CS203388B1 - Process for preparing polyestere resins - Google Patents

Description

The present invention relates to the preparation of polyester resins in a manner that allows the reaction to proceed faster. This shortens the production time of the polyester resin and, at the same time, significantly reduces the proportion of organic impurities in wastewater and fumes.

One method of preparing polyester resins is by direct polyesterification, which is most commonly used on an industrial scale. There is a multivalent reaction of saturated polyesters. or unsaturated carboxylic acids or derivatives thereof, most often anhydrides and alkyl esters, with polyhydric alcohols. Polyesterification is carried out at a temperature of 100 to 260 ° C, most often at 160 to 240 ° C, at a rate such that losses on the volatile glycols or anhydrides are minimized. It is operated by the so-called melt process, the azeotropic or vacuum process / J. Hlezíva et al .: Polyesters ”, SNTL, Prague 1,979, Kunststoff-Handbuch, Bd. Vlil, '' Polyester '', Carl Hauser Verlang, Munchen, West Germany, Corporate 'Article Paint Manufacture, 47, No. 6 July / August 1977 / H, Kaiser: Farbe u. Lack, 8 4, 1, 23-27, (1978), under a protective layer of inert gases (Cs. U.S. Pat. No. 125,577, U.S. Pat. Germany No. 1,265,414, U.S. Pat. USSR No. 228,272], The Intensity of Inerting Gases Above or into the Reaction Mix (U.S. Pat. No. 3,109,831-4) or the Evaporation Rate of an Azeotropic Solvent (U.S. Pat. U.S. Pat. No. 2,892,813] is to be kept at a low level according to these procedures, as otherwise there will be a large leakage of glycols, respectively. other reactants. The vacuum process generally results in significant volatile components leakage from the reaction mixture. The improvement of the esterification conditions allows for another process in which the preparation of the polyester resin is accelerated by simultaneous intensive injection of inert gas and scrubbing of the volatile components and inert gases / en. Certificate No. 170 442 /. This efficient process for preparing polyester resins requires a powerful inert gas source.

It has now been found that a very good effect can be achieved by the simpler process of the present invention, which relates to a process for preparing polyester resins by reacting polycarboxylic acids containing from 4 to 10 carbon atoms or functional derivatives thereof. modifying compounds, in particular from the group of monovalent alcohols or monocarboxylic acids, at atmospheric or reduced pressure, at a temperature of 100 to 260 ° C and optionally in the presence of inert solvents.

It is an object of the invention that the vapors of the by-products of the reaction, especially water, formed during the reaction, are fed together with the entrained vapors of the volatile reactants and possibly also of the solvents into a vertical column. As they pass through the column, they are contacted with a countercurrent polyester resin and / or ^a mixture of its reactants, or solutions thereof in inert organic solvents. The trapped condensed vapors of the reactants, optionally with some of the solvents, are returned to the reaction space and the by-product vapors, optionally with the solvent vapors, are sent to the column passage for condensation in a separate space.

This process can be carried out under normal pressure in the apparatus as well as under vacuum, and it is particularly advantageous to conduct an initial phase of polyesterification where significant by-product reaction products, in particular water, are developed under atmospheric pressure.

Conventional polyesters can be used to prepare the polyester resins of the present invention. stainless steel reactor with electric induction or resistance heating, possibly with heating by means of heat transfer medium. The reactor is equipped with a suitable stirrer, thermometers, appropriate outlets, feeds for feedstock dosing, event. Above the reactor is a vertical column, the function of which is to capture and condense the escaping glycols and other volatile components, but to pass through the reaction by-products. The type of column, type of packing or the like is suitable to be selected according to the size of the apparatus, the type of starting reactants in terms of their reactivity, etc. It is preferred that the column is provided with a heating jacket with one or more sections. At the bottom or middle of the column there is a vapor feed from the reactor, from the bottom, optionally provided as a separating vessel, is returned to the reactor by reflux. The column head is connected to a descending condenser, one or two separating vessels and an anthology. The device is supplemented with metering pumps to pump a polyester resin reaction mixture or a solution thereof in inert solvents into the column head.

The reaction is carried out by introducing the reactants into the reactor, melting them and then homogenizing them with stirring, then heating the reaction mixture to a temperature of 140-170 ° C, at which vapor of the secondary reactants starts to be released. lead to a vertical column. Reflux may be a solution of the preformed polyester in an inert organic solvent, a solution of the reaction mixture in an inert organic solvent, the melt of the reaction mixture or the polyester itself, or a combination thereof. This reflux controls the temperature regime of the column.

The temperature of the dosed reflex should be substantially lower than the reaction temperature. of the mixture in the reactor, and can vary according to the viscosity of the reflux in the range of from 20 to 150 ° C. an absorption or extraction agent for the glycols and other volatiles leaving the reactor, the vapors of water and / or inert solvents being readily removed from the refluxing liquid in the column. The organic solvent may in this case absorb the latent heat released by condensation of the glycols at reflux. The relatively small quantity of inert gas used as a protective atmosphere above the level of the reaction precipitate does not in any way diminish either the dimensions or the running of the column.

According to known methods, it was possible to start with esterification under vacuum, which is considered to be its last stage. up to relatively low acid numbers of the reaction mixture. The process according to the invention achieves a significant reduction in the polyesterification time precisely because it is possible to commence the polyesterification under vacuum much earlier, as the polyesterification proceeds very quickly under vacuum. The disadvantage of, for example, the vacuum process, in which there has previously been a significant leakage of reactants, with the present process in which the volatile components are trapped in the reaction mixture, but at a lower temperature than the reaction mixture in the reactor, is minimized.

