EP0342985B1

EP0342985B1 - Antifoam ingredient

Info

Publication number: EP0342985B1
Application number: EP89305057A
Authority: EP
Inventors: Richard Llewelyn Davies; James Nicholson
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1988-05-20
Filing date: 1989-05-18
Publication date: 1994-11-30
Anticipated expiration: 2009-05-18
Also published as: EP0342985A2; GB8811954D0; GB2222598A; DE68919533T2; ES2066850T3; EP0342985A3; GB8911373D0; AU627458B2; AU3488689A; GB2222598B; DE68919533D1; ZA893780B

Description

TECHNICAL FIELD

The present invention relates to a particulate antifoam ingredient suitable for incorporation into powdered detergent products, and to processes for the production of the antifoam ingredient.

BACKGROUND AND PRIOR ART

Detergent products containing anionic and/or nonionic surfactants which are particularly suitable for fabric washing generally have a tendency in use to produce excessive foam. This can be a problem particularly with drum-type washing machines, and it is accordingly usual to include an antifoam agent in the detergent formulation.
The use of silicone oils (liquid organopolysiloxanes) as antifoam agents in detergent powders is well known. Silicone oils, being liquid at ambient temperatures, are especially effective for reducing foaming in the low-temperature wash, but their incorporation into detergent powders presents problems.
Detergent powders containing silicone oils carried on particulate carrier materials are disclosed in the prior art. For example, GB 1 378 874 (Dow Corning) discloses the use of sodium tripolyphosphate as a carrier for silicone oils; GB 2 009 223 (Henkel) discloses silicone oils carried on alkali metal phosphate, polyphosphate, silicate, aluminosilicate, carbonate, sulphate, polycarboxylate or phosphonate, or magnesium silicate; GB 1 407 997 (Procter & Gamble) discloses silicone oils carried on sodium carbonate, sodium tripolyphosphate, sodium silicate, clay, starch, kieselguhr or Fuller's Earth. These various antifoam granules can be admixed with a detergent powder to form a low-foam product.
EP 266 863A (Unilever) discloses antifoam materials liquid at ambient temperature, including silicone oils, sorbed onto highly porous sodium-carbonate-based salts, notably light soda ash, and the crystal-growth-modified salts sodium carbonate monohydrate, sodium sesquicarbonate and Burkeite. The use of porous carrier materials is shown substantially to reduce deactivation of the antifoam on storage.
Although the antifoam granules described and claimed in EP 266 863A give excellent foam control in both fresh and stored powders, it has been found that they can affect detrimentally the dispensing properties of certain powder formulations in the washing machine: that is to say, the presence of the granules in those powders can cause excessive amounts to be left behind in the machine's dispenser rather than washed through into the drum. This is obviously undesirable because it leads to powder wastage and dispenser messing.
The present inventors have now discovered that this problem can be alleviated, while acceptable foam control can still be obtained, if a carrier salt is chosen that has even finer pores than the carbonate-based salts disclosed in EP 266 863A. A preferred salt having an especially fine pore structure is sodium perborate monohydrate.
GB 1 451 951 (Dow Corning) discloses the use of the non-porous carrier material, sodium perborate tetrahydrate, as a carrier for silicone oil antifoam. The silicone oil is carried on the surface of the perborate salt.

DEFINITION OF THE INVENTION

The present invention accordingly provides a particulate antifoam ingredient suitable for incorporation into a detergent powder composition, the antifoam ingredient comprising

(i) an antifoam material comprising silicone oil, sorbed into
(ii) a porous particulate carrier material soluble or disintegratable in water and having:
- (a) a volume of pores of diameter less than 0.5 micrometres of at least 0.2 ml/g, and
- (b) a pore size distribution such that at least 50% of the total volume of pores of diameter less than 30 micrometres is constituted by fine pores of diameter less than 0.5 micrometres.

DETAILED DESCRIPTION OF THE INVENTION

The antifoam ingredient of the invention has two essential elements: the silicone oil antifoam agent, and the porous particulate carrier material. Other components, for example, additional antifoam agents, may if desired also be present.

