GB1570999A - Process for agglomerating a substance from a liquid system - Google Patents

Description

(54) PROCESS FOR AGGLOMERATING A SUBSTANCE FROM A LIQUID SYSTEM (71) We, CIBA-GEIGY AG, a body corporate organised according to the laws of Switzerland, of Basle, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to processes for agglomerating a substance from a liquid system as well as to the agglomerates produced by means of these processes: and also to the use of these processes for the isolation of a solid from a suspension.

DOS 2,412,369 discloses a process for producing non-dusty, readily wettable and rapidly soluble granulates, in which process the substance to be granulated is suspended in a liquid not dissolving this substance, and to the suspension is then added a second liquid which wets to dissolve the said substance, and which is immiscible or only partially miscible with the first liquid, and the mixture is maintained in a state of turbulence until agglomerates or granules of the said substance are formed, which are separated and dried.

It has now been discovered that it is also possible to effect the agglomeration of a substance in two or more liquids which are completely miscible with one another. It has been shown that, surprisingly, the granulating process in a liquid system of this kind is more rapid and that the granules obtained are more uniform in size than those obtained by the process described in DOS 2,412,369. Furthermore, there is the advantage that toxicologically completely safe solvent systems, such as water/ethanol, can be used, a factor which in food technology is of significance in that the granules no longer contain traces of toxicologically inadmissible solvents.

The process according to the invention of agglomerating a substance from a liquid system with subsequent separation and drying, which liquid system is composed of at least two liquids, which at 200C are completely miscible with one another, at least one of which is organic, is characterised by being carried out by either.

A) if the solid substance to be agglomerated is not in the form of a suspension in a liquid not dissolving said substance, suspending the substance in a said liquid, adding to the suspension a second liquid which is completely miscible with the first liquid, said second liquid being capable of dissolving said solid substance, and stirring the mixture of said solid substance and first and second liquid until agglomerates of the solid substance are formed in the liquid system; or B) adding, with stirring, a mixture of liquids consisting of a first liquid which does not dissolve said solid substance and a second liquid which dissolves said solid substance and which is completely miscible with the first liquid, to said solid substance, and stirring the solid liquid system until agglomerates of the solid substance are formed; C) adding, with stirring, the solid substance to be agglomerated to a mixture of a first organic liquid which does not dissolve said solid substance, and a second organic liquid which dissolves said solid substance and which is completely miscible with the first liquid, and stirring the solid substance containing liquid system, until agglomerates of said solid substance are formed; or D) adding to a suspension of the solid substance to be agglomerated in a liquid not dissolving said solid substance, a second liquid said first liquid being water and said second liquid being an organic liquid completely miscible with water, not capable of dissolving said substance and capable of extracting water from the suspension, and stirring the mixture of said substance and the first and second liquid until agglomerates of the solid substance are formed in the liquid system.

The resulting agglomerates can be separated from the liquid system in known manner, for example by filtration under suction or by normal filtration, and dried by known methods.

The substance to be agglomerated can be a homogeneous substance or a mixture of substances, and can belong to a variety of different classes of substances and can be inorganic or organic.

The substances may be for example: dyes, pigments, optical brighteners or textile auxiliaries, pharmaceutical products, mixtures of active substances used in the manufacture of tablets, pest-control agents, foodstuffs and food supplements such as coffee powder, milk powder or flour; antimicrobics and bacteriostatics; animal feeding stuffs, plant protection products; detergents, paper auxiliaries (e.g. gluing agents), photochemicals, leather chemicals, polymers such as plastics, plastic additives, synthetic resin moulding compounds, explosives, building materials, coal, ores, catalysts, chemicals, fertilisers, intermediates for cement manufacture, starting materials for ceramic products and also raw materials for powder metallurgy.

The dyes may be of all possible classes, both coloristically and chemically, which are suitable for aqueous or organic application. For example they may be basic or cationic dyes, acid dyes, sulphur dyes, vat dyes, mordant dyes, chrome dyes, disperse dyes or direct dyes, and the dyes can contain fibre-reactive groups. It is understood that foodstuff dyes and, for example, leather dyes can also be agglomerated.

