Aqueous liquid bleach composition

Abstract: An aqueous liquid bleaching composition is described having a pH from 1 to 6.5 and comprising a solid, particulate, substantially water-insoluble organic peroxy acid such as diperoxydodecanedioic acid. This peroxy acid is stably suspended in the aqueous liquid by a structurant combination of secondary alkane sulphonate and fatty acid.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to an aqueous liquid bleaching composition comprising a solid, substantially water-insoluble organic peroxy acid, which composition may be used for the treatment of fabrics and hard surfaces. 2. The Prior Art Suspending agents for solid, substantially water-insoluble organic peroxy acids in aqueous media have been reported in a number of patents. U.S. Patent 3,996,152 (Edwards et al.) discloses use of non-starch thickening agents such as Carbopol 940 R to suspend bleaches such as diperazelaic acid at low pH in aqueous media. Starch thickening agents were found useful in similar systems as reported in U.S. Patent 4,017,412 (Bradley). Thickening agents of the aforementioned types form gel-like systems which upon storage at elevated temperatures exhibit instability problems. When used at higher levels, these thickeners are more stable but now cause difficulties with pourability. U.S. Patent 4,642,198 (Humphreys et al.) reports a further advance in this technology by the use of surfactants as structurants. A wide variety of detergents including anionics, nonionics and mixtures thereof were reported as effective. Among the nonionics listed were alkoxylated condensation products of alcohols, of alkyl phenols, of fatty acids and of fatty acid amides. According to the examples, particularly preferred are the combinations of sodium alkylbenzene sulphonate and C₁₂-C₁₅ primary alcohols condensed with 7 moles ethylene oxide. European patent specification 201 958 discloses diperoxydodecanedioic acid containing liquid bleach compositions having a pH in the range 3.5 to 4.1 and also comprising linear alkyl benzene sulphonates and ethoxylated fatty alcohols. EP-A-0 176 124 (DeJong et al.) reports similar low pH aqueous suspensions of peroxy carboxylic acids. This art informs that surfactants other than alkylbenzene sulphonate have a detrimental effect upon chemical stability of the peroxy carboxylic acid-containing suspensions. Experimental data therein shows a number of well-known detergents causing suspension destabilization. These destabilizing detergents include lauryl sulphate, C₁₅ alkyl ether sulphate, ethoxylated nonyl phenol, ethylene oxide/propylene oxide copolymer and secondary alkane sulphonate. EP-A-0 240 481 (Boer et al.) seemingly also finds some special significance in the use of alkylbenzene sulphonate and suggests that the structured diperoxy acid bleach suspensions be substantially free of other surfactants. The patent then discloses a cleaning procedure whereby a first composition of the low pH surfactant structured 1,12-diperoxydodecanedioic acid can be used in a combination with a second high pH cleaning liquid containing further surfactants, enzyme and evidently neutralized C₁₂-C₁₅ fatty acid. U.S. Patent 4, 655, 781 (Hsieh et al.) reports the structuring of surface-active peroxy acids in substantially non-aqueous media at pH 7 to 12. Surfactants experimentally investigated included linear alkylbenzene sulphonate, fatty acids and sodium alkyl sulphate. A problem which has been noted with all the foregoing systems is that while chemical and physical stability may have been improved within the lower temperature range, there still remain instability problems at slightly elevated temperatures. Consequently, it is an object of the present invention to provide an improved aqueous liquid bleach composition comprising a solid, substantially water-insoluble organic peroxy acid wherein the above drawbacks are mitigated. More specifically, it is an object of the present invention to provide an aqueous suspension of a solid, substantially water-insoluble organic peroxy acid which is chemically and physically storage stable throughout a wide range of temperatures. These and other objects of the present invention will become apparent as further details are provided in the subsequent discussion and Examples. SUMMARY OF THE INVENTION An aqueous liquid bleaching composition having a pH of from 1 to 6.5, comprising from 