Thermotropic liquid crystal polyester material monomer synthesis process
By adding organic base to the esterification reaction between 6-hydroxy-2-naphthoic acid and acetic anhydride, the reaction temperature and time were controlled, and the synthesis of 6-acetoxy2-naphthoic acid was successfully achieved with high yield, solving the problems of high reaction temperature, long time and high amount in the prior art, and achieving the effect of simple operation, mild conditions, low cost and high yield.
Patent Information
- Application Number
- CN202411881271.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-04-11
AI Technical Summary
In the preparation of 6-acetoxy2-naphtholic acid, the reaction temperature is high, the reaction time is long, and the amount of acetic anhydride is high, and there are disadvantages. New synthesis plans need to be proposed to reduce the reaction temperature and increase the reaction rate.
Using the method of organic alkali involved, acetic anhydride was added to the reaction solution of 6-hydroxy-2-naphthoic acid and organic alkali in a stirred state, and the reaction temperature was controlled to be 15-35°C and the reaction time was 6-24 hours. The white product 6-acetoxy2-naphthoic acid was obtained by filtration, beating and drying.
The high yield esterification reaction of 6-hydroxy-2-naphthoic acid and acetic anhydride is achieved. The reaction operation is simple, the conditions are mild, and the cost is low. The yield is as high as 80% to 90%, making it easy to purify.
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Figure CN119798075A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of polymer materials, and in particular to a synthesis process of thermotropic liquid crystal polyester material monomers. Background Art
[0002] Thermotropic liquid crystal polyester (LCP) has the property of low dielectric loss and can be used for high-frequency transmission. The new material after being compounded with polyimide and functional materials has ultra-low D k With D f It is the preferred polymer substrate for the high-frequency communication industry. Aromatic hydroxycarboxylic acids, such as 6-acetoxy-2-naphthoic acid, are used as monomers for synthesizing thermotropic liquid crystal polyester materials. The currently reported method for preparing 6-acetoxy-2-naphthoic acid is mainly to directly acylate 6-hydroxy-2-naphthoic acid with acetic anhydride under acid catalysis. The acid catalysis uses acids such as sulfuric acid and p-toluenesulfonic acid; however, this synthesis method has the disadvantages of high reaction temperature, long reaction time, and high acetic anhydride dosage. Therefore, it is necessary to propose a new synthesis scheme for 6-acetoxy-2-naphthoic acid to solve the shortcomings of the current preparation of 6-acetoxy-2-naphthoic acid, reduce the reaction temperature, and increase the reaction rate. Summary of the invention
[0003] The present invention aims to provide a process for synthesizing a thermotropic liquid crystal polyester material monomer, so as to realize the esterification reaction of 6-hydroxy-2-naphthoic acid and acetic anhydride and synthesize 6-acetoxy-2-naphthoic acid in one step with high yield.
[0004] To achieve the above object, the present invention proposes the following technical scheme: a process for synthesizing a thermotropic liquid crystal polyester material monomer, comprising: adding acetic anhydride to a reaction solution of 6-hydroxy-2-naphthoic acid and an organic base in a stirring state, and continuing the reaction to the reaction end point, and filtering, beating and drying the reaction solution in sequence to obtain a white product 6-acetoxy-2-naphthoic acid;
[0005] The structural formula of the 6-acetoxy-2-naphthoic acid is:
[0006]
[0007] Furthermore, the molar ratio of 6-hydroxy-2-naphthoic acid to acetic anhydride in the reaction solution to which acetic anhydride is added for further reaction is 1.0:1.5 to 1.0:3.5.
[0008] Furthermore, the organic base in the reaction solution is one of diisopropylamine, pyridine, 1,8-diazobispiro[5.4.0]undec-7-ene, triethylamine, n-butylamine, piperidine and 2-tert-butyl-1,1,3,3-tetramethylguanidine.
[0009] Furthermore, the mass of the organic base added to the reaction solution is no more than 3 times the mass of the 6-hydroxy-2-naphthoic acid added.
