AU711510B2 - Biocidal compositions - Google Patents

Description

BIOCIDAL COMPOSITIONS The invention relates to biocidal compositions and methods for controlling micro organisms using such compositions.

Known biocidal compositions generally suffer from the disadvantage that they have no lasting effect. In other words, after they are applied to a surface their biocidal effect decreases rapidly, especially if the surface is washed.

According to a first aspect of the present invention there is provided a method of controlling microorganisms at :1 a hard surface, which method comprises: s15 applying to the hard surface where such control *is required a biocide and a copolymer comprising chain units, Al, of the formula -OCnH 2 n- where n is 2 or 3 and chain ester units, A2, of the formula (A2) 0 where R is a hydrophobic group; the mole ratio of units Al 20 to A2 being from 1:10 to 3000:1 and the copolymer having a number average molecular weight of from 1000 to 100,000; and (ii) removing the biocide and the copolymer from said hard surface.

In a second aspect of the present invention, there is provided a composition suitable for controlling microorganisms at a hard surface which comprises an aqueous solution, suspension or dispersion of a biocide and a copolymer comprising chain units, A3, of the formula: (O-CnH 2 (A3) II II 0 0 where m represents an integer of from 12 to 230, n is 2 or 3 and R is a hydrophobic group and chain ester units, A4, of the formula O-CnH2n-O-C-R-C-- (A4) II II 0 0 where n is 2 or 3 and R is a hydrophobic group; the mole ratio of units A3 to A4 being from 1:10 to 3000:1 and the copolymer having a number average molecular weight of from 1000 to 100,000; with the proviso that the biocide is not a mono-quaternary ammonium biocide.

R is preferably an alkylene group, a cycloalkylene 9 WO 97/06675 PCT/GB96/02025 2 group, or an arylene group. The alkylene group preferably has six or more carbon atoms, the cycloalkylene group preferably has 4 to 10 carbon atoms, especially cyclohexylene and the arylene group is preferably a metaor para- phenylene or naphthylene group. The groups represented by R may optionally be substituted. Suitable substituents include

C

1 6 -alkyl, for example methyl, or hydrophilic groups such as sulphonic acid groups, optionally in alkali metal salt form, for example sodium The copolymer preferably has a molecular weight from 2000 to 30,000. The molar ratio of units Al to A2 is preferably from 1:1 to 100:1.

It will be appreciated that such copolymers possess a hydrophobic part which will give some adherence to the surface, resisting removal by water and weak surfactant solutions, and a hydrophilic part which will allow migration of the biocide through to the surface of the polymer, particularly when the surface is rinsed with water or an aqueous solution. The chain units Al are generally hydrophilic while the chain ester units A2 are hydrophobic.

The copolymers used preferably comprise chain units of the formula WO 97/06675 PCT/GB96/02025 3 -(O-CnH2n)m-O-C-R-C- (A3) O O where m represents an integer from 12 to 230 and n and R are as defined above, especially polyoxyethylene terephthalate units, and chain units of formula: (A4) O 0 where n and R are as defined above, especially polyethylene terephthalate units.

Preferred polymers are those having an A3:A4 molar ratio of from 1:10 to 10:1, preferably from 1:2 to 1:6.

The units A3 preferably contain (OCnH 2 n)m groups having a molecular weight of from 500, preferably 1000, to 10,000, especially about 3400. The polymer preferably has a total WO 97/06675 PCT/GB96/02025 4 molecular weight of from 1000 to 100,000, preferably from 15,000 to 35,000 especially about 20,000. Preferably m is an integer from 14 to 110, particularly about Thus typical copolymers which may be used are as follows: polymers derived from ethylene terephthalate and polyethylene oxide terephthalate at mole ratio from about 1:10 to 10:1, said polyethylene oxide 0 terephthalate containing ethylene oxide units with a number average molecular weight from about 500 to about 10,000, the polymer having a number average molecular weight of about 1,000, to 100,000: (ii) polymers derived from propylene terephtalate and polyethylene oxide terephthalate at a mole ratio from about 1:10 to about 10:1, said polyethylene oxide terephthalate containing ethylene oxide units with a number average molecular weight from about 500 to about 10,000, and the polymer having a number average molecular weight of about 1,000 to 100,000, or (iii) polymers derived from ethylene terephthalate and/or propylene terephthalate in any'ratio and polyethylene oxide and/or polypropylene oxide in any ratio such that the mole ratio of ethylene terephthalate plus WO 97/06675 PCT/GB96/02025 5 propylene terephthalate to polyethylene oxide plus polypropylene oxide is from about 1:10 to about 10:1, said ethylene oxide units -and said propylene oxide units each having a number average molecular weight from about 250 to about 10,000, the polymer having a number average molecular weight of about 1,000 to about 100,000.

