阅读说明：本技术 一种低介电常数液晶聚合物薄膜及其制备方法 (Low-dielectric-constant liquid crystal polymer film and preparation method thereof ) 是由 王阳 任忠平 孙志忠 于 2021-09-08 设计创作，主要内容包括：本发明涉及一种低介电常数液晶聚合物薄膜及其制备方法。本发明的液晶聚合物薄膜包括的液晶聚合物由以下单体制成：6-羟基-2-萘甲酸、对苯二甲酸、4,4'-(六氟异亚丙基)二酚。制备步骤为预聚、固相缩聚、混炼、挤出、牵伸、卷绕、热处理。通过引入新型单体4,4'-(六氟异亚丙基)二酚,获得的液晶聚合物薄膜具有较低的介电常数,同时兼具良好的力学性能、低的介电损耗和吸水率,满足于5G高频高速的使用需求,具有广阔的应用场景。(The invention relates to a liquid crystal polymer film with low dielectric constant and a preparation method thereof. The liquid crystal polymer film of the present invention comprises a liquid crystal polymer made from the following monomers: 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4' - (hexafluoroisopropylidene) diphenol. The preparation steps comprise prepolymerization, solid-phase polycondensation, mixing, extrusion, drafting, winding and heat treatment. By introducing the novel monomer 4,4' - (hexafluoroisopropylidene) diphenol, the obtained liquid crystal polymer film has a low dielectric constant, has good mechanical properties, low dielectric loss and water absorption, meets the use requirement of 5G high frequency and high speed, and has a wide application scene.)

1. A low dielectric constant liquid crystal polymer film comprises a liquid crystal polymer, and is characterized in that the liquid crystal polymer is prepared from the following monomers: 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4'- (hexafluoroisopropylidene) diphenol, wherein the mole percentage of the 6-hydroxy-2-naphthoic acid in each monomer is 45-70 mol%, the sum of the mole percentages of the terephthalic acid and the 4,4' - (hexafluoroisopropylidene) diphenol is 30-55 mol%, and the sum of the mole percentages of the three monomers is equal to 100 mol%.

2. A method for preparing the low dielectric constant liquid crystal polymer film of claim 1, comprising the steps of:

s1: putting a monomer of 6-hydroxy-2-naphthoic acid, terephthalic acid, 4' - (hexafluoroisopropylidene) diphenol, an acetylation reagent of acetic anhydride, a catalyst of 2, 5-diaminopyridine and an antioxidant of stannous chloride into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and carrying out solid-phase polycondensation under the protection of nitrogen to prepare a high-molecular-weight liquid crystal polymer;

s3: mixing the prepared liquid crystal polymer by a double-screw extruder, and exhausting; melt extrusion, and side blowing cooling; drafting and winding to obtain a nascent liquid crystal polymer film;

s4: the as-spun film obtained in step S3 is subjected to heat treatment to obtain a liquid crystal polymer film.

3. The method of claim 2, wherein the amount of acetic anhydride added in step S1 is 1.0 to 2.3 times the total molar number of hydroxyl groups in 6-hydroxy-2-naphthoic acid and 4,4' - (hexafluoroisopropylidene) diphenol.

4. The method of claim 2, wherein the 2, 5-diaminopyridine is added in an amount of 20-400ppm based on the total weight of 6-hydroxy-2-naphthoic acid, terephthalic acid, and 4,4' - (hexafluoroisopropylidene) diphenol in step S1.

5. The method of claim 2, wherein the stannous chloride is added in an amount of 0.1-0.25% based on the total weight of 6-hydroxy-2-naphthoic acid, terephthalic acid, and 4,4' - (hexafluoroisopropylidene) diphenol in step S1.

6. The method for preparing a low dielectric constant liquid crystal polymer film according to claim 2, wherein the step S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 160 ℃ of 135 ℃ for 2-10 h; heating to 320 ℃ at the speed of 0.35-1.0 ℃/min, and preserving the heat for 2-3 h; and (3) flushing 0.1-1.0MPa of nitrogen into the polymerization kettle, discharging the prepolymer through a discharge valve with 8-10 holes and the diameter of 2-4mm, crushing, sieving with a 20-30 mesh sieve, and drying at the temperature of 160 ℃ for 1-5h to obtain the prepolymer.

7. The method for preparing a low dielectric constant liquid crystal polymer film according to claim 2, wherein the step S2 is specifically: and carrying out solid-phase polycondensation on the prepared prepolymer in a rotary kiln at 195-320 ℃ under the protection of nitrogen for 10-46h to prepare the liquid crystal polymer.

