High-strength dry unsaturated polyester thermoset material and preparation method and application thereof

Abstract

The application relates to the technical field of unsaturated resin materials, in particular to a high-strength dry-type unsaturated polyester thermosetting material and a preparation method and application thereof. The high-strength dry-type unsaturated polyester thermosetting material comprises the following components in parts by weight: solid unsaturated polyester 25-35 parts, inorganic filler 50-70 parts, release agent 1-3 parts, peroxide curing agent 0.8-1.2 parts, silane coupling agent 0.5-1 part, reinforcing agent 20-30 parts and surface pretreatment carbon black 0.5-1.5 parts. The high-strength dry-type unsaturated polyester thermosetting material prepared by the application has excellent mechanical properties and low molding shrinkage, and has excellent heat resistance when applied to injection molding or bonding fixation of a motor rotor.

Description

Technical Field

[0001] This invention relates to the field of unsaturated resin materials technology, specifically to a high-strength dry unsaturated polyester thermosetting material, its preparation method, and its application. Background Technology

[0002] Unsaturated polyester molding materials possess advantages such as high tracking index, good arc resistance, excellent electrical properties, halogen-free flame retardancy, good heat resistance, low water absorption, good dimensional stability, and room temperature storage. However, traditional unsaturated polyester resins have some inherent defects: 1. High brittleness and poor toughness, easily cracking upon impact. 2. High shrinkage rate: leading to poor dimensional accuracy and surface ripples, affecting appearance. 3. Weak interfacial bonding with fillers / fibers, affecting the full realization of the overall mechanical properties of the composite material. These defects severely restrict the application expansion of unsaturated resins in the demanding application scenario of motor rotor injection molding filling / fixing bonding.

[0003] In the prior art, patent CN110467791B discloses an unsaturated resin-based composite material and its preparation method and application. The raw materials of the unsaturated resin-based composite material include unsaturated resin, thermally conductive filler, and modifier. The unsaturated resin is unsaturated polyester resin and / or vinyl ester resin, the thermally conductive filler is alumina and silicon carbide, and the modifier is polyethylene and / or polytetrafluoroethylene. The weight ratio of the modifier to the thermally conductive filler is 15~25:400~650, and the weight ratio of the thermally conductive filler to the unsaturated resin is 400~650:120~150. The thermal conductivity of the unsaturated resin-based composite material in this invention is >2 W / m·K, which is more than twice that of traditional unsaturated polyester resin and / or vinyl ester resin-based composite materials. Furthermore, the unsaturated resin (unsaturated polyester resin and / or vinyl ester resin) exhibits good compatibility with the thermally conductive filler, avoiding the problem of excessive hardness caused by the addition of thermally conductive filler. The material's Barcol hardness is ≤70, reducing wear on the mold and contact parts. However, non-polar polyethylene and polytetrafluoroethylene, used as modifiers, have poor compatibility with polar unsaturated polyester / vinyl ester resins, resulting in deteriorated mechanical properties and increased molding shrinkage of the unsaturated resin-based composite material.

[0004] Patent CN115028979B discloses a method for preparing unsaturated resin sheet molding compound, comprising the following steps: mixing unsaturated polyester resin and a low-shrinkage agent uniformly to obtain a resin matrix; adding an initiator, thickener, low-shrinkage agent, and inorganic filler to the resin matrix, mixing uniformly, and then adding polyester fibers, a release agent, reinforcing fibers, and inorganic filler, and kneading in a kneader to obtain the unsaturated resin sheet molding compound; wherein the polyester fibers need to be pretreated before being added to the resin matrix, and the pretreatment includes the following steps: subjecting the obtained raw polyester fibers to drying and degradation treatments in sequence to obtain partially degraded polyester fibers; the degradation treatment includes at least one of enzymatic degradation treatment and chemical degradation treatment. However, polyester fibers that have undergone enzymatic or chemical degradation will generate a large number of active groups such as carboxyl termini and hydroxyl groups on their surface or inside. These acidic or hydrophilic groups will preferentially react with the alkaline thickener in the system, consuming the thickener, which may lead to excessively rapid thickening, affecting the processing fluidity of the unsaturated resin sheet molding compound, and causing a decrease in its mechanical properties.

