# US 5,707,406 A · Method of manufacturing aluminum fluoride anhydride > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,707,406 A - Document ID: US5707406A - Status: Granted - Kind: A - Application number: 08/791,931 - Filed: 1997-01-29 - Granted: 1998-01-13 - Earliest claimed: 1993-05-06 - Assignees: Onoda Chemical Industry Co., Ltd. - Inventors: Motohiko Asano; Masahiro Numata; Koji Okamoto; Takashi Goda - Web page: https://patentgrep.com/patent/US5707406A ## CPC - C01F 7/50: Fluorides - C01P 2004/32: Spheres - C01P 2004/52: highly monodisperse size distribution - C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer - C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00}) - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract A method of manufacturing aluminum fluoride anhydride by means of a wet method. This method is featured in that a seed crystal of AlF.sub.3.3H.sub.2 O containing not more than 5% of fine particle 40 .mu.m or less in diameter is added into the super-saturated solution of aluminum fluoride in such a ratio that the total surface area of the seed crystal is in the range of 40-100 m.sup.2 per 1 kg of AlF.sub.3.3H.sub.2 O to be precipitated until an initial concentration of the super-saturated solution is reduced to 1.6%. The initial concentration of the super-saturated solution is adjusted to 8 to 15%. Resultant slurry is heated under agitation, thereby precipitating in batch-wise large AlF.sub.3.3H.sub.2 O particles which are then separated, dried and dehydrated. ## Claims ### Claim 1 A method of manufacturing aluminum fluoride anhydride having an average particle diameter of 100 .mu.m or more, which comprises the steps of: (a) preparing an initial super-saturated solution of aluminum fluoride; (b) preparing primary AlF.sub.3.3H.sub.2 O seed crystals containing not more than 5 weight % of fine particles of 40 .mu.m or less in particle diameter; (c) adding said AlF.sub.3.3H.sub.2 O seed crystals into the super-saturated solution of aluminum fluoride in an amount such that a total surface area of all the added seed crystals is in a range of 40-100 m.sup.2 per 1 kg of AlF.sub.3.3H.sub.2 O calculated as the amount of AlF.sub.3.3H.sub.2 O necessary to be precipitated from the initial super-saturated solution of AlF.sub.3 to reduce the concentration of AlF.sub.3 in the initial super-saturated solution to 1.6 weight %; thereafter, (d) if the concentration of the AlF.sub.3 dissolved in the resultant super-saturated solution after addition of said seed crystals is above 13 weight % or below 9 weight %, adjusting the concentration to 9 to 13 weight %; thereafter (e) heating the resultant aluminum fluoride super-saturated solution to a temperature ranging from 75.degree. to 106.degree. C.; thereafter (f) allowing crystals to precipitate from the resultant super-saturated solution of aluminum fluoride under agitation, using a batch crystallization method in a crystallizer; (g) repeating at least once the steps of (c) to (f) by using the crystals obtained in the step (f) and containing not more than 5 weight % of fine particle of 40 .mu.m or less in particle diameter as seed crystals; (h) separating AlF.sub.3.3H.sub.2 O having an average particle diameter of 100 .mu.m or more from a resultant slurry of AlF.sub.3.3H.sub.2 O after crystallization; (i) drying the AlF.sub.3.3H.sub.2 O thus separated; and (j) dehydrating the AlF.sub.3.3H.sub.2 O thus dried to remove combined water to produce aluminum fluoride anhydride; and wherein the aluminum fluoride anhydride has a fluidity factor "a" which is less than 0.135, where fluidity factor "a" is a constant defined by the following empirical equation: P/C=1/ab+P/a P . . . =pressure (Pa) C . . . =Degree of decrease in apparent volume (-) defined by C=(Vo-V)/Vo Vo=initial volume (m.sup.3) V=A volume under pressure (m.sup.3) a,b=Constants. 