[0010] Furthermore, the solvent in the reaction solution is one of 1,4-dioxane, acetonitrile, water, acetone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.
[0011] Furthermore, the amount of the solvent in the reaction solution is 3 to 5 times the sum of the mass of 6-hydroxy-2-naphthoic acid and acetic anhydride.
[0012] Furthermore, the solvent used for pulping is one or more of methyl tert-butyl ether, ethyl ether, 1,4-dioxane, acetonitrile, dichloromethane, petroleum ether and ethyl acetate.
[0013] Furthermore, the reaction temperature of the reaction solution to which acetic anhydride is added for further reaction is 15 to 35° C., and the reaction time is 6 to 24 hours.
[0014] Furthermore, the organic base in the reaction solution is diisopropylamine, pyridine or triethylamine.
[0015] Furthermore, the solvent in the reaction solution is water, N,N-dimethylformamide or dimethyl sulfoxide.
[0016] It can be seen from the above technical solutions that the technical solutions of the present invention have the following beneficial effects:
[0017] The invention discloses a synthetic process for a thermotropic liquid crystal polyester material monomer, comprising: adding acetic anhydride to a reaction solution of 6-hydroxy-2-naphthoic acid and an organic base in a stirring state, reacting for 6 to 24 hours under a temperature condition of 15 to 35° C., filtering, beating and drying the reaction solution in sequence to obtain a white product, 6-acetoxy-2-naphthoic acid; wherein the molar ratio of 6-hydroxy-2-naphthoic acid to acetic anhydride in the reaction solution is 1.0:1.5 to 1.0:3.5, and the organic base is selected from diisopropylamine, pyridine, 1,8-diazobispiro[5.4.0]undec-7-ene, triethylamine, n-butylamine, piperidine or 2-tert-butyl-1,1,3,3-tetramethylguanidine. The present invention realizes the esterification reaction of 6-hydroxy-2-naphthoic acid and acetic anhydride by using the method of organic base participation for the first time, and synthesizes 6-acetoxy-2-naphthoic acid with high yield in one step. Compared with the acid-catalyzed preparation of 6-acetoxy-2-naphthoic acid in the prior art, the present invention not only has the advantages of simple synthesis route, simple reaction operation, mild reaction conditions, low cost, etc., but also has high reaction yield of 80% to 90%, and is easy to purify.
[0018] When the 6-acetoxy-2-naphthoic acid prepared by the present invention is used as a monomer for preparing a thermotropic liquid crystal polyester material with excellent mechanical, dielectric and heat-resistant properties, the output of the thermotropic liquid crystal polyester material can be increased and the production cost can be reduced, and the thermotropic liquid crystal polyester material has excellent application prospects in the fields of high-frequency transmission and the like.
[0019] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.
[0020] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings are not drawn to scale according to actual reference objects. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the accompanying drawings, in which:
[0022] Figure 1 The product 6-acetoxy-2-naphthoic acid in Example 1 1 H NMR spectrum;
[0023] Figure 2 The product 6-acetoxy-2-naphthoic acid in Example 1 13 C NMR spectrum;
[0024] Figure 3 The HPLC spectrum of the product 6-acetoxy-2-naphthoic acid in Example 1 is shown in FIG. DETAILED DESCRIPTION
[0025] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meaning understood by people with general skills in the field to which the present invention belongs.
[0026] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular form of "a", "an" or "the" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. "Include" or "comprises" and other similar words mean that the elements or objects appearing before "include" or "comprises" include the features, wholes, steps, operations, elements and / or components listed after "include" or "comprises", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.
[0027] Based on the scheme disclosed in the prior art of directly acylating 6-hydroxy-2-naphthoic acid with acetic anhydride under acid catalysis to obtain 6-acetoxy-2-naphthoic acid, which has the disadvantages of high reaction temperature, long reaction time, and high amount of acetic anhydride, a one-step method for synthesizing 6-acetoxy-2-naphthoic acid with the participation of an organic base is proposed, which is not only simple to operate, but also has mild reaction conditions and high yield.
