US2975142A

US2975142A - Granular water-soluble perborate-containing salt mixture

Info

Publication number: US2975142A
Application number: US582885A
Authority: US
Inventors: Schmidt Joachim; Meinhold Werner
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1955-06-11
Filing date: 1956-05-04
Publication date: 1961-03-14
Anticipated expiration: 1978-03-14
Also published as: DE1417132A1; BE548170A; US2972584A; NL207905A; DE1417131A1; FR1153767A; NL110775C; CH350274A; GB811658A

Description

March 14, 1961 GRANULAR WATER- Filed May 4, 1956 J. SCHMIDT ETAL 2,975,142

SOLUBLE PERBORATE-CONTAINING SALT MIXTURE 2 Sheets-Sheet 1 INVENTOR JOACH/M SCHMIDT WERNER ME/NHOLD BY [3% W ATTORNEY:

March 14, sc MlDT ET GRANULAR WATER-SOLUBLE PERBORATE-CONTAINING SALT MIXTURE Filed May 4, 1956 2 Sheets-Sheet 2 4:. a INVENTOR JOACH/M SCHMIDT WERNER MEI/VHOLD ATTORNEYs GRANULAR WATER-SOLUBLE PERBORATE- CONTAINING SALT MIXTURE Joachim Schmidt and Werner Meinhold, Dusseldorf- Benrath, Germany, assignors to Henkel & Cie. G.m. b.I-I., Dusseldorf-Holthausen, Germany, a corporation of Germany Filed May 4, 1956, Ser. No. 582,885

Claims priority, application Germany June 11, 1955 11 Claims. (Cl. 252186) This invention relates to granular, water-soluble perborate-containing salt mixtures.

Perborates are frequently used in detergents and bleaching agents as oxygen-liberating materials. Since perborates are temperature-sensitive, particularly in the presence of water, they must be mixed with the detergents and bleaching agents after the liquid or paste has been converted into a powder by drying.

The commercially available borates generally are in solid, finely divided form, having a relatively small particle size. Since the particle size of the commercially available borate is frequently about one-tenth to onehundredth that of the other components of the detergent, the same would tend to separate out upon transportation and storage.

In order to overcome this difi'iculty, attempts have been made to produce perborates of low bulk weight by heating the same on hot surfaces. In this connection, however, the particles formed do not have the necessary mechanical strength, and, unless the operation is very carefully effected, there is a strong tendency of the perborates to decompose.

One object of this invention is the granulation of finely divided perborates into a more coarsely granular form, which may be mixed with detergents and bleaching agents without any tendency toward separation.

A further object of this invention is a novel, granular, perborate salt mixture, which may be used in the same manner as a conventional perborate being mixed with detergent and bleaching agents without any tendency toward separation. These, and still further objects will become apparent from the following description, read in conjunction with the drawings, in which:

Fig. 1 is a diagrammatic representation of a plant set-up for efiecting the process in accordance with the invention;

Fig. 2a is a diagrammatic front elevation partly in section, showing an embodiment of a granulating device for use in accordance with the invention;

Fig. 2b is a diagrammatic side elevation partially in section, showing the granulating device of Fig. 2a;

Fig. 2c is a diagrammatic perspective view showing the granulating device of Fig. 2a;

Fig. 3a is a diagrammatic side elevation partially in section, showing a further embodiment of a granulating device for use in the process in accordance with the invention; and

Fig. 3b is a diagrammatic front elevation showing the granulating device of Fig. 3a with a portion of the drum rim cut away.

In accordance with the invention, a novel, granular salt mixture containing a perborate, which may be used in the conventional manner in detergents and bleaching agents without any tendency toward separation is formed by moving a finely divided, water-soluble perborate, and preferably sodium perborate, on a support surface for contact between the individual divided particles, While 2,975,142 Patented Mar. 14, 1961 spraying the perborate with an aqueous solution of an inorganic salt capable of crystallizing with the binding of water of crystallization. The aqueous salt solution sprayed should contain an amount of water not substantially in excess of the amount of water capable of being bound as water of crystallization by the salt mixture formed, and the contact of the perborate in the aqueous solution should be effected at a temperature allowing crystallization of the salt solution.

