Porous low-dielectric liquid crystal polyarylester film and preparation method thereof

Abstract

The invention relates to the technical field of low-dielectric film preparation, in particular to a porous low-dielectric liquid crystal polyarylester film and a preparation method thereof. The preparation method comprises the following steps: respectively carrying out heat treatment and fibrillation treatment on the liquid crystal polyarylate fibers; then, mixing the liquid crystal polyarylester fibers which are respectively subjected to heat treatment and fibrillation treatment, and making paper to form liquid crystal polyarylester fiber paper; and then, carrying out hot pressing on the liquid crystal polyarylate fiber paper. The preparation method solves the problems of poor compatibility and poor dispersibility caused by the need of adding a second component in the existing preparation method, and also solves the problem of high difficulty in molecular design modification in the synthesis process of the liquid crystal polyarylate; the prepared porous low-dielectric liquid crystal polyarylester film has low dielectric loss and good dielectric constant and tensile strength.

Description

Technical Field

[0001] The invention relates to the technical field of low dielectric film preparation, and in particular to a porous low dielectric liquid crystal polyarylate film and a preparation method thereof. Background Art

[0002] Liquid crystal polyarylate is a thermotropic liquid crystal polymer, that is, liquid crystal will be formed when the temperature reaches the glass transition temperature or above the melting point. Liquid crystal polyarylate contains a large number of aromatic rings on the main chain, the structure is symmetrical and regular, and there is no polar group, which makes the liquid crystal polyarylate film show excellent intrinsic low dielectric properties, such as its dielectric constant is 2.9 to 3.2, and the dielectric loss is 0.002 to 0.0045. At the same time, it can remain stable in a wide high frequency range (such as 30GHz to 110GHz), has extremely low water absorption, excellent mechanical properties, intrinsic flame retardancy, good chemical stability and thermal stability. Therefore, liquid crystal polyarylate is a new development direction of low dielectric film materials, and can also be used as a flexible copper clad laminate substrate.

[0003] However, the existing liquid crystal polyarylate film has many shortcomings. Further analysis shows that the above shortcomings may be caused by its preparation method. The specific analysis is as follows: the processing and molding methods of traditional plastic films include cast film molding, calendering molding and extrusion blow molding, but liquid crystal polyarylate is very easy to orient its molecular chain under the action of force field because it has rigid liquid crystal primitives. Therefore, when the liquid crystal polymer flows through the die, spinneret hole or flow channel, even if the shear rate is very low, its orientation degree can reach the molecular orientation degree of general flexible chain polymer after post-stretching. At the same time, the relaxation time of its molecular chain segment is relatively long, and the oriented ordered structure is easy to retain and not easy to relax. This makes the orientation structure of the liquid crystal polyarylate molecular chain strongly dependent on the process conditions near the melt temperature. Therefore, processing liquid crystal polyarylate film using traditional film forming methods will cause the liquid crystal polyarylate molecular chains to be arranged and oriented along the extrusion direction, forming a high degree of uniaxial orientation, which makes its strength in the non-oriented direction extremely low, and it is very easy to break, wrinkle or have uneven thickness during the subsequent blowing or stretching process, which greatly increases the difficulty of film processing. Therefore, this obvious anisotropy generated when processing liquid crystal polyarylate film using traditional film forming methods has greatly limited the application and development of liquid crystal polymer materials in the field of films.

[0004] Most of the existing technologies use the following methods for improvement, but the following improvement methods also have many defects. Specifically as follows: (1) Adding a second component (such as polyester PET or polyetherimide PEI) during melt blending to enhance the entanglement between liquid crystal polyarylate molecules, however, this will lead to the prepared liquid crystal polyarylate film having poor compatibility and dispersibility between different molecules. At the same time, the addition of the second component may cause the dielectric properties of the final liquid crystal polyarylate film to decrease due to the presence of an interface with the liquid crystal polyarylate. (2) Molecular design modification is performed during the synthesis of liquid crystal polyarylate, such as introducing a fatty chain to enhance the entanglement between molecules. However, when the liquid crystal polyarylate is molecularly designed, the aromatic polycyclic structure of its main chain, that is, the liquid crystal polyarylate molecular chain lacks highly reactive functional groups, making it difficult to directly modify the molecular structure and making the synthesis difficult. It can be seen that at present, the preparation and processing of liquid crystal polyarylate films is still a difficult problem in the industry.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a porous low-dielectric liquid crystal polyarylate film and a preparation method thereof. The embodiment of the present invention provides a novel preparation method of a porous low-dielectric liquid crystal polyarylate film, which solves the problem of poor compatibility and poor dispersibility caused by the need to add a second component in the existing preparation method, and also solves the problem of difficulty in molecular design modification during the synthesis of liquid crystal polyarylate. The prepared porous low-dielectric liquid crystal polyarylate film has low dielectric loss and good dielectric constant and tensile strength.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising: heat-treating and fibrillating liquid crystal polyarylate fibers respectively;

[0009] Then, the liquid crystal polyarylate fibers that have been subjected to heat treatment and fibrillation treatment are mixed and made into paper to form liquid crystal polyarylate fiber paper;

[0010] Next, the liquid crystal polyarylate fiber paper is heat-pressed.

[0011] In an optional embodiment, the step of heat treatment includes: heating the liquid crystal polyarylate fiber;

[0012] Preferably, the heat treatment conditions include: temperature of 80-150° C. and time of 2-10 h.

