Antimony trioxide,Antimony trioxide Masterbatch: July 2007

Tuesday, July 31, 2007

[+/-] : Magnesium price to increase on a high freight

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Friday, July 27, 2007

[+/-] : Global antimony market to reach 169,000 mt by 2010

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Antimony trioxide is a major compound used in flame retardant formulations in plastic, textile, paint, and rubber industries. Worldwide antimony market is characterized by slow growth and a significant decline in prices in the past few years. Decline in demand forced several producers to cut down production and diversify their business. Price control measures taken by China, the largest producer of antimony, are likely to show a considerable impact on the market.

China is the leading antimony producer accounting for over 85% of global antimony and antimony trioxide market mine production, as stated by Global Industry Analysts, Inc. Other major producers include South Africa, Bolivia, Russia, Tajikistan, and Kyrgyzstan. Antimony trioxide is a major compound used in flame retardant formulations in plastic, textile, paint and rubber industries. Tajikistan is projected to be the fastest growing region with a CAGR of about 4.5% over the ten-year analysis period. Global antimony demand is primarily derived from the flame retardant sector that consumes 60-65% of the global antimony and 90% of global antimony trioxide produce. Plastics sector in Asia also forms a key consumer of antimony. As much as 80% of the Japanese output of antimony trioxide is consumed by the flame retardant sector. Antimony trioxide demand is forecast to surpass antimony metal demand.

Key players dominating the global antimony and antimony trioxide market include Gredmann Group, Hsikwangshan Twinkling Star, Metorex, Nanning Antimony Product Factory, SICA, United States Antimony Corporation, and Guangdong Jiefu.

＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊
DONGGUAN JIEFU FLAME-RETARDED MATERIALS CO.,LTD
Sam Xu
Tel: 86-755-83474911
Fax: 86-755-83474980
Mobile:13929211059

E-mail: xubiao_1996(at)hotmail.com samjiefu(at)gmail.com
Add: jiefu industrial park shuiping industrail district dalang town dongguan GD,P.R.C
blog:http://antimony-trioxide.blogspot.com
website:http://www.jiefu.com

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Thursday, July 26, 2007

[+/-] : sell antimony trioxide,antimony ingot

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[+/-] : Surface-modified antimony trioxide particles

publish Metal Supplier at 2:00 AM 0 comment

Fire retardant compositions comprising organic polymer, organic fire retardant compound and particles of antimony oxide surface-modified with poly(dialkylsiloxane) or condensation residue thereof, often exhibit enhanced physical properties as compared with similar compositions employing untreated antimony oxide particles
Particles of antimony oxide, usually in conjunction with one or more organic fire retardant compounds, have been incorporated with organic polymers to provide a composition having improved fire retardant properties as compared with the organic polymer itself. While enhancing the fire retardant properties of the composition, the antimony oxide particles often have an adverse effect on other properties, particularly physical properties such as tensile strength, flexural strength, flexural modulus, impact strength and heat distortion temperature.

Various suggestions have been made in the literature for surface-modification of antimony oxide particles to improve the physical properties of the composition while still enjoying the fire retardant benefits provided by antimony oxide. Notable among these is U.S. Pat. No. 4,394,469 which describes surface-modification of antimony oxide particles with polysiloxanes represented by the formula: ##STR1## where R, R' and R" may, among others, be alkyl. The sum of a and b is from 2 to 1000, but the patent unequivocally requires that the ratio a/b must be more than 0.5. Indeed, the patent indicates a preference for b to be equal to zero.

It has now been found that particles of antimony oxide may be treated with poly(dialkylsiloxane) to produce surface-modified antimony oxide particles which provide fire retardancy to organic polymer compositions and which provide enhanced physical properties, particularly impact strength and heat distortion temperature, to such compositions as compared to those provided by untreated antimony oxide particles. The poly(dialkylsiloxane) employed in treating the antimony oxide particles according to this invention have substantially no, if any at all, hydrogen bonded directly to silicon atoms and they have substantially no, if any at all, silicon atoms bonded directly to other silicon atoms. They do have, however, a small amount of hydroxyl, methoxy, and/or ethoxy functionality which is essential for their function in the invention.

Accordingly, one embodiment of the invention is particles of antimony oxide surface-modified with poly(dialkylsiloxane) or condensation residue thereof, wherein the poly(dialkylsiloxane) is represented by the formula ##STR2## in which: (a) each R.sub.1 and R.sub.2 are alkyl groups, (b) the average value of i is in the range of from 0 to 2, and (c) the average value of n is such that the number average molecular weight of said poly(dialkylsiloxane) is in the range of from about 700 to about 5000.

The value of i may vary in the range indicated depending upon whether the terminal groups (i.e., the oxygen-containing groups attached to the first and last silicon atoms of the chain) of individual compounds in the mixture are hydroxyl, methoxy, or ethoxy.

The two terminal groups of any individual molecule may be the same or different. However in mixtures of molecules which are characteristic of the poly(dialkylsiloxanes), the average identities of the two terminal groups may be taken as the same.

When the value of i is zero, the terminal groups of Formula I are hydroxyl. When the value of i is one, the terminal groups are methoxy. When the value of i is two, the terminal groups are ethoxy. Although the value of i will independently be 0, 1, or 2 for any individual terminal group of a particular molecule, the average value of i for mixtures may be any number in the range of from 0 to 2, including numbers which are integers and numbers which are not integers. In many cases, the average value of i is in the range of from 0 to 1. Preferably, the average value of i is zero or one. It is especially preferred that the average value of i be zero. The average value of i may be determined analytically or by a knowledge of the starting materials used to prepare the poly(dialkylsiloxane).

The value of n for any particular compound will be a positive integer, while the average value of n for a mixture of compounds constituting the poly(dialkylsiloxane) may be a positive integer or a positive number which is not an integer. The average value of n is calculated from the number average molecular weight. The number average molecular weight may be found experimentally or it may be calculated from the distribution of individual compounds using the equalities: ##EQU1## where M.sub.n is the number average molecular weight;

M.sub.j is the molecular weight of molecules of species j;

N.sub.j is the number of molecules of species j;

w.sub.j is the mass, expressed in grams, of molecules of species j; and

m.sub.j is the mass, expressed in gram-moles, of molecules of species j.

While the number average molecular weight of the poly(dialkylsiloxane) is usually in the range of from about 700 to about 5000, it is often in the range of from about 1000 to about 3000. A number average molecular weight in the range of from about 1500 to about 2000 is preferred. Number average molecular weights of about 1700 are especially preferred.

The alkyl groups of the poly(dialkylsiloxane) are generally lower alkyl groups containing from 1 to about 4 carbon atoms. In most cases the alkyl groups are methyl, ethyl, or methyl and ethyl. It is preferred that the alkyl groups be substantially all methyl.

The percent by weight of the terminal groups in the poly(dialkylsiloxane) may be calculated from the formula ##EQU2##

Although it is not desired to be bound by any theory, it is believed that the surfaces of antimony oxide particles have hydroxyl groups attached to antimony atoms. When the poly(dialkylsiloxane) is applied to the particles and heated, it is further believed that at least some of the terminal groups of the poly(dialkylsiloxane) condense with at least some of the hydroxyls of the particle surface to form ##STR3## bonds and evolve water and/or alcohol, depending upon the identities of the terminal groups. It is also believed that some of the terminal groups of the poly(dialkylsiloxane) condense with other terminal groups of the same or different poly(dialkylsiloxane) molecule to form siloxane bonds and evolve water and/or alcohol. Ring structures, linear structures (including those of increased molecular weight) and, if some poly(siloxane) having hydroxy and/or alkoxy functionality greater than two is also present, network structures may result.

Whether the antimony oxide particles are at least partially coated with a film or whether the particles exhibit chains or loops of poly(dialkylsiloxane) that extend outwardly from the particles of antimony oxide and into the organic polymer matrix upon compounding with organic polymer is not known. It is believed, however, that ##STR4## bonding between the particle and the poly(dialkylsiloxane) structure does, at least in part, occur.

The poly(dialkylsiloxanes) of Formula I are themselves well known, and many of them are items of commerce. See, for example, Encyclopedia of Polymer Science and Technology, volume 12, John Wiley & Sons, Inc., New York (1970), pages 472-482, 486-487, 497-499, and 519-526, the disclosures of which are incorporated herein by reference.

The particles of antimony oxide to be treated with the poly(dialkylsiloxane) usually have equivalent spherical diameters less than about 11 micrometers, although a small fraction may have equivalent spherical diameters above this value. Often the equivalent spherical diameters are essentially in the range of from about 0.1 to about 10 micrometers. Equivalent spherical diameters in the range of from about 0.3 to about 5 micrometers are preferred. A small fraction of fines, that is, particles having equivalent spherical diameters less than the lower value stated in either range, is frequently present. The equivalent spherical diameter of a particle, as used herein and in the claims, is that determined using a Sedigraph 5000D particle size distribution analyzer (Micromeritics Instrument Corporation) in accordance with the accompanying instruction manual. Briefly, the instrument obtains localized density as the particles settle in a liquid. From this and the settling rate, and assuming the particles are spheres, the equivalent spherical diameters are calculated.

Antimony trioxide and antimony pentoxide are the common antimony oxides and particles of either or both may be used in the invention. Antimony trioxide particles are preferred.

