High-thermal-conductivity unsaturated polyester bulk molding compound as well as preparation method and application thereof

Abstract

The invention relates to the field of thermosetting composite materials, and particularly discloses a high-thermal-conductivity unsaturated polyester bulk molding compound as well as a preparation method and application thereof. The high-thermal-conductivity unsaturated polyester bulk molding compound is prepared from the following raw materials in parts by weight: 25 to 35 parts of unsaturated polyester resin, 15 to 25 parts of chopped glass fiber, 40 to 70 parts of alpha-aluminum oxide, 5 to 7 parts of low shrinkage agent, 0.5 to 1.5 parts of initiator and 1 to 3 parts of lubricant. According to the unsaturated polyester bulk molding compound disclosed by the invention, alpha-aluminum oxide is adopted as a filler, so that the heat-conducting property of the unsaturated polyester bulk molding compound is remarkably improved, the unsaturated polyester bulk molding compound can meet the heat dissipation requirement of a high-power LED, and meanwhile, the unsaturated polyester bulk molding compound also has relatively low production cost and relatively high stability.

Description

Technical Field

[0001] The present application relates to the field of thermosetting composites, specifically to the field of bulk molding compounds, and more specifically, it relates to a high thermal conductivity unsaturated polyester bulk molding compound and a preparation method thereof. Background Art

[0002] Polymer composites have the advantages of high strength, easy manufacturing of complex shapes, good corrosion resistance, and economic efficiency, and are one of the most widely used composite materials at present. Thermosetting resins are widely used as the matrix of polymer composites due to their excellent adhesion, heat resistance, and mechanical properties. Based on different manufacturing methods of thermosetting resin composites, one of them is bulk molding compounds, that is, unsaturated polyester bulk molding compounds, which are usually used for mass production of small geometric parts.

[0003] Unsaturated polyester bulk molding compounds, also known as bulk molding compounds (BMC materials), are abbreviated as BMC materials. They are mainly bulk materials composed of chopped glass fibers, unsaturated resins, fillers, and various additives after being fully mixed. BMC materials were first applied abroad in the 1960s and then developed greatly in the 1970s and 1980s. Due to their excellent electrical properties, mechanical properties, heat resistance, and chemical corrosion resistance, and their adaptability to various molding processes, they are increasingly favored by users and are widely used in the transportation, sanitary facilities, construction, household appliances, and electrical industries.

[0004] The fillers used in existing BMC materials mainly include clay, talc, hollow glass microspheres, mica, carbon black, and calcium carbonate, etc. Calcium carbonate is usually selected to reduce the price, but using calcium carbonate as a filler will result in a lower thermal conductivity of BMC materials, usually 0.2 - 0.5 W / (m·k), which cannot meet the heat dissipation requirements of high-power LEDs. Although some researchers have proposed using aluminum nitride to replace or partially replace calcium carbonate, the extremely high cost of aluminum nitride limits its popularization in large-scale applications. At the same time, the sensitivity of aluminum nitride to moisture in the air makes it prone to hydrolysis reactions, thus affecting the thermal conductivity of the material. Summary of the Invention

[0005] In order to solve the above technical problems, the present application provides a high thermal conductivity unsaturated polyester bulk molding compound and a preparation method and application thereof.

[0006] In the first aspect, a high thermal conductivity unsaturated polyester bulk molding compound provided by the present application adopts the following technical solution: A high thermal conductivity unsaturated polyester bulk molding compound, the raw materials used include the following components in parts by weight: Unsaturated polyester resin 25 - 35 parts; Chopped glass fiber 15 - 25 parts; 40 - 70 parts of α-aluminum oxide; 5 - 7 parts of low shrinkage agent; 0.5 - 1.5 parts of initiator; 1 - 3 parts by weight of lubricant.

[0007] By adopting the above technical solution, the present application introduces a high content of α-aluminum oxide as a filler. By utilizing its high thermal conductivity characteristics, the thermal conductivity of the material is significantly improved, enabling the material to meet the application scenarios with high heat dissipation requirements such as high-power LEDs. At the same time, compared with materials such as aluminum nitride, α-aluminum oxide also has the advantage of low price, which can greatly reduce the production cost of the material and can be widely applied in many occasions. In addition, α-aluminum oxide has good compatibility with components such as unsaturated polyester resin and chopped glass fiber, ensuring the overall mechanical strength and processing performance of the material, so that the material can maintain excellent formability and heat resistance while meeting the high thermal conductivity requirements, and is particularly suitable for occasions with high requirements for heat dissipation performance.

[0008] The low shrinkage agent of the present application includes one of polystyrene, polymethyl methacrylate, and styrene-butadiene-styrene block copolymer.