In one embodiment, in order to impart a slight ionic character, or increased hydrophilicity, to the polymer, the polymer is end-capped with a hydrophilic group. Suitable hydrophilic groups include those containing a sulpho group, for example those of formula (MO 3 S) (C 6

H

4 or

(MO

3 S) (CH,),(CH 2 CHO) (CnH 2 nO)y where M is a suitable cation, for example an alkali metal ion especially sodium, X is O or 1, y is from 0 to 4 and n is as defined above, monoesters of ethylene glycol or propylene glycol. They may be added during the preparation of the base polyester.

Generally, the molar quantity of the hydrophilic group in the total molar quantity of units A2 used in such preparation is from 0 to Suitable polymers include those disclosed in US-A- 4,770,666 in groups B, C and D, US-A-4,116,885,

US-A-

3,962,152, GB-A-2,196,013, US-A-4,702,857, US-A-4,711,730, US-A-4,713,194, US-A-3,416,952, US-A-4,427,557 and US-A- 4,201,824, which also describe methods for their WO 97/06675 PCT/GB96/02025 6 preparation which are, of course, well known.

The polymer is used as an aqueous solution, suspension or dispersion. It may optionally be solubilised or dispersed in water with the assistance of solubilising or dispersing agents such as non-ionic surfactants, in particular a fatty alcohol ethoxylate such as C 12 or C 14 alkyl ethoxylates. The use of a dispersion or suspension is generally preferred since such formulation will adhere better to the surface than solutions.

Biocides which may be used in the compositions of the present invention include: a) Quaternary ammonium and phosphonium biocides: Cocoalkyl benzyl dimethyl ammonium chloride;

C

1214 -alkyl benzyl dimethyl ammonium chloride; Lauryl C 214 -alkyl-benzyl dimethyl ammonium chloride; Coco-alkyl 2 ,4-dichlorobenzyl dimethyl ammonium chloride; Tetradecyl benzyl dimethyl ammonium chloride; diisobutyl phenoxy-ethoxy-ethyl dimethyl-benzyl ammonium chloride; Lauryl pyridinium chloride;

C

12 1 4 -alkyl-benzyl imidazolinium chloride; Myristyl trimethyl ammonium bromide; Cetyl trimethyl ammonium bromide; Didecyl dimethyl ammonium chloride; Dioctyl dimethyl ammonium chloride; and Myristyl triphenyl phosphonium bromide.

b) Amphoteric biocides: N- 8 -alkyl-3-aminopropyl)glycine derivatives such as (dodecyl)(aminopropyl)glycine; N-(N'-(N"-C,_8-alkyl-2-aminoethyl)-2-aminoethyl)-glycine WO 97/06675 WO 9706675PCT/GB96/02025 -7 derivatives such as (dodecyl) (di-ethylene diamine)glycine; and N,N-bis -Cs,-i-alkyl-2-aminoethyl) -glycine derivatives.

C) Amijnes:. ami-nopropyl) -N-dodecyl-1,3.

