A sisal polishing wheel setting glue and a preparation method thereof

Abstract

The application relates to the adhesive technical field and discloses a sisal polishing wheel setting adhesive and a preparation method thereof, wherein the sisal polishing wheel setting adhesive is prepared by compounding a specific formula of vinyl-acrylic emulsion, silica sol, ethylene-vinyl acetate copolymer emulsion and a thickening agent; the vinyl-acrylic emulsion is prepared by deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, a functional monomer, a composite emulsifier and an oxidation-reduction initiation system through a specific pre-emulsification-step-by-step dropping process. The functional monomer is introduced to participate in copolymerization, a chemical bridge between a polymer and sisal fibers is constructed, the composite silica sol forms a Si-O-Si inorganic network and produces strong hydrogen bond action with the organic polymer chain, the VAE emulsion is added to improve the flexibility of the adhesive film and the wettability of the plant fibers, the three are synergistic, a stable interpenetrating network structure is formed, and the technical problems that the traditional setting adhesive is poor in temperature resistance, insufficient in wear resistance, difficult to consider environmental protection and performance at the same time are solved.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a sisal polishing wheel shaping adhesive and its preparation method. Background Technology

[0002] Sisal polishing wheels are grinding and polishing tools made primarily from natural sisal fibers through a process of combing, web laying, resin impregnation, molding, and curing. They are widely used for surface finishing of materials such as metal, wood, and stone. The shaping adhesive, as a key material that imparts shape, structural strength, and durability to the sisal wheel, directly determines its lifespan, polishing precision, and work efficiency. Currently, the shaping of sisal polishing wheels mainly relies on the following types of adhesive systems:

[0003] Phenolic resin: It has excellent heat resistance and rigidity, but has obvious defects: a) The curing temperature is usually as high as 150℃ or above, resulting in high energy consumption; b) The cured adhesive layer is brittle and is prone to micro-cracks under high-speed polishing impact, leading to fiber shedding; c) Free formaldehyde may be released during production and use, posing a great environmental pressure.

[0004] Epoxy resins offer high bonding strength but are also expensive. Solvent-based epoxy resins release large amounts of volatile organic compounds (VOCs) during curing, which contradicts the trend of green manufacturing; while water-based epoxy resins often fall short in terms of water resistance and high-temperature and humid heat resistance.

[0005] Ordinary emulsion adhesives (such as vinyl acetate homopolymer emulsion, i.e., white glue, VAE emulsion): environmentally friendly and non-toxic, easy to use. However, they have a low glass transition temperature (Tg) and poor heat resistance. Under the high temperature environment generated by high-speed polishing (locally reaching above 120°C), the adhesive film is prone to softening and becoming sticky, causing sisal fibers to fly off or fall off. This not only shortens the wheel life, but the fallen fibers and softened adhesive can also contaminate the workpiece surface, causing blackening. In addition, the hardness and wear resistance of this type of adhesive are usually insufficient, making it difficult to withstand long-term wear.

[0006] The main shortcomings of existing sisal polishing wheel shaping adhesive technology can be summarized as follows: the contradiction between temperature resistance and environmental protection: high-performance phenolic and epoxy resins are often accompanied by high energy consumption or VOC problems, while environmentally friendly water-based emulsions do not meet the temperature resistance standards; single mechanical properties: high-hardness resins have poor toughness, while emulsions with good toughness have low hardness, making it difficult to simultaneously meet the comprehensive mechanical requirements of polishing wheels for being hard but not brittle and tough but not sticky.

[0007] Weak interfacial bonding with plant fibers: Most synthetic adhesives have limited chemical affinity with polar sisal fibers (rich in hydroxyl groups) and mainly rely on physical anchoring. The interface is easily damaged by factors such as moisture and heat, leading to degumming. Poor process adaptability: The viscosity curves and curing speeds of existing adhesives are not well matched with the impregnation and molding processes of sisal fibers, affecting production efficiency and product uniformity.

[0008] Therefore, developing a shaping adhesive that can simultaneously meet the requirements of high temperature resistance (≥120℃), high wear resistance, high strength, environmental protection and solvent-free properties, and excellent interfacial bonding with sisal fibers has become an urgent need to improve the quality of sisal polishing wheels and promote technological upgrading in the industry. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a sisal polishing wheel shaping adhesive and its preparation method, aiming to solve the technical problems of insufficient temperature resistance, poor wear resistance, poor environmental performance, and weak interfacial bonding with sisal fibers in existing sisal polishing wheel shaping adhesives.

[0010] The technical solution of the present invention is as follows:

[0011] A sisal polishing wheel shaping adhesive, comprising, by weight parts: 100 parts of vinyl acetate-acrylic emulsion, 5-20 parts of silica sol, 10-20 parts of ethylene-vinyl acetate copolymer emulsion, and 0.5-2 parts of thickener; wherein the raw materials of the vinyl acetate-acrylic emulsion include: deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomers, anionic emulsifiers, nonionic emulsifiers, oxidants, and reducing agents.

