阅读说明：本技术 实现液晶高分子横向吹胀的吹膜装置及制备方法 (Film blowing device for realizing transverse blowing of liquid crystal polymer and preparation method ) 是由 李良彬 赵浩远 于 2020-11-24 设计创作，主要内容包括：一种实现液晶高分子横向吹胀的吹膜装置及薄膜制备方法,该制备方法包括通过吹膜模头的液晶高分子熔体形成液晶高分子型胚；液晶高分子型胚在温度为T-m-150℃～T-m-10℃的压缩气体的吹胀下形成膜泡,其中,T-m为液晶高分子的熔点；膜泡经过冷却定型后形成液晶高分子薄膜。本发明提供一种实现液晶高分子横向吹胀的吹膜装置及薄膜制备方法,用于增大熔点T-m为260～350℃的热致型液晶高分子材料在吹膜加工过程中的横向吹胀,提高液晶高分子薄膜沿横向的力学强度。(A film blowing device for realizing transverse blowing of liquid crystal polymer and a film preparation method are provided, the preparation method comprises the steps of forming a liquid crystal polymer parison by a liquid crystal polymer melt of a film blowing die head; liquid crystal polymer parison at temperature T m ‑150℃～T m Formation of a bubble under inflation of a compressed gas at-10 ℃, wherein T m A melting point of a liquid crystal polymer; and cooling and shaping the film bubble to form the liquid crystal polymer film. The invention provides a film blowing device for realizing transverse blowing of liquid crystal polymer and a film preparation method, which are used for increasing melting point T m The film is transversely blown by a thermotropic liquid crystal high polymer material at 260-350 ℃ in the film blowing processing process, and the transverse mechanical strength of the liquid crystal high polymer film is improved.)

1. A preparation method for realizing transverse inflation of liquid crystal polymer comprises the following steps:

forming a liquid crystal polymer parison by the liquid crystal polymer melt of the film blowing die head;

liquid crystal polymer parison at temperature T_m-150℃～T_mFormation of a bubble under inflation of a compressed gas at-10 ℃, wherein T_mA melting point of a liquid crystal polymer;

and cooling and shaping the film bubble to form the liquid crystal polymer film.

2. The production method according to claim 1,

the atmosphere outside the film bubble in the blowing step is inert protective atmosphere; the temperature of the inert protective atmosphere is T_m-30℃～T_m-5℃。

3. The production method according to claim 1,

the temperature of the die head is T_m-5℃～T_m+40 ℃ where, T_mIs the melting point of the liquid crystal polymer.

4. The production method according to claim 1,

in the cooling and shaping step, the cooling is gradually realized at a cooling speed of less than or equal to 20 ℃/min until the temperature is less than or equal to T_m-130℃。

5. The production method according to claim 1,

a melting point T of the liquid crystalline polymer_mIs 260 to 350 ℃;

the liquid crystal polymer has a blow-up ratio of 1.5-8.5 and a traction ratio of 2-25;

the thickness of the liquid crystal polymer film is 15-250 μm.

6. The utility model provides a realize blown film equipment of horizontal inflation of liquid crystal polymer, includes and gets into accuse temperature forming device, it includes to get into accuse temperature forming device:

the blowing unit is connected with a mouth die of the extruder and is used for blowing the liquid crystal polymer parison;

the temperature control air inlet unit is sleeved on the inflation unit, and gas in the temperature control air inlet unit plays a role in supporting and protecting the film bubble;

the heating element of the heating unit is arranged on the side wall of the temperature control forming device and is used for controlling the temperature of the surrounding atmosphere when the film bubble is transversely blown;

the air outlet of the cooling unit is arranged on the side wall of the temperature-controlled forming device and is used for cooling the film bubble; and

and the control unit controls the units to operate according to preset conditions.

7. The film blowing apparatus according to claim 6,

the inflation unit comprises an air inlet mandrel;

the air inlet core rod is provided with a plurality of air outlet holes with diameters from small to large in the direction far away from the neck mold, and the diameter of each air outlet is 1/15-1/3 of the diameter of the air inlet core rod.

