GB2220932A - Anti-foam composition - Google Patents

Description

ANTI-FOAM COMPOSITION The present invention relates to anti-foam compositions and more particularly to solid, especially powder, anti-foam compositions.

Anti-foam compositions are used to reduce the amount of foaming in a system. Such compositions are extensively used for incorporation into detergents for use in washing machines, particularly of the front-loading type, or dish washers. When mixed with detergents it is important that the anti-foam and the detergent do not interact and interfere with the action of the other. The anti-foam component of many anti-foam compositions is, or includes, a silicone compound. The silicone compounds which are used in anti-foam compositions are typically liquids and in order to minimise interaction with a detergent it is desirable that the anti-foam is a solid material. There have been many proposals of anti-foam compositions in which the liquid silicone is incorporated into a solid, either on the surface of a solid as is described, inter alia, in GB 1378874 or the silicone is encapsulated, at least partially, in a suitable material as is described, inter alia, in GB 1407997, GB 1523957 and EP-A-0210721. However, whilst systems of this type have some useful characteristics we have found that they are not suitable for use in all situations in which an anti-foam composition is required.

Many agrochemical materials such as herbicides, insecticides and fungicides are sold either as solid materials or as concentrated liquids. In either case, in order to apply these agrochemical materials they are diluted with water and applied by a spraying device. However, the dilution of the agrochemical can result in foaming of the mixture which may be exacerbated during the spraying operation, particularly if the ground is uneven. Foaming may result in loss of the mixture from the spray tank, uneven spraying or failure to achieve the desired dilution of the agrochemical. To reduce such foaming, the addition of an anti-foam composition to the agrochemical is desirable. However, it is desirable that the anti-foam composition gives a rapid effect since foaming usually occurs soon after mixing the agrochemical with water and hence a rapid anti-foam effect is necessary to counteract foaming. We have found that systems which are effective as anti-foam materials in detergents generally do not provide a sufficiently quick anti-foam effect to be useful in an agrochemical mixture.

We have now obtained an anti-foam composition which provides a sufficiently quick anti-foam effect, which is storage stable and which may be mixed with an agrochemical and still retain much of its efficacy.

According to the present invention there is provided a solid anti-foam composition which comprises a particulate absorbent solid having on the surface thereof an anti-foam mixture of an anti-foam compound releasably enclosed in a mixture of a solid surfactant and a liquid surfactant.

Any anti-foam compound which is effective as an anti-foam material in an aqueous medium may be used in the anti-foam composition of the present invention. The anti-foam compound is very conveniently a silicone anti-foam compound such as a polydiorganosiloxane, which may or may not be end-capped. The silicone is especially a polydimethylsiloxane which is terminated with hydr tyl radicals or end-capped with a non-reactive group, in particular a triorganosiloxy group such as a trimethylsiloxy group.

The silicone is typically a liquid. Suitable silicone liquids which can be used in the compositions of the present invention have a molecular weight which is such that the liquid has a viscosity, measured at 250C, in the range of at least 50mm's and not more than 20000mm2s 1. Particularly suitable silicone liquids have a viscosity of at least lOOmm2s 1 and not more than 1OOOOmm2s1, especially from 500mm2s 1 to 2500mm2s 1 as measured by an Ostwald U-tube viscometer or a rotating spindle viscometer, such as a Brookfield RVF viscometer, depending on the viscosity of the liquid.

More specifically, when the viscosity is less than about lOOOmm2s , an Ostwald U-tube viscometer is used and the Brookfield viscometer is used to measure higher viscosities.

The anti-foam compound is typically used in the form of a particulate solid in the liquid anti-foam compound. The particulate solid may be present in an amount of from 12 up to 100Z by weight of the anti-foam compound and typically is present in an amount of from 1Z up to 20% by weight. The particulate solid can be selected from inorganic oxides, carbonates and silicates and solid organic materials, for example amide such as ethylene diamine distearimide.

The particulate solid is typically an inorganic oxide such as alumina or, preferably, silica. The particulate solid preferably is one having a high specific surface area which is typically at least 50m for example at least 100m g . If the particulate solid is silica, a suitable type of silica is fumed or precipitated silica.

The solid is preferably one which has been treated to render it hydrophobic. Any suitable technique may be used to render the solid hydrophobic. A preferred hydrophobic solid is silyllated silica, that is silica on the surface of which are organisilicon groups such as result from the treatment of silica with a triorganosilicon halide such as trimethylchlorosilane or hexamethyldisilazane.

The solid surfactant can be a cationic, anionic, amphoteric or nonionic surfactant. The solid surfactant is conveniently a nonionic surfactant. The solid surfactant is very desirably a water soluble or dispersible material. Preferred solid surfactants have a melting point of at least 300C. We have found that the storage stability of the anti-foam composition of the present invention improves as the melting point of the solid surfactant is increased.

However, in general the rate at which the anti-foam composition dissolves or disperses in water is adversely affected by an increase in the melting point of the solid surfactant. Hence, it is generally preferred that the melting point of the solid surfactant does not exceed 1000C and especially does not exceed 600C. For many applications an effective anti-foam composition is obtained using, as the solid surfactant component, a material having a melting point of about 400 C. It will be appreciated that the melting point of the solid surfactant should be such that the anti-foam composition remains solid under the ambient conditions in which it is to be used.

Hence, for use in an environment in which the ambient temperature is high, that is at least 300C, it is advisable to use a solid surfactant having a melting point which is at least 40do.

The liquid surfactant can be a cationic, anionic, amphoteric or nonionic surfactant and is conveniently a non-ionic surfactant.

The liquid surfactant is very desirably a water soluble or dispersible material. The liquid surfactant should have a melting point which is such that the material is liquid under ambient conditions and preferably the melting point is below 100C and especially does not exceed OOC.

The solid and liquid surfactants should not react together and hence interfere with the action of one another. Thus, although one or both of the solid and liquid surfactants may be an ionic material, it is not desirable for one to be anionic and the other cationic. Both the solid and liquid surfactants may be anionic or both may be cat ionic but it is preferred that at least one is nonionic and especially that both are nonionic.

The solid and liquid surfastants may be of the "low foam" type. By "low foam" is meant a material which, when used as a 0.1Z w/v solution in water in the Ross-Miles test, gives a foam height of not more than 30mm at 250C. It is preferred that the liquid surfactant is of the low foam type.

Both the solid and liquid surfactants may be oxyalkylated compounds, particularly polyoxyethylated compounds.

Thus, the solid surfactant may be a polyoxyalkylated, especially a polyoxyethylated, ester, phenol, ether, amine or alcohol. The polyoxyalkylated group is typically one containing at least 10 and not more than 400 oxyalkylene, especially oxyethylene, groups. The solid surfactant is preferably a material which contains, on average, at least 20 and not more than 250 oxyethylene groups.

If the solid surfactant is a polyoxyalkylated alcohol it is preferred that the alcohol is a higher alcohol, that is one containing more than six carbon atoms, and particularly one containing at least eight carbon atoms. The alcohol may be a mixture of hydrocarbyl groups, for example a mixture of alkyl groups containing 13 to 15 carbon atoms or alternatively a mixture of nonyl groups. The alcohol may be a saturated or unsaturated alcohol, for example nonyl, tridecyl, pentadecyl, hexadecyl, octadecyl, or octadecenyl. Examples of poiyoxyalkylated alcohols include a polyoxyethylated (20) synthetic primary alcohol mixture containing 13 to 15 carbon atoms, a polyoxyethylated (30) octadecyl alcohol and a polyoxyethylated (20) hexadecyl alcohol, the number in brackets indicating the average number of oxyethylene (C2H4O) groups per molecule.

The solid surfactant may be a polyoxyalkylated phenol, particularly an alkylphenol such as a 4-higher alkylphenol. A convenient phenol is 4-nonylphenol containing a mixture of isomeric nonyl groups. Examples of polyoxyalkylated phenols include polyoxyethylated (20) 4-nonylphenol and polyoxyethylated (30) 4-nonylphenol.

Alternatively, the solid surfactant may be an oxyalkylated ester. Such esters may be oxyalkylated carboxylic acids wherein the acids contain more than six carbon atoms and particularly at least 10 carbon atoms, for example dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, an unsaturated acid such as 9-octadecenoic acid, or an acid or mixture of acid derived from vegetable or animal sources, such as, for example, a mixture of tallow acids. Oxyalkylated esters of this type conveniently contain, on average, from 5 to 100 oxyalkylene groups, which are typically oxyethylene groups. Other oxyethylated esters may be preformed esters which contain at least one unreacted -OH group, for example a sorbitan monoester or an ester of a hydroxy acid such as 12-hydroxyoctadecanoic acid or 12-hydroxy-9-octadecenoic acid.

Suitable sorbitan monoesters include sorbitan mono-octadecanoate.

Oxyalkylated esters, for example the triesters or mixtures containing predominantly the triesters, of glycerol with 12-hydroxyoctadecanoic acid or with 12-hydroxy-9-octadecenoic acid may be used, for example such esters containing, on average, between 20 and 200 oxyethylene groups, such materials having a melting point which is generally in the range from 300 to 500C.

We have obtained solid anti-foam compositions which have a useful combination of properties using, as the solid surfactant, an oxyethylated mixed ester, predominantly the triester, of glycerol either with 12-hydroxyoctadecanoic acid or with 12-hydroxy-9-octadecenoic acid containing, on average, between 20 and 200 oxyethylene groups.

The liquid surfactant may be of the same general type as the solid surfactant but will contain few oxyalkylene groups. Typically liquid surfactants of this type contain less than 20 oxyalkylene, especially oxyethylene, groups on average, and particularly contain not more than 15 oxyalkylene, especially oxyethylene groups. Liquid surfactants include oxyalkylated phenols such as polyoxyethylated (9) 4-octylphenol, polyoxyethylated (8) 4-nonylphenol and polyoxyethylated (12) 4-nonylphenol; oxyalkylated alcohols such as polyoxyethylated (6) tridecyl alcohol, polyoxyethylated (12) tridecyl alcohol and polyoxyethylated (7) alcohol mixture containing 8 to 10 carbon atoms, and oxyalkylated esters.