[0012] The sisal polishing wheel shaping adhesive, wherein the raw materials of the vinyl acetate-acrylic emulsion, by mass parts, include: 100 parts deionized water; 50-70 parts vinyl acetate; 1-6 parts butyl acrylate; 10-20 parts methyl methacrylate; 1-3 parts acrylic acid; 1-10 parts functional monomers; 0.5-2 parts anionic emulsifier; 0.1-2 parts nonionic emulsifier; 0.1-0.2 parts oxidant; and 0.1-0.2 parts reducing agent.

[0013] The sisal polishing wheel shaping adhesive, wherein the anionic emulsifier is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate monoester, and sodium dodecyl diphenyl ether disulfonate.

[0014] The sisal polishing wheel shaping adhesive, wherein the nonionic emulsifier is one or both of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

[0015] The sisal polishing wheel shaping adhesive, wherein the functional monomer is one or more of silane coupling agent, hydroxypropyl acrylate and N-hydroxymethylacrylamide.

[0016] The sisal polishing wheel shaping adhesive, wherein the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0017] The sisal polishing wheel shaping adhesive, wherein the oxidant is one or more of sodium persulfate, ammonium persulfate, and potassium persulfate; and the reducing agent is one or a mixture of two of sodium formaldehyde sulfoxylate and sodium bisulfite.

[0018] The sisal polishing wheel shaping adhesive, wherein the silica sol has a particle size of 10-30 nm and a solid content of 20-40%; and the ethylene-vinyl acetate copolymer emulsion has a vinyl acetate content of 65-75% and a solid content of 45-55%.

[0019] The sisal polishing wheel shaping adhesive, wherein the thickener is a polyacrylic acid-based alkali-swelling thickener or a polyurethane-based associative thickener.

[0020] A method for preparing the sisal polishing wheel shaping adhesive as described in this invention, comprising the steps of:

[0021] Preparation of acrylic emulsion:

[0022] Pre-emulsification: Add 60-80% of the total mass of deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomers, 60-80% of the total mass of anionic emulsifier and nonionic emulsifier to a pre-emulsification kettle according to the formula. Stir at 800-1500 rpm for 20-40 minutes at room temperature and pressure to obtain a uniform and stable pre-emulsion.

[0023] Seed polymerization: Add the remaining deionized water and remaining anionic emulsifier to the reactor, heat to 78-82℃, then add 5-15% of the total mass of the pre-emulsion as seed solution, followed by 40-60% of the total mass of oxidant and 40-60% of the total mass of reducing agent, and react at 78-82℃ for 20-40 minutes;

[0024] Droplet polymerization: Maintain the reaction temperature at 75-80℃, and simultaneously begin to drop the remaining pre-emulsion into the reactor, while adding the remaining oxidant and reducing agent dropwise at the same time, controlling the dropping time to 240-300 minutes;

[0025] Post-processing: After the addition is complete, keep warm at 75-80℃ for 40-60 minutes, then cool down to 45-55℃ and discharge to obtain the acetic acid-propylene emulsion;

[0026] The styling adhesive is prepared by mixing the acrylic emulsion, silica sol, ethylene-vinyl acetate copolymer emulsion and thickener in a certain proportion under stirring conditions to obtain the sisal polishing wheel styling adhesive.

[0027] Beneficial Effects: The sisal polishing wheel shaping adhesive provided by this invention, through the above-mentioned ingenious formula design and preparation process, achieves the following significant technological advancements: Excellent high-temperature resistance: the glass transition temperature (Tg) can reach above 45℃, and the long-term operating temperature exceeds 130℃, far exceeding that of ordinary VAE or white latex (approximately 90℃), effectively solving the problem of adhesive layer softening and fiber shedding under high-speed, high-temperature operation; Excellent wear resistance and long lifespan: the wear amount of the composite adhesive layer is as low as below 0.03g, significantly increasing the polishing wheel's service life from the industry average of 45 hours to over 80 hours; Ultra-high adhesive strength and interfacial stability: tensile shear strength reaches... It achieves a strength of over 8.5 MPa and retains a high strength retention rate (>98%) after being placed at room temperature or aging under humid heat. This is due to the dual effects of the chemical bonding bridge of the silane coupling agent and the physical interlocking of the silica sol. It has excellent environmental friendliness: the entire system uses deionized water as the dispersion medium, with no formaldehyde or organic solvent volatilization, complying with the strictest environmental regulations. It has good process adaptability: the viscosity is adjustable, it has a fast and deep wetting speed for sisal fibers, and it is suitable for various sizing processes such as impregnation, roller coating, and spraying. The curing temperature requirement is low (100-120℃ is sufficient), saving energy and reducing consumption. It has good overall polishing effect: the sisal wheel polishing of the workpiece has a high surface finish and no blackening or contamination. Attached Figure Description

[0028] Figure 1 The present invention provides a flowchart of a method for preparing a sisal polishing wheel shaping adhesive.

