WO2012156369A1

WO2012156369A1 - Dishwashing process comprising a basic and acidic cleaning step

Info

Publication number: WO2012156369A1
Application number: PCT/EP2012/058933
Authority: WO
Inventors: Christoph MAUL; Dirk Kullwitz
Original assignee: Ecolab Inc
Current assignee: Ecolab Inc
Priority date: 2011-05-19
Filing date: 2012-05-14
Publication date: 2012-11-22
Anticipated expiration: 2013-11-19
Also published as: WO2012155986A1

Abstract

The present invention relates to a process for cleaning tableware using a basic cleaning step followed by an acidic cleaning step, boths steps having a defined small pH-interval.

Description

Dishwashing process comprising a basic and acidic cleaning step

Technical field of the invention This invention relates generally to the field of machine dishwashing processes, e.g. for cleaning tableware or other surfaces soiled with food remains. More particular this invention relates to field of continuous or discontinuous machine dishwashing processes in single or multi-tank dish machines.

Background of the invention

Dish washing machines, especially industrial dish washing machines are known in the field. In this context dish washing methods are known in which basic cleaning steps are altered with acidic cleaning steps, e.g. from the EP 1 477 552 Al which is hereby incorporated by reference. These washing methods have been described to be effective against starch deposits.

However, there is a constant need for improved dish washing processes to further increase the efficiency of cleaning tableware, especially tableware having starch deposited on it.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dishwashing process which allows an efficient cleaning of tableware, especially of tableware having starch deposits.

This object is solved by a process according to Claim 1. Accordingly, a process for continuous or discontinuous machine dishwashing is provided, comprising the steps of a) Applying a first basic cleaning step whereby the cleaning solution has a pH of ≥10,6 and ≤10,9 b) Applying an acidic cleaning step whereby the cleaning solution has a pH of ≥1 and ≤2 c) Applying a second basic cleaning step whereby the cleaning solution has a pH of ≥10,5 and ≤13 Surprisingly it has been found that such a process has for a wide range of applications within the present invention at least one of the following advantages:

By using this process it is possible to reach a satisfying cleaning result, especially concerning the removal of starch

By using this process it is possible to operate without periodical stripping processes of the ware to remove long term starch build up.

By using this process the cleaning result and finish of glass and stainless steel ware is improved . By using this process it is possible to operate without periodical de-liming of the process equipment .

By using this process the pH value of the process water to be disposed will be reduced to a more favourable value.

According to a preferred embodiment of the invention in step c) the cleaning solution has a pH of ≥10,6 and 10,9.

Alternatively, according to a preferred embodiment of the invention in step c) the cleaning solution has a pH of >11 and 12,5. According to a preferred embodiment of the invention, step a) is performed at a temperature of ≥30°C and ≤70°C

According to a preferred embodiment of the invention, step b) is performed at a temperature of ≥55°C and ≤85°C

According to a preferred embodiment of the invention, step c) is performed at a temperature of ≥30°C and ≤70°C

According to a preferred embodiment of the invention, step a) is performed for ≥8s and ≤60s.

According to a preferred embodiment of the invention, step b) is performed for ≥10s and ≤20s. According to a preferred embodiment of the invention, step c) is performed for ≥20s and ≤60s. In the following the three steps of the invention are described in more detail:

Step a) : First alkaline cleaning step

Step a) is the first alkaline cleaning step in the context of the invention and is performed using a cleaning solution having a pH of ≥10,6 and ≤10,9. This pH can be achieved e.g. by using hydroxide solution and/or hydroxide/buffer solution, especially hydroxide/ phosphate buffer solution

Furthermore the cleaning solution used in step a) may include one or more of the following ingredients:

- Complexing agents, Chelants, Builders

- Surfactants

- Corrosion inhibitors

- Processing additives The cleaning solution is sprayed onto the tableware trough a rotating washing arm as a heavy water curtain.

