CN111497173B - Method for preparing liquid crystal polymer film - Google Patents
Method for preparing liquid crystal polymer film Download PDFInfo
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- CN111497173B CN111497173B CN202010356909.6A CN202010356909A CN111497173B CN 111497173 B CN111497173 B CN 111497173B CN 202010356909 A CN202010356909 A CN 202010356909A CN 111497173 B CN111497173 B CN 111497173B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/07—Flat, e.g. panels
- B29C48/08—Flat, e.g. panels flexible, e.g. films
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/14—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the particular extruding conditions, e.g. in a modified atmosphere or by using vibration
- B29C48/146—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the particular extruding conditions, e.g. in a modified atmosphere or by using vibration in the die
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
- B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/92—Measuring, controlling or regulating
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2948/00—Indexing scheme relating to extrusion moulding
- B29C2948/92—Measuring, controlling or regulating
- B29C2948/92504—Controlled parameter
- B29C2948/92704—Temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2948/00—Indexing scheme relating to extrusion moulding
- B29C2948/92—Measuring, controlling or regulating
- B29C2948/92819—Location or phase of control
- B29C2948/92942—Moulded article
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/12—Polymers characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2427/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2427/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2427/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08J2427/18—Homopolymers or copolymers of tetrafluoroethylene
Abstract
The invention relates to a preparation method of a liquid crystal polymer film, which comprises the steps of blending 5-25% of polytetrafluoroethylene granules and 75-95% of liquid crystal high molecular polymer granules according to the mass percentage, carrying out melt granulation by an extruder to obtain surface layer blended granules, respectively feeding the surface layer blended granules and the liquid crystal high molecular polymer core layer granules into corresponding screw extruders for melt extrusion, controlling the melting point of an extruded product to be 10 ℃ below Tm to 30 ℃ below Tm during extrusion, flowing out a melt with two surfaces and a core layer thereof after passing through a melt pipe, a three-layer adapter and a three-layer die head, ultrasonic vibration perpendicular to the flow direction of the melt is applied to the three-layer die head and acts on the melt, after the melt is shaped through a middle gap of the first and second shaping rollers, and transversely stretching, slitting, drawing and rolling to obtain the liquid crystal polymer film with the two surface layers and the core layer structure. The invention simplifies the processing procedure, has small anisotropy and low dielectric constant, and can reduce the manufacturing cost.
Description
Technical Field
The invention relates to a preparation method of a liquid crystal polymer film, belonging to the technical field of liquid crystal polymer film manufacturing.
Background
Liquid Crystal Polymer (LCP) is an anisotropic aromatic polyester Polymer material consisting of rigid molecular chains, can exist in a Liquid Crystal phase under certain conditions, has Liquid fluidity and Crystal anisotropy, and is a novel high-performance special engineering plastic developed in the early 80 s. Liquid crystals self-organize at a molecular level and are classified into three types, thermotropic liquid crystals, lyotropic liquid crystals, and photo-induced liquid crystals. In either type of LCP, the molecular backbone of the LCP has a large number of rigid benzene ring structures, which determine the specific physical and chemical properties and processing properties of the LCP. The LCP has a high degree of regularity of molecular chains, so that after being heated to a liquid crystallization temperature, the melt of the LCP becomes water-like if a slight shearing force is applied, and the characteristic makes the LCP have a high technical threshold when being processed into an isotropic material.
LCP materials have excellent physical properties, very high dimensional stability and dimensional accuracy, almost zero creep, wear resistance, linear expansion rate close to metal, excellent heat resistance, flame retardant property, good chemical stability, excellent weather resistance and electrical characteristics and the like. The electric characteristics of the dielectric ceramic are in the whole radio frequency range up to 110GHz, the dielectric constant with constant value can be almost kept, and the consistency is good; the tangent loss is very small, only 0.002, and is only increased to 0.0045 even at 110GHz, so that the method is very suitable for millimeter wave application; has very small thermal expansion characteristic and can be used as an ideal high-frequency packaging material.
