RU2755709C1 - Method for producing plasticiser for pvc dioctyl terephthalate - Google Patents

Abstract

FIELD: polymers.

SUBSTANCE: invention relates to a method for producing plasticisers for polymer materials from processing byproducts, such as terephthaloyl chloride (TCL) waste bottoms. Proposed is a method for producing a plasticiser of dioctyl terephthalate (DOTP) including esterification of terephthaloyl chloride waste bottoms consisting of unreacted terephthalic acid, terephthaloyl chloride and ferric chloride used in the synthesis of TCL as a catalyst, executed in 2 stages, wherein the reaction mass is heated from 91 to 100°C at the first stage, and at the second stage of esterification, the catalyst tetrabutoxytitanium is introduced to execute the synthesis at a temperature of 184 to 200°C.

EFFECT: production of a DOTP plasticiser from terephthaloyl chloride waste bottoms, significantly expanding the raw material source.

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Description

The invention relates to a method for producing plasticizers for polymeric materials from secondary processing products, such as terephthaloyl chloride (TFC) bottoms.

The proposed plasticizer dioctyl terephthalate (DOTP) is a mixture of esters. Currently, there are numerous plasticizers based on esters of dicarboxylic acids - phthalic, adipic, sebacic, etc. with alcohols containing at least 8 carbon atoms. The disadvantage of these plasticizers obtained from pure compounds is their high cost.

A known method of producing a plasticizer for polyvinyl chloride (PVC), where normal and isoamyl alcohols are used as raw materials (patent RU No. 2171267 1999). The disadvantage of this plasticizer is the low flash point - 190 ° C.

Also known is a method of obtaining a plasticizer for PVC from the bottoms of the production of butyl alcohols (patent RU No. 2235716 2003). The disadvantage of this plasticizer is an even lower flash point of 185 ° C, the presence in the product of "heavy" ether impurities that worsen the plasticizing properties, the product is dark in color. According to this technology, phthalic anhydride is used to obtain dicarboxylic acid, which is considered a toxic substance of hazard class III.

The closest in technical essence and the achieved effect is a method for producing a DOTP plasticizer using 2-ethylhexanol isolated during vacuum distillation of the distillation residue of 2-ethylhexanol rectification (KOREG) (patent RU No. 2404156 20.11.2010). The disadvantage of this technology is the low concentration of 2-ethylhexanol, the high content of glycols and heavy ethers in the distillate due to the fuzzy separating vacuum distillation of KOREG. After re-loading the recycle of 2-ethylhexanol, the esterification time sharply increases, the conversion for technical terephthalic acid decreases, which leads to an increase in the consumption of raw materials per ton of manufactured products.

The technical problem of the invention is to obtain a plasticizer DOTP for the production of PVC, consisting of esters obtained from 2-ethylhexanol and bottoms waste terephthaloyl chloride, which significantly expands the source of raw materials.

The problem is solved by the claimed method for producing dioctyl terephthalate plasticizer by esterification using 2-ethylhexanol and a catalyst. For esterification, the bottom waste of terephthaloyl chloride is used, consisting of unreacted terephthalic acid, terephthaloyl chloride, and ferric chloride, used in the synthesis of TPC as a catalyst, in a molar ratio of alcohol: bottom waste = 3: 1. The process is carried out in 2 stages, while in the first stage the reaction mixture is heated from 91 to 100 ° C, which leads to the formation of an acidic catalyst hydrogen chloride released during the decomposition of TPH and ferric chloride present in the bottom waste, with a concentration of up to 30% , and at the second stage of esterification, a catalyst tetrabutoxytitanium (0.3-0.6% of the mass of the reaction mass) is introduced to carry out the synthesis at a temperature of 184-200 ° C.

The claimed method is implemented as follows.

In a reactor with a stirrer equipped with a Dean-Stark attachment and a reflux condenser, 2-ethylhexanol is charged together with the still waste of terephthaloyl chloride in a molar ratio of alcohol: still waste = 3: 1, heat is turned on.

At a temperature of 91 ° C, the esterification process begins, the catalyst is hydrogen chloride released during the decomposition of TPC and ferric chloride, which is present in the bottom waste.

