阅读说明：本技术 用于5g通信的液晶聚合物薄膜及其制备方法 (Liquid crystal polymer film for 5G communication and preparation method thereof ) 是由 翟盼 郭建君 虞成城 于 2020-05-07 设计创作，主要内容包括：本发明公开了一种用于5G通信的液晶聚合物薄膜及其制备方法,制备方法包括：将液晶聚合物树脂的熔体通过具有环形缝隙的模头进行挤出,得到挤出物；将所述挤出物冷却至玻璃化转变温度以下,然后以第一拉伸比进行卷绕,得到预取向管状薄膜；将所述预取向管状薄膜加热至玻璃化转变温度和热变形温度之间,然后以第二拉伸比进行卷绕,同时以预设吹胀比膨胀所述预取向管状薄膜,得到所述液晶聚合物薄膜。本发明可以获得TD和MD方向上具有良好的机械性能以及尺寸稳定性优异的液晶聚合物薄膜。(The invention discloses a liquid crystal polymer film for 5G communication and a preparation method thereof, wherein the preparation method comprises the following steps: extruding the melt of the liquid crystal polymer resin through a die head with an annular gap to obtain an extrudate; cooling the extrudate to below the glass transition temperature, and then winding at a first draw ratio to obtain a pre-oriented tubular film; heating the pre-oriented tubular film to a temperature between the glass transition temperature and the heat distortion temperature, then winding at a second drawing ratio, and expanding the pre-oriented tubular film at a preset blow-up ratio to obtain the liquid crystal polymer film. The invention can obtain the liquid crystal polymer film with good mechanical properties and excellent dimensional stability in TD and MD directions.)

1. A preparation method of a liquid crystal polymer film for 5G communication is characterized in that a melt of liquid crystal polymer resin is extruded through a die head with an annular gap to obtain an extrudate; cooling the extrudate to below the glass transition temperature, and then winding at a first draw ratio to obtain a pre-oriented tubular film; heating the pre-oriented tubular film to a temperature between the glass transition temperature and the heat distortion temperature, then winding at a second drawing ratio, and expanding the pre-oriented tubular film at a preset blow-up ratio to obtain the liquid crystal polymer film.

2. The method of claim 1, wherein the annular gap has a rectangular shape, the length of the annular gap is 10 to 20 times the width of the annular gap, and the width of the annular gap is 0.5 to 5 mm.

3. The method for preparing a liquid crystal polymer film for 5G communication according to claim 1, wherein the first stretching ratio is 1 to 2.5.

4. The method for preparing a liquid crystal polymer film for 5G communication according to claim 1, wherein the second stretching ratio is 1 to 4.

5. The method of claim 4, wherein the preset inflation ratio is at least twice the second stretching ratio.

6. The method for preparing a liquid crystal polymer film for 5G communication according to claim 1, wherein the step of extruding the melt of the liquid crystal polymer resin through a die having an annular gap further comprises: drying the liquid crystal polymer resin at 150-170 ℃ for 4-6 h.

7. The method of producing a liquid crystal polymer film for 5G communication according to claim 1, wherein the temperature at the time of extrusion is from (Tm-10 ℃) to (Tm +50 ℃), Tm representing the melting point of the liquid crystal polymer.

8. A liquid crystal polymer film for 5G communication, characterized by being prepared by the method for preparing a liquid crystal polymer film for 5G communication according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a liquid crystal polymer film for 5G communication and a preparation method thereof.

Background

Since 1965 Kevlar, the first liquid crystal polymer product, was introduced to DuPont, its superior properties were valued. After the liquid crystal polymer is heated and melted or dissolved by a solvent, the rigidity of a solid substance is lost, the fluidity of a liquid crystal substance is obtained, the ordered arrangement of crystalline substance molecules is still kept, and therefore, the liquid crystal polymer is anisotropic in physical properties and forms a transition state with partial properties of crystals and liquid. Due to the unique chain structure and the ordered arrangement among molecules, the liquid crystal polymer has excellent comprehensive physical and mechanical properties, such as high thermal deformation temperature, dimensional stability, excellent mechanical property, electrical property, irradiation resistance, chemical resistance, aging resistance, self-flame retardance, low permeability and the like, and is widely applied to the fields of electronics, electricity, automobile industry and the like.

Since electromagnetic waves have the characteristics that the higher the frequency, the shorter the wavelength, and the easier the attenuation in a propagation medium, the higher the frequency, the smaller the loss of the antenna material is required. PI films (polyimides) are used as antenna manufacturing materials in the 4G era, and PI materials have excellent advantages of high temperature resistance, low temperature resistance, high electrical insulation, corrosion resistance and the like, and are mainly used as insulating materials in FPCs. However, PI has a large loss at a frequency of 2.4GHz or more, cannot be used at a frequency of 10GHz or more, has a large moisture absorption, is not reliable enough, and is gradually replaced in the high-frequency 5G era. The Liquid Crystal Polymer (LCP) has excellent electrical properties, can keep the dielectric constant even at extremely high frequency and has consistency; the dielectric loss and the conductor loss are small, and the method can be applied to millimeter wave treatment; the thermoplastic property is strong, and the multilayer lamination is easy to realize. With the advent of the 5G era with high frequency and high speed, the excellent properties of LCP films will replace PI as a new flexible board material. Therefore, the Liquid Crystal Polymer (LCP) film has bright application prospect and huge market value in the age of 5G.

