CS230075B1 - Distilling method to refine technical dian - Google Patents

Description

The invention relates to a process for refining technical diania by distillation,

Dian, 2,2 ^, -bis- (4-hydroxyphenyl) propane, commercially bisphenol A, is an important chemical raw material for the production of epoxy resins, polycarbonates, flame retardants, antioxidants and the like.

It is generally prepared by acid-catalyzed condensation of phenol with acetone. The easiest way to isolate diane from the reaction mixture after the condensation reaction is to distil off all the more volatile fractions than dian, namely, unreacted acetone, water residue and excess phenol. However, such an isolated product has only limited applicability, for example for the production of some less demanding epoxy resins, some types of flame retardants, and the like.

For example, dian can be purified by crystallization from organic solvents such as alcohols, aromatics, chlorinated aliphatic or aromatic hydrocarbons, etc., or mixtures thereof. In this process, a saturated solution of diane in a solvent is first prepared at elevated temperature, then cooling of the solution to precipitate diane crystals of high purity. The crystalline dian is separated from the mother liquor, washed and freed from solvent.

The advantage of this crystallization process is the preparation of a high purity product and the possibility to carry out the refining operation completely independently of the preparation of the technical process. However, the process has a number of drawbacks, in particular a complex apparatus with a number of operations to dissolve the diane in the solvent, crystallize with strict adherence to the prescribed temperature regime, solid phase isolation requiring slurry handling, solvent removal from the product, solvent recovery from waste mother liquor.

Another often used way of refining Diana is in his

230,075 crystallization in the form of a phenol-dian adduct from a phenol-dian-impurity melt. After its isolation, the adduct is suitably decomposed, for example by distilling off the phenol, thereby insulating the refined dian, which is again of high purity. Despite this advantage, however, this process also has a number of serious disadvantages. Crystallization from phenol is even more demanding than crystallization from solvent, since the whole process takes place in the phenol melt at normal temperature setting. Isolation of the adduct and its washing with phenol should therefore be carried out in tempered filters or centrifuges. The adduct crystals must then be melted and phenol-free again. The crystallization itself proceeds with a relatively low yield of diane from the feed mixture. This causes further process difficulty - significant volumes of both phenol and unprocessed Diana need to be recycled, so the refining plant must be in close proximity to the actual production of Diana.

Extraction, usually with chlorinated hydrocarbons or aromatics, is also recommended for refining the diane in conjunction with another purification operation. Thus, purification of the extracted diane by dissolving it in aqueous lye, decolouring the alkaline solution with bisulfite is described. or by introducing sulfur dioxide and finally recovering the diane by acidifying the alkaline solution with acid or carbon dioxide. The difficulty of this procedure, both apparatus and raw material, is quite evident. Extraction is also used as a finishing operation after simple dianu distillation under vacuum, where more volatile constituents distilling together with diane, especially phenol, are just being removed from the crystallized distillate by extraction. This process is also very demanding in terms of equipment, and again introduces another component into the process, the solvent to be regenerated. In addition, solvents suitable for diane extraction, chlorinated hydrocarbons or aromatics are very harmful to health, so these processes are associated with considerable hygiene problems.

All the refining processes described provide a high purity dian suitable for the preparation of all types of epoxy resins and polycarbonates. As shown by industry practice, this high purity is not absolutely necessary for the preparation of epoxy resins. In some cases, it was even found that the presence of some

230,075 by-products of the condensation reaction in diane even improves the utility values of some types of epoxy resins. In all cases, however, the epoxy resin is required with minimal dian phenol content and the presence of coloring substances deteriorating or causing the resulting resin _PR Company difficulties in the technological process.

As experimentally verified, a dian refined by the process of the invention satisfies these conditions. The method of refining technical dian by distillation of dian and subsequent partial condensation is according to the invention in that the distillation is carried out from the film by flash or differential distillation at a pressure of 10 Pa to 1 kPa and a temperature of up to 260 ° C. ° C depending on the pressure used, the more volatile fractions leaving the partial condensation in the form of vapors leading to further condensation and being collected separately from the product.

The process according to the invention is comparatively simpler in operation and more manageable in operation than the known processes. The product is suitable for use in the preparation of epoxy resins and flame retardants.

The examples below illustrate embodiments of the invention. Example 1

A 1 liter distillation flask with a thermometer and nitrogen capillary was connected to a transducer that conducted the vapors to a partial condenser in which the dian product was condensed. The partial condenser was cooled by evaporation of a suitable liquid having a boiling point of about 155 ° C, which condensed in the reflux condenser and flowed back into the partial condenser. The vapors that did not condense in the partial condenser were fed to an air-cooled condenser in which the front, lower boiling condensates condensed. The inerts from this end condenser were drawn to a single-stage oil rotary pump. The outer surfaces of the transducer and the partial condenser were tempered by an additional electrical heating tape.

Into the distillation flask was charged 579 g of crushed Diana. After

230 075 by melting, tempering the apparatus and adjusting the vacuum to 0.07 kPa, distillation was started. Within 125 min, 503 g of distilled diane (86.9% batch) were obtained. The distillation residue in the flask was 47.0 g (8.1%), and the distillation bottoms condensed in the final condenser yielded 5 g (0.9%). The temperature of the melt in the flask during the distillation was 202 to 205 ° C, the vapor temperature of the diane was 195 to 198 ° C.

Example 2

The molten dian was pumped from the tank by a metering pump at a rate of 4.3 kg / h. into a rotor film evaporator. The vapors were discharged to a partial condenser, cooled by evaporation of the liquid boiling at 155 ° C, where a refined dian (4.1 kg / h) condensed, which was discharged through a barometric cap and flaked. The non-condensed fractions went from the partial condenser to another water-cooled condenser, where they condensed and were removed again via a barometric cap. The distillation residue was continuously withdrawn from the bottom of the rotor evaporator by a pump. A pressure of 53.3 Pa was maintained in the system. The current analyzes are again shown in Table 1. Table 1

Analysis of the currents of Examples 1 and 2 Example 1 Example 2

handle distillate handle distillate residue ο, ρ-dian% wt 4.42 4.58 3.74 3.37 0.80 codimer% includes. 0.31 0.30 0, 56 0.47 0.15 ρ, ρ-dian wt 93.49 94.68 93.03 94.02 51,45 BPX wt 0.96 0.12 1.20 0.31 39.80 phenol% hmdt 0.48 0.02 0.20 0.06 0.00 melting point ° C 152.3 155.1 153.5 153.5 - light transmittance% 92 97 94 97.7 w.

Color evaluated by light transmittance determined on the photocolour meter, solution layer 3 cm, solution of 40% diane in ethanol.

Claims (1)

OBJECT OF THE INVENTION 230 Process for refining technical distillation by distillation and subsequent partial condensation, characterized in that the distillation is carried out from the film by flash or differential distillation at a pressure of 10 Pa to 1 kPa and a temperature of up to 260 ° C, followed by partial condensation of the product at 140 to 190 ° G in Depending on the pressure used, the more volatile fractions leaving the partial condensation in the form of vapors lead to further condensation and are collected separately from the product.