CZ9794A3 - Process for preparing sodium salts of acrylic and malic acid copolymers - Google Patents

Abstract

Sodium salts of copolymers of acrylic acid and maleic acid form polyelectrolytes used as additives for washing detergents. They are prepared in the following manner: isopropanol is added to an aqueous solution of maleic acid at a temperature of 50 to 70 degrees C partially neutralized by a solution of sodium carbonate and/or hydroxide, the reaction mixture is heated up to polymerisation temperature of 80 to 90 degrees C, and the reducing component of the reduction-oxidation initiation system is added and then the mixture of acrylic acid, partially neutralized by the aqueous solution of sodium carbonate and/or hydroxide with isopropanol is gradually added simultaneously to the aqueous solution of the oxidative component of the initiation system. When the addition of this solution is completed, the polymerisation is completed by heating the reaction mixture to a temperature of 80 to 90 degrees for at least 15 minutes. Then the product is slowly neutralized with an aqueous solution of NaOH, or isopropanol may be distilled from it.<IMAGE>

Description

In the context of reducing the content of alkaline phosphates in detergents intended for washing, mainly due to ecological, toxicological and economic reasons, a number of raw materials for their substitution have been investigated. Based on the knowledge gained so far, partial replacement of phosphates can be solved by application of synthetic aluminosilicates, so-called zeolites. However, the use of these substances in the preparation of detergents is accompanied by a decrease in the detergency effect, especially in the secondary. The presence of zeolites in the laundry detergent formulations is associated with a negative effect on the textile material in terms of secondary detergency, which is manifested in the incrustation of the textile due to its repeated washing. Based on this experience, the possibility of suppressing the formation of incrusts has been studied and the result has been found that minimizing the decrease in secondary detergent effect can be achieved by applying carboxylates, i.e. synthetic polymeric compounds containing free carboxyl groups (usually in sodium salt). 6 wt. in the detergent formula. In addition to powder detectors, they are increasingly being used in the preparation of liquid detergents. Polyelectrolytes based on sodium salts of copolymers of acrylic acid and maleic acid (eg European Patent Nos. 124 913, 133 566, 137 669, 221 777, Japanese Patent No. 57 192500) have proven to be well-suited as incrustation inhibitors in detergents. , U.S. Pat. No. 3625 189, 3707 806, etc.). The basic problem with the preparation of maleic acid-acrylic acid copolymers is the difficulty of copolymerizing both monomers due to large differences in relative reactivity values. Therefore, it is necessary to prepare these copolymers by special processes (e.g., European Pat. Nos. 113 048, 337 259, Japanese Pat. Nos. 57 168906, 59 064613, 60 212412, U.S. Pat. Nos. 3233 776, 3244 989, Pat. No. 4,710,537, etc.). However, a disadvantage of all the prior art processes is the considerable difficulty of achieving a high degree of conversion of the maleic component, resulting in the presence of up to several X of free maleic anhydride or maleic acid in the product.

SUMMARY OF THE INVENTION

The above drawbacks are solved by the present invention relating to a process for the preparation of sodium salts of acrylic acid / maleic acid copolymers by radical copolymerization of monomeric acids and / or their alkali salts in an aqueous environment at elevated temperatures and in the presence of a redox oxidation initiator system and chain transfer agent. The essence of the present invention is that 100 wt. parts of maleic anhydride and 110 to 140 wt. parts of water, heated to a temperature of 50 to 70 ° C and neutralized with a solution of 40 to 60 wt. parts by weight of carbonate and / or sodium hydroxide in 120 to 180 wt. 2 to 20 wt. of isopropanol and the reaction mixture is heated to a polymerization temperature of 80 to 90 ° C. An aqueous solution of 5 to 30 wt. parts of the initiator system reducing component in 10 to 60 wt. parts by weight of water and then, over a period of 2 to 6 hours, a mixture of 200 to 300 wt. parts by weight of acrylic acid, partially neutralized with a solution of 120 to 150 wt. parts of carbonate and / or hydroxide

