Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-05-28
2001-05-22
Kumar, Shailendra (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S134000, C564S136000, C564S137000, C564S152000, C564S201000, C554S035000, C554S036000
Reexamination Certificate
active
06235933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention describes a process for preparing, purifying and isolating &bgr;-hydroxyalkylamides which are used as chemical intermediates and as chemical crosslinkers for carboxyl-functional polyesters and acrylates in solvent-based surface coatings and powder coatings. The use in powder coatings in particular places very high demands on the physical form of the &bgr;-hydroxyalkylamides. Only free-flowing powders, i.e. not soft, sticky or waxy powders, are suitable for use in powder coatings.
2. Description of the Prior Art
&bgr;-Hydroxyalkylamides are prepared by aminolysis of alkyl esters by &bgr;-aminoalcohols in the presence of basic catalysts such as sodium hydroxide or sodium methoxide, with the &bgr;-aminoalcohols being used in excess in most cases wing to the selectivity of the reaction. In the case of liquid &bgr;-hydroxyalkylamides, the unreacted &bgr;-aminoalcohols have to be removed from the reaction mixture before the &bgr;-hydroxyalkylamides can be used. In the case of solid &bgr;-hydroxyalkylamides, the isolation and purification of the &bgr;-hydroxyalkylamides is carried out either by crystallization in a solvent (J. Coat. Tech., 50(643), 49-55 (1978), U.S. Pat. No. 4,076,917, U.S. Pat. No. 4,727,111) or, specifically in the case of solid &bgr;-hydroxyethylamides, directly from the reaction mixture in a solvent-free slurry process (U.S. Pat. No. 5,101,073).
In the case of crystallization in solvents, the &bgr;-hydroxyalkylamides are generally either added to a hot solvent such as methanol and/or acetone or the solvent is added to the &bgr;-hydroxyalkylamides. After cooling the solution and crystallization, the &bgr;-hydroxyalkylamides are then filtered off and freed of solvent by drying. The yield is reduced by the solubility in the solvent used. In addition, the catalyst remaining in the reaction mixture can lead to undesirable secondary reactions, e.g. to diacetone alcohol when using acetone as solvent, which also results in losses in the recovery of the solvent used. It is also found that unreacted &bgr;-aminoalcohols also coprecipitate as undesired impurities in the crystallization and, in addition, &bgr;-aminoalcohols act as solubilizers which have an adverse effect on the crystallization. As a result, the yield of &bgr;-hydroxyalkylamides is reduced further.
Specifically the preparation of solid &bgr;-hydroxyethyl-amides can be carried out in the melt in a solvent-free slurry process. The slurry process (U.S. Pat. No. 5,101,073) is based on the equilibrium reactions which proceed in the preparation of &bgr;-hydroxyethylamides being shifted in the direction of the desired end product &bgr;-hydroxyethylamide, the desired &bgr;-hydroxyethylamide being precipitated from the melt by heating in a particular temperature range and the melt crystallizing as a result. In the case of substances where the desired &bgr;-hydroxyalkylamide does not precipitate from the melt, e.g. in the case of &bgr;-hydroxypropylamides, the slurry process fails. In addition, the slurry process is restricted to the use of equimolar amounts of alkyl esters and &bgr;-hydroxyethylamines. The slurry process gives, when equimolar amounts of dialkyl esters and &bgr;-hydroxy-ethylamines are used in the presence of basic catalysts such as sodium hydroxide or sodium methoxide, not only the desired monomeric &bgr;-hydroxyethylamides (I) but also, as by-products, dimers (II) and esteramides (III). Furthermore, the reaction product still contains &bgr;-hydroxyethlamine.
where m=0 to 10 and R is a C1-C5-alkyl group.
An important process step in the preparation of &bgr;-hydroxyalkylamides by aminolysis of alkyl esters by &bgr;-aminoalcohols in the presence of basic catalysts such as sodium hydroxide or sodium methoxide is the removal of unreacted &bgr;-aminoalcohols from the reaction mixture.
