DE2423895A1 - PROCESS FOR MANUFACTURING METALLIC MATERIAL IN PARTICULATE FORM - Google Patents

Description

PATENTANWÄLTE D 59 Siegen

DIPL-ING. ERICH SChUBERl Marburger Tor2 - PO Box

DIPL.- ING. ROLF PÜRCKHAUER ^{Telephone: (0271} > ⁵⁴⁰⁷ °

Telegram address: Patschub, Siegen

1 May 5, 1974

United Kingdom Atomic Energy Authority, 11 _r Charles II Street, London SWlY 4QP, England

For this application, priority becomes from the UK patent application No. 23793/73 of the 18th time 1973 claimed.

Process for the production of metal-containing material in particle form

The invention relates to the production of metalliferous Material in particle or particle form and is used in the manufacture of such a material, which is mainly in the form of very small spheres.

In GB-PS 1,175,834 (= US-PS 3,495,954) and GB-PS 1,286,871 (= U.S. Patent 3,716,605) is a method of forming Particles made of metal-containing compounds, e.g. spheres of irregular grain size, are described. Briefly summarized is a Salt solution of one or more metals with an organic polymer which forms a complex with the metal ions, and drops of the resulting viscous mixture are mixed with brought into contact with another solution or gas, which or which the metal content of each drop as an insoluble The compound that is bound to the polymer precipitates Pieces, hereinafter referred to as gel precipitate, can

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lightly filtered out for further treatment, washed and handled.

In GB-PS 1 231 385 (C = US-PS 3 776 987) a process is disclosed which has process steps similar to those described above, but is the starting material an aqueous sol of the metal or metals in question, rather than a solution.

GB-PS 1 350 389 (= ÜS-Serial No. 170 99 ¹ * of August 11, 1997) describes a further relevant process in which the mixture of the solution or the sol and the polymer is not formed into drops before it is brought into contact with the precipitant. Instead, the precipitant is gradually added to the mixture while the latter is stirred to prevent solidification. The gel bodice in this case is just an irregular material; the other methods mentioned can produce a spherical material, although aggregation difficulties may occur for spheres less than about 60 microns in diameter.

Usually the formation of the gel precipitate brings one Double decomposition reaction between the precipitant and a metal salt present in the solution or the sol with itself; in Reality are the same well-known reactions that would be used to break the connection in the absence of the To precipitate polymers.

After washing, the bits, e.g., spheres or other particles, obtained from all of the above methods can be used accordingly the desired end product can be further treated. For example they can be heated to drive off the polymer and essentially only the metal compound or compounds to leave behind in the bits. Often these .connections Be metal oxides. In suitable cases, the compounds, in particular oxides, in a reducing atmosphere

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Sphere are heated to produce elemental metal particles.

The present method makes it possible _t gel precipitates, which are generated by the the aforementioned method similar in composition to produce mainly very small particles of spherical shape, without the problem of aggregation of the particles when they are formed. Spherical particles down to 1 micron in diameter can be produced. The particles may contain the metal compound or compounds bound to the polymer, the metal compound or compounds alone, or the metal or metals in elemental form, depending on the subsequent treatment. These small particles find numerous uses. Depending on their nature, the end products can find applications in areas such as metal powder, ceramics, flame or plasma spraying, pigments, pharmaceuticals, agricultural chemicals, catalysts, etc. One advantage of the process is the high purity of the product obtained.

According to the invention, there is a method for producing metal-containing material in particle form therein,

that pieces of a metal-containing gel precipitate, as previously explained, are formed;

that the precipitated pieces in the presence of a liquid Phase are subjected to a grinding and dispersing process in order to produce an intermediate product, which is suitable for spray drying;

and that the intermediate product is spray-dried to produce a to form particulate or granular product.

With "bits of a metal-containing gel precipitate" are meant pieces obtained by mixing a salt solution or a sol or a mixture thereof, one or more Metals with a soluble organic polymer compound and

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Bringing the mixture into contact with a precipitant Precipitating the metal or metals of the salt or sol as an insoluble compound or compounds is prepared with the polymer in each piece. Such bits can for example by the method which are shown in the aforementioned GB-PS 1 175 83.4, 1 286 871, 1 231 385, 1 350 389 and in the associated British Patent Applications Nos. 41613/73 and 18011/74 are described.

It is believed that in some cases the grinding and dispersing process may increase hydration of the Gel precipitation brings with it.

