Nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylester and preparation method thereof

Abstract

The invention relates to nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylester and a preparation method thereof, and the nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylester is obtained by introducing a triazine ring-containing branched monomer into a thermoplastic liquid crystal polyarylester main chain structure. The nitrogen-containing polyarylester does not contain halogen, so that the prepared nitrogen-containing polyarylester is a green and environment-friendly flame-retardant material, has the properties of high strength, high modulus and the like of the traditional polyarylester, and is suitable for the fields of electronics, automobiles and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high polymer materials, and particularly relates to a nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylate and a preparation method thereof. BACKGROUND

[0002] Under the double driving of electronic component miniaturization and rapid development of new energy vehicles, the flame-retardant safety standards of engineering plastics continue to improve. The preparation method of traditional flame-retardant materials is to add halogen-containing flame retardants in the synthesis system, but since the halogen-containing flame-retardant materials will produce toxic gases during combustion, which will cause harm to human life and environment, so it is necessary to find an environmentally friendly and non-toxic flame-retardant material to meet the requirements of people on the flame-retardant performance of materials and comply with the concept of green environmental protection.

[0003] Liquid crystal polyarylate has been widely used in connectors, sensors and other precision parts due to its main chain rigidity and molecular ordered orientation characteristics, while having high mechanical strength and a heat distortion temperature of above 300 DEG C. However, the existing solutions for improving the flame-retardant performance of LCP all have significant defects. Chinese patent CN 102675616 B reports a phosphorus-containing flame-retardant polyarylate, and after adding the phosphorus-containing substance, a polyarylate with a carbon residue rate of 45-70% under 700 DEG C in air atmosphere can be obtained. However, the addition amount of the phosphorus-containing substance reaches 40-48 wt%, which not only greatly increases the raw material preparation cost, but also limits the mechanical properties of the material. Chinese patent CN 118206772 A reports a new type of graphene-rich DOPO type phosphorus-containing high-efficiency composite flame-retardant polyarylate, and after adding the composite flame-retardant, a polyarylate with a carbon residue rate of 40-80% under 700 DEG C in air atmosphere can be obtained. Although the proportion of the composite flame-retardant component is only 1-15 wt%, the preparation of the composite flame-retardant involves oxidation with concentrated sulfuric acid, which not only has high production cost, but also produces a large amount of acidic wastewater, which is not environmentally friendly. How to obtain a liquid crystal polyarylate with both flame-retardant property and high mechanical property is a subject with great application value. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylate and a preparation method thereof. The present application provides a polyarylate, characterized in that the structure of the liquid crystal polyarylate is as follows:

[0005]

[0006] wherein Ar is one of ; x+y+z=1, n=8-18.

[0007] Further, the structure of the polyarylate comprises:

[0008]

[0009] one of the group consisting of n = 8-18.

[0010] The application provides a preparation method of polyarylate, comprising:

[0011] The monomer I, the monomer II, the monomer III, acetic anhydride and a catalyst are mixed, and an acetylation reaction is carried out under the condition of a protective gas, and then an ester exchange reaction is carried out, and vacuum is extracted to obtain the liquid crystal polyarylate.

[0012] The monomer I is a branched monomer containing a triazine ring; the monomer II comprises p-hydroxy benzoic acid; the monomer III comprises terephthalic acid; and the catalyst comprises potassium acetate.

[0013] The mass ratio of the branched monomer containing a triazine ring, the p-hydroxy benzoic acid and the terephthalic acid is 15-25:50-70:15-25.

[0014] The feeding amount of the acetic anhydride is 1-1.5 times of the total amount of the hydroxyl groups contained in the monomers.

[0015] The feeding amount of the catalyst is 0.1-0.3 wt% of the total mass of the three monomers.

[0016] The branched monomer containing a triazine ring comprises one of a branched imide monomer AMEA-imide containing a triazine ring and a branched amide monomer MEA-amide containing a triazine ring.

[0017] The MEA-imide is prepared from melamine and 4-hydroxyphthalic anhydride, and the MEA-amide is prepared from melamine and acetic anhydride.

[0018] The monomer I, the monomer II and the monomer III comprise:

[0019] The monomer I is any one of the monomers I-i-ii.

[0020] The acetylation reaction is carried out at a temperature of 135-145℃ for 45-75 min.

[0021] The by-product acetic acid of the acetylation reaction is collected by means of nitrogen blowing and a condensation reflux device.

[0022] The ester exchange reaction is carried out at a temperature rising rate of 0.5-1.5℃ / min, to 300-320℃, and vacuum is extracted, the vacuum degree is kept in the range of 1-3 mbar, the reaction is carried out for 30-60 min, and the vacuum extraction is stopped after the reaction is completed.

