A novel mirror-polished PVA sponge grinding wheel and a preparation method thereof

Abstract

The present application relates to a kind of novel mirror polishing PVA sponge grinding wheel, it is characterized in that, the grinding wheel is mainly made of the following mass percentage of raw materials: polyvinyl alcohol 10-50%, phenolic resin liquid 1-10%, abrasive 10-70%, isocyanate curing agent 1-30%, catalyst 0.1-1%, foaming agent 0.5-2%, bubble uniformizing agent 0.5-2%, and the balance is water.Processing workpiece using the grinding wheel, on the one hand, the grinding wheel guarantees that it has strong wear resistance and grinding force, and based on the unique pore structure of its system, the grinding wheel can quickly remove grinding heat when grinding workpiece, does not occur jam, realizes stable, long time continuous grinding;On the other hand, based on the characteristics of the binder in its system has buffering property, the blade tip of abrasive produces corresponding vibration when the grinding wheel is running and contacting with workpiece, so that the abrasive cuts into uniformization, does not produce relatively deep scratch on the grinding surface, finally obtains uniform, mirror surface of processing surface.

Description

Technical Field

[0001] This invention relates to a precision polishing abrasive, particularly a PVA grinding wheel, specifically a novel mirror-polishing PVA sponge grinding wheel, which features a green and environmentally friendly manufacturing process, a controllable reaction process, excellent heat dissipation performance during processing, and good durability. Background Technology

[0002] Polishing is a processing technique that utilizes the high-speed rotation of a polishing tool and the mechanical micro-cutting and chemical action of the polishing medium to modify the surface of mechanical parts. It can improve surface roughness, eliminate defects such as scratches and micro-cracks; reduce the surface friction coefficient and improve wear resistance; improve the surface stress distribution; improve part precision and ensure assembly processability; and increase the surface gloss and service life of parts and the entire machine. Depending on the processing technology, polishing techniques can be mainly divided into mechanical polishing, chemical polishing, electrochemical polishing, and composite polishing. Among these, PVA grinding wheels, due to their unique structural characteristics and excellent processing properties, have gradually replaced traditional polishing wheels and become the most commonly used polishing abrasive in mechanical polishing.

[0003] PVA (polyvinyl alcohol) grinding wheels, also known as PVA sponge grinding wheels, are resin abrasives made by casting a hard elastomer structure formed by the acetalization of polyvinyl alcohol as the abrasive carrier. PVA grinding wheels have high porosity, low grinding heat, and are less likely to burn the workpiece; they also have good elasticity, strong polishing ability, and are less prone to clogging. They are often used to replace traditional polishing wheels and polishing belts to improve polishing efficiency.

[0004] The traditional manufacturing process of PVA grinding wheels mainly includes six steps: resin preparation, mixing, casting, aldehyde curing, washing, and drying. First, a polyvinyl alcohol aqueous solution is prepared; then hydrochloric acid, abrasives, and other additives are added sequentially, and the slurry system is uniformly dispersed through mechanical stirring. Under the action of hydrochloric acid, a formaldehyde or butyraldehyde aqueous solution is added, causing a condensation reaction between the polyvinyl alcohol and the formaldehyde or butyraldehyde. Once the system reaches a certain viscosity, it is immediately poured into a mold cavity. The mold filled with the slurry is placed in a curing oven for deep aldehyde curing. After the aldehyde curing reaction is complete, the mold is removed, washed, and dried. Finally, after machining and inspection, the finished product is obtained. Currently, PVA grinding wheels are widely used in polishing various metals and non-metals. However, it should be pointed out that there are some shortcomings in the preparation and processing of traditional PVA grinding wheels, such as: 1) The raw materials such as hydrochloric acid, formaldehyde and butyraldehyde are highly toxic, which cannot guarantee the safety of production and use; 2) The space for acetalization reaction is limited by the barrier effect of abrasive, which leads to the inability to achieve the desired degree of acetalization in the production of PVA grinding wheels. As a result, the adhesion between abrasive and abrasive carrier is not strong, making it easy for abrasive to fall off during the processing of PVA grinding wheels, resulting in poor grinding wheel durability; 3) The acetalization reaction has poor stability and is not easy to control, making it difficult to achieve stable mass production of PVA grinding wheels. Summary of the Invention

