RU2537403C1 - Method of obtaining epoxy resin, modified with epoxyphosphazenes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes interaction of diatomic phenol, epichlorohydrin and chlorocyclophosphazene. As chlorocyclophosphazene used is hexachlorocyclotriphosphazene or its mixture with higher chlorocyclophosphazenes[NPCl₂]_n, where n=4-15. Synthesis is carried out by direct interaction of said reagents in presence of bases. Diphenol is taken in quantity from 2 to 120 moles per NPCl₂ unit, and epichlorohydrin is taken in not less than 2-fold excess with respect to diphenol.

EFFECT: elaboration of simple and technological method of synthesis of epoxyphosphazenes, characterised by high content of epoxy groups and easily compatible with industrial epoxy resins of ED type with application of available resources.

3 cl, 7 ex

Description

The invention relates to phosphorus-containing epoxy resins, which are used as components of non-combustible and heat-resistant composite materials. Phosphazene compounds with reactive epoxy groups are a key component of such epoxy resins and cause high heat resistance and incombustibility.

Known methods for the synthesis of epoxyphosphazenes [US Patent No. 7671147, Japan Patent No. 2007153748] by the reaction of epichlorohydrin with hydroxyaryloxyphosphazenes, which are pre-synthesized by the demethylation reaction of n-methoxyphenoxycyclophosphazene. The latter, in turn, is obtained by the interaction of chlorocyclophsophasenes with n-methoxyphenol. The disadvantage of analogues is the technological complexity: the preparation of epoxyphosphazenes involves at least 4 reaction stages; it is necessary to isolate and purify intermediate substances and use a large number of toxic solvents (tetrahydrofuran, toluene, chloroform, ethyl acetate, methanol).

The closest in technical essence and the achieved effect is a method for producing epoxyphosphazenes [Kireyev V.V. et al. // High Molecule. conn. B. 2011.V. 53. Number 7. P.1142-1149] by the reaction of hydroxyaryloxyphosphazenes based on hexachlorocyclotriphosphazene (HCF) and diphenylolpropane (DPP) with epichlorohydrin (ECG), carried out in an alkaline alcohol solution.

The specified method, selected as a prototype, has several disadvantages, the main of which is the low content of epoxy groups (10.53%). In addition, the product is a solid high molecular weight (M _w = 769000) substance, which complicates its introduction into the composition and processing, and contains 1.92-2.20% chlorine, which limits its practical use for environmental reasons. Another disadvantage of this method is its low technology and difficulty in conditions other than laboratory due to the following factors:

1. The need for preliminary synthesis of hydroxyaryloxyphosphazenes, including an additional step for the production of diphenylolpropane phenolates, the latter being unsafe on an enlarged scale due to the need to use alkali metals;

2. The need to use sulfuric acid to neutralize the alkaline environment (sulfuric acid can help reduce the content of epoxy groups due to their interaction with acid);

3. The duration of the process due to the need to obtain sodium phenolates of hydroxyaryloxyphosphazenes before the introduction of epichlorohydrin by prolonged exposure of the oligomer in a solution of alcohol alkali, since it is poorly soluble in alcohol and its translation into a phenolate form requires preliminary swelling;

4. The initial hexachlorocyclotriphosphazene is difficult to access due to the complexity of the process of its isolation from a mixture of chlorocyclophsophasenes obtained by ammonolysis of phosphorus pentachloride.

The objective of the present invention is to develop a simple and technologically advanced method for the synthesis of epoxyphosphazenes characterized by a high content of epoxy groups and easily compatible with industrial epoxy resins of the ED-20 type using available reagents.

The problem is solved in that a method for producing an epoxy resin modified with epoxyphosphazenes by direct interaction of reagents: diatomic phenol, chlorocyclophosphazene and epichlorohydrin, which performs the function of both reagent and solvent, in the presence of bases carried out in one stage is proposed.