In particular, these raw materials and mixtures thereof may be used to prepare the polyester resins of the present invention. Of the polyhydric alcohols ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol ₍ 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, dipropylene glycol, cyclohexanediols, xylylene glycols,

AND

Λ low molecular weight polyalkylene glycols and sulfite-substituted derivatives thereof. Among the alcohols, glycerine, trimethylolethane, trimethylolpropane, pentaerythritol, unsaturated acids and their functional derivatives can be used phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, tetrahydrophthalic anhydride, chlorotetrahydrophthalic anhydride, anhydride, It is preferred to use acrylic acid, maleic acid, fumaric acid, maleic anhydride, their halogenated and methyl derivatives, chloromaleic acid, itaconic acid, citraconic acid and their anhydrides. In particular, olefinic unsaturated compounds capable of copolymerization with unsaturated polyesters, in particular styrene, its halogenated derivatives, methyl methacrylate, butyl methacrylate, acrylonitrile, acrylamide, dialyl phthalate, dialyl fumarate, trialyl cyanurate, can be used as modifying components. Among the other components, in particular, low molecular weight epoxy, phenolic and isocyanate compounds are suitable.

The process for preparing the polyester resins of the present invention can greatly accelerate the preparation of the polyesters and reduce the loss of volatile reactants without the need for a larger quantity of inert gas.

Example 1

To a 1500 liter reactor equipped with induction heating, anchor stirrer, cooling or heating coil, thermometers and a 1 500 mm J _g column with a 25 mm length of Raschig rings, a descending cooler, a separating vessel for distillate and metering pump weighing 154.7 kg / 1.0452 kgmol / phthalic anhydride, 351.5 kg / 2.4042 kgmol / adipic acid, 500 kg / 4.7990 kgmol / neopentyl glycol and 27.5 kg / 0 2030 kgmol / triinetylolpropane. Induction heating is switched on and the reaction mixture is carefully melted. Stirring is then started and the temperature is raised to 155-160 ° C when the esterification water begins to release. At this point, dosing begins in the column head; by means of a pump, the reaction mixture, cooled in the inlet pipe to 100 ° C by condensate. Depending on the heating intensity, the amount of reflux is adjusted to a volume of 40 to 70 kg / h. The temperature at the top of the column is maintained at 95-110 ° C by means of this feed. The resin with the run-off column captures neopentyl glycol and leaves the bottom of the column back into the reactor below the level of the reaction mixture. Water vapors are passed through the column to a descending condenser where they condense. Upon reaching the acid value of the reaction mixture of 100 mg KOH / g, a water pump apparatus is connected and at a pressure of 10 kPa and at a reflux temperature of 100 ° C, 20 to 40 kg / h, the esterification is complete when the acid number of the reaction mixture is 10 to 12. mg KOH / g. The esterification time is 10.5 h and the losses on the volatile glycols are less than 1.5 wt.% Of its feed.

Example 2

397.7 kg of 1,2-propylene glycol are charged to the reactor described in Example 1 and 394.8 kg of isophthalic acid and 233 kg of maleic anhydride are added with stirring. The heating of the reactor is switched on and the reaction mixture is heated, respectively. it is allowed to rise to a temperature of 150 ° C, at which point the reaction water begins to leave. From the beginning of the distillation, a solution of this unsaturated polyester in xylene, brought to a temperature of about 80 ° C, was fed into the top of the column using a metering pump. The amount of the dosing solution is in the range of 25 to 40 kg / h. The temperature in the column is kept at 90-100 ° C. The reaction mixture is gradually heated to 210 ° C during distillation. When this temperature is reached, the apparatus is connected to a vacuum pump and the reactor pressure is reduced to 7 to 8 kPa. The amount of reflux fed is reduced to 10-20 kg / h and the esterification is continued until the acid value of the reaction mixture is below 35 mg KOH / g.

When this value is reached, the esterification is terminated, the reflux dosing is stopped, the apparatus is disconnected from the pump and the reactor pressure is brought to atmospheric pressure. The reaction mixture was cooled to 150 ° C, when 0.02% by weight of the hydroquinone mixture was added, 598 kg of styrene was added to give a 60X polyester resin solution. Polyesterification time is 12 hours in total and the loss of propylene glycol is less than 2% by weight of the feedstock.

Claims (1)

pRedmEtvynXlezu Process for preparing polyester resins by reacting polycarboxylic acids containing from 4 to 10 carbon atoms or functional derivatives thereof, polyhydric alcohols containing from 2 to 20 carbon atoms and optionally modifying compounds, in particular from the group of monovalent alcohols or monocarboxylic acids, at atmospheric or reduced pressure, 100 DEG-260 DEG C. and optionally in the presence of inert solvents, characterized in that the reaction by-product vapors formed, in particular water, during the reaction, are fed together with the entrained vapors of the volatile reactants or solvents to a vertical column. they are brought into contact with the counter-flowing polyester resin and / or a mixture of its reactants, or their solutions in inert organic solvents, while the condensed reaction vapors are trapped h the components, optionally with a portion of the solvents, are returned to the reaction space and the by-products or solvent vapors, after passing through the column, are condensed in a separate space,