The silicone oil antifoam agent

Polysiloxanes which can be employed as antifoam agents have the structure:

wherein R and R', which may be the same or different, are alkyl or aryl groups having from 1 to 6 carbon atoms; and x is an integer of at least 20.
The preferred polysiloxanes are polydimethylsiloxanes, where both R and R' are methyl groups.
The polysiloxanes usually have a molecular weight of from 500 to 200 000 and are generally non-volatile. They generally have kinematic viscosities ranging from 50 to 2 000 000 mm²/s, preferably from 500 to 50 000 mm²/s, more preferably from 3000 to 30 000 mm²/s, at 25°C. The polysiloxanes are generally end-blocked with trimethylsilyl groups, but other end-blocking groups are also suitable.
Examples of suitable commercially available polysiloxanes are the polydimethyl siloxanes, "Silicone 200 Fluids", available from Dow Corning.
In this specification, the term "silicone oil" has been used to denote liquid polysiloxane.

Optional antifoam promoter

Advantageously, the antifoam ingredient of the invention also contains an antifoam promoter, that is, a particulate substance which is capable of promoting the antifoam function of the silicone oil. The antifoam promoter will generally be a substance which is deployed as finely divided water-insoluble solid particles when the antifoam ingredient is contacted with a large volume of water, as in the washing machine. The antifoam promoter may be itself particulate, or it may be a precursor which is converted to particulate form under wash conditions.
An especially preferred antifoam promoter is particulate silica that has been converted to a hydrophobic form. Hydrophobic silica may be prepared by treating any silica, for example, precipitated silica or pyrogenic silica, with a suitable hydrophobing reagent, for example, a chloralkylsilane, especially dimethyldichlorosilane, or an alcohol, especially octanol. Hydrophobic silica is also commercially available, for example, as Sipernat (Trade Mark) D10 and D17 ex Degussa, Wacker (Trade Mark) HDK P100/M and HDK P100H ex Wacker-Chemie, and Cabosil (Trade Mark) N70 TS ex Cabot Corporation.
The hydrophobic silica should preferably have a surface area greater than 50 m²/g and a mean particle size less than 10 micrometres, preferably less than 3 micrometres.
Also available commercially are mixtures of silicone oil and hydrophobic silica, for example, DB 100 ex Dow Corning, VP 1132 ex Wacker-Chemie, and Silcolapse (Trade Mark) 430 ex ICI. These materials may be prepared by a method in which the silica is rendered hydrophobic in situ, by the silicone oil, by heating with high shear rate stirring. The use of these mixtures in the antifoam ingredient of the invention is especially convenient.

The porous particulate carrier

The carrier material in the antifoam ingredient of the invention is a material having a network of especially fine intraparticle pores. The carrier material must possess a high - volume at least 0.2 ml/g, preferably at least 0.3 ml/g - of fine pores of diameter less than 0.5 micrometres. Furthermore, the pore size distribution of the carrier material must be such that at least 50% of the volume of pores of diameter less than 30 micrometres is constituted by fine pores of diameter less than 0.5 micrometres. Advantageously at least 50% of the volume of pores of diameter less than 30 micrometres is constituted by very fine pores of diameter less than 0.3 micrometres.
Extremely fine pores of diameter less than 0.01 micrometres can be of limited value because of the extended processing period needed for the silicone to be absorbed fully into such pores.
Pore volumes and pore size distributions may be measured by the recognised technique of mercury intrusion porosimetry. From discontinuities in the mercury intrusion curve it is possible to distinguish to some extent between (relatively large) inter-particle voids and (generally smaller) intraparticle pores. It is generally a reasonable approximation to say that, for a material having substantial intraparticle porosity, the volume of pores of diameter less than 30 micrometres corresponds substantially to the total intraparticle pore volume.
It is therefore another reasonable approximation to say that the porous particulate carrier material used in the antifoam ingredient of the invention has a mean intraparticle pore diameter of less than 0.5 micrometres, preferably less than 0.3 micrometres; the smallest mean pore diameter disclosed in EP 266 863A (Unilever) is 2.0 micrometres, for crystal-growth-modified sodium sesquicarbonate.
An especially preferred carrier material having the requisite pore structure is sodium perborate monohydrate. This should be distinguished from the commercially available tetrahydrate which has a quite different crystal structure and little or no intraparticle porosity, and is therefore unsuitable for use in the present invention.
Mercury intrusion measurements have given the following values for the volume of pores of diameter <30 micrometres constituted by pores of diameter <0.5 micrometres, and by pores of diameter <0.3 micrometres:
The aforementioned EP 266 863A (Unilever) discloses crystal-growth-modified Burkeites modified by 0.44% polymer, having mean pore diameters of 2.6 and 3.0 micrometres. It will be seen from the Table above that the pore size distribution of modified Burkeite depends on the amount of crystal-growth-modifying polymer employed, and the use of a higher level of polymer can give a higher level of useful porosity that is just within the scope of the present invention, but not, however, within the preferred embodiment of the invention constituted by materials having at least 50% of <0.3 micrometre pores. Of the materials investigated, only sodium perborate monohydrate has been found to satisfy that condition and to have a high enough intraparticle porosity.
The following Table gives further information about pore volumes and pore size distributions of some carrier materials:
It will be seen that light soda ash and sodium perborate tetrahydrate are essentially non-porous in the context of micropores: in each case the volume of pores smaller than 0.5 micrometres is substantially less than 0.2 ml/g. As previously indicated, the use of any carrier with such low microporosity is outside the scope of the present invention.
Another requirement for the porous particulate carrier material is that it must be sufficiently soluble or dispersible, and sufficiently fast dissolving or dispersing, in the wash liquor for effective delivery of the silicone antifoam during the wash cycle in an automatic washing machine.