1 to 40% by weight of a solid, particulate, substantially water-insoluble organic peroxy acid; characterised in that it also comprises from 1 to 30% by weight of a C₈-C₂₂ secondary alkane sulphonate; and a fatty acid present in an amount of from 0.5 to 10% by weight to stabilize said peroxy acid against phase separation from the aqueous liquid. DETAILED DESCRIPTION OF THE INVENTION It has now been discovered that water-insoluble organic peroxy acids can be stably suspended in low pH water by a combination of a C₈-C₂₂ secondary alkane sulphonate and a fatty acid. Heretofore, it had not been realized that the goal of broad temperature stability could be attained by combination of these two specific surfactants. Thus, the compositions of this invention will require a fatty acid, especially a C₁₂-C₁₈ alkyl monocarboxylic acid. Suitable fatty acids include lauric (C₁₂), myristic (C₁₄), palmitic (C₁₆), margaric (C₁₇), stearic (C₁₈) acids and mixtures thereof. Sources for these acids may be coconut oil which is rich in the lauric constituents, tallow oil which is rich in the palmitic and stearic constituents and mixtures of coconut/tallow oils. Particularly preferred are coconut/tallow combinations of about 80:20 ratio. Amounts of the fatty acids range from 0.5 to 10%, preferably from 1 to 5%, optimally from 2 to 3% by weight. The other necessary structuring surfactant is a C₈-C₂₂ secondary alkane sulphonate. Secondary alkane sulphonates are commercially available from Hoechst under the trademark Hostapur SAS 60. Amounts of this sulphonate material will range from 1 to 30%, preferably from 5 to 20%, optimally between 8 and 10% by weight. Organic peroxy acids usable for the present invention are those that are solid and substantially water-insoluble compounds. By "substantially water-insoluble" is meant herein a water-solubility of less than about 1% by weight at ambient temperature. In general, peroxy acids containing at least 7 carbon atoms are sufficiently insoluble in water for use herein. These materials have the general formula: wherein R is an alkylene or substituted alkylene group containing from 6 to 22 carbon atoms or a phenylene or substituted phenylene group, and Y is hydrogen, halogen, alkyl, aryl or The organic peroxy acids usable in the present invention can contain either one or two peroxy groups and can be either alkphatic or aromatic. When the organic peroxy acid is aliphatic, the unsubstituted acid has the general formula: where Y can be, for example, H, CH₃, CH₂Cl, COOH or COOH; and n is an integer from 6 to 20. When the organic peroxy acid is aromatic, the unsubstituted acid has the general formula: wherein Y is hydrogen, alkyl, alkylhalogen or halogen, or COOH or COOOH. Typical monoperoxy acids useful herein include alkyl peroxy acids and aryl peroxy acids such as: (i) peroxybenzoic and ring-substituted peroxybenzoic acids, e.g. peroxy-α-naphthoic acid; (ii) aliphatic and substituted aliphatic monoperoxy acids, e.g. peroxylauric acid and peroxystearic acid. Typical diperoxy acids useful herein include alkyl diperoxy acids and aryldiperoxy acids, such as: (iii) 1,12-diperoxydodecanedioic acid; (iv) 1,9-diperoxyazelaic acid; (v) diperoxybrassylic acid, diperoxysebacic acid and diperoxyisophthalic acid; (vi) 2-decyldiperoxybutane-1,4-dioic acid; (vii) 4,4′-sulphonylbisperoxybenzoic acid. The preferred peroxy acids are 1,12-diperoxydodecanedioic acid (DPDA) and 4,4′-sulphonylbisperoxybenzoic acid. The particle size of the peroxy acid used in the present invention is not crucial and can be from 1 to 2,000 microns, although a small particle size is favoured for laundering application. The composition of the invention contains from 1 to 40% by weight of the peroxy acid, preferably from 2 to 30%, optimally between 2 and 10% by weight. Aqueous liquid products encompassed by the invention will have preferably a viscosity in the range of from 50 to 20,000 centipoises (0.05 to 20 Pascal seconds) measured at a shear rate of 21 second ⁻¹ at 25°C. In most cases, however, products will have a viscosity of from 0.2 to 12 PaS, preferably between 0.5 and 1.5 PaS. Also of importance is that the aqueous liquid bleaching compositions of this invention have an acidic pH in the range of from 1 to 6.5, preferably from 2 to 5. Further, it will be advantageous to use in the compositions of this invention an additional amount of hydrogen peroxide, preferably