Propanedianine.

d) Phenolics: Parachiorometaxylenol, dichiorometaxylenol, phenol, m-cresol, o-cresol, p-cresol, o-phenyl-phenol, 4 -chloro-rn-cresol, chioroxylenol, 6-namyl-m-cresol, resorcinol, resorcinol monoacetate, p-tertbutyl-phenol and o-benzy1-p-chlorophenol or biologically active, water soluble salts of these compounds, e.g. the alkali metal salts; e) Chlorhexidine and its salts for example chlorhexidine gluconate; is f) Iodophors, hypochlorite salts and chlorine release agents, e.g. sodium dichloroisocyanurate; g) Polyguaternary ammonium biocides such as poly hydroxye thylene (dime thyl imino) ethylene (dimethylimino) methylene dichloride] poly [oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride] poly [hydroxyethylene (dimethylimino) 2 -hydroxypropyl (dimethylimino) methylene dichioride] and the polymer of IH-imidazole with (chloromethyl) oxirane.

The polymer is preferably used at a concentration of from 1 to 80*- by weight, preferably from 5 to 500% more preferably from 10 to 300%, for example about 15%s, by WO 97/06675 PCT/GB96/02025 8 weight. The biocide is preferably used in a concentration range of from 0.1% to 20% by weight, preferably from 1 to more preferably from 1 to for example about by weight.

The surface to be treated may be a hard surface or, for example, a textile fabric or a flexible polymer surface or a coating. Thus the compositions can be used to advantage during household or industrial laundry processes.

The amount of solid active ingredient deposited on the hard surface per 2m is typically 0.01 to preferably 0.lg to Ig of the biocide and 0.lg to preferably 1 to 5g of the polymer. For a textile fabric, the amount deposited is typically 0.001% to 10%, preferably 0.01% to for example about of the biocide and 0.001% to 10%, preferably 0.01% to for example about of the polymer, by weight based on the weight of fabric.

A particular advantage of the compositions according to the invention is that they provide a sustained biocidal effect when applied to a hard surface. This sustained effect is resistant to washing of the surface. The polymer used in the composition has the advantage that it is biodegradable by virtue of the ester linkage present in the backbone of the polymer. Another advantage of the compositions is that they may easily be removed from the surface to which they have been applied by the application WO 97/06675 PCT/GB96/02025 -9of an alkali.

A further advantage of the compositions is that there is no need for the polymer to contain cationic grouping to enhance hydrophilicity. The presence of such grouping, especially cationic nitrogen groupings, tends to give rise to effluent problems because polymers with such groupings are frequently toxic to fish.

Application to textile surfaces extends the biocidal effect during normal use. Thus the presence of the polymer resists removal of the biocide if the fabric becomes damp or is subject to a light water spray or rinse during use.

Thus the composition finds utility for general hospital laundry, including sheets, nurses' uniforms, surgeons' gowns, doctors' white coats, clothing aprons, used in some sensitive industries such as the food industry, cleaning cloths and towels, e.g. hand towels, at home or in industrial areas, clothing and uniforms worn during participation in energetic sporting activities and personal clothing, particularly worn next to the skin, e.g.

socks and undergarments.

It is convenient to apply the composition towards the end of the laundry treatment thus avoiding any possible incompatability between the normal anionic detergent systems and the biocide, e.g. quaternary biocides. Thus, the following are typical procedures: Apply the biocide plus polymer in the final water WO 97/06675 PCT/GB96/02025 10 rinse.

Apply the biocide plus polymer together with a fabric softener if compatible, e.g. quaternary biocides are compatible with cationic and amnphoteric softeners.

(bl) It may be convenient to add the biocide plus polymer and softener formulation separately to the washing machine.

(b2) Alternatively, the biocide plus polymer may be incorporated into the fabric softener formulation itself.

In some cases the biocide plus polymer may be added with minimal water at a separate stage before drying.

This ensures maximum transfer to the fabric or sheet.

The extended biocidal effect will be observed on most normal fabrics and polymer surfaces. Many biocides such as quaternary ammonium based products are naturally substantive to many such surfaces but the effect is improved by the presence of the polymer. Fabrics include those of natural fibres such as cotton and wool, modified natural products such as cellulose acetates, synthetic WO 97/06675 PCT/GB96/02025 11 polymers such as polyester, polyamide and acrylics, and coated fabrics, for example PVC coated polyester.

