阅读说明：本技术 一种高耐热液晶聚酯酰胺薄膜及其制备方法 (High-heat-resistance liquid crystal polyester amide film and preparation method thereof ) 是由 王阳 任忠平 李东伟 于 2021-08-31 设计创作，主要内容包括：本发明属于高分子聚合物技术领域,具体涉及一种高耐热液晶聚酯酰胺薄膜及其制备方法。本发明的液晶聚酯酰胺薄膜包括液晶共聚物,所述的液晶共聚物由以下单体制成：对羟基苯甲酸、6-羟基-2-萘甲酸、对苯二甲酸、2-氨基-6-羟基苯并噻唑。制备步骤为预聚、固相缩聚、混炼、熔融挤出、牵引、收卷、热处理。通过引入新型单体2-氨基-6-羟基苯并噻唑,获得薄膜的拉伸强度、介电常数及介电损耗因子皆可与现有液晶薄膜相媲美,还可有效提高液晶共聚物薄膜的耐热稳定性,制得的液晶共聚物薄膜熔点可达340℃以上,经298℃、10s、3次漂锡试验无变形变色。(The invention belongs to the technical field of high molecular polymers, and particularly relates to a high-heat-resistance liquid crystal polyesteramide film and a preparation method thereof. The liquid crystal polyester amide film comprises a liquid crystal copolymer, wherein the liquid crystal copolymer is prepared from the following monomers: p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole. The preparation steps comprise prepolymerization, solid-phase polycondensation, mixing, melt extrusion, traction, rolling and heat treatment. By introducing the novel monomer 2-amino-6-hydroxybenzothiazole, the tensile strength, dielectric constant and dielectric loss factor of the obtained film can be comparable with those of the existing liquid crystal film, the heat-resistant stability of the liquid crystal copolymer film can be effectively improved, the melting point of the prepared liquid crystal copolymer film can reach more than 340 ℃, and the film does not deform or discolor after 298 ℃, 10s and 3 times of tin bleaching tests.)

1. A high heat-resistant liquid crystal polyester amide film comprises a liquid crystal polymer, and is characterized in that the liquid crystal copolymer is prepared from the following monomers: the composite material comprises p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid and 2-amino-6-hydroxybenzothiazole, wherein the molar percentage of the p-hydroxybenzoic acid is 60.5-70 mol%, the molar percentage of the 6-hydroxy-2-naphthoic acid is 24-36.7 mol%, the sum of the molar percentages of the terephthalic acid and the 2-amino-6-hydroxybenzothiazole is 2.8-6.0 mol%, and the sum of the molar percentages of the four monomers is equal to 100 mol%.

2. A method for preparing the highly heat-resistant liquid-crystalline polyesteramide film according to claim 1, wherein the method comprises the steps of:

s1: putting monomers of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, an acetylation reagent of acetic anhydride, a catalyst of 2-dimethylaminopyridine and antioxidant tin powder into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and performing solid phase polycondensation in a nitrogen atmosphere to prepare high polymer liquid crystal polyarylate amide;

s3: mixing polyarylate amide by a screw extruder, and exhausting; melt extrusion, side blowing cooling, traction and rolling to prepare a polyesteramide nascent film;

s4: and carrying out heat treatment on the nascent film to obtain a polyesteramide finished film.

3. The method of preparing a highly heat-resistant liquid-crystalline polyesteramide film according to claim 2, wherein the amount of acetic anhydride added in step S1 is 1.0 to 3.0 times the total number of moles of hydroxyl groups and amine groups in p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole.

4. The method of preparing a highly heat-resistant liquid crystal polyesteramide film according to claim 2, wherein the amount of 2-dimethylaminopyridine added in step S1 is 10-500ppm based on the total weight of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and 2-amino-6-hydroxybenzothiazole.

5. The method of preparing a highly heat-resistant liquid crystalline polyesteramide film according to claim 2, wherein the tin powder is added in an amount of 0.2% to 0.5% based on the total weight of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole in step S1.

