Dish washing process

Details Dish washing process Dish washing process

2000-02-04

2002-10-15

El-Arini, Zeinab (Department: 1746)

Cleaning and liquid contact with solids

Processes

Work handled in bulk or groups

C134S041000, C510S521000, C510S522000

Reexamination Certificate

active

06463939

ABSTRACT:

TECHNICAL FIELD
The present invention is in the field of machine dishwashing. More specifically, the invention encompasses automatic dishwashing detergents and rinse aids and a process for using them.
BACKGROUND OF THE INVENTION
To wash articles in a commercially available dish washing machine entails using three product types. Salt is added to the salt compartment to soften the water, a dish washing formulation is used to clean the articles and a rinse aid is used to ensure that the articles are rinsed with no streaks or smears.
The salt in the machine does not have to be replaced every wash, however it is inconvenient for consumers replace the salt.
The present invention relates to a process of washing dishes that obviates/lessens the need for salt in a machine dish washing formulation.
DESCRIPTION OF THE INVENTION
Accordingly, the present invention provides a process for washing articles in a mechanical washing machine comprising the steps of:
i) treating the articles with a wash liquor comprising a dishwashing composition and; said composition when undiluted circulated comprising greater than 20 wt.% of a bicarbonate salt; followed by
ii) treating the articles with a rinsing solution comprising a rinse aid the rinse aid when undiluted comprising at least 20wt% of a water-soluble acid builder or salt thereof; wherein minimal rejuvenation of ion exchange material within the machine is needed.
The invention also discloses use of citric acid in a rinse aid composition for use in an automatic dishwashing machine so no salt is required for the rejuvenation of ion exchange material within the machine, use of bicarbonate salt in a dishwashing composition for use in an automatic dishwashing machine so no salt is required for the rejuvenation of ion exchange material within the machine and use of a chelating agent in a dish washing composition for use in an automatic dish washing machine so no salt is required for the rejuvenation of ion.
The invention further relates to a kit of parts for use in an automatic dishwashing machine comprising:
(i) a first container of rinse aid composition;
(ii) a second container of dishwashing composition and;
(iii) instructions that no salt is to be added to the machine.
DETAILED DESCRIPTION OF THE INVENTION
Dish Washing Composition
European dish washers have within them ion exchanger materials which soften the water thus aiding the cleaning of utensils and lessening deposition of insoluble salts. The ion exchange material is regenerated by the use of salt(sodium chloride), put into the machine by the consumer. Most machines have a dial which the consumer sets to a pre-determined level depending on the hardness of the water supplied to the machine. Depending on the machine type the machine softens water in two ways:
On a hard water setting it either regenerates the ion exchange material frequently (e.g. every 2 washes) or it adds a high quantity of saturated sodium chloride solution to the ion exchange material (e.g. 75 ml). Correspondingly on a low water setting it either regenerates the ion-exchanger infrequently (every 5 washes) or it adds lower quantities of saturated sodium chloride solution to the ion exchange material each wash (e.g. 30 ml).
The present invention has found that the ion exchange material does not need to be as frequently rejuvenated if formulations according to the invention are used. Preferably the ion exchange material does not need to be rejuvenated; that is no salt needs to be added to the machine.
Thus a machine that frequently doses salt every 5 washes will when used with the formulation of the invention only need to dose e.g. every 2 washes, thus the dial can be set accordingly. Alternatively a machine that doses salt every wash at a dose of 25 g will only need to dose at less than 10 g
At very high water harness only 40 washes from a 1kg pack of salt can be achieved, but using formulations according to the invention greater than 100 washes can be achieved.
Thus, in the present invention minimal rejuvenation of ion exchange material means that the average level of salt that is needed per wash can be represented by the following formula:
degree of hardness of water—30×25/40 g
When the degree of water hardness is 30 or less, no salt is added.
Builder Material
The detergency builder system is preferably water-soluble and more preferably comprises a bicarbonate salt, preferably sodium or potassium bicarbonate most especially sodium bicarbonate. Bicarbonate salts are particularly preferred as builders as they also have a buffering capacity. It is preferable if the bicarbonate is present at a level greater than 20 wt% of the total composition, more particularly at least 24-wt% of the total composition.
It is preferable if the builder further comprises a carboxylate or polycarboxylate builder containing from one to four carboxy groups, particularly selected from monomeric polycarboxylates or their acid forms, homo or copolymeric polycarboxylic acids or there salts in which the polycarboxylate comprises at least two carboxylic radicals selected from each other by not more than two carbon atoms. Preferred carboxylates include the polycarboxylate materials described in U.S. Pat. No. 2,264,103, including the water-soluble alkali metal salts of mellitic acid and citric acid, dipicolinic acid, oxydisuccinic acid and alkenyl succinates. The water-soluble salts of polycarboxylate polymers and copolymers, such as are described in U.S. Pat. No. 3,308,067 are also be suitable for use with the invention.
Of the builder materials listed in the above paragraph, the preferred polycarboxylates are hydroxycarboxylates containing up to three carboxy groups per molecule, especially citric acid or its salt, particularly sodium citrate. It is preferable if the carboxylate builder is present at a level of at least 20 wt% of the total formulation, more preferably at a level greater than 30 wt%.
It is preferred if the weight ratio of polycarboxylate builder to bicarbonate builder is at least 1:1, preferably greater than 3:2
Further soluble detergency builder salts which can be used with the present invention are poly-valent inorganic and poly-valent organic builders, or mixtures thereof. Non-limiting examples of suitable water-soluble, inorganic alkaline detergency builder salts include the alkali metal carbonates, borates, phosphates, polyphosphates, tripolyphosphates, phosphono carboxylates. Specific examples of such salts include the sodium and potassium tetraborates, carbonates, tripolyphosphates, orthophosphates and hexametaphosphates. However it is preferable if the detergent formulation is free or only has low levels (5% or less) of builder salts which precipitate during the wash in the presence of calcium, an example of such a salt is sodium tripolyphosphate.
In preferred builder systems the weight ratio of alkali metal bicarbonate to alkali metal carbonate is greater than 1:1, preferably greater than 2:1 in particularly preferred systems the builder does not comprises a alkali metal carbonate.
Other suitable detergency builders organic alkaline compounds such as water-soluble amino polyacetates, e.g. sodium and potassium ethylenediamine tetraacetates, nitrilotriacetates and N-(2-hydroxyethyl)nitrilodiacetates; water-soluble salts of phytic acid, e.g. sodium and potassium phytates; water-soluble polyphosphonates, including sodium, potassium and lithium salts of ethane-1-hydroxy-
1, 1-
diphosphonic acid; sodium, potassium and lithium salts of methylenediphosphonic acid and the like.
It is to be understood that, while the alkali metal salts of the foregoing inorganic and organic poly-valent anionic builder salts are preferred for use herein from an economic standpoint, the ammonium, alkanolammonium, e.g. triethanol-ammonium, diethanolammonium, and the like, water-soluble salts of any of the foregoing builder anions are useful herein.
Mixtures of organic and/or inorganic builder salts can be used herein.
While any of the poly-valent builder materials are useful herein, the compositions of the invention are preferably free of phosphate bui

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