JP2003507307A - Alkali metal fluoride and alkaline earth metal fluoride having flowability - Google Patents

Abstract

  (57) [Summary] A mixture comprising an alkali metal fluoride or an alkali metal fluoride or a mixture of two or more thereof and 2% by weight or less of silicic acid, preferably exothermic silicic acid. Furthermore, the use of the production process and the mixture in the production of high-purity metals, the use in silver brazing, the use as a catalyst in the conversion of organic compounds and the use as fluorinating agents for organic compounds are disclosed.

Description

Detailed Description of the Invention

The present invention relates to a flowable alkali metal fluoride, alkaline earth metal fluoride or a mixture of two or more thereof, a method for producing the same and use in producing a high-purity metal, use in silver brazing, It relates to the use as a catalyst in the reaction of organic compounds and as a fluorinating reagent for organic compounds.

Alkali metal fluorides and alkaline earth metal fluorides are important chemicals with versatile industrial applications. For example, anhydrous potassium fluoride is used as a flux in the production of high purity metals, in silver brazing, as a catalyst in organic synthesis and as a fluorinating reagent for organic compounds.

At room temperature, anhydrous potassium fluoride is a thermodynamically more stable hyperhydrate (KF).
* 2H ₂ O; KF * 4H ₂ O). Therefore, these compounds are strongly hygroscopic, and attention must be paid to atmospheric humidity during use.

Another undesirable property of potassium fluoride is its tendency to cure. Immediately after the production of potassium fluoride, it is in a normal state and has a perfect fluidity, but it hardens in a very short time and becomes a sticky and lumpy snow. During wrapping or fiber drum packing in polyethylene liners, potassium fluoride takes the form of a cardboard box or fiber drum and retains that form even after the jacket is removed. Therefore, this property makes handling of potassium fluoride very difficult, for example during filling of the reaction vessel through the manhole. To prevent baking, for example baking of potassium fluoride, to date, US Pat.
806, 332, as described in the introduction, finely divided compounds, such as talcum, mica, diatomite, hydroxyapatite, sodium sulfate, stearic acid or sodium polyacrylate, a mixture of fluoride and additives. Used in an amount of a few percent by weight. For the desired reduction of the baking tendency, it is necessary to add a few weight percent of the compound and the resulting alkali metal fluoride or alkaline earth metal fluoride, especially potassium fluoride, is highly contaminated, for example: It is not possible to achieve a purity requirement of more than 99% by weight of alkali metal fluoride and / or alkaline earth metal fluoride for some applications, such as the production of high purity metals. Furthermore, these additives have to be very evenly dispersed in the final product in order to exhibit full efficiency, but have proved infeasible for the mass production required. ing.

Other suggestions for preventing baking of potassium fluoride have been found in the above-mentioned US Pat. No. 4,806,33.
Has been done in 2. It describes a method of contacting potassium fluoride with gaseous carbon dioxide to prevent the curing of anhydrous potassium fluoride which adsorbs the gas.

With respect to the above-mentioned prior art, the object of the present invention is to provide a process for the production of free-flowing, preferably anhydrous alkali metal fluorides and / or alkaline earth metal fluorides, and the compounds themselves. . The process according to the invention is carried out in a simple manner and provides a product which is still free-flowing after storage for several months.

This object can be achieved by the process of the invention and the products obtained by this process. Accordingly, the present invention provides a mixture comprising an alkali metal fluoride or an alkaline earth metal fluoride or a mixture of two or more thereof and 2% by weight or less of silicic acid, preferably pyrogenic silicic acid, as well as a dry alkali metal fluoride. And a dry alkaline earth metal fluoride or a mixture of two or more thereof with 2% by weight or less of silicic acid, based on the total weight of the mixture.

The alkali metal fluoride and / or alkaline earth metal fluoride used in the present invention is not particularly limited. Preferably, the invention relates to a mixture comprising lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride and / or calcium fluoride, more preferably potassium fluoride. The content of alkali metal fluorides and / or alkaline earth metal fluorides, especially potassium fluoride, is preferably at least 99% by weight, more preferably at least 99.5% by weight.

The mixture according to the invention further comprises silicic acid, preferably pyrogenic silicic acid, more preferably hydrophobized pyrogenic silicic acid, in particular from 99.8% by weight, based on the total weight of silicic acid. Contains a large amount of silicon dioxide. This silicic acid is generally highly disperse, with about 50-
Very large BE of 400 m ² / g, preferably about 150-400 m ² / g and especially about 250-400 m ² / g
Provides T specific surface area. The silicic acid is preferably spherical particles composed of an amorphous substance having a diameter in the range of 27 to 40 nm, preferably 10 to 20 nm. Highly dispersed silicic acid, also known as amorphous pyrogenic silica, is commercially available under the tradename Aerosil®. Among these highly dispersed silicic acids,
Silica hydrophobized with silanes, such as dichlorodimethylsilane, is preferred. In particular, Aerosil (R) 130, Aerosil (R) 150, Aerosil (R) 200
, Aerosil (R) 300, Aerosil (R) 380, Aerosil (R) OX5
0, Aerosil (R) TT600, Aerosil (R) MOX80, Aerosil (R) MOX170, Aerosil (R) COK84, and Aerosil (R) R972 may be mentioned, among which Aerosil (R) ) R972 is preferred. In addition, Sip
Silicic acids marketed under the tradenames ernat® (Degussa) and Cab-O-Sil® can also be used.

In the mixture according to the invention, the silicic acid content is below 2% by weight, preferably 1% by weight
Hereafter, it is more preferably 0.5% by weight or less, and each value is based on the total weight of the mixture.

