EP0081908A1

EP0081908A1 - Low foaming liquid detergent compositions

Info

Publication number: EP0081908A1
Application number: EP82306014A
Authority: EP
Inventors: Ho Tan Tai; Jelles Vincent Boskamp
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1981-11-13
Filing date: 1982-11-11
Publication date: 1983-06-22
Also published as: ZA828332B; AU9029682A; AU547579B2

Abstract

A low foaming liquid detergent composition is used for fabric washing. It has a non-Newtonian or «false body structure imparted by micellar interaction of surfactant and electrolyte and contains a polysiloxane anti-foam in suspension. Preferably, though not essentially the pH of the liquid is below 9.5.

Description

This invention relates to liquid detergent compositions.
Liquid detergent compositions for fabric washing are popular in the United States and are gaining in popularity in Europe. Some such liquids are formulated to be substantially unbuilt, but the performance of these is markedly inferior to conventional fabric washing powders, especially since it is very difficult to incorporate oxygen bleaches into liquids. While this inferiority is well recognised it is also very difficult to incorporate sufficient quantities of detergency builder compound into a liquid without rendering the liquid unstable and liable to precipitate.
One way in which we have approached the. problem of incorporating adequate quantities of builder into a liquid detergent is to formulate the liquid so that it has a 'structure' or 'false body'. The builder compound is then suspended in the liquid, semi-permanently.
There are two basic ways of making structured or false body liquids. One way is to rely on the micellar interaction set up between an anionic surfactant, a nonionic surfactant and an electrolyte. If a combination of this sort is incorporated into a liquid it is possible to produce a structure which is capable of suspending as much as 50% of quite dense particles such as sodium tripolyphosphate. The second way of making a structured liquid is to use an auxiliary thickener such as a clay or a polymer. Again quite large amounts of particulate material can be suspended in-such liquids, but in our experience their viscosity is more sensitive to changes in formulation.
This invention-relates to the first type of structured liquid, the micellar type.
We believe we are one of the very few organisations who have investigated the application of micellar structured liquids to the field of fabric washing in automatic washing machines. Hitherto, the structured liquids produced or patented by our competitors have generally been part of hard surface cleaning compositions such as scouring cleansers. Such compositions are very different from fabric washing compositions in that the detergency required of them is much lower and the consideration of the amount of foam developed is not especially important. In fabric washing compositions, on the other hand, the amount of foam developed is critical, since if the compositions develop large amounts of foam, then they will not be suitable for use in automatic (drum-type) washing machines.
This invention relates to a structured liquid detergent composition of the micellar type which is low-foaming and which is suitable for use in automatic washing machines.
Accordingly the present invention provides a low-foaming detergent composition comprising a micellar structured liquid and a liquid polysiloxane anti-foam compound, characterised in that the anti-foam compound is unprotected and is maintained in homogeneous suspension by the structure of the liquid.
Preferably, the composition has a pH of 9.5 or less.
By the term a "liquid polysiloxane anti-foam compound" is meant a mixture of a liquid polysiloxane and particles of a hydrophobic substance. Examples of hydrophobic substances are hydrophobic silica and calcium alkyl phosphates. Liquid polysiloxane anti-foam compounds are available commercially. For example, the Dow Chemical Company markets a mixture of a liquid polysiloxane and a hydrophobic silica under the trademark DB100.
The essence of this invention is that, contrary to what would be expected, it is possible to incorporate the well-known polysiloxane anti-foam compounds into micellar structured liquid detergent compositions without the necessity for protecting them. In the past it has always been thought that if an anti-foam of this type is to effective in detergent solution it will be necessary to protect it, for instance by encapsulating it, by absorbing it on some absorbent from which it can be readily desorbed, or by forming it into a composite particle such as a pan-granulated granule. However, we have now found that when intended for structured liquids, it is unnecessary to take these precuations. Without wishing to be limited to any particular theory it is now thought that the reason for the efficacy of unprotected liquid polysiloxane anti-foam compounds in .the compositions of the invention is that individual droplets of the siloxane are held separately in suspension by the structure of the micellar-liquid and are not allowed to coalesce.
The pH of the structured micellar liquid is an important sub-feature of the invention since it is believed that at pHs higher than 9.5 the liquid polysiloxane anti-foam compound tends to be deactivated and so we prefer the pH to be no higher than 9.5.
In a preferred aspect, the invention provides a stable homogeneous aqueous structured micellar liquid detergent composition having a pH of 9.5 or less and containing 18 to 35% by weight of sodium tripolyphosphate and 6 to 15% by weight of an active detergent mixture comprising

