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...
Patent
1998-03-23
2000-09-26
Nutter, Nathan M.
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...
524812, 524815, 524555, 526 84, 526 87, 5263073, C08F 332, C08J 4100, C08L 3700
Patent
active
061243965
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with novel, water-soluble, cationic, modified acrylamide copolymers branched in a precisely determined way and especially with DADMAC-acrylamide copolymers of high molecular weight and with a process for manufacturing them. Copolymers of this type are useful for water-treatment processes as flocculating agent for purification of industrial waters, as sludge conditioner for municipal water or as drainage and retention aid in paper manufacture.
Due to the increasing environmental awareness in carrying out industrial processes and from the point of view of the diminishing supplies of water, related with the need for reusing it, water-soluble polymers with high-molecular weight are today products of increasing economical importance. Polyelectrolytes with high-molecular weight are utilized in a large number of industrial processes in order to influence the degree of separation of solid substances for liquid streams by coagulation, flocculation, clarification, deposition, retention or other mechanisms.
Polymerization of diallyldimethylammonium chloride (DADMAC) leads to water-soluble cationic polymers. In contrast to this, after polymerization, acrylamide gives water-soluble polymers which are essentially nonionic in nature. Therefore, copolymerization of DADMAC and acrylamide monomers leads to the formation of copolymers with different cationic properties, depending on the amount of DADMAC units incorporated into the copolymer chain.
Copolymerization of DADMAC and acrylamide in solution is well known and is described, for example, in U.S. Pat. No. 2,923,701. It is also known that the molecular weight of the obtained copolymers is limited when a solution polymerization process is used. Therefore, in many examples from the state of the art, an attempt is made to overcome this by using an emulsion polymerization technique. According to the teaching of U.S. Pat. No. 3,920,599, for example, stable water-in-oil copolymer emulsions are prepared or the preparation of stable emulsion copolymers of DADMAC and acrylamide is published in U.S. Pat. No. 4,077,930, which can be inverted by the addition of water. In other patents, it is explained that the utilization of different types of initiators is to be preferred for latex copolymerization, as in the case of U.S. Pat. No. 4,439,500, in which ammonium persulfate is the preferred free-radical initiator, or in the case of the CA Patent No. 2,021 984, in which 2,2'-azobis-(2,4-dimethyl)-valeronitrile is disclosed as outstanding initiator. The addition of chain-transfer agents to prevent gel formation during polymerization is always considered necessary. Suitable chain-transfer agents are added at the beginning of the polymerization process. Examples of such additives are lower alkanols or mercaptoalcohols but halogenated hydrocarbons have also been used to suppress gel formation. The content of otherwise similarly performed synthesis methods is the use of special types of chain transfer agents. Thus, in the case of the CA Patent No. 2,063,656, the necessity of addition of sodium formate at the end of the polymerization, in order to obtain a gel-free latex copolymer, is disclosed. In contrast to that, in EP Patent No. 0,363,024, the preferred utilization of sodium hypophosphite is explained as a chain transfer agent. The addition of the chain-transfer agent is also carried out here at the end of the process, just before the last heating period, in order to minimize the residual monomer content.
Due to the greatly different reactivities of acrylamide and DADMAC in free radical polymerization, different copolymerization parameters arise (Jaeger et al., Acta Polymerica 36 (1985), 100-102). Therefore, in an intermittent copolymerization process, acrylamide-rich polymer chains are formed in the initial phase. Later, due to the rapidly diminishing acrylamide concentration in the reaction mixture, the amount of DADMAC gradually increases in the copolymer. In addition, the reaction stops at a DADMAC conversion of approximately 80%. This disadvantage
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Cramm Jeffrey R.
Hahn Mathias
Jaeger Werner
Whipple Wesley L.
Breininger Thomas M.
Martin Michael B.
Nalco Chemical Company
Nutter Nathan M.
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