EP0239195A1

EP0239195A1 - Liquid detergent compositions

Info

Publication number: EP0239195A1
Application number: EP87300720A
Authority: EP
Inventors: Johannes Henricus Maria Rek
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1986-01-30
Filing date: 1987-01-28
Publication date: 1987-09-30
Also published as: DE3760366D1; GB8602327D0; EP0239195B1

Abstract

An aqueous liquid alkaline structured detergent composition comprising a nonionic detergent surfactant, a detergency builder, a dissolved sodium silicate, an alkaline agent and a structuring polymer agent, the amount of all dissolved sodium silicate material and the amount of all alkaline agent being such that the resultant amount of the alkali metal silicate is at least 10% by weight of the total composition and the weight ratio of the amount of free sodium cations to the amount of silicate anions expressed in terms of silicon dioxide being equal to or below 0.7:1, sufficient alkaline agent being present to provide the composition at an aqueous solution concentration of 1 % by weight with a pH value of at least 11.

Description

The present invention relates to liquid detergent compositions and, particularly, to such compositions having a high alkalinity and comprising a high level of silicate.
Alkaline liquid detergent compositions are well known in the fabric- and dishwashing art. They require a high pH and high buffer capacity to deliver detergency, to saponify or neutralise acidic soils and emulsify oils.
It is also well known that silicates are attractive materials to provide buffer capacity and alkalinity since, in addition to these properties, they contribute to soil-deflocculation, anti-redeposition, water-softening, corrosion-inhibition and chemical stability of active chlorine.
To formulate fully, a liquid detergent composition, it is often required to have an aqueous liquid medium which is capable of suspending particulate or undissolved materials which may be present due to the necessary high levels of some of the functional components. Although by internal or external structuring, it has been possible to formulate aqueous liquid media capable of providing the required suspending properties, it has proved difficult to formulate such compositions having a high alkalinity and comprising a high level of silicate which do not suffer from unacceptable rheological behaviour, in particular under non-ideal low-temperature conditions. The large increase in viscosity which results from crystallisation of the silicate under non-ideal low-temperature conditions, gives rise to a serious reduction in pumpability which, particularly in the industrial and semi-industrial applications of such liquids, is unacceptable.
To avoid the crystallisation problem, the formulator of this type of composition is therefore forced either to reduce the level of the commonly used sodium metasilicate to well below 10% by weight, or to use silicates of higher solubility, such as the neutral or alkaline waterglasses, and accept the concomitant lower alkalinity and hence lower performance.
In the United States Patent No. 4,556,504, structured alkaline built liquid detergent compositions are disclosed, comprising high levels of the more alkaline silicates, such as sodium metasilicate. The structured medium is based on a mixed ethylene/propylene oxide alcohol condensate and a cross-linked polyacrylate polymer. In general, these compositions have a good stability and rheology at a wide temperature range. However, it has been found that, under practical cold-storage conditions, silicate crystal formation takes place owing to the presence of unintended nucleating sites such as corroded metal parts, debris and the like. Owing to such crystal formation, the viscosity of the liquid composition sharply increases and the pumpability of the composition is reduced to an unacceptable level.
We have now found that the above disadvantages can be mitigated by limiting the weight ratio of the total amount of free sodium ions to the amount of silicate anions to below a certain value and supplementing alkalinity by non-sodium alkali.
Accordingly, the present invention provides an aqueous liquid alkaline structured detergent composition comprising a nonionic detergent surfactant, a detergency builder, a dissolved sodium silicate, an alkaline agent and a structuring polymer agent, the amount of all dissolved sodium silicate material and the amount of all alkaline agent being such that the resultant amount of the alkali metal silicate is at least 10% by weight of the total composition and the weight ratio of the amount of free sodium cations to the amount of silicate anions expressed in terms of silicon dioxide is equal to or below 0.7:1, sufficient alkaline agent being present to provide the composition at an aqeuous solution concentration of 1% by weight with a pH value of at least 11.
The compositions according to the invention provide aqueous liquid aqueous liquid structured detergent agents of high alkalinity and having high silicate levels. These are readily pourable and pumpable under non-ideal practical cold storage conditions and are easily formulated with conventional, readily available detergent ingredients.
The liquid detergent compositions of the invention comprise, as a first essential ingredient, a nonionic detergent surfactant, primary examples of which are the condensation products of ethylene oxide, propylene oxide and/or butylene oxide with alkylphenols, primary or secondary aliphatic alcohols, and fatty acid amides. Primary straight-chain alcohols are preferred. In general, the number of carbon atoms in the alcohol or amide portion is from 7 to 24, preferably from 8 to 18 and most preferably from 12 to 15. The average number of moles of alkylene oxide in the above nonionics varies from 1 to 30, mixtures of different nonionics including nonionics of a higher degree of alkoxylation also being suitable. Preferably, the alcohol or amide is condensed with from 4 to 15 moles of ethylene oxide optionally in combination with propylene oxide, and most preferably they are condensed with 6 to 12 moles of ethylene oxide.
The nonionic detergent surfactant is normally present in an amount of at least 2% by weight of the composition, the amount of 2 to 5% by weight being preferred for dishwashing applications, the amount of 5 to 15% by weight being preferred for fabric-washing applications.
The nonionic detergent surfactant can be used as sole detergent surfactant as in general will be the case in dishwashing compositions where only minor amounts of e.g. anionic detergent surfactants are acceptable.