As electronic devices move toward thinner, more complex, requirements for LCPs have increased dramatically. Nowadays, the communication speed is faster and faster, and 5G communication is moving to the world. Since this new technology is located in the high frequency range, higher demands are placed on the materials. LCP has very low water absorption and better dielectric stability than high temperature nylon. LCP has ultralow warpage, high fluidity and dimensional stability, and is suitable for being applied to a 5G high-speed connector. The apparent viscosity of the LCP material is greatly influenced by the shearing speed and the temperature, strong anisotropy is shown in the flowing direction, and the film forming rate is low in the actual manufacturing process, so that high technical difficulty is set for the preparation of the LCP film. The present market discloses the manufacturing technology, patents or products of LCP film, mainly including Superex, Japan Colorado, Japan village institute, Japan Sumitomo chemical, the above mentioned enterprises involve the film blowing and hot pressing manufacturing process, or the manufacturing method of using the support body first and then peeling off, the LCP film manufacturing process is complicated and the manufacturing cost is high.
Disclosure of Invention
The invention aims to provide a preparation method of a liquid crystal polymer film, which can simplify the processing procedure, has small anisotropy and low dielectric constant and can reduce the manufacturing cost.
The technical scheme for achieving the aim of the invention is as follows: a method for preparing a liquid crystal polymer film is characterized by comprising the following steps: the method comprises the following steps of (1),
(1) blending 5-25% of polytetrafluoroethylene granules and 75-95% of liquid crystal high polymer granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules, wherein the melting point Tm of the liquid crystal high polymer is more than or equal to 300 ℃;
(2) feeding the surface layer blended granules into a double-screw extruder, feeding the core layer granules of a liquid crystal high polymer with the mass percentage of 100% into another single-screw extruder, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be 10 ℃ below Tm to 30 ℃ below Tm during extrusion, enabling the extruded product to flow out of a melt with two surface layers and the core layer thereof after passing through a melt pipe, a three-layer adapter and a three-layer die head, and applying ultrasonic vibration perpendicular to the flow direction of the melt at the three-layer die head and acting on the melt so as to improve the homodromous of the melt in the flow direction;
(3) the melt flowing out of the die head vertically passes through the middle gap of a first group of shaping rollers for primary shaping, then vertically enters the middle gap of a second group of shaping rollers and flows out from the horizontal direction for secondary shaping, the temperature of the first group of shaping rollers is controlled to be 5-50 ℃ below Tm, the temperature of the second group of shaping rollers is 10-20 ℃ lower than that of the first group of shaping rollers, and the temperature of the shaped soft sheet is more than or equal to 80 ℃ below Tm;
(4) the soft sheet starts to be transversely stretched at the outlet of the second group of shaping rollers, the transverse stretching multiple is 3-15 times, and the temperature of the soft sheet during stretching is controlled to be more than or equal to 60 ℃ below Tm;
(5) and cutting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with two surface layers and a middle core layer structure.
According to the invention, the liquid crystal polymer film is prepared in a three-layer co-extrusion mode, and the polytetrafluoroethylene granules with a specific proportion are added into the surface layer blending granules of the liquid crystal polymer film, so that the characteristics of non-adhesiveness, lubricating effect and the like of the surface of the polytetrafluoroethylene material are utilized, the obvious anisotropy of the liquid crystal high polymer material and a core layer caused by contact friction with a wall in the flowing process is effectively reduced, and the defect that the pure liquid crystal high polymer material is easy to skin in the extrusion process is overcome. The invention utilizes the polytetrafluoroethylene material with extremely high melt viscosity, reduces the melting point of an extruded material during extrusion, and can melt the material by utilizing the shearing force of an extruder so as to solve the technical problem that the fluidity of the liquid crystal high polymer melt is not beneficial to subsequent film forming by stretching. The dielectric constant of the polytetrafluoroethylene material in the surface layer is lower than that of the liquid crystal high polymer material, and the polytetrafluoroethylene material is added in a certain proportion, so that the dielectric constant of the liquid crystal polymer film can be reduced. In the three-layer co-extrusion manufacturing process, the melting point of an extrudate, the temperatures of the front and rear two groups of shaping roller sets, the temperature of the shaped soft sheet and the temperature of the soft sheet during transverse stretching are controlled, so that the phenomenon of hydration caused by overheating of a liquid crystal high polymer material can be reduced, and the yield of a film product is improved. The invention adopts the directional linear propagation characteristic of ultrasonic waves in a uniform medium, and before a melt flows out of a die head, the melt is subjected to ultrasonic vibration in the direction vertical to the flow direction of the melt to reduce the mechanical anisotropy of the melt in the flow direction, and meanwhile, the melt is subjected to transverse stretching in the direction vertical to the flow direction of the liquid crystal high polymer to offset the longitudinal mechanical strength of the melt, thereby simplifying the processing procedures, reducing the equipment investment by adopting conventional equipment, improving the yield, reducing the manufacturing cost and obtaining a liquid crystal polymer film product with better isotropy.
