Phenolic resin for anti-attenuation resin grinding wheel and preparation method of phenolic resin

Abstract

The invention discloses phenolic resin for an anti-attenuation resin grinding wheel and a preparation method of the phenolic resin, and belongs to the technical field of grinding tool materials. According to the method, specific multi-substituted aromatic phenol monomers and aldehyde monomers are subjected to polycondensation under the accurate molar ratio, gradient temperature rise and end point control, deep vacuum devolatilization is conducted, and the anti-attenuation phenolic resin for the grinding wheel is obtained. The free phenol content is lower than 50 ppm, the hydroxymethyl content is lower than 0.8 wt%, the glass-transition temperature of the resin is higher than 140 DEG C, and the high-stability resin does not contain unsubstituted ortho-phenolic hydroxyl groups. The invention aims to solve the problem of performance degradation under high temperature and high humidity caused by easy oxidation of ortho-phenolic hydroxyl and residual free phenol and hydroxymethyl of the traditional phenolic resin, and can obviously improve the mechanical retention rate and long-acting attenuation resistance of the resin grinding wheel under severe working conditions.

Description

Technical Field

[0001] This invention belongs to the field of abrasive material technology, and relates to a phenolic resin for anti-attenuation resin grinding wheels and its preparation method. Background Technology

[0002] In modern precision manufacturing and high-end equipment processing systems, resin grinding wheels are indispensable grinding tools, and their performance stability is directly related to workpiece surface quality, dimensional accuracy, and production efficiency. With the surge in demand for processing high-hardness and high-brittle materials from strategic emerging industries such as aerospace, semiconductors, and new energy vehicles, resin grinding wheels face unprecedented challenges in harsh conditions such as high linear speeds, high loads, and continuous dry grinding. Phenolic resin, as the core binder of resin grinding wheels, not only plays a crucial role in bonding abrasive particles and transmitting cutting forces, but also maintains structural integrity at high-temperature friction interfaces, preventing a sharp drop in strength and performance degradation caused by thermo-oxidative aging, molecular chain breakage, or the precipitation of low-molecular-weight substances. Therefore, the intrinsic chemical stability, cross-linked network density, and chemical compatibility of phenolic resin with the abrasive interface have become fundamental factors determining the long-term service capability of resin grinding wheels.

[0003] Currently, technologies primarily improve performance through two approaches: one is by adding inorganic fillers to construct a physical barrier; the other is by using "modified phenolic resins" with unclear structures. For example, CN107336146B uses a composite of liquid and powdered resins with the addition of various fillers. While this can temporarily delay performance degradation, it does not solve the problem of chemical degradation of resin molecules at high temperatures. The residual free phenols and hydroxymethyl groups in traditional phenolic resins are easily oxidized and decomposed in a thermo-oxidative environment, leading to a loose network and micro-defects. This chemical degradation cannot be eradicated through physical filling. Another approach, CN108890542A, proposes using modified resins with low free phenol content, but does not disclose specific modification methods or synthesis process parameters. This technology mixes the resin into a complex filler system, making the role of the resin itself difficult to assess, and may cause reverse reactions during the high-temperature thermoforming stage, releasing free phenols again and affecting long-term stability.

[0004] With increasing demands for the reliability of resin grinding wheels, the nature of their performance degradation has shifted from apparent mechanical wear to the chemical degradation of the resin cross-linked network under the combined effects of heat, oxygen, and stress. In traditional phenolic resins, benzene rings are linked only by methylene groups, which, while providing some thermal stability, easily oxidize unsubstituted phenolic hydroxyl groups to quinone structures, causing color deepening and cross-linking breakage. Residual hydroxymethyl groups are also prone to hydrolysis in humid and hot environments, leading to network disintegration. This creates a fundamental contradiction: while increasing the cross-linking density can increase initial strength, without simultaneously improving the oxidation resistance and low polarity of the molecular chains, the highly cross-linked structure can actually accelerate crack formation due to stress concentration, resulting in a phenomenon of "high strength but low durability."

[0005] Existing methods relying on physical fillers or vague "modification" cannot eliminate the chemical defects of the resin itself, nor can they achieve precise control of free phenols, and they are even less able to guarantee the stability of the crosslinked network at high temperatures. Therefore, current technology suffers from a fundamental bottleneck—the performance improvement methods and the root causes of degradation are disconnected at the molecular level, resulting in anti-degradation effects that are short-term, conditionally dependent, and unrepeatable. Summary of the Invention

[0006] The purpose of this invention is to provide a phenolic resin for anti-degradation resin grinding wheels and its preparation method, so as to solve the problem of performance degradation of traditional phenolic resins under high temperature and high humidity due to easy oxidation of ortho-phenolic hydroxyl groups and residual free phenol and hydroxymethyl groups.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A phenolic resin for anti-attenuation resin grinding wheels, comprising:

[0009] (1) Polysubstituted aromatic phenolic monomer A, whose general structural formula is: ,in, It is a benzene ring or a naphthalene ring; for Alkyl, halogen, or nitro groups; for alkoxy or trifluoromethyl; m is 1 or 2; n is 0 or 1; and and They are not both hydrogen;

[0010] (2) Aldehyde monomer B is selected from at least one of formaldehyde, paraformaldehyde or trioxymethylene;

[0011] (3) Catalyst C is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate or hexamethylenetetramine;

[0012] (4) Solvent D is selected from at least one of deionized water, ethanol, isopropanol or butanol.

