CS210447B1 - A process for the continuous preparation of low molecular weight epoxy resins and glycidyl compounds - Google Patents

Abstract

The present invention relates to a process for the continuous preparation of low molecular weight epoxy resins and glycidyl compounds. A mixture of the starting phenols or alcohols with epiehydrohydrin and the addition catalysts is passed through the reactor at a temperature of 40-120 ° C. The resulting chlorohydrin ether solution in the excess reaction solvent is passed to the top of a vertical column with through-flow baffles and a stirring device, where solid alkali hydroxide is simultaneously metered in at the prescribed amount. The reaction mixture is gradually passed through a column where dehydrochlorination of chlorohydrate occurs at 40-90 ° C. The solution product in the reaction solvent is collected at the bottom of the column above the inorganic phase layer containing water and alkali chloride. The two mutually inconceivable phases are withdrawn from the column continuously or periodically, whereby the product solution is removed to isolate the product by conventional means.

Description

The invention relates to a continuous process for the preparation of low-molecular-weight epoxy resins and glycidyl compounds, providing products of higher purity and higher yield.

Low molecular weight epoxy resins are prepared in a multiple molar excess of epichlorohydrin. Its reaction with polyhydric phenols, in particular bisphenols, for example flsphenol A (dian), bisphenol S or 1 novolaks, in the presence of a catalyst, water and optionally a reaction modifier produces the corresponding chlorohydrinethers first. These addition products further react in an alkaline environment by condensation to form glycidyl ethers while releasing alkali chloride and water. However, the quality of the final product and the course or amount of side reactions depend on many factors.

Low-molecular-weight epoxy resins are usually prepared in heated β reactors, also equipped with tubular cooling, stirrer and reflux condenser. This process is usually batch-like and allows only a small amount of mechanization or automation, for example, for the addition of alkaline hydroxide or maintaining the temperature regime in the reactor.

Continuous processes for the preparation of low-molecular-weight epoxy resins based on cascading (Australian Pat. No. 229 316, French Pat. No. 1 216 317, Pat.

U.S. Patent No. 2,986,551, Brit. U.S. Pat. No. 880 423) or serial (French Pat. No. 1,148,526, German Pat. No. 1,091,749, Swedish Pat. No. 185,840, US Pat. No. 2,840,541, British Pat. No. 785,415) arrangement of a series of smaller reactors (Australian Pat. No. 229,317, French Pat. No. 1,214,196, US Pat. No. 1,131,413, US Pat. No. 2,986,552, British Pat. No. 849,036). The introduction of the reactants and the introduction of the reaction mixture from one reactor to the other or the removal of the resulting substances are controlled so that the volume of the reaction mixture in the individual reactors is substantially constant. The solution of the obtained epoxy resins is sent through a condenser to a separator where the aqueous phase is separated from the organic phase. This is then continuously washed with water, the solvent and epichlorbydrin are removed and the epoxy resin obtained is purified by filtration.

The disadvantages of these processes are the high demands on energy consumption, production time, equipment operation and process control. In addition, the apparatus requires a large amount of space and is typically characterized by high purchase costs, particularly when combining batch processes with continuous operations, such as evaporation of solvents on a vacuum film evaporator or continuous washing of the organic phase with water or continuous removal of salt formation. If not, the full capacity of reactors, reservoirs, separators, washing equipment, filters, centrifuges or vacuum film evaporators etc. is not utilized, etc. The complexity of the technological process and the larger number of operations and thus the equipment increase the probability of problems and non-production character.

Aliphatic or cycloallphatic glyoidyl ethers or phenylglycidyl ethers, which are mostly used as reactive diluents of epoxy resins, are also prepared by a similar process. The only difference is that the reaction proceeds in excess of alcohol. As addition catalysts, in addition to the alkali metal hydroxide, also known compounds of the quaternary ammonium salt type, sulfonium, phosphonium, arzonium or stibinium salts, tertiary amines and the like can be used.

The basic requirement for continuous processes for the preparation of low-molecular-weight epoxy

210 447 dianes, or phenolic novolaks, or said glycidyl ethers is that the reaction mixture consists essentially of only the starting components and those reaction products which do not interfere in any way with the natural separation of the individual final components of the synthesis. Another requirement is the low sensitivity of the individual reaction phases to the temperature and time conditions in the column, which is particularly important during the running-in of the column or the transition to the production of a new product until the equilibrium conditions in the column are stabilized. These requirements are relatively easy to meet in the case of the preparation of aliphatic glycidyl ethers.

It is known to continualise the technological process for producing low molecular weight epoxy resins using aqueous alkaline hydroxide solutions. E.g. in Pat. NSR no.