Adding the above type of polymer to protect the biocide has a secondary benefit, particularly on substrates such as polyester and polyamides. The excellent soil release characteristics of this polymer during laundry washing can be displayed.

Suitable fabric softeners include: 1. Simple Dialkyl quaternary ammonium compounds of general formula: R1\+,CH 3 N X R2 CH3 2. Alkyl amido quaternary ammonium compounds of general formula: R 1-CONH-CH 2

CH

2 CH2CH 2 0H

N

R2-CONH-CH 2

CH

2

CH

3

X

WO 97/06675 WO 9706675PCT/GB96/02025 12 3. Alkyl Imidazolinium compounds of general formula: R I I A-CH2CH 2 -N

CH

2 CH3 CR2 4. Dialkyl Imidazolinium compounds of general formula: Ri-C-N I

I

R2-B-CH2CR 2 -N CR12

CR

3 CR2 5. Dialkyl ester quaternary ammonium compounds of general formula:

CR

3 0 CR3 0 In these f ormulae, R, and R 2 which can be the same or different, each independently represents a long chain aliphatic group, e.g.

C

16

C

1 such as tallow, WO 97/06675 PCT/GB96/02025 13 hydrogenated tallow, stearyl or oleyl.

X is an anion such as halide, preferably chloride, or methosulphate

(CHSO

4 A is hydroxyl (OH) or amino (NH 2 and B is an ester group or an amido group NH) Such softeners are typically present in the composition in an amount of from 2 to 20%, preferably 3 to especially about 10% by weight.

Such softener formulations can optionally contain other ingredients such as colouring agents, perfumes, optical brighteners and stabilising solvents such as isopropanol.

According to the present invention there is further provided a method of controlling microorganisms at a locus which comprises applying to the locus where such control is required a biocide and a copolymer as defined above, for example in the form of a composition according to the invention. A suitable locus is a hard surface, for example glazed and unglazed ceramic, glass, PVC, formica and other hard plastics, stainless steel or other painted or unpainted metals, and painted or unpainted wood, as well as WO 97/06675 PCT/GB96/02025 14 a flexible polymer surface.

The compositions according to the present invention are preferably used in the method of the invention in diluted form at dilutions from 20 to 500 times, preferably 50 to 100 times. In laundry applications, the composition will normally be diluted by the washing/rinsing water.

The microorganisms which may be controlled by the method of the present invention include: Gram negative bacteria: Pseudomonas aeruginosa; Escherichia coli; and Proteus mirabilis.

(ii) Gram positive bacteria: Staphvlococcus aureus; and Streptococcus faecium.

(iii) Other harmful food bacteria: Salmonella typhimurium; Listeria monocytogenes; Camvplobacter ieiuni; and Yersinia enterocolitica.

(iv) Yeasts: Saccharomyces cerevisiae; and Candida albicans.

Fungi: Asperqillus niger; Fusarium solani; and Pencillium chrysogenum.

(vi) Algae: Chlorella saccharophilia; Chlorella emersonii; Chlorella vulgaris; and Chlamvdomonas eucametos.

The microorganisms controlled by the method of the present invention are preferably Gram negative microorganisms, especially Pseudomonas aerucinosa, Gram positive microorganisms, especially Staphylococcus aureus, and fungi e.g. Aspergillus niger.

WO 97/06675 PCT/GB96/02025 15 The following examples illustrate the invention. In the Examples the Gram negative bacteria Pseudomonas Aeroqinosa has been chosen as it is known to be difficult to kill. The positive results obtained using the compositions of the invention show that the compositions will be effective over a wide range of known microorganisms.

EXAMPLE 1 Two disinfectant concentrates (DC1 and DC2) were prepared each with the formulation shown in Table 1 below Table 1 DC1 DC2 Biocide 2.5% Polymer 14.25% 0 Water to 100% to 100% In the above Table the biocide used was C 12 14 -alkyl benzyl dimethyl ammonium chloride and the polymer was of the following formula: WO 97/06675 PCT/GB96/02025 16 CH2-CH2-C CH2 CH 2 Oc

O

having a molecular weight of about 20000g/mol. The percentages in the Table are percentages by weight.