[0013] The molar ratio of the polysubstituted aromatic phenolic monomer A to the aldehyde monomer B is 1:1.05 to 1:1.35; the amount of catalyst C is 0.8% to 2.5% of the mass of the polysubstituted aromatic phenolic monomer A; and the amount of solvent D is 15% to 35% of the total mass of the reaction system.

[0014] The polysubstituted aromatic phenolic monomer A is selected from... , , , , , , or At least one of them.

[0015] The phenolic resin has a number-average molecular weight of 850 to 1200 g / mol, a weight-average molecular weight of 1800 to 2500 g / mol, and a molecular weight distribution index of 1.8 to 2.3; the viscosity of the phenolic resin at 25°C is 350 to 600 mPa·s; the gel time of the phenolic resin is 90 to 150 seconds (170°C); and the curing exothermic peak temperature of the phenolic resin is 165 to 185°C.

[0016] The phenolic resin does not contain unsubstituted ortho-phenolic hydroxyl groups; all ortho-hydroxyl groups are substituted. Alkyl, halogen, nitro or trifluoromethyl substitution; the crosslinking network of the phenolic resin is composed of methylene bridges, dimethylene ether bridges and a small amount of methylene ketone bridges, wherein the proportion of methylene bridges is not less than 85%, the proportion of dimethylene ether bridges is not more than 12%, and the proportion of methylene ketone bridges is not more than 3%.

[0017] After heat aging at 150°C for 72 hours, the phenolic resin retains a tensile strength of not less than 92%, a flexural strength of not less than 90%, and an impact strength of not less than 88%; after damp heat aging at 85°C and 85% relative humidity for 168 hours, the tensile strength retains a tensile strength of not less than 89%, a flexural strength of not less than 87%, and an impact strength of not less than 85%.

[0018] To achieve the above-mentioned objective, the present invention also provides a method for preparing phenolic resin for anti-attenuation resin grinding wheels, characterized by comprising the following steps:

[0019] Step S1: Add polysubstituted aromatic phenol monomer A, solvent D and catalyst C to the reaction vessel, stir and heat to 50 to 60°C, keep warm for 30 minutes to allow all components to fully dissolve and activate.

[0020] Step S2: Within 30 to 60 minutes, aldehyde monomer B is added dropwise to the reaction system in two stages. In the first stage, 60% of the total amount is added, and the reaction temperature is controlled at 60 to 70°C. In the second stage, the remaining 40% is added, and the reaction temperature is controlled at 70 to 80°C.

[0021] Step S3: After the addition is complete, raise the temperature to 85 to 95°C at a rate of 1.0 to 1.5°C / min, and keep the temperature for 1.5 to 2.5 hours. During this period, take a sample every 30 minutes to measure the solid content and viscosity of the reaction solution. When the solid content reaches 68% to 72% and the viscosity reaches 350 to 600 mPa·s, terminate the reaction.

[0022] Step S4: Cool the reaction solution to below 60°C, add an acidic neutralizing agent to adjust the pH to 6.5 to 7.5, let it stand to separate the layers, and then separate the aqueous phase.

[0023] Step S5: Transfer the organic phase to a thin-film evaporator and perform vacuum devolatilization under conditions where the absolute pressure is not higher than 50 Pa and the material temperature is not higher than 110 °C to remove residual monomers and low-molecular-weight byproducts until the free phenol content is lower than 50 ppm.

[0024] Step S6: Cool the devolatilized resin to room temperature, pulverize and sieve to obtain phenolic resin powder with a particle size of 40 to 100 mesh.

[0025] In step S2, aldehyde monomer B is added in the form of a 37% to 40% mass fraction of formaldehyde aqueous solution, solid paraformaldehyde, or triformaldehyde; if paraformaldehyde or triformaldehyde is used, it needs to be pre-dissolved with solvent D at 60°C for 15 minutes.

[0026] In step S4, the acid neutralizing agent is selected from at least one of phosphoric acid, citric acid, acetic acid or oxalic acid, and the amount added is based on the residual alkaline catalyst in the neutralization system.

[0027] In step S5, the scraping speed of the thin-film evaporator is 200 to 400 rpm, the material residence time is 8 to 15 minutes, and an inert gas is introduced for protection during the devolatilization process. The inert gas is nitrogen or argon, and the flow rate is 0.5 to 2.0 L / min.

[0028] The preparation method is carried out under an inert atmosphere throughout, and the top of the reactor is equipped with a condensation reflux device and a tail gas absorption system to ensure zero emissions of volatile organic compounds.

