223800
Reexamination Certificate
active
06410042
ABSTRACT:
The present invention relates to crop protection granules based on the active substance tetrahydro-3,5-dimethyl-1,3,5-thiadiazine-2-thione.
U.S. Pat. No. 2,838,389 describes the use of tetrahydro-3,5-dimethyl-1,3,5-thiadiazine-2-thione of the formula (I), common name dazomet, as a soil decontaminant in agriculture and horticulture.
For an end user incorporating dazomet into the soil by mechanical means, it is fundamentally of prime advantage to be able to use dust-free granules.
A process for preparing such substantially dust-free granules is described in EP A 618 912. By adding alkylenediamines of the general formula R
1
NH—A—NHR (III) (R and R
1
independently are hydrogen or C
1
-C
4
-alkyl and A is a 1,2-ethylene, 1,3-propylene or 1,4-butylene bridge) in the course of dazomet's preparation, control is exerted over crystallization or granulation and so substantially dust-free dazomet granules are obtained with qualities advantageous to the end user. Corresponding products are obtainable commercially under the trade name Basamid from BASF Aktiengesellschaft.
Forest Prod. J. 43(2): 41-44 (1993), Acta Horticulture 382 (1995) p. 110 ff. and Food and Fiber Science, 27(2) 1995, pp. 183-197 and further references cited therein describe the use of dazomet granules and the mode of action of the released product methyl isothiocyanate
CH
3
—N═C═S (II)
(MITC), which functions as the actual biologically active agent. Accordingly, dazomet itself can be regarded merely so to speak as a prodrug precursor.
Comparatively little is known even now about the nature and activation of the release of MITC from dazomet in the soil. The literature does, however, reveal that the soil pH, transition metals or, for example, soil moisture and soil temperature all have a part to play. This is confirmed by our own studies.
The dazomet granules prepared in accordance with the abovementioned EP 0 618 912, although being substantially dust-free, have but a very limited influence over the release of MITC and are therefore unable to provide a completely satisfactory solution to one application problem: the control of active substance release, and especially the retarding thereof.
Thus it has been found when using such dazomet granules that, given high soil temperatures of more than 30° C. and sufficient soil moisture, MITC is released very quickly and then when the granules are incorporated into the soil, especially in glasshouse applications, MITC may lead to temporary mucosae and eye irritations in the absence of proper ventilation and use.
It would therefore be desirable for this utility to retard the release of MITC to a sufficient degree to give the personnel charged with applying the product sufficient time to leave the glasshouse before the active substance is released.
An alternative soil decontaminant, gaseous methyl bromide, has disadvantages in terms of its known ozone harmfulness.
Metam fluid and metam-sodium are of only limited glasshouse utility owing to their very rapid and strong propensity to evolve gas, or even, as for example in California, are no longer approved.
The “Montreal Protocol on Substances that deplete the Ozone Layer” in Part IV: Assessment of the Economic Viability of Methyl Bromide Alternatives, April 1997 Report Vol. II cites on page 260 the use of dazomet as a potential alternative for methyl bromide but points to problems in its application by untrained users.
It is an object of the present invention to provide crop protection granules based on the active substance tetrahydro-3,5-dimethyl-3,5-thiadiazine-2-thione in which there is delayed and/or controlled release of the active substance.
We have found that this object is achieved by crop protection granules based on the active substance tetrahydro-3,5-dimethyl-1,3,5-thiadiazine-2-thione which comprise an outer shell which makes up from 0.1 to 50% by weight of the overall weight of the granules and of which at least 50% by weight consists of sulfur compounds or sulfur itself.
The subclaims and the subsequent description reveal preferred embodiments of the invention.
The invention additionally relates to a method of combating nematodes, soil-dwelling insects, germinating plants, soil bacteria and soil fungi by treating the soil with an effective amount of from 1 to 1000 kg/ha of soil surface of the granules of the invention.
The invention gives preference to dazomet granules as obtained by the process described in EP 618 912, i.e. to products in whose preparation from 0.1 to 10 mol % of diaminoalkylene compounds R
1
NH—A—NHR (R, R
1
and A are as defined at the outset) are added. For further preparation details reference is made to EP 618 912.
The outer shell preferably makes up from 1 to 35 and, in particular, from 2 to 25% by weight of the granules.
Preferably from 55 to 100 and, with particular preference, from 75 to 100% by weight of the shell consists of sulfur compounds or elemental sulfur.
A particularly preferred shell material is elemental sulfur, especially those products which can be employed in the form of aqueous dispersions.
Thus it has surprisingly been found that aqueous sulfur dispersions, such as aqueous redispersion concentrates of the commercial product Kumulus® DF, are particularly suitable as shell constituents.
An advantage of using such shell materials is that they can be applied to the dazomet granules by the fluidized bed technique without the occurrence of disadvantages in processing, such as agglomeration, formation of coarse grains or disadvantages in terms of the abrasion behavior.
Such sulfur dispersions are preferably prepared by one of the following techniques:
Technique A
Sulfur suspension concentrates by aqueous grinding techniques from elemental sulfur with appropriate auxiliaries
Elemental sulfur, such as sulfur powder, is suspended in water, judiciously with the addition of wetting agents and dispersants and, if desired, with the addition of a binder. The still coarse sulfur suspension is then comminuted, preferably in plain or stirred ballmills with grinding media—for example, glass grinding media or other mineral or metallic grinding media—having a size (average diameter) of in general 0.1-30 mm, preferably 0.6-2 mm, until the average particle size is preferably less than 10 &mgr;m.
Technique B
Sulfur suspension concentrates from melt-spray sulfur granules redispersed in water
Melt-spray sulfur granules are obtained by melting elemental sulfur, such as sulfur powder, by heating it to temperatures of more than 120° C. and spraying the resulting melt, directly or following the addition of wetting agents and dispersants, in an appropriate spraying device, such as in a spray tower, generally with cooling, to form the spray sulfur granules.
Examples of suitable wetting agents and dispersants for both techniques are the following auxiliaries from the following classes of substance:
Fatty acid polyoxyethylene esters, such as lauryl alcohol polyoxyethylene ether acetate,
alkyl polyoxyethylene or polyoxypropylene ethers, such as those of isotridecyl alcohol, and fatty alcohol polyoxyethylene ethers,
alkylaryl alcohol polyoxyethylene ethers, such as octylphenol-polyoxyethylene ether or tributylphenol polyoxyethylene ether,
ethoxylated isooctyl-, octyl- or nonylphenol or castor oil, sorbitol esters,
arylsulfonic acids, alkylsulfonic acids, alkylsulfuric acids or their alkali metal, alkaline earth metal and ammonium salts, especially salts of arylsulfonic acids, examples being lignin-, phenol-, naphthaline- and dibutylnaphthalinesulfonic acids,
alkylsulfonic acids, alkylarylsulfonic acids, alkylsulfuric, lauryl ether sulfuric and fatty alcohol sulfuric acids, fatty acids, sulfated hexa-, hepta- and octadecanols and fatty alcohol glycol ethers,
condensates of sulfonated naphthaline and its derivatives with formaldehyde,
condensates of naphthalinesulfonic acids with phenol and formaldehyde, and
protein hydrolysates.
In addition, lignin sulfite waste liquors and methylcellulose are also particularly suitable.
Examples which may be mentioned here are:
Benzenesulfonic acid an
Kober Reiner
Probeck Erich
Schroeder Manfred
Sendhoff Norbert
Stadler Reinhold
BASF - Aktiengesellschaft
Keil & Weinkauf
Levy Neil S.
LandOfFree
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