Forming Method of Liquid Crystal Polymer Film and Film Blowing Equipment

Abstract

A forming method for a liquid crystal polymer film and a blown film device. The blown film device includes an extruder; a coextrusion die head, which is arranged at the end of the extruder. The coextrusion die head includes a plurality of distribution channels and a coextrusion flow channel. The ends of the plurality of distribution channels are all connected to the starting end of the coextrusion flow channel; the number of the distribution channels is greater than or equal to 5; a first air ring, which is connected to the die orifice of the coextrusion die head; and a second air ring, which is arranged above the first air ring. The forming method for a liquid crystal polymer film and the blown film device provided by the present invention can directly prepare a monolayer or multilayer liquid crystal polymer film with anisotropy continuously adjustable by adjusting the blow-up ratio, die head temperature, and coextrusion layer combination, and has substantial characteristics and remarkable technical progress compared with the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of polymer film processing, and in particular to a liquid crystal polymer film forming method and film blowing equipment. Background Art

[0002] With the gradual development of communication equipment and technology, the production and preparation of high-performance high-frequency substrate materials has become an indispensable part of the development of high-frequency wireless communications. Most traditional flexible circuit board substrates use polyimide film as the insulating substrate for the metal plate, but due to the high hygroscopicity of polyimide film and poor high-frequency dielectric properties, it is difficult to meet the high-frequency and high-speed application requirements of the wireless communication industry. Liquid crystal polymer film will replace traditional materials with its unique properties such as extremely low dielectric constant and dielectric loss (dielectric constant is about 3 in the frequency range of 1 to 60GHz, and dielectric loss is less than 0.003), low hygroscopicity (<0.04%), and excellent dimensional stability, and become a key film material in the high-frequency era.

[0003] In the prior art, high-frequency flexible copper-clad laminates are usually obtained by laminating a single-layer liquid crystal polymer film with copper foil. Preferably, a type I liquid crystal polymer film with a higher melting point is used as the core layer of the substrate, and a type II liquid crystal polymer with a lower melting point is used as the bonding layer of the substrate. However, due to the inherent high heat resistance and rigid rod-like structure of liquid crystal polymers, single-layer liquid crystal polymer films can usually only be obtained by rotary die blowing, biaxial stretching technology, laminate stretching method or coating method. If it is necessary to prepare a multi-layer liquid crystal polymer substrate with better performance, different types of liquid crystal polymer films can only be hot-pressed and composited by lamination technology. In addition, liquid crystal polymers solidify rapidly below the melting point, and stratification is very likely to occur in the thickness direction during film processing. In addition, when a single-layer liquid crystal polymer film is processed into a copper-clad laminate, there are also problems such as low peel strength between the film and the copper foil. Summary of the invention

[0004] In view of this, one of the main purposes of the present invention is to provide a liquid crystal polymer film forming method and film blowing equipment, in order to at least partially solve at least one of the above technical problems.

[0005] In order to achieve the above object, as one aspect of the present invention, a film blowing device for a liquid crystal polymer film is provided, comprising:

[0006] Extruder;

[0007] A co-extrusion die head, which is arranged at the end of the extruder, and the co-extrusion die head comprises a plurality of branch channels and a co-extrusion channel, and the ends of the plurality of branch channels are connected to the starting end of the co-extrusion channel; the number of the branch channels is greater than or equal to 5;

[0008] A first air ring connected to the die of the co-extrusion die head; and

[0009] The second air ring is arranged above the first air ring.

[0010] As another aspect of the present invention, a method for forming a liquid crystal polymer film is also provided. Using the blown film equipment as described above, it includes:

[0011] Set the process parameters of the extruder;

[0012] Convey different materials to the co-extrusion runner through different shunt runners respectively;

[0013] The materials passing through the co-extrusion runner form a film bubble under the air flow of the die core;

[0014] Traction the film bubble to form the liquid crystal polymer film under the action of the air flow of the first air ring and the air flow of the second air ring.

[0015] Based on the above technical solutions, the method for forming a liquid crystal polymer film and the blown film equipment of the present invention have at least one or a part of the following advantages compared with the prior art:

[0016] 1. To ensure the uniformity and continuity of the co-extruded material containing liquid crystal polymer when extruded from the die, the key to solving this problem is, first, to improve the plasticization effect of the co-extruded material and the uniformity of the melt by setting a filtering structure in the die head, and second, to set an appropriate length of the co-extrusion runner to achieve the uniformity of the material distribution in the circumferential direction, solving the problems of blowing and bursting, poor uniformity, and difficulty in multi-layer lamination during the preparation of the liquid crystal polymer film. By regulating the co-extruded layer materials, liquid crystal polymer films with different structural types and precisely adjustable anisotropy can be obtained;