[0028] Specifically, the process for synthesizing a monomer of a thermotropic liquid crystal polyester material disclosed in the present invention is characterized in that it comprises: adding acetic anhydride to a reaction solution of 6-hydroxy-2-naphthoic acid and an organic base in a stirring state, continuing the reaction to the reaction end point, filtering, beating and drying the reaction solution in sequence to obtain a white product 6-acetoxy-2-naphthoic acid; the reaction formula is shown in the following formula (1); wherein the reaction temperature of the reaction solution in which acetic anhydride is added to continue the reaction is 15 to 35° C., and the reaction time is 6 to 24 hours; the molar ratio of 6-hydroxy-2-naphthoic acid to acetic anhydride in the reaction solution in which acetic anhydride is added to continue the reaction is 1.0:1.5 to 1.0:3.5, and the mass of the organic base added to the reaction solution does not exceed the mass of the organic base added to the 6-hydroxy-2-naphthoic acid. -2-naphthoic acid, the organic base is selected from diisopropylamine, pyridine, 1,8-diazobispiro[5.4.0]undec-7-ene, triethylamine, n-butylamine, piperidine and 2-tert-butyl-1,1,3,3-tetramethylguanidine; the amount of solvent in the reaction solution is 3 to 5 times the mass of 6-hydroxy-2-naphthoic acid and acetic anhydride, and the solvent is selected from 1,4-dioxane, acetonitrile, water, acetone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; in addition, the solvent used for pulping is one or more of methyl tert-butyl ether, ethyl ether, 1,4-dioxane, acetonitrile, dichloromethane, petroleum ether and ethyl acetate.
[0029]
[0030] The following is a further detailed introduction to the synthesis process of the thermotropic liquid crystal polyester monomer disclosed in the present invention in conjunction with specific embodiments and drawings. In which, yield = actual mass of the obtained product / theoretical mass of the obtained product, and conversion rate is the purity of the obtained product.
[0031] Example 1
[0032] Prepare a 100ml three-necked round-bottom flask and mechanical stirring for the reaction device; add 20ml of deionized water and 2.8ml (2.0 equivalents) of triethylamine to the three-necked round-bottom flask, turn on the stirring and add 1.88g 6-hydroxy-2-naphthoic acid; when the reaction liquid is completely converted into black liquid and the 6-hydroxy-2-naphthoic acid is completely dissolved, acetic anhydride is added, first 1 ml of acetic anhydride solution is added, and the reaction color does not change significantly; after reacting for 0.5 hours, 1 ml of acetic anhydride solution is added again to precipitate acetylation products; continue to react for 0.5 hours and then add 1 ml of acetic anhydride solution, a large amount of acetic anhydride products are precipitated, and then continue to react for 5 hours; after the reaction is completed, the reaction liquid is filtered with a 100 ml suction funnel, and the water solution is continuously filtered until it is colorless and transparent; the obtained light yellow solid is added to the dichloromethane solution and stirred, and then filtered to obtain a white solid; the white solid is placed in a 60°C vacuum oven and dried, and finally 6-acetoxy 2-naphthoic acid is obtained, and the obtained product mass is 2.07g, the yield is 90%, and the conversion rate is 100%. Wherein, an appropriate amount of ice cubes are added during the complete dissolution of 6-hydroxy-2-naphthoic acid to prevent the raw material from deteriorating. Figure 1 The product 6-acetoxy-2-naphthoic acid is shown 1 H NMR spectrum, the specific characterization data are as follows: 1 H NMR (400 MHz, DMSO-d6) δ13.10 (s, 1H), 8.65 (s, 1H), 8.19 (d, J = 8.8 Hz, 1H), 8.08–7.96 (m, 2H), 7.77 (d, J = 2.4 Hz, 1H), 7.42 (dd, J = 8.8, 2.4 Hz, 1H), 2.35 (s, 3H); the hydrogen spectrum was consistent with the structure of the expected product. Figure 2 The product 6-acetoxy-2-naphthoic acid is shown 13 C NMR spectrum, the specific characterization data are as follows: 13 C NMR (101 MHz, DMSO-d6) δ169.2, 167.3, 150.0, 135.5, 130.9, 130.4, 130.1, 127.9, 127.8, 125.8, 122.6, 118.6, 20.9; the carbon spectrum was consistent with the structure of the expected product. Figure 3 The HPLC spectrum of the product 6-acetoxy-2-naphthoic acid is shown in MeCN / H2O=1:1, and the HPLC spectrum is consistent with the expected product spectrum structure.