[0029] Figure 2 The image shows a comparison of the wear levels of the sisal polishing wheels made with the sizing adhesive in Example 1 and Comparative Example 1 after polishing for 1 hour. The white area on the left represents the state of the sisal polishing wheel in Example 1 after polishing, showing no blackening and good temperature resistance. The right area represents the state of the sisal polishing wheel in Comparative Example 1 after polishing, showing blackening, poor temperature resistance, and greater wear. Detailed Implementation

[0030] This invention provides a sisal polishing wheel shaping adhesive, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining this invention and are not intended to limit this invention.

[0031] This invention provides a sisal polishing wheel shaping adhesive, which comprises, by weight percentage: 100 parts of vinyl acetate-acrylic emulsion, 5-20 parts of silica sol, 10-20 parts of ethylene-vinyl acetate copolymer emulsion, and 0.5-2 parts of thickener; the raw materials of the vinyl acetate-acrylic emulsion include: deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomers, anionic emulsifiers, nonionic emulsifiers, oxidants, and reducing agents.

[0032] The sisal polishing wheel shaping adhesive system provided in this embodiment is not a simple physical blend, but rather achieves multi-level synergy between organic and inorganic phases, rigid and flexible segments, and chemical bonding and physical entanglement through molecular design. Among them, vinyl acetate emulsion serves as the basic adhesive resin and continuous phase of the system, providing the main film-forming properties and adhesion; silica sol serves as an inorganic reinforcing phase and a temperature-resistant modifier, uniformly dispersed in the polymer matrix; ethylene-vinyl acetate copolymer emulsion serves as a flexibility modifier and wetting accelerator; and a thickener is used to adjust the rheological properties of the system to meet the requirements of the impregnation process.

[0033] Specifically, silica sol is a dispersion of nano-sized SiO2 particles in deionized water, possessing a huge specific surface area and abundant surface silanol groups (Si-OH). Its application in sisal polishing wheel setting adhesive has the following functions:

[0034] As a heat-resistant framework: During the curing process, a dense hydrogen bond network is formed between silica sol particles and between the particles and the polar groups (such as -COOH, -OH) on the polymer chain; when heated, this inorganic hydrogen bond network is more stable than the organic molecular chain and can effectively inhibit the thermal movement of the polymer chain, thereby significantly improving the heat distortion temperature and high temperature strength retention of the adhesive.

[0035] Wear resistance enhancement: High-hardness nano-SiO2 particles are uniformly dispersed in a relatively soft polymer matrix, playing a hard filling and load-bearing role, significantly improving the surface hardness and abrasion resistance of the film.

[0036] Interface strengthening and penetration: Nanoscale silica sol particles can penetrate into the micropores and gaps on the surface of sisal fibers (the average pore size of sisal fibers is 10-20μm). The Si-OH on its surface forms strong hydrogen bonds with the -OH of the fiber, and achieves mechanical interlocking through capillary action, which greatly enhances the physical bond between the adhesive and the fiber.

[0037] Catalytic crosslinking: The acidic Si-OH on the surface of silica sol can catalyze the condensation reaction between carboxyl groups and methoxy groups of silane coupling agents, promoting the formation of crosslinked networks.

[0038] In this embodiment, the amount of silica sol used is 5-20 parts. Too little will result in an insignificant reinforcing effect; too much may lead to particle agglomeration, increasing the brittleness of the adhesive layer and causing a sharp increase in viscosity, which will affect the process. As an example, the particle size of the silica sol is 10-30 nm, and the solid content is 20-40%, but it is not limited to these values.

[0039] In this embodiment, the VAE emulsion is a copolymer of vinyl acetate and ethylene. The vinyl acetate content of the ethylene-vinyl acetate copolymer emulsion is 65-75%, and the solid content is 45-55%. The introduction of ethylene segments gives it a lower film-forming temperature, better flexibility, and water resistance. Its application in sisal polishing wheel setting adhesive has the following effects:

[0040] Toughening and stress dispersion: VAE film has excellent flexibility and elasticity, and can form island structure or interpenetrating network with the harder vinyl acetate-silica sol composite system to absorb and disperse the impact energy and shear stress generated during polishing, prevent crack propagation, and improve the fatigue life of the adhesive layer.

[0041] Improved wetting and spreading: VAE emulsions have excellent wettability and permeability on porous and rough plant fiber surfaces, which can quickly fill the gaps between fibers, ensuring full contact between the adhesive and the fiber, laying the foundation for subsequent chemical bonding and physical anchoring.

[0042] Low-temperature performance: Improves the flexibility of adhesives in low-temperature environments and prevents brittleness.

[0043] The VAE emulsion provided in this embodiment has good compatibility with the vinyl acetate emulsion. When the two are blended to form a film, the polymer chains entangle with each other. At the same time, extensive hydrogen bonds can be formed between the acetate groups on the VAE segments, the carboxyl groups on the vinyl acetate segