Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With halogen – nitrogen – oxygen – or phosphorus containing...
Reexamination Certificate
2000-04-07
2002-03-26
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With halogen, nitrogen, oxygen, or phosphorus containing...
C510S382000, C510S383000
Reexamination Certificate
active
06362152
ABSTRACT:
TECHNICAL FIELD
The invention relates to concentrated aqueous formulations of a sodium salt of o-phenylphenol. The invention relates more specifically to aqueous formulations that exhibit excellent color stability while containing high concentrations of sodium o-phenylphenate. The invention relates especially to such formulations containing from about 15 to about 75 weight percent of sodium o-phenylphenate.
BACKGROUND OF THE INVENTION
O-phenylphenol (OPP) is well known in the art as an antimicrobial, disinfectant and preservative. Sodium salts of o-phenylphenol are available commercially, for example, as DOWICIDE A and DOWICIDE 25L (from the Dow Chemical Company). NaOPP is described, for example, in U.S. Pat. Nos. 3,503,885; 3,850,864; 5,420,015; and 5,380,624.
NaOPP is frequently provided commercially in the form of a concentrated, aqueous composition. The concentrate is typically diluted to a concentration that is desirable for antimicrobial use. However, concentrated aqueous NaOPP compositions generally exhibit poor color stability. Storage at room temperature, even for a few days, can cause the compositions to turn light brown. With additional time, the compositions can turn dark brown. While the color of the composition does not significantly impact the antimicrobial efficacy of the composition, the color can impart a negative perception to the customer.
In addition to color degradation, aqueous solutions of NaOPP are prone to undergoing additional deleterious processes. Haziness can form as a result of suspended particles. A process known as “oiling-out” can occur in which a non-soluble oily layer can form and either float or sink to the bottom of the product. Sedimentation, or the setting out of solid particles, can also occur.
It is known in the art that compositions containing phenols generally have poor color stability. While approaches for improving the color stability of phenol compositions have been developed, these approaches have generally been designed to improve the color stability of compositions containing relatively low phenol concentrations.
Thus, a need remains for development of aqueous compositions containing high concentrations of NaOPP that exhibit improved color stability.
SUMMARY OF THE INVENTION
The present invention is directed to a color stable aqueous solution that contains a relatively high concentration of sodium o-phenylphenate. The aqueous solutions of NaOPP prepared according to the present invention exhibit an absorbance at 400 nanometers of at most one-half the absorbance exhibited by untreated solutions after incubation for 72 hours at 44° C. and 4 hours under ultraviolet light. The aqueous solution is useful as a concentrate that can be diluted to a desirable antimicrobial concentration level prior to application.
Accordingly, the invention is found in a color-stable concentrate composition containing about 15 to about 75 weight percent sodium o-phenylphenate, about 0.1 to about 5 weight percent of an oxygen scavenger, and about 0.1 to about 2 weight percent of a free radical scavenger selected from the group consisting of N,N-diethylhydroxylamine, N-isopropylhydroxylamine, and hydroxylamine, with the balance being water.
The invention is also found in a color stable composition that includes about 15 to about 75 weight percent of sodium o-phenylphenate, about 0.1 to about 5 weight percent of sodium sulfite, about 0. 1 to about 2 weight percent of N,N-diethylhydroxylamine, and up to about 40 weight percent of ethylene glycol or propylene glycol, with the balance being water.
The invention is further directed to a method of preparing a color-stable concentrate solution. The method includes blending or mixing in an aqueous solution of about 15 to about 75 weight percent sodium o-phenylphenate about 0.1 to about 5 weight percent of an oxygen scavenger and about 0.1 to about 2 weight percent of a free radical scavenger selected from the group consisting of N,N-diethyl-hydroxylamine, N-isopropylhydroxylamine, and hydroxylamine.
The invention is also directed to a method of preparing a color stable concentrate solution that includes the steps of reacting in-situ o-phenylphenol and sodium hydroxide in an aqueous solution, in amounts necessary to prepare about 15 to about 75 weight percent sodium o-phenylphenate. The aqueous solution also includes about 0.1 to about 5 weight percent of an oxygen scavenger and about 0.1 to about 2 weight percent of a free radical scavenger selected from the group consisting of N,N-diethylhydroxylamine, N-isopropylhydroxyl-amine, and hydroxylamine.
DETAILED DESCRIPTION OF THE INVENTION
The aqueous concentrate compositions described herein exhibit excellent color stability. While prior art compositions containing relatively high levels of sodium o-phenylphenate are prone to color degradation or instability, the compositions espoused by the invention exhibit substantially reduced levels of color degradation or instability. We have found that the inclusion of several adjuvants result in a composition with desirable color stability performance. Specifically, we have found oxygen scavengers and free radical scavengers to be quite useful We have found that the use of solubilizers can be beneficial in helping to solubilize otherwise insoluble degradation products of the sodium o-phenylphenate.
As used herein, the term “oxygen scavenger” is used to describe compounds that can absorb, neutralize or otherwise remove oxygen from solution. It is believed that molecular oxygen, if not removed, can react with o-phenylphenol and sodium salts thereof to form color bodies. Oxygen scavengers are also known as antioxidants. A wide number of oxygen scavengers are known in the art. Examples of oxygen scavengers suitable for use herein include sodium sulfite, sodium pyrosulfite, sodium thiosulfate, sodium dithionite and sodium hypophosphite. Preferred oxygen scavengers include sodium sulfite.
The sodium o-phenylphenate compositions of the invention include about 0.1 to about 5 weight percent of an oxygen scavenger. Preferably, the oxygen scavenger is present in the composition at a concentration of about 0.5 to about 1.0 weight percent. All compositions discussed herein are described in terms of weight percent, based upon the total weight of the composition.
The term “free radical scavenger” refers to compounds that can absorb, neutralize or otherwise remove free radicals from the compositions of the invention. A free radical scavenger can remove free radicals that would otherwise participate in degradation reactions. Free radicals can be generated via thermal or light induction. A number of free radical scavengers are known to those of skill in the art. Useful free radical scavengers are hydroxylamines, for example. A preferred free radical scavenger is N,N-diethylhydroxylamnine. The compositions of the invention contain about 0.1 to about 2 weight percent of a free radical scavenger.
The compositions of the invention may also include a solubilizer that can function to solubilize non-water soluble sodium o-phenylphenoate degradation products. Solubilizing the degradation products helps to prevent components from separating, thereby reducing visible haze. Examples of useful solubilizers include alkylene diols such as ethylene glycol and propylene glycol. Solubilizers can be present at a concentration as high as 40 weight percent. Preferably, the compositions of the invention contain about 5 to about 10 weight percent of a solubilizer.
Another optional component is a metal ion scavenger or chelant. These are used to complex with metal ions in solution, thereby preventing the ions from catalyzing reactions between oxygen and sodium o-phenylphenate or other organic materials. Examples of useful chelants are triethanolamine and aminocarboxylates such as ethylenediaminetetraacetic acid (EDTA), especially tetrasodium EDTA. If used, the metal ion scavenger or chelant is present at a concentration of about 0.01 to about 2 weight percent. Preferably, the chelant is present at a concentration of about 0.01 to 0.05 weight percent.
The compositi
Carsten Dawn L.
Gartner Charles D.
Walter, Jr. Richard W.
Young Tracy L.
Gupta Yogendra N.
Petruncio John M
The Dow Chemical Company
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