[0009] The initiator of the present application includes tert-butyl peroxybenzoate (TBPB) and benzoyl peroxide (BPO).

[0010] The lubricant of the present application is zinc stearate.

[0011] Preferably, the α-aluminum oxide includes spherical α-aluminum oxide and flaky α-aluminum oxide with a weight ratio of (1.5 - 2.5):1.

[0012] By adopting the above technical solution, the present application uses spherical α-aluminum oxide and flaky α-aluminum oxide in a certain proportion and combination, which can give full play to the synergistic effect between the two, thereby further improving the thermal conductivity of the material. Specifically, spherical α-aluminum oxide can be filled in large quantities in the material matrix to increase the filling rate of the thermal conductivity filler, so that the thermal conductivity filler can be interconnected in the material matrix to form a "sea-sea" structure, constituting a continuous thermal conduction network path; the flaky α-aluminum oxide further enhances the heat conduction efficiency through its special morphology. The synergistic effect of the two enables the material to have extremely high thermal conductivity while ensuring relatively high mechanical strength, and can meet the heat dissipation requirements of high-power LEDs.

[0013] Preferably, the spherical α-aluminum oxide includes spherical α-aluminum oxide with a particle size of 0.7 μm, spherical α-aluminum oxide with a particle size of 5 μm, and spherical α-aluminum oxide with a particle size of 70 μm in a weight ratio of (11 - 12):(25 - 26):(62 - 63).

[0014] By adopting the above technical solution, the present application uses spherical α-aluminum oxide composed of a mixture of multi-scale particle sizes, which can give full play to the synergistic effect between different particle sizes. Compared with using spherical α-aluminum oxide with a single particle size, it can further improve the thermal conductivity of the material. Among them, the spherical α-aluminum oxide with a particle size of 0.7 μm can fully fill the tiny pores inside the material matrix, and the small-sized particles can fill between the large-sized particles, forming more heat conduction paths in the material matrix, thereby improving the density and thermal conductivity of the material; the spherical α-aluminum oxide with a particle size of 5 μm can play an intermediate transition role, optimize the packing structure between particles, further improve the thermal conductivity efficiency of the material and enhance the mechanical strength of the material; the spherical α-aluminum oxide with a particle size of 70 μm can provide good fluidity, facilitating processing and forming.

[0015] Preferably, the flaky α-aluminum oxide is prepared by the following method: Amorphous alumina, AlF3 and anhydrous isopropanol with a weight ratio of 10:(0.2 - 0.4):1 are mixed and ball-milled for 4 - 6 h, and then vacuum-dried at a temperature of 115 - 125 °C to remove anhydrous isopropanol to obtain amorphous alumina powder. After that, the amorphous alumina powder is calcined at a temperature of 1150 - 1250 °C for 2.5 - 3.5 h and then held for 4 - 6 h to obtain flaky α-aluminum oxide.

[0016] By adopting the above technical solution, the present application uses amorphous alumina mixed and ball-milled with AlF3 and a solvent and undergoes high-temperature calcination treatment, which can form flaky α-aluminum oxide with good morphology and high thermal conductivity characteristics. Compared with preparation methods such as the molten salt method, the flaky α-aluminum oxide prepared by this preparation method has higher purity and performance, and at the same time has good dispersibility and is not easy to agglomerate in the material matrix.

[0017] Preferably, the α-aluminum oxide is modified by the following method: The coupling agent is dispersed in the solvent to obtain a modifier with a coupling agent content of 0.2 - 1.5 wt%. Then the modifier is mixed and stirred with α-aluminum oxide for 10 - 15 min, and then heated to 80 - 85 °C. It is kept stirred at this temperature for 30 - 35 min, and then cooled to room temperature. It is dried at a temperature of 115 - 125 °C for 4.5 - 5.5 h and then vacuumed down to room temperature to obtain the modified α-aluminum oxide; among them, the coupling agent includes one of octyltrimethoxysilane, dodecyltrimethoxysilane and hexadecyltrimethoxysilane; the solvent includes water and / or isopropanol; the mass-volume ratio of α-aluminum oxide to the modifier is 8 - 12 g / mL.

[0018] Preferably, the coupling agent is dodecyltrimethoxysilane, the solvent is water, and the content of the coupling agent in the modifier is 0.5 wt%.

