Cleaning compositions for solid surfaces – auxiliary compositions – Auxiliary compositions for cleaning – or processes of preparing – Textile softening or antistatic composition
Reexamination Certificate
2001-02-01
2003-10-07
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Auxiliary compositions for cleaning, or processes of preparing
Textile softening or antistatic composition
C510S223000, C510S230000, C510S421000, C510S434000, C510S476000, C510S477000, C510S488000, C510S514000, C510S525000
Reexamination Certificate
active
06630440
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a machine dishwasher rinse aid formulation useful for promoting wetting of the rinse water as well as preventing hard water precipitation on substrates and thereby reducing spotting and filming of the dried substrate surface. More particularly, the invention relates to compatibilization of a low foaming nonionic surfactant with a low molecular weight acidic or neutralized poly(meth)acrylic acid, to foam a stable, non-phase separating aqueous rinse aid dispersion under acidic conditions, without the aid of a high molecular weight compatibilizing polymer and without requiring an additional high cloud point nonionic surfactant.
BACKGROUND OF THE INVENTION
Rinse aids are used in commercial and institutional machine dishwashers and very often, also in household automatic dishwashers. During the rinse cycle, a final rinse of fresh water serves to displace pre-final rinse water and its attendant detergent and soil residues. Rinse aid formulations are aqueous solutions containing a low foam nonionic surfactant. During the rinse cycle, the rinse aid is injected into the final fresh water rinse at a concentration of about 100 to about 500 ppm. The surfactant in the rinse water lowers the surface tension of the rinse water and improves the wetting action of the rinse water on the somewhat hydrophobic substrate surfaces. Improved wetting reduces the tendency of the rinse water to form drops containing dissolved solids on the substrate surface which give rise to spots upon drying. Accordingly, the functions of the surfactant in the rinse aid are to effectively reduce the surface tension during the draining period and to be low foaming so as to avoid traces of foam on the rinsed substrate which result in a residue upon evaporation. While low foam surfactant have improved the wetting of rinse water on substrates, they have not completely eliminated spotting and streaking problems. It is known that the addition of a low molecular weight neutralized polyelectrolyte, such as polyacrylate, to the rinse water can further reduce spotting and filming or streaking.
It is known that poly(meth)acrylic acid polymers are especially useful because they do not contribute to foam formation and do not interfere with the soil defoaming activity of the low foam surfactants. It is also known that a major obstacle to the use of low molecular weight poly(meth)acrylic acid polymers in rinse aids is the incompatibility of these polymers in aqueous rinse aid formulations containing low foam surfactants. Combining such polymers and sur ants in water results in phase separation. Upon standing for a short period of time the water containing these polymers and surfactants will form two or more layers of different compositions. This phase separation is obviously unsatisfactory since non-uniform addition of the desired components will occur as the formulation is injected into the dishwashing machine. For example, the formulation may contain too little surfactant to provide adequate wetting or too much surfactant, leading to excessive foam.
It is known to combine low molecular weight polyclectrolytes with low foam surfactants in detergent formulations. One reference discloses the desirability for combining polyelectrolytes with low foam surfactants in rinse aid concentrates. However, this reference requires the use of an alkali neutralized high molecular weight polymer to compatibilize the low foam nonionic surfactant with a low molecular weight neutralized poly(meth)acrylic acid in order to form a stable, non-phase separating aqueous rinse aid dispersion.
It is also known to formulate a stable rinse aid composition by mixing a low foam nonionic surfactant, an acrylic acid polymer of molecular weight 1000 to 250,000, and an additional nonionic surfactant having a cloud point of at least 70 degrees C, to serve as a stabilizer.
It is an object of the present invention to formulate an aqueous rinse aid containing a low foam nonionic surfactant and a low molecular weight neutralized, partially neutralized, or non-neutralized poly(meth)acrylic acid without the use of a compatibilizing high molecular weight polymer or a high cloud point co-surfactant. It is a further object of the invention to provide a stable aqueous rinse aid dispersion which reduces spotting and filming while improving sheeting action and drainage.
