CN114920688A - Method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate - Google Patents
Method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate Download PDFInfo
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- CN114920688A CN114920688A CN202210478316.6A CN202210478316A CN114920688A CN 114920688 A CN114920688 A CN 114920688A CN 202210478316 A CN202210478316 A CN 202210478316A CN 114920688 A CN114920688 A CN 114920688A
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- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
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- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/41—Preparation of salts of carboxylic acids
- C07C51/412—Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part
Abstract
The invention relates to a method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate. The method comprises the following steps: (1) adding a sodium hydroxide aqueous solution into a 2, 5-dihydroxy terephthalic acid solution, and reacting without adding or adding stannous chloride to obtain a reaction solution 1; (2) adding sodium sulfite or sodium sulfide into a 2,3,4, 5-tetraaminopyridine trihydrochloride solution for reaction to obtain a reaction solution 2; (3) and slowly dropwise adding the reaction solution 2 into the reaction solution 1 for reaction, adjusting the pH value, cooling, carrying out suction filtration, washing and drying. The method has the advantages of simple synthesis, mild reaction, equivalent molar ratio of the prepared TD salt and high yield.
Description
Technical Field
The invention belongs to the field of preparation of high polymer materials, and particularly relates to a method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate.
Background
Poly [2, 5-dihydroxy-1, 4-phenylene pyridine diimidazole ] (PIPD) has excellent mechanical property, excellent heat resistance and flame resistance and good bonding property with thermosetting resin because of the special hydrogen bond network structure along the radial direction of the fiber, namely between molecules. Therefore, the polymer has a huge application prospect in the fields of national defense and military, aerospace and aviation, automobile application and the like.
Preparation method of polymer PIPD: one is that under the protection of inert gas, two monomers with equal molar ratio undergo condensation polymerization reaction in solution through a removing reaction process to obtain a polymer with high viscosity and high molecular weight; the other is to prepare two monomers (2,3,5, 6-tetraaminopyridine and 2, 5-dihydroxyterephthalic acid) into a salt (TD salt) form, and carry out condensation polymerization reaction in a solution. Compared with the two methods, the former method needs to carry out the reaction process of removing the hydrochloric acid in the polymerization process, prolongs the polymerization reaction time, reduces the reaction efficiency, easily damages experimental equipment by the removed corrosive gas, easily oxidizes the tetraaminopyridine monomer for removing the hydrochloric acid, and is difficult to obtain the prepolymer with higher polymerization degree. The TD salt form polymerization reaction has the advantage of more accurate equimolar feeding, and provides a guarantee for obtaining a polymer with high molecular weight. At present, the preparation method of the TD salt has the advantages of difficult control of equimolar ratio and low yield.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate, so as to overcome the defects of large molar ratio difference and low yield of TD salt prepared in the prior art.
The invention provides a method for preparing 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate, which comprises the following steps:
(1) dissolving 2, 5-dihydroxy terephthalic acid (DHTA) in water, adding a sodium hydroxide aqueous solution, and reacting without adding or adding stannous chloride to obtain a reaction solution 1;
(2) dissolving 2,3,4, 5-tetraaminopyridine trihydrochloride (TAP & 3HCl) in water, and adding sodium sulfite or sodium sulfide for reaction to obtain a reaction solution 2;
(3) and (3) slowly dropwise adding the reaction liquid 2 in the step (2) into the reaction liquid 1 for reaction, adjusting the pH value to acidity, cooling, performing suction filtration, washing and drying to obtain the 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate.
Preferably, the molar ratio of the 2, 5-dihydroxyterephthalic acid to the sodium hydroxide in the step (1) is 1:3 to 1: 4.
Preferably, the ratio of the 2, 5-dihydroxyterephthalic acid to water in the step (1) is 1g:30 mL-1 g:50 mL.
Preferably, the concentration of the sodium hydroxide aqueous solution in the step (1) is 3-5 mol/L.
Preferably, the stannous chloride is added in the step (1) in an amount of 5-20% of the mole of the 2, 5-dihydroxyterephthalic acid.
Preferably, the stirring speed in the step (1) is 300-500 r/min.