[0023] After the preparation reaction of the liquid crystal polyarylate is finished, the product is naturally cooled to room temperature under the protection of nitrogen atmosphere, removed from the reaction container and crushed to obtain the nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylate.

[0024] The application provides application of any of the liquid crystal polyarylates in the fields of electronics and automobiles.

[0025] Beneficial effects

[0026] (1) The application provides a nitrogen-containing flame-retardant thermoplastic liquid crystal polyarylate and a preparation method thereof. The preparation method adopts melt polycondensation, is simple to operate, does not produce three wastes and is suitable for large-scale industrial production.

[0027] (2) The prepared wholly aromatic polymer has high molecular weight, contains nitrogen atoms and does not contain halogens, has good flame-retardant performance and does not produce toxic gases harmful to human bodies and the environment, is an environment-friendly flame-retardant material and can be widely applied in the fields of electronics and automobiles. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 (A) heating curve; (B) cooling curve of the melt crystallization behavior of Examples 1-2 and Comparative Example 1;

[0029] Figure 2 (A) TGA curve; (B) DTG curve of the thermal decomposition curve of Examples 1-2 and Comparative Example 1;

[0030] Figure 3 Polarizing microscope photos of Examples 1-2 and Comparative Example 1;

[0031] Figure 4 Complex viscosity-time-temperature curves of Examples 1-2 and Comparative Example 1;

[0032] Figure 5 MCC test curves of Examples 1-2 and Comparative Example 1. DETAILED DESCRIPTION

[0033] The application will be further described below in combination with specific examples. It should be understood that the examples are only used to illustrate the application and not used to limit the scope of the application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0034] The sources and specification parameters of raw materials and reagents used in the experiments are shown in Table 1.

[0035] Table 1 Raw materials and reagents used in the experiments

[0036] Name Specification Factory p-hydroxybenzoic acid 99％ Zhengzhou Alpha terephthalic acid 99％ Zhengzhou Alpha acetic acid AR Shanghai Lingfeng Chemical Reagent Co., Ltd. acetic anhydride AR Yonghua Chemical Co., Ltd. potassium acetate 99％ Shanghai Aladdin

[0037] Example 1

[0038] A nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate was prepared in this example by the following method: MEA-imide (I-i) (103.6 g, 0.15 mol), p-hydroxybenzoic acid (II) (96.7 g, 0.7 mol), terephthalic acid (III) (24.9 g, 0.15 mol), 107.2 g of acetic anhydride and 0.67 g of potassium acetate were put into a 250 mL three-necked flask, vacuum was applied for 10 min under mechanical stirring until the reaction mixture was free of bubbles on the liquid surface, and nitrogen was introduced. When the device was filled with nitrogen, the reaction mixture was heated to 135°C, and condensed water was introduced for acetylation for 75 min, then heating was carried out at a rate of 0.5°C / min to 300°C, and the by-product acetic acid was collected by nitrogen blowing and condensation reflux device. When the reaction temperature reached 300°C, the viscosity change of the product was observed, and when the product showed a climbing rod state, the nitrogen was turned off, and the reaction was carried out for 60 min under a vacuum of 1 mbar to further collect small molecules of acetic acid in the reaction product. After the reaction was completed, nitrogen was introduced into the device again, and after overnight cooling, the product was taken out of the flask and crushed to obtain a nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate, the structural formula of which is as follows:

[0039]

[0040] wherein n = 8-17.

[0041] Example 2

[0042] A nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate was prepared in this example by the following method: MEA-amide (I-ii) (63.1 g, 0.25 mol), p-hydroxybenzoic acid (II) (69.1 g, 0.5 mol), terephthalic acid (III) (41.5 g, 0.25 mol), 51.1 g of acetic anhydride and 0.17 g of potassium acetate were put into a 250 mL three-necked flask, vacuum was applied for 10 min under mechanical stirring until the reaction mixture was free of bubbles on the liquid surface, and nitrogen was introduced. When the device was filled with nitrogen, the reaction mixture was heated to 145°C, and condensed water was introduced for acetylation for 45 min, then heating was carried out at a rate of 1.5°C / min to 320°C, and the by-product acetic acid was collected by nitrogen blowing and condensation reflux device. When the reaction temperature reached 320°C, the viscosity change of the product was observed, and when the product showed a climbing rod state, the nitrogen was turned off, and the reaction was carried out for 30 min under a vacuum of 3 mbar to further collect small molecules of acetic acid in the reaction product. After the reaction was completed, nitrogen was introduced into the device again, and after overnight cooling, the product was taken out of the flask and crushed to obtain a nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate, the structural formula of which is as follows:

[0043]

[0044] wherein n = 9-18.

