Closed-loop recyclable high-thermal-conductivity liquid crystal epoxy resin and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses closed-loop recyclable high-thermal-conductivity liquid crystal epoxy resin and a preparation method thereof. Comprising the following steps: mixing 4, 4-dihydroxybiphenyl, a binary carboxyl compound and a catalyst, and reacting to obtain the carboxyl-terminated biphenyl polyester. And cross-linking the carboxyl-terminated biphenyl polyester and bisphenol A epoxy resin to obtain the high-thermal-conductivity liquid crystal epoxy resin capable of being recycled in a closed-loop manner. The high-thermal-conductivity liquid crystal epoxy resin capable of being subjected to closed-loop recovery can be subjected to closed-loop recovery and rapid degradation in a sodium hydroxide aqueous solution at normal temperature. The obtained closed-loop recyclable high-thermal-conductivity liquid crystal epoxy resin has excellent mechanical properties, thermal conductivity, self-repairing performance and recycling performance, is simple in preparation process, and is expected to be applied to the fields of microelectronic devices, electrical insulation equipment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a high thermal conductivity liquid crystal epoxy resin material capable of closed-loop recycling and a preparation method thereof. Background Art

[0002] In recent years, microelectronic devices and electrical insulation equipment have been continuously developing towards miniaturization. However, due to the coupling contradiction between the thermal conductivity and thermomechanical properties of traditional thermally conductive epoxy resin composites, they cannot meet the growing heat dissipation requirements of high-power, high-frequency, and high-voltage insulation packaging applications. The low thermal conductivity, poor toughness, and non-reprocessability of thermosetting epoxy resins severely restrict their applications and sustainable development in the field of flexible electronics.

[0003] Liquid crystal epoxy resin is a unique epoxy resin that forms an ordered structure through the self-assembly of mesogenic units and has the characteristic of intrinsic high thermal conductivity. The special structural characteristics enable LCE to not only retain the beneficial physical properties of epoxy resin but also have a significantly enhanced thermal conductivity. Therefore, liquid crystal epoxy resin has become a promising solution for thermal management and has the potential to solve the key problems and technical bottlenecks that hinder the increasing miniaturization of microelectronic devices and electrical equipment. However, the orientation arrangement of liquid crystal units and the cross-linked network structure are the key factors affecting its actuation performance, and there is a competitive relationship between the molecular chain cross-linking and molecular orientation arrangement processes. Therefore, how to regulate the orientation arrangement of liquid crystal units in liquid crystal epoxy resin remains challenging. Introducing dynamic covalent bonds into the preparation and performance regulation of liquid crystal epoxy resin and using dynamic covalent cross-linking to replace steady-state cross-linking to solve the contradiction in the process of liquid crystal unit orientation and network structure formation is expected to become an effective strategy for developing new high-performance liquid crystal epoxy resins. Summary of the Invention

[0004] In order to solve the deficiencies existing in the prior art, the present invention provides a high thermal conductivity liquid crystal epoxy resin material capable of closed-loop recycling and a preparation method thereof.

[0005] The present invention solves the above technical problems with the following technical solutions:

[0006] A high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling is prepared as follows:

[0007] 4,4-dihydroxybiphenyl, a dicarboxylic acid compound, a solvent, and a catalyst are mixed and reacted at 100 - 120 °C for 1 - 2 hours. After removing the solvent, a carboxyl-terminated biphenyl polyester is obtained. The carboxyl-terminated biphenyl polyester and bisphenol A epoxy resin are cured at 80 - 100 °C for 30 - 60 minutes to obtain a high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling.

[0008] Further, the dicarboxylic acid compound is One of the following, the solvent is one of N,N-dimethylformamide, toluene, xylene, methanol, ethanol, tetrahydrofuran, 1,4-dioxane or ethyl acetate; the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid and heteropolyacid, and the mass ratio of 4,4-dihydroxybiphenyl, dicarboxylic compound, solvent and catalyst is: 1:(1.1-1.4):(4.3-5.0):(0.025-0.021).