From a chemical point of view, suitable dyes include nitroso, nitro, monoazo, disazo, trisazo, polyazo, stilbene, carotenoid, diphenylmethane, triarylmethane, xanthene, acridine, quinoline, methine, thiazole, indamine, indophenol, azine, oxazine, thiazine, lactone, aminoketone, hydroxyketone, anthraquinone, indigoid and phthalocyanine dyes, as well as 1:1 - or 1:2 - metal - complex dyes.

The optical brighteners which are used for white "tinting" may belong to any class of brighteners: they are, for example, stilbene compounds such as cyanuric derivatives of 4,4' - diaminostilbene - 2,2' disulphonic acid or distyryl- biphenyls, coumarins, benzocoumarins, pyrazines, pyrazolines, oxazines, mono - or dibenzoxazolyl, mono - or dibenzimidazolyl compounds as well as naphthalic acid imides or naphthotriazole and v-triazole derivatives.

By "textile auxiliaries" are meant chemicals that are required in the processing of the various textile fibres into finished fabrics, such as raw-wool detergents, lubricants, sizing agents, milling agents, impregnating agents, preserving agents, finishing agents, desizing agents, kier-boiling agents, bleaching auxiliaries, dyeing auxiliaries such as dispersing agents and levelling agents, printing auxiliaries, carbonising auxiliaries, mercerising auxiliaries, preparations for producing resistance to creasing and to shrinking, and antistatic preparations.

Pest-control agents are in general known They are used, e.g., to destroy plant pests (e.g. fungicides, insecticides, acaricides, nematicides, molluscicides and rodenticides), and to prevent plant diseases.

Antimicrobics are antimicrobial substances which are intended to or serve to retard or prevent disadvantageous changes caused by microorganisms in feedstuffs.

Bacteriostatics are substances which inhibit or prevent the growth of bacteria.

By detergents are meant those substances which are composed of, e.g., a) a surfaceactive synthetic substance, a washing raw material; b) a washing auxiliary (detergent additive); c) special additives such as sodium perborate, magnesium silicate, optical bleaching agents and wetting agents; and d) extenders. Both the detergent as such and the individual constituents can be granulated according to the invention.

Finally, polymers can be granulated, by which are meant macromolecular organic compounds which are obtained by transformation of natural products or by synthesis, including plastics materials.

All these substances, both in the pure or preferably in a commercial form, can be present as dried press cake or as a suspension, including a moist aqueous or organic press cake, whereby the liquid on which this press cake or suspension is based can be identical to the suspension liquid or granulating liquid. If the starting material is a suspension, suitable materials are, inter alia, those resulting, for example, after synthesis. A very frequent situation is that of aqueous press cake of water-soluble substances which are precipitated, for example, by salt. Here the water is indeed the suspension liquid, but at the same time it also has the function of the liquid which brings about agglomeration. In order that a controlled agglomeration can occur in this case, there must be added a liquid which does not dissolve the dye but is capable of extracting water from the suspension so that it can extract from the press cake that amount of water which is in excess of that required for the agglomeration process. It serves therefore as the suspension agent during agglomeration.

Liquids which do not dissolve the substance to be agglomerated, i.e. which serve as the suspension liquid, may be either water or an organic liquid which satisfies this condition. Of course, a mixture of such liquids can be used.

A further liquid which wets to dissolve the substance to be agglomerated and which is completely miscible at 200C with the suspension liquid is, in the case where the suspension liquid is water, an organic liquid, or a mixture of such liquids, 100% miscible with water at 200C; suitable such organic liquids include lower (i.e. of 1 to 6 carbon atoms) aliphatic alcohols such as ethanol, methanol and, in particular, propyl alcohol such as n - and iso - propyl alcohol, or ketones such as acetone. A preferred mixture is water/ethanol and water/n propyl alcohol.

It is understood that, conversely, the suspension liquid can be of organic nature and the other liquid can be water.

