CLEANING COMPOSITION

Abstract

A composition for cleaning membranes used in food processing comprising an amine oxide and an alkyl sulfate, the composition maintaining good cleaning performance whilst leaving a low residue of surfactant on the membrane that is cleaned using the composition. A method of use of the composition is also presented.

Claims

11: A method of cleaning a membrane comprising: applying a composition comprising at least one amine oxide and at least one alkyl sulfate to the membrane; and rinsing the membrane to remove at least a majority of the composition from the membrane.

12: The method of claim 11, wherein the membrane comprises less than 50 mg/m.sup.2 of the composition after rinsing the membrane.

13: The method of claim 11, wherein the membrane comprises less than 20 mg/m.sup.2 of the composition after rinsing the membrane.

14: The method of claim 11, wherein the at least one amine oxide comprises lauryldimethylamine oxide.

15: The method of claim 11, wherein the at least one alkyl sulfate comprises 2-ethylhexyl sulfate.

16: The method of claim 11, wherein the composition comprises from 10 ppm to 1000 ppm of the at least one amine oxide.

17: The method of claim 11, wherein the composition comprises from 10 ppm to 500 ppm of the at least one alkyl sulfate.

18: The method of claim 11, wherein the composition comprises a plurality of amine oxides.

19: The method of claim 11, wherein the at least one amine oxide comprises lauryldimethylamine oxide, and wherein the at least one alkyl sulfate comprises 2-ethylhexyl sulfate.

20: The method of claim 11, wherein the membrane is used to process a food product or a beverage.

21: The method of claim 20, wherein the membrane is used to process a dairy product, a fruit juice, or an alcoholic beverage.

22: The method of claim 11, wherein the membrane is a polymeric membrane.

23: The method of claim 22, wherein the membrane comprises polyamide, polyether sulfone, polysulfone, polyvinyldifluoride, polypropylene, or polyacrylnitrile.

24: The method of claim 11, wherein the membrane is a ceramic membrane.

25: The method of claim 11, wherein the membrane comprises a polymeric backing layer.

26: The method of claim 11, wherein the composition has a pH of more than 8.

27: The method of claim 11, wherein the composition has a pH of less than pH 5.

28: The method of claim 11, wherein the composition further comprises an enzyme.

29: The method of claim 11, wherein the composition further comprises a stabilizer.

30: A method of cleaning a membrane comprising: diluting a concentrated composition comprising at least one amine oxide and at least one alkyl sulfate; applying the diluted composition to the membrane; and rinsing the membrane to remove at least a majority of the composition from the membrane.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0073] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

[0074] FIG. 1 is a chart showing the cleaning performance of test cleaning compositions and surfactant residue remaining on a membrane cleaned using the compositions.

DETAILED DESCRIPTION

[0075] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts.

[0076] The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

[0077] To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an”, and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

[0078] The behaviour of a number of surfactants on a porous structure such as a membrane was tested on common ultrafiltration membranes as follows.

Method

[0079] Different types of commercially available polymeric ultrafiltration membranes were tested. Membrane materials: PES: polyether sulfone, PS: polysulfone. Membrane backing material: PE: polyethylene, PP: polypropylene. For example, the HFK 131 membrane has a polyether sulfone membrane with a polyethylene backing material this is indicated in table 1 below as PES/PE.

Pre-Cleaning of Membranes

[0080] Membranes were pre-rinsed with deionised water (DI water) at 2 m.sup.3/hour for 5 minutes at standard conditions (room temperature and 1 bar pressure). The membranes were then cleaned using citric acid (pH 2.5) for 20 minutes at 40° C., before being rinsed in DI water for 10 minutes. The membranes were further cleaned using sodium hydroxide (NaOH) at pH 11.5 for 20 minutes at 40-45° C.

[0081] Before and after each stage of cleaning of the membrane, the pure water flux was determined to monitor the concentration of any contaminants on the membranes

Surfactant Screening

[0082] 1000 ppm active surfactant solution (in DI water) was recirculated at 40-45° C., 2 bars, in alkaline conditions pH 11.5 at a feed flow of 5 m.sup.3/h, through 0.15 m.sup.2/membrane type for 30 minutes on pre-cleaned and conditioned ultrafiltration membranes (by the process described above).

[0083] One surfactant (sodium 2-ethylhexyl sulfate) was tested in both alkaline and acidic conditions (pH 2.5).

[0084] Any residue on the membranes was extracted with acetonitrile at 80° C., 100 bars with Accelerated Solvent Extraction (ASE) in two cycles. The resulting solution was analyzed by liquid chromatography to determine the surfactant concentration extracted from the membrane surface.

[0085] The membranes were then rinsed in DI water for 10 minutes at 2 m.sup.3/hour and 1 bar. Samples were taken every minute from concentrate and total permeate side for surface tension measurements. Again, pure water flux was determined as previously described. The cleaned membranes were then analysed to determine the mass of surfactant residue that remained on the membrane after the above cleaning procedure.

[0086] The results of a variety of different commercially available surfactants and surfactant blends tested on membranes with a porous structure are shown below in Table 1.