No. 523,696 discloses a two-stage process wherein both the first and second dehydrochlorination phases are carried out in pressure vessels at a pressure of 2 to 5-10 bar and at a temperature of 80 to 140 ° C. The description of the device indicates that it is not easy and that working with pressure reactors is obviously not easy.

Technologically more preferred are processes in which alkali hydroxides are used in solid form (e.g. according to AO No. 190 205). They are simpler to operate, less time-consuming and technologically compliant, as they are based only on the basic reactants, thus guaranteeing full capacity utilization * reducing waste and thus facilitating the separation of end products. Particularly suitable is a process with the addition of a minor amount of a reaction modifier, such as isopropyl alcohol, ethanol and the like (No. AO No. 198 753), reducing or possibly eliminating the formation of polymeric substances. However, solid alkali hydroxide procedures have not been continualized yet.

This problem is solved by the present invention, which relates to a process for the continuous preparation of low molecular weight epoxy resins and glyoidyl compounds by the reaction of monovalent or polyhydric phenols, in particular bisphenols and phenolic novolaks, or monohydric or molar alcohols with epiohlorohydrin or derivatives thereof; in the presence of reaction modifiers. SUMMARY OF THE INVENTION A 10 to 65% solution of the phenolic or alcoholic component in epichlorohydrin and / or β-methyllepiohlorohydrin, comprising an addition catalyst and optionally a reaction modifier and optionally preheated to a temperature of 40 to 70 ° C, with continuous passage for 30 to 240 minutes with a temperature of 40 to 120 ° C to react the components. The resulting reaction intermediate is then, after optional cooling, fed to a further separate reaction medium, where the temperature is maintained at 40-90 ° C, and at the same time continuous alkali hydroxide hydroxide is added in an amount corresponding to a mass of approx. The ratio of the added hydroxide to the feed intermediate 0.05 to 0.6: 1. The reaction mixture is passed through the medium at said temperature for 30 to 180 minutes, resulting in a possible heterogeneous mixture containing, on the one hand, solid alkali chloride and / or a saturated aqueous solution thereof and a solution of a low molecular weight epoxy resin in epichlorohydrin or γ-methylepiohlorohydrin or a glyoidyl compound in alcohol. After the two immiscible phases of the mixture were separated from each other, the organic phase was taken continuously to isolate the product. Alkali hydroxide in an amount of 10 to 20 wt. or from the group consisting of quaternary ammonium salts, phosphonium salts, sulfonium salts, arzonium, stibine salts and tertiary amines in an amount of 0.01 to 2.0 wt. %, based on the phenolic or alcoholic content. The reaction modifiers used are aliphatic saturated monovalent alcohols, preferably secondary and tertiary, β / or ketones having a carbon number of 1 to 5 in an amount of 0.2 to 1.6 moles for each mole of the phenolic or alkanol starting component.

As a rule, a solution consisting of the two basic reactants, the addition catalysts and the optional reaction modifier is prepared in a separate process vessel, which simultaneously serves as a reservoir of the reaction mixture for this production process. After pre-heating to a temperature of 40 to 70 ° C, this is fed to a flow reactor where epichlorohydrin is added to the phenolic or alcoholic component during the flow of the mixture at 40 to 120 ° C for 30 to 240 minutes. The resulting solution of chlorohydrin ether in excess of the reaction solvent leaving the reactor and forming the reaction intermediate is, after optional cooling, sent to dehydrohalogenation. For this stage of preparation, a vertical column equipped with a through-wall baffles and a stirrer is best suited. The intermediate product obtained by the above operation is continuously fed to the top of the column and at the same time solid alkali hydroxide is metered in, for example in the form of pellets, scales, lenses, etc. The mixture of both components is then mixed by means of a mixing device. passing through the column. This pathway, which is set for a period of from 30 to 180 minutes, at the internal column temperature of 40 to 90 ° C, reacts with the components, i.e. dehydrogenation of the chlorohydrin ether by alkali hydroxide, resulting in two immiscible phases that collect at the bottom of the column. At the bottom of the column, an inorganic phase containing reaction water and an alkaline chloride is separated, over which there is an organic phase consisting of either an epoxy resin solution in excess epichlorohydrin or γ-methylepichlorohydrin or a glycidyl compound in excess mono- or polyhydric alcohol. Due to the ratio of the amount of water released and the alkaline chloride, the waste inorganic phase is a substantially saturated aqueous solution of this chloride which contains several times the amount of undissolved chloride.

This mixture is removed from the column either continuously or at certain intervals. Likewise, the organic phase is removed from the bottom of the column and is subjected to washing and isolation of the product by known methods, for example by means of a vacuum film evaporator. In order to keep the level of the inorganic phase constant during the process, a system of nozzles is installed at the bottom of the column in the space of the organic phase to inject water into the system in the required amount. The falling particles of the resulting alkaline chloride are then freed from the adhering organic phase by passing through a saturated aqueous solution. The organic phase proceeds upward through the space between the double jacket within the bottom of the column, during which time it is further stripped of inorganic constituents so that an almost pure organic phase flows out of the column for final processing.