In the case where the suspension liquid and the other liquid are both organic and satisfy the condition of being 100% miscible with each other at 200 C, suitable mixtures include: Frigen ll3TR (1,1,2 - tri - chloro - 1,2,2 - trifluoro - ethane)/isopropanol, Frigen 113TR/ethanol, n butanollbenzene, benzene/n - propanol, ligroin/isopropanol, methanol/formamide, methanol/ethylene dichloride, perchloroethylene/iso - or n- propanol, and propanol/butanol. Particularly good results are obtained however with the following liquid mixtures: Frigen 113TR/methanol, toluene/methanol, perchloroethylene/methanol and 1,1,1 - trichloroethane/methanol. "Frigen" is a Registered Trade Mark.

The amounts of the individual liquids can vary within wide limits. Ratios of suspension liquid to granulating liquid are typically from 1:99 to 99:1 (by volume). Preferred ratios are from 30:70 to 80:20, especially about 60:40.

It is advantageous if agglomeration occurs in the presence of auxiliaries. Such auxiliaries are, for example: binding agents, typically present in an amount from 1 to 20% relative to the substance to be agglomerated, diluting agents, typically present in an amount from 1 to 1000% relative to the substance to be agglomerated, dispersing agents or surface-active agents, which may be nonionic, anionic or cationic depending on the solid substance, typically present in an amount from 0.1 to 10% relative to the substance to be agglomerated.

In addition to surface-active agents, protective colloids can be added in amounts of up to, say, 20%.

The binding agents serve in particular to increase the mechanical strength of the agglomerates. Suitable binding agents include e.g.: polyvinyl alcohol, cellulose derivatives such as carboxymethylcellulose and hydroxypropylcellulose, polyvinylpyrrolidone as well as dextrin.

Suitable diluting agents are, in particular, salts such as alkali salts of inorganic acids, e.g. of hydrochloric acid, sulphuric acid and phosphoric acid, and, in particular, NaCI, Na2SO4 (Glauber's salt) and phosphate salts.

Good agglomeration results can be obtained especially where the process of agglomeration is performed from a liquid system having at least two liquids completely miscible at 200 C, and containing auxiliaries and, in particular, diluting agents, especially salts. This salt can be already present in the substance to be agglomerated, or it can be separately added to the liquid system, or it can be present by virtue of the substance itself being of the nature of a salt, e.g. in the case of cationic dyes.

Agglomeration usually occurs at a temperature of 5 to 1000C, especially 15 to 50"C, in the course of 10 to 20 minutes.

The agglomerates resulting from the process are of the most varied forms, such as spherical, lenticular, elongated or rodshaped. The diameter of these forms is generally 100 to 1000 microns, and these agglomerates are very uniform in size.

Larger agglomerates can however be produced, which can be converted, depending on the length of stirring, into granules which are over 1000 microns in size.

These agglomerates or granulates have the advantages that compared with the powder form of the corresponding substance, they have a much b.etter wetting property as well as a higher rate of dissolving and more rapid dispersibility, possessing in certain cases "instant" properties; and also that they are non-dusty.

Furthermore, they are very free-flowing and also have a high bulk weight. it is possible in this manner to obtain from substances soluble in water or in organic medium granulates having "instant" properties, i.e.

with immediate breaking down in the solvent. The resulting agglomerates or granulates can in general be dispersed or dissolved easily, and without the use of special stirring devices, in the application medium. Also to be emphasised is the high mechanical stability of the solid granules which can be obtained.

The yield of these granulates can be up to 100%. With the correct choice of liquids, granulation is in most cases complete, with the result that there is a separation of a clear liquid phase from the solid phase of the agglomerates.

A special application for the process is the isolation and drying of solids from a suspension, the procedure being such that, for example, this suspension with at least one further liquid, which wets to dissolve the solids contained in the suspension liquid and which is completely miscible with this liquid, is subjected to a thorough mixing until agglomerates of the solids are formed, which are then separated from the liquid system and optionally dried.

The following Examples further illustrate the invention. Temperatures are given in degrees Centigrade.

Example 1 33 g of aqueous press cake consisting of 33 per cent by weight of the dye from an autocondensation product of p - nitrotoluene - 2 - sulphonic acid and 67 per cent by weight of water is slowly stirred into a paste at 200 with 17 g of n - propyl alcohol. As stirring proceeds there are gradually formed granules which settle out.