8. The film blowing apparatus according to claim 6,

the temperature control air inlet unit comprises a temperature control air ring;

the control unit adjusts the temperature and the flow of the gas in the temperature control air ring according to the requirement.

9. The film blowing apparatus according to claim 6,

the cooling unit comprises a cooling air ring;

the cooling unit further comprises a circulating air hole, and the circulating air hole is formed in the upper portion of the side wall of the temperature control forming device.

10. The film blowing apparatus according to claim 6,

the film blowing equipment further comprises a film bubble diameter detection device, and the film bubble diameter detection device is arranged on one side of an outlet of the temperature control forming device.

Technical Field

The invention relates to the technical field of liquid crystal sub-film processing, in particular to a film blowing device for realizing transverse blowing of liquid crystal polymers and a preparation method thereof.

Background

The liquid crystal polymer has extremely low dielectric constant and dielectric loss factor under high electromagnetic wave frequency, simultaneously has extremely low water absorption rate and excellent heat resistance, and is expected to become one of key flexible circuit board substrates in the high-frequency communication era.

The thermotropic liquid crystal polymer material for film processing has a molecular main chain of wholly aromatic polyester containing benzene rings or naphthalene ring structures, the molecular chain has extremely low flexibility, a local ordered nematic liquid crystal structure is formed above a melting point, the nematic liquid crystal structure can enable the liquid crystal polymer material to be rapidly solidified and molded in the cooling process, and when a liquid crystal polymer melt is subjected to a flow field with a specific direction, high molecular orientation can be generated in the flow field direction.

When the liquid crystal polymer is prepared into a film by utilizing a blown film processing technology, the severe shearing brought by the extrusion flow channel and the longitudinal traction of the traction roller to the extrusion type blank can enable the liquid crystal polymer to generate high orientation along the traction direction, the film bubble is weak along the transverse interaction force, the film bubble is easy to break in the blowing process, the transverse blowing of the liquid crystal polymer is limited, and the finally obtained liquid crystal polymer film has high anisotropy and poor transverse mechanical property.

In the prior art, the ABA co-extrusion film blowing technology is utilized to solve the problem of poor transverse film forming property of a liquid crystal polymer blown film, and the preparation of the film is realized by taking a middle layer of liquid crystal polymer film by an outer layer of polytetrafluoroethylene film; however, the polytetrafluoroethylene material used for the outer layer is a material which is difficult to melt blown film, which puts higher demands on the design of the die, and the melt processing of fluoroplastics also brings more challenges to the practical industrial production.

Disclosure of Invention

In view of the above, one of the main objectives of the present invention is to provide a film blowing apparatus and a manufacturing method thereof for realizing the lateral blowing of liquid crystal polymer, so as to at least partially solve at least one of the above technical problems.

In order to achieve the above object, as one aspect of the present invention, there is provided a method for preparing a liquid crystal polymer by lateral blowing, comprising:

forming a liquid crystal polymer parison by the liquid crystal polymer melt of the film blowing die head;

liquid crystal polymer parison at temperature T_m-150℃～T_mFormation of a bubble under inflation of a compressed gas at-10 ℃, wherein T_mA melting point of a liquid crystal polymer;

and cooling and shaping the film bubble to form the liquid crystal polymer film.

As another aspect of the present invention, there is also provided a film blowing apparatus for realizing transverse blowing of liquid crystal polymer, including an entering temperature-controlled forming apparatus, the entering temperature-controlled forming apparatus including:

the blowing unit is connected with a mouth die of the extruder and is used for blowing the liquid crystal polymer parison;

the temperature control air inlet unit is sleeved on the inflation unit, and gas in the temperature control air inlet unit plays a role in supporting and protecting the film bubble;

the heating element of the heating unit is arranged on the side wall of the temperature control forming device and is used for controlling the temperature of the surrounding atmosphere when the film bubble is transversely blown;

the air outlet of the cooling unit is arranged on the side wall of the temperature-controlled forming device and is used for cooling the film bubble; and

and the control unit controls the units to operate according to preset conditions.

