阅读说明：本技术 液晶聚合物薄膜的制备方法 (Method for preparing liquid crystal polymer film ) 是由 翟盼 郭建君 虞成城 于 2020-03-10 设计创作，主要内容包括：本发明公开了一种液晶聚合物薄膜的制备方法,将液晶聚合物树脂与助推剂进行混合,得到预混料；将所述预混料压制成坯体,将所述坯体进行推挤成型,得到预制棒；将所述预制棒压延成型,得到液晶聚合物基带；将所述液晶聚合物基带依次进行纵向拉伸和横向拉伸,得到拉伸基带；将所述拉伸基带烧结成型,得到液晶聚合物薄膜。采用推挤成型、拉伸和烧结成型工艺相结合的方式来成型液晶聚合物薄膜,可有效避免液晶聚合物熔体沿机械方向取向流动,薄膜的各向异性得到显著改善。(The invention discloses a preparation method of a liquid crystal polymer film, which comprises the steps of mixing liquid crystal polymer resin with a boosting agent to obtain a premix; pressing the premix into a green body, and performing extrusion molding on the green body to obtain a preform; performing calendaring molding on the prefabricated rod to obtain a liquid crystal polymer base band; sequentially carrying out longitudinal stretching and transverse stretching on the liquid crystal polymer base band to obtain a stretched base band; and sintering and molding the stretched base band to obtain the liquid crystal polymer film. The liquid crystal polymer film is formed by combining extrusion forming, stretching and sintering forming processes, so that the liquid crystal polymer melt can be effectively prevented from flowing along the mechanical direction in an oriented mode, and the anisotropy of the film is remarkably improved.)

1. The preparation method of the liquid crystal polymer film is characterized in that liquid crystal polymer resin is mixed with a boosting agent to obtain a premix; pressing the premix into a green body, and performing extrusion molding on the green body to obtain a preform; performing calendaring molding on the prefabricated rod to obtain a liquid crystal polymer base band; sequentially carrying out longitudinal stretching and transverse stretching on the liquid crystal polymer base band to obtain a stretched base band; and sintering and molding the stretched base band to obtain the liquid crystal polymer film.

2. The method of claim 1, further comprising, before mixing the liquid crystal polymer resin with the propellant: drying the liquid crystal polymer resin at 150-170 ℃ for 4-6 h.

3. The method of preparing a liquid crystal polymer film according to claim 1, wherein the promoter is at least one of liquid paraffin, petroleum ether and alkane.

4. The method for preparing a liquid crystal polymer film according to claim 1, wherein the weight ratio of the liquid crystal polymer resin to the pushing aid is (25-32): (1-2).

5. The method for preparing a liquid crystal polymer film according to claim 1, wherein the premix is allowed to stand for 10 to 12 hours.

6. The method for preparing a liquid crystal polymer film according to claim 1, wherein the temperature of the extrusion molding is 60 to 80 ℃; the temperature of the calendering molding is 50-70 ℃.

7. The method of claim 1, further comprising, prior to the longitudinal stretching: and drying the liquid crystal polymer base band for 30-60 min at 120-140 ℃.

8. The method for preparing a liquid crystal polymer film according to claim 1, wherein the temperature of the longitudinal stretching is 200 to 300 ℃ and the time is 4 to 8 min; the temperature of the transverse stretching is 170-250 ℃.

9. The method for preparing a liquid crystal polymer film according to claim 1, wherein the sintering temperature is 260 to 350 ℃ and the sintering time is 40 to 80 seconds.

10. The method of producing a liquid crystal polymer film according to claim 1, further comprising: and cooling the liquid crystal polymer film.

Technical Field

The invention relates to the technical field of high molecular materials, in particular to a preparation method of a liquid crystal polymer film.

Background

After the liquid crystal polymer is heated and melted or dissolved by a solvent, the rigidity of a solid substance is lost, so that the fluidity of a liquid crystal substance is obtained, and the ordered arrangement of crystalline substance molecules is still maintained, so that the liquid crystal polymer has anisotropy on physical properties and forms a transition state with partial properties of crystals and liquid. Due to the rigid chain structure and the ordered arrangement among molecules, the liquid crystal polymer has excellent comprehensive physical and mechanical properties, good dimensional stability and low hygroscopicity, and has been widely applied to the fields of aerospace, electronics and electricity, automobile industry and the like.

