AU4555997A

AU4555997A - Antimicrobial cleaning compositions

Info

Publication number: AU4555997A
Application number: AU45559/97A
Authority: AU
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1996-09-20
Filing date: 1997-09-16
Publication date: 1998-04-14
Also published as: ZA978415B; BR9712076A; GB9619682D0; HUP9904411A3; WO1998012294A1; HUP9904411A2; PL332310A1; AR008451A1; CA2266353A1; EP0929633A1; SK35399A3

Description

ANTIMICROBIAL CLEANING COMPOSITIONS

Technical Fi ld

The present invention relates to a cleaning composition and to a method of treating surfaces with the said composition.

Background to the Invention

Hard-surface cleaning compositions generally comprise one or more surfactants, and, optionally, one or more hygiene agents .

Typically, the surfactants used in such cleaning compositions are selected from anionic, nonionic, amphoteric and cationic surfactants. Nonionics are very commonly used due to their effectiveness on fatty soils and the ease with which their foaming can be controlled. A known manner in which foaming can be controlled involves including in the composition relatively low levels of a solubilised hydrophobic oil such as an iso-paraffin and a relatively low level on product of a surfactant such as a fatty acid soap which forms a calcium salt insoluble in dilute aqueous solution. Both the oil and the soap components are soluble/miscible in the composition forming a stable product until (hard) water is added whereupon the combination of oil and the particles of calcium salt formed in situ acts as a 'foam breaker' for a second (main) surfactant. This greatly aids in the rinsing of the compositions as excessive foaming is prevented. As well as the effect on the salt content of the composition on dilution with hard water it is known to exploit the changes in acidity/alkalinity which occur on dilution. Thus acidic general purpose cleaning compositions based on the high foaming anionic surfactant magnesium PAS and an organic acid such as citric are known which are neutralised to pH 4.0 with a base such as ammonia to give improved cleaning e fectiveness especially as regards lime soaps and lime scales whilst maintaining cleaning efficiency against fatty/greasy soils. It is known to include in such formulations C10-18 fatty acids which have a foam boosting effect on the surfactants in acid solution, and which, on addition of several volumes of alkaline water form a precipitate of the fatty acid with calcium present to give a foam-suppressing effect which aids rinsing and removal of the foam produced by use of the product .

In addition to surfactants it is known to incorporate polymers in hard surface cleaning compositions. These polymers provide benefits both in initial and repeated cleaning. In order to obtain benefits from the presence of polymers it is often useful to formulate compositions in an acidic pH range. Typically the pH of the compositions is in the range 3-4.5, with preferred values around 4.5. Polymer containing compositions are difficult to antifoam: the presence of iso-paraffins and fatty acids reduce the performance in neat usage and, in particular, the recleaning properties of the product. Overall the isoparaffin/fatty acid antifoaming system does not provide a sufficiently low foam profile and ease of rinsability for some consumers. Brief Description of the Invention

We have determined that an effective antifoaming system can be based on the synergism between four different components: a branched fatty chain nonionic including a small amount of free monobranched alcohol; a low level of ethoxylated/propoxylated nonionic surfactant and a fatty acid.

Accordingly a first aspect of the present invention relates to a cleaning composition of pH 2-6 comprising 1- 30%wt on product of an alkoxylated nonionic surfactant, less than 50%wt of total surfactant of anionic surfactant and 0.005-5%wt on product of a water soluble, anionic polymer having an average molecular weight of less than 1,000,000, wherein, the ratio of polymer : nonionic is 0.1:1 or less, said product being CHARACTERISED IN THAT :

a) the ethoxylated nonionic surfactant is a material of the general formula: R- (EO)_w-OH wherein EO is a residue of ethylene glycol, w is 1-10 and R is a C_β- C₁₈ alkyl or alkyl phenyl group;

b) the composition further comprises a monocarboxylic fatty acid of general formula: R-_^-COOH wherein R. is a