[0017] 2. Since the liquid crystal polymer will quickly solidify after being below the melting point, the first air ring is set in the transverse blowing stage to reduce the influence of the cooling air flow on it, increasing the blowing ratio in the transverse direction of the film bubble and ensuring the plasticity of the liquid crystal polymer. When the difference between the crystallization temperature of the liquid crystal polymer material to be processed and the ambient temperature around the film bubble is greater than 150 °C, increase the temperature of the air flow in this stage; in the film cooling and solidification stage, it is necessary to accurately adjust the cooling process according to the characteristics of the material to prevent defects such as wrinkles and deformation of the film due to rapid cooling;

[0018] 3. The method for forming a liquid crystal polymer film and the blown film equipment provided by the present invention can directly prepare single-layer or multi-layer liquid crystal polymer films with continuously adjustable anisotropy by adjusting the blowing ratio, die head temperature, and co-extruded layer combination, having substantial characteristics and remarkable technical progress compared with the prior art;

[0019] 4. The forming method of the liquid crystal polymer film and the blown film equipment provided by the present invention, due to the co-extrusion process of five or more layers, the liquid crystal polymer layer located in the middle layer is protected by other co-extrusions, and its surface layer will not rapidly cool and solidify. The crystallization and solidification in the thickness direction are more controllable, significantly weakening the delamination effect of the film in the thickness direction. At the same time, an adhesive layer can be set on the film surface, which is particularly suitable for the processing and preparation of flexible copper clad laminates.

[0020] 5. The forming method of the liquid crystal polymer film and the blown film equipment provided by the present invention have the advantages of simple equipment manufacturing, low energy consumption, etc. At the same time, various structural combinations can be carried out according to the use requirements, with relatively wide adaptability and outstanding industrial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0022] Figure 1 It is a schematic structural diagram of the five-layer co-extrusion blown film processing provided by the embodiment of the present invention;

[0023] Figure 2 It is a schematic structural diagram of the multi-layer co-extruded liquid crystal polymer composite film prepared by the embodiment of the present invention.

[0024] Description of the reference numerals in the drawings:

[0025] 1 - Co-extrusion die head; 2 - Heating sleeve; 3 - 7 - Flow channels; 8 - Co-extrusion flow channel; 9 - Air inlet of the first air ring; 10 - Lower disc of the first air ring; 11 - Upper disc of the first air ring; 12 - Turbulence ring of the first air ring; 13 - Air inlet hole of the die core; 14 - Annular die orifice; 15 - Film bubble; 16 - Air inlet of the second air ring; 17 - Lower disc of the second air ring; 18 - Upper disc of the second air ring; 19 - Turbulence ring of the second air ring; 20 - Chevrons; 21 - Traction roller; 22 - Composite film. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0027] The present invention solves the problems of blowing and bursting, poor uniformity, and difficulty in multi-layer lamination during the preparation of liquid crystal polymer films. By regulating the co-extrusion layer materials, liquid crystal polymer films with different structural types and precisely adjustable anisotropy can be obtained. The present invention directly obtains single-layer or multi-layer liquid crystal polymer films by using a multi-layer co-extrusion blown film technique; the present invention can precisely regulate the anisotropy of the liquid crystal polymer films; the prepared liquid crystal polymer films have good uniformity and no obvious delamination in the thickness direction; the liquid crystal polymer films prepared by the present invention have significant advantages when laminated with copper foils to prepare flexible copper clad laminates.

[0028] The present invention discloses a blown film device for liquid crystal polymer films, comprising:

[0029] An extruder;

[0030] A co-extrusion die head, which is arranged at the end of the extruder. The co-extrusion die head includes a plurality of distribution channels and a co-extrusion flow channel. The ends of the plurality of distribution channels are all connected to the starting end of the co-extrusion flow channel; the number of the distribution channels is greater than or equal to 5;

[0031] A first air ring, connected to the die orifice of the co-extrusion die head; and

[0032] A second air ring, arranged above the first air ring.

[0033] In some embodiments of the present invention, a filtering structure is provided at the front end of each of the distribution channels;

[0034] In some embodiments of the present invention, the ratio of the co-extrusion flow channel to the diameter of the die orifice is 0.5 - 50.

[0035] In some embodiments of the present invention, the co-extrusion die head further includes a die core, and the die core is a structure that transitions from a conical shape to a cylindrical shape;

[0036] In some embodiments of the present invention, the forming device further includes a heating jacket for heating the co-extrusion die head.

[0037] In some embodiments of the present invention, the first air ring is connected to a first temperature control unit for regulating the air flow temperature of the first air ring;

[0038] In some embodiments of the present invention, the second air ring is connected to a second temperature control unit for regulating the air flow temperature of the second air ring.