[0033] The difference between Example 2-4 and Example 1 is only that the type of organic base is replaced, and other reaction conditions remain unchanged. The results are shown in Table 1 below. When other organic bases such as diisopropylamine, pyridine, and 1,8-diazobispiro[5.4.0]undec-7-ene (DBU) are used, the conversion rate of the reaction reaches 100% and the yield is 60%-90%.
[0034] Table 1 shows the product yields and reactant conversion rates corresponding to different organic bases in Examples 1-4
[0035] Serial number Organic base Molecular mass / density Reaction dosage Solvents Yield Conversion rate Example 1 Triethylamine 101.19 / 0.728 2.0 equivalent <![CDATA[H2O]]> 90％ 100％ Example 2 Diisopropylamine 101.2 / 0.722 2.0 equivalent <![CDATA[H2O]]> 90％ 100％ Example 3 Pyridine 79.1 / 0.978 2.0 equivalent <![CDATA[H2O]]> 86％ 99％ Example 4 DBU 152.24 / 1.019 2.0 equivalent <![CDATA[H2O]]> 60％ 100％
[0036] When the base used is other organic bases such as n-butylamine, piperidine, 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG), the reaction yield is low, and the reaction conversion rate is only 15%-73%, as shown in Examples 5-7 shown in Table 2 below.
[0037] Table 2 shows the product yields and reactant conversion rates corresponding to different organic bases in Examples 5-7
[0038] Serial number Organic base Molecular mass / density Reaction dosage Solvents Yield Conversion rate Example 5 n-Butylamine 73.14 / 0.74 2.0 equivalent <![CDATA[H2O]]> 78％ 15％ Example 6 Piperidine 85.15 / 0.930 2.0 equivalent <![CDATA[H2O]]> 75％ 25％ Example 7 BTMG 171.28 / 0.85 2.0 equivalent <![CDATA[H2O]]> 50％ 73％
[0039] In Example 8, compared with Example 1, the amount of organic base used in the reaction process was reduced to 1.0 equivalent. The results showed that the conversion rate and yield of the product reaction were reduced, as shown in Table 3 below.
[0040] Table 3 shows the product yield and reactant conversion rate corresponding to different amounts of organic base used in Examples 8 and 9
[0041] Serial number Organic base Molecular mass / density Reaction dosage Solvents Yield Conversion rate Example 1 Triethylamine 101.19 / 0.728 2.0 equivalent <![CDATA[H2O]]> 90％ 100％ Example 8 Triethylamine 101.19 / 0.728 1.0 equivalent <![CDATA[H2O]]> 75％ 85％
[0042] Compared with Example 1, when the solvent of the reaction system is modified to a polar aprotic solvent such as N,N-dimethylformamide and dimethyl sulfoxide, the conversion rate of the reaction remains unchanged, and the yield is reduced to 80% and 84%; when acetone is used as the solvent, the yield of the reaction is 79%; when dichloromethane is used as the solvent, the yield of the reaction is only 48%, as shown in Table 4 below.
[0043] Table 4 shows the product yield and reactant conversion rate corresponding to different amounts of organic base used in Examples 9-12
[0044]
[0045]
[0046] Compared with Example 1, when the organic base used in the replacement reaction is a basic inorganic salt, such as potassium phosphate and potassium carbonate, the conversion rate of the reactant is only 56% and 49% in Comparative Examples 1 and 2; the specific results are shown in Table 5 below. Comparative Example 3 shows the reaction conditions without adding a base, and the results show that the reaction cannot proceed smoothly; in Comparative Example 4, when the reaction is acid-catalyzed, that is, concentrated sulfuric acid is catalyzed and heated at 60°C, the addition amount is 0.1 mL, and 8 mL of acetic anhydride is used as a solvent, the reaction can obtain the monomer with a yield of 98%.