% sodium in 300 to 400 wt. parts of water, with 5 to 100 wt. 10 parts by weight of isopropanol; parts of the oxidation component of the initiator system in 20 to 100 wt. % water, optionally up to 30 wt. this solution is added before and / or after the addition of the partially neutralized acrylic acid / isopropanol mixture is added. After completion of the addition of the aqueous solution of the oxidation component of the initiator system, the polymerization is completed by heating the reaction mixture to 80-90 ° C for at least 15 minutes and finally the product is slowly neutralized by 100-300 wt. parts of a 35 to 50% aqueous solution of sodium hydroxide and optionally isopropanol is distilled off. At least one of sodium, potassium or ammonium metabisulfite, bisulfite, sulphite, dithionite and thiosulfate is used as the reducing component of the initiator system and at least one of sodium, potassium or ammonium peroxodisulfate is used as the oxidizing component of the initiator system,

By selecting conditions such as pH, polymerization temperature, monomer initiation and metering process or polymerization atmosphere, the process allows the preparation of products having a maleic acid content in the copolymer of greater than 40% by weight. and having a free maleic acid content of less than 0.1% by weight in the product. This positive result is achieved by combining the following factors together. Firstly, the disadvantageous values of the copolymerization parameters of the two monomers used are eliminated by the gradual addition of a more reactive acrylic acid, and it has been shown that at least partial neutralization of the two monomers facilitates the process. The rapid progress of copolymerization and the achievement of a suitable molecular weight are ensured by the use of a water-soluble reduction-oxidation system at the indicated concentrations and further by the use of isopropanol as a molecular weight regulator by radical transfer.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

100 wt. parts of maleic anhydride and 125.3 wt. of water and the mixture is heated while stirring with both maleic and nanhydride

The resulting molten mixture is neutralized with a solution in 131.8 wt. parts of water to a temperature of 60 ° C and water, which 46.6 wt. By neutralizing maleic anhydride, a heterogeneous mixture of sodium maleate and water is obtained, which is heated to 85 ° C with stirring, at which the maleate is already dissolved in water. To this solution was added 6.66 wt. parts of isopropanol; and an initial dose of a reduction-oxidation system consisting of 15.98 wt. parts by weight of sodium metabisulfite dissolved in 39.44 wt. % water and 10 wt. solution

23.78 wt. parts of ammonium peroxodisulfate in water. After this initiation of the aqueous solution, the resulting &quot; 8.81 wt. The polymerization by dropwise partial neutralization of 276.5 wt. parts by weight of acrylic acid with a solution of 139.21 wt. parts of calcined soda in 393.2 wt. 16.74 wt. parts of isopropanol. 80% by weight of the aqueous neutralized acid are added to the reactor at the same time as the paracrylic acid is added. % of the total ammonium persulphate solution mentioned above. Both components, i.e. partially neutralized acrylic acid and the oxidizing component of the initiator, are slowly and uniformly added dropwise to the reactor over a period of 4 hours, the polymerization temperature being maintained at 85 + 2 ° C throughout. After completion of the dropwise addition, the remaining 10 wt. solution of ammonium peroxodisulfate and the mixture was allowed to polymerize for 15 minutes. Finally, the resulting copolymer is neutralized with a 78.8 wt. parts of sodium hydroxide in 78.8 wt. isopropanol was distilled off at 90 ° C.

The product is a slightly yellowish aqueous solution of sodium salt of a copolymer of acrylic acid with maleic acid having a dry weight of 40% by weight. and a viscosity of 20% solution (dry weight) of 30 + 10 mPa · s at 25 ° C. The residual acrylic acid content is so low that it cannot be determined by liquid chromatography, the residual maleic anhydride content is less than 0.003% by weight. The product has a pH of 8 and mol. weight 70 000 + 15 000.

Example 2

100 wt. part by weight of maleic anhydride and 115 wt. part of water and the mixture is heated to 60 ° C with stirring. The mixture of molten maleic anhydride and water was neutralized with a 42.6 wt. parts of sodium hydroxide in 170 wt. 50 ° C. Neutralization of the maleic anhydride yields a heterogeneous mixture of sodium maleate and water, which is further heated with stirring to 85 ° C, at which the mixture is already in the form of a homogeneous aqueous solution. 18 wt. a portion of isopropanol and an initial dose of a redox oxidation initiation system consisting of a 25 wt. part by weight of sodium metasulfite in 50 wt. parts of water and 10 wt. % of a solution prepared by dissolving 35 wt. % sodium peroxodisulfate in 96 wt. parts of water. The polymerization is then initiated by dropwise addition of an aqueous solution resulting from the partial neutralization of 210 wt. parts of acrylic acid with a 92 wt. % sodium hydroxide in 320 wt. parts of water containing 80 wt. part of isopropanol. In addition to this solution, the remaining 90 wt. % of a sintered sodium peroxydisulfate solution. Both components were slowly added uniformly to the reactor at 90 + 2 ° C for 2 hours. The mixture was allowed to dopolymerize for 30 minutes, then the reactor contents were neutralized with 120 wt. parts of 50% aqueous sodium hydroxide solution and finally isopropanol is distilled off at 90 ° C.