Based on the technical scheme, the film blowing device for realizing transverse blowing of the liquid crystal polymer and the preparation method thereof have at least one or part of the following advantages compared with the prior art:

1. the invention provides a film blowing device for realizing transverse blowing of liquid crystal polymer and a film preparation method, which are used for increasing melting point T_mThe film is transversely blown by a thermotropic liquid crystal high polymer material at 260-350 ℃ in the film blowing processing process, so that the transverse mechanical strength of the liquid crystal high polymer film is improved;

2. according to the film blowing device and the method, the liquid crystal polymer film blowing forming process is placed into an atmosphere system with accurately controllable external fields such as temperature and atmosphere, and the transverse blowing performance of the liquid crystal polymer is improved according to the structural characteristics of the liquid crystal polymer;

3. compared with the prior art for improving the film blowing performance of the liquid crystal polymer, the invention considers the influence of compressed gas blowing and film cooling shaping on the middle blowing forming process, effectively overcomes the transverse blowing defect of the liquid crystal polymer, and improves the continuous film forming capability of the liquid crystal polymer;

4. the liquid crystal polymer film prepared by the invention has low anisotropy and excellent transverse physical property;

5. the invention provides the liquid crystal polymer film blowing device and the film preparation method for realizing the transverse blowing of the liquid crystal polymer, which have the advantages of wide application range, simple and convenient process flow and high automation degree.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a film blowing device provided in an embodiment of the present invention;

FIG. 2 is a wide-angle X-ray diffraction pattern of a liquid crystal polymer film prepared according to an example of the present invention.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

In order to solve the problem that the prepared film has high anisotropy because thermotropic liquid crystal polymer materials are highly oriented along the traction direction in the film blowing process and film bubbles are easy to break in the blowing process, the structure and the crystallization and solidification behaviors of liquid crystal polymers are deeply researched, and the key for increasing the blowing ratio of the blown liquid crystal polymer is found out how to ensure the tensile property of the liquid crystal polymers in the film bubble blowing stage and cooperatively control the processes of blowing and cooling.

Because the melting point of the liquid crystal polymer is higher, the extruded melt can be rapidly solidified if directly contacting low-temperature air, and transverse inflation cannot be carried out, so that the temperature is too low in an atmosphere at a certain temperature in the inflation process, the stretchability of the film bubble is reduced, the temperature is too high, the viscosity of the liquid crystal polymer is low, the melt strength is poor, traction cannot be carried out, and the liquid crystal polymer can be prevented from being oxidized under a long-time high-temperature condition by inert gas protection. By co-ordinationThe inflation and air ring blowing device for controlling compressed air can ensure that the film bubble has excellent film bubble stability and ensures the flatness of the film under the condition of obtaining a large inflation ratio. The invention provides a film blowing device for realizing transverse blowing of liquid crystal polymer and a film preparation method, which are used for increasing the melting point T_mThe transverse blow-up ratio of the thermotropic liquid crystal high polymer material at 260-350 ℃ in the film blowing processing process.

The invention relates to a film blowing device for realizing transverse blowing of liquid crystal polymer and a film preparation method, which are used for increasing the melting point T_mThe film is transversely blown by a thermotropic liquid crystal high polymer material at the temperature of 260-350 ℃ in the film blowing processing process, and the prepared film has good transverse physical properties and low anisotropy. Under the control of a temperature control forming system, the annular parison extruded from the neck mold is kept in a state of being capable of transversely blown and stretched in a blowing stage, and is gradually cooled and solidified in a cooling stage to reduce the defects of wrinkling and layering; the temperature control air inlet unit, the temperature control air ring blowing device and the film bubble diameter detection device jointly determine the transverse inflation ratio of the liquid crystal polymer, and compressed air enters the film bubble through the air inlet core rod, so that the stability of the inflated film bubble is effectively improved.