[0029] In a preferred embodiment of the present invention, when the phenolic resin is used to prepare resin grinding wheels, it is mixed with abrasive, filler, lubricant, and coupling agent in a mass ratio, wherein the phenolic resin accounts for 8% to 15% of the total formulation mass, the abrasive accounts for 65% to 80%, the filler accounts for 5% to 12%, the lubricant accounts for 1% to 3%, and the coupling agent accounts for 0.5% to 1.5%; the abrasive is selected from at least one of brown fused alumina, white fused alumina, silicon carbide, cubic boron nitride, or diamond; the filler is selected from at least one of alumina micro powder, silicon micro powder, mica powder, or talc powder; the lubricant is selected from at least one of graphite, molybdenum disulfide, or polytetrafluoroethylene micro powder; and the coupling agent is selected from... , Or at least one of the titanate coupling agents.

[0030] The preparation process of the resin grinding wheel includes mixing, pre-pressing, hot-pressing curing and post-treatment. The hot-pressing curing temperature is 170 to 190°C, the pressure is 30 to 50 MPa, and the holding time is 30 to 60 minutes. The post-treatment includes step-curing at 180 to 220°C for a total duration of 8 to 12 hours.

[0031] After the resin grinding wheel continuously dry-grinds the GCr15 bearing steel test block at a linear velocity of 35 m / s for 120 minutes, the grinding ratio is not less than 18, and the surface roughness is... The value is not higher than 0.63μm, and the radial wear of the grinding wheel is not higher than 0.15mm; after 200 cycles of intermittent grinding of the cemented carbide test block at a linear speed of 50m / s, its profile retention rate is not less than 93%, and there are no cracks, chips or loose structures.

[0032] The phenolic resin for anti-degradation resin grinding wheels and its preparation method described in this invention eliminate easily oxidized sites through molecular structure design. Combined with precise synthesis control and deep devolatilization process, this fundamentally solves the performance degradation problem caused by residual free phenol, unstable hydroxymethyl groups, and easy oxidation of ortho-phenolic hydroxyl groups in traditional phenolic resins. This resin not only possesses excellent initial mechanical properties but also exhibits outstanding structural stability in long-term thermo-oxidative and humid environments. This ensures that the resin grinding wheel maintains stable grinding efficiency and geometric accuracy under harsh conditions such as high load, high linear speed, and continuous dry grinding, meeting the urgent demand for ultra-long-life grinding tools in high-end manufacturing fields such as aerospace engine blades, semiconductor wafer cutting, and new energy vehicle motor shafts.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0034] This invention introduces a polysubstituted aromatic phenolic monomer with a specific structure to completely eliminate unsubstituted phenolic hydroxyl groups at the ortho position at the molecular level, blocking the pathway for them to be oxidized to quinone structures under thermo-oxidative conditions. This fundamentally inhibits the degradation of the resin's cross-linking network and the problem of color deepening, overcoming the paradox of "high strength and low resistance" in traditional resins and fundamentally solving the problem of chemical instability of phenolic resins.

[0035] This invention utilizes a combination of gradient dripping, endpoint monitoring, and deep vacuum devolatilization processes to ensure that the free phenol content is consistently below 50 ppm and the residual hydroxymethyl content is below 0.8 wt%, significantly lower than that of traditional resins, where the free phenol content is often >200 ppm. This significantly reduces the microporous defects and reverse reaction risks caused by the volatilization of small molecules, ensuring the structural stability of the resin during high-temperature molding and long-term use.

[0036] The resin obtained by this invention has a glass transition temperature higher than 140℃ and a thermogravimetric initiation temperature higher than 320℃. After thermal aging at 150℃ for 72 hours, the mechanical strength retention rate is ≥92%, and after humid heat aging at 85℃ / 85%RH for 168 hours, the retention rate is ≥87%. This indicates that it can maintain excellent network integrity and performance retention under high temperature and high humidity coupling environment, and simultaneously improve thermal stability and humid heat stability.

[0037] The grinding wheel made of this resin, after dry grinding GCr15 steel at 35m / s for 120 minutes, has a grinding ratio ≥18 and radial wear ≤0.15mm. After intermittent grinding of cemented carbide at 50m / s for 200 cycles, the profile retention rate is ≥93%, with no cracks or chipping. It meets the stringent requirements of aerospace, semiconductor and other fields for high-precision and long-life grinding tools, giving the resin grinding wheel excellent grinding performance and long service life.

[0038] This invention features clearly defined and precisely controllable parameters throughout the entire process, from monomer selection, molar ratio, reaction temperature gradient, endpoint determination to post-processing. This avoids the problems of traditional methods relying on experience and large batch fluctuations, and has good feasibility for large-scale production. Through a systematic innovation of "molecular structure design - synthesis process control - deep purification", this invention elevates phenolic resin from a passive bonding material to an active anti-attenuation functional unit, realizing long-term stable service of resin grinding wheels under harsh working conditions such as high speed, heavy load, and dry grinding. It has significant technological progress and application value. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the preparation method of phenolic resin for anti-attenuation resin grinding wheels according to the present invention;

[0040] Figure 2 This is a schematic diagram of the local structure of the phenolic resin molecule in this invention, showing how the ortho-substituents eliminate easily oxidized phenolic hydroxyl groups. Detailed Implementation

[0041] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present invention and not to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0043] In the embodiments of the present invention, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of the present invention shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on the present invention; the term "multiple" in the present invention refers to two or more (including two).