[0013] In an optional embodiment, the fibrillation treatment step includes: dispersing the liquid crystal polyarylate fibers in a solvent;

[0014] Preferably, the solvent comprises at least one of water, a C1-C10 alcohol solvent, and a C3-C8 ketone solvent;

[0015] Preferably, the stirring conditions for the fibrillation treatment include: a stirring speed of 14000-25000 r / min and a time of 30-90 s.

[0016] In an optional embodiment, the mass ratio of the heat-treated liquid crystal polyarylate fibers to the fibrillation-treated liquid crystal polyarylate fibers is (1-9): (9-1).

[0017] In an optional embodiment, the method includes: forming the liquid crystal polyarylate fiber paper by wet papermaking.

[0018] In an optional embodiment, the step of forming the liquid crystal polyarylate fiber paper includes: mixing the heat-treated liquid crystal polyarylate fibers and the fibrillated liquid crystal polyarylate fibers with a dispersion, then removing the dispersion to form a liquid crystal polyarylate blank paper, and drying and shaping.

[0019] In an optional embodiment, the conditions for mixing the heat-treated liquid crystal polyarylate fibers and the fibrillated liquid crystal polyarylate fibers include: a stirring speed of 14000-25000 r / min, a stirring time of 60-150 s;

[0020] Preferably, the dispersant in the dispersion is selected from a polymer, preferably any one of polyethylene glycol PEO, polyvinyl alcohol PVA and polyacrylic acid PAA;

[0021] Preferably, the dispersion is selected from any one of polyethylene glycol at a concentration of 0.1-0.5wt%, polyvinyl alcohol at a concentration of 0.1-0.5wt%, and polyacrylic acid at a concentration of 0.1-0.5wt%.

[0022] Preferably, the conditions for drying the liquid crystal polyarylate blank paper include: a drying temperature of 80-150° C. and a drying time of 4-5 hours;

[0023] Preferably, the shaping conditions include: shaping temperature of 200-250° C., shaping pressure of 3-6 MPa, and shaping time of 5-10 min.

[0024] In an optional embodiment, the hot pressing conditions include: the hot pressing temperature is 200-260° C., the hot pressing pressure is 1-5 MPa, and the hot pressing time is 5-10 min.

[0025] In an optional embodiment, the liquid crystal polyarylate fibers are selected from liquid crystal polyarylate staple fibers;

[0026] Preferably, the length of the liquid crystal polyarylate short fibers is 3-10 mm.

[0027] In an optional embodiment, the step of forming the liquid crystal polyarylate fiber includes: pre-treating the liquid crystal polyarylate resin and then performing melt spinning.

[0028] In a second aspect, an embodiment of the present invention provides a porous low-dielectric liquid crystal polyarylate film, which is prepared by the above-mentioned porous low-dielectric liquid crystal polyarylate film preparation method.

[0029] The present invention has the following beneficial effects:

[0030] (1) The preparation method provided in the embodiment of the present invention can use only liquid crystal polyarylate fibers as functional preparation raw materials by performing different treatments on liquid crystal polyarylate fibers, without the need to introduce other polymers or second components, thereby solving the problems of reduced compatibility, dispersibility and dielectric properties caused by the second component.

[0031] (2) The embodiment of the present invention can solve the problems of film breakage, wrinkles and uneven thickness caused by large anisotropy of traditional melt processing by preparing liquid crystal polyarylate fiber into liquid crystal polyarylate fiber paper and then hot pressing to form a porous low dielectric liquid crystal polyarylate film.

[0032] (3) The preparation method provided in the embodiment of the present invention only uses liquid crystal polyarylate fiber as a functional preparation raw material, does not require synthetic modification, has a simple processing technology, a short preparation process, and is suitable for large-scale production.

[0033] (4) The preparation method provided in the embodiment of the present invention has a wide range of raw materials and does not require the use of a large amount of toxic and harmful reagents during the preparation process. It is green and environmentally friendly and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A schematic diagram of the preparation process of a porous low-dielectric liquid crystal polyarylate film provided in an embodiment of the present invention;

[0036] Figure 2 The cross-sectional scanning electron microscope images of the liquid crystal polyarylate film with different proportions of components provided in Experimental Example 1 of the present invention;

[0037] Figure 3The surface scanning electron microscope images of the liquid crystal polyarylate film prepared at different hot pressing temperatures provided in Experimental Example 2 of the present invention;

[0038] Figure 4 This is a graph showing the change of the internal pore structure of the liquid crystal polyarylate film with the hot pressing temperature provided in Experimental Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0040] Traditional plastic film processing and molding methods include cast film molding, calendering molding, extrusion blow molding, etc., but liquid crystal polyarylate is very easy to orient its molecular chain under the action of force field because of its rigid liquid crystal unit. When the liquid crystal polymer flows through the die, spinneret hole or flow channel, even if the shear rate is very low, its orientation degree can reach the molecular orientation degree of general flexible chain polymer after post-stretching. At the same time, the relaxation time of its molecular chain segment is long, and the oriented ordered structure is easy to retain and not easy to relax, which makes the orientation structure of liquid crystal polyarylate molecular chain strongly dependent on the process conditions near the melt temperature. Processing liquid crystal polyarylate film using traditional film forming methods will cause the liquid crystal polyarylate molecular chain to be arranged and oriented along the extrusion direction, forming a high degree of uniaxial orientation, so that its strength in the non-oriented direction is extremely low, and it is very easy to break during the subsequent blowing or stretching process. This obvious anisotropy generated when processing liquid crystal polyarylate film by traditional film forming methods greatly limits the application and development of liquid crystal polymer materials in the field of films. Based on the above problems, an embodiment of the present invention provides a novel method for preparing a porous low-dielectric liquid crystal polyarylate film, which improves the problem of easy breakage caused by high film orientation during melt processing.