The invention discloses a preparation method for realizing transverse inflation of liquid crystal polymer, which comprises the following steps:

forming a liquid crystal polymer parison by the liquid crystal polymer melt of the film blowing die head;

liquid crystal polymer parison at temperature T_m-150℃～T_mFormation of a bubble under inflation of a compressed gas at-10 ℃, wherein T_mA melting point of a liquid crystal polymer;

and cooling and shaping the film bubble to form the liquid crystal polymer film.

In some embodiments of the invention, the atmosphere outside the bubble in the step of blowing is an inert protective atmosphere; the temperature of the inert protective atmosphere is T_m-30℃～T_m-5℃。

In some embodiments of the invention, the temperature of the die is T_m-5℃～T_m+40 ℃, wherein Tm is the melting point of the liquid crystal polymer.

In some embodiments of the invention, the cooling in the cooling and shaping step is gradually carried out at a cooling rate of less than or equal to 20 ℃/min until the temperature is less than or equal to T_m-130℃。

In some embodiments of the present invention, the melting point T of the liquid crystal polymer_mIs 260 to 350 ℃;

in some embodiments of the present invention, the liquid crystal polymer has a blow-up ratio of 1.5 to 8.5 and a draw-down ratio of 2 to 25;

in some embodiments of the present invention, the thickness of the liquid crystal polymer film is 15 to 250 μm.

The invention also discloses a film blowing device for realizing the transverse blowing of the liquid crystal polymer, which comprises an entering temperature control forming device, wherein the entering temperature control forming device comprises:

the blowing unit is connected with a mouth die of the extruder and is used for blowing the liquid crystal polymer parison;

the temperature control air inlet unit is sleeved on the inflation unit, and gas in the temperature control air inlet unit plays a role in supporting and protecting the film bubble;

the heating element of the heating unit is arranged on the side wall of the temperature control forming device and is used for controlling the temperature of the surrounding atmosphere when the film bubble is transversely blown;

the air outlet of the cooling unit is arranged on the side wall of the temperature-controlled forming device and is used for cooling the film bubble; and

and the control unit controls the units to operate according to preset conditions.

In some embodiments of the invention, the inflation unit comprises an air inlet mandrel;

in some embodiments of the invention, the air inlet mandrel is provided with a plurality of air outlet holes with diameters from small to large along the direction away from the die, and the diameters of the air outlet holes are 1/15-1/3 of the diameter of the air inlet mandrel.

In some embodiments of the invention, the temperature controlled air intake unit comprises a temperature controlled air ring;

in some embodiments of the invention, the control unit adjusts the temperature and flow of gas within the temperature controlled wind ring as desired.

In some embodiments of the invention, the cooling unit comprises a cooling air ring;

in some embodiments of the present invention, the cooling unit further includes a circulation air hole, and the circulation air hole is disposed at an upper portion of the sidewall of the temperature-controlled forming device;

in some embodiments of the invention, the film blowing equipment further comprises a bubble diameter detection device, and the bubble diameter detection device is arranged on the outlet side of the temperature-controlled forming device.

In an exemplary embodiment, the invention provides a film blowing device for realizing transverse blowing of liquid crystal polymer, the film blowing device comprises an extruder, a temperature control forming device and a bubble diameter detection device, and the temperature control forming device comprises a blowing unit, a temperature control air inlet unit, a cooling unit and a control unit. The inflation unit, the temperature control air inlet unit and the cooling unit are regulated and controlled by the control unit to ensure that the melting point T is_mThe thermotropic liquid crystal polymer material at 260-350 ℃ keeps a tensile deformation state in an inflation stage, the transverse inflation of compressed gas to a liquid crystal polymer parison is increased, the inflated liquid crystal polymer film bubble can be gradually cooled and solidified in a cooling forming stage, and the defects of wrinkling, layering and the like of the liquid crystal polymer film in a rapid cooling process are reduced.

In some embodiments of the present invention, the inflation unit includes an air inlet mandrel and an inflation control assembly, the air inlet mandrel is connected to a die of the extruder, the air blown out from the air inlet mandrel is used for inflating the liquid crystal polymer parison, the inflation control assembly can control the temperature, flow rate, air inflow and the like of the compressed air in the air inlet mandrel, so as to realize controllable adjustment of the compressed air, and the air inlet mandrel ensures that the compressed air in the initial stage uniformly and stably enters the inside of the film bubble.

