GB2232420A

GB2232420A - Liquid detergent compositions

Info

Publication number: GB2232420A
Application number: GB8912390A
Authority: GB
Inventors: Hidde Frankena
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1989-05-30
Filing date: 1989-05-30
Publication date: 1990-12-12
Also published as: GB8912390D0

Abstract

An aqueous clear or translucent liquid detergent composition being substantially free of synthetic anionic surfactant materials, said composition comprising: (i) a mixture of surfactant materials comprising a C 8-24 mono- or dicarboxylic fatty acid material, or salts thereof, and a nonionic surfactant; and (ii) a C 1-7 mono-, di- or tri carboxylic acid or derivatives thereof. o

Description

LIOUID DETERGENT COMPOSITION The present invention relates to clear or translucent liquid detergent compositions which are substantially free of synthetic anionic surfactant materials.

In the formulation of isotropic aqueous liquid detergent compositions it is sometimes preferred to make the composition clear or translucent. Generally such compositions are characterised by the complete solubilisation of ingredients and the absence of any structure. Clear or translucent liquid detergent compositions are appreciated by the users, mainly because of their fresh and clean appearance. It is an object of the present invention to provide clear or translucent aqueous liquid detergent compositions.

It is a second object of the present invention to provide aqueous liquid detergent compositions which are environmentally more friendly. For the purpose of the present invention it is therefore desired to formulate liquid detergent compositions which are substantially free of synthetic anionic surfactant materials. Such compositions are not only environmentally more acceptable, also they are believed to be advantageous in that they are milder for the fabrics to be washed and they give rise to less skin problems.

In the formulation of aqueous liquid detergent compositions which are substantially free of synthetic anionic surfactant materials it is preferred to incorporate a fatty acid surfactant or salt thereof.

These materials, often referred to as soaps, provide good detergency and softness to cloths and are completely biodegradable.

Soap containing liquid detergent compositions, however, often suffer from the disadvantage that they are not completely clear or translucent but slightly cloudy. The cloudiness of these liquids is believed to originate from the presence of calcium soaps which are formed if some calcium impurities are present in the product.

These calcium impurities may for instance be introduced by using tap water in the preparation of the formulation.

For preventing the occurence of cloudiness in soap containing liquid detergents it is therefore considered advantageous to incorporate one or more materials in the compositions which are able to prevent negative effects of the eventual calcium impurities on the quality of the product.

In the selection of appropiate materials for this purpose, however, several problems are encountered. For example it was found that some calcium binding materials although suitable for the prevention of calcium soap formation are less suitable for the formulation of clear and translucent detergent compositions, because they tend to bind with calcium to form a complex which causes cloudiness and/or discoloring of the product. Examples of such materials are the carbonate builder materials such as potassium carbonate. Other calcium binding materials are sometimes less preferred for environmental reasons, examples of these materials are phosphonate materials such as materials of the DEQUEST range ex Monsanto.

Surprisingly it has now been found that one or more of the above problems can be solved and one or more of the above mentioned objects can be met and a stable, mild, aqueous liquiddetergent composition with good detergency properties and attractive clear or translucent appearance can be obtained, provided that the surfactant materials and the calcium binding materials are carefully chosen.

Accordingly the present invention relates to an aqueous clear or translucent liquid detergent composition being substantially free of synthetic anionic surfactant materials, said composition comprising: (i) a mixture of surfactant materials comprising C 8-24 mono- or dicarboxylic fatty acid material, or salts therof, and a nonionic surfactant; and (ii) a C 1-7 mono-, di- or tri carboxylic acid or derivatives thereof.

The surfactant materials used in compositions of the invention preferably comprise a saponified fatty acid surfactant material selected from the group of mono- or dicarboxylic acids having from 8 to 24 carbon atoms in the main chain, or mixtures thereof. Both saturated and unsaturated fatty acid materials can be used.

Suitable mono carboxylic acid salt surfactants for use in compositions of the invention are for example soaps; by the term 'soap' is meant an alkali metal soap of a long chain mono-carboxylic acid, for example one containing 12 to 18 carbon atoms. Typical acids of this kind are oleic acid, ricinoleic acid and fatty acids derived from castor oil, rapeseed oil, groundnut oil, coconut oil, palmkernel oil or mixtures thereof. The sodium or potassium soaps of these acids including mixtures of both forms are preferably used. A preferred soap mixture includes a mixture of coconut and oleic soap in weight ratios of from 5:1 to 1:5.

Suitable di carboxylic acid surfactants are for example alkyl or alkenyl succinic acids or their salts.

