Hydrocarbon anti-foam granules

Abstract

 Anti-foam granules for use in detergent compositions to prevent over-foaming in automatic washing machines contain hydrophobic silica and a mixture of liquid and solid hydrocarbons. This active material is sorbed on a core material which produces a mechanical action on addition to water, for example sodium perborate monohydrate or gelatinised starch.

Description

[0001] This invention relates to anti-foam granules for use in detergent compositions and to a process_for their preparation.

[0002] The low-foaming fabric washing powder market in Europe is now well developed and a number of different anti-foam compounds have been used to suppress the inherent tendency of powders containing anionic and nonionic surfactants to over-foam when used in front-loading, drum type washing machines. For instance, mixtures of certain alkyl phosphoric acids with hydrocarbon waxes, certain silicone oil/hydrophobic silica mixtures and liquid hydrocarbons have all been used as an alternative to soap as anti-foam, and a number of other proposals have been made and are published in the patent literature.

[0003] Amongst the latter publications is French patent No 2 416 946, which relates to compositions containing a special mixture of liquid hydrocarbon with either a solid hydrocarbon or a fatty acid ester and a hydrophobic silica. Specifically the anti-foam system consists of:

A (1) 30-98% of a liquid hydrocarbon;

(2) 2-70% of an auxiliary substance selected from solid hydrocarbons (M Pt 35-100°C) and long chain fatty acid esters of fatty alcohols, or mixtures thereof; and

B 0.1-25% of hydrophobic silica.

[0004] We too have been studying the use of mixtures of hydrophobic silica with hydrocarbons of various descriptions and have discovered that if these materials are incorporated into a granule based on a substrate which produces a mechanical action on addition to water, then it is not necessary to use the proportions specified in French patent No 2 416. 946, but it is possible to use mixtures containing much less of the liquid component. There are a number of types of substrate which will produce a mechanical action on the granule. For example gelatinised starch is a substrate which swells rapidly on addition to water thereby breaking up the structure of the granule and leading to extremely good dispersion of the hydrocarbon. Similarly sodium perborate monohydrate is both extremely water-soluble and also evolves gas when immersed, both properties being ones which tend to break up the granule.

[0005] Accordingly the present invention provides a detergent composition containing an anionic detergent active compound and/or a nonionic surfactant and anti-foam granules comprising hydrophobic silica and a mixture of liquid and solid hydrocarbons, characterised in that the liquid hydrocarbon component constitutes less than 30% by weight of the total hydrocarbon and in that the silica and the mixture of liquid and solid hydrocarbons are sorbed on a core of a material producing a mechanical action on addition to water.

[0006] A second aspect of the invention provides two alternative processes for manufacturing granules for use in the compositions. According to this aspect the invention provides first a process for the production-of anti-foam granules which comprises:

(a) forming a molten mixture of the liquid and solid hydrocarbons together with the hydrophobic silica;

(b) spraying the molten mixture onto agitated particles of the core material.

[0007] Secondly, it provides a process for the production of anti-foam granules which comprises:

(a) forming a molten mixture of the liquid and solid hydrocarbons together with the hydrophobic silica;

'(b) admixing the molten mixture with particles of the core material; and

(c) grinding the resultant mass to granules.

[0008] Normally speaking, the compositions of the invention will contain both a nonionic surfactant and an anionic detergent active compound. In general compositions which contain both types of detergent produce lower amounts of foam than those which contain only anionic surfactant and consequently lower amounts of anti-foam granule will be required to control the foam.

[0009] Typical anionic detergent active compounds, which may be present in amounts of from about 2 to 35% by weight of the finished compositions are sodium alkylbenzene sulphonates, preferably the C₁₀-C₁₆ alkyl compounds, sodium primary and secondary alkyl sulphates, preferably the C₁₀-C₂₂ alkyl sulphates, sodium olefine sulphonates, preferably the C₁₀-C₁₈ sulphonates and sodium alkane sulphonates. Soaps of fatty acids may also be present, preferably the sodium and potassium salts of C₁₀-C₂₂ fatty acids, both saturated and unsaturated. Where soap is the sole anionic surfactant it may be present in an amount up to about 65% by weight of the finished composition, down to about 0.2% by weight when other anionic surfactants are present. Typical soaps which can be used are those formed from coconut oil, tallow, hydrogenated tallow, hydrogenated rapeseed oil and natural oils containing high proportions of oleic acid such as sunflower oil.