The amount of poly(dialkylsiloxane) or condensation residue thereof remaining on the particles after treatment can vary widely. Ordinarily the poly(dialkylsiloxane) or condensation residue thereof constitutes from about 0.1 to about 15 weight percent of the surface-modified antimony oxide particles. From about 0.5 to about 5 percent by weight is preferred.

A class of poly(dialkylsiloxanes) which is especially useful in the present invention is represented by the formula ##STR5## in which: (a) the average value of x is in the range of from 0 to 2, (b) the average value of y is in the range of from 0 to 1, and (c) the average value of m is such that the number average molecular weight of the poly(dialkylsiloxane) is in the range of from about 700 to about 5000.

The average value of x is usually in the range of from 0 to 1. Preferably the average value of x is either zero or one. It is especially preferred that the average value of x be zero.

In any individual molecule, the two alkyl groups attached to any silicon atom may be the same or different, and similarly the alkyl groups attached to different silicon atoms may be the same of different. However in mixtures of molecules which are characteristic of the poly(dialkylsiloxanes), the average identities of the alkyl groups may be taken as the same.

When the value of y is zero, the alkyl groups of Formula II are methyl. When the value of y is one, the alkyl groups are ethyl. Although the value of y will independently be 0 or 1 for any individual alkyl group, the average value of y for a multiplicity of alkyl groups may be any number in the range of from 0 to 1, including integers and fractional numbers. It is preferred that the average value of y be zero. The average value of y may be determined analytically or by a knowledge of the starting materials used to prepare the poly(dialkylsiloxane).

The principles discussed above in respect of the average values of i and n, are also applicable to the average values of x and m, respectively. The ranges of number average molecular weight discussed above are also applicable to the poly(dialkylsiloxane) of Formula II.

The surface-modified antimony oxide particles of the invention may be prepared by admixing antimony oxide particles with the poly(dialkylsiloxane). Uniformity of distribution of the poly(dialkylsiloxane) is favored by the use of high shear and vigorous agitation during mixing. When it is desired to reduce the viscosity of the poly(dialkylsiloxane), inert solvent may be included. Examples of suitable inert solvents include aromatic hydrocarbons such as toluene, xylene, and the like, chlorinated aromatic hydrocarbons such as chlorobenzene and the like, and/or chlorinated aliphatic hydrocarbons such as 1,2-dichloroethane and the like. When used, the inert solvent may be removed from the surface modified particles by evaporation at ambient or elevated temperatures. The relative amounts of antimony oxide particles and poly(dialkylsiloxane) which are admixed may vary considerably, but usually the weight ratio of the poly(dialkylsiloxane) to the antimony oxide particles used in forming the surface-modified particles is in the range of from about 0.1:100 to about 18:100. A weight ratio in the range of from about 0.5:100 to about 6:100 is preferred.

A small amount of ammonia and/or amine may, if desired, be included with the liquid admixed with the antimony oxide particles, or otherwise introduced to the mixture, in order to catalyze the condensation of hydroxyl groups as discussed more fully below. When present, the amount of ammonia and/or amine employed may vary considerably, but preferably from about 0.1 to about 0.2 percent by weight of the antimony oxide particles is used.

After mixing, the treated particles are usually heated at temperatures ordinarily in the range of from about 50.degree. C. to about 250.degree. C. to condense at least some the poly(dialkylsiloxane) with at least some of the surface hydroxyl groups of the particles. In general, the presence of ammonia and/or amine permits the condensation reaction to proceed at lower temperatures than if ammonia and amine are absent. When ammonia and/or amine is present, heating is usually conducted at temperatures in the range of from about 50.degree. C. to about 100.degree. C. From about 60.degree. C. to about 70.degree. C. is preferred. When ammonia and amine are absent, heating is typically conducted at temperatures in the range of from about 160.degree. C. to about 220.degree. C. From about 180.degree. C. to about 200.degree. C. is preferred. The duration of heating may be widely varied, but often heating is conducted from about 1 to about 5 hours. From about 11/2 to about 21/2 hours is preferred.

Another embodiment of the invention is a composition comprising organic polymer, organic fire retardant compound and particles of antimony oxide surface-modified with poly(dialkylsiloxane) or condensation residue thereof, which surface-modified particles have been earlier described.

The organic polymer may be flammable or non-flammable, but usually it is flammable. Typically the organic polymer is thermoplastic, but it may be thermosetting. The organic polymer may be a homopolymer, a copolymer, a terpolymer, an interpolymer, or a mixture of polymers. Examples of polymers which may be used include acrylonitrile-butadiene-styrene interpolymer or graft polymer, polystyrene, high density poly-ethylene, low density polyethylene, polyesters, polyamides, and polycar-bonates. The preferred organic polymers are acrylonitrile-butadiene-styrene graft polymer, poly(ethylene terephthalate), polypropylene, and polyamides.

The amounts of surface-modified antimony oxide particles which are present in compositions of the invention are subject to wide variation. Ordinarily the weight ratio of the surface-modified particles to the organic polymer is in the range of from about 0.5:100 to about 30:100. In many cases the weight ratio is in the range of from about 1:100 to about 15:100. A weight ratio in the range of from about 1.5:100 to about 10:100 is preferred.

The types of organic fire retardant compounds which may be used in the compositions of the invention may be widely varied. In most, but not all, cases the organic fire retardant compound is halogen-containing organic fire retardant compound. Of these, chlorine-containing organic fire retardant compound and bromine-containing organic fire retardant compound are preferred. Bromine-containing organic fire retardant compound is preferred. Only one organic fire retardant compound or a mixture of such compounds may be employed as desired.

Examples of organic fire retardant compounds which may be used include octabromodiphenyl oxide, decabromodiphenyl oxide, 1,2-bis(tribromophenoxy)ethane, N-methylhexabromodiphenylamine, poly[2,2-bis(bromomethyl)trimethylene carbonate], and any of the usual halogen-containing organic fire retardants.

The amounts of organic fire retardant compound present in the compositions of the invention may also be widely varied. Ordinarily the weight ratio of organic fire retardant compound to organic polymer is in the range of from about 1:100 to about 40:100. In many instances the weight ratio is in the range of from about 2:100 to about 30:100. A weight ratio in the range of from about 4:100 to about 25:100 is preferred.

One or more other materials which increase fire retardancy may optionally also be present in the composition. Examples of such materials include zinc oxide, zinc borate, boric acid, borax, and ferric oxide. The amounts of these materials are also subject to wide variation. When used, they are usually present in the composition of the invention in an amount in the range of from about 0.1 to about 15 percent by weight. An amount in the range of from about 1 percent to about 10 percent by weight is preferred.

The compositions of the invention may optionally contain plasticizers, pigments, dyes, tints, antioxidants, visible light stabilizers, ultraviolet light stabilizers, resinous pigment dispersants or grinding vehicles, and the like.

The listing of optional ingredients discussed above is by no means exhaustive. These and other ingredients may be employed in their customary amounts for their customary purposes so long as they are not antagonistic to good polymer formulating practice.

The compositions of the invention have fire retardant characteristics and find many uses. Typically, they may be extruded into fibers, films or other shapes, or molded, shaped or formed into substantially any form. Many of the compositions may be used as adhesives. Where the polymers of the composition are soluble in solvent or are dispersible in liquid nonsolvents such as water, organic nonsolvent or miscible systems of water and organic liquid, the composition may be employed in coating compositions.

The invention is further described in conjunction with the following examples which are to be considered illustrative rather than limiting, and in which all parts are parts by weight and all percentages are percentages by weight unless otherwise specified.

EXAMPLE I

A solution was formed by admixing 1.38 grams of poly(dimethylsiloxane)diol of number average molecular weight about 1700 and containing about 2 percent hydroxyl by weight (Silicone Fluid F-212; SWS Silicones Corporation) with 100 milliliters of toluene. A one-liter, threenecked flask equipped with a stirrer was charged with 275 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles and the mixture was stirred. One hundred milliliters of toluene was added to form a fairly thick fluid slurry. The flask was placed in a heated oil bath and the mixture was stirred while the temperature of the oil bath was increased from about 65.degree. C. to about 200.degree. C. Stirring was then continued for 2 hours while the temperature of the oil bath was held in the range of from about 180.degree. C. to about 200.degree. C. Volatile materials were allowed to escape from the flask during the heating. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask after removal of the stirrer weighed 270 grams and contained about 0.5 percent by weight poly(dimethylsiloxane)diol or condensation residue thereof.

EXAMPLE II

Five grams of Silicone Fluid F-212 was admixed with 100 milliliters of toluene to form a solution. A one-liter, three necked flask equipped as in Example I was charged with 250 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles and the mixture was stirred while heating the flask in an oil bath. As the temperature of the oil bath rose from about 100.degree. C. to about 190.degree. C. and volatile materials were allowed to escape from the flask, a paste formed which was difficult to stir. Stirring was nevertheless continued for 2 hours while the temperature of the oil bath was held at 170.degree. C. to 180.degree. C. and while further volatile materials were allowed to escape. The flask was then removed from the oil bath and cooled. The surface-modified particles in the flask after removal of the stirrer weighed 254.9 grams and contained about 2 percent by weight poly(dimethylsiloxane)diol or condensation residue thereof.