They are filtered off and dried at 400 in vacuo to give 10 g of dye granulate. This is dust free and very readily soluble in cold water.

Example 2 50 g of the dye according to Example 1 (powder) is suspended in 50 g of n - propyl alcohol with stirring at 200 C. To the suspension is added dropwise 30 ml of water whilst stirring is maintained. After some time, granules are formed which are filtered off and then dried in vacuo at 400 The resulting product is a dye granulate which is dust free and which rapidly dissolves in cold water.

It is however also possible to change the addition of the two liquids by mixing 50 g of the same dye with 30 g of water to obtain a thick paste, and to add to this paste, with stirring at 200 C, 50 g of n - propyl alcohol.

Granules separate out from the suspension after about 15 minutes as stirring continues.

These granules are filtered off and dried at 400 in vacuo.

Example 3 20 g of the pulverulent dye of the formula

is suspended in 60 g of Frigen (113TR). To the suspension is added dropwise at 200, with stirring, 12.5 ml of methanol. The dye becomes granulated after about 15 minutes.

Small granules form which are filtered off and dried at 400. The product obtained is a dust free dye granulate which is readily wetted and which dissolves rapidly.

Example 4 20 g of the pulverulent dye of the formula

is suspended in 60 g of Frigen at 200. To this suspension is added dropwise, with stirring, 5 ml of methanol. After 15 minutes' stirring, the dye has become completely granulated.

The granules are filtered off and dried at 400 to give a dust free, easily wettable and readily soluble dye granulate.

Example 5 20 g of the pulverulent dye of the formula

is suspended in 50 g of Frigen at 200. To the suspension is added 3.5 ml of methanol.

Granules are formed on stirring which are filtered off and dried at 400. The resulting product is a dust free, easily wettable dye granulate.

A dust free dye granulate is likewise obtained by using, instead of the liquid system Frigen/methanol, identical amounts of the liquid system toluene/methanol, with otherwise the same procedure.

Example 6 20 g of the pulverulent dye of the formula

is suspended at 200 in 80 ml of Frigen. To the suspension is added dropwise 30 ml of methanol. Fine granules form immediately and these are filtered off and dried at 400 in vacuo. The granulate is dust free, readily wettable and rapidly soluble.

The granules can also be produced by mixing the dye into a paste with about 20 ml of methanol, and then suspending this paste, with stirring, in 80 ml of Frigen.

Example 7 7 g of the dye according to Example 6 is suspended at 20 in 25 g of toluene and to the suspension is added dropwise 10 ml of methanol. After subsequent stirring for a quarter of an hour, the dye has become granulated. The small granules formed are filtered off and dried at 400 in vacuo to give a dust free dye granulate.

Example 8 20 g of the pulverulent dye according to Example 4 is suspended at 200 in 50 g of toluene, and to the suspension is added, with stirring, 7 ml of methanol. Granules are formed, which are filtered off and dried at 400 to give a dust free dye granulate.

Example 9 50 ml of Frigen is mixed at 200 with 7 ml of methanol to give a homogeneous liquid.

This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 5 is added with stirring. There are formed granules which are filtered off and dried at 500 in vacuo. The product obtained is a dust free, easily wettable dye granulate.

If 90 ml of Frigen andlO ml of methanol are used instead of the 50 ml of Frigen and 7 ml of methanol, the result is likewise a good granulation. Conversely, it is also possible to place the dye into the beaker and to then add the mixture of the two liquids.

Example 10 60 ml of Frigen is mixed with 5 ml of methanol at 200. This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 4 is added with stirring. Excellent granules are formed spontaneously; these are filtered off and dried at 400.

Example 11 50 ml of perchloroethylene is mixed with 5 ml of methanol at 200. This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 4 is introduced. Granules are formed upon stirring and are filtered off and then dried at 40".

Example 12 5 g of finely ground coffee is suspended in 45 ml of ethanol. An addition is then slowly made, with turbulent stirring, of 8 ml of an aqueous salt solution (consisting of 8 ml of water and 2 g of sodium chloride). The resulting coffee granules are filtered off and dried. There is thus obtained a coffee granulate which is instantly soluble in cold water.