In some embodiments of the invention, the air inlet core rod is provided with air outlet holes with diameters from small to large along the longitudinal direction of the bubble from the outlet of the die, and when the diameter of the air inlet hole of the air inlet core rod is D, the diameter of the air outlet hole is D/15-D/3, and more preferably D/12-D/4.

In some embodiments of the present invention, the lower end of the air inlet mandrel is connected to the upper end surface of the air ring, the inflation unit is mainly used for adjusting and controlling the temperature of the surrounding atmosphere when the film bubble is inflated, so that the liquid crystal polymer is still in a stretchable deformation state, therefore, the part is composed of the temperature control component and the heating element, the appearance performance of the blow molding device can be cylindrical, cuboid, prism and the like, the main body shape of the film bubble is cylindrical, the appearance shape of the blow molding device is set to be cylindrical with the diameter larger than that of the film bubble from the viewpoint of heating uniformity, the heating element comprises a heating block, a heating plate, a heating wire, a heating pipe and the like, and from the viewpoint of practicability, the heating wire or the heating pipe is wound on the inner wall of the cylindrical blow molding device, the heating power of the heating element is controlled by the temperature control system to control the temperature, and the nitrogen blown by the air ring can make the temperature distribution in the blow molding device more uniform.

In some embodiments of the present invention, the temperature-controlled air inlet unit includes a temperature-controlled air ring and a temperature-controlled heating assembly, and the temperature-controlled heating assembly can realize controllable adjustment of the temperature, the flow rate, and the air input of the air entering the temperature-controlled air ring, so as to realize controllable adjustment of the ambient temperature at the bubble inflation stage. The gas blown out by the temperature control air ring can adopt inert gas to play a role in protecting the film bubble. Meanwhile, the air outlet of the temperature control air ring can be adjusted to adjust the blowing angle of the temperature control air ring.

In some embodiments of the invention, the temperature control air inlet unit is composed of a compressed gas generating assembly and a temperature control heating assembly, the temperature control air ring is fixed on the upper end surface of the die head and is connected with a stepless speed regulating fan and the temperature control heating assembly, the temperature control heating assembly is positioned between the temperature control air ring and the stepless speed regulating fan and is used for heating gas, the temperature of the gas is controlled by regulating the heating power, and the stepless speed regulation is preferably realized by adopting a centrifugal fan with stepless speed regulation. Compressed gas generated by the compressed gas generating assembly is heated to a set temperature through the temperature control heating assembly and enters the inlet of the air inlet core rod, the form of the compressed gas generating assembly is not limited in the invention, the compressed gas generating assembly comprises an air compressor, a high-pressure nitrogen cylinder and the like, and from the practical point of view, the air compressor is preferentially adopted, and the gas flow rate and the gas inlet amount are controlled by controlling the gas pressure and the pneumatic knob; the form of the temperature-controlled heating element is not limited in the present invention, and various known heating forms including, but not limited to, electric heating, infrared heating, induction heating, electron beam heating, etc. may be employed, and from the viewpoint of practicality, electric heating is preferably employed, and the heating element includes, but not limited to, a heating block, a heating plate, a heating wire, a heating pipe, etc. and the temperature is controlled by adjusting the heating power of the heating element.

In some embodiments of the invention, the bubble diameter detection device can realize real-time measurement of the bubble diameter, and can realize feedback of the temperature control air inlet unit and the temperature control air ring blowing device through the temperature control forming device, so as to obtain the bubble diameter required by the target.

In some embodiments of the present invention, the cooling unit includes a cooling air ring and a cooling air ring control assembly, the cooling air ring is disposed above the temperature control air ring, and the cooling air ring control assembly can control the temperature, flow rate, air inflow, and the like of the air blown out from the cooling air ring to realize the segmented adjustment of the ambient temperature around the bubble, so as to gradually cool and solidify the liquid crystal polymer film.