[0005] This invention addresses the technical problems existing in the preparation and processing of traditional PVA grinding wheels by providing a novel mirror-polishing PVA sponge grinding wheel. When using this grinding wheel to process workpieces, on the one hand, the wheel ensures strong wear resistance and grinding force, and based on its unique porous structure, it can quickly dissipate grinding heat during grinding, preventing clogging and achieving stable, long-term continuous grinding. On the other hand, based on the buffering properties of the binder within the system, the abrasive tip vibrates accordingly during wheel operation and contact with the workpiece, resulting in uniform abrasive penetration and preventing deep scratches on the grinding surface, ultimately yielding a uniform, mirror-like machined surface.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned novel mirror-polished PVA sponge grinding wheel.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A novel mirror-polished PVA sponge grinding wheel is mainly made of the following raw materials in the following mass percentages: 10-50% polyvinyl alcohol, 1-10% phenolic resin liquid, 10-70% abrasive, 1-30% isocyanate curing agent, 0.1-1% catalyst, 0.5-2% foaming agent, 0.5-2% foam leveling agent, and the balance being water.

[0009] Specifically, the polyvinyl alcohol is selected from water-soluble polyvinyl alcohols with a degree of polymerization of 500-2000 and a degree of hydrolysis of 87-89%. For example, the polyvinyl alcohol can be one or more of the following models provided by Guangzhou Haina Chemical Co., Ltd: 0988, 1088, 1288, 1588, 1788, and 2088.

[0010] Furthermore, the phenolic resin solution is selected as an aqueous phenolic resin solution, with a solid content of 70-85% and a free phenol content of 13-18%. For example, the phenolic resin solution can be one or more of the models RA-L5102 and RA-L5107 provided by Tongcheng New Materials Group Co., Ltd.

[0011] Specifically, the abrasive can be one or more common abrasives such as silicon carbide, cerium oxide, and white corundum, with a particle size range of 40#-1000#.

[0012] Specifically, the isocyanate curing agent is a small molecule water-based isocyanate curing agent; the catalyst can be an organic bismuth catalyst whose main component is bismuth isooctanoate or bismuth neodecanoate; the foaming agent can be cyclopentane or pentane, etc.; and the foam leveling agent is a rigid foam stabilizer. Furthermore, the isocyanate curing agent is one or more of the following water-based isocyanate curing agents provided by Shanghai Yuanhe Chemical Co., Ltd: Bayhydrol UH 2593-1, Bayhydur Ultra 3100 CN, Bayhydur Ultra 305, Bayhydur Ultra 304, Bayhydur 2655, Bayhydur Ultra 2487-1, and Bayhydur 2547; the catalyst can be an organic bismuth catalyst of model DY-20 provided by Shanghai Deyin Chemical Co., Ltd.; the foaming agent is provided by Shanghai Aladdin Biochemical Technology Co., Ltd.; and the foam leveling agent is one or more of the following models: H-3903, H-3609, and H-3908 provided by Zhongshan Dongjun Chemical Co., Ltd.

[0013] This invention also provides a method for preparing the above-mentioned novel mirror-polished PVA sponge grinding wheel, which includes the following steps:

[0014] S1. Preparation of polyvinyl alcohol aqueous solution: Pour polyvinyl alcohol into water, heat and stir to dissolve, and obtain polyvinyl alcohol aqueous solution; when heating, place it in a water bath with a temperature range of 50-90℃ and use a stirrer to continuously vibrate and stir. The stirrer speed can be set to 300-400 rpm, and the stirring time can be 60-90 min; the mass percentage range of polyvinyl alcohol aqueous solution is approximately 20-35 wt%.

[0015] S2. Preparation of polyvinyl alcohol / phenolic resin mixture: Remove the polyvinyl alcohol aqueous solution prepared in S1 from the water bath environment, cool it to room temperature, add phenolic resin solution, and continuously vibrate and stir with a stirrer to obtain polyvinyl alcohol / phenolic resin mixture; the room temperature range is 25±5℃; the stirrer speed can be set to 300-400rpm.

[0016] S3. Preparation of polyvinyl alcohol / phenolic resin / abrasive mixed slurry: Under the continuous stirring action of the agitator, abrasive is added to the mixed liquid system prepared in S2, and the abrasive is continuously stirred to disperse the abrasive evenly, thus obtaining polyvinyl alcohol / phenolic resin / abrasive mixed slurry; the agitator speed can be initially set to 300-400 rpm, and can be increased to 500-700 rpm after the abrasive is added.

[0017] S4. Gelation treatment: Place the mixed slurry prepared in S3 into a water bath at a temperature of 70-90℃, add the catalyst, foaming agent and foam leveling agent respectively, stir continuously to make the system uniformly mixed, then add the isocyanate curing agent to carry out the gelation reaction, and the reaction time is 1-3h.

[0018] S5. Casting and molding: After the reaction is complete, the mixture obtained in S4 is poured into the mold;

[0019] S6. Post-processing: Place the mold in a hot oven for curing. After curing, remove the mold and take out the grinding wheel blank. After washing, drying and conventional machining, the PVA sponge grinding wheel is obtained.

[0020] Specifically, in step S5, to prevent sticking, the mold surface can be pre-treated with a release agent; the release agent can be a fluorinated release agent, such as a fluorinated high-efficiency release agent of model DS-608 provided by Dongguan Dongrui Electronic Technology Co., Ltd.

[0021] Furthermore, in step S6, the temperature range of the hot oven is 60-120℃, and the curing time is 10-12h.

[0022] The present invention also provides a novel mirror-polished PVA sponge grinding wheel prepared by the above preparation method.

[0023] This invention relates to a novel mirror-polishing PVA sponge grinding wheel, manufactured using a casting molding process with a special synthetic resin-bonded abrasive. The special synthetic resin binder is produced through a low-temperature chemical reaction between polyvinyl alcohol, phenolic resin, and an isocyanate curing agent within the system. Polyvinyl alcohol, as the main structural component of this synthetic resin binder, possesses excellent soft elasticity, giving the PVA grinding wheel unique cushioning properties. Phenolic resin provides isocyanate reaction sites, enhancing the adhesion and holding power of the abrasive. The isocyanate curing agent, as a small-molecule curing agent, can chemically react with polyvinyl alcohol and phenolic resin to form a three-dimensional cross-linked network structure, thereby endowing the PVA grinding wheel with excellent wear resistance and grinding force. The abrasive consists of common abrasives such as silicon carbide and cerium oxide, used for polishing workpieces.

[0024] This invention addresses the technical problems existing in the preparation and processing of traditional PVA grinding wheels, and provides a novel PVA grinding wheel made by replacing formaldehyde or butyraldehyde aqueous solution with water-based phenolic resin liquid, and by adding a small molecule isocyanate curing agent to make it gel with polyvinyl alcohol / phenolic resin / abrasive mixture slurry. The formulation system used to prepare PVA grinding wheels ensures safe production and use, meeting environmental protection requirements. By introducing isocyanate curing agents into the polyhydroxy system to form a highly reactive system, and adding phenolic resin liquid to further provide isocyanate reaction sites, the reaction degree between isocyanate and polyvinyl alcohol / phenolic resin / abrasive mixture in the system can be effectively promoted, improving the adhesion strength between abrasive and abrasive carrier, enhancing abrasive holding force, and increasing grinding wheel durability. At the same time, the viscosity of the gelation reaction between isocyanate curing agents and polyvinyl alcohol / phenolic resin / abrasive mixture is moderate, and by adjusting the isocyanate ratio and the content of additives such as catalysts and foaming agents, the reaction process can be controlled and the grinding wheel performance can be adjusted, ultimately achieving the goal of stable mass production of PVA grinding wheels. When using this grinding wheel to process workpieces, on the one hand, the grinding wheel ensures strong wear resistance and grinding force, and based on its unique porous structure, it can quickly dissipate grinding heat during grinding without clogging, achieving stable and long-term continuous grinding; on the other hand, based on the buffering characteristics of the binder in its system, the abrasive tip vibrates accordingly when the grinding wheel is running and in contact with the workpiece, making the abrasive cut uniform and preventing deep scratches on the grinding surface, ultimately resulting in a uniform, mirror-like machined surface.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) The PVA sponge grinding wheel of this invention replaces the acetalization process of polyvinyl alcohol with formaldehyde or butyraldehyde aqueous solution in traditional PVA grinding wheels with a gelation process of small molecule isocyanate curing agent with polyvinyl alcohol / phenolic resin / abrasive mixture in existing PVA grinding wheels. On the one hand, the raw materials are non-toxic and pollution-free, and the production process is green and environmentally friendly; on the other hand, the viscosity of the gelation reaction is moderate, and by adjusting the isocyanate ratio and the content of additives such as catalysts and foaming agents, the reaction process can be controlled and the grinding wheel performance can be adjusted, ultimately achieving stable mass production of PVA grinding wheels.

[0027] 2) The PVA sponge grinding wheel of the present invention forms a highly reactive system by introducing isocyanate curing agent into the multi-hydroxy system and adding phenolic resin liquid to further provide isocyanate reaction sites, which can effectively promote the reaction degree of isocyanate with polyvinyl alcohol / phenolic resin / abrasive mixture, improve the bonding strength between abrasive and abrasive carrier, enhance abrasive holding force, and improve grinding wheel durability.

[0028] 3) The PVA sponge grinding wheel of the present invention forms a cross-linking binder system by reacting polyvinyl alcohol, phenolic resin and isocyanate curing agent in the system, which makes the grinding wheel have strong wear resistance and grinding force; at the same time, based on the unique pore structure in its system, the grinding wheel can quickly dissipate grinding heat when grinding the workpiece, without clogging or burning the workpiece, and achieve stable and long-term continuous processing.

[0029] 4) The PVA sponge grinding wheel of this invention has elastic and cushioning properties in its internal binder. This allows the abrasive tip to vibrate during wheel operation and contact with the workpiece, resulting in uniform abrasive penetration and preventing deep scratches on the grinding surface. Ultimately, this leads to a brighter grinding surface and a higher surface roughness grade. Furthermore, based on these structural features, the grinding wheel is more easily matched to the workpiece's grinding surface shape during processing, ensuring good processing results even on curved workpieces and producing a uniform, mirror-like surface.

[0030] 5) The PVA sponge grinding wheel of the present invention has low raw material and manufacturing equipment costs, and the product preparation process is simple and stable, making it easy to mass-produce and promote. Attached Figure Description

[0031] Figure 1 This is a simplified process flow diagram of the present invention;

[0032] Figure 2 This is a SEM image (1500x magnification) of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in Example 1 of the present invention.

[0033] Figure 3This is a SEM image (400x magnification) of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in Example 1 of the present invention.

[0034] Figure 4 This is a SEM image (400x magnification) of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in Example 2 of the present invention.

[0035] Figure 5 SEM schematic diagram (1500x magnification) of a cross section of a conventional commercially available PVA sponge grinding wheel (Comparative Example 1).

[0036] Figure 6 SEM schematic diagram (400x magnification) of a cross section of a conventional commercially available PVA sponge grinding wheel (Comparative Example 1). Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] A novel mirror-polished PVA sponge abrasive wheel is made from the following raw materials in the indicated weight percentages: 14.5% polyvinyl alcohol (model 1788), 3% aqueous phenolic resin liquid (model RA-L5102), 20% abrasive (1000# silicon carbide), 17.5% aqueous isocyanate curing agent (model Bayhydrol UH 2593-1), 0.2% organic bismuth catalyst (model DY-20), 1.5% foaming agent cyclopentane, 1% foam stabilizer (rigid foam stabilizer, model H-3903), and 42.3% distilled water.

[0040] Specifically, the fabrication of the novel mirror-polishing PVA sponge grinding wheel with dimensions D150*H25*T25 and a grit size of 1000# in this embodiment includes the following steps (see process flow). Figure 1 ):

[0041] S1. Preparation of polyvinyl alcohol aqueous solution: Weigh 112.05g of polyvinyl alcohol and pour it into 326.86g of distilled water. Under the conditions of water bath temperature of 85℃ and stirrer speed of 400rpm, continuously vibrate and stir for 75min to prepare a polyvinyl alcohol aqueous solution with a mass percentage of 25.53%.

[0042] S2. Preparation of polyvinyl alcohol / phenolic resin mixture: The polyvinyl alcohol aqueous solution prepared in S1 was removed from the water bath and cooled to room temperature. Then, 23.18g of aqueous phenolic resin solution was added, and the stirrer was continuously vibrated and stirred at a speed of 400rpm to prepare the polyvinyl alcohol / phenolic resin mixture.

[0043] S3. Preparation of polyvinyl alcohol / phenolic resin / abrasive mixed slurry: Under the continuous stirring action of the stirrer at a speed of 400 rpm, 154.55 g of silicon carbide abrasive was slowly added to the mixed liquid system prepared in S2. Then the stirrer speed was increased to 600 rpm and the stirring was continued to vibrate and stir to prepare polyvinyl alcohol / phenolic resin / abrasive mixed slurry.

[0044] S4. Gelation treatment: The mixed slurry prepared in S3 was placed in a water bath at 75°C. Then, 1.55g of catalyst, 11.59g of foaming agent and 7.73g of foam leveling agent were added. The mixture was stirred continuously at 600rpm to make the system uniform. Then, 135.23g of water-based isocyanate curing agent was added, and the gelation reaction was carried out for 1.5h.

[0045] S5. Casting and Molding: After the components in the S4 system have reacted for 1.5 hours, the mixture is poured into a mold that has been sprayed with a fluorinated high-efficiency release agent (model DS-608). It should be noted that to ensure sufficient reaction and uniform foaming among the components of the grinding wheel within the mold, the material should be added to 90% of the mold volume. Specifically, in this embodiment, a total of 695.46g of slurry is added.

[0046] S6. Post-treatment: Place the mold filled with slurry in S5 into an 85℃ oven for 10 hours for curing. After curing, remove the mold and take out the grinding wheel blank. After washing, drying and machining, the PVA sponge grinding wheel is finally obtained.

[0047] Figure 2 A 1500x magnified SEM image of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in this embodiment is provided. Figure 2 As can be seen, the special synthetic resin binder that serves as the abrasive carrier in this PVA grinding wheel system has a structure containing a large number of small independent pores and is based on polyvinyl alcohol. This provides a structural basis for the excellent buffering properties of the PVA grinding wheel, which in turn causes the abrasive tip to vibrate accordingly when the grinding wheel is running and in contact with the workpiece. This makes the abrasive cut uniform and prevents deep scratches on the grinding surface, ultimately resulting in a uniform, mirror-like machined surface.

[0048] Figure 3 A 400x magnified SEM image of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in this embodiment is provided. Figure 3As can be seen, the PVA grinding wheel system contains a large number of voids and continuous large-sized holes, which provides a structural basis for the PVA grinding wheel to quickly dissipate grinding heat and prevent clogging when grinding workpieces, thus achieving stable and long-term continuous grinding.

[0049] Example 2

[0050] A novel mirror-polished PVA sponge abrasive wheel is made from the following raw materials in the following weight percentages: 10% polyvinyl alcohol (model 2088), 5% aqueous phenolic resin liquid (model RA-L5107), 25% abrasive (a combination of 320# silicon carbide and 320# white corundum abrasive, each accounting for 50% by weight), 20% aqueous isocyanate curing agent (model Bayhydur Ultra 3100 CN), 0.3% organic bismuth catalyst (model DY-20), 0.5% foaming agent n-pentane, 0.5% foam stabilizer (rigid foam stabilizer, model H-3908), and 38.7% distilled water.

[0051] Specifically, the fabrication of the novel mirror-polishing PVA sponge grinding wheel with dimensions D210*H65*T35 and a grit size of 320# in this embodiment includes the following steps:

[0052] S1. Preparation of polyvinyl alcohol aqueous solution: Weigh 241.02g of polyvinyl alcohol and pour it into 932.76g of distilled water. Under the conditions of water bath temperature of 90℃ and stirrer speed of 400rpm, continuously vibrate and stir for 90min to prepare a polyvinyl alcohol aqueous solution with a mass percentage of 20.53%.

[0053] S2. Preparation of polyvinyl alcohol / phenolic resin mixture: The polyvinyl alcohol aqueous solution prepared in S1 was removed from the water bath and cooled to room temperature. Then, 120.51g of aqueous phenolic resin solution was added, and the stirrer was continuously vibrated and stirred at a speed of 400rpm to prepare the polyvinyl alcohol / phenolic resin mixture.

[0054] S3. Preparation of polyvinyl alcohol / phenolic resin / abrasive mixed slurry: Under the continuous stirring action of the stirrer at a speed of 400 rpm, 602.56 g of the prepared combined abrasive was slowly added to the mixed liquid system prepared in S2. Then the stirrer speed was increased to 600 rpm and the stirring was continued to vibrate and stir to prepare polyvinyl alcohol / phenolic resin / abrasive mixed slurry.

[0055] S4. Gelation treatment: The mixed slurry prepared in S3 was placed in a water bath at 85°C. Then, 7.23g of catalyst, 12.05g of foaming agent and 12.05g of foam leveling agent were added. The mixture was stirred continuously at 600rpm to make the system uniform. Then, 482.05g of water-based isocyanate curing agent was added and the gelation reaction was carried out for 2 hours.

[0056] S5. Casting and Molding: After the components in the S4 system have reacted for 2 hours, the mixture is poured into a mold that has been sprayed with a fluorinated high-efficiency release agent. It should be noted that to ensure sufficient reaction and uniform foaming among the components of the grinding wheel within the mold, the material should be added to 90% of the mold volume. Specifically, in this embodiment, a total of 2169.22g of slurry is added.

[0057] S6. Post-treatment: Place the mold filled with slurry in S5 into a 95℃ oven for 12 hours for curing. After curing, remove the mold and take out the grinding wheel blank. After washing, drying and machining, the PVA sponge grinding wheel is finally obtained.

[0058] Figure 4 A SEM image of the cross-section of the novel mirror-polished PVA sponge grinding wheel prepared in this embodiment is provided. Figure 4 As can be seen, compared to the grinding wheel prepared in Example 1, the grinding wheel system prepared in Example 2 contains a small amount of voids and a small amount of continuous large-sized pores. This is because, compared to the grinding wheel system in Example 1, the grinding wheel formulation in Example 2 has an increased proportion of isocyanate, an increased amount of catalyst, and a decreased amount of foaming agent and foam leveling agent, thereby increasing the degree of gelation reaction and decreasing the foaming ratio.

[0059] Comparative Example 1

[0060] The comparative example grinding wheel is a commercially available PVA sponge grinding wheel. Specifically, the commercially available PVA sponge grinding wheel is a 150mm outer diameter, 1000# grit PVA grinding wheel provided by Dongguan Qisheng Abrasive Materials Co., Ltd.

[0061] Figure 5 A SEM image of the cross-section of a commercially available PVA grinding wheel (comparative example 1) magnified 1500 times is provided. Figure 5 As can be seen from this, the resin binder, which acts as the abrasive carrier in the commercially available PVA grinding wheel system, has a dense overall structure and contains a small number of large-sized independent pores.

[0062] Figure 6 A SEM image of the cross-section of a commercially available PVA grinding wheel (comparative example 1) magnified 400 times is provided. Figure 6 It can be seen that the overall structure of the commercially available PVA grinding wheel system is uniformly connected, with a small number of gaps and a small number of small continuous holes.

[0063] The grinding wheels prepared in Examples 1 and 2, respectively, were compared with the grinding wheel of Comparative Example 1 on a precision horizontal spindle surface grinder of Hangzhou Machine Tool Factory to perform polishing tests on stainless steel materials. The physical properties, processing parameters and processing effects of each grinding wheel are shown in Table 1.

[0064] Table 1 Comparison of physical properties, processing parameters, and processing effects of grinding wheels in Examples 1, 2, and Comparative Example 1

[0065]

[0066] The data in Table 1 shows that:

[0067] 1) Compared to the PVA sponge grinding wheel prepared in Example 2 of this invention, the grinding wheel in Example 1 has a lower overall Shore hardness, a more porous internal structure, and a higher porosity. This is because we effectively controlled the degree of gelation reaction and foaming ratio within the system by adjusting the isocyanate ratio, the content of catalyst, foaming agent, and foam leveling agent in the grinding wheel formulation, thereby achieving regulation of the overall hardness, structure, and porosity of the grinding wheel.

[0068] 2) The PVA sponge grinding wheels prepared in Examples 1 and 2 of this invention exhibit no chip adhesion during processing, and the workpieces after processing have uniform textures and no burns. In contrast, the commercially available PVA sponge grinding wheel of Comparative Example 1 shows slight chip adhesion during processing, and the workpieces after processing exhibit slight burns. This is because, compared to the grinding wheel of Comparative Example 1, the grinding wheels of Examples 1 and 2 have a more porous overall structure and higher porosity. The numerous internal voids and continuous large-sized pores significantly increase the chip holding and removal space of the grinding wheel, resulting in the superior processing performance of the PVA sponge grinding wheel of this invention under the same processing conditions.

[0069] 3) Compared to the 150mm outer diameter and 1000# grit wheel of Comparative Example 1, the surface roughness Ra of the workpiece processed by the grinding wheel of Example 1 can reach 0.01-0.02μm, which is significantly better than the 0.04-0.05μm of the grinding wheel of Comparative Example 1. This is because, compared to the polyvinyl alcohol methyl acetal / butyral resin binder in the grinding wheel system of Comparative Example 1, the special synthetic resin binder prepared by low-temperature chemical reaction in the grinding wheel system of Example 1 has better elasticity and buffering properties, which makes the abrasive penetration more uniform, thereby obtaining a brighter grinding surface and a higher surface roughness level. At the same time, based on the unique physical properties of the grinding wheel of the present invention, the grinding wheel of the present invention is more likely to match the shape of the workpiece grinding surface during the processing, ensuring that the grinding wheel also has a good processing effect on curved workpieces, and can obtain a uniform, mirror-like processed surface.

[0070] 4) Compared to the grinding wheel of Comparative Example 1, the grinding wheels of Examples 1 and 2 of this invention have superior grinding wheel durability, with a lower dressing frequency (more than 63 dressings, superior to 37 dressings in Comparative Example 1) and a longer lifespan (more than 12,000 dressings, far superior to 7,500 dressings in Comparative Example 1). This is because the introduction of isocyanate curing agent into the grinding wheel system of this invention forms a highly reactive system with the polyhydroxy components, and the addition of phenolic resin liquid further provides isocyanate reaction sites, effectively promoting the reaction degree of isocyanate with polyvinyl alcohol / phenolic resin / abrasive mixture, improving the adhesion strength between abrasive and abrasive carrier, enhancing abrasive holding force, and making abrasive less prone to falling off, thereby improving grinding wheel durability.