Detailed Description
The preparation method of the liquid crystal polymer film is carried out according to the following steps.
(1) 5-25% of polytetrafluoroethylene PTFE granules and 75-95% of liquid crystal polymer LCP granules are blended according to mass percentage, and melted and granulated by an extruder to prepare surface layer blended granules, wherein the melting point Tm of the liquid crystal polymer is more than or equal to 300 ℃. The liquid crystal high molecular polymer comprises thermotropic liquid crystal polymer or modified liquid crystal polymer or polymer containing the thermotropic/modified liquid crystal polymer component. Such as the liquid crystal polymers I, II and III on the market, the liquid crystal polymer derivatives or modified liquid crystal polymers, or the blends with other polymers. According to the invention, the polytetrafluoroethylene granules with a certain proportion are added into the surface layer, and the extruded product has liquid crystal characteristics and can be stretched into a film at a certain temperature.
(2) Feeding the surface layer blending granules into a double-screw extruder, feeding the liquid crystal high polymer core layer granules with the mass percentage of 100% into another single-screw extruder, carrying out melt extrusion on the surface layer blending granules and the core layer granules through the respective corresponding screw extruders, and controlling the melting point of an extruded product to be 10 ℃ below Tm to 30 ℃ below Tm during extrusion, wherein the melting point is measured by a DSC method, and if the blend has two melting point peaks, the high melting point peak is taken as a reference. Because the melting point of the extrudate is reduced to 10-30 ℃, the granules can be melted by utilizing the shearing force, thereby further reducing the phenomenon that the LCP material is easy to cause hydration due to overheating and improving the yield of film products. The extrudate flows out of the melt with two surface layers and a core layer after passing through the melt pipe, the three-layer adapter and the three-layer die head, the temperature of the melt pipe and the three-layer die head is controlled within the range of 5 ℃ below Tm to 20 ℃ below Tm, ultrasonic vibration perpendicular to the flow direction of the melt is applied to the melt and acts on the melt, and mechanical anisotropy of the melt in the flow direction can be reduced by utilizing good directional vibration of the ultrasonic so as to improve the homodromous of the melt in the flow direction.
(3) The melt flowing out of the die head vertically passes through the middle gap of the first group of shaping rollers for primary shaping, then vertically enters the middle gap of the second group of shaping rollers and flows out from the horizontal direction for secondary shaping, the sheet is changed from the vertical direction to the horizontal direction, the temperature of the first group of shaping rollers is controlled to be between 5 ℃ below Tm and 50 ℃ below Tm, the temperature of the second group of shaping rollers is lower than the temperature of the first group of shaping rollers by 10-20 ℃, and the temperature of the shaped soft sheet is more than or equal to 80 ℃ below Tm.
The middle gap of the first group of shaping rollers and the middle gap of the second group of shaping rollers can be adjusted, a melt is slightly extruded when flowing through the middle gap of the first group of shaping rollers and the middle gap of the second group of shaping rollers, the thickness tolerance of the soft sheet can be adjusted by adjusting the middle gap, the length of the second group of shaping rollers is smaller than the width of the shaped soft sheet, and enough space is ensured to enter the transverse zipper clamp at the two edges of the soft sheet. The first set of shaping rollers and the second set of shaping rollers are ceramic rollers or metal rollers, the surfaces of which are plated with Teflon layers, and the Teflon layers are not adhered to the surface layer at a high temperature, so that the yield of liquid crystal polymer film products is further improved.
