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Preparation method of 4-(5-amino-6-hydroxy-2-benzoxazolyl) benzoic acid (ABA)

A technology of benzoxazolyl and benzoic acid, which is applied in the field of preparation of 4-benzoic acid (ABA), can solve the problems of PBO polymerization degree restriction, polymerization process hindered, difficult to achieve equivalence ratio, etc., to reduce sodium ion content , improve polymerization efficiency, and facilitate the recovery of solvents

Inactive Publication Date: 2015-01-28
YANCHENG DRAGON CHEM
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] (1) The polymerization operation is complicated and the increase in the molecular weight of PBO is limited: due to the oxidative decomposition of DAR 2HCl and the easy sublimation of TPA, the molar ratio r of the two monomers changes randomly during high-temperature polycondensation, and it is difficult to achieve an equivalent ratio, and the heterogeneous phase The polymerization reaction is very slow; 2500-3500ppm Sn in the monomer 2+ Sn generated after anti-oxidation 3+ The degree of polymerization inhibition, coupled with the interference of removing HCl and its gas for a long time, limits the further improvement of the degree of polymerization of PBO, and the actual strength and modulus are less than 30% and 55% of the theoretical value.
[0006] (2) The raw material polymerization grade monomer DAR·2HCl is difficult to prepare and the utilization rate is low, which leads to the high price of PBO: the synthesis yield of DAR·2HCl monomer is low, the stability is poor, and the quality is difficult to meet the requirements of polymerization grade; DAR·2HCl in PBO The theoretical value of the atom utilization rate is only 61.77%, and the molecular mass of DAR that effectively participates in the reaction is only 65.77% of the molecular weight of the key monomer DAR·2HCl (34.23% is only used for protection), plus the price of polymer-grade monomers Up to $120 / kg+, making PBO cost quite high
[0017] But since the reducing agent uses Na 2 S 2 o 4 , the dosage is large (2.0-3.0 times the mass of MNB), plus NaHSO 3 As an ABAS eluting agent, Na 2 S 2 o 4 The product of the reduction reaction is Na 2 SO 3 、Na 2 SO 4 , so that the product contains more than 3% sulfite substances, the metal ion content is 8000~15000ppm, the polymerization process is hindered, and the intrinsic viscosity of PBO prepared in a 40ml glass polymerizer is only 15dL / g (only compared with the literature ( Polymer preprints, 1990,31(2),681-682) is slightly higher at 12.5 dl / g), and there is pollution of sulfite inorganic substances

Method used

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  • Preparation method of 4-(5-amino-6-hydroxy-2-benzoxazolyl) benzoic acid (ABA)
  • Preparation method of 4-(5-amino-6-hydroxy-2-benzoxazolyl) benzoic acid (ABA)
  • Preparation method of 4-(5-amino-6-hydroxy-2-benzoxazolyl) benzoic acid (ABA)

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] Example 1: Preparation of 4-(5-amino-6-hydroxyl-2-benzoxazolyl)benzoic acid (ABA)

[0044] Add 12g (0.038mol) methyl 4-(5-nitro-6-hydroxy-2-benzoxazolyl)benzoate (MNB), 306g methanol, 45g water and 5.36g (0.096mol) to the reaction vessel KOH, stirred and heated to 75°C and refluxed, the material changed from a yellow suspension to a red floc, and continued to react for 1 hour. Then put in 1.2g of ferrous chloride, 2.4g of activated carbon, 10.2g (0.163mol) of 80% hydrazine hydrate in turn, raise the temperature to 75°C for reflux reaction for 2h, the reaction solution turns orange yellow, filter while hot to remove the waste carbon, and add the filtrate dropwise 19g of concentrated hydrochloric acid precipitated a yellow solid, filtered, washed with water, and dried in vacuo to obtain 9.52g of the product ABA, with a purity of 96.2%, metal ions (K + , Fe 2+ ) The total content is 3252ppm, and the yield is 92.25%.