As a result of the process, a salt mixture forms, in which substantially all of the water sprayed is bound as water of crystallization, and in which a granular perborate salt mixture is formed, the granules of which are composed of individual, finely divided water-soluble perborate particles, such as sodium perborate particles bound together by inorganic salt crystals containing water of crystallization. The perborate is present in the mixture in amount ranging from 15% by weight trihydrate to 95% anhydride, as, for example, in the case of sodium perborate in amount ranging from 15% NaBO .H O 3H O to 95% by weight NaBO .H O and preferably to 65% by weight of NaBO H O The perborate may be admixed with a solid divided inorganic salt, such as the same salt used in the sprayed solution in calcined form prior to the spraying and there may be present in the mixture, and/ or preferably in the solution the customary stabilizers for perborate compounds, such as magnesium silicate or other water insoluble silicates, magnesium soaps, magnesium phosphates, metastannic acid, etc.

The finely divided perborate, when the same is sprayed, may be moved in any desired manner, so that the individual particles contact each other to conglomerate, and may, for example, be sprayed in conventional rotating granulation devices. The perborate particles, however, may not be eddied or atomized in a gas stream such as air.

The perborate particles struck by the sprayed solution adhere to other perborate particles which have preferably not been wetted by the solution, and there is formed a granulate which consists of a plurality of perborate particles of original size, which are bonded together by the sprayed aqueous solution of inorganic salts. Since perborate particles, in the preferred embodiment of the process, are at room temperature, while the solution is generally sprayed at higher temperature, the solution cools down and solidifies with the formation of the solid salts which contain water of crystallization. There is thus produced a solid granulate of perborate particles of original size, which are cemented to each other, this granulate, upon being introduced into water, rapidly breaking up into the original perborate particles, due to the dissolving of the layer of inorganic salts containing water of crystallization located between or on the perborate particles, so that the entire original surface of the perborate powder is offered the water. Accordingly, these particles dissolve almost as rapidly as the non-granulated perborates of the original size.

As starting material, there is used primarily sodium perborate of the formula:

not limited to the use of perborates of the indicated particle size.

Inorganic salts which take up water of crystallization upon crystallizing are, for example, the carbonates and ortho-, pyroand polyphosphates, as well as the sulfates of the alkalis, particularly sodium and potassium. Mixtures of different salts may also be employed, in which connection the mixtures may contain identical or different cations and/or identical or different anions. It is advisable to use rapidly crystallizing solutions of salts which give off little heat of crystallization upon crystallization. This, however, is not absolutely necessary for the preparation of perborates of good solubility and stability, since the heat of crystallization which is liberated upon the solidification of the spray solution can be removed by cooling the originally formed, still solidifying or just solidified granulates in any conventional manner. The quantity of water to be added in the form of a solution of inorganic salts should be such that the added water can be bound by the inorganic salts present in the form of water of crystallization. If partially or completely dehydrated'perborates are granulated, they also are to be included among the inorganic salts which can take up water of crystallization. The quantity of water in ratio to the quantity of inorganic salts can vary within wide limits and can be so adjusted that the inorganic salts in the finished granulate are present between the lowest possible hydrate stage and the highest possible hydrate stage. It has been found advisable to regulate the water content in such a manner that the water-vapor partial-pressure of the finished granulates is not higher than the waterwapor partial-pressure of Na CO .7H O. The regulation of the degree of hydration of the inorganic salts used for the granulation is possible not only by the adjustment of a given concentration of the solution to be sprayed, but may be effected by admixing these salts in calcined form to the perborate. Finally, the water content of the granulates obtained can be reduced by carefully drying them, for example, in a stream of air.

The quantity of the spray solution of inorganic salts, the concentration of which can lie between 10% by weight and the saturation concentration at the temperature in question is dependent inter alia on the particle size of the perborates to be granulated and the size of the desired granulates. This quantity decreases with an increase in the particle size of the starting perborate and increases with the size of the desired granulates. If it is merely desired to convert perborate powder into granulates, then, in many cases, depending on the desired particle size of the granules, such small quantities of solution will be sufficient so that the granulate contains 95% and preferably 65% by weight NaBO .H O- the balance consisting of salt hydrate including possible stabilizers. Generally, more solution is employed, so that in the granulate, in addition to NaBO .H O .3I-I O there are present 540% by Weight and preferably 20-30% by weight of salt hydrate. may be of interest to prepare salt mixtures of lower perborate content which are intended, for example, for mixing with other detergent components. In this case, the NaBO .H O .3H O content can drop to 15% by weight. The quantity of solution which is sprayed onto the perborate or perborate salt mixture to be granulated is, for example, in the range of 5-45, and preferably -25% by weight referred to the granulate to be produced.

The temperature of the spray solution can have any desired value between room temperature (about C.) and the boiling point of the solution under normal pressure, but temperatures of more than 95 C. are seldom used. There are generally employed hot solutions-of inorganic salts of such concentration that upon cooling they precipitate solid salts or even entirely solidify. For this reason, the storage tanks, the conduits, and the nozzles should be heated. Furthermore, it is advisable In many cases, however, it

, between 5-200 seconds.

to work under such conditions of concentration and temperature that the temperature variations within certain limits cannot lead to the depositing of solid salts containing water of crystallization thus clogging in the apparatus.

It has already been mentioned that upon the solidification of the applied aqueous solution, a greater or lesser amount of heat of crystallization is liberated. It may be desirable to still remove this heat as far as possible, while it is being given off. In such cases the granulate is cooled, the cooling possibly starting directly after the formation of the not yet entirely solidified granules.

For the carrying out of the method of the invention, there is used an apparatus which brings about a continuous change in surface of the salt to be granulated, which is contained therein, so that each particle is struck at least once by a drop of the sprayed solution during the time that it remains in the apparatus. The process is preferably carried out in rotating tubes, drums, or plates, .in which connection the axes of rotation of the tubes or drums may be horizontal or inclined, and the plates themselves may be horizontal or inclined. The material to be granulated is charged into the apparatus and passes through the same. The salt solution is sprayed onto the moving perborate mass, the nozzle as far as possible being of such a nature that the atomized solution of inorganic salts is distributed as uniformly as possible over a surface against which the moving perborate mass strikes. Furthermore, nozzles which send out a fanshaped jet have proven preferable. In this connection, the fan of atomized solution should preferably form a right angle with the direction of motion of the material.

The apparatus can be provided with stationary or with co-rotating inserts, which, however, 'should extend extensively in the direction of motion of the material to be granulated, so that as little friction as possible with the material passing through takes place, the continuous passage of the material is favored, and contact of already formed granules with fresh or only partially granulated material is extensively avoided. Such inserts are, for example, worms, scraper plates, or deflector plates located in the direction of motion of the material along which the material slides. By means of these inserts, the result is obtained that the time of stay of each particle in the apparatus is as close as possible to the average time of stay of the entire material. The time of stay of the material can vary within wide limits, as, for example, However, a time ofstay of 301-0O seconds has proven advisable. In this way there is obtained a gentle treatment of the primarily formed, still deformable granules. In case of a longer time of stay, there takes place, to be sure, a formation of larger granules, but at the same time, there must be expected an undesired deformation of the still unhardened granules. For this reason, it is advisable either to adjust the operating conditions in such a manner that granules of the desired size are formed in one operation, or else to subject an already granulated material to repeated granulation processes only after it is already solidified and preferably also cooled. Two or more consecutive granulation processes, however, should in general only be employed when a different salt is sprayed onto the granules in each granulation process.

