RU2656477C1 - Method of obtaining the lead stearate dibasic - polyvinylchloride stabilizer - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the field of chemical technology for the production of heat stabilizers for extrusion processing of PVC resins, salts of organic carboxylic acids and bivalent lead, and is aimed at eliminating known drawbacks, inherent in previously developed methods of obtaining this class of compounds. Method for producing lead stearate dibasic – stabilizer of polyvinyl chloride includes mixing in an aqueous environment of lead oxide, stearic acid and a catalyst, followed by heating and stirring the resulting suspension, aging, further heating up to 92–95 °C, followed by filtration and drying of the resulting product, during the synthesis of lead stearate dibasic components is heated to 55–60 °C and maintained at this temperature for 30–40 minutes, and ammonium chloride is used as the catalyst for the synthesis of the lead stearate dibasic.

EFFECT: technical result of the invention will make it possible to exclude from the technology taken for the prototype a number of operations: preparation of raw materials, introduction of caustic soda, interaction of the initial components with caustic soda, circulation of the reaction mixture, intermediate holding at 45 °C and 90–98 °C, acidity control, and reduces to simplifying the process, reducing costs, improving environmental safety and protecting the environment.

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Description

FIELD OF TECHNOLOGY

The invention relates to methods for producing thermal stabilizers of polyvinyl chloride resins (PVC) in the process of their extrusion processing.

BACKGROUND

A number of methods are known for producing PVC thermal stabilizers based on carbon salts of lead of both neutral composition (stearate, phthalate, lead) and the basic salts of this metal (dibasic stearate, lead phthalate).

1. Until recently, the classical method for producing lead salts of carboxylic acids is the method developed by the Research Institute of Polymer Materials (NIIPM) according to TU NIIPM P-242-61, TU NIIPM P-350-63. The method is based on the exchange reaction in an aqueous medium between soluble lead salts and previously prepared aqueous solutions of sodium (less often potassium) salts of the corresponding carboxylic acids. As a result of this reaction, the carboxylic salts of lead precipitate, and the soluble products of the exchange reaction — alkali metal salts — remain in the solution.

The precipitate is separated by decantation from the solution, washed several times with demineralized water, filtered and dried in a fluidized bed dryer.

The main disadvantages of this method are:

1.1. Multi-stage production process.

1.2. The use of expensive soluble salts of this metal as a source of lead.

1.3. The need to convert organic acids to a water-soluble state through their interaction with alkaline bases.

1.4. The need to wash the target product from soluble impurities and the general requirement to reduce the electrical conductivity of the finished product.

1.5. The formation of large volumes of wash water, subject to its own disposal due to the presence in their composition of residual amounts of dissolved lead salts.

2. A known method for producing carboxylic salts of fatty acids of heavy metals by exposure to an aqueous solution of a salt of the corresponding metal in the form of a solution prepared and heated to a temperature of 60-98 ° C with a solution of alkaline salts of carboxylic acids, previously obtained by alkaline hydrolysis of the corresponding vegetable oil, fat or their mixtures at a temperature of 60-100 ° C in the presence of an initial additive of sodium stearate (oleate) in an amount of 0.5-1.0% by weight of hydrolyzable oil or fat, followed by separation of the resulting composition of salts and the aqueous phase by filtration, centrifugation or extraction with an organic solvent (Application: 2003129153/04, 09/29/2003, Kursk State Technical University (KSTU).

The disadvantages of this method of producing carbon salts are:

2.1. Preliminary preparation and heating of aqueous solutions of salts of heavy metals.

2.2. Sophisticated technology for the preparation of water-soluble compounds of carboxylic acids obtained from plant or animal raw materials.

2.3. The need to introduce alkali metal stearates (oleates) into the prepared solutions of fatty acids.

2.4. The difficulty of separating the resulting composition into the target product and by-products, the use of extraction with organic solvents, the requirements for the hydrolysis of the oil and fat product in an inert gas stream.

3. A known method of producing thermal stabilizers of chlorine-containing hydrocarbons, based on the interaction of stearic acid and oxides or hydroxides of calcium, zinc, barium, magnesium or lead in the form of individual or mixed salts of stearic acid, in the solid phase with vigorous stirring in the presence of sodium hydroxide or potassium hydroxide 0 , 05-0.15% by weight of stearic acid, propylene carbonate, dimethylformamide, hexametapol, sulfolane or dimethyl sulfoxide in an amount of 0.005-0.05% by weight of stearic acid at a temperature of 40-95 C in a twin screw reactor, that allows to create a continuous process for preparing polymers of chlorinated heat stabilizers. The catalysts of the process - sodium hydroxide or potassium hydroxide, propylene carbonate, dimethylformamide, hexametapol, sulfolane, dimethyl sulfoxide contribute to a significant increase in surface activity of the substrate and obtain products in the form of a homogeneous fine powder (RF Patent 2391360 C2, published April 21, 2008)

The disadvantages of this method of producing carbonic salts of lead include:

3.1. The need to introduce into the composition of the reaction mass a complex composition of catalysts based on inorganic and organic components.

3.2. The complexity of adjusting the composition of the resulting product due to the significant amount of catalyst components.

3.3. The inability to obtain the exact ratio of the components of thermostabilizers during mechanical mixing of the starting materials.

