Difunctional biphenyl compounds, preparation, and uses

Abstract

A difunctional biphenyl compounds corresponding to formula (I) ##STR00001##
wherein Alk, Alk′ and R are as defined in the description. These compounds are suitable as hardeners for thermosetting resins, especially epoxy resins.

Claims

1. A difunctional biphenyl compound having the formula (I): ##STR00029## wherein: Alk is a linear or branched alkyl group having from 1 to 6 carbon atoms, Alk′ is a linear or branched alkyl group having from 1 to 6 carbon atoms, and R is selected from —CH.sub.2—NH.sub.2, —N═C═O and —NH.sub.2; it being understood that the compound of formula (I) is not 3,4-dimethoxydianiline.

2. The biphenyl compound as claimed in claim 1, of formula (I) wherein Alk is a methyl group.

3. The biphenyl compound as claimed in claim 1, of formula (I) wherein Alk′ is a methyl group.

4. The biphenyl compound as claimed in claim 1, which consists of is: 3,4-dimethoxydivanyllylamine, or 3,4-dimethoxydiphenylisocyanate.

5. A process for preparing a compound of formula (I): ##STR00030## wherein: Alk is a linear or branched alkyl group having from 1 to 6 carbon atoms, Alk′ is a linear or branched alkyl group having from 1 to 6 carbon atoms, and R is selected from —CH.sub.2—NH.sub.2, —N═C═O and —NH.sub.2; which process comprises: a) providing a product selected from the group consisting of vanillin, analogues of vanillin having an —O—(C.sub.2-C.sub.6)alkyl group in the 3-position, esters of vanillin and analogues of said esters having an —O—(C.sub.2-C.sub.6)alkyl group in the 3-position; b) dimerizing said product to obtain a dimer, c) treating said dimer obtained to convert its phenolic —OH functions to —OAlk′ alkoxy functions and either its aldehyde functions to aminomethyl functions (—CH.sub.2—NH.sub.2) or its ester functions to isocyanate (—N═C═O) or amino (—NH.sub.2) functions.

6. The process as claimed in claim 5, wherein the product selected in step a) is vanillin of natural origin or a vanillin ester obtained from vanillin of natural origin.

7. The process as claimed in claim 5, wherein the product selected in step a) is vanillin or a vanillin analogue having an O—(C.sub.2-C.sub.6)alkyl group in the 3-position, and wherein step c) comprises c1) either alkylating the phenolic —OH functions of the dimer obtained in step b) then converting the aldehyde functions of said alkylated dimer to oxime functions, or converting the aldehyde functions of said dimer to oxime functions then alkylating the phenolic —OH functions of said dimer with oxime functions, in order to obtain an alkylated divanillyl oxime; and c2) reducing said alkylated divanillyl oxime to obtain an alkylated divanillyl amine having the formula (I) wherein R=—CH.sub.2—NH.sub.2.

8. The process as claimed in claim 5, wherein the product selected in step a) is a vanillin ester or an analogue of said ester having an —O—(C.sub.2-C.sub.6)alkyl group in the 3-position; and wherein step c) comprises c1) either saponifying the dimer obtained in step b) to obtain a divanillic acid and alkylating the phenolic —OH functions of said divanillic acid, or alkylating the phenolic —OH functions of said dimer to obtain an alkylated divanillyl ester and saponifying said alkylated divanillyl ester, to obtain an alkylated divanillic acid; c2) acylating said alkylated divanillic acid to obtain an alkylated acyl diazide; c3) carrying out a Curtius rearrangement on said alkylated acyl diazide to obtain a dialkoxydiphenyl isocyanate having the formula (I) wherein R=—N═C═O; and c4) optionally, hydrolyzing said dialkoxydiphenyl isocyanate to obtain an alkylated dianiline of formula (I) wherein R=—NH.sub.2.

9. A method of obtaining a thermoset resin, which comprises reacting a thermosetting resin with a compound of formula (I): ##STR00031## wherein: Alk is a linear or branched alkyl group having from 1 to 6 carbon atoms, Alk′ is a linear or branched alkyl group having from 1 to 6 carbon atoms, and R is selected from —CH.sub.2—NH.sub.2, —N═C═O and —NH.sub.2.