However, in particular, in fabric-washing compositions, the nonionic detergent surfactant can also be used in combination with other detergent surfactants which may be of any conventional type. Suitable are the synthetic anionic detergent surfactants of the sulphate and sulphonate types, such as the sodium, potassium and ammonium salts of the C₉-C₂₀ alkyl benzene sulphonic acids, of the C₈-C₂₂ primary or secondary alkane sulphonic acids, of the Ca-C24 olefin sulphonic acids, of the sulphonated carboxylic acids, of the C₈-C₂₂ alkyl sulphuric acids, and of the Ca-C24 alkyl polyglycolethersulphuric acids containing up to 10 moles of ethylene oxide. Also suitable are alkali metal or alkanolamine soaps of C₁₀-C₂₄ fatty acids; cationic detergent surfactants, such as the quaternary ammonium compounds, in particular the dialkyl dimethyl ammonium halogenides; and amphoteric or zwitterionic detergent surfactants, such as N-alkylamino acids, and sulphobetaines. In view of cost, preference is given to mixtures of nonionic and anionic detergent surfactants.
The total amount of detergent surfactant in the fabric-washing oriented applications varies from 5 to 40% by weight of the composition, from 5 to 25% by weight being the preferred range.
The detergent compositions of the invention are built compositions and preferably contain from 5% to 35%, in particular 10% to 30% and most preferably from 10% to 25% by weight of a detergency builder. Typical examples of suitable detergency builders are the phosphate builders, such as sodium or potassium salts of triphosphoric acid, pyrophosphoric acid, orthophosphoric acid, polymetaphosphoric acid and mixtures thereof. Further suitable builders include the alkyl phosphonate esters, the carbonate salts, the zeolites, and the organic builders, such as the alkali metal citrates and polycarboxylates, in particular the nitrilotriacetates, and mixtures thereof.
An essential feature of the present invention is the inclusion of a high level of silicate in fully dissolved form. The selection of the silicate(s) should be such that in the final composition, the weight ratio of the amount of free sodium cations to the amount of silicate anions expressed in terms of silicon dioxide is equal to or below 0.7:1. Preferably, this is achieved by using a single sodium silicate which can be represented by the formula Na₂O.(SiO₂)_n, with n = >1.1. Suitable examples thereof are sodium disilicate, sodium trisilicate, and the alkaline and neutral waterglasses, and the mixtures thereof. In particular, the neutral waterglasses, i.e. Na₂O·(SiO₂)_3.3-3.5, are preferred. The liquid detergent compositions comprise at least 10% by weight of the sodium silicate to benefit fully from the advantages derived from the silicate component.
Preferably, the sodium silicate is included in the range of from 10 to 25% by weight of the total composition, the range of from 15 to 22% being especially preferred.
In view of the relatively low alkalinity of the sodium silicates suitable for inclusion in the present compositions, it is necessary to supplement alkalinity to provide the composition at an aqueous solution concentration of 1% by weight with a pH value of at least 11. A feature of the present invention is that such should occur while keeping the weight ratio of the amount of free sodium cations to the amount of silicate anions (as expressed in terms of silicon dioxide) equal to or below 0.7:1. Accordingly, any alkaline agent capable of providing a 1% solution of the composition with a pH value of at least 11 and not introducing free sodium anions in an amount which would exceed the above-specified ratio is suitable. Preferably, potassium hydroxide is used. The amount of alkaline agent is dictated by the required pH value and varies from 5 to 30% by weight of the total composition.
Preferably, a combination of neutral waterglass and potassium hydroxide in an about equal weight ratio is used, or else with the potassium hydroxide in some excess.
In the final composition, the weight ratio of the amount of free sodium cations (introduced by whatever source) and the amount of silicate anions (as expressed in terms of silicon dioxide) should be equal to or below 0.7:1, a weight ratio equal to or below 0.6:1, in particular 0.5:1, being preferred. A preferred lower end to all of these ratio ranges is 0.1:1.
A pH value of at least 11 at a 1% product concentration has been found adequate, but pH values of at least 12 are preferred for dishwashing and heavy duty fabric-washing applications.
The present compositions are externally structured and for this purpose they contain a structuring or thickening polymeric agent compatible with and stable to the high alkalinity of the compositions. Particularly suitable are the water-soluble polymers of acrylic acid, cross-linked with about 1% of a polyallyether of sucrose having an average of about 5.8 allyl groups for each sucrose molecule, the polymer having a molecular weight in excess of 1,000,000. Examples of such polymers are found in the Carbopol series, such as Carbopol 934, 940 and 941. Carbopol is the Registered trademark of B F Goodrich Co Ltd, the manufactures of these polymers. The preferred polymer is Carbopol 941. Depending on the viscosity which is desired, they are included in the range of from 0.1% to 1% by weight. Preferably they are included in the range of from 0.2% to 0.8% by weight of the total composition.
Suitable viscosities of the compositions of the present invention range from 0.3 to 30 Pa.s, in particular from 0.4 to 1.5 Pa.s (measured at 20°C and 20 sec 1).
The liquid detergent compositions may further contain any of the adjuvants conventionally used in this type of composition, e.g. sequestering agents such as ethylenediaminetetraacetate and diethylenetetraamine methylene phosphoric acid; soil-suspending and anti-redeposition agents such as carboxylethylcellulose, polyvinylpyrrolidone and the maleic anhydride/vinylmethylether copolymer; fluorescent agents; anti-oxidants; hydrotropes; conditioning agents; perfumes; germicides and colourants. Further, the addition of lather-depressors such as liquid polysiloxane or wax anti-foam compounds; alkaline stable enzymes; bleaches, such as e.g. sodium sulphite and potassium dichlorocyanurate, may be necessary to formulate a complete detergent composition suitable for use in machine washing operations.
The invention will now be further illustrated in the following examples, all amounts being in percentages by weight unless otherwise specified.
The formulation according to Examples 1 to 9 are physically stable at 37°C, 20°C and -5°C.

