Cleaning compositions for solid surfaces – auxiliary compositions – Auxiliary compositions for cleaning – or processes of preparing – Dishwasher rinse composition
Reexamination Certificate
1999-04-09
2001-01-09
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Auxiliary compositions for cleaning, or processes of preparing
Dishwasher rinse composition
C510S276000, C510S318000, C510S361000, C510S362000, C510S398000, C510S433000, C510S434000, C510S477000, C510S480000, C510S488000, C510S490000
Reexamination Certificate
active
06172036
ABSTRACT:
TECHNICAL FIELD
The present invention relates to rinsing (rinse aid) compositions, particularly acidic rinsing compositions containing an amino tricarboxylic acid.
BACKGROUND OF THE INVENTION
Rinse aid compositions designed for use in automatic dishwasher machines are well known. These compositions are added during the rinsing cycle of the machine, separately from the detergent composition employed in the main wash cycle(s). The ability to enhance rinsing, and in particular the ability to prevent spot and film formation are common measures of rinse aid performance.
Rinse aid compositions typically contain components such as nonionic surfactants and/or hydrotropes which aid the wetting of the items in the rinse, thereby improving the efficacy of the rinsing process. These surfactants, and rinse aid compositions in general, are not designed for the achievement of a primary soil removal purpose.
The general problem of the formation of deposits as spots and films on the articles in the wash/rinse, and on the dishwasher machine parts is well known in the art.
Whilst the general problem of deposit formation is known, a full understanding of the many facets of the problem is however still an active area of research.
A range of deposit types can be encountered. The redeposition of soils or the breakdown products thereof, which have previously been removed from the soiled tableware in the washload, provides one deposit type. Insoluble salts such as calcium phosphate or carbonate, calcium fatty acid salts (lime soaps), or certain silicate salts are other common deposit types. Composite deposit types are also common. Indeed, once an initial minor deposit forms it can act as a “seeding centre” for the formation of a larger, possibly composite, deposit structure.
Deposit formation can occur on a range of commonly encountered substrate surfaces including plastic, glass, metal and china surfaces. Certain deposit types however, show a greater propensity to deposit on certain substrates. For example, lime soap deposit formation tends to be a particular problem on plastic substrates.
The formation of insoluble carbonate and phosphate, especially calcium carbonate and phosphate, deposits are a particular problem in the machine dishwashing art. The Applicants have found that the formation of insoluble salt deposits occur most noticeably in the rinse cycle of the dishwasher machine. Deposit build up is most apparent on the heater element of the dishwasher machine.
The Applicants have found that the problem of insoluble salt deposit formation may be effectively ameliorated by the inclusion of amino tricarboxylic acid (ATCA) into a rinse aid formulation.
The Applicants have also found that ATCA can bind magnesium ions reducing the formation of insoluble magnesium salts, such as magnesium silicate on the articles in the wash.
The Applicants have also found that the more effective control of calcium carbonate and phosphate deposition can also lead to benefits in the prevention of the formation of other deposit types, particularly lime soap deposits and silicate deposits.
Lime soap deposits are most commonly encountered when the washload contains fatty soils, which naturally contain levels of free fatty acids, and when lipolytic enzymes are components of the formulation. Lipolytic enzymes catalyse the degradation of fatty soils into free fatty acids and glycerol. Silicate is a common component of machine dishwashing formulations, where it is added for its china care capability.
SUMMARY OF THE INVENTION
There is provided a rinse aid composition containing an amino tricarboxylic acid or its salts or complexes having the general formula:
where R
1
, R
2
and R
3
are alkyl groups or substituted alkyl groups of chain length C1 to C4; n is 0 or 1; and X is an organic substituent group.
The pH of said composition as a 1% solution in distilled water at 20° C. is preferably less than 7.
DETAILED DESCRIPTION OF THE INVENTION
Amino Tricarboxylic Acid (ATCA)
The first essential component of the compositions in accord with the invention is an amino tricarboxylic acid or one of its salts or complexes.