The content of the epoxyphosphazene component in the resulting epoxy resin is regulated in the range from 1 to 70 wt.% By varying the amount of diphenol from 120 to 2 moles with respect to the NPCl ₂ chlorophosphazene unit, diphenol is taken in excess (> 2 mol, preferably from 3 mol per unit [PNCl ₂ ]) to avoid gelation and excessive molecular weight increase. Diphenylolpropane (because it is the main raw material for the synthesis of epoxy resins) or another diatomic phenol is preferably used as the diatomic phenol. Sodium or potassium alkali or tertiary amines (pyridine, triethylamine, quinoline) are used as the base. As chlorophosphazene, not only individual hexachlorocyclotriphosphazene is used, as in the prototype, but also its mixture with higher chlorocyclophosphazenes [NPCl ₂ ] _{n = 4-15} . The use of a mixture of chlorocyclophosphazenes instead of individual HCF significantly reduces the cost of the product, since there is no laborious process of isolating the latter from the mixture and cleaning it. Washing of the product from salts and possible residual alkali is carried out with water, and not with a solution of sulfuric acid, as in the prototype.

To reduce the chlorine content, two methods are used: 1) preliminary exposure of the reaction mixture before the introduction of alkali over potassium carbonate and 2) the gradual introduction of alkali and diphenol in a ratio of 2: 1 during the reaction.

The invention is illustrated by the following examples.

Example 1. The reagents are taken in accordance with this recipe:

hexachlorocyclotriphosphazene 0.1 mol (35 g) epichlorohydrin 2000 ml

calculated on the NPCl link of ₂ hexachlorocyclotriphosphazene:

diphenylolpropane 0.2 mol (138 g) potassium alkali 0.4 mol (270 g)

In a reactor equipped with a mechanical stirring device and a refrigerator, chlorocyclophsophazene, DPP and ECG are charged and mixed until the solid reagents are completely dissolved in ECG. Then, dry potassium alkali is loaded in portions with stirring; the alkali loading rate is determined by the temperature of the reaction mixture, which should not exceed 60-65 ° С. After loading all the alkali, the reaction is carried out for 1-2 hours at a temperature of not more than 65 ° C. At the end of the process, excess epichlorohydrin is distilled off under reduced pressure, the mixture of oligomers is dissolved in toluene. The toluene solution is repeatedly washed with water to remove salts and alkali residues. For the best removal of alkali residues, additionally, gaseous CO ₂ can be passed through the solution. The organic phase is separated, toluene is distilled off under vacuum at a temperature of 120 ° C. The resulting mixture of oligomers is a clear, viscous, resinous liquid with an epoxyphosphazene content of 70% by weight. The yield is 95%, the molecular weight of the epoxyphosphazene fraction is 1500-1900, the low molecular weight fraction is diphenylolpropane diglycidyl ether. The mass fraction of epoxy groups and chlorine is respectively 17.0% and 1.8%.

Example 2. The reagents are taken in accordance with this recipe:

hexachlorocyclotriphosphazene 0.1 mol (35 g) epichlorohydrin 20,000 ml

calculated on the NPCl link of ₂ hexachlorocyclotriphosphazene:

diphenylolpropane 12 mol (8255 g) potassium alkali 24 mol (4055 g)

The reaction is carried out as in example 1. The resulting mixture of oligomers is a transparent viscous gummy liquid with an epoxyphosphazene content of 1 wt.%. The yield is 95%, the molecular weight of the epoxyphosphazene fraction is 1500-1900, the low molecular weight fraction is diphenylolpropane diglycidyl ether. The mass fraction of epoxy groups and chlorine, respectively, is 24.5% and 0.1%.

Example 3. The synthesis is carried out as described in example 1 or 2, with the exception that instead of hexachlorocyclophosphazene use its mixture with higher cyclic homologues [PNCl ₂ ] _n , where n = 4-15. Get a mixture of oligomers, which is a transparent viscous gummy liquid with a phosphazene content of 70-1 wt.%, Yield 93%. Product characteristics are similar to those shown in example 1, except that the molecular weight of the phosphazene fraction increases and lies in the range of 1800-6000.

Example 4. The process is carried out as in examples 1-, with the exception that instead of potassium alkali, an equivalent amount of sodium alkali or pyridine, triethylamine or quinoline is used. Product characteristics are similar to those in examples 1-3.