ranging from 1 to 10% by weight. This peroxide component has been found quite effective in preventing the staining of metal surfaces when in contact with the low pH organic peroxy acid compositions. Electrolytes may be present in the composition to provide further structuring advantage. The total level of electrolyte may vary from 1.5 to 30%, preferably from 2.5 to 25% by weight. Since most commercial surfactants contain metal ion impurities (e.g. iron and copper) that can catalyze peroxy acid decomposition in the liquid bleaching composition of the invention, those sulphonates and fatty acids are preferred which contain a minimal amount of these metal ion impurities. The peroxy acid instability results from its limited, though finite, solubility in the suspending liquid vase and it is this part of the dissolved peroxy acid which reacts with the dissolved metal ions. It is known that certain metal ion complexing agents can remove metal ion contaminants from the composition of the invention and so retard the peroxy acid decomposition and markedly increase the lifetime of the composition. Examples of useful metal ion complexing agents include dipicolinic acid, with or without a synergistic amount of a water-soluble phosphate salt; dipicolinic acid N-oxide; picolinic acid; ethylene diamine tetraacetic acid (EDTA) and its salts; various organic phosphonic acids or phosphonates such as hydroxyethylidenediphosphonic acid, ethyl diamine tetra-(methylene phosphonic acid), and diethylene triamine penta-(methylene phosphonic acid). Other metal complexing agents known in the art may also be useful, the effectiveness of which may depend strongly on the pH of the final formulation. Generally, and for most purposes, levels of metal ion complexing agents in the range of from 10-1000 ppm are effective to remove the metal ion contaminants. In addition to the components discussed above, the liquid bleaching compositions of the invention may also contain certain optional ingredients in minor amounts, depending upon the purpose of use. Typical examples of optional ingredients are suds-controlling agents, fluorescers, perfumes, colouring agents, abrasives, hydrotropes and antioxidants. Any such optional ingredient may be incorporated provided that its presence in the composition does not significantly reduce the chemical and physical stability of the peroxy acid in the suspending system. The following Examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight of the total composition unless otherwise stated. EXAMPLE 1 A series of liquid bleach compositions were prepared by suspending 1,12-diperoxydodecanedioic acid in various surfactant structured liquid compositions. These formulations are outlined in Table I. Preparation of these compositions involved dissolving the appropriate amount of sodium sulphate in 10% of the water used in the formulation. Meanwhile, 35-50% of the total water was heated to 45-50°C. Fatty acid, e.g. lauric acid, was slowly added to the reactor with stirring until it had melted. Where a longer chain fatty acid was used, a higher water temperature was employed. Temperature was maintained at 45°C and secondary alkane sulphonate was then added. Hydroxyethylidenediphosphonic acid was added and the pH adjusted to 4. The sodium sulphate solution was added and the mixture stirred for about 5 minutes. DPDA was then charged to the reactor and stirred at 30-40°C for 30 minutes, then cooled with stirring. Ingredients % by weight A B C D E F G Secondary alkane sulphonate 9.0 8.0 7.0 8.0 9.0 9.0 9.0 Lauric acid 2.0 2.0 2.0 3.0 - - - Myristic acid - - - - 2.0 - - Palmitic acid - - - - - 2.0 - Stearic acid - - - - - - 2.0 Anhydrous sodium sulphate 3.0 5.0 3.0 4.0 3.0 3.0 3.0 DPDA 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Dequest 2010® 0.07 0.07 0.07 0.07 0.07 0.07 0.07 Water + 10% sulphuric acid to adjust pH to 3.5-4.5 ------------balance ------------- All the liquids in Table I formed stable suspensions and were easily pourable. No separation was observed after two months storage at room temperature. Furthermore, no physical separation occurred after 30 days at 50°C. EXAMPLE 2 The following liquid bleach compositions were prepared according to the method of Example 1 by suspending 1,12-diperoxydodecanedioic acid in various surfactant structured liquid compositions as listed in Table II. Compositions H through M formed