[0019] By adopting the above technical solution, the present application modifies α-aluminum oxide with a coupling agent, which can significantly improve the surface properties of α-aluminum oxide. Specifically, the introduction of the coupling agent can enhance the interfacial bonding force between α-aluminum oxide and unsaturated polyester resin, thereby improving the overall mechanical properties of the material. At the same time, the modification treatment can also effectively reduce the agglomeration phenomenon of α-aluminum oxide in the material matrix, making its dispersion more uniform, and further improving the thermal conductivity and comprehensive mechanical properties of the material. And it has been experimentally proven that under the modification conditions where the coupling agent is dodecyltrimethoxysilane, the solvent is water, and the content of the coupling agent in the modifier is 0.5 wt%, the modification effect on α-aluminum oxide is better.

[0020] Preferably, the bulk molding compound further comprises 1.72 - 8.52 parts by weight of a polyurethane prepolymer.

[0021] Preferably, the polyurethane prepolymer is prepared by the following method: At a temperature of 60 - 65 °C, a diol and toluene diisocyanate with a molar ratio of 1:(1.7 - 2.3) are mixed, then the temperature is raised to 85 - 90 °C and reacted for 2.5 - 3.0 h. After that, the temperature is lowered to 50 - 55 °C and hydroxyethyl methacrylate is added. The addition amount of hydroxyethyl methacrylate is 12 - 13 wt% of the total amount of the diol and toluene diisocyanate. After the reaction is completely exothermic, the reaction temperature is maintained at 80 - 85 °C and continued to react for 1.5 - 2.0 h to obtain the polyurethane prepolymer.

[0022] By adopting the above technical solution, the present application uses a diol and toluene diisocyanate as reaction raw materials and adds a certain amount of hydroxyethyl methacrylate to prepare a polyurethane prepolymer. After adding this substance to the material, it can utilize the flexible chain segments contained therein to improve the fluidity and plasticity of the material, form a network structure to buffer tensile energy, and effectively reduce the phenomenon of local crack generation due to stress concentration. And the polyurethane prepolymer also has good dispersibility in the material matrix, and at the same time can form a tight interfacial layer with chopped glass fibers through double bonds and hydrogen bonds, improving the compatibility between the components in the material, thereby further improving the overall mechanical properties of the material.

[0023] In a second aspect, a preparation method of a high thermal conductivity unsaturated polyester bulk molding compound provided by the present application adopts the following technical solution: A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound includes the following steps: The unsaturated polyester resin, low shrinkage agent, initiator and lubricant are mixed and stirred at a rotation speed of 800 - 1000 rpm for 10 - 15 min, then α-aluminum oxide is added in several portions and kneaded and stirred for 6 - 10 min. After that, chopped glass fibers are added and stirring is continued at a rotation speed of 200 - 300 rpm for 5 - 8 min. After the chopped glass fibers are completely wetted, a high thermal conductivity unsaturated polyester bulk molding compound is obtained.

[0024] By adopting the above technical solution, in this application, the unsaturated polyester resin, low shrinkage agent, initiator and lubricant are mixed and stirred at a high rotation speed to ensure that each component can be fully and evenly mixed, thereby improving the overall performance of the material. And adding α-aluminum oxide in several portions for kneading and stirring can effectively reduce the possibility of filler agglomeration, improve the dispersion of the filler in the material matrix, and further improve the thermal conductivity and mechanical properties of the material. Finally, adding chopped glass fibers and stirring at a lower rotation speed can ensure that the chopped glass fibers are fully wetted by the resin matrix, enhancing the mechanical strength and heat resistance of the material. In addition, the preparation method of this application is simple and efficient, suitable for large-scale industrial production, and can prepare an unsaturated polyester bulk molding compound with high thermal conductivity, meeting the requirements of high-power LED heat dissipation and other high-temperature application scenarios.

[0025] In the third aspect, this application provides an application of a high thermal conductivity unsaturated polyester bulk molding compound in an LED inlay lamp panel and a housing or bracket of a heating electrical appliance.

[0026] By adopting the above technical solution, due to the use of α-aluminum oxide as a filler, the high thermal conductivity unsaturated polyester bulk molding compound of this application significantly improves the thermal conductivity of the material and can effectively meet the heat dissipation requirements of high-power LEDs. At the same time, the combination of unsaturated polyester resin and chopped glass fibers endows the material with excellent mechanical properties and heat resistance, making it show good structural stability and durability in the application of LED inlay lamp panels and housings or brackets of heating electrical appliances. In addition, the material also has excellent electrical properties and chemical corrosion resistance, further broadening its application scope in complex working environments.

[0027] In summary, this application has the following beneficial technical effects: 1. The unsaturated polyester bulk molding compound of this application significantly improves its own thermal conductivity by using α-aluminum oxide as a filler, enabling it to meet the heat dissipation requirements of high-power LEDs, and at the same time having a low production cost and high stability; 2. The preparation method of this application has a simple process, is easy to operate, the raw materials are easily available, and the cost is low, and it is suitable for large-scale industrial production. Detailed implementation mode

[0028] The following further elaborates on this application in combination with examples.