A hard surface having an area of 25cm 2 which had previously been sterilised by wiping with isopropyl alcohol was treated with 3ml of each of the disinfectant concentrates after appropriate dilution e.g. 100X and then dried at 45 0 C. The tile is then washed consecutively with a water spray or sponge and dried again at 45 0 C. 0.25ml of an aqueous medium containing about 108 cfu's/ml of the gram negative bacteria Pseudomonas Aerucinosa was then spread over the treated hard surface. The surface was then allowed to stand for the contact times shown in Table 2 below. This was to allow the biocide time to migrate through the polymer layer and kill the bacteria on the surface. The surfaces were then dried at 370C.

The surviving organisms were recovered using a sterile cotton wool swab, previously wetted with a neutralising medium. The whole surface was carefully swabbed by wiping it across back and forth several times.

The swab was transferred to 9ml of neutralising medium WO 97/06675 PCT/GB96/02025 17 comprising 3% Tween 80% and 2% soya lecithin which was then plated out using 10-fold serial dilutions onto nutrient agar. The plates were incubated at 370C for 48 hours and the survivors were counted.

Control tests were carried out using a clean hard surface of the same area and using the same method except that no polyester or biocide was applied.

The sustained biocidal effect of the compositions of the invention was measured by washing the hard surface with a sponge before treating it with microorganisms using the method described above. The sponge treatment involved the use of a Gardener-Scrub washing machine, which pushes a sponge soaked in water across the surface, which is mounted horizontally, at a pressure of 5.6g/cm 2 For each "wash" in Table 2 below, the sponge passed over the surface twice.

The results shown in Table 2 below were obtained: Table 2 Formulation Dilution Contact Number of washes and used Time(h) Logo Reduction obtained 0 1 2 4 DC1 100x 1 4.6 4.4 2.8 2.47 DC1 100x 3 DC2 100x 1 6.0 1.82 0.3 0.10 WO 97/06675 PCT/GB96/02025 18 The Log,, 10 reduction in the number of bacteria was calculated as follows: Log,, 10 reduction= Log 10 (N/n) where N represents the number of bacteria (cfu's/ml) recovered from the control and n represents the number of bacteria (cfu's/ml) recovered from the test sample. A Log 10 reduction of 5 shows an excellent result particularly for food contact areas and a Log 0 reduction of 3 shows a satisfactory result for general disinfection.

The results show that DC1 resists the abrasive sponge treatment very well. There is still a Log 10 reduction of about 3 after two washes. The increase in contact time from 1 hour to 3 hours gives a higher kill factor, presumably because the polymer coating slows down the biocide action as the biocide must first diffuse through the polymer film before it can attack the bacteria. When a longer time of contact is used, the Log 10 reduction after two washes is likely to be above 3.

EXAMPLE 2 This Example was carried out in a manner identical to that of Example 1 (with dilution 100X) except that instead of washing with a sponge the surfaces were subjected to non abrasive washing with a water spray. This involved mounting the WO 97/06675 PCT/GB96/02025 19 surface vertically and spraying it with Ig of water from a hand held trigger spray for each wash. The results shown in Table 3 below were obtained: Table 3 Formulation Contact Number of water sprays and Log, 1 Time(h) Reduction obtained 0 1 2 4 8 12 D.C.1 1 4.6 4.52 6.0 3.6 2.16 1.46 D.C.1 3 D.C.2 1 6.0 5.82 3.4 0.8 0.05 0.0 The low values at washes 0 and 1 for formulation DC1 with a contact time of 1 hour are caused by the slowing of biocidal action by the polymer coating. By the second wash sufficient polymer is removed and the time delay is long enough to increase the rate of biocidal action. Further washes gradually remove biocide and the protecting polymer and so the kill rate decreases. The film still protects against at least four water sprays when it provides a Log, 1 reduction of 3 at least.