C₈-C₁₈ alkyl group;

c) the composition further comprises a mixed propoxylated/ethoxylated nonionic surfactant of general formula: R₂- [ (EO) _x ( PO) _y] -OH wherein EO and PO are residues of ethylene and propylene glycol, x is 1-10, y is 1-10, and R₂ is a C_B-C₁ alkyl group, and,

d) the composition further comprises a monobranched alcohol of the general formula R₃-0H wherein R₃ is a branched C_β-C₁₈ alkyl group. A second aspect of the present invention provides a process for cleaning surfaces which comprises the step of treating the surface with a composition of pH 2-6 comprising: l-30%wt on product of an alkoxylated nonionic surfactant, less than 50%wt of total surfactant of anionic surfactant and 0.005-5%wt on product of a water soluble, anionic polymer having an average molecular weight of less than 1,000,000, wherein, the ratio of polymer : nonionic is 0.1:1 or less, said product being CHARACTERISED IN THAT :

a) the ethoxylated nonionic surfactant is a material of the general formula: R- (EO)_w-OH wherein EO is a residue of ethylene glycol, w is 1-10 and R is a C₈- C₁₈ alkyl or alkyl phenyl group;

b) the composition further comprises a monocarboxylic fatty acid of general formula: R.-COOH wherein R_j is a C_B-C_{l a} alkyl group;

c) the composition further comprises a mixed propoxylated/ethoxylated nonionic surfactant of general formula: R_?- [ (EO) _x (PO) _y] -OH wherein EO and PO are residues of ethylene and propylene glycol, x is 1-10, y is 1-10, and R₂ is a C₈-C₁₈ alkyl group, and,

d) the composition further comprises a monobranched alcohol of the general formula R₃-OH wherein R₃ is a branched C₈-C₁₈ alkyl group.

It is believed that the combination of the these components gives a superior anti foaming effect when the composition is diluted with sufficient water of pH >6 to raise the pH of the dilute composition to above 6. Detailed Description of the Invention

In order that the invention may be further understood it will be described hereafter with reference to preferred features and materials. Where percentages of components are used they are weight percents unless stated otherwise and where ratios are used they are weight ratios unless stated otherwise.

Ethoxylated Nonionics

Nonionic, ethoxylated surfactants are present in the compositions of the invention. These surfactants are believed to engage in a synergistic interaction with the polymer, to improve cleaning and aid the removal of soil subsequently deposited.

Suitable nonionic detergent active compounds can be broadly described as compounds produced by the condensation of ethylene oxide groups, which are hydrophillic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The length of the hydrophillic or polyoxyethylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophillic and hydrophobic elements.

Particular examples include the condensation product of aliphatic alcohols having from 8 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as a coconut oil ethylene oxide condensate having from 3 to 10 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains from 6 to 12 carbon atoms with 3 to 10 moles of ethylene oxide per mole of alkylphenol .

The preferred alkoxylated alcohol nonionic surfactants are ethoxylated alcohols having a chain length of C9-C11 and an EO value of at least 3 but less than 10. Particularly preferred nonionic surfactants include the condensation products of C₁₀ synthetic alcohols with 3-8 moles of ethylene oxide. The preferred ethoxylated alcohols have a calculated HLB of 10-16.

The material available in the marketplace as ' DOBANO 91.5EO' (TM) comprises a high proportion of a C₉__n alcohol with five moles of ethoxylation and has been found to be a suitable source of nonionic surfactant in compositions according to the invention.

The amount of nonionic detergent active to be employed in the composition of the invention will generally be from 0.1 to 30%wt, preferably from 1 to 20%wt, and most preferably from 3 to 10%wt for non-concentrated products. Concentrated products will have 10-20%wt nonionic surfactant present, whereas dilute products suitable for spraying will have 0.1-5%wt nonionic surfactant present. In particularly preferred embodiments of the invention, typical levels of ethoxylated nonionic surfactant fall in the range 5-8%wt for non-concentrates and 13-16% for concentrates .

Polymers

In the context of the present invention, anionic polymers are those which carry a negative charge or similar polymers in protonated form. Mixtures of polymers can be employed. It should be noted that the beneficial effect of anionic polymers is significantly reduced by the presence of anionic surfactants. For this reason , and for reasons elaborated below, the level of anionic surfactants in the compositions of the invention should be minimised.