[0041] Specifically, the method for preparing a porous low-dielectric liquid crystal polyarylate film comprises heat treating and fibrillating the liquid crystal polyarylate fibers respectively, and then making paper from the two treated fibers to form liquid crystal polyarylate fiber paper, and then hot pressing to form a liquid crystal polyarylate film.

[0042] For a detailed flow chart, see Figure 1 , the specific implementation plan is as follows:

[0043] S1, forming liquid crystal polyarylate fibers;

[0044] The liquid crystal polyarylate resin is pretreated and then melt-spun. Specifically, the liquid crystal polyarylate resin is vacuum dried and pretreated, wherein the pretreatment conditions include: a temperature of 100-150°C and a time of 6-12 hours. Liquid crystal polyarylate primary fibers are prepared by using a melt spinning machine with a metering pump specification of 0.2-0.5cc / r at a spinning temperature of 290-350°C, a metering pump speed of 10-30r / min, and a winding speed of 100-500m / min, and finally the liquid crystal polyarylate short fibers are obtained by cutting. Among them, the length of the liquid crystal polyarylate short fibers is 3-10 mm.

[0045] The pretreatment can fully remove the moisture contained in the liquid crystal polyarylate resin, thereby preventing the liquid crystal polyarylate resin from being degraded.

[0046] It should be noted that: (1) The liquid crystal polyarylate resin used in the embodiments of the present invention can be directly purchased from the market, such as Jiangmen Dezhongtai Plastic Engineering Co., Ltd., brand A300, batch number 200924-3.

[0047] (2) The melt spinning machine and the conditions corresponding to the melt spinning machine are only an example of an embodiment of the present invention. It is understandable that other spinning machines in the prior art can be used as long as they can perform melt spinning to obtain polyarylate primary fibers.

[0048] (3) The liquid crystal polyarylate fibers used in the embodiment of the present invention are liquid crystal polyarylate staple fibers. In particular, the length limitation of the liquid crystal polyarylate staple fibers is only an example of the embodiment of the present invention. Liquid crystal polyarylate fibers of other lengths may also be selected as long as they can be used for subsequent papermaking to form liquid crystal polyarylate fiber paper.

[0049] S2. Treatment of liquid crystal polyarylate fibers;

[0050] The liquid crystal polyarylate fibers are subjected to heat treatment and fibrillation treatment respectively; specifically, part of the liquid crystal polyarylate fibers are subjected to heat treatment, for example, the liquid crystal polyarylate fibers are placed in a drum oven for vacuum heat treatment at a temperature of 80-150° C. for 2-10 hours.

[0051] Part of the liquid crystal polyarylate fibers are subjected to fibrillation treatment. The liquid crystal polyarylate fibers are dispersed in a solvent and subjected to fibrillation treatment using a high-speed stirrer. The stirring speed is 14000-25000 r / min, and the stirring time is 30-90 s; the solvent includes at least one of water, C1-C10 alcohol solvents, and C3-C8 ketone solvents; for example, including but not limited to one or more of ionized water, ethanol, methanol, and acetone.

[0052] The melting temperature of the heat-treated liquid crystal polyarylate fiber of the embodiment of the present invention increases significantly, and it can be used as a structural framework for forming a liquid crystal polyarylate film, so that it will not melt during the subsequent hot pressing process. The liquid crystal polyarylate fiber after fibrillation treatment has an increased specific surface area, and melts during the hot pressing melting process. As an adhesive, it can increase the cohesive area, increase the inter-fiber bonding force, and finally obtain a uniform liquid crystal polyarylate film. And according to the above records, it can be seen that the porous low-dielectric liquid crystal polyarylate film provided by the embodiment of the present invention contains only one raw material of liquid crystal polyarylate fiber, and no additional raw materials need to be added. There will be no problem of poor compatibility and dispersibility between raw materials, and there is no problem of reduced dielectric properties caused by the introduction of multiple raw materials.

[0053] S3, forming liquid crystal polyarylate fiber paper;

[0054] The liquid crystal polyarylate fibers that have been subjected to heat treatment and fibrillation treatment are mixed and made into paper to form liquid crystal polyarylate fiber paper. The specific process is as follows:

[0055] The liquid crystal polyarylate fibers that have been heat-treated and the liquid crystal polyarylate fibers that have been fibrillated are mixed and stirred in proportion and dispersed, wherein the stirring speed is 14000-25000 r / min and the stirring time is 60-150 s; the mass ratio of the liquid crystal polyarylate fibers that have been heat-treated and the liquid crystal polyarylate fibers that have been fibrillated is (1-9):(9-1).

[0056] It should be noted that in the mass ratio of the heat-treated liquid crystal polyarylate fibers to the fibrillated liquid crystal polyarylate fibers, the fibrillated liquid crystal polyarylate fibers refer to the mass of the liquid crystal polyarylate fibers not containing the fibrillated solvent.