The column is divided into four zones by temperature. In the upper part, i.e. about one quarter of the column height, the temperature is maintained at 40-70 ° C, another zone representing about one-half of the column height is heated to 70-90 ° C and the temperature of the third column is spontaneous it drops to 40 to 50 ° C. In the lowest, i.e., fourth, zone, the pro4 is cooled

210 447 duct also by the inflow of cold water. In practice, there is no need to heat the column if it is sufficiently heat insulated, since the intermediate product preheated in the reactor (and possibly cooled) to the desired temperature already flows into the upper part. In the second zone, the temperature of the reaction mixture rises due to the liberated dissolution heat of the alkali hydroxide and the reaction heat, while in the remaining zones the temperature spontaneously decreases.

Said continuous process for the preparation of low molecular weight types of palm epoxy resins, epoxidized novolaks and alkyl or phenylglyoldyl ethers substantially reduces the loss of epichlorohydrin by alkaline hydrolysis during the synthesis, since its contact time with the alkaline medium is very short. Unwanted polymeric substances are formed in the reaction mixture, forming villi, tendons and the like, so that the problems associated with their removal and disposal are eliminated. Also, brine and solid alkaline chloride, which fall off as by-products of the reaction, are free of most impurities. The products produced are light, clear, characterized by a low content of organically bound chlorine, a high content of epoxy groups and good durability during curing.

The continuous process of the invention, especially when automated, fully utilizes the capacity of the production equipment and contributes greatly to increasing labor productivity and reducing raw material and energy consumption, labor and waste.

Example 1

Epiohlorohydrin gradually flows into the vessel equipped with the stirrer, bisphenol A is introduced and solid sodium hydroxide in the form of pellets and a diameter of 5-8 mm in a 6: 1: 0.3115 molar ratio is also metered. The reaction mixture was not passed through a tubular reactor heated to 60 ° C for a flow time of 30 minutes. The resulting intermediate is fed to a vertical reaction column in which a temperature of 60-80 ° C is maintained and at the same time solid sodium hydroxide is introduced into the mass. ratio 1: 0.0952. The flow time of the reaction mixture is 120 minutes.

A solution of the epoxy resin in epichlorohydrin is discharged from the reaction column, which is washed continuously, and the resin is then isolated on a film vacuum evaporator. The obtained epoxy resin is almost colorless, clear and contains 0.18 wt. organically bound chlorine and 0.550 epoxy equivalent per 100 g, its lifetime at 140 ° C with phthalic anhydride is 245 minutes. The yield was 73% of theory based on epiohlorohydrin.

Example 2

The procedure is as in Example 1, except that isopropyl alcohol is also dosed with the starting components in a molar ratio of 0.8: 6.0 to epichlorohydrin. The quality of the epoxy resin obtained does not differ significantly from the product prepared according to Example 1. The resulting effect is an increased yield of the resin based on epiohlorohydrin, i.e. up to 85% of theory.

No polymeric substances are formed during the synthesis.

Example 3

3 moles of epichlorohydrin, equivalent (depending on the phenolocyl hydroxyl group content) pulverized by low molecular weight, are simultaneously introduced into a vessel equipped with a stirrer and reflux condenser.

210,447 mole of phenol-formaldehyde novolak, 0.8425 mole of isopropanol, 0.15 mole of sodium hydroxide in the form of pellets and 0.2164 mole of water. The reaction mixture was passed through the reactor at 65-70 ° C for 30 minutes. The intermediate product obtained is further fed to the upper part of the reaction column, to which sodium hydroxide of the same grain in weight by weight is simultaneously metered. ratio 1: 0.0865. The column is maintained at a temperature of 80-65 ° C, the reaction time of the reaction mixture through the column being 90 minutes.

A novolak epoxy resin solution is discharged from the column, which is washed continuously and excess solvents are evaporated on a film vacuum evaporator. The novolak-based epoxy resin obtained is yellow-colored, clear, contains 0.554 equivalent of epoxy groups per 100 g and 0.22% by weight. organically bound chlorine. Its gelation time with hexahydrophthalic anhydride at 130 ° C is 70 minutes.

Example 4

In a vessel equipped with a stirrer and a reflux condenser, epichlorohydrin, a 60% epichlorohydrin solution of phenol-formaldehyde novolak and a 50% aqueous solution of chlorocholine chloride in a molar ratio of 2.5: 1 (eq): 0.0127 were simultaneously introduced while stirring. This reaction mixture flows through the reactor at 90 ° C for 180 minutes. The resulting intermediate is fed to the top of the reaction column, where pelletized sodium hydroxide in wt. ratio 1: 0.13.