6. The method for preparing a highly heat-resistant liquid crystal polyesteramide film according to claim 2, wherein said step S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 130-150 ℃ for 2-9 h; heating to 320 ℃ at the speed of 0.1-1.0 ℃/min, and preserving the heat for 2-3 h; flushing 0.1-1.0MPa nitrogen into the polymerization kettle, discharging the reaction materials through a discharge valve with 8-10 holes with the diameter of 2-4mm, crushing, sieving with a 20-30 mesh sieve, and drying at the temperature of 140 ℃ for 1-3h to obtain the prepolymer.

7. The method for preparing a highly heat-resistant liquid crystal polyesteramide film according to claim 2, wherein said step S2 is specifically: and carrying out solid-phase polycondensation on the prepared prepolymer in a rotary kiln at 195-320 ℃ in the nitrogen atmosphere for 12-48h to prepare the liquid crystal polyester amide.

8. The method for preparing a highly heat-resistant liquid crystalline polyesteramide film as claimed in claim 2, wherein the screw extruder extruding temperature in step S3 is 280-360 ℃.

9. The method of preparing a highly heat-resistant liquid-crystalline polyesteramide film according to claim 2, wherein the cross-blowing temperature in step S3 is 20-50 ℃.

10. The method as claimed in claim 2, wherein the heat treatment temperature in step S4 is 200-300 ℃ and the time is 8-60 h.

Technical Field

The invention belongs to the technical field of high-molecular copolymers, and particularly relates to a high-heat-resistance liquid crystal polyester amide film and a preparation method thereof.

Background

With the arrival of the 5G era, higher requirements on high frequency and high transmission speed are put forward by photoelectric, aerospace, national defense and mobile communication. Liquid Crystal copolymers (Liquid Crystal polymers) can almost maintain constant dielectric constant in the whole radio frequency range up to 110GHz, have good consistency and very small tangent loss, are only increased to 0.0045 even at 110GHz, are very suitable for millimeter wave application, and thin film products prepared by the Liquid Crystal copolymers are favored in the 5G field.

In order to meet the application requirements in the 5G field, the development of a liquid crystal copolymer with a lower dielectric constant and a lower dielectric loss factor and a corresponding film product is far from enough, the high temperature resistance of the liquid crystal copolymer is equally important, and the use stability of a film material can be directly influenced. At present, researches on improving the high temperature resistance of a film from resin raw materials are few, and mainly by adding metal elements, for example, a patent US6755991 discloses a liquid crystal polyester composition comprising at least one aromatic dicarboxylic acid, at least one naphthalene ring-containing carboxylic acid and at least one alkali metal with the content of 1-1000 ppm, the liquid crystal polyester composition prepared by the invention has improved whiteness and impact strength, and the effect description mentions that the heat resistance is improved, but does not describe any reference data on the improvement of the heat resistance; for another example, patent CN105907058B discloses that adding 0.1-300ppm by weight of metallic strontium element into a resin composition improves its heat resistance stability, and this invention needs to strictly control the addition amount of metallic strontium element, which makes the operation difficult, and therefore, the content of strontium element in the composition needs to be specially measured, which makes the process complicated, and the patent only mentions that the liquid crystal resin can be made into a film product, but does not describe how to make the film and how to make the film product.

At present, the melting point of the existing heat-resistant liquid crystal polymer film is generally about 310 ℃, the melting point can pass 288 ℃, 10s and 3 times of tin bleaching tests, and the melting point of only one highly heat-resistant liquid crystal polymer film which is developed happily can reach 335 ℃, but the tin bleaching test condition is not disclosed. In view of the above problems, the inventors have introduced a novel monomer copolymerization mode to improve the heat resistance of the liquid crystal polymer, so that the melting point of the liquid crystal polymer film can be raised to 340-.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provide a high-heat-resistance liquid crystal copolymer film, and the heat resistance of the liquid crystal copolymer film can be effectively improved by introducing a novel monomer 2-amino-6-hydroxybenzothiazole into the liquid crystal copolymer, so that the stability of the liquid crystal copolymer film is improved, and the requirements of more high-frequency high-speed transmission application scenes are met.