[0057] The embodiment of the present invention can control the pore structure of the porous liquid crystal polyarylate film by controlling the mass ratio of the heat-treated liquid crystal polyarylate fibers and the fibrillated liquid crystal polyarylate fibers and the temperature of subsequent hot pressing.

[0058] Then, the mixture is transferred to the barrel of the sheet machine and mixed with the dispersion. Then, the drain valve is opened to drain the dispersion to obtain the liquid crystal polyarylate blank paper spread on the filter screen. The surface is washed three times with deionized water to remove a small amount of dispersion attached. Then, it is transferred to the felt cloth and placed in an oven at 80-150°C to fully dry for 4-5 hours. The dried liquid crystal polyarylate blank paper is hot-pressed on a flat vulcanizer at a setting temperature of 200-250°C, a setting pressure of 3-6MPa, and a setting time of 5-10min to obtain the liquid crystal polyarylate fiber paper.

[0059] Among them, the dispersant in the dispersion is selected from a polymer, preferably any one of polyethylene glycol PEO, polyvinyl alcohol PVA and polyacrylic acid PAA; for example, the dispersion liquid is selected from any one of polyethylene glycol PEO with a concentration of 0.1-0.5wt%, polyvinyl alcohol with a concentration of 0.1-0.5wt% and polyacrylic acid with a concentration of 0.1-0.5wt%.

[0060] S4, hot pressing;

[0061] The liquid crystal polyarylate fiber paper is hot pressed. Specifically, the prepared liquid crystal polyarylate fiber paper is selected, two layers of liquid crystal polyarylate fiber paper are stacked flatly, and placed in a fully automatic high-temperature hot press for hot pressing, with a preheating time of 1-3 minutes, a hot pressing temperature of 200-260° C., a hot pressing pressure of 1-5 MPa, and a hot pressing time of 5-10 minutes. A porous low-dielectric liquid crystal polyarylate film with different pore structures is obtained.

[0062] The embodiment of the present invention adopts the method of hot pressing film formation of fiber paper to prepare porous low dielectric liquid crystal polyarylate film, which solves the problem of high orientation of liquid crystal polyarylate caused by traditional melt processing, and further solves the problems of easy rupture, wrinkles and uneven thickness of the film. According to the above records, it can be seen that the preparation method provided by the embodiment of the present invention does not require molecular structure modification design during the synthesis process, which solves the problem of difficult synthesis.

[0063] In a second aspect, an embodiment of the present invention provides a porous low-dielectric liquid crystal polyarylate film, which is prepared by the above-mentioned porous low-dielectric liquid crystal polyarylate film preparation method.

[0064] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0065] Example 1

[0066] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0067] S1, forming liquid crystal polyarylate short fibers;

[0068] Liquid crystal polyarylate resin (purchased from Jiangmen Dezhongtai Plastic Engineering Co., Ltd.) was vacuum dried in a vacuum drum oven for pretreatment, and the conditions were 100°C for 6 hours. Liquid crystal polyarylate primary fibers were prepared by a melt spinning machine with a metering pump specification of 0.3cc / r at a spinning temperature of 320°C, a metering pump speed of 20r / min, and a winding speed of 300m / min, and finally cut to obtain liquid crystal polyarylate short fibers. The length of the liquid crystal polyarylate short fibers is 3-10mm.

[0069] S2. Treatment of liquid crystal polyarylate fibers;

[0070] The liquid crystal polyarylate short fibers were placed in a drum oven for vacuum heat treatment at a temperature of 80° C. for 3 hours.

[0071] The liquid crystal polyarylate short fibers are dispersed in deionized water, and the liquid crystal polyarylate fibers are fibrillated using a high-speed stirrer. The stirring speed of the stirrer is 20000 r / min, and the stirring time is 60 s.

[0072] S3, forming liquid crystal polyarylate fiber paper;

[0073] The above-mentioned heat-treated liquid crystal polyarylate short fibers and the fibrillated liquid crystal polyarylate short fibers were stirred and dispersed in a mass ratio of 1:9, wherein the stirring speed was 20000r / min and the stirring time was 60s. After stirring, blending and dispersing, they were transferred to the barrel of the sheet-making machine and mixed with a PEO dispersion with a concentration of 0.3wt%. The drain valve was opened to drain the dispersion to obtain a liquid crystal polyarylate blank paper laid on the filter screen, and the surface was washed three times with deionized water to remove a small amount of dispersion attached, and then it was transferred to a felt cloth and placed in an oven at 100°C to fully dry for 4h. The dried liquid crystal polyarylate blank paper was hot-pressed on a flat vulcanizer, with a setting temperature of 200°C, a setting pressure of 3MPa, and a setting time of 5min to obtain a liquid crystal polyarylate fiber paper.

[0074] S4, hot pressing;

[0075] The prepared fiber paper was selected, two layers of fiber paper were stacked flatly, and then placed in a fully automatic high-temperature hot press for hot pressing, with a preheating time of 2 min, a hot pressing temperature of 200° C., a hot pressing pressure of 1 MPa, and a hot pressing time of 5 min.

[0076] Example 2

[0077] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0078] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0079] S2. Treatment of liquid crystal polyarylate fibers;

[0080] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 110° C., time 3 hours.

