CS238698B1 - Trapping and returning method of volatile organic substances - Google Patents

Abstract

Elimination of volatile reaction losses components from the production of elkyd resins by melt procedure. Oele was achieved by ebsorption of volatile the components entrained in the gas stream in the absorber a mixture of raw materials at temperature 80 to 150 and returning them to the production process. Volatile substances formed by phthalic anhydride and optionally one major fraction vapor of the reaction water produced in the initial water phase of polyesterification, along with torn down organic substances are introduced into the absorbent where they pass through the absorption layer liquid, not maintained at temperature in the range of 80 to 150 ° C, consisting of natural glycerin and aliphatic monocarboxylic esters acid of iodine number 80 up to 205 g / 100 g and / or aliphatic aonocarboxylic acids C 1 -C 6 acids and / or polyols alcohols with carbon numbers 2 to 6 and / or partial esters of these alcohols with aliphatic monocarboxylic acids C 8 to C 8, preferably from the alcoholysis product vegetable oils with alcoholic alcohols, and after capture of volatile organic compounds materials, especially phthalic anhydride, are absorbent liquid together with trapped organic from the absorption space during or after termination of the polyesterification and is preferably fed to the reaction space, where it is processed into an alkyd resin.

Description

The present invention relates to a process for capturing b in the deposition of volatile organic compounds during production.

alkyd resins. This method is suitable for the melting process for the preparation of alkyds in which phthalic anhydride is used as the dibasic acid.

When manufacturing? alkyd which? still constitutes the most important binder base for the preparation of paints, using two basic technological processes, melting and solvent.

Despite the numerous advantages of solvent-based manufacturing processes, such as easier control of the production process, higher and more uniform slurry quality, shorter production times, etc., the melting process is still used, and in some cases also preferred here, such as in isophthalic alkyd production. .

The advantages of the melting process are lower investment costs for control, lower energy consumption, since there is no need for solvent recycling energy and lower fire risk. A considerable disadvantage of the melting process is the escape of volatiles, especially phthalic anhydride, during the polyesterification process.

In the present process, in the first stage of the polyesterification, the esterification water vapors along with the entrained reactants are usually discharged into a condenser, where the springs are condensed and after removal of most of the reaction water a gas stream, usually inert (nitrogen, carbon dioxide) ), which facilitates removal of the reaction water from the reaction mixture.

The gas stream together with the by-products, especially water and longer entrained substances, the main component being phthalic anhydride, the most commonly used dibasic carboxylic compound in the production of alkyds, is discharged from the reactor through a special line, usually under vacuum generated by a fan. the wet scrubber and the gas are discharged to the outside atmosphere for longer.

Significant disadvantages of this method are the loss of volatile reaction components, especially violet anhydride or volatile alcohol, contamination and clogging of the equipment by these substances, the necessity of regular frequent cleaning of the exhaust pipe, separator, fan, often with necessary shutdown of the production equipment and last but not least environment by drift of volatile organic compounds into the atmosphere during dryness of the waste water during wet separation.

These disadvantages are overcome by the process of trapping and returning volatile organic compounds leaving the reaction zone during the polyesterification in the gas stream during the fusion process for producing alkyd resins modified with vegetable oils and / or aliphatic monocarboxylic acids or other substances according to the invention by volatile components in the gas stream consisting of the predominantly phthalic anhydride and, in the case, the major part of the reaction vapor produced in the initial phase of the polyesterification, together with entrained organic substances, are introduced into the absorption space where they pass through a layer of absorbent liquid maintained there; a lot in the range of 80 to 150 ° C, consisting of natural esters of glycerin and aliphatic monocarboxylic acids having an iodine value of 80 to 205 gJ / 100 g and / or aliphatic monocarboxylic acids C 8 to C ₂₂ and / or polyhydric alcohols having a carbon number of 2 to 6; / or partial The esters of these alcohols with aliphatic monocarboxylic acids C8 to _C22 , preferably from the vegetable oil alcoholysis product of polyhydric alcohols, and after entrapment of volatile organic compounds, in particular phthalic anhydride, the absorption liquid together with the entrained organic compounds are removed from the absorption space during or after The polyesterification is preferably fed to the reaction space where it is processed to an alkyd resin.

By the method according to the invention, the losses of volatile raw materials, especially phtolanhydride or volatile polyalcohols, are considerably reduced, air and wastewater pollution is considerably reduced, the necessity of frequent cleaning of production equipment is eliminated, production cycle is shortened. In particular, the production equipment and its operation are simplified due to a reduction in the gas flow rates and thus a decrease in the reaction water withdrawal rate due to clogging of the plant with phthalic anhydride.