10. The method as claimed in claim 9, wherein in formula (I) Alk is a methyl group.

11. The method as claimed in claim 9, wherein in formula (I) Alk′ is a methyl group.

12. The method as claimed in claim 9, wherein the compound of formula (I) is 3,4-dimethoxydivanyllylamine, 3,4-dimethoxydianiline or 3,4-dimethoxydiphenylisocyanate.

13. The method as claimed in claim 9, wherein the thermosetting resin is selected from the group consisting of epoxy resins, polycarbonate resins, polycarboxylic acid resins, polyol resins and polyamide resins.

14. The method as claimed in claim 13, wherein in formula (I) R=—CH.sub.2—NH.sub.2 or —NH.sub.2 and wherein the thermosetting resin is an epoxy resin containing at least one polyepoxide biphenyl compound selected from the group consisting of: diglycidyl ether of bisphenol, monomer or oligomer, diglycidyl ether of divanillyl alcohol (DiGEDVA), triglycidyl ether of divanillyl alcohol (TriGEDVA), tetraglycidyl ether of divanillyl alcohol (TetraGEDVA), and mixtures of at least two of said glycidyl ethers of divanillyl alcohol.

15. A thermoset resin obtained by the method of claim 9.

16. A thermoset resin obtained by the method of claim 14.

Description

EXAMPLE 1

(1) Synthesis of 3,4-dimethoxydivanillylamine (of formula (I) wherein Alk=Alk′=—CH.sub.3 and R=—CH.sub.2—NH.sub.2) from divanillin (DV)

(2) The different steps of the reaction scheme below (corresponding to the one in the first line on page 15) were successively implemented.

(3) ##STR00009## ##STR00010##

1a. Synthesis of Divanillin (DV)

(4) The preparation of divanillin was carried out according to the procedure described in Example 1 of patent application EP 3 002 333. Specifically, the procedure was as follows.

(5) Vanillin (20 g) (the one used, marketed by the company Acros, was not biosourced. For all intents and purposes, it is indicated that the biosourced vanillin marketed by Borregaard (NO) could have been used) was solubilized in acetone (160 mL) and acetate buffer (1.5 L, prepared from 2.63 g acetic acid and 8.4 g sodium acetate). Laccase from Trametes versicolor (170 mg) was added to the resulting mixture. In order to be recycled in active form, said laccase requires oxygen. The reaction medium was therefore left under stirring with constant air bubbling for 24 hours. Divanillin was then recovered by filtration of the buffer solution through a Büchner filter. The filtrate was recovered and reused for further dimerization reactions.

1a′. Purification of Synthesized Divanillin (DV)

(6) Traces of vanillin were likely to be present in the recovered divanillin. To remove them, said divanillin was solubilized in an aqueous solution of NaOH (200 mL at 0.5 M; a few drops of 5 M solution were conveniently added to facilitate solubilization). A large volume of ethanol (600 mL) was then added to the solution as well as an aqueous solution of hydrochloric acid (115 mL at 2 M) until a pH=3 was reached for the mixture. Both divanillin and vanillin are indeed soluble at basic pH in ethanol. Divanillin, on the other hand, is not soluble in ethanol at acidic pH, unlike vanillin. The addition of acid therefore allows the two products to be separated by precipitation of divanillin.

(7) The resulting product was filtered and dried in an oven to remove all traces of solvent.

(8) The synthesis and purification operations were repeated. The yield was approximately 95% each time.

(9) Obtaining divanillin (DV) was confirmed by NMR spectroscopy:

(10) ##STR00011##

(11) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm): δ 9.69 (s, H.sub.7), 7.57 (d, H.sub.1), 7.16 (d, H.sub.5), 3.76 (s, H.sub.8).

(12) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 191.62 (s, C.sub.7), 150.88 (s, C.sub.3), 148.61 (s, C.sub.2), 128.64 (s, C.sub.6), 128.21 (s, C.sub.4), 125.02 (s, C.sub.5), 109.6 (s, C.sub.1), 56.25 (C.sub.8).

1b. Synthesis of Methylated Divanillin (mDV)

(13) This was done according to the procedure described in Example 9 of patent application EP 3 002 333. Specifically, the procedure was as follows.

(14) 26 mmol of divanillin (≈8 g) and 15.2 g of potassium carbonate (110 mmol) were dissolved in 120 mL of DMF. 9.6 mL of iodomethane (158 mmol) was then slowly added to the mixture. After 16 h stirring at 80° C., the mixture was filtered and the resulting solution was poured into cold water. The methylated compound precipitated and was recovered by filtration and dried under vacuum. Yield of 80%.

