EP1131400B1 - Method for producing tenside granulates - Google Patents

Abstract

The invention relates to a method for producing tenside granulates containing anionic tensides, by means of granulation and simultaneous drying in the fluidised bed, in the presence of volatile bases. The invention also relates to the use of the inventive tenside granulates for producing especially pH-neutral detergents and oral hygiene products.

Description

The invention relates to a process for the preparation of surfactant granules containing anionic surfactants by granulation and simultaneous drying in the fluidized bed, which is carried out in the presence of volatile bases, and their use for the preparation of particular pH-neutral detergents, dishwashing detergents and cleaning agents and oral hygiene products.

Anionic surfactants such as alkyl sulfates and alkyl ether sulfates are common surfactants, which find a wide application in cleaning processes of all kinds due to their high washing power. Due to their manufacturing process, these are usually obtained in salt form as aqueous solutions or pastes, which are converted into their powder or granules, for example, by conventional drying technology, especially in the spray tower or in granulating. At the drying temperatures prevailing there, however, pH-neutral solutions or pastes of the alkyl (ether) sulfate would decompose autocatalytically into the corresponding olefinic base and the corresponding salts of hydrogen sulfate, which themselves act as acid in aqueous solution. For this reason, such pastes according to the prior art are provided with a so-called alkali reserve, ie such pastes are mixed with an excess of free hydroxides, in particular of sodium hydroxide. The sodium hydroxide is then able to trap the possibly formed by autocatalysis acid and so stop the decomposition process. Since the alkali reserve is added in excess, usually in such amounts that, for example, a fatty alcohol sulfate paste has a pH above 10, small residual amounts of unused sodium hydroxide always remain in the aqueous solution or paste of the alkyl (ether) sulfates. Even after the drying process of the solutions or pastes to the corresponding powders or granules, the residual amounts of the alkali reserve are present as minor constituents of the anionic surfactants. However, these residual alkali components in the anionic surfactants cause problems in a number of applications, as they may cause odors and color shifts, for example due to undesirable interactions with perfume raw materials or dyes. In addition, there are a number of application fields, for example in cosmetics or in the field of so-called pH-neutral detergents, dishwashing detergents and cleaners for which pH-neutral anionic surfactants are desired.

From the German patent application DE-A1- 43 04 062 discloses a process for the preparation of anionic surfactant containing granules prepared by granulation and simultaneous drying from aqueous pastes. For this purpose, aqueous pastes of the anionic surfactants in the acid form, as well as an aqueous alkaline solution separately charged with a gaseous medium (air, nitrogen) and sprayed separately or combined at a high propellant gas pressure in the fluidized bed plant. With this method, the energy demand associated with the drying of the aqueous anion pastes can be reduced. According to this disclosure, alkaline solutions of hydroxides, carbonates or hypochlorites of sodium or potassium are used to neutralize the anionic surfactants in the acid form. However, these remain in the produced anion granules, so that even after this process the disadvantages of the prior art are not overcome.

From the DE 197 07 649 C1 discloses a process for producing detergent raw materials by simultaneous drying and granulation of aqueous pastes in a thin film evaporator. The drying of these pastes is carried out at a temperature in the range of 120-130 ° C in the presence of a Alkalicarbonatzusatzes to paste and / or an alkaline gas stream.

It is an object of the present invention to provide a novel process for the preparation of anionic surfactant granules which overcomes the disadvantages of the prior art. According to the new process, on the one hand, the autocatalytic decomposition of the anionic surfactants during their drying should continue to be effectively prevented. In contrast to the previous methods, however, no disturbing residual amounts of alkaline substances should be present in the resulting surfactant granules. Furthermore, it was within the scope of the invention desired to produce anionic surfactants as granules with a high bulk density, which have only slightly dusty shares.

Surprisingly, the object has been achieved by adding to the aqueous, anionic surfactant (in salt form) containing surfactant pastes before and / or during the granulation and simultaneous drying in the fluidized bed with volatile bases.