The above object of the present invention can be achieved by the following technical solutions: a high heat-resistant liquid crystal polyester amide film comprising a liquid crystal copolymer made from the following monomers: the composite material comprises p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid and 2-amino-6-hydroxybenzothiazole, wherein the molar percentage of the p-hydroxybenzoic acid is 60.5-70 mol%, the molar percentage of the 6-hydroxy-2-naphthoic acid is 24-36.7 mol%, the sum of the molar percentages of the terephthalic acid and the 2-amino-6-hydroxybenzothiazole is 2.8-6.0 mol%, and the sum of the molar percentages of the four monomers is equal to 100 mol%.

Preferably, the molar ratio of terephthalic acid to 2-amino-6-hydroxybenzothiazole is 1: 1.

the second purpose of the invention is to provide a preparation method of the liquid crystal polyester amide film, which specifically comprises the following steps:

s1: putting monomers of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, an acetylation reagent of acetic anhydride, a catalyst of 2-dimethylaminopyridine and antioxidant tin powder into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and performing solid-phase polycondensation in a nitrogen atmosphere to obtain high-molecular liquid crystal polyesteramide;

s3: mixing the polyesteramide through a screw extruder, and exhausting; melt extrusion, side blowing cooling, traction and rolling to prepare a polyesteramide nascent film;

s4: and carrying out heat treatment on the prepared nascent film to obtain the polyester amide finished film.

The weight average molecular weight of the liquid crystal polyester amide prepared by the invention is (3.1-4.0) × 10⁴。

Preferably, the amount of acetic anhydride added is 1.0 to 3.0 times the total number of moles of hydroxyl groups and amine groups in p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole.

Preferably, the 2-dimethylaminopyridine is added in an amount of 10 to 500ppm based on the total weight of the p-hydroxybenzoic acid, the 6-hydroxy-2-naphthoic acid, the terephthalic acid and the 2-amino-6-hydroxybenzothiazole.

Preferably, the addition amount of the tin powder is 0.2-0.5 percent of the total weight of the p-hydroxybenzoic acid, the 6-hydroxy-2-naphthoic acid, the terephthalic acid and the 2-amino-6-hydroxybenzothiazole.

Preferably, the step S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 130-150 ℃ for 2-9 h; heating to 320 ℃ at the speed of 0.1-1.0 ℃/min, and keeping the temperature for 2-3 h; flushing 0.1-1.0MP nitrogen into the polymerization kettle, discharging the reaction materials through a discharge valve with 8-10 holes with the diameter of 2-4mm, crushing, sieving with a 20-30 mesh sieve, and drying at the temperature of 140 ℃ for 1-3h to obtain the prepolymer.

Preferably, the step S2 is specifically: and carrying out solid-phase polycondensation on the prepared prepolymer in a rotary kiln at 195-320 ℃ in the nitrogen atmosphere for 12-48h to prepare the liquid crystal polyester amide.

Preferably, the extrusion temperature of the screw extruder in the step S3 is 280-360 ℃.

Preferably, the cross-blowing temperature in the step S3 is 20 to 50 ℃.

Preferably, the heat treatment temperature in the step S4 is 200-300 ℃, and the time is 8-60 h.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, by introducing the novel monomer 2-amino-6-hydroxybenzothiazole, the tensile strength, the dielectric constant and the dielectric loss factor of the liquid crystal copolymer film can be compared favorably with those of the existing liquid crystal copolymer film, more remarkably, the heat resistance of the liquid crystal copolymer film is effectively improved, the melting point of the liquid crystal copolymer film is increased to 340-345 ℃, and the liquid crystal copolymer film is free from deformation and discoloration after being subjected to tin bleaching tests at 298 ℃, 10s and 3 times, so that the requirements of application scenes at higher temperature can be met.

