Method for preparing carboxyl-modified cyclosiloxane and low dielectric porous polyamide liquid crystal material and method for preparing same

Abstract

This invention relates to a method for preparing carboxyl-modified cyclosiloxanes and a low-dielectric porous polyamide liquid crystal material and its preparation method. The liquid crystal material is produced by polycondensation of three monomers: an aromatic diamine, an aromatic dicarboxylic acid, and a carboxyl-modified cyclosiloxane. The monomers are then extruded separately using two extruders to form a non-foamed surface layer and a supercritical foamed core layer, which are then co-extruded to form the final product. This liquid crystal polymer material has a smooth and flat surface layer, a porous core layer, adjustable density, low dielectric constant and dielectric loss, and maintains excellent mechanical properties, meeting the demand for low-dielectric materials in 5G technology development.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method for preparing carboxyl-modified cyclosiloxanes and a low-dielectric porous polyamide liquid crystal material and its preparation method. Background Technology

[0002] Due to the high symmetry of the molecular backbone and the restricted movement of the main chain caused by the liquid crystal structure, liquid crystal polymers exhibit low dielectric constants and dielectric losses at high frequencies. Therefore, with the increasingly stringent performance requirements (especially dielectric properties) for materials in 5G devices, liquid crystal polymer materials have promising applications in high-speed connectors, 5G base station antenna elements, 5G mobile phone antennas, and high-frequency circuit boards.

[0003] Polyamide liquid crystal materials possess excellent comprehensive properties such as high strength, high temperature resistance, and good dimensional stability. However, their processability and bending resistance are relatively poor, and their dielectric constant is still relatively high, thus limiting their widespread application in the 5G technology field. By improving the processability and dielectric properties of polyamide liquid crystal materials, their applications can be further broadened to meet the material performance requirements of 5G technology development. Summary of the Invention

[0004] Objective of the invention: To address the problems existing in the prior art, the present invention provides a method for preparing carboxyl-modified cyclosiloxanes and a low-dielectric porous polyamide liquid crystal material and the same method. The porous polyamide liquid crystal material has low dielectric constant and low dielectric loss, excellent mechanical properties and is easy to process.

[0005] Technical solution: The present invention provides a method for preparing the above-mentioned carboxyl-modified cyclosiloxane, comprising the following steps: mixing and stirring an olefinic monomer and a cyclosiloxane in a molar ratio of 5 to 8:1, adding a chloroplatinic acid isopropanol solution with a concentration of 0.01 g / mL, accounting for 0.1 to 0.3% of the total fraction of the olefinic monomer and the cyclosiloxane, and reacting at 55 to 65°C for 3 to 6 hours to obtain the carboxyl-modified cyclosiloxane.

[0006] Preferably, the olefinic monomer includes at least one of the following: vinylacetic acid, 4-pentenoic acid, 5-hexenoic acid, 6-heptenoic acid, and 7-octenic acid.

[0007] Preferably, the cyclosiloxane is 1,3,5,7-tetramethylcyclotetrasiloxane or 1,3,5,7,9-pentamethylcyclopentasiloxane.

[0008] The present invention also provides a low dielectric porous polyamide liquid crystal material, which is formed by the polycondensation reaction of three monomers: an aromatic diamine, an aromatic dicarboxylic acid, and a carboxyl-modified cyclosiloxane prepared by the above method.

[0009] Preferably, the aromatic diamine comprises at least one of the following: 2,3-diaminotoluene, 2,5-dimethyl-1,4-phenylenediamine, tetramethyl-p-phenylenediamine, 3,5-dimethyl-1,2-phenylenediamine, 2,4-dimethyl-1,5-phenylenediamine, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, o-toluidine, 3,3',5,5'-tetramethylbenzidine, 1,4-diaminonaphthalene, (6-amino-2-naphthyl)amine, 2,7-naphthylenediamine, 2,2-bis(4-aminophenyl)propane, and 2,2-bis(4-aminophenyl)hexafluoropropane.

[0010] Preferably, the aromatic dicarboxylic acid includes at least one of the following: biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, [2,2-binaphthyl]-6,6'-dicarboxylic acid, 3,3'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, isophthalic acid, 5-methylisophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid.