Preferably these materials include a C12-18 alkyl or alkenyl chain. Preferred is the use of the alkali metal salts of these materials, specific examples of such materials include sodium lauryl succinate, sodium dodecenyl succinate, potassium myristyl succinate etc.

The surfactant material for use in a composition according to the present invention also comprises a nonionic surfactant material. Suitable nonionic materials include for example the reaction products of alkylene oxides and/or polyols with C6-22 hydrophobic moieties, the tertiary phosphine oxides and the dialkyl sulphoxides.

Examples of these materials include the reaction products of alkylene oxides, usually ethylene oxide, with alkyl (C6-C22) phenols, generally 3 to 25 EO, i.e.

3 to 25 units of ethylene oxide per molecule; the condensation products of aliphatic (C8-C18) primary or secondary alcohols with ethylene oxide, generally 2 to 30 EO, e.g. 6 to 20 EO. Another example of suitable nonionics are nonionics obtained by first ethoxylating and subsequently propoxylating an organic hydroxyl group-containing radical, e.g. an aliphatic primary or secondary C8-C18 alcohol.

Other suitable nonionic detergent active materials have the formula RO(cnH2no)x(cH2cH(oH)cH2o)yH wherein R is an alkyl or alkenyl group having from 8 to 25 (preferably from 9 to 15) carbon atoms, n is 2 to 4, x is from 0 to 15 (preferably 0 to 6), y is from 1 to 20 (preferably from 1 to 7) and the alkylene oxide and glycerol groups are arranged in random or block formation. Preferably the molecule is terminated with at least one glycerol group.

The non ionic material may also comprise an alkyl poly saccharide surfactant having the formula RO(CnH2nO)x Zy or RCOO(CnH2nO)x Zy wherein Z is a moiety derived from a reducing saccharide containing from 5 to6 carbon atoms, preferably a glucose, galactose, glucosyl or galactosyl residue or mixtures thereof; R is a hydrophobic group selected from the group consisting of alkyl, alkenyl, alkyl phenol, hydroxy alkyl phenyl or hydroxy alkyl groups or mixtures thereof in which the alkyl groups contain from about 8 to about 20 carbon atoms, preferably from about 10 to about 16 carbon atoms, most preferably from about 12 to about 14 carbon atoms. n is 2 to 4 and x is o to 30, preferably 0 to 10 most preferably 0. The alkyl chain can be attached to the sugar residue at the 1-, 2-, 3-, 4-, 5 or 6 positions.

Y is a number from 1 to 10, preferably 1 to 4, most preferably 1 to 2.

The intersaccharide bonds can be e.g. between the one position of the additional saccharide units and the 2-, 3-, 4- and/or 6 positions on the preceding saccharide units.

Additionally the hydroxyl groups on the sugar residue may in part be substituted at the 1-, 2-, 3-, 4-, or 6 positions by short alkyl chains of C1 to C4, preferably 02.

In addition to the two above mentioned surfactant materials, compositions of the present invention may contain one or more additional surfactants not being synthetic anionic surfactant materials. These materials may for instance be selected from the group zwitterionic, cationic or amphoteric classes.

The level of surfactant materials in a composition of the present invention is preferably more than 5 % by weight, more preferred more than 10 % by weight, especially preferred more than 15 % by weight, most preferred more than 20 % by weight of the composition.

The level of surfactant material is generally less than 70 % by weight, preferably less than 60 % by weight, most preferred less than 50 % by weight of the composition.

Especially preferred are surfactant systems which are predominantly constituted by the above mentioned two essential surfactant components, preferably more than 90% of the surfactant materials is a mixture of the fatty acid surfactant and the nonionic surfactant, most preferably the surfactant system is substantially free of surfactants other than these materials. The weight ratio of fatty acid surfactant to nonionic surfactant is preferably from 10:1 to 1:5, more preferred from 5:1 to 1:2, typically about 3:1.

The second essential component of detergent compositions acccording to the invention is a C 1-7 mono-, di- or tri carboxylic acid or derivatives thereof, capable of binding calcium. Examples of these materials are propionic acid, acrylic acid, maleic acid, carboxy methyl oxy succinic acid, acetic acid, caproic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, tartaric acid, dipicolinic acid and citric acid and the various isomers of these acids. Suitable derivatives include salts of these acids and homo- or copolymers of these acids. Preferred salts are the alkali metal and ammonium salts of these acids. Preferred polymers are the copolymers of acrylic acid and maleic acid, provided they do not negatively affect the clear appearance of the product.