(a) a water-soluble anionic sulphonate or sulphate detergent;
(b) an alkali metal soap of a fatty acid having 12 to 18 carbon atoms;
(c) a nonionic detergent;

^-1

Water-soluble anionic sulphonate detergents suitable for use in the compositions of the invention are for example the alkali metal salts of C₁₀-C₁₆ alkylbenzene sulphonates, C₁₀-C₂₀ alkane sulphonates, and C₁₀-C₂₀ olefin sulphonates, the alkali metal salts of alkylbenzene sulphonates being preferred, especially those derived from alkylbenzenes having a C₁₀-C₁₄ alkyl chain and average molecular weight of approximately 225-245.
Water-soluble anionic sulphate detergents are for example primary and secondary alkyl sulphates and alkylether sulphates having an alkyl chain length of about 8 to 20 carbon atoms, preferably 12 to 18 carbon atoms eg lauryl sulphate.
Typical examples of fatty acids having 12 to 18 carbon atoms 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 can be used, the potassium soaps being preferred.
Suitable nonionic detergents for use in the present invention are fatty acid alkylolamides; alkylene oxide condensates of alkyl phenols or aliphatic alcohols, alkylamines, fatty acid alkylolamides and alkyl mercaptans; and amine oxides. Ethylene oxide condensates and mixtures of ethylene oxide condensates with fatty acid alkylolamides are preferred.
Particularly suitable ethylene oxide condensates, such as ^C ₁₃-C₁₅ alcohols condensed with 6-8 moles of ethylene oxide per-mole of alcohol have hydrophilic- lipophilic balance (HLB) values of between 11 and 15.
Preferably the compositions of the invention have a viscosity of from 0.2 to 0.8 Pa s measured at 20°C and at a shear rate of 21 seconds ; a sodium tripolyphosphate content of 20 to 32% by weight and an active detergent mixture content of 7 to 14% by weight.
While it is normally necessary to have the surfactant mixture in the stated ratios in the aqueous compositions in order to achieve a stable product within the desired viscosity range, it has been found that it is also important to mix the ingredients, properly agitated, in the proper sequence in order to produce a product of uniform quality from batch to batch. If the mixing sequence and proper agitation disclosed below are not followed, varying rheological properties and reduced suspending capability can occur. If the mixing order and proper agitation as described below are followed, then successive batches especially when mixed in the same vessel will produce products of uniform viscosity and stability.
The ingredients are preferably mixed in the following manner.
The quantity of water is charged into a suitable mixing vessel provided with a stirrer. Anionic detergents, including soap, are then mixed into the water with moderate stirring. Desirably slight heating'to about 70°C is applied to dissolve the anionic detergents completely in the water. The sodium triphosphate is then mixed into the aqueous anionic detergent solution with continued stirring whilst maintaining the temperature at the appropriate level of about 70-75°C until a homogeneous mass is obtained. The nonionic detergent is then-mixed into the mass and stirring is continued.
Finally the mixture is cooled under constant agitation and water is added, if necessary, to compensate evaporation loss during the first stages of operation. Thereafter perfume and the liquid polysiloxane anti-foam compound may be added when the product is at substantially ambient temperature.
The liquid detergent composition of the invention may further contain any of the adjuncts normally used in fabric washing detergent compositions eg sequestering agents such as ethylene-diaminetetraacetate; alkali silicates for adjusting the pH; soil suspending and anti-redeposition agents such as sodium carboxymethylcellulose, polyvinylpyrrolidone etc; fluorescent agents; perfumes, germicides and colourants.
Further the addition of lather depressors other than liquid polysiloxane anti-foam compounds; enzymes, particularly proteolytic and amylolytic enzymes; reducing peroxygen or chlorine bleaches, such as sodium sulphite, sodium perborate and potassium dichlorocyanurate, including bleach activators, such as N,N,N',N'-tetraacetylethylene- diamine, may be necessary or desirable to formulate a complete heavy duty detergent composition suitable for use in washing machine operations. These ingredients can be employed in the liquid detergent compositions of the invention without danger of undue decomposition during storage if a proper protective coating is applied.

