Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-01-02
2002-11-19
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S310000, C528S315000, C528S317000, C528S422000, C528S495000, C528S50200C, C528S503000
Reexamination Certificate
active
06482917
ABSTRACT:
The present invention relates to a process for the preparation of pulverulent, cationic, crosslinked polymers based on monoethylenically unsaturated monomers containing a quaternized or quaternizable nitrogen atom, by free-radical polymerization in supercritical carbon dioxide.
It is known in general terms that supercritical carbon dioxide can be used as solvent in the preparation of polymers by free-radical polymerization. For example, EP-A 220 603 describes a process for the preparation of uncrosslinked, pulverulent polymers based on N-vinyl monomers and/or ethylenically unsaturated carboxylic esters by free-radical polymerization in supercritical carbon dioxide. EP-A 239 035 describes the preparation of crosslinked, pulverulent polymers based on monoethylenically unsaturated carboxylic acids, or amides and/or esters thereof by polymerization in supercritical carbon dioxide. In the known processes, the reaction mixture and liquid carbon dioxide are generally introduced into a pressure vessel, and the supercritical state induced by increasing the temperature and pressure. However, it is disadvantageous here that the different solubilities of the monomers and crosslinking agents in the solvent means that products of nonuniform morphology or nonuniform chemical composition may be formed.
It is an object of the present invention to find an improved process for the preparation of crosslinked polymers.
We have found that this object is achieved by a process for the preparation of pulverulent, cationic, crosslinked polymers based on monoethylenically unsaturated monomers containing a quaternized or quaternizable nitrogen atom by free-radical-initiated polymerization, which comprises carrying out the polymerization in supercritical carbon dioxide as inert diluent with mixing at from 31° C. to 150° C. and above 73 bar.
The polymerization is carried out under pressure in supercritical carbon dioxide as inert diluent. The properties of carbon dioxide in the liquid and supercritical states have been reported by J. A. Hyatt, J. Org. Chem. 49, (1984), 5097-5101. According to this article, the critical point of carbon dioxide is at about 31° C. and 73 bar. The polymerization is preferably carried out under pressure in supercritical carbon dioxide at above about 31° C., the critical temperature of carbon dioxide. The upper temperature limit for the preparation of the polymers is 10° C. above the commencement of this softening range of the respective polymers formed. For most polymers, the upper value for this temperature limit is 150° C. The polymerization is preferably carried out at from 30 to 130° C. The reaction temperature need not be kept constant; it is also possible to set up a stepped or ramped temperature profile. It is advisable to set the temperatures at the beginning of the reaction to values in the range from 31 to 100° C. The pressures are above 73 bar, preferably in the range from 80 to 300 bar, particularly preferably from 120 to 250 bar.
The novel process is preferably carried out by firstly introducing carbon dioxide in the solid, liquid or gaseous state into the reaction space of a pressure apparatus which is conventional per se, then converting the carbon dioxide into the supercritical state by increasing the pressure to above 73 bar and the temperature to above 31° C., then setting the reaction temperature, and subsequently metering in the starting materials. The starting materials, such as monomers, free-radical initiators, crosslinking agents and, if desired, polymerization regulators, may be metered in individually or in the form of mixtures. Thus, it may be advisable, for example, to dissolve the free-radical initiators in the monomers. The procedure selected depends essentially on the solubilities of the individual components in one another and in the diluent. However, it is also possible to introduce all or some of the starting materials into the reaction space and then to add the carbon dioxide. If desired, starting materials can be metered in during the reaction (semibatch procedure).
The polymerization reaction is initiated with the aid of polymerization initiators which decompose to form free radicals. It is possible to use all initiators which are known for the polymerization of the monomers, for example initiators which decompose to form free radicals with half-value periods of less than 3 hours at the selected temperature. If the polymerization is carried out at different temperatures by starting the polymerization of the monomers at a low temperature and completing the polymerization at a significantly higher temperature, it is advantageous to use at least two different initiators which have an adequate decomposition rate in the temperature range selected in each case.
Based on 100 parts by weight of the monomer mixture, from 100 to 3000 parts by weight, preferably from 200 to 1500 parts by weight, of carbon dioxide are used. The carbon dioxide is preferably anhydrous. The polymerization reaction can be carried out batchwise or continuously with mixing of the reactants in pressure apparatuses of appropriate design. In order to dissipate the heat formed during the polymerization, it is desirable for the pressure apparatuses to have a cooling system. They must of course also be heatable in order to heat the reaction mixture to the respective temperature desired for the polymerization. The pressure apparatuses should have mixing means, for example stirrers (blade, impeller, multistage pulsed countercurrent or ribbon stirrers) or vanes.
The novel process is particularly suitable for the preparation of pulverulent, cationic, crosslinked polymers.
These pulverulent, cationic, crosslinked polymers are obtainable by free-radical-initiated polymerization of
(a1) from 1 to 99.99% by weight of a free-radical-polymerizable monomer containing a quaternized or quaternizable nitrogen atom, or a mixture of such monomers,
(a2) from 5 to 95% by weight of an N-vinyllactam,
(b) from 0.01 to 20% by weight of a monomer which effects crosslinking, and
(c) from 0 to 50% by weight of a further free-radical-copolymerizable monomer.
Suitable monomers (a1) are selected from one of the following groups:
N-vinylimidazole derivatives of the formula (I)
in which R
1
, R
2
and R
3
, independently of one another, are hydrogen, C
1
-C
4
-alkyl or phenyl, preferably 2-methyl-N-vinylimidazole or N-vinylimidazole;
N,N-diallylamines of the formula (II),
in which R
4
is a C
1
-C
24
-alkyl radical, preferably N,N-diallyl -N-methylamine.
Under the polymerization conditions in accordance with the invention, such diallylamines react with ring closure:
N,N-dialkylaminoalkyl derivatives of acrylic or methacrylic acid, of the formula (III)
in which R
5
and R
6
, independently of one another, are hydrogen or methyl, Z is a nitrogen atom where X=0, R
7
is a linear or branched C
1
-C
24
-alkylene radical, and R
8
and R
9
, independently of one another, are C
1
-C
24
-alkyl radicals.
Suitable monomers of the formula (III) are, for example, N,N-dimethylaminomethyl (meth)acrylate, N,N-diethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-diethylaminobutyl (meth)acrylate, N,N-dimethylaminohexyl (meth)acrylate, N,N-dimethylaminooctyl (meth)acrylate, N,N-dimethylaminododecyl (meth)acrylate, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)butyl]methacrylamide, N-[8-(dimethylamino)octyl]methacrylamide, N-[12-(dimethylamino)dodecyl]-methacrylamide, N-[3-(diethylamino)propyl]methacrylamide and N-[3-(diethylamino)propyl]acrylamide, and mixtures thereof.
Preferred monomers (a1) are 3-methyl-1-vinylimidazolium chloride and methosulfate, dimethyldiallylammonium chloride, and N,N-dimethylaminoethylmethacrylate and N-[3-(dimethylamino)propyl]methacrylamide, each of which has, if desired, been quaternized by methyl chloride, dimethyl sulfate or diethyl sulfate.
Particularly preferred monomers (a1) are 3-methyl-1-vinylimidazol
Dieing Reinhold
Hildebrandt Volker
Zeitz Katrin
BASF - Aktiengesellschaft
Truong Duc
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