[0011] The present invention also provides a method for preparing the above-mentioned low-dielectric porous polyamide liquid crystal material, comprising the following steps:

[0012] S1. Aromatic diamine and aromatic dicarboxylic acid in a molar ratio of 1:1 are added to an amide-salt solvent and mixed evenly. The mixture is reacted at 100-120℃ under nitrogen protection for 2-5 h. Then, 1-5% of the total mass of aromatic diamine and aromatic dicarboxylic acid is added to a carboxyl-modified cyclosiloxane. The reaction is continued for 2-4 h. The reactants are then added to anhydrous methanol for precipitation, filtered, washed, and vacuum dried to obtain polyamide liquid crystal solid powder.

[0013] S2: The above-mentioned polyamide liquid crystal solid powder is added to a co-extrusion foaming extruder, melted and plasticized at 270~310℃. The main and auxiliary extruders of the co-extrusion foaming extruder extrude a supercritical foamed core layer and a non-foamed surface layer, respectively. The material is then co-extruded through a co-extrusion composite die head to obtain a low-dielectric polyamide liquid crystal material with a smooth and flat surface layer and a closed porous core layer.

[0014] Preferably, the amide-salt solvent is composed of N-2-methylpyrrolidone, pyridine, triphenyl phosphite and anhydrous lithium chloride, wherein the volume ratio of N-2-methylpyrrolidone, pyridine and triphenyl phosphite is 100:25~50:15~30, and the concentration of anhydrous lithium chloride is 2.5~5%.

[0015] Preferably, the main extruder is a supercritical CO2 foaming extruder, with a supercritical CO2 injection flow rate of 5~10 mL / min and an injection pressure of 10~20 MPa.

[0016] Preferably, the rotational speed of both the main extruder and the auxiliary extruder is 30~50 r / min.

[0017] Beneficial Effects: This invention utilizes carboxyl-modified cyclosiloxanes followed by polycondensation with aromatic diamines and aromatic dicarboxylic acids to obtain a liquid crystal polyamide block copolymer with a star-shaped branched structure. The introduction of carboxyl-modified cyclosiloxanes into the liquid crystal polyamide increases its toughness through flexible carbon chains, while the cyclosiloxane groups provide steric hindrance. The combined effect of these two factors lowers the melting temperature of the resulting liquid crystal and improves its processing performance. The star-shaped branched structure reduces the anisotropy of traditional linear liquid crystal polyamides. The liquid crystal polyamide block copolymer is extruded using two extruders to create a non-foamed surface layer and a supercritical foamed core layer, respectively, and then co-extruded using a co-extrusion composite die head. The prepared low-dielectric porous polyamide liquid crystal material has a smooth and flat surface layer and a closed porous core structure, which has excellent mechanical properties compared with traditional through-porous materials. The closed porous structure combined with the cyclic pore structure of carboxyl-modified cyclosiloxane can also significantly reduce the dielectric constant of the material. In addition, the number of pores can be changed by adjusting the amount of supercritical CO2 injected, thereby controlling the dielectric constant and density of the polyamide liquid crystal material. Attached Figure Description

[0018] Figure 1 Flowchart of the fabrication process for low-dielectric porous polyamide liquid crystal materials. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] Example 1:

[0021] The low-dielectric porous polyamide liquid crystal material in this embodiment is prepared by polycondensation of 2,3-diaminotoluene, terphenyl dicarboxylic acid, and carboxyl-modified cyclosiloxane, and the preparation method is as follows:

[0022] 10 mL of 1,3,5,7-tetramethylcyclotetrasiloxane and 62 μL of 0.01 g / mL isopropanol chloroplatinate solution were added to 21 mL of 4-pentenoic acid. After stirring and mixing evenly, the mixture was reacted at 60 °C for 4 h to obtain carboxyl-modified cyclosiloxane.

[0023] 2.8 g of 2,3-diaminotoluene, 4.9 g of terphenyl dicarboxylic acid, and 2.5 g of anhydrous lithium chloride were dissolved in 100 mL of N-2-methylpyrrolidone. Then, 30 mL of pyridine and 15 mL of triphenyl phosphite were added and mixed thoroughly. The mixture was then reacted at 100 °C for 4 h under nitrogen protection. After that, 0.15 g of carboxyl-modified cyclosiloxane was added and the reaction was continued for 3 h. The reactants were then precipitated in anhydrous methanol, filtered, washed, and vacuum dried to obtain polyamide liquid crystal solid powder.

[0024] Polyamide liquid crystal solid powder was added to a co-extrusion foaming extruder. The main and auxiliary extruders were both set to a speed of 50 r / min. The main extruder was a supercritical CO2 foaming extruder with a supercritical CO2 injection flow rate of 5 mL / min and an injection pressure of 10 MPa. The temperature in each zone was between 290 and 305℃. The main and auxiliary extruders extruded a supercritical foamed core layer and a non-foamed surface layer, respectively. The resulting material was co-extruded through a co-extrusion composite die to obtain a low-dielectric polyamide liquid crystal material with a smooth and flat surface layer and a closed-loop porous core layer. For the specific preparation process, see [link to detailed process flow]. Figure 1 . Example

[0025] This embodiment provides a method for preparing carboxyl-modified cyclosiloxane and a low-dielectric porous polyamide liquid crystal material and its preparation method. The method is the same as in Application Example 1, except that the supercritical CO2 injection flow rate described in Example 1 is replaced with 8 mL / min instead of 5 mL / min. Example

[0026] This embodiment provides a method for preparing carboxyl-modified cyclosiloxane and a low-dielectric porous polyamide liquid crystal material and its preparation method. The method is the same as in Application Example 1, except that the supercritical CO2 injection flow rate described in Example 1 is replaced with 10 mL / min instead of 5 mL / min. Example

[0027] The low-dielectric porous polyamide liquid crystal material in this embodiment is prepared by polycondensation of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 5-methylisophthalic acid, and carboxyl-modified cyclosiloxane, and the preparation method is as follows:

[0028] 10 mL of 1,3,5,7,9-pentamethylcyclopentasiloxane and 123 μL of 0.01 g / mL isopropanol chloroplatinate solution were added to 31 mL of 6-heptenic acid. After stirring and mixing evenly, the mixture was reacted at 55 °C for 6 h to obtain carboxyl-modified cyclosiloxane.

[0029] 4.1 g of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 4.1 g of 5-methylisophthalic acid, and 5 g of anhydrous lithium chloride were dissolved in 100 mL of N-2-methylpyrrolidone. Then, 40 mL of pyridine and 30 mL of triphenyl phosphite were added and mixed thoroughly. The mixture was then reacted at 120 °C for 2 h under nitrogen protection. After that, 0.08 g of carboxyl-modified cyclosiloxane was added and the reaction was continued for another 2 h. The reactants were then precipitated in anhydrous methanol, filtered, washed, and vacuum dried to obtain polyamide liquid crystal solid powder.

[0030] Polyamide liquid crystal solid powder was added to a co-extrusion foaming extruder. The rotation speed of the main and auxiliary extruders of the co-extrusion foaming extruder was set to 30 r / min. The main extruder was a supercritical CO2 foaming extruder with a supercritical CO2 injection flow rate of 8 mL / min and an injection pressure of 15 MPa. The temperature of each zone was 275~290℃. The main and auxiliary extruders extruded a supercritical foamed core layer and a non-foamed surface layer, respectively. The material was then co-extruded through a co-extrusion composite die head to obtain a low-dielectric polyamide liquid crystal material with a smooth and flat surface layer and a closed porous core layer. Example

[0031] This embodiment provides a method for preparing carboxyl-modified cyclosiloxane and a low-dielectric porous polyamide liquid crystal material and the method thereof. The method is the same as in Application Example 4, except that the carboxyl-modified cyclosiloxane described in Example 4 is replaced with 0.25g instead of 0.08g. Example

[0032] This embodiment provides a method for preparing carboxyl-modified cyclosiloxane and a low-dielectric porous polyamide liquid crystal material and the method thereof. The method is the same as in Application Example 4, except that the carboxyl-modified cyclosiloxane described in Example 4 is replaced with 0.41g instead of 0.08g.

[0033] The physical performance test results of the above embodiments are shown in Table 1. The dielectric properties were tested at 10 GHz according to the IPC-TM-6502.5.5.9 method, the melting temperature was tested using DSC, the tensile strength was tested according to GB / T 1040, and the impact strength was tested according to GB / T 1043.

[0034] Table 1. Physical property data of the low-dielectric porous polyamide liquid crystal materials prepared in Examples 1 to 6

[0035]

[0036] Comparing Examples 1-3, the data in Table 1 above shows that as the amount of supercritical CO2 injected increases, the number of pores inside the polyamide liquid crystal material increases, while the dielectric constant of the gas is low, so the dielectric constant and dielectric loss gradually decrease; although the mechanical properties of the polyamide liquid crystal material are somewhat reduced, it still maintains high strength.

[0037] Comparing Examples 4-6, the data in Table 1 above shows that as the content of carboxyl-modified cyclosiloxane increases, the dielectric constant and dielectric loss of the polyamide liquid crystal material gradually decrease, while the melting temperature and tensile strength increase. This is because the cyclic porous structure of carboxyl-modified cyclosiloxane has a high molar volume, which can reduce the dielectric value of the material; at the same time, the carboxyl groups can react with the polyamide prepolymer, acting as network crosslinking points, improving the heat resistance and tensile strength of the material. However, crosslinking also leads to brittleness of the material, reducing the impact strength of the polyamide liquid crystal material.