, где

, О, S, SO₂. Установлено, что природа исходного дифенола мало влияет на характеристики продукта, в том числе на растворимость, содержание хлора и эпоксидных групп и выход продукта.Example 5. The process is carried out as in example 1-4, with the exception that instead of diphenylolpropane, an equivalent amount of its substituted (halogen, alkyl) or hydroquinone, resorcinol, or diphenols of the type is used

where

, O, S, SO ₂ . It was established that the nature of the starting diphenol has little effect on the characteristics of the product, including solubility, the content of chlorine and epoxy groups, and the yield of the product.

Example 6. The reagents are taken in accordance with this recipe:

hexachlorocyclotriphosphazene 0.1 mol (35 g) epichlorohydrin 4000 ml

calculated on the NPCl link of ₂ hexachlorocyclotriphosphazene:

diphenylolpropane 0.4 mol (276 g) potassium alkali 0.8 mol (540 g)

The synthesis is carried out as described in examples 1, 3-5, with the exception that the amount of diphenol and base taken according to the recipe is introduced into the reaction mixture in two equal portions: the first immediately and the second after 30 minutes of the reaction gradually over an hour. In this case, the chlorine content in the product compared with example 1 is reduced by 3-4 times.

Example 7. The synthesis is carried out as described in examples 1-5, however, before the introduction of the base, the reaction mixture is kept over potassium carbonate or a carbonate of another alkali metal, taken in an amount of 200 mol. % with respect to diphenol at the same temperature as in the subsequent reaction (60 ° C). In this case, the chlorine content in the product compared to example 1 is reduced by 2-3, and the maximum epoxyphosphazene content increases to 80-85% (with a ratio of NPCl ₂ : diphenol equal to 1: 2).

As can be seen from the above examples, in contrast to the prototype, the product is not pure epoxyphosphazene, but its mixture is a diane epoxy resin of the ED-20 type, and the content of the epoxyphosphazene component can be adjusted from 1 to 70 wt.%. This fact brings a positive effect, consisting in the fact that even at a 70% epoxyphosphazene content, the product is a liquid (in the prototype a solid), miscible with ED-20 in any proportions, which makes it possible to use the product as an epoxy modifier resins, and for their complete replacement.

The main characteristics of the obtained epoxyphosphazene resins are higher than that of the prototype: the content of epoxy groups (wt.%) Is not less than 17.0 (10.5 for the prototype), the chlorine content is not more than 1.8% (1.9-2.2 prototype), and the chlorine content can be reduced to <1.0% (examples 6 and 7). Compared with the prototype, the number of reaction stages is reduced from 3 to 1, the reaction time is reduced by more than 5 times, of the additional solvents in the invention, only toluene is used, the prototype requires dioxane, acetone, tetrahydrofuran, ethanol.

Another important advantage of the method proposed in the present invention is that it can be carried out in some existing manufactures of ED-20 or ED-24 diane epoxy resins or analogues (those obtained by a homogeneous method in epichlorohydrin medium), i.e. can be easily integrated into existing production.

Claims (3)

1. A method of producing an epoxy resin modified with epoxyphosphazenes by reacting diatomic phenol, epichlorohydrin and chlorocyclophosphazene, characterized in that hexachlorocyclotriphosphazene is used as chlorocyclophosphazene or its mixture with higher chlorocyclophosphazenes [NPCl ₂ ] _{n = 4-15} , the synthesis is carried out by direct reaction of the above reagents the presence of bases, moreover, diphenol is taken in an amount of from 2 to 120 moles per NPCl ₂ unit, and epichlorohydrin is taken in at least a 2-fold excess with respect to diphenol. 2. The method according to claim 1, characterized in that before the introduction of the base the reagents are incubated for at least 1 hour in the presence of alkali metal carbonates. 3. The method according to claim 1, characterized in that the diphenol and the base are not introduced into the reaction mixture immediately, but in two portions, the first at the beginning of the reaction and the second at least 30 minutes after its start, and the first portion should contain at least 2 moles of diphenol.