[0045] Comparative Example 1

[0046] A thermoplastic liquid crystalline polyarylate was prepared in this comparative example as follows: m-Hydroxybenzoic acid (31.5 g, 0.25 mol), p-hydroxybenzoic acid (II) (69.1 g, 0.5 mol), terephthalic acid (III) (41.5 g, 0.25 mol), 51.1 g of acetic anhydride and 0.14 g of potassium acetate were charged into a 250 mL three-necked flask, and vacuum was applied for 10 min under mechanical stirring until the reaction mixture was free of air bubbles, and then nitrogen was introduced. When the device was filled with nitrogen, the reaction mixture was heated to 140°C, and water was introduced for acetylation for 60 min, and then heated to 310°C at a rate of 1°C / min, and the by-product acetic acid was collected by nitrogen blowing and condensation reflux device. When the reaction temperature reached 310°C, the viscosity of the product was observed, and when the product showed a climbing rod state, the nitrogen was turned off, and the reaction was continued for 45 min under a vacuum of 2 mbar to further collect small molecules of acetic acid in the reaction product. After the reaction was completed, nitrogen was introduced into the device again, and after overnight cooling, the product was taken out of the flask and crushed to obtain a nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate, the structure of which is as follows:

[0047]

[0048] wherein n = 8-18.

[0049] Performance tests were conducted on Examples 1-2 and Comparative Example 1

[0050] (1) Differential scanning calorimetry test (DSC)

[0051] The test procedure was as follows: under a nitrogen atmosphere, the temperature was raised from 40°C to 400°C at a rate of 20°C / min, held for 2 min, then lowered to 40°C at a rate of 20°C / min, held for 2 min, and after eliminating the thermal history, the same temperature raising and lowering procedure was repeated, and the liquid crystal phase transition temperature was T K-N .

[0052] (2) Thermogravimetric analysis test (TGA)

[0053] The test procedure was as follows: under a nitrogen atmosphere, the temperature was raised from 40°C to 600°C at a rate of 10°C / min. The temperature corresponding to 5% weight loss was taken as the thermal decomposition temperature (T d 5％ ).

[0054] (3) Hot stage polarizing microscope test (POM)

[0055] From room temperature (25°C), temperature was increased at 20°C / min, and a certain shear force was applied when the beginning of melting was observed, and the transition of liquid crystal phase was observed.

[0056] (4) Rheological behavior test

[0057] The test procedure was as follows: air atmosphere, temperature was increased from 50°C to 370°C at a rate of 3°C / min, frequency was 1 Hz, and amplitude was 0.1%.

[0058] (5) Flame retardant performance test

[0059] Heat release rate was tested by micro calorimeter (MCC), sample mass was 5-10 mg, and the test was carried out in an O2 / N2 mixed gas atmosphere.

[0060] Limiting oxygen index test (LOI) was carried out according to GB / T 2406.2-2009 standard, top surface ignition method was used for determination, and the burning length was observed. If the sample continued to burn for more than 180 s or the burning flame spread to the clamp, it was recorded as "X" indicating burning. If the sample could not be ignited, or was extinguished after a period of time, it was recorded as "O" indicating non-combustion. By taking the oxygen index domain value of combustion and non-combustion to continue the test, the limiting oxygen index value was finally obtained.

[0061] Gaseous products released during thermal decomposition were tested by thermogravimetric infrared spectrometer (TG-IR). Sample mass: 5-10 mg; test conditions: heated from 30°C to 700°C in air atmosphere, temperature increasing rate was 10°C / min, and infrared wavelength range: 400-4000 cm -1 .

[0062] Examples 1-2 and Comparative Example 1 were subjected to DSC test in nitrogen atmosphere at a temperature increasing / decreasing rate of 20°C / min, see Figure 1 and Table 2: the thermoplastic liquid crystalline polyarylate obtained from Comparative Example 1 had a glass transition at 112°C, i.e. its T g = 112°C; the nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylates obtained from Examples 1-2 did not have obvious glass transition steps.

[0063] Examples 1-2 and Comparative Example 1 were subjected to TGA test at a temperature increasing rate of 10°C / min, see Figure 2 and Table 2: the T d 5％ of the thermoplastic liquid crystalline polyarylate obtained from Comparative Example 1 was 490°C; the nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylates obtained from Examples 1-2 had lower thermal decomposition temperatures (T d 5％ ) compared with Comparative Example 1, which were 420°C and 440°C respectively, which was helpful for the initial formation of carbon layer.