According to a preferred embodiment of the present invention, Step a) is performed at a temperature of ≥30 and ≤70°C, which means that the cleaning solution which is applied to the tableware has this temperature. More preferred, step a) is performed at a temperature of ≥40 and ≤65°C, yet more preferred ≥50 and ≤60°C Step a) preferably is performed for ≥8s and ≤60s, more preferred for ≥20s and ≤30s. However, it should be noted that the duration of step a) is not limiting for the invention, only for some preferred applications within the same. Step b) : Acidic cleaning step

Step b) is the acidic cleaning step in the context of the invention and is performed using a cleaning solution having a pH of ≥1 and ≤2. This pH can be achieved e.g. by using an inorganic or organic acid.

Suitable acidic compounds in the context of this invention which are insofar preferred are sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propanoic acid, glycolic acid, citric acid, maleic acid, lactic acid, gluconic acid, alkanesulfonic acid, amidosulfonic acid, succinic acid, glutaric acid, adipic acid, phosphonic acids, polyacrylic acids or mixtures thereof and, in a most particularly embodiment, from formic acid, glycolic acid, gluconic acid, amidosulfonic acid or the alkanesulfonic acids, more particularly methanesulfonic acid or mixtures thereof. Especially preferred is methanesulfonic acid. Furthermore the cleaning solution used in step b) may include one or more of the following ingredients:

- Surfactants

- Hydrotropes

- Stabilizer

- Processing additives In a preferred embodiment of the process according to the invention, the cleaning solution is allowed to act on the tableware and the soil for a certain contact time (during which spraying stops) .

In another preferred embodiment, the tableware is not intentionally sprayed during the contact time.

Alternatively or additionally, the cleaning solution is sprayed onto the tableware as a fine, gentle mist-like liquid spray.

Alternatively or additionally, the cleaning solution is applied to the tableware as foam.

Alternatively or additionally, the cleaning solution is applied to the tableware in droplet form or by the Ecolab process known commercially as thin film cleaning (TFC) . According to a preferred embodiment of the present invention, Step b) is performed at a temperature of ≥55 and ≤85°C, which means that the cleaning solution which is applied to the tableware has this temperature. More preferred, step b) is performed at a temperature of ≥60 and <80°C and

Step b) preferably is performed for ≥10s and ≤20s. However, it should be noted that the duration of step b) is not limiting for the invention, only for some preferred applications within the same.

Step c) : Second alkaline cleaning step Step c) is the second alkaline cleaning step in the context of the invention and is performed using a cleaning solution having a pH of ≥10,5 and ≤13, preferably ≥10,6 and ≤10,9. This pH can be achieved e.g. by using hydroxide solution and/or hydroxide/buffer solution, especially hydroxide/ phosphate buffer solution

- Complexing agents, Chelants, Builders

- Surfactants

- Corrosion inhibitors

- Processing additives

The cleaning solution is sprayed onto the tableware trough a rotating washing arm as a heavy water curtain.

According to a preferred embodiment of the present invention, Step c) is performed at a temperature of ≥30 and ≤70°C, which means that the cleaning solution which is applied to the tableware has this temperature. More preferred, step c) is performed at a temperature of ≥40 and ≤65°C, yet more preferred ≥50 and ≤60°C

Step c) preferably is performed for ≥20s and ≤60s, more preferred ≥45s and ≤55s. However, it should be noted that the duration of step c) is not limiting for the invention, only for some preferred applications within the same. According to a further preferred embodiment of the present invention, the process furthermore comprises a step d) being a neutral rinsing step. This embodiment will be described in more detail later on.

Step d) is the neutral rinsing step in the context of the invention and is performed using a rinse aid solution having a pH of ≥5 and ≤7. The rinse aid solution used in step d) may include one or more of the following ingredients:

- Surfactants

- Organic and/or inorganic acids

- Auxiliaries

- Hydrotropes

- Processing additives

In a preferred embodiment of the process according to the invention, the cleaning solution is allowed to act on the tableware and the soil for a certain contact time (during which spraying stops) , as it step d) usually is the last step in the dishwashing cycle.

According to a preferred embodiment of the present invention, Step d) is performed at a temperature of ≥55 and ≤85°C, which means that the cleaning solution which is applied to the tableware has this temperature. More preferred, step b) is performed at a temperature of ≥60 and <80°C.

Step d) preferably is performed for ≥5s and ≤15s, preferably ≥9s and ≤12s. However, it should be noted that the duration of step d) is not limiting for the invention, only for some preferred applications within the same. The afore mentioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pursuant field can be applied without a limitation.