8. The method as claimed in claim 2, wherein the extruding temperature of the twin-screw extruder in the step S3 is 280-345 ℃.

9. The method of claim 2, wherein the cross-blowing temperature is 20-50 ℃ and the drawing speed is 8-36m/min in the step S3.

10. The method as claimed in claim 2, wherein the heat treatment temperature in step S4 is 210-305 ℃ and the time is 12-55 h.

Technical Field

The invention belongs to the technical field of high molecular polymers, and particularly relates to a low dielectric constant liquid crystal polymer film and a preparation method thereof.

Background

Liquid Crystal Polymer (LCP) is a novel high-performance special engineering plastic developed in the early 80 th century, belongs to wholly aromatic polyester, can exist in a Liquid Crystal phase form under certain conditions, has the characteristics of high molecular weight and spontaneous orientation of molecules, enables the Liquid Crystal Polymer to show excellent performances such as high strength, high modulus, low dielectric loss, low hygroscopicity, high bending resistance, good processing fluidity and the like, and is a high-new material with great application potential. Liquid crystal polymer films are useful as insulating substrates in printed circuits due to their excellent heat resistance, low moisture absorption, and low dielectric constant and dielectric loss. The dielectric constant is a main factor influencing the propagation speed of signals, the smaller the dielectric constant is, the more favorable the transmission of the signals is, and with the coming of the 5G high-frequency high-speed era, the electronic information technology puts higher requirements on the dielectric constant of the liquid crystal polymer film.

The prior art patent CN111320848A discloses a low dielectric constant liquid crystal polymer composition, which obtains a composite material with a lower dielectric constant through the synergistic effect of liquid crystal polymer category screening and corresponding functional components, but the polymer composition mainly shows a lower dielectric constant under a low frequency condition, which is difficult to meet the high frequency and high speed transmission requirements of the 5G era, and the components and the corresponding processing process of the polymer composition are complicated, and the problem of uneven mixing exists when the components are mixed, meanwhile, the disclosure does not describe the preparation of the corresponding liquid crystal polymer film, and those skilled in the art cannot know whether the liquid crystal polymer composition can be used for manufacturing the film. Patent CN112080291A discloses a liquid crystal polymer film for a 5G communication flexible copper clad laminate and a preparation method thereof, wherein the preparation method comprises the following steps: carrying out liquid nitrogen freezing and crushing on a polytetrafluoroethylene raw material to obtain polytetrafluoroethylene powder; mixing a liquid crystal polymer solution with the polytetrafluoroethylene powder to obtain a mixture; and coating the mixture on a substrate, and then carrying out annealing treatment to obtain the liquid crystal polymer film. Although the liquid crystal polymer film with low dielectric constant, low dielectric loss, smooth surface and certain mechanical strength can be prepared by the physical blending mode, the film is made of the lyotropic liquid crystal polymer, and when the lyotropic liquid crystal polymer is used for preparing the film by a coating method, the film obtained by coating is thin, the solvent is difficult to completely volatilize, and the film is easy to foam in subsequent processing. In addition, the particle size of the polytetrafluoroethylene obtained after liquid nitrogen freeze-pulverization is difficult to control accurately.

In view of the above problems, the inventors prepared a thermotropic liquid crystalline polymer film with a low dielectric constant by introducing a novel monomer to perform chemical copolymerization.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provide a low-dielectric-constant liquid crystal polymer film, wherein the dielectric constant of the liquid crystal polymer film can be effectively reduced by introducing a novel monomer 4,4' - (hexafluoroisopropylidene) diphenol into the liquid crystal polymer, so that the use requirement of 5G high frequency and high speed is met.

The above object of the present invention can be achieved by the following technical solutions: a low dielectric constant liquid crystal polymer film comprising a liquid crystal polymer made from the following monomers: 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4'- (hexafluoroisopropylidene) diphenol, wherein the mole percentage of the 6-hydroxy-2-naphthoic acid in each monomer is 45-70 mol%, the sum of the mole percentages of the terephthalic acid and the 4,4' - (hexafluoroisopropylidene) diphenol is 30-55 mol%, and the sum of the mole percentages of the three monomers is equal to 100 mol%.

