DE2652776A1 - Stabilised sodium percarbonate mfr. - by precipitating in presence of silicate, then increasing the silicate content of the mother liquor - Google Patents

Abstract

Stabilised sodium percarbonate mfr - by precipitating in presence of silicate, then increasing the silicate content of the mother liquor. Prepn. of sodium percarbonate (I) comprises precipitating (I) from a soln. (pref. of sodium carbonate and hydrogen peroxide) contg. silicate, to obtain particles with a limited quantity (pref. 0.1-2.0 wt %) of silicate distributed in and through them. Sufficient silicate is then deposited on the surface of the particles to improve their resistance to external contaminants. (I) is stabilised against both its intrinsic instability (e.g due to Fe present in reactants) and instability due to external causes. Loss of active oxygen content, agglomeration and corrosion are prevented. (I) can be stored in bulk, safely for several months or even weeks, e.g. prior to in corporation into detergent compsns. Only small amts. of stabiliser, and no special appts. are required.

Description

"Process for the production of sodium percarbonate"

The invention relates to a process for the production of sodium percarbonate, especially of sodium percarbonate, which has an increased stability during storage Has.

Sodium percarbonate, the commercially available oxygen-active product, made by treating sodium carbonate with hydrogen peroxide has the Disadvantage that it decomposes quickly when stored. For the decomposition of the sodium percarbonate various factors are responsible, e.g. impurities within the crystals or agglomerates, or external influences, e.g. contact with impurities, like water or metal ions, e.g. iron, which is known to be hydrogen peroxide decompose. In addition, sodium percarbonate in granulate form is only low Has thermal conductivity, so that when storing or transporting larger quantities the exothermic decomposition under almost adiabatic conditions takes place. If the rate of decomposition is sufficiently high, there is heat loss less than the newly formed heat, so that the temperature of the percarbonate rises, which in turn increases the rate of decomposition. If nothing is done about it, so the temperature of the uncontrollable decomposition is soon reached the sodium percarbonate decomposes completely and: steam and oxygen are produced. That is why it is of the greatest economic importance to counteract sodium percarbonate Stabilize decomposition. It also means the decomposition of sodium percarbonate a risk in extreme cases where the pressure of the container is released Gas that cannot escape quickly enough through the existing openings, is torn open. Also remains after the total decomposition of the sodium percarbonate at least part of the product back in the form of a hydrated melt, which can only be removed from the container with great effort and expense.

Sodium percarbonate is used in larger quantities for up to several weeks or even months before being incorporated into detergents. While During storage, the product can absorb moisture from the environment. Besides that the equipments for handling sodium percarbonate exist in larger ones Soft steel quantities. The polymer coating that often protects this equipment However, it is caused by contact with the percarbonate, which acts as an abrasive removed. Therefore, in practice, it is difficult to prevent the percarbonate comes into contact with external impurities.

Percarbonate in granulate form consists of agglomerations of individual ones Crystals. To overcome both problems, i.e. decomposition from external impurities and its own instability caused by contact with the output connections Existing impurities, e.g. iron, you have to - the granulate both internally as well as stabilize externally.

Although it was previously known that the stabilization of percarbonate Although it is desirable to distinguish between internal instability and external instability induced decomposition was not clearly recognized. That is why in a well-known Process2 generally described as a wet process, the percarbonate thereby produced, -ass -man mixed with a solution of sodium carbonate with hydrogen peroxide and separating the precipitated percarbonate from the mother liquor. In this procedure the solution becomes larger during the crystallization of the percarbonate added to sodium silicate. The single percarbonate crystals are on this Well protected, the excess silicate serves to protect the granulate from larger ones Fine impurities. The percarbonate granulate produced in this way however, is of varying quality and often only has a small amount available Oxygen content, a -relatively low bulk density and accordingly a high brittleness compared to silicate-free percarbonate granules. That's why Products made in this way are rarely incorporated into detergents less suitable.

The large amounts of silicate used now also make the . Production more difficult because the percarbonate granulate with the usual Equipment, e.g. with centrifuges, is difficult to drain. To this disadvantage To eliminate, an attempt was made to add less silicate to the percarbonate. It was however found that the product is not stable enough and too quickly loses available oxygen. Although these percarbonates are suitable physical Properties, se extremely decompose because of internal instability. easy and are therefore too dangerous for storage in larger quantities.

