LIQUID DETERGENT COMPOSITIONS

Abstract: The invention pertains to aqueous liquid detergent com­ positions having improved non-corrosive properties which comprise an effective amount of silica having a surface area greater than 200 m²/gram. The inclusion of silica provides good non-corrosive properties both in respect to metal and enamel surfaces.

Description: LIQUID DETERGENT COMPOSITIONS The present invention- relates to liquid detergent compositions and in particular to aqueous liquid detergent compositions having improved non-corrosive properties. It is desirable to include an anti-corrosion agent in detergent compositions in order to inhibit the corrosive and discolouring influence of the washing liquid on metal or enamel parts of washing machines and to prevent thereby the malfunctioning of the machines or the discolouring of fabrics which come into contact with such corroded parts. Aqueous liquid detergent compositions containing corrosion inhibiting agents are known in the art. Generally used are soluble silicates, such as metasilicate, orthosilicate and sesquisilicate. Apart from their corrosion inhibiting action, such compounds provide the liquid detergent composition with a highly alkaline environment, which is not always a desirable circumstance, especially if in such compositions alkali-sensitive ingredients are used. Further anticorrosive agents described in the detergent art include sulphites, nitrites, carbonates, borax or organic compounds such as benzoates. It has now been found that the corrosive action of aqueous liquid detergent compositions can be reduced to a significant extent by incorporation of silica of such type and in such amount that in the wash liquor a certain threshold concentration of dissolved silica is established. Accordingly the present invention provides aqueous liquid detergent compositions with improved noncorrosive properties, comprising conventional detergent ingredients and an effective amount of silica of the type to be defined hereafter. It has been found that in.order to achieve optimal anti-corrosion protection the silica must be present in the wash liquor in a dissolved form at a concentration of at least 120 ppm by weight and preferably 150 ppm by weight. According to the present invention therefore, in order to provide the required amount of dissolved silica in the wash liquor to ensure adequate anti-corrosion protection, the silica will in general be incorporated in the liquid detergent composition in an amount which is the equivalent of from about 1% to 10% by weight, preferably from 1.5% to 5% by weight and most preferably from 2% to 4% by weight of the liquid detergent composition which is intended for use at an in-wash product dosage of 10 g/I. If a liquid detergent composition is formulated having a preferred in-wash product dosage which is different from 10 g/litre, the amount of silica that should be incorporated to achieve adequate anti-corrosion protection must be adjusted accordingly, such that the amount thereof corresponds with the ranges as defined for 10 g/l product dosage. The silica to be used in the present invention should have a surface area which is greater than 200 m2 per gram and preferably greater than 350 m2 per gram or even 500 m2 per gram. The upper limit of the surface area is not a critical factor, but normally surface areas range to about 1200 m2 per gram. In general such silicas have elementary particle sizes of less than about 30 nm, in particular less than about 25 nm. Preferably, elementary particle sizes are less than 20 nm or even 10 nm. There is no critical lower limit of the elementary particle size; the lower limit is governed by other factors such as the manner of manufacture etc. In general, commercially available silicas have elementary particle sizes of 1 nm or more. Suitable forms of silica include amorphous silica, such as precipitated silica, pyrogenic silica and silica gels, such as hydrogels, xerogels and aerogels, or the pure crystal forms quartz, tridymite or crystobalite, but the amorphous forms of silica are preferred. Suitable silicas may readily be obtained commercially. They are sold, for instance, under the Registered Trade Names of Aerosil 380 (ex Degussa Corp., N.J., USA), Cab-O-Sil M5 (ex Cabot Corp., Ill, USA), Tixosil 38A (ex SI Chimie, France) and Gasil 200 (ex Crosfield, UK). The liquid detergent compositions of the invention further comprise as essential ingredient an active detergent material, which may be an alkali metal or