The preferred polymers in embodiments of the present invention are polymers of acrylic or methacrylic acid or maleic anhydride, or a co-polymer of one or more of the same either together or with other monomers. Particularly suitable polymers include polyacrylic acid, polymaleic anhydride and copolyτners of either of the aformentioned with ethylene, styrene and methyl vinyl ether.

The most preferred polymers are maleic anhydride co- polymers, preferably those formed with styrene, acrylic acid, methyl vinyl ether and ethylene. Preferably, the molecular weight of the polymer is at least, 5000, more preferably at least 50,000 and most preferably in excess of 100,000. As the molecular weight increases the cleaning benefit of the polymer is reduced. 'VERSICOL Ell' (RTM) ex Allied Colloids has been found to be a suitable polymer.

Typically, the compositions comprise at least 0.01wt% polymer, on product. Preferably the level of polymer is 0.05-5.0wt% at which level the anti-resoiling benefits become particularly significant. More preferably 0.1- 3.0wt%, most preferably 0.2-1.5wt%, of polymer is present. We have determined that higher levels of polymer do not give significant further advantage with common dilution factors, while increasing the cost of compositions. However, for very concentrated products which are diluted prior to use, the initial polymer level can be as high as 5%w. Fattv Acids

As mentioned above, it is believed essential that the monocarboxylic fatty acid is capable of forming a calcium salt which is no more than sparingly soluble in aqueous solutions of foaming surfactants.

The monocarboxylic fatty acid is typically present at a level of 0.2-4.5%wt on product: the upper levels of this range being used for more highly concentrated compositions .

Preferably the monocarboxylic fatty acid content is in the range 0.2-3.0%wt, most preferably in the range 0.3-2.0%wt. In embodiments of the invention the level of fatty acid is preferably such that the ratio of ethoxylated nonionic to monocarboxylic fatty acid falls in the range 4:1-1:1, more preferably 3:1-2:1 as nonionic: moncarboxylic fatty acid.

More preferably, the monocarboxylic fatty acid is a mixture of saturated fatty acids having an average carbon chain length in the range 10-16, more preferably 12-14. Coconut fatty acids or a synthetic equivalent thereof are particularly preferred.

Propoxvlated/Ethoxvlated Nonionics

The mixed propoxylated/ethoxylated nonionic surfactant preferably has x is 4-8, y is 1-5.

Preferably R₂ is a C₉-C₁₇ alkyl group, i.e. while a range of materials may be present the average chain length is of 9-17 carbons. BIODAC 6S50 (TM) , a commercially available (C12- 15)6EO/2PO ethoxylated alcohol, is a suitable propoxylated/ethoxylated nonionic for use in embodiments of the present invention. This C12-C15 alcohol condensate has a cloud point in distilled water of 36 - 41°C, a mean molecular weight: 534 - 623 and a carbon chain composition of:

C12 = 41% C13 = 10%

C14 = 37%

C15 = 12%

It is preferable that the weight ratio of the fatty acid to the propoxylated/ethoxylated nonionic falls in the range 1:3-1:10 as fatty acid: nonionic. Ratios of 1:5-1:8 are particularly preferred, with a ratio of 1:6 being used in typical embodiments of the invention.

Preferred levels of the propoxylated/ethoxylated nonionic range from 2-10%wt with levels of 3-6%wt on product being preferred.

Monobranched Alcohol

The monobranched alcohol may be added as a separate component or, more conveniently, use may be made of the residual monobranched alcohol which is present in certain ethoxylated nonionic surfactants. In preferred embodiments of the invention no additional monobranched alcohol is added to the composition.

It is believed that during the ethoxylation process which is commonly used to prepare ethoxylated nonionic surfactants from alcohol feedstocks, the ethoxylation of linear alcohols proceeds more quickly than that of the branched alcohols. Thus, where a mixed alcohol feedstock is used, i.e. a synthetic mixture of linear and branched alcohols, the reaction will initially proceed with the ethoxylation of the linear alcohols while the branched alcohols will react to a lesser extent. The product obtained from this process can comprise a residue of unreacted monobranched alcohol .

