Detergent compositions

Abstract: A detergent composition having improved antiredeposition properties on polyester fabrics contains a polyalkylene oxide/vinyl acetate graft copolymer, and also contains dipicolinic acid or a salt or derivative thereof.

Description: TECHNICAL FIELD The present invention relates to fabric washing detergent compositions having improved antiredeposition properties. BACKGROUND AND PRIOR ART Redeposition of soil removed from washed articles back onto the articles themselves is a well-known problem which is of particular significance with textile fabrics, and many solutions to this problem have been suggested. Classically, sodium carboxymethyl cellulose was incorporated into fabric washing compositions, and that compound is still used today. More recently, copolymers of ethylene or vinyl methyl ether and maleic anhydride, copolymers of acrylic acid and maleic anhydride, and homopolymers of acrylic acid have been suggested in the patent literature; see, for example, GB-A-1 269 848 (Procter & Gamble) and GB-A-1 460 893 (Unilever). EP 219 048A (BASF) discloses the use of graft copolymers of polyalkylene oxide with vinyl acetate as greying inhibitors in the washing and post-wash treatment of synthetic textile fabrics. We have now discovered that detergent compositions containing a graft copolymer of this type in conjunction with a dipicolinic acid salt exhibit surprisingly enhanced soil suspension (antiredeposition) properties on polyester fabrics. The use of dipicolinic acid, its salts and derivatives as detergency builders is disclosed in GB-A-1 342 095 (Unilever). DEFINITION OF THE INVENTION The present invention provides a detergent composition comprising: (a) from 2 to 50% by weight of a detergent active system comprising one or more anionic, nonionic, cationic, zwitterionic or amphoteric surfactants; (b) from 0.5 to 60% by weight of a compound of the general formula I and/or a water-soluble or water-dispersible salt thereof: wherein R represents a hydrogen atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, an alkyl-substituted amino group, a carboxyl group, or a C₁₋₄ alkyl group; and (c) from 0.1 to 3% by weight of a graft copolymer of (i) a polyalkylene oxide of molecular weight (number average) 2000 - 100 000 containing units of ethylene oxide, propylene oxide and/or butylene oxide with (ii) vinyl acetate (optionally saponified to an extent of up to 15%) in a weight ratio of (i) to (ii) of from 1:0.2 to 1:10. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to detergent compositions containing three specified ingredients - a surfactant system, a dipicolinic acid compound, and a graft copolymer - which may additionally contain any other conventional detergent ingredients, for example, other builders, bleach systems, antifoam systems, fluorescers, inorganic salts, and other materials well known to those skilled in formulating detergents. The compositions of the invention may take any suitable form, for example, powders, liquids or bars. The surfactant system The total amount of detergent-active material (surfactant) in the compositions of the invention is from 2 to 50% by weight, and is preferably from 5 to 40% by weight. The compositions of the invention may contain one or more soap or non-soap anionic, nonionic, cationic, amphoteric or zwitterionic surfactants, or combinations of these. Many suitable detergent-active compounds are available and are fully described in the literature, for example, in "Surface-Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch. The preferred detergent-active compounds that can be used are soaps and synthetic non-soap anionic surfactants and nonionic surfactants. Synthetic anionic surfactants are well known to those skilled in the art. Examples include alkylbenzene sulphonates, particularly sodium linear alkylbenzene sulphonates having an alkyl chain length of C₈-C₁₅; primary and secondary alkyl sulphates, particularly sodium C₁₂-C₁₅ primary alcohol sulphates; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates. Suitable nonionic detergent compounds which may be used include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example, aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Specific nonionic detergent compounds are alkyl (C₆₋₂₂) phenol-ethylene oxide condensates, the condensation products of linear or branched aliphatic C₈₋₂₀ primary or secondary alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long-chain tertiary amine oxides, tertiary phosphine oxides, and dialkyl sulphoxides. Especially preferred are the primary and secondary alcohol ethoxylates, especially the C₁₂₋₁₅ primary and secondary alcohols ethoxylated with an average of from 5 to 20 moles of ethylene oxide per mole of alcohol. It may also be desirable to include one or more soaps of fatty acids. These are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower or hardened rape seed oil. A preferred type of detergent composition suitable for use in most automatic fabric washing machines contains anionic and nonionic surfactant together in a weight ratio of at least 0.67:1, preferably at least 1:1, and more preferably within the range of from 1:1 to 10:1. Soap may also be present if desired. The dipicolinic acid compound Hereinafter, the compound of the formula (I) in acid or wholly or partially neutralised salt form will be referred to as the dipicolinic acid compound. This compound is present in the compositions of the invention in an amount of from 0.5 