The product is a slightly yellowish aqueous solution of sodium salt of a copolymer of acrylic acid with maleic acid having a dry weight of 35% by weight. and a viscosity of 20% solution (dry weight) of 15 + 5 mPa.s at 25 ° C. The residual acrylic acid content does not exceed 0.005% by weight, the residual maleic anhydride content is less than 0.01% by weight. the pH of the product is 7, a molecular weight of 10,000 to 30,000.

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Example 3

100 wt. parts of maleic anhydride and 135 wt. parts of water, the mixture is heated to 60 ° C with stirring and then neutralized with a solution of 41.5 wt. parts of calcined soda in 128 rumble, parts of water at 50 ° C. Neutralization of maleic anhydride yields a heterogeneous mixture of sodium maleic acid and water, which is further heated to 85 ° C to form a homogeneous solution. 3 wt. parts of isopropanol and an initial dose of a redox oxidation initiation system consisting of a 7 wt. parts of sodium metabisulfite in 14 wt. % water and 10 wt. solution of 15 wt. % of ammonium peroxodisulfate in 50 wt. parts of water. After addition of these initiators, polymerization is initiated by dropwise addition of an aqueous solution prepared by neutralizing 290 wt. parts by weight of acrylic acid with a solution of 148 wt. parts of calcined soda in 480 wt. parts of water and containing 7 wt. parts of isopropanol. Simultaneously with this solution, 80 wt. % of the above ammonium peroxodisulfate solution. Both components were added slowly and evenly to the reactor at 80 + 2 ° C for 6 hours. After completion of the dropwise addition of these components, the remaining 10 wt. % of the above ammonium persulfate solution and the mixture was allowed to polymerize for 15 minutes. Finally, the mixture is neutralized in the reactor by 300 wt. parts of a 35% aqueous sodium hydroxide solution.

The product consisted of a slightly yellowish aqueous solution of sodium salt of a copolymer of acrylic acid with maleic acid having a dry weight of 42% by weight. and a viscosity of 20% solution (based on dry matter content) of 60 ± 20 mPa.s at 25 ° C. The residual acrylic acid content is so low that it cannot be determined by liquid chromatography, the residual maleic anhydride content is less than 0.004% by weight. The product has a pH of 8.5 and a molecular weight of 120,000 + 30,000.

Claims (2)

A process for the preparation of sodium salts of acrylic acid / maleic acid copolymers by radical copolymerization of monomeric acids and / or their alkali salts in an aqueous environment at elevated temperatures and in the presence of polymerization initiators and chain transfer agents, characterized in that 100 wt. parts of maleic anhydride and 110 to 140 wt. parts of water, heated to a temperature of 50 to 70 ° C and neutralized with a solution of 40 to 60 wt. parts by weight of carbonate and / or sodium hydroxide in 120 to 180 wt. 2 to 20 wt. The reaction mixture is then heated to a polymerization temperature of 80 to 90 ° C, an aqueous solution of 5 to 30 wt. parts of the initiator system reducing component in 10 to 60 wt. 200 to 300 wt. parts by weight of acrylic acid, partially neutralized with a solution of 120 to 150 wt. parts by weight of carbonate and / or sodium hydroxide in 300 to 400 wt. parts of water, with 5 to 100 wt. 10 parts by weight of isopropanol; parts of the oxidation component of the initiator system in 20 to 100 wt. % water, optionally up to 30 wt. this solution is added before and / or after the addition of the partially neutralized acrylic acid / isopropanol mixture is added, after completion of the addition of the aqueous solution of the oxidation component of the initiator system, polymerization is completed by heating the reaction mixture at 80-90 ° C for at least 15 minutes; finally, the product is slowly neutralized over 100 to 300 wt. parts of a 35 to 50% aqueous solution of sodium hydroxide and optionally isopropanol is distilled off. 2. The process according to claim 1, wherein at least one of the disulfite, bisulfite, sulfite, dithionite and sodium, potassium or ammonium thiosulfate is used as the reducing component of the initiator system. 2. The process of claim 1 wherein at least one of sodium, potassium or ammonium peroxodisulfate is used as the oxidizing component of the initiator system.