Preferably, the reaction in step (1) is: reacting for 20-40 min at 50-60 ℃ under nitrogen.
Preferably, the water in steps (1) and (2) is deoxygenated water.
Preferably, the molar ratio of the 2,3,4, 5-tetraaminopyridine trihydrochloride in the step (2) to the 2, 5-dihydroxyterephthalic acid in the step (1) is 1: 1.1-1: 1.2.
Preferably, the amount of the sodium sulfite or sodium sulfide added in the step (2) is 10 to 20 percent of the mole of the 2,3,4, 5-tetraaminopyridine trihydrochloride.
Preferably, the ratio of the 2,3,4, 5-tetraaminopyridine trihydrochloride to the water in the step (2) is 1g:30 mL-1 g:50 mL.
Preferably, the reaction in step (2) is: and reacting for 15-30 min at normal temperature.
Preferably, the pH value is adjusted to be 3-5 in the step (3).
Preferably, stannous chloride is not added in the step (1) for reaction, and the pH value is adjusted to 3-5 in the step (3).
Preferably, stannous chloride is added in the step (1) for reaction, sodium sulfite is added in the step (2), and the pH value is adjusted to 3-4 in the step (3).
Preferably, stannous chloride is added in the step (1) for reaction, sodium sulfide is added in the step (2), and the pH value is adjusted to 3-4 in the step (3).
Preferably, the pH value is adjusted in the step (3) by using deoxidized dilute hydrochloric acid, and the concentration of the dilute hydrochloric acid is 0.5-1 mol/L.
Preferably, the washing in step (3) is: and (4) under the protection of nitrogen, washing with deoxygenated water for three times, and then washing with deoxygenated ethanol for 2-3 times.
Preferably, the drying in step (3) is: and drying in a vacuum drying oven at 60 ℃ for 20-24 h.
Preferably, the reaction temperature in the step (3) is 50-60 ℃, and the reaction time is 20-40 min.
The invention mainly optimizes the mole ratio of the TD salt by changing the step feeding sequence and different types of reducing agents and improves the yield. Compared with a one-pot reaction strategy, the method for alkalizing DHTA first and then neutralizing the DHTA with TAP & 3HCl has the advantages that two reaction substrates can fully react, and the phenomenon that sodium hydroxide reacts with TAP & 3HCl preferentially in the one-pot reaction to cause asynchronous reaction of the two substrates is avoided, so that the fractional reaction yield is obviously improved, and the molar ratio is equal. The mode of changing the reducing agent into sodium sulfite and sodium sulfide and combining with stannous chloride can improve the reducing property as the reducing agent separately for stannous chloride, can effectively prevent TAP & 3HCl from being oxidized after HCl removal, and then can improve the yield, and is also effective for improving the equivalent molar ratio.
Advantageous effects
The method has the advantages of simple synthesis, mild reaction, equivalent molar ratio of the prepared TD salt and high yield. The TD salt prepared by the method can be applied to PIPD polymerization to improve the molecular weight and shorten the reaction time.
Drawings
FIG. 1 is a nuclear magnetic spectrum of the TD salt prepared in example 1.
FIG. 2 is a TAP fragment mass spectrum of the TD salt prepared in example 1.
FIG. 3 is a DHTA fragment mass spectrum of the TD salt prepared in example 1.
FIG. 4 is an infrared spectrum of the TD salt prepared in example 1.
Figure 5 is a nuclear magnetic spectrum of the TD salt prepared in example 2.
FIG. 6 is the TAP fragment mass spectrum of the TD salt prepared in example 2.
Figure 7 is a DHTA fragment mass spectrum of the TD salt prepared in example 2.
FIG. 8 is an infrared spectrum of the TD salt prepared in example 2.
Figure 9 is a nuclear magnetic spectrum of the TD salt prepared in example 3.
FIG. 10 is a TAP fragment mass spectrum of the TD salt prepared in example 3.
FIG. 11 is a DHTA fragment mass spectrum of the TD salt prepared in example 3.
FIG. 12 is an IR spectrum of a TD salt prepared in example 3.
Figure 13 is a nuclear magnetic spectrum of the TD salt prepared in example 4.