BACKGROUND ART
U.S. Pat. Nos. 3,563,901 and 4,443,270 disclose hydrotropes such as sodium xylene sulfonate, cumene sulfonate and short chain alkyl sulfates, used for raising the cloud point of low foam surfactants to permit the formulation of stable aqueous concentrates.
U.S. Pat. No. 4,203,858 discloses a low foaming, phosphate-free, dishwashing composition comprising an alkali metal or ammonium carbonate, such as sodium carbonate, a water soluble salt of a polyelectrolyte having a molecular weight of from about 500 and 4,000 and optionally up to 10 weight percent of a foam-suppressing nonionic surfactant. Typical of the polyelectrolytes are acrylic, methacrylic, maleic and itaconic acid polymers. Homopolymers and copolymers of acrylic and methacrylic acid having a molecular weight ranging from 504 to 1291 are preferred. The '858 patent discloses that the major differences between this composition and prior polyclectrolytes-built dishwashing compositions are the low concentration of polyelectrolyte and the poor metal ion sequestering capability of these polyelectrolytes.
Other references disclosing poly(meth)acrylic acids and their salts in detergent and cleaning applications include U.S. Pat. Nos. 3,671,440; 3,853,981; 3,950,260; 3,933,673; 3,922,230 and 4,521,332. These references do not disclose the desirability of combining polyelectrolytes with low foam surfactants in rinse aid concentrates.
U.S. Pat. No. 4,678,596 discloses the use of an alkali neutralized high molecular weight polymer to compatibilize the low foam nonionic surfactant with a low molecular weight neutralized poly(meth)acrylic acid in order to form a stable, non-phase separating aqueous rinse aid dispersion. Other related references include European Patent Nos. 245,987 and 308,221.
EPO 308221B1 discloses a rinse aid composition containing a low foam nonionic surfactant, an acrylic acid polymer of molecular weight 1000 to 250,000, and an additional nonionic surfactant having a cloud point of at least 70 degrees C, to serve as a stabilizer.
All of the above references either (I) require the use of a high molecular weight compatibilizing polymer, or (ii) require an additional nonionic surfactant having a cloud point of at least 70 degrees C, in order to provide a stable non-phase separating rinse aid.
U.S. Pat. No. 5,739,099 discloses a rinse aid composition comprising a blend of nonionic, cationic, anionic zwitterionic and amphoteric surfactants, hydrotropes, and copolymers of alkylene oxide adducts of allyl alcohol and acrylic acid useful in reducing spotting and filming of dishware.
U.S. Pat. No. 5,516,452 discloses a rinse aid composition utilizing an anionic hydrotrope and a blend of two nonionic surfactants, such as alcohol alkoxylate and a block copolymer of ethylene oxide and propylene oxide.
SUMMARY OF THE INVENTION
The invention meets the needs above by providing a stable aqueous rinse aid dispersion. In one aspect of the present invention, the rinse aid dispersion includes: (i) a low foaming nonionic surfactant present in a range of from about 2% to about 80% by weight of the rinse aid dispersion; (ii) a hydrotrope present in a range of from about 0.5% to about 20% by weight of the rinse aid dispersion; and (iii) a poly(meth)acrylic acid polymer present in a range of from about 0.1% to about 15% by weight of the rinse aid dispersion. The poly(meth)acrylic acid polymer has a weight average molecular weight in a range of from about 1000 to about 50,000. The rinse aid dispersion has a pH in a range of from about 2 to about 6.
In another aspect of the present invention, the rinse aid includes: (i) a low foaming nonionic surfactant present in a range of from about 2% to about 80% by we
Foley Peter Robert
Song Xiaoqing
Gupta Yogendra N.
Mruk Brian P.
The Procter & Gamble & Company
Waugh Kevin L.
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