alkanolamine soap of C10-C24 fatty acid, including polymerized fatty acids, or an anionic, nonionic, cationic, zwitterionic or amphoteric synthetic detergent material, or a mixture of any of these. The anionic synthetic detergents are synthetic detergents of the sulphate- and sulphonate-types. Examples thereof are salts (including sodium, potassium, ammonium and substituted ammonium salts, such as mono-, di- and triethanolamine salts) of Cg-C20 alkyl benzene sulphonates, C8-C22 primary or secondary alkane sulphonates, C8-C24 olefin sulphonates, sulphonated polycarboxylic acids, prepared by sulphonation of the pyrolized product of alkaline earth metal citrates, e.g. as described in British Patent Specification No. 1 062 179, C8-C22 alkyl sulphates, C8-C24 alkyl polyglycol ethersulphates, (containing up to 10 moles of ethylene oxides); further examples are described in "Surface Active Agents and Detergents" (Vol. I and II) by Schwartz, Perry and Berch. Examples of nonionic synthetic detergents are the condensation products of ethylene oxide, propylene oxide and/or butylene oxide with C8-C18 alkylphenols, C8-C18 primary or secondary aliphatic alcohols, C8-C18 fatty acid amides; further examples of nonionics include tertiary amine oxides with one C8-C18 alkyl chain and two C1-C3 alkyl chains. The above reference also describes further examples of nonionics. The average number of moles of ethylene oxide and/or propylene oxide present in the above nonionics varies from 1 to 30; mixtures of various nonionics, including mixtures of nonionics with a higher degree of alkoxylation, may also be used. Examples of cat ironic detergents are the quaternary ammonium compounds such as alkyl dimethyl ammonium halogenides. Examples of amphoteric or zwtterionic detergents are N-alkylamino acids, sulphobetaines and condensation products of fatty acids with protein hydrolysates, but owing to their relatively high cost they are usually used in combination with an anionic or a nonionic detergent. Mixtures of the various types of active detergents may also be used, and preference is given to mixtures of an anionic and a nonionic detergent-active compound. Soaps (in the form of their sodium, potassum, and substituted ammonium salts,such as of poly merized fatty acids, may also be used, preferably in conjunction with an anionic and/or a nonionic synthetic detergent. The amount of the active detergent material varies from 1 to 60%, preferably from 2 to 40% and particularly preferably from 5 to 25% by weight. When a soap is incorporated, the amount thereof is from 1 to 408 by weight. Although not necessarily, the liquid compositions of the invention preferably also comprise up to 60% of suitable builder materials, such as sodium1 potassium and ammonium or substituted ammonium pyro- and tripolyphosphates, -ethylenediamine tetraacetates, -nitrilotriacetates, -ether polycarboxylates, -citrates, -carbonates, -orthophosphates, zeolites, carboxymethyloxysuccinates, etc. Particularly preferred are the polyphosphate builder salts, nitrilotriacetates, citrates, zeolites, and mixtures thereof. In general the builders are present in an amount of from 1 to 60%, preferably from 5 to 50% by weight of the final composition. The amount of water present in the detergent compositions of the invention varies from 10 to 70% by weight. Other conventional materials may be present in the liquid detergent compositions of the invention, for example sequestering agents, such as ethylenediaminetetraphosphonic acid; non-builder electrolytes, such as alkalimetal-chlorides, -bromides, -nitrates and -sulphates; soil-suspending agents, such as sodium carboxymethylcellulose, polyvinylpyrrolidone or the maleic anhydride/vinylmethylether copolymer; hydrotropes; dyes; perfumes; alkaline materials, such as silicates; optical brighteners; germicides; anti tarnishing agents; suds boosters; suds depressants, such as liquid polysiloxane anti-foam compounds; enzymes, particularly proteolytic enzymes, such as the commercially available subtilisins Maxatase O (ex Gist- Brocades N.V., Delft, The Netherlands), Alcalaseand Esperase CR (both ex Novo Industri A/S, Copenhagen, Denmark), amylolytic and cellulolytic enzymes; enzyme stabilizing systems, such as a mixture of a polyol with boric acid or an alkalimetal borate; oxygen liberating bleaches, such as sodium perborate or percarbonate, diperisophthalic anhydride with or without bleach precursors, such as tetraacetyl ethylene diamine; or chlorine liberating