The invention includes the finding that anionic surfactant granules which have no or lower residual amounts of alkaline substances are obtainable with the method according to the invention, so that they do not cause any undesired interactions with perfume or dyes. Furthermore, the invention includes the knowledge that by the ubiquitous presence of the volatile bases in the fluidized bed are effectively reduced even at the most remote locations of the apparatus, for example in the filter, decomposition of already formed dried anionic surfactants under thermal stress and Wandandbackungen the decomposed product can be reduced.

An object of the present invention therefore relates to a process for the preparation of surfactant granules, wherein after dissolving the surfactant granules in water, the aqueous solution has a pH value between 7 and 9.5, by granulation and simultaneous drying of an aqueous, anionic surfactant in salt form containing surfactant the fluidized bed, characterized in that prior to or during the granulation and simultaneous drying volatile bases in amounts of 0.05 to 5 wt .-% - based on the active substance of the anionic surfactants in aqueous surfactant preparation in the form

For the purposes of the present invention, aqueous surfactant preparations containing anionic surfactants are used for the process. In the simplest case, these are aqueous surfactant preparations which contain exclusively anionic surfactants. These are preferably used in the form of aqueous pastes, in particular with an active substance content of from 25 to 90% by weight, based on aqueous anionic surfactant paste.

Typical examples of anionic surfactants are fatty alcohol sulfates, fatty alcohol ether sulfates, glycerol ether sulfates, hydroxy mixed ether sulfates, monoglyceride (ether) sulfates, fatty acid amide (ether) sulfates and alkyl oligoglucoside sulfates. If the anionic surfactants contain polyglycol ether chains, they may have a conventional, but preferably a narrow homolog distribution.

For the purposes of the invention, preference is given to using fatty alcohol sulfates and / or fatty alcohol ether sulfates as anionic surfactants. Particularly suitable are those which follow the formula (I) ,

R ¹ O- (CH ₂ CH ₂ O) _m SO ₃ X (I)

in which R ^{1 is} a linear or branched alkyl and / or alkenyl radical having 6 to 22 carbon atoms, m is 0 or numbers from 1 to 10 and X is an alkali and / or alkaline earth metal, ammonium, alkylammonium, alkanolammonium or glucammonium.

Particularly preferred is the use of sulfates based on technical C _12/14 - or C _12/18 alcohol _fractions , based on natural oils and fats such as coconut oil, palm kernel oil, palstearin or tallow or even based on Ziegleralkoholen bwz. also of oxo alcohols in the range of C8 to C15 (or mixtures thereof of the abovementioned linear alcohols of natural oils and fats or Ziegleralkoholen with oxo alcohols) in the form of their sodium, potassium and / or magnesium salts.

Typical examples of ether sulfates of alcohols ethoxylated with on average 1 to 10 and in particular 2 to 5 moles of ethylene oxide are selected from the group caproic alcohol, capryl alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, Elaidyl alcohol, petroselinyl alcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol and brassidyl alcohol and their technical mixtures, in the form of their sodium and / or magnesium salts. The ether sulfates may have both a conventional and a narrow homolog distribution.

The aqueous surfactant preparations to be used for the purposes of the invention may contain, in addition to the anionic surfactants necessarily contained, optionally further surfactants or also additives which are preferably ingredients of detergents and cleaners.

Nonionic surfactants are preferably present in the aqueous surfactant preparations as further surfactants. Suitable nonionic surfactants are liquid alkoxylated, advantageously ethoxylated, in particular primary alcohols having preferably 9 to 18 carbon atoms and an average of 1 to 12 moles of ethylene oxide (EO) per mole of alcohol, wherein the underlying alcohols may be methyl-branched linearly or in the 2-position, or linear and methyl-branched radicals in the mixture, as they are usually present in Oxoalkoholresten. In particular, the nonionic surfactants of the type described are derived from linear alcohols of natural origin having 12 to 18 C atoms, such as coconut oil, tallow fatty acid or oleyl alcohol. The degrees of ethoxylation given represent statistical means which, for a particular product, may be an integer or a fractional number. Preferred alcohol ethoxylates have a narrow homolog distribution (narrow range ethoxylates, nre). In particular, alcohol ethoxylates are preferred which have on average 2 to 8 ethylene oxide groups.

The preferred ethoxylated alcohols include, for example, C ₉ -C ₁₁ -oxoalcohol with 7 EO, C ₁₃ -C ₁₅ -oxoalcohol with 3 EO, 5 EO or 7 EO and in particular C ₁₂ -C ₁₄ -alcohol with 3 EO or 4 EO, C ₁₂ -C ₁₈ -alcohols with 3 EO, 5 EO or 7 EO and mixtures of these, such as mixtures of C ₁₂ -C ₁₄ -alcohol with 3 EO and C ₁₂ -C ₁₈ -alcohol with 5 EO.

Furthermore, as nonionic surfactants alkyl glycosides of the general formula RO- (G) _X , in which R is a primary straight-chain or methyl-branched in the 2-position aliphatic radical having 8 to 22, preferably 12 to 18 carbon atoms, G is a symbol which represents a glycose unit having 5 or 6 carbon atoms, and the degree of oligomerization x is between 1 and 10, preferably between 1 and 2, and in particular less than 1.4, to be contained in the aqueous Tensidzubereitungsformen.

If nonionic surfactants are present in the aqueous surfactant preparations with the anionic surfactants, their amount used can vary within wide ranges. As a rule, the nonionic surfactants are present in amounts of up to 50% by weight, calculated as the active substance and based on the active substance of the surfactants, in the aqueous surfactant preparations.

As further constituents, the aqueous surfactant preparation may contain additives, which are preferably ingredients of detergents and cleaners, preferably in amounts of from 0.001 to 80% by weight, based on the active substance of the aqueous surfactant preparation. Particularly preferred additives are inorganic builders such as zeolites, SKS6, sodium carbonate, sodium sulfate, Aerosil and / or organic builders such as starch, cellulose, cellulose ethers, microcrystalline cellulose and the like.

For the purposes of the invention, aqueous pastes are preferred as aqueous surfactant preparations containing as surfactants exclusively anionic surfactants, in particular fatty alcohol sulfates and / or fatty alcohol ether sulfates in the form of their sodium, potassium and / or magnesium salts. Such pastes are commercially available and currently have an addition of aqueous hydroxides as alkali reserve. In order to avoid the unwanted autocatalysis, the aqueous hydroxides are added according to the prior art, usually in amounts such that beispielswesie Fettalkoholsulfatpasten (measured as 1 wt.% Aqueous solution) a pH above 10 have. The addition of the aqueous hydroxides takes place during the preparation of the fatty alcohol sulfates by means of continuous neutralization.

According to the present invention it is now possible to use both high concentration and low concentration pastes of anionic surfactants with lower levels of alkali reserves. As a rule, the anionic surfactant pastes have such an amount of alkali reserves that the pH is between 7 and 9.5. Such pH values of the anionic surfactant pastes can already be set in the neutralization step after sulfation of the alcohols by addition of the calculated amount of hydroxides, in particular sodium hydroxide, during the preparation of the sulfates. This is recommended in particular for highly viscous anionic surfactant pastes, in particular those which have active substance contents of 60 to 90% by weight. In the case of low-viscosity anionic surfactant pastes with active substance contents below 30% by weight, the same procedure can be followed. However, commercially available low-viscosity anionic surfactant pastes with high alkali reserves can also be added subsequently, preferably first with customary inorganic and / or organic acids, for example citric acid, phosphoric acid, lactic acid, glycolic acid. Gluconic acid or sulfuric acid, especially citric acid, neutralize, preferably to a pH between 7 and 9.5. If desired, the acids can also be used to set a lower pH below 7, for example in the case of low-viscosity fatty alcohol ether sulfate pastes. In the context of the invention, it is of course also possible to use neutral aqueous pastes of anionic surfactants, which have not additionally been stabilized by the addition of hydroxides with an alkali reserve. For the purposes of the present invention, all anionic surfactants (pastes) having a pH of between 7 and 9.5 are considered to be pH-neutral anionic surfactants (pastes).

