USE OF OXIDISED POLYSACCHARIDES IN DETERGENT COMPOSITIONS

Abstract: Polycarboxy polysaccharides, in particular dicarboxymaltodextrins, having a molecular weight between 1,600 and 12,000 and having a degree of oxidation (DO) of 0.12-0.6 carboxyl groups per anhydromonose unit, can be used as a cobuilder, in particular as an anti-redeposition and soil dispersing agent in detergent compositions.

Description: Use of oxidised polysaccharides in detergent compositions The invention relates to the use of polycarboxy polysaccharides in detergent compositions. Detergent compositions contain a builder to neutralise the effect of water hardness, dissolution of soil and the like. Although phosphate is an effective builder, its use is undesired for environmental reasons. Zeolites have largely replaced phosphates as builder. However, they require the presence of a cobuilder which prevents the redeposition of soil and the precipitation of calcium carbonate, and improves whiteness of the washed laundry. Synthetic polymers, such as polyacrylates have found extensive use as cobuilders, but they are poorly biodegradable. Thus there is need for biodegradable and yet effective cobuilder materials for use in textile washing compositions, dish-washing compositions and the like. EP- A- 755944 discloses a method for the production of oxidising maltodextrins having a DE (dextrose equivalent) between 2 and 20, especially a DE of 11-14, using oxygen or hydrogen peroxide under alkaline conditions in the absence of a catalyst followed by bleaching. This oxidation results in conversion of the reducing end groups in arabinonic acid groups. The product can be used as a cobuilder in detergent compositions wherein it improves whiteness and reduces inorganic incrustation, or as a binder or thickening agent. An oxidised starch having a molecular weight from 500 to 60,000 wherein at least 60% of the C6 groups have been oxidised to carboxyl groups and 5-40% of the C2-C3 groups have been oxidised to carboxyl groups by catalytic oxidation with HNO 3 / H 2 SO 4 / NO 2 , is described in EP-A-542496. It is useful as a soil dispersant, builder and cleaning auxiliary. The use of dicarboxylic polysaccharides such as dicarboxy starch and dicarboxy amylodextrins as a calcium sequestering agent has been described in various documents, e.g. Kohn and Tihlarik, Coll. Czech. Chem. Commun. 49 (1984) 2116, EP-A-427349 and NL-A-8802907. A simpler process for the production of relatively short-chain oxidised poly- saccharides has been found, which results in products having improved cobuilder properties. The products especially have excellent anti-redeposition and soil dispersant properties, combined with full biodegradability. The use of these products according to the invention is characterised by the features of the appending claims. An advantage of the preparation process is that inexpensive, commercially available starch and other readily available carbohydrates can be used as a starting material, which can directly yield oxidation products of the required degree of oxidation and required molecular weight. The polysaccharides to be oxidised according to the invention are primarily starch and starch derivatives such as hydrolysed starch and carboxymethyl starch. Other glucans, such as cellulose derivatives, 1,3-glucans or 1,6-glucans, galactomannans (e.g. guar) and other vegetal and bacterial gums, can also be used. These have molecular weights of 1600-12,000 (10-75 anhydromonose units), preferably of 2000-10,000 (12-60 amu's), most preferably 2900-7300 (18-40 amu's). Other classes of suitable poly-saccharides are fructans (e.g. inulin), which can be used with molecular weights from about 240 upwards, especially 500-12,000, more preferably 1600-5000 (10-30 amu's), and pentosans, such as xylans (hemicellulose), e.g. from waste carbohydrates, with molecular weights of 1500-12,000, preferably 2000-8000, most preferably 2600- 6600 (20-50 amu's). The degree of oxidation is preferably from 0.12 to 0.6, preferably from 0.15 to 0.55, especially form 0.2 to 0.5. The oxidised polysaccharides are preferably obtained by treatment of the poly- saccharide (e.g. starch) with a hypochlorite solution at pH 7.5-10, especially at pH 8-9, the hypochlorite being added gradually in order to be able to maintain the pH more or less constant by addition of a base. The reaction temperature can be e.g. between 0 and 40 °C, especially at ambient temperature. The oxidised product can be isolated by known techniques, including ethanol precipitation and freeze-drying. Such precipitation has the advantage of removing products that have excessive degrees of oxidation. Other processes that result in C2-C3 oxidation of glucans, mannans, xylans etc. (or C3-C4 oxidation in fructans) are also suitable, for example oxidation with periodate (cf. WO 95/12619 or Nieuwenhuizen et al, StarchlStάrke, 37 (1985) 192-200), followed by chlorite oxidation. Other oxidations can also be used, e.g. oxidation with hydrogen peroxide in the presence of acetylated polysaccharides, or oxidation with hydrogen peroxide in the presence of copper and magnesium or other oxidation catalysts. Combinations of oxidation processes may also be used. For adjusting the chain length of the oxidised products, a hydrolysis step (acid or enzymatic) may precede or follow the oxidation step. The invention also pertains to detergent compositions containing a polycarboxy polysaccharide as described above as a cobuilder, anti-redeposition agent and/or soil dispersant. Typically, the composition contains 0.5-5 wt.