[0039] In some embodiments of the present invention, the first air ring includes a first air ring spoiler ring; the first air ring spoiler ring has an inverted frustum shape, and the inclination angle α1 of the frustum shape is ≤ 30°;

[0040] In some embodiments of the present invention, the second air ring includes a second air ring spoiler ring; the second air ring spoiler ring has an inverted frustum structure, and the inclination angle α2 of the frustum structure is ≥ 45°.

[0041] The present invention also discloses a method for forming a liquid crystal polymer film, which uses the blow molding device as described above, and includes:

[0042] Setting the process parameters of the extruder;

[0043] Conveying different materials to the co-extrusion channel through different shunt channels respectively;

[0044] The materials passing through the co-extrusion channel form a film bubble under the air flow of the die core;

[0045] Traction the film bubble so that the film bubble forms the liquid crystal polymer film under the action of the air flow of the first air ring and the air flow of the second air ring.

[0046] In some embodiments of the present invention, when the difference between the crystallization temperature T c of the liquid crystal polymer material to be processed and the ambient temperature T a of the film bubble is greater than 150 °C, set the air flow temperature of the first air ring to be T c -100 °C to T c +30 °C;

[0047] In some embodiments of the present invention, the air flow temperature of the second air ring is T c -200 °C to T c -120 °C;

[0048] In some embodiments of the present invention, the blow-up ratio is controlled to be 1.2 to 8.0 in the step of forming the film bubble;

[0049] In some embodiments of the present invention, set the extrusion pressure of the extruder to be 0.1 to 15.0 Mpa.

[0050] In some embodiments of the present invention, different liquid crystal polymer films with different structures are obtained by setting different materials in several shunt channels.

[0051] In some embodiments of the present invention, several shunt channels at least include a first shunt channel, a second shunt channel, a third shunt channel, a fourth shunt channel, and a fifth shunt channel arranged in sequence; the third shunt channel contains liquid crystal polymer material.

[0052] In some embodiments of the present invention, the third shunt channel contains liquid crystal polymer material, and the other shunt channels contain non-liquid crystal polymer material; or,

[0053] The third runner is filled with liquid crystal polymer material, and at least one layer in the second and fourth runners is filled with adhesive material; or,

[0054] The third runner is filled with liquid crystal polymer material, at least one of the second and fourth runners is filled with liquid crystal polymer material, and the first and fifth runners are filled with adhesive material; or,

[0055] The second, third, and fourth runners are all filled with liquid crystal polymer material, and at least one of the first and fifth runners is filled with adhesive material.

[0056] The present invention discloses a forming method and a blown film device for a liquid crystal polymer film. By using a multi-layer co-extrusion method, the preparation of single-layer and multi-layer liquid crystal polymer films is realized. The blown film device includes a special die head for co-extruding liquid crystal polymer with five or more layers and a supporting forming and cooling system.

[0057] The structural characteristics of the special die head for co-extruding multi-layer liquid crystal polymer blown film are as follows: a filtering structure is provided at the front end of the die head runner, and before the material enters the co-extrusion runner, unfully plasticized solid particles can be filtered out; the ratio of the length of the co-extrusion runner to the diameter of the die orifice is 0.5 - 50 to ensure the uniformity of the extruded tubular parison;

[0058] The structure of the forming and cooling system includes a first air ring and a second air ring: between the die orifice outlet and the haul-off roll, there are multiple stages of forming and cooling equipment, namely the first air ring and the second air ring, to gradually realize the lateral inflation and cooling solidification of the film bubble, etc. Both the first air ring and the second air ring are equipped with stepless speed regulation fans, which can regulate the flow rate and wind of the air flow, and the temperature of the air flow can be heated or cooled through temperature control equipment; the processing blow-up ratio is 1.2 - 8.0, more preferably 1.2 - 6.5. As the blow-up ratio increases, the anisotropy of the film gradually decreases, and the physical properties in the transverse direction gradually improve. The extrusion pressure of the extruder for processing the liquid crystal polymer material is 0.1 - 15.0 MPa, more preferably 0.5 - 10.0 MPa. Since the viscosity of the liquid crystal polymer melt is relatively low, with the increase of the extrusion pressure, the backflow of the material can be reduced, and the extrusion stability of the material can be improved. However, when the extrusion pressure is too high, it will cause material leakage from the device and affect the processing life of the screw at the same time.

[0059] By using the method of multi-layer co-extrusion, the preparation of a multi-layer co-extruded composite film containing a liquid crystal polymer material is realized. The structural characteristics of the five-layer co-extruded composite film are IIIA / IIA / I / IIB / IIIB, where the I layer is a liquid crystal polymer layer, the IIA layer and the IIB layer are functional layers, and the IIIA layer and the IIIB layer are protective layers; directly peeling off the I layer can obtain a single-layer liquid crystal polymer film. When the IIA and IIB layers are liquid crystal polymers, peeling off the IIIA and IIIB layers can obtain a multi-layer co-extruded liquid crystal polymer film. When the IIA and IIB layers are adhesives, peeling off the IIIA and IIIB layers can obtain a single-layer liquid crystal polymer film with an adhesive layer; the thickness of the single-layer liquid crystal polymer film is 5-200 μm, and the thickness of the multi-layer liquid crystal polymer film is 8-500 μm.