For the purposes of the invention, it is now advantageous that such pH-neutral anionic surfactant-containing surfactant pastes are granulated and dried in the presence of volatile bases. In the context of the compounds, the term bases is preferably to be understood as meaning those compounds which, in the sense of the Broenstedt base definition, are capable of taking up protons. These are compounds which are already bases in themselves, such as ammonia or amines, as well as compounds which release by decomposition first bases, such as ammonium carbonate. As volatile such bases are referred to in the context of the invention, if they are preferably in the fluidized bed plants prevailing temperatures, especially at 60 ° C and below, are gaseous. Particularly suitable volatile bases are those which are volatile even at room temperature (about 20 ° C.), such as ammonia and / or mono-, di- and trialkylamines having 1 and / or 2 carbon atoms in the alkyl radical. Particularly suitable is ammonia. Ammonia can be used as gas or in the form of its aqueous solutions such as concentrated ammonia. For the purposes of the present invention, the volatile bases are added preferably in amounts of from 0.05 to 5, in particular 0.1 to 1,% by weight, calculated as the active substance content of base and based on the active substance content of anionic surfactants in the aqueous surfactant preparation.

The volatile bases may be added to an embodiment of the present invention corresponding to the anionic surfactant-containing surfactant pastes just prior to their granulation and simultaneous drying. The volatile bases, in particular ammonia, in the form of their aqueous solutions, in particular concentrated ammonia, are added to the aqueous anionic surfactant preparations, which may have previously been pH neutral, before they are injected into the fluidized bed apparatus and subjected to granulation and simultaneous drying. However, it is also possible for the surfactant preparations containing aqueous anionic surfactants to be pre-adjusted to pH neutral, and irrespective of this, to inject an aqueous base solution into the fluidized-bed apparatus. This can be done either in parallel with the help of a multi-piston pump. However, it is also possible to feed the aqueous surfactant preparations with the anionic surfactants as usual via a nozzle into the fluidized bed apparatus and to inject the aqueous base solutions, in particular concentrated ammonia, preferably above the sieve bottom of the fluidized bed apparatus. Since there is negative pressure above the sieve bottom, the aqueous base solution is simply sucked into the fluidized bed. According to a second embodiment of the present invention, the volatile bases are added to the fluidizing air supplied for granulation and drying in the fluidized bed apparatus. Appropriately, according to this embodiment, the aqueous, optionally pH neutral adjusted anionic surfactant preparations are injected here in the fluidized bed apparatus and are only there in the presence of the fluidized air supplied with the volatile bases, preferably ammonia as a gas, granulated and dried. Of course, it is also possible within the scope of the invention to combine two or more of the described embodiments with one another.

The aqueous surfactant preparations containing anionic surfactants, preferably the aqueous anionic surfactant pastes, can be granulated alone or mixed with solid support materials in the fluidized bed and dried at the same time. In the fluidized bed, the water evaporates from the preparation (paste), resulting in dried to dried germs, which are coated with the optionally admixed carrier materials, granulated and dried again at the same time. If carrier materials are to be mixed, they are mixed simultaneously with the aqueous surfactant preparations (pastes), but separately from these, preferably via an automatically controlled solids dosage. If carrier materials are mixed in the context of the invention, these are preferably inorganic carrier materials and in particular alkali metal carbonates, alkali metal sulphates, crystalline or amorphous alkali metal silicates, crystalline or amorphous sheet silicates and / or zeolites. The proportion of carrier materials to surfactant is not critical and may be in the weight ratio of 0: 100 to 50: 50, preferably 80:20.

For the purposes of the present invention, preference is given to granulation and simultaneous drying in the continuous fluidized bed, by the so-called SKET process. Preferably used fluidized bed apparatuses have bottom plates (sieve bottom) with a diameter between 0.4 and 5 m, for example 1.2 m or 2.5 m. As a bottom plate perforated bottom plates, a Contidurplatte (commercial product of the company Hein & Lehmann, Federal Republic of Germany) or perforated bottom plates can be used, the holes (openings) are covered by a mesh with meshes less than 600 microns. In this case, the grid can be arranged within or above the passage openings. However, the grid is preferably located directly below the openings of the inflow base. Advantageously, this is realized so that a metal gauze is sintered with the appropriate mesh size. Preferably, the metal gauze consists of the same material as the distributor plate, in particular of stainless steel. Preferably, the mesh size of said grid is between 200 and 400 microns.