[0044] This invention provides a phenolic resin for anti-attenuation resin grinding wheels and its preparation method. This technical solution, through the synergistic effect of molecular structure design, precise control of the reaction process, and optimization of post-processing, yields a phenolic resin with excellent thermal stability, hydrothermal stability, and mechanical strength retention. It is suitable for manufacturing resin grinding wheels under harsh conditions such as high-load, high-speed dry grinding. The following detailed description, in conjunction with specific embodiments, will ensure that those skilled in the art can fully reproduce the described technical content based on this specification.

[0045] The phenolic resin for anti-aging resin grinding wheels is prepared by polycondensation reaction of polysubstituted aromatic phenolic monomer A, aldehyde monomer B, catalyst C, and solvent D. The general structural formula of polysubstituted aromatic phenolic monomer A is as follows: , It is a benzene ring or a naphthalene ring; for Alkyl, halogen, or nitro groups; for alkoxy or trifluoromethyl; m is 1 or 2; n is 0 or 1; and and The phenolic monomers are not all hydrogen atoms. This structural feature ensures that all ortho- and ortho-positions of the phenolic hydroxyl groups are occupied by substituents, thereby eliminating easily oxidized unsubstituted ortho- and ortho-position phenolic hydroxyl groups at the molecular level. Aldehyde monomer B is selected from at least one of formaldehyde, paraformaldehyde, or trioxymethylene; catalyst C is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, or hexamethylenetetramine; solvent D is selected from at least one of deionized water, ethanol, isopropanol, or butanol.

[0046] The molar ratio of polysubstituted aromatic phenolic monomer A to aldehyde monomer B is controlled within the range of 1:1.05 to 1:1.35 to ensure sufficient cross-linking while avoiding excessive aldehyde leading to increased side reactions. The amount of catalyst C is 0.8% to 2.5% of the mass of polysubstituted aromatic phenolic monomer A. This range effectively catalyzes hydroxymethylation and polycondensation reactions while avoiding excessive alkalinity residue that could affect subsequent neutralization and devolatilization. The amount of solvent D is 15% to 35% of the total mass of the reaction system, used to adjust the viscosity of the reaction system, promote mass transfer, and control the exothermic rate.

[0047] In a preferred embodiment of the present invention, the polysubstituted aromatic phenolic monomer A is specifically selected from... , , , , , , or At least one of these monomers. These monomers all meet the structural requirements of ortho-dual substitution or ortho-para substitution, effectively blocking the oxidation pathway at the ortho position of the phenolic hydroxyl group.

[0048] The prepared phenolic resin has well-defined physicochemical parameters: a number-average molecular weight of 850 to 1200 g / mol, a weight-average molecular weight of 1800 to 2500 g / mol, and a molecular weight distribution index of 1.8 to 2.3; a viscosity of 350 to 600 mPa·s at 25°C; a gel time of 90 to 150 seconds at 170°C; and a curing exothermic peak temperature of 165 to 185°C as determined by differential scanning calorimetry. Its crosslinking network is mainly composed of methylene bridges. Dimethylene ether bridge and a small amount of methylene ketone bridges The composition includes methylene bridges comprising no less than 85%, dimethylene ether bridges comprising no more than 12%, and methylene ketone bridges comprising no more than 3%. This cross-linked structure combines high thermal stability with moderate flexibility, which is beneficial to the structural integrity of the grinding wheel under high stress cycling.

[0049] After heat aging at 150℃ for 72 hours, the phenolic resin retains a tensile strength retention rate of no less than 92%, a flexural strength retention rate of no less than 90%, and an impact strength retention rate of no less than 88%. After damp heat aging at 85℃ and 85% relative humidity for 168 hours, the tensile strength retention rate is no less than 89%, the flexural strength retention rate is no less than 87%, and the impact strength retention rate is no less than 85%. These performance indicators demonstrate that the resin exhibits excellent structural stability in long-term thermo-oxidative and humid environments.

[0050] This invention also provides a method for preparing phenolic resin for anti-attenuation resin grinding wheels, the method comprising the following steps:

[0051] Step S1: Add the polysubstituted aromatic phenol monomer A, solvent D and catalyst C to a reactor equipped with a stirrer, thermometer, reflux condenser and inert gas inlet tube. Stir and heat to 50 to 60°C under nitrogen or argon protection, and keep at this temperature for 30 minutes to allow all components to fully dissolve and activate the active centers of the catalyst.

[0052] Step S2: Over 30 to 60 minutes, aldehyde monomer B is added dropwise to the reaction system in two stages. In the first stage, 60% of the total amount is added, with the reaction temperature controlled at 60 to 70°C. In the second stage, the remaining 40% is added, with the reaction temperature controlled at 70 to 80°C. This gradient addition process effectively controls the hydroxymethylation reaction rate and avoids localized overheating and byproduct formation. If paraformaldehyde or trioxymethylene is used as the aldehyde source, it must be pre-dissolved with a portion of solvent D at 60°C for 15 minutes to form a uniform dispersion before dropwise addition.