Detailed Description

The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the present invention is not limited to these examples. In the present invention, unless otherwise specified, the starting materials or reagents used are those conventionally used, and the methods used are those conventionally used.

Detailed description of the preferred embodiments

A high heat-resistant liquid crystal polyester amide film comprising a liquid crystal copolymer made from the following monomers: the composite material comprises p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid and 2-amino-6-hydroxybenzothiazole, wherein the molar percentage of the p-hydroxybenzoic acid is 60.5-70 mol%, the molar percentage of the 6-hydroxy-2-naphthoic acid is 24-36.7 mol%, the sum of the molar percentages of the terephthalic acid and the 2-amino-6-hydroxybenzothiazole is 2.8-6.0 mol%, and the sum of the molar percentages of the four monomers is equal to 100 mol%.

The preparation method of the liquid crystal polyester amide film comprises the following steps:

s1: putting monomers of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, an acetylation reagent of acetic anhydride, a catalyst of 2-dimethylaminopyridine and antioxidant tin powder into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and performing solid-phase polycondensation in a nitrogen atmosphere to obtain high-molecular liquid crystal polyesteramide;

s3: mixing the polyesteramide through a screw extruder, and exhausting; melt extrusion, side blowing cooling, traction and rolling to prepare a polyesteramide nascent film;

s4: and carrying out heat treatment on the prepared nascent film to obtain the polyester amide finished film.

In the above production method, the amount of acetic anhydride added is preferably 1.0 to 3.0 times the total number of moles of hydroxyl groups and amine groups in p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole.

In the above production method, the 2-dimethylaminopyridine is preferably added in an amount of 10 to 500ppm based on the total weight of the p-hydroxybenzoic acid, the 6-hydroxy-2-naphthoic acid, the terephthalic acid and the 2-amino-6-hydroxybenzothiazole.

In the above preparation method, the amount of tin powder added is preferably 0.2% to 0.5% of the total weight of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and 2-amino-6-hydroxybenzothiazole.

In the above preparation method, preferably, S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 130-150 ℃ for 2-9 h; heating to 320 ℃ at the speed of 0.1-1.0 ℃/min, and keeping the temperature for 2-3 h; flushing 0.1-1.0MPa nitrogen into the polymerization kettle, discharging the reaction materials through a discharge valve with 8-10 holes with the diameter of 2-4mm, crushing, sieving with a 20-30 mesh sieve, and drying at the temperature of 140 ℃ for 1-3h to obtain the prepolymer.

In the above preparation method, preferably, S2 is specifically: and carrying out solid-phase polycondensation on the prepared prepolymer in a rotary kiln at 195-320 ℃ in the nitrogen atmosphere for 12-48h to prepare the liquid crystal polyester amide.

In the above preparation method, the extrusion temperature of the screw extruder in the step S3 is preferably 280-360 ℃.

In the above production method, preferably, the cross-air blowing temperature in the step S3 is 20 to 50 ℃.

In the preparation method, the heat treatment temperature in the step S4 is preferably 200-300 ℃, and the time is preferably 8-60 h.

The embodiments of the present invention will be described in detail by the following examples and comparative examples. The monomer formulations of examples 1-4 of the invention are shown in Table 1:

table 1: monomer ratios in examples 1-4

Example 1

Putting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, acetic anhydride accounting for 1.0 time of the total mole number of hydroxyl and amino in the p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole, 2-dimethylaminopyridine accounting for 10ppm of the total weight of the four monomers and tin powder accounting for 0.2 percent of the total weight of the four monomers into a Hastelloy polymerization kettle according to the proportion of No. 1 monomer, and then keeping the mixture at 130 ℃ for 2 hours; heating to 300 ℃ at the speed of 0.1 ℃/min, and keeping the temperature for 2 h; flushing 0.1MPa nitrogen into a polymerization kettle, discharging the reaction materials through an 8-hole discharge valve with the diameter of 2mm, crushing, sieving with a 20-mesh sieve, and drying at 140 ℃ for 1h to obtain a prepolymer;

subjecting the obtained prepolymer to solid phase polycondensation in a rotary kiln at 195 deg.C for 12h in nitrogen atmosphere to obtain liquid crystal polyesteramide with weight average molecular weight of 3.35 × 10⁴；