[0047] Table 5 shows the effects of different reaction conditions on product yield and reactant conversion rate of Comparative Examples 1-4
[0048] Serial number Alkaline inorganic salt Molecular weight Addition amount Solvents Yield Conversion rate Comparative Example 1 <![CDATA[K3PO4]]> 212 1.0 equivalent <![CDATA[H2O]]> 80％ 56％ Comparative Example 2 <![CDATA[K2CO3]]> 138 1.0 equivalent <![CDATA[H2O]]> 95％ 49％
[0049] The data of the above-mentioned Examples 1-12 and Comparative Examples 1-4 show that, compared with the traditional acid-catalyzed acetylation reaction, the method for synthesizing 6-acetoxy-2-naphthoic acid with triethylamine is carried out at room temperature, and the amount of acetic anhydride used is half of the amount used for acid catalysis; that is, the synthesis process proposed by the present invention has the advantages of mild reaction conditions, simple operation steps, and low reaction energy consumption, which greatly reduces the production cost of the polymerization monomer and provides an excellent monomer synthesis method for the synthesis of high-performance thermotropic liquid crystal polyester polymerization. In addition, it is found that when the selected organic base is diisopropylamine, the reaction can also obtain the product with a good yield, but the cost of diisopropylamine is higher than that of triethylamine; when an alkaline inorganic salt is used to replace the organic base to participate in the reaction, the conversion efficiency of the reaction is not high, and the introduction of metal ions into the product monomer leads to the D k The value is relatively higher, which affects the performance of the thermotropic liquid crystal polyester material. In addition, the reaction solvent used in the present invention can obtain the acetylated product with a good conversion rate and yield under the same conditions, but when water is used as the solvent, it is cheap and easy to obtain, not only the conversion rate and yield are good, but also the generated wastewater is easy to treat.
[0050] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.
Claims
1. A process for synthesizing a thermotropic liquid crystal polyester monomer, characterized in that: include: Add acetic anhydride to the reaction solution of 6-hydroxy-2-naphthoic acid and organic base under stirring and continue the reaction to the reaction end point, and the reaction solution is filtered, pulped and dried in sequence to obtain a white product 6-acetoxy-2-naphthoic acid; The structural formula of the 6-acetoxy-2-naphthoic acid is:
2. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The molar ratio of 6-hydroxy-2-naphthoic acid to acetic anhydride in the reaction solution to which acetic anhydride is added for further reaction is 1.0:1.5 to 1.0:3.
5.
3. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The organic base in the reaction solution is one of diisopropylamine, pyridine, 1,8-diazobispiro[5.4.0]undec-7-ene, triethylamine, n-butylamine, piperidine and 2-tert-butyl-1,1,3,3-tetramethylguanidine.
4. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The mass of the organic base added to the reaction solution shall not exceed 3 times the mass of the 6-hydroxy-2-naphthoic acid added.
5. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The solvent in the reaction solution is one of 1,4-dioxane, acetonitrile, water, acetone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.
6. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The amount of the solvent in the reaction solution is 3 to 5 times the mass of the total of 6-hydroxy-2-naphthoic acid and acetic anhydride.
7. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The solvent used for pulping is one or more of methyl tert-butyl ether, ethyl ether, 1,4-dioxane, acetonitrile, dichloromethane, petroleum ether and ethyl acetate.
8. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The reaction temperature of the reaction solution to which acetic anhydride is added for continued reaction is 15 to 35° C., and the reaction time is 6 to 24 hours.
9. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The organic base in the reaction solution is diisopropylamine, pyridine or triethylamine.
10. The process for synthesizing the thermotropic liquid crystal polyester monomer according to claim 1, characterized in that: The solvent in the reaction solution is water, N,N-dimethylformamide or dimethyl sulfoxide.