Preferably, the molar ratio of terephthalic acid to 4,4' - (hexafluoroisopropylidene) diphenol is 1: 1.

the second object of the present invention is to provide a method for preparing the liquid crystal polymer film, wherein the method specifically comprises the following steps:

s1: putting a monomer of 6-hydroxy-2-naphthoic acid, terephthalic acid, 4' - (hexafluoroisopropylidene) diphenol, an acetylation reagent of acetic anhydride, a catalyst of 2, 5-diaminopyridine and an antioxidant of stannous chloride into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and carrying out solid-phase polycondensation under the protection of nitrogen to prepare a high-molecular-weight liquid crystal polymer;

s3: mixing the prepared liquid crystal polymer by a double-screw extruder, and exhausting; melt extrusion, and side blowing cooling; drafting and winding to obtain a nascent liquid crystal polymer film;

s4: the as-spun film obtained in step S3 is subjected to heat treatment to obtain a liquid crystal polymer film.

Preferably, the amount of acetic anhydride added is 1.0 to 2.3 times the total molar number of hydroxyl groups in 6-hydroxy-2-naphthoic acid and 4,4' - (hexafluoroisopropylidene) diphenol.

Preferably, the 2, 5-diaminopyridine is added in an amount of 20 to 400ppm based on the total weight of 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4' - (hexafluoroisopropylidene) diphenol.

Preferably, the addition amount of the stannous chloride is 0.1-0.25% of the total weight of the 6-hydroxy-2-naphthoic acid, the terephthalic acid and the 4,4' - (hexafluoroisopropylidene) diphenol.

Preferably, the step S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 160 ℃ of 135 ℃ for 2-10 h; heating to 320 ℃ at the speed of 0.35-1.0 ℃/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 160 ℃ for 1-5h 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 ℃ under the protection of nitrogen for 10-46h to prepare the liquid crystal polymer.

Preferably, the extrusion temperature of the twin-screw extruder in the step S3 is 280-345 ℃.

Preferably, the cross-blowing temperature in the step S3 is 20-50 ℃, and the drawing speed is 8-36 m/min.

Preferably, the heat treatment temperature in the step S4 is 210-305 ℃, and the time is 12-55 h.

The weight average molecular weight of the macromolecular liquid crystal polymer prepared by the invention is 30000-42000.

The catalyst used in the present invention is 2, 5-diaminopyridine, whereas conventional catalysts such as: one or more of zinc acetate, manganese acetate, sodium acetate, potassium acetate, cobalt acetate, lithium acetate, titanate, dibutyltin laurate, dibutyltin oxide, antimony trioxide or ethylene glycol antimony can hardly cause reaction, or the conversion rate is low, and a high-molecular-weight polymer cannot be formed, so that a high-performance liquid crystal polymer film cannot be prepared.

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

according to the invention, by introducing the novel monomer 4,4' - (hexafluoroisopropylidene) diphenol, the tensile strength, dielectric loss and water absorption rate of the film can be compared favorably with those of the existing liquid crystal polymer film, the dielectric constant of the liquid crystal polymer film can be effectively reduced, and the prepared liquid crystal polymer film has excellent insulating property and can meet the use requirements of 5G high frequency and high speed. In addition, the filler is not needed, the processing window of the thickness of the film is large, and the preparation process is simple and easy to control.

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 conventional ones, and the methods used are conventional ones.

Detailed description of the preferred embodiments

A low dielectric constant liquid crystal polymer film comprising a liquid crystal polymer comprising the following monomers: 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4'- (hexafluoroisopropylidene) diphenol, wherein the mole percentage of the 6-hydroxy-2-naphthoic acid in each monomer is 45-70 mol%, the sum of the mole percentages of the terephthalic acid and the 4,4' - (hexafluoroisopropylidene) diphenol is 30-55 mol%, and the sum of the mole percentages of the three monomers is equal to 100 mol%.

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

s1: putting a monomer of 6-hydroxy-2-naphthoic acid, terephthalic acid, 4' - (hexafluoroisopropylidene) diphenol, an acetylation reagent of acetic anhydride, a catalyst of 2, 5-diaminopyridine and an antioxidant of stannous chloride into a Hastelloy polymerization kettle for prepolymerization to prepare a prepolymer;

s2: discharging the prepolymer from the Hastelloy kettle, crushing, and carrying out solid-phase polycondensation under the protection of nitrogen to prepare a high-molecular-weight liquid crystal polymer;

s3: mixing the prepared liquid crystal polymer by a double-screw extruder, and exhausting; melt extrusion, and side blowing cooling; drafting and winding to obtain a nascent liquid crystal polymer film;

s4: the as-spun film obtained in step S3 is subjected to heat treatment to obtain a liquid crystal polymer film.

