Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1996-12-20
2001-05-29
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C426S271000, C426S330400, C426S422000
Reexamination Certificate
active
06239206
ABSTRACT:
The present invention relates to complexes of heavy metal ions and a polymer which are suitable for selective removal of undesirable or interfering organic or inorganic compounds from liquids.
To enhance the sensory quality of water and beverages, it is frequently necessary to remove metal ions or other undesirable constituents. Polymeric sorbents have already been used for this purpose. Thus, DE-A-1945749 describes a process for removing phenols and/or metals from an aqueous medium (including beverages) using a polymeric sorbent which contains basic or cationic groups. Use of the described sorbent specific to beverages is restricted to removing very low amounts of iron and copper from beer (Fe content: 0.26 ppm, Cu content: 0.06 ppm). High sorption capacity is therefore not required.
EP-A-88964 describes a process for preparing insoluble polymers which can swell only a little in water and are made of a basic N-vinylheterocycle, and copolymers thereof with up to 30% by weight of copolymerizable monomer. Complexing transition metal cations for preparing catalysts based on the described polymers is proposed. These polymers, especially as adsorber resins, have a broad spectrum of application. They adsorb proteins very well, especially enzymes, and are also suitable for removing interfering polyphenols and dyes from aqueous solutions by adsorption.
EP-A-438713 describes a process for removing heavy metal ions from beverages by using polymers based on N-vinylheterocycles and copolymerizable monomers, which were prepared in the absence of an initiator. The same polymers are used according to EP-A-641521 for removing aluminum ions from beverages.
Polymer-metal complexes are frequently used as catalysts. DE-A 24 37 133 thus describes an oxygen-sensitive polyvinylpyridine-copper complex and its use as catalyst for carboxylating alcohols. U.S. Pat. No. 3 652 676 discloses a polyvinylpyridine-transition metal complex as hydroformylation catalyst, which was prepared using an initiator.
Surprisingly, it has now been found that complexes may be prepared, based on the polymers described in EP-A-438713 and EP-A-641521, which are outstandingly suitable for selective removal of undesirable organic or inorganic compounds from liquids. The complexes can also be used as catalysts.
The invention therefore relates to complexes of heavy metal ions and a polymer which contains 50-99.5% by weight of at least one basic vinylheterocycle having a pK
a
of at least 3.8 and, copolymerized, 0-49.5% by weight of another copolymerizable monomer and which is obtainable in the absence of polymerization initiators in the presence of 0.5-10% by weight of a crosslinker, based on the monomers.
For the purposes of the invention, basic vinylheterocycles are saturated and aromatic heterocycles containing a vinyl group and at least one basic tertiary ring nitrogen having a pK
a
of at least 3.8. Apart from the vinyl, the ring can also bear 1, 2 or 3 alkyls having 1 to 4 carbons, phenyl or benzyl and/or can also be fused to a second saturated or aromatic ring. Preferably, the polymer comprises a 5- or 6-membered vinylheterocycle which has one or two ring nitrogens and which can have one or two of the said groups as substituents and/or can be benzo-fused. Particularly preferably, they are unsubstituted or substituted vinylpyridines or N-vinylimidazoles. Specific examples are: N-vinylimidazole (VI) and derivatives such as 2-methyl-1-vinylimidazole, 4-methyl-1-vinylimidazole, 5-methyl-1-vinylimidazole, 2-ethyl-1-vinylimidazole, 2-propyl-1-vinylimidazole, 2-isopropyl-1-vinylimidazole, 2-phenyl-1-vinylimidazole, 1-vinyl-4,5-benzimidazole, 2-vinylpyridine, 4-vinylpyridine and 2-methyl-5-vinylpyridine. Mixtures of basic vinylheterocycles can also be used.