Example 1 • Ϊ

To a reactor containing 10 m ^J is impregnated with 4360 kg soya oil was added 1000 kg of pentaerythritol and 1.2 kg of lead oxide. The mixture is heated to 250-260 ° C with stirring and maintained at this temperature until alcoholysis is complete. The mixture is then cooled, mixed with 1780 kg of phthalic anhydride and the absorber content from the previous batch is added. It is heated to the esterification temperature. 60 kg of the alcoholysate obtained from the alcoholysis of soybean oil with glycerine are introduced into the absorption apparatus and heated to 105-110 ° C. When the temperature of the reaction mixture reaches 160-170 ° C, the reaction water begins to cleave, the vapors passing through the absorber and leaving to the condensate. At 210-215 ° C, where most of the esterification water distilled off, nitrogen was introduced to the bottom of the reactor. The temperature is gradually raised to 240 ° C. The nitrogen stream, along with phthalic anhydride vapors and esterification water residues, is passed through a layer of absorption liquid maintained at a temperature of 130-145 ° C in which the phthalic anhydride is trapped. Nitrogen with water residues enters the condenser in which the water condenses and the nitrogen enters the atmosphere. The course of the reaction is monitored by measuring consistency and acid number. After reaching an acid number below 10 mg KOH / g and a consistency of 50% solution in white spirit for 45 to 55 seconds, the product was cooled and discharged. The contents of the absorber are discharged into the reactor after completion of the alcoholysis of the following batch.

Example 2

2150 kg of linseed oil were charged into the reactor and heated to 200 ° C. 1000 kg of glycerin are then metered in over one hour and 0.8 kg of calcium oxide are added. The reactor contents were heated to 250-255 ° C and held at this temperature until alcoholysis was complete. Then 950 kg of tung oil is added. The box is cooled below 180 ° C, 800 kg of phthalic anhydride are added and the reactor contents are discharged from the previous operation. The reaction mixture is heated to the esterification temperature. At the same time, 80 kg of linseed oil is infused into the absorber and heated to 110 ° C. The esterification water vapor passes through the absorbent liquid layer and exits the absorber into a water-scrubbed conduit in which the esterification water vapor condenses.

When the temperature of the reaction mixture reached 215 ° C, nitrogen was introduced to the bottom of the reactor. The gas stream, together with the phthalic anhydride vapors, is passed through an absorption liquid layer in which the phthalic anhydride is collected. The gas with the remainder of the reaction water is discharged into the atmosphere via a water-sprayed pipe condensing water vapor. The temperature of the reaction mixture gradually increased to 230 ° C.

The progress of the reaction is controlled by monitoring the consistency and acid number. Upon reaching an acid number of 18 to 22 mg KOH / g ae, the contents of the reactor absorber and the abserb are emptied and immediately filled with 80 kg of flax alley. Up to a total of 15 mg KOH / g and a 50% solution in toluene of 26 to 30 was achieved and the product cooled and discharged from the reactor. The contents of the abserb a are discharged into the reactor before the start of the next batch.

Example 3

Weigh 2 720 kg of the fatty acids of the cocoa alley, 1,700 kg of glycerin and 2,710 phthalic anhydride, and the ebaah abserbers from the previous batch are weighed. The mixture was heated to 210 ° C.

Vapor esterification defects a and adv through the empty absorber to the condenser. After 1 hour at 210 ° C, 20 kg of monoethylene glycol and 20 kg of glycerin are introduced into the absorber and the temperature of the absorption liquid is maintained at 95-105 ° C.

At the same time ae begins to introduce carbon dioxide to the bottom of the reactor. The temperature of the reaction mixture was gradually increased to 230 ° C. Carbon dioxide β by phthalic anhydride and partly by glycerin and esterification water vapor is introduced into the absorber where ae captures phthalic anhydride and glycerin. Carbon dioxide with the remaining vapors passes through the condenser into the atmosphere.

The progress of the reaction is monitored by measuring the acid number and consistency. After reaching an acid number below 25 mg KOH / g and having a consistency of 50% Rosty in xylene for 45 to 50 seconds, the product is cooled and discharged. The contents of the absorber are discharged into the reactor at the same time as another batch is charged.

In all examples, the consistency of a 50% solution in xylene was measured on a spout cup DIN 4/20 ⁰ C.

Claims (1)

SUBJECT OF THE INVENTION A process for capturing and returning volatile organic compounds leaving the reaction zone during polyesterification in a gas stream in a melt process for producing vegetable oil modified β / or aliphatic monocarboxylic acids or other substances, characterized in that the volatile components in the gas stream are removed. consisting predominantly of phthalic anhydride and optionally 1 major portion of the water reaction vapors formed in the initial phase of the polyetherflkaee, together with entrained organic substances, are introduced into the absorption space where they pass through an absorbent liquid layer maintained at 80-150 ° C consisting of natural esters glycerin and aliphatic momocarboxylic acids having an iodine number of 80 to 205 g / 100 g and / or aliphatic monocarboxylic acids C 8 to C ₂₂ and / or polyhydric alcohols and a number of carbon atoms of 2 to 6 and / or partial esters of these alcohols and the aliphatic monocarboxylic acids C8 to _C22 , preferably from the alcoholic product of vegetable oils with polyhydric alcohols, and after entrapment of volatile organic compounds, in particular phthalic anhydride, the absorption liquid together with the entrapped organic compounds drained from the absorption space during or after polyesterification and preferably is fed into the reaction space, where it is processed to alkyd resin ·