[0053] Step S3: After the addition is complete, raise the temperature to 85 to 95°C at a rate of 1.0 to 1.5°C / min and maintain the temperature for 1.5 to 2.5 hours. During this period, take samples every 30 minutes to measure the solid content and viscosity of the reaction solution. Terminate the reaction immediately when the solid content reaches 68% to 72% and the viscosity reaches 350 to 600 mPa·s. This endpoint control strategy ensures a narrow molecular weight distribution and controllable functional group content in the resin.

[0054] Step S4: Cool the reaction solution to below 60°C and add an acidic neutralizing agent to adjust the pH to 6.5 to 7.5. The acidic neutralizing agent is selected from at least one of phosphoric acid, citric acid, acetic acid, or oxalic acid, and the amount added is based on completely neutralizing the residual alkaline catalyst in the system. After standing and separating the layers, separate and discard the aqueous phase, retaining the organic phase.

[0055] Step S5: Transfer the organic phase to a thin-film evaporator and perform vacuum devolatilization under conditions where the absolute pressure does not exceed 50 Pa and the material temperature does not exceed 110 °C. During the devolatilization process, the scraper rotation speed is controlled at 200 to 400 rpm, the material residence time is 8 to 15 minutes, and nitrogen or argon is introduced as a protective gas at a flow rate of 0.5 to 2.0 L / min. This deep devolatilization process can efficiently remove residual free phenols, unreacted aldehydes, and low-molecular-weight condensation byproducts, resulting in a final resin with a free phenol content of less than 50 ppm and a residual hydroxymethyl content of less than 0.8 wt%.

[0056] Step S6: Cool the devolatilized resin to room temperature, crush it using a mechanical crushing device and pass it through a standard sieve to obtain phenolic resin powder with a particle size of 40 to 100 mesh, which facilitates uniform mixing with the grinding wheel formulation components in the subsequent process.

[0057] In a preferred embodiment of the present invention, when phenolic resin is used to prepare resin grinding wheels, it is mixed with abrasive, filler, lubricant, and coupling agent in a mass ratio. The phenolic resin accounts for 8% to 15% of the total formulation mass, the abrasive accounts for 65% to 80%, the filler accounts for 5% to 12%, the lubricant accounts for 1% to 3%, and the coupling agent accounts for 0.5% to 1.5%. The abrasive is selected from at least one of brown fused alumina, white fused alumina, silicon carbide, cubic boron nitride, or diamond; the filler is selected from at least one of alumina micro powder, silicon micro powder, mica powder, or talc powder; the lubricant is selected from at least one of graphite, molybdenum disulfide, or polytetrafluoroethylene micro powder; and the coupling agent is selected from... , Or at least one of the titanate coupling agents.

[0058] The manufacturing process of resin grinding wheels includes four stages: mixing, pre-pressing, hot-pressing curing, and post-treatment. Mixing is performed using a high-speed mixer to ensure thorough dispersion of the resin powder and all components. Pre-pressing is carried out at 5 to 10 MPa to form a preliminary blank. Hot-pressing curing is conducted at 170 to 190°C and 30 to 50 MPa, with a holding time of 30 to 60 minutes, allowing the resin to fully cross-link and cure. Post-treatment employs a stepped heating and curing process, with a temperature range of 180 to 220°C and a total duration of 8 to 12 hours, to eliminate internal stress and increase cross-linking density.

[0059] The resin grinding wheel prepared by the above process, after continuous dry grinding of a GCr15 bearing steel test block at a linear velocity of 35 m / s for 120 minutes, showed a grinding ratio of not less than 18 and a surface roughness of [missing information]. The value is not higher than 0.63μm, and the radial wear of the grinding wheel is not higher than 0.15mm. After 200 cycles of intermittent grinding of cemented carbide test blocks at a linear speed of 50m / s, the profile retention rate is not less than 93%, and there are no cracks, chips or loose structures, demonstrating excellent geometric accuracy retention and structural integrity.

[0060] The technical effects of the present invention are further illustrated below through several specific embodiments and comparative examples. All embodiments were strictly performed according to the aforementioned preparation method, while the comparative examples deviate from the scope defined by the present invention in terms of key parameters.

[0061] Example 1, will 122.2 g (1.0 mol), 150 g of deionized water, and 1.22 g of sodium hydroxide were added to a 2 L four-necked reactor. Under nitrogen protection, the mixture was stirred and heated to 55 °C, and maintained at this temperature for 30 minutes. Then, over 45 minutes, 126.5 g of a 37% formaldehyde aqueous solution (containing 1.55 mol of formaldehyde, a phenol-formaldehyde molar ratio of 1:1.55) was added dropwise in two stages. In the first stage, 75.9 g was added at 65 °C; in the second stage, 50.6 g was added at 75 °C. After the addition was complete, the temperature was increased to 90 °C at a rate of 1.2 °C / min, and the reaction was maintained for 2.0 hours. During this period, a sample was taken, and the solid content was measured to be 70.3%, and the viscosity was 480 mPa·s. The reaction was then terminated. The temperature was lowered to 55 °C, and a 10% citric acid aqueous solution was added to adjust the pH to 7.0. After standing and separating the phases, the aqueous phase was discarded. The organic phase was transferred to a thin-film evaporator and volatilized for 12 minutes under the conditions of an absolute pressure of 45 Pa, a material temperature of 105 °C, a scraping speed of 300 rpm, and a nitrogen flow rate of 1.0 L / min, yielding a light yellow transparent resin. Gas chromatography-mass spectrometry analysis showed that the free phenol content was 38 ppm; nuclear magnetic resonance (NMR) integral analysis showed that the hydroxymethyl content was 0.65 wt%; and the glass transition temperature was determined by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) measured the 5% thermogravimetric initiation temperature under a nitrogen atmosphere as 148℃. The temperature was 328℃. The resin was pulverized and passed through a 60-mesh sieve to obtain the resin of Example 1.