Mixing, exhausting and melting the liquid crystal polyester amide at 280 ℃ by a double-screw extruder; extruding the obtained melt out of a circular die with the diameter of 40mm and the die gap interval of 0.5mm, carrying out blowing under the conditions of the blowing ratio of 5.5 and the drawing ratio of 1.9, carrying out side blowing at 20 ℃ for cooling and shaping, drawing and rolling to obtain a polyesteramide primary film with the average thickness of 50 mu m;

heating the polyester amide nascent film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the sheet at a speed of 3m/min in a hot rolling device equipped with a heat-resistant rubber roller and a heating metal roller to prepare a laminate of a thermoplastic liquid crystal polymer film/aluminum foil, and placing the laminate in a heat treatment furnace at 290 ℃ for 30 seconds; under the protection of nitrogen, the mixture is subjected to heat treatment at 200 ℃ for 8 hours; thereafter, the aluminum foil was peeled off to obtain a polyesteramide film having an average thickness of 50 μm.

Example 2

Putting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, acetic anhydride accounting for 2 times of the total mole number of hydroxyl and amino in the p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole, 2-dimethylamino pyridine accounting for 100ppm of the total weight of the four monomers and tin powder accounting for 0.3 percent of the total weight of the four monomers into a Hastelloy polymerization kettle according to the proportion of No. 2 monomers, and then keeping the mixture at 140 ℃ for 5 hours; heating to 305 ℃ at the speed of 0.4 ℃/min, and keeping the temperature for 2 h; flushing 0.5MPa nitrogen into a polymerization kettle, discharging the reaction materials through an 8-hole discharge valve with the diameter of 3mm, crushing, sieving with a 25-mesh sieve, and drying at 145 ℃ for 2 hours to obtain a prepolymer;

subjecting the obtained prepolymer to solid phase polycondensation in a rotary kiln at 240 ℃ for 24h under nitrogen atmosphere to obtain liquid crystal polyesteramide with weight average molecular weight of 3.42 × 10⁴；

Mixing and exhausting the prepared liquid crystal polyester amide at 300 ℃ by a double-screw extruder; extruding the obtained melt out of a circular die with the diameter of 40mm and the die gap interval of 0.5mm, carrying out blowing under the conditions of the blowing ratio of 5.5 and the drawing ratio of 1.9, carrying out side blowing at 20 ℃ for cooling and shaping, drawing and rolling to obtain a polyesteramide primary film with the average thickness of 50 mu m;

heating the polyester amide nascent film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the sheet at a speed of 3m/min in a hot rolling device equipped with a heat-resistant rubber roller and a heating metal roller to prepare a laminate of a thermoplastic liquid crystal polymer film/aluminum foil, and placing the laminate in a heat treatment furnace at 290 ℃ for 30 seconds; under the protection of nitrogen, the mixture is subjected to heat treatment at 220 ℃ for 24 hours; thereafter, the aluminum foil was peeled off to obtain a polyesteramide film having an average thickness of 50 μm.

Example 3

Putting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, acetic anhydride accounting for 2.4 times of the total mole number of hydroxyl and amino in the p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole, 2-dimethylaminopyridine accounting for 400ppm of the total weight of the four monomers and tin powder accounting for 0.4 percent of the total weight of the four monomers into a Hastelloy polymerization kettle according to the proportion of No. 3 monomers, and then keeping the mixture at 145 ℃ for 7 hours; heating to 310 ℃ at the speed of 0.8 ℃/min, and preserving heat for 3 h; flushing 0.8MPa nitrogen into a polymerization kettle, discharging the reaction materials through a 10-hole discharge valve with the diameter of 3mm, crushing, sieving with a 30-mesh sieve, and drying at 150 ℃ for 3 hours to obtain a prepolymer;

subjecting the obtained prepolymer to solid phase polycondensation in a rotary kiln at 300 ℃ for 36h under nitrogen atmosphere to obtain liquid crystal polyesteramide with weight average molecular weight of 3.76 × 10⁴；