The material available in the marketplace as ' DOBANOL

91.5EO' (TM) comprises a high proportion of a C₉__u alcohol with five moles of ethoxylation and sufficient free monobranched alcohol to be a suitable source of both monobranched alcohol and ethoxylated nonionic surfactant in compositions according to the invention.

EH:

While the pH of the composition can fall in the range 2.0- 6.0 it is preferable that the pH of the composition is 3.0-4.5. It is believed that above pH 4.5 the benefit of the polymer falls off and below pH 3.0 surface damage may occur. The preferred pH range is 3.2-4.0. The most preferred pH is around 3.75. Compositions having a pH of less than 3.0 will damage enamel surfaces.

Citric acid is particularly preferred to regulate the acidity balance. Typical levels of citrate range from 0.5-5%, with higher levels of 5-10% being used in concentrates and lower levels of 0.1-1% being used in sprayable products. Citric can be replaced by other suitable buffering agents to maintain the pH in this range. These are preferably other polycarboxylic fatty acids . Citric is also preferred for environmental reasons, a lack of residues and it is believed to be the most cost/weight-effective acid.

Sodium hydroxide is generally used to regulate the pH to the required level.

Antimicrobials

Optional antimicrobial agents used in the compositions of the present invention are benzoic acid derivatives, dicarboxylic acids, C.-C₆ alkanols and mixtures thereof

Typical levels of the antimicrobial agent in formulations range from 0.01 to 8%, with levels of 0.05-4wt%, particularly around 2% being preferred for normal compositions and up to two or four times that concentration being present in so called, 'concentrated' products. Although both the normal and concentrated products can be used neat it will be commonplace for these to be diluted by the user before use. For sprayable products, which are seldom diluted prior to use, the concentration of the antimicrobial agent will be in the range 0.05-0.5%wt.

In general, whatever the strength of the product the ratio of the nonionic surfactant to the antimicrobial agent will preferably be in the range 50:1 to >1:1, more preferably 30:1 to >1 : 1 i.e. an excess of nonionic will be present relative to the antimicrobial.

-Amongst the benzoic acid derivatives a preferred antimicrobial agent is salicylic acid, which gives better hygiene results than benzoic and shows a very marked improvement as compared with sorbic acid. Alternative benzoic acid derivatives are the polyhydroxyl carboxylic acids in which at least two hydroxyl groups are present and at least one of the hydroxyl groups is ortho- to the carboxylic acid group. The remaining hydroxyl group or groups can be in the remaining ortho-, para- or meta- configurations. The polyhydroxyl carboxylic acids exhibit the same synergy as the mono hydroxylic acid derivative (salicylic acid) but are believed to be less irritant .

We have determined that, in the presence of nonionic surfactant, salicylic acid derivatives methylated at positions 3-6 exhibit an additional antimicrobial action over that obtained with salicylic acid. This is particularly true for gram positive bacteria and yeasts.

The preferred alkyl substituted ortho-hydroxy aromatic carboxylic acid of the general formula:

R.-C₆H₃(OH) (COOH)

wherein R, is C^^ alkyl, and the hydroxyl group is ortho to the carboxyl group on the benzene ring structure.

Preferably the alkyl substituted ortho-hydroxy aromatic carboxylic acids are substituted at the 3, 4 or 5- position, relative to the carboxyl group. Preferred chain lengths for the alkyl group are C, _₆ , with methyl substituted acids being particularly preferred. Particularly preferred acids are 2-hydroxy 5-methyl benzoic acid, 2-hydroxy 4-methyl benzoic acid and 2- hydroxy 3-methyl benzoic acid.

Amongst the dicarboxylic acids, succinic acid is preferred. Amongst the alkanols, the C₂-C₅ alcohols are preferred. These include ethanol and isopropanol. Isopropanol has been found to be particularly effective and is particularly preferred among the alkanols.

Minors and Optional Components

The composition according to the invention can contain other minor, inessential ingredients which aid in their cleaning performance and maintain the physical and chemical stability of the product.