EXAMPLE III

Eleven grams of Silicone Fluid F-212 was admixed with 100 milliliters of toluene to form a solution. A one-liter, three-necked flask equipped as in Example I was charged with 275 grams of antimony trioxide having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles. The flask was placed in a heated oil bath and the mixture was stirred while the temperature of the oil bath was increased from about 120.degree. C. to between 180.degree. C. and 190.degree. C. Stirring was then continued for 2 hours while the temperature of the oil bath was held in the range of from about 170.degree. C. to about 190.degree. C. During heating in the oil bath volatile materials were allowed to escape from the flask. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask after withdrawal of the stirrer weighed 286.2 grams and contained about 4 percent by weight poly(dimethylsiloxane)diol or condensation residue thereof.

EXAMPLE IV

A solution was formed by admixing 22 grams of Silicone Fluid F-212 and 200 milliliters of toluene. A one-liter, three-necked flask equipped as in Example I was charged with 275 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles. The flask was placed in a heated oil bath and the mixture was stirred while heating in the manner of Example I. Volatile materials were allowed to escape from the flask during heating. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask contained about 7 percent by weight poly(dimethylsiloxane)diol or condensation residue thereof.

EXAMPLE V

A solution was formed by admixing 5.5 grams of dialkoxy-terminated poly(dialkylsiloxane) of number average molecular weight about 1500 (Silicone Fluid F-540; SWS Silicones Corporation) with 100 milliliters of toluene. Silicone Fluid F-540 is dialkoxy-terminated poly(dialkylsiloxane) in which the terminal groups are methoxy and/or ethoxy groups and in which about 3 to about 4 percent by number of the alkyl groups attached to the silicon atoms are octadecyl groups with the remainder being methyl groups. A one-liter, three-necked flask equipped as in Example I was charged with 275 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles. The flask was placed in a heated oil bath and the mixture was stirred while heating in the manner of Example III. Volatile materials were allowed to escape from the flask during heating. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask after withdrawal of the stirrer weighed 276.7 grams and contained about 2 percent by weight dialkoxy-terminated poly(dialkylsiloxane) or condensation residue thereof.

EXAMPLE VI

A solution was formed by admixing 11.0 grams of Silicone Fluid F-540 with 100 milliliters of toluene. A one-liter, three-necked flask equipped as in Example I was charged with 275 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The solution was added to the antimony trioxide particles. The flask was placed in a heated oil bath and the mixture was stirred while heating in the manner of Example III. Volatile materials were allowed to escape from the flask during heating. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask after withdrawal of the stirrer weighed 280 grams and contained about 4 percent by weight dialkoxy-terminated poly(dialkylsiloxane) or condensation residue thereof.

EXAMPLE VII

A two-liter, three-necked flask equipped as in Example I was charged with 500 grams of antimony trioxide particles having equivalent spherical diameters of from about 0.2 to about 4 micrometers. The flask was placed in a heated oil bath and the antimony oxide particles were stirred for about 15 to 20 minutes while the temperature of the oil bath was held at 140.degree. C. to 195.degree. C. The stirring caused the antimony trioxide particles to become well fluidized with air. Over a period of 31/2 hours, 9.7 grams of Silicone Fluid F-212 was slowly added dropwise from an addition funnel while the temperature of the oil bath was held at 140.degree. C. to 195.degree. C. Upon completion of the addition, the temperature of the oil bath was held at about 195.degree. C. while stirring was continued for 11/2 hours. Volatile materials were allowed to escape from the flask during heating. The flask was removed from the oil bath and cooled. The surface-modified particles in the flask after withdrawal of the stirrer weighed 508.7 grams and contained about 2 percent by weight poly(dimethylsiloxane)diol or condensation residue thereof.

EXAMPLE VIII

A series of compositions, each containing 76.34 percent by weight acrylonitrile-butadiene-styrene graft polymer (hereinafter "ABS"), 17.74 percent by weight 1,2-bis(2,4,6-tribromophenoxy)ethane (hereinafter "TBPE", and 5.92 percent by weight antimony trioxide particles (either surface-modified or untreated), was tested for fire retardance and for physical properties. For each of the compositions tested, ABS was introduced into a mixer and melted. A mixture of the antimony oxide particles and the TBPE was added to the melt and the materials were mixed until uniform to produce the composition. After cooling, each composition was chopped into small pieces and injection molded into bars. The bars were tested for flammability in accordance with the procedure of Vertical Burning Test 94, dated Feb. 1, 1974, of Underwriters Laboratories, Inc., and in accordance with Standard Method of Test for Flammability of Plastics Using the Oxygen Index Method, ASTM Standard Method D 2863-70, American Society for Testing and Materials. Five bars of each composition were tested for physical properties. The identifies of the antimony trioxide particles, the results of flammability testing and the results of physical testing are shown in Table 1. The values reported for physical testing are mean values and each is followed by the standard deviation. The untreated antimony trioxide particles had equivalent shperical diameters of from about 0.2 to about 4 micrometers.

TABLE 1
__________________________________________________________________________
Antimony Trioxide Particles
Untreated
Example II
Example III
Example V
Example VI
__________________________________________________________________________
Tensile Strength, megapascals
39.921 .+-. 0.207
36.060 .+-. 0.207
35.232 .+-. 0.138
38.817 .+-. 0.207
39.921 .+-. 0.276
Flexural Strength, megapascals
74.257 .+-. 0.276
69.223 .+-. 0.276
68.810 .+-. 0.276
71.637 .+-. 0.345
74.325 .+-. 0.345
Flexural Modulus, megapascals
2530 .+-. 21
2441 .+-. 28
2482 .+-. 34
2475 .+-. 14
2510 .+-. 34
Notched Izod Impact Strength,
171.9 .+-. 19.8
214.0 .+-. 25.1
227.9 .+-. 25.6
195.9 .+-. 18.1
176.7 .+-. 16.0
newton-meters/meter
Heat Distortion Temperature
61.75 66.50 66.50 67.75 68.0
(264 psi; 1820 kPa), .degree.C.
Specific Gravity
1.2858 1.2846 1.2858 1.2884 1.2880
Melt Index (Condition G),
2.778 2.632 2.721 2.512 2.792
grams/10 minutes
UL-94 Classification
V-2 V-2 V-2 V-2 V-2
UL-94 After Flame Time,
6.7 6.8 1.8 1.5 2.1
seconds
__________________________________________________________________________

EXAMPLE IX

A second series of compositions were prepared and tested for physical properties according to the procedure of Example VIII. The identities of the antimony trioxide particles and the results of physical testing are shown in Table 2.

TABLE 2
______________________________________
Antimony Trioxide Particles
Untreated Example I
______________________________________
Tensile Strength, megapascals
41.989 37.990
Flexural Strength, megapascals
73.429 72.809
Flexural Modulus, megapascals
2448 2537
Notched Izod Impact Strength,
152.7 171.3
newton-meters/meter
Heat Distortion Temperature
66.5 67.8
(264 psi; 1820 kPa), .degree.C.
Specific Gravity 1.221 1.223
Melt Index (Condition G),
2.63 2.74
grams/10 minutes
______________________________________

The data of Examples VIII and IX show that the values of Notched Izod Impact Strength and Heat Distortion Temperature were substantially greater for compositions formulated with surface-modified antimony trioxide particles according to the invention than for compositions formulated with untreated antimony oxide particles.

The milling of antimony oxide with poly(ethylene terephthalate) has been observed to often result in decreases in intrinsic viscosity and various physical properties. It is believed that the antimony oxide catalytically causes scission of ester bonds of the poly(ethylene terephthalate) and that formulation of the surface-modified antimony oxide particles of the invention with poly(ethylene terephthalate) will result in more stable compositions.

Although the present invention has been described with reference to specific details of certain embodiments thereof, it is not intended that such details should be regarded as limitations upon the scope of the invention except insofar as they are included in the accompanying claims.

＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊
DONGGUAN JIEFU FLAME-RETARDED MATERIALS CO.,LTD
Sam Xu
Tel: 86-755-83474911
Fax: 86-755-83474980
Mobile:13929211059

E-mail: xubiao_1996(at)hotmail.com samjiefu(at)gmail.com
Add: jiefu industrial park shuiping industrail district dalang town dongguan GD,P.R.C
blog:http://antimony-trioxide.blogspot.com
website:http://www.jiefu.com

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[+/-] : Hydrometallurgical process for the production of antimony

publish Metal Supplier at 1:54 AM 0 comment

A hydrometallurgical process for pollution-free recovery of metallic antimony from stibnite and other antimony-containing materials by (a) reduction of ferric chloride by such materials to produce ferric chloride and antimony (III) chloride, (b) recovery of metallic antimony, preferably by electrolysis, (c) regeneration of the ferric chloride, and (d) purge of impurities. Optionally, the metallic antimony thus produced may be subsequently oxidized if desired to produce high purity antimony oxide. The process is amenable to cyclical operation.
The most important source of antimony is ores containing the mineral stibnite, antimony trisulfide (Sb.sub.2 S.sub.3). In deposits where stibnite has been exposed to oxidation, a number of oxide minerals may be formed; these include stibiconite (Sb.sub.3 O.sub.6 (OH)), cervantite (Sb.sub.2 O.sub.4 or Sb.sub.2 O.sub.3 -- Sb.sub.2 O.sub.5), valentenite (Sb.sub.2 O.sub.3), senarmonite (Sb.sub.2 O.sub.3), and kermasite (2 Sb.sub.2 S.sub.3 -- Sb.sub.2 O.sub.3) an oxysulfide. Occasionally, native metallic antimony is also found associated with these deposits.