Suitable crosslinkers are those which contain in the molecule two or more unconjugated vinyl groups which can be copolymerized by free radicals. Those which are particularly suitable are alkylenebisacrylamides such as methylenebisacrylamide and N,N′-bisacryloylethylenediamine, and N,N′-divinylethyleneurea (N,N′-divinylimidazolidone), N,N′-divinylpropyleneurea, ethylidene-bis-3-(N-vinylpyrrolidone), N,N′-divinyldiimidazolyl-(2,2′)-1,4-butane and 1,1′-bis(3,3′-vinylbenzimidazolid-2-one)-1,4-butane. Other useful crosslinkers are, for example, alkylene glycol di(meth)acrylates, such as ethylene glycol di(meth)acrylate and tetramethylene glycol di(meth)acrylate, aromatic divinyl compounds such as divinylbenzene and divinyltoluene and allyl acrylate, divinyldioxane, pentaerythritol triallyl ether and mixtures of these. When polymerization takes place in the presence of water, only crosslinkers soluble in the aqueous monomer mixture are suitable.
The same applies to comonomers which can be copolymerized in amounts of up to 49.5%, preferably up to 40% by weight, based on the total monomer mixture. Comonomers which can be used are, for example, styrene, acrylic esters, vinyl esters, acrylamide, preferably N-vinyllactams such as 3-methyl-N-vinylpyrrolidone, in particular N-vinylcaprolactam and N-vinylpyrrolidone (VP).
To carry out the polymerization without solvent, the mixture of monomers, comprising basic vinylheterocycle, the crosslinker and with or without a comonomer, is rendered inert by introducing nitrogen and is then heated to from 100 to 200° C., preferably from 150 to 180° C. It is advantageous to pass a gentle nitrogen stream into the mixture. It is particularly advantageous to bring the batch to the boil by applying reduced pressure. Depending on the type of monomers used and the temperature selected, the mixture then polymerizes in the course of from 1 to 20 hours. For example, when 2-methyl-1-vinylimidazole is polymerized in the presence of 2% N,N′-divinylethyleneurea at 150° C. with agitation by a powerful agitator and at a pressure of 310 mbar, the first polymer particles form after 2.5 h, and after 10 h the batch comprises a brownish powder. After it is washed with water and dried, the polymer is obtained in the form of a coarse powder in yields of over 90%.
A preferred method of preparation is precipitation polymerization in water. The monomer concentration in the reaction batch is expediently chosen so that the batch remains readily stirrable over the entire period of the reaction. If there is insufficient water, the polymer granules actually become sticky, so that stirring becomes more difficult than without any water. With conventional stirred tanks, the expedient monomer concentration, based on the aqueous mixture, is from approximately 5 to 30% by weight, preferably from 8 to 15% by weight. It can be increased to 50% by weight if vigorous agitators are available. It can also be expedient to begin the polymerization with a relatively concentrated solution and then to dilute it with water in the course of the reaction. Polymerization is expediently carried out at a pH above 6, in order to avoid possible saponification of the comonomers and/or crosslinker. The pH can be adjusted by adding small amounts of bases such as sodium hydroxide or ammonia or conventional buffer salts such as soda, sodium hydrogen carbonate or sodium phosphate. Oxygen can be excluded by keeping the polymerization batch at the boiling point, and/or using an inert gas such as nitrogen, as mentioned above. The polymerization temperature can be from 30° to 150° C., preferably from 40 to 100° C.
It may occasionally be advantageous to add small amounts—from 0.01 to 1% by weight, based on the monomer mixture—of a reducing agent such as sodium sulfite, sodium pyrosulfite, sodium dithionite, ascorbic acid and the like, to completely remove dissolved oxygen prior to or at the beginning of the polymerization.
In a particularly preferred embodiment of the precipitation polymerization, the water-soluble comonomer (preferably VP or an N-vinyllactam), some of the crosslinker, water with or without a buffer and a reducing agent are heated in a gentle nitrogen stream until the first polymer particles appear. A mixture of the vinylheterocycle and the remai
Fussnegger Bernhard
Stein Stefan
BASF - Aktiengesellschaft
Keil & Weinkauf
Mulcahy Peter D.
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