2. ### Claim 2 (depends on 1) The method according to claim 1, wherein for said heating step, the temperature ranges from 85.degree. to 95.degree. C. ### Claim 3 (depends on 1) The method according to claim 1, wherein in step (f), said resultant super-saturated solution of aluminum fluoride is agitated by using a blade so as to prevent AlF.sub.3.3H.sub.2 O from accumulating at the bottom of the crystallizer. ### Claim 4 (depends on 1) The method according to claim 1, wherein said seed crystals are spherical in shape. ### Claim 5 (depends on 1) The method according to claim 1, wherein said aluminum fluoride anhydride obtained after the dehydrating step contains 1% or less of particles passing through a 44 .mu.m sieve. ### Claim 6 (depends on 1) The method according to claim 1, wherein said AlF.sub.3.3H.sub.2 O seed crystals containing not more than 5 weight % of fine particles of 40 .mu.m or less in particle diameter are prepared from the slurry containing 30% or more of AlF.sub.3.3H.sub.2 O obtained as a result of crystallization step (f). ### Claim 7 (depends on 1) The method according to claim 1, wherein said AlF.sub.3.3H.sub.2 O seed crystals containing not more than 5 weight % of fine particles of 40 .mu.m or less in particle diameter are prepared from the filter cake obtained from a slurry resulting from the crystallization step (f). ### Claim 8 (depends on 1) The method according to claim 1, wherein said step (g) is repeated until 60 weight % or more of AlF.sub.3.3H.sub.2 O obtained from the crystallization is enlarged to have a particle diameter of 100 .mu.m or more. ### Claim 9 A method of manufacturing aluminum fluoride anhydride having a particle diameter of 100 .mu.m or more in average and, which comprises the steps of: preparing an initial super-saturated solution of aluminum fluoride; preparing AlF.sub.3.3H.sub.2 O seed crystals containing not more than 5 weight % of fine particles of 40 .mu.m or less in particle diameter; adding said AlF.sub.3.3H.sub.2 O seed crystals into the super-saturated solution of aluminum fluoride in an amount such that a total surface area of all the added seed crystals is in a range of 40-100 m.sup.2 per 1 kg of AlF.sub.3.3H.sub.2 O calculated as the amount of AlF.sub.3.3H.sub.2 O necessary to be precipitated from the initial super-saturated solution of AlF.sub.3 to reduce the concentration of AlF.sub.3 in the initial super-saturated solution to 1.6 weight %; thereafter, if the concentration of the AlF.sub.3 dissolved in the resultant super-saturated solution after the addition of said seed crystals is above 13 weight % or below 9 weight %, adjusting the concentration to 9 to 13 weight %; thereafter heating the resultant aluminum fluoride super-saturated solution to a temperature ranging from 75.degree. to 106.degree. C.; thereafter allowing crystals to precipitate from the resultant aluminum fluoride super-saturated solution, while agitating, by way of a batch crystallization method in a crystallizer; separating AlF.sub.3.3H.sub.2 O having an average particle diameter of 100 .mu.m or more from a resultant slurry of AlF.sub.3.3H.sub.2 O after crystallization; drying the AlF.sub.3.3H.sub.2 O thus separated; and dehydrating the AlF.sub.3.3H.sub.2 O thus dried to remove combined water to produce aluminum fluoride anhydride; and wherein the aluminum fluoride anhydride has a fluidity factor "a" which is 0.14 or less, where fluidity factor "a" is a constant defined by the following empirical equation: P/C=1/ab+P/a P=Pressure (Pa) C=Degree of decrease in apparent volume (-) defined by C=(Vo-V)/Vo Vo=initial volume (m.sup.3) V=A volume under pressure (m.sup.3) a,b=Constants. 10. ### Claim 10 (depends on 9) The method according to claim 9, wherein said aluminum fluoride anhydride is spherical in shape and smooth in surface texture. ### Claim 11 (depends on 9) The method according to claim 9, wherein said aluminum fluoride anhydride obtained after the dehydrating step contains 1 weight % or less of particles passing through a 44 .mu.m sieve. ### Claim 12 (depends on 9) The method according to claim 9, wherein for said heating step, the temperature ranges from 85.degree. to 95.degree. C. ### Claim 13 (depends on 9) The method according to claim 9, the crystal precipitation step, said resultant super-saturated solution of aluminum fluoride is agitated by using a blade so as to prevent AlF.sub.3.3H.sub.2 O from accumulating at the bottom of the crystallizer. ### Claim 14 (depends on 9) The method according to claim 9, wherein seed crystals having an average diameter of about 80 .mu.m are used so that large crystals having a particle diameter of 100 .mu.m or more are obtained in one crystallizing process.