Preparation method of closed porous benzoxazine resin-based low dielectric material

Abstract

The invention discloses a method for preparing a closed porous benzoxazine resin-based low dielectric material, the preparation method comprising the following steps: dissolving the prepared poly-α-methylstyrene star polymer and the benzoxazine of a specific structure in a proper solvent in a certain proportion to form a uniform true solution, pouring the solution into a preheated mold after vacuum degassing, and curing the solution by gradient heating; during the curing process, the poly-α-methylstyrene star polymer with a low thermal decomposition temperature (polymerization upper limit temperature T c =61 o C) After thermal decomposition, closed pores with uniform pore size are formed to obtain a closed porous benzoxazine resin-based low dielectric material. The closed porous material prepared by the present invention has uniform pore size distribution, uniform pore distribution, low dielectric constant and high breakdown strength, and has excellent mechanical strength and dimensional stability, and can be used in the field of high-frequency copper clad laminates.

Description

Technical Field

[0001] The invention relates to the field of functional polymer materials, and in particular to a method for preparing a closed porous benzoxazine resin-based low dielectric material. Background Art

[0002] With the development of modern electronic technology, the resin matrix of copper-clad laminate materials as signal transmission carriers needs to have excellent dielectric properties, mechanical strength and dimensional stability. Traditional copper-clad laminates mostly use epoxy, polyimide and polytetrafluoroethylene as the matrix. The dielectric properties and high temperature resistance of epoxy-based copper-clad laminates are poor, while the water resistance and processability of polyimide-based copper-clad laminates are relatively poor. PTFE-based copper-clad laminates have excellent dielectric properties and heat resistance, but the cost of their production is high. Relatively speaking, benzoxazine resins have many new advantages such as simple molding and polymerization conditions, low melt viscosity; volume expansion and shrinkage rate during polymerization is close to zero; good heat resistance and small change in dielectric properties with frequency. However, the dielectric constant of benzoxazine resin is still relatively high, while the dielectric constant of air can be as low as 1. Introducing a porous structure into benzoxazine resin can significantly reduce its dielectric constant. However, the porous polymers prepared at this stage are mostly a large number of pores with random shapes and sizes and through-holes. Such porous resins have low breakdown voltages and poor mechanical strength. Summary of the invention

[0003] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a method for preparing a closed porous benzoxazine resin low dielectric material. The method has a simple preparation process and strong versatility. The prepared closed porous benzoxazine resin has uniform pore size and adjustable size, and the pores are evenly distributed in the resin, so that it has a low dielectric constant, a high breakdown voltage and mechanical strength.

[0004] Technical solution: The present invention provides a method for preparing a closed porous benzoxazine resin low dielectric material, which is characterized by comprising the following steps:

[0005] S1: Add phenol, aromatic primary amine and trioxymethylene into a container in sequence, then add solvent toluene and stir to mix evenly, then heat to 80-100 o C for 8-10 h; after the reaction, wash thoroughly with deionized water, dry with anhydrous magnesium sulfate, and finally recrystallize to obtain benzoxazine monomer. The reaction process is as follows:

[0006] ;

[0007] S2: Add α-methylstyrene, multi-arm RAFT agent and metal phthalocyanine catalyst into another container, then add solvent N, N-dimethylformamide and stir to form a uniform solution, introduce high-purity argon gas to remove oxygen dissolved in the solution and seal the container; then use an LED visible light source with a suitable wavelength to irradiate the polymerization for 2-5 hours; pour the reaction solution obtained by polymerization into a large amount of n-hexane for precipitation, filter and vacuum dry to obtain a poly-α-methylstyrene star polymer;

[0008] S3: fully dissolving the above-mentioned benzoxazine monomer and poly-α-methylstyrene star polymer in N, N-dimethylformamide solvent, removing the solvent after dissolution, then curing by gradient heating, and finally naturally cooling to obtain a closed porous benzoxazine resin-based low dielectric material.

[0009] Further, in S3, the specific steps of the gradient temperature curing are as follows: at 160-260 o At least two temperatures are selected within the C temperature range for gradient temperature curing, and the curing is carried out at each temperature for 2-3 hours.

[0010] Further, in S3, the solvent is removed by the following method: the dissolved solution is heated at 55-65 o C oven for 10-14 h to remove the N, N-dimethylformamide solvent.

[0011] Preferably, the molar ratio of phenol, aromatic amine and trioxymethylene in S1 is 1:1:0.67.

[0012] Preferably, the weight ratio of the monomer α-methylstyrene, the multi-arm RAFT agent and the metal phthalocyanine catalyst in S2 is 100:0.2-0.5:0.05.

[0013] Preferably, the multi-arm RAFT agent in S2 is prepared by the esterification reaction of polyol and 4-cyano-4-(thiobenzoyl)valeric acid catalyzed by N, N-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP), and its structure is any one of the following or a combination thereof:

[0014] .

[0015] Preferably, the polyol is any one of pentaerythritol, dipentaerythritol or xylitol, or a combination thereof.

