Process for de-hazing of polyglycosides

Abstract

Process for treating an aqueous solution of an alkyl polyglycoside, wherein the process comprises the following steps: (a) providing a melt or an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 20 to 80 % by weight, (b) treating the solution at a pH value in the range of from 11 to 13 with peroxide, (c) adding a di-, tri- or polycarboxylic acid to the solution obtained from step (b) and thus adjusting the pH value to a value of from 6.0 to 7.0 and thus de-gassing, (d) re-adjusting the pH value of the de-gassed solution from step (c) to 8.5 to 12.0, thereby obtaining an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 15 to 80% by weight and transparent for the naked human eye.

Description

[0001] Process for de-hazing of polyglycosides

[0002] The present invention is directed towards a process for treating an aqueous solution of an alkyl polyglycoside, wherein the process comprises the following steps:

[0003] (A) providing a melt or an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 20 to 80 % by weight,

[0004] (B) treating the solution at a pH value in the range of from 10 to 13 with peroxide,

[0005] (C) adding an organic acid to the solution obtained from step (b) and thus adjusting the pH value to a value of from 6.0 to 7.0 and thus de-gassing,

[0006] (D) adjusting the pH value of the de-gassed solution from step (c) to a value from 8.5 to 12.0, thereby obtaining an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 15 to 80% by weight and transparent for the naked human eye.

[0007] In addition, the present invention is directed to aqueous solutions

[0008] Alkyl polyglycosides are versatile surfactants, for example for laundry detergents and automatic dishwashing detergents as well as hand dishwash detergents and personal care applications such as, but not limited to soaps, lotions and shampoos. They offer numerous technical advantages such as good foaming in hand dishwash applications and in shampoos, and they are biodegradable. However, their storage stability sometimes leave room for improvements. It has been observed that in particular after bleaching operations as suggested in EP 0437460 A, a haze may remain or occur. Such haze formation upon longer storage such as one month or more is disadvantageous because it makes precise following of formulation recipes difficult.

[0009] It was an objective of the present invention to provide a process that is suitable for providing transparent solutions of alkyl polyglycosides with high storage stability. It was further an objective of the present invention to provide aqueous solutions that are transparent and have a good storage stability. It was further an objective of the present invention to provide applications for aqueous solutions of alkyl polyglycosides that are transparent.

[0010] Accordingly, the process defined at the outset has been found, hereinafter also referred to as “inventive process” or “process according to the (present) invention”. The inventive process comprises four steps, step (a), step (b), step (c), and step (d), hereinafter in short also referred to as (a), (b), (c), and (d), respectively. Steps (a) to (d) are performed subsequently. Steps (a) to (d) are described n more detail below. Step (a) includes to providing a melt or an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 20 to 80 % by weight, preferably 40 to 70% by weight. The concentration may be determined by evaporation of the volatiles at 140 °C and to constant weight in vacuo. The term “in vacuo" refers to a maximum pressure of 5 mbar. At higher temperatures, the alkyl polyglycoside(s) may start to decompose. Melts may have a concentration of alkyl polyglycoside of 93% by weight or even higher, further components being selected from catalyst as free acid or preferably neutralized with alkali, and unreacted starting materials.

[0011] Melt or aqueous solution as provided in step (a) may contain organic solvents, for example ethanol, monopropylene glycol (1 ,2-propane diol), ethylene glycol and others, for example up to in total 60 % by weight, referring to water, preferably up to 40 % by weight, more preferably up to 10% by weight. Such organic solvent is miscible with water without emulsion formation. More preferably, no organic solvents are contained.

[0012] Melt or aqueous solution provided in step (a) may contain substances that stem from the synthesis of alkyl polyglycoside, for example residual alcohol such as R1-OH. R1is defined below. The content of residual alcohol is preferably below 5% by weight, referring to the respective alkyl polyglycoside, more preferably below 1% by weight.

[0013] Melt or aqueous solution as provided in step (a) may contain dark impurities and may have a brown to black appearance.

[0014] Aqueous solution provided in step (a) may further contain at least one hydrotrope such as cumene sulfonate or linear alkyl benzene sulfonate or its respective alkali metal salt such as the sodium salt. Aqueous solution provided in step (a) may further contain catalyst such as p- toluene sulfonic acid or sulfuric acid or the respective alkali metal salts, especially the respective sodium salts. Aqueous solution provided in step (a) may have any pH value, from 1 to 13. Before commencement of step (b) or at its very beginning, the pH is adjusted to 10 to 13, preferably 11.5 to 12.5. Suitable means of pH value adjustment are bases such as NaOH and in particular Mg compounds such as Mg(OH)2and MgO.

[0015] In the context of the present invention, the pH value refers to 20°C unless specifically indicated otherwise. The pH value may advantageously be determined potentiometrically.

[0016] In one embodiment of the present invention, 97% by weight of the particles of Mg(OH)2and MgO, respectively, used in step (b) pass mesh 325 (opening: 44 pm). Preferably, such Mg(OH)2and MgO, respectively, has a maximum particle diameter in the range of from 25 to 37 pm. In one embodiment of the present invention, alkyl polyglycoside in the solution provided in step (a) has the general formula (I)

[0017] (G)u-OR1(I)

[0018] The variable u is the degree of polymerization and is in the range of from 1.1 to 4, preferred are 1.1 to 2 and in particularly preferred are 1.2 to 1.8. In the context of the present invention, the variable u refers to average values, and u is not necessarily a whole number. In a specific molecule only whole groups of G can occur, thus, the variable u assumes a value of 1 or 2 or 3 or 4 or 5 or more. It is preferred to determine u by High Temperature Gas Chromatography (HTGC).

[0019] R1is selected from C4-Ci8-alkyl, straight chain or branched, linear being preferred.

[0020] G is selected from monosaccharides with 4 to 6 carbon atoms, preferably from glucose and xylose and even more preferably, G is glucose or a combination of glucose and up to 20 mol-% xylose.

[0021] In one embodiment of the present invention, R1is selected from linear C4-Ci6-alkyl, for example n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, myristyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, and n-octadecyl. Preferred are n-butyl, n- hexyl, n-heptyl, n-octyl, n-decyl, n-dodecyl, n-tridecyl, myristyl, n-hexadecyl, and n-octadecyl. In embodiments wherein the respective alkyl polyglycoside is made from a sugar and a bio-based alcohol such as alcohols derived from palm kernel oil, R1is selected from a combination of linear C4-Ci8-alkyls.

[0022] In one embodiment of the present invention, R1is selected from branched Ce-Cis-alkyl, with one or more branchings, for example one or two or three. Preferably, a branching is in the 2- position, thus derived from a Guerbet alcohol, or the branched Ce-Cis-alkyl is iso-alkyl. Examples are iso-hexyl, 2-methylpentyl, iso-heptyl, 2-ethylhexyl, iso-heptyl, iso-octyl, isononyl, isodecyl, 2-(n-propyl)heptyl (“2-propylheptyl”), 2-isopropyl-heptyl, 2-isopropyl-5-methylhexyl, 2-n- propyl-6-methylhexyl, combinations of at least two of 2-propylheptyl, 2-isopropyl-heptyl, 2- isopropyl-5-methylhexyl, and 2-n-propyl-6-methylhexyl, 2-n-butyloctyl, iso-dodecyl, iso-tridecyl, iso-myristyl, iso-pentadecyl, iso-hexadecyl, iso-octadecyl.

[0023] Another preferred example is 3-ethyl 8-methyl decyl. In a more preferred embodiment, alkyl polyglycoside is selected from branched Cs-Cis-alkyl polyglycosides such as compounds of general average formula (1.1).

[0024] R2R3-CHCH2-O-GU-H (1.1) wherein:

[0025] R2is hydrogen or Ci-Ce-alkyl, straight-chain or branched, in particular ethyl, n-propyl, isopropyl, n-butyl and iso-butyl,

[0026] R3is -(CH2)2-R2, straight-chain or branched, wherein R2is defined as above.

[0027] G is defined as above, more preferably glucose, or glucose with up to 20 mole-% of xylose.

[0028] II is in the range of from 1.1 to 4, preferred are 1.1 to 2 and in particularly preferred are 1.2 to 1.8, u being an average number, vide supra.

[0029] In step (b), the melt or aqueous solution as provided in step (a) is treated with peroxide. The pH value is adjusted to 10 to 13, preferably 11.5 to 12.5 before or at the beginning of step (b).

[0030] Suitable examples of peroxide are organic peroxides, e.g., tert.-butyl peroxide, (CHshC-OOH. Preferred peroxides are those whose decomposition products are very volatile or may remain in the aqueous solution obtained at the end of step (b). More preferably, H2O2is selected as peroxide.

[0031] In one embodiment of the present invention, 0.1 to 0.5% by weight of peroxide is used, referring to alkylpolyglycoside.

[0032] Step (b) may be performed at ambient temperature, ambient temperature being in the range of from 15 to 25°C, or at a higher temperature, for example 26 to 95°C. Preferred is 80 to 90°C.

[0033] Peroxide may be added in bulk or - for safety reasons - diluted with a solvent, for example with water or monopropylene glycol and mixtures of monopropylene glycol and water. Water is preferred, especially in concentrations higher than 20% by weight. H2O2may be used in aqueous solution, e.g., as 35% by weight or less aqueous solution. Tert.-butyl peroxide is preferably used in aqueous solution as well. Step (b) may be performed continuously or discontinuously. In continuous embodiments, the duration corresponds to the average residence time. The duration of step (b) may be in the range of from 5 to 40 hours, preferred are 10 to 30 hours.

[0034] The duration of step (b) may be steered by determining the color, for example by determining the Klett or Hazen color number of an aliquot of the reaction medium. When the desired color is reached, the excess of peroxide is decomposed by further storage at elevated temperature, especially 80 to 90°C.

[0035] In a preferred embodiment of the present invention, step (b) is performed under elevated pressure, for example 1.3 to 2 bar absolute. The elevated pressure may be obtained by pressurizing the vessel in which step (b) is performed with, e.g., nitrogen or a noble gas such as argon.

[0036] In one embodiment of the present invention, step (b) is performed in a stirred tank reactor, especially under stirring.

[0037] At the end of step (b), a bleached solution of alkyl polyglycoside is obtained.

[0038] Step (c) includes adding an organic acid to the aqueous solution from step (b), and thus adjusting the pH value to a value of from 6.0 to 7.0, preferably 6.0 to 6.5. At a pH value significantly above 7.0, for example 8.0 or above, the degassing will be very slow or not even take place at all. At a pH value significantly below 6.0, for example 4.5, the de-gassing may take place too fast and become uncontrollable, for example by generation of a lot of foam in a short time.

[0039] Examples of organic acids are monocarboxylic acids such as formic acid, acetic acid, benzoic acid and lactic acid, dicarboxylic acids such as adipic acid, succinic acid, tartaric acid, malic acid, terephthalic acid, maleic acid, and glutamic acid.

[0040] In a preferred embodiment, a di-, tri- or polycarboxylic acid is added to the solution obtained from step (b)

[0041] Suitable dicarboxylic acids are adipic acid, succinic acid, tartaric acid, malic acid, a combination of succinic acid, glutamic acid and adipic acid, adipic acid, sebacic acid, and tartaric acid being preferred.

[0042] A suitable polycarboxylic acid, thus compounds with four or more carboxylic acid groups per molecule, is glutamic acid N,N-diacetic acid (“GLDA”). Preferred are tricarboxylic acids such as mesic acid and in particular citric acid and methylglycine N,N-diacetic acid (MGDA). More preferred is citric acid.

[0043] Dicarboxylic acid, tricarboxylic acid and polycarboxylic acid may be added as free acids or with all but at least one carboxylic acid groups neutralized. However, it is preferred to add dicarboxylic acid, tricarboxylic acid or polycarboxylic acid, as the case may be, as free acid.

[0044] Di-, tri- or polycarboxylic acid may be added in bulk or as aqueous solution. Citric acid is preferably added in bulk, while glutamic acid N,N-diacetic acid is preferably added in aqueous solution.

[0045] During addition of di-, tri- or polycarboxylic acid, it is preferred to control the pH value in order to arrive at the pH value of 6.0 to 7.0.

[0046] Step (c) may be performed at a temperature in the range of from 15 to 70°C. In embodiments wherein the inventive process is performed as a batch process, it is preferred to perform step (c) in the same vessel as step (b). Even more preferably, in such embodiments, step (c) is performed immediately after step (b) and in the same vessel and at the same temperature.

[0047] Step (c) may be performed under stirring. When the adjustment of the pH value has taken place, a degassing may be observed. The gas evolved is mainly CO2.

[0048] The addition of di-, tri- or polycarboxylic acid may be performed in one step or in at least two steps. Addition of di-, tri- or polycarboxylic acid may be performed in one gush or over some time, such as five minutes to 60 minutes.

[0049] After completion of addition of di-, tri- or polycarboxylic acid, it is preferred to start stirring or continue stirring for up to 24 hours, preferably 30 minutes to 5 hours.

[0050] Step (c)may be performed continuously or discontinuously.

[0051] In one embodiment of the present invention, it is observed that the reaction medium in step (c) is quite viscous and the gas evolution is hindered through foaming. In such embodiments it is preferred to apply shear force to allow the evolving gas to leave the reaction medium. I a preferred embodiment of the present invention, step (c) is performed in a vessel equipped with a rotating cylindrical wire cage. The reaction medium is then hurled again the vessel walls and allows any gas bubbles to leave quickly instead of formation of a long-lasting foam.

[0052] When no more degassing is observed, it is preferred to terminate step (c). The evolution of gas may be monitored by infrared or by precipitation of the CO2 as calcium carbonate.

[0053] Step (c) is preferably performed continuously by adding the di-, tri- or polycarboxylic acid to the bleached solution from step (b) and transferring it with a pump into a rotating cage inside a jacketed vessel. The rotating cage throws the mixture onto the wall of the vessel, thus facilitating the separation of the liberated CO2.

[0054] Step (d) includes adjusting the pH value of the de-gassed solution from step (d) to a value from 8.5 to 12.0, preferably 10 to 11.5. The pH value at the end of step (d) may be the same as in step (a) or may be higher or lower.

[0055] For adjusting the pH value, a base like the trisodium salt of methyl glycine diacetic acid (“MGDA”) or of citric acid and may be added. Sodium hydroxide is possible as well.

[0056] Step (d) may be performed in the same vessel as step (c). It is preferred to perform step (d) immediately after step (c). Stirring may be continued during step (d).

[0057] It is possible to perform step (d) at a higher or lower temperature than step (c) but it is preferred to perform step (d) at the same temperature as step (c).

[0058] In a more preferred embodiment, steps (b) to (d) are performed at ambient temperature.

[0059] By performing the inventive process, aqueous solutions of alkyl polyglycoside with a concentration in the range of from 15 to 80% by weight and transparent for the naked human eye are obtained. They have excellent storage stability.

[0060] A further aspect of the present invention is directed towards an aqueous solution, hereinafter also referred to as inventive aqueous solutions, with a pH value in the range of from 8.0 to 12.0, preferably 8.5 to 11.5, and comprising

[0061] (A) 15 to 80% by weight of alkyl polyglycoside, preferred are 40 to 70% by weight,

[0062] (B) 0.05 to 1 % by weight of an Mg compound, calculated as Mg, preferred are 0.1 to 0.5 % by weight, and (C) a salt of citric acid or MGDA or GLDA, preferably a potassium or sodium salt, more preferably the sodium salt, or a magnesium salt of citrate, MGDA or GLDA, wherein said aqueous composition has a transparent appearance. The appearance may be determined with the naked human eye.

[0063] Percentages refer to the total respective inventive aqueous solution.

[0064] Component (C) may be present in the range of from 0.5 to 5% by weight, calculated as free acid(s), preferably 1 to 3 % by weight.

[0065] Alkali metal salts of citric acid are, e.g., the monoalkali metal salt, the dialkali metal salt, and the trialkali metal salt. Alkali metal salts of MGDA are the monoalkali metal salt, the dialkali metal salt, and the trialkali metal salt. Alkali metal salts of GLDA are the monoalkali metal salt, the dialkali metal salt, the trialkali metal salt, and the tetraalkali metal salt, in each case especially the respective potassium salts or more preferably the respective sodium salts. The degree of neutralization depends on the pH value.

[0066] Examples of magnesium salts of citrate are the mono-magnesium salt and Mg3(citrate)2.

[0067] In other embodiments, magnesium compound (B) is a magnesium salt of citrate, MGDA or GLDA (C) and adopts both roles, and no separate alkali metal salts of citrate, MGDA or GLDA are contained.

[0068] Without wishing to be bound by any theory, the magnesium salt of MGDA or GLDA may rather be viewed as a complex than a salt.

[0069] The amount of alkali metal salt (C) - or magnesium salt of citrate, MGDA or GLDA, respectively - is preferably in the range of from 0.1 to 5.0 % by weight. The amount is calculated as free acid.

[0070] In a preferred embodiment of the present invention, the pH value of inventive aqueous solutions is in the range of from 8.3 to 12.0, preferably 10 to 11.5. The pH value may advantageously be determined potentiometrically.

[0071] Alkyl polyglycoside (A) has been defined above. In one embodiment of the present invention, inventive aqueous solutions have a color number (Hazen) in the range of from 100 to 400, determined in a 10 % by weight aqueous solution.

[0072] Inventive aqueous solutions exhibit a high transparency and thus no haze. In addition, they exhibit a high storage stability. Even after 6 weeks at 30°C, no significant haze may be detected. Inventive aqueous solutions can thus be stored even in summers without the need of installing a stirrer in the storage vessel.

[0073] A further aspect of the present invention relates to the use of inventive aqueous solution for the manufacture of liquid laundry detergent compositions and personal care formulations such as liquid shampoos and liquid soaps. A further aspect is a process for making liquid laundry detergent compositions or personal care formulations by mixing an inventive aqueous solution with at least one further ingredient selected from anionic surfactants, colorants, polymers, especially cationic polymers, fragrance, thickeners (viscosity enhancer), or biocides.

[0074] As solvent, liquid laundry detergent compositions contain mainly water, for example at least 50 vol-% with respect to solvent, preferably at least 80 vol-%. The term solvent includes the water.

[0075] In one embodiment of the present invention, inventive compositions may comprise solvents other than water, for example ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec.- butanol, ethylene glycol, propylene glycol, 1,3-propane diol, butane diol, glycerol, diglycol, propyl diglycol, butyl diglycol, hexylene glycol, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, and phenoxyethanol, preferred are ethanol, isopropanol or propylene glycol.

[0076] In one embodiment of the present invention, inventive compositions comprise 0.5 to 12 % by weight of organic solvent, referring to the total respective composition. In another embodiment, inventive compositions do not contain solvents other than water.

[0077] In many embodiments of the present invention, liquid laundry formulations contain at least one anionic surfactant, for example alkyl sulfates, especially C -C2o-alkyl sulfate, or alkyl ether sulfate, for example C -C2o-alkyl sulfate with 3 to 7 ethylene oxide groups, and the respective sodium salts.

[0078] In many embodiments of the present invention, liquid laundry formulations contain at least one amphoteric surfactant, sometimes also referred to as zwitterionic surfactants. Amphoteric surfactants bear a positive and a negative charge in the same molecule under use conditions. Pre- ferred examples of amphoteric surfactants are so-called betaine-surfactants. Many examples of betaine-surfactants bear one quaternized nitrogen atom and one carboxylic acid group per molecule. A particularly preferred example of amphoteric surfactants is cocamidopropyl betaine (lauramidopropyl betaine).

[0079] Further examples of zwitterionic surfactants are amine oxide surfactants are compounds of the general formula (II)

[0080] R4R5R6N^O (II) wherein R4, R5and R6are selected independently from each other of aliphatic, cycloaliphatic or C2-C4-alkylene groups, for example Cio-C2o-alkylamido moieties. Preferably, R4is selected from Cs-C2o-alkyl or C2-C4-alkylene Cio-C2o-alkylamido and R5and R6are both methyl.

[0081] A particularly preferred example is lauryl dimethyl aminoxide, sometimes also called lauramine oxide. A further particularly preferred example is cocamidylpropyl dimethylaminoxide, sometimes also called cocamidopropylamine oxide.

[0082] Inventive compositions may contain further ingredients such as fragrance, perfumes, dyestuffs and the like.