WO 97/06675 PCT/GB96/02025 20 EXAMPLE 3 Disinfectant concentrates having the formulation shown in Table 4 below were prepared: Table 4 DC3 DC4 Biocide 1.0% Polymer 14.7% 0% Water to 100% to 100% The biocide used was Poly[hydroxyethylene(dimethyliminio)- 2-hydroxy propyl (dimethyliminio)methylene dichloride].

The polymer used was the polymer of formula as in Example 1. The percentages are percentages by weight.

This Example was carried out in the same way as Example 2 except that disinfectant concentrates DC3 and DC4 were used. The results obtained are shown in Table below: WO 97/06675 PCT/GB96/02025 21 Table Formulation Dilution Contact Number of water sprays used Time(h) and Log, 1 Reduction obtained 0 1 2 4 DC3 100x 24 6.0 6.0 4.9 0.19 DC4 100x 24 6.0 2.96 2.02 The polymer quaternary ammonium biocide is a relatively slow acting biocide and so testing was carried out after an 24 hour contact time. When the polymer is present, the biocide resists at least 2 water sprays before its effectiveness is greatly reduced.

EXAMPLE 4 The same biocide and polymer as in Example 1 was used to prepare disinfectant Concentrate Biocide Polymer Water to 100% After dilution 100x, 5ml of the diluted formulation was added WO 97/06675 PCT/GB96/02025 22 to a petri dish followed by a small square (5cm x 5cm) of polyester fabric weighing 0.2g. The liquid was dried off at 0 C to deposit all the biocide plus polymer on the fabric which now contains Biocide 2.5% w/w (2 gms per square meter of fabric) Polymer 5.0% w/w (4 gms per square meter of fabric) A control sample of fabric was treated as above with 5mls of water without the biocide present.

0.25 ml of an aqueous medium containing about 108 cfu's per ml of the Gram-negative bacteria Pseudomonas aeruginosa was then spread over the surface of both fabric samples.

of nutrient agar was then poured over both samples of fabric followed by incubation at 37 0 C for 48 hours.

Few bacteria survived on the treated fabric compared to extensive growth on the untreated control fabric.

EXAMPLE a) The same procedure was followed as in Example 4 but the treated fabric square was subsequently dipped for seconds in a beaker of water before re-drying at 45 0

C

followed by addition of bacteria and covering with nutrient agar as before.

23 b) A similar control treatment was carried out using biocide without the polymer.

Disinfectant Concentrate DC6:

S

*5

S

S

S

5*SS a

S

*I S Biocide Water In this experiment the growth of bacteria was very much more extensive on the sample b) when the polymer was not used.

It is clear that the polymer helps to prolong the effect of the biocide to light rinsing with water.

Throughout this specification and the claims which 15 follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (23)

1. A method of controlling microorganisms at a hard surface, which method comprises: applying to the hard surface where such control is required a biocide and a copolymer comprising chain units, Al, of the formula -OCnH2n- where n is 2 or 3 and chain ester units, A2, of the formula (A2) II II O O where R is a hydrophobic group; the mole ratio of units Al to A2 being from 1:10 to 1: 3000:1 and the copolymer having a number average molecular weight of from 1000 10 to 100,000; and *i (ii) removing the biocide and the copolymer from said hard surface.

2. A method according to claim 1 wherein the biocide and copolymer are applied in the form of a composition which comprises an aqueous solution, suspension or dispersion of the biocide and the copolymer.

3. A method according to claim 1 or 2 in which R is an alkylene group of six or more carbon atoms, a cycloalkylene group of from 4 to 10 carbon atoms or an arylene group.

4. A method according to any one of the preceding claims wherein the copolymer has a number average molecular weight of from 2000 to 30,000.