& lternative liquid surfactants are ethylene oxide/propylene oxide copolymers, particularly those containing ethylene oxide blocks and propylene oxide blocks. Materials of this type include compounds in which the ethylene oxide/propylene oxide copolymer segments are condensed onto an alcohol or amine, for example an alcohol containing more than six carbon atoms or a diamine such as ethylene diamine. Typically the ethylene oxide content of these copolymers is at least 4, and not more than 40, ethylene oxide units.

The propylene oxide content of these copolymers is typically at least 3, and not more than 120, propylene oxide units. Examples of compounds having copolymer segments condensed onto an alcohol or amine include compounds of the type RO(PO)m(EO)nH and [HO(EO)w(PO) ]2 N(CH2)aN [(OP)y(OE) OH]2 where R is an alkyl group, or mixture of alkyl groups, containing more than six carbon atoms; EO is an ethylene oxide group; PO is a propylene oxide group; m is an integer with an average value of at least 6; n is an integer with an average value of at least 4; a is an integer with a value of from 2 to 6; w is an integer with an average value of at least 2; x is an integer with an average value of at least 4; y is an integer with an average value of at least 4; z is an integer with an average value of at least 2; wherein the values of w, x, y and z may be different in the different groups attached to the nitrogen atom. Compounds of this type include a compound in which R is a mixture of alkyl groups containing 13 to 15 carbon atoms, m has an average value of from 6 to 15 and n has an average value of from 4 to 20, and a compound in which a is two, w and z each, independently, have an average value of from 2 to 10 and x and y each, independently, have an average value of from 4 to 30.

A suitable liquid surfactant is of the type HO(PO)b(EO)c(PO)dH or HO(EO) (PO),(EO) H g where b, c, d, e, f and g are integers; f, or the sum of b + d, has an average value of from 14 to 75; c, or the sum of e + g, has an average value of from 3 to 45; and the values of b, c and d or e, f and g are such that the ethylene oxide units are less than 50% by weight of the copolymer.

The copolymer very preferably contains at least 10% by weight of ethylene oxide units and typically contains not more than 45% by weight of ethylene oxide units, for example from 12 up to 35Z by weight of ethylene oxide units. Suitable copolymers of this type have an average molecular weight of at least 1000 and typically the average molecular weight does not exceed 10,000. Particularly useful copolymers have an average molecular weight in the range 1500 to 5000. Polymers of this type are typically obtained by the condensation of propylene oxide onto a polyoxyethylene glycol base or by the condensation of ethylene oxide onto a polyoxypropylene glycol base. As noted previously herein, the liquid surfactant is preferably of the low foam type (as hereinbefore defined).

The solid surfactant or the liquid surfactant, or the mixture thereof, can include a small proportion of a thickening agent. Suitable thickening agents are finely divided solids, particularly inorganic oxides for example hydrophilic silica especially fumed silica. The thickening agent is very conveniently a solid having a high surface area, for example in excess of 100m2/g.

The final component of the solid powder anti-foam compositiof is a particulate absorbent solid. The particulate absorbent solid can be, for example, an inorganic oxide, carbonate or silicate. The particulate solid is typically a solid having a high surface area and preferably is porous. A suitable absorbent solid is hydrophilic silica, especially a precipitated silica, particularly 2 aving a surface area 2 least 2-1, for example 400m -1 one having a surface area of at least 200m g , for example 400m g or even higher. In general the type of silica which is suitable for use as a thickening agent is not suitable for use as the particulate absorbent solid.

A solid anti-foam composition in accordance with the present invention which has a useful combination of properties consists essentially of a hydrophilic silica having a surface area of at least 200m g and having on the surface thereof a polydimethylsiloxane having a viscosity of from 500 to 2500mm2s 1 and containing a hydrophobic silica having a surface area of at least Som g wherein the polydimethylsiloxane is releasably enclosed in a mixture of an oxyethylated mixed ester, predominantly the triester, of glycerol with either 12-hydroxyoctadecanoic acid or 12-hydroxy-9-octadecenoic acid, an ethylene oxide/propylene oxide block copolymer obtained either by the condensation of propylene oxide onto a polyoxyethylene glycol base or by the condensation of ethylene oxide into a polyoxypropylene glycol base, and a thickening agent which is hydrophilic silica having a surface area of at least 100m2g1.

The solid anti-foam composition is preferably in a powder form that is a free flowing particulate material having essentially spherical particles.

The proportions of the components of the anti-foam composition of the present invention can be varied in dependence on the nature of the components. The anti-foam compound may form up to 25% by weight of the composition and in general forms at least 5% by weight of the composition. Preferably the composition contains 10% up to 20% by weight, for example about 15% by weight, of the anti-foam compound. The anti-foam compound is typically a silicone liquid and may contain a particulate solid in an amount of up to 100% by weight of the silicone compound, and this is typically from 1% to 20% by weight of the silicone compound.