[0029] Material source The unsaturated polyester resin of this application is purchased from Jinling Resins Co., Ltd., and the grade is H856-902.

[0030] Since there is no significant difference in the effects of using polystyrene, polymethyl methacrylate, and styrene-butadiene-styrene block copolymer as low shrinkage agents, in the specific implementation mode of this application, polystyrene is taken as an example for illustration; the polystyrene of this application is purchased from Shanghai Suzhimei High Polymer Co., Ltd., and the grade is HI650.

[0031] Since the tert-butyl peroxybenzoate (TBPB) / benzoyl peroxide (BPO) initiation system is a commonly used initiation system in the art, in the specific implementation mode of this application, the weight ratio of the two is taken as 1:1 for illustration; the tert-butyl peroxybenzoate of this application is purchased from Wanqing Chemical Technology Co., Ltd., and the grade is TRIGONOX 279; the benzoyl peroxide of this application is purchased from Wanqing Chemical Technology Co., Ltd.

[0032] The spherical α-aluminum oxide of this application is purchased from Hangzhou Jiuli Biological Materials Co., Ltd.

[0033] The chopped glass fiber of this application is purchased from Tai'an Hongtong New Materials Co., Ltd., with a specification of 3.0 - 4.5 mm and a diameter of 13 μm.

[0034] The amorphous alumina of this application is purchased from Shandong Jinyufeng New Materials Co., Ltd., with a boiling point of 2980 °C and a melting point of 2054 °C.

[0035] The AlF3 of this application is purchased from Wuhan Kamik Technology Co., Ltd.

[0036] The polyester diol of this application is purchased from Beijing Baiyuan Chemical Co., Ltd., with a grade of XC-488 and Mn = 500.

[0037] The toluene diisocyanate of this application is purchased from Nanjing Top Environmental Protection Technology Co., Ltd., and the grade is TDI-80.

[0038] The hydroxyethyl methacrylate of this application is purchased from Shandong Chuangying Chemical Co., Ltd.

[0039] The octyltrimethoxysilane of this application is purchased from Shandong Bosheng Chemical Co., Ltd., with a CAS number of 3069-40-7.

[0040] The cetyltrimethoxysilane of this application is purchased from Shandong Aite Chemical Co., Ltd., with a CAS number of 16415-12-6.

[0041] The dodecyltrimethoxysilane of this application is purchased from Shandong Yuanjin New Materials Co., Ltd., with a CAS number of 3069-21-4.

[0042] Preparation Example 1.1 Flaky α-aluminum oxide was prepared by the following method: 10 kg of amorphous aluminum oxide, 0.2 kg of AlF3 and 1 kg of anhydrous isopropanol were mixed and ball-milled for 4 h, and then vacuum-dried at 115 °C to remove anhydrous isopropanol to obtain amorphous aluminum oxide powder. After that, the amorphous aluminum oxide powder was calcined at 1150 °C for 3.5 h and then held at a constant temperature for 4 h to obtain flaky α-aluminum oxide.

[0043] Preparation Example 1.2 Flaky α-aluminum oxide was prepared by the following method: 10 kg of amorphous aluminum oxide, 0.4 kg of AlF3 and 1 kg of anhydrous isopropanol were mixed and ball-milled for 6 h, and then vacuum-dried at 125 °C to remove anhydrous isopropanol to obtain amorphous aluminum oxide powder. After that, the amorphous aluminum oxide powder was calcined at 1250 °C for 2.5 h and then held at a constant temperature for 6 h to obtain flaky α-aluminum oxide.

[0044] Preparation Example 1.3 The difference from Preparation Example 1.2 is that flaky α-aluminum oxide was prepared by the molten salt method. Specifically, 10 kg of aluminum hydroxide was mixed with 5 kg of molten salt (a composite salt of Na2SO4-K2SO4 with a mass ratio of 1:1), ultrasonic-dispersed with deionized water and then dried. Then, 0.4 kg of AlF3 was added and thoroughly ground. After ensuring uniform mixing, it was calcined at 1200 °C for 3 h to obtain flaky α-aluminum oxide, and then washed and dried to finally obtain the product.

[0045] Preparation Example 1.4 The difference from Preparation Example 1.2 is that AlF3 was not added, and the rest was the same as Preparation Example 1.2.

[0046] Preparation Example 2.1 The polyurethane prepolymer was prepared by the following method: At 60 °C, polyester diol and toluene diisocyanate with a molar ratio of 1:1.7 were mixed, and then the temperature was raised to 85 °C and reacted for 3.0 h. After that, the temperature was lowered to 50 °C and hydroxyethyl methacrylate was added. The addition amount of hydroxyethyl methacrylate was 12 wt% of the total amount of polyester diol and toluene diisocyanate. After the reaction was completely exothermic, the reaction temperature was maintained at 80 °C and continued to react for 2.0 h to obtain the polyurethane prepolymer.

[0047] Preparation Example 2.2 The polyurethane prepolymer was prepared by the following method: At a temperature of 65 °C, polyester diol and toluene diisocyanate with a molar ratio of 1:2.3 were mixed, then the temperature was raised to 90 °C and reacted for 2.5 h. After that, the temperature was lowered to 55 °C and hydroxyethyl methacrylate was added. The addition amount of hydroxyethyl methacrylate was 13 wt% of the total amount of polyester diol and toluene diisocyanate. After the reaction was completely exothermic, the reaction temperature was maintained at 85 °C and continued to react for 1.5 h to obtain a polyurethane prepolymer.

[0048] Example 1.1 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, comprising the following steps: 2.5 kg of unsaturated polyester resin, 0.7 kg of polystyrene, 0.05 kg of initiator (0.025 kg of tert-butyl perbenzoate, 0.025 kg of benzoyl peroxide) and 0.3 kg of zinc stearate were mixed and stirred at a speed of 800 rpm for 15 min, then 4 kg of spherical α-aluminum oxide (particle size of 5 μm) was added in 3 portions, and kneaded and stirred for 6 min. After that, 2.5 kg of chopped glass fiber was added and continued to stir at a speed of 200 rpm for 8 min. After the chopped glass fiber was completely wetted, a highly thermally conductive unsaturated polyester bulk molding compound was obtained.

[0049] Example 1.2 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, comprising the following steps: 3.5 kg of unsaturated polyester resin, 0.5 kg of polystyrene, 0.15 kg of initiator (0.075 kg of tert-butyl perbenzoate, 0.075 kg of benzoyl peroxide) and 0.1 kg of zinc stearate were mixed and stirred at a speed of 1000 rpm for 10 min, then 7 kg of flaky α-aluminum oxide (particle size of 5 μm) was added in 3 portions, and kneaded and stirred for 10 min. After that, 1.5 kg of chopped glass fiber was added and continued to stir at a speed of 300 rpm for 5 min. After the chopped glass fiber was completely wetted, a highly thermally conductive unsaturated polyester bulk molding compound was obtained.

[0050] Example 2.1 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Example 1.2 in that: 7 kg of α-aluminum oxide includes spherical α-aluminum oxide and flaky α-aluminum oxide with a weight ratio of 1.5:1. The spherical α-aluminum oxide is specifically 4.2 kg, and the flaky α-aluminum oxide is specifically 2.8 kg; the particle size of the spherical α-aluminum oxide is 5 μm; the flaky α-aluminum oxide is the flaky α-aluminum oxide prepared in Preparation Example 1.1.

[0051] Example 2.2 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide includes spherical α-aluminum oxide and flaky α-aluminum oxide with a weight ratio of 2.5:1. Specifically, the spherical α-aluminum oxide is 5 kg and the flaky α-aluminum oxide is 2 kg; the particle size of the spherical α-aluminum oxide is 5 μm; the flaky α-aluminum oxide is the flaky α-aluminum oxide prepared in Preparation Example 1.2.

[0052] Example 2.3 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide includes spherical α-aluminum oxide and flaky α-aluminum oxide with a weight ratio of 1:1. Specifically, the spherical α-aluminum oxide is 3.5 kg and the flaky α-aluminum oxide is 3.5 kg, and the rest are the same as those in Example 1.2.

[0053] Example 2.4 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide includes spherical α-aluminum oxide and flaky α-aluminum oxide with a weight ratio of 3:1. Specifically, the spherical α-aluminum oxide is 5.25 kg and the flaky α-aluminum oxide is 1.75 kg, and the rest are the same as those in Example 1.2.

[0054] Example 3.1 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 2.2 in that: the spherical α-aluminum oxide includes spherical α-aluminum oxide with a particle size of 0.7 μm, spherical α-aluminum oxide with a particle size of 5 μm and spherical α-aluminum oxide with a particle size of 70 μm with a weight ratio of 11:26:62, and the rest are the same as those in Example 1.2.

[0055] Example 3.2 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 2.2 in that: the spherical α-aluminum oxide includes spherical α-aluminum oxide with a particle size of 0.7 μm, spherical α-aluminum oxide with a particle size of 5 μm and spherical α-aluminum oxide with a particle size of 70 μm with a weight ratio of 12:25:63, and the rest are the same as those in Example 1.2.

[0056] Example 4.1 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 2.2 in that: the flaky α-aluminum oxide prepared in Preparation Example 1.2 is replaced with the flaky α-aluminum oxide prepared in Preparation Example 1.3, and the rest are the same as those in Example 2.2.

[0057] Example 4.2 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Example 2.2 in that the flaky α-aluminum oxide prepared in Preparation Example 1.2 is replaced with the flaky α-aluminum oxide prepared in Preparation Example 1.4, and the rest is the same as in Example 2.2.

[0058] Example 5.1 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Example 1.2 in that 7 kg of α-aluminum oxide is subjected to a modification treatment, and the rest is the same as in Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse octyltrimethoxysilane in isopropanol to obtain a modifier with an octyltrimethoxysilane content of 0.2 wt%, and then mix 0.875 L of the modifier with 7 kg of α-aluminum oxide and stir for 10 min, then heat up to 80 °C, keep stirring at this temperature for 35 min, then cool to room temperature, dry at a temperature of 115 °C for 5.5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0059] Example 5.2 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Example 1.2 in that 7 kg of α-aluminum oxide is subjected to a modification treatment, and the rest is the same as in Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse cetyltrimethoxysilane in a mixed solvent of isopropanol and water (the volume ratio of isopropanol to water is 9:1) to obtain a modifier with a cetyltrimethoxysilane content of 1.5 wt%, and then mix 0.583 L of the modifier with 7 kg of α-aluminum oxide and stir for 15 min, then heat up to 85 °C, keep stirring at this temperature for 30 min, then cool to room temperature, dry at a temperature of 125 °C for 4.5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0060] Example 5.3 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Example 1.2 in that 7 kg of α-aluminum oxide is subjected to a modification treatment, and the rest is the same as in Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse dodecyltrimethoxysilane in water to obtain a modifier with a dodecyltrimethoxysilane content of 0.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at a temperature of 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0061] Example 5.4 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Examples 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as in Examples 1.2; the specific operation of the modification treatment of α-aluminum oxide is to disperse octyltrimethoxysilane in water to obtain a modifier with an octyltrimethoxysilane content of 0.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0062] Example 5.5 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Examples 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as in Examples 1.2; the specific operation of the modification treatment of α-aluminum oxide is to disperse cetyltrimethoxysilane in water to obtain a modifier with a cetyltrimethoxysilane content of 0.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0063] Example 5.6 A preparation method of a highly thermally conductive unsaturated polyester bulk molding compound, which is different from Examples 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as in Examples 1.2; the specific operation of the modification treatment of α-aluminum oxide is to disperse dodecyltrimethoxysilane in isopropanol to obtain a modifier with a dodecyltrimethoxysilane content of 0.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0064] Example 5.7 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as that of Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse dodecyltrimethoxysilane in a mixed solvent of isopropanol and water (the volume ratio of isopropanol to water is 9:1) to obtain a modifier with a dodecyltrimethoxysilane content of 0.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0065] Example 5.8 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as that of Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse dodecyltrimethoxysilane in water to obtain a modifier with a cetyltrimethoxysilane content of 0.2 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0066] Example 5.9 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: 7 kg of α-aluminum oxide is subjected to modification treatment, and the rest is the same as that of Example 1.2; the specific operation of the α-aluminum oxide modification treatment is to disperse dodecyltrimethoxysilane in water to obtain a modifier with a cetyltrimethoxysilane content of 1.5 wt%, and then mix 0.7 L of the modifier with 7 kg of α-aluminum oxide and stir for 12 min, then heat up to 83 °C, keep stirring at this temperature for 33 min, then cool to room temperature, dry at 120 °C for 5 h, and then vacuum down to room temperature to obtain the modified α-aluminum oxide.

[0067] Example 6.1 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: after the chopped glass fibers are completely wetted, they are also fully stirred evenly with 172 g of the polyurethane prepolymer prepared in Preparation Example 2.1 in a kneader and naturally cured at room temperature in a closed environment for 3 d, and the rest is the same as that of Example 1.2.

[0068] Example 6.2 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: after the chopped glass fibers are completely wetted, they are also fully stirred and mixed evenly with 852 g of the polyurethane prepolymer prepared in Preparation Example 2.2 in a kneader, and naturally cured at room temperature for 5 d in a closed environment, and the rest is the same as that of Example 1.2.

[0069] Example 6.3 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: after the chopped glass fibers are completely wetted, they are also fully stirred and mixed evenly with 50 g of the polyurethane prepolymer prepared in Preparation Example 2.2 in a kneader, and naturally cured at room temperature for 5 d in a closed environment, and the rest is the same as that of Example 1.2.