TABLE-US-00001 TABLE 1 Summary of test results showing the residue remaining on test membranes in mg/m.sup.2. Where blends of surfactants were used, x/y gives the residue of surfactant X and surfactant Y respectively. Concentrations of surfactants are 1000 ppm unless otherwise stated below. Polymer/ Cleaning composition Membrane Backing A B C D E F G HFK 131 PES/PE 950 400 200 4 6 0.04/10   0.04/3   UFX pHT PS/PP* 550 100 60 1 0.5 1/11 2/9 GR6 1PP PS/PP 850 300 100 1 3 0.5/14   0.2/5   GR70PE PS/PE 1750 300 300 2 2 1/13  1/30 UP010 PES/PE 1100 500 200 2 5 1/19 1/6 A is 2-propylheptanol ethoxylales (10M ethylene oxide). B is lauryldimethylamine oxide C is alkylbenzene sulfonate sodium salt (C.sub.10-C.sub.14). D is sodium 2-ethylhexyl sulfate, acidic. E is sodium 2-ethylhexyl sulfate, alkaline. F is sodium 2-ethylhexyl sulfate, alkaline 300 ppm + lauryldimethylamine oxide 100 ppm. G is sodium 2-elhylhexyl sulfate, alkaline 50 ppm + lauryldimethylamine oxide 100 ppm.

[0087] As can be seen from the results in Table 1, ABS had a superior residue performance (i.e., a lower mass of surfactant remained on the membrane after cleaning) compared to lauryldimethylamine oxide. On the other hand, 2-propylheptanol ethoxylates lead to a significantly higher surfactant residue than these standard membrane cleaning surfactants (˜factor of 2).

[0088] The backing materials of the membranes has also been shown to produce different results (compare GR61PP with GR70PE, for example).

Cleaning Performance Versus Surfactant Residue

[0089] Whilst a low surfactant residue is important for membrane cleaning compositions, it is also important that the cleaning performance of the cleaning composition is of a high standard.

[0090] Accordingly, tests were carried out to determine the cleaning performance of a number of cleaning compositions and compared this result with the surfactant residue that remained on a membrane that was cleaned using those compositions.

[0091] The cleaning performance of the test cleaning compositions was determined by measuring the percentage of butterfat removed from a membrane and was carried out using the following method:

[0092] PS coupons were prepared by pre-cleaning in methanol for 30 seconds and being allowed to dry. The coupons were then weighed to get the clean coupon weight. A homogenous layer of butter was applied to the coupons and the dried weight recorded.

[0093] Surfactant solutions were prepared and heated to 45° C. The surfactant solutions were stirred at 240 rpm and the pH was brought to pH 11 using NaOH. The coupons were suspended in the surfactant solutions for ten minutes, before being rinsed with deionised water and allowed to dry overnight. The coupons were then weighed to record the weight of butter that had been removed by the surfactant solution.

[0094] The results are shown in FIG. 1. The surfactant residue on the membrane cleaned using the compositions is shown normalised to the residue of lauryldimethylamine oxide, a common surfactant used in the art to clean membranes.

[0095] As can be seen, lauryldimethylamine oxide showed good cleaning performance, removing 50% of the butterfat from the membrane, but there remained a high residue of the surfactant on the membrane after rinsing of the membrane.

[0096] In contrast, alkylbenzene sulfonate sodium salt (ABS) showed a reduced cleaning performance and an improved residue performance compared to NPE and the amine oxide composition. The sodium 2-ethylhexyl sulfate composition showed very good residue performance but poor cleaning performance.

[0097] Surprisingly, the cleaning composition comprising the combination of the lauryldimethylamine oxide and the sodium 2-ethylhexyl sulfate maintained a similar, if slightly reduced, cleaning performance to the amine oxide alone, whilst also maintaining the good residue performance of the sodium 2-ethylhexyl sulfate composition.

[0098] Comparative pure water flux impact studies (data not shown) also showed that lauryldimethylamine oxide had the highest pure water flux impact of standard commercially available surfactants used for membrane cleaning, and surprisingly, the addition of an alkyl sulfate such as sodium 2-ethylhexyl sulfate to the lauryldimethylamine oxide did not have a negative impact of the pure water flux impact of the composition. This is a further demonstration of the surprising retention of the superior cleaning performance of the amine oxide even when combined with alkyl sulfate.

[0099] The reduction in residue performance was further studied in relation to the volume of water used to rinse a membrane. Table 2 below shows a comparison of the residue remaining on a membrane, as measured by the surface tension of the rinse water runoff, for lauryldimethylamine oxide (AO) alone and lauryldimethylamine oxide in combination with sodium 2-ethylhexyl sulfate (AS).

TABLE-US-00002 TABLE 2 Surface tension of rinse water that has been used to rinse a membrane cleaned using with a cleaning composition comprising lauryldimethylamine oxide (AO) compared to a membrane cleaned using a cleaning composition comprising lauryldimethylamine oxide and sodium 2-ethylhexyl sulfate (AS). AO AO + AS Rinse Volume [l] Surface tension [N/m] Surface tension [N/m]  4000 30.1 26.2  8000 — 30.8 12000 40.8 52.7 16000 — 60.7 20000 52.0 61.3

[0100] As can be seen, the combination composition is removed at a faster rate than the composition comprising the lauryldimethylamine oxide only.

[0101] In further studies, it was shown that the cleaning performance of the lauryldimethylamine oxide was largely unaffected by the concentration of sodium 2-ethylhexyl sulfate.

[0102] In contrast, other cleaning compositions comprising a blend of surfactants that were tested, such as a composition comprising lauryldimethylamine oxide and oleic acid sulfonate potassium salt, showed that the cleaning performance of the amine oxide decreased proportionally to the concentration of the oleic acid sulfonate potassium salt.

[0103] Accordingly, the composition comprising the combination of lauryldimethylamine oxide and sodium 2-ethylhexyl sulfate was found to be surprisingly efficacious for use as a cleaning composition for membranes, especially those membranes used to process food products such as dairy products. 1.-10. (canceled)