Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1991-09-18
1993-07-06
Hruskoci, Peter
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210735, C02F 156, C02F 1114
Patent
active
052250881
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the use of copolymers containing copolymerized N-vinylformamide units as flocculants and dewatering agents for the treatment of wastewaters and sludges.
JP-A-118 406/86 discloses water-soluble polyvinylamines which are prepared by polymerizing N-vinylformamide or mixtures of N-vinylformamide with other water-soluble monomers, such as acrylamide, N,N-dialkylacrylamides or diallyldialkylammonium salts and then hydrolyzing the polymers with a base, for example ethylamine, diethylamine, ethylenediamine or morpholine. The polyvinylamines are used as drainage aids and retention aids in papermaking and as flocculants for wastewaters.
U.S. Pat. No. 4,421,602 discloses polymers which are obtainable by partial hydrolysis of poly-N-vinylformamide with acids or bases. As a result of hydrolysis, these polymers contain vinylamine and N-vinylformamide units. They are used, for example, as drainage aids, flocculants and retention aids in papermaking. According to U.S. Pat. No. 4,444,667, partially hydrolyzed poly-N-vinylformamides are used as flocculants for sludges.
EP-A-0 220 603 discloses, inter alia, that N-vinylformamide can be subjected to copolymerization together with basic acrylates, such as dimethylaminoethyl acrylate, or N-vinylimidazolines, in supercritical carbon dioxide. The resulting finely divided copolymers are used, in partially hydrolyzed form, in which they contain vinylamine units, for example as retention aids and flocculants in papermaking and as flocculants for sludges.
It is an object of the present invention to provide flocculants and dewatering agents which as far as possible are more effective than those known to date and are industrially more readily obtainable.
We have found that this object is achieved, according to the invention, by the use of nonhydrolyzed copolymers which contain, as copolymerized units,
(a) from 99 to 1 mol % of N-vinylformamide and
(b) from 1 to 99 mol % of one or more water-soluble basic monomers of the formula ##STR1## where R.sup.1 is H, CH.sub.3, C.sub.2 H.sub.5, R.sup.2, R.sup.3 and R.sup.4 are each H, CH.sub.3, C.sub.2 H.sub.5 or (--CH.sub.2 --CH.sub.2 --O--).sub.n H, R.sup.5 and R.sup.6 are each C.sub.1 -C.sub.10 -alkyl, A is C.sub.1 -C.sub.6 -alkylene, n is from 1 to 6 and Y.sup..crclbar. is an anion, as flocculants for wastewaters and dewatering agents for sludges.
The advantage of the nonhydrolyzed copolymers containing N-vinylformamide units over the hydrolyzed copolymers used to date, which contain vinylamine units after hydrolysis, is that the hydrolysis, which is difficult to carry out in many cases, is dispensed with and effective assistants for the abovementioned applications are obtainable by direct copolymerization.
A suitable monomer (a) of the copolymers is N-vinylformamide. This monomer is used in the synthesis of the copolymers in an amount of from 1 to 99, preferably from 60 to 95, mol %.
Suitable monomers of group (b) are compounds of the formula I, of which the following compounds may be mentioned by way of example:
Other suitable monomers of group (b) are the compounds of the formula II. Compounds of this type are, for example, diallyldimethylammonium chloride, diallyldimethylammonium bromide, diallyldiethylammonium chloride and diallyldiethylammonium bromide. Diallyldimethylammonium chloride is preferably used. The anion Y.sup..crclbar. is an acid radical and is preferably chloride, bromide, iodide, sulfate, methosulfate or ethosulfate.
Among the monomers of group (b), the compounds of the formula I or II may be used either alone or as a mixture with one another for the synthesis of the copolymers. It is also possible to use a plurality of compounds of the formula I or II in the copolymerization with the monomer (a). The monomers of group (b) are used for the synthesis of the copolymers in an amount of from 99 to 1, preferably from 40 to 5, mol %.
The copolymerization of the monomers (a) and (b) is carried out in aqueous solution in the presence of a polymerization initiator which decomposes into free radicals
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Buechner Karl-Heinz
Hartmann Heinrich
Moench Dietmar
BASF - Aktiengesellschaft
Hruskoci Peter
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