[0010] Typical nonionic surfactants, are ethoxylated primary and secondary alcohols of from 8 to 25 carbon atoms containing from 3 to 25 moles of ethylene oxide per mole of alcohol. These materials may generally be present in an amount of from 1 to 25% by weight, based on the weight of the finished composition.

[0011] Typical detergency builders which can be used are the water-soluble phosphates, carbonates, percarbonates and aluminosilicates, particularly.the sodium and potassium salts of these compounds. Organic builders may also be used, examples being sodium carboxymethyloxysuccinate, sodium citrate, sodium polyacrylates and sodium nitrilotriacetate. Any of these compounds, or any other builder compound, in any suitable mixture, may be used in amounts of from 5 to 60% by weight of the finished composition. Other components which will normally be present are bleaching agents, corrosion inhibitors, anti-redeposition agents, fluorescers, stabilisers and substantial proportions of water.

[0012] The invention will be further illustrated by means of the following example:

Example

[0013] Six detergent powders having the following formulations were prepared by conventional slurry-making, spray-drying and dry-dosing techniques.

[0014] The general experimental technique for assessment of. the efficacy of various anti-foam granules in suppressing the foam produced by these powders is as follows:

First each powder was subjected to accelerated ageing by storing it in an E3 unlaminated cardboard carton for 2 or 4 weeks at 37°C and 60% relative humidity.

[0015] 200 gms of the powder was placed in the powder dispenser of a Brandt 433 washing machine containing 4 Kg of clean clothes. The clothes were then washed, using the main wash cycle which heats up to 90°C, and using water of 30° French hardness. Foam height was measured against an arbitrary scale attached to the window of the washing machine.

[0016] The anti-foam granules for incorporation into powders were prepared by forming a molten mixture of the liquid hydrocarbon, the solid hydrocarbon and silica and spraying the mixture onto the sorbent in a pan granulator.

[0017] The formulations of the granules were as follows:

[0018] The above granules were incorporated into the powders as shown in the table and the foam produced was assessed as described.

[0019] It can be seen that whilst initially the foam level is . moderate it decreases as the temperature rises to a satisfactory level. On the other hand, some deactivation after storage (accelerated test) is noticed; nevertheless, the foam control of the granules remains quite satisfactory.

Claims

1. A detergent composition containing an anionic detergent active compound and/or a nonionic surfactant and anti-foam granules comprising hydrophobic silica and a mixture of liquid and solid hydrocarbons, characterised in that the liquid hydrocarbon component constitutes less than 30% by weight of the total hydrocarbon and in that the silica and the mixture of liquid and solid hydrocarbons are sorbed on a core of a material producing a mechanical action on addition to water.

2. A detergent composition according to claim 1 wherein the material producing a mechanical action on addition to water comprises gelatinised starch.

3. A detergent composition according to claim 1 or claim 2 wherein the material producing a mechanical action on addition to water comprises sodium perborate monohydrate.

4. A detergent composition according to any one of the preceding claims wherein the liquid hydrocarbon component comprises from 15-25% by weight of the total hydrocarbon.

5. A detergent composition according to any one of the preceding claims wherein the balance of the hydrocarbon component is a petroleum jelly or a paraffin wax having a drop-melting point of 50°C or higher.

6. A process for the production of anti-foam granules in accordance with claim 1 comprises:

(a) forming a molten mixture of the liquid and solid hydrocarbons together with the hydrophobic silica and

(b) -spraying the molten mixture onto agitated . particles of the core material.

7. A process for the production of anti-foam granules in accordance with claim 1 which comprises:

(a) forming a molten mixture of the liquid and solid hydrocarbons together with the hydrophobic silica,

(b) admixing the molten mixture with particles of the core material; and

(c) grinding the resultant mass to granules.