In some embodiments of the invention, the cooling unit further comprises a circulating air hole, the cooling air ring is connected with an air flow generating assembly, the air flow generating assembly blows cooling air flow into the cooling air ring, the cooling air flow is blown to the formed film bubble from an air blowing opening of the air ring, hot air flow is discharged from the circulating air opening to the temperature-control forming device, cooling of the film bubble is realized, a temperature-control assembly is connected between the air flow generating assembly and the cooling air ring, the temperature of the blown cooling air flow can be controlled, and finally the purpose of regulating and controlling the cooling rate of the film bubble is achieved by cooperatively controlling the temperature and the flow rate of the air flow, so that controllable cooling is realized.

In some embodiments of the present invention, the extruder connected to the temperature-controlled forming device may be a single-layer film blowing die or a co-extrusion film blowing die with two or more layers.

In some embodiments of the present invention, the inflation ratio of the liquid crystal polymer is 1.5 to 8.5, for example, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, by controlling the temperature, flow rate, air intake amount, etc. of the compressed gas in the air intake mandrel; the draft ratio is 2 to 25, for example, 2, 3, 5, 8, 10, 12, 15, 18, 20, 22, 25.

In some embodiments of the present invention, the thickness of the liquid crystal polymer film is 15 to 250 μm, such as 15 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm.

The embodiment of the invention also provides a preparation method of the liquid crystal polymer film, which is carried out according to the following steps:

the liquid crystal polymer melt after being melted and plasticized by the extruder passes through a film blowing die head, and the temperature of the die head is T_m-5℃～T_m+40 ℃, more preferably T_m～T_mAt 30 ℃, the mixture is extruded from an annular neck mold through the drawing of a traction roller and enters a temperature control forming device, and the temperature of compressed gas (the temperature of which is T) in an air inlet core rod is controlled_m-150℃～T_mThe liquid crystal polymer parison is still in a state of being stretched and deformed at the temperature of minus 10 ℃, compressed gas enters the liquid crystal polymer parison from the gas inlet mandrel to transversely blow the liquid crystal polymer parison, gas blown from the air outlet of the temperature control air ring plays a role in supporting and stabilizing the blown film bubble, the blown film bubble is gradually cooled and solidified under the cooling of the gas in the cooling air ring, and particularly, the gas in the cooling air ring gradually realizes the cooling and solidification of the film bubble at the cooling speed of less than or equal to 20 ℃/min until the temperature of the film bubble is less than or equal to T_m-130 ℃, more preferably at a temperature ≦ T_mAnd the bubble diameter detection device connected with an ultrasonic sensor measures the diameter of the bubble, when the diameter of the bubble is not in a set range, the bubble diameter is adjusted by feeding back the inflation unit and the temperature control air inlet unit, the bubble with the set diameter enters a traction roller through a herringbone plate and then enters a rolling system or a film post-treatment system through a guide roller and the like, and finally the liquid crystal polymer film with excellent transverse physical properties is obtained.

Further, the temperature of the surrounding environment of the bubble of the blowing unit is T_m-30℃～T_m-5 ℃, more preferably T_m-20℃～T_m-5℃。

Further, the gas in the blowing unit and the cooling unit is an inert atmosphere, so that the atmosphere surrounding the bubble is an inert atmosphere, and the inert atmosphere is preferably dry nitrogen gas from the viewpoint of economic and protective effects.

Further, the liquid crystal polymer has a blow-up ratio of 1.5 to 8.5, more preferably 2.5 to 8.5, and a draw-down ratio of 2 to 25, more preferably 2 to 15.

Further, the thickness of the liquid crystal polymer film is 15-250 μm.

The technical solution of the present invention is further illustrated by the following specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific examples are given by way of illustration only and the scope of the present invention is not limited thereto.