If a cooling of the granules is desired, this can be effected in all known apparatus such as, for example,

' cooling towers, cooling drums, etc. Cooling in parallel flow or counter-flow of the material conveyed or eddied in a stream of air has proven particularly suitable. It is also possible to allow the material which is to be cooled to trickle down in a vertical pipe or tower and blow cold air against it at a speed which is somewhat less than the velocity of fall of the granules. in this way, the cooling of the granules can be combined with an air sifting.

One apparatus for the carrying out of the process of J the invention is shown in Fig. 1. The perborate to be granulated is located in the storage vessel 1 and passes via the flow regulating or metering device 2 into the funnel 3, which conducts it to the granulating device 4, which is represented here as an oblique rotating plate. The storage vessel 5 contains a calcined salt, which may be used as an auxiliary agent in the granulation, and which can be conducted via the metering device 6 into the hopper 3, where it mixes with the perborate. The pressure vessel 7 contains a preferably hot solution of the salt contained in the storage vessel 5 or of another salt which crystallizes combining with water of crystallization. The vessel 7 is placed under pressure by a gas via the conduit 8 and the reducing valve 9, so that the solution passes through the line 10, which can be provided with heating means ll to the nozzle 12 and from there is sprayed onto the granulating plate or tray 4. The granulating plate 4, which is shown in greater detail in Figs. 2ac, will be described later. The granulated material passes over the rim of the plate into the funnel 13 and from there into the pipeline 14 and the vessel 15. Air is forced into this vessel 15 by the fan 16 via the conduit 17 and the throttle valve 18. Part of this air flows in the pipeline 14 in counter-current to the granulate which has just been formed at such a speed that the speed of fall of the granulate in conduit 14 is strongly reduced, the granulate at the same time being cooled. The granulate falls-to the bottom in container 15 and is conducted at the lower funnel-shaped part of the vessel 15 through the remaining part of the air forced into said vessel into the down conduit 19, which is connected with the lower part of the riser conduit 20. Through the lower open end of the riser conduit 20, air is drawn in from the fan 27 at such a rate that the entire perborate is raised through this riser conduit into the separator 21. The air leaves the separator through the conduit 22 and passes to the cyclone 23,

where the fine, non-granulated or insufliciently granulated particles entrained by the stream of air are separated and returned through conduit 24 to the funnel 3. The stream of air is drawn 01f through fan 27, the throttle valve 26 and the conduit 25 from the cyclone 23. The perborate separated in the vessel 21 leaves the separator at its lower opening and falls onto the shaking screen 28; the material falling through the shaking screen is the granulate of the desired particle size and is discharged through the conduit 29. The coarsely granular material remaining on the screen 28 is carefully comminuted in the mill 30. The conduit 31 conveys the material emerging from the mill under the vacuum prevailing in the separator 21 back into the separator, where the dust particles are removed.

Figures 2a-2c show the granulating plate 4 of Fig. 1 in detail, and Fig. 2a is a projection of the granulating device on a plane parallel to the granulating plate 46. Fig. 2b shows the granulating device in section through a vertical plane coinciding with the axis of rotation of plate 40, and Fig. 2c shows the apparatus in perspective.

Referring to Figs. 2a-2c, the granulation takes place on the inclined rotatable granulating plate 4t) provided with a rim 52, which plate is driven by a variable geared motor 41. The geared motor 41 rests on a block 37 and is swingably supported, together with the latter on a base 42 via a pin 43. A locking device 44 permits the fixing of the desired angle of inclination. The material to be granulated is conducted via the hopper 3 and the charging pipe 46 to the plate 40, where it is moved over the surface of the plate by the rotation of the latter. The main portion of the material to be granulated collects on the rim of the plate at a place which is a greater or lesser distance from the deepest point of the plate, depending on the quantity of the material and the velocity of rotation of the plate, and forms there a mass 39, which is continuously rolled around. A part of the material is carried along at the rim of the plate in the direction of motion and then falls back from the upper rim over the inclined plate to the lower rim of the plate. The quantity of the material carried along in this manner and the width of the surface taken up by the material which falls back, can be regulated by the speed of rotation and the inclination of the plate. The backwardfalling material trickles in the form of similar curves or parallel lines 47 back over the inclined plate, and combines with the mass 39 located at the lower rim of the plate. In this way a continuous change in the surface of the material to be granulated, located on the plate, is obtained.

Onto the material trickling down in accordance with the lines 47, there is now directed the preferably fanshaped jet 48 of atomized solution, which is conducted to the nozzle 49 via a conduit 50, provided with the accompanying heating coil 51. Insofar as a fan-shaped nozzle jet is used, it is advisable to adjust it in such a manner that the lines 47 form right angles with the generatrix of the jet 48. The sprayed particles now come into contact with the mass 39 of the material to be granulated and have an opportunity there to agglomerate with other particles of material. It may happen that sprayed granules stick to the rim 52 of plate 40. These granules are scraped off from the plate rim 52 by a stationary scraper 53, which is connected by the holding device 38 with the bearing block 37 of the motor 41. The scraper 53 is developed as a guide plate, the shape of which is identical to the curve of fall of the outermost lines 47. As a result of this, material particles are deflected without strong friction into the desired direction of motion. Behind the scraper 53, there is in this way produced a surface which is free of material onto which the starting material to be granulated falls.

The shape of lines 47 is dependent, inter alia, on the particle size of the materials falling along these lines. Since the coarse granules have narrower curves of fall, the granulates migrate, corresponding to the increasing particle size, towards the left, out of the region of the nozzle jet 48, and, finally fall, following the arrows 54, into the hopper 55, where they are further Worked in the manner described above.

The granulation can also be effected in a rotating drum, which is shown in longitudinal section in Fig. 3a

and in cross-section in Fig. 3b. The material to be granulated is conducted via the hopper 60 and the pipe 61 into the drum 62. It is partially raised there by the rotary motion of the drum and forms the continuously moving mass 58 in the latter. The stripper 64 prevents too extensive a lifting of the material and a baking of the sprayed particles on the wall of the drum. The solution used for the spraying is introduced through the pipe 56 into the inside of the drum 62, and is converted there by the nozzles 57 into the spray jets 63. The spraying need not be effected over the entire length of the pipe. If only the central region 66 of the pipe 62 is used for the spraying, there takes place in the upper region 65, where the material enters, a mixing of the components to be granulated, and in the lower region 67 of the pipe the particles struck by the solution have an opportunity to bake together with other particles of the mass 58 to be granulated. The granulates emerge from the drum along the path shown by the arrow 68.

The following examples are given by way of illustration and not limitation:

Example 1 For the carrying out of the process, there was employed an apparatus in accordance with Fig. l, which was provided with a granulating plate in accordance with Pigs. Za-Zc. 1,270 lag/hr. of a dry perborate, which contained about of the water of crystallization corresponding to the formula Na BO .H O .3H O and also 123 kg/hr. of calcined soda were conducted continuously onto the granulating plate, the size, inclination, and velocity of rotation of which were such that the average time of stay of the perborate was 30-40 seconds. 397 kg./hr. of a 30% soda solution of a temperature of about 50 C. were sprayed by means of a nozzle 49 onto the perborate-soda mixture whichrtrickled down along the lines '47 over the plate. The spray jet was fan-shaped. The line of contact of the fan on the plate surface was in this connection practically perpendicular to the flow lines 4-7 of the perborate particles. About 500 m. /hr of air of a temperature of 15-25" C. was passed in counter-current in conduit 14 to the granulate which trickled down from the plate. The time of stay of the granulates in the conduit was about seconds. The material passed together with a part of the stream of air from the fan fan 16 via the conduit 19 into the riser pipe 20, in which the material was conducted upward With an air velocity of about 8-9 meters per second and a velocity of its own of 13 meters per second. Afterthe separation of the finelypulverized portion (about 50 kg./hr.) in the separator 21 and cyclone 23, which was returned to the hopper 3, and separation of the oversize kg./hr) inthe shaking screen 28 (inside mesh width 2.5 mm.), there were obtained at the screen outlet 29 1,790 kg./hr. of a granulate of the composition:

Percent by weight NaBO .H O 46.2

(=71% by weight NaBO .H O .3I-I O) Na CO Water of crystallization 40.3

The screen analyses of the starting materials and of the granulate are set forth in the table after Example 2.

Example 2 In the apparatus according to Example 1, 840 kg./hr. of the perborate used in the said example, and 101 kg. of calcined soda were sprayed with 179 kg./hr. of soda solution of a temperature of about C. The granulate was cooled in the pipe by conducting about 400 m. /hr. of air at a temperature of 1S25 C. in counter-current to it. The time of stay of the material in the tube 14- was about 7 seconds. The air velocity prevailing in the riser 20 was about 7-8 m./sec., and the velocity of the material itself 1-2 m./sec. In the cyclone 23, there were obtained kg./hr. of fine materials, which were conducted to the hopper 3. From the shaking screen 28, there emerged 1,120 kg./hr. of granulate of the following composition:

Percent by weight Perborate (=75% by weight NaBO .H O .3H O) 48.7 Soda 11.5 Water of crystallization 39.8

The screen analyses of the starting materials and of the granulates are the following:

Percentage of Fractions in Weight Percent Mesh Aperture of the The size of the granulates to be produced in accord- A dry granular detergent is made by spraying an aqueous paste of the said detergent in hot air. The screen analysis of the detergent is the following:

Percentage of Mesh aperture of the screen in mm. the fractions in Weight percent parts by weight of this granular detergent are mixed with 20 parts by weight of a granular perborate obtained according to the Examples 1 or 2. The mixture does not separate in handling transportation and storage as it does when the perborate is used in the not agglomerated state.

The chemical composition of the detergent obtained by spraying was the following one:

Percent by weight Water up to by weight.

As avoiding of separation is a matter of grain size and not of chemical composition, detergents of any chemical composition may be used instead of the above.

If the granular perborates should contain stabilizing agents these should be present in an amount of 05-20 percent by weight, calculated on the Na BO .H O present in the salt mixture.

While the invention has been described in detail with reference to the specific embodiments shown, various changes and modifications will become apparent to the skilled artisan, which fall within the spirit of the invention and the scope of the appended claims.

We claim:

' 1. Process for the production of granular salt mixtures containing perborates, which comprises moving a finely divided, water-soluble perborate on a support surface for contact between the individual divided particles, while spraying the perborate with an aqueous solution of an inorganic salt capable of crystallizing with the binding of water of crystallization, said solution being unsaturated with respect to said inorganic salt at the temperature of operation, the contact of the perborate and aqueous salt solution being effected 'at a temperature allowing crystallization of the salt solution and agglomeration between individual divided perborate particles, said salt solution sprayed containing an amount of water not substantially in excess of the amount of water capable of being bound as water of crystallization by the salt' mixture formed the quantity of solution which is sprayed onto the perborate to be granulated being in the range of 545% by weight based on the granulate to be produced, and recovering the granular agglomerated perborate particle salt mixture formed containing substantially all of the water sprayed as water of crystallization.

2. Process according to claim 1, in which said aqueous salt solution is a salt solution of a. member selected from the group consisting of alkali metal carbonates, phosphates, sulfates, and mixtures thereof.

3. Process according to claim 1, which includes cooling the mixture after said spraying.

4. Process according to claim 1, in which said aqueous salt solution sprayed contains a quantity of water not in excess of the amount capable of producing a salt mixture 9 with a vapor pressure equivalent to the vapor pressure of Na2CO3-7H20.