Examples 10-13

The formulations according to Examples 10 to 13 are physically stable at 37°C, 20°C and -5°C.

Claims

1. An aqueous liquid alkaline structured detergent composition comprising a nonionic detergent surfactant, a detergency builder, a dissolved sodium silicate, an alkaline agent and a structuring polymer agent, the amount of all dissolved sodium silicate material and the amount of all alkaline agent being such that the resultant amount of the alkali metal silicate is at least 10% by weight of the total composition and the weight ratio of the amount of free sodium cations to the amount of silicate anions expressed in terms of silicon dioxide being equal to or below 0.7:1, sufficient alkaline agent being present to provide the composition at an aqueous solution concentration of 1% by weight with pH value of at least 11.

2. A composition according to claim 1, wherein the nonionic detergent surfactant is selected from the condensation products of ethylene oxide, propylene oxide and/or butylene oxide with alkylphenols, primary or secondary aliphatic alcohols, and fatty acid amides.

3. A composition according to either preceding claim, wherein the nonionic detergent surfactant is present in an amount of at least 2% by weight.

4. A composition according to any preceding claim, wherein the detergency builder is present in an amount of from 5 to 35% by weight.

5. A composition according to any preceeding claim, wherein the composition contains a single sodium silicate which can be represented by the formula Na₂0.(Si0₂)_n where n > 1.1.

6. A composition according to claim 5, wherein the dissolved sodium silicate is selected from sodium disilicate, sodium trisilicate, and the alkaline and neutral waterglasses, and the mixtures thereof.

7. A composition according to any preceding claim, wherein the sodium silicate is present in the range of from 10 to 25% by weight of the total composition.

8. A composition according to any preceding claim and comprising from 5 to 30% by weight of potassium hydroxide.

9 A composition according to any preceding claim and comprising a composition of neutral waterglass and potassium hydroxide in about equal weight ratio.

10. A composition according to any preceding claim, wherein the weight ratio of the amount of free sodium cations to the amount of silicon anions is equal to or below 0.6:1.

11. A composition according to any preceding claim, wherein the pH of the composition is at least 12.

12. A composition according to any preceding claim, having a viscosity in the range of from 0.3 to 30 Pa.s.