The invention therefore relates to a method for production of sodium percarbonate, which is characterized in that a) sodium percarbonate from a silicate solution as solid particles that contain a small amount of silicate contain, precipitates, and b) a sufficient amount of silicate to end to ensure external protection against contamination on which particles precipitate.

A small amount of silicate is understood here to mean an amount that increases the resistance to internal decomposition, i.e.

at least 0> 1 percent by weight of silicate, calculated as silicon dioxide, However, less than the amount at which the dehydration of the product is significantly more difficult will. It should be emphasized that the sodium percarbonate is dried with conventional Solid-liquid separation equipment, such as centrifuges, the more difficult it becomes, the more Silicate containing percarbonate. Less than 0.6 weight percent is desirable, preferably less than 0.4 percent by weight of silicate, if the percarbonate is produced in a wet process will, i.e. when the water is removed in centrifuges.

In another embodiment of the method according to the invention, in which an aqueous solution of sodium percarbonate is mixed with crystal nuclei or is sprayed onto crystal nuclei and the solid sodium percarbonate by evaporation of the water is produced, - larger amounts of silicate can be used, generally up to about 1.0 percent by weight in the process according to the invention it- desirably that the silicate be uniform within each percarbonate particle is distributed. In the wet process, this can be achieved by changing the silicate concentration controlled in the aqueous solution during the precipitation of the sodium percarbonate.

It was found that the silicate uptake, expressed as a percentage the total amount of silicate present in the solution, with increasing amount in the Solution decreases, and that the concentration of silicate in the solution at which the precipitating percarbonate contains more silicate than the prescribed amount, easily can be determined A suitable starting concentration of silicate is below 5 g / liter, preferably 0.3 to 2.0 g / liter, so that the percarbonate precipitate Contains 0.1 to 0.4 percent by weight of silicate. Assuming the silicate concentration is controlled in such a way that the particles do not absorb more silicate than the prescribed one Amount, the total amount of silicate can be present in the solution at the beginning.

However, some of the silicate can also be used during the precipitation admit, either continuously or in small increments Servings.

Suitable silicates for addition during precipitation in the invention Processes are alkali metal or alkaline earth metal silicates, but preferably sodium silicate. The silicate is preferably added in aqueous solution, although an addition in solid form is also possible.

A preferred embodiment of the method according to the invention is characterized in that a concentrated aqueous solution von.Natriumcarbonat and sodium chloride, which contains 0.3 to 2 liters of sodium silicate, expressed as silicon dioxide> contains, at a temperature of 15 to 250C continuously or discontinuously mixed with a hydrogen peroxide solution. After the addition, the. Solution in Wet process cooled to 5 to 150C. In general, the greater part of the Sodium percarbonam already at the-higher temperature, so that only a -low Amount remains in solution that precipitates on cooling. The addition of silicate, preferably in aqueous solution, can take place during the addition of hydrogen peroxide.

In another embodiment of the method according to the invention, in which the water is evaporated, practically the total amount is available Silicate retained in the sodium percarbonate solution in the solid percarbonate, so that by adjusting the weight ratio of silicate to percarbonate in of the solution also the - silicate content of the solid percarbonate adjusts.

Step b) of the inventive method, in which the precipitated Percarbonate is treated with silicate to protect the particles from external contamination to protect, can either before or after the separation of the precipitate from Mother liquor take place. The separation is often carried out by centrifugation.

Is a stage of the process according to the invention before the separation the precipitation is carried out, the additional addition of silicate is preferred strictly controlled.

then in the process according to the invention one can da @@ stages a) and b) incorporate it into a cycle by adding an aqueous solution of sodium carbonate, Sodium chloride and sodium silicate mixed with hydrogen peroxide, 2) the sodium percarbonate fails, 3) the solution with at least 0.5 g / liter of silicate, calculated as silicon dioxide, added, JI> separates the percarbonate from the mother liquor and 5) at least one The starting compounds are added to part of the mother liquor and returned to stage 1).