The solid surfactant is present in an amount such that the anti-foam composition is solid. Typically the solid surfactant is present in an amount from 5% up to 35% by weight of the composition, preferably from 10% up to 30% by weight of the composition, for example about 20% by weight.

The liquid surfactant may be present in an amount of up to 60Z by weight of the anti-foam composition and preferably is at least 20% by weight of the composition. In general the composition contains 30% up to 45%, for example about 40%, by weight of the liquid surfactant.

If a thickening agent is present, the amount of this preferably does not exceed 5% by weight of the anti-foam composition.

In general about 1Z by weight of a thickening agent is present.

The particulate absorbent solid may be present in an amount of up to 50% by weight of the anti-foam composition. In general at least 10% by weight of the particulate absorbent solid is present and especially at least 20% by weight, for example 25Z by weight.

Preferred anti-foam compositions in accordance with the present invention are powders, can be stored for a prolonged period of time with little loss of efficacy and give a rapid anti-foam effect. The anti-foam composition can be used in agrochemical formulations either by pre-mixing the anti-foam composition with a solid agrochemical formulation or the anti-foam composition may be added separately to the agrochemical formulation during dilution prior to use.

Thus, as a further aspect of the present invention there is provided an agrochemical composition which includes an anti-foam composition in accordance with the present invention.

If the agrochemical composition is a solid, the anti-foam composition may be blended with it using any suitable solids blending technique, for example by tumble blending.

If the agrochemical compoeition is in liquid form, for example as a concentrate, the anti-foam composition is conveniently added when-the concentrate is diluted prior to spraying.

The anti-foam composition is used in an amount which is preferably not more than 1Z by weight relative to the total agrochemical composition. The amount of the anti-foam composition is generally not less than 0.022 by weight. The amount of the anti-foam composition will be dependent to at least some extent on the foaming characteristics of the agrochemical composition in the absence of the anti-foam composition. In general, a mixture having a satisfactory combination of properties is obtained when the proportion of the-anti-foam composition is from 0.1 up to 0.5Z by weight relative to the agrochemical composition.

The agrochemical composition may contain a herbicide, an insecticide or a fungicide, or may be a mixture containing at least two components which may be of the same or different types. The agrochemical composition may be a commercially available composition.

The agrochemical composition may contain only one or more herbicides, insecticides or fungicides, However, many agrochemical compositions include an inert filler and also, to assist in wetting and dispersion of the active ingredient of the agrochemical, a wetting agent, a dispersant, or both. Any suitable wetting agent or dispersant may be used.

The anti-foam composition can cause a substantial reduction in the initial foam height together with a decrease in the time taken for all of the foam to disappear. Furthermore, this effect is essentially unaffected even when the anti-foam composition has been stored at ambient temperature, or even at a higher temperature such as 400C, for several months.

The anti-foam compositions of the present invention may be prepared by any suitable technique. A convenient technique is to coat the particulate absorbent solid with a liquid mixture of all of the other components of the composition. The liquid mixture may be poured onto the particulate absorbent solid whilst vigorously agitating the latter. Alternatively, the liquid mixture may be sprayed from a suitable spraying device onto the particulate absorbent solid, whilst agitating the solid. The spraying device is conveniently an atomiser of the type which is used in spray drying processes, for example an atomising nozzle or an atomising disc.

The liquid mixture should be at a temperature in excess of the melting point of the solid surfactant and its preferably at a temperature of at least 500C. However, the temperature of the liquid mixture preferably does not exceed 100"C.

The liquid mixture may be prepared by adding the components thereof to each other in any suitable order. Thus, the liquid surfactant may be mixed with the solid surfactant at a temperature above the melting point of the solid surfactant, adding the optional thickening agent and then adding the anti-foam compound, including any particulate solid which is admixed with the anti-foam compound.

Alternatively, the liquid surfactant and the anti-foam compound may be premixed, the solid surfactant then added in the molten state, followed by the optional thickening agent. Once the liquid mixture has been obtained, it is conveniently coated onto the particulate absorbent solid without undue delay.

The anti-foam compositions of the present invention are particularly suitable for use with agrochemical compositions since they quickly give a rapid anti-foam effect when added to water.

However, the anti-foam compositions can be used in any application in which control of foaming is desired and, in particular, for applications in which a rapid anti-foam effect is required.

In order that the various aspects of the present invention may be more readily understood, various embodiments thereof are set out in the accompanying non-limiting examples, which are by way of illustration only. In the examples, and comparative examples, all parts are parts by weight unless indicated to the contrary.

Example 1 In a stainless steel beaker of capacity 500cm3 were placed 17.3 parts of an alpha,omega-trimethylsiloxypolydimethyl siloxane fluid having a viscosity in the range 950 to 1050mm2s 1 and containing 4.228% by weight relative to the siloxane fluid of a fumed, silyllated, hydrophobic silica. To the beaker and its contents were added 44.55 parts of a liquid nonionic surfactant obtained by the condensation of propylene oxide onto a polyoxyethylene glycol base. The liquid surfactant contained about 20% by weight of ethylene oxide units and had an average molecular weight of about 3200. The siloxane fluid was agitated to ensure adequate mixing during the addition of the liquid surfactant by using a Greaves laboratory stirrer type GM-A, operating at 3000 rpm.