[0009] Further, the mass ratio of the bisphenol A epoxy resin and the carboxyl-terminated biphenyl polyester is 1:(9.3-8.0).

[0010] The present invention also provides the above-mentioned method for recycling the high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure, specifically:

[0011] Soak a kind of high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure to be degraded in a solvent containing 4,4-dihydroxybiphenyl, and degrade it for 0.5-2 hours at normal pressure and 25-90 °C to obtain a degradation liquid. Add a dicarboxylic compound to the degradation liquid, and remove the solvent to obtain the recycled high thermal conductivity liquid crystal epoxy resin.

[0012] Further, the solvent is one of N,N-dimethylformamide, toluene, xylene, methanol, ethanol, tetrahydrofuran, 1,4-dioxane, ethyl acetate. The mass ratio of the high thermal conductivity liquid crystal epoxy resin, 4,4-dihydroxybiphenyl and the solvent is: 1:(0.39-0.37):(10.2-10.0).

[0013] Further, the mass ratio of the degradation liquid and the dicarboxylic compound is: 1:(0.53-0.43).

[0014] Compared with the prior art, the technical solution of the present invention has the following advantages and beneficial effects:

[0015] 1. The high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure prepared by the present invention has excellent mechanical and thermal conductivity properties.

[0016] 2. The present invention realizes the non-destructive degradation recycling and closed-loop recycling of the high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure, and the retention rates of the mechanical properties and thermal conductivity properties of the material after three times of recycling and reuse are 100%;

[0017] 3. The high thermal conductivity liquid crystal epoxy resin material prepared by the present invention and its preparation method have simple processes, mild reaction conditions, and are suitable for industrial production. Specific Embodiments

[0018] Example 1 A method for preparing a high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure, the steps are as follows:

[0019] 20.0 g of 4,4-dihydroxybiphenyl, 28.8 g of 4,4'-dithiobisbutyric acid, 100 g of N,N-dimethylformamide and 0.49 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 2 hours. After removing N,N-dimethylformamide, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 30.9 mg KOH / g, and its number-average molecular weight measured by GPC was 3634 g / mol. 2 g of E51 and 18.5 g of the carboxyl-terminated biphenyl polyester were mixed and cured at 100 °C for 30 minutes to obtain a high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure.

[0020] 10.0 g of the high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure to be degraded was immersed in methanol containing 3.7 g of 4,4-dihydroxybiphenyl, and degraded at normal pressure and 25 °C for 2 hours to obtain a degradation solution. 5.3 g of 4,4'-dithiobisbutyric acid was added to the degradation solution, and after removing methanol, the recycled high thermal conductivity liquid crystal epoxy resin was obtained. The recycling of the high thermal conductivity liquid crystal epoxy resin was completed three times according to the above steps.

[0021] Example 2 A preparation method of a high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure, the steps are as follows:

[0022] 20.0 g of 4,4-dihydroxybiphenyl, 25.4 g of 3,3'-dithiobispropionic acid, 93.1 g of methanol and 0.45 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 1.5 hours. After removing methanol, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 33.2 mg KOH / g, and its number-average molecular weight measured by GPC was 3382 g / mol. 2 g of E51 and 17.2 g of the carboxyl-terminated biphenyl polyester were mixed and cured at 100 °C for 25 minutes to obtain a high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure.

[0023] 10.0 g of the high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure to be degraded was immersed in ethanol containing 3.9 g of 4,4-dihydroxybiphenyl, and degraded at normal pressure and 25 °C for 1 hour to obtain a degradation solution. 5.0 g of 3,3'-dithiobispropionic acid was added to the degradation solution, and after removing ethanol, the recycled high thermal conductivity liquid crystal epoxy resin was obtained. The recycling of the high thermal conductivity liquid crystal epoxy resin was completed three times according to the above steps.