Other antifoam agents

Silicone oils are especially effective for foam control in low-temperature wash programmes. It may be advantageous to include in the antifoam ingredient of the invention one or more further antifoam agents to enhance antifoam performance at higher wash temperatures.
Preferred materials include hydrocarbons which are solid or semi-solid at ambient temperature but which liquefy at temperatures within the range from about 30 to about 90^oC, for example, microcrystalline and oxidised microcrystalline waxes, paraffin wax and petroleum jelly. Petroleum jelly, which is especially preferred, is a semi-solid hydrocarbon mixture usually having a liquefaction point of from about 35 to about 50^oC.
As antifoam promoter for the hydrocarbon, there is advantageously present an alkylphosphoric acid or salt thereof. These can be derived from acids having the structure:

where A is -OH or R²O(EO) _m-, R¹ and R² are the same or different C₁₂-C₂₄, preferably C₁₆-C₂₂, straight or branched chain, saturated or unsaturated alkyl groups, especially C₁₆-C₁₈ linear saturated groups and m and n are the same or different and are O or an integer of from 1 to 6. Preferably A is -OH and n is O, so that the compound is a monoalkyl phosphoric acid, preferably with a linear alkyl group. If any ethylene oxide (EO) groups are present in the alkyl phosphoric acid, they should not be too long in relation to the alkyl chain length to make their respective calcium or magnesium salts soluble in water during use.
In practice, the alkyl phosphoric acid or salt is usually a mixture of both mono-and di-alkylphosphoric acid residues, with a range of alkyl chain lengths. Predominantly monoalkyl phosphates are usually made by phosphorylation of alcohols or ethyoxylated alcohols, when n or m is an integer of from 1 to 6, using a polyphosphoric acid. Phosphorylation may alternatively be accomplished using phosphorus pentoxide, in which case the mixed mono-and di-alkyl phosphates are produced. Under optimum reaction conditions, only small quantities of unreacted materials or by-products are produced, and the reaction products advantageously can be used directly in the antifoam ingredient.
The substituted phosphoric acids of the above structure either as the partial salt, or preferably as the full salt. When the antifoam ingredient comprising an alkyl phosphoric acid is added to the detergent composition, it will normally be neutralised by the more basic ingredients of the composition, to form usually the sodium salt, when the detergent composition is dispersed in water. When using the composition in hard water, the insoluble calcium and/or magnesium salt can then be formed, but in soft water some of the alkyl phosphate can remain as the alkali metal, usually sodium, salt. In this case, the addition of calcium and/or magnesium ions, in the form of a water-soluble salt thereof is necessary to form the particulate, insoluble corresponding salts of the alkyl phosphate. If the alkyl phosphate is employed as the alkali metal or ammonium salt form, then again the calcium and/or magnesium salt is formed on use in hard water.
It is also possible to use a preformed insoluble alkyl phosphoric acid salt, with a polyvalent cation which is preferably calcium, although aluminium, barium, zinc, magnesium or strontium salts may alternatively be used. Mixtures of the insoluble alkyl phosphoric acid salts with the free acid or other soluble salts, such as alkali metal salts, can also be used if desired. The preferred insoluble alkly phosphoric acid salts need not be totally water-insoluble, but they should be sufficiently insoluble that undissolved solid salt is present in the wash liquor, when the antifoam ingredient forms part of a detergent product employed in the laundering of fabrics.
The preferred alkyl phosphate used in accordance with the invention is stearyl phosphate.
A particularly preferred antifoam material for use in the antifoam ingredient of the invention comprises a silicone oil; hydrophobic silica; a hydrocarbon, preferably petroleum jelly; and an alkyl phosphoric acid or salt thereof, preferably stearyl phosphate.