In the above production method, the amount of acetic anhydride added is preferably 1.0 to 2.3 times the total molar number of hydroxyl groups in 6-hydroxy-2-naphthoic acid and 4,4' - (hexafluoroisopropylidene) diphenol.

In the above production method, the 2, 5-diaminopyridine is preferably added in an amount of 20 to 400ppm based on the total weight of 6-hydroxy-2-naphthoic acid, terephthalic acid and 4,4' - (hexafluoroisopropylidene) diphenol.

In the above preparation method, the stannous chloride is preferably added in an amount of 0.1 to 0.25% based on the total weight of 6-hydroxy-2-naphthoic acid, terephthalic acid, and 4,4' - (hexafluoroisopropylidene) diphenol.

In the above preparation method, preferably, S1 is specifically: putting the raw materials into a Hastelloy polymerization kettle, and keeping the temperature at 160 ℃ of 135 ℃ for 2-10 h; heating to 320 ℃ at the speed of 0.35-1.0 ℃/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 160 ℃ for 1-5h 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 ℃ under the protection of nitrogen for 10-46h to prepare the liquid crystal polymer.

In the above preparation method, the extrusion temperature of the twin-screw extruder in the step S3 is preferably 280-345 ℃.

In the above preparation method, preferably, the cross-blowing temperature in the step S3 is 20 to 50 ℃, and the drawing speed is 8 to 36 m/min.

In the above preparation method, preferably, the heat treatment temperature in the step S4 is 210-305 ℃, and the time is 12-55 h.

The embodiments of the present invention will be described in detail by the following examples and comparative examples. The monomer formulations of examples 1-5 of the invention are shown in Table 1:

table 1: monomer ratios in examples 1-5

Example 1

Putting 6-hydroxy-2-naphthoic acid, terephthalic acid, 4'- (hexafluoroisopropylidene) diphenol, acetic anhydride accounting for 1.0 time of the total mole number of hydroxyl in the 6-hydroxy-2-naphthoic acid and the 4,4' - (hexafluoroisopropylidene) diphenol, 2, 5-diaminopyridine accounting for 20ppm of the total weight of the three monomers and stannous chloride accounting for 0.10 percent of the total weight of the three monomers into a Hastelloy polymerization kettle according to the proportion of the No. 1 monomer, and then keeping the mixture at 135 ℃ for 2 hours; heating to 300 ℃ at the speed of 0.35 ℃/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 130 ℃ for 1h to obtain a prepolymer;

carrying out solid phase polycondensation on the prepared prepolymer in a rotary kiln at 195 ℃ for 10h under the protection of nitrogen to prepare a liquid crystal polymer, wherein the weight average molecular weight of the liquid crystal polymer is 30000;

rolling and exhausting the prepared liquid crystal polymer at 280 ℃ by a double-screw extruder; melt-extruding at a discharge rate of 50kg/h, and cooling with side-blown air at 20 ℃; drafting at 23m/min, and winding to obtain a nascent liquid crystal polymer film with the average thickness of 50 μm;

heating the nascent liquid crystal polymer film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the film on a hot rolling device provided with a heat-resistant rubber roller and a heating metal roller at a speed of 3m/min to prepare a laminated body consisting of a thermoplastic liquid crystal polymer film/an aluminum foil, and placing the laminated body in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 210 ℃ for 12 hours; thereafter, the aluminum foil was peeled off to obtain a liquid crystal polymer film having a thickness of 50 μm.

Example 2

Putting 6-hydroxy-2-naphthoic acid, terephthalic acid, 4'- (hexafluoroisopropylidene) diphenol, acetic anhydride accounting for 1.3 times of the total mole number of hydroxyl in the 6-hydroxy-2-naphthoic acid and the 4,4' - (hexafluoroisopropylidene) diphenol, 2, 5-diaminopyridine accounting for 90ppm of the total weight of the three monomers and stannous chloride accounting for 0.15 percent of the total weight of the three monomers into a Hastelloy polymerization kettle according to the proportion of the No. 2 monomer, and then keeping the mixture at 143 ℃ for 4 hours; heating to 305 ℃ at the speed of 0.48 ℃/min, and keeping the temperature for 2 h; flushing 0.4MPa nitrogen into a polymerization kettle, discharging reaction materials through an 8-hole discharge valve with the diameter of 3mm, crushing, sieving with a 25-mesh sieve, and drying at 140 ℃ for 2 hours to obtain a prepolymer;