A solid surfactant which had a melting point range of 420-480C and was a mixed ester, predominantly the triglyceride, of 12-hydroxyoctadecanoic acid which had been oxyethylated using 200 moles of ethylene oxide per mole of the triglyceride was heated to 500C. 12.4 Parts of the molten material were added to the vigorously stirred mixture of the siloxane fluid and liquid surfactant at a temperature of 700C. To the stirred mixture thus obtained was added, while continuing to stir, 0.75 part of a hydrophilic silica ( > 99.8X silica) having a surface area of 200 + 25m2g-1 and having an average primary particle size of 12 nanometres. This mixture was then mixed to obtain a homogeneous flowable composition at a temperature of about 700C.

The resulting flowable composition was added over a period of one minute to 25 parts of a hydrophilic silica (99% silica) having a surface area of 450m g The hydrophilic silica was agitated in a domestic food mixer and mixing was continued throughout the addition of the flowable composition and for about 10 minutes after the addition was complete to give a free flowing powder.

The composition obtained was subjected to an anti-foam test procedure as set out hereafter.

Anti-foam test procedure The apparatus used comprised a stainless steel beaker of 5dm3 capacity having an outlet tube welded into the beaker, with the centre of the tube being 2.5cm from the base of the beaker. The outlet tube was connected through a length of pressure tubing (about 100cm) to a centrifugal circulation pump. One end of a further length of pressure tubing (about 65cm) was connected to the outlet of the pump and the other end was clamped to direct the flow of water into the stainless steel beaker at the top.

The beaker was provided with a mark all the way round the interior of the beaker to indicate a capacity of 2.5dm3. Further lines were marked at 2.54cm intervals about the 2.5dm9 mark.

In carrying out the test, 2.5dm3 of deionised water were placed in the beaker and circulated through the tubing and pump at a rate of 500dm3/hour. 0.2g of the anti-foam was added, as a solid, to the circulating water. The anti-foam was allowed to disperse for one minute and then 25cm9 of a 15% w/v solution of a detergent (the ammonium salt of ethoxylated lauryl alcohol sulphate) in water was added and a stopwatch was started to time the build-up of foam.

Circulation of the water plus additives was continued and the time taken for the foam to rise past each mark was recorded.

The results obtained in the presence and absence of various anti-foam compositions, some of which had been stored for several months at ambient temperature, are set out in Table One.

Table One

Run Anti- Time (in seconds) to reach marks No. Foam Mark Mark Mark Mark Mark T Type (a) 1 2 3 4 5 I NIL 4 11 25 41 62 II 1 15 194 282 365 467 III 1S 29 157 272 360 460 IV NIL 7 24 47 80 114 V I 9 86 195 321 468 VI IS 7 24 76 125 184 VII NIL 4 11 21 32 51 VIII II 6 22 95 202 330 IX IIS 4 11 19 29 40 Notes to Table One (a) NIL indicates that foaming was carried out in the absence of an anti-foam material. Several repeats were carried out at different times and the results in the absence of an anti-foam material are quoted. before results obtained during the same series of tests in the presence of an anti-foam material.

1 is the product of Example 1.

1S is the product of Example 1 after being stored for 5 months

I is an anti-foam material prepared as described in Example 1 with the exception that the solid surfactant was omitted.

IS is anti-foam material I after being stored for 3 months at ambient temperature (20-25"C).

II is an anti-foam material prepared as described in Example 1 with the exception that the liquid nonionic surfactant was omitted.

IIS is anti-foam material II after being stored for 3 days at ambient temperature (20-250C).

It will be observed that anti-foam material I (not according to the invention) is effective initially but is much less effective after being stored. It will be further observed that anti-foam material II (also not according to the invention) does not provide a quick anti-foam effect and deteriorates after only a few days storage. It will be appreciated that runs I and IV to IX are for comparative purposes and that runs II and III are obtained using the product of Example 1, which is a material in accordance with the present invention.

Example 2 A sample of the product of Example 1 was stored at 40 C over a period of 3.5 months. The anti-foam effect of the stored product was then determined using the anti-foam test procedure set out previously. The result obtained is set out in Table Two together with the result for the product of Example 1 as prepared.

Table Two

Run Anti- N Time (in seconds) to reach marks No. Foam | Mark Mark Mark Mark Mark Type (a)(b) 1 2 3 4 5 II 1 1 15 194 282 365 467 X 2 1 31 153 261 345 450 Notes to Table Two (a) is as defined in Notes to Table One.

(b) 2 is the product of Example 2 (that is the Example 1 product which has been stored for 3.5 months at 40"C).

It will be observed that the anti-foam characteristics of anti-foam types 1 and 2 are very similar and hence the anti-foam characteristics of the product of Example 1 are essentially unchanged after being stored for 3.5 months at 40 C.