The reaction column is maintained at a temperature of 80-60 ° C and the flow time of the reaction mixture is 180 minutes. The isolation of the resin from the prepared product is the same as in Example 3.

The obtained novolak epoxy resin is yellow, clear, contains 0.542 equivalents of epoxy groups per 100 g, 0.27 wt. of organically bound chlorine and its durability at curing with hexahydrophthalic anhydride at 130 ° C is 40 minutes.

Example 5

Epichlorohydrin, n-butanol and a 30% aqueous solution of tetramethylammonium iodide are fed to a stirrer tank at a rate such that the molar ratio of the components is 1: 4: 0.02. The resulting reaction mixture is then passed through a reactor heated to 90 ° C to the reactor flow time was 120 minutes. The resulting addition intermediate is then transferred to a vertical reaction column, where solid pellet-shaped sodium hydroxide is simultaneously introduced in an amount such that the composition is in the form of a pelletized solid. the ratio of addition intermediate to NaOH was 1: 0.13. The mixture was passed through the column at 70 ° C for 80 minutes. A solution of n-butyl glycidyl ether in butanol is withdrawn from the reaction vertical column to a wash column and after continuous washing goes to a film vacuum evaporator where the butanol is distilled off and returned to production. The obtained n-butyl glycidyl ether is a yellowish mobile liquid with a characteristic odor, containing 0.736 gram equivalents of epoxy groups in 100 g and 0.48% by weight. organically bound chlorine.

Example 6

Epichlorohydrin, benzyl alcohol and a 25% aqueous solution of triphenylallylphosphonium bromide in an amount such that the molar ratio of the components is 3: 1: 0.05 are fed to a stirred tank. The resulting reaction mixture is then passed through a reactor heated to 100 ° C so that the flow time through the reactor is 85 minutes. The resulting addition intermediate then arrives at

210 447 vertical reaction columns, where solid pellet-shaped potassium hydroxide is simultaneously introduced in such an amount that the molar ratio of the intermediate to KOH is 1: 0.17. The mixture was passed through the column at 58 ° C for 115 minutes. A solution of benzylglyol ether in epichlorohydrin is withdrawn from the reaction vertical column to a washing column and after continuous washing, unreacted epichlorohydrin is distilled off from it by means of a film vacuum evaporator and returned to production.

The benzylglyeidylether obtained is a light yellow color viscous liquid and contains 0.562 gram equivalents of epoxy groups in 100 g and 0.41% by weight. organically bound chlorine.

Claims (3)

SUBJECT OF THE INVENTION A process for the continuous preparation of low molecular weight epoxy resins and glyoidyl compounds by the reaction of mono- or polyhydric phenols, in particular flsphenols and phenolocular binders, or monohydric or polyhydric alcohols with epichlorohydrin or its derivatives and dehydrochlorination of the resulting chlorohydrin ethers by solid alkali hydroxides, optionally characterized in that a 10 to 65% solution of the phenolic or alkali component in epichlorohydrin and / or? -methylepichlorohydrin, containing an addition catalyst and optionally a reaction modifier and optionally preheated to a temperature of 40 to 70 ° C, is passed continuously for 30 to 240 minutes temperature of 40 to 120 ° 0 to react the components, the resulting reaction intermediate is then, after cooling if necessary, brought to another separate reaction medium, where the temperature is maintained 40 to 90 [deg.] C. and where solid alkali hydroxide is continuously metered in at a rate corresponding to the weight of the mixture. 0.05 to 0.6: 1, the reaction mixture is passed through the medium at said temperature for 30 to 180 minutes, resulting in a heterogeneous mixture containing, on the one hand, solid alkali chloride, after the possible addition of water in the final flow phase; and / or a saturated aqueous solution thereof and a solution of a low molecular weight epoxy resin in epichlorohydrin or γ-methylepichlorohydrin or a glyoidyl compound in an alcohol from which the organic phase is continuously removed after separation of the two immiscible phases to isolate the product. 2. A process according to claim 1, wherein the adioe catalyst is an alkali hydroxide in an amount of 10 to 20% by weight. or fabrics include a quaternary! ammonium salts, phosphonium salts, sulfonium salts, arzonium salts, stihine salts and tertiary amines in an amount of 0.01 to 2.0% by weight, based on the content of the phenolic or alcoholic component. 3. A process according to claim 1, wherein the reaction modifiers used are aliphatic saturated monovalent alcohols, preferably secondary and tertiary alcohols, and / or ketones having a carbon number of 1 to 5 in an amount of 0.2 to 1.6 moles for each. mole of phenolic or alcoholic starting discount.