A range of polymers that are used to form the gel precipitate suitable, is disclosed in the aforementioned patents, this range in the present process however, it is not to be regarded as exhaustive. As explained there, the selection of suitable polymers for use with is given Salts or brines are a matter of routine experimentation. Albeit a general guide for choosing one suitable polymer for a good formation of a gel precipitate from the nature of the metal ion and the complex! Properties of the polymer can be derived, so the final criterion is empirical. For example, polymers that are proved to be suitable for divalent cobalt ions, such as galactomannan gums, also for divalent nickel and iron ions found suitable. In a similar way, higher-order states »e.g. Th (IV), Zr (IV) and U (VI), good gel precipitates formed with many glucose based polymers such as dextran. The empirical selection makes no difficulty, however, as the suitability of a given polymer can easily be judged by whether the desired gel precipitate is obtained formed or not. In addition, it can turn out that some polymers are difficult to dissolve in a given solution or sol and are therefore less suitable.

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In the case of sols in particular, some polymers can be a cause instant precipitation of them when added, and such incompatible polymers are of course not satisfactory.

^ Suitable polymers include polyhydroxy compounds such as for example polysaccharides and polyalcohols. From polysaccharides, dextran and galactic gums, such as for example, Karobe and Guar mentioned. Other polysaccharides include cellulose derivatives such as hydroxypropylmethyl cellulose and hydroxyethyl cellulose, (e.g. 'Oellulosize' der Union Carbide) and starch derivatives, such as Wisprofloc P and Wisprofloc W from W.A. Scholten's chemical Fabrieken N ^ V, Holland. Among the polyalcohols, there can be polyvinyl alcohol be mentioned. However, this list is not intended to be exhaustive. Some polycarboxyl, polyamine and polyacrylamide compounds can also be used.

The precipitant is selected according to the metal compound that is to be precipitated. If precipitation is to be effected from a salt solution, the precipitating agent is one which is known to react with that solution to produce the desired precipitate, usually by a double decomposition. The latter will often be a metal oxide or hydroxide, in which case the precipitant is expediently an alkaline solution, for example sodium or ammonium hydroxide or lime or sodium carbonate; or it may be an alkaline gas such as ammonia., are used. When a carbonate precipitate solution is used, the oxide of the metal or metals can be readily formed subsequently by heating the precipitated carbonate, as is well known. As is also known, uranium oxide is normally not produced by direct precipitation, but rather by precipitation with ammonia as ammonium diuranate, which is then heated to drive off ammonia and water.

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When the precipitation is effected from an aqueous metal sol is to be, then the desired precipitant is expediently an alkaline solution or a gas known about is that it causes the sol to precipitate on its own. Such a precipitation usually causes a double decomposition reaction with those ions that are present in the sol and work to stabilize it.

Known acidic precipitants can also be used.

Other gel particles precipitated by such double decomposition can be obtained, include, for example, metal phosphates, sulfides, silicates and (with further treatment) titanates, aluminates and tungstates.

The proportions and concentrations of the metal salt or sol, the polymer and the precipitant are not critical and can change within wide limits. Corresponding values (and, as already mentioned, a suitable polymer) can be achieved through Similar simple experiments can be determined for each particular application of the method, taking economic factors into account considered.

Metals precipitated as gel pieces from solutions of their salts or sols for use in the present process include iron, barium, chromium, copper, cobalt, nickel, zinc, yttrium, zirconium, thorium, uranium, tungsten, manganese, Lead, titanium, hafnium, aluminum and rare earths, however, is this list is not exhaustive.

The crushing and dispersing of the pieces can be done in different ways Way. For example, a colloid mill can be used. In such a mill the pieces are made in the presence of the liquid in which they are to be dispersed, introduced between two closely spaced surfaces, the

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are in relative rotation to each other. Other means of Comminution and dispersion of the precipitation product to the required degree, which are used in appropriate cases may include vibratory agitators and various types of mixers, although these latter means are less effective are called a colloid mill. Another device that has the required grinding and dispersing effect and in some cases a fine grinder is suitable (or Fluid Power Mill). The special device that is used to crush and disperse the precipitated pieces used to make the intermediate for spray drying too form is not a critical feature of the present procedure, provided it becomes a satisfactory one for the purpose Intermediate product generated.