In the case of certain coffee powders, the moist granules are sticky. This stickiness can be avoided by using for granulation a mixture of the salt solution with ethanol (in the ratio 7:1).

Example 13 5 g of finely ground coffee is suspended in 45 ml of isopropanol. An addition is then slowly made, with turbulent stirring, of 6 ml of aqueous sodium chloride solution (20% NaCI). The resulting coffee granules are filtered and dried. There is thus obtained a coffee granulate which is rapidly soluble in cold water.

WHAT WE CLAIM IS: 1. A process for agglomerating a solid substance from a liquid system and subsequently separating and drying it, which liquid system is composed of at least two liquids, which at 200C are completely miscible with one another, at least one of which is organic, wherein said process is carried out by either A) if the solid substance to be agglomerated is not in the form of a suspension in a liquid not dissolving said substance, suspending the substance in a said liquid, adding to the suspension a second liquid which is completely miscible with the first liquid, said second liquid being capable of dissolving said solid substance, and stirring the mixture of said solid substance and first and second liquid until agglomerates of the solid substance are formed in the liquid system; or B) adding, with stirring, a mixture of liquids consisting of a first liquid which does not dissolve said solid substance and a second liquid which dissolves said solid substance and which is completely miscible with the first liquid, to said solid substance, and stirring the solid liquid system until agglomerates of the solid substance are formed; C) adding, with stirring, the solid substance to be agglomerated to a mixture of a first organic liquid which does not dissolve said solid substance, and a second organic liquid which dissolves said solid substance and which is completely miscible with the first liquid, and stirring the solid substance containing liquid system, until agglomerates of said solid substance are formed, or D) adding to a suspension of the solid dissolving said solid substance, a second substance to be agglomerated in a liquid not liquid said first liquid being water and said second liquid being an organic liquid completely miscible with water not capable of dissolving said substance and capable of extracting water from the suspension, and stirring the mixture of said substance and the first and second liquid until agglomerates of the solid substance are formed in the liquid system.

2. Process according to claim I wherein the liquid system consists of water and an organic liquid that is 100% miscible with water at 200 C.

3. Process according to claim 2 wherein the organic liquid is a lower aliphatic alcohol.

4. Process according to claim 3 wherein the organic liquid is ethanol or, n - or iso propyl alcohol.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Example 8

   20 g of the pulverulent dye according to Example 4 is suspended at 200 in 50 g of toluene, and to the suspension is added, with stirring, 7 ml of methanol. Granules are formed, which are filtered off and dried at 400 to give a dust free dye granulate.

   Example 9

   50 ml of Frigen is mixed at 200 with 7 ml of methanol to give a homogeneous liquid.

   This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 5 is added with stirring. There are formed granules which are filtered off and dried at 500 in vacuo. The product obtained is a dust free, easily wettable dye granulate.

   If 90 ml of Frigen andlO ml of methanol are used instead of the 50 ml of Frigen and 7 ml of methanol, the result is likewise a good granulation. Conversely, it is also possible to place the dye into the beaker and to then add the mixture of the two liquids.

   Example 10

   60 ml of Frigen is mixed with 5 ml of methanol at 200. This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 4 is added with stirring. Excellent granules are formed spontaneously; these are filtered off and dried at 400.

   Example 11

   50 ml of perchloroethylene is mixed with 5 ml of methanol at 200. This mixture is placed into a beaker, and 20 g of the pulverulent dye according to Example 4 is introduced. Granules are formed upon stirring and are filtered off and then dried at 40".

   Example 12

   5 g of finely ground coffee is suspended in 45 ml of ethanol. An addition is then slowly made, with turbulent stirring, of 8 ml of an aqueous salt solution (consisting of 8 ml of water and 2 g of sodium chloride). The resulting coffee granules are filtered off and dried. There is thus obtained a coffee granulate which is instantly soluble in cold water.

   In the case of certain coffee powders, the moist granules are sticky. This stickiness can be avoided by using for granulation a mixture of the salt solution with ethanol (in the ratio 7:1).