Processes for preparing the antifoam ingredient

The essential step in all methods for preparing antifoam ingredients according to the present invention is the mixing of the silicone oil with the carrier material, whereby penetration of silicone oil into the intraparticle pore system of the carrier material occurs. Any suitable mixing equipment may be used, for example, a rotating drum.
If other antifoam agents are present, these may be admixed separately, or together with the silicone oil. If, as is preferred, hydrophobic silica is also to be included, at least part of the total hydrophobic silica is preferably admixed together with the silicone oil to the carrier material. This procedure is obviously followed if, as is convenient, the silicone oil used is one of the previously mentioned preformed mixtures containing hydrophobic silica.
Other antifoam ingredients, such as hydrocarbons (petroleum jelly) and alkyl phosphate, are preferably mixed with the carrier material in a separate stage after application of the silicone oil. If desired, further hydrophobic silica may be introduced at this stage. Additionally or alternatively, hydrophobic silica may be applied in fine dry powder form after all liquid ingredients have been applied, as disclosed in the aforementioned EP 266 863A (Unilever): this has the added benefit of improving the flow properties of the antifoam ingredient.
A preferred process according to the invention therefore comprises the following steps:

(i) mixing the silicone oil, optionally together with hydrophobic silica, with the porous particulate carrier, whereby penetration of silicone oil into the pores of the carrier occurs, and subsequently
(ii) admixing any remaining antifoam material, optionally including hydrophobic silica, with the product of step (i), and
(iii) optionally admixing hydrophobic silica in dry powder form with the product of step (ii).

It will be seen that hydrophobic silica may be incorporated during either or both of steps (i) and (ii), and/or in a separate, subsequent step (iii).
A process for preparing the especially preferred antifoam ingredient of the invention mentioned previously comprises the following steps:

(i) mixing the silicone oil, optionally together with hydrophobic silica, with the porous particulate carrier, whereby penetration of silicone oil into the pores of the carrier occurs,
(ii)
- (a) admixing the hydrocarbon, alkyl phosphoric acid or salt thereof and optionally hydrophobic silica at a temperature at which the hydrocarbon is substantially liquid or pasty,
- (b) spraying the resulting liquid or pasty mixture onto the product of step (i), and
(iii) optionally admixing hydrophobic silica in dry powder form with the product of step (ii).

When the hydrocarbon is petroleum jelly, the mixture in step (ii) is conveniently sprayed on at a temperature of about 55-90^oC, the higher temperatures being avoided if the carrier material is thermally unstable.
It is, however, also within the scope of the invention to premix all antifoam agents, including the silicone oil, and to apply them together to the carrier material, or to apply the various antifoam agents simultaneously but separately to the carrier material.

Proportions of silicone oil and carrier

The silicone oil preferably constitutes from 1 to 30% by weight of the total antifoam ingredient, more preferably from 10 to 25% by weight. In general the maximum limit on the proportion of silicone oil is higher, the higher the porosity of the carrier material : for very porous materials (> 0.3 ml/g) it is appropriate for silicone oil to constitute up to 30% by weight of the total antifoam ingredient, but for carrier materials having a porosity of about 0.2 ml/g, an upper limit of 20% by weight of the antifoam material is more suitable.

Use in detergent compositions

The antifoam ingredient of the invention is especially suitable, and intended, for incorporation in a particulate detergent composition. Such a composition may suitably be formulated to contain from 0.03 to 1.5% by weight, preferably from 0.1 to 1.0% by weight, of silicone oil.
Detergent compositions of the invention also contain one or more detergent-active compounds and one or more detergency builders, and may contain other conventional components, for example, inorganic salts, sodium silicate, bleaching agents, bleach precursors, bleach stabilisers, enzymes, antiredeposition agents, fluorescers, perfumes and other materials well known to the skilled detergent formulator. Suitable components for detergent compositions in accordance with the present invention are described below in more detail.