[0060] For the multi-layer co-extruded composite film containing a liquid crystal polymer film, taking five-layer co-extrusion as an example, its structural characteristics are that it forms III A / II A / I / II B / III B structure, the I layer is a liquid crystal polymer layer, and II A layer, II B layer are functional layers, and III A layer, III B layer are protective layers. The following options are available for its structural combination:

[0061] a. The I layer is a liquid crystal polymer layer, and the other layers are all non-liquid crystal polymer layers, and a single-layer liquid crystal polymer film can be obtained;

[0062] b. The I layer is a liquid crystal polymer layer, and at least one of the functional layers II A layer, II B layer is an adhesive material, and a single-layer liquid crystal polymer film with an adhesive layer can be obtained;

[0063] c. The I layer is a liquid crystal polymer layer, and at least one of the functional layers II A layer, II B layer is a liquid crystal polymer material, and a two-layer or three-layer co-extruded liquid crystal polymer film can be obtained;

[0064] d. The I layer is a liquid crystal polymer layer, the functional layers II A layer, II B layer are both liquid crystal polymer materials, and at least one of the protective layers III A layer, III B layer is an adhesive material, and a multi-layer co-extruded liquid crystal polymer film with an adhesive layer can be obtained.

[0065] When preparing the multi-layer co-extruded liquid crystal polymer film, the I layer and the functional layers II A layer, IIB The liquid crystal polymer materials of the layers can be the same liquid crystal polymer material or different liquid crystal polymer materials; when co-extruding seven or more layers, III A layer, III B layer is provided with IV A layer, IV B layer and more co-extruded layers and more types of structural combinations; the thickness of the single-layer liquid crystal polymer film is 5-200 μm, and the thickness of the multi-layer liquid crystal polymer film is 8-500 μm.

[0066] In the present invention, the liquid crystal polymer material is a liquid crystal copolyester material that can be melt-extruded and has a melting point of 200-400 °C; the liquid crystal polymer material can be a pure liquid crystal copolyester material or a blend containing one or more liquid crystal copolyester materials.

[0067] Among these liquid crystal copolyesters, polymers containing at least 2-hydroxy-6-naphthoic acid and / or p-hydroxybenzoic acid as repeating units are preferred, and copolymers containing (i) repeating units of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid, (ii) at least one aromatic hydroxycarboxylic acid selected from 2-hydroxy-6-naphthoic acid and p-hydroxybenzoic acid, at least one aromatic diol selected from 4,4'-dihydroxybiphenyl and hydroquinone, and repeating units of at least one aromatic dicarboxylic acid selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid are particularly preferred.

[0068] In the above liquid crystal copolyesters, thermoplastic resins such as fluororesin, polyphenylene sulfide, polyether ether ketone, polyamide, polyester amide, polyethylene terephthalate and its modified resins, and polyolefin can be added within the range not affecting the effects of the present invention; various additives such as slip agents and antioxidants; fillers such as glass and ceramics.

[0069] In the present invention, the adhesive material is an olefin copolymer or a copolymer of an olefin and an unsaturated carboxylic acid or unsaturated carboxylic anhydride; the non-liquid crystal polymer materials of the functional layer and the protective layer include various materials that can be processed by blown film, such as polyethylene, polypropylene, polybutene, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polyvinyl chloride, polystyrene, poly(4-methylpentene), polyethylene terephthalate, nylon, polylactic acid, polybutylene adipate / terephthalate, fluororesin, etc.; the non-liquid crystal polymer material can be one of the aforementioned resins or a blend containing one or more of the aforementioned resins.

[0070] In the present invention, the materials are pretreated in a vacuum drying oven before extrusion molding, and the pretreatment temperature and time are determined according to the properties of the processed materials.