Conventionally, metallic antimony is recovered from these materials or from concentrates prepared therefrom by iron precipitation, direct smelting, or by smelting of oxides formed by roasting thereof. The choice of the pyrometallurgical process steps selected is dictated by the characteristics and quality of the feedstock available and the product(s) desired. The application of any of these pyrometallurgical processes in the production of metallic antimony or high grade antimony oxide results in atmospheric pollution and substantial direct loss of contained antimony.

Pollutants introduced into the atmosphere include suspended paticulates, volatilized antimony trioxide, and gaseous oxides of sulfur. Of these air contaminants, it has been found that the sulfur oxides are the most difficult to control. Meeting existing and proposed air quality control regulations and standards, therefore, is becoming increasingly difficult. The process disclosed herein involves the production of no gaseous discharge stream; hence none of the above-enumerated problems are encountered or involved. The enhanced recovery of the antimony from the processed ore and the elimination of atmospheric-pollutants are readily apparent advantages of this process.

Additionally, substantial losses of antimony content in solid residues, such as liquation residues and slags, of pyrometallurgical processes is generally encountered when these techniques are practiced. Laboratory data obtained for reactions in the process herein disclosed indicate that recoveries between 95 and 100 percent of the contained antimony content in the feedstock are reasonable and practical.

Various attempts have been made in the prior art to devise a successful commercial hydrometallurgical process for producing metallic antimony.

While the desirable characteristics of an economically feasible hydrometallurgical process have long been recognized, the successful development of a commercial process has eluded the prior at. Attempts at developing a commercial process utilizing a ferric chloride as a lixiviant for antimony are disclosed in Bonneville, British Pat. No. 2203 (1870); Butterfield, British Pat. No. 9052 (1896); and Tugov, "Hydrometallurgical Method for Obtaining Metallic Antimony from Concentrates," International Chemical Engineering, V: 1, pp. 5 - 8 (January, 1965).

The Butterfield patent and the Tugov article were expressly concerned with recovery of metallic antimony, but the methods disclosed in both references are unsatisfactory commercially because of their requirement of the use of scrap iron to precipitate the metallic antimony from the antimony chloride solution. This requirement, with the waste products attendant to antimony precipitation with scrap iron, makes these previously described processes commercially impractical and undesirable.

Holmes, U.S. Pat. No. 2,331,395 (1943), discloses an electrolytic hydrometallurgical process for the production of metallic antimony. However, the Holmes process requires the systematic addition of caustic soda (sodium hydroxide) to the process, and produces certain barium salts as an undesirable by-product (which are regenerated as a necessary reactant by a heating process); whereas the process disclosed herein completely regenerates its solutions for some antimony-containing materials, and produces elemental sulfur (which may be removed and sold) as its by-product. Further more, the Holmes process is based upon an alkaline sulfide leaching solution (particularly sodium sulfide), whereas the process disclosed herein is based upon a ferric chloride leaching solution.

SUMMARY OF THE INVENTION

The object of the prsent invention is to provide a hydrometallurgical process for the extraction of metalic antimony from antimony-containing materials, whereby the pollution effects of conventional pyrometallurgical processes are avoided, and yet such process is competitive with the conventional pyrometallurgical processes. The present invention contemplates essentially complete dissolution of the contained antimony, production of electrolytic grade metallic antimony, regeneration of reagents, and removal of impurities from the process solutions. Other objects and advantages of the present invention will appear from the following descriptions, examples, and claims.

It has been discovered that these objectives can be accomplished by use of a process having four basic stages which can be briefly described as two solution reduction stages, a metal recovery stage, and a solution regeneration stage. A fifth stage, metal oxidation, is added to obtain an antimony oxide product from the produced metal if desired.

In the first solution present stage, partially leached reacted antimony-containing materials are contacted with a solution metallic hydrochloric acid, ferric chloride, and antimony (III) chloride (SbCl.sub.3). The resultant reduction of part of the ferric chloride results in the formation of a solution containing hydrochloric acid, ferrous chloride, ferric chloride, and additional amounts of antimony (III) chloride. An excess of ferric chloride and hydrochloric acid is provided to ensure virtually complete dissolution of the antimony. The time required for accomplishing essentially complete dissolution of the antimony is temperature dependent for a given particle size. In the case of antimony sulfide, most of the sulfur is not completely oxidized and can be recovered in elemental form.

In the second solution reduction stage, the ferric chloride in the solution from the first solution reduction stage is mostly reduced to ferrous chloride by the addition to the solution of antimony-containing materials. Concurrently a portion of the antimony content of the antimony-containing material is solubilized as antimony (III) chloride. To prevent hydrolysis of the antimony (III) chloride in solution, a suitable excess quantity of hydrochloric acid is included and maintained in the process solution throughout the process.

The metal recovery and solution regeneration stages are carried out in the cathode and anode sections respectively of a diaphragm-type cell. In the metal recovery stage, the antimony (III) chloride from the second solution reduction stage is electrolyzed to deposit metallic antimony at the cathode. The solution, now partially depleted of its antimony content, is passed to the anode section where the ferric chloride content is regenerated. The electrolysis is arranged so as to deposit at the cathode an amount of antimony equal to that dissolved into the process solution during the cycle, and preferably not the entire amount of antimony in the solution. Any additional oxidation requuired beyond that furnished by anodic reactions may be obtained by exposing the solution to air or oxygen either prior to introduction into the anolyte system of the electrolytic cell or after withdrawal therefrom, or both.

While it is possible to combine the two solution reduction stages, it has been found that satisfactory achievement of all the desired objectives is difficult and can be achieved only by very precise metering of reactants and by the use of extremely long reaction times.

Treatment of oxidized antimony compounds in the process gives rise to the necessity of providing for reduction in the solution regeneration stage unless the formation of chlorine gas is desirable. Such reduction can be provided by contacting the solution with a reducing gas such as hydrogen or hydrogen sulfide. If the latter is used, provision should be made for removal from the circulating stream of the sulfur formed by the reaction. The formation of chlorine ordinarily should be avoided since such formation would encourage oxidation of any sulfur species present to sulfate. However, if the chlorine gas is a desirable by-product of the process, additional reduction in the solution regeneration stage is not necessary. The removal of chlorine as a by-product of the process may require the addition of hydrochloric acid. The additional hydrochloric acid will be removed from the system in the form of the chlorine by-product and excess water.

Excess water in the circuit, whether formed by process reactions or introduced from external sources, may be removed by distillation to minimize dilution of the solution. Fractionation of the water vapor removed is required to permit recovery of any hydrogen chloride as a relatively concentrated solution so it can be returned to the circuit. Approximately one-quarter pound of water is formed for each pound of antimony metal derived from oxide in the feedstock. Other potential sources of water additions to the circuit include bound water with the feed materials, feedstock moisture, and that applied to wash the valuable process solution from solids residue when removed from the process. The concentrated process solution stream may also be advantageously used as a source of a bleed stream for purification or removal of unwanted soluble contaminants from the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a simplified flow diagram for treatment of antimony-containing materials.

FIG. 2 diagrammatically presents a stoichiometric molar balance illustrating the basic chemistry of the process as applied to stibnite.

FIG. 3 diagrammatically presents a stoichiometric molar balance illustrating the basic chemistry of the process as applied to a mixed feed containing antimony metal, oxide, and sulfide.

FIG. 4a and FIG. 4b is a detailed flowsheet showing one embodiment of the disclosed process.

FIG. 5 is a detailed flowsheet showing an embodiment in which the second reduction stage is conducted in three steps.

DESCRIPTION OF PREFERRED EMBODIMENTS

The simplified basic process for the treatment of antimony-containing material will be readily understood from the diagram of FIG. 1. The basic chemistry of the process is illustrated by the stoichiometric molar balance of FIG. 2 as applied to stibnite and of FIG. 3 as applied to a mixture of antimony metal, oxide, and sulfide. The principal reactions occurring for various minerals in the ore concentrates in the reduction stages of the process are presently believed to be as follows:

1. Antimony metal

Sb.sup.0 + 3FeCl.sub.3 .fwdarw. SbCl.sub.3 + 3FeCl.sub.2

2. Antimony sulfide (Stibnite)

Sb.sub.2 S.sub.3 + 6FeCl.sub.3 .fwdarw. 2SbCl.sub.3 + 6FeCl.sub.2 + 3S.sup.0

sb.sub.2 S.sub.3 + 6HCl .fwdarw. 2SbCl.sub.3 + 3H.sub.2 S

3. antimony Oxide (Senarmontite)

Sb.sub.2 O.sub.3 + 6HCl .fwdarw. 2SbCl.sub.3 + 3H.sub.2 O

4. Antimony Oxide (Stibconite)

Sb.sub.3 O.sub.6 OH + 13HCl + 4FeCl.sub.2 .fwdarw. 3SbCl.sub.3 + 4FeCl.sub.3 + 7H.sub.2 O.

for a more complete description of the preferred embodiments, however, reference should be made to FIG. 4 and the following description.