(4) And the soft sheet starts to be transversely stretched at the outlet of the second group of shaping rollers, the transverse stretching multiple is 3-15 times, the temperature of the soft sheet during stretching is controlled to be more than or equal to 60 ℃ below Tm, and the transverse stretching is carried out in the direction vertical to the LCP flow direction so as to offset the longitudinal mechanical strength of the melt and obtain better isotropy.
(5) And cutting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with two surface layers and a middle core layer structure, wherein the surface layer thickness of the liquid crystal polymer film is more than or equal to 2 mu m.
Example 1
Selecting LCP granules Tm as 305 ℃, blending 5 percent of PTFE granules and 95 percent of LCP granules according to mass percent, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 275 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be 30 ℃ below Tm, enabling the extruded product to flow out of a melt with two surface layers and a core layer thereof through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 285 ℃, enabling the melt flowing out of the die head to vertically pass through a middle gap of a first group of sizing rollers for primary sizing, then vertically entering a middle gap of a second group of sizing rollers at the temperature and enabling the melt to flow out from the horizontal direction for secondary sizing, controlling the temperature of the first group of sizing rollers to be 255 ℃, controlling the temperature of the second group of sizing rollers to be 240 ℃, and enabling soft sheets at the temperature of 225 ℃ after sizing to start to transversely stretch at the outlet of the second group of sizing rollers, controlling the temperature of transverse stretching at 245 ℃, controlling the stretching ratio to be 3, slitting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with the two surface layers and the middle core layer structure, wherein the total thickness of the liquid crystal polymer film is 50 mu m, and the thickness of the single surface layer is 2 mu m.
Example 2
Selecting LCP granules Tm being 310 ℃, blending 10% of PTFE granules and 90% of LCP granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 290 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be below 20 ℃ below Tm, enabling the extruded product to flow out of a melt with two surface layers and the core layer thereof through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 300 ℃, enabling the melt flowing out of the die head to vertically pass through a middle gap of a first group of sizing rollers for primary sizing, then vertically enter a middle gap of a second group of sizing rollers at a temperature and flow out from the horizontal direction for secondary sizing, changing the vertical direction of a sheet into the horizontal direction, controlling the temperature of the first group of sizing rollers to be 270 ℃, controlling the temperature of the second group of sizing rollers to be 260 ℃, and transversely stretching the soft sheet with the temperature of 250 ℃ after shaping at the outlet of a second group of shaping rollers, controlling the temperature of transverse stretching at 260 ℃, and controlling the stretching ratio to be 5, slitting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with the two surface layers and the middle core layer structure, wherein the total layer thickness of the liquid crystal polymer film is 50 mu m, and the thickness of the single surface layer is 5 mu m.
Example 3
Selecting LCP granules Tm of 318 ℃, blending 25 percent of PTFE granules and 75 percent of LCP granules according to mass percent, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 293 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be below 25 ℃ below Tm, enabling the extruded product to flow out of a melt with two surface layers and the core layer through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 313 ℃, vertically enabling the melt flowing out of the die head to pass through a middle gap of a first group of sizing rollers for primary sizing, vertically entering a middle gap of a second group of sizing rollers at a temperature and horizontally flowing out for secondary sizing, changing the temperature of the first group of sizing rollers from the vertical direction to the horizontal direction, controlling the temperature of the first group of sizing rollers to be 313 ℃, controlling the temperature of the second group of sizing rollers to be 298 ℃, and transversely stretching the soft sheet with the temperature of 278 ℃ after shaping at the outlet of a second shaping roller, controlling the temperature of transverse stretching at 290 ℃, and controlling the stretching ratio to be 8, slitting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with the two surface layers and the middle core layer structure, wherein the total layer thickness of the liquid crystal polymer film is 100 mu m, and the thickness of the single surface layer is 10 mu m.