Water released during esterification together with hydrogen chloride is removed from the system in the form of hydrochloric acid, with a concentration of up to 30%. After removing hydrogen chloride and water from the reaction mixture, the catalyst tetrabutoxytitanium (TBT) is introduced into the reactor. With constant stirring of the mixture in the reactor, the temperature is raised to 184 ° C, at which the esterification process begins. Water released during esterification in the form of an azeotrope of 2-ethylhexanol is distilled off from the solution, and 2-ethylhexanol is returned to the reaction zone. TBT is introduced into the reaction medium from 0.3 to 0.6% of the reaction mass. After the release of the calculated amount of water at a temperature of 184-200 ° C, the synthesis ends. The synthesis time is 4 to 5 hours. Next, a vacuum distillation is started to remove 2-ethylhexanol, which is used in re-synthesis. The TBT catalyst is destroyed by an aqueous solution of soda, with a concentration of 5.0%.

Example 1. In a reactor with a stirrer equipped with a Dean-Stark attachment and a reflux condenser, the bottoms of TPC weighing 77.02 g and 241.52 g of 2-ethylhexanol are loaded. The reaction mixture is heated to 91 ° C. at which action esterification begins. In this case, hydrochloric acid is distilled off from the reaction zone, the concentration of which can reach up to 30%. After distilling off hydrochloric acid, 0.45 g TBT catalyst (0.3 wt% of the reaction mass) is loaded into the reactor. The reaction mixture is heated to 184 ° C and the process is finished at 200 ° C. When the calculated amount of water is released, the synthesis stops. A vacuum of 80-100 mm is created in the reactor. Hg for the distillation of 2-ethylhexanol. When the temperature reaches 145-148 ° C, the distillation of alcohol stops. To destroy the TBT catalyst, a 5.0% sodium carbonate solution is pumped into the reactor. After the destruction of the catalyst, DOTP is separated from the aqueous solution of soda by stratification and is dried from water at a temperature of 100-130 ° C. The yield of the product is 181, 39 g. Conversion is achieved on the bottoms of 99.4%. The synthesis time is 5 hours.

Example 2. A method of obtaining a plasticizer DOTP based on 2-ethylhexanol and bottoms of TPC according to example 1, differs in that 0.67 g of the TBT catalyst (0.44% of the mass of the reaction mass) is added. The process conditions are the same as in example 1. The product yield is 182, 41 g. The conversion of the distillation residues of TPC is 99.56%, the synthesis time is 4.6 hours.

Example 3. A method of obtaining a plasticizer DOTP based on 2-ethylhexanol and bottoms of TPC according to example 1, differs in that 0.71 g of TBT catalyst (0.6% of the mass of the reaction mass) is added. The process conditions are the same as in example 1. The product yield is 182.49 g. Conversion on bottoms of TPC 99.57%, synthesis time is 4.59 hours.

With the introduction of TBT less than 0.3% of the reaction mass, the esterification time increases, the raw materials are not completely consumed, the conversion of esterification decreases, and the consumption of raw materials increases.

With the introduction of TBT more than 0.6% of the mass. from the reaction mass, there is an overrun of the catalyst, but a noticeable improvement in performance is not observed. The established optimal amount of catalyst is from 0.3% to 0.6% of the reaction mass.

As a result of the study, the possibility of obtaining DOTP from the bottoms of TPC and the optimal amount of catalyst (0.3-0.6% of the mass of the reaction mass) for the esterification of the bottoms of TPC and 2-ethylhexanol was established.

Claims (1)

A method of producing dioctyl terephthalate plasticizer for PVC by esterification of terephthaloyl chloride bottom waste using 2-ethylhexanol and a catalyst, characterized in that terephthaloyl chloride bottom waste is used for esterification, consisting of unreacted terephthaloic acid, terephthaloyl chloride and terephthalochloride used as a catalyst molar ratio alcohol: bottoms waste = 3: 1, carried out in 2 stages, while in the first stage the reaction mixture is heated from 91 to 100 ° C, which leads to the formation of an acidic catalyst hydrogen chloride released during the decomposition of terephthaloyl chloride and ferric chloride present in the bottom waste, moreover, hydrogen chloride, which is a catalyst for the esterification of terephthaloyl chloride at the first stage of esterification, is distilled off together with the released water from the reaction zone with the formation of hydrochloric acid with a concentration of up to 30% in the distillate, and to complete the process on the second stage of esterification is introduced by the catalyst tetrabutoxytitanium (0.3-0.6% wt. from the reaction mass) to carry out the synthesis of dioctyl terephthalate at a temperature of 184-200 ° C, then after the synthesis of the target product is completed, the excess of 2-ethylhexanol is distilled off under vacuum, and the tetrabutoxytitanium catalyst is destroyed with a 5.0% aqueous solution of soda.