[0064] The polarizing test was performed by using hot stage polarizing microscope for Examples 1-2 and Comparative Example 1, see Figure 3 After being heated to the liquid crystal phase transition temperature, both of them showed nematic phase schlieren texture.

[0065] The melt viscosity of Examples 1-2 and Comparative Example 1 was measured by rheological test, see Figure 4 and Table 2: the melt viscosity of the thermoplastic liquid crystalline polyarylate obtained in Comparative Example 1 was 1.87 x 10 6 Pa·s; the melt viscosity of the nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate obtained in Examples 1-2 was significantly reduced, being 0.6 x 10 6 Pa·s and 0.81 x 10 6 Pa·s respectively, indicating that the introduction of MEA-imide into the liquid crystal main chain improved the processability of the thermoplastic liquid crystalline polyarylate, and made it have a wider processing window.

[0066] The flame-retardant property of Examples 1-2 and Comparative Example 1 was measured by limiting oxygen index (LOI) test, see Figure 5 and Table 2: the temperature corresponding to the peak heat release rate of the thermoplastic liquid crystalline polyarylate obtained in Comparative Example 1 was 534℃, and the LOI value was 33.8%; compared with Comparative Example 1, the temperature corresponding to the peak heat release rate of the nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate obtained in Example 1 was reduced (523℃), and the LOI value was increased (44.6%), indicating that the introduction of MEA-imide effectively improved the flame-retardant property of the liquid crystalline polyarylate. This is because the formed carbon residue after combustion is more compact and complete, which improves the graphitization degree of the liquid crystalline polyarylate. In addition, the TG-IR results show that a large amount of non-combustible gases such as CO2, NH3 and H2O can be released during the combustion process of the examples, and the synergistic effect of the condensed phase and the gas phase makes the flame-retardant property of the liquid crystalline polyarylate effectively improved.

[0067] The technical solution adopts a simple and easy-to-control one-pot method for melt polycondensation, avoiding the use of strong corrosive solvents in traditional methods and reducing the emission of harmful waste. The branched monomer containing triazine ring introduced in the examples not only improves the flame-retardant efficiency of the liquid crystalline polyarylate, but also avoids the toxicity problem of traditional halogen-based flame retardants. The nitrogen-containing flame-retardant thermoplastic liquid crystalline polyarylate of the present application has a clean synthesis process, meets the demand of sustainable development, and is suitable for electronic, automotive and other fields.

[0068] Table 2 Physical property table of Examples 1-2 and Comparative Example 1

[0069]

Claims

1. A polyarylate, characterized in that The structure of the polyarylate is shown below: Where Ar is One of the following; x+y+z=1, n=8~18.

2. The polyarylate according to claim 1, characterized in that The structure of the polyarylate comprises: One of the following, wherein n=8~18.

3. A method for preparing polyarylate, comprising: The monomer I, monomer II, monomer III, acetic anhydride and a catalyst are mixed, and an acetylation reaction is carried out under protective gas conditions, followed by an ester exchange reaction, while vacuuming to obtain a liquid crystal polyarylate.

4. The preparation method according to claim 3, characterized in that The monomer I comprises a triazine ring-branched monomer; the monomer II comprises p-hydroxybenzoic acid; the monomer III comprises terephthalic acid; and the catalyst comprises potassium acetate.

5. The preparation method according to claim 3, characterized in that: The molar ratio of the triazine ring branching monomer, p-hydroxybenzoic acid, and terephthalic acid is 15-25:50-70:15-25; The amount of acetic anhydride added is 1 to 1.5 times the amount of the total hydroxyl substances contained in the monomer; The catalyst feed amount is 0.1-0.3 wt% of the total weight of the three monomer feeds.

6. The preparation method according to claim 3, characterized in that: The triazine ring-branched monomer includes one of a triazine ring-branched imide monomer MEA-imide and a triazine ring-branched amide monomer MEA-amide.

7. The preparation method according to claim 3, characterized in that: The acetylation reaction temperature is 135-145° C., and the reaction time is 45-75 minutes.

8. The preparation method according to claim 3, characterized in that: The transesterification reaction is carried out while vacuuming: the temperature is raised at a heating rate of 0.5-1.5°C / min to 300-320°C for the transesterification reaction, and vacuuming is carried out at the same time, with the vacuum range maintained at 1-3 mbar for 30-60 minutes.

9. Use of the polyarylate according to any one of claims 1 to 2 in the fields of electronics and automobiles.

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