Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Heavy metal containing doai
Reexamination Certificate
1999-02-19
2002-02-26
Dees, Jose G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Heavy metal containing doai
C424S400000, C424S489000, C424S499000, C424S502000, C514S597000, C514S769000, C514S772000, C514S777000, C514S784000, C514S785000, C514S788000, C514S951000
Reexamination Certificate
active
06350779
ABSTRACT:
The invention relates to a process for preparing a piece-form material comprising calcium formate of the formula Ca(HCOO)
2
, fine-grained calcium formate, with or without the addition of one or more auxiliaries with or without the admixture of one or more further application-promoting components is subjected to a compression and, if appropriate, the resulting material is then fed to a comminution and/or fractionation stage to establish defined particle sizes. The invention further relates to compressed calcium-formate-comprising material having a particle size range of 0.2-5 mm.
Calcium formate is a light crystalline solid, which is used commercially, for example, in the following fields:
additive in the animal nutrition field (pig, cattle and turkey feed)
use in the building material industry field (improving the hardening of cement, gypsum and jointing compounds, and also antifreezes for mortar)
preparation of formic acid
auxiliary in the leather industry
aid in the production of high-gloss papers
treatment of scrubbing waters in flue gas desulphurization
aid in ensilation.
Calcium formate is produced in various ways, for example by reacting formic acid with calcium hydroxide or by the action of carbon monoxide on calcium hydroxide. Syntheses of this type are described, for example, in Ullmann's Enzyklopädie der Technischen Chemie [Ullmann's Encyclopaedia of Industrial Chemistry] (4th edition), Vol. 7. pp. 366 and 370.
The most important industrial production of calcium formate is carried out in the course of various processes which are known in the literature for preparing polyols, in which calcium formate is obtained as by-product (cf. Ullmann, 5th edition, Vol. A 12, p. 29). The preparation of trimethylolpropane from n-butyraldehyde and formaldehyde using calcium hydroxide as base may be mentioned as an example here. In this process, calcium formate is produced as a coupled product.
Calcium formate may be crystallized, isolated and purified using techniques which are known in principle. Examples of crystallization techniques usable here which may be mentioned by way of example are the evaporative crystallization of aqueous solutions possibly comprising organic material, cooling crystallization and spray-drying. Examples of suitable isolation techniques which may be mentioned by way of example are filtration or centrifugation. Possible purification operations which may be mentioned as examples are redissolution, dispersion, washing and extraction with suitable solvents. If appropriate, one or more suitable drying steps follow such operations or sequences of operations, of which, as suitable processes, hot-air drying, contact drying and vacuum drying may be mentioned as examples.
Common to all these processes is the fact that they deliver polydisperse products which are distinguished by characteristic, more or less broad particle size distributions. In all known industrial processes for preparing calcium formate, significantly high proportions of the total crystals are present in particular in the fine-grained region at particle diameters <0.2 mm. However, for various applications, a product is preferably needed which has a particularly high proportion of coarse-grained particles as far as possible in piece form. The reasons for this can be, for example, certain requirements of occupational hygiene, according to which handling calcium formate having dust contents can pose problems which can only be remedied by additional technical measures which cause economic disadvantages. Other reasons are due to the physical behaviour of fine-grained calcium formate. If, for example, fine-grained calcium formate or calcium formate having high fine-grained contents is introduced into certain commercial coarse-grained structured or shaped animal feed or sililation components, this is frequently associated with considerable mixing problems and with undesirable separations in the further handling of the finished mixture. These effects can restrict the use of calcium formate which is advantageous per se in many fields of application. Although coarse-grained contents can be separated successfully using suitable techniques such as classification, screening and sifting, firstly this causes additional costs, and secondly the fine-grained contents remaining can be supplied to further use only with considerable additional expenditure, in that they are, for example, redissolved, crystallized, isolated and dried and then again fed to the fractionation process. Precisely in processes where calcium formate is only obtained as a by-product, it is frequently not technically or economically expedient to modify the isolation of the preferentially sought-after main product in such as manner that calcium formate arises in fractions which are as coarse-grained as possible.
To convert fine-grained or pulverulent solids into piece-form material, in principle various agglomeration techniques are available whose use can also be considered in principle in the case of crystalline calcium formate. However, experiments which have been carried out to moisten calcium formate, for example by adding small amounts of water in such a manner that larger crystal assemblies are produced on the basis of cohesion of fine particles, generally lead, owing to the hygroscopic properties of dry calcium formate, to the formation of undefined lumps in addition to fine-grained material in unchanged form. Owing to the extremely brittle behaviour of crystalline calcium formate, in addition, shaping processes for compression are not successful by themselves, since the particles produced in these processes have a tendency to crumble readily and as a result unwanted fine-grained contents are generated. Attempts to repress this effect by adding binder immediately fail due to the different application requirements which are made on account of the variety of uses of calcium formate and which frequently do not permit contamination by other additives.
With a view to preparing principally various animal feed products and sililation auxiliaries, there was therefore the object of preparing a calcium-formate-based coarse-grained material as far as possible in piece form which conforms with the requirements of having a particle size distribution which is as narrow as possible and therefore easy to process with a fine grain content which is simultaneously as low as possible. In addition, there was the object of finding a technically feasible economic path for the preparation of such a product. This object is achieved by the product according to the invention and the path according to the invention for its preparation.
It has surprisingly been found that, in contrast to current prejudices and experimental compacting which has proceeded unsuccessfully, piece-form calcium formate having satisfactory application properties can nevertheless be obtained if the heterodisperse fine-grained material which was typically obtained after isolation and purification as by-product of a process for preparing polyols, such as trimethylolethane, trimethylolpropane or pentaerythritol, is subjected to a compression, preferably a compacting, within a defined pressure range. If, for example, pressures are employed below the pressure range which is characteristic of the process according to the invention, piece-form calcium formate can be prepared without the addition of suitable auxiliaries only in comparatively fragile form which has, for example, extremely unfavourable storage properties, such as elevated breakage instability and increased hygroscopicity. If pressures are employed above the pressure range which is characteristic of the process according to the invention, unfortunately, firstly the economic efficiency suffers, secondly an extremely compact material is produced which has a markedly increased, undesirable stability to breakage and, as a result, processing disadvantages, such as lower dissolution rate, increased hardness, higher energy consumption for any downstream fragmentation required, and increased abrasion properties.
The inven
Baumgartner Hanspeter
Klausener Alexander
Linde Günter
Noack Achim
Bayer Aktiengesellschaft
Choi Frank
Dees Jos,e G.
Eyl Diderico van
Gil Joseph C.
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