FI91161C - Process for preparing aqueous solutions of polyacrylic acids, their copolymers and salts - Google Patents

Description

i 91161

Process for the preparation of polyacrylic acids, their copolymers and salts in aqueous solution - Forfarånde for frametail-nlng av vattelosningar av polyacrylsyror, deras copolymer och salter 5

The present invention relates to a process for preparing aqueous solutions of polyacrylic acids, their copolymers and their salts, formed from homopolymers of acrylic acid and its salts, or polymers of acrylic acid, methyl acrylate, methyl methacrylate, acrylamide, methacrylamide and their salts. ammonium, sodium or potassium persulfates, hydrogen peroxide and organic peroxides, or oxidation-reduction pairs of the aforementioned compounds with sodium metabisulfite, sodium bisulfite or ascorbic acid in an aqueous medium and in an open atmosphere.

In this connection, reference should be made, as will be apparent from the following description by Kay, that the salts of the polymers obtained are primarily sodium, potassium or ammonium salts. The reference to low molecular weight means that the average molecular weight is less than 20,000 and preferably between 5,000 and 10,000.

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Aqueous solutions of the products according to the invention are used in a large number of industrial products and in processes for the processing and / or storage of these products, which involve the dispersion of charges, pigments and generally organic and inorganic substances in an aqueous substance.

It has long been known to prepare polyacrylic derivatives by polymerizing using radicals and starting from the corresponding acidic monomers and the copolymerizable products selected in each case. Some such methods have been described in such works as the Enciclopedia de Technologia Quimica (Kirk-Othmer). In these methods 2, the manner in which the organic solvent is used and the method in which water is used are generally used.

The disadvantage of using an organic solvent (toluene, benzene, tert-butanol, etc.) is that it may then be necessary to remove the reactant in order to obtain products which are completely soluble in water. Also, the disadvantages that must be taken with regard to equipment and safety measures when using flammable solvents must not be forgotten.

Therefore, to date, water has been preferred over a method that is technically feasible. This method does not have any very serious disadvantages, especially when a small amount of monomers is used, which can be up to 30% of the total solution. At values higher than this figure, the polymerization is made more difficult, since in this case a strong evolution due to the exothermic process is required. In this process, initiators such as hydrogen superoxide, sodium or potassium persulfate or organic peroxides and redox systems are generally used.

In order for the products according to the invention to obtain both technically and economically the best results, one important condition is, among other things, that the final concentration of the dissolved polymer be obtained as high as possible. Thus, in some applications it is possible to add a very low dose of treatment agents to the systems to be treated, with the further advantage that in this way the carefully agreed amounts of the various components are not substantially altered. In addition, it is important - and this is one of the primary objects of the present invention - that the manufacturing process should make it possible to obtain polymers with a reproducibility of at least 5% with respect to the parameters determining the molecular size. This is one of the main difficulties in already known methods, li 91161 3 in which, as also mentioned in the patent literature, "the reproducibility of an industrial event from one to another is often deficient".

The products according to the invention can be used in technical dispersion methods which, on the other hand, bring with them a wide range of applications in various fields: a) Dispersion methods , paper! etc.).

b) Dispersion methods for dispersing salts which are not water-soluble and which may separate on the surfaces of pipes, equipment or materials to be treated.

Thus, for example, in dispersers for rinsing bottles, in carbonation processes for the production of sugar from sugar cane and sugar beet, in the treatment of boiler water 20, in the refrigeration circuits of large industries (chemistry, refineries, foundries, power plants and nuclear power plants, etc.).

The preparation process is carried out according to the invention under conditions characterized in that the monomers and catalysts are added at intervals of 5 to 30 minutes, the number of time intervals or breaks being of the order of at least 10, and according to the program the water is maintained at , the monomer content of which is between 10 and 30%, after which it is heated for a time between 4 and 5 hours at a temperature of not less than 70 ° C, and finally, after cooling, the reaction product is neutralized with alkaline hydroxide.

35 In the following embodiments, the above features are concretized.

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Example 1:

To a reaction vessel equipped with a reflux condenser, stirrer, heating, cooling and temperature control was added 32.53 kg of deionized water, after which it was cooled to 5 ° C. After this temperature was reached, 4.46 kg of acrylic acid and 0.10 kg of potassium persulfate, 0.27 kg of hydrogen peroxide (30%) in 0.275 kg of water and 0.26 kg of sodium bisulfate-10 were added simultaneously. In 1.6 kg of deionized water. After 15 minutes, equal amounts of ingredients were added again. This event was repeated a total of 10 times. After these additions, the pulp was heated to 70 ° C and maintained at this temperature for 4 hours. It was then recooled and neutralized with 52 kg of sodium hydroxide (50% in water).

152.5 kg of an aqueous polymer solution with a solids content of 60.9 kg and an intrinsic viscosity of 0.145 were obtained.

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Example 2:

To the same reaction vessel as in Example 1, 34 kg of deionized water was added and a mixture of 3.35 kg of acrylic acid and 1.11 kg of methacrylic acid and 0.28 kg of sodium bisulphite in 1.6 kg of deionized water was added simultaneously at 5 ° C. 0.1 kg of potassium persulfate, 0.30 kg of hydrogen peroxide (30%) in 0.275 kg of deionized water.

This event was repeated a total of 10 times under the conditions specified in Example 1.

After the additions, the mass was heated to 70 ° C and kept constant at this temperature for 4 hours. The pulp 35 was then cooled and neutralized with 48.2 kg of sodium hydroxide (50% in water).

II

91161 5

150 kg of an aqueous polymer solution with a solids content of 40.0% and an intrinsic viscosity of 0.195 by analysis were obtained.

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Claims (3)

A process for preparing aqueous solutions of polyacrylic acids, nilden copolymers and their salts consisting of homopolymers of acrylic acid and its salts or copolymers of acrylic acid, methyl acrylate, methyl methacrylate, ammonium amide, methacrylamide and salts thereof. sodium or potassium persulfates, hydrogen peroxide and organic peroxides, or oxidation-reduction pairs of the aforementioned compounds in a mixture of sodium metabisulfite, sodium bisulfite or ascorbic acid in an aqueous medium and in an open atmosphere, known in the art. at intervals of at least 10 minutes, with a number of intervals or breaks of the order of at least 10, and according to the program a starting point of water kept at a temperature between 5 and 15 ° C, with a monomer content between 10 and 30%, after which for 4 to 5 hours at a temperature of not less than 70 ° C, and finally, after cooling, the reaction product is neutralized with alkaline hydroxide. Process for the preparation of aqueous solutions of polyacrylic acids, their copolymers and their salts according to Claim 1, characterized in that the polymerization initiators are potassium persulphate and hydrogen peroxide at a total concentration of 1 to 10% by weight of the monomer and sodium bisulphite having a concentration of 3 to 30%. - 30% by weight of monomer. Process for the preparation of aqueous solutions of polyacrylic acids, their copolymers and their salts according to Claim 1 or 2, characterized in that the amounts of monomer which are added stepwise together with the catalysts are between 1/10 and 1/14 of the total monomer used. 91161