[0083] Inventive compositions used as or in shampoos or liquid soaps may further contain at least one surfactant selected from alkyl sulfates, alkyl ether sulfates such as n-Ci2H25-(EO)3-OSC>3 Na or n-Ci4H29-(EO)3-OSC>3 Na, alkylether carboxylates such as n-Ci2H25-CO-NH-CH2CH2-O-(EO) - CH2-COO-Na, or those with 3 to 5 or 10 ethoxy groups, sulfo succinates, each alone or in combinations of at least two, in addition thickeners (viscosity enhancers), film forming agents such as polyquaternium compounds, especially those known as polyquaternium-1 to polyquaternium- 43, UV absorbents, for example based on benzophenone or camphor, and preservatives, for example parabene, 2-phenoxy ethanol, benzoic acid, urea or condensates of urea, and salicylic acid.

[0084] Further - optional - surfactants used in shampoos or liquid soaps are betains, vide supra, sulfobetains, sorbitol ether esters. Further - optional ingredients used in shampoos are hydrolyzed proteins, re-fattening agents, humidifiers, and dispersing agents as well as solubilizers.

[0085] The present invention is further illustrated by the following working examples. General remarks: Percentages refer to percent by weight unless specifically defined otherwise.

[0086] Step (c.1) was performed in a degassing apparatus. The degassing apparatus was a glass vessel with a cylindrical wire cage rotating inside the vessel. When operated, the cylindrical wire cage hurls foam and liquid phase with bubbles against the glass walls of the vessel, and the bubbles are destroyed quickly.

[0087] Step (a.1): A brown melt of n-Cs / Cw-alkyl-polyglucoside, variable u = 1.4, was provided. It had a pH value of 8.2 and contained 0.015 mol-% linear Ci2-alkylbenzenesulfonate per mole of glucoside. It was diluted with de-salinated water in a weight ratio water : melt of 9:10. An amount 0.1% by weight of MgO was added, referring to n-Cs / Cw-alkyl-polyglucoside.

[0088] Step (b.1): Step (b.1) was performed in analogy to EP 0 650 491 B1 , Example 1. Residual peroxide was then destroyed by storing at 87.8°C for 20 hours.

[0089] Step (c.1):

[0090] The bleached solution from step (b.1) was transferred into the degassing apparatus as described above and pre-preheated to 70°C. The flow was continued with a pump at a rate of 1900 g / h. An aqueous solution of citric acid (50%) was continuously added at a rate of 56 ml / h to the bleached solution from step (b.1). A pH value of 6.9 was determined in the aqueous solution. The resulting solution was hurled against the vessel wall by the rotation of the cylindrical wire cage, and the solution ran down in the wire cage. Released gas was discharged upwards. A pale yellow fluid was obtained.

[0091] Steps (d.1) to (d.5)

[0092] The fluid obtained from step (c.1) was divided into 5 portions, d.1) to (d.5). Aqueous NaOH was added to bring the pH to 8.0 (d.1), 8.9 (d.2), 10.2 (d.3), 11.3 (d.4), and 12.1 C-(d.5). The portions were further divided into 6 samples. Each set of 6 portions with the same pH was then mixed with varying amounts of MGDA-Na3as aqueous 40% by weight solution (0%, 0.1 %, 0.5%, 1%, 2.5%, and 5%). The pH value did not change. The resultant aqueous solutions sol.1- 1 to sol 1.4 and C-sol.1-6 up to C-sol.5-6 were stored at 30°C for 2 months.

[0093] After the storage period, the haziness of the samples was determined. To measure the turbidity the colour of a sample was measured before and after filtration. If a sample is hazy, a lower colour number (Hazen) was measured after the filtration. Table 1 shows the compositions of inventive and comparative aqueous solutions and the test results.

[0094] Table 1 : compositions and storage stability of inventive aqueous solutions All concentrations in % by weight, referring to the entire aqueous solution.

[0095] Haze: after storage

[0096] (A.1): n-Cs / Cw-alkyl-polyglucoside, variable u = 1.4

[0097] (B.1): MgO (C.1): citric acid

[0098] (C.2): MGDA calculated as free acid, CH3-CH(COOH)-N(CH2COOH)

[0099] Comparative example: Due to the foam formation, the degassing apparatus could not be used for safety reasons.

[0100] Steps (a.1) and (b.1) were repeated as above.

[0101] Step (b.1): Step (b.1) was performed in analogy to EP 0 650 491 B1 , Example 1. Residual peroxide was then destroyed by storing at 87.8°C for 20 hours.