Example 3 The procedure of Example 1 was repeated with the exceptions that the proportions of materials were changed and -a different solid surfactant was used. The solid surfactant had a melting point of about 330C and was the triglyceride of 12-hydroxy-9-octadecenoic acid which had been ethoxylated using 54 moles of ethylene oxide per mole of the triglyceride. The composition was prepared using 15.4 parts of the siloxane fluid containing the hydrophobic silica, 39.6 parts of the liquid non-ionic surfactant, 19.3 parts of the solid surfactant of melting point 330C, 0.7 parts of the hydrophilic silica 2 -1 of surface area 200 + 25m g and 25 parts of the hydrophilic silica of surface area 450m2g 1.

Example 4 A sample of the product of Example 3 was stored at 40 C over a period of one month.

Example 5 The procedure of Example 3 was repeated with the exception that a different solid surfactant was used. The solid surfactant had a melting point of about 39"C and was the triglyceride of 12-hydroxyoctadecanoic acid which had been ethoxylated using 54 moles of ethylene oxide per mole of the triglyceride.

Example 6 A sample of the product of Example 4 was stored at 400C over a period of 3.5 months.

The materials described in Examples 3 to 6 were subjected to the anti-foam test procedure set out previously. The results obtained are set out in Table Three.

Table Three

Run Anti- 2 Time (in seconds) to reach marks No. Foam Mark Mark Mark Mark Mark Type (c) 1 2 3 4 5 XI 3 64 286 386 499 601 XII 4 - 50 190 271 359 468 XIII 5 25 236 400 509 675 XIV 6 12 115 213 260 400 Notes to Table Three (c) 3 to 6 indicate the products of Examples 3 to 6 respectively.

Examples 7 to 18 The products of Examples 1 and 5, and samples of these products which had been stored for several months, were mixed with an agrochemical formulation.

A wettable powder agrochemical formulation was prepared by blending together 46 parts of Argirec B-24 (finely divided kaolin available from Blancs Mineraux de Paris), 50 parts of 6-chloro-N-ethyl-N'-isopropyl-J '3, 5-triazinediyl-2,4-diamine (atrazine, used as the active ingredient in herbicide formulations), 3 parts of a sodium naphthalene sulphonic acid/formaldehyde condensate and one part of an oxyethylated (average degree of ethoxylation 6.9) mixed alkyl (containing 8 to 10 carbon atoms) alcohol absorbed on a precipitated silica in a weight ratio of 2:1.

The blend obtained was then milled for one minute in a fly-cutter mill at 20,000 rpm.

To the resulting agrochemical formulation was blended a sample of one of the products of Examples 1 or 5, or a sample thereof which had been stored for several months, to give an anti-foam level of 0.1%, 0.25% or 0.5% wt relative to the total agrochemical formulation. Blending of the agrochemical formulation and the anti-foam powder was effected using a laboratory roller blender.

The resulting agrochemical/anti-foam mixtures were tested to determine wetting time, suspensibility, initial foam height and foam collapse time using the following procedures.

Wetting time 100(+1)cm3 of WHO standard hard water (342 ppm) was placed into a 250cm3 beaker. 5(10.l)g of the agrochemical formulation was weighed out, care being taken to keep the powder in a non-compacted state. All of the powder was added at once by dropping it onto the water from a position level with the rim of the beaker, without causing undue agitation of the liquid surface. A stop-watch was started when the powder was added to the water and the time (to the nearest second) noted for the powder to become completely wet, and to sink, this being the wetting time.

Suspensibility A weighed amount (3-5g) of the agrochemical formulation was stirred in about 20cm3 of WHO standard hard water (342 ppm). The resulting suspension was rinsed into a measuring cylinder (100cm3 or 250cm3) and the volume was made up to 100cm3 using a further quantity of the standard hard water. The cylinder was inverted 30 times and allowed tstand for 30 minutes. The upper 90% of the liquid was withdrawn with a suction tube, taking care not to disturb any sediment. The remaining 10Z of the liquid was transferred to an evaporating dish and dried to a constant weight in an oven at 50 C.

The residual powder was weighed accurately. The X suspensibility was obtained from the relationship Z suspensibility - 10 x 100(X-Y) 9 X where X is the weight of the agrochemical formulation used; and Y is the weight of the residual powder.

Foam test 4.5g of the agrochemical formulation were suspended in 150cm3 of WHO standard hard water (342 ppm). The resulting suspension was recirculated for 5 minutes from a 0.5dm3 vessel having a diameter of 8cm using a peristaltic pump and a jet. The pump was then switched off and the foam height noted. The time for all the foam to disappear (foam collapse time) was noted if this was less than 60 seconds. The height of any foam remaining after 5 minutes was also noted in appropriate cases.

The compositions used, and the results obtained, are set out in Table Four.