Detergent active compounds

A detergent composition which is particularly suited to the incorporation of an antifoam ingredient according to the invention will generally comprise one or more detergent active compounds which can be chosen from soap and non-soap anionic, cationic, nonionic, amphoteric or zwitterionic detergent active compounds and mixtures thereof. Many suitable detergent-active compounds are commercially available and are fully described in the literature, for example in "Surface Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch.
The preferred detergent-active compounds which can be used are soaps and synthetic non-soap anionic and nonionic compounds.
Soap is a water-soluble or water-dispersible alkali metal salt of an organic acid, and the preferred soaps are sodium or potassium salts, or the corresponding ammonium or substituted ammonium salts of an organic acid. Examples of suitable organic acids are natural or synthetic aliphatic carboxylic acids of from 10 to 22 carbon atoms, especially the fatty acids of triglyceride oils such as tallow, coconut oil and rape seed oil.
Synthetic anionic non-soap detergent active compounds are usually water-soluble alkali metal salts of organic sulphates and sulphonates having alkyl radicals containing from about 8 to about 22 carbon atoms, the term alkyl being used to include the alkyl portion of higher aryl radicals.
Preferred examples of suitable anionic detergent compounds are primary and secondary alkyl sulphates, particularly sodium C₁₂-C₁₅ primary alcohol sulphates; sodium, potassium and ammonium alkyl benzene sulphonates, particularly linear alkyl benzene sulphonates having an alkyl chain length of C₈-C₁₅; sodium alkyl glyceryl ether sulphates; dialkyl sulphosuccinates; fatty acid ester sulphonates; alkane sulphonates; olefin sulphonates, or mixtures thereof. The preferred anionic detergent compounds are sodium (C₁₁-C₁₅) alkyl benzene sulphonates and sodium (C₁₆-C₁₈) alkyl sulphates.
Examples of suitable nonionic detergent compounds which may be used include the reaction products of alkylene oxides, usually ethylene oxide with alkyl (C₆-C₂₂) phenols, generally 2 to 25 EO, i.e. 2 to 25 units of ethylene oxide per molecule: the condensation products of aliphatic (C₈-C₂₅) primary or secondary linear or branched alcohols with ethylene oxide, generally 2 to 30 EO, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long-chain tertiary amine oxides, long-chain tertiary phosphine oxides and dialkyl sulphoxides.
Mixtures of detergent-active compounds, for example mixed anionic or mixed anionic and nonionic compounds may advantageously be used in the detergent compositions.
Cationic, amphoteric or zwitterionic detergent-active compounds optionally can also be used in the detergent compositions, but this is not normally desired owing to their relatively high cost. If any cationic, amphoteric or zwitterionic detergent-active compounds are used, it is generally is small amounts in products based on the much more commonly used synthetic anionic and/or nonionic detergent-active compounds.
The detergent active compound of the detergent powder composition will generally comprise from 5 to 40%, preferably from 8 to 30% by weight of the composition, and can be incorporated into the composition by spray-drying, spray-on or as a separately prepared adjunct.

Bleaching materials

Bleaching materials include peroxy bleach compounds, such as inorganic persalts and organic peracids. Inorganic persalts can be used in combination with suitable transition metal catalysts or organic peracid precursors as activators for the persalt. Preferably, peroxy bleach compounds are employed together with an activator therefor.
The inorganic persalt acts to release active oxygen in solution, and the activator therefor is usually an organic compound having one or more reactive acyl residues, which cause the formation of peracids, the latter providing a more effective bleaching action at a low temperature, that is, in the range from 20 to 60^oC, than is possible with the inorganic persalt itself.
The ratio by weight of the peroxy bleach compound to the activator in the detergent composition may vary from 30:1 to about 1:1, preferably from 15:1 to 2:1.
Typical examples of suitable peroxy bleach compounds are inorganic persalts such as alkali metal perborates, both tetrahydrates and monohydrates, alkali metal percarbonates, persilicates and perphosphates and mixtures thereof. Sodium perborate is the preferred inorganic persalt, particularly sodium perborate monohydrate and sodium perborate tetrahydrate.
Preferred activators for peroxy bleach compounds are N-diacylated and N,N′-polyacylated amines and especially N,N,N′,N′-tetraacetyl ethylenediamine (TAED). It is preferred to use the activator in granular form, especially when it is present in a finely divided form, in an amount up to 10% by weight of the composition, preferably from 2 to 6% by weight of the composition.
The bleaching material component when present will generally comprise from 1 to 30%, preferably from 5 to 20% by weight of the detergent composition.