stable suspensions and were easily pourable. Compositions N, O and P did not form stable suspensions. For compositions H through M no separation was observed after two months storage at room temperature. Furthermore, no physical separation occurred after 30 days at 50°C. This example demonstrates that if a fatty acid mixture is used, the mixture must be predominantly C₁₂-C₁₈. EXAMPLE 3 Experiments were performed to determine the relative suspending power of secondary alkane sulphonate/fatty acid against that of sodium alkylbenzene sulphonate/ethoxylated nonionic. The comparative formulations are outlined in Table III. Ingredients % by weight Q R Secondary alkane sulphonate 9.0 - Sodium alkylbenzene sulphonate - 6.65 C₁₂-C₁₅ primary alcohol/9 moles ethylene oxide - 2.85 Lauric acid 1.92 - Myristic acid 0.08 - Anhydrous sodium sulphate 3.0 6.65 DPDA 4.9 5.21 Dequest 2010® 0.07 0.07 water + 10% sulphuric acid to adjust pH 3.5-4.5 -- balance -- Storage stability tests were conducted at 40° and 50°C and are reported in Table IV. From Table IV, it is seen that the alkylbenzene sulphonate/ethoxylated nonionic combination R had inferior chemical stability relative to that of the secondary alkane sulphonate/fatty acid structured system Q. Composition R began to crack and physically separate after only 3-5 days. Composition Q remained physically stable throughout the 28 day period of the study. Even at 40°C storage, there was a significant advantage of composition Q over that of R. EXAMPLE 4 Composition Q of Example 3 was tested for bleaching performance on tea- and clay-soiled cloths in the presence of a laundry detergent the composition of which is outlined below. Laundry Detergent Ingredients Weight% Sodium alkylbenzene sulphonate 17.5 Pentasodium tripolyphosphate 29.9 Sodium silicate 9.5 Sodium sulphate 31.9 Sodium carboxymethylcellulose 0.35 Water 10.85 The cloths were subjected to a 15 minute isothermal wash at 40°C with a dosage of 1.5 g/l of detergent and 1.3 g/l of composition Q (where present) and a water hardness of 12° French. Bleaching performance was determined by measuring the reflectance at 460 nm before and after washing using a Gardener reflectometer. Bleaching is indicated by the increase in reflectance, labelled ΔR in the following table. Cloth Tea ΔR Clay ΔR Detergent -1.9 19.0 Detergent plus composition Q 5.2 26.5 From Table V, it is seen that the DPDA bleach is highly effective against both tea and clay stains.

Claims: An aqueous liquid bleaching composition having a pH of from 1 to 6.5, comprising from 1 to 40% by weight of a solid, particulate, substantially water-insoluble organic peroxy acid; characterised in that it also comprises from 1 to 30% by weight of a C₈-C₂₂ secondary alkane sulphonate; and a fatty acid present in an amount of from 0.5 to 10% by weight to stabilize said peroxy acid against phase separation from the aqueous liquid. A composition according to claim 1, wherein said peroxy acid is 1,12-diperoxydodecanedioic acid. A composition according to claim 1, wherein said peroxy acid is 4,4'-sulphonylbisperoxybenzoic acid. A composition according to claim 1, 2 or 3, wherein said fatty acid is a C₁₂-C₁₈ fatty alkyl monocarboxylic acid. A composition according to claim 4, wherein said C₁₂-C₁₈ fatty acid is selected from the group consisting of lauric, myristic, palmitic, margaric, stearic and acid mixtures thereof. A composition according to any of the above claims 1-5, wherein said peroxy acid is present in an amount between 2 and 10% by weight. A composition according to any of the above claims 1-6, wherein said secondary alkane sulphonate is present in an amount between 5 and 20% by weight. A composition according to claim 7, wherein said secondary alkane sulphonate is present in an amount between 8 and 10% by weight. A composition according to claim 1, wherein the fatty acid is present in an amount of from 2 to 3% by weight. A composition according to any of the above claims 1-9, having a viscosity from 0.05 to 20 PaS measured at a shear rate of 21 sec⁻¹at 25°C. A composition according to any of the above claims 1-10, further comprising from 1 to 10% by weight of additional hydrogen peroxide.

Inventors: ARONSON MICHAEL PAUL, REREK MARK EDWARD, ARONSON, MICHAEL PAUL, REREK, MARK EDWARD
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1989
Main classification: C11D3
IPC codes: C11D3, C11D7, C11D17, D06L3