Table Four

Example Anti-foam WT | Susp. Foam Height (i) - or Type Amount (secs) (%) I CT Complex (a)(c)(d) (%)(e) (f) (h) (cm) (secs) A - NIL 25 91 3 0.5* 7 1 0.1 35 85 1.0 15 8 1 0.25 35 86 1.0 15 9 1 0.5 35 85 0.5 5 10 1S 0.1 35 84 1.5 10 11 1S 0.25 35 87 1.0 < 5 12 1S 0.5 30 85 0.5 < 5 13 5 0.1 35 85 1.5 10 14 5 0.25 35 86 1.0 5 15 5 0.5 35 79 < 0.5 < 5 16 55 0.1 35 84 1.0 < 5 17 5S 0.25 30 83 0.5 < 5 18 5S 0.5 40 73 0.5 < 5 Notes to Table Four (a) is as defined in Note (a) to Table One.

(c) is as defined in Note (c) to Table Three.

(d) 5S is the product of Example 5 after being stored for 5 months at ambient temperature (20-25"C).

(e) x by weight relative to the weight of the total agrochemical formulation (not total of agrochemical and anti-foam).

(f) WT is wetting time determined as described.

(h) suspensibility (X) is determined and calculated as described.

(i) determined as described in the Foam test, I is initial foam height and CT is foam collapse time, * indicates foam did not collapse and is the height of the foam remaining after 5 minutes.

Example 19 The procedure described in Example 1 was repeated with the exception that the liquid non-ionic surfactant used was replaced by a liquid non-ionic surfactant obtained by the condensation of ethylene oxide onto a polyoxypropylene glycol base. The liquid surfactant contained about 13% by weight of ethylene oxide units and had an average molecular weight of about 2070.

Example 20 The procedure of Example 19 was repeated with the exception that the liquid surfactant contained about 30% by weight of ethylene oxide units and had an average molecular weight of about 2580.

Example 21 The procedure of Example 19 was repeated with the exception that the liquid surfactant contained 16% by weight of ethylene oxide units and had an average molecular weight of about 2860.

Example 22 The procedure of Example 19 was repeated with the exception that the liquid surfactant contained about 24% by weight of ethylene oxide units and had an average molecular weight of about 3560.

The materials described in Examples 19 to 22 were subjected to the anti-foam test procedure set out previously.

The results obtained are set out in Table Five.

Table Five

Run Anti- Time (in seconds) to reach marks No. -Foam Mark Mark Mark Mark Mark Type (j) 1 2 3 4 5 XV NIL 4 12 23 33 53 XVI 19 87 249 328 410 600 XVII 19S 56 220 322 397 511 XVIII 20 30 116 187 298 500 XIX 20S 46 207 294 363 425 XX 21 100 222 300 360 404 XXI 21S 104 229 291 336 400 XXII 22 72 271 397 476 569 XXIII 22S 85 261 340 412 600 XXIV 1R 78 194 246 303 394 XXV 1RS 47 190 256 1 311 406 Notes to Table Five (j) 19, 20, 21 and 22 are the products of Examples 19 to 22 respectively.

19S, 20S, 21S and 22S are the products of Examples 19 to 22 respectively which have been stored for three weeks at ambient temperature.

1R was a freshly prepared repeat sample of the product of Example 1.

IRS was a sample of 1R which had been stored for three weeks at ambient temperature.

Claims (45)

1. A solid anti-foam composition comprising a particulate absorbent solid having on the surface thereof an antifoam mixture of an antifoam compound releasably enclosed in a mixture of a solid surfactant and a liquid surfactant.

2. A composition as claimed in claim 1 wherein the anti-foam compound is a polydiorganosiloxane.

3. A composition as claimed in claim 2 wherein the polydiorganosiloxane is a liquid having a viscosity of at least 50mm2s-1.

4. A composition as claimed in claim 3 wherein the liquid polydimethylsiloxane has a viscosity of from 500 to 2500mm2 S

5. A composition as claimed in any one of claims 2 to 4 wherein the polydiorganosiloxane is a liquid and contains a hydrophobic silica.

6. A composition as claimed in any one of claims 1 to 5 wherein the solid surfactant has a melting point of at least 300C.

7. A composition as claimed in claim 6 wherein the solid surfactant has a melting point-of at least 400C.

8. A composition as claimed in any one of claims 1 to 7 wherein the solid surfactant has a melting point of not more than 100"C.

9. A composition as claimed in any one of claims 1 to 8 wherein the solid surfactant is a non-ionic surfactant.

10. A composition as claimed in any one of claims 1 to 9 wherein the liquid surfactant has a melting point below 10"C.

11. A composition as claimed in claim 10 wherein the liquid surfactant has a melting point of not more than OOC.

12. A composition as claimed in any one of claims 1 to 11 wherein the liquid surfactant is a non-ionic surfactant.

13. A composition as claimed in claim 12 wherein the solid surfactant and the liauid surfactant are both non-ionic surfactants.

14. A composition as claimed in any one of claims 1 to 13 wherein at least one of the solid surfactant and the liquid surfactant is of the low foam type.

15. A composition as claimed in any one of claims 1 to 14 wherein at least one of the solid surfactant and the liquid surfactant is an oxyalkylated compound.

16 A composition as claimed in claim 15 wherein the solid surfactant is a polyoxyalkylated ester, phenol, alcohol, amine or ether.

17. A composition as claimed in claim 16 wherein the solid surfactant contains, on average, at least 10 and not more than 400 oxyalkylene groups.