For the purposes of the invention, the process is preferably carried out at fluidized air velocities of between 1 and 8 m / s and in particular between 1.5 and 5.5 m / s. The discharge of the granules is advantageously carried out by size classification of the granules. This classification is preferably carried out by means of an opposing air flow (classifier air), which is regulated so that only particles from a certain particle size removed from the fluidized bed and smaller particles are retained in the fluidized bed. The incoming air is composed of the heated or unheated classifier air and the heated floor air. The soil air temperature is preferably between 80 and 400 ° C. The fluidizing air is cooled by heat losses and by the heat of vaporization and is preferably about 5 cm above the bottom plate 60 to 120 ° C, preferably 65 to 90 ° C and especially 70 to 85 ° C. The air outlet temperature is preferably between 60 and 120 ° C, in particular below 80 ° C. Further advantageous embodiments of the method according to the invention can be found in the still unpublished German patent application P 197 504 24.8 as well as in the European patent specification EP-B-603 207.

For the granulation and drying in the fluidized bed, it is favorable that at the beginning of the process, a starting material is present, which serves as an initial carrier for the sprayed surfactant paste. Suitable starting compounds are the surfactant granules optionally containing carrier materials themselves, which have already been obtained in a preceding process sequence, or the carrier materials can be used as starting material. In particular, surfactant granules obtained with a particle size in the range between 0.1 and 1.6 mm are already used as starting material from one of the preceding process sequences.

The granules obtained from the fluidized bed are then preferably cooled in a separate fluidized bed and classified by means of a sieve into granules with particle sizes between 0.1 and 1.6 mm as a good grain fraction and in granules above 1.6 mm as an oversize fraction, while particles below 0, 1 mm already in the fluidized bed in an exhaust filter during drying, separated there from the exhaust air and then fed as seed material back into the fluidized bed. The oversize fraction is ground and also returned to the fluidized bed.

For the purposes of the present invention, the surfactant granules are considered to be dried, provided that the content of free water is preferably below 10% by weight, in particular from 0.1 to 2% by weight, based in each case on the finished granules.

According to the inventive method surfactant granules are obtained with high bulk density, preferably above 500 g / l and in particular between 550 and 1000 g / l. The active substance content varies depending on the addition of carrier materials used and in particular is more than 50% by weight, preferably between 85 and 98% by weight.

The surfactant granules obtained by the process of the invention are pH neutral, i. after dissolution of the surfactant granules in water, the aqueous solution has a pH between 7 and 9.5. Furthermore, the surfactant granules are dust-free and pourable and not or barely tacky, so that they are easy to handle in big bags and silierfähig.

In the washing, rinsing and cleaning agents, the granules according to the invention may be present in customary amounts, preferably in the range from 0.1 to 50% by weight, based on average. The surfactant granules produced according to the invention are preferably suitable for the preparation of pH-neutral detergents, dishwashing detergents and cleaners, such as pH-neutral powder cleaners and pH-neutral soaps, and also detergents, such as toilet stones, mixed with dyes. The pH-neutral washing, rinsing and cleaning agents may be in powdery, granulated or particulate form.

Examples Preparation of pH-neutral fatty alcohol sulfate granules example 1

10,000 kg of a 65 wt .-% sodium lauryl sulfate (52% C 12/21% C 14/10% C 16/17% C 18) containing aqueous paste having a free alkali content of 0.1 wt .-% sodium hydroxide were continuously injected with 2,000 kg per hour at a temperature of 70 ° C in the fluidized bed plant (SKET plant), the drying air at entry into the fluidized bed had a temperature of 170 ° C, at the outlet of 100 ° C. The fluidized bed had a temperature of 60 ° C. During the continuous feeding of the surfactant paste were continuously above the sieve bottom of the SKET plant 12 kg of a 25% aq. Ammonia solution is fed by means of a metering pump in the fluidized bed.

After 5 hours, 6,600 kg of sodium lauryl sulfate were obtained as granules having a particle size in the range of 0.1 to 1.6 mm, a bulk density of 620 g / liter and a water content of 1.5 wt .-%.

