Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Reexamination Certificate
1998-12-23
2002-04-09
Gupta, Yogendra N. (Department: 1751)
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
C134S025200, C134S025300, C134S025500, C134S029000, C510S197000, C510S219000, C510S221000, C510S225000, C510S226000, C510S228000, C510S363000, C510S372000, C510S374000, C510S378000, C510S380000, C510S381000, C510S393000, C510S530000
Reexamination Certificate
active
06368420
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cleaning compositions and their use in mechanical warewashing, especially in institutional or industrial, multi-tank or single-tank systems having multiple cleaning and rinsing zones or steps.
BACKGROUND OF THE INVENTION
A conventional multi-tank industrial warewashing machine consists of a conveyor belt system having separate prewash, wash, rinse and drying zones. Fresh wash water is introduced into the rinse zone of the machine and is passed cascade-fashion towards the prewash zone while dishware is transported in a countercurrent direction.
The dishwashing compositions used in such machines generally comprise a cleaning ingredient such as an aqueous solution of a caustic agent (e.g. sodium hydroxide), a sequestering agent such as sodium tripolyphosphate, and a chlorine bleaching agent. Contact time of the cleaning composition with the dishware is typically quite short, e.g. about 1 minute. The cleaned dishware is generally rinsed in the final rinse station, using a dilute solution of a rinse aid containing a nonionic surfactant.
A conventional single-tank industrial warewashing machine can be either a ‘dump’ or a ‘re-use’ machine. In single tank machines of the ‘dump’ type, the rinse water is used for the next wash cycle. Examples of ‘dump’-type machines are the low-temperature single-tank machines which are currently on the US market. Hypochlorite is dosed in the rinse of these US machines in order to comply with US hygiene requirements.
In re-use machines, the water used for the rinse step falls into the tank that contains the detergent solution.
In a variation of the conventional multi-tank system described above, a cleaning component is separately introduced into a prewash or wash zone while the bleaching agent is subsequently introduced into a second wash zone, followed by the rinse zone. As the dishware passes through each zone, most of the solution is circulated within the zones concerned.
One problem which arises in industrial warewashing is the build-up of starch residues. Starch residues are especially hard to remove when dishware is subjected to high temperatures during food preparation and such foods are left for a long time on heated substrates during distribution. A proposed solution to this problem is disclosed by EP-A-282,214. This document relates to a process for cleaning dirty dishware with a non-directional mistlike spray of a strongly alkaline solution.
An industrial dishwashing process using a low alkaline detergent and an enzyme dosed into either a rinsing or washing bath of the dishwasher is described in WO-94/27488 (Henkel-Ecolab). The publication describes a means of compensating for degradation of the enzyme, particularly an amylase, during standstill phases by adding intermittent doses of the enzyme to the washing zone.
German Patent Specification DE-A-4 219 620 describes a domestic dishwasher in which bleach and enzyme containing components are dosed in different stages of the wash process. The enzyme is added during the pre-rinse or at the very beginning of the wash cycle. The bleach is added only during the cleaning cycle after a predetermined time once the wash liquor reaches a desired temperature. There are no examples or suitable compositions described in the specification.
EP-A-510,761 refers to liquid machine dishwashing compositions comprising enzyme material and wax encapsulated bleach particles, and suitable for use in domestic dishwashing machines. These compositions were found to exhibit remarkable storage stability.
WO-96/16152 discloses a cleaning system for a multi-tank mechanical warewashing machine, wherein enzyme and bleach are dosed into different wash tanks or zones of the machine. When applying this last-mentioned cleaning system, good starch and tea-stain removal can be obtained, particularly at moderate enzyme levels.
However, for cost reasons and for reasons of optimal operator safety it is desired to reduce the enzyme concentration in cleaning systems for mechanical warewashing and we found that starch and tea stain removal leave to be desired when applying the system of WO-96/16152 with low enzyme levels.
It is an object of the present invention to provide a cleaning system for an industrial mechanical warewashing machine, which can be effectively applied with low enzyme levels.
It is another object of the invention to provide a cleaning system with which both effective tea-stain removal and good starch removal can be achieved in one cleaning cycle.
It is a further object of the invention to provide an enzymatic cleaning system with which efficient removal of bleachable stains can be achieved.
It is a still further object of the invention to provide a cleaning system in which bleach decomposition in wash tanks or zones does not occur during off-time, and which consequently enables the operator to dose the right amount of bleach material for every wash cycle.
We have now surprisingly found that these objects can be achieved when applying a cleaning system having a bleach component and an enzyme component, wherein the bleach component is dosed into the post-rinse
DEFINITION OF THE INVENTION
Consequently, in a first aspect the present invention provides a chemical cleaning system for a multi-tank or a single-tank mechanical warewashing machine, having at least two separate components for aqueous dissolution or dilution to respective use concentrations, a first component comprising an enzyme or a mixture of an enzyme and a cleaning agent, and a second component comprising a bleach, wherein the first component is introduced into a wash zone or step and wherein the second component is introduced into a post-rinse zone or step.
A highly effective method of warewashing in a multi-tank or single tank, industrial or institutional machine is also described, said method comprising the steps of:
(1) formulating at least two separate components of a chemical cleaning system for aqueous dissolution or dilution to respective use concentrations, a first component comprising an enzyme or a mixture of an enzyme and a cleaning agent, and a second component comprising a bleach;
(2) introducing the first component into a wash zone or step, to clean dirty dishware;
(3) introducing the second component into a post-rinse zone or step to effectively complete the cleaning of the dishware.
DETAILED DESCRIPTION OF THE INVENTION
When using the system of the present invention, it was found that effective starch and stain removal performance could be obtained, even at low enzyme levels in the wash liquor. Reason is that the present system allows for maximum contact times in the wash zones or steps between the enzymes and the dishware to be cleaned owing to minimum enzyme deactivation.
Furthermore, the amount of bleach to be dosed during every wash can be optimised when applying this system.
In systems of the prior art in which the bleach is dosed in one of the wash zones or steps, it is always needed to compensate for bleach deactivation due to the presence of soil in the machine and especially occuring during off-time. In the system of the present invention this is not required since the bleach is dosed in the post-rinse.
The system of the present invention can be applied at a wide range of pH-values. Preferably, the pH of the wash liquor in the wash tank or step in which the enzyme is dosed is in the range of 7-11.5.
The pH of the rinse water in which the bleach material is dosed is desirably in the range of 7-10.5
The system pH is the pH of the aqueous solution resulting from dissolution or dilution to the use concentration of that component which contains most of the cleaning agent. This system pH is of course different from the pH of the neat component, before dilution.
Typical aqueous dissolution or dilution rates (dosing rates) for the component containing the (most) cleaning agent are such that the weight of component per unit volume of water are in the range of from 0.5 to 5 g/l, preferably from 1 to 4 g/l, more preferably from 1 to 3 g/l.
The cleaning agent content of that component ma
Angevaare Petrus Adrianus
Flu Paul
Nicholson John Richard
Schepers Frederik Jan
Diversey Lever Inc.
Gupta Yogendra N.
Mruk Brian P.
LandOfFree
Detergent composition and method for warewashing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detergent composition and method for warewashing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detergent composition and method for warewashing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2863513