18. A composition as claimed in either claim 16 or claim 17 wherein the solid surfactant is a product obtained by oxyalkylating a preformed ester which contains at least one unreacted -OH group.

19. A composition as claimed in claim 18 wherein the solid surfactant is an oxyethylated mixed ester of glycerol either with 12-hydroxyoctadecanoic acid or with 12-hydroxy-9-octadecenoic acid.

20. A composition as claimed in any one of claims 15 to 19 wherein the liquid surfactant is a polyoxyalkylated ester, phenol, alcohol, amine or ester.

21. A composition as claimed claims 20 wherein the~liquid surfactant contains, on average, less than 20 oxyalkylene groups.

22. A composition as claimed in any one of claims 15 to 19 wherein the liquid surfactant is an ethylene oxide/propylene oxide copolymer.

23. A composition as claimed in claim 22 wherein the liquid surfactant is of the type HO(PO)b(EO)c(PO)dH or HO(EO) e (PO) (EO) H g where b, c, d, e, f and g are integers; f, or the sum of b + d, has an average value of from 14 to 75; c, or the sum of e + g, has an average value of from 3 to 45; and the values of b, c and d or e, f and g are such that the ethylene oxide units are less than 50% by weight of the copolymer.

24. A composition as claimed in claim 23 wherein the values of b, c and d or e, f and g are such that the ethylene oxide units are less than 45% by weight of the copolymer.

25. A composition as claimed in claim 24 wherein the values of b, c and d or e, f and g are such that the ethylene oxide units are at least 10Z by weight of the copolymer.

26. A composition as claimed in any one of claims 23 to 25 wherein the copolymer has an average molecular weight of at least 1000 and not more than 10,000.

27. A composition as claimed in any one of claims 1 to 26 wherein the solid surfactant, the liquid surfactant or a mixture thereof contains a thickening agent.

28. A composition as claimed in any one of claims 1 to 27 wherein the particulate absorbent solid is an inorganic oxide, carbonate or silicate.

29. A composition as claimed in claim 28 wherein the particulate absorbent solid is silica having a surface area of at least 2O0m2g1.

30. A composition as claimed in claim 1 consisting essentially 2 of hydrophilic silica having a surface area of at least -1 of a hydrophilic silica having a surface area of'at least 200m g and having on the surface thereof a polydimethylsiloxane having a viscosity of from 500 to 2500mm2s 1 and containing a hydrophobic 2 -1 silica of surface area at least 50m g wherein the poly- dimethylsiloxane is releasably enclosed in a mixture of an oxyethylated mixed ester of glycerol with either 12-hydroxyoctadecanoic acid or 12-hydroxy-9-octadecenoic acid, an ethylene oxide/propylene oxide block copolymer either obtained by the condensation of propylene oxide onto a polyoxyethylene glycol base or by the condensation of ethylene oxide onto a polyoxypropylene glycol base and a thickening agent which is hydrophilic silica having a 2 -1 surface area of at least 100m g

31. A composition as claimed in any one of claims 1 to 30 wherein the anti-foam compound is present in an amount of at least 5X, up to 25%, by weight of the composition.

32. A composition as claimed in claim 31 wherein the anti-foam compound is a silicone liquid and contains a particulate solid in an amount of from 1Z up to 20Z by weight of the anti-foam compound.

33. A composition as claimed in any one of claims 1 to 32 wherein the solid surfactant is present in an amount of from 5%, up to 35Z, by weight of the composition.

34. A composition as claimed in any one of claims 1 to 33 wherein the liquid surfactant is present in an amount of from at least 20%, up to 60Z, by weight of the composition.

35. A composition as claimed in any one of claims 1 to 34 which includes a thickening agent in an amount which does not exceed 51 by weight of the composition.

36. A composition as claimed in any one of claims 1 to 35 wherein the particulate absorbent solid is present in an amount of at least 10%, up to 50Z, by weight of the composition.

37 A composition as claimed in any one of claims 1 to 36 which is in powder form.

38. An agrochemical composition which contains an anti-foam composition as claimed in any one of claims 1 to 37.

39. A composition as claimed in claim 38 which is a blend of solid materials.

40 A liquid agrochemical composition as claimed in claim 38 which is a dispersion or emulsion of an agrochemical in water.

41. An agrochemical composition as claimed in any one of claims 38 to 40 which contains 0.02 tolZ by weight of the anti-foam composition relative to the total agrochemical composition.

42. A process for the preparation of a composition as claimed in any one of claims 1 to 37 which comprises coating the particulate absorbent solid with a liquid mixture of all of the other components of the composition.

43. A process as claimed in claim 42 wherein the liquid mixture is sprayed onto the particulate absorbent solid whilst agitating the solid.

44. A process as claimed in either claim 42 or claim 43 wherein the liquid mixture is at a temperature of at least 50"C.

45. A process as claimed in any one of claims 42 to 44 wherein the liquid mixture is obtained by mixing together the liquid surfactant and the anti-foam compound, adding the solid surfactant in the molten state to the mixture and optionally adding a thickening agent to the mixture thus obtained.