Preferred C 1-7 carboxylic acid materials have the ability to bind calcium ions. Preferably the pK (Ca2+) is more than 3.0, more preferred more than 3.5.

Surprisingly it has been found that especially the use of citric acid or its salts is advantageous. Not only are these materials derivable from natural sources, they also provide an environmental acceptable product, which is clear and has an attractive light yellow natural appearance and which does not suffer from noticeable discoloration. Further advantages of the use of citric acid or its salts are that the builder capacity of the product is increased, therewith increasing the washing performance and that the material works as an antioxidant material, therewith reducing the oxidising of unsaturated fatty acid materials in the composition, therewith preventing the occurence of unpleasant odours.

Especially preferred is the use of a citrate material, most preferred is the use of sodium citrate or potassium citrate. Preferably at least 80 % of the C 1-7 acid material is citric acid or a salt thereof, most preferably the C 1-7 acid material is substantially free of materials other that citric acid or its salts.

The level of C 1-7 acid material in the composition is preferably from 0.5 to 15 % of the composition, more preferred from 1.0 to 10 % of the composition, especially preferred from 1.5 to 7.5 % of the composition, most preferred from 2.0 to 5 % of the composition.

The liquid detergent compositions of the invention can contain any of the conventional additives in the amounts in which such additives are normally employed in liquid fabric washing detergent compositions. In selecting the additives for use in compositions of the present invention it is preferred to select mainly those ingredients which do not affect the two important aspects of the present invention : clear or translucent appearance and environmental acceptability.

One class of materials which may be present in compositions of the present invention are so-called hydrotropes, that is materials which assist in the solubilisation of the ingredients of the composition, well known hydrotrope material are the short chain alcohols such as ethanol and methanol. Other materials which also serve as hydrotropes, but also as buffering agents and enzyme stabilisers in the presence of a boron compound are the mono- di- or tri-alkanol amines, however, although the use of these materials are not excluded from the scope of the present invention, it is preferred to use other materials instead of these alkanol amines. Possible replacements of alkanolamines are polyols especially glycerol and propylene glycol. Of these especially the use of glycerol is preferred.The preferred level of these materials is from 2-20%, preferably from 5-15t by weight of the composition.

Examples of other additives, usually present in minor amounts are fluorescent agents, perfumes, enzymes such as proteases and amylases or mixtures therof, as well as germicides and colourants. In the choice of these materials it is also preferred only to use those materials which do not have a negative impact on the environment.

When enzymes are included, for instance at levels of from 0.1 to 2 % by weight of the composition, then the compositions of the present invention preferably also contain boric acid, boric oxide, borax or sodium ortho-, meta- or pyroborate, generally at from 0.25 to 15%, preferably from 0.5 to 10%, most preferably from 0.5 to 3% by weight of the composition, the amount being calculated as boric acid containing an equivalent amount of boron.

The compositions according to the present invention optionally also comprise a bleach, preferably a peroxide bleach. Examples of suitable peroxide compounds include hydrogen peroxide, the alkali metal peroxides, the perborates, persulfates, peroxy disulfates, perphosphates, the crystalline peroxyhydrates formed by reacting hydrogen peroxide with urea i.e. urea peroxide or with alkali metal carbonate i.e. alkalimetal percarbonates. Also encapsulated bleaches may be used. Preferred peroxide bleaches are sodium perborate tetra- and mono hydrates and sodium percarbonate. Although it is preferred that the bleaches are completely soluble in the system to give a clear product, it is also possible that bleaches are used which are only partially soluble in the system.

These partially soluble bleach particles were found not to provide cloudy systems, but systems wherein the bleach particles are present as clearly distinct glimmering particles dispersed in a clear matrix. These pearlescent translucent systems are particularly preferred by the user.

The bleach component is preferably added in an amount corresponding to 0.1 to 15% by weight of active oxygen, more preferred from 0.5 to 10% active oxygen, typically from 1.0 to 5.0% active oxygen. If the bleach is hydrogen peroxide, this is preferably used at a level of from 1.5 to 7.5 % by weight of the composition, preferably in such an amount that it can deliver from about 100 to 150 mg/litre active oxygen in the wash.

The balance of the composition is water, which is usually present to the extent of about 40% to about 75% by weight, preferably about 45% to about 65% by weight.