[0005] Therefore, there is an urgent need in the market for a high-strength dry unsaturated polyester thermosetting material with excellent mechanical properties and low molding shrinkage. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to obtain a high-strength dry unsaturated polyester thermosetting material with excellent mechanical properties and low molding shrinkage.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a high-strength dry-type unsaturated polyester thermosetting material, comprising the following components by weight: 25-35 parts unsaturated polyester, 50-70 parts inorganic filler, 1-3 parts release agent, 0.8-1.2 parts peroxide curing agent, 0.5-1 part silane coupling agent, 20-30 parts reinforcing agent, and 0.5-1.5 parts surface pretreatment carbon black; wherein the unsaturated polyester is a composition of crystalline unsaturated polyester resin and non-crystalline unsaturated polyester resin.

[0008] Preferably, the peroxide curing agent is tert-butyl peroxide.

[0009] To address the aforementioned issues, this application presents a high-strength dry-type unsaturated polyester thermosetting material with excellent mechanical properties and low molding shrinkage, obtained by mixing unsaturated polyester, inorganic fillers, release agents, peroxide-based curing agents, silane coupling agents, reinforcing agents, and surface-pretreated carbon black. By adding a silane coupling agent, this application enhances the interfacial bonding between the resin, inorganic fillers, and reinforcing agents, thereby improving the mechanical and electrical properties of the unsaturated resin material.

[0010] In some embodiments, the mass ratio of the crystalline unsaturated polyester resin to the non-crystalline unsaturated polyester resin is 1:(3.2-3.6).

[0011] In some embodiments, the inorganic filler is one or more of aluminum hydroxide, calcium carbonate, and silica powder.

[0012] Preferably, the inorganic filler is a composition of aluminum hydroxide and silica powder, with a mass ratio of 1:(0.5-1.5).

[0013] Preferably, the aluminum hydroxide has a particle size of 5-15 μm, and the silicon micropowder has a particle size of 90-100 μm.

[0014] This application can effectively reduce molding shrinkage by adding a high content of inorganic fillers with different particle sizes.

[0015] In some embodiments, the release agent is zinc stearate and / or calcium stearate.

[0016] In some embodiments, the silane coupling agent is one or more of KH-570, A-151, A-172, A-186, and Nanda-41.

[0017] Preferably, the silane coupling agent is A-186.

[0018] In some embodiments, the reinforcing agent is a composition of chopped glass fibers and glass fiber powder.

[0019] Preferably, the mass ratio of the chopped glass fiber to the glass fiber powder is 1:(0.3-0.6).

[0020] In some embodiments, the chopped glass fibers have a diameter of 10-12 μm and a length of 3-6 mm.

[0021] In some embodiments, the glass fiber powder has an average particle size of 800-1250 mesh.

[0022] This application reduces the brittleness of the material and increases its strength by adding glass fibers of different lengths in an interlaced distribution.

[0023] In some embodiments, the preparation method of the surface pretreated carbon black includes the following steps: adding carbon black to tetrahydrofuran, ultrasonically treating for 50-70 min, adding p-chloromethylstyrene, purging with nitrogen for 20-40 min, adding azobisisobutyronitrile under nitrogen protection, heating to 65-75℃ and reacting for 12-24 h, cooling to room temperature, adding to methanol, stirring for 30-60 s, centrifuging and collecting the precipitate, washing with methanol and tetrahydrofuran alternately 3-5 times, and drying to obtain the surface pretreated carbon black.

[0024] Carbon black often contains active groups such as carboxyl groups, phenolic hydroxyl groups, and lactone groups on its surface. Direct addition to unsaturated resin systems may preferentially consume peroxide-based curing agents, affecting the curing of the unsaturated resin and reducing its mechanical and heat resistance properties, while also increasing its molding shrinkage. To address these issues, this application employs an in-situ polymerization method to coat poly(p-chloromethylstyrene) onto the surface of carbon black to obtain surface-pretreated carbon black. On one hand, poly(p-chloromethylstyrene) has good compatibility with unsaturated resins and forms a barrier between carbon black particles, effectively preventing secondary agglomeration and improving the dispersibility of the surface-pretreated carbon black in unsaturated polyesters. On the other hand, the barrier formed between the active groups on the carbon black surface and the curing agent shields the free radical trapping sites on the carbon black surface, reducing their negative impact on polymerization kinetics and thus improving the mechanical and heat resistance properties of the unsaturated resin material. Furthermore, the benzyl chloride group on the shell of poly(p-chloromethylstyrene) can react with the silane coupling agent, enabling the surface-pretreated carbon black to exhibit long-term dispersion stability in the resin matrix. In addition, the poly(p-chloromethylstyrene) segments are thermoplastic polymers, which can effectively control the micropore size distribution, which is beneficial to improving the mechanical properties of unsaturated polyester materials and reducing their molding shrinkage.

[0025] In some embodiments, the mass ratio of the carbon black to p-chloromethylstyrene is 1:(1-5).

[0026] A second aspect of this invention provides a method for preparing a high-strength dry-type unsaturated polyester thermosetting material, comprising the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent, release agent, etc. into a mixer and stir at room temperature for 5-10 minutes. Add surface pretreatment carbon black and peroxide curing agent and stir at room temperature for 5-10 minutes. Then add reinforcing agent and stir at low speed at room temperature for 1-2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed through a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die head. Granulation and cooling yield granular unsaturated polyester material. S3. The granular unsaturated polyester material obtained in S2 is directly packaged to obtain granular dry unsaturated polyester thermosetting material; or the granular unsaturated polyester material obtained in S2 is put into a patting machine, automatically weighed and pressed into patties to obtain patty dry unsaturated polyester thermosetting material.

[0027] Preferably, the extruder barrel is divided into several independent temperature control sections along the material conveying direction. Each temperature control section is equipped with a heating device and a cooling water passage to achieve segmented temperature control. After the material enters the extruder through the feeding system, the material temperature gradually increases under the conveying and shearing mixing action of the screw, eventually reaching 80-100℃. The extrusion die temperature is controlled at 90-100℃. The extruded material is granulated by a hot pelletizing device, and the length of the obtained particles is controlled by adjusting the rotation speed of the pelletizing blades.

[0028] Preferably, the pressing and molding process uses a 60-ton hydraulic press, and the mold has a multi-cavity structure; an automatic weighing system is provided to accurately weigh and add a predetermined weight of material to each cavity; during the pressing and molding process, the hydraulic press automatically matches and adjusts the pressing pressure according to the preset pressing height, thereby obtaining a cake with high consistency.

[0029] The unsaturated polyester material in this application, based on its physical morphology, can be prepared as either a cake or granules. The cake form facilitates preheating and weighing, making it suitable for automated metering and feeding of molding compounds; the granules, on the other hand, possess good flowability and feeding uniformity, making them more suitable for the screw conveyor system of injection molding machines. By selecting different forms, this material can flexibly adapt to the needs of various rotor injection molding coating processes, ensuring a tight coating of the magnets during high-speed injection molding.

[0030] The third aspect of this invention provides an application of a high-strength dry unsaturated polyester thermosetting material in the injection molding or bonding fixation of an electric motor rotor.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention obtains a high-strength dry unsaturated polyester thermosetting material with excellent mechanical properties and low molding shrinkage by mixing unsaturated polyester material, release agent, curing agent, silane coupling agent, reinforcing agent and carbon black.

[0032] (2) This invention reduces the brittleness of the material and increases its strength by adding glass fibers of different lengths to form an interlaced distribution. By adding a high content of inorganic fillers of different particle sizes, the molding shrinkage rate can be effectively reduced. This invention also adds silane coupling agent to make the resin and inorganic fillers and reinforcing agents have better interfacial bonding force, so that the unsaturated resin material can achieve better mechanical properties.

[0033] (3) The surface-pretreated carbon black obtained by coating poly(p-chloromethylstyrene) on the surface of carbon black by in-situ polymerization has good dispersibility in unsaturated polyester. The poly(p-chloromethylstyrene) shell can play a barrier role, reducing the influence of the surface active groups of carbon black on the curing reaction of unsaturated resin materials. Furthermore, the benzyl chloride group on the poly(p-chloromethylstyrene) shell can react with the silane coupling agent, so that the surface-pretreated carbon black exhibits long-term dispersion stability in the resin matrix, which is beneficial to improving the mechanical properties of unsaturated polyester materials and reducing their molding shrinkage. Detailed Implementation

[0034] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0035] In the following examples and comparative examples, except for the surface pretreatment carbon black, all other compounds and related reagents used were commercially available. The crystalline unsaturated polyester resin was a terephthalic crystalline unsaturated polyester, and the non-crystalline unsaturated polyester resin was an isophthalic non-crystalline unsaturated resin. The average particle size of aluminum hydroxide was 10 μm. The average particle size of silica powder was 95 μm. The diameter of the chopped glass fiber was 11 μm and the length was 3 mm. The average particle size of the glass fiber powder was 1000 mesh. The carbon black was of type N-550.

[0036] Preparation Example 1 The preparation method of surface pretreated carbon black-1 includes the following steps: 1g of carbon black is added to 10ml of tetrahydrofuran, and ultrasonic treatment is carried out for 60min at a power of 200W and a frequency of 30kHz. 2.5g of p-chloromethylstyrene is added, and nitrogen gas is introduced for 30min. Under nitrogen protection, 0.01g of azobisisobutyronitrile is added, and the temperature is raised to 70℃ and reacted for 18h. After cooling to room temperature, it is added to 20ml of anhydrous methanol, stirred for 45s, and centrifuged at 9000rpm for 12min. The precipitate is collected, washed 4 times alternately with anhydrous methanol and anhydrous tetrahydrofuran, and dried at 60℃ to obtain surface pretreated carbon black-1.

[0037] Preparation Example 2 The preparation method of surface pretreated carbon black-2 is the same as that in preparation example 1, except that the amount of chloromethylstyrene added is 6g.

[0038] Example 1 A high-strength dry unsaturated polyester thermosetting material, by weight, comprises the following components: 30 parts unsaturated polyester, 60 parts inorganic filler, 2 parts zinc stearate, 1 part tert-butyl peroxide, 0.7 parts A-186 silane coupling agent, 25 parts reinforcing agent, and 1 part surface pretreatment carbon black-1.

[0039] The unsaturated polyester is a composition of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin, with a mass ratio of 1:3.4.

[0040] The inorganic filler is a composition of aluminum hydroxide and silica powder in a mass ratio of 1:1.

[0041] The reinforcing agent is a composition of chopped glass fibers and glass fiber powder in a mass ratio of 1:0.45.

[0042] The preparation method of the high-strength dry unsaturated polyester thermosetting material in this embodiment includes the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent, mold release agent, etc. to a mixer and stir at room temperature for 7 minutes. Add surface pretreatment carbon black and peroxide curing agent and stir at room temperature for 7 minutes. Then add reinforcing agent and stir at low speed at room temperature for 2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die. Granulation and cooling yield granular unsaturated polyester material. The material temperature is 90°C and the extrusion die temperature is 95°C. S3. The granular unsaturated polyester material obtained in S2 is directly packaged to obtain granular dry unsaturated polyester thermosetting material; or the granular unsaturated polyester material obtained in S2 is put into a patting machine, automatically weighed and pressed into patties to obtain patty dry unsaturated polyester thermosetting material.

[0043] Example 2 A high-strength dry unsaturated polyester thermosetting material, by weight, comprises the following components: 25 parts unsaturated polyester, 50 parts inorganic filler, 1 part zinc stearate, 0.8 parts tert-butyl peroxide, 0.5 parts A-186 silane coupling agent, 20 parts reinforcing agent, and 0.5 parts surface pretreatment carbon black-1.

[0044] The unsaturated polyester is a composition of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin, with a mass ratio of 1:3.2.

[0045] The inorganic filler is a composition of aluminum hydroxide and silica powder in a mass ratio of 1:0.5.

[0046] The reinforcing agent is a composition of chopped glass fibers and glass fiber powder in a mass ratio of 1:0.3.

[0047] The preparation method of the high-strength dry unsaturated polyester thermosetting material in this embodiment includes the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent, mold release agent, etc. to a mixer and stir at room temperature for 5 minutes. Add surface pretreatment carbon black and peroxide curing agent and stir at room temperature for 10 minutes. Then add reinforcing agent and stir at room temperature at low speed for 2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die. Granulation and cooling yield granular unsaturated polyester material. The material temperature is 80°C and the extrusion die temperature is 100°C. S3. The granular unsaturated polyester material obtained in S2 is directly packaged to obtain granular dry unsaturated polyester thermosetting material; or the granular unsaturated polyester material obtained in S2 is put into a patting machine, automatically weighed and pressed into patties to obtain patty dry unsaturated polyester thermosetting material.

[0048] Example 3 A high-strength dry unsaturated polyester thermosetting material, by weight, comprises the following components: 35 parts unsaturated polyester, 70 parts inorganic filler, 3 parts zinc stearate, 1.2 parts tert-butyl peroxide, 1 part A-186 silane coupling agent, 30 parts reinforcing agent, and 1.5 parts surface pretreatment carbon black-1.

[0049] The unsaturated polyester is a composition of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin, with a mass ratio of 1:3.6.

[0050] The inorganic filler is a composition of aluminum hydroxide and silica powder in a mass ratio of 1:1.5.

[0051] The reinforcing agent is a composition of chopped glass fibers and glass fiber powder in a mass ratio of 1:0.6.

[0052] The preparation method of the high-strength dry unsaturated polyester thermosetting material in this embodiment includes the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent, release agent, etc. into a mixer and stir at room temperature for 10 minutes. Add surface pretreatment carbon black and peroxide curing agent and stir at room temperature for 5 minutes. Then add reinforcing agent and stir at room temperature at low speed for 1 minute to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die. Granulation and cooling yield granular unsaturated polyester material. The material temperature is 100℃ and the extrusion die temperature is 90℃. S3. The granular unsaturated polyester material obtained in S2 is directly packaged to obtain granular dry unsaturated polyester thermosetting material; or the granular unsaturated polyester material obtained in S2 is put into a patting machine, automatically weighed and pressed into patties to obtain patty dry unsaturated polyester thermosetting material.

[0053] Example 4 A high-strength dry unsaturated polyester thermosetting material and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the surface pretreated carbon black-1 is replaced with an equal amount of surface pretreated carbon black-2.

[0054] Example 5 A high-strength dry-type unsaturated polyester thermosetting material and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the mass ratio of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin is 1:4.

[0055] Example 6 A high-strength dry unsaturated polyester thermosetting material and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the inorganic filler is aluminum hydroxide.

[0056] Example 7 A high-strength dry unsaturated polyester thermosetting material and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that the reinforcing agent is chopped glass fiber.

[0057] Comparative Example 1 An unsaturated polyester material and its preparation method are described. The specific implementation method is the same as in Example 1, except that the surface pretreatment carbon black-1 is replaced with an equal amount of carbon black.

[0058] Comparative Example 2 An unsaturated polyester material and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the unsaturated polyester is an isophthalic non-crystalline unsaturated polyester resin.