[0062] Example 2, will 150.2 g (1.0 mol), 180 g isopropanol, and 2.25 g of 25% ammonia (1.5% of the phenol mass) were added to the reactor, and the temperature was raised to 58°C and maintained for 30 minutes. 46.5 g of paraformaldehyde (containing 1.55 mol of formaldehyde) was pre-dissolved with 50 g of isopropanol at 60°C for 15 minutes. The solution was added dropwise in two stages over 50 minutes: 27.9 g at 68°C in the first stage, and 18.6 g at 78°C in the second stage. After the addition was complete, the temperature was raised to 88°C at 1.0°C / min and maintained for 2.2 hours. The sample showed a solid content of 69.8% and a viscosity of 520 mPa·s. The temperature was lowered to 58°C, and the pH was adjusted to 6.8 with 10% acetic acid. The organic phase was then volatilized for 10 minutes at 50 Pa, 108°C, 350 rpm, and 1.2 L / min nitrogen. The obtained resin had a free phenol content of 42 ppm and a hydroxymethyl content of 0.72 wt%. It is 145℃. The temperature was 325℃. After pulverizing and sieving, the resin of Example 2 was obtained.

[0063] Example 3, will 150.2 g (1.0 mol), 200 g butanol, and 2.25 g sodium carbonate (1.5% of the phenol mass) were added to the reactor and activated at 60℃ for 30 minutes. 132.8 g of a 37% formaldehyde aqueous solution (containing 1.65 mol of formaldehyde, phenol-formaldehyde molar ratio 1:1.65) was added dropwise in two stages: 79.7 g at 70℃ and 53.1 g at 80℃, for a total time of 55 minutes. The mixture was then heated to 92℃ and held for 2.0 hours, resulting in a solid content of 71.1% and a viscosity of 560 mPa·s. After cooling, the pH was adjusted to 7.2 with phosphoric acid. Thin-film evaporation conditions were 40 Pa, 110℃, 400 rpm, nitrogen 1.5 L / min, for 10 minutes. The resulting resin had a free phenol content of 35 ppm and a hydroxymethyl content of 0.60 wt%. It is 150℃. The temperature was set to 332°C to obtain the resin of Example 3.

[0064] Example 4, will 162.1 g (1.0 mol), 160 g of ethanol, and 2.43 g of hexamethylenetetramine (1.5% of the phenol mass) were added to the reactor and activated at 52°C for 30 minutes. 51.3 g of paraformaldehyde (containing 1.70 mol of formaldehyde) was pre-dissolved in 60 g of ethanol. The mixture was added dropwise in two stages over 40 minutes: 30.8 g at 62°C and 20.5 g at 72°C. The mixture was then heated to 86°C and held for 2.5 hours, resulting in a solid content of 68.5% and a viscosity of 420 mPa·s. After cooling, the pH was adjusted to 6.6 with oxalic acid. The devolatilization conditions were 48 Pa, 102°C, 250 rpm, nitrogen 0.8 L / min, and 14 minutes. The resulting resin contained 45 ppm of free phenol and 0.78 wt% of hydroxymethyl groups. It is 142℃. The temperature was set to 322°C to obtain the resin of Example 4.

[0065] To verify the necessity of the technical solution of this invention, several comparative examples were set up. Comparative Example 1 used 94.1g (1.0mol) of ordinary phenol, 111.0g (1.35mol) of 37% formaldehyde, 1.41g (1.5%) of sodium hydroxide, and 150g of water. Phenolic resin was prepared using a conventional one-step dropwise addition process (dropwise addition at 70℃ for 60 minutes, followed by holding at 85℃ for 2 hours). Only atmospheric pressure distillation was performed to remove water; deep vacuum devolatilization was not performed. The free phenol content was measured to be 320ppm, and the hydroxymethyl content was 1.85wt%. It is 125℃. The temperature is 295℃. This resin contains a large number of unsubstituted ortho-phenolic hydroxyl groups, and its molecular structure is susceptible to thermal and oxygen attack.

[0066] Comparative Example 2 The reaction mixture consisted of 122.2 g (1.0 mol) of phenol and 111.0 g (1.35 mol) of formaldehyde, but the catalyst dosage was only 0.5% (0.61 g NaOH). The reaction temperature was poorly controlled (fluctuating by ±10℃ during dropping), and the polycondensation endpoint was determined empirically (stopped after 2 hours of heat treatment). Furthermore, vacuum devolatilization was not performed. The resulting resin had a free phenol content of 180 ppm, a hydroxymethyl content of 1.20 wt%, a molecular weight distribution index of 2.8, and a gel time that fluctuated between 80 and 170 seconds, exhibiting poor batch-to-batch consistency.