[0071] In summary, the preparation method of the novel mirror-polished PVA sponge grinding wheel of this invention can ensure production and use safety and meet the requirements of environmental protection in production. By introducing an isocyanate curing agent into the polyhydroxy system to form a highly reactive system, and adding phenolic resin liquid to further provide isocyanate reaction sites, the degree of gelation reaction in the system can be effectively promoted, the adhesion strength between the abrasive and the abrasive carrier can be improved, the abrasive holding force can be enhanced, and the durability of the grinding wheel can be improved. At the same time, the viscosity of the gelation reaction in the grinding wheel system is moderate, and by adjusting the isocyanate ratio and the content of additives such as catalysts and foaming agents, the reaction process can be controlled, the performance of the grinding wheel can be adjusted, and ultimately the goal of stable mass production of PVA grinding wheels can be achieved.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel method for preparing a mirror-polished PVA sponge grinding wheel, characterized in that, Includes the following steps: S1. Preparation of polyvinyl alcohol aqueous solution: Pour polyvinyl alcohol into water, heat and stir to dissolve, and obtain polyvinyl alcohol aqueous solution; S2. Preparation of polyvinyl alcohol / phenolic resin mixture: After cooling the polyvinyl alcohol aqueous solution prepared in S1 to room temperature, add phenolic resin solution and continuously vibrate and stir to obtain polyvinyl alcohol / phenolic resin mixture. S3. Preparation of polyvinyl alcohol / phenolic resin / abrasive mixed slurry: Under the continuous stirring action of the agitator, abrasive is added to the mixed liquid system prepared in S2, and the abrasive is continuously stirred to disperse the abrasive evenly, thus obtaining polyvinyl alcohol / phenolic resin / abrasive mixed slurry. S4. Gelation treatment: Place the mixed slurry prepared in S3 into a water bath at a temperature of 70-90℃, add the catalyst, foaming agent and foam leveling agent respectively, stir continuously to make the system uniformly mixed, then add the isocyanate curing agent to carry out the gelation reaction, and the reaction time is 1-3h. S5. Casting and molding: After the reaction is complete, the mixture obtained in S4 is poured into the mold; S6. Post-processing: Place the mold in a hot oven for curing. After curing, remove the mold and take out the grinding wheel blank. After washing, drying and conventional machining, the desired result is obtained. The novel mirror-polishing PVA sponge abrasive wheel is mainly made of the following raw materials in the following weight percentages: 10-50% polyvinyl alcohol, 1-10% phenolic resin liquid, 10-70% abrasive, 1-30% isocyanate curing agent, 0.1-1% catalyst, 0.5-2% foaming agent, 0.5-2% foam leveling agent, and the balance being water. The isocyanate curing agent is an aqueous isocyanate curing agent; The catalyst is an organic bismuth catalyst whose main component is bismuth isooctanoate or bismuth neodecanoate, the foaming agent is cyclopentane or pentane, and the foam leveling agent is a rigid foam stabilizer.

2. The method for preparing the novel mirror-polished PVA sponge grinding wheel as described in claim 1, characterized in that, In step S5, to prevent sticking, the mold surface is pre-treated with a release agent; the release agent is a fluorinated release agent.

3. The method for preparing the novel mirror-polished PVA sponge grinding wheel as described in claim 1, characterized in that, In step S6, the temperature range of the hot oven is 60-120℃, and the curing time is 10-12h.

4. The method for preparing the novel mirror-polished PVA sponge grinding wheel as described in claim 1, characterized in that, The polyvinyl alcohol used is a water-soluble polyvinyl alcohol with a degree of polymerization of 500-2000 and a degree of hydrolysis of 87-89%.

5. The method for preparing the novel mirror-polished PVA sponge grinding wheel as described in claim 1, characterized in that, The phenolic resin solution is selected from water-based phenolic resin solutions, with a solid content of 70-85% and a free phenol content of 13-18%.

6. The method for preparing the novel mirror-polished PVA sponge grinding wheel as described in claim 1, characterized in that, The abrasive is one or more of silicon carbide, cerium oxide, and white corundum, with a particle size range of 40#-1000#.

7. A novel mirror-polished PVA sponge grinding wheel prepared by the preparation method described in any one of claims 1 to 6.

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