Mixing the prepared liquid crystal polyester amide at 330 ℃ by a double-screw extruder, and exhausting; extruding the obtained melt out of a circular die with the diameter of 40mm and the die gap interval of 0.5mm, carrying out blowing under the conditions of the blowing ratio of 5.5 and the drawing ratio of 1.9, carrying out side blowing at 20 ℃ for cooling and shaping, drawing and rolling to obtain a polyesteramide primary film with the average thickness of 50 mu m;

heating the polyester amide nascent film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the sheet at a speed of 3m/min in a hot rolling device equipped with a heat-resistant rubber roller and a heating metal roller to prepare a laminate of a thermoplastic liquid crystal polymer film/aluminum foil, and placing the laminate in a heat treatment furnace at 290 ℃ for 30 seconds; under the protection of nitrogen, the mixture is subjected to heat treatment at 250 ℃ for 48 hours; thereafter, the aluminum foil was peeled off to obtain a polyesteramide film having an average thickness of 50 μm.

Example 4

Putting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 2-amino-6-hydroxybenzothiazole, acetic anhydride accounting for 3.0 times of the total molar number of hydroxyl and amino in the p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 2-amino-6-hydroxybenzothiazole, 2-dimethylaminopyridine accounting for 500ppm of the total weight of the four monomers and tin powder accounting for 0.5 percent of the total weight of the four monomers into a Hastelloy polymerization kettle according to the proportion of No. 4 monomers, and then keeping the mixture at 150 ℃ for 9 hours; heating to 320 ℃ at the speed of 1.0 ℃/min, and preserving heat for 3 h; flushing 1.0MPa nitrogen into a polymerization kettle, discharging the reaction materials through a 10-hole discharge valve with the diameter of 4mm, crushing, sieving with a 30-mesh sieve, and drying at 160 ℃ for 3 hours to obtain a prepolymer;

subjecting the obtained prepolymer to solid phase polycondensation in a rotary kiln at 320 ℃ for 48h under nitrogen atmosphere to obtain liquid crystal polyesteramide with weight average molecular weight of 4.0 × 10⁴；

Mixing and exhausting the prepared liquid crystal polyester amide at 360 ℃ by a double-screw extruder; extruding the obtained melt out of a circular die with the diameter of 40mm and the die gap interval of 0.5mm, carrying out blowing under the conditions of the blowing ratio of 5.5 and the drawing ratio of 1.9, carrying out side blowing at 20 ℃ for cooling and shaping, drawing and rolling to obtain a polyesteramide primary film with the average thickness of 50 mu m;

heating the polyester amide nascent film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the sheet at a speed of 3m/min in a hot rolling device equipped with a heat-resistant rubber roll and a heated metal roll to prepare a laminate of a thermoplastic liquid crystal polymer film/aluminum foil, and laminating the laminate on a pressPlacing the furnace in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 300 ℃ for 60 hours; thereafter, the aluminum foil was peeled off to obtain a polyesteramide film having an average thickness of 50 μm.

Comparative example 1

This comparative example differs from example 3 only in that the mole percentages of the four monomers are 68 mol% of p-hydroxybenzoic acid, 25 mol% of 6-hydroxy-2-naphthoic acid, 3.5 mol% of terephthalic acid, and 3.5 mol% of 2-amino-6-hydroxybenzothiazole, respectively, and the rest is the same as example 3; the weight average molecular weight of the prepared liquid crystal polymer is 3.43 multiplied by 10⁴。

Comparative example 2

This comparative example differs from example 3 only in that the molar amounts of the four monomers were 68 mol% of p-hydroxybenzoic acid, 30 mol% of 6-hydroxy-2-naphthoic acid, 1 mol% of terephthalic acid, and 1 mol% of 2-amino-6-hydroxybenzothiazole, respectively, and the other was the same as example 3; the weight average molecular weight of the prepared liquid crystal polymer is 3.31 multiplied by 10⁴。