After step a) of the process according to the invention, @ in general remains a certain amount of silicate in the solution, which is not enough to deposit enough silicate on the percarbonate particles. That's why the Mother liquor further silicate added, preferably during or at the end of the cooling period. The addition of silicate is allowed. of course not be done, bever one a considerable amount of percarbonate has precipitated, otherwise there is a risk of that a larger amount of percarbonate granulate more than the prescribed amount contains of silicate. Preferably enough silicate is added that 0.2 to 0.6 Weight percent silicate are deposited on the particles. The exact amount can easily be determined by experiment, in general a quantity is sufficient, which increases the silicate concentration in the solution to 0.5 to 2.0 g / liter. In large-scale It is common practice to use all or part of the mother liquor in plants a collecting vessel and they are there with more sodium carbonate and hydrogen peroxide to move. If the expensive step of silicate removal is not performed, so the silicate present in the mother liquor is returned. Therefore it is possible that the percarbonate crystals that fail in the first stage, contain more than the prescribed amount of silicate. However, it has been found that the solution can be achieved by strictly adhering to the amount of silicate in the second stage, so that 0.3-0.5 weight percent silicate on the particles are precipitated, the precipitate gives the particles considerable protection against external contaminants and also / silicate content in the Solution is low enough to recycle the mother liquor without difficulty can.

The method according to the invention has the advantage that the stabilization of percarbonate against external and internal decomposition without additional Equipment and with only a very small amount of stabilizer can.

As an alternative or in addition, you can use the wet precipitation, which was separated from the mother liquor by centrifugation, or the dry one Bring percarbonate into contact with silicate using conventional coating methods, e.g.

by slurrying in an aqueous silicate solution, e.g. a vane stirrer, or by spraying in a fluid bed, a rotating drying plate or drum dryer. Since these coating processes are not part of the percarbonate production process, Significant amounts of silicate are deposited on the particles. Naturally you can add silicate to protect Hes percarbonate against external contamination it is carried out in several stages, in practice / however it is advisable to use the silicate to be added in a single step.

In the process of the present invention, the percarbonate particles are preferred sprayed with an aqueous silicate solution containing other compounds, the water is then evaporated.

This process allows the percarbonate particles to be treated with a mixture of sodium carbonate and other mineral salts, in which the silicates are dispersed. This way you can coat the particles in a Stage, and this is the most effective way to counteract the particles to protect external contamination.

In general, the temperature of the aqueous Solution / about 250C above / 25oc below the temperature of the particles to be sprayed.

A concentrated aqueous solution is expediently used when spraying Solution of the various coating agents used, preferably as saturated as possible Solution. In this way, the amount of water to be evaporated is as small as possible held.

During the spraying and evaporation, the percarbonate particles become held at a temperature below the decomposition temperature, in general below 90 ° C, preferably between 30 and 800C.

The evaporation takes place simultaneously with the spraying and in the same Environment or in a separate apparatus. In general, it will be a continuous Spray and dry processes are used, e.g. a fluidized bed or other conventional one Contraption. If a fluidized bed is used, the temperature of the fluidized bed is about 30 to 80 ° C.

The use of a fluid bed has proven to be particularly beneficial, on the one hand, because the spraying and evaporation are carried out simultaneously in the same device takes place, on the other hand -because these processes are hermetic and more homogeneous Coating permitted.

Any inert gas, in particular air, is suitable as a fluidizing agent. This gas can be heated-up to that temperature of the fluidized bed to keep at the desired height. The heat can also be supplied in other ways, e.g.

through a number of tubes that-are in the fluidized bed.

The process according to the invention can, however, also be carried out batchwise will.

If stage b) of the process according to the invention also comes from the mother caustic separated percarbonate particles or with particles that are obtained by evaporation of the Water was carried out, so is the least on the particles The amount of silicate to be deposited is again 0.2 percent by weight, but in contrast to the continuous process, where the mother liquor is recycled an amount of silicate above about 0.6 percent by weight is not critical, the upper limit is therefore determined more by economic considerations. In practice it will be generally 0.2 to 5.0 percent by weight, preferably at least 0.4 percent by weight, e.g. 0.4 to 1.5 weight percent silicate deposited on the particles.

It was found that the ability of the silicate to affect the Surface of the particles precipitate, due to the presence of carbonate in the surface is affected.

The percarbonate particles are wet process under normal conditions dried, enough mother liquor remains in the percarbonate particles, ass 0.1 to 0.4 percent by weight of silicate give the particles sufficient protection. Will However stricter drying methods are used, e.g. to reduce the mother liquor content to reduce the particles to the content of silicate-free percarbonate, so increases the ability of the silicate to protect the particles from external contamination, away.