carrying out solid phase polycondensation on the prepared prepolymer in a rotary kiln at 230 ℃ for 20h under the protection of nitrogen to prepare a liquid crystal polymer, wherein the weight average molecular weight of the liquid crystal polymer is 33000;

rolling and exhausting the prepared liquid crystal polymer at 300 ℃ by a double-screw extruder; melt-extruding at a discharge rate of 50kg/h, and cooling with side-blown air at 30 ℃; drafting at 23m/min, and winding to obtain a nascent liquid crystal polymer film with the average thickness of 50 μm;

heating the nascent liquid crystal polymer film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the film on a hot rolling device provided with a heat-resistant rubber roller and a heating metal roller at a speed of 3m/min to prepare a laminated body consisting of a thermoplastic liquid crystal polymer film/an aluminum foil, and placing the laminated body in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 240 ℃ for 25 h; thereafter, the aluminum foil was peeled off to obtain a liquid crystal polymer film having a thickness of 50 μm.

Example 3

Putting 6-hydroxy-2-naphthoic acid, terephthalic acid, 4'- (hexafluoroisopropylidene) diphenol, acetic anhydride accounting for 1.6 times of the total mole number of hydroxyl groups in the 6-hydroxy-2-naphthoic acid and the 4,4' - (hexafluoroisopropylidene) diphenol, 2, 5-diaminopyridine accounting for 230ppm of the total weight of the three monomers and stannous chloride accounting for 0.18 percent of the total weight of the three monomers into a Hastelloy polymerization kettle according to the proportion of the No. 3 monomer, and then keeping the mixture at 148 ℃ for 6 hours; heating to 310 ℃ at the speed of 0.65 ℃/min, and keeping the temperature for 2.5 h; flushing 0.6MPa nitrogen into a polymerization kettle, discharging 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;

carrying out solid phase polycondensation on the prepared prepolymer in a rotary kiln at 270 ℃ for 33h under the protection of nitrogen to prepare a liquid crystal polymer, wherein the weight average molecular weight of the liquid crystal polymer is 36500;

rolling and exhausting the prepared liquid crystal polymer at 330 ℃ by a double-screw extruder; melt-extruding at a discharge rate of 50kg/h, and cooling with side-blown air at 40 ℃; drafting at 23m/min, and winding to obtain a nascent liquid crystal polymer film with the average thickness of 50 μm;

heating the nascent liquid crystal polymer film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the film on a hot rolling device provided with a heat-resistant rubber roller and a heating metal roller at a speed of 3m/min to prepare a laminated body consisting of a thermoplastic liquid crystal polymer film/an aluminum foil, and placing the laminated body in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 270 ℃ for 38 hours; thereafter, the aluminum foil was peeled off to obtain a liquid crystal polymer film having a thickness of 50 μm.

Example 4

Putting 6-hydroxy-2-naphthoic acid, terephthalic acid, 4'- (hexafluoroisopropylidene) diphenol, acetic anhydride accounting for 2.0 times of the total mole number of hydroxyl in the 6-hydroxy-2-naphthoic acid and the 4,4' - (hexafluoroisopropylidene) diphenol, 2, 5-diaminopyridine accounting for 310ppm of the total weight of the three monomers and stannous chloride accounting for 0.22 percent of the total weight of the three monomers into a Hastelloy polymerization kettle according to the proportion of the 4# monomer, and then keeping the mixture at 155 ℃ for 8 hours; heating to 315 ℃ at the speed of 0.8 ℃/min, and keeping the temperature for 2.5 h; flushing 0.8MPa 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 155 ℃ for 4 hours to obtain a prepolymer;

carrying out solid phase polycondensation on the prepared prepolymer in a rotary kiln at 295 ℃ for 40h under the protection of nitrogen to prepare a liquid crystal polymer, wherein the weight average molecular weight of the liquid crystal polymer is 39000;

rolling and exhausting the prepared liquid crystal polymer at 360 ℃ by a double-screw extruder; melt-extruding at a discharge rate of 50kg/h, and cooling by side blowing at 50 ℃; drafting at 23m/min, and winding to obtain a nascent liquid crystal polymer film with the average thickness of 50 μm;

heating the nascent liquid crystal polymer film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the film on a hot rolling device provided with a heat-resistant rubber roller and a heating metal roller at a speed of 3m/min to prepare a laminated body consisting of a thermoplastic liquid crystal polymer film/an aluminum foil, and placing the laminated body in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 290 ℃ for 47 h; thereafter, the aluminum foil was peeled off to obtain a liquid crystal polymer film having a thickness of 50 μm.