bleaches, such as dichlorocyanurate; anti-oxidants, such as sodium sulphites; opacifiers; fabric softening agents; stabilizers, such as polysaccharide hydrocolloids, e.g. partially acetylated xanthan gum, commercially available as "Kelzan" (ex Kelco Comp., New Jersey, USA); buffers and the like. The invention is further illustrated by the following Examples, in which parts and percentages are by weight, unless indicated otherwise. Example I The following composition was prepared: Ingredient: Sodium dodecyl benzene sulphonate 5.0 C13-C15 linear primary alcohol, condensed with 7 moles of alkylene oxide (a mixture of ethylene- and propyleneoxide in a weight ratio of 92:8) 2.0 Anhydrous sodium tripolyphosphate 21.0 Amorphous silica (elem. particle size 10 nm, surface area 700 m2/g) 3.0 Sodium carboxymethylcellulose 0.2 Foam depressant 0.3 Example I, Ingredients (continued) 8 Optical brightener 0.1 Stabilizer 0.2 Proteolytic enzyme * Enzyme stabilizer 10.0 Perfume 0.25 Water balance pH 8.0 * The enzyme was added in such an amount that the final product had a proteolytic activity of 9 GU/mg (733 GU/mg = 1 Anson unit/g). To demonstrate the corrosion inhibiting action of the compositions of the present invention the aforementioned composition was tested comparatively under various temperature conditions and degrees of water hardness. Al-corrosion test In order to assess the corrosive action of a test wash liquor, circular plates of pure aluminium (99.5% Al) having a surface area of 40 cm2 were cleaned to remove surface grime and contaminants. They were rinsed with distilled water, dipped in methanol and airdried. After being weighed the plates were subjected to the test liquor for a period of 8 hours, during which time the solution was stirred continuously. Subsequently the plates were cleaned, dried and weighed. The corrosive action of the test liquor was expressed in weight loss of aluminium per m2 and per hour. In all tests the liquid detergent composition was dosed to the wash liquor at a concentration of 10 grams/litre, unless stated otherwise. Corrosion versus waterhardness test By means of the corrosion test described above the composition of Example I was compared with a control composition (i.e. the example composition without the silica) at various degrees of water hardness at a temperature of 85"C. The hardness of the water is expressed in degrees of French hardness (one degree French hardness is equivalent to 10 mg CaCO3 per litre). The following results were obtained: FH(Ca:Mg = 3:1) Weight loss of aluminium (g/m2/h) Comp.of Coinp.of Example I Control 0 1 4.0 12.5 1 2.4 25 c 0.1 1.1 37.5 1 0.4 50 1 c 0.1 Corrosion versus temperature test By means of the corrosion test described above the composition of Example I was compared with the control composition at various temperatures using demineralized water for the wash liquor. The following results were obtained: Temperature ("C) Weight loss of aluminium (g/m2/h) Comp.of Comp.of Example I Control 30 1 0.4 40 1 0.8 50 c 0.1 1.2 60 1 1.8 70 1 2.8 85 1 4.0 These results clearly show the corrosion inhibiting effect of the silica. Example II The following composition was prepared: Ingredient: Sodium dodecyl benzene sulphonate 7.0 C13-C15 lin. prim. alcohol, condensed with 7 moles of alkylene oxide (a mixture of ethylene oxide and propylene oxide in a weight ratio of 92:8) 2.0 Coconut potassium soap 1.0 Sodium tripolyphosphate 23.8 Amorphous silica (elem. particle size 10 nm, surf.area 700 m2/g) 2.0 Enzyme stabilizer 7.0 Proteolytic enzyme 9 GU/mg Sodium carboxymethylcellulose 0.1 Optical brightener 0.1 Foam depressant 0.2 Perfume 0.3 Water balance pH 7.8 To illustrate the corrosive action as a function of product dosage (and accordingly as a function of silica concentration) the composition of Example II was submitted to the corrosion test and compared with a control composition at different product dosages at a temperature of 85"C, using demineralized water for the wash liquor. The following results were obtained: Product dosage Silica Weight loss of aluminium (g/l) (ppm) (in g/m2/h) Comp. of Ex. II Control 10 200 c 0.1 4.0 9 180 c 0.1 4.0 8 160 < 0.1 3.9 7 140 0.5 3.8 6 120 0.8 3.8 These results clearly indicate that effective corrosion inhibition is provided if the product dosage is above 6 g/l, which corresponds to 120 ppm by weight of silica. Example III The following composition was prepared: Ingredient Sodium dodecylbenzene sulphonate 8.0 Sodium laurylethersulphate 0.5 C12 lin.