FIG. 14 is a nuclear magnetic spectrum of the TD salt prepared in comparative example 1.
FIG. 15 is a TAP fragment mass spectrum of the TD salt prepared in comparative example 1.
FIG. 16 is a DHTA fragment mass spectrum of the TD salt prepared in comparative example 1.
FIG. 17 is an infrared spectrum of TD salt prepared in comparative example 1.
FIG. 18 is a nuclear magnetic spectrum of the TD salt prepared in comparative example 2.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention can be made by those skilled in the art after reading the teaching of the present invention, and these equivalents also fall within the scope of the claims appended to the present application.
Example 1
A two-necked flask was taken (thoroughly dried), DHTA (1.32g, 6.6mmol) was added, the flask was evacuated to exchange nitrogen three times, deoxygenated water (50mL) was added (ultra-clean water with nitrogen removed), NaOH (0.8g, 19.8mmol) was weighed again and dissolved in 5mL of aqueous solution, and the solution was deoxygenated by bubbling nitrogen through the solution. The sodium hydroxide solution was added to the DHTA solution, and the original solution was seen to gradually dissolve,it appeared reddish brown and finally turned black, and was heated to 50 ℃ for 30 minutes. A two-neck flask was charged with TAP-3 HCl (1.4g, 5.6mmol) and Na 2 SO 3 (0.09g,0.71mmol) of solid, evacuated to exchange nitrogen gas three times, dissolved at room temperature by adding deoxygenated water (50mL) and reacted for 20 min. The solution is yellow brown. Mixing the two reaction solutions, adding the reaction solution in the step 2 into the mixed solution in the step 1, slowly adding, generating air bubbles immediately during adding, separating out solids, wherein the solids are light yellow, the more the solids are separated out along with the addition, and reacting for 30 minutes at 50 ℃ after the addition is finished. The reaction was cooled and diluted hydrochloric acid (sparge) was added to bring the pH to 4. Transfer quickly to suction filter to get solid while rinsing with cold water (bubble), and cold ethanol (bubble) to get light yellow solid. Vacuum drying at 60 deg.C for 24 h. 2.2g were obtained, yield 95.7%.
The equation for this embodiment is as follows:
as can be seen from fig. 1, δ ═ 6.72 corresponds to the a position of tetraaminopyridine, and δ ═ 7.21 corresponds to the b position of dihydroxyterephthalic acid. And the corresponding ratio is 1:2.07, i.e., an equimolar ratio, which is advantageous in increasing the polymerization molecular weight and shortening the polymerization time.
As can be seen from FIGS. 2 and 3, no molecular ion peak at m/z 337 (molecular weight of TD salt) appears in the entire spectrum. Since TAP and DHTA are present in solution phase in each free form, no complex salt thereof could be detected. m/z 140 is [ TAP + H] + Molecular ion peak of (1). m/z 197 is [ DHTA-H] - Molecular ion peak of (1).
As can be seen in FIG. 4, at 3440cm -1 The peak at the position is an absorption peak of an intramolecular hydrogen bond formed by a phenolic hydroxyl group, and the peak is 3120cm -1 Is at-NH stretching vibration peak, 1660cm -1 1420cm of an expansion vibration peak where C is O -1 Is the stretching vibration peak of the pyridine ring, 784cm -1 The position is a skeleton vibration absorption peak of a benzene ring.
