WO1999061567A1

WO1999061567A1 - Lubricant compositions

Info

Publication number: WO1999061567A1
Application number: PCT/EP1999/003237
Authority: WO
Inventors: Michael Peter Corby
Original assignee: Unilever N.V.; Unilever Plc
Priority date: 1998-05-29
Filing date: 1999-05-06
Publication date: 1999-12-02
Also published as: AU4770599A; AR018389A1

Abstract

An aqueous antimicrobial conveyor track lubricant composition is provided, comprising: (a) an effective lubricating amount of neutralised C8-C22 fatty acid soap; (b) an effective antimicrobial amount of silver ions; (c) an amount of base sufficient to set the pH of the composition at from 8 to 11. Furthermore, the invention provides a concentrate, which upon dilution with water, forms this aqueous antimicrobial composition. The invention also relates to the use of silver ions as an antimicrobial constituent in a soap based conveyor track lubricant composition.

Description

Lubricant Compositions

Field of the invention

The present invention relates to lubricant compositions. More specifically, it relates to lubricant compositions for use in lubricating the tracks which convey bottles, cans and similar containers.

Background of the invention

Beverages are sold in a variety of containers such as glass bottles, plastic bottles, plastic containers, cans or waxed carton packs . These containers are conveyed through a number of stations in a plant where they are filled with the desired beverage; the containers are conveyed from one station to another by a track which is usually of stainless steel when the containers are glass bottles, or of plastic material such as polypropylene or an acetyl resin (sold under the name Delrin) when the containers are other than glass bottles. Such tracks will hereinafter be referred to as "conveyor track".

When the containers are being filled with beverage, at a filling station on the packaging plant they are kept at a fixed position under the filling station while the conveyor track continues to move forward below the container. There are other locations in the plant, e.g. when the container is being closed and sealed, when the container must also be kept stationary while the conveyor track continues to move. In addition, blockage of the path along which the containers are travelling can occur if a container falls over or gets jammed. In such instances it is important that the conveyor track is properly lubricated so that the track can continue to move even though the containers on the track are temporarily prevented from advancing.

For many years, lubricants based on neutralised fatty acids or soaps have been used in dilute solutions to lower the friction between the containers and the conveyor tracks. These soap-based lubricants are generally recognised as being excellent lubricants both providing a trouble free packaging operation. Furthermore, when properly formulated they are compatible with the materials, such as the inks, used to print beverage cans and with the materials of the beverage bottles to be transported (such as polyethylene terephthalate) .

Other types of conveyor track lubricants frequently applied are synthetic lubricants based on amines, betaines and imidazolines . These synthetic lubricants are recognised generally as being inferior to the soap based lubricants as far as coefficients of friction are concerned. Besides, such synthetic lubricants are generally not compatible with the printing inks used on beverage cans.

On the other hand, the synthetic lubricants are generally recognised as being effective in controlling microbiological growth on the conveyor chains themselves. Hence they are used where ink compatibility is not a problem and/or where the requirements of lubricity are not so severe for example when packaging speeds are relatively low. If packaging speeds are high and/or ink compatibility is essential, then the soap based lubricants are preferred.

However, soap based lubricants have always exhibited the problem that they exhibit a lack of microbicidal effect. The consequence of this lack of microbiological kill is that within relatively short periods of time the conveyor tracks generally take on a grey slimy appearance, resulting in both unsighty operation and unpleasant odour.

In order to avoid this happening, conveyor track systems used in the processing and packaging of beverages are commonly treated with both an antimicrobial compound and a lubricating compound, in order to reduce the population of micro-organisms, such as bacteria, yeast and mould, which tend to grow on the system and produce slime.

Unfortunately, those anti-microbial compounds known to be particularly effective for controlling microbiological populations on a conveyor track system are difficult to combine with fatty acid soaps because many of these antimicrobial compounds are deactivated by anionic fatty acids. For example, cationic quaternary ammonium compounds, which are widely recognised for their antimicrobial activity are not generally employed as an antimicrobial compound in combination with lubricants based on fatty acid soap on conveyor track systems, because they tend to be deactivated by the anionic fatty acid soap.

However, because of their effectiveness as an antimicrobial compound, quaternary ammonium salts have been employed in lubricating compositions which are fatty acid free. For instance, WO 96/02616 discloses a conveyor track biocidal lubricant comprising a phosphate ester, as the lubricating ingredient, and further containing an aromatic biocidal quaternary ammonium compound.

However, such fatty acid free lubricant compositions have generally proven to be less effective for lubricating the load bearing surface of a conveyor track system than those which are based on fatty acid soap.