to 60%. Preferably, R in the formula represents a hydrogen atom, that is to say, the compound is dipicolinic acid itself or a salt thereof. Another preferred compound is one in which R is a hydroxyl group. The compound is conveniently in the form of an alkali metal salt, more preferably the sodium salt. Any suitable solubilising cation may, however, be employed. As mentioned previously, these compounds are known detergency builders. They may be used as the sole builders in the compositions of the invention, or they may be used in conjunction with one or more other builders. According to a preferred embodiment of the invention, the dipicolinic acid compound is used in conjunction with a crystalline or amorphous alkali metal aluminosilicate. The aluminosilicate is preferably present in an amount of from 10 to 60% by weight, more preferably from 20 to 50% by weight. In this embodiment of the invention, the dipicolinic acid compound is suitably present in a relatively minor amount, for example, from 1 to 10% by weight. The alkali metal (preferably sodium) aluminosilicates used in this embodiment of the invention may be either crystalline or amorphous or mixtures thereof, and they have the general formula: 0.8-1.5 Na₂O. Al₂O₃. 0.8-6 SiO₂. These materials contain some bound water and are required to have a calcium ion exchange capacity of at least about 50 mg CaO/g. The preferred sodium aluminosilicates contain 1.5-3.5 SiO₂ units (in the formula above). Both the amorphous and the crystalline materials can be prepared readily by reaction between sodium silicate and sodium aluminate, as amply described in the literature. Suitable crystalline sodium aluminosilicate ion-exchange detergency builders are described, for example, in GB-A-1 473 201 (Henkel) and GB-A-1 429 143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well-known commercially available zeolites A and X, and mixtures thereof. Especially preferred is zeolite 4A. Other builders may also be included in the compositions of the invention if necessary or desired: suitable organic or inorganic water-soluble or water-insoluble builders will readily suggest themselves to the skilled detergent formulator. Inorganic builders that may be present include alkali metal (generally sodium) ortho-, pyro- and tripolyphosphate, and carbonate; while organic builders include nitrilotriacetates, citrates and carboxymethyloxysuccinates. This list is not intended to be exhaustive. The total level of detergency builder is generally within the range of from 20 to 80% by weight. According to a preferred embodiment of the invention, the compositions contain less than 10% by weight of inorganic phosphate builders, and are more preferably substantially free of inorganic phosphate. The graft copolymer The graft copolymers used in the compositions of the present invention are described and claimed in EP 219 048A (BASF). They are obtainable by grafting a polyalkylene oxide of molecular weight (number average) 2000 - 100 000 with vinyl acetate, which may be partially saponified, in a weight ratio of polyalkylene oxide to vinyl acetate of 1:0.2 to 1:10. The vinyl acetate may optionally be saponified to an extent of up to 15%. The polyalkylene oxide may contain units of ethylene oxide, propylene oxide and/or butylene oxide; polyethylene oxide is preferred. Preferably the polyalkylene oxide has a number-average molecular weight of from 4000 to 50 000, and the weight ratio of polyalkylene oxide to vinyl acetate is from 1:0.5 to 1:6. Especially preferred are polymers derived from polyethylene oxide of molecular weight 2000-50 000 and having a weight ratio of polyethylene oxide to vinyl acetate of from 1:0.5 to 1:6. A material within this definition, based on polyethylene oxide of molecular weight 6000 (equivalent to 136 ethylene oxide units), containing approximately 3 parts by weight of vinyl acetate units per 1 part by weight of polyethylene oxide, and having itself a molecular weight of 24 000, is commercially available from BASF as Sokalan (Trade Mark) HP22. The polymers are present in the compositions of the invention in amounts of from 0.1 to 3% by weight, preferably from 0.3 to 1% by weight. Optional ingredients As well as the ingredients - surfactant system, dipicolinic acid compound, other builder and graft copolymer - already discussed, the compositions of the invention may contain any other non-interfering ingredients known to be suitable for incorporation into detergent compositions. For example, the detergent compositions according to the invention may suitably contain a bleach system. Preferred are peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which may be employed in conjunction with activators to improve bleaching action at low wash temperatures. The skilled detergent worker will have no difficulty in applying the normal principles to choose a suitable bleach system. Other materials that may be present in the detergent compositions of the invention include sodium silicate, fluorescers, inorganic salts such as sodium sulphate, enzymes, lather control agents or lather boosters as appropriate, pigments, and perfumes. Again, this list is not intended to be exhaustive. Preparation of detergent compositions Detergent compositions of the invention may be prepared by any suitable method. Detergent powders are suitably prepared by spray-drying a slurry of compatible heat-insensitive components, and then spraying on or postdosing those ingredients unsuitable for processing via the