In the treatment of antimony ore concentrates comprised principally of sulfide, together with some oxides and metal the fresh ore concentrates are added to a reduction stage in which they are contacted with a partially reduced solution. This reduction stage is herein referred to as the "second solution reduction stage" and it is indicated by numeral 1 (FIG. 4). The fresh ore concentrates are introduced into the second solution reduction stage 1 through line 2. As used herein "fresh" or "raw" refers to antimony-containing materials not previously reacted with any reagents in the process. Ferric chloride, along with antimony (III) chloride, ferrous chloride, and hydrochloric acid are introduced into the second solution reduction stage 1 by metering pump 3 through line 4. In the second solution reduction stage 1, which is essentially closed to the atmosphere, the ferric chloride in the solution is substantially reduced to ferrous chloride by reaction with the sulfide ore concentrates at near atmosphere boiling, about 105.degree. C. The oxide components of the fresh ore concentrates react with the excess hydrochloric acid present to form antimony (III) chloride and water. The process may be operated in such a manner as to produce hydrogen sulfide gas, if desired, by taking advantage of the reaction between the antimony sulfide and a portion of the excess hydrochloric acid. The hydrogen sulfide gas may be used subsequently in the anolyte reduction step or destroyed by reaction with ferric chloride in the first solution reduction stage 54. In any event, operation of the process in such a manner as to produce a controlled amount of hydrogen sulfide gas in the second solution reduction stage 1 insures a high degree of reduction of ferric chloride to ferrous chloride, and it is preferable that said reduction be substantially complete to minimize the power to the electrolytic cell ncessary to deposit the antimony.

The partially reacted ore concentrates, as well as the solution containing essentially ferrous chloride, antimony (III) chloride, and hydrochloric acid, are passed through line 5 to solution-solids separations device 6, where the solids are separated from the solution by gravity sedimentation.

Arsenic contamination may be introduced into the solution by the arsenic content of the ore concentrates. If a high degree of purity of the deposited antimony is necessary or desirable, then the arsenic must be removed from the solution prior to introduction into the catholyte section of the electrolytic cell. This can be done by a modification of the second solution reduction stage 1.

The introduction of hydrogen sulfide (H.sub.2 S) into the arsenic containing solution will precipitate the arsenic as a sulfide. The precipitate may then be separated from the solution by sedimentation, filtering, or other appropriate means, and removed.

The arsenic removal may be accomplished by treating a bleed stream from the second solution reduction stage 1. Hydrogen sulfide gas can be introduced into the bleed stream, wherein the arsenic will be precipitated as a sulfide, and removed.

Alternatively, as shown in FIG. 5, the second solution reduction stage 1 may be broken into three steps. In the first step, a portion of the fresh ore concentrates, metallic antimony, or other antimony containing materials are introducted into container 1a through conduit 2a where they are contacted with the incoming partially reduced solution. The ferric chloride in the solution is substantially reduced to ferrous chloride, but the reactions are not allowed to continue to the point where hydrogen sulfide gas is generated. The solution is separated from the solids by separator 6a and then passed through line 7a to a second container 1b for the second step of the second reduction stage. In the second step, hydrogen sulfide gas (generated by the third step) is reacted with the reduced solution in the second container to completely reduce the ferric chloride to ferrous chloride and to precipitate the arsenic as a sulfide. The precipitate may then be separated by separator means 6b from the solution by sedimentation, filtering, or other appropriate means, and removed. The reduced solution, stripped of the arsenic precipitate, is passed through line 7b to a third container 1c. In the third step, additional antimony sulfide containing materials are introduced through line 2b into container 1c in quantities in excess of the amount required to reduce essentially all of the ferric chloride in the third container to ferrous chloride. The excess antimony-containing materials then react with the hydrochloric acid in the solution in the third container to produce hydrogen sulfide gas. This gas may be passed through line 39a to be used in the second step immediately preceding, and/or the hydrogen sulfide gas may be passed through line 39 to be used in the anolyte reduction step or first solution reduction stage 54 as discussed herein.

The solution from separator 6, or 6c of FIG. 5, containing essentially ferrous chloride, antimony (III) chloride, and hydrochloric acid, is then passed through line 7 to filter 8. This filter serves to entrap and remove from the solution any suspended particulate matter which may be contained in the solution exiting separator 6. This clarification is desirable since any particulates passing into the metal recovery stage could serve as a source of contamination of the metal product. The filtered electrolyte solution then passes through line 9 to pregnant solution reservoir 10 where it is stored prior to introduction into the metal recovery stage. Metal recovery is achieved by electrolysis wherein the basic reaction in the catholyte compartment is:

Sb.sup..sup.+3 + 3e .fwdarw. Sb.sup.0.

Metering pump 11 introduces the pregnant liquor into the circulating catholyte stream in the catholyte sections of the electrolytic cells. In these portions of the electrolytic cells, which are partitioned from the anolyte sections with diaphragms, the antimony (III) chloride is electrolyzed to deposit metallic antimony at the cathodes by the reaction indicated above. The antimony metal may be deposited as individual cathodes for intermittent withdrawal or in the form of electrolytic granules, or powder for continuous withdrawal. To provide agitation and displacement of the solution in contact with the surface of the cathode in order to promote the desired type of antimony deposition, positive circulation of the catholyte solution is maintained by circulating pump 14. Recycling catholyte solution from catholyte reservoir 15 enters the pump suction through line 16, fresh feed liquor joins this stream through line 12. Temperature control in the catholyte circulating system is maintained by heat exchanger 18 through which a portion or all of the catholyte stream passes prior to entering the catholyte section of the elctrolytic cell through line 19. Since the second solution reduction stage 1 is preferably operated at near the atmospheric boiling point, the catholyte solution may require cooling before being allowed to enter the electrolytic cell. The product slurry containing metallic antimony particles suspended in the catholyte solution leaves the catholyte section of the electrolytic cell and is passed through line 20 to solution-solids separations device 21, where the metallic antimony solids are separated from the solution by any desired means, such as gravity sedimentation. The solution overflows the solution-solids separations device and passes through line 2 to catholyte reservoir 15.

The metallic antimony solids, together with some solution, pass from solution-solids separations device 21 through line 23 to washing filter 24, where the catholyte solution is removed. The filtrate and wash solutions are returned to the catholyte reservoir 15 through line 26. The cleaned and washed metallic antimony solids leave the washing filter device through line 25. This electrolytic antimony metal is of high purity, and may be converted into other products if desired.

Excess catholyte, approximately equal in volume to the amount of pregnant liquor and wash water introduced into the catholyte section of the electrolytic cell, leaves catholyte reservoir 15 through overflow line 27 and enters anolyte reservoir 28. Regeneration of the solution is accomplished by oxidation of the ferrous chloride to ferric chloride in the anolyte section of the diaphragm-equipped electrolytic cell. Here, an electrolytic reaction, concurrently induced with the reaction in the cathode reaction, occurs:

3Fe.sup..sup.+2 .fwdarw. 3Fe.sup..sup.+3 + 3e.

The circulation requirements in the anolyte section of the cell are not as critically related to process performance as in the catholyte section; however, sufficient circulation is required to prevent local overoxidation and the attendant formation of chlorine gas. Circulation pump 30 withdraws anolyte from reservoir 28 through line 29. The anolyte is then introduced into the anolyte section of the electrolytic cell 32 through line 31. Overflow from the cell returns to anolyte reservoir 28 through line 33.

Oxidic type compounds of antimony present in the fresh feed concentrates are solubilized by neutralization reactions with the excess hydrochloric acid in the process solution. The subsequent recovery of metallic antimony from solution by electro-deposition would result in a net overoxidation of the solution in the regeneration stage, and loss of acid, unless compensating reactions are introduced. As indicated earlier in this description, hydrogen sulfide gas can be generated at a controlled rate in the second solution reduction stage 1 by reacting a portion of the sulfidic component of the raw feed with some of the excess hydrochloric acid in the process solution. The required amount of hydrogen sulfide gas is introduced into anolyte reduction unit 37 through line 39, whereby ferric iron is reduced as indicated in the equation:

2Fe.sup..sup.+3 + H.sub.2 S .fwdarw. 2Fe.sup.+2 + 2H.sup..sup.+1 + S.sup.0.

continuous, prolonged, or extensive inclusion of oxidic compounds in the feed could require the external generation and addition of hydrogen sulfide, or some other appropriate, non-contaminating reducing agent, as opposed to reliance on internal generation in the second solution reduction stage 1. Compensating reactions need not be introduced if the production of chlorine gas as a by-product is desired, in which case the loss of hydrochloric acid could be compensated for by the addition of acid to the system.

Because of certain practical inefficiencies in the system, a pure antimony sulfide feed introduced into the system through line 2 could result in a small excess reduction potential for the system. This will not ordinarily occur in practice because of the presence of a certain amount of oxidic compounds of antimony contained in the feed, which provide excess oxidation potential as already discussed. However, should the composition of the feed result in a net excess reduction potential for the system, a compensating oxidation step can be added to the system. For example, the substantially regenerated solution leaving the electrolytic cell can be further oxidized by bubbling oxygen or an oxygen-containing gas such as air through the solution to further oxidize the ferrous chloride to ferric chloride, as shown by the equation:

4FeCl.sub.2 + 0.sub.2 + 4 HCl .fwdarw. 4FeCl.sub.3 + 2H.sub.2 O.

it may be desirable to conduct this reaction under 40 - 50 p.s.i.g. to increase the reaction rate. However, the reaction will operate satisfactorily with either the cooled solution leaving the electrolytic cell (40.degree. - 50.degree. C.) or the heated solution to be introduced into the first solution reduction stage 54 (near atmospheric boiling). Thus, this oxidation step can be operated as a bleed stream off of the feed liquor reservoir 44, or this step can be inserted into the system at line 43, line 47, line 49, line 50, or at any other appropriate location in the system.

