Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2001-03-29
2003-09-09
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S226000, C510S379000, C510S381000, C510S446000, C510S505000
Reexamination Certificate
active
06617297
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to automatic dishwashing tablets with improved chlorine stability. More specifically, it relates to the use of certain nonionic surfactants in machine dishwashing detergent tablets containing chlorinating agents.
BACKGROUND OF THE INVENTION
Most machine dishwashing detergents contain a chlorine bleach component that provides sanitization and stain removal properties. Incorporation of nonionic surfactants in these detergent formulations is also highly desirable. The nonionic surfactants typically used are low foaming, are good defoamers of protein food soils, and provide wetting properties to reduce the appearance of spots and film on dishware, thus providing good sheeting action.
Chlorinating agents degrade conventional defoaming nonionic surfactants such as ethylene oxide/propylene oxide block copolymers and fatty alcohol oxyalkylates. As the chlorinating agent attacks the nonionic surfactant, the bleach is depleted and the surfactant is destroyed. Thus, desirable low-spotting filming and defoaming properties are lost along with the sanitizing and de-staining properties of the chlorinating agent.
Nonionic surfactants are commonly incorporated in automatic dishwashing detergent powders containing a chlorinating agent. In powdered detergents, the contact between the nonionic surfactant and the chlorine source is less intimate than in pressed tablets and stability can be maintained for the shelf life of the product.
In tablets, on the other hand, chlorine stability is significantly poorer than in powdered detergent formulations. One reason may be that the compression of the ingredients to form the tablet increases the contact between the nonionic surfactant and the chlorine source and degradation is accelerated.
Pressed automatic dishwasher detergent tablets, which have become more popular with the consumer over the past few years, present a special challenge for the formulator to produce a tablet with sufficient chlorine stability such that the sanitization and stain removing properties remain high throughout the shelf life of the product. Thus, from the time that the tablet is manufactured to the time of purchase and up until ultimate end use by the consumer, the shelf life may be six months or longer. An ideal formulation would retain most or all of its chlorine stability over that time period.
In order to predict the shelf life, it has been found convenient to determine the chlorine content in the tablet as a function of time during an accelerated aging test at elevated temperatures. As a rule of thumb, a tablet has sufficient chlorine stability if greater than 80 percent of the chlorine in the tablet remains active for eight weeks with the tablet stored at 120° F.
Automatic dishwashing tablets containing nonionic surfactants and a chlorine bleach compound are disclosed in U.S. Pat. No. 6,025,315 to Gorlin, the disclosure of which is hereby incorporated by reference. According to Gorlin et al '315, an automatic dishwashing composition in the form of a table comprises an alkali metal phosphate detergent builder salt, an alkali metal carbonate, a lubricant, a dialkali metal disilicate, a nonionic surfactant, and a wax-coated chlorine bleach compound.
Multiple layer detergent tablets are also known in the art as evidenced by U.S. Pat. No. 5,133,892 to Chun et al (the entire content of which is incorporated hereinto by reference. Multiple layer tablets are useful because incompatible materials can be incorporated into different layers, with an increase in shelf life.
SUMMARY OF THE INVENTION
According to the present invention, certain nonionic surfactants have been found to provide improved chlorine stability in machine dishwashing detergent tablet formulations (i.e., exhibit greater than 80 percent of the chlorine in the tablet remains active for eight weeks with the tablet stored at 120° F.) as compared to the alcohol alkoxylate nonionic surfactants that are typically used in such an end-use application. The use of these nonionic surfactants allow such formulations to retain their cleaning and defoaming properties for longer periods of time as compared to formulations containing conventional nonionic polyether surfactants.
According to particularly preferred embodiments, there is provided according to the present invention a solid automatic dishwasher detergent tablet comprising a chlorine source to provide 0.5 to 5 percent available chlorine; and 1 to 10 percent by weight of one or more nonionic surfactants having the following structure
R—(AO1)
x
(AO2)
y
—OR′
wherein:
R is a C
6
-C
18
alkyl group,
AO1 represents propylene oxide or a mixture of propylene oxide and other alkylene oxides,
AO2 represents ethylene oxide or a mixture of ethylene oxide and other alkylene oxides,
R′ is an alkyl, arylalkyl, or benzalkyl group with 1 to about 10 carbon atoms,
x is 2-20, y is 0-20, and the sum of x plus y is 5 or greater.
In another embodiment, a method for increasing the chlorine stability of the pressed automatic dishwashing detergent tablet is provided, wherein there is incorporated in the tablet a surfactant of the structure given above.
In accordance with the invention, the chlorine stability of the tablet is such that greater than 80 percent of the chlorine in the table remains active for eight weeks when the tablet is stored at 120° F.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.
DETAILED DESCRIPTION OF THE INVENTION
The automatic dishwasher detergent tablets of the invention necessarily comprise a chlorine source. The chlorine source is most preferably present in an amount to provide from about 0.1 to about 5 percent available chlorine by weight, preferably from about 0.5 to 5 percent available chorine, and most preferably from about 0.5 to 3 percent available chlorine.
Conventional chlorine bleach compounds may be employed in the compositions of this invention, such as dichloroisocyanurate, dichlorodimethylhydantoin, or chlorinated trisodium phosphate. Other examples of chlorine sources include sodium hypochlorite, potassium hypochlorite, monobasic calcium hypochlorite, dibasic magnesium hypochlorite, potassium dichloroisocyanurate, sodium dichloroisocyanurate, trichlorocyanuric acid, 1,3-dichloro-5,5-dimethylhydantion, N-chlorosulfamide, Chloramine T, Dichloramine T, Chloramine B, and Dichloramine B.
Preferred chlorine sources are chlorinated isocyanurates including potassium dichloroisocyanurate, sodium dichloroisocyanurate, sodium dichloroisocyanurate dihydrate, trichlorocyanuric acid, and dichloroisocyanurate. A commercially available chlorine compound is ACL-59 from Monsanto, which is potassium dichloro-s-triazenetrione (i.e. potassium dichloroisocyanurate).
It is typical to formulate dishwasher tablets to a desired chlorine level. Thus, preferred formulations of the invention contain from about 0.5 to about 5 percent available chlorine. Thus, the actual amount of the chlorine compound(s) noted above should be present in the tablet at a level somewhat greater than the desired available chlorine level to ensure that the desired level of chlorine is provided. For example, the use of 3.3 percent ACL-59 provides about 2 percent available chlorine in a pressed dishwasher detergent tablet formulation of the present invention.
Chlorine stable surfactants are incorporated into the dishwasher detergent tablet compositions of the present invention. Chlorine stable surfactants of the invention are represented by the formula
R—(AO1)
x
(AO2)
y
—OR′.
In the formula, R is a C
6
to C
18
alkyl group. For example, R can represent the residue of a fatty alcohol having 6 to 18 carbon atoms. Examples of such fatty alcohols include decyl alcohol, lauryl alcohol, and stearyl alcohol, as well as the commercially available blends of alcohols, such as C
12
to C
15
alcohols, or C
10
to C
13
alcohols. In a preferred embodiment, R will be in the range of approximately C
12
to C
15
.
Mente Glenis R.
Welch Michael C.
Zack Kenneth L.
BASF Corporation
Douyon Lorna M.
Nixon & Vanderhye PC
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