The separation of the excess &bgr;-aminoalcohol by dissolution in a suitable solvent such as methanol and subsequent removal of the &bgr;-aminoalcohol by means of an ion exchanger is known from the abovementioned literature. The desired &bgr;-hydroxyalkylamide is subsequently obtained by distilling off the solvent. However, this method is only suitable for the laboratory scale, since the removal of by-products by means of ion exchangers is only suitable for separating off small amounts of by-products. If a high proportion of by-products is present, i.e. when using a large excess of &bgr;-aminoalcohol in the reaction, such a process is very complicated and uneconomical in industry.
SUMMARY OF THE INVENTION
Starting from U.S. Pat. No. 5,101,073, it is an object of the present invention to provide a process which is improved in respect of the purity, yield and variability of the &bgr;-hydroxyalkylamides to be prepared, and also to provide for their use.
It has now surprisingly been found that in the preparation of &bgr;-hydroxyalkylamides by aminolysis of alkyl esters using an excess of &bgr;-aminoalcohols in the presence of basic catalysts such as sodium hydroxide or sodium methoxide, unreacted &bgr;-aminoalcohols can be removed directly from the reaction mixture by distillation after the basic catalyst has previously been destroyed, e.g. by means of an inorganic or organic acid such as hydrochloric acid or acetic acid. An excess of &bgr;-aminodialcohol in the preparation of the &bgr;-hydroxyalkylamides increases the selectivity of the reaction in the direction of the desired monomeric end product. This results in an even purer product, which in the case of solid &bgr;-hydroxyalkylamides is also reflected in an increase in the melting point and in an improved crystallization behavior. The &bgr;-hydroxyalkylamides prepared in this way have a very high purity. Suitable methods of removing the unreacted aminoalcohol are, apart from classical distillation at Th atmospheric pressure or under reduced pressure, particularly short-path, thin-layer and falling-film distillation, since these distillation methods are particularly gentle on the product, as a result of which undesirable secondary reactions caused by excessively long thermal stress can be avoided. If the catalyst is not destroyed, undesirable secondary reactions can take place during the distillation, for example the above-described diners (III) which have an adverse effect on the product properties of the &bgr;-hydroxyalkylamides, e.g. on the melting point or the crystallization behavior in the case of solid &bgr;-hydroxyalkylamides, can be formed again. A further advantage of destroying the catalyst is that the excess &bgr;-aminoalcohols can be recovered in pure form without by-products and can be utilized for further reactions. Liquid &bgr;-hydroxyalkylamides can be used directly without a further work-up step. In the case of solid &bgr;-hydroxyalkylamides, the end product is isolated either directly by crystallization of the reaction product or by crystallization from a solvent, since the abovementioned disadvantages no longer occur when crystallization is performed after destruction of the catalyst and removal of unreacted &bgr;-aminoalcohol. The process can be carried out batchwise and/or continuously.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention provides a process for preparing &bgr;-hydroxyalkylamides (IV)
where A is a chemical bond or a polyvalent organic group or, when n=0, A can be hydrogen or a monovalent organic group, where the monovalent or polyvalent organic group is selected from among saturated or unsaturated (C1-C60) alkyl, cycloalkyl, aryl, carboxyalkenyl, alkoxycarbonyl-alkenyl or trialkylenamino groups, with lower alkenyl groups, i.e. alkenyl groups having from 1 to 20 carbon atoms, being preferred for the three last-named groups. R1 is hydrogen or a C1-C5-alkyl group, R2 is hydrogen, a C1-C5-alkyl group or:
n is an integer from 1 to 10 and n′ is an integer from 0 to 2. In the absence of solvents, alkyl esters are reacted with &bgr;-aminoalcohols in the presence of basic catalysts, where, to improve the selectivity, the ratio of equivalents of e
Gisler Rene
Kaplan Andreas
Reich Albert
Ems-Chemie AG
Kumar Shailendra
Marshall & Melhorn LLC
LandOfFree
Process for preparing &bgr;-hydroxyalkylamides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for preparing &bgr;-hydroxyalkylamides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing &bgr;-hydroxyalkylamides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452011