Therefore, unlike standard procedures, it is desirable, at least retain some amount of mother liquor in the percarbonate particles, preferably so much that at least 2 percent by weight of sodium carbonate, based on the particles, are pre-banded in the surface layer. This amount is generally higher than is normally allowed, as an increased content of mother liquor additional drying and therefore causes additional costs. However, is the content of mother liquor not high enough in the percarbonate particles or the particles become due to evaporation of water, the sodium carbonate content can be increased by that one slurried the particles in a sodium carbonate solution or with the Solution sprayed and then dried.

A mixture of sodium carbonate and Sodium sulfate, which may also be applied to the surface of the percarbonate Contains silicate.

The sodium sulfate, carbonate and silicate are preferred in such amounts or that the molar ratio of carbonate / sulfate is between 0.5 and 5 The best results are obtained with a molar ratio of about 3. The amount of silicate present in the coating agent is generally 1 to 20 percent by weight, preferably 2 to 15 percent by weight, based on the Coating agent and calculated as Silica.

The amount of solid coating agent advantageously corresponds to 0.5 up to 20 percent by weight, preferably 3 to 15 percent by weight, based on the percarbonate. An amount of 0.5 percent by weight is sufficient to at least partially remove the percarbonate to be covered and to ensure increased stability. The mixture will be like this set that at least 0.2, but preferably at least 0.4 percent by weight Silicate can be deposited on the surface of the percarbonate. In general however, it is not convenient to use an amount of 20 percent by weight of the coating agent to exceed.

The particles coated with the sulfate / carbonate / silicate mixture can can be incorporated into cleaning agents without further treatment.

If the sodium percarbonate in the wet process of the invention Process produced, the total amount of silicate in or on the percarbonate crystals at least 0.6 percent by weight, but preferably not more than about 1.0 percent by weight, calculated as silica. Expediently, the amount in the precipitate distributed amount of silicate about 0.2 to 0.4 percent by weight and that on the surface the amount of particles deposited is about 0.4 to 0.5 percent by weight.

The sodium percarbonate produced in the process according to the invention shows improved physical properties compared to the products that Contain large amounts of silicate that was not added in a controlled manner. the Products manufactured in the process according to the invention are against internal and also Very stable decomposition caused by external influences.

The examples illustrate the invention.

The stability of the percarbonate against internal decomposition, i.

not triggered by moisture from the atmosphere, is used in the following experiment determined: A percarbonate sample is heated to 1050C and at this temperature Leave for 2 hours.

The available oxygen content is measured before and after the experiment measured, the loss of oxygen is expressed as a percentage of what was originally present Expressed oxygen.

Samples with poor values in this experiment are for storage unsuitable in large quantities.

In order to determine the influence of external impurities, a Sample of dry percarbonate with 10 percent by weight of an aqueous solution containing 530 ppm iron (III) ions as iron (III) chloride contains, sprayed. That sprayed Sodium percarbonate is poured into a 500 ml Dewar vessel at room temperature. The vessel is packed to the brim by tapping it lightly, the percarbonate is opened Edge height streaked.

During the next 2 days, the temperature of the vessel will be constant controlled This experiment corresponds to the calculated decomposition rates at 70 ° C in the presence of moisture and in practical handling and storage of larger amounts of percarbonate.

Ex. 1 4500 liters of a sodium carbonate solution, which each Liter 250 g sodium carbonate, 160 g sodium chloride and 0.7 g sodium silicate, calculated as silicon dioxide, is mixed with 46 liters of 65 percent hydrogen peroxide at 25 ° C and at the same time with 44 liters of sodium silicate solution in a weight ratio of Na2O @ SiO2 of 1: 3.3 and a specific weight of 1.33 continuously added. The solution is cooled to 15 ° C and mixed with a further 44 liters of sodium silicate solution the same composition added. Centrifugation gives 750,000 g Sodium percarbonate that is dried.

The dry product contains 0.6 percent by weight sodium silicate, calculated as SiO2. The product only loses 10% of the available oxygen and shows after 3 days in the iron-catalyzed decomposition experiment no evidence of an uncontrollable decomposition.

