Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-09-17
2002-03-05
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C291S027000, C252S182260, C252S182290
Reexamination Certificate
active
06353137
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a stable aromatic amine composition comprising an aromatic amine group containing compound and a small quantity of a carboxylic acid. The present invention also relates to a method for preventing the discoloration of aromatic amine group containing compounds, and to a process for the production of light colored aromatic amine based polyether polyols.
One of the problems or disadvantages associated with amine group containing compounds is the tendency of these compounds to discolor. Discoloration of some amine group containing compounds such as, for example, ortho-toluenediamine (o-TDA), darken quickly upon exposure to air, while others such as, for example, aniline, are more stable and darken slower over time. The aliphatic amine group containing compounds also discolor over time at room temperature, but generally speaking, these discolor at a much slower rate than the aromatic amine group containing compounds.
U.S. Pat. No. 3,595,918 relates to the stabilization of tolylene diamine. This reference discloses that tolyenediamine can be stablized against discoloration by the addition of an ascorbic acid in an amount of 0.05% to about 5% by weight. Ascorbic acid, isoascorbic acid and their mixtures are the only compounds disclosed as being suitable for stabilizing tolyene diamine. These two compounds are actually cyclic lactones, not free carboxylic acids.
Amine group containing compounds are known to be suitable initiators for preparing polyether polyols. Various amine initiated polyether polyols and the process for their production are described in, for example, U.S. Pat. Nos. 3,264,268, 3,314,995, 3,446,848, 3,462,492, 3,499,009, 4,209,609, 4,391,728, 4,421,871 and 4,562,290, and as described in British Patents 1,073,664,1,311,095 and 1,398,185.
U.S. Pat. No. 4,877,879 describes the stabilization of polyether polyols prepared from amine initiators in the presence of alkaline catalysts. This reference suggests that the addition of an excess amount of a reducing agent, particularly formic acid, is effective in neutralizing the alkaline catalyst, thereby stabilizing the reactivity of the polyether polyol. This is described as being particularly effective for aliphatic amine initiators containing a tertiary nitrogen as the resultant polyether reacts with an alkylene oxide to yield a dark, color-forming quaternary amine complex.
The use of discolored amine group containing compounds as initiators in the production of polyether polyols results in the polyether polyols also being discolored. The dark color of the resultant polyether polyols is irreversible. Therefore, a means of preventing discoloration of amine group containing compounds and/or reducing the color of polyether polyols started from amine group containing compounds are commercially desirable.
One way of avoiding/preventing discoloration of these amine group containing compounds and polyether polyols prepared from these compounds, is to immediately form polyether polyols from the amine group containing compounds after distillation, before they come into contact with air. This, however, requires that the amine group containing compounds and the resultant polyether polyols be produced in the same plant, with no time lapse between the point of distilling the amine containing compounds and when these are used as initiators to form polyether polyols. Otherwise, stringent engineering measures are required to ensure that the amine compounds are oxygen-free at all points in the process between the time they are purified and used. Currently, it is necessary to keep the entire process totally under nitrogen to prevent and/or minimize this discoloration.
In accordance with the present invention, it was found that the addition of a relatively small quantity of certain groups of compounds to aromatic amine compounds surprisingly formed compositions which are stable against discoloration. This is true even after storing the treated aromatic amine compositions in a 100° C. oven for 1 week. Polyether polyols can then be produced from these treated aromatic amine compounds, without the derogatory color effects one would normally expect.
SUMMARY OF THE INVENTION
This invention relates to stable aromatic amine compositions comprising:
a) from 0.001 to 10% (preferably 0.1 to 1%, most preferably from 0.1 to 0.5%) by weight, based on 100% by weight of component b), of at least one organic compound containing at least one carboxylic acid group, wherein the organic compound contains from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, and most preferably from 1 to 6 carbon atoms, and
b) at least one aromatic amine group containing compound.
The present invention also relates to a process for stabilizing the color of an aromatic amine group containing compound. This process comprises 1) adding a) from 0.001 to 10% (preferably 0.1 to 1%, most preferably from 0.1 to 0.5%) by weight, based on 100% by weight of component b), of at least one organic compound containing at least one carboxylic acid group, wherein the organic compound contains from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, and most preferably from 1 to 6 carbon atoms, to b) at least one aromatic amine group containing compound. Ortho-toluenediamine is a preferred aromatic amine in which discoloration can be prevented or minimized by adding a small quantity of one of these organic compounds.
The present invention also relates to a process for the production of stable, light colored aromatic amine-based polyether polyols comprising alkoxylating an aromatic amine group containing compound, wherein b) said aromatic amine group containing compound has been treated with a) from 0.001 to 10% (preferably from 0.1 to 1%, most preferably 0.1 to 0.5%) by weight, based on 100% by weight of the aromatic amine group containing compound, of at least one organic compound containing at least one carboxylic acid group, wherein said compound contains from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, and most preferably from 1 to 6 carbon atoms. The addition of a small quantity of an organic compound containing at least one carboxylic acid group, wherein the compound contains from 1 to 20 carbon atoms is effective in preventing or minimizing the discoloration of aromatic amine group containing compounds, and thereby allows light colored polyether polyols to be produced therefrom.
DETAILED DESCRIPTION OF THE INVENTION
As used in the present invention, the term stable with respect to the aromatic amine compositions of the present invention means that the color of these is lighter than the standard when stored for at least 1 week at a temperature of ≧25° C. The standard is the corresponding untreated aromatic amine. The treated amine compositions varied in color from a pale pink to a ruby red, based on a visual assessment. These colors were then defined by the reflectance values (L, a, b) using a Hunterlab Color QuestII unit.
In accordance with the present invention, suitable organic compounds containing at least one carboxylic acid group wherein the organic compound contains from 1 to 20 carbon atoms (preferably from 1 to 10 carbon atoms, most preferably from 1 to 6 carbon atoms) are suitable for preventing discoloration of aromatic amine group containing compounds. The number of carbon atoms set forth above is intended to be inclusive of the carbon atom in the carboxylic acid group(s). Suitable examples of these organic aliphatic compounds include, for example, mono- and polycarboxylic acid groups, aliphatic compounds containing mono- and polycarboxylic acid groups and at least one hydroxyl groups, aromatic compounds containing mono- and polycarboxylic acid groups, aromatic compounds containing mono- and polycarboxylic acid groups and at least one hydroxyl group, and compounds containing mono- and polycarboxylic acid groups and one or more ether groups, amine groups or thio groups.
The suitable aliphatic compounds containing mono- and polycarboxylic acid groups typically contain from 1 to 20 carbon atoms
Bayer Corporation
Brown N. Denise
Gil Joseph C.
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