[0067] Comparative Example 3 used a blend of liquid phenolic resin and powdered phenolic resin from Example 1 (CN107336146B). The resin molecular structure was not modified, and the hydroxymethyl content was not controlled. Testing revealed that this blended resin still contained unsubstituted phenolic hydroxyl groups and exhibited poor thermo-oxidative stability.

[0068] Comparative Example 4, referring to CN108890542A, used commercially available "low-free-phenol phenolic resin powder." Testing revealed that its free phenol content was 90 ppm, but the hydroxymethyl content was as high as 1.5 wt%, and the ortho-positions were not fully substituted. During hot pressing at 150℃, a reverse hydroxymethylation reaction occurred, releasing free phenol, leading to micropores and stress concentration inside the grinding wheel.

[0069] Comparative Example 5 will use the example from Example 1 The resin was replaced with equimolar amounts of phenol, with all other conditions remaining unchanged. Although the free phenol content was reduced to 60 ppm by devolatilization, the tensile strength retention rate after 72 hours of heat aging at 150°C was only 76% due to the unsubstituted ortho positions, which was far lower than the 93% in Example 1.

[0070] Comparative Example 6 reduced the amount of aldehyde monomer used in Example 1 to phenol:aldehyde = 1:0.95, resulting in insufficient crosslinking density. The resulting resin... At only 110℃, the curing is incomplete, resulting in low strength in the finished grinding wheel, which is prone to chipping during grinding.

[0071] Comparative Example 7 omitted step S5 (vacuum devolatilization) from Example 1 and only underwent atmospheric pressure drying. The resulting resin had a free phenol content of 150 ppm and a hydroxymethyl content of 1.1 wt%. After being made into a grinding wheel, it absorbed moisture and softened under a humid and hot environment of 85°C / 85%RH, resulting in a 35% decrease in flexural strength.

[0072] In Comparative Example 8, the devolatilization temperature in Example 1 was increased to 130°C, which exceeded the resin softening point. This caused some molecular chains to cross-link prematurely, resulting in a sharp increase in viscosity. Consequently, the resin could not be evenly dispersed in the grinding wheel formulation, leading to localized embrittlement and uneven grinding.

[0073] To systematically evaluate the overall performance of the resins of the present invention, standardized performance tests were performed on the resins prepared in Examples 1 to 4 and Comparative Examples 1, 5, and 7. The results are shown in the table below:

[0074]

[0075] The above data indicates that only by simultaneously satisfying five technical requirements—specific polysubstituted phenol monomers, precise molar ratio, gradient temperature control, endpoint monitoring, and deep devolatilization—can a product be obtained that combines low free phenol, low hydroxymethyl content, and high... With Gao Anti-degradation phenolic resin. The absence of any single element leads to a significant deterioration in performance.

[0076] Furthermore, the resin from Example 1 was mixed with 75% brown fused alumina, 10% alumina micro powder, 2% graphite, and 1% [unclear text - likely a specific ingredient or component] at a mass ratio of 10%. The mixture was pre-pressed, cured by hot pressing at 180℃ / 40MPa / 45min, and then cured in a stepped manner at 200℃ for 10 hours to obtain a resin grinding wheel. This grinding wheel was used for continuous dry grinding of GCr15 bearing steel at a linear velocity of 35m / s for 120 minutes, with a grinding ratio of 18.5. The diameter is 0.60 μm and the radial wear is 0.13 mm. After 200 cycles of intermittent grinding of YG8 cemented carbide at a linear speed of 50 m / s, the profile retention rate is 94.2% and there are no structural defects.

[0077] In summary, this invention eliminates easily oxidized sites through molecular structure design and, combined with precise synthesis control and a deep devolatilization process, fundamentally solves the performance degradation problems of traditional phenolic resins caused by residual free phenol, unstable hydroxymethyl groups, and easy oxidation of ortho-phenolic hydroxyl groups. This technical solution not only possesses full feasibility but also demonstrates significant application value in high-end manufacturing, meeting the urgent needs of aerospace engine blades, semiconductor wafer dicing, and new energy vehicle motor shafts for ultra-long-life abrasive tools.

Claims

1. A phenolic resin for anti-attenuation resin grinding wheels, characterized in that, The phenolic resin component includes: Polysubstituted aromatic phenolic monomer A has the following general structural formula: ,in It is a benzene ring or a naphthalene ring. for Alkyl, halogen, or nitro groups for Alkoxy or trifluoromethyl, m is 1 or 2, n is 0 or 1, and and They are not both hydrogen; Aldehyde monomer B is selected from at least one of formaldehyde, paraformaldehyde, or trioxyformaldehyde; Catalyst C is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, or hexamethylenetetramine; Solvent D is selected from at least one of deionized water, ethanol, isopropanol, or butanol; The molar ratio of the polysubstituted aromatic phenolic monomer A to the aldehyde monomer B is 1:1.05 to 1:1.35; the amount of catalyst C is 0.8% to 2.5% of the mass of the polysubstituted aromatic phenolic monomer A; and the amount of solvent D is 15% to 35% of the total mass of the reaction system. The phenolic resin does not contain unsubstituted ortho-phenolic hydroxyl groups, has a free phenol content of less than 50 ppm, a residual hydroxymethyl content of less than 0.8 wt%, a glass transition temperature higher than 140°C, and a thermal weight loss initiation temperature higher than 320°C.

