Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1987-02-13
1990-05-15
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523337, 523339, 524801, C08K 320
Patent
active
049258842
DESCRIPTION:
BRIEF SUMMARY
Polyelectrolytes in the form of liquid dispersions, designated as emulsion polymers, are used in technology, in water and waste-water processing and in various manufacturing processes as flocculating, water-removal, and retention aids, as viscosity-intensifying additives in exploration and crude oil extraction, in the production of textiles, and, more recently, in cosmetic preparations
As described in DE-PS No. 1089173 the production of emulsion polymers takes place by the radical polymerisation of water-soluble monomers. Preferably acrylamide and other acrylic acid derivatives that are contained in the disperse, aqueous phase of finely divided water-in-oil emulsions.
These products are economically produced if the polymer fraction in the product (dissolved in water) possesses the required effectiveness in its intended application, and if the polymer fractions within the product, apart from the non-effective portions (the hydrophobic phase formed from the liquid hydrocarbons and emulsifiers and water), is sufficiently high For this reason, it is desirable to prepare emulsion polymers that are as highly concentrated as possible.
During the production of the emulsion polymers the concentration of the polymer portion is determined--in addition to the solubility of the monomers--by the fact that the radical polymerisation of the quoted monomers is a rapid, strongly exothermic process, so that the reaction heat that is generated in proportion to the concentration of the monomers and to the speed of polymerisation has to be eliminated. In addition to the known monomer-supply process, several other production methods are described as solutions to this problem. U.S. Pat. No. 3,767,629 proposes the inhibition of polymerisation by a sporadic air supply to the monomer emulsion as a means of controlling the course of polymerisation. DE-OS No. 28 11 422 proposes a reduction of the speed of polymerisation by the addition of heavy-metal ions in the monomer phase. However, all of these processes entail the disadvantage that the polymerisation reaction is very often too strongly inhibited, so that polymerisation as a whole is impaired and the quality of the polymers does not reach the optimal possible level.
According to U.S. Pat. No. 4,070,321, the reaction is controlled by adjusting the pH value of the monomer phase for producing high-molecular anionic polymers. However, regulation of polymerisation by way of the pH value of the aqueous phase is inadequate for the production of concentrated products.
It is already known that work can be carried on in two stages in order to produce concentrated products.
In the first stage, low-concentrated products are produced by the adiabatic process, and in the second stage an increase in the polymer content is achieved by distillation with the renewed addition of heat, optionally with the addition of hydrocarbons distilled azeotropically, by the separation of water and with a small proportion of the hydrocarbons (U.S. Pat. Nos. 4,021,399 and 4,090,992). However, this process entails additional expenditures of energy and time. Furthermore, the polymers have to be stabilized by special additives (U.S. Pat. No. 3,507,840), in order that they retain their effectiveness for technical applications for a longer period of time. In addition, it is also known that the polymerisation heat can be eliminated by distillate reflux cooling at low pressure (DD-PS No. 145 401 and U.S. Pat. No. 4,078,133). This process entails the disadvantage that the refluxing free quantity of water can lead to inhomogeneity in the water-in-oil polymer dispersion and dilute the polymer portion that is effective in the product.
The technique of concentration by means of azeotropic distillation of prepared polymer dispersions has been improved recently by DE-OS No. 3224994, in particular by suitable changes in the apparatus used but without the elimination of the disadvantages inherent in such a two-stage process.
Proceeding from the preceding described prior art it is an object of the present invention to create a pro
REFERENCES:
patent: 4021399 (1977-05-01), Hunter et al.
patent: 4037040 (1977-07-01), Trapasso et al.
patent: 4154910 (1979-05-01), Tanaka et al.
Chemical Abstracts, vol. 88, No. 14, Apr. 3, 1978, p. 29, Abstract 90451s.
Hubner Wolfgang
Schroers Otto
Chemische Fabrik Stockhausen GmbH
Mulcahy Peter
Schofer Joseph L.
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