Anolyte is fed by metering pump 35 through line 34 to anolyte reduction unit 37 through line 36. The reaction slurry containing elemental sulfur suspended in reduced anolyte passes through line 38 to filter 40 where the elemental sulfur is separated from the reduced slution. The reduced solution is passed through line 41 and returned to anolyte reservoir 28.

The regenerated solution containing predominately ferric chloride, antimony (III) chloride, and hydrochloric acid passes through line 43 from anolyte reservoir 28 into the oxidation stage feed liquor reservoir 44. Since the first solution reduction stage 54 is preferably operated at the atmospheric boiling temperature, it is necessary to heat the regenerated solution which leaves the electrolytic cell at approximately 40.degree.-50.degree. C. To accomplish this, the feed liquor passes through line 45, circulating pump 46 and line 47 to heat exchanger 48 and then is returned through line 49 to reservoir 44.

The heated, regenerated solution is passed through lines 50 and 52 by metering pump 51 to another solution reduction stage, which is herein referred to as the "first solution reduction stage" and it is designated in the drawings by numeral 54. The partially reacted ore concentrate solids from solution-solids separations device 6 are introduced into the first solution reduction stage 54 through line 53. Elemental sulfur from filter 40 is inroduced through line 42 and excess hydrogen sulfide gas generated in the second solution reduction stage 1 and not consumed in anolyte reduction stage 37 is introduced through line 39. The first solution reduction stage 54 is substantially closed to the atmosphere, and the ferric chloride in the process solution reacts with the solids at near the atmospheric boiling point (105.degree.) so as to essentially completely dissolve the antimony content therefrom.

The resultant slurry from the first solution reduction stage 54, containing elemental sulfur, insoluble residue, ferric chloride, ferrous chloride, antimony (III) chloride, and hydrochloric acid, is passed through line 55 to solution-solids separations device 56. In this device, gravity sedimentation is used to separate the insoluble residue and sulfur from the solution containing ferric chloride, ferrous chloride, antimony (III) chloride, and hydrochloric acid. The solution is passed through line 60 to water removal accumulator 62. The solids are removed from separator 56 through line 57 to a washing filter 58 where substantially all remaining process liquor is displaced. The filtered and washed solids, which include elemental sulfur and insoluble residues, are removed through line 59, and the recovered liquors are passed through line 61 to water removal accumulator 62.

The elemental sulfur passed out of the process through line 59 can be used as a raw material for the production of the hydrogen sulfide gas required in anolyte reduction unit 37 when oxidic antimony compounds are present in the feed concentrate.

If desired, the elemental sulfur can then be separated from the insoluble residue by heating the solids to a temperature at which the sulfur liquefies, followed by filtration.

Another procedure provides for the high temperature separation of the aqueous solution from the molten sulfur and insoluable residues during the first solution reduction stage 54. The temperature for gravity separation of the phases should be established above the melting point of sulfur (which is about 115.degree. C), and safely below the temperature at which a rapid rise is the viscosity of the liquid sulfur occurs (which is about 159.degree. C) to facilitate the decantation of the aqueous solution from the molten sulfur and insoluable residues. A temperature of approximately 140.degree. C is recommended. Since atmospheric boiling for the first solution reduction stage 54 at atmospheric pressure is about 105.degree. C, it becomes necessary to conduct the first solution reduction stage 54 in a suitable pressurized separation device to achieve the solution temperatures necessary to utilize this procedure. The molten sulfur, together with the insoluable residues, is withdrawn from the device. The still molten sulfur can be separated from the included solids, or the sulfur can be cooled below its melting point, causing it to crystallize, and be subsequently separated from the included solids. An advantage of this procedure is the accelerated reaction rates for the reactions of first solution reduction stage 54 resulting from the elevated operating temperature and pressure.

An important contribution of the hydrochloric acid in the process is to prevent the hydrolysis of the antimony chloride. The exact concentration at which hydrolysis occurs is somewhat dependent on solution composition and circuit temperature; however, laboratory data suggests that with minimum levels of hydrochloric acid (in the range of 2 - 5 percent) no difficulty is encountered.

Effective methods for monitoring and controlling the process of this disclosure have been developed. Measurement of the EH (oxidation-reduction potential) and pHE (hydrogen ion potential) of the process solution satisfactorily reveals the progress of the chemical reactions through the various steps of the process. Data derived from laboratory bench tests have revealed the following readings in Table I as typical for satisfactory process performance:

TABLE I
______________________________________
Process Solution EH: +mv.sup.1
pHE: +mv.sup.1
______________________________________
First Solution Reduction Stage
Discharge +330 +440
Second Solution Reduction Stage
Discharge +240 +440
Metal Recovery Stage (Catholyte)
+300 +420
Solution Regeneration Stage (Anolyte)
+640 +420
______________________________________
.sup.1 Reference Electrode Ag-AgCl.sub.2

Similarly, laboratory tests were run to demonstrate the two solution reduction stages at about 105.degree. C and at atmospheric pressure with active boiling under total reflux conditions. The pertinent data are tabulated below in Table II.

TABLE II
__________________________________________________________________________
Reaction
% Sb Oxidation Potential
__________________________________________________________________________
Material Time Solubilized
In-mv Out-mv
__________________________________________________________________________
A.
First Solution
Reduction
Sb (metal)
4 Hr.
100.0 +633 +483
Sb.sub.2 S.sub.3
4 Hr.
94.9 +639 +325
B.
Second Solution
Reduction
Sb.sub.2 S.sub.3
1 Hr.
84.7 +420 +240
Sb.sub.2 O.sub.3
2 Hr.
99.4 +188 +291
__________________________________________________________________________

Generally, the reactions of the two solution reduction stages 1 and 54 proceed at a rapid enough rate to obviate the necessity of pressurizing these stages to decrease reaction time. However, it has been discovered that for certain oxidic compounds of antimony, such as stibiconite, it may be desirable to pressurize either one of the two solution reduction stages to reduce the time ncessary to solubilize these compounds. The degree to which one of the solution reduction stages is pressurized will depend upon the degree to which it is desired to reduce the corresponding reaction times. Also, it may be desirable to pressurize the first solution reduction stage to utilize the high temperature sulfur separation technique previously discussed.

It will be evident from the foregoing disclosures that the chemistry of the process technically requires no scheduled addition of reagents other than those which can be developed internally. Of course, with continuous, prolonged, or extensive inclusion of oxidic compounds in the feed stock, it is necessary to add an appropriate reducing agent, such as hydrogen sulfide, to the cycle at the anolyte reduction step. Practically however, the inventory of required reagents in the process solutions must be maintained by compensation for vapor or solution losses. Vapor losses, which may include hydrogen chloride and hydrogen sulfide, are held to a minimum by utilizing closed reaction vessels, reflux condensers, temperature controls, etc. Solution losses, aside from accidential spills, are essentially restricted to that associated with the solids discharged from the process. This can be controlled by washing. However, an economic balance will exist between the loss of values with the solids and the loading on the water removal system. The ions which are required for make-up of the process solutions are chloride and iron. Additional iron may be provided from any material or compound which can be solubilized in the process and which would not introduce interfering or undesirable contaminants. Materials which could be considered would include metallic iron, certain sulfides such as Pyrrhotite, or chemical salts such as ferric or ferrous chloride. Additional chloride ions may be introduced by chlorine gas, hydrochloric acid, or one of the iron chlorides, as examples.

The practice of this invention is not limited to the use of any special equipment. The stages and process steps described herein may be conducted on a batch or continuous basis, and in any appropriate conventional equipment, including for example, reactors, containers and vessels which may be made open or closed to the atmosphere by conventional means. Of course, closed vessels are desirable to minimize solution losses and pollutants. Moreover, each stage or step as described herein may be conducted in one or more reactors, vessels, or containers. Further, the use of available compartmented, divided, or segmented units of equipment is within the contemplation of this invention.

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[+/-] : Continuous antimony pentoxide production

publish Metal Supplier at 1:51 AM 0 comment

This invention concerns an improved means of oxidizing aqueous dispersions of antimony trioxide to colloidal hydrous antimony pentoxide in a continuous flow system. The oxidant is hydrogen peroxide and the continuous flow system nominally consists of a static mixer and a tubular reactor.
This invention relates to a process for making antimony pentoxide.

Colloidal antimony pentoxide is frequently used as a metals passivation additive and a specialty fire retardant.