% of the cobuilder prepared according to the invention, and further a detergent (12-25, especially 16-20 wt.%), a zeolite or silicate builder (15-30, especially 20-28 wt.%), a carboxylate such as sodium citrate (3-5 wt.%), a bleaching agent such as sodium perborate (10-20 wt.%), a catalyst such as TAED (3-4 wt.%), and optional further components such as enzymes (about 1-2 %: amylases, proteases), foaming or defoaming agents, odorants and the like. Example 1 Starch was oxidised generally according to Floor, "Oxidation of maltodextrins and starch with alkaline sodium hypochlorite", Thesis, Chapter 6, Delft (NL), 1989, as follows: 75 g of potato starch was suspended in 250 ml water. The pH was adjusted to 8.5. The appropriate amount of sodium hypochlorite solution (4% or 16% active chlorine) was added at a rate of 10 ml/min for the first half hour and 20 ml/min afterwards for 4 % Cl 2 (2.5 and 5 ml/min, respectively, for 15% CI2) at ambient temperature. The pH was maintained at 8.5 by the addition of 5 M NaOH. After 20 h the pH was adjusted to 9 and 500 ml of ethanol 98% was added. The suspension was stored at -4°C for 16 h and then decanted. The precipitate was dissolved in 150 ml water and 300 ml of ethanol was added. The suspension was again stored at -4°C for 16 h and then decanted. The precipitate was dissolved in 150 ml water and the solution was freeze-dried. By varying the starting material and the amount of hypochlorite, four different products were obtained after precipitation: DCS-1: Paselli 6 (molecular weight of native starch reduced by a factor 6), 550 ml 4% Cl 2 , dicarboxy content 9% (carboxyl content 0.36 per anhydromonose unit), MW about 5400; DCS-2: Paselli 2, 500 ml 15% Cl 2 , dicarboxy content 19% (carboxyl content 0.48), MW about 3200; DCS-3: native potato starch, 390 ml 15% Cl , dicarboxy content 18% (carboxyl content 0.36), MW about 4700; DCS-4: native potato starch, 500 ml 15% Cl 2 , dicarboxy content 21% (carboxyl content 0.48), MW about 3600. Example 2 350 g (dry weight) of native potato starch was suspended by stirring (450 rpm) in 350 ml of demineralised water. The suspension was heated to 45 °C at pH 7-8 and 97.2 ml of hydrogen peroxide (30% by weight in water) was added in 4 min (14.6 ml/min). The pH was slowly increased to 10.5 by addition of 1 M sodium hydroxide. When the pH had reached a value of 10.0, additional hydrogen peroxide was added (80- 100 ml) in 2-3 h and the pH slowly decreased. After all hydrogen peroxide had been added, the pH increased was to 10.4. The mixture was kept at about 60°C and pH 10.4 for three hours the start of the sodium hydroxide addition. The product was worked up as in example 1, by ethanol addition, and freeze-drying. Degree of oxidation 18% (carboxyl content 0.36); molecular weight about 5,000. Example 3: Wash tests Two co-builders were tested in a standard heavy duty formulation (HDF: see table 1) during 25 wash cycles using the 60°C cotton washing programme without prewash. Three products were tested: product A: HDF with cobuilder of the invention (polydicarboxy starch, prepared by the process of example 1, degree of oxidation 27.3% (= carboxyl content about 55), molecular weight around 5,000; product B: HDF with cobuilder of the invention (polydicarboxy starch, prepared by the process of example 1, degree of oxidation 17.7% (= carboxyl content about 34), molecular weight around 5,000. product R: HDF with reference cobuilder Sokalan CP 5 (a commercial polyacrylate cobuilder) The following criteria of washing performance were tested: Primary washing effects on artificially soiled test fabrics averaged over 8 wash cycles; Greying after 25 wash cycles on white test fabrics; - Chemical damage according to DEN 54270 after 25 washes at standard cotton test fabric; Inorganic incrustation after 25 washes at standard cotton test fabric according to ISO 2267, DEN 53919, part 1. Table 1: Heavy duty formulation The washing tests were carried out in commercial drum-type domestic washing machines Miele Novotronic W 918. The test of each product was made in alternating machines, in order to avoid effects caused by specific differences of the machines. The tests were carried out at a water hardness of 2.86 mmol/1 in a 60°C cotton programme without prewash. The total machine load was 4.5 kg. The dosage of formulation was 80 g per wash. Primary washing effects: Artificially soiled test fabrics (10 x 10 cm 2 ) were washed using four new sets of test fabrics for each wash cycle. Four test fabrics as mentioned in table 2, which were fixed on one PES/Co carrier fabric (PES = polyester, Co = cotton) (40 x 50 cm 2 ) were applied. The swatches were washed in a single wash cycle, dried and ironed cautiously on the left side (the side not subjected to instrumental measurement). Cleaning performance was quantified through reflectance measurement using an automatic reflectometer (Datacolour Spectraflash SF 500) according to EEC 456 at a wavelength of 460 nm without UV to eliminate the influence of optical brightener. Arithmetical means and confidence intervals at 95% statistical certainty of eight wash cycles were calculated and are summarized in table 2. Table 2: Primary washing effects; reflectancy values at 460 nm Secondary washing effects: The following white test fabrics were washed in order to obtain information about cumulative effects: - Inorganic incrustation, chemical damage and greying on standard cotton test fabric according to ISO 2267, DLN 53919, part 1 (Co 11 A in table 3); Greying on cotton terry cloth (Co terry in table 3); Greying on polyester/cotton test fabric (PES/Co in table 3). The ash content gives information about inorganic incrustations caused by the detergents during the washes and was determined on standard cotton (DIN 53919, part 1) after 25 wash cycles according to DIN 44983, part 21. Soil redeposition (greying) was determined reflectometrically after 25 wash cycles according to DEN 53919, part 2. Chemical damage is comparable to fibre decomposition of cotton caused by the washing process. It was determined through intrinsic viscosity of solutions of standard cotton 11A after 25 washes according to DIN 54270, part 3. The results are summarized in table 3. Table 3: Secondary washing effects after 25 cycles

Claims: Claims 1. Use of a polycarboxy polysaccharide having a molecular weight between 1,600 and 12,000 and having a degree of oxidation (DO) of 0.12-0.6 carboxyl groups per anhydromonose unit, as a cobuilder, in particular as an anti-redeposition and soil dispersing agent in detergent compositions. 2. Use according to claim 1, wherein said polysaccharide is a maltodextrin with an average degree of polymerisation (DP) of 10-75, preferably of 12-60 anhydroglucose units. 3. Use according to claim 1, wherein said hydrolysed polysaccharide is a pentosan with an average degree of polymerisation (DP) of 12-90, preferably of 15-60 anhydro- pentose units. 4. Use according to any one of claims 1-3, wherein said polycarboxy polysaccharide has a degree of oxidation of 0.15-0.5 carboxyl groups per monosaccharide unit. 5. Use according to any one of claims 1-4, wherein said polycarboxy polysaccharide is used at a level of 0.5-5 wt.% of the detergent composition. 6. Use according to any one of claims 1-5, wherein said polycarboxy polysaccharide is obtained by oxidation of the native or solubilised polysaccharide using hypochlorite at a pH of between 7.5 and 10. 7. Use according to any one of claims 1-5, wherein said polycarboxy polysaccharide is obtained by oxidation of the native or solubilised polysaccharide using periodate followed by oxidation with chlorite, if necessary including the step of partially hydrolysing the polysaccharide before or after oxidation. 8. Use according to any one of claims 1-5, wherein said polycarboxy polysaccharide is obtained by oxidation of the native or solubilised polysaccharide using hydrogen peroxide, optionally in the presence of an acylated polysaccharide or a metal catalyst. 9. Use according to any one of claims 6-8, wherein the oxidation is followed by a separation step, such as selective precipitation, to remove products having an excessive degree of oxidation. 10. Detergent composition containing, on dry substance basis, 0.5-5 wt.% of a polycarboxy polysaccharide as defined in any one of claims 1-7 as a cobuilder, in addition to 12-25 wt.% of a detergent, 15-30% of a zeolite builder, and further conventional components.

Inventors: LANGEROCK RIK JULIA RAOUL, SLAGHEK THEODOOR MAXIMILIAAN, TIMMERMANS JOHANNES WILHELMUS, VAN DE WATERING CORNELIS GERAR, VISSER HERMANNA ANTHONIA ANGEN, LANGEROCK, RIK, JULIA, RAOUL, SLAGHEK, THEODOOR, MAXIMILIAAN, TIMMERMANS, JOHANNES, WILHELMUS, VAN DE WATERING, CORNELIS, GERARDUS, VISSER, HERMANNA, ANTHONIA, ANGENITA, HELENA
Applicants: INST VOOR AGROTECH ONDERZOEK, LANGEROCK RIK JULIA RAOUL, SLAGHEK THEODOOR MAXIMILIAAN, TIMMERMANS JOHANNES WILHELMUS, VISSER HERMANNA ANTHONIA ANGEN, WATERING CORNELIS GERARDUS VAN, INSTITUUT VOOR AGROTECHNOLOGISCH ONDERZOEK (ATO-DLO), LANGEROCK, RIK, JULIA, RAOUL, SLAGHEK, THEODOOR, MAXIMILIAAN, TIMMERMANS, JOHANNES, WILHELMUS, VAN DE WATERING, CORNELIS, GERARDUS, VISSER, HERMANNA, ANTHONIA, ANGENITA, HELENA
Application year: 1998
Main classification: C11D3
IPC codes: C11D3