The amino tricarboxylic acid (ATCA) is selected from the group having the general formula as shown below.
where R
1
, R
2
and R
3
are an alkyl group or substituted alkyl group of chain length C1 to C4, and n is 0 or 1. X is an organic substitutent group, that is a substituent typically encountered in organic compounds, but excluding X being a hydrogen substituent. X can thus for example be an alkyl, aryl, alkenyl or alkaryl group optionally substituted by any functionality including for example, amino, hydroxyl, amide and ether functionalities. X may also be an organic functional group including for example an amine, hydroxyl, amide, ester or ether group. X is preferably an alkyl group, most preferably a methyl or ethyl group. ATCA is most preferably methyl glycine diacetic acid, that is where R
1
═R
2
═a—CH—
2
group, n is 0 and X═CH
3
.
ATCA can be present at levels of greater than 0.5% by weight, preferably from 0.5% to 40% by weight, most preferably from 1% to 15% by weight of the rinsing composition.
ATCA acts as a cation complexing chelant. ATCA forms water-soluble chelates with calcium, magnesium, lead, copper, zinc, cadmium, mercury, manganese, iron, aluminium and other cationic polyvalent ions. The stability constant (measured as log K
MeZ
) of ATCA-calcium chelate is greater than 5.0, preferably greater then 6.0. The stability constant of the preferred ATCA compound, methyl glycine diacetic acid (MGDA) is 7.0. The stability constant, log K
MeZ
is measured in a solution of ionic strength of 0.1, at a temperature of 25° C. The figure of>5.0 for logK
MeZ
indicates that the ratio of the concentration of the undissociated [CaATCA
−
] to the dissociated complex [Ca
2+
][ATCA
3−
], is>10
5
:1
The ATCA component may be present in its acid form or in the form of one of its salts or complexes with a suitable counter cation. Preferably any salts/complexes are water soluble, with the alkali metal and alkaline earth metal salts/complexes being especially preferred.
pH of the compositions
In a highly preferred aspect of the invention the compositions have a pH as a 1% solution in distilled water at 20° C. of less than 7, preferably from 0.5 to 6.5, most preferably from 1.0 to 5.0.
The pH of the compositions may be adjusted by the use of various pH adjusting agents. Preferred acidification agents include inorganic and organic acids including, for example, carboxylate acids, such as citric and succinic acids, polycarboxylate acids, such as polyacrylic acid, and also acetic acid, boric acid, malonic acid, adipic acid, fumaric acid, lactic acid, glycolic acid, tartaric acid, tartronic acid, maleic acid, their derivatives and any mixtures of the foregoing. Bicarbonates, particularly sodium bicarbonate, are useful pH adjusting agents herein. A highly preferred acidification acid is citric acid which has the advantage of providing builder capacity to the wash solution.
Heavy metal ion sequestrants
Heavy metal ion sequestrants are useful components herein. By heavy metal ion sequestrants it is meant components which act to sequester (chelate) heavy metal ions. These components may also have calcium and magnesium chelation capacity, but preferentially they bind heavy metal ions such as iron, manganese and copper.
Heavy metal ion sequestrants are preferably present at a level of from 0.005% to 20%, more preferably from 0.1% to 10%, most preferably from 0.2% to 5% by weight of the compositions.
Heavy metal ion sequestrants, which are acidic in nature, having for example phosphonic acid or carboxylic acid functionalities, may be present either in their acid form or as a complex/salt with a suitable counter cation such as an alkali or alkaline metal ion, ammonium, or substituted ammonium ion, or any mixtures thereof. Preferably any salts/complexes are water soluble. The molar ratio of said counter cation to the heavy metal ion sequestrant is preferably at least
Cruickshank Graeme Duncan
Smith Peter Andrew
Bolam Brian M.
Boyer Charles
Hasse Donald E.
Ogden Necholus
The Procter & Gamble & Company
LandOfFree
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