For example, the composition can contain detergent builders. In general, the builder, when employed, preferably will form from 0.1 to 25% by weight of the composition.

Optionally, the composition can include one or more amphoteric surfactants, preferably betaines, or other surfactants such as amine-oxide and alkyl-amino- glycinates. Betaines are preferred for reasons of cost, low toxicity (especially as compared to amine-oxide) and wide availability. It is believed that amphoteric surfactants show a slight synergy with some organic acids (when present) as regards antimicrobial effects.

Typical betaines in compositions according to the invention are the amido-alkyl betaines, particularly the amido-propyl betaines, preferably having an aliphatic alkyl radical of from 8 to 18 carbon atoms and preferably having a straight chain. These betaines are preferred as they are believed to comprise relatively low levels of nitrosamine precursors although other betaines, such as alkyl betaines, can be used in the compositions of the invention. Typical levels of amphoteric range from 0.01 to 8%, with levels of l-5wt%, particularly around 2% being preferred for normal compositions and up to four times the concentration being present in so called, concentrated products. As with the nonionic surfactant, lower levels or around 0.05-1% will be employed in sprayable products and higher levels of, typically, around 4%wt in concentrates. In general, the ratio of the betaine to the aromatic carboxylic acid will be in the range 1:3 to 3:1, with approximately equal levels on a weight basis being preferred.

Metal ion sequestrants, including ethylenediaminetetraacetates , aminopolyphosphonates (such as those in the DEQUEST^R range) and phosphates and a wide variety of other poly-functional organic acids and salts, can also optionally be employed. It is believed that the hygiene performance of the composition is improved by the presence of a metal ion sequesterant .

Hydrotropes, are useful optional components. It is believed that the use of hydrotropes enables the cloud point of the compositions to be raised without requiring the addition of anionic surfactants. The presence of both anionic surfactants and betaine is believed to be detrimental to the formulations as these surfactants interact with the amphoterics, when present, and to form a complex which inhibits the synergistic hygiene activity of the amphoterics with the organic acid. Preferably the formations according to the invention are free of anionic surfactants when betaine is present, or contain low levels of anionic surfactants, i.e. less than 50% of the total level of surfactant present and preferably less than 50% of the level of the betaine in the product. Anionics are compatible with the solely alcohol ethoxylate based compositions of the present invention when the level is below 50%wt of the total surfactant present, but their level should be minimised in view of their interactions with the polymers . Preferably the level of anionic is below 30% of the total surfactant content of the composition and more preferably below 10% of the surfactant content. It is possible to make compositions which contain little or no anionic surfactant.

Suitable hydrotropes include, alkali metal toluene sulphonates, urea, alkali metal xylene and cumene sulphonates, polyglycols, >20EO ethoxylated alcohols, short chain, preferably C₂-C₅ alcohols and glycols. Preferred amongst these hydrotropes are the sulphonates, particularly the cumene, xylene and toluene sulphonates.

Typical levels of hydrotrope range from 0-5% for the sulphonates . Correspondingly higher levels of urea and alcohols are required. Hydrotropes are not always required for dilute, sprayable products, but may be required if lower EO or longer alkyl ethoxylates are used or the cloud point needs to be raised considerably. Typically, the cloud point of the final composition should preferably be in the range 45-50 Celcius. The cumene sulphonate is the most preferred hydrotrope. For ethoxylated nonionic levels of around 7%wt on product levels of SCS will generally be in the range 0.6-0.8wt% for ethoxylated nonionic levels of around 14%wt levels of SCS will generally be in the range 1.0-1.2wt%.

Compositions according to the invention can also contain, in addition to the ingredients already mentioned, various other optional ingredients such as, solvents, colourants, optical brighteners, soil suspending agents, detersive enzymes, compatible bleaching agents, gel-control agents, freeze-thaw stabilisers, further bactericides , perfumes and opacifiers. A suitable preservative is PROXEL LV (TM) .

It is preferred that compositions of the invention are essentially free of solvents, i.e. that they comprise less than 0.5% of glycol ethers and C1-C6 linear alcohols.