Usually the bits are washed thoroughly before they are crushed and dispersed. The relative ease with which the pieces can be washed (for example in comparison with "slimy" precipitation products) makes it possible to obtain an end product of high purity. Normally the liquid in which the gel precipitate is broken up and dispersed is also the liquid · »· be the speed in which the precipitate or the precipitation product was finally washed, namely usually water. The amount of water which is present during the grinding and dispersing process will depend on the solids concentration, which is desired in the intermediate product which is to be spray dried. Usually it is not necessary be to filter the gel precipitate from the washing liquid, a simple pouring is sufficient. The rest The water content after decanting can be sufficient for that Mix directly to the colloid mill or other comminuting agent Dispersing device can be fed directly, however If a more dilute intermediate is desired, it can be used

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additional water or other liquid can be added to the feed mixture.

The spray drying can be carried out in a conventional spray dryer, for example of the spinning disc or nozzle type. The conditions under which the spray drying takes place are regulated experimentally in a known manner so that a product of the required specification results. For example, a "Niro Mobile Minor", which is a spinning disk type, manufactured by Niro Atomiser Ltd., Copenhagen, Denmark, at speeds of 35,000-1,000 rpm, inlet temperatures of 245-325 ° C and outlet temperatures of 90-12O ⁰ C used. The intermediate product was added at rates of 2-3 l / h with solids concentrations of 1-8 % in water. Under these conditions, with a variety of compounds, the dried product, after having passed through the cyclone separator integral with said pulverizer, is mainly spherical with a particle size in the range of 1-30 microns, mainly 5-20 microns. The density of the individual dried particles is usually about 70 % of theoretical.

The product produced by spray drying consists of particles in which the precipitated metal compound with the polymer ". Such particles are used, for example, in the pharmaceutical sector. By igniting the particles in an oxidizing atmosphere, the polymer is driven off and in many cases the metal compound is converted into the oxide. Oxide particles are used, for example, as dispersion enhancers in powder metallurgy and use in flame or plasma spraying. Suitable oxides can be reduced in metal powder. The size distribution or scattering of the product can be reduced by known air screening techniques.

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The main part of the product produced by spray drying consists of particles which are essentially spherical. the remaining particles are of a less regular shape. They arise probably due to incomplete chopping of the falsified Bits and by the fact that sprayed particles hit the walls of the dryer before they dry completely are. Such particles can have "flats" on their surfaces, for example. The presence of part of such less regular particles is not detrimental for most purposes. The present invention is not limited to any limited particular degree of sphericity or proportion of essentially spherical particles. In the examples below the word "spherical", as applied to the products, is used in a broad sense and does not mean any such particular degree or proportion.

Before crushing and dispersing the washed gel precipitate can "further soluble or insoluble materials are added which are in the intermediate product and thus finally be incorporated into the spray-dried particles. It is also possible to remove insoluble materials prior to the gel precipitation step bring in. Such additions enable composite particles to be represented, in which the particles are used as a means of transport or carrier for the additive is effective. So the dried particle can be a matrix for the metal compound form associated with the polymer in which finely divided particles of an insoluble additive are contained. For example, graphite can be brought together with appropriate compounds so that the composite dried particles are converted into carbide by a subsequent heat treatment can be.

Some examples of the present method will now be described:

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example 1 Elsen (III) oxide / guar gum

Guar gum (5 [beta] / l of the metal salt solution) was added to a solution of iron (III) chloride (20-4Og Pe / 1) with stirring. Ammonium hydroxide (^ 8 M) to pH 9 was added to this viscous solution with stirring in order to precipitate an aqueous ferric oxide gel precipitate. After aging the gel precipitate in excess alkali for 30 minutes, it was washed by decantation until the washes were neutral and chloride-free. The granular gel precipitate was crushed and dispersed using a colloid mill (manufactured by Premier Colloid Mills Ltd.) operating with a plate spacing of 0.005 inches (125 microns). The concentration of iron in the reducing intermediate was changed between 15 and 30 g Pe / 1 by adding different amounts of water before grinding. The intermediate product was spray-dried in a Peinstmahl device (Niro Mobile Minor) under the following conditions: flow rate 2.4 l / h, inlet temperature 295 ° C and outlet temperature 100-115 ° C. Small changes ( -10%) had no measurable effect on the properties of the dried gel precipitate. The dried product was spherical, 100 % less than microns in diameter, and about 75 % between 5 and 15 in diameter; Micron. When reduced in hydrogen at 725 ° C for 3 hours; a fine, spherical iron powder was obtained, which is suitable for metallurgical fabrication.