   Example 13

   5 g of finely ground coffee is suspended in 45 ml of isopropanol. An addition is then slowly made, with turbulent stirring, of 6 ml of aqueous sodium chloride solution (20% NaCI). The resulting coffee granules are filtered and dried. There is thus obtained a coffee granulate which is rapidly soluble in cold water.

   WHAT WE CLAIM IS: 1. A process for agglomerating a solid substance from a liquid system and subsequently separating and drying it, which liquid system is composed of at least two liquids, which at 200C are completely miscible with one another, at least one of which is organic, wherein said process is carried out by either A) if the solid substance to be agglomerated is not in the form of a suspension in a liquid not dissolving said substance, suspending the substance in a said liquid, adding to the suspension a second liquid which is completely miscible with the first liquid, said second liquid being capable of dissolving said solid substance, and stirring the mixture of said solid substance and first and second liquid until agglomerates of the solid substance are formed in the liquid system; or B) adding, with stirring, a mixture of liquids consisting of a first liquid which does not dissolve said solid substance and a second liquid which dissolves said solid substance and which is completely miscible with the first liquid, to said solid substance, and stirring the solid liquid system until agglomerates of the solid substance are formed; C) adding, with stirring, the solid substance to be agglomerated to a mixture of a first organic liquid which does not dissolve said solid substance, and a second organic liquid which dissolves said solid substance and which is completely miscible with the first liquid, and stirring the solid substance containing liquid system, until agglomerates of said solid substance are formed, or D) adding to a suspension of the solid dissolving said solid substance, a second substance to be agglomerated in a liquid not liquid said first liquid being water and said second liquid being an organic liquid completely miscible with water not capable of dissolving said substance and capable of extracting water from the suspension, and stirring the mixture of said substance and the first and second liquid until agglomerates of the solid substance are formed in the liquid system.
2. 2. Process according to claim I wherein the liquid system consists of water and an organic liquid that is 100% miscible with water at 200 C.
3. 3. Process according to claim 2 wherein the organic liquid is a lower aliphatic alcohol.
4. 4. Process according to claim 3 wherein the organic liquid is ethanol or, n - or iso propyl alcohol.
5. 5. Process according to any one of claims

   1 to 4 wherein the liquid system consists of organic liquids which are 100% miscible with one another at 200 C.
6. 6. Process according to claim 5 wherein the organic liquid mixture used is 1,1,2 trichloro - 1,2,2 - trifluoroethane/ methanol, toluene methanol or perchloroethylene/methanol.
7. 7. Process according to any one of claims 1 to 6 wherein the volume ratio of the suspension liquid to the granulating liquid is 1:99 to 99:1.
8. 8. Process according to claim 7 wherein the said ratio is 30:70 to 80:20.
9. 9. Process according to claim 7 wherein the said ratio is about 60--40.
10. 10. Process according to any one of claims 1 to 9 wherein the agglomeration is performed at a temperature of 5 to 100"C.
11. 11. Process according to claim 10 wherein the agglomeration is performed at a temperature of 15 to 500C.
12. 12. Process according to any one of claims 1 to 11 wherein one or more auxiliaries are added to the system.
13. 13. Process according to claim 12 wherein an auxiliary is added to the liquid or to the substance to be agglomerated.
14. 14. Process according to claim 12 or 13 wherein the auxiliary is a binder, dispersing agent, surface-active agent and/or a protective colloid.
15. 15. Process according to claim 14 wherein a diluting agent is present with the auxiliary.
16. 16. Process according to claim 15 wherein the diluting agent is an alkali salt of an inorganic acid.
17. 17. Process according to any one of claims 1 to 14 which is carried out according to A.
18. 18. Process according to any one of claims 1 to 14 which is carried out according to C.
19. 19. A process according to claim 1 substantially as described in any one of Examples 1 to 11.
20. 20. A process according to claim 1 substantially as described in Example 12 or 13.
21. 21. A solid substance whenever agglomerated by a process as claimed in any one of claims 1 to 16 and 20.
22. 22. A solid substance whenever agglomerated by a process as claimed in any one of claims 17 to 19.