(15) Obtaining methylated divanillin (mDV) was confirmed by NMR spectroscopy:

(16) ##STR00012##

(17) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 9.94 (d, H.sub.9), 7.58 (d, H.sub.1), 7.45 (d, H.sub.5), 3.95 (s, H.sub.7), 3.67 (s, H.sub.8).

(18) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 152.00 (s, C.sub.3), 144.81 (s, C.sub.2), 137.64 (s, C.sub.6), 132.12 (s, C.sub.4), 120.33 (s, C.sub.5), 110.18 (s, C.sub.1), 62.63 (s, C.sub.9), 59.91 (s, C.sub.8), 55.52 (C.sub.7).

1c. Synthesis of Methylated Divanillyl Oxime (mDVO)

(19) 1 g of hydroxylammonium chloride (7 mmol) and 2 g of sodium acetate (12 mmol) were dissolved in 20 mL of ethanol (+4 mL water). 2 g of methylated divanillin (6 mmol) was then added to the mixture. After 2 h at 100° C., the mixture was extracted with dichloromethane (DCM) and washed with water. The organic phase was evaporated using a rotary evaporator. The recovered product was then dried under vacuum. Yield of 85%.

(20) Obtaining methylated divanillin oxime (mDVO) was confirmed by NMR spectroscopy:

(21) ##STR00013##

(22) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 11.58 (s, H.sub.10), 8.10 (s, H.sub.9), 7.30 (d, H.sub.1), 6.98 (d, H.sub.5), 3.87 (s, H.sub.7), 3.56 (s, H.sub.8).

(23) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 152.66 (s, C.sub.2), 147.81 (s, C.sub.9), 147.25 (s, C.sub.3), 131.87 (s, C.sub.6), 128.69 (s, C.sub.4), 121.69 (s, C.sub.5), 108.78 (s, C.sub.1), 59.88 (s, C.sub.8), 55.6 (s, C.sub.7).

(24) The spectra are shown in FIGS. 1A and 1B respectively.

1d. Synthesis of Methylated Divanillyl Amine (mDVAm)

(25) 1 g of methylated divanillyl oxime (2.7 mmol) and 1 mL of Raney nickel were solubilized in 30 mL of ethanol. The mixture was placed in a pressurized reactor under 12 bars of hydrogen. After 16 h at 70° C., the mixture was filtered and the ethanol was evaporated under vacuum. The resulting product was solubilized in dichloromethane (DCM) and washed with water. The DCM was then evaporated under vacuum. Yield of 70%.

(26) Obtaining methylated divanillyl amine (mDVAm) was confirmed by NMR spectroscopy:

(27) ##STR00014##

(28) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 7.04 (m, H.sub.5), 6.69 (m, H.sub.1), 3.79 (m, H.sub.8), 3.63 (s, H.sub.7), 3.48 (m, H.sub.9).

(29) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 151.75 (s, C.sub.2), 144.46 (s, C.sub.3), 136.04 (s, C.sub.6), 132.36 (s, C.sub.4), 121.78 (s, C.sub.5), 111.41 (s, C.sub.1), 60.05 (s, C.sub.8), 55.65 (s, C.sub.7), 51.62 (s, C.sub.9).

(30) The spectra are shown in FIGS. 2A and 2B respectively.

EXAMPLE 2

Synthesis of 3,4-dimethoxydiphenylisocyanate and 3,4-dimethoxydianiline

(31) ((of formula (I) wherein, respectively, Alk=Alk′=—CH.sub.3 and R=—N═C═O and Alk=Alk′=—CH.sub.3 and R=—NH.sub.2) from methyl vanillate

(32) The different steps of the reaction scheme below (corresponding to the one in the second line on page 15) were successively implemented.

(33) ##STR00015## ##STR00016##

2a. Synthesis of Methyl Divanillate (DVE)

(34) For the preparation of methyl divanillate, starting from methyl vanillate (VE) (distributed by the company Sigma-Aldrich), a procedure has been followed which is very similar to that described for the preparation of divanillin in point 1.a above. In fact (for this dimerization) the procedure described in Example 4 of patent application EP 3 002 333 was used.