Accordingly, it is an object of the present invention to produce a micribiologically effective conveyor lubricating composition showing both effective lubricity and effective microbiological action.

It has surprisingly been found, that this object can be achieved by a fatty acid soap based lubricant composition further containing silver ions.

Definition of the invention

Accordingly, in one aspect the present invention provides an aqueous antimicrobial conveyor track lubricant composition comprising (a) an effective lubricating amount of C₈ - C₂₂ fatty acid soap;

(b) an effective antimicrobial amount of silver ions;

(c) an amount of base sufficient to set the pH of the composition at from 8 - 11. Usually, an effective amount of a sequestrant to control any hard water salts in the solution at these alkaline pHs, is also present in the composition of the invention. In an other aspect, the invention provides a concentrate which, upon dilution with water, forms an aqueous antimicrobial track lubricant composition according to the invention. In a further aspect, the invention relates to the use of silver ions as an antimicrobial constituent in a soap based conveyor belt lubricant composition.

Detailed description of the invention

Dilute lubricant composition

For many years, silver ions have been known to possess biocidal properties.

We have now unexpectedly found that the use of very low levels of silver ions (either in the form of a complex, preferably silver nitrate, or as such) in soap-based conveyor track lubricants will not only control the growth of micro-organisms but actually kill those organisms in a diluted chain lubricant system.

For environmental reasons, only very low levels of silver ions would be allowable in aqueous track lubricant "use" compositions. That is likely to be the reason that nobody has thought of coupling the biocidal effect of silver with a chain lubricant system before.

Preferably, the silver ions in component (b) of the aqueous lubricant composition of the invention are present in an amount of 0.1 ppm to 5 ppm, based on the total weight of the composition. The preferred concentration of the silver ions in component (b) is 0.25 - 1 ppm based on the weight of the aqueous composition. If the amount of the silver ions is too low, negligeable biocidal activity is obtained. Too high a concentration will affect adversely the environmental acceptability and the cost of the product. Generally, the aqueous lubricant composition of the invention comprises an effective lubricating amount of C8- C22 fatty acid soap, C14-C18 fatty acid soap being preferred. The fatty acid soap is desirably present in the aqueous lubricant composition of the invention at a level of from 0.0025 to 1.25% by weight.

The identity of the base in component (c) of the aqueous composition of the invention is not critical provided that adjustment of the pH of the lubricant into the required range can be effected without affecting adversely the properties of the lubricant.

Preferably, an alkanola ine base or an inorganic base of the type MOH, in which is a metal from group I of the periodic table, is used. Where an alkanolamine base is to be used, this is preferably methanola ine or triethanolamine. The preferred inorganic base is NaOH or

KOH.

The amount of the base is such that the fatty acid soap present is solubilized completely and that the pH of the aqueous lubricant composition of the invention is in the range of from 8 to 11, preferably from 8 to 9.5.

Concentrate

According to a further aspect of the present invention, there is provided a concentrate which is suitable for preparing an aqueous track lubricant composition according to the present invention, by dilution with water. Said concentrate comprises (a) 5% to 25% by weight of the fatty acid soap, (b) 25 to 500 ppm of the silver ions, and (c) a sufficient amount of base to result in a pH upon dilution of from 8 to 11.

In a preferred embodiment, the concentrate of the invention further comprises a betaine, preferably a betaine of formula C₁₂-Cι₄ -N (CH₃) ₂ -CH₂COOH. Whilst betaines are not themselves generally biocidal, incorporation of such betaines in the present concentrate was found to increase the biocidal activity of the silver ions present therein.

Optionally, the concentrate further comprises a sequestrant such as EDTA. The presence of the sequestrant is useful in hard water areas so as to form complexes with metal ions such as calcium ions which would otherwise precipitate components of the concentrate. Typically, the sequestrant is present in an amount of up to 10% by weight, preferably from 1 to 5% by weight, based on the total weight of the concentrate .

The concentrate of the invention may further comprise other additional components. For example, a nonionic alcohol may be included in the concentrate composition as a nonionic surfactant to enhance the wetting and detergency properties of the concentrate.

Typical nonionic surfactants include ethoxylated alcohols of the type R₆- (OCH₂CH₂) _mCH₂-OH in which R₆ is a C₆ to C₂₀ alkyl group and m is in the range of from 1 to 50. The value of m is selected in accordance with the intended final use of the lubricant composition. As m increases the nonionic surfactant gives higher detergency but also more foam. Typically, the nonionic surfactant is present in the concentrate in an amount of up to 20% by weight, preferably 0.5 to 10% by weight, based on the total weight of the concentrate. Synperonic A3 (sold by ICI - C.A.S. registry number 68213-23-0) is a good example of a nonionic surfactant useful in the present invention.