Example 2
A two-necked flask was taken (thoroughly dried), DHTA (1.32g, 6.6mmol) was added, the flask was evacuated to exchange nitrogen three times, deoxygenated water (50mL) was added (ultra-clean water with nitrogen removed), NaOH (0.8g, 19.8mmol) was weighed again and dissolved in 5mL of aqueous solution, and the solution was deoxygenated by bubbling nitrogen through the solution. The sodium hydroxide solution was added to the DHTA solution, the original solution was seen to gradually dissolve, appearing reddish brown, and finally a blackish solution, heated to 50 ℃, reacted for 30 minutes. A two-neck flask was charged with TAP-3 HCl (1.4g, 5.6mmol) and Na 2 S (0.055g, 0.71mmol) as a solid, evacuated and purged with nitrogen three times, and then dissolved in deoxygenated water (50mL) at room temperature for 20 min. The solution is yellow brown. Mixing the two reaction solutions, adding the reaction solution in the step 2 into the mixed solution in the step 1, slowly adding, generating air bubbles immediately during adding, separating out solids, wherein the solids are light yellow, the more the solids are separated out along with the addition, and reacting for 30 minutes at 50 ℃ after the addition is finished. The reaction was cooled and diluted hydrochloric acid (sparge) was added to bring the pH to 3. The solid was quickly transferred to suction filtration and rinsed with cold water (bubbling) and cold ethanol (bubbling) to give a pale green solid. Vacuum drying at 60 deg.C for 24 h. 2.28g are obtained, with a yield of 99.2%.
As can be seen from fig. 5, δ 6.72 corresponds to the a-position of tetraaminopyridine, and δ 7.21 corresponds to the b-position of dihydroxyterephthalic acid. And the corresponding ratio is 1:2.01, which means an equimolar ratio, which is advantageous in increasing the polymerization molecular weight and shortening the polymerization time.
As can be seen from FIGS. 6 and 7, no molecular ion peak of m/z 337 (molecular weight of TD salt) appears in the entire spectrum. Since TAP and DHTA are present in solution phase in each free form, no complex salt thereof could be detected. m/z 140 is [ TAP + H] + Molecular ion peak of (1). m/z 197 is [ DHTA-H] - Molecular ion peak of (1).
As can be seen from FIG. 8, at 3445cm -1 The peak at the position is an absorption peak of an intramolecular hydrogen bond formed by a phenolic hydroxyl group, and the peak is 3120cm -1 Is at-NH stretching vibration peak, 1660cm -1 The peak is C ═ O stretching vibration peak, 1435cm -1 Is located at 782cm of stretching vibration peak of pyridine ring -1 Skeleton vibration sucker with benzene ringAnd (6) peak collection.
Example 3
A two-necked flask was selected (thoroughly dried), DHTA (1.32g, 6.6mmol) was added, stannous chloride (0.14g, 0.52mmol) was added, nitrogen was evacuated and exchanged three times, deoxygenated water (50mL) was added (ultra-clean water was purged with nitrogen to remove oxygen), NaOH (0.8g, 19.8mmol) was weighed again and dissolved in 5mL of aqueous solution, and the solution was purged with nitrogen to remove oxygen. The sodium hydroxide solution was added to the DHTA solution, the original solution was seen to gradually dissolve, appearing reddish brown, and finally a blackish solution, heated to 50 ℃, and reacted for 30 minutes. A two-neck flask was charged with TAP-3 HCl (1.4g, 5.6mmol) and Na 2 SO 3 (0.09g,0.71mmol) of solid, nitrogen was evacuated three times and deoxygenated water (50mL) was added. Dissolving at normal temperature for 20 min. The solution was completely dissolved and appeared yellow-brown. Mixing the two reaction solutions, adding the reaction solution in the step 2 into the mixed solution in the step 1, slowly adding, generating air bubbles immediately during adding, separating out solids, wherein the solids are light yellow, the more the solids are separated out along with the addition, and reacting for 30 minutes at 50 ℃ after the addition is finished. The reaction was cooled and diluted hydrochloric acid was added (bubbled) to bring the pH to 3. The solid was quickly transferred to suction filtration and rinsed with cold water (bubbling) and cold ethanol (bubbling) to give a pale green solid. Vacuum drying at 60 deg.C for 24 h. 2.24g were obtained, yield 97.4%.
As can be seen from fig. 9, δ 6.73 corresponds to the a-position of tetraaminopyridine, and δ 7.23 corresponds to the b-position of dihydroxyterephthalic acid. And the corresponding ratio is 1:1.98, which indicates an equimolar ratio, which is advantageous in increasing the polymerization molecular weight and shortening the polymerization time.
As can be seen from FIGS. 10 and 11, no molecular ion peak of m/z 337 (molecular weight of TD salt) appears in the entire spectrum. Since TAP and DHTA are present in solution phase in each free form, no complex salt thereof could be detected. m/z 140 is [ TAP + H] + Molecular ion peak of (2). m/z 197 is [ DHTA-H] - Molecular ion peak of (1).