Example 1

4 Kg batches A, B and C of aqueous liquid detergent composition were prepared: 705 grams of water were charged into a 5 litre vessel provided with a stirrer. The appropriate amounts of sodium silicate, sodium carboxymethylcellulose, sodium alkylbenezene sulphonate, potassium oleate and fluorescent agent, were successively introduced and mixed into the water with moderate stirring under slight heating until the temperature reached about 60-70°C. Heating was stopped and 1080 grams of sodium tripolyphosphate was mixed into the aqueous solution with continued stirring until a homogeneous mass was obtained. Thereafter the appropriate amounts of alcoholethoxylate and ethanolamide nonionic surfactants were mixed into the mass. The mixture was then allowed to cool under constant agitation and thereafter additional water, perfume and the liquid polysiloxane anti-foam compound were added.
A stable, white opaque, homogeneous and pourable liquid detergent of the following composition was obtained:
The liquids were then stored for 8 days at 37°C following which their foaming properties were assessed in a Brandt 432 (registered trademark) Washing Machine using the 60° and 95°C cycles. The load was 4 kg of cotton cloth or 2 kg of synthetic cloth and 200 grams of powder was used in each wash cycle.
The height of suds appearing at the port-hole of the washing machines was measured against an arbitrary scale at a series of time intervals during the heat-up period and the temperature of the wash liquor was measured simultaneously.
The results for Compositions A, B and C are shown in Table 1.
It can be seen from the table that although compositions A and C, having pHs of 8.9 and 8.0 respectively produce satisfactory volumes of foam, composition B, of pH 10.5 over-foams.

Example 2 -

Three liquid detergent compositions which were unstructured were prepared by a conventional mixing method to the following formulations:
While these liquids were initially creamy and homogeneous, they separated into two layers after storage, the liquid polysiloxane anti-foam compound floating to the top.

Example 3

Two compositions, G and H, having the following formulations were prepared:
The pH of both compositions was adjusted to at least 12. The viscosity of composition G was 650 cp and that of H, 1100 cp.

^* Tegosipon WM100 (registered Trade Mark).

The two compositions were stored for two months at 37°C and were found to show no substantial deterioration in foam controlling capacity.

Claims

1. A low-foaming detergent composition comprising a micellar structured liquid and a liquid polysiloxane anti-foam, characterised in that the anti-foam compound is unprotected and is maintained in homogeneous suspension by the structure of the liquid.

2. A low-foaming aqueous detergent composition according to claim 1 characterised in that the structured liquid is formed by the micellar interaction between an anionic surfactant, a nonionic surfactant and an electrolyte.

3. A low-foaming aqueous detergent composition according to any one of the preceding claims characterised in that a detergency builder in solid form is maintained in homogeneous suspension by the structure of the liquid.

4. A low-foaming aqueous detergent composition according to claim 3 characterised in that the detergency builder comprises sodium tripolyphosphate.

5. A low-foaming aqueous detergent composition according to any one of the preceding claims characterised by having a viscosity of 0.20 to 1.5 of Pascal seconds measured at 20°C and at 21 seconds ^-1 shear rate.

6. A low-foaming aqueous detergent composition according to any one of the preceding claims characterised in that the content of surfactant is from 8-14% by weight.

7. A low-foaming aqueous detergent composition according to claim 5 characterised in that the content of sodium tripolyphosphate is from 25-32% by weight.