[0016] Preferably, the mass ratio of the benzoxazine monomer to the poly-α-methylstyrene star polymer in S3 is 10: 1-5.

[0017] Preferably, the benzoxazine monomer structural formula in S1 is any one of the following or a combination thereof:

[0018] .

[0019] Preferably, the metal phthalocyanine catalyst in S2 is any one of aluminum phthalocyanine, zinc phthalocyanine or magnesium phthalocyanine or a combination thereof; and / or, the LED visible light source in S2 is any one of red, yellow or white LED lamps.

[0020] Beneficial effects:

[0021] 1. The present invention rationally designs and synthesizes benzoxazine monomers and star-shaped polymers to achieve complete mutual solubility at the molecular level. The true solution is used as a precursor to simultaneously achieve polymerization of benzoxazine and thermal decomposition of the star-shaped polymer by gradient temperature curing. During the curing process, the poly-α-methylstyrene star-shaped polymer with a low thermal decomposition temperature (polymerization upper limit temperature T c = 61 o C) After thermal decomposition, closed pores with uniform pore size are formed, thereby preparing a closed porous benzoxazine resin-based low-dielectric material with uniform pore size (determined by the size of the star-shaped polymer), adjustable porosity, and uniform pore distribution. This material has low dielectric constant, high breakdown voltage, mechanical strength and thermal stability. This process is suitable for the preparation of other resin-based closed porous materials and has strong versatility.

[0022] 2. The present invention prepares star-shaped polymers by visible light-induced RAFT polymerization catalyzed by metal phthalocyanine. The process is green and efficient, and the size of the star-shaped polymer can be flexibly adjusted according to the polymerization time. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with specific embodiments.

[0024] Embodiment 1:

[0025] Phenol (0.2 mol), aniline (0.2 mol) and trioxymethylene (0.134 mol) were added to a round-bottom flask in sequence, and then 100 ml of toluene was added and stirred to mix well, and then the temperature was raised to 80 o C for 8 h. After the reaction, the mixture was fully washed with deionized water three times, dried with anhydrous magnesium sulfate, and finally recrystallized to obtain a benzoxazine monomer. The reaction process is as follows:

[0026]

[0027] Add α-methylstyrene (5 g), multi-arm RAFT agent A (10 mg) and aluminum phthalocyanine (2.5 mg) to a round-bottom flask, then add solvent N, N-dimethylformamide (10 ml) and stir to form a uniform solution, pass high-purity argon gas for 15 minutes to remove the oxygen dissolved in the solution, and seal the round-bottom flask with a rubber stopper. Transfer the round-bottom flask to a red LED visible light source for irradiation polymerization for 5 hours. Then open the seal of the round-bottom flask, pour the reaction solution into a large amount of n-hexane for precipitation, filter and vacuum dry to obtain a poly-α-methylstyrene star polymer.

[0028] The benzoxazine monomer (10 g) and poly-α-methylstyrene star polymer (2 g) prepared above were fully dissolved in N, N-dimethylformamide (10 ml) solvent. After dissolution, the solution was poured into a silica gel mold and heated at 60 o C oven for 8 h to remove the solvent. Then the temperature was increased gradually to cure at 180 o C. 200 o C. 220 o C and 240 o C for 2 h, and finally naturally cooled to obtain a closed porous benzoxazine resin-based low dielectric material.

[0029] Embodiment 2:

[0030] This embodiment provides a method for preparing a closed porous benzoxazine resin low dielectric material. The method is the same as that of Application Example 1 except that the mass of the added poly-α-methylstyrene star polymer described in Example 1 is replaced from 2 g to 3 g.

[0031] Embodiment 3:

[0032] This embodiment provides a method for preparing a closed porous benzoxazine resin low dielectric material. The method is the same as that of Application Example 1 except that the mass of the added poly-α-methylstyrene star polymer described in Example 1 is replaced from 2 g to 5 g.

[0033] Embodiment 4:

[0034] Phenol (0.2 mol), naphthylamine (0.2 mol) and trioxymethylene (0.134 mol) were added to a round-bottom flask in sequence, and then 100 ml of toluene was added and stirred to mix well, and then the temperature was raised to 100 °C. o C for 10 h. After the reaction, the mixture was fully washed with deionized water three times, dried with anhydrous magnesium sulfate, and finally recrystallized to obtain a benzoxazine monomer. The reaction process is as follows:

[0035]

[0036] Add α-methylstyrene (5 g), multi-arm RAFT agent B (15 mg) and aluminum phthalocyanine (2.5 mg) to a round-bottom flask, then add solvent N, N-dimethylformamide (10 ml) and stir to form a uniform solution, pass high-purity argon gas for 15 min to remove the oxygen dissolved in the solution, and seal the round-bottom flask with a rubber stopper. Transfer the round-bottom flask to a red LED visible light source for irradiation polymerization for 2 h. Then open the seal of the round-bottom flask, pour the reaction solution into a large amount of n-hexane for precipitation, filter and vacuum dry to obtain a poly-α-methylstyrene star polymer.

[0037] The benzoxazine monomer (10 g) and poly-α-methylstyrene star polymer (3 g) prepared above were fully dissolved in N, N-dimethylformamide (10 ml) solvent. After dissolution, the solution was poured into a silica gel mold and heated at 60 o C oven for 8 h to remove the solvent. Then the temperature was increased gradually to cure at 180 o C. 200 o C. 220 o C and 240 o C for 2 h, and finally naturally cooled to obtain a closed porous benzoxazine resin-based low dielectric material.

[0038] Embodiment 5:

[0039] This embodiment provides a method for preparing a closed porous benzoxazine resin low dielectric material. The method is the same as Application Example 4 except that the irradiation polymerization time under the red LED visible light source described in Example 4 is replaced from 2 hours to 3 hours.

[0040] Embodiment 6:

[0041] This embodiment provides a method for preparing a closed porous benzoxazine resin low dielectric material. The method is the same as Application Example 4 except that the irradiation polymerization time under the red LED visible light source described in Example 4 is replaced from 2 hours to 5 hours.

[0042] Table 1 Performance test results of closed porous benzoxazine resin-based low dielectric materials prepared in different embodiments

[0043]

[0044] From Examples 1-3, it is found that as the amount of poly-α-methylstyrene star polymer added increases, the porosity of the prepared closed porous resin increases, causing its dielectric constant and dielectric loss tangent to gradually decrease. Since the pore size of the closed pores is uniform and uniformly distributed in the resin, even when the amount of poly-α-methylstyrene star polymer added is high, the porous material still maintains a high breakdown strength and tensile strength.

[0045] By changing the polymerization time of preparing the poly-α-methylstyrene star polymer, the arm length of the star polymer can be changed, thereby effectively changing the volume of the star polymer, making the pore diameter in the prepared closed porous resin smaller. From Examples 4-6, it is found that when the porosity remains basically unchanged, as the pore diameter decreases, its breakdown strength and tensile strength tend to increase.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a closed porous benzoxazine resin-based low dielectric material, characterized in that: The following steps are involved: S1: Add phenol, aromatic primary amine and trioxymethylene into a container in sequence, then add solvent toluene and stir to mix evenly, then heat to 80-100 o C for 8-10 h; after the reaction, wash thoroughly with deionized water, dry with anhydrous magnesium sulfate, and finally recrystallize to obtain benzoxazine monomer. The reaction process is as follows: ； S2: Add α-methylstyrene, multi-arm RAFT agent and metal phthalocyanine catalyst into another container, then add solvent N, N-dimethylformamide and stir to form a uniform solution, introduce high-purity argon gas to remove oxygen dissolved in the solution and seal the container; then use an LED visible light source with a suitable wavelength to irradiate the polymerization for 2-5 hours; pour the reaction solution obtained by polymerization into a large amount of n-hexane for precipitation, filter and vacuum dry to obtain a poly-α-methylstyrene star polymer; The multi-arm RAFT agent is prepared by the esterification reaction of polyol and 4-cyano-4-(thiobenzoyl)valeric acid catalyzed by N, N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, and its structure is any one of the following or a combination thereof: ； The LED visible light source is any one of red, yellow or white LED lights; S3: The benzoxazine monomer and the poly-α-methylstyrene star polymer are fully dissolved in N, N-dimethylformamide solvent, the solvent is removed after dissolution, and then the temperature is increased gradually to cure at 180 o C. 200 o C. 220 o C and 240 o C for 2 h, and finally naturally cooled to obtain a closed porous benzoxazine resin-based low dielectric material.

2. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to claim 1, characterized in that: In S3, the solvent is removed by: The dissolved solution was heated at 55~65 o C oven for 10-14 h to remove the N, N-dimethylformamide solvent.

3. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to claim 1, characterized in that: The molar ratio of phenol, aromatic amine and trioxymethylene in S1 is 1:1:0.

67.

4. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to claim 1, characterized in that: The weight ratio of the monomer α-methylstyrene, the multi-arm RAFT agent and the metal phthalocyanine catalyst in S2 is 100:0.2-0.5:0.

05.

5. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to claim 1, characterized in that: The polyol is any one of pentaerythritol, dipentaerythritol and xylitol or a combination thereof.

6. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to claim 1, characterized in that: The mass ratio of the benzoxazine monomer to the poly-α-methylstyrene star polymer in S3 is 10: 1-5.

7. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to any one of claims 1 to 6, characterized in that: The benzoxazine monomer structural formula in S1 is any one of the following or a combination thereof: 。 8. The method for preparing a closed porous benzoxazine resin-based low dielectric material according to any one of claims 1 to 6, characterized in that: The metal phthalocyanine catalyst in S2 is any one of aluminum phthalocyanine, zinc phthalocyanine or magnesium phthalocyanine or a combination thereof.

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