Example 2 Mixed iron (III) aluminum (III) oxide / Wis prof loc P

A solution of iron (III) nitrate and aluminum ^ III) nitrate with different iron-aluminum ratios (total metal 65g / 3)

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Wisprofloc P (50 g / l of the metal salt solution) was added with stirring. To this viscous solution, ammonium hydroxide (/ v ^ 8 M) was added to pH 9 with stirring to precipitate a mixed aqueous oxide gel precipitate. After aging for 30 minutes, the precipitate or the precipitate was washed by pouring off until the washes were neutral. The granular gel precipitate was crushed and dispersed using a colloid mill and spray dried as an intermediate product containing 50g metal / liter under conditions substantially the same as those used in Example 1. The density of the spherical dried gel precipitate as measured using Stokes's rule was about 70 % of theoretical The product was convertible to a mixed iron-aluminum oxide by heating to drive off the polymer

Example 3 NlckeHlD-Hydroxid / Guar-Gumml

Guar gum (5 g / l of the metal salt solution) was added to a solution of nickel (II) nitrate ( ^{1 IOg Ni / 1) with stirring.} Sodium hydroxide (H M) to pH 9 was added to this viscous solution with stirring. The aqueous nickel (II) hydroxide gel precipitate thus formed. was aged in the excess alkali for 30 minutes and then washed until the washes were neutral. After crushing and dispersion using a colloid mill, the resulting intermediate product was spray-dried with a content of 20 g Ni / 1 in a "Niro Mobile Minor" under the following conditions: flow rate of 3 »5 l / h, inlet temperature of 29o ° C and outlet temperature of 100 ⁰ C. The particle size of the spherical spray dried product was 100 % less than 25 microns with up to 75 % between 5 and 15 microns. Burn

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in air at 50O ⁰ C for 2 hours gave oxide spheres of similar size, which are suitable for plasma spraying after removal of abrasion (less than 5 microns) by rinsing.

Example M

Mixed Hafnlum (IV) - Titan (IV) -Oxyd / Wisprofloc W (and Wisprofloc P)

A mixed oxide gel precipitate was produced from hafnium (IV) oxychloride and titanium (IV) chloride (~ 120g total metal / l) and Wisprofloc W (30g / l of the metal salt solution) by precipitation with ammonium hydroxide (8 M). After aging, washing, comminuting and dispersing, as described in Example 3, the resulting intermediate product with a content of ^ 60g Mstall / 1 was spray-dried, as described in Example 3. The particle size of the dry spherical product was 100 % less than 25 microns by 10 % less than 5 microns. An X-ray analysis showed that burning (were used much lower than 1500 ⁰ C, which previously for HfO ₂ -TiO. -Pulvergemische ₂₎ at 800 ° C gave hafnium.

Similar results were obtained when Wisprofloc P was used instead of Wisprofloc W.

Example 5 Cobalt (II) hydroxide / guar gum

A gel precipitate was prepared from a cobalt (II) sulfate solution (11, 25 g Co / 1), the guar gum (2g / l of the metal salt solution) contained, and a gel precipitate was formed by the addition of

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Sodium hydroxide (8 M) formed to pH 8.5 with stirring. The precipitate was washed eight times by pouring it off with 1-1 volume of demineralized water. The granular gel precipitate was crushed and dispersed using a Silverstone vibratory stirrer. The resulting intermediate contained ~ 50g Co / 1 and was spray dried using a "Miro Mobile Minor" under the following conditions: flow rate 2.4 l / h, inlet temperature 295 ° C and outlet temperature 105 ° C. A spherical product similar to that described in Example 3 was obtained. Firing the spray-dried product in air at 600 ° C produced black cobalt (II) -obalt (III) oxide with little aggregation. Reducing the product at 75O ⁰ C in hydrogen for 2 hours yielded a spherical metal powder with little aggregation (accumulations of up to 70 microns). The piles were easily broken and the powder was suitable for metallurgical fabrication.

Example 6 .
Zinc (II) hydroxide / guar gum

A gel precipitate was produced from a zinc (II) sulfate solution (65g Zn / 1), which guar gum (5g / l of the metal salt solution) and a gel precipitate was formed by adding ammonium hydroxide (10 M) to pH 8.5 with stirring. The granular gel precipitate was washed by decantation, crushed and dispersed using a colloid mill as well as an intermediate product with a content of 30g Zh / 1, as in Example 1 described, spray-dried.

Example 7 Mixed nickel (II) -elsen (III) -oxide / guar gum

In a modification of Example 3, guar gum becomes one

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mixed solution of nickel (II) - and iron (III) nitrates added. Sodium hydroxide is added with stirring to form a mixed iron-nickel-oxide gel precipitate. By crushing and dispersing the washed precipitate to form an intermediate and spray drying as in Example 3, spheres are produced. By firing the balls in air at * K) O-500 ° C, the polymer is removed and a gel ^; mixed metal oxide left. The resulting spheres are suitable for plasma spraying, the high temperature achieved converting the mixed oxides into a nickel-ferrite coating.