As a further optional component of the concentrate, alcohols or polyols may be used to modify the viscosity of the concentrate. Typically, isopropanol is used for this purpose in an amount of up to 20% by weight, preferably 5 to 15% by weight, based on the total weight of the concentrate .

Hydrotropes may also be present in the concentrate primarily to impart stability to the formulation. A typical hydrotrope is urea, which is preferably present in an amount of around 15% by weight, based on the total weight of the concentrate.

The lubricant composition of the invention should be able to eliminate or at least control the level of microbial contamination on the slats and undersites of the conveyor.

For preparing the aqueous lubricant composition from said concentrate, the concentrate is diluted in water in the range 0.1 to 5%, preferably 0.5 to 2% (volume/volume). Water used for the dilution is preferably soft or softened. The exact dilution of the concentrate depends on factors such as the speed of the conveyor track, the type of package or container being carried by the track, the total loading on the track and the amount of soiling caused by spillage .

Dilution of the lubricant concentrate is normally performed at a central dispenser, and the diluted lubricant composition is then pumped to spray nozzles at the point of use. There are some areas of the conveyor track that require very little lubricant. Typically these are the zones before the filler and before the pasteurizer. In these regions secondary dilution is often employed. On the other hand, the lubricant is likely to be at its highest use concentration at and after the filler.

A further embodiment of the invention, giving greater flexibility and hence probably reduced cost for equivalent effect, is to use the aforesaid lubricant (s) without the silver incorporated into the concentrate form and to add silver ions directly to the water used for dilution of the lubricant or to add the silver ions to the diluted aqueous lubricant solutions. A great range of dilutions for a silver containing 'additive' is available but again the silver content of the 'use solution' is in the range 0.1 to 5 ppm as silver. This can be arrived at by high dilution (typically (0.01%v/v) of a 1% solution of silver ions or by the use of a 1% v/v solution of a 0.01% silver containing solution. The actual prefered dilution will depend heavily on the equipment to be used for the dilution operation.

The invention will now be further illustrated by the following Examples. Compositions

Example A

A liquid soap based track lubricant of the prior art was made by mixing the following ingredients, of which the levels are within the indicated ranges: Ingredient %wt

Potassium hydroxide 5-10

EDTA 0-5 Olefin sulphonate 10-20

Fatty acid 15-25

Water balance

Examples B-D Three other liquid soap based lubricants of the prior art were used, having the following compositions:

Example B Example C Example D

Ingredients (%wt) (%wt) (% t)

EDTA 0-2 3.0 -

Potassium hydroxide 2-5 - 2-5

Monoethanolamine - 3.2 -

Triethanolamine - - 2-5

Fatty acid 15-25 13.6⁽¹⁾ 15-20

Olefin sulphonate 0-10 1.0⁽³⁾ -

Isopropanol - 8.5 -

Nonionic surfactant - 5.1⁽²> 0-4

Preservative 0-5 0.5⁽⁴⁾ -

Water balance balance balance

Notes : A. The ingredients of the lubricant of Example C for which exact concentrations are given, are: ( 1 ) oleic acid

(2) C13-C15 7E0 ethoxylated alcohol

(3) C14-C16 alpha olefin sulphonate

(4) NN' methylene bis (5 methyloxazolidine) B. With regard to the lubricants of Examples B and D, the levels of the ingredients are within the indicated ranges.

Examples 1-4 Liquid antimicrobial soap-based track lubricant according to the present invention were prepared by adding to the lubricant compositions of Examples A-D 170 ppm silver nitrate (equal to 100 ppm silver ions) .

As a result, the composition of the lubricant of Example 1 is equal to that of Example A, apart from the 170 ppm silver nitrate present therein. Similarly, apart from the

170 ppm silver nitrate level, the compositions of the lubricants of Examples 2-4 are equal to those of respectively Examples B-D.

Testing procedure

Aqueous lubricant use solutions containing 1% vol. of the lubricant compositions of Examples A and 1 were prepared by diluting said lubricant compositions with distilled water. Furthermore, further diluted aqueous use solutions of these lubricant compositions -said solutions having concentrations of 0.5%v/v respectively 0.75 %v/v - were prepared by dilution with softened water.

In addition, aqueous lubricant use solutions containing 0.5% vol. of the lubricant compositions of Example B-D and

2-4 were prepared by diluting said lubricant compositions with distilled water. While applying these use solutions, suspension tests according to standard method BS 3286 were carried out so as to measure the antimicrobial 'killing' performance (measured in terms of log-reduction) of the aqueous use solutions concerned with respect to Pseudomonas Aeruginosa (NCMIB 10421) .

