Cleaning and liquid contact with solids – Processes – Work handled in bulk or groups
Reexamination Certificate
2000-11-02
2002-02-12
Delcotto, Gregory (Department: 1751)
Cleaning and liquid contact with solids
Processes
Work handled in bulk or groups
C510S220000, C510S224000, C510S228000, C510S504000, C510S226000, C510S446000, C510S447000
Reexamination Certificate
active
06345633
ABSTRACT:
FIELD OF THE DISCLOSURE
The present disclosure is in the field of machine dishwashing. More specifically, the disclosure relates to automatic dishwashing detergents in granular, liquid, gel, solid and tablet form which contain a cationic, water soluble surfactant for the purpose of improving the final appearance of washed plastic articles.
BACKGROUND
Machine dishwashing detergents constitute a generally recognized distinct class of detergent compositions. In general, machine dishwashing detergents are mixtures of ingredients whose purpose, in combination, is to breakdown and remove food soils; to inhibit foaming caused by certain food soils; to promote the wetting of wash articles in order to minimize or eliminate visually observable spotting and filming; to remove stains such as might be caused by beverages such as coffee and tea or by vegetable soils such as carotenoid soils; to prevent a buildup of soil films on wash ware surfaces; and to reduce or eliminate tarnishing of flatware. It is particularly critical to a consumer's perception of how well a machine dishwashing detergent performs that residual spotting and filming on wash articles be controlled or prevented entirely.
In conventional institutional and domestic dishwashing, a strongly alkaline solution is produced and used to wash dishes, glasses, and other cooking and eating utensils. One or more rinse cycles then follow this main wash cycle, in which any removed soil as well as the remaining detergent are expelled from the washing machine. A subsequent drying cycle may optionally be employed. Ordinary tap water can be used in preparing the strongly alkaline cleaning and rinse solutions, however, in European applications, this tap water is often treated (softened) to remove hardness ions such as calcium and magnesium with the result that hard water residues on washware are reduced. Nevertheless, spotting and filming from soil residues and precipitates can remain a problem, especially if the ion exchange unit serving the dishwashing machine is operating inefficiently. This problem can be minimized with a machine dishwashing composition containing a relatively high level of polyphosphate which acts to sequester hardness ions and to aid in soil removal and stabilization. In addition, these detergents usually contain a chlorine bleaching system for stain removal and for an added cleaning boost via oxidation of proteinaceous soils, thus helping to eliminate spotting on glassware.
Although the cleaning performance of these conventional detergent compositions is satisfactory, high phosphate levels, chlorine bleach, and high alkalinity have potential environmental and consumer drawbacks. As a result, an alternative technology was developed to deliver less alkaline products. Similarly, nonphosphated builders are substituted to further improve the environmental profile of the composition. As a consequence of the reduced cleaning efficiency of the modified composition, various detersive enzymes including amylolytic and proteolytic enzymes are included in the detergent composition in order to boost removal of starchy and proteinaceous soils, respectively. Because these enzymes are not compatible with chlorine bleach systems, an oxygen bleaching system can be substituted which can result in a reduction in bleach performance. Often, enzymatic compositions based on oxygen bleaches are formulated with a phosphate builder, in markets where local legislation will allow, to assure good overall performance. An unfortunate weakness in the performance of this alternative technology, both in formulations which are phosphated (i.e., containing inorganic phosphate builder salts) and those which are nonphosphated, is that they can often leave wash ware spotted or with a visible coating of film which is aesthetically unacceptable in both domestic and institutional environments. A consumers perception of residual spotting and filming can give rise to an unfavorable rating of an otherwise premium performing machine dishwashing product.
In order to substantially prevent the formation of spotting and filming, dedicated additives are included into the wash and/or rinse cycles of the washing machine. Preferably, dedicated rinse aids have commonly been added to the water used for performing the rinsing step(s). The precise mechanism through which rinse aids work is not established. One theory holds that a surfactant in the rinse aid is adsorbed on the washware surface at temperatures at or above its cloud point, and thereby reduces the solid/liquid interfacial energy and contact angle. This reduction leads to the formation of a continuous sheet which drains evenly from the surface and minimizes the formation of spots and film. The delivery of a similar sheeting action from the main wash has thus far proven very difficult.
Commonly available rinse aids have primarily focused on reducing spotting and filming on surfaces such as glass, ceramics, china, and metal. However, plastic washware is becoming more commonly used, especially in the institutional market. A special problem with plasticware is the possible chemical attack and crazing of the ware in the presence of certain components of the rinse aid or of the main wash detergent formulation. Many effective rinse aid components, such as fatty alcohol or alkyl phenol-based nonionic surfactants, also strongly attack plastic articles. The terms plasticware and plastic articles are defined herein to include articles composed of polycarbonate, melamine, polypropylene, polyester resin, polysulfone, and the like.
It is an object of the present disclosure to provide compositions, suitable for use in machine dishwashing methods, having the ability to provide excellent sheeting properties on plastic wash articles and so producing said articles which are aesthetically acceptable and free from spots and film. Further, such an acceptable plasticware appearance is achieved without endangering said articles due to attacking or crazing. Surprisingly, it has been discovered that a preferred embodiment of the present disclosure can deliver this appearance benefit from the main wash while at the same time maintaining an overall good cleaning performance towards soiled articles.
U.S. Pat. No. 5,298,289 describes the treatment and after-treatment of surfaces, especially metals, with derivatives of polyphenol compounds. These compositions are also said to be useful in treating plastic and painted surfaces to improve rinsability without water breaks. The surfactants employed are a combination of previously known anionic and nonionic surfactants.
European Patent Publication 0,432,836 describes the use of alkyl polyglycoside surfactants in rinse aid compositions on polycarbonate.
U.S. Pat. Nos. 5,880,088 and 5,880,089 discuss a rinse aid composition consisting, in part, of a polyalkylene oxide modified poly dimethylsiloxane or polybetaine modified polysiloxane surfactant, in combination with a fluorinated hydrocarbon surfactant. This composition is claimed to be compatible with plasticware.
The prior art is silent on the use of cationic surfactants in machine dishwashing formulations for the improvement of the final appearance of plastic washware.
SUMMARY
It has now been discovered that a class of water soluble, cationic surfactants provide an unexpected and enhanced appearance benefit to plastic articles when incorporated in the dishwashing process, as evidenced, in part, by a reduction in the formation of spots and film on the washed articles. For a preferred class of water soluble, cationic surfactants, it has surprisingly also been discovered that this enhanced benefit is not accompanied by any compromise in the article durability due to chemically caused attack or crazing.
The essential surfactants may be incorporated at any point in the dishwashing process and have been found to improve the appearance of washed plastic articles. Thus, the surfactants may be incorporated into typical detergent or rinse aid formulations and in any desired form such as tablets, powders, granulates, pastes, liquids, and gels. Addition
Carnali Joseph Oreste
Tartakovsky Alla
Delcotto Gregory
Unilever Home & Personal Care USA , division of Conopco, Inc.
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