Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1997-01-03
1998-06-09
Burn, Brian M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564404, C07C20902
Patent
active
057636656
DESCRIPTION:
BRIEF SUMMARY
This application is a 35 U.S.C. 371 of PCT/EP95/02594, filed Jul. 5, 1995.
The present invention relates to a process for the preparation of crystalline N-methylol(meth)acrylamide from paraformaldehyde and (meth)acrylamide in the presence of a suitable catalyst.
N-Methylol(meth)acrylamide is used as a monomer component with crosslinking properties in a number of polymers, predominantly in polymer emulsions, which are used as adhesives and coating materials, as binders for paints and fibers and as material for textile or paper coating.
Processes for the preparation of crystalline N-methylolacrylamide are known. Thus, U.S. Pat. No. 3,064,050 describes such a process in which acrylamide and paraformaldehyde in highly concentrated aqueous solution are reacted using a basic catalyst. The disadvantages of this process are a) the relatively low product yields of about 50% which are obtained in one operation, b) the recycling of the mother liquors which is therefore required and c) the drying of the product obtained by filtration.
U.S. Pat. No. 2,864,861 discloses a process for obtaining N-methylolacrylamide which dispenses with the use of any solvents. In this known process, a product melt is produced in a stirred kettle from the solid reactants paraformaldehyde and acrylamide using a catalytic amount of triethylamine and is allowed to solidify to solid N-methylolacrylamide after the end of the reaction by cooling. If this process were scaled up to a large industrial plant, it would not be possible to achieve the following: of heat and hence the danger of polymerization; stirred kettle.
It is an object of the present invention to provide a solvent-free process for the preparation of N-methylol(meth)acrylamide in which the abovementioned features are also achievable on the large industrial scale.
We have found that this object is achieved, according to the invention, by the processes defined in the claims. In particular, (meth)acrylamide and paraformaldehyde are reacted using a suitable catalyst in one process step to give crystalline N-methylol(meth)acrylamide by carrying out the reaction in a reactor, preferably in a self-purging screw apparatus. The reactor is designed in such a way that the reaction mixture is exposed to significant shear loads, as in screw extruders or in disk mixers. These apparatuses are known per se, and the degree or the intensity of mechanical mixing for the reaction and the crystallization is therefore also defined. Preferably used reactors are those which transmit to the reaction mixture a shear load which, based on the power consumption per unit volume of content, is of the same order to magnitude as that of the commercial apparatuses stated in the Examples, the material contained being the same.
Below, (meth)acrylamide is to be understood as meaning acrylamide and/or methacrylamide. Suitable catalysts are tertiary amines or alkali metal carbonates, in particular potassium carbonate. This process, which can be operated by either a continuous or batchwise procedure, gives a free-flowing product with small quality fluctuations. The mode of operation of the Discotherm B used for carrying out the present process will be described in detail below:
Highly self-purging reactors are preferably used for the preparation of N-methylol(meth)acrylamide. Such a reactor is, for example, a Discotherm B from List AG, 4422 Arisdorf, Switzerland, in which the required residence time can be realized.
The Discotherm B (DTB) is a batchwise or continuous kneading apparatus. It consists of a horizontal cylindrical barrel with a concentric stirring shaft on which disk elements are mounted in planes at right angles to the axis and kneader-mixer bars on the outer circumference. Static counter-hooks which clean the shaft and the disk elements are fastened in the barrel. The degree of self-purging of the apparatus is 90%. The remaining 10% are purged by means of product movements. The axial transport is ensured by the arrangement of the disk elements with kneader-mixer bars and by the shape of the counter-hooks.
REFERENCES:
patent: 2864861 (1958-12-01), Wohnseidler et al.
patent: 2864862 (1958-12-01), Sutherland
patent: 3064050 (1962-11-01), Saunders
patent: 3898279 (1975-08-01), Hoke
patent: 5220065 (1993-06-01), Takayanagi et al.
Bohn Michael
Bott Kaspar
Domschke Thomas
BASF - Aktiengesellschaft
Burn Brian M.
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