[0045] Product characterization:

[0046] 1 H-NMR ...

Embodiment 2~7

[0049] Embodiment 2~7: the preparation of ABA

[0050] Adopt 12 g MNB and 10.2g 80% industrial hydrazine hydrate to feed and operate similarly to Example 1, get different parameters (methanol, water, KOH, hydrochloric acid consumption) to prepare ABA according to the parameter range described in the present invention, the results are shown in Table 1 :

[0051] Table 1 Preparation of ABA monomer from MNB by KOH hydrolysis followed by hydrazine hydrate reduction "one-pot method"

[0052]

Embodiment 9

[0059] Embodiment 9: Preparation of ABA

[0060] Add 10g (0.032mol) 4-(5-nitro-6-hydroxy-2-benzoxazolyl) methyl benzoate (MNB), 1.98g activated carbon, 1.4g ferric chloride, 5.9g (0.094mol) 80% hydrazine hydrate and 202g methanol, stirred and heated to reflux reaction for 3.5h, the material changed from yellow to brown, then added 4.95g (0.12mol) NaOH and 8g water to the reaction vessel for 3h, the material dissolved into Orange yellow, filter while hot to remove waste carbon, add concentrated hydrochloric acid dropwise to the filtrate to pH=6~7, a yellow solid precipitates, filter, wash with water, and dry in vacuum to obtain 6.35g of the product ABA, with a purity of 95.34%, metal ions (Na + , Fe 2+ ) The total content is 4415ppm, and the yield is 73.84%. The infrared spectrum of the product obtained is identical to the infrared absorption of Example 1.

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Abstract

The invention discloses a preparation method of 4-(5-amino-6-hydroxy-2-benzoxazolyl) benzoic acid (ABA), which comprises the following steps of: using 4-(5-nitro-6-hydroxy-2-benzoxazolyl) methyl benzoate shown by a formula (I) as a raw material, firstly conducting ester group hydrolysis and then conducting nitro reduction to obtain the ABA shown by a formula (IV), or firstly conducting nitro reduction and then conducting ester group hydrolysis to obtain the ABA shown by the formula (IV), wherein hydrazine hydrate is used as reducing agent and Fe<2+> / C or Fe<3+> / C is used as catalyst during reduction, the catalyst Fe<2+> / C is a catalyst system consisting of ferrous salt and activated carbon and the catalyst Fe<3+> / C is a catalyst system consisting of ferric salt and activated carbon. The ABA prepared by adopting the method does not generate any harmful gas and cause any interference during preparation of PBO (cis-poly (p-phenylene-2, 6-benzobisoxazole)) through polycondensation, does not contain organic polymerization inhibiting impurities DMF (dimethyl formamide) and contains metal ions with content being low.

Description

(1) Technical field [0001] The invention relates to a preparation method of 4-(5-amino-6-hydroxyl-2-benzoxazolyl)benzoic acid (ABA). (2) Background technology [0002] PBO is the abbreviation of cis-poly (p-phenylene-2,6-benzobisoxazole), which is cis-poly-p-phenylene benzobisoxazole. PBO fiber is an organic fiber with the best tensile and heat resistance properties , which is composed of AA-type monomer 4,6-diaminoresorcinol hydrochloride (DAR 2HCl) and BB-type monomer terephthalic acid (TPA) containing P 2 o 5 After mixing and polycondensing PBO liquid crystal solution in PPA solvent (see formula (1)), the AS-type as-spun yarn is obtained by dry-jet wet spinning, and finally obtained by high-temperature heat treatment above 600°C. [0003] [0004] Japan's Toyobo Corporation commercialized the high-performance PBO fiber - Zylon-HM in 1998 by Dow chemical patent authorization, and has been monopolizing production and supply. However, due to the corrosion and interfere...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D263/57
Inventor 金宁人何彪方海波
Owner YANCHENG DRAGON CHEM
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