In the current electronic information era, a Printed Circuit Board (PCB) is a portable electronic product with three kinds of facilities occupying the broad market, and has become an indispensable important component of the electronic industry for the most critical electronic parts such as satellite transmission and communication products. With the rapid development of electronic information products, particularly microwave devices, the requirements of high density, digitization, high frequency, application in special environments, and the like have posed a great challenge to the manufacturing process of high frequency boards. PCBs used in the high frequency field are required to have excellent dielectric properties, i.e., low dielectric constant and low dielectric dissipation factor. The liquid crystal polymer film is especially suitable for being applied to the field of high-frequency transmission due to the fact that the liquid crystal polymer has outstanding dielectric property, excellent physical and mechanical comprehensive properties, good dimensional stability and low hygroscopicity. Liquid crystal polymer films, while having the above-mentioned good properties, suffer from the significant drawback of mechanical anisotropy. Liquid crystalline polymers cannot be blown and stretched after extrusion as web polymers because they are too highly oriented in the machine flow direction in the die, but too weak in the non-oriented direction to be stretched after extrusion, and the resulting film articles have significant differences in mechanical properties in the TD and MD directions. The thickness uniformity of the liquid crystal polymer film prepared by adopting the traditional extrusion blowing film forming process is difficult to control, the TD direction orientation is too high, and the yield is low. The liquid crystal polymer film prepared by the extrusion casting process along the machine direction has too high orientation and is difficult to transversely stretch, so that the transverse mechanical property of the film is poor.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provides a preparation method of a liquid crystal polymer film, which can obviously improve the anisotropy of the film.

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

a preparation method of a liquid crystal polymer film comprises the steps of mixing liquid crystal polymer resin with a boosting agent to obtain a premix; pressing the premix into a green body, and performing extrusion molding on the green body to obtain a preform; performing calendaring molding on the prefabricated rod to obtain a liquid crystal polymer base band; sequentially carrying out longitudinal stretching and transverse stretching on the liquid crystal polymer base band to obtain a stretched base band; and sintering and molding the stretched base band to obtain the liquid crystal polymer film.

The invention has the beneficial effects that: the liquid crystal polymer film is formed by combining extrusion forming, stretching and sintering forming processes, so that the liquid crystal polymer melt can be effectively prevented from flowing along the mechanical direction in an oriented mode, the mechanical property of the film can be effectively improved, the tensile strength of the film can reach 172-178 MPa in the MD direction and 164-170 MPa in the TD direction, and the anisotropy of the film is remarkably improved.

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 liquid crystal polymer film is formed by combining extrusion forming, stretching and sintering forming processes, so that the liquid crystal polymer melt can be effectively prevented from flowing along the mechanical direction in an oriented mode, and the mechanical property of the film can be effectively improved.

A preparation method of a liquid crystal polymer film comprises the steps of mixing liquid crystal polymer resin with a boosting agent to obtain a premix; pressing the premix into a green body, and performing extrusion molding on the green body to obtain a preform; performing calendaring molding on the prefabricated rod to obtain a liquid crystal polymer base band; sequentially carrying out longitudinal stretching and transverse stretching on the liquid crystal polymer base band to obtain a stretched base band; and sintering and molding the stretched base band to obtain the liquid crystal polymer film.

From the above description, the beneficial effects of the present invention are: the liquid crystal polymer film is formed by combining extrusion forming, stretching and sintering forming processes, so that the liquid crystal polymer melt can be effectively prevented from flowing along the mechanical direction in an oriented mode, the mechanical property of the film can be effectively improved, the tensile strength of the film can reach 172-178 MPa in the MD direction and 164-170 MPa in the TD direction, and the anisotropy of the film is remarkably improved. The liquid crystal polymer resin used in the present invention may be a highly heat-resistant type (type I) or heat-resistant type (type II) liquid crystal polymer resin, and commercially available products are used.

Further, the mixing of the liquid crystal polymer resin and the boosting agent further comprises: drying the liquid crystal polymer resin at 150-170 ℃ for 4-6 h.

As can be seen from the above description, drying can be carried out to remove moisture and other volatile impurities from the resin.

Further, the boosting agent is at least one of liquid paraffin, petroleum ether and alkane.

As can be seen from the above description, the type of boosting agent can be selected as desired.

Further, the weight ratio of the liquid crystal polymer resin to the boosting agent is (25-32): (1-2).

Further, standing the premix for 10-12 hours.

As can be seen from the above description, the premix is allowed to stand to uniformly mix the liquid crystal polymer resin and the propellant.

Further, the extrusion molding temperature is 60-80 ℃; the temperature of the calendering molding is 50-70 ℃.

Further, the longitudinal stretching further comprises: and drying the liquid crystal polymer base band for 30-60 min at 120-140 ℃.

Further, the temperature of the longitudinal stretching is 200-300 ℃, and the time is 4-8 min; the temperature of the transverse stretching is 170-250 ℃.

Furthermore, the sintering and forming temperature is 260-350 ℃, and the time is 40-80 s.

Further, the method also comprises the following steps: and cooling the liquid crystal polymer film.

As can be seen from the above description, the micro-scale structure obtained by cooling and solidifying is oriented to obtain a liquid crystal polymer film with good longitudinal and transverse dimensional stability.