Referring to fig. 1, an embodiment of the present invention provides a film blowing apparatus for implementing lateral blowing of liquid crystal polymer and a method for preparing a film, wherein a liquid crystal polymer melt 3 melted and plasticized by an extruder passes through a film blowing die head 1, a heating jacket 2 controls the temperature of the die head 1 to be T_m-5℃～T_m+40 ℃, extruded from the ring-shaped neck mold 4 by the drawing of the drawing roll 18 and enters a temperature control forming device, the temperature control forming device is simultaneously coordinated with the temperature control air inlet unit 6, the temperature control air inlet unit 8, the blowing unit 10, the cooling unit 14 and the bubble diameter detection device 15 by the control unit 16, when the parison enters the temperature control forming device, the temperature control air inlet unit 6 heats the compressed nitrogen to raise the temperature to T_m-150℃～T_mThe temperature is-10 ℃, heated gas uniformly enters the interior of the melt parison through the gas inlet mandrel 5 under the control of the temperature control gas inlet unit 6, and meanwhile, the temperature control assembly 9 controls the atmosphere temperature in the blow molding stage to be T under the control of the blow unit 10_m-30℃～T_mAt-5 ℃, circulating dry nitrogen is used as protective gas, and the temperature is T by the temperature control gas inlet unit 8_m-30℃～T_mDry nitrogen at the temperature of-5 ℃ is blown to the blowing-up melt parison through the temperature control air ring air outlet 7, the film bubble is gradually blown up along with the increase of the gas pressure in the melt parison, the blown-up film bubble is stabilized under the support of the blowing of the temperature control air ring and is gradually pulled to be cooled, and the dry nitrogen at the lower temperature is controlled by the cooling unit 14 to be blown from the cooling air ring 12Blowing into the periphery of the blown film bubble 11, discharging high-temperature nitrogen on the outer surface of the film bubble 11 through a circulating air hole 13, controlling the cooling rate of the film bubble to be less than or equal to 20 ℃/min by a cooling forming device 14, and reducing the temperature of the film bubble to be less than or equal to T_mLeaving the temperature-controlled forming device at minus 130 ℃, and causing the liquid crystal polymer film to generate the defects of wrinkling, layering and the like at an excessively high cooling rate, meanwhile, the thermal convection in the bubble blowing and cooling stages is also intensified, the precise control on different forming stages of the bubble is lost, when the formed bubble 11 passes through a bubble diameter detection device 15 provided with an ultrasonic sensor, the diameter of the film bubble is obtained, the diameter of the film bubble is fed back to the temperature control air inlet unit 6 and the temperature control air inlet unit 8 through the master control unit 16, the air inlet amount/air discharge amount and the air flow speed are adjusted, the film bubble 11 with a specific diameter enters a traction roller through a herringbone plate 17, then passes through a plurality of guide rollers 19 to obtain a liquid crystal polymer film, and the liquid crystal polymer film enters a rolling or post-processing system 20 as required until the preparation of the liquid crystal polymer film is completed.

The mechanical property of the film is tested by using a universal testing machine, and the test is carried out according to the GB/T1040.3-2006 method.

The invention uses a mechanical contact thickness gauge to test the thickness of the film, and the test is carried out according to the method of ASTM D645.

The invention adopts a wide-angle X-ray diffraction technology to characterize the anisotropy of the prepared liquid crystal polymer film, and calculates the orientation degree of the liquid crystal polymer film through the azimuthal angle integral of the crystal face of the liquid crystal polymer (110).

The invention utilizes a thermomechanical analysis Technology (TMA) to measure the longitudinal and transverse thermal expansion coefficients of the liquid crystal polymer film by referring to a GB/T36800.2-2018 method.