[0071] Please refer to Figure 1 As shown, a forming method and a blown film device for a liquid crystal polymer film according to an embodiment of the present invention utilize a multi-layer co-extrusion method to realize the preparation of single-layer and multi-layer liquid crystal polymer films. The blown film device includes a special co-extrusion die head for liquid crystal polymer film with five or more layers of co-extrusion and a supporting forming and cooling system; the liquid crystal polymer material and the protective layer material are respectively added into the extruder, melted and plasticized by the extruder and then enter the co-extrusion die head 1. According to the structural combination of the multi-layer co-extruded composite film, different processing materials respectively enter the flow channels 3-7. The materials first pass through a filtering structure in their respective shunt channels to filter out the solid particles that are not fully melted. The filtering structure is preferably a high-precision filter screen, and the mesh number of the filter screen is preferably 16-100 meshes. The filtered melt finally converges into the co-extrusion flow channel 8. The ratio of the length of the co-extrusion flow channel to the die diameter is 0.5-50. Adjusting this ratio can adjust the thickness distribution of the functional polymer material in the co-extrusion stage of the die head and ensure the circumferential uniformity of the materials. Here, the die core adopts a structure that transitions from a conical shape to a cylindrical shape, effectively increasing the length of the co-extrusion flow channel under the condition of a certain die head height. The heating jacket 2 ensures that the processed materials after filtration are always in a molten state; the multi-layer co-extruded materials are evenly extruded from the annular die head 14. At the same time, the air flow enters the first air ring from the air inlet 9 of the first air ring. The air flow forms a uniform and stable air flow through the turbulence channel composed of the lower disc 10 and the upper disc 11 of the first air ring and blows towards the film bubble 15. The air ring is connected with a stepless speed regulation fan, which can regulate the flow rate and air volume of the air flow. When the difference between the crystallization temperature T c of the liquid crystal polymer material to be processed and the ambient temperature T a around the film bubble is greater than 150 °C, the temperature of the air flow of the first air ring can be heated by a temperature control device so that the liquid crystal polymer will not solidify immediately and is still in a state of stretchable deformation. The temperature control device, that is, the first temperature control unit, is connected between the air inlet 9 of the first air ring and the stepless speed regulation fan, and the air flow generated by the fan is heated by controlling the heating power of the heating element in the first temperature control unit. The temperature of the heated air flow is T c -100 °C to T c+30℃, with the increase of air flow temperature, the deformability of the film bubble increases, but if the temperature is too high, the strength of the film bubble decreases and it will collapse and be difficult to inflate. The structure of the first wind ring spoiler ring 12 makes the air flow blown to the film bubble 15 and then quickly dispersed to the surroundings of the film bubble, weakening the upward air flow around the film bubble 15, while supporting the film bubble forming and reducing the influence on the lateral inflation. Here, the inclination angle α1 of the first wind ring spoiler ring 12 is ≤30°; the inflation air flow enters the film bubble 15 from the core air inlet 13 to cause the film bubble 15 to inflate laterally, and the traction ring just above the die head The guide roller 21 pulls the film bubble 15 longitudinally, and the film bubble 15 is pulled to the second air ring located directly above the first air ring. The cooling airflow enters the second air ring from the air inlet 16 of the second air ring. The cooling airflow passes through the turbulence channel composed of the second air ring lower plate 17 and the second air ring upper plate 18 to form a uniform and stable airflow blowing toward the film bubble 15. A second temperature control unit is arranged between the second air ring air inlet 16 and the stepless speed regulating fan. The temperature of the airflow generated by the fan is controlled by controlling the heating power of the heating element in the second temperature control unit. The temperature of the cooling airflow of the second air ring is T c -200℃~T c -120℃, as the air flow temperature decreases, the cooling effect of the film bubble is improved, but if the temperature is too low, it will cause uneven cooling between the multi-layer co-extruded layers, resulting in defects such as wrinkles and stratification. The structure of the second air ring spoiler ring 19 allows the inflated film bubble to be gradually cooled. The inclination angle α2 of the second air ring spoiler ring 19 is ≥45°. The cooled and solidified film bubble enters the traction roller 21 through the herringbone plate 20, thereby obtaining a multi-layer co-extruded composite film 22 containing liquid crystal polymers; the structure of the multi-layer co-extruded composite film 22 finally obtained is as follows Figure 2 shown.

[0072] The technical solution of the present invention is further described below by means of specific embodiments in combination with the accompanying drawings. It should be noted that the following specific embodiments are only used as examples, and the protection scope of the present invention is not limited thereto.

[0073] The chemicals and raw materials used in the following examples are either commercially available or homemade by known preparation methods.

[0074] The performance tests in the following embodiments are as follows:

[0075] Peel strength

[0076] A peeling test piece with a width of 5 mm was made using the prepared liquid crystal polymer substrate. At room temperature, the bonding surface of the liquid crystal polymer film and the metal layer was peeled off from the edge. The liquid crystal polymer film layer was fixed on the flat plate with a double-sided tape. The metal layer was peeled off in a 90° direction at a speed of 50 mm / min. The peeling load was recorded with a digital push-pull dynamometer. When the peeling length was greater than 50 mm, the peeling strength was calculated based on the average load value during the peeling process.

[0077] Mechanical properties and thickness

[0078] In the present invention, a universal testing machine is used to test the mechanical properties of the film, and the test is carried out with reference to the method of GB / T 1040.3-2006. A mechanical contact thickness gauge is used to test the film thickness, and the test is carried out with reference to the method of ASTM D645.

