Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-04-16
2001-03-20
Barts, Samel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S433000
Reexamination Certificate
active
06204412
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods of manufacturing alkylated diphenylamine compositions and the compositions formed thereby. In particular, the invention relates to methods of manufacturing alkylated diphenylamine compositions by reaction of unsubstituted diphenylamine with two or more olefins.
BACKGROUND OF THE INVENTION
Unsubstituted diphenylamine can be used as an antioxidant, but it tends to yellow. A number of alkylated diphenylamines have shown good antioxidant activity in, for example, lubricating oils and polymeric molding compositions. These alkylated diphenylamines are typically low in yellow coloring and are resistant to further yellowing.
Antioxidant compositions have been formed by alkylating unsubstituted diphenylamine to produce a mixture of alkylated diphenylamines. Suitable alkylated diphenylamine compositions for use as antioxidants are liquids at room temperature (for example, 25° C.) that contain no more than 3 wt. % unsubstituted diphenylamine, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition.
Alkylation reactions of unsubstituted diphenylamine typically produce, among other reaction products, symmetrically disubstituted diphenylamines (e.g., dioctyldiphenylamine or dibutyldiphenylamine). Symmetrically disubstituted diphenylamines typically increase the melting point of the alkylated diphenylamine composition. In sufficient amounts (depending on the particular symmetrically disubstituted diphenylamine and the other components of the composition), the result is a solid alkylated diphenylamine composition rather than a liquid. For example, a composition with 25 wt. % or more dioctyldiphenylamine (based on the total weight of substituted and unsubstituted diphenylamine) is typically solid at room temperature. Thus, to obtain the desired liquid compositions with low amounts of unsubstituted diphenylamine, a balance must be found between forming symmetrically disubstituted diphenylamine and leaving unsubstituted diphenylamine in the composition.
The formation of alkylated diphenylamine compositions by reacting unsubstituted diphenylamine with diisobutylene is described in U.S. Pat. No. 5,750,787 and references cited therein. However, diisobutylene may not be sufficiently reactive to reduce the amount of unsubstituted diphenylamine in the alkylated diphenylamine composition to less than 3 wt. % in a suitable period of time and/or without increasing the amount of dioctyldiphenylamine in the alkylated diphenylamine composition above 25 wt. %, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition.
A second olefin, which is more reactive with unsubstituted diphenylamine than diisobutylene under the reaction conditions, may be added to scavenge or reduce the amount of unsubstituted diphenylamine. Examples of such olefins include isobutylene, styrene, and &agr;-methylstyrene. In conventional methods, the second olefin is added after the reaction of unsubstituted diphenylamine and diisobutylene is substantially complete or has proceeded to a particular point. According to the method described in U.S. Pat. No. 5,750,787, incorporated herein by reference, the desired alkylated diphenylamine composition is formed if the second olefin is added after the reaction between unsubstituted diphenylamine and diisobutylene has produced a reaction composition with less than 25 wt. % dioctyldiphenylamine, less than 25 wt. % unsubstituted diphenylamine, and greater than 50 wt. % monooctyldiphenylamine, based on the total weight of unsubstituted and substituted diphenylamine in the reaction composition.
The components of the alkylated diphenylamine compositions may affect other properties of the composition. For example, it is believed that both symmetric and asymmetrically disubstituted diphenylamines provide better color stability than monosubstituted diphenylamines when mixed with resins. Because symmetrically disubstituted diphenylamines increase the melting point of the composition and may result in the formation of solid, rather than liquid, compositions, the amount of symmetrically disubstituted diphenylamine(s) is typically limited. However, asymmetrically disubstituted diphenylamines, such as butyloctyldiphenylamine, have less effect on the melting point while typically providing the better color stability.
SUMMARY OF THE INVENTION
Generally, the present invention relates to the formation of dialkylated diphenylamine compositions. One embodiment is a method of manufacturing an alkylated diphenylamine composition. Unsubstituted diphenylamine and at least one compound selected from the group of diisobutylene and &agr;-olefins having formula (I)
where R
1
, R
2
, and R
3
are functional groups that do not substantially interfere with alkylation of unsubstituted diphenylamine via the &agr;-olefinic bond of the &agr;-olefin, are combined in the presence of a clay catalyst to form a reactive composition. A second olefin composition is added to and reacted with the reactive composition. The resulting reaction product is an alkylated diphenylamine composition having no more than 3 wt. % unsubstituted diphenylamine, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition.
Typically, at least a portion of the second olefin composition is added to the reactive composition prior to forming, in the reactive composition, at least 50 wt. % monoalkylated diphenylamine, based on the total weight of substituted and unsubstituted diphenylamine in the reactive composition at the time the addition of the second olefin composition is initiated. In some instances, at least a portion of the second olefin composition is added to the reactive composition within 30 minutes, and, in some cases, within 10 minutes, of beginning to combine the unsubstituted diphenylamine and diisobutylene or &agr;-olefin of formula (I). The second olefin composition typically includes at least one second olefin that is more reactive (i.e., reacts more quickly) with unsubstituted diphenylamine than diisobutylene and/or &agr;-olefins having formula (I) under the same reaction conditions.
The alkylated diphenylamine composition formed by this method may, in some embodiments, include no more than 25 wt. % dioctyldiphenylamine, at least 25 wt. % butyloctyldiphenylamine, and/or no more than 40 wt. % monosubstituted diphenylamines, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition.
Another embodiment of the invention includes reacting unsubstituted diphenylamine, diisobutylene, and isobutylene in the presence of a clay catalyst to form an alkylated diphenylamine composition that includes at least 25 wt. % butyloctyldiphenylamine, no more than 3 wt. % unsubstituted diphenylamine, and no more than 25 wt. % dioctyldiphenylamine, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition. This alkylated diphenylamine may also include, at least in some instances, no more than 40 wt. % monosubstituted diphenylamines, based on the total weight of substituted and unsubstituted diphenylamine in the alkylated diphenylamine composition.
Yet another embodiment of the invention is a method of manufacturing a lubricating fluid composition. In this method, an alkylated diphenylamine composition is made as described above and then combined with a lubricant to form the lubricating fluid composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is believed to be applicable to methods of forming alkylated diphenylamine compositions and the compositions formed thereby. In particular, the present invention is directed to methods of forming alkylated diphenylamine compositions by the reaction of a) unsubstituted diphenylamine with b) diisobutylene and/or at least one &agr;-olefin having the formula (I)
where R
1
, R
2
, and R
3
are functional groups that do not substantially interfere with alk
Barts Samel
Black Bruce E.
Calloway Valerie L.
Davis Brian J.
Dunlap Thoburn T.
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