[0081] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0082] The operating conditions of S3 and S4 are consistent with those of Example 1.

[0083] Example 3

[0084] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0085] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0086] S2. Treatment of liquid crystal polyarylate fibers;

[0087] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 150° C., time 3 hours.

[0088] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0089] The operating conditions of S3 and S4 are consistent with those of Example 1.

[0090] Example 4

[0091] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0092] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0093] S2. Treatment of liquid crystal polyarylate fibers;

[0094] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 100° C., time 5 hours.

[0095] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0096] S3, forming liquid crystal polyarylate fiber paper;

[0097] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 9:1, and the other conditions are the same as those in Example 1.

[0098] S4, hot pressing;

[0099] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 5 MPa, hot pressing time 5 min.

[0100] Example 5

[0101] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0102] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0103] S2. Treatment of liquid crystal polyarylate fibers;

[0104] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 100° C., time 5 hours.

[0105] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0106] S3, forming liquid crystal polyarylate fiber paper;

[0107] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 6:4, and the other conditions are the same as those in Example 1.

[0108] S4, hot pressing;

[0109] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 5 MPa, hot pressing time 5 min.

[0110] Example 6

[0111] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0112] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0113] S2. Treatment of liquid crystal polyarylate fibers;

[0114] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 100° C., time 5 hours.

[0115] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0116] S3, forming liquid crystal polyarylate fiber paper;

[0117] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 1:9, and the other conditions are the same as those in Example 1.

[0118] S4, hot pressing;

[0119] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 5 MPa, hot pressing time 5 min.

[0120] Example 7

[0121] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0122] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0123] S2. Treatment of liquid crystal polyarylate fibers;

[0124] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature of 120° C. and time of 10 hours.

[0125] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0126] S3, forming liquid crystal polyarylate fiber paper;

[0127] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 4:6, and the other conditions are the same as those in Example 1.

[0128] S4, hot pressing;

[0129] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0130] Example 8

[0131] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0132] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0133] S2. Treatment of liquid crystal polyarylate fibers;

[0134] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature of 120° C. and time of 10 hours.

[0135] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0136] S3, forming liquid crystal polyarylate fiber paper;

[0137] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 4:6, and the other conditions are the same as those in Example 1.

[0138] S4, hot pressing;

[0139] Hot pressing conditions: preheating time 2 min, hot pressing temperature 240°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0140] Example 9

[0141] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0142] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0143] S2. Treatment of liquid crystal polyarylate fibers;

[0144] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature of 120° C. and time of 10 hours.

[0145] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0146] S3, forming liquid crystal polyarylate fiber paper;

[0147] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 4:6, and the other conditions are the same as those in Example 1.

[0148] S4, hot pressing;

[0149] Hot pressing conditions: preheating time 2 min, hot pressing temperature 260°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0150] Example 10

[0151] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0152] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0153] S2. Treatment of liquid crystal polyarylate fibers;

[0154] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 150° C., time 7 hours.

[0155] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0156] S3, forming liquid crystal polyarylate fiber paper;

[0157] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 1:9, the setting temperature is 230° C., and the other conditions are the same as those in Example 1.

[0158] S4, hot pressing;

[0159] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 3 MPa, hot pressing time 5 min.

[0160] Embodiment 11

[0161] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0162] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0163] S2. Treatment of liquid crystal polyarylate fibers;

[0164] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 150° C., time 7 hours.

[0165] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0166] S3, forming liquid crystal polyarylate fiber paper;

[0167] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 1:9, the setting temperature is 250° C., and the other conditions are the same as those in Example 1.

[0168] S4, hot pressing;

[0169] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 3 MPa, hot pressing time 5 min.

[0170] Example 12

[0171] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0172] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0173] S2. Treatment of liquid crystal polyarylate fibers;

[0174] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 150° C., time 7 hours.

[0175] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 20000 r / min, the stirring time is 60 s; and the solvent is deionized water.

[0176] S3, forming liquid crystal polyarylate fiber paper;

[0177] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers to the fibrillated liquid crystal polyarylate staple fibers is 1:9, and the other conditions are the same as those in Example 1.

[0178] S4, hot pressing;

[0179] Hot pressing conditions: preheating time 2 min, hot pressing temperature 220°C, hot pressing pressure 3 MPa, hot pressing time 5 min.

[0180] Embodiment 13

[0181] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film, comprising:

[0182] The liquid crystal polyarylate short fibers prepared in Example 1 were used for subsequent operations, and the operations were basically the same as in Example 1, with only some operating conditions being different, as follows:

[0183] S2. Treatment of liquid crystal polyarylate fibers;

[0184] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 80° C., time 3 hours.

[0185] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 14000 r / min, the stirring time is 90 s; and the solvent is ethanol.

[0186] S3, forming liquid crystal polyarylate fiber paper;

[0187] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers and the fibrillated liquid crystal polyarylate staple fibers is 2:8, the stirring speed is 18000r / min, the stirring time is 60s, the dispersion is PEO with a concentration of 0.5wt%, and the other conditions are the same as in Example 1.

[0188] S4, hot pressing;

[0189] Hot pressing conditions: preheating time 2 min, hot pressing temperature 200°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0190] Embodiment 14

[0191] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film. The basic operation of the preparation method is consistent with that of Example 1, except for some operating conditions, which are as follows:

[0192] S1, forming liquid crystal polyarylate short fibers;

[0193] The conditions of vacuum drying pretreatment include: temperature of 120°C and time of 6 hours.