[0079] Example 1

[0080] Using the film forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a single-layer liquid crystal polymer film for the adhesive layer is prepared. The structural combination of the multilayer co-extruded composite film is: III A (Polyethylene) / II A (Adhesive) / I(Liquid crystal polymer) / II B (Adhesive) / III B (Polyethylene); the liquid crystal polymer material is a liquid crystal copolyester of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, with a melting point of 260 °C and a crystallization temperature T c of 215 °C, the adhesive material is ethylene / vinyl acetate copolymer with a melting point of 95 °C, and the polyethylene is low-density polyethylene containing 1% anti-blocking agent with a melting point of 112 °C; before processing, the liquid crystal polymer material is dried and pretreated in a vacuum drying oven at a drying temperature of 130 °C for 5 hours. After the pretreatment, the liquid crystal polymer material, ethylene / vinyl acetate copolymer and polyethylene material are added to the blown film equipment provided in the above examples. The extrusion pressure range of the extruder where the liquid crystal polymer is located is 0.6-3.0 MPa. The air ring of the forming and cooling system is adjusted, the air outlet temperature of the first air ring is 245 °C, and the air outlet temperature of the second air ring is 50 °C, so that the film bubble reaches stability at a blow-up ratio of 5.0; finally, the polyethylene protective layer on the surface layer is peeled off to obtain a liquid crystal polymer film with a total thickness of about 60 μm and adhesive layers on both sides. The tensile strength of the film in the drawing direction is 235 MPa, the elongation at break is 35%, the tensile strength perpendicular to the drawing direction is 210 MPa, and the elongation at break is 33%, indicating that the obtained liquid crystal polymer film has excellent mechanical properties.

[0081] Example 2

[0082] Using the method for forming a liquid crystal polymer film and the blown film device provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The difference between this embodiment and Embodiment 1 is that the extrusion pressure range is 0.1 - 2.5 MPa, the air outlet temperature of the first air ring is 200 °C, the air outlet temperature of the second air ring is 50 °C, the blow-up ratio of the film bubble is 1.2, and finally a liquid crystal polymer film with a total thickness of about 90 μm and adhesive layers on both sides is obtained. The tensile strength of the film in the drawing direction is 327 MPa, the elongation at break is 21%, the tensile strength perpendicular to the drawing direction is 189 MPa, and the elongation at break is 25%, indicating that the obtained liquid crystal polymer film has excellent mechanical properties.

[0083] Example 3

[0084] Using the method for forming a liquid crystal polymer film and the blown film device provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The difference between this embodiment and Embodiment 1 is that the blow-up ratio of the film bubble is 8, and finally a liquid crystal polymer film with a total thickness of about 35 μm and adhesive layers on both sides is obtained. The tensile strength of the film in the drawing direction is 227 MPa, the elongation at break is 36%, the tensile strength perpendicular to the drawing direction is 219 MPa, and the elongation at break is 35%, indicating that the obtained liquid crystal polymer film has excellent mechanical properties.

[0085] Example 4

[0086] Using the method for forming a liquid crystal polymer film and the blown film device provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The structural combination of the multi-layer coextruded composite film is: III A (Polyethylene) / II A (Polyethylene) / I(Liquid crystal polymer) / II B (Polyethylene) / III B (Polyethylene); The liquid crystal polymer material is a liquid crystal copolyester of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, with a melting point of 280 °C, and the crystallization temperature T cThe temperature is 234°C, the polyethylene is low-density polyethylene containing 1% anti-blocking agent, the air outlet temperature of the first air ring is 250°C, the air outlet temperature of the second air ring is 80°C, and the melting point is 112°C; before processing, the liquid crystal polymer material is dried and pretreated in a vacuum drying oven at a drying temperature of 150°C for 5 hours. After the pretreatment, the liquid crystal polymer material and the polyethylene material are added to the blown film equipment provided in the above embodiment. The extrusion pressure range of the extruder where the liquid crystal polymer is located is 0.5 - 5.0 MPa, and the air rings of the forming and cooling systems are adjusted so that the film bubble reaches stability at a blow-up ratio of 4.5; finally, the polyethylene protective layer on the surface layer is peeled off to obtain a single-layer liquid crystal polymer film with a thickness of about 25 μm. The obtained liquid crystal polymer film and a copper foil with a thickness of 18 μm are hot-pressed for 3 minutes at a temperature of 285°C and a pressure of 4 MPa to prepare a copper-clad laminate, and the bonding strength of the laminate is tested to be 0.85 N / mm.