[0024] Example 3 A preparation method of a high thermal conductivity liquid crystal epoxy resin that can be recycled by ring closure, the steps are as follows:

[0025] 20.0 g of 4,4-dihydroxybiphenyl, 22.0 g of 2,2'-dithiodiacetic acid, 86.1 g of tetrahydrofuran and 0.42 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 1 hour. After removing tetrahydrofuran, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 35.9 mg KOH / g, and its number-average molecular weight measured by GPC was 3129 g / mol. 2 g of E51 and 16.0 g of the carboxyl-terminated biphenyl polyester were mixed and cured at 100 °C for 30 minutes to obtain a recyclable high thermal conductivity liquid crystal epoxy resin with a closed-loop structure.

[0026] 10.0 g of the recyclable high thermal conductivity liquid crystal epoxy resin to be degraded was immersed in ethyl acetate containing 3.9 g of 4,4-dihydroxybiphenyl and degraded at 25 °C under atmospheric pressure for 1.5 hours to obtain a degradation solution. 4.3 g of 2,2'-dithiodiacetic acid was added to the degradation solution, and after removing ethyl acetate, the recycled recyclable high thermal conductivity liquid crystal epoxy resin was obtained. The above steps were completed three times for recycling.

[0027] Example 4 A method for preparing a recyclable high thermal conductivity liquid crystal epoxy resin with a closed-loop structure, the steps are as follows:

[0028] 20.0 g of 4,4-dihydroxybiphenyl, 31.9 g of 4,4'-dithiobutanoic acid, 106.6 g of toluene and 0.52 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 1.5 hours. After removing toluene, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 57.9 mg KOH / g, and its number-average molecular weight measured by GPC was 1936 g / mol. 2 g of E51 and 9.8 g of the carboxyl-terminated biphenyl polyester were mixed and cured at 110 °C for 1.5 hours to obtain a recyclable high thermal conductivity liquid crystal epoxy resin with a closed-loop structure.

[0029] 10.0 g of the recyclable high thermal conductivity liquid crystal epoxy resin to be degraded was immersed in xylene containing 5.1 g of 4,4-dihydroxybiphenyl and degraded at 25 °C under atmospheric pressure for 1 hour to obtain a degradation solution. 8.2 g of 4,4'-dithiobutanoic acid was added to the degradation solution, and after removing xylene, the recycled high thermal conductivity liquid crystal epoxy resin was obtained. The above steps were completed three times for recycling. Example 5 A method for preparing a recyclable high thermal conductivity liquid crystal epoxy resin with a closed-loop structure, the steps are as follows:

[0030] 20.0 g of 4,4-dihydroxybiphenyl, 28.2 g of 3,3'-dithiodipropionic acid, 98.8 g of 1,4-dioxane and 0.48 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 1.5 hours. After removing 1,4-dioxane, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 62.5 mgKOH / g, and its number-average molecular weight measured by GPC was 1796 g / mol. After mixing 2 g of E51 and 9.1 g of the carboxyl-terminated biphenyl polyester, it was cured at 110 °C for 1.5 hours to obtain a recyclable high thermal conductivity liquid crystal epoxy resin that can be closed-loop recycled.

[0031] 10.0 g of the recyclable high thermal conductivity liquid crystal epoxy resin to be degraded was immersed in acetone containing 4.8 g of 4,4-dihydroxybiphenyl, and degraded at normal pressure and 25 °C for 1 hour to obtain a degradation solution. 6.8 g of 3,3'-dithiodipropionic acid was added to the degradation solution, and after removing acetone, a recycled high thermal conductivity liquid crystal epoxy resin was obtained. The above steps were completed three times for recycling. Example 6 A preparation method of a recyclable high thermal conductivity liquid crystal epoxy resin that can be closed-loop recycled, the steps are as follows:

[0032] 20.0 g of 4,4-dihydroxybiphenyl, 24.5 g of 2,2'-dithiodiacetic acid, 91.2 g of ethyl acetate and 0.45 g of p-toluenesulfonic acid were mixed and reacted at 100 °C for 1 hour. After removing ethyl acetate, a carboxyl-terminated biphenyl polyester was obtained. The acid value of the carboxyl-terminated biphenyl polyester was 67.8 mgKOH / g, and its number-average molecular weight measured by GPC was 1655 g / mol. After mixing 2 g of E51 and 8.4 g of the carboxyl-terminated biphenyl polyester, it was cured at 100 °C for 40 minutes to obtain a recyclable high thermal conductivity liquid crystal epoxy resin that can be closed-loop recycled.

[0033] 10.0 g of the recyclable high thermal conductivity liquid crystal epoxy resin to be degraded was immersed in DMSO containing 4.4 g of 4,4-dihydroxybiphenyl, and degraded at normal pressure and 25 °C for 1 hour to obtain a degradation solution. 5.4 g of 2,2'-dithiodiacetic acid was added to the degradation solution, and after removing DMSO, a recycled high thermal conductivity liquid crystal epoxy resin was obtained. The above steps were completed three times for recycling.

[0034] Comparative Example 1

[0035] 20 g of E51 and 12.2 g of 4,4'-dithiobutyric acid were mixed evenly and cured at 100 °C for 30 minutes.

[0036] Table 1 Performance of the recyclable high thermal conductivity liquid crystal epoxy resin described in Examples 1-6

[0037]

[0038] Table 2 Performance of the recyclable high thermal conductivity liquid crystal epoxy resin described in Examples 1-6 after being recycled three times

[0039]

[0040]

Claims

1. A high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling is prepared by the following method steps: Mix 4,4'-dihydroxybiphenyl, a dicarboxylic acid compound, a solvent and a catalyst, and react at 100-120 °C for 1-2 hours. After removing the solvent, a carboxyl-terminated biphenyl polyester is obtained. Cure the carboxyl-terminated biphenyl polyester and bisphenol A epoxy resin at 80-100 °C for 30-60 minutes to obtain the high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling.

2. The dicarboxylic compound according to claim 1 is one of them, the solvent is one of N,N-dimethylformamide, toluene, xylene, methanol, ethanol, tetrahydrofuran, 1,4-dioxane or ethyl acetate; the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid and heteropolyacid, and the mass ratio of 4,4'-dihydroxybiphenyl, dicarboxylic compound, solvent and catalyst is: 1:(1.1 - 1.4):(4.3 - 5.0):(0.025 - 0.021).

3. The mass ratio of the bisphenol A epoxy resin and the carboxyl-terminated biphenyl polyester according to claim 1 is 1:(9.3-8.0).

4. A method for recycling a high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling according to claim 1 includes the following steps: (a) Immerse the high thermal conductivity liquid crystal epoxy resin to be degraded in a solvent containing 4,4'-dihydroxybiphenyl, and degrade at normal pressure and 25-90 °C for 0.5-2 hours to obtain a degradation solution. (b) Add a dicarboxylic acid compound to the degradation solution, and remove the solvent to obtain the recycled high thermal conductivity liquid crystal epoxy resin.

5. A method for recycling a high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling according to claim 4, wherein the solvent is one of N,N-dimethylformamide, toluene, xylene, methanol, ethanol, tetrahydrofuran, 1,4-dioxane, ethyl acetate. The mass ratio of the high thermal conductivity liquid crystal epoxy resin, 4,4'-dihydroxybiphenyl and the solvent is: 1:(0.39-0.37):(10.2-10.0).

6. A method for recycling a high thermal conductivity liquid crystal epoxy resin capable of closed-loop recycling according to claim 4, wherein the mass ratio of the degradation solution and the dicarboxylic acid compound is: 1:(0.53-0.43).

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