Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-10-02
2004-07-20
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S424000, C510S426000, C510S428000, C510S446000, C510S447000, C510S488000, C510S400000, C510S492000, C510S501000, C510S506000
Reexamination Certificate
active
06764989
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to cleaning compositions and methods for making and using such compositions. More particularly, the invention relates to light duty liquid cleaning compositions containing &agr;-sulfofatty acid ester and methods for making and using such compositions.
Soaps made from animal fats have been used for many years to clean dishes, utensils and other materials. More recently, cleaning compositions have been formulated using other surfactants to enhance their cleaning performance. Typical surfactants include anionics, nonionics, zwitterionics, ampholytics, cationics and those described in
Surface Active Agents
, Volumes I and II by Schwartz, Perry and Berch (New York, Interscience Publishers), in
Nonionic Surfactants
, ed. by M. J. Schick (New York, M. Dekker, 1967), and in McCutcheon's
Emulsifiers
&
Detergents
(1989 Annual, M.C. Publishing Co.), the disclosures of which are incorporated herein by reference.
Nonionic surfactants provide good cleaning properties and can also act as defoaming agents. Nonionic surfactants are typically manufactured by alkoxylation of alcohols, fatty acids or esters. For example, nonionic surfactants can be synthesized by ethoxylating an alcohol or fatty acid with ethylene oxide; ethoxylation adds ethoxy groups (—OCH
2
CH
2
—) to the active hydrogen of the alcohol or fatty acid. (See, e.g., U.S. Pat. Nos. 5,627,121; 4,835,321; 4,820,673; 4,775,653; 4,754,075; 4,239,917; and International Patent Publication No. WO 85/00365, the disclosures of which are incorporated herein by reference.) Other nonionic surfactants include amine oxides and alkanolamides. Alkanolamides can be alkoxylated to form alkoxylated alkanolamides. (See, e.g., U.S. Pat. Nos. 6,034,257 and 6,034,257, the disclosures of which are incorporated herein by reference.) Nonionic surfactants alone, however, generally lack sufficient cleaning performance for some light duty applications.
Nonionic surfactants are often combined with inorganic or organic salts of a polyvalent metal cation, particularly magnesium cations. The metal salts provide several benefits, such as improved cleaning performance in dilute usage, particularly in soft water areas. Although magnesium is the preferred multivalent metal from which the salts are formed, other polyvalent metal ions can also be used. The use of polyvalent metal salts can be limited, however, because they can be insoluble in the aqueous phase of the system. In particular, changes in the pH of the aqueous phase can cause precipitation of the metal salts and deposition of dishes or utensils cleaned with the composition.
Anionic surfactants can also be combined with nonionic surfactants. Recently, interest in &agr;-sulfofatty acid esters (also referred to herein as “sulfofatty acids”) as an anionic co-surfactant has increased due to the improved cleaning properties of this class of surfactants over a range of water hardness conditions. The use of &agr;-sulfofatty acid esters has not been widely accepted, however, due to several disadvantages of such sulfofatty acids. One disadvantage is that di-salts form during manufacture of &agr;-sulfofatty acid esters. (Di-salts form by hydrolysis of the ester bond of the &agr;-sulfofatty acid ester to form sulfonated fatty acid salts.) While mono-salts of &agr;-sulfofatty acid esters have the desired surface active agent properties, di-salts have several undesirable properties that degrade the performance of the resulting composition. For example, the Kraft point of a C
16
methyl ester sulfonate (“MES”) di-salt is 65° C., as compared to 17° C. for the mono-salt form of C
16
MES. (The Kraft point is the temperature at which the solubility of an ionic surfactant becomes equal to its critical micelle concentration; below the Kraft point, surfactants form precipitates instead of micelles.) Thus, the higher the Kraft point leads to more di-salt precipitates from the composition. The resulting poor di-salt solubility in cool and even slightly hard water is a disadvantage in most applications. The presence of large amounts of di-salt in &agr;-sulfofatty acid ester, therefore, results in a poorer quality &agr;-sulfofatty acid ester product, characterized by degraded performance and reduced application flexibility.
A related problem is that di-salts form during storage and in detergent formulations. In particular, mono-salts of &agr;-sulfofatty acid ester hydrolyze in the presence of moisture and a high pH component to form di-salts. For example, in detergent formulations where MES is well mixed with high pH components under aqueous conditions, the MES will hydrolyze nearly completely to the di-salt form. High pH components include builders, such as silicates or carbonates, and bases, such as sodium hydroxide (NaOH). This chemical instability discourages the use of &agr;-sulfofatty acid esters in many applications.
Another problem associated with &agr;-sulfofatty acid ester-containing detergent compositions is pH drift in unbuffered liquid formulations. In concentrated solutions of such sulfofatty acids, the pH of the solution drifts towards the acidic (lower) range. pH drift interferes with other cleaning components in the composition. To prevent pH drift, buffering or alkalizing agents are added to detergents. Buffering or alkalizing agents, such as caustic soda (NaOH), cause additional di-salt formation, however, which decreases the performance of the &agr;-sulfofatty acid ester.
&agr;-Sulfofatty acid esters also have limited solubility in concentrated solutions. For example, phase separation occurs in concentrated aqueous solutions of C
16
or C
18
&agr;-sulfofatty acid esters if the sulfofatty acid ester is not adequately solubilized.
Thus, there is a need for light duty liquid cleaning compositions comprising &agr;-sulfofatty acid ester that exhibit reduced di-salt formation. There is a further need for a light duty liquid in cleaning compositions that are stabilized and exhibit reduced pH drift and/or phase separation by the &agr;-sulfofatty acid ester.
SUMMARY OF THE INVENTION
The present invention provides cleaning compositions comprising &agr;-sulfofatty acid ester. Effective amounts of &agr;-sulfofatty acid ester and hydrotrope are combined to form a cleaning composition, such as a light duty liquid cleaning composition. The composition further includes nonionic surfactant, such as alkoxylated alkanolamide and/or amine oxide.
The &agr;-sulfofatty acid ester and the hydrotrope form a stabilized composition. In one embodiment, the hydrotrope solubilizes the &agr;-sulfofatty acid ester in solution and reduces phase separation. In a second embodiment, effective amounts of the &agr;-sulfofatty acid ester and the hydrotrope reduce pH drift in the composition, thereby reducing additional di-salt formation. In another embodiment, effective amounts of the &agr;-sulfofatty acid ester and the hydrotrope reduce additional di-salt formation by sparing the need for alkalizing agents. In still another embodiment, effective amounts of the &agr;-sulfofatty acid ester and the hydrotrope provide multiple stabilizing effects. In a preferred embodiment, the hydrotrope is urea. The urea is typically substantially free of ammonium carbamate.
The nonionic surfactants can be, for example, an alkoxylated alkanolamide and/or an amine oxide. The nonionic surfactants improve the cleaning performance of the composition. In a preferred embodiment the nonionic surfactant and &agr;-sulfofatty acid ester spare the requirement for polyvalent metal salts. The composition can optionally include other cleaning components, such as, for example, alkyl poly-glucosides, n-methyl glucamides and other glucose and/or galactose derived surfactants.
Methods of making cleaning compositions comprising &agr;-sulfofatty acid ester are also provided. Such methods generally include providing &agr;-sulfofatty acid ester, hydrotrope and nonionic surfactant, and mixing these components to form the composition. The method optionally further includes adding other cleaning components to the
Huish Paul Danton
Jensen Laurie A.
Libe Pule B.
Huish Detergents, Inc.
Ogden Necholus
Townsend and Townsend / and Crew LLP
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