FIG. 12 shows that the thickness is 3345cm -1 The peak at the position is an absorption peak of an intramolecular hydrogen bond formed by a phenolic hydroxyl group, which is 3113cm -1 Is at-NH stretching vibration peak, 1660cm -1 Stretching vibration with C ═ ODynamic peak, 1435cm -1 Is located at 784cm of the stretching vibration peak of the pyridine ring -1 The position is a skeleton vibration absorption peak of a benzene ring.
Example 4
This example is different from example 3 in that Na is added 2 SO 3 (0.09g,0.71mmol) solid was replaced with Na 2 S (0.055g, 0.71mmol) was otherwise the same as in example 3. The final product was 2.26, 98.2% yield. The corresponding ratio of the a position of the tetraaminopyridine to the b position of the dihydroxyterephthalic acid in the nuclear magnetic hydrogen spectrum is 1: 2.03.
As can be seen from fig. 13, δ ═ 6.72 corresponds to the a position of tetraaminopyridine, and δ ═ 7.21 corresponds to the b position of dihydroxyterephthalic acid. And the corresponding ratio is 1:2.03, which means an equimolar ratio, which is advantageous in increasing the polymerization molecular weight and shortening the polymerization time.
Comparative example 1
A two-necked flask was taken (thoroughly dried), DHTA (1.32g, 6.6mmol) was added, the flask was evacuated to exchange nitrogen three times, deoxygenated water (50mL) was added (ultra-clean water with nitrogen removed), NaOH (0.8g, 19.8mmol) was weighed again and dissolved in 5mL of aqueous solution, and the solution was deoxygenated by bubbling nitrogen through the solution. The sodium hydroxide solution was added to the DHTA solution, the original solution was seen to gradually dissolve, appearing reddish brown, and finally a blackish solution, heated to 50 ℃, and reacted for 30 minutes. A two-neck flask was charged with TAP.3 HCl (1.4g, 5.6mmol) and stannous chloride (0.19g, 0.71mmol), evacuated to exchange nitrogen gas three times, and dissolved in deoxygenated water (50mL) at room temperature for 20 min. The solution is yellow brown. Mixing the two reaction solutions, adding the reaction solution in the step 2 into the mixed solution in the step 1, slowly adding, generating air bubbles immediately during adding, separating out solids, wherein the solids are light yellow, the more the solids are separated out along with the addition, and reacting for 30 minutes at 50 ℃ after the addition is finished. The reaction was cooled and diluted hydrochloric acid (sparge) was added to bring the pH to 3. Transfer quickly to suction filtration to get solid while rinsing with cold water (bubbling), and cold ethanol (bubbling) to get light green solid. Vacuum drying at 60 deg.C for 24 h. 2.03g was obtained, yield 89.2%.
As can be seen from fig. 14, δ ═ 6.72 corresponds to the a position of tetraaminopyridine, and δ ═ 7.21 corresponds to the b position of dihydroxyterephthalic acid. And the corresponding ratio is 1:2.57, and the molar ratio is greatly different, which is not beneficial to the increase of the molecular weight of the polymer.
As can be seen from FIGS. 15 and 16, no molecular ion peak of m/z 337 (molecular weight of TD salt) appears in the entire spectrum. Since TAP and DHTA are present in solution phase in each free form, no complex salts thereof could be detected. m/z 140 is [ TAP + H] + Molecular ion peak of (1). m/z 197 is [ DHTA-H] - Molecular ion peak of (1).
FIG. 17 shows that the thickness is 3345cm -1 The peak at the position is an absorption peak of an intramolecular hydrogen bond formed by a phenolic hydroxyl group, which is 3113cm -1 Is at-NH stretching vibration peak, 1660cm -1 A telescopic vibration peak of 1430cm where C is O -1 Is the stretching vibration peak of the pyridine ring, 784cm -1 The position is a skeleton vibration absorption peak of a benzene ring.