Detergent builders

Builders include soaps, inorganic and organic water-soluble builder salts, as well as various water-insoluble and so-called "seeded" builders, whose function is to soften hard water by solubilisation or by removal by other means (e.g. by sequestration, precipitation or ion exchange) of calcium and to a lesser extent magnesium salts responsible for water hardness, thereby improving detergency.
Soaps which can function as detergency builders are those as defined hereinbefore as capable of functioning also as detergent active compounds.
Inorganic detergency builders include, for example, water-soluble salts of phosphates, pyrophosphates, orthophosphates, polyphosphates, phosphonates and polyphosphonates. Sodium tripolyphosphate is an especially preferred water-soluble inorganic builder.
Non-phosphorus-containing inorganic water-soluble sequestrants can also be selected for use as detergency builders. Specific examples of such non-phosphorus, inorganic builders include borate, silicate and aluminate salts. The alkali metal, especially sodium or potassium, salts are particularly preferred.
Organic non-phosphorus-containing, water-soluble detergency builders include, for example, the alkali metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates, succinates, oxalates and polyhydroxysulphonates.
Preferred organic water-soluble non-phosphorus-containing builders include sodium citrate, sodium oxydisuccinate, sodium mellitate, sodium nitrilotriacetate, and sodium ethylenediaminetetraacetate. Other builders can include organic polymers such as polyacrylates, maleate, acetal carboxylates and copolymers.
Another type of detergency builder material useful in the compositions and products of the invention comprise a water-soluble material capable of forming a water-insoluble reaction product with water hardness cations, such as alkali metal or ammonium salts of carbonate, bicarbonates and sesquicarbonate optionally in combination with a crystallisation seed which is capable of providing growth sites for said reaction product.
Other types of builder that can be used include various substantially water-insoluble materials which are capable of reducing the hardness content of laundering liquors by an ion-exchange process.
Examples of such ion-exchange materials are the complex aluminosillicates, i.e. zeolite-type materials, which are useful presoaking or washing adjuncts which soften water by removal of calcium ion. Both the naturally occurring and synthetic "zeolites", especially Zeolite A and hydrated Zeolite A materials are useful as builders.
The detergency builder component when present will generally comprise from about 1% to 90%, preferably from about 5% to 75% by weight of the detergent composition

Other ingredients

Further ingredients which can optionally be employed in the detergent compositions of the invention include anti-redeposition agents such as sodium carboxymethyl-cellulose, polyvinyl pyrrolidone and the cellulose ethers such as methyl cellulose and ethyl hydroxyethyl cellulose; stabilisers such as ethylenediamine tetramethylene phosphonate and diethylenetriamine pentamethylene phosphonate; fabric-softening agents; inorganic salts such as sodium and magnesium sulphate: and - usually present in very minor amounts - optical brighteners, fluorescers, enzymes such as proteases and amylases, anti-caking agents, thickeners, germicides and colourants.
Various detergency enzymes well-known in the art for their ability to degrade and aid in the removal of various soils and stains can also optionally be employed in the compositions according to this invention. Detergency enzymes are commonly used at concentrations of from about 0.1% to about 1.0% by weight of such compositions. Typical enzymes include the various proteases, lipases, amylases, and mixtures thereof, which are designed to remove a variety of soils and stains from fabrics.
It may also be desirable to include one or more antideposition agents in the compositions of the invention to decrease a tendency to form inorganic deposits on washed fabrics. The amount of any such antideposition agent when employed is normally from 0.1% to 5% by weight, preferably from 0.2% to 2.5% by weight of the composition. The preferred antideposition agents are anionic polyelectrolytes, especially polymeric aliphatic carboxylates, or organic phosphonates.
It may also be desirable to include in the detergent compositions an amount of an alkali metal silicate, particularly sodium ortho-, meta-or preferably neutral or alkaline silicate. The presence of such alkali metal silicates at levels of at least 1% and preferably from 5% to 15% by weight of the product, is advantageous in decreasing the corrosion of metal parts in washing machines, besides providing some measure of building and giving processing benefits and generally improved powder properties. The more highly alkaline ortho-and meta-silicates would normally only be used at lower amounts within this range, in admixture with the neutral or alkaline silicates.
The detergent compositions of the invention are usually required to be alkaline, but not too strongly alkaline as this could result in fabric damage and also be hazardous for domestic use. In practice the compositions should preferably provide a pH of from about 8.5 to about 11 in use in the aqueous wash liquor. It is preferred in particular for domestic products to yield pH of from about 9.0 to about 10.5 as lower pH values tend to be less effective for optimum detergency, and more highly alkaline products can be hazardous if misused. The pH is measured at the lowest normal usage concentration of 0.1% w/v of the product in water of 12^oH (Ca)(French permanent hardness, calcium only) at 50^oC so that a satisfactory degree of alkalinity can be assured in use at all normal product concentrations.
The invention is further illustrated by the following non-limiting Examples, in which parts and percentages are by weight unless otherwise stated.