(35) Obtaining methyl divanillate was confirmed by NMR spectroscopy:

(36) ##STR00017##

(37) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 9.51 (s, H.sub.8), 7.46 (d, H.sub.1), 7.45 (d, H.sub.5), 3.90 (s, H.sub.7), 3.80 (s, H.sub.10).

(38) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 166.09 (s, C.sub.9), 148.88 (s, C.sub.3), 147.47 (s, C.sub.2), 125.40 (s, C.sub.5), 124.36 (s, C.sub.6), 119.48 (s, C.sub.4), 110.92 (s, C.sub.1), 56.01 (s, C.sub.7), 51.79 (s, C.sub.10).

2b. Synthesis of Divanillic Acid (DVAc)

(39) This saponification was carried out according to the procedure described in Example 13 of patent application EP 3 002 333. Specifically, the procedure was as follows. 10 mmol of methyl divanillate (≈2.5 g) was dissolved in 30 mL of methanol. 3 g of sodium hydroxide solution (75 mmol) were added to the solution. The resulting solution was heated under reflux for 4 h. The reaction was stopped by adding 2.5 mL of water to the reaction medium. The aqueous phase was acidified with hydrochloric acid and the generated diacid precipitated. Yield of 92%.

(40) Obtaining divanillic acid (DVAc) was confirmed by NMR spectroscopy:

(41) ##STR00018##

(42) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm): δ 9.39 (s, H.sub.8), 7.45 (d, H.sub.1), 7.41 (d, H.sub.5), 3.89 (s, H.sub.7).

(43) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 167.18 (s, C.sub.9), 148.36 (s, C.sub.3), 147.22 (s, C.sub.2), 125.44 (s, C.sub.6), 124.19 (s, C.sub.4), 120.44 (s, C.sub.5), 111.05 (s, C.sub.1), 55.89 (s, C.sub.7).

2c. Synthesis of Methylated Divanillyl Acid (mDVAc)

(44) The etherification was carried out as described above under point 1b, i.e. according to the procedure described in Example 9 of patent application EP 3 002 333. Specifically, the process was as follows.

(45) 26 mmol of divanillic acid and 15.2 g of potassium carbonate (110 mmol) were dissolved in 120 mL of DMF. 9.6 mL of iodomethane (158 mmol) was then slowly added to the mixture. After 16 h at 80° C., the mixture was filtered and the resulting solution was poured into cold water. The methylated compound precipitated and was recovered by filtration and dried under vacuum. The typical yield was 80%.

(46) Obtaining methylated divanillic acid (mDVAc) was confirmed by NMR spectroscopy:

(47) ##STR00019##

(48) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 12.94 (s, H.sub.10), 7.58 (d, H.sub.1), 7.39 (d, H.sub.5), 3.91 (s, H.sub.7), 3.61 (s, H.sub.8).

(49) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 166.83 (s, C.sub.9), 152.20 (s, C.sub.3), 150.07 (s, C.sub.2), 131.34 (s, C.sub.6), 125.91 (s, C.sub.4), 124.13 (s, C.sub.5), 112.93 (s, C.sub.1), 60.28 (s, C.sub.8), 55.87 (s, C.sub.7).

2d. Synthesis of 3,4-Dimethoxydiphenylazide Acyl (mDVAz)

(50) 3 mmol of methylated divanillic acid was dissolved in 15 mL of THF and 5 mL of water. The solution was cooled to 0° C. and 2.4 mL of triethylamine in 4 mL of THF were added dropwise to the mixture. 1.8 mL of ethyl chloroformate were then added to the mixture. The resulting mixture was then stirred for 2 h at 0° C. A solution of sodium azide (1.2 g in 4 mL of water) was added dropwise to the mixture and stirred for 2 h at 0° C., then left for 2 h at room temperature. Cold water was then gradually added to the reaction medium to precipitate the solid. The precipitate was filtered and then dissolved in dichloromethane (DCM), washed with water. The organic phase was evaporated using a rotary evaporator. Yield of 60%.

(51) Obtaining 3,4-dimethoxyphenyl acyl diazide (mDVAz) was confirmed by NMR spectroscopy:

(52) ##STR00020##

(53) .sup.1H NMR (400 MHz, CDCl3, δ (ppm)): δ 7.61 (d, H.sub.1), 7.55 (d, H.sub.5), 3.96 (s, H.sub.7), 3.74 (s, H.sub.8).