Comparative example 2
A two-necked flask was selected (thoroughly dried) and DHTA (1.32g, 6.6mmol), TAP.3 HCl (1.4g, 5.6mmol) and Na were added 2 S (0.055g, 0.71mmol) as a solid, evacuated and purged with nitrogen three times, and deoxygenated water (100mL) was added and dissolved at room temperature for 20 min. The solution was completely dissolved and appeared yellow-brown. NaOH (0.8g, 19.8mmol) was weighed out and dissolved in 5mL of an aqueous solution, and the solution was purged with nitrogen to remove oxygen. Adding sodium hydroxide solution into the mixed solution, heating to 50 ℃, and reacting for 30 minutes. Mixing the two reaction solutions, generating bubbles immediately when adding, observing that the original solution is gradually dissolved, then separating out solid which is yellow, the more the solid is separated out along with the addition, and reacting for 30 minutes at 50 ℃ after the addition is finished. The reaction was cooled and diluted hydrochloric acid (sparge) was added to bring the pH to 3. Transfer quickly to suction filtration to get solid while rinsing with cold water (bubbling), and cold ethanol (bubbling) to get light green solid. Vacuum drying at 60 deg.C for 24 h. 1.56g was obtained, yield 66.5%.
As can be seen from fig. 18, δ 6.72 corresponds to the a-position of tetraaminopyridine, and δ 7.21 corresponds to the b-position of dihydroxyterephthalic acid. And the corresponding ratio is 1:2.98, and the molar ratio is greatly different, which is not beneficial to the increase of the molecular weight of the polymer.
Claims (8)
1. A method of making 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxyterephthalate comprising:
(1) dissolving 2, 5-dihydroxy terephthalic acid in water, adding a sodium hydroxide aqueous solution, and reacting without adding or adding stannous chloride to obtain a reaction solution 1;
(2) dissolving 2,3,4, 5-tetraaminopyridine trihydrochloride in water, and adding sodium sulfite or sodium sulfide for reaction to obtain a reaction solution 2;
(3) and (3) slowly dropwise adding the reaction liquid 2 in the step (2) into the reaction liquid 1 in the step (1) for reaction, adjusting the pH value to acidity, cooling, carrying out suction filtration, washing and drying to obtain the 2,3,5, 6-tetraaminopyridine-2, 5-dihydroxy terephthalate.
2. The method according to claim 1, wherein the molar ratio of 2, 5-dihydroxyterephthalic acid to sodium hydroxide in the step (1) is 1:3 to 1: 4.
3. The method of claim 1, wherein the concentration of the aqueous sodium hydroxide solution in the step (1) is 3 to 5 mol/L.
4. The method according to claim 1, wherein the stannous chloride is added in an amount of 5-20% based on the mole of 2, 5-dihydroxyterephthalic acid in step (1).
5. The method according to claim 1, wherein the reaction in step (1) is: reacting for 20-40 min at 50-60 ℃ under nitrogen.
6. The method according to claim 1, wherein the molar ratio of the 2,3,4, 5-tetraaminopyridine trihydrochloride in the step (2) to the 2, 5-dihydroxyterephthalic acid in the step (1) is 1:1.1 to 1: 1.2; the dosage of the added sodium sulfite or sodium sulfide accounts for 10 to 20 percent of the mol of 2,3,4, 5-tetraaminopyridine hydrochloride.
7. The method of claim 1, wherein the reaction in step (2) is: and reacting for 15-30 min at normal temperature.
8. The method according to claim 1, wherein the reaction temperature in the step (3) is 50-60 ℃, and the reaction time is 20-40 min; adjusting the pH value to 3-5.
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| CN103224625A (en) * | 2013-04-23 | 2013-07-31 | 南京理工大学 | Preparation method for poly(2,5-dihydroxyl-1,4-phenylene pyridobisimidazole) |
| CN104059017A (en) * | 2014-06-06 | 2014-09-24 | 南京理工大学 | Complex salt and method for preparing high-molecular-weight poly-p-phenylenepyridino-bisiminazole (PIPD) from same |
| CN109265341A (en) * | 2018-11-20 | 2019-01-25 | 河南大学 | A kind of synthetic method of 5-ALA hydrochloride |
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