The most preferred formulations according to the present invention, excluding minors such as perfumes, preservative and colour, comprise:

a) 5-16%wt of an ethoxylated mixed linear and branched alcohol nonionic surfactant having an ethoxylation value of 5-10 and an average carbon chain length of 8-14;

b) 0.2-1.5%wt of a polymer of acrylic or methacrylic acid or maleic anhydride, or a co-polymer of one or more of the same either together or with other monomers having an average molecular weight of 50000- 1000000;

c) 2-10% of a 4-8EO/1-5PO ethoxylated alcohol with an average carbon chain length of 12-15;

d) 0.3-2.0%wt of a saturated fatty acid having an average carbon chain length of 12-14, and;

e) 0-5%wt of an alkali metal sulphonate hydrotrope;

In order that the invention may be further understood it will be described further by way of the following non- limiting examples and with reference to the sole accompanying figure. Examples

The following compositions (A and B) were prepared by mixing the following components.

A% B%

Nonionic (Dobanol 91.5) .0 14.0 Nonionic EO/PO (BIODAC L6S50) 0 6.0 Polyacrylate Versicol Ell) 5 1.0 Coco Fatty Acid 5 1.0 Citric acid 6 1.2

Sodium Hydroxide -- to pH 3.75 --

Sodium Cumene Sulphonate -- to cp 45-50 -- Preservative (Proxel LV) 0.016 0.016 Perfume 0.38-0.5 0.76-1.0 Water qv qv Viscosity ( Pas) 20 80

Both were stable compositions.

The foam profile of Example A was determined during dilution with Italian tap water of 24 French hardness, measuring the foam height as the product was diluted from a concentration of 24 g/1 to 3 g/1 to model the rinsing process. Results are shown in the accompanying figure.

From the figure it can be seen that as the composition is diluted the pH of the diluted composition rises and the both the foam height and the foam persistence are reduced markedly .

Claims

1. A cleaning composition of pH 2-6 comprising l-30%wt on product of an alkoxylated nonionic surfactant, less than 50%wt of total surfactant of anionic surfactant and 0.005-5%wt on product of a water soluble, anionic polymer having an average molecular weight of less than 1,000,000, wherein, the ratio of polymer : nonionic is 0.1:1 or less, said product being CHARACTERISED IN THAT :

a) the ethoxylated nonionic surfactant is a material of the general formula: R- (EO)_w-OH wherein EO is a residue of ethylene glycol, w is

1-10 and R is a C₈-C₁₈ alkyl or alkyl phenyl group;

b) the composition further comprises a monocarboxylic fatty acid of general formula:

Ri-COOH wherein R. is a C₈-C₁₈ alkyl group;

c) the composition further comprises a mixed propoxylated/ethoxylated nonionic surfactant of general formula: R₂- [ (EO) _x ( PO) _y] -OH wherein EO and PO are residues of ethylene and propylene glycol, x is 1-10, y is 1-10, and R₂ is a C_fi-C₁₈ alkyl group, and,

2. Composition according to claim 1 wherein the ethoxylated nonionic surfactant has an EO value of at least 3 but less than 10.

3. Composition according to claim 1 wherein the anionic polymer is selected from the group comprising polyacrylic acid, polymaleic anhydride and copolymers of either of the aformentioned with ethylene, styrene and methyl vinyl ether.

4. Composition according to claim 1 wherein the level of fatty acid is such that the ratio of ethoxylated nonionic to monocarboxylic fatty acid falls in the range 4:1-1:1

5. Composition according to claim 1 wherein the propoxylated/ethoxylated nonionic surfactant preferably has x is 4-8, y is 1-5.

Composition according to claim 1 which comprises:

b) 0.2-1.5%wt of a polymer of acrylic or methacrylic acid or maleic anhydride, or a co- polymer of one or more of the same either together or with other monomers having an average molecular weight of 50000-1000000;

e) 0-5%wt of an alkali metal sulphonate hydrotrope.

7. A process for cleaning a surface which comprises the step of treating the surface with a composition according to any one of claims 1-6 in neat or dilute form and subsequently rinsing with water.