[0070] Example 6.4 A preparation method of a high thermal conductivity unsaturated polyester bulk molding compound, which is different from that of Example 1.2 in that: after the chopped glass fibers are completely wetted, they are also fully stirred and mixed evenly with 1 kg of the polyurethane prepolymer prepared in Preparation Example 2.2 in a kneader, and naturally cured at room temperature for 5 d in a closed environment, and the rest is the same as that of Example 1.2.

[0071] Comparative Example 1 It is different from Example 1.2 in that: α-aluminum oxide is replaced by calcium carbonate, and the rest is the same as that of Example 1.2.

[0072] Performance testing 1. Thermal conductivity: The unsaturated polyester bulk molding compounds prepared in the above examples and preparation examples are made into tablets by means of compression molding, and the tablets are cut into flat blocks with a size of 20×20 mm and a thickness of 0.15 mm, and then the thermal conductivity is detected by referring to the method in ASTM D-5470.

[0073] 2. Mechanical properties: Referring to the method in GB / T 23641-2018, the bending strength and impact strength of the specimens prepared by compression molding in the above examples and comparative examples are detected. The specimen specifications are 300 mm×300 mm×4 mm. When testing the bending strength, the loading speed is 10 mm / min, the impact strength is the simply supported beam impact strength, and the non-notch through-thickness impact test (i.e., the specimen stands upright) is carried out, and the pendulum impact energy is 4 J.

[0074] The above performance test results are shown in Table 1.

[0075] Table 1 Performance test result table Data analysis: As can be seen from Table 1, the thermal conductivity of the high thermal conductivity unsaturated polyester bulk molding compound prepared in Examples 1.1 - 1.2 of this application is 1.812 - 1.875 W / m·k, the flexural strength is 91.24 - 91.85 MPa, and the impact strength is 26.31 - 26.64 MPa. The experimental results show that the bulk molding compound prepared in this application has high thermal conductivity and mechanical properties.

[0076] The difference between Examples 2.1 - 2.4 and Example 1.2 is that spherical α-aluminum oxide and flaky α-aluminum oxide with two different morphologies are used in combination. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Examples 2.1 - 2.4 are all higher than those of Example 1.2. The experimental results show that using these two α-aluminum oxides with different morphologies in combination can further improve the thermal conductivity and mechanical properties of the material. Among them, the thermal conductivity, flexural strength, and impact strength of Examples 2.1 - 2.2 are slightly higher than those of Examples 2.3 - 2.4. The experimental results show that when the ratio between these two α-aluminum oxides with different morphologies is further optimized, the thermal conductivity and mechanical properties of the material can be further improved.

[0077] The difference between Examples 3.1 - 3.2 and Example 2.2 is that a multi-scale particle size mixture is used in the spherical α-aluminum oxide. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Examples 3.1 - 3.2 are all higher than those of Example 2.2. The experimental results show that compared with using a single particle size, using a multi-scale particle size mixture can further improve the thermal conductivity and mechanical properties of the material.

[0078] The difference between Examples 4.1 - 4.2 and Example 2.2 is that the flaky α-aluminum oxide is prepared by the traditional molten salt method or without adding AlF3. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Examples 4.1 - 4.2 are lower than those of Example 2.2. The experimental results show that the properties of the flaky α-aluminum oxide prepared by the molten salt method or without adding AlF3 are slightly worse, and its dispersibility in the material matrix is slightly worse, thus reducing the thermal conductivity and mechanical properties of the material.

[0079] The difference between Examples 5.1 - 5.9 and Example 1.2 is that the α-aluminum oxide is modified. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Examples 5.1 - 5.9 are all higher than those of Example 1.2. The experimental results show that further modifying the α-aluminum oxide can significantly improve the dispersibility of the α-aluminum oxide in the material matrix, thereby further improving the thermal conductivity and mechanical properties of the material.

[0080] Among them, by comparing the data between Examples 5.1 - 5.9, it can be found that the thermal conductivity and mechanical properties of the material prepared in Example 5.3 are the best. This indicates that when the types of coupling agents, solvents, and the content of coupling agents in Example 5.3 are further optimized, the thermal conductivity and mechanical properties of the material can be further improved.

[0081] The difference between Examples 6.1 - 6.4 and Example 1.2 is that a certain amount of polyurethane prepolymer is further added to the material. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Examples 6.1 - 6.4 are all higher than those of Example 1.2. The experimental results show that the addition of polyurethane prepolymer can improve the compatibility of components in the material, thereby improving the thermal conductivity of the material to a certain extent and significantly improving the mechanical properties of the material. Among them, the thermal conductivity, flexural strength, and impact strength of Examples 6.1 - 6.2 are slightly higher than those of Examples 6.3 - 6.4, which indicates that when the addition amount of polyurethane prepolymer is further optimized, the thermal conductivity and mechanical properties of the material can be further improved.