In all of the above examples the gel-precipitated bits are used formed by adding the precipitant to a salt-polymer solution, as in the process mentioned in the opening paragraph GB-PS 1 350 38I is described. As is in this patent it is possible to use an aqueous sol for the salt solution in appropriate cases. Mixtures of a solution and a compatible one Sols, i.e., one that is not precipitated or otherwise degenerated by mixing with the solution, can also be used will. In addition, instead of gradually adding the precipitant to the viscous mixture of salt and / or sol and polymer with stirring, as in the aforementioned patent, also possible, gradually reducing the viscous mixture Add stirring to the precipitant, for example as described in the associated British patent application 41613/73. It As mentioned earlier, the processes according to British patents 1 175 83 ^, 1 286 871 and 1 231 385 are also possible to be used in which the salt-polymer solution or the sol-polymer system is added dropwise to a liquid precipitant, under conditions that, as described there, a Generate precipitation of irregular "gravel grains". At . Using the latter method, it is convenient to use the precipitant liquid to stir when the mixed drops fall, both for economic reasons, to the required

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Reduce amount of precipitant as well as production a gravelly precipitate that is easy to crush and disperse. It is undesirable to do the above To operate processes under conditions that produce coherent spheres (as also in the cited patents described), as the latter is more difficult to crush and disperse in the intermediate product required for spray drying are.

The inventive method is of course not based on that Use of the particular substances, devices and conditions mentioned in the examples is limited.

Patent claims

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Claims (13)

η 025 m / a 15 · ΜΑΙ m claims 1. A method for producing a metal-containing material in particulate form, characterized in that pieces with a salt solution is mixed one or more I-Tetalle with an organic polymer v a _f metal-containing gel precipitate formed / ground, which forms a complex with the metal ions , and wherein drops of the resulting viscous mixture are brought into contact with another solution or gas which precipitates the metal content of each drop as an insoluble compound associated with the polymer, causing the precipitated bits to undergo a grinding and dispersing process in the presence of a liquid phase be subjected to produce an intermediate product suitable for spray drying, and that this intermediate product is spray dried to form a particulate or granular product. 2. The method according to claim 1, characterized in that the crushing and dispersing process by means of a Colloid mill or a vibratory stirrer. 3. The method according to claim 1 or 2, characterized in that the precipitated pieces are substantially irregular Particles are formed. Yy. Method according to claim 3, characterized in that the precipitated pieces by mixing together a precipitating solution and a mixture of the salt solution or the sol with the soluble polymeric organic compound is formed with stirring v / earth. 5. The method according to claim 4, characterized in that the precipitated pieces are formed by adding the precipitating solution to the mixture of the salt solution or the sol with the soluble polymeric organic compound is added with stirring. 409849/0887 6. The method according to claim 5 »characterized in that the precipitated pieces by what is described in GB-PS 1,350,389 Procedures are formed. 7. The method according to claim ¹ J, characterized in that the "precipitated pieces are formed in that the mixture of the salt solution or the sol with the soluble polymeric compound is added to the precipitation solution with stirring. 8 »Method according to one or more of Claims 1 to 7» characterized in that the precipitated bits are formed from a salt solution of the metal or metals. 9 · The method according to claim 7, characterized in that the precipitated pieces by the in the associated British Patent application ^ 1613/73 described method formed will. 10. The method according to claim 9, characterized in that the precipitated pieces from a salt solution of the metal or of the metals formed. 11. The method according to one or more of claims 1 to 8, characterized in that before the comminution and dispersion process another soluble or insoluble material mixed with the precipitated bits and thereby in the spray-dried granular product is incorporated. 12. The method according to claim 9 or 10, characterized in that that prior to the grinding and dispersing process, another soluble or insoluble material with the precipitated pieces mixed and thereby incorporated into the spray-dried granular product. 40 9849/0887 13. The method according to one or more of claims 1 to 8, characterized in that prior to forming the precipitated
Pieces of an insoluble material are added to the mixture of the salt solution or the sol with the soluble polymeric organic compound and thereby incorporated into the spray-dried granular product. I ¹ I. The method according to claim 9 or 10, characterized in that before the formation of the precipitated pieces an insoluble material is added to the mixture of the salt solution or the .Sols with the soluble polymeric organic compound and thereby introduced into the spray-dried granular product. 409849/0887