At present, the main methods for producing liquid crystal polymer films are extrusion blow molding and extrusion casting. Since the liquid crystal polymer has a high degree of orientation under the action of a shearing force, there is a significant disadvantage of mechanical anisotropy, that is, a film prepared by a conventional method has high mechanical properties in the MD Direction (Machine Direction) and poor tensile strength in the TD Direction (perpendicular to the Machine Direction). Therefore, the anisotropy of liquid crystal polymer films limits their application in high frequency transmission applications.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provided are a liquid crystal polymer film for 5G communication and a method for manufacturing the same, which can obtain a liquid crystal polymer film having good mechanical properties in TD and MD directions and excellent dimensional stability.

In order to solve the technical problems, the invention adopts the technical scheme that:

a preparation method of a liquid crystal polymer film for 5G communication comprises the steps of extruding a melt of liquid crystal polymer resin through a die head with an annular gap to obtain an extrudate; cooling the extrudate to below the glass transition temperature, and then winding at a first draw ratio to obtain a pre-oriented tubular film; heating the pre-oriented tubular film to a temperature between the glass transition temperature and the heat distortion temperature, then winding at a second drawing ratio, and expanding the pre-oriented tubular film at a preset blow-up ratio to obtain the liquid crystal polymer film.

The invention adopts another technical scheme that:

a liquid crystal polymer film for 5G communication is prepared according to the preparation method of the liquid crystal polymer film for 5G communication.

The invention has the beneficial effects that: the melt is extruded and then wound at a certain draw ratio to obtain a pre-oriented tubular film, and the pre-oriented tubular film is simultaneously blown and stretched to enable the film to be biaxially oriented in the TD direction and the MD direction, so that the liquid crystal polymer film with good mechanical properties and excellent dimensional stability in the TD direction and the MD direction can be obtained.

Detailed Description

In order to explain the technical content, the objects and the effects of the present invention in detail, the following description will be given with reference to the embodiments.

The most key concept of the invention is as follows: the pre-oriented tubular film is simultaneously blown and stretched to enable the film to be subjected to biaxial orientation in the TD direction and the MD direction, so that the liquid crystal polymer film with good mechanical property and good dimensional stability is obtained.

A preparation method of a liquid crystal polymer film for 5G communication comprises the steps of extruding a melt of liquid crystal polymer resin through a die head with an annular gap to obtain an extrudate; cooling the extrudate to below the glass transition temperature, and then winding at a first draw ratio to obtain a pre-oriented tubular film; heating the pre-oriented tubular film to a temperature between the glass transition temperature and the heat distortion temperature, then winding at a second drawing ratio, and expanding the pre-oriented tubular film at a preset blow-up ratio to obtain the liquid crystal polymer film.

From the above description, the beneficial effects of the present invention are: the melt is extruded and then wound at a certain draw ratio to obtain a pre-oriented tubular film, and the pre-oriented tubular film is simultaneously blown and stretched to enable the film to be biaxially oriented in the TD direction and the MD direction, so that the liquid crystal polymer film with good mechanical properties and excellent dimensional stability in the TD direction and the MD direction can be obtained. The tensile strength of the prepared liquid crystal polymer film in TM and MD directions is about 160-180 MPa, and the linear expansion coefficient is about 12-19 ppm/DEG C.

Furthermore, the shape of annular gap is the rectangle, the length of annular gap is 10 ~ 20 times of width, the width of annular gap is 0.5 ~ 5 mm.

As can be seen from the above description, the extrudate has some orientation in the MD after extrusion through the annular gap.

Further, the first stretching ratio is 1-2.5.

Further, the second stretching ratio is 1-4.

Further, the preset blow-up ratio is at least twice the second draw ratio.

Further, before extruding the melt of the liquid crystal polymer resin through a die having an annular gap, the method further comprises: drying the liquid crystal polymer resin at 150-170 ℃ for 4-6 h.

As can be seen from the above description, drying the liquid crystal polymer resin can remove small molecular substances such as moisture, and improve the quality of the final liquid crystal polymer film.

Further, the temperature at the time of extrusion is from (Tm-10 ℃) to (Tm +50 ℃), and Tm represents the melting point of the liquid crystal polymer.

As can be seen from the above description, the extrusion temperature should not be too high or too low, too low a viscosity is too high to facilitate molding, and too high a viscosity may cause degradation of the liquid crystal polymer.

The invention relates to another technical scheme which is as follows:

a liquid crystal polymer film for 5G communication is prepared according to the preparation method of the liquid crystal polymer film for 5G communication.