EXAMPLES 1 to 3

Antifoam ingredients were prepared to the following formulations (in parts):

Example	1	2	3	A	B
Sodium perborate monohydrate¹	68.0	68.0	-	-	-
Burkeite²	-	-	68.0	-	-
Light soda ash	-	-	-	68.0	-
Sodium perborate tetrahydrate	-	-	-	-	68.0
Silicone oil/silica³	18.0	18.0	18.0	18.0	18.0
Stearyl phosphate⁴	-	2.4	2.4	2.4	-
Petroleum jelly	-	9.6	9.6	9.6	-
Hydrophobic silica⁵	-	2.0	2.0	2.0	2.0

¹ Interox (Trade Mark) A
² with 3.8% polymer; see below
³ DB 100 (Trade Mark) ex Dow Corning
⁴ Alf (Trade Mark) 5 ex Lankro Chemicals
⁵ Sipernat (Trade Mark) D10 ex Degussa

The Burkeite was prepared by the following method. An aqueous slurry was prepared containing sodium polyacrylate added before or at the same time as sodium carbonate and sodium sulphate; and sodium alkaline silicate and water. The slurry was spray-dried to a powder; nonionic surfactant was post-dosed and absorbed into the powder, giving a composition of the following formulation:

%

Sodium carbonate 21.2

Sodium sulphate 57.1

Sodium polyacrylate 3.8

Sodium alkaline silicate 9.4

Nonionic surfactant 4.7

Moisture to 100
The antifoam ingredients were prepared as follows. Those of Examples 1 and B were prepared by spraying the silicone oil/silica (DB 100) onto the carrier material in suitable mixing equipment. Those of Examples 3 and A were prepared by first spraying the silicone oil/silica (DB 100) onto the carrier material, then spraying on a molten mixture of petroleum jelly, stearyl phosphate and hydrophobic silica at about 60^oC in a separate step in the same mixer. The antifoam ingredient of Example 2 was prepared by first spraying the silicone oil/silica (DB 100) onto the carrier material, then spraying on a molten mixture of petroleum jelly and stearyl phosphate at about 60^oC in a separate step in the same mixer, then finally dry-mixing the hydrophobic silica with the remaining ingredients.

A detergent powder was prepared to the following formulation by conventional spray-drying and postdosing techniques:

	Parts
Linear alkylbenzene sulphonate (Na salt)	6.00
Nonionic surfactant	8.00
Sodium tripolyphosphate	25.00
Sodium polyacrylate	1.00
Sodium alkaline silicate	6.00
Sodium sulphate	25.75
Sodium carbonate	5.00
Sodium perborate	9.50
TAED granules	2.25
Enzyme granules	0.50
Fluorescer	0.30
Minor ingredients, moisture	to 100

Each of the five antifoam ingredients was postdosed at a 1% level (equal to 0.18% of silicone oil DB100 in the final product) to a sample of the detergent powder described above. The dispensing behaviour of each of the five powders thus obtained, and of the detergent powder itself (Comparative Example C), was determined by means of a standard procedure. In that procedure, 200 g of the product under test was placed in a dispenser unit as fitted to a Hoover Matchbox (Trade Mark) 3263H washing machine; water at 10^oC was allowed to flow at 2 litres/minute for 2 minutes over the powder; and the wet residue remaining after pouring off excess water was determined by weighing. It will be appreciated that these conditions of very low water temperature and very slow water flow were deliberately chosen to be much more severe than those likely to be encountered in normal usage.

The dispensing results were as follows:

Example	Carrier	Dispenser residue (g)
C	-	6
1	Sodium perborate monohydrate	13
2	Sodium perborate monohydrate	26
3	Burkeite (3.8% polymer)	66
A	Light soda ash	118
B	Sodium perborate tetrahydrate	95

These results show that the detrimental effect of silicone-based antifoam ingredients on dispensing can be substantially alleviated by the use of a microporous carrier in accordance with the invention. Sodium perborate monohydrate, with its especially favourable pore size distribution, is particularly good. Modified Burkeite can be acceptable provided that the level of the crystal-growth-modifying polymer is high enough to give a sufficient volume of small pores.
The lather control behaviour of fresh and stored samples of the powder of Example 1 was also examined. Samples were stored at three different temperatures (15^oC, 28^oC, and 37^oC) at 70% relative humidity for 2 weeks. All gave satisfactory lather control throughout the wash, and in every case lather was absent at the end of the machine cycle.