3.4. The presence of unreacted alkali in the finished product, which negatively affects the quality of the finished product

4. The closest method to the claimed is a method for producing lead dibasic stearic acid - a stabilizer of polyvinyl chloride, including the preparation of raw materials, the interaction of sodium hydroxide, lead oxide and stearic acid in a heated state with vigorous stirring, while the process is carried out in the solid phase, followed by precipitation and synthesis dibasic stearic acid lead, by heat treatment of the suspension of the latter, circulation of the suspension, filtration, drying, packaging and packaging of the finished product. During the synthesis of the heat stabilizer, caustic soda is charged, an aqueous suspension of lead lead is prepared, solid stearic acid is loaded, the reaction mass is heated to a temperature of 45 ° C, kept at this temperature for 15-20 minutes, then the temperature is raised to 60-65 for 25-35 minutes ° C and incubated for 40-60 minutes to obtain a homogeneous mass, and the circulation of the suspension is carried out throughout the synthesis cycle. After the synthesis of lead stearic acid dibasic suspension is subjected to heat treatment to aggregate particles by heating to a temperature of 90-98 ° C, holding for 10-15 minutes with continuous stirring until the acid number of the product is not more than 1 mg KOH / g (RF Patent 2,506 253 C1, published 02/10/2014).

The disadvantages of this method of producing heat stabilizers include the following:

4.1. Multi-stage process.

4.2. Requirement of the stage of preparation of raw materials.

4.3. Conducting the synthesis process in the solid phase.

4.4. Use in the process of caustic component - sodium hydroxide.

4.5. The need to use circulation during the process, which leads to higher prices and, accordingly, to the complexity of the technological scheme.

4.6. A multi-stage heating and holding system for reacting components in the synthesis process.

4.7. The need for control on the presence of alkalis in the finished product.

4.8. The formation of large quantities of wash water requiring special treatment before disposal.

SUMMARY OF THE INVENTION

The goal that can be achieved by the present invention is the development of a simple one-stage method for producing lead dibasic stearic acid - a stabilizer of polyvinyl chloride, characterized by a simplification of the process, cost reduction, increased environmental safety and environmental protection.

The technical result, which can be obtained using the present invention, is reduced to a method for producing lead dibasic stearic acid - a stabilizer of polyvinyl chloride, which includes mixing in the aqueous medium the calculated amounts of lead oxide, ammonium chloride, carboxylic acid or a mixture of various carboxylic acids, followed by heating to 55 -60 ° C, stirring the resulting suspension, holding at this temperature for 30-40 minutes, further heating to 92-95 ° C, followed by filtration, drying the obtained product The product, in addition, ammonium chloride is used as a synthesis catalyst.

DETAILED DESCRIPTION OF THE INVENTION

The synthesis process is carried out in a vessel equipped with a mechanical stirrer and a heating system. When the stirrer is switched on, the required amount of water is poured into the vessel (which is subsequently constantly in the system and used repeatedly), the calculated amount of lead oxide (lead lead), carboxylic acid (stearic, phthalic, terephthalic, etc.) is loaded, depending on the required chemical composition of thermal stabilizers and from 0.7 to 1.5% of the loaded mass of lead oxide of the catalyst - ammonium chloride. The synthesis of thermostabilizer begins almost immediately after loading all the components.

After the start of the reaction, the temperature is gradually raised to 55-65 ° C and the mixture is kept at this temperature for 25-30 minutes to guarantee the completion of all ongoing synthesis processes.

Then the reaction mass is heated to 92-95 ° C for the processes of agglomeration of particles of the obtained heat stabilizer and completion of the hydrolysis of low molecular weight compounds of lead and carboxylic acids. When the set temperature is reached, the heat treatment process is completed, heating is stopped, the aqueous suspension is sent for filtration, followed by drying and packaging of the resulting product.

Filtered water is again sent to the head of the process to obtain the next amount of thermal stabilizer.

The proposed method for producing lead thermal stabilizers by the direct synthesis of lead oxide and carboxylic acids in the presence of a catalyst for ammonium chloride differs from the prototype in the following:

1. The simplicity and versatility of a one-stage method for producing thermal stabilizers of extrusive processing of PVC based on lead salts and carboxylic acids, which allows to obtain a wide range of finished products.

2. The absence of intermediate stages in the preliminary mixing of the starting components.

3. An exception to the process of synthesis of caustic components - alkalis.

4. An exception to the technological process of washing the finished product from traces of alkali and other readily soluble reaction by-products.

5. The exception of the final control for the presence of residual alkalinity in the finished product.

6. The ease of the process.

7. The exception to the technological operation is continuous circulation in the synthesis process.

8. The absence of intermediate stages of exposure of the reaction products at a certain temperature.

9. Low energy costs for the synthesis.

10. Reducing the environmental load on the environment by eliminating the discharge or treatment of ballast water containing lead compounds.

Claims (1)

A method of producing lead dibasic stearic acid - a stabilizer of polyvinyl chloride, comprising mixing in an aqueous medium lead oxide, stearic acid and a catalyst, followed by heating and stirring the resulting suspension, holding, further heating to 92-95 ° C, followed by filtration and drying of the resulting product, characterized the fact that during the synthesis of lead dibasic stearic acid, the starting components are heated to 55-60 ° C, kept at this temperature for 30-40 minutes, and as a catalyst, Ammonium chloride is used for the synthesis of lead stearic acid dibasic.