U.S. Pat. No. 4,348,301 discloses a means of making hydrous antimony pentoxide by contacting hydrogen peroxide and an antimony trioxide aqueous slurry in a batch system with and without a stabilizer. The stabilizer is generally an alkanolamine, alkanolamine salt, alpha-hydroxycarboxylic acid or a polyhydroxy alcohol and reportedly functions as a catalyst thereby increasing the reaction rate and producing a colloidal suspension of smaller average particle size. As previously noted, this prior art discloses use of the reaction in a batch reactor system. In such a system, the reactants are initially loaded into a vessel where they are well mixed and remain until the desired degree of conversion is obtained. The resultant mixture is then discharged. While the reaction is ongoing, the composition or degree of conversion is changing with time but at any point within the reactor, the composition is generally uniform. Batch reactors are extremely simple to operate and are frequently used for the preparation of small quantities of specialty chemicals. However batch reactors are limited in throughput capacity, are difficult to scale-up, and are often energy and manpower intensive.

Because of the inherent limitations associated with the operation of a batch reactor, continuous flow processes are frequently preferred when possible. One alternative used by those skilled in the art is to place tank reactors in series wherein the effluent stream from the upstream reactor becomes the influent stream to the downstream reactor. Each tank possesses a reactant of progressively greater conversion and at steady-state conditions, the degree of conversion in each tank becomes a fixed value. However, the residence time of the reactant species in a given tank may differ significantly as reactant which has just entered the tank is mixed with reactant which has been there for a significant period of time. This phenomenom is referred to as back-mixing. The high degree of mixing in each tank assures a uniform overall composition and the effluent from a given tank is representative of the actual composition within the tank. Limitations associated with the tank reactors in series include the need for many tanks when high conversion is desired, the process equipment is expensive to buy and to maintain, the high degree of mixing requires significant energy input, the significant difficulties exist with repsect to process scale-up.

A second approach for a continuous flow reactor system is to inject the reactants into a pipe (i.e., a tubular reactor) of sufficient length and obtain the desired product in the produced effluent. Tubular reactors are easy to design and operate and inexpensive to construct. However, non-uniform velocity distributions, radial temperature gradients and poor radial mixing can limit practical applications when high viscosity fluids are involved. U.S. Pat. No. 4,022,710 discloses hydrous antimony pentoxide production via the reaction of hydrous antimony trioxide with hydrogen peroxide without a stabilizer but in a continuous flow, fixed diameter reactor. The desired antimony trioxide concentration in the feed is stated to be 1 to 20 wt %, with 5 to 10 wt % being preferred. A hydrogen peroxide to antimony trioxide mole ratio of not less than 3 and preferably 5 to 10 is taught. A nominal operating temperature of 90.degree. C. is disclosed. To obtain a colloidal product of desired particle size and to avoid plugging of the reactor, this art discloses the requirement that fluid mixing in the reactor be minimized and that the internals of the reactor be constructed of a non-wetting material. To minimize fluid mixing, the art requires all bends be removed from the system and the operation at flow velocities which minimize fluid mixing. Problems associated with the plugging of the reactor were apparently resolved by constructing the reactor of a non-wetting resin, preferably tetrafluoroethylene, rather than stainless steel. From a practical perspective, these restrictions significantly increase the reactor cost on a per unit throughout basis.

Although the art is silent, the Examples and operational restrictions cited in `710` indicate that process operation was restricted to the laminar flow regime (Reynolds Number <2000) and that these conditions were incorrectly referred to as "plug flow" (a possible Japanese to English translation error). For smooth circular pipes and Newtonian fluids, those skilled in the art recognize a departure from laminar flow conditions when a dimensionless number, DV.rho./.mu., is greater than approximately 2000. This dimensionless group is referred to as the Reynolds number wherein D is the pipe diameter, V is the superficial velocity defined as the total volumetric flow rate (Q) divided by the cross-sectional area available to flow (A), .rho. is the bulk fluid density, and .mu. is the bulk fluid viscosity. The art teaches that a transition zone from laminar to turbulent flow exists for Reynolds Numbers between 2000 and 4000 and that turbulent flow exists at Reynolds Numbers greater than 4000.

When operating in the laminar region, fluid flow is solely in the axial direction and fluid mixing is minimal and primarily by diffusional effects. The lack of mixing restricts heat transfer and can result in nonuniformities in temperature which can result in nonuniformities in reaction rate and product produced. The velocity profile is a maximum at the center of the pipe and decreases in a parabolic manner to zero at the wall. Therefore when a slug of fluid is injected into the pipe, the fluid injected at the center will be produced well before that injected near the wall. When operating at laminar flow conditions, the residence time of a given fluid element when flowing through the pipe will be dependent on the point of injection on the entrance cross-section.

When operating in the turbulent flow regime, chaotic mixing is superimposed on the bulk axial flow. As a result, the velocity profile from the center of the pipe to the wall is nearly constant. This results in nearly uniform compositions and temperatures at a given radial cross-section and all fluid elements will have similar residence times regardless of where injected on the entrance cross section. As assemblage or slug of fluid elements simultaneously injected into the tube at turbulent flow conditions will advance like a plug through the pipe. In the literature, this condition is routinely referred to as "plug flow".

SUMMARY OF THE INVENTION

It is an object of this invention to make high purity colloidal antimony pentoxide.

It is a further object of this invention to conduct the reaction in a continuous manner.

It is yet a further object of this invention to obtain the operational benefits of using a tubular reactor.

And it is still yet a further object that reactor volume, reactor length, and construction and operation costs be minimized on a per unit throughput basis.

In accordance with this invention, a process for the continuous production of colloidal antimony pentoxide by the reaction of hydrogen peroxide with antimony trioxide in a static mixer/tubular reactor flow system is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram for a process capable of continuous antimony pentoxide production.

FIG. 2 is a flow diagram for the experimental system of Examples I and II.

DETAILED DESCRIPTION OF THE INVENTION

This invention concerns an improved means of oxidizing antimony trioxide to antimony pentoxide in a continuous flow system by the following reaction.

Sb.sub.2 O.sub.3 +2H.sub.2 O.sub.2 .fwdarw.Sb.sub.2 O.sub.5 +2H.sub.2 O

The reactant, antimony trioxide has limited solubility in water and primarily exists as a suspended solid in an aqueous-based slurry. The product, hydrous antimony pentoxide, has limited solubility in water and will for the most part, exist in a colloidal form. Hydrous antimony pentoxide hereinafter refers to a metal oxide wherein the antimony metal primarily exists in the +5 oxidization state and may contain waters of association and/or hydration. Colloidal refers to a suspension of discrete matter in a continuous medium wherein the discrete matter possesses at least one dimension in the range of 10 to 1,000 Angstrom.

Key and distinguishing characteristics of this process are (1) the chosen operating conditions (reactant concentrations, temperature, stabilizer etc.), (2) the unique in-situ fluid flow phenomena resulting from the reactor flow system design, and (3) the manner of process start-up and operation.

The viscosity of the antimony trioxide reactant slurry behaves in a non-Newtonian manner. This behavior is demonstrated in Table I wherein the viscosity is observed to decrease as shear rate (RPM) increases. Such non-Newtonian phenomenena is referred to as pseudoplastic behavior and is frequently observed in muds, slurries, and polymer solutions. Tables I and II show that the fluid viscosities of the reactant and product will be significant (i.e., generally greater than 1000 cp). Calculations indicate that at practical operating conditions for flow in open tubes, the Reynolds number for both the reactant and the product streams will be significantly less than 2000 and therefore, fluid flow will be in the laminar or streamline flow regime. (See Example I for calculated Reynolds numbers at representative flow conditions.) Streamline flow implies that mixing in the radial direction is extremely low and as a result an operator faces significant problems when blending reactants and attempting to heat the fluid to a uniform temperature with an external heat transfer fluid. These difficulties may accentuate plugging problems. Design problems were further complicated in the present study by the observation that carbon-steel catalyzes the decomposition of hydrogen peroxide and carbon-steel can be heavily fouled by the colloid product.

In the present invention, the preferred mode for obtaining acceptable product is (1) heating the antimony trioxide aqueous dispersion to the desired process temperature, (2) combining the aqueous dispersion and the hydrogen peroxide reactant immediately upstream of a static mixer, (3) using the static mixer to efficiently mix and initiate the reaction between the high viscosity trioxide-bearing stream and the low viscosity hydrogen peroxide bearing stream, and (4) providing sufficient residence time downstream of the static mixer for 100% conversion.

TABLE I
______________________________________
Viscosity of 31 wt % Sb.sub.2 O.sub.3 Feedstream.sup.a
Temperature
Shear 24.degree. C.
62.degree. C.
92.degree. C.
______________________________________
20 RPM 4050 cp 11300 cp 17300 cp
50 2220 5480 5720
100 1450 2430 2830
______________________________________
.sup.a Brookfield Digital Viscometer Model DVII with #6 spindel.

TABLE II
______________________________________
Viscosity of 8.8 wt % Antimony Pentoxide.sup.a
Temperature
Shear 25.degree. C.
61.degree. C..sup.b
91.degree. C..sup.c
______________________________________
20 RPM 1750 cp 2350 cp 200 cp
50 1640 1080 180
100 1580 195 80
______________________________________
.sup.a Brookfield Digital Viscometer Model DVII with #6 spindel.
.sup.b Canon-Fenske viscometer value of approximately 550 cp at 54.degree
C.
.sup.c Data suspect because of skin forming on top of solution.

The flow system nominally consists of a single hydrogen peroxide injection port/static mixer arrangement and a tubular reactor possessing sufficient residence time to insure complete reaction of the antimony trioxide prior to leaving the system. (See FIG. 1). Residence time downstream of the static mixer can be increased by lowering the flowrate or increasing the system volume by increasing the length of the tubular reactors or increasing the diameter of the tubular reactors. For operation simplicity and cost-effectiveness, the latter is preferred. Operation with multiple injection port/static mixer arrangements or static mixers located between downstream tubular reactors to enhance mixing have been successfully demonstrated but because of operational simplicity, the preferred embodiment is a single injection port/static mixer arrangement. It is preferred that the aqueous dispersion be preheated or cooled to the desired process temperature either by batch treatment or flowing through a preheater or chiller. The hydrogen peroxide may or may not be preheated or precooled. If not, it is preferred that the aqueous dispersion be heated above or cooled below the desired process temperature so as to result in an aqueous dispersion/peroxide mixture whose temperature approximates the desired process temperature. Temperature control for the static mixer and tubular reactor can be provided by jacketing said vessels. Because the reaction is exothermic, downstream cooling capabilities are required for accurate temperature control. As noted, the tubular reactor located downstream of the static mixer must possess sufficient residence time to insure complete reaction of the antimony trioxide. The residence time can be reduced somewhat by the inclusion of additional downstream static mixers which break up and mix the fluid stream lines. The preferred material of construction is stainless steel although other non-wetting materials would also be applicable. Upon completion of the reaction, the antimony pentoxide product should be cooled to near room temperature prior to storage, for instance, by flowing through a suitable heat exchanger.

A key factor distinguishing this process from the prior art is the mixing of antimony trioxide slurry and hydrogen peroxide reactant and the accompanying reaction which occurs during said mixing in the static mixer. A static mixer is defined as an in-line, no-moving-part, continuous mixing unit. The energy required for fluid mixing comes from the pressure drop across the unit. When properly designed, the flow characteristics of fluids injected into the mixer approach those of ideal plug flow. Such mixing enables more uniform temperatures and rates of reaction within the mixer and apparently affects the subsequent reaction in the downstream tubular reactor. Although wishing not to be bound by theory, the inclusion of the static mixer in the current processing scheme apparently enhances colloid nucleation and the initial reaction and thereby enables a product of suitable quality to be obtained at conditions not foreseen by the prior art.

The aqueous dispersion of antimony trioxide is prepared by adding antimony trioxide to water. It is preferred that the antimony trioxide particle size be ultrafine and that it contain minimal impurities and inert/unreacted material. The antimony trioxide aqueous slurry should preferably contain 1 to 45 weight percent antimony trioxide, more preferably 10 to 40 weight percent, and most perferably 25 to 35 weight percent antimony trioxide in water. A major advantage of the greater antimony trioxide concentrations is the elimination of or a reduction in the size of any subsequent step for concentrating the hydrous antimony pentoxide.

The reaction can be conducted either with or without a stabilizer. The stabilizer is added primarily to suppress foaming although the benefits reported in `310` in batch systems wherein the stabilizer apparently catalyzes the reaction, enables operation at lower temperatures, and produces a pentoxide product possessing a smaller particle size may also be present in this continuous flow system. Typical stabilizers include the alkanolamines, alkanolamine salts, the alpha-hydroxy carboxylic acids and polyhydroxy alcohols. The preferred stabilizers are the alkanolamine salts because of their additional foam suppression capabilities. The most preferred stabilizer is an alkanolamine salt prepared by adding triethanolamine and phosphoric acid to the aqueous dispersion and thoroughly mixing. The stabilizer concentration should be an amount effective to stabilize foaming and/or catalyze the reaction. Preferable concentrations are 1 to 15 weight percent stabilizer in the aqueous dispersion. For the preferred triethanolamine phosphate stabilizer, the preferred concentration in the aqueous dispersion is 1 to 11 weight percent triethanolamine and 0.3 to 4 weight percent phosphoric acid. In the most preferred mode, about 7 weight percent triethanolamine and about 2 weight percent phosphoric acid are combined in the aqueous dispersion. When using a stabilizer, temperature is not a key parameter. Under such conditions, the process can be operated over a 0.degree. to 150.degree. C. regime. The preferred operating range is 0.degree. to 90.degree. C. When not using stabilizers, a temperature sufficient for appreciable reaction is required. A temperature greater than 90.degree. is generally preferred and most preferred is a temperature in the 90.degree. to 150.degree. C. range. When operating above 100.degree. C., process vessels capable of pressurization are required because of operation above the boiling point of the aqueous dispersion.

Minimally, a stoichiometric amount of hydrogen peroxide must be added to the antimony trioxide. The stoichiometry is 2 moles hydrogen peroxide per 1 mole antimony trioxide. A stoichiometry of 2.0 to 2.5 is preferred. The concentration of hydrogen peroxide in water is not critical but should be sufficient to avoid unnecessary dilution of the antimony pentoxide product. Preferable concentrations are 30 to 40 wt % hydrogen peroxide in water and the most preferred is about 33 wt %.

A potential problem area in the operation of any process is the start-up procedure. To avoid plugging problems, the preferred start-up procedure comprises (1) flowing water through the entire flow system at process conditions, (2) initiating the flow of hydrogen peroxide at the injection port or ports, and finally (3) injecting the antimony trioxide slurry at the aqueous dispersion injection port.

The following examples are provided to illustrate the practice of the invention and are not intended to limit the scope of the invention or the the appended claims in any way.

EXAMPLE I

A flow diagram for the experimental system used in this Example is presented in FIG. 2. The antimony trioxide slurry was prepared by adding 500.4 pounds antimony trioxide to an aqueous solution consisting of 30 pounds phosphoric acid and 112.6 pounds of triethanolamine. These components were thoroughly mixed in the slurry mix tank. Representative viscosity values of the feedstream are presented in Table I. The lower half of the tank was jacketed and tempered water was run through the jacket to provide slight preheating to the slurry.

The material of construction for the flow system was stainless steel. Prior to contacting with 33 wt % hydrogen peroxide, the slurry was preheated by running through a heat exchanger consisting of forty feet of 0.5 inch diameter tubing inside a pipe jacket. The slurry was pumped using a progressive cavity pump. The temperature of the water in the jacket was controlled so as to heat the slurry to the initial reaction temperature of 85.degree. C. Flowrates were 0.28 gal/min hydrogen peroxide solution and 1.0 gal/min slurry. The molar ratio of hydrogen peroxide to antimony trioxide was 2.15. The hydrogen peroxide was injected immediately upstream of a 12 element Chemineer static mixer sized to ensure good contact between the slurry and the hydrogen peroxide. Upon injection, the viscosity of the slurry was noted to decrease. Assuming a fluid viscosity of 1000 cp, the Reynolds number for the 0.5 in. and 1.5 in. diameter tubular reactors were approximately 10 and 3.6 which is significantly less than 2000 and therefore well into the laminar flow regime.

Referring to FIG. 2, tubular reactors 1A and 1B were 0.5 in. diameter and had respective lengths of 20 and 40 ft. The remaining downstream reactors were each 1.5 in. diameter and 20 ft long. All tubular reactors were jacketed and maintained at a constant temperature. All static mixers were Chemineer 12 element mixers or the equivalent. The respective plug flow residence times in the 0.5 and 1.5 in diameter reactors were about 0.48 and 7.25 min. When operating at 85.degree. C., the reaction was essentially complete after flowing through the 0.5 in diameter tubing. The product was a clear, yellow green liquid and met specification requirements for Phil-Ad.TM. CA-6000.

EXAMPLE II

The same conditions were employed as in Example I except the process temperature was reduced to 30.degree. C. Although the reaction was not complete after flow through the 0.5 in. diameter reactor (plug flow residence time of 0.48 min.), 100% conversion was obtained after flow through the 1.5 in. diameter reactor (additional plug flow residence time of about 7.25 min.). The product met specifications for Phil-Ad.TM. CA-6000.

EXAMPLE III

The transmittance of a representative product sample was determined using a Hitachi Model 100-20 spectrophotometer. For a 0.53 wt % antimony pentoxide sample, a transmittance of 65.7% was obtained.

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Antimony trioxide,Antimony trioxide Masterbatch

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[+/-] : Global antimony market to reach 169,000 mt by 2010

Thursday, July 26, 2007

[+/-] : sell antimony trioxide,antimony ingot

[+/-] : Surface-modified antimony trioxide particles

[+/-] : Hydrometallurgical process for the production of antimony

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Examples of Antimony Trioxide Mixture Flame-Retarded Polymers

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Flame retardant mechanism of antimony trioxide with Polymers

Antimony trioxide,Antimony trioxide Masterbatch

Tuesday, July 31, 2007

[+/-] : Magnesium price to increase on a high freight

Friday, July 27, 2007

[+/-] : Global antimony market to reach 169,000 mt by 2010

Thursday, July 26, 2007

[+/-] : sell antimony trioxide,antimony ingot

[+/-] : Surface-modified antimony trioxide particles

[+/-] : Hydrometallurgical process for the production of antimony

[+/-] : Continuous antimony pentoxide production

Examples of Antimony Trioxide Mixture Flame-Retarded Polymers

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*****About Me*****

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Welcome to my blog!!

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JIEFU's products can be used as substitute to Chemtura's and Albemarle's

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