2. The phenolic resin for anti-attenuation resin grinding wheels according to claim 1, characterized in that, The polysubstituted aromatic phenolic monomer A is selected from... , , , , , , or At least one of them.

3. The phenolic resin for anti-attenuation resin grinding wheels according to claim 1, characterized in that, The phenolic resin has a number-average molecular weight of 850 to 1200 g / mol, a weight-average molecular weight of 1800 to 2500 g / mol, and a molecular weight distribution index of 1.8 to 2.3; a viscosity of 350 to 600 mPa·s at 25°C; a gel time of 90 to 150 seconds at 170°C; and a curing exothermic peak temperature of 165 to 185°C.

4. The phenolic resin for anti-attenuation resin grinding wheels according to claim 1, characterized in that, The crosslinking network of the phenolic resin is composed of methylene bridges, dialysyl ether bridges and methylene ketone bridges, wherein the proportion of methylene bridges is not less than 85%, the proportion of dialysyl ether bridges is not more than 12%, and the proportion of methylene ketone bridges is not more than 3%.

5. The phenolic resin for anti-attenuation resin grinding wheels according to claim 1, characterized in that, After heat aging at 150°C for 72 hours, the phenolic resin retains a tensile strength of not less than 92%, a flexural strength of not less than 90%, and an impact strength of not less than 88%; after damp heat aging at 85°C and 85% relative humidity for 168 hours, the tensile strength retains a tensile strength of not less than 89%, a flexural strength of not less than 87%, and an impact strength of not less than 85%.

6. The phenolic resin for anti-attenuation resin grinding wheels according to claim 1, characterized in that, When used to prepare resin grinding wheels, it is mixed with abrasive, filler, lubricant and coupling agent in the following mass ratio: phenolic resin accounts for 8% to 15%, abrasive accounts for 65% to 80%, filler accounts for 5% to 12%, lubricant accounts for 1% to 3% and coupling agent accounts for 0.5% to 1.5%. The resin grinding wheel is hot-pressed and cured at 170 to 190°C and 30 to 50 MPa for 30 to 60 minutes, and then post-cured in a stepped manner at 180 to 220°C for 8 to 12 hours. After continuous dry grinding of GCr15 bearing steel at a linear velocity of 35 m / s for 120 minutes, the grinding ratio is not less than 18, the surface roughness Ra value is not higher than 0.63 μm, and the radial wear is not higher than 0.15 mm.

7. A method for preparing a phenolic resin for an anti-attenuation resin grinding wheel, applied to the phenolic resin for an anti-attenuation resin grinding wheel as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Add polysubstituted aromatic phenolic monomer A, solvent D and catalyst C to the reaction vessel, stir and heat to 50 to 60°C, and keep warm for 30 minutes; Step S2: Add aldehyde monomer B in two stages over 30 to 60 minutes. In the first stage, add 60% of the total amount while controlling the temperature at 60 to 70°C. In the second stage, add the remaining 40% while controlling the temperature at 70 to 80°C. Step S3: After the addition is complete, the temperature is increased to 85 to 95°C at a rate of 1.0 to 1.5°C / min, and the reaction is maintained for 1.5 to 2.5 hours. The reaction is terminated when the solid content of the reaction liquid reaches 68% to 72% and the viscosity reaches 350 to 600 mPa·s. Step S4: Cool down to below 60℃, add an acidic neutralizing agent to adjust the pH to 6.5 to 7.5, let stand to separate the aqueous phase; Step S5: Vacuum devolatilize the organic phase under an absolute pressure not exceeding 50 Pa and a material temperature not exceeding 110 °C until the free phenol content is less than 50 ppm; Step S6: After cooling, crush and sieve to obtain phenolic resin powder with a particle size of 40 to 100 mesh.

8. The method for preparing phenolic resin for anti-attenuation resin grinding wheels according to claim 7, characterized in that, In step S2, the aldehyde monomer B is added in the form of a 37% to 40% mass fraction of formaldehyde aqueous solution, solid paraformaldehyde, or triformaldehyde; if paraformaldehyde or triformaldehyde is used, it is pre-dissolved with a portion of solvent D at 60°C for 15 minutes.

9. The method for preparing phenolic resin for anti-attenuation resin grinding wheels according to claim 7, characterized in that, The acid neutralizing agent in step S4 is selected from at least one of phosphoric acid, citric acid, acetic acid or oxalic acid; in the vacuum devolatilization process of step S5, the scraping speed is 200 to 400 rpm, the material residence time is 8 to 15 minutes, and nitrogen or argon gas is introduced for protection, with a gas flow rate of 0.5 to 2.0 L / min.

10. The method for preparing phenolic resin for anti-attenuation resin grinding wheels according to claim 7, characterized in that, The entire reaction is carried out under an inert atmosphere. In step S1, the reactor is equipped with a condensation reflux device and a tail gas absorption system.

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