(54) .sup.13C NMR (400 MHz, CDCl3, δ (ppm)): δ 171.85 (s, C.sub.9), 152.79 (s, C.sub.3), 152.39 (s, C.sub.2), 131.69 (s, C.sub.6), 125.81 (s, C.sub.4), 125.23 (s, C.sub.5), 112.78 (s, C.sub.1), 61.10 (s, C.sub.8), 56.22 (s, C.sub.7).

(55) The spectra are shown in FIGS. 3A and 3B respectively.

2e. Synthesis of 3,4-Dimethoxydiphenylisocyanate (mDVI)

(56) In a Schlenk tube under inert atmosphere (nitrogen), 0.5 mmol of 3,4-dimethoxyphenyl acyl diazide was dissolved in 3 mL of dry toluene. The mixture was stirred and heated to 80° C. for 8 h. The toluene was then evaporated using a rotary evaporator at 60° C. Yield of 80%.

(57) Obtaining 3,4-dimethoxyphenyl diisocyanate (mDVI) was confirmed by NMR spectroscopy:

(58) ##STR00021##

(59) .sup.1H NMR (400 MHz, CDCl3, δ (ppm)): δ 6.65 (d, H.sub.1), 6.58 (d, H.sub.5), 3.88 (s, H.sub.7), 3.64 (s, H.sub.8).

(60) .sup.13C NMR (400 MHz, CDCl3, δ (ppm)): δ 153.41 (s, C.sub.3), 144.82 (s, C.sub.2), 132.46 (s, C.sub.6), 128.72 (s, C.sub.4), 124.71 (s, C.sub.9), 118.91 (s, C.sub.5), 108.86 (s, C.sub.1), 60.99 (s, C.sub.8), 56.13 (s, C.sub.7).

(61) The spectra are shown in FIGS. 4A and 4B respectively.

2f. Synthesis of 3,4-Dimethoxydianiline (mDVAn)

(62) 3 mmol of potassium hydroxide were added to 0.75 mmol of 3,4-dimethoxyphenyl diisocyanate in solution in toluene. The mixture was stirred and heated for 12 h at 80° C. The toluene was evaporated under vacuum. The resulting product was solubilized in ethyl acetate and washed with water. The organic phase was then evaporated using a rotary evaporator. Yield of 10%.

(63) Obtaining 3,4-dimethoxyphenyldianiline (mDVAn) was confirmed by NMR spectroscopy:

(64) ##STR00022##

(65) .sup.1H NMR (400 MHz, CDCl3, δ (ppm)): δ 6.23 (d, H.sub.1), 5.90 (d, H.sub.5), 4.79 (s, H.sub.9), 3.72 (s, H.sub.7), 3.38 (s, H.sub.8).

(66) .sup.13C NMR (400 MHz, CDCl3, δ (ppm)): δ 152.47 (s, C.sub.3), 144.22 (s, C.sub.2), 136.90 (s, C.sub.6), 133.35 (s, C.sub.4), 107.48 (s, C.sub.5), 98.42 (s, C.sub.1), 59.97 (s, C.sub.8), 55.18 (s, C.sub.7).

(67) The spectra are shown in FIGS. 5A and 5B respectively.

EXAMPLE 3

(68) Polyepoxides Obtained from a Thermosetting Epoxy Resin and a Hardener The epoxy resins used were: diglycidyl ether of bisphenol A (DGEBA), of formula:

(69) ##STR00023##

(70) marketed by Sigma-Aldrich under the trade name D.E.R.® 332, and the tetraglycidyl ether of divanillyl alcohol (TetraGEDVA), the preparation and formula of which are specified below.

(71) TetraGEDVA was obtained (like its homologues: di- and tri-epoxidised (DiGEDVA and TriGEDVA) (see below)) under the conditions specified below, from divanillin, synthesized and purified under the conditions described in Example 1 above (more precisely in points 1a and 1a′ of said Example 1). A) From said divanillin, divanillyl alcohol was first prepared as follows (it would have been possible to proceed according to Example 8 of patent application EP 3 002 333).