Example 5

Putting 6-hydroxy-2-naphthoic acid, terephthalic acid, 4'- (hexafluoroisopropylidene) diphenol, acetic anhydride accounting for 2.3 times of the total mole number of hydroxyl in the 6-hydroxy-2-naphthoic acid and the 4,4' - (hexafluoroisopropylidene) diphenol, 2, 5-diaminopyridine accounting for 400ppm of the total weight of the three monomers and stannous chloride accounting for 0.25 percent of the total weight of the three monomers into a Hastelloy polymerization kettle according to the proportion of the No. 1 monomer, and then keeping the mixture at 160 ℃ for 10 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 an 8-hole discharge valve with the diameter of 2mm, crushing, sieving with a 20-mesh sieve, and drying at 160 ℃ for 5 hours to obtain a prepolymer;

carrying out solid-phase polycondensation on the prepared prepolymer in a rotary kiln at 320 ℃ for 46h under the protection of nitrogen to prepare a liquid crystal polymer, wherein the weight-average molecular weight of the liquid crystal polymer is 42000;

rolling and exhausting the prepared liquid crystal polymer at 280 ℃ by a double-screw extruder; melt-extruding at a discharge rate of 50kg/h, and cooling with side-blown air at 20 ℃; drafting at 23m/min, and winding to obtain a nascent liquid crystal polymer film with the average thickness of 50 μm;

heating the nascent liquid crystal polymer film and aluminum foil with thickness of 50 μm at 270 deg.C under pressure of 10kg/cm²Pressing the film on a hot rolling device provided with a heat-resistant rubber roller and a heating metal roller at a speed of 3m/min to prepare a laminated body consisting of a thermoplastic liquid crystal polymer film/an aluminum foil, and placing the laminated body in a heat treatment furnace at 290 ℃ for 30 s; under the protection of nitrogen, the mixture is subjected to heat treatment at 305 ℃ for 55 h; thereafter, the aluminum foil was peeled off to obtain a liquid crystal polymer film having a thickness of 50 μm.

Comparative example 1

This comparative example is different from example 4 only in that the molar amounts of the three monomers were 40 mol% of 6-hydroxy-2-naphthoic acid, 30 mol% of terephthalic acid and 30 mol% of 4,4' - (hexafluoroisopropylidene) diphenol, respectively, and the weight average molecular weight of the liquid crystal polymer obtained by the polymerization was 33400, except that the other examples were the same as example 4.

Comparative example 2

This comparative example differs from example 4 only in that the molar percentages of the three monomers were 75 mol% for 6-hydroxy-2-naphthoic acid, 12.5 mol% for terephthalic acid, and 12.5 mol% for 4,4' - (hexafluoroisopropylidene) diphenol, respectively, and the other components were the same as in example 4, and the weight average molecular weight of the liquid crystal polymer obtained by polymerization was 32600.

Comparative example 3

This comparative example differs from example 4 only in that the monomer 4,4' - (hexafluoroisopropylidene) diphenol was replaced with an equal mole percent of biphenyldiphenol, and the polymerization reaction produced a liquid crystalline polymer having a weight average molecular weight of 33700, all as in example 4.

Comparative example 4

This comparative example differs from example 4 only in that the catalyst 2, 5-diaminopyridine was replaced with manganese acetate of equal mass, and the weight average molecular weight of the liquid crystalline polymer obtained by polymerization was 21860, which is otherwise the same as in example 4.

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

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

(2) tensile strength: ASTM D882;

(3) water absorption (25 ℃, 24h in water, 1 mmt): GBT 6283-2008.

Table 2: results of Performance test of liquid Crystal Polymer films obtained in examples 1 to 5 and comparative examples 1 to 3

As can be seen from Table 2, when the ratio or components of the monomer formula are changed, the liquid crystal polymer film has adverse effects on the properties of the liquid crystal polymer film, and the final use of the liquid crystal polymer film is affected, and the liquid crystal polymer film obtained by adopting the formula and the process disclosed by the invention has a low dielectric constant, good mechanical properties, low dielectric loss and water absorption, meets the use requirements of 5G high frequency and high speed, and has a wide application scene.

It should be noted that, those skilled in the art can obtain films with different thicknesses by adjusting and controlling the discharge amount or the drawing speed of the liquid crystal polymer according to actual needs, and details are not repeated here.

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.