Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-08-31
2002-03-12
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S433000, C564S308000, C564S309000, C544S102000, C544S103000, C544S035000
Reexamination Certificate
active
06355839
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for preparation of alkylated diphenylamine that is liquid at room temperature. More specifically, this invention relates to a process for alkylation of diphenylamine (DPA) with polyisobutylene (PIB) oligomers having a molecular weight in the range of 120 to 600 and having a methylvinylidene content of at least 25%. Preferably, the reaction is carried out in the presence of a clay catalyst, but other types of catalysts can be used. The alkylated diphenylamine prepared by the disclosed process exhibits excellent antioxidant characteristics in lubricating oil formulations.
BACKGROUND OF THE INVENTION
Alkylated diarylamines, such as alkylated diphenylamine, are well known in the art to be effective stabilizers or antioxidants in a wide variety of organic materials, including, among other organic materials, mineral oil derived lubricants and synthetic lubricants. In this use, light colored, liquid (at about 20° C.) products are desirable for a number of practical reasons.
Alkylation of diarylamines, such as diphenylamine, with olefins in the presence of suitable alkylation catalysts is well known in the art. For example, U.S. Pat. No. 2,943,112 (Popoff et al.) teaches a two step process whereby alkylation of diphenylamine with relatively unreactive olefins, such as secondary alkenes (column 4, line 9-23), is followed by an alkylation reaction with more reactive olefins to scavenge the unreacted diphenylamine. Popoff also teaches the use of acid activated clay as an alkylation reaction catalyst to achieve the desired light color. (See also, U.S. Pat. No. 3,452,056 wherein acid clay, AlCl
3
and ZnCl
2
are mentioned as suitable catalysts).
Similarly, Franklin, U.S. Pat. No. 4,824,601, (column 1, lines 26-67), teaches the use of acidic clay catalysts to alkylate diphenylamine and further teaches that a light colored, liquid product may be prepared by process comprising reacting the alkylation reactants within certain molar ratios and temperature ranges for a time sufficient to ensure the alkylated product contains less than 25% dialkylated diphenylamine. This low proportion of dialkylated diphenylamine is disclosed as necessary to avoid the formation of crystallized, solid products, which are not advantageous in terms of ease of handling, transportation, storage and incorporation into the substrate to be stabilized.
More recently, addressing the same problem; that is, preparing an effective antioxidant from diphenylamine that is liquid at room temperature, Lai in U.S. Pat. Nos. 5,672,752 (Lai 1) and 5,750,787 (Lai 2), teaches processes for alkylating diphenylamine with linear alpha olefins (Lai 1) and diisobutylene (Lai 2) in the presence of a clay catalyst. These processes, as disclosed, selectively result in a higher proportion of monoalkylated diphenylamine and a lower proportion of unsubstituted diphenylamine and/or disubstituted or polysubstituted diphenylamines. These patents further disclose that to obtain the desired liquid product, the ratio of olefin to diphenylamine in the reaction mixture, together with reaction temperature and time is important to give a product mixture with less than 25% dioctyldiphenylamine, less than 25% unreacted diphenylamine and greater than 50% by weight monooctyldiphenylamine based on the total weight of the diphenylamine and alkylated DPA.
In U.S. Pat. No. 6,204,412 (Lai 3) Lai discloses yet another method of alkylating diphenylamine to obtain a light colored, liquid product, which comprises a two step method wherein, in the second step, a second olefin is added to the reaction mixture containing diphenylamine and diisobutylene (and/or an alpha-olefin of the disclosed formula) to scavenge or reduce the amount of unreacted diphenylamine in the product As with Lai 1 and Lai 2, specific mole ratio ranges, reaction temperatures and reaction times are disclosed as important to obtain the desired alkylated diphenylamine that is liquid at room temperature.
SUMMARY OF THE INVENTION
The present invention relates to the preparation of alkylated diphenylamine and other alkylated aromatic amine antioxidant compositions using highly reactive polyisobutylenes as the alkylating reagent. Highly reactive polyisobutylenes (HR PIB) are valued for use in the lubricating oil additive industry and are commercially produced in the chemical industry. These valued HR PIB polymers are characterized by the presence of significant amounts of 2-methylvinylidene isomers, R(CH
3
)C═CH
2
where R is a PIB residue, and a molecular weight preferably in the range of about 500 to 5000. Such 2-methylvinylidene polyisobutylenes are typically prepared using boron trifluoride catalysis. The preparation of such polyisobutylenes in which the methylvinylidene isomer comprises a high percentage of the total olefin composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808, the disclosures of which are incorporated herein by reference.
It is generally known by those skilled in the art that the commercial HR PIB production process described above generates a HR PIB distillate byproduct that; (i) contains mostly C
8
H
16
to C
28
H
56
oligomers (average C
14
H
28
), (ii) exhibits a relatively low average molecular weight of about 200 and, (iii) contains 2-methylvinylidene in the amount of at least about 25%. This low molecular weight distillate byproduct, which amounts to several percent of total HR PIB production, has little value and is typically sold as a waste product. Thus, a need exists in the chemical industry to develop a valuable use for the HR PIB distillate byproduct. It is the object of the present invention to meet this need by providing a novel process for preparation of a valuable alkylated diphenylamine antioxidant that is liquid at room temperature (about 20° C.) using the HR PIB distillate byproduct, or fractions thereof. For purposes of this invention, the term “polyisobutylene” refers to the HR PIB distillate byproduct and is further defined as comprising a mixture of highly reactive polyisobutylene oligomers, said mixture containing mostly C
8
H
16
to C
28
H
56
oligomers (average C
14
H
28
), exhibiting a molecular weight in the range of about 120 to about 600 (an average of about 200), containing a 2-methylvinylidene amount of at least about 25% and containing diisobutylene (C
8
) in a fractional amount ranging from 0% to about 50%.
There are several advantages to using the presently employed polyisobutylene oligomers to alkylate diphenylamine and other aromatic amines, including, for example: (1) the alkylation reaction can be carried out at elevated temperatures under low pressure; (2) flexibility in utilizing a new, previously wasted feedstock, which can be comprised of specific carbon number fractions, a mixture of selected fractions or, most desirably, use of the total, unfractionated HR PIB distillate byproduct, with or without removal of inert solvent (2% to 10%); (3) the alkylation reaction can be carried out at relatively lower temperatures, which because of the greater reactivity afforded by the presence of 2-methylvinylidene results in a liquid alkylated product and no solid product as is usual in low temperature reactions with conventional diisobutylene, and; (4) milder, low temperature reaction conditions can be employed to control fragmentation.
Accordingly, the present invention provides a novel, one-step, process for the preparation of alkylated diphenylamine, which comprises reacting diphenylamine with polyisobutylene in the presence of a suitable alkylation catalyst at a suitable alkylation reaction temperature less than about 200° C., wherein said polyisobutylene contains at least about 25% of a methylvinylidene isomer and wherein the number average molecular weight of said polyisobutylene is in the range of about 120 to about 600 and wherein the mole ratio of said polyisobutylene to said diphenylamine is in the range of 1.0:1.0 to 4.0:1.0 and forming an alkylated diphenylamine product wherein said alkylated diphenylamine product is liquid at room temperature and atmospheric p
Barts Samuel
Chevron U.S.A. Inc.
Ellinwood Steven R.
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