(72) The purified divanillin (20 g) was reduced with sodium borohydride (NaBH.sub.4) to form divanillyl alcohol. To this end, it was solubilized in 0.5 M sodium hydroxide (180 mL; a few drops of 5 M solution were conveniently added to facilitate solubilization). Then NaBH.sub.4 (3 g) was added and the resulting mixture was kept under stirring until completely dissolved. After one hour of stirring, the reaction was stopped by adding, dropwise, an aqueous solution of hydrochloric acid (160 mL at 2 M) until a pH=3 was reached. The divanillyl alcohol then precipitated. It was recovered by filtration. The recovered product was dried in an oven. Synthesis was repeated. The yield was approximately 80% each time.

(73) Obtaining divanillyl alcohol (DVA) was confirmed by NMR spectroscopy:

(74) ##STR00024##

(75) 1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 8.22 (s, H9), 6.88 (d, H1), 6.67 (d, H5), 5.01 (t, H10), 4.41 (d, H7), 3.82 (s, H8).

(76) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 147.94 (s, C3), 142.77 (s, C2), 133.08 (s, C6), 125.92 (s, C4), 121.83 (s, C5), 109.50 (s, C1), 63.38 (s, C7), 56.25 (s, C8).

(77) B) The resulting divanillyl alcohol was then epoxidized with epichlorohydrin under “different” conditions to obtain different mixtures of several multi-epoxide compounds.

(78) B1) The conditions used to obtain a mixture of 25% TriGEDVA and 75% TetraGEDVA (% by mass) are described in detail below. In a first step, divanillyl alcohol (20 g) was mixed with epichlorohydrin (100 mL) and tetrabutylammonium bromide (TEBAC) (2 g). TEBAC is a phase transfer agent that allows phenol to react with epichlorohydrin, introduced in excess to form a di-epoxide. The reaction mixture was left under stirring at 80° C. for 1.5 h; then it was cooled to room temperature. Subsequently, an aqueous sodium hydroxide (NaOH) solution (160 mL at 10 M: 10 NaOH eq./OH) was added. The addition of the base closed the open epoxides but also deprotonated the benzyl alcohols which, in turn, were epoxidized by nucleophilic substitution with epichlorohydrin. The solution was then mechanically stirred for 20 h in a cold water bath. At the end of the reaction, dichloromethane (DCM) (300 mL) was added to the reaction medium to precipitate the salts (NaCl). The liquid phases were separated from the reaction medium and the salts rinsed off with 100 mL of DCM. The liquid phases were combined and the aqueous phase was extracted with 2×50 mL of DCM. The individual organic phases were combined and washed with 100 mL of water. The organic phase was concentrated using a rotary evaporator and the epichlorohydrin was finally evaporated under vacuum. The yield was quantitative. The proportion of di-, tri- and tetraepoxide compounds was quantified by high-performance liquid chromatography (HPLC). The apparatus used was a SpectraSYSTEM®, mounted with a Phenomenex 5p C18 100A column. The detector used was a SpectraSYSTEM® UV2000 system from Thermo Separation Products. The analyses were performed with an eluent composed of acetonitrile and water in a 50/50 isocratic proportion. The chromatograph obtained is shown in the attached FIG. 6.

(79) B2) The procedure described in B1) above was reproduced (in all respects) but with the addition of an aqueous solution of NaOH (50 mL at 5 M) and with mechanical stirring for only 1 h. A mixture of 80% DiGEDVA, 15% TriGEDVA and 5% TetraGEDVA (% by mass) was then obtained.

(80) B3) The procedure described in B1) above was repeated (in all respects) but with the addition of an aqueous solution of NaOH (50 mL at 5 M) and with mechanical stirring for only 8 h. A mixture of 35% DiGEDVA, 50% TriGEDVA and 15% TetraGEDVA (% by mass) was then obtained.

(81) In order to obtain, in isolation, the various multi-epoxide compounds (di-, tri- and tetraepoxides, constituent elements of epoxy resins (taken alone or in a mixture)), a purification step by flash or instantaneous chromatography, on a Grace Reveleris® apparatus, equipped with a silica cartridge and a UV detector, was carried out on the mixtures, using a dichloromethane/methanol solvent gradient of 99/1 to 90/10 (by volume) for 30 minutes.

(82) The identity of these multi-epoxide compounds was confirmed by NMR spectroscopy:

(83) ##STR00025##

(84) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 7.0 (d, H.sub.1), 6.71 (d, H.sub.5), 5.16 (t, H.sub.10), 4.47 (d, H.sub.7), 3.88 (m, H.sub.11), 3.83 (s, H.sub.8), 3.74 (m, H.sub.11b), 2.95 (m, H.sub.12), 2.6 (t, H.sub.13), 2.36 (t, H.sub.13b).