BRIEF DESCRIPTION OF THE EXAMPLES Additional details, features, characteristics and advantages of the object of the invention are disclosed in the following description of the examples, which - in exemplary fashion - show several embodiments and examples of a process according to the invention. The examples are to be understood merely to further illustrate the invention and are not binding.

Example I Cleaning of table cups and table plates in a MEIKO DV80.2 dishwashing machine sold by Meiko company, Offenburg, Germany . For each test, 3 dry, clean table cups were soiled by being dipped in a coffee and milk brew at 70°C for 25 times (1 min in the solution followed by 1 min drying each dipping cycle) and afterwards dried for 2 hours at 90°C according to a standardized test protocol.

Furthermore for each test 3 dry, clean table cups were dipped in a black tea and milk brew at 70°C for 25 times (1 min in the solution followed by 1 min drying each dipping cycle) and afterwards dried for 2 hours at 90°C according to a standardized test protocol.

The cleaning tests were carried out in a Meiko DV80.2 hood-type dishwashing machine according to the following scheme: a) Cleaning for 25 seconds at a temperature of around 60 °C with a 0.2% by weight aqueous solution of an alkaline detergent, the solution having a pH of about 10,9.

The exact temperature and pH is given in the table below:

Table I

b) Cleaning for 5 seconds at a temperature of 63 °C with a 0.2% by weight aqueous solution of an acidic detergent, the solution having a pH of around 1,5. c) Cleaning for 49 s seconds at a temperature of 63 °C with a 0.2% by weight aqueous solution of an alkaline detergent, the solution having a pH of about 12. d) Rinsing for 12 seconds at a temperature of 83 °C with fresh water

The cleaning was evaluated by scoring on a scale of 1 (= no visible sign of cleaning) to 10 (= complete removal of soil), resulting in a the score given in Table II below:

Table II

Comparative Examples

As comparative examples, the above-described test were conducted with a different pH in step a) , otherwise everything was analogous.

Comparative Example Test Series I

In this test series, a lower pH in step a) was used as is shown in Table III

Table III Test No. 1 2 3

°C 62 67 56

pH 10,36 10,36 10, 34

This resulted in the following scores (Table IV) :

Table IV

Test No. 1 2 3

Coffee & Milk 3 3 3

Tea & Milk 1 1 1

Comparative Example Test Series II

In this test series, a higher pH in Step a) was used as can be seen in Table V:

Table V

Test No. 1 2 3

°C 62 61 60

pH 11,37 11, 33 11,34

This resulted in the following scores (Table VI) :

Table VI

Test No. 1 2 3 Coffee & Milk 8 8 8

Tea & Milk 7 7 8

As can be seen from the examples and comparative examples, in the pH interval according to the invention the results are better than with lower or higher pH.

The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporate by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by the way of example only and is not intending as limiting. In the claims, the wording "comprising" does not exclude other elements or steps, and the identified article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures can not be used to advantage. The inventions scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed .

Claims

Claims 1.

A process for continuous or discontinuous machine dishwashing comprising the steps of a) Applying a first basic cleaning step whereby the cleaning solution has a pH of ≥10,6 and ≤10,9. b) Applying an acidic cleaning step whereby the cleaning solution has a pH of ≥1 and ≤2 c) Applying a second basic cleaning step whereby the cleaning solution has a pH of ≥10,5 and ≤13

2.

The process according to claim 1, whereby in step c) the cleaning solution has a pH of ≥10,6 and ≤10,9

3.

The process according to claim 1, whereby in step c) the cleaning solution has a pH of ≥11 and ≤12,5

4.

The process according to any of the claims 1 to 3, wherein step a) is performed at a temperature of ≥30°C and <70°C

5.

The process according to any of the claims 1 to 4, wherein step b) is performed at a temperature of ≥55°C and <85°C

6.

The process according to any of the claims 1 to 5, wherein step c) is performed at a temperature of ≥30°C and <70°C

7.

The process according to any of the claims 1 to 6, wherein step a) is performed for ≥8s and ≤60s

8.

The process according to any of the claims 1 to 7, wherein step b) is performed for ≥10s and ≤20s.

The process according to any of the claims 1 to 8, wherein step c) is performed for ≥20s and ≤60s.