[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing carboxyl-modified cyclosiloxanes, characterized in that, Mix olefin monomers and cyclosiloxanes in a molar ratio of 5 to 8:1 until homogeneous. Add isopropanol chloroplatinate solution with a concentration of 0.01 g / mL, which accounts for 0.1 to 0.3% of the total fraction of olefin monomers and cyclosiloxanes. React at 55 to 65 °C for 3 to 6 h.

2. The method for preparing carboxyl-modified cyclosiloxanes according to claim 1, characterized in that, The olefinic monomer is at least one of the following: vinylacetic acid, 4-pentenoic acid, 5-hexenoic acid, 6-heptenoic acid, and 7-octenic acid.

3. The method for preparing carboxyl-modified cyclosiloxanes according to claim 1 or 2, characterized in that, The cyclosiloxane is 1,3,5,7-tetramethylcyclotetrasiloxane or 1,3,5,7,9-pentamethylcyclopentasiloxane.

4. A low-dielectric porous polyamide liquid crystal material, characterized in that, The carboxyl-modified cyclosiloxane is formed by the polycondensation reaction of three monomers: an aromatic diamine, an aromatic dicarboxylic acid, and a carboxyl-modified cyclosiloxane prepared by any one of claims 1 to 3.

5. The low-dielectric porous polyamide liquid crystal material according to claim 4, characterized in that, The aromatic diamine is at least one of the following: 2,3-diaminotoluene, 2,5-dimethyl-1,4-phenylenediamine, tetramethyl-p-phenylenediamine, 3,5-dimethyl-1,2-phenylenediamine, 2,4-dimethyl-1,5-phenylenediamine, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, o-toluidine, 3,3',5,5'-tetramethylbenzidine, 1,4-diaminonaphthalene, (6-amino-2-naphthyl)amine, 2,7-naphthyldiamine, 2,2-bis(4-aminophenyl)propane, and 2,2-bis(4-aminophenyl)hexafluoropropane.

6. The low-dielectric porous polyamide liquid crystal material according to claim 4 or 5, characterized in that, The aromatic dicarboxylic acid is at least one of the following: biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, [2,2-binaphthyl]-6,6'-dicarboxylic acid, 3,3'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, isophthalic acid, 5-methylisophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid.

7. A method for preparing a low-dielectric porous polyamide liquid crystal material according to any one of claims 4 to 6, characterized in that, Includes the following steps: S1: Aromatic diamine and aromatic dicarboxylic acid in a molar ratio of 1:1 are added to an amide-salt solvent and mixed evenly. The mixture is reacted at 100-120℃ under nitrogen protection for 2-5 h. Then, 1-5% of the total mass of aromatic diamine and aromatic dicarboxylic acid is added to a carboxyl-modified cyclosiloxane. The reaction is continued for 2-4 h. The reactants are then added to anhydrous methanol for precipitation, filtered, washed, and vacuum dried to obtain polyamide liquid crystal solid powder. S2: The above-mentioned polyamide liquid crystal solid powder is added to a co-extrusion foaming extruder, melted and plasticized at 270~310℃. The main and auxiliary extruders of the co-extrusion foaming extruder extrude a supercritical foamed core layer and a non-foamed surface layer, respectively. The material is then co-extruded through a co-extrusion composite die head to obtain a low-dielectric polyamide liquid crystal material with a smooth and flat surface layer and a closed porous core layer.

8. The method for preparing the low-dielectric porous polyamide liquid crystal material according to claim 7, characterized in that, The amide-salt solvent is composed of N-2-methylpyrrolidone, pyridine, triphenyl phosphite and anhydrous lithium chloride, wherein the volume ratio of N-2-methylpyrrolidone, pyridine and triphenyl phosphite is 100:25~50:15~30, and the concentration of anhydrous lithium chloride is 2.5~5%.

9. The method for preparing the low-dielectric porous polyamide liquid crystal material according to claim 7, characterized in that, The main extruder is a supercritical CO2 foaming extruder, with a supercritical CO2 injection flow rate of 5~10 mL / min and an injection pressure of 10~20 MPa.

10. The method for preparing the low-dielectric porous polyamide liquid crystal material according to claim 7, characterized in that, The main extruder and the auxiliary extruder both operate at speeds of 30-50 r / min.

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