(85) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 152.33 (s, C.sub.3), 144.47 (s, C.sub.2), 138.26 (s, C.sub.6), 132.59 (s, C.sub.4), 120.86 (s, C.sub.5), 110.79 (s, C.sub.1), 74.22 (s, C.sub.11), 63.14 (s, C.sub.7), 56.18 (s, C.sub.8), 50.53 (s, C.sub.12), 43.97 (s, C.sub.13).

(86) The spectra are shown in FIGS. 7A and 7B respectively.

(87) ##STR00026##

(88) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 7.01 (d, H.sub.1), 6.75 (d, H.sub.5), 5.18 (t, H.sub.10), 4.47 (d, H.sub.7 H.sub.14).sub.1 3.92 (m, H.sub.1), 3.84 (s, H.sub.8), 3.76 (m, H.sub.11b), 3.69 (m, H.sub.15), 3.29 (m, H.sub.15b), 3.14 (m, H.sub.16), 2.97 (m, H.sub.12), 2.72 (m, H.sub.17), 2.6 (m, H.sub.13), 2.5 (m, H.sub.17b), 2.36 (m, H.sub.13b). .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 152.02 (s, C.sub.3′), δ 151.89 (s, C.sub.3), 144.38 (s, C.sub.2′), 143.68 (s, C.sub.2), 138.12 (s, C.sub.6′), 133.39 (s, C.sub.6), 132.06 (s, C.sub.4′), 131.76 (s, C.sub.4), 121.78 (s, C.sub.5—), 120.26 (s, C.sub.5), 111.55 (s, C.sub.1′), 110.46 (s, C.sub.1), 73.85 (s, C.sub.14), 71.81 (s, C.sub.15), 70.79 (s, C.sub.11), 62.67 (s, C.sub.7), 55.90 (s, C.sub.8), 50.42 (s, C.sub.12), 50.16 (s, C.sub.16), 43.42 (s, C.sub.13 C.sub.17).

(89) The spectra are shown in FIGS. 8A and 8B respectively.

(90) ##STR00027##

(91) .sup.1H NMR (400 MHz, DMSO-d6, δ (ppm)): δ 7.02 (d, H1), 6.76 (d, H5), 4.50 (s, H14), 3.92 (m, H11), 3.86 (s, H8), 3.76 (m, H11b), 3.70 (m, H15), 3.28 (m, H15b), 3.14 (m, H16), 2.97 (m, H12), 2.73 (m, H17), 2.60 (m, H13), 2.55 (m, H17b), 2.35 (m, H13b).

(92) .sup.13C NMR (400 MHz, DMSO-d6, δ (ppm)): δ 152.10 (s, C3), 144.51 (s, C2), 133.51 (s, C6), 131.81 (s, C4), 121.83 (s, C5), 111.52 (s, C1), 73.77 (s, C14), 71.90 (s, C15), 63.14 (s, C11), 55.79 (s, C8), 50.30 (s, C12), 50.03 (s, C16), 43.44 (s, C13 C17).

(93) The spectra are shown in FIGS. 9A and 9B respectively.

(94) More specifically, this purification step was carried out on the mixture obtained at the end of step B1 above to isolate the TetraGEDVA (thermosetting epoxy resin) which was tested with different types of hardeners. The amine type hardeners tested were: diamino diphenyl sulfone (DDS), marketed by Sigma Aldrich. This conventional hardener has the formula:

(95) ##STR00028##
and 3,4-dimethoxydianiline of formula (I) (see Example 2 above).

(96) The hardener was used, for each test, in the stoichiometric ratio: epoxy/amine=2/1. The polyepoxide (epoxy resin+hardener) was generated, in small quantities (a few mg), during the implementation of differential scanning calorimetry (DSC). Its glass transition temperature (Tg) was thus determined directly.

(97) The rate of residual coke, after degradation at 900° C., determined by thermogravimetric analysis (TGA) (Char900), was determined on this small quantity generated during the DSC analysis. The results are shown in Table 1 below.

(98) TABLE-US-00001 TABLE 1 Properties DGEBA/DDS DGEBA/mDVAn TetraGEDVA/mDVAn Tg (° C.) 204 176 212 Char900 (%) 18 28 48

(99) The figures in this table confirm the interest of the compounds of the invention.