Comparative Example 1 The procedure of Example 1 is repeated, with the difference that no more sodium silicate solution is added at 150C will. The dry product contains only 0.3 percent by weight Silicate, calculated as SiO2. In the decomposition attempt, it only loses 10.8 after 2 hours % of available oxygen, suggesting that the product is opposite internal decomposition is relatively stable. In the second attempt, however, it warms up by itself to 1000C and completely decomposes after It, It hours. Kinetic Studies prove that the rate of decomposition of the percarbonate in the presence of 10 weight percent water is high. The product is therefore vis-à-vis external Impurities not stable and therefore suitable for transport and storage in larger quantities Quantities not suitable.

Comparative Example 2 According to the procedure of Comparative Example 1 a silicate-free sodium percarbonate is produced. This product will then Sprayed with a sodium silicate solution in a ~ Lödige-Morton mixer until a Silicate content of the dry product of 1.0 percent by weight, calculated as Si02, is reached.

The treated and the untreated product are at loss investigated on available oxygen. The loss of available oxygen is practically the same for both products, i.e. spraying with the silicate solution no significant impact on the resistance of the product to internal Decomposition. In contrast, however, the untreated product decomposes in the The experiment catalysed with iron ions was complete after 3 hours, whereas the sprayed one product shows no signs of deterioration after 48 hours. That suggests that the sprayed product is stabilized against decomposition caused by external influences is.

For example 1. 2 50 liters of sodium silicate solution with a weight ratio of Na 2 O: SiO 2 of 1.0: 3.3 and a specific gravity of 1.15 are 6.0 Liters of an aqueous solution of 250 μl of sodium carbonate and 100 g / liter of sodium chloride mixed.

The solution is transferred to another vessel and at 25 0C with Hydrogen peroxide added. The mixture becomes the same with another 50 liters Sodium silicate solution mixed and cooled to 50C. The sodium percarbonate will centrifuged off and dried. The dry product contains 0.6 percent by weight Sodium silicate, calculated as Si02.

The loss of available oxygen is only 10.1%.

After 3 days in the iron ion catalyzed decomposition test shows the product shows no signs of total decomposition.

The product is thus against both internal and external decomposition very stable.

Example 3 Sodium percarbonate produced according to Example 2 is used after centrifugation divided into 5 equal portions. The first serving will centrifuged again under more severe conditions to add 28 ml of mother liquor remove. The second portion is centrifuged to remove 16 ml of mother liquor. The fourth and fifth portions are made with the mother liquor obtained in this way treated. These samples are examined in the iron ion catalyzed decomposition test, 75 ml of an aqueous iron (III) solution being used instead of 1G percent by weight. The results are summarized in the table.

Table ~ Experiment content of mother liquor Time for complete (mi) (ml) Decomposition (hours) 1 -28 1.5 2 -16 1.5 3 0 2.25 4 +16 - 3 5 +28 24 The cheapest The effect of any mother liquor still present in the product is therefore clear.

Example 4 the sodium percarbonate, / according to BE-PS 760 508 produced was with an active oxygen content of 14.2 percent by weight and a silicate content of 0.68 percent by weight, is sprayed with about 150 ml of percarbonate of a solution, the 8.7 weight percent sulfate, 19.4 weight percent sodium carbonate and 1.9 weight percent Contains sodium silicate. The coated product then contains 0.96 percent by weight Silicate, 0.98 percent by weight sulfate and 2.18 percent by weight carbonate.

The device used for this consists of a cylinder with a Diameter of 15 cm and a height of 77 cm, the one at the bottom with a gas distribution plate with 2 mm holes and a system of tubes for steam heating in one effective pressure of 1 kg / cm2 is provided.

First 3 kg of the homogeneous sodium percarbonate particles are put into this device introduced. Air is passed through the gas distribution plate, creating the fluidized bed is kept at a 0 temperature of 60 to 70 C. By a spray device, which is located on the wall of the cylinder at a height of 11 cm from the floor, the aqueous solution of the coating agent is sprayed in at 70 to 80 ° C. The coating solution obtained by mixing the aqueous solution of about 30% carbonate and sulfate with 72 g of a 360-Baume'-sodium silicate solution with a molar ratio of SiO2 / Na20 from 3: 1. The height of the fluid bed is 30 cm.

After spraying in the aqueous solution, the coated sodium percarbonate particles become deducted.

The stability of the product in the presence of iron is increased by spreading in a thin layer of a sample of 450 g percarbonate particles on a polymer base certainly.