5. Process according to claim 1, in which said finely divided perborate is sprayed while being rotated in a totating granulating device.

6. Process according to claim 1, in which said perborate is admixed with a solid, divided, inorganic salt prior to said spraying.

7. Process according to claim 1, in which said perborate is a sodium perborate.

8. Process according to claim 1, in which said spraying is effected in the presence of a stabilizer for the perborate.

9. Process according to claim 1, in which the quantity of solution which is sprayed onto the perborate to be granulated is in the range of 10-25% by weight based on the granulate to be produced.

10 10. Process according to claim 6, in which said solid, divided, inorganic salt is the same salt as the salt form ing said aqueous salt solution.

11. Process according to claim 10, in which said solid,

divided, inorganic salt is a calcined salt.

References Cited in the file of this patent UNITED STATES PATENTS 1,989,759 Longue et a1. Feb. 5, 1935 2,767,146 Bonewitz et al Oct. 16, 1936 2,308,992 Mertens Jan. 19, 1943 2,524,394 Madorsky Oct. 3, 1950 2,706,178 Young Apr. 12, 1955 2,763,618 Hendrix Sept. 18, 1956 2,765,239 Siegrist Oct. 2, 1956 UNITED STATES PATENT OFFICE CERTIFICATION OI CORRECTION Patent No. 2,975,142 March 14', "1961' Joachim Schmidt et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 44, for "perborates" read perborate column 6, line 75, the formula should appear as shown below instead of as in the patent:

NaBO ,H O .3H O

column 8, line 38, the formula should appear as shown below instead of as in the patent:

NaBO .H O

Signed and sealed this 1st day of August 1961 (SEAL) Attest:

ERNEST W0 SWIDER DAVID Lo LADD Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2,975,142 March 14, 1961 Joachim Schmidt et a1.

NaBO II-I O Signed and sealed this 1st day of August 1961.

(SEAL) Attest:

DAVID Lo LADD Attesting Officer

Claims

1. PROCESS FOR THE PRODUCTION OF GRANULAR SALT MIXTURES CONTAINING PERBORATES, WHICH COMPRISES MOVING A FINELY DIVIDED, WATER-SOLUBLE PERBORATE ON A SUPPORT SURFACE FOR CONTACT BETWEEN THE INDIVIDUAL DIVIDED PARTICLES, WHILE SPRAYING THE PERBORATE WITH AN AQUEOUS SOLUTION OF AN INORGANIC SALT CAPABLE OF CRYSTALLIZING WITH THE BINDING OF WATER OF CRYSTALLIZATION, SAID SOLUTION BEING UNSATURATED WITH RESPECT TO SAID INORGANIC SALT AT THE TEMPERATURE OF OPERATION, THE CONTACT OF THE PERBORATE AND AQUEOUS SALT SOLUTION BEING EFFECTED AT A TEMPERATURE ALLOWING CRYSTALLIZATION OF THE SALT SOLUTION AND AGGLOMERATION BETWEEN INDIVIDUAL DIVIDED PERBORATE PARTICLES, SAID SALT SOLUTION SPRAYED CONTAINING AN AMOUNT OF WATER NOT SUBSTANTIALLY IN EXCESS OF THE AMOUNT OF WATER CAPABLE OF BEING BOUND AS WATER OF CRYSTALLIZATION BY THE SALT MIXTURE FORMED THE QUANTITY OF SOLUTION WHICH IS SPRAYED ONTO THE PERBORATE TO BE GRANULATED BEING THE RANGE OF 5-45% BY WEIGHT BASED ON THE GRANULATE TO BE PRODUCED, AND RECOVERING THE GRANULAR AGGLOMETRATED PERBORATE PARTICLE SALT MIXTURE FORMED CONTAINING SUBSTANTIALLY ALL OF THE WATER SPRAYED AS WATER OF CRYSTALLIZATION.