slurry. The skilled detergent formulator will generally have no difficulty in deciding which components should be included in the slurry and which should be postdosed or sprayed on. The graft copolymer is available as a solution having a solids content of 20% which is stable at slurry processing temperatures and can be incorporated in the slurry without problems, provided that the pH is maintained below 12. Similarly, the dipicolinic acid compound can normally be included in the slurry. The invention is further illustrated by the following non-limiting Examples, in which parts and percentages are by weight unless otherwise stated. EXAMPLE Four detergent compositions were prepared to the following formulation by conventional slurry-making, spray-drying and postdosing techniques: % Sodium linear alkylbenzene sulphonate 9.0 Nonionic surfactant 7EO 4.0 Zeolite 4A (hydrated basis) 24.0 Sodium alkaline silicate 5.0 Sodium sulphate 19.3 Sodium carbonate 7.0 Sodium carboxymethylcellulose 0.5 Fluorescer 0.7 Sodium perborate monohydrate 8.0 Tetraacetylethylenediamine (76% granules) 3.0 Enzyme granules 0.5 DPA 0 or 2.0 Graft copolymer (Sokalan HP22) 0 or 0.5 Water and minor ingredients to 100.0 Details of the four compositions are shown in the table below. The soil suspension (antiredeposition) properties of the compositions were compared by means of the following procedure. Two new, clean, unwashed polyester test cloths were washed together with five soiled cloths in a tergotometer at 60°C in 50° (French) hard water (Ca:Mg ratio 4:1) at a liquor to cloth ratio of about 50:1, the wash liquor containing 4 g/l of the detergent composition under test. The soiled cloths carried a range of different soils such as clay, oil, fat, proteinaceous, and ink. The wash cycle was repeated a further nine times, the soiled cloths being replaced by new soiled cloths (with the same range of soils) for each wash cycle. The reflectance of the two new cloths was measured before washing, and after the tenth wash cycle. The reduction in reflectance of the washed fabrics after ten washes is shown in the following table; the lower the reduction in reflectance, the less redeposition had occurred. Example Reflectance change (delta R 460* ) A control -6.0 B 0.5% Sokalan HP22 -7.1 C 2.0% DPA -3.8 1 0.5% Sokalan HP22 + 2.0% DPA -2.2 It will be seen that Composition 1 illustrates the invention while Compositions A to C are comparative. The graft copolymer Sokalan HP22 had little effect on its own on redeposition. The sodium dipicolinate alone had quite a substantial beneficial effect on redeposition, but the effect was very considerably enhanced by the presence of the graft copolymer.

Claims: A detergent composition comprising: (a) from 2 to 50% by weight of a detergent active system comprising one or more anionic, nonionic, cationic, zwitterionic or amphoteric surfactants; characterised in that it further comprises: (b) from 0.5 to 60% by weight of a compound of the general formula I and/or a water-soluble or water-dispersible salt thereof: wherein R represents a hydrogen atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, an alkyl-substituted amino group, a carboxyl group, or a C₁₋₄ alkyl group; and (c) from 0.1 to 3% by weight of a graft copolymer of (i) a polyalkylene oxide of molecular weight (number average) 2000 - 100 000 containing units of ethylene oxide, propylene oxide and/or butylene oxide with (ii) vinyl acetate (optionally saponified to an extent of up to 15%) in a weight ratio of (i) to (ii) of from 1:0.2 to 1:10. A detergent composition as claimed in claim 1, characterised in that R represents a hydrogen atom. A detergent composition as claimed in claim 1 or claim 2, characterised in that it further comprises from 10 to 60% by weight of a crystalline or amorphous sodium aluminosilicate builder. A detergent composition as claimed in claim 3, characterised in that it comprises from 20 to 50% by weight of aluminosilicate builder. A detergent composition as claimed in claim 3 or claim 4, characterised in that the compound (b) is present in an amount of from 1 to 10% by weight. A detergent composition as claimed in any preceding claim, characterised in that it contains less than 10% by weight of inorganic phosphate builder. A detergent composition as claimed in claim 6, characterised in that it is substantially free of inorganic phosphate builders. A detergent composition as claimed in any preceding claim, characterised in that the graft copolymer (c) is obtainable by grafting (i) a polyalkylene oxide of molecular weight (number average) 4000 - 50 000 containing ethylene oxide, propylene oxide and/or butylene oxide units with (ii) vinyl acetate (optionally saponified to an extent of up to 15%) in a weight ratio of polyalkylene oxide to vinyl acetate of 1:0.5 to 1:6. A detergent composition as claimed in any one of claims 1 to 7, characterised in that the graft copolymer (c) is obtainable by grafting a (i) polyethylene oxide of molecular weight (number average) 2000 - 50 000 with (ii) vinyl acetate (optionally saponified to an extent of up to 15%) in a weight ratio of polyethylene oxide to vinyl acetate of 1:0.5 to 1:6. A detergent composition as claimed in any preceding claim, characterised in that the graft copolymer (c) is present in an amount of from 0.3 to 1.0% by weight.

Inventors: BOSKAMP JELLES VINCENT, BOSKAMP, JELLES VINCENT
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1989
Main classification: C11D3
IPC codes: C11D3, C11D10