EXAMPLE 4

An antifoam ingredient was prepared, by the method described in Example 2 above, to the following formulation:

	Parts
Sodium perborate monohydrate	74.40
Silicone oil/silica	14.40
Stearyl phosphate	1.92
Petroleum jelly	7.68
Hydrophobic silica	1.60
The ingredients were as specified in earlier Examples.

This antifoam ingredient, when postdosed at a 1.25% level (equal to 0.18% of silicone oil DB 100 in the final product) to the detergent powder used in earlier Examples, gave satisfactory dispensing and foam control results. It was slightly more free flowing than the antifoam ingredient of Example 2 because of its higher proportion of carrier material.

Claims

A particulate antifoam ingredient suitable for incorporation into a detergent powder composition, the antifoam ingredient comprising
(i) an antifoam material omprising silicone oil, sorbed into

(ii) a porous particulate carrier material soluble or disintegratable in water,
characterised in that the porous particulate carrier material has
(a) a volume of pores of diameter less than 0.5 micrometres of at least 0.2 ml/g, and

(b) a pore size distribution such that at least 50% of the total volume of pores of diameter less than 30 micrometres is constituted by fine pores of diameter less than 0.5 micrometres.
An antifoam ingredient as claimed in claim 1, characterised in that the porous particulate carrier material has a volume of pores of diameter less than 0.5 micrometres of at least 0.3 ml/g.
An antifoam ingredient as claimed in claim 1 or claim 1, characterised in that the porous particulate carrier material has a pore size distribution such that at least 50% of the total volume of pores of diameter less than 30 micrometres is constituted by fine pores of diameter less than 0.3 micrometres.
An antifoam ingredient as claimed in any preceding claim, characterised in that the porous carrier material comprises sodium perborate monohydrate.
An antifoam ingredient as claimed in any preceding claim, characterised in that the antifoam material comprises silicone oil and hydrophobic silica.
An antifoam ingredient as claimed in any preceding claim, characterised in that the antifoam material also comprises a hydrocarbon.
An antifoam ingredient as claimed in any preceding claim, characterised in that the antifoam material also comprises an alkyl phosphoric acid or salt thereof.
An antifoam ingredient as claimed in claim 6 or claim 7, characterised in that the antifoam material comprises a silicone oil, hydrophobic silica, a hydrocarbon, and an alkyl phosphoric acid or salt thereof.
An antifoam ingredient as claimed in claim 8, characterised in that the antifoam material comprises silicone oil, hydrophobic silica, petroleum jelly and alkyl phosphate.
An antifoam ingredient as claimed in any preceding claim, characterised in that it comprises from 1 to 30% by weight of silicone oil.
A process for the preparation of an antifoam ingredient as claimed in claim 1, characterised in that it includes the step of mixing the silicone oil, optionally together with hydrophobic silica, with the porous particulate carrier, whereby penetration of silicone oil into the pores of the carrier occurs.
A process as claimed in claim 11, characterised in that it comprises the steps of:
(i) mixing the silicone oil, optionally together with hydrophobic silica, with the porous particulate carrier, whereby penetration of silicone oil into the pores of the carrier occurs, and subsequently

(ii) admixing any remaining antifoam material, optionally including hydrophobic silica, with the product of step (i), and

(iii) optionally admixing hydrophobic silica in dry powder form with the product of step (ii).
A process for the preparation of an antifoam ingredient as claimed in claim 8, characterised in that it comprises the steps of:
(i) mixing the silicone oil, optionally together with hydrophobic silica, with the porous particulate carrier, whereby penetration of silicone oil into the pores of the carrier occurs,

(ii)
(a) admixing the hydrocarbon, alkyl phosphoric acid or salt thereof and optionally hydrophobic silica at a temperature at which the hydrocarbon is substantially liquid or pasty,

(b) spraying the resulting liquid or pasty mixture onto the product of step (i), and

(iii) optionally admixing hydrophobic silica in dry powder form with the product of step (ii).
A particulate detergent composition comprising one or more detergent-active compounds, one or more detergency builders, and optionally other components, characterised in that it comprises an antifoam ingredient as claimed in any one of claims 1 to 10, in an amount such as to provide from 0.03 to 1.5% by weight of silicone oil in the detergent composition.
A particulate detergent composition as claimed in claim 14, characterised in that it comprises the antifoam ingredient in an amount such as to provide from 0.1 to 1.0% by weight of silicone oil.