The sample is treated with a solution of 1.4 percent by weight iron (IID chloride sprayed. After homogenization, the resulting product is placed in a Dewar vessel filled in, the temperature changes are introduced into the mixture with a Thermocouple certainly. After 48 hours there is no evidence of degradation, the product is therefore stable against external contamination. In comparison, it decomposes an uncoated sodium percarbonate made in the same way and was examined accordingly, after 4 hours or less.

Claims (25)

Claims process for the production of sodium percarbonate, d u r c h e k e k e n n 2 e i c h n e t that a) sodium percarbonate from a silicate-containing solution as solid particles that contain a small amount of silicate, brings about precipitation, and b) a sufficient amount of silicate to make an external Ensure protection against contaminants upon which particles precipitate. 2. The method according to claim 1, characterized in that in Step.a) the sodium percarbonate precipitates from a solution which is 0.3 to 2.0 percent by weight Contains silicate calculated as silicon dioxide. 3. The method according to claim 1 and 2, characterized in that one in step a) sodium percarbonate precipitates 0.1 to 0.4 percent by weight Contains silicate calculated as silicon dioxide. 4. The method according to claim 1 to 3, characterized in that one in stage a) particles precipitate which contain at least 0.3 percent by weight of silicate, calculated as silicon dioxide. 5. The method according to claim 1 to 4, characterized in that one Step a) and b) built into a cycle process by 1) a aqueous solution of sodium carbonate, sodium chloride and sodium silicate with hydrogen peroxide added, 2) the sodium percarbonate precipitates, 3) the solution with at least 0.5 liters Silicate, calculated as silicon dioxide, added, 4) the percarbonate from the mother liquor separates and 5> at least part of the mother liquor with the starting compounds added and recycled in stage 1). 6. The method according to claim 1 to 5, characterized in that one in step 3) a solution is used which contains 0.5 to 2.0 liters of silicate. 7. The method according to claim 1 to 4, characterized in that one separating the sodium percarbonate from the solution. 8. The method according to claim 1, characterized in that in Stage a) evaporates the silicate-containing percarbonate solution. 9. The method according to claim 1 and 8, characterized in that one evaporates a sodium percarbonate solution containing 0.1 to 1.0 percent by weight of silicate /, calculated as silicon dioxide. 10. The method according to claim 1 to 9, characterized in that the8 in stage b) the silicate is precipitated onto the particles in the presence of a carbonate. 11. The method according to claim 1 to 10, characterized in that at least 2.0 percent by weight of sodium carbonate, based on the particles precipitates the particles. 12. The method according to claim 1 to 10, characterized in that one in stage b) a mixed salt of sodium sulfate, sodium carbonate and sodium silicate precipitates on the particles. 13. The method according to claim 1 to 12, characterized in that a mixed salt is used, its molar ratio of carbonate to sulfate Is 0.5: 1 to 5: 1. 14. The method according to claim 1 to 13, characterized in that a salt is used whose carbonate to sulfate molar ratio is about 3: 1 amounts to. 15. The method according to claim 1 to 14, characterized in that 0.5 to 20 percent by weight of the mixed salt, based on the sodium percarbonate, precipitates. 16. The method according to claim 1 to 15, characterized in that 3 to 15 percent by weight of the mixed salt, based on the sodium percarbonate, precipitates. 17. The method according to claim 1 to 16, characterized in that a mixed salt is used which calculates up to 20% by weight of silicate than silicon dioxide. 18. The method according to claim 1 to 17, characterized in that a mixed salt is used which calculates from 2 to 15 weight percent silicate than silicon dioxide. 19. The method according to claim 1 to 18, characterized in that a mixed salt in which the silicate is dispersed is used. 20. The method according to claim 1, 7 to 19, characterized in that the silicate by spraying the sodium percarbonate particles with an aqueous Solution of the silicate and optionally the other compounds precipitates. 21. The method according to claim 1, 7 to 20, characterized in that the sodium percarbonate particles are sprayed into a fluidized bed. 22. The method according to claim 21, characterized in that the Maintains the fluidized bed at a temperature of 30 to 800C 23. The method according to claim 1, 7 to 20, characterized in that the aqueous solution at a temperature sprayed in the range of # 25 ° C of the temperature of the particles. 24. The method according to claim 1, 7 to 20, characterized in that saturated aqueous solutions are used. 25. Sodium percarbonate, produced according to claims 1 to 24.