[0059] Performance testing The unsaturated polyester materials obtained in the above embodiments and comparative examples were tested, and the test methods are shown in Table 1: Table 1 The test results are shown in Table 2: Table 2 As shown in Table 1, the high-strength dry-curing unsaturated polyester thermosetting materials in Examples 1-3 of this invention exhibit low molding shrinkage and excellent mechanical properties. A comparison between Example 4 and Example 1 reveals that changing the ratio of carbon black to p-chloromethylstyrene may cause homopolymerization of monomers not grafted onto the carbon black surface, forming free p-chloromethylstyrene micro-regions that hinder the diffusion of unsaturated polyester molecular chains, thus affecting the curing effect and deteriorating the mechanical properties and increasing the shrinkage of the unsaturated polyester material. A comparison between Example 5 and Example 1 shows that changing the ratio of the two unsaturated polyester resins affects the mechanical properties of the unsaturated polyester material. The mechanical properties and shrinkage rate of the unsaturated polyester material deteriorate when the inorganic filler is only aluminum hydroxide. The mechanical properties and shrinkage rate of the unsaturated polyester material deteriorate when the reinforcing agent is only chopped glass fiber. The mechanical properties and shrinkage rate of the unsaturated polyester material deteriorate when the reinforcing agent is only chopped glass fiber. The mechanical properties and shrinkage rate of the unsaturated polyester material are poor when no surface pretreatment carbon black is used. The mechanical properties and shrinkage rate of the unsaturated polyester material are poor when only isophthalic amorphous unsaturated polyester resin is used as the resin matrix.

[0060] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-strength dry-type unsaturated polyester thermosetting material, characterized in that, The product comprises, by weight, the following components: 25-35 parts unsaturated polyester, 50-70 parts inorganic filler, 1-3 parts release agent, 0.8-1.2 parts peroxide curing agent, 0.5-1 part silane coupling agent, 20-30 parts reinforcing agent, and 0.5-1.5 parts surface pretreatment carbon black; wherein the unsaturated polyester is a composition of crystalline unsaturated polyester resin and non-crystalline unsaturated polyester resin.

2. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The mass ratio of the crystalline unsaturated polyester resin to the non-crystalline unsaturated polyester resin is 1:(3.2-3.6).

3. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The inorganic filler is one or more of aluminum hydroxide, calcium carbonate, aluminum oxide, and silica powder.

4. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The release agent is zinc stearate and / or calcium stearate.

5. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The silane coupling agent is one or more of the following: KH-570, A-151, A-172, A-186, and Nanda-41.

6. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The reinforcing agent is a composition of chopped glass fibers and glass fiber powder.

7. The high-strength dry-type unsaturated polyester thermosetting material according to claim 1, characterized in that, The method for preparing the surface-pretreated carbon black includes the following steps: adding carbon black to tetrahydrofuran, ultrasonically treating for 50-70 min, adding p-chloromethylstyrene, purging with nitrogen for 20-40 min, adding azobisisobutyronitrile under nitrogen protection, heating to 65-75℃ and reacting for 12-24 h, cooling to room temperature, adding to methanol, stirring for 30-60 s, centrifuging and collecting the precipitate, washing with methanol and tetrahydrofuran alternately 3-5 times, and drying to obtain the surface-pretreated carbon black.

8. The high-strength dry-type unsaturated polyester thermosetting material according to claim 7, characterized in that, The mass ratio of carbon black to p-chloromethylstyrene is 1:(1-5).

9. A method for preparing a high-strength dry-type unsaturated polyester thermosetting material according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent, release agent, etc. into a mixer and stir at room temperature for 5-10 minutes. Add surface pretreatment carbon black and peroxide curing agent and stir at room temperature for 5-10 minutes. Then add reinforcing agent and stir at low speed at room temperature for 1-2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed through a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die head. Granulation and cooling yield granular unsaturated polyester material. S3. The granular unsaturated polyester material obtained in S2 is directly packaged to obtain granular dry unsaturated polyester thermosetting material; or the granular unsaturated polyester material obtained in S2 is put into a patting machine, automatically weighed and pressed into patties to obtain patty dry unsaturated polyester thermosetting material.

10. The application of a high-strength dry-processed unsaturated polyester thermosetting material according to any one of claims 1-8 or a high-strength dry-processed unsaturated polyester thermosetting material obtained by the preparation method according to claim 9, characterized in that, Used for injection molding or bonding fixation of motor rotors.

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