[0194] Liquid crystal polyarylate primary fibers were prepared by using a melt spinning machine with a metering pump specification of 0.4cc / r at a spinning temperature of 320°C, a metering pump speed of 30r / min, and a winding speed of 500m / min, and finally cut to obtain liquid crystal polyarylate staple fibers, wherein the length of the liquid crystal polyarylate staple fibers was 5mm.

[0195] S2. Treatment of liquid crystal polyarylate fibers;

[0196] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 80° C., time 3 hours.

[0197] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 17000 r / min, the stirring time is 30 s; and the solvent is deionized water.

[0198] S3, forming liquid crystal polyarylate fiber paper;

[0199] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers and the fibrillated liquid crystal polyarylate staple fibers is 2:8, the stirring speed is 18000r / min, the stirring time is 60s, the dispersion liquid is PEO with a concentration of 0.4wt%, and the other conditions are the same as Example 1.

[0200] S4, hot pressing;

[0201] Hot pressing conditions: preheating time 2 min, hot pressing temperature 200°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0202] Embodiment 15

[0203] The embodiment of the present invention provides a method for preparing a porous low-dielectric liquid crystal polyarylate film. The basic operation of the preparation method is consistent with that of Example 1, except for some operating conditions, which are as follows:

[0204] S1, forming liquid crystal polyarylate short fibers;

[0205] The conditions of vacuum drying pretreatment include: temperature of 150°C and time of 12h.

[0206] Liquid crystal polyarylate primary fibers were prepared by using a melt spinning machine with a metering pump specification of 0.2cc / r at a spinning temperature of 350°C, a metering pump speed of 10r / min, and a winding speed of 100m / min, and finally cut to obtain liquid crystal polyarylate staple fibers, wherein the length of the liquid crystal polyarylate staple fibers was 5mm.

[0207] S2. Treatment of liquid crystal polyarylate fibers;

[0208] The conditions for heat treatment of the liquid crystal polyarylate short fibers include: temperature 80° C., time 3 hours.

[0209] The conditions for fibrillating the liquid crystal polyarylate short fibers include: the stirring speed of the stirrer is 25000 r / min, the stirring time is 90 s; and the solvent is acetone.

[0210] S3, forming liquid crystal polyarylate fiber paper;

[0211] The mass ratio of the heat-treated liquid crystal polyarylate staple fibers and the fibrillated liquid crystal polyarylate staple fibers is 2:8. The stirring speed of the two is 18000r / min, the stirring time is 60s, the dispersion liquid is PEO with a concentration of 0.3wt%, the drying temperature is 80°C, the time is 4h, and the other conditions are the same as Example 1.

[0212] S4, hot pressing;

[0213] Hot pressing conditions: preheating time 2 min, hot pressing temperature 200°C, hot pressing pressure 1 MPa, hot pressing time 5 min.

[0214] Comparative Example 1

[0215] The liquid crystal polyarylate resin was pretreated by vacuum drying in a vacuum drum oven at 120°C for 6 hours. Liquid crystal polyarylate primary fibers were prepared by a melt spinning machine with a metering pump specification of 0.4cc / r at a spinning temperature of 320°C, a metering pump speed of 30r / min, and a winding speed of 500m / min. Finally, the liquid crystal polyarylate staple fibers were obtained by cutting.

[0216] Fibrillation treatment: The liquid crystal polyarylate short fibers are dispersed in a solvent, and the liquid crystal polyarylate fibers are fibrillated using a high-speed mixer, the stirring speed of the mixer is 17000 r / min, and the stirring time is 30 seconds; the solvent is deionized water. The liquid crystal polyarylate short fibers are not subjected to heat treatment.

[0217] Untreated polyarylate staple fibers and fibrillated liquid crystal polyarylate staple fibers were mixed in different mass ratios, and a certain amount of dispersant was added, with a mass ratio of 2:8. After being blended and dispersed in a high-speed mixer with a stirring speed of 18000r / min and a stirring time of 60s, they were transferred to the barrel of the sheet-making machine and mixed with a PEO dispersion with a concentration of 0.4wt%. The drain valve was opened to drain the dispersion to obtain a liquid crystal polyarylate blank paper laid on the filter screen. The surface was washed three times with deionized water to remove a small amount of attached dispersion, and then it was transferred to a felt cloth and placed in an oven at 110°C to fully dry for 4h. The dried liquid crystal polyarylate blank paper was hot-pressed on a flat vulcanizer, with a hot-pressing temperature of 200°C, a hot-pressing pressure of 3MPa, and a hot-pressing time of 5min to obtain a liquid crystal polyarylate fiber paper.

[0218] The prepared fiber paper was selected, two layers of fiber paper were stacked flat, and then placed in a fully automatic high-temperature hot press for hot pressing, with a hot pressing temperature of 200°C, a preheating time of 2 minutes, a hot pressing pressure of 1 MPa, and a hot pressing time of 5 minutes. Porous liquid crystal polyarylate films with different pore structures were successfully prepared.