5. A method according to any one of the preceding claims wherein the mole ratio of units Al to A2 is from 1:1 to 100:1.

6. A method according to any one of the preceding claims wherein the copolymer comprises chain units A3: S S. S 9 *S e 9* S S. *.S a a S -(O-CnH 2 (A3) II II 0 O where m represents an integer of from 12 to 230 and n and R are as defined above, and chain units of formula: -O-CnH2n-O-C-R-C- (A4) II II 0 0 where n and R are as defined above.

7. A method according to any one of claims 1 to 4 wherein the 5 copolymer is end capped with a hydrophilic group containing a sulfo group.

8. A method according to any one of claims 2 to 7 wherein the composition is in the form of a dispersion or suspension.

9. A method according to any one of the preceding claims in which the biocide is a quaternary ammonium or phosphonium biocide, an amphoteric biocide, 10 an amine, a phenolic compound, chlorhexidine, an iodophor or a polyquaternary ammonium biocide.

10. A method according to any one of claims 2 to 9 wherein the composition comprises from 5 to 50% by weight of copolymer and from 1 to 10% by weight of a biocide.

11. A method according to claim 10 wherein the composition comprises from 10 to 30% by weight of copolymer and from 1 to 5% by weight of biocide.

12. A method according to any one of claims 2 to 11 wherein the composition is diluted 50 to 100 times before use.

13. A method according to any one of the preceding claims wherein the microorganism is a Gram negative microorganism.

14. A method according to any one of the preceding claims wherein the hard surface is a glazed or unglazed ceramic, glass, PVC, a hard plastics material, a painted or unpainted metal or a painted or unpainted wood. A method of controlling microorganisms at a hard surface, which method consists essentially of applying to the hard surface where such control is required a biocide and a copolymer comprising chain units, Al, of the formula -OCnH 2 n- where n is 2 or 3 and chain ester units, A2, of the formula: (A2) II II 0 O where R is a hydrophobic group; the mole ratio of units Al to A2 being from 1:10 to 3000:1 and the copolymer having a number average molecular weight of from 1000 to 100,000. 10 16. A method according to claim 1 substantially as described in any one of the Examples.

17. A composition suitable for controlling microorganisms at a hard S: surface which comprises an aqueous solution, suspension or dispersion of a biocide and a copolymer comprising chain units, A3, of the formula: -(O-CnH 2 (A3) O O where m represents an integar of from 12 to 230, n is 2 or 3 and R is a hydrophobic group and chain ester units, A4, of the formula o o O-CnH2n-O-C-R-C-- (A4) O O where n is 2 or 3 and R is a hydrophobic group; the mole ratio of units A3 to A4 being from 1:10 to 3000:1 and the copolymer having a number average molecular weight of from 1000 to 100,000; with the proviso that the biocide is not a mono-quaternary ammonium biocide.

18. A composition according to claim 17 in which R is an alkylene group of six or more carbon atoms, a cycloalkylene group of from 4 to 10 carbon atoms or an arylene group.

19. A composition according to claim 17 or 18 wherein the copolymer has a number average molecular weight of from 2000 to 30,000. A composition according to any one of claims 17 to 19 wherein the mole ratio of units A3 to A4 is from 1:1 to 100:1.

21. A composition according to any one of claims 17 to 19 wherein the polymer is end capped with a hydrophilic group containing a sulfo group.

22. A composition according to any one of claims 17 to 19 which is in the form of a dispersion or suspension.

23. A composition according to any one of claims 17 to 19 in which the biocide is a phosphonium biocide, an amphoteric biocide, an amine, a phenolic compound, chlorhexidine, an iodophor or a polyquaterary ammonium biocide.

24. A composition according to any one of claims 17 to 23 which comprises from 5 to 50% by weight of polymer and from 1 to 10% by weight of a biocide. S: 15 25. A composition according to claim 24 which comprises from 10 to by weight of polymer and from 1 to 5% by weight of biocide.

26. A composition according to claim 17 substantially as described in any one of the Examples.

27. A method according to claim 1 or a composition according to claim 1 20 or a composition according to claim 17 substantially as hereinbefore described with reference to the Examples. DATED this 29th day of July 1999 Rhodia Limited. By its Patent Attorneys DAVIES COLLISON CAVE