EP0110472B1

EP0110472B1 - Liquid detergent compositions

Info

Publication number: EP0110472B1
Application number: EP83201655A
Authority: EP
Inventors: Cornelis Bernard Donker; John Raymond Samuel
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1982-11-26
Filing date: 1983-11-21
Publication date: 1988-06-22
Also published as: CA1221293A; JPS59140300A; AU2162683A; ATE35283T1; ZA838713B; NZ206355A; EP0110472A3; JPS6119678B2; AU550913B2; EP0110472A2; BR8306514A; DE3377140D1

Abstract

The invention pertains to aqueous liquid detergent compositions having improved non-corrosive properties which comprise an effective amount of silica having a surface area greater than 200 m<2>/gram. The inclusion of silica provides good non-corrosive properties both in respect to metal and enamel surfaces.

Description

The present invention relates to liquid detergent compositions and in particular to aqueous liquid detergant 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 anti-corrosive 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 non-corrosive properties, comprising conventional detergent ingredients and an effective amount of silica having a surface area greater than 200 m²/g.
In FR-A-2.300.800 detergent compositions are described, which contain 1-40% by weight of a silica with a particle size of less than 20 microns and a surface area of preferably greater than 200 m²/g. This silica is used in a composition comprising orthophosphate for the purpose of catching away the insoluble calcium ortho- and pyrophosphates formed in the wash liquor. These compositions may furthermore comprise water-soluble silicates as corrosion inhibitors. In contrast thereto, the silica of the present invention must dissolve in the wash liquor in order to achieve the corrosion inhibition properties of the invention.
It has been found that in order to achieve optimal anti-corrosion protection, from 1% to 10% of the silica must be present in a form such that in the wash liquor when dosed at 10 g/I, the silica is 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 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/I 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 Marks of Aerosil 380 (ex Degussa Corp., N. J., USA), Cab-O-Sil M5 (ex Cabot Corp., III, USA), Tixosil 38A (ex SI Chimie, France) and Gasil 200 (ex Crosfield, UK).
The liquid detergent compositions of the invention further comprise an active detergent material, which may be an alkali metal or alkanolamine soap of C_l6-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 tri-ethanolamine salts) of C₉―C₂₀ alkyl benzene sulphonates, C_a-C₂₂ primary or secondary alkane sulphonates, Cg-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. 1 082 179, C_a-C₂₂ alkyl sulphates, C_e-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 C_6-C_l. alkyl chain and two C,-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 cationic detergents are the quaternary ammonium compounds such as alkyl dimethyl ammonium halogenides.
Examples of amphoteric or zwitterionic 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, potassium, and substituted ammonium salts, such as of polymerized 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% in general, 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 40% by weight.
Although not necessarily, the liquid compositions of the invention preferably also comprise up to 60% of suitable builder materials, such as sodium, 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 in general.
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@ (ex Gist-Brocades N. V., Delft, The Netherlands), Alcalase@ and Esperase@ (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:
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.

AI-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 air-dried. 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 CaC0₃ per litre).
The following results were obtained:

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:
These results clearly show the corrosion inhibiting effect of the silica.

Example II

The following composition was prepard:
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:
These results clearly indicate that effective corrosion inhibition is provided if the product dosage is above 6 g/I, which corresponds to 120 ppm by weight of silica.

Example III

The following compositon was prepared:
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:
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 equalled 10% by weight of the composition.
The following results were obtained at 85°C, zero water hardness and 10 g/litre in-wash product dosage.

Example V

The composition according to Example II was tested on its effectiveness in protecting enamel from corrosion attack.
The silica as specifed 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 90°C, was subjected to an enamel adapted corrosion test similar to the above described AI-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: ^.

Claims

1. An aqueous liquid detergent composition comprising conventional detergent ingredients and from 1 to 10% by weight of silica with a surface area of greater than 200 m²/g, characterised in that the silica is included in such an amount that when dosed in a wash liquor at a rate of 10 g/I, at least 120 ppm by weight of silica is dissolved.

2. A detergent composition according to claim 1, further characterised in that the silica has a surface area which is greater than 500 m²/g.

3. A detergent composition according to claim 1 or 2, further characterised in that the silica is included in an amount of from 2 to 4% by weight of the total composition.

4. A detergent composition according to any one of the preceding claims, further characterised in that the silica has an elementary particle size of less than 10 nm.

5. A method of preventing corrosion of machine parts during washing, characterised in that a composition according to any one of the preceding claims is applied in the washing process.