Comparative example 3

This comparative example differs from example 3 only in that the monomer 2-amino-6-hydroxybenzothiazole was replaced with an equimolar percentage of p-aminophenol, the rest being the same as example 3; the weight average molecular weight of the prepared liquid crystal polymer is 3.2 multiplied by 10⁴。

Comparative example 4

The comparative example is different from the example 3 only in that the existing conventional catalyst zinc acetate is adopted, and the rest is the same as the example 3; the weight average molecular weight of the prepared liquid crystal polymer is 2.3 multiplied by 10⁴。

The following performance tests were conducted for the above examples and comparative examples, and the test results are shown in table 2:

(1) tensile strength: ASTM D882;

(2) dielectric constant and dielectric dissipation factor: SPDR,15 GHz;

(3) melting point: after the test LCP film was completely melted by heating at a rate of 20 ℃/min, the melt was quenched at a rate of 50 ℃/min to 50 ℃, and then heated at a rate of 20 ℃/min, and the position of the endothermic peak appearing at that time was recorded as the melting point of the film.

(4) And (3) testing thermal stress:

A. cutting the film into test samples of 5cm multiplied by 5cm, preparing 2 samples from the same film product, dividing the samples into 2 groups according to the test temperature from low to high, and marking the samples;

B. placing a sample to be tested in an oven, baking for 6h at the temperature of 120 ℃, taking out, and placing in a dryer to cool to room temperature;

C. removing the test sample from the desiccator with a long-handled clamp;

D. adjusting the temperature of the tin furnace to 288 +/-1 ℃, removing tin slag on the surface of the tin furnace, placing a sample on the surface of the tin furnace, standing for 10s +/-1 s, taking out, and naturally cooling to room temperature to finish the primary tin floating process;

E. d, repeating the marked sample to finish the tin bleaching process for 3 times, and then taking out the sample to be cooled and cleaning the sample;

F. observing whether the sample film has deformation discoloration or not, wherein the deformation discoloration is recorded by using a check mark, and the deformation discoloration is recorded by using an X;

G. the tin furnace temperature was adjusted to 298 ℃. + -. 1 ℃ and the D, E, F procedure was repeated.

Table 2: results of property test of the liquid-crystalline polyesteramide films obtained in examples 1 to 4 and comparative examples 1 to 4:

as can be seen from Table 2, the melting point of the film prepared by the conventional formula is 308 ℃, the film can pass a tin bleaching test at 288 ℃ but cannot pass a tin bleaching test at a higher temperature when a high temperature resistance test is carried out, the finished film obtained by adopting the formula disclosed by the invention has good dielectric property and mechanical property and excellent heat resistance, the melting point of the prepared film can reach over 340 ℃, and the prepared film does not deform or discolor after the tin bleaching test at 298 ℃. In addition, as can be seen from table 2, it is also important to control the addition amount of the novel formula monomer, for example, when the addition amount of the novel formula monomer exceeds a limited upper limit (3%), the melting point of the film is improved, but the tensile strength is obviously reduced, and when the addition amount of the novel formula monomer is lower than a limited lower limit (1.4%), the melting point of the film is not obviously improved, and the film cannot pass the 298 ℃ tin-floating test, compared with example 3, in comparative example 1. In addition, the inventor tries to adopt the currently commonly used acetic acid catalyst to carry out polymerization reaction, and finds that the prepared polymer has small viscosity and low molecular weight, and can not be subjected to blow molding film forming in the subsequent film forming process.

The diameter and the die gap interval of the annular die can be set by a person skilled in the art according to actual film making equipment, and then the inflation ratio and the draft ratio are adjusted to obtain films with different thicknesses, wherein the range of the inflation ratio can be 1.8-7, and the range of the draft ratio can be 1.5-12, which are not described in detail herein.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.