Log reductions were measured at exposure times of 5 minutes, 10 minutes, 30 minutes, and 60 minutes. The results of the tests with the 1% v/v use solutions of Examples A and 1 are shown in Table 1.

TABLE 1

Product Log reduction in Pseud. Aeruginosa t=5min. t=10min. t=30min. t=60min. Lubricant of Ex.A <1.4 <1.4 <1.4 <1.4 Lubricant of Ex.l 2.4 4.7 >6.1 >6.1

When comparing the log reduction figures for the prior art lubricant of Example A with the lubricant according to the invention of Example 1, it can be concluded that the presence of the silver ions results in a drastic increase of the 'killing' performance of the lubricant. Considering the low concentration of the silver ions applied (1 ppm in the aqueous 'use' solution) , this effect is quite unexpected.

The results of the tests with the 0.5%v/v and 0.75%v/v use solutions of Examples A and lare shown in Table 2. TABLE 2

Product Cone . Log reduction in Pseud. Aeruginosa %v/v t=5min. t=10min. t=30min. t=60min. Lubr . of Ex. .A 0.5 3.3 3.8 4.6 4.7

Lubr. of Ex. .A 0.75 4.4 4.9 3.4 5.1

Lubr. of Ex, .1 0.5 4.1 6.4 6.1 >6.4

Lubr. of Ex .1 0.75 5.6 >6.4 >6.4 >6.4

When considering Table 2, it can be noticed that also at concentrations of 0.5%v/v and 0.75%v/v the lubricant of Example 1 (according to the present invention) shows a better 'killing performance' than the prior art lubricant of Example A.

The results of the tests with the 0.5%v/v use solutions of Examples B-D and 2-4 are shown in Table 3.

TABLE 3

Product Log reduction in Pseud. Aeruginosa t=5min. t=10min . t=30min. t=60m:

Lubricant of Ex. B 3.3 3.4 3.4 3.6 Lubricant of Ex. 2 6.6 7.0 >7.6 >7.6 Lubricant of Ex. C 3.6 3.6 3.7 3.8 Lubricant of Ex. 3 5.6 >7.6 >7.6 >7.6 Lubricant of Ex. D 4.0 4.1 4.2 4.2 Lubricant of Ex. 4 5.8 6.3 7.2 >7.6

When considering the log reduction figures shown in Table 3, it can be derived that, for all these commercial lubricants, the addition of silver ions results in a drastic increase of the 'killing' performance of the lubricant .

Claims

1. An aqueous antimicrobial conveyor track lubricant composition, comprising

(a) an effective lubricating amount of neutralised C₈- C₂₂ fatty acid soap;

(b) an effective antimicrobial amount of silver ions; and

(c) an amount of base sufficient to set the pH of the composition at from 8 to 11.

2. An aqueous lubricant composition according to claim 1, wherein the silver ions originate from silver complexes.

3. An aqueous lubricant composition according to claim 1 or 2, wherein the silver ions are present at a concentration of 0.1 to 5.0 ppm.

4. An aqueous lubricant composition according to any of claims 1-3, wherein the fatty acid soap is C╬╣₄- C╬╣₈ fatty acid soap.

5. An aqueous lubricant composition according to any of claims 1-4, wherein the fatty acid soap is present at a concentration of from 0.0025% to 1.25% by weight.

6. An aqueous lubricant composition according to any of claims 1-5, wherein the base of component (c) is selected from the group consisting of an alkanolamine base and an inorganic base of the type MOH, in which M is a metal from group I of the periodic table.

7. A concentrate suitable for preparing an aqueous conveyor track lubricant composition according to any of the preceeding claims, wherein the concentrate comprises

(a) 5% - 25% by weight of the fatty acid soap;

(b) 12.5 to 500 ppm of the silver ions;

(c) a sufficient amount of the base to result in a pH upon dilution of from 8 - 11, wherein %wt is based on the weight of the concentrate.

8. A concentrate according to claim 7, further comprising a betaine .

9. A concentrate according to claim 7 or 8, further comprising a sequestrant, in an amount of up to 10% by weight .

10. Use of silver ions as an antimicrobial ingredient in an aqueous, soap based conveyor track lubricant composition having a pH of 8 to 11.

11. Use of silver ions as an antimircobial ingredient according to claim 10, wherein the silver ions are added directly to the water of dilution prior to the dilution of the lubricant with said water or are added directly to the aqueous lubricant composition after dilution thereof.