Example 1

The liquid crystal polymer film is prepared by using the film blowing device for realizing the transverse blowing of the liquid crystal polymer and the film preparation method provided in the above embodiment. The liquid crystal high polymer material is liquid crystal copolyester of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, and the melting point is 280 ℃. Before processing, the liquid crystal polymer material is subjected to drying pretreatment in a vacuum drying oven, wherein the drying temperature is 150 ℃ and the drying time is 5 hours. The pretreated liquid crystal polymer material is sufficiently melted and plasticized by an extruder and enters the device provided by the above embodiment. The temperature of the die head 1 is 310 ℃, the temperature of compressed nitrogen is 260 ℃, the temperature of the bubble in the bubble inflation molding stage is 270 ℃, the cooling rate of the bubble in the bubble cooling stage is 20 ℃/min, and the film is finally pulled out of the temperature control molding system when the temperature is reduced to 100 ℃; the bubble blowing ratio was 1.5, the draw ratio was 10, the thickness of the final liquid crystal polymer film was 90 μm, and heat-treated in an oven at 250 ℃ for 5 hours. The parameters and properties of the finally obtained liquid crystal polymer film were measured according to the above-mentioned methods, and the results are shown in Table 1.

Example 2

The same method as in example 1 was used, except that the bubble blowing ratio was 3.0, as in example 1.

Example 3

The same method as in example 1 was used, except that the bubble blowing ratio was 4.0, as in example 1.

Example 4

The same method as in example 1 was used, except that the bubble blowing ratio was 5.0, as in example 1.

Example 5

The same method as in example 1 was used, except that the bubble blowing ratio was 6.0, as in example 1.

Example 6

The same method as in example 4 was used, except that the draw ratio of the bubble was 8.5, as in example 4.

Example 7

The same method as in example 6 was used except that the temperature in the bubble inflation molding stage was 260 ℃.

Example 8

The same procedure as in example 6 was used, except that the temperature decrease rate in the bubble cooling stage was 10 ℃/min.

TABLE 1

The longitudinal direction of the film is parallel to the drawing direction during processing, and the transverse direction of the film is perpendicular to the drawing direction during processing.

As can be seen from table 1, the film blowing device provided by the present invention can realize the transverse blowing of the film bubble in a larger range, and the transverse blowing capability of the liquid crystal polymer is significantly improved, as can be seen from examples 1 to 5, with the increase of the blowing ratio, the anisotropy of the film is gradually reduced, the longitudinal and transverse mechanical properties and the thermal expansion coefficient of the film are gradually close, and when the blowing ratio is large, the transverse mechanical property of the film is excellent; from the examples 5 and 6, it can be known that the liquid crystal polymer film with low anisotropy can be obtained by having a relatively close draw ratio and blow-up ratio in the film blowing process; from examples 7 and 8, it is understood that a liquid crystal polymer film having low anisotropy and excellent transverse physical properties can be prepared by the film preparation method provided by the present invention.

As can be seen from fig. 2, when the blow-up ratio is relatively small, the diffraction rings of the (110) crystal planes are concentrated in the horizontal direction, and a symmetric diffraction arc is shown, which indicates that the anisotropy of the liquid crystal polymer film is relatively high, and as the blow-up ratio is increased, the (110) crystal planes show isotropic diffraction rings, which indicates that the orientation degree of the liquid crystal polymer film is significantly reduced.

In summary, the film blowing device and the film preparation method for realizing the transverse blowing of the liquid crystal polymer provided by the invention can increase the melting point T_mThe transverse blow-up ratio of the thermotropic liquid crystal polymer material at 260-350 ℃ in the film blowing processing process is increased, and the transverse mechanical strength of the liquid crystal polymer film is improved; the liquid crystal polymer film prepared by the invention has lower anisotropy and excellent transverse physical property; the device and the method have the advantages of simple processing technology, wide application range and high automation control degree.

Parts of the invention not described in detail are well known in the art.

It should be noted that, although the invention has been shown and described with reference to the specific exemplary embodiments thereof, it should be understood by those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and various changes and modifications may be made therein without departing from the spirit and scope of the invention, and it is intended that the invention encompass such changes and modifications as fall within the scope of the claims and the equivalent technical scope of the invention.

In particular, various combinations and/or combinations of features recited in the various embodiments and/or claims of the present invention can be made without departing from the spirit and teachings of the invention, even if such combinations or combinations are not explicitly recited in the present invention. All such combinations and/or associations are within the scope of the present invention. The scope of the invention should, therefore, be determined not with reference to the appended claims, but should instead be determined with reference to the following claims.