Preparation method of epoxy resin with high dielectric constant

Abstract

The invention relates to the technical field of high polymer materials, and discloses a preparation method of high-dielectric-constant epoxy resin. The method comprises the following steps: (1) carrying out copolymerization reaction on bisphenol A epoxy resin and polytetrafluoroethylene at 80-100 DEG C for 2-3 hours; (2) adding a dicyandiamide curing agent into the reaction product obtained in the step (1), and carrying out gradient heating for curing; and (3) adding surface-modified barium titanate nanoparticles into the product obtained in the step (2), performing ultrasonic treatment, performing casting molding, and performing annealing treatment. According to the method, through molecular level design, the dielectric constant is remarkably improved while the excellent mechanical property of the epoxy resin is maintained, the dielectric loss (tan delta) and the thermal stability are optimized, and a high-performance base material is provided for electronic devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a preparation method of high dielectric constant epoxy resin. BACKGROUND

[0002] Epoxy resin is widely used in electronic packaging, circuit board and other fields due to its excellent adhesion, chemical stability and electrical insulation. However, the dielectric constant of traditional bisphenol A type epoxy resin is low, which can easily lead to signal delay and energy loss in high frequency applications, and it is difficult to meet the demand of high frequency signal transmission. In the prior art, the methods for improving the dielectric properties of epoxy resin mainly include the following three types: Inorganic filler composite: by adding barium titanate, strontium titanate and other high dielectric constant ceramic particles, the ε value can be significantly improved, but it will increase the brittleness of the material, the interface compatibility is poor, and the filler addition amount exceeding 15wt% will easily cause agglomeration, affecting the processing performance.

[0003] Polar group introduction: introducing polar groups such as cyano and nitro groups into the molecular chain of epoxy resin can enhance the molecular polarizability, but it will reduce the heat resistance and mechanical strength of the material.

[0004] Copolymerization modification: using fluorine-containing monomers or liquid crystal monomers to copolymerize with epoxy resin can control the arrangement order of molecular chain, but the synthesis process is complex and the cost is high.

[0005] In addition, the existing methods generally have high dielectric loss, especially at high frequency (>1MHz), the tanδ value increases significantly, resulting in signal attenuation. Therefore, developing a preparation method of epoxy resin with high dielectric constant, low dielectric loss and excellent mechanical properties has become an important research direction in the field of electronic materials. SUMMARY

[0006] In order to overcome the problems existing in the prior art, the present application provides a preparation method of high dielectric constant epoxy resin, which is designed at the molecular level to significantly improve the dielectric constant while maintaining the excellent mechanical properties of epoxy resin, and to optimize the dielectric loss (tanδ) and thermal stability, providing high-performance substrates for electronic devices.

[0007] In order to achieve the above purpose, the present application provides a preparation method of high dielectric constant epoxy resin, which comprises the following steps: (1) copolymerizing bisphenol A type epoxy resin with polytetrafluoroethylene at 80-100℃ for 2-3 hours; (2) adding dicyandiamide curing agent to the reaction product obtained in step (1) and curing by gradient heating; (3) adding surface modified barium titanate nanoparticles to the product obtained in step (2), ultrasonic, pouring into shape and annealing.

[0008] Preferably, the weight ratio of the use amount of the bisphenol A type epoxy resin, the polytetrafluoroethylene, the dicyandiamide type curing agent and the surface modified barium titanate nanoparticles is 100:3-8:15-25:5-15.

[0009] Preferably, the epoxy equivalent weight of the bisphenol A type epoxy resin is 180-220 g / eq.

[0010] Preferably, the fluorine content of the polytetrafluoroethylene is 30-50 wt%.

[0011] Preferably, the surface modifier for surface modification of the barium titanate nanoparticles is a silane coupling agent.

[0012] Preferably, the silane coupling agent is at least one of KH-550, KH-560 and KH-570.

[0013] Preferably, the use amount of the surface modifier is 5-15 wt% of the barium titanate nanoparticles.

[0014] Preferably, in step (2), the curing is a gradient temperature curing process: first pre-curing at 80℃ for 1 hour; then heating to 140℃ for 2-3 hours.

[0015] Preferably, in step (3), the ultrasonic conditions include: power of 250-350 W, time of 20-50 minutes.

[0016] Preferably, in step (3), after casting, it is left to stand at 15-40℃ and relative humidity of 40-70% for 15-40 hours.

[0017] Preferably, in step (3), the annealing conditions include: temperature of 70-90℃, time of 1-3 hours.

[0018] Compared with the prior art, the present application has at least the following advantages: (1) Monomer selection and modification: bisphenol A type epoxy resin is selected as the matrix, the benzene ring structure in the molecular chain of which can provide inherent dielectric response, and tetrafluoroethylene derivative is introduced for copolymerization modification, so as to enhance the molecular polarizability by using the high electronegativity of fluorine atom and reduce dielectric loss.

[0019] The surface of the inorganic filler is modified by using a silane coupling agent, so as to improve the interfacial compatibility with the epoxy resin and reduce the agglomeration phenomenon. (2) Crosslinking agent optimization: dicyandiamide type curing agent is selected, and a three-dimensional network structure is formed by curing, so as to reduce free volume and dielectric loss.

[0020] After curing, internal stress is eliminated by annealing treatment to improve material stability. The annealing process is carried out under nitrogen protection to prevent the influence of oxidation reaction on dielectric properties. (3) Nanocomposite technology: Surface-modified barium titanate nanoparticles (particle size 50-100 nm, specific surface area 10-20 m² / g) are dispersed in epoxy resin, and the addition amount is controlled at 5-15 wt%. Uniform distribution of particles is ensured by ultrasonic dispersion to avoid agglomeration.

[0021] Preferably, the composite ratio is optimized by experiment. When the addition amount exceeds 15 wt%, the tensile strength and elongation at break of the material decrease significantly, while the dielectric constant increases limitedly. (4) Process parameter control: Two-step mixing is adopted: pre-reaction of epoxy resin and curing agent, then addition of nanofiller to ensure uniform dispersion.

[0022] (5) Effect data: Electric property improvement: The dielectric constant (ε) is increased to 6.0-8.0 at a test frequency of 1 MHz, which is more than 50% higher than that of traditional epoxy resin, and the ε value remains stable at high frequency (1-10 MHz) with a fluctuation range of less than 5%. Dielectric loss reduction: The dielectric loss tangent (tanδ) is less than 0.02, meeting the demand of high-frequency application, and the tanδ value is reduced by 30% compared with traditional materials at 5G communication frequency band (3.5 GHz).

[0023] Mechanical property retention: Tensile strength ≥ 80 MPa, elongation at break ≥ 5%, with high dielectric and good toughness, capable of bearing mechanical stress in high-frequency signal transmission. Thermal stability optimization: Thermal decomposition temperature (TGA) ≥ 350℃, glass transition temperature (Tg) ≥ 120℃, suitable for high-temperature working environment. DETAILED DESCRIPTION

[0024] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0025] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and values. The endpoints of the ranges of values, the endpoints of the ranges of values and single values between the endpoints of the ranges of values, and single values between the endpoints of the ranges of values can be combined with one another to form new ranges or values not expressly mentioned herein, and these new ranges and values are to be considered as being included within the scope of the present disclosure.

[0026] The preparation method of the high-dielectric-constant epoxy resin provided by the present application comprises the following steps: (1) copolymerization of bisphenol A type epoxy resin and polytetrafluoroethylene at 80-100°C for 2-3 hours; (2) adding dicyandiamide curing agent to the reaction product obtained in step (1) and curing by gradient temperature rising; (3) adding surface-modified barium titanate nanoparticles to the product obtained in step (2), ultrasonicating, casting and annealing.

[0027] In a preferred embodiment, the weight ratio of the bisphenol A type epoxy resin, the polytetrafluoroethylene, the dicyandiamide curing agent and the surface-modified barium titanate nanoparticles can be 100:3-8:15-25:5-15.

[0028] In the present application, step (1) uses bisphenol A type epoxy resin and polytetrafluoroethylene for copolymerization, which can reduce dielectric loss.

[0029] In some embodiments, the epoxy equivalent weight of the bisphenol A type epoxy resin can be 180-220 g / eq.

[0030] In some embodiments, the fluorine content of the polytetrafluoroethylene can be 30-50 wt%, for example, it can be 30 wt%, 35 wt%, 40 wt%, 45 wt% or 50 wt%. Preferably, the amount of fluorine-containing monomer polytetrafluoroethylene added can be controlled to be 3-8 wt% of the bisphenol A type epoxy resin, for example, it can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt% or 8 wt%; too high an amount of polytetrafluoroethylene added can result in too strong hydrophobicity of the material, affecting the interfacial adhesion performance.

[0031] In the present application, dicyandiamide curing agent is selected, and through curing, a three-dimensional network structure can be formed, free volume can be reduced, and dielectric loss can be reduced.

[0032] Preferably, the gradient temperature rising curing process is used to pre-cure at low temperature first, and then cure at high temperature, which can avoid uneven material performance caused by local overheating. In a preferred embodiment, in step (2), the curing is a gradient temperature rising curing process: pre-curing at 80°C for 1 hour first; then raising the temperature to 140°C for 2-3 hours for curing.

[0033] Preferably, the amount of the surface-modified barium titanate nanoparticles is 5-15 wt% of the bisphenol A type epoxy resin, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%. It is found through experiments that when the amount exceeds 15 wt%, the tensile strength and elongation at break of the material decrease significantly, while the dielectric constant increases only limitedly. Therefore, limiting the amount of the surface-modified barium titanate nanoparticles in this range can make the prepared epoxy resin have higher tensile strength and elongation at break, as well as higher dielectric constant.

[0034] In the present application, the surface modification of the inorganic filler with the silane coupling agent can improve the interfacial compatibility of the inorganic filler and the epoxy resin, reduce the agglomeration phenomenon, and further improve the comprehensive performance of the material. In a preferred embodiment, the surface modifier for surface modification of the barium titanate nanoparticles in step (3) can be a silane coupling agent. Further, the silane coupling agent can be selected conventionally in the art. In some embodiments, the silane coupling agent is at least one of KH-550, KH-560 and KH-570.

[0035] In some preferred embodiments, the amount of the surface modifier can be 5-15 wt% of the barium titanate nanoparticles, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%.

[0036] The method for surface modification of the barium titanate nanoparticles with the silane coupling agent is not limited and can be a conventional operation in the art.

[0037] In an embodiment, the method for surface modification of the barium titanate nanoparticles with the silane coupling agent comprises: calcining the barium titanate nanoparticles at 500°C to remove surface organic matter, then soaking in 2 mol / L NaOH solution to remove the coating layer, washing to neutral and drying; mixing the silane coupling agent solution with the barium titanate, ultrasonic oscillation for 8 hours to promote the reaction, centrifugal separation of the unreacted coupling agent, washing with acetone and n-hexane for 3 times, and vacuum drying at 50°C for 4 hours to obtain the modified product.

[0038] In some embodiments, the particle size of the barium titanate nanoparticles can be 50-100 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0039] In another embodiment, the specific surface area of the barium titanate nanoparticles can be 10-20 m 2 / g.

[0040] In this invention, ultrasonic dispersion ensures uniform distribution of barium titanate nanoparticles and avoids agglomeration. In some embodiments, the ultrasonic conditions in step (3) include: power of 250-350W and time of 20-50 minutes.

[0041] In this invention, after casting, the material thickness is controlled to be 0.5-2 mm. Furthermore, after casting, the material is left to stand for 15-40 hours at 15-40°C and 40-70% relative humidity.

[0042] In this invention, the annealing process is carried out under an inert atmosphere to prevent oxidation from affecting the dielectric properties. In some embodiments, in step (3), the annealing temperature can be 70-90°C, for example 70°C, 75°C, 80°C, 85°C or 90°C; the time can be 1-3 hours, for example 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, to eliminate internal stress in the material.

[0043] An epoxy resin with high dielectric constant, low dielectric loss and excellent mechanical properties can be prepared by the method described in this invention.

[0044] In this invention, the parallel-plate capacitor method is used to test the dielectric constant and dielectric loss of epoxy resin. The testing principle is as follows: the parallel-plate capacitor method calculates the relative dielectric constant by measuring the capacitance without a dielectric (vacuum / air) and the capacitance after inserting an epoxy resin sample. The dielectric loss tangent is indirectly calculated by the phase difference between the current and voltage under AC voltage. The experimental steps include: 1. Sample preparation: Process the epoxy resin into a thin sheet of uniform thickness (usually 0.1-2 mm), ensuring a smooth surface. 2. Instrument zeroing: Zero the instrument using an LCR meter or dielectric constant meter when there is no sample between the parallel-plate electrodes. 3. Capacitance measurement: Measure the capacitance without a dielectric. Insert the resin sample and measure the capacitance. Data recording: Repeat the measurement 6 times, recording parameters such as thickness and electrode diameter. The test frequency is 1 MHz. 4. Calculate the dielectric constant and dielectric loss.

[0045] In this invention, the tensile strength and elongation at break of epoxy resin are determined in accordance with GB / T 1040 "Determination of tensile properties of plastics".

[0046] The following examples further illustrate the preparation method of a high dielectric constant epoxy resin according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0047] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0048] In the following embodiments: The preparation process of barium titanate nanoparticles modified with KH-550 silane coupling agent includes: calcining barium titanate nanoparticles at 500℃ to remove surface organic matter, then soaking them in 2mol / L NaOH solution to remove the coating layer, washing them until neutral, and drying them; mixing barium titanate with KH-550 silane coupling agent solution, the amount of KH-550 silane coupling agent being 10% by weight of the barium titanate nanoparticles, ultrasonically vibrating for 8 hours to promote the reaction, centrifuging to separate the unreacted coupling agent, washing three times with acetone and n-hexane, and vacuum drying at 50℃ for 4 hours to obtain the modified product.

[0049] Example 1 S1. 100 parts of bisphenol A type epoxy resin (epoxy equivalent 180-220 g / eq) and 5 parts of vinylidene fluoride (fluorine content 40 wt%) were copolymerized at 90°C for 2.5 hours. S2. Add 20 parts of dicyandiamide curing agent (purity ≥98%) to the reaction product obtained in step S1, pre-cur at 80℃ for 1 hour, and then heat to 140℃ for 3 hours. S3. Add 10 parts of barium titanate nanoparticles (particle size 80nm, specific surface area 15m² / g) modified with KH-550 silane coupling agent to the product obtained in step S2, and ultrasonically disperse for 30 minutes at a power of 300W. S4. The product obtained in step S3 is cast into a film with a thickness of 1 mm, and then left to stand for 24 hours at 25°C and 50% relative humidity. Then, it is annealed for 2 hours under nitrogen protection at 80°C.

[0050] The measured dielectric constant ε=7.2, dielectric loss tanδ=0.015, tensile strength 85MPa, and elongation at break 6%.

[0051] Example 2 S1. 100 parts of bisphenol A type epoxy resin (epoxy equivalent 180-220 g / eq) and 3 parts of vinylidene fluoride (fluorine content 30 wt%) were copolymerized at 80°C for 3 hours. S2. Add 15 parts of dicyandiamide curing agent to the reaction product obtained in step S1, pre-cur at 80°C for 1 hour, and then heat to 130°C for 2.5 hours. S3. Add 5 parts of barium titanate nanoparticles (particle size 60nm, specific surface area 12m² / g) modified with KH-560 silane coupling agent to the product obtained in step S2, and ultrasonically disperse for 30 minutes at a power of 350W. S4. Cast the product obtained in step S3 into a film with a thickness of 0.5 mm, let it stand for 24 hours at 25°C and 50% relative humidity, and then anneal it at 80°C for 2 hours.

[0052] The measured dielectric constant ε=6.5, dielectric loss tanδ=0.018, tensile strength 82MPa, and elongation at break 5.5%.

[0053] Example 3 S1. 100 parts of bisphenol A type epoxy resin (epoxy equivalent 180-220 g / eq) and 8 parts of vinylidene fluoride (fluorine content 50 wt%) were copolymerized at 100°C for 2 hours. S2. Add 25 parts of dicyandiamide curing agent to the reaction product obtained in step S1, pre-cur at 80°C for 1 hour, and then heat to 150°C for 2 hours. S3. Add 15 parts of barium titanate nanoparticles (particle size 100nm, specific surface area 18m² / g) modified with KH-570 silane coupling agent to the product obtained in step S2, and ultrasonically disperse for 30 minutes at a power of 250W. S4. The product obtained in step S3 is cast into a film with a thickness of 2 mm, and then left to stand for 24 hours at 25°C and 50% relative humidity. Then, it is annealed for 2 hours under nitrogen protection at 80°C.

[0054] The measured dielectric constant ε=8.0, dielectric loss tanδ=0.020, tensile strength 78MPa, and elongation at break 5% were obtained.

[0055] Example 4 S1. 100 parts of bisphenol A type epoxy resin (epoxy equivalent 180-220 g / eq) and 6 parts of vinylidene fluoride (fluorine content 35 wt%) were copolymerized at 85°C for 2 hours. S2. Add 25 parts of dicyandiamide curing agent to the reaction product obtained in step S1, pre-cur at 80°C for 1 hour, and then heat to 150°C for 2 hours. S3. Add 12 parts of barium titanate nanoparticles (particle size 100nm, specific surface area 18m² / g) modified with KH-570 silane coupling agent to the product obtained in step S2, and ultrasonically disperse for 30 minutes at a power of 300W. S4. The product obtained in step S3 is cast into a film with a thickness of 2 mm, and then left to stand for 24 hours at 25°C and 50% relative humidity. Then, it is annealed for 2 hours under nitrogen protection at 80°C.

[0056] The measured dielectric constant ε=7.8, dielectric loss tanδ=0.019, tensile strength 83MPa, and elongation at break 5.7% were obtained.

[0057] Comparative Example 1 The curing process did not involve gradient heating and the barium titanate nanoparticles were not modified.

[0058] The specific process includes: S1. 100 parts of bisphenol A type epoxy resin (epoxy equivalent 180-220 g / eq) and 3 parts of vinylidene fluoride (fluorine content 30 wt%) were copolymerized at 80°C for 3 hours. S2. Add 15 parts of dicyandiamide curing agent to the reaction product obtained in step S1, and cure directly at 130°C for 2.5 hours without gradient heating. S3. Add 5 parts of unmodified barium titanate nanoparticles (particle size 60nm, specific surface area 12m² / g) to the product obtained in step S2, and ultrasonically disperse for 30 minutes at a power of 350W. S4. Cast the product obtained in step S3 into a film with a thickness of 0.5 mm, let it stand for 24 hours at 25°C and 50% relative humidity, and then anneal it at 80°C for 2 hours.

[0059] The measured dielectric constant ε=5.8, dielectric loss tanδ=0.025, tensile strength 75MPa, and elongation at break 4.5% were obtained.

[0060] As can be seen from the examples and comparative examples, the method described in Examples 1-4, through gradient temperature curing, surface modification of barium titanate nanoparticles, and copolymerization with fluorinated monomers, results in a high dielectric constant, low dielectric loss, and high tensile strength and elongation at break, achieving a balance between dielectric constant and mechanical properties. In contrast, Comparative Example 1, without gradient temperature curing and without modification of the barium titanate nanoparticles, exhibits a lower dielectric constant, a higher tanδ value, and decreased mechanical properties. Therefore, the epoxy resin prepared using the method of this invention exhibits superior performance.

[0061] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0062] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a high dielectric constant epoxy resin, characterized in that, The method includes the following steps: (1) Copolymerize bisphenol A type epoxy resin with polytetrafluoroethylene at 80-100℃ for 2-3 hours; (2) Add dicyandiamide-based curing agent to the reaction product obtained in step (1) and cure it by gradient heating; (3) Add surface-modified barium titanate nanoparticles to the product obtained in step (2), sonicate, cast and anneal.

2. The method according to claim 1, characterized in that, The weight ratio of the bisphenol A type epoxy resin, the polytetrafluoroethylene, the dicyandiamide curing agent, and the surface-modified barium titanate nanoparticles is 100:3-8:15-25:5-15.

3. The method according to claim 1 or 2, characterized in that, The epoxy equivalent of the bisphenol A type epoxy resin is 180-220 g / eq.

4. The method according to any one of claims 1-3, characterized in that, The fluorine content of the polytetrafluoroethylene is 30-50 wt%.

5. The method according to any one of claims 1-4, characterized in that, The surface modifier for surface modification of barium titanate nanoparticles is a silane coupling agent.

6. The method according to claim 5, characterized in that, The silane coupling agent is at least one of KH-550, KH-560 and KH-570; And / or, the amount of the surface modifier is 5-15% by weight of the barium titanate nanoparticles.

7. The method according to any one of claims 1-6, characterized in that, In step (2), the curing is a gradient temperature curing process: first, pre-curing at 80℃ for 1 hour; then heating to 140℃ for 2-3 hours.

8. The method according to any one of claims 1-7, characterized in that, In step (3), the conditions for ultrasound include: power of 250-350W and time of 20-50 minutes.

9. The method according to any one of claims 1-8, characterized in that, In step (3), after casting, the mixture is left to stand for 15-40 hours at 15-40℃ and 40-70% relative humidity.

10. The method according to any one of claims 1-9, characterized in that, In step (3), the annealing conditions include: a temperature of 70-90°C and a time of 1-3 hours.