Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Specific organic component
Reexamination Certificate
1998-11-24
2001-09-25
Delcotto, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Specific organic component
C510S499000, C510S509000, C510S370000, C510S372000, C564S298000, C564S002000
Reexamination Certificate
active
06294514
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improvement in a chemical process for preparing mono-long chain amine oxide surfactants, whereby the active content of the surfactant is greater than about 30%, by weight of the amine, and nitrite, nitrosamine and residual hydrogen peroxide levels are suppressed.
BACKGROUND OF THE INVENTION
The preparation of mono-long chain amine oxide surfactants by the oxidation of tertiary amines is of considerable commercial interest. Such surfactants are widely used in commercial cleaning compositions, especially high sudsing dishwashing detergents. Such concentrated solutions are especially useful in formulating concentrated or “compact” liquid detergent compositions which are now favored by many consumers and generally contain lower amounts of water than conventional detergents. However, the formulation of mono-long chain amine oxide surfactants containing high levels, i.e., greater than about 30%, by weight of the amine, has proven to be a difficult problem to overcome. Typically, mono-long chain amine oxide surfactants containing above 30% active result in an unhandleable gel especially when a phase modifying solvent is not incorporated. Also, some sources of mono-long chain amine oxide surfactants may be contaminated with residual amounts of nitrite materials, especially inorganic nitrites. Contamination by such nitrites may be tolerable under many circumstances. For some uses however, the presence of nitrites may be undesirable, since they can react with other ingredients which may be present in the fully formulated detergent compositions.
U.S. Pat. No. 5,583,258, issued Dec. 10, 1996 to Hawkins describes an economical process for preparing concentrated (greater than 30%) free flowing aqueous amine oxide solutions having reduced levels of nitrites and nitrosamines, and achieving said free flowing properties without the use of phase-modifying solvents. In that process, tertiary amine and hydrogen peroxide are reacted in the presence of up to 2.5% alkali metal bicarbonate (based on weight of the amine). The reaction temperature is in the range of 40-100° C. and the ratio of hydrogen peroxide to amine is 95%-125% of stoichiometric. The Hawkins reference is silent with respect to residual levels of hydrogen peroxide.
It has now been found that the presence of even relatively small amounts of hydrogen peroxide (i.e. in excess of 50 ppm or so) in amine oxides used in formulation of liquid detergents can result in odor problems, especially if the liquid detergents contain diamine compounds such as diaminopentane, which is a very effective buffer for use in such compositions. Also, when used in formulation of liquid detergents containing enzymes to enhance cleaning, amine oxides containing such relatively small amounts of hydrogen peroxide can cause degradation of the enzymes.
It is an objective of the present invention to produce high active aqueous amine oxides having residual hydrogen peroxide levels of less than 50 ppm, as well as having suppressed levels of nitrites and nitrosamines, and having free flowing properties without the use of phase modifying solvents.
It is another objective of the invention to produce said amine oxides at minimal reaction time.
All documents referred to herein are incorporated by reference and all percentages and ratios are “by weight” unless specified otherwise.
SUMMARY OF THE INVENTION
The present invention relates to a process for preparing aqueous mono-long chain amine oxide surfactant compositions having an active content of 30% or more, wherein said process comprises:
A. forming an aqueous solution of bicarbonate, the amount of said bicarbonate being from about 0.3% to about 2.5% by weight of the amine used in subsequent StepB and wherein said bicarbonate is selected from the group consisting of alkali metal bicarbonates, alkaline earth metal bicarbonates, bicarbonate precursors, and mixtures thereof,
B. adding a tertiary amine having the general formula:
wherein each R
1
and R
2
are C
1
-C
4
alkyl or hydroxyalkyl groups; and R
3
is a C
8
to C
18
alkyl or alkenyl group; and
C. oxidizing said amine with hydrogen peroxide to form the corresponding mono-long chain amine oxide having the general formula:
wherein R
1
, R
2
, and R
3
are defined as above; wherein the reaction exotherm is allowed to reach a temperature within the range of about 60° C. to about 70° C. and is then maintained within that range until the hydrogen peroxide level is 50 ppm or less and wherein said process is essentially free of any phase modifying solvent.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, it has been found that high active, free flowing aqueous amine oxide compositions having suppressed levels of nitrites and nitrosamines and very low levels of residual hydrogen peroxide can be prepared, while minimizing reaction time. The process of the present invention is an improvement over U.S. Pat. No. 5,583,258 in that in addition to achieving a free flowing, high active amine oxide composition with suppressed levels of nitrites and nitrosamines, the present process also enables the production of said compositions with minimal levels (less than 50 ppm) hydrogen peroxide at reduced reaction time.
The present invention relates to a process for preparing aqueous mono-long chain amine oxide surfactant compositions containing greater than 30% amine oxide, which comprises:
A. forming an aqueous solution of bicarbonate, the amount of said bicarbonate being from about 0.3% to about 2.5% by weight of the amine used in Step B, and wherein said bicarbonate is selected from the group consisting of alkali metal bicarbonates, alkaline earth metal bicarbonates, bicarbonate precursors, and mixtures thereof,
B. adding a tertiary amine having the general formula:
wherein each R
1
and R
2
are C
1
-C
4
alkyl or hydroxyalkyl groups;
and R
3
is a C
8
to C
18
alkyl or alkenyl group; and
C. oxidizing said amine with hydrogen peroxide to form the corresponding mono-long chain amine oxide having the general formula:
wherein R
1
, R
2
, and R
3
are defined as above; wherein the reaction exotherm is allowed to reach a temperature within the range of about 60° C. to about 70° C. and is then maintained within that range until the hydrogen peroxide level is 50 ppm or less and wherein said process is essentially free of any phase modifying solvent.
Mono-long chain amine oxide compositions produced by the present process contain greater than 30% amine oxide, typically 31% to 38%, preferably 32-37%.
Amine
The amines used as starting material in the present process have the following formula:
wherein each R
1
and R
2
are C
1
-C
4
alkyl or hydroxyalkyl groups, preferably methyl groups, and R
3
is a C
8
to C
18
, preferably a C
10
-C
18
, more preferably a C
12
-C
16
alkyl or alkenyl group.
Hydrogen Peroxide
The oxidation step herein is conducted using hydrogen peroxide or a source of hydrogen peroxide, or hydrogen peroxide generated in situ. The oxidation is conducted in water. Hydrogen peroxide is commercially available in aqueous solutions of various strengths up to 90%, which makes it a convenient oxidizing agent for forming amine oxide solutions at the desired concentration.
Bicarbonate Material
The bicarbonate material is selected from the group consisting of alkali metal bicarbonates, alkaline-earth metal bicarbonates, ammonium bicarbonate, and mixtures thereof. It will also be understood that bicarbonate precursors can be used in place of bicarbonate salts, e.g., alkali metal carbonates can be used to generate bicarbonate in situ. Preferably said bicarbonate material is ammonium bicarbonate, and more preferably, sodium bicarbonate. The bicarbonate material is present at a level of from about 0.3% to 2.5%, by weight of amine, preferably at a level of from about 1% to about 2.1%, by weight of amine.
Process
The process is preferably carried out at a pH in the range of from about 7 to about 10, more preferably from about 8 to about 10.
Typically, amine oxide surfactan
Camp Jason J.
Delcotto Gregory
The Procter & Gamble & Company
Turner Frank C.
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