Example 4
Selecting LCP granules Tm being 309 ℃, blending 12% of PTFE granules and 88% of LCP granules according to mass percent, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 285 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be below 24 ℃ and flowing out a melt with two surface layers and the core layer thereof through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 295 ℃, carrying out primary sizing on the melt flowing out of the die head by vertically passing through a middle gap of a first group of sizing rollers, vertically entering a middle gap of a second group of sizing rollers at a temperature and flowing out from the horizontal direction for secondary sizing, changing the vertical direction of a sheet into the horizontal direction, controlling the temperature of the first group of sizing rollers to be 290 ℃, controlling the temperature of the second group of sizing rollers to be 278 ℃, and transversely stretching a soft sheet with the temperature of 269 ℃ after shaping at the outlet of a second shaping roller, controlling the temperature of transverse stretching at 275 ℃, and controlling the stretching ratio to be 12, slitting, drawing and rolling the stretched film to obtain the liquid crystal polymer film with the structure of the two surface layers and the middle core layer, wherein the total thickness of the liquid crystal polymer film is 100 mu m, and the thickness of the single surface layer is 10 mu m.
Example 5
Selecting LCP granules Tm being 300 ℃, blending 8% of PTFE granules and 92% of LCP granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 275 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be 25 ℃ below Tm, enabling the extruded product to flow out of a melt with two surface layers and the core layer thereof through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 285 ℃, vertically enabling the melt flowing out of the die head to pass through a middle gap of a first set of sizing rollers for primary sizing, vertically enabling the melt to enter a middle gap of a second set of sizing rollers at a temperature and horizontally enabling the melt to flow out for secondary sizing, changing the vertical direction of a sheet into the horizontal direction, controlling the temperature of the first set of sizing rollers to be 265 ℃, controlling the temperature of the second set of sizing rollers to be 255 ℃, and transversely stretching the soft sheet with the temperature of 245 ℃ after shaping at the outlet of a second group of shaping rollers, controlling the temperature of transverse stretching at 255 ℃ and the stretching ratio at 15, slitting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with the two surface layers and the middle core layer structure, wherein the total thickness of the liquid crystal polymer film is 75 microns, and the thickness of the single surface layer is 5 microns.
Example 6
Selecting LCP granules Tm being 300 ℃, blending 28% of PTFE granules and 72% of LCP granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 300 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be Tm at the moment, finding that the extruded product is easy to skin and cause extrusion difficulty in the extrusion process, enabling the extruded product to flow out of a melt with two surface layers and a core layer through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 300 ℃, vertically enabling the melt flowing out of the die head to pass through a middle gap of a first group of sizing rollers for primary sizing, vertically enabling the melt to enter a middle gap of a second group of sizing rollers with the temperature being 300 ℃, enabling the second group of sizing rollers to flow out from the horizontal direction for secondary sizing, controlling the temperature of the first group of sizing rollers to be 290 ℃, and (3) after shaping, starting transverse stretching of the soft sheet with the temperature of 280 ℃ at the outlet of a second shaping roller, controlling the transverse stretching temperature at 290 ℃, and controlling the stretching ratio to be 10, wherein the soft sheet cannot be stretched into a film.
Example 7
Selecting LCP granules Tm being 325 ℃, blending 15% of PTFE granules and 85% of LCP granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules. Feeding the surface layer blended granules into a double-screw extruder, feeding 100 mass percent of LCP core layer granules into another single-screw extruder, controlling the temperature of the two screw extruders to be 315 ℃, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be below 10 ℃ below Tm, allowing the extruded product to flow out of a melt with two surface layers and a core layer thereof through a melt pipe, a three-layer adapter and a three-layer die head, controlling the temperature of the melt pipe and the three-layer die head to be 315 ℃, allowing the melt flowing out of the die head to vertically pass through a middle gap of a first set of sizing rollers for primary sizing, vertically enter a middle gap of a second set of sizing rollers at a temperature and flow out from the horizontal direction for secondary sizing, changing the temperature of the sheets from the vertical direction to the horizontal direction, controlling the temperature of the first set of sizing rollers to be 300 ℃ and the temperature of the second set of sizing rollers to be 280 ℃, and transversely stretching the soft sheet with the temperature of 255 ℃ after shaping at the outlet of a second shaping roller set, controlling the temperature of transverse stretching at 275 ℃, and controlling the stretching ratio to be 7, slitting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with the two surface layers and the middle core layer structure, wherein the total thickness of the liquid crystal polymer film is 50 mu m, and the thickness of the single surface layer is 5 mu m.