A 1% aqueous solution of the granules showed a pH of 8.8 at 25 ° C. 500 g of this sodium lauryl sulfate granules were stored at 80 ° C. for 72 hours in a porcelain dish in a drying oven. After this time, no gray specks could be detected in the product.

Example 2

As in Example 1, 10,000 kg of a 65 wt .-% sodium lauryl sulfate (52% C12 / 21% C 14/10% C 16/17% C 18) containing aqueous paste with a free alkali content of 0.1 wt .-% sodium hydroxide continuously injected with 2000 kg per hour at a temperature of 70 ° C in the fluidized bed plant (SKET plant), wherein the drying air had on entering the fluidized bed at a temperature of 180 ° C, at the outlet of 90 ° C. The fluidized bed had a temperature of 70 ° C. 24 kg of a 25% aq. Ammonia solution was mixed by means of a forced-controlled Multi-piston metering pump fed continuously together with the aqueous surfactant paste in the fluidized bed of the SKET system.

After 5 hours, 6.580 kg of sodium lauryl sulfate were obtained as granules having a particle size in the range of 0.1 to 1.6 mm, a bulk density of 590 g / liter and a water content of 1.3 wt .-%.

A 1% aqueous solution of the granules showed a pH of 9.5 at 25 ° C. 500 g of this sodium lauryl sulfate granules were stored at 80 ° C. for 72 hours in a porcelain dish in a drying oven. After this time, no gray specks could be detected in the product.

Comparative Example 1

As in Example 1, 10,000 kg of a 65 wt .-% sodium lauryl sulfate (52% C12 / 21% C 14/10% C 16/17% C 18) containing aqueous paste with a free alkali content of 0.1 wt .-% sodium hydroxide continuously injected with 2,000 kg per hour at a temperature of 70 ° C in the fluidized bed plant (SKET plant), wherein the drying air had on entering the fluidized bed at a temperature of 160 ° C, at the outlet of 90 ° C. The fluidized bed had a temperature of 60 ° C.

After 5 hours, 6.580 kg of sodium lauryl sulfate were obtained as granules having a particle size in the range of 0.1 to 1.6 mm, a bulk density of 600 g / liter and a water content of 1.2 wt .-%.

A 1% aqueous solution of the granules showed a pH of 9.2 at 25 ° C. 500 g of this sodium lauryl sulfate granules were stored at 80 ° C. for 72 hours in a porcelain dish in a drying oven. After this time, gray specks appeared isolated in the product, which were isolated and had an acidic pH.

Claims (7)

1. A process for the production of surfactant granules, wherein after dissolving the surfactant granules in water, the aqueous solution has a pH of between 7 and 9.5, by granulation and simultaneous drying of an aqueous surfactant preparation containing anionic surfactants in salt form, in the fluidized bed, characterized in that volatile bases are added in quantities of 0.05 to 5% by weight, based on active substance of the anionic surfactants in the aqueous surfactant preparation in the form of aqueous solutions before or during the granulation and simultaneous drying.
2. A process as claimed in claim 1, characterized in that aqueous pastes of anionic surfactants with an active surfactant content of 25 to 90% by weight, based on paste, are used as the aqueous surfactant preparations.
3. A process as claimed in claim 1 or 2, characterized in that sulfates of fatty alcohols containing 6 to 22 carbon atoms in the form of their salts are used as the anionic surfactants.
4. A process as claimed in claim 1 or 2, characterized in that sulfates of oxo alcohols containing 6 to 15 carbon atoms in the form of their salts are used as the anionic surfactants.
5. A process as claimed in any of claims 1 to 4, characterized in that concentrated aqueous ammonia is used as the volatile bases.
6. A process as claimed in any of claims 1 to 5, characterized in that the granulation and simultaneous drying is carried out with admixing of one or more inorganic and/or organic solids.
7. A process as claimed in any of claims 1 to 6, characterized in that the granulation and simultaneous drying is carried out in the continuous fluidized bed (SKET process), the granules being discharged from the fluidized bed via a sizing classification.