-prim. alcohol condensed with 8 moles of ethylene oxide 2.5 Sodium pyrophosphate 11.0 Amorphous silica (elem. part. 10 nm, surface area 700 m2/g) 7.5 Enzyme stabilizer 10.0 Proteolytic enzyme 9 GU/mg Optical brightener 0.2 Water balance pH 8.0 The above composition was submitted to an experiment equivalent to the one carried out in Example II. As the above product should be used at a much lower dosage, the investigated range of product dosages is different. The following results were obtained: Product dosage Silica Weight loss of aluminium (g/l) (ppm) (in g/m2/h) Comp. of Ex. III Control 3.0 225 c 0.1 1.7 2.5 188 c 0.1 1.5 2.0 150 0.4 1.3 1.5 113 0.7 1.1 The above test shows that at least 120 ppm and preferably 150 ppm of silica should be present in the wash liquor in order to provide effective corrosion inhibition. Example IV To illustrate the anti-corrosive action of various types of silica the corrosion test was performed on a set of composition prepared according to the formulation of Example 2 but differing therefrom in the type of silica employed. The amounts of silica incorporated equaled 10% by weight of the composition. The following results were obtained at 850C, zero water hardness and 10 g/litre in-wash product dosage. Silica Type Elem.part. Surface Weight loss size area of (nm) (m2/g) aluminium 9/m2/h) control - - - 4.0 Durosil I) precipitated 25 50 3.1 Neosyl ET 2) precipitated 30 250 0.1 Tixosil 38A 3) hydrogel 20 250 0.0 Gasil WP 1 2) hydrogel 1.5-2.0 850 0.0 Cab-O-Sil M5 4) pyrogenic 14 200 0.0 Aerosil 380 1) pyrogenic 7 380 0.0 Gasil 35 2) xerogel 3-5 300 0.0 Gasil 200 2) xerogel 1.5-2.0 700 0.0 1) ex Degussa, Germany 4) ex Cabot Corp.Ill.,USA 2) ex Crosfield, UK 3) ex SI France Example V The composition according to example II was tested on its effectiveness in protecting enamel from corrosion attack. The silica as specified in example II was included in an amount of 2.5% by weight. This composition at an in-wash dosage of 12 g/litre, zero waterhardness and 900C, was subjected to an enamel adapted corrosion test similar to the above described Al-corrosion test. As enamel corrosion is a somewhat slower process than metal corrosion, enamel covered steel plates were used having a surface area of 100 cm2 and the testing time was extended to a period of 24 hours. Results indicate a significant anti-corrosive action: Weight loss of enamel mg/dm2/24 hours for the control composition 101 for the sample composition 19

Claims: CLAIMS 1. Aqueous liquid detergent composition with improved non-corrosive properties, comprising conventional detergent ingredients characterized in that it further comprises an effective amount of silica having a surface area which is greater then 200 m2/gram. 2. Detergent composition according to claim 1, characterized in that the silica is included in such amount that at the suitable in-wash dosage of the total detergent product a concentration of at least 120 ppm by weight of dissolved silica is established in the wash liquor. 3. Detergent composition according to claim 1 or 2, characterized in that the silica is included in an amount of from about 1 to 10% by weight of the total composition. 4. Detergent composition according to any one of the preceding claims, characterized in that the silica has an elementary particle size of less than 30 nm. 5. Detergent composition according to any one of the preceding claims, characterized in that the silica has a surface area which is. greater than 500 m2/gram. 6. Detergent compostion according to any one of the preceding claims, characterized in that the silica is included in an amount of from 2 to 4% by weight of the total composition. 7. Detergent composition according to any one of the preceding claims, characterized in that the silica has an elementary particle size of less than 10 nm. 8. Detergent composition according to any one of the preceding claims, comprising from 5 to 25% by weight of detergent active materials of the anionic, nonionic, cationic and/or zwitterionic type, from 5 to 50% by weight of builder materials, characterized in that the silica is included in an amount of from 2 to 4% by weight of the total composition. 9. Method of preventing corrosion of machine parts during washing, characterized in that a composition according to any one of the preceeding claims is applied in the washing process.

Inventors: DONKER, CORNELIS BERNARD, SAMUEL, JOHN RAYMOND
Applicants: UNILEVER NV, UNILEVER PLC
Application year: 1983
Main classification: C11D3
IPC codes: C11D3