FI91161B - The process prepares aqueous solutions of polyacrylic acids, their copolymers and salts - Google Patents

Description

91161

Process for the preparation of aqueous solutions of polyacrylic acids, their copolymers and salts - Förfarande för frametäll-Ning av vattelösningar 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 consisting of homopolymers of acrylic acid and its salts or copolymers of acrylic acid, methyl acrylate, methyl methacrylate, acrylamide, methacrylamide and their salts using , sodium or potassium persulfates, hydrogen peroxide and organic peroxides, or oxidation-reduction pairs of the above-mentioned 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 seen from the following description, 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 have use 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 polymerization 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, a method using an organic solvent and a method using water are generally used.

The disadvantage of using an organic solvent (toluene, benzene, tert-butanol, etc.) is that it may 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, the method using water has been preferred rather because it is technically possible. This method does not have any very serious disadvantages, especially when a low amount of monomers is used, which can be up to 30% of the total solution. At values higher than this figure, the polymerization becomes more difficult, since in this case a strong heat generation must be controlled, which is due to the exothermic process taking place. This process generally uses initiators such as hydrogen superoxide, sodium or potassium persulfate, or organic peroxides and redox systems.

In order to obtain the best results both technically and economically with the products according to the invention, 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 very low doses of treatment agents to the systems to be treated, with the consequent advantage that in this way the carefully matched 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 allow the production of polymers 35 with a reproducibility with respect to molecular size parameters of at least 5%. 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, offer a wide range of applications in various fields: a) Dispersion methods which provide stable suspensions of products such as batches, pigments and salts (ceramics, dyes, paper) under time and / or conditions etc.) · b) Dispersion methods for dispersing salts which are insoluble in water and which may separate on the surfaces of pipes, equipment or materials to be treated.

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

The preparation process according to the invention is carried out under conditions characterized in that the monomers and catalysts are added at intervals of 5 to 30 minutes, the number of intervals or breaks being of the order of at least 10, and according to the program to an initial amount of water maintained between 5 and 15 ° C. , wherein the monomer content is between 10 and 30%, followed by heating 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.

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, followed by cooling 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 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 this temperature was maintained for 4 hours. It was then re-cooled 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 at 5 ° C, 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. 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).

Il 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 the preparation of aqueous solutions of polyacrylic acids, their copolymers and their salts formed by homopolymers of acrylic acid and its salts or copolymers of acrylic acid, methyl acrylate, methyl methacrylate, acrylic anide, methacrylamide and their salts, using polymerization, consists of ammonium, sodium or potassium persulfates, hydrogen peroxide and organic peroxides, or the above-mentioned oxidation-reduction rates of sodium metabisulphite, sodium bisulphite or ascorbic acid in aqueous medium and open atmosphere, characterized in that the monomers and catalysts lytera is added during 5-30 minute intervals, the number of intervals or breaks being of the order of at least 10, and according to the program in the starting amount of water, the temperature of which is between 5 and 15 ° C, whereby the monomer content is between 10 - 30% and then heated below a time between 4 and 5 hours at a temperature not below 70 ° C, and finally, the reaction product is neutralized after its cooling with alkaline hydroxide. Process according to claim 1 for preparing aqueous solutions of polyacrylic acids, their copolymers and their salts, characterized in that polymerization initiators are potassium persulfate and hydrogen peroxide, their total concentration being 1 to 10% calculated on the weight of the monomer and sodium bisulfite, 3 - 30% by weight of the monomer. 30 Process according to claim 1 or 2 for the preparation of aqueous solutions of polyacrylic acids, their copolymers and their salts, characterized in that the amount of monomers added stepwise together with the catalysts is between 1/10 and 1/14 in total of the amount. used monomer.