[0102] Step C-(c.7):

[0103] 160.74 g of bleached solution from step (b.1) was transferred into a beaker equipped with a stirrer and thermometer and pH electrode and heated to 45°C. 3 g of an aqueous solution of sulfuric acid (50%) were added dropwise to the bleached solution from step (b.1). A pH value of 6.0 was determined in the aqueous solution. Stirring was continued for 24 hours. Gas release was observed. A lot of foam was formed, and as a result, the loss of water and alkyl polyglycoside was considerable. A pale yellow fluid was obtained.

[0104] Step C-(d.7)

[0105] An amount of 5 g of 30% by weight aqueous NaOH solution was added to the fluid obtained from step C-(c.6). A pH value of 11 was reached. The resulting solution was diluted with 42 g demineralized water in order to compensate for the losses in step C-(c.7) and stored over 14 hours at 40°C. Strong turbidity was observed.

Claims

Patent claims1. Process for treating an aqueous solution of an alkyl polyglycoside, wherein the process comprises the following steps:(a) providing a melt or an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 20 to 80 % by weight,(b) treating the solution at a pH value in the range of from 10 to 13 with peroxide,(c) adding an organic acid to the solution obtained from step (b) and thus adjusting the pH value to a value of from 6.0 to 7.0 and thus de-gassing,(d) adjusting the pH value of the de-gassed solution from step (c) to a value from 8.5 to 12.0, thereby obtaining an aqueous solution of an alkyl polyglycoside with a concentration in the range of from 15 to 80% by weight and transparent for the naked human eye.

2. Process according to claim 1 wherein alkyl polyglycoside has the general formula (I)(G)u-OR1(I)R1is selected from C4-Ci8-alkyl, straight chain or branched, linear being preferred, u is in the range of from 1.1 to 4, andG is selected from monosaccharides with 4 to 6 carbon atoms.

3. Process according to claim 1 or 2 wherein organic acid from step (c) is selected from di-, tri- or polycarboxylic acids.

4. Process according to any of the preceding claims wherein organic acid in step (c) is citric acid or methylglycine N,N-dicarboxylic acid (MGDA).

5. Process according to any of the preceding claims wherein the alkyl polyglycoside is selected from linear C4-Ci6-alkyl polyglycosides and branched Cs-Cis-alkyl polyglycosides according to formula (1.1)R2is Ci-C4-alkyl,R3is -(CH2)2-R2,G1is selected from monosaccharides with 4 to 6 carbon atoms, and u in the range of from 1.1 to 4.

6. Process according to any of the preceding claims wherein step (b) is performed in the presence of MgO.

7. Process according to any of the preceding claims wherein the peroxide used in step (b) is H2O2.

8. Process according to any of the preceding claims wherein step (b) is performed at a pH value in the range of from 8.5 to 13.

9. Process according to any of the preceding claims wherein step (c) is performed in a vessel equipped with a rotating cylindrical wire cage.

10. Aqueous solution with a pH value in the range of from 8.3 to 13 comprising(A) 15 to 80% by weight of alkyl polyglycoside,(B) 0.05 to 1 % by weight of an Mg compound, calculated as Mg, and(C) a salt of citric acid or MGDA or GLDA, or a magnesium salt of citrate, MGDA or GLDA, wherein said aqueous composition has a transparent appearance.

11. Solution according to claim 10 wherein the pH value is in the range of from 10 to 11.5.

12. Solution according to claim 10 or 11 wherein alkyl polyglycoside has the general formula(I)(G)u-OR1(I)R1is selected from C4-Ci8-alkyl, straight chain or branched, linear being preferred, u is in the range of from 1.1 to 4, andG is selected from monosaccharides with 4 to 6 carbon atoms.

13. Solution according to any of claims 10 to 12 wherein the alkyl polyglycoside is selected from linear C4-Ci6-alkyl polyglycosides and branched Cs-Cis-alkyl polyglycosides according to formula (1.1)R2is Ci-C4-alkyl,R3is -(CH2)2-R2,G1is selected from monosaccharides with 4 to 6 carbon atoms, and u in the range of from 1.1 to 4, u being an average number.

14. Use of a solution according to claims 10 to 13 for the manufacture of liquid laundry detergent compositions, liquid soaps and liquid shampoos.

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