[0082] The difference between Comparative Example 1 and Example 1.2 is that traditional calcium carbonate is used as the filler. As can be seen from Table 1, the thermal conductivity, flexural strength, and impact strength of Comparative Example 1 are all lower than those of Example 1.2. The experimental results show that replacing calcium carbonate with α-aluminum oxide can improve the thermal conductivity and mechanical properties of the material.

[0083] The examples of this specific implementation manner are all preferred examples of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A high thermal conductivity unsaturated polyester bulk molding compound, characterized in that: The raw materials used include the following components in parts by weight: Unsaturated polyester resin 25-35 parts; 15-25 parts of chopped glass fiber; 40-70 parts of α-alumina; 5-7 parts of low shrinkage agent; Initiator 0.5-1.5 parts; Lubricant 1-3 parts by weight.

2. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 1, characterized in that: The α-alumina includes spherical α-alumina and flaky α-alumina in a weight ratio of (1.5-2.5):

1.

3. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 2, characterized in that: The spherical α-alumina includes spherical α-alumina with a particle size of 0.7 μm, spherical α-alumina with a particle size of 5 μm, and spherical α-alumina with a particle size of 70 μm in a weight ratio of (11-12):(25-26):(62-63).

4. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 2, characterized in that: The flaky α-alumina is prepared by the following method: Amorphous alumina, AlF3 and anhydrous isopropanol in a weight ratio of 10:(0.2-0.4):1 are mixed and ball-milled for 4-6 hours, and then vacuum-dried at a temperature of 115-125°C to remove the anhydrous isopropanol to obtain amorphous alumina powder. Thereafter, the amorphous alumina powder is calcined at a temperature of 1150-1250°C for 2.5-3.5 hours, and then kept warm for 4-6 hours to obtain flaky α-alumina.

5. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 1, characterized in that: The α-alumina is modified by the following method: A coupling agent is dispersed in a solvent to obtain a modifier with a coupling agent content of 0.2-1.5wt%, and then the modifier and α-alumina are mixed and stirred for 10-15min, and then the temperature is raised to 80-85°C, and the mixture is kept warm and stirred at this temperature for 30-35min, and then cooled to room temperature, and dried at a temperature of 115-125°C for 4.5-5.5h, and then vacuum cooled to room temperature to obtain modified α-alumina; wherein the coupling agent includes one of octyltrimethoxysilane, dodecyltrimethoxysilane and hexadecyltrimethoxysilane; the solvent includes water and / or isopropanol; and the mass volume ratio of α-alumina and the modifier is 8-12g / mL.

6. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 5, characterized in that: The coupling agent is dodecyltrimethoxysilane, the solvent is water, and the content of the coupling agent in the modifier is 0.5wt%.

7. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 1, characterized in that: The bulk molding compound further comprises 1.72-8.52 parts by weight of a polyurethane prepolymer.

8. The high thermal conductivity unsaturated polyester bulk molding compound according to claim 7, characterized in that: The polyurethane prepolymer is prepared by the following method: At a temperature of 60-65°C, diol and toluene diisocyanate in a molar ratio of 1:(1.7-2.3) are mixed, then the temperature is raised to 85-90°C for reaction for 2.5-3.0 hours, then the temperature is lowered to 50-55°C and hydroxyethyl methacrylate is added, the amount of hydroxyethyl methacrylate added is 12-13wt% of the total amount of diol and toluene diisocyanate, and after the reaction is completely exothermic, the reaction temperature is maintained at 80-85°C and the reaction is continued for 1.5-2.0 hours to obtain a polyurethane prepolymer.

9. A method for preparing the high thermal conductive unsaturated polyester bulk molding compound according to claim 1, characterized in that: The following steps are involved: The unsaturated polyester resin, low shrinkage agent, initiator and lubricant are mixed and stirred at a speed of 800-1000 rpm for 10-15 minutes, and then α-alumina is added in multiple times, kneaded and stirred for 6-10 minutes, and then short glass fibers are added, and stirring is continued at a speed of 200-300 rpm for 5-8 minutes to completely wet the short glass fibers to obtain a high thermal conductivity unsaturated polyester bulk molding compound.

10. Use of the high thermal conductivity unsaturated polyester bulk molding compound according to claim 1 in LED recessed light panels and heating electrical appliance housings or brackets.

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