[0087] Example 5

[0088] Using a forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The structural combination of the multi-layer co-extruded composite film is: III A (Polyethylene) / II A (Low melting point liquid crystal polymer) / I(High melting point liquid crystal polymer) / II B (Low melting point liquid crystal polymer) / III B (Polyethylene); the high melting point liquid crystal polymer material is a liquid crystal copolyester of p-hydroxybenzoic acid, biphenol, and terephthalic acid, with a melting point of 320°C and a crystallization temperature T c1 being 283°C, the low melting point liquid crystal polymer material is a liquid crystal copolyester of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, with a melting point of 280°C and a crystallization temperature T c2 being 234°C, the polyethylene is low-density polyethylene containing 1% anti-blocking agent, with a melting point of 112°C; before processing, the liquid crystal polymer materials are respectively dried and pretreated in a vacuum drying oven. The drying temperature of the high melting point liquid crystal polymer is 180°C, and the drying temperature of the low melting point liquid crystal polymer is 150°C, and the drying time is 5 hours for both. After the pretreatment, the liquid crystal polymer materials and the polyethylene material are added to the blown film equipment provided in the above embodiment. The extrusion pressure range of the extruder where the liquid crystal polymer is located is 6.0 - 10.0 MPa, and the air rings of the forming and cooling systems are adjusted. The air outlet temperature of the first air ring is 290°C, and the air outlet temperature of the second air ring is 100°C, so that the film bubble reaches stability at a blow-up ratio of 3.0; finally, the polyethylene protective layer on the surface layer is peeled off to obtain a three-layer co-extruded liquid crystal polymer film with a total thickness of about 80 μm.

[0089] Example 6

[0090] Using the forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The difference between this example and Example 5 is that the extrusion pressure range is 8.0 - 15.0 MPa, the air outlet temperature of the first air ring is 305 °C, the air outlet temperature of the second air ring is 100 °C, the blow-up ratio is 8.0, and the total thickness is about 55 μm for the three-layer co-extruded liquid crystal polymer film.

[0091] Example 7

[0092] Using the forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a multi-layer liquid crystal polymer film is prepared. The difference between this example and Example 5 is that the extrusion pressure range is 0.5 - 5.0 MPa, the blow-up ratio is 4.5, and the total thickness is about 70 μm for the three-layer co-extruded liquid crystal polymer film. The obtained liquid crystal polymer film and a copper foil with a thickness of 18 μm are hot-pressed for 3 min at a temperature of 295 °C and a pressure of 4 MPa to prepare a copper-clad laminate, and the bonding strength of the laminate is tested to be 0.93 N / mm.

[0093] Comparative Example 1

[0094] Using the forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a multi-layer co-extruded liquid crystal polymer film is prepared. The difference between this comparative example and Example 5 is that only the first air ring works and the second air ring stops working; during the blown film processing of the liquid crystal polymer film, it is observed that small wrinkles appear on the surface of the film bubble before it enters the take-up roll. Although the blow-up ratio of the film bubble can still reach 3, the stability of the film bubble is poor, and phenomena such as tensile resonance and flutter are likely to occur. Finally, the obtained liquid crystal polymer film has obvious wrinkles on the surface. The obtained three-layer co-extruded liquid crystal polymer film is cut into strips with a width of 5 mm, placed in liquid nitrogen for 30 s, and then brittle broken to obtain the cross-section of the film. After surface gold spraying treatment, it is observed under the condition of an accelerating voltage of 2 kV, and significant delamination is observed in the thickness direction of the film.

[0095] Comparative Example 2

[0096] Using the forming method and blown film equipment for a liquid crystal polymer film provided in the above specific embodiments, a multi-layer co-extruded liquid crystal polymer film is prepared. The difference between this comparative example and Example 5 is that only the second air ring works and the first air ring stops working; the multi-layer polymer parison extruded from the die head is quickly cooled and solidified. When the blow-up ratio reaches 1.2, the film bubble bursts and it is difficult to continue lateral blowing, and the film bubble swings severely from side to side during longitudinal traction.

[0097] It can be seen from Comparative Example 1 and Comparative Example 2 that the main function of the first air ring is to improve the stretchability of the multi-layer polymer parison. During the transverse inflation stage, the air flow can support the film bubble without affecting the transverse inflation, enabling the film bubble to have excellent film blowing stability while achieving large inflation; the function of the second air ring is to gradually and controllably cool the formed film bubble, prevent wrinkles caused by different shrinkage rates of different co-extruded layer materials, and weaken the skin-core structure with delamination caused by the rapid curing of liquid crystal polymers; the synergistic effect of the first air ring and the second air ring can obtain a liquid crystal polymer film with a specific blow-up ratio and excellent film properties, and the anisotropy of the film can be controllably adjusted by the blow-up ratio, draw ratio, air flow temperature and flow rate of the first air ring.