To ensure effective detergency, the liquid detergent compositions should be alkaline, and it is preferred that they should provide a pH within the range of about 8.5 to 12, preferably about 9 to about 11, when used in aqueous solutions of the composition at the recommended concentration. To meet this requirement, the undiluted liquid composition should preferably be of a pH between 7 and 12.5, for example about pH 8.5 to about 12.5. It should be noted that an excessively high pH, e.g. over about pH 13, is less desirable for domestic safety. If a bleach such as hydrogen peroxide is present in the liquid composition, then the pH is generally from 7.5 to 10.5, preferably 8 to 10, and especially 8.5 to 10, to ensure the combined effect of good detergency and good physical and chemical stability.The ingredients in any such highly alkaline detergent composition should, of course, be chosen for alkaline stability, especially for pH-sensitive materials such as enzymes, and a particularly suitable proteolytic enzyme. The pH may be adjusted by addition of a suitable alkaline material.

The viscosity of the liquid detergent should preferably be less than 1000 mPas at 25"C, measured at 21 S-1, more preferably less than 600 mpas; especially suitable are viscosities of 80 to 400 mPas.

The compositions of the invention may be prepared in any suitable way; a preferred method of preparing the composition of the present invention, however comprises the following steps: ( i ) forming an aqueous solution of the C 1-7 acid component in water; and ( ii) adding the surfactant materials to this aqueous solution.

This method is especially advantageous in that the calcium binding C 1-7 acid material is contacted with the water before the surfactants are added, this allows the reaction of the calcium binding materials with calcium ions eventually present in the water before the addition of the surfactants. It has been found that under these circumstances, even if tap water were to be used for the preparation of the detergent compositon, a particularly attractive appearance of the product is obtained, and less discoloration is observed during storage.

In use the liquid detergent compositions of the present invention will generally be diluted with water to form an aqueous wash liquor for the washing of fabrics, for example in a washing machine. Preferably the wash liquor will comprise from 0.1 to 10 % by weight of the liquid detergent composition, preferably from 5 to 15 g/litre.

The mildness of the products of the present invention makes them particularly suitable for manual washing of fabrics.

The present invention will now be illustrated by way of the following Examples.

Example 1 Aqueous liquid detergent compositions of the following formulations were prepared by first adding the potassium carbonate or the sodium citrate to tap-water of ambient temperature, followed by the addition of the remaining ingredients in the listed order.

EXAMPLE I II % bv weight Coconut.10 EO 10.0 10.0 coconut fatty acid 11.3 11.3 oleic acid 16.3 16.3 boric acid 1.0 1.0 glycerol 10.0 10.0 ethanol 6.5 6.5 potassium carbonate 3.0 -sodium citrate -- 3.0 1:1 KOH/NaOH 4.8 4.8 1:1 protease/amylase 0.25 0.25 water balance The compositions I (for comparison) and II (according to the invention) both had directly after preparation a light yellow natural color and were clear. The compositions were stored for 2 weeks at 4 0 C, after storage composition I had a light brown color and was slightly cloudy, composition II had still the attractive light yellow natural color and was still clear.

Composition II was used for the washing of cotton fabrics in an automatic washing machine. The dosage was 200 ml of liquid detergent, 4 kg of terry towel clothes were washed at 60 OC. The detergency performance of product proved to be good, the pieces of cotton had a soft touch, no skin irritations were observed by using the terry towels for drying purposes.

From the above it is clear that composition II according to the invention is clearly preferably in comparison with product I.

Claims

1. An aqueous clear or translucent liquid detergent composition being substantially free of synthetic anionic surfactant materials, said composition comprising: (i) a mixture of surfactant materials comprising a C 8-24 mono- or dicarboxylic fatty acid material, or salts therof, and a nonionic surfactant; and (ii) a C 1-7 mono-, di- or tri carboxylic acid or derivatives thereof.

2. A composition according to claim 1, wherein the mixture of surfactant materials comprises a C12-18 soap.

3. A composition according to claim 1, wherein the mixture of surfactant materials comprises a C12-18 alkyl or alkenyl succinic acid or a salt thereof.

4. A composition according to claim 1, 2 or 3 wherein the mixture of surfactant materials comprises an ethoxylated (2-30 EO) Cg-18 alcohol.

5. A composition according to one or more of the preceeding claims comprising citric acid or a salt thereof.

6. A composition according to one or more of the preceeding claims comprising 0.1 to 2% of enzymes, 0.5-3% of a boron compound and 5-15% of glycerol.

7. Method of preparing a liquid detergent composition according to one or more of the preceeding claims, comprising the steps of (i) forming an aqueous solution of the C17 mono-, di- or tri-carboxylic acids or derivatives thereof.

(ii) adding the surfactant materials to this aqueous solution.

8. Method of treating fabrics comprising the contacting of the fabrics with an aqueous liquor comprising from 0.1 to 10% by weight of a composition according to claim 1.