[0219] Comparative Example 2:

[0220] The liquid crystal polyarylate resin was pretreated by vacuum drying in a vacuum drum oven at 120°C for 6 hours. Liquid crystal polyarylate primary fibers were prepared by a melt spinning machine with a metering pump specification of 0.4cc / r at a spinning temperature of 320°C, a metering pump speed of 30r / min, and a winding speed of 500m / min. Finally, the liquid crystal polyarylate staple fibers were obtained by cutting.

[0221] Heat treatment: The liquid crystal polyarylate staple fibers were placed in a rotary drum oven for vacuum heat treatment at a temperature of 80° C. for 3 hours. The liquid crystal polyarylate staple fibers were not subjected to fibrillation treatment.

[0222] Untreated polyarylate staple fibers and heat-treated liquid crystal polyarylate staple fibers were mixed in different mass ratios, and a certain amount of dispersant was added, with a mass ratio of 4:6. After being blended and dispersed in a high-speed mixer with a stirring speed of 18000r / min and a stirring time of 60s, they were transferred to the barrel of the sheet-making machine and mixed with a PEO dispersion with a concentration of 0.4wt%. The drain valve was opened to drain the dispersion to obtain a liquid crystal polyarylate blank paper laid on the filter screen. The surface was washed three times with deionized water to remove a small amount of attached dispersion, and then it was transferred to a felt cloth and placed in an oven at 90°C to fully dry for 4h. The dried liquid crystal polyarylate blank paper was hot-pressed on a flat vulcanizer, with a hot-pressing temperature of 210°C, a hot-pressing pressure of 3MPa, and a hot-pressing time of 5min to obtain a liquid crystal polyarylate fiber paper.

[0223] The prepared fiber paper was selected, two layers of fiber paper were stacked flat, and then placed in a fully automatic high-temperature hot press, with a hot pressing temperature of 220°C, a preheating time of 3 minutes, a hot pressing pressure of 1 MPa, and a hot pressing time of 5 minutes. Porous liquid crystal polyarylate films with different pore structures were successfully prepared.

[0224] Comparative Example 3:

[0225] The liquid crystal polyarylate resin was pretreated by vacuum drying in a vacuum drum oven at 120°C for 6 hours. Liquid crystal polyarylate primary fibers were prepared by a melt spinning machine with a metering pump specification of 0.4cc / r at a spinning temperature of 320°C, a metering pump speed of 30r / min, and a winding speed of 500m / min. Finally, the liquid crystal polyarylate staple fibers were obtained by cutting.

[0226] Heat treatment: Place the liquid crystal polyarylate staple fibers in a rotary drum oven for vacuum heat treatment at a temperature of 80°C for 3 hours. Fibrillation treatment: Disperse the liquid crystal polyarylate staple fibers in a solvent and use a high-speed stirrer to perform fibrillation treatment on the liquid crystal polyarylate fibers. The stirring speed of the stirrer is 17000 r / min and the stirring time is 30 seconds. The solvent is deionized water.

[0227] Heat-treated liquid crystal polyarylate staple fibers and fibrillated liquid crystal polyarylate staple fibers were mixed in different mass ratios, and a certain amount of dispersant was added, with a mass ratio of 1:9. After being blended and dispersed in a high-speed mixer with a stirring speed of 18000r / min and a stirring time of 60s, they were transferred to the barrel of the sheet-making machine and mixed with a PEO dispersion with a concentration of 0.4wt%. The drain valve was opened to drain the dispersion to obtain a liquid crystal polyarylate blank paper laid on the filter screen, and the surface was washed three times with deionized water to remove a small amount of dispersion attached, and then it was transferred to a felt cloth and placed in an oven at 110°C to fully dry for 4h. The dried liquid crystal polyarylate blank paper was hot-pressed on a flat vulcanizer, with a hot-pressing temperature of 200°C, a hot-pressing pressure of 3MPa, and a hot-pressing time of 5min to obtain a liquid crystal polyarylate fiber paper.

[0228] The prepared fiber paper was selected, two layers of fiber paper were stacked flat, and then placed in a fully automatic high-temperature hot press, with a hot pressing temperature of 180°C, a preheating time of 2 minutes, a hot pressing pressure of 1 MPa, and a hot pressing time of 5 minutes. Porous liquid crystal polyarylate films with different pore structures were successfully prepared.

[0229] Experimental Example 1

[0230] The porous low dielectric liquid crystal polyarylate films of Examples 4-6 and Comparative Examples 1-2 were scanned by electron microscope. The results are shown in Figure 2 .

[0231] according to Figure 2 It can be seen that the cross section of the liquid crystal polyarylate film obtained by hot pressing the heat-treated fiber and the untreated fiber and the fibrillated fiber and the untreated fiber is rough, the degree of mutual adhesion is low, and there are many defects inside. After hot pressing the heat-treated fiber and the fibrillated fiber in different proportions, the film formed is uniform inside, smooth on the surface and tightly bonded.

[0232] Experimental Example 2

[0233] The porosity of the porous low dielectric liquid crystal polyarylate films of Examples 7-9 and Comparative Example 3 was tested by electron microscope scanning and mercury intrusion porosimetry. The results are shown in Figure 3-4 .Depend on Figure 3 It can be seen that when the hot pressing temperature is low, the fibrillated fibers melt, but the heat-treated fibers basically do not melt, so obvious fibers can still be observed on the surface. At this time, the internal compactness is low and the porosity is large. As the temperature increases, the heat-treated fibers partially melt, and the fibrillated fibers melt more, forming a uniform film, with increased internal compactness and reduced porosity. Figure 4 The porosity changes. As the temperature increases, the porosity gradually decreases, achieving the regulation of the pore structure.