The main properties of the prepared liquid crystal polymer film are as follows GB/T13542.2-2009 and IEC 62631-2-1: 2018, and the detection results are shown in Table 1.
TABLE 1
The invention adopts a method of three-layer coextrusion and transverse stretching to obtain the liquid crystal polymer film product with uniform tolerance, small anisotropy and lower dielectric constant.
Claims (7)
1. A method for preparing a liquid crystal polymer film is characterized by comprising the following steps: the method comprises the following steps of (1),
(1) blending 5-25% of polytetrafluoroethylene granules and 75-95% of liquid crystal high polymer granules according to mass percentage, and carrying out melt granulation by an extruder to obtain surface layer blended granules, wherein the melting point Tm of the liquid crystal high polymer is more than or equal to 300 ℃;
(2) feeding the surface layer blended granules into a double-screw extruder, feeding the core layer granules of a liquid crystal high polymer with the mass percentage of 100% into another single-screw extruder, carrying out melt extrusion on the surface layer blended granules and the core layer granules through the respective corresponding screw extruders, controlling the melting point of an extruded product to be 10 ℃ below Tm to 30 ℃ below Tm during extrusion, enabling the extruded product to flow out of a melt with two surface layers and the core layer thereof after passing through a melt pipe, a three-layer adapter and a three-layer die head, and applying ultrasonic vibration perpendicular to the flow direction of the melt at the three-layer die head and acting on the melt so as to improve the homodromous of the melt in the flow direction;
(3) the melt flowing out of the die head vertically passes through the middle gap of a first group of shaping rollers for primary shaping, then vertically enters the middle gap of a second group of shaping rollers and flows out from the horizontal direction for secondary shaping, the temperature of the first group of shaping rollers is controlled to be 5-50 ℃ below Tm, the temperature of the second group of shaping rollers is 10-20 ℃ lower than that of the first group of shaping rollers, and the temperature of the shaped soft sheet is more than or equal to 80 ℃ below Tm;
(4) the soft sheet starts to be transversely stretched at the outlet of the second group of shaping rollers, the transverse stretching multiple is 3-15 times, and the temperature of the soft sheet during stretching is controlled to be more than or equal to 60 ℃ below Tm;
(5) and cutting, drawing and rolling the stretched film material to obtain the liquid crystal polymer film with two surface layers and a middle core layer structure.
2. The method for producing a liquid-crystalline polymer film according to claim 1, characterized in that: the temperature of the melt pipe and the temperature of the three-layer die head are controlled within the range of 5 ℃ below Tm to 20 ℃ below Tm.
3. The method for producing a liquid-crystalline polymer film according to claim 1, characterized in that: the first group of shaping rollers and the second group of shaping rollers are ceramic rollers or metal rollers, and the surfaces of the first group of shaping rollers and the second group of shaping rollers are plated with Teflon layers and are used for preventing the rollers from being adhered to the surface layer at a high temperature.
4. The method for producing a liquid-crystalline polymer film according to claim 1 or 3, characterized in that: the middle gap of first group design roller group and the middle gap of second group design roller can be adjusted, and the fuse-element appears slightly crowded state when flowing through the middle gap of first group design roller group and the middle gap of second group design roller.
5. The method for producing a liquid-crystalline polymer film according to claim 1, characterized in that: the length of the second group of shaping rollers is less than the width of the shaped soft sheet.
6. The method for producing a liquid-crystalline polymer film according to claim 1, characterized in that: the thickness of the single-side surface layer of the liquid crystal polymer film is more than or equal to 2 mu m.
7. The method for producing a liquid-crystalline polymer film according to claim 1, characterized in that: the liquid crystal high molecular polymer comprises thermotropic liquid crystal polymer or modified liquid crystal polymer or polymer containing the thermotropic/modified liquid crystal polymer component.
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