A particularly preferred mixture according to the invention comprises 99 to 99.8% by weight potassium fluoride and 0.2 to 1% by weight silicic acid, as described above. For some hard-tested applications, the mixture is virtually anhydrous, i.e. less than 0.3% by weight, preferably less than 0.2% by weight, based on the total weight of the mixture after spray drying. It is desirable to exhibit a water content that is less than 0.1% by weight.

As mentioned at the outset, in the process according to the invention for producing the mixtures according to the invention, the alkali metal fluorides and / or alkaline earth metal fluorides are used in dry form. The method for drying the fluoride is not particularly limited. Especially vacuum drying,
Circulating air drying, fluidized bed drying and spray drying can be mentioned, preferably spray drying of solutions containing alkali metal fluorides and / or alkaline earth metal fluorides is used. The spray drying is performed according to a conventionally known method, the inlet temperature of the spray drying is preferably in the range of 300 to 600 ° C., and the outlet temperature is 130.
It is in the range of to 190 ° C, preferably 150 to 170 ° C.

The invention further relates to the use of the mixtures according to the invention as catalysts for the reaction of organic compounds, in the brazing of silver, in the production of high-purity metals, especially tantalum, as fluorinating reagents for organic compounds, especially aromatic compounds. It relates to the use of the mixture prepared by the method of the invention.

[0014]   The invention will be described in several examples.

[0015]

Example 1 (Laboratory test) From a new product, 500 g of anhydrous potassium fluoride (water content <0.3% by weight) was quickly weighed to give 2 liters of polyethylene lining (low density polyethylene monofoil). , Thickness 100 μm, 1 g / m ² * d), sealed, and tabulated with the additives shown in Table 1.
Mixed in the amount shown in le1. The sample was subsequently stored in a laboratory hood at room temperature.

Two 500 g samples of potassium fluoride without additives (blind samples) were stored under the same conditions for comparison. At the beginning of the experiment, all samples were free of lumps and flowable. After 6 months, the samples were examined. For this, the sample was inverted several times and the flowability was compared with the control sample by visual judgment. In addition, the weight gain was measured by measuring the amount of water taken up through the polyethylene lining. After 6 months of storage, laboratory samples containing highly dispersed Aerosil® type silicic acid were
The flowability was maintained. Only a few lump formations could be detected. This mass could be easily broken with little force. In contrast, the samples containing calcium phosphate, Tamol® and poly (ethylene glycol) as additives, as well as the blind samples, hardened into a single mass. Under the influence of force, these samples were broken into large pieces, but no flow was observed.

[0017]   The experimental results are summarized in Table 1.

[0018]

[Table 1]

Example 2 (Production Experiment) An aqueous solution containing 37% potassium fluoride was dried in a spray dryer using hot air having an inlet temperature of 400 ° C. and an outlet temperature of 180 ° C. An exothermic Aerosil® 200 is weighed by a differential batch metering means placed after the outlet of the spray tower and fed to potassium fluoride on the way through the conveying screw in the course of cooling down to 0.5% by weight of dioxide. It was mixed with fluoride in a mixer in such a way that a mixture with a silicon content was obtained. 25 kg of the resulting mixture was stored for 6 months in a fiber drum sealed with polyethylene lining. After a storage period of 6 months, this material was treated with pyrogenic silicic acid to obtain a water uptake of about 1% by weight and good flowability. The comparative sample without silicic acid as additive stored under the same conditions cured. Under the influence of force, the product was broken into large chunks.

Sieve analysis of the product revealed that the mass of comparative material could not be completely destroyed during sieving. For the material without silicic acid, the sieve residue on the 75 μm woven wire increased from 11% at the beginning of the storage period to 23% at the end of the storage period. For the Aerosil® treated material, sieving showed no significant changes after a storage period of 6 months. The results of the sieve analysis are summarized in Table 2.

[0021]

[Table 2]

[Procedure amendment]

[Submission date] February 21, 2002 (2002.2.21)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Contents of correction]

[Claims]

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, C N, CR, CU, CZ, DK, DM, EE, ES, FI , GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, K Z, LC, LK, LR, LS, LT, LU, LV, MA , MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, S K, SL, TJ, TM, TR, TT, TZ, UA, UG , US, UZ, VN, YU, ZA, ZW

Claims (8)

[Claims] 1. A mixture comprising a mixture containing silicic acid, preferably 2% by weight or less of pyrogenic silicic acid, and an alkali metal fluoride, an alkaline earth metal fluoride or two or more thereof. 2. A mixture according to claim 1, comprising potassium fluoride as the alkyl metal fluoride. 3. Mixture according to claim 1 or 2, characterized in that it comprises 0.2 to 2% by weight of silicic acid, based on the total weight of the mixture. 4. The mixture according to any one of claims 1 to 4, wherein 99 to 99.8% by weight of potassium fluoride and 0.2 to 1% by weight, respectively, relative to the total weight of the mixture.
A mixture containing silicic acid of. 5. The method for producing the mixture according to claim 1, wherein the dry alkali metal fluoride, the dry alkaline earth metal fluoride or a dry mixture of two or more thereof is used. A method comprising mixing with 2% by weight or less of silicic acid, based on the total weight of the mixture. 6. The method according to claim 5, wherein the dry alkali metal fluoride or dry alkaline earth metal fluoride or a dry mixture of two or more thereof is alkali metal fluoride or alkaline earth metal fluoride. Obtained by spray drying a solution containing a compound or a mixture of two or more thereof. 7. The method according to claim 6, wherein the spray drying is 300 to 600 ° C.
And an outlet temperature in the range of 130 to 190 ° C. 8. A mixture according to any one of claims 1 to 4 or claims 5 to 7.
The use of a mixture, which can be prepared by the method according to any one of claims 1 to 3, in the manufacture of high purity metals, in silver brazing, as a catalyst in the reaction of organic compounds,
And use as a fluorinating reagent for organic compounds.