[0234] Experimental Example 3

[0235] The porous low dielectric liquid crystal polyarylate films of Examples 1-15 and Comparative Examples 1-3 were tested for tensile strength, dielectric constant, and dielectric loss, wherein the test method for tensile strength refers to GB / T1040.3-2006 and GB / T13542.2-2021, and the test method for dielectric constant and dielectric loss refers to GB / T13542.2-2021. The results are shown in the table below.

[0236] Performance Indicators Tensile strength(MPa) Dielectric constant at 1MHz Dielectric loss at 1MHz Comparative Example 1 48 3.72 0.0220 Comparative Example 2 50 3.64 0.0236 Comparative Example 3 42 3.50 0.0255 Example 1 62 3.43 0.0231 Example 2 65 3.56 0.0219 Example 3 63 3.33 0.0210 Example 4 67 3.46 0.0213 Example 5 69 3.49 0.0221 Example 6 61 3.59 0.0226 Example 7 59 3.55 0.0217 Example 8 64 3.57 0.0230 Example 9 63 3.62 0.0233 Example 10 57 3.61 0.0229 Embodiment 11 62 3.41 0.0211 Example 12 61 3.44 0.0216 Example 13 58 3.52 0.0221 Embodiment 14 69 3.50 0.0213 Embodiment 15 66 3.61 0.0211

[0237] According to the above results, the performance of the liquid crystal polyarylate fiber after heat treatment and fibrillation is not as good as that of the untreated fiber sample after hot pressing. In addition, when the hot pressing temperature is low, the short fibers are not fully melted, which reduces the mechanical properties of the film. However, due to the pores inside, it has excellent dielectric properties.

[0238] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a porous low dielectric liquid crystal polyarylate film, characterized in that: include: The liquid crystal polyarylate fibers are subjected to heat treatment and fibrillation treatment respectively; Then, the liquid crystal polyarylate fibers that have been subjected to heat treatment and fibrillation treatment are mixed and made into paper to form liquid crystal polyarylate fiber paper; Next, the liquid crystal polyarylate fiber paper is heat-pressed.

2. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 1, characterized in that: The heat treatment step includes: heating the liquid crystal polyarylate fiber; Preferably, the heat treatment conditions include: temperature of 80-150° C. and time of 2-10 h.

3. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 1, characterized in that: The fibrillation treatment step includes: dispersing the liquid crystal polyarylate fibers in a solvent; Preferably, the solvent comprises at least one of water, a C1-C10 alcohol solvent, and a C3-C8 ketone solvent; Preferably, the stirring conditions for the fibrillation treatment include: a stirring speed of 14000-25000 r / min and a time of 30-90 s.

4. The method for preparing a porous low dielectric liquid crystal polyarylate film according to any one of claims 1 to 3, characterized in that: The mass ratio of the heat-treated liquid crystal polyarylate fiber to the fibrillation-treated liquid crystal polyarylate fiber is (1-9): (9-1).

5. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 4, characterized in that: include: The liquid crystal polyarylate fiber paper is formed by wet papermaking.

6. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 4, characterized in that: The steps of forming the liquid crystal polyarylate fiber paper include: mixing the heat-treated liquid crystal polyarylate fibers and the fibrillated liquid crystal polyarylate fibers with a dispersion, then removing the dispersion to form a liquid crystal polyarylate blank paper, and drying and shaping.

7. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 6, characterized in that: The conditions for mixing the heat-treated liquid crystal polyarylate fibers and the fibrillated liquid crystal polyarylate fibers include: a stirring speed of 14000-25000 r / min and a stirring time of 60-150 s; Preferably, the dispersant in the dispersion is selected from a polymer, preferably any one of polyethylene glycol, polyvinyl alcohol and polyacrylic acid; Preferably, the dispersion is selected from any one of polyethylene glycol at a concentration of 0.1-0.5wt%, polyvinyl alcohol at a concentration of 0.1-0.5wt%, and polyacrylic acid at a concentration of 0.1-0.5wt%. Preferably, the conditions for drying the liquid crystal polyarylate blank paper include: a drying temperature of 80-150° C. and a drying time of 4-5 hours; Preferably, the shaping conditions include: shaping temperature of 200-250° C., shaping pressure of 3-6 MPa, and shaping time of 5-10 min.

8. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 1, characterized in that: The hot pressing conditions include: hot pressing temperature of 200-260° C., hot pressing pressure of 1-5 MPa, and hot pressing time of 5-10 min.

9. The method for preparing a porous low dielectric liquid crystal polyarylate film according to claim 1, characterized in that: The liquid crystal polyarylate fibers are selected from liquid crystal polyarylate staple fibers; Preferably, the length of the liquid crystal polyarylate short fibers is 3-10 mm; Preferably, the step of forming the liquid crystal polyarylate fiber comprises: pre-treating the liquid crystal polyarylate resin and then performing melt spinning.

10. A porous low dielectric liquid crystal polyarylate film, characterized in that: The porous low-dielectric liquid crystal polyarylate film is prepared by the method for preparing the porous low-dielectric liquid crystal polyarylate film according to claim 1.

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