[0098] In summary, the forming method and film blowing equipment for a liquid crystal polymer film provided by the present invention can obtain a single-layer or multi-layer liquid crystal polymer film with excellent mechanical properties and low anisotropy. At the same time, the anisotropy of the liquid crystal polymer film can be controllably adjusted according to different usage requirements; the multi-layer liquid crystal polymer film has a very high bonding strength when thermally pressed and compounded with copper foil, which is of great significance for the industrial preparation of high-frequency multi-layer flexible copper clad laminates.

[0099] The parts not elaborated in detail in the present invention belong to the well-known technologies in the art.

[0100] It should be noted that although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, those skilled in the art should understand that the present invention is not limited to the above embodiments. Any modifications or variations to the present invention that do not depart from the spirit and scope of the present invention, provided that such modifications and variations fall within the scope of the claims of the present invention and equivalent technical scope, then the present invention also means to include such modifications and variations.

[0101] In particular, without departing from the spirit and teachings of the present invention, the features recited in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recited in the present invention. All such combinations and / or combinations are within the scope of protection of the present invention. Therefore, the scope of the present invention is not only determined by the appended claims, but also limited by the equivalents of the appended claims.

Claims

1. A blown film device for a liquid crystal polymer film, comprising: Extruder; Coextrusion die head, which is arranged at the end of the extruder. The coextrusion die head includes a plurality of flow channels and a coextrusion flow channel. The ends of the plurality of flow channels are all connected to the starting end of the coextrusion flow channel, and the number of the flow channels is greater than or equal to 5; The first air ring is connected to the die lip of the coextrusion die head, and the first air ring is connected with a first temperature control unit for adjusting the air flow temperature of the first air ring; The second air ring is arranged above the first air ring, and the second air ring is connected with a second temperature control unit for adjusting the air flow temperature of the second air ring; and The haul-off roll is arranged above the second air ring; Wherein, the ratio of the length of the coextrusion flow channel to the die lip diameter is 0.5 - 50; The coextrusion die head further includes a die core, and the die core is a structure that transitions from a conical shape to a cylindrical shape; The first air ring includes a first air ring spoiler ring; The first air ring spoiler ring has an inverted frustum shape, and the inclination angle α1 of the frustum shape ≤ 30°; When the difference between the crystallization temperature T c of the liquid crystal polymer material to be processed and the ambient temperature T a of the film bubble is greater than 150 °C, the air flow temperature of the first air ring is set to T c - 100 °C to T c + 30 °C; The air flow temperature of the second air ring is T c -200°C to T c -120°C; In the step of forming the film bubble, control the blow-up ratio to be 1.2 to 8.

0.

2. The blown film device according to claim 1, wherein, A filtering structure is provided at the front end of each of the flow channels.

3. The blown film device according to claim 1, wherein, The blown film equipment further includes a heating jacket for heating the coextrusion die head.

4. The blown film device according to claim 1, wherein, The second air ring includes a second air ring spoiler ring; The second air ring spoiler ring has an inverted frustum shape, and the inclination angle α2 of the frustum shape ≥ 45°; 5. A forming method for a liquid crystal polymer film, using the blown film device according to any one of claims 1 to 4, comprising: Set the process parameters of the extruder; Convey different materials to the coextrusion flow channel through different flow channels respectively; The materials passing through the coextrusion flow channel form a film bubble under the air flow of the die core; Haul the film bubble so that the film bubble forms the liquid crystal polymer film under the action of the air flow of the first air ring and the air flow of the second air ring.

6. The forming method according to claim 5, wherein, When the difference between the crystallization temperature T of the liquid crystal polymer material to be processed c and the ambient temperature T of the film bubble a is greater than 150 °C, set the air flow temperature of the first air ring to T c -100 °C to T c +30 °C; The air flow temperature of the second air ring is T c -200°C to T c -120°C; In the step of forming the film bubble, control the blow-up ratio to be 1.2 to 8.0; Set the extrusion pressure of the extruder to be 0.1 to 15.0 Mpa.

7. The forming method according to claim 5, wherein, Different liquid crystal polymer films with different structures are obtained by arranging different materials in a plurality of flow channels.

8. The forming method according to claim 5, wherein, The plurality of flow channels at least include a first flow channel, a second flow channel, a third flow channel, a fourth flow channel and a fifth flow channel arranged in sequence; The third flow channel contains liquid crystal polymer material.

9. The molding method according to claim 8, wherein, The third flow channel contains liquid crystal polymer material, and the other flow channels all contain non-liquid crystal polymer material; or, The third flow channel contains liquid crystal polymer material, and at least one layer in the second flow channel and the fourth flow channel is adhesive material; or, The third flow channel contains liquid crystal polymer material, at least one of the second flow channel and the fourth flow channel is liquid crystal polymer material, and the first flow channel and the fifth flow channel contain adhesive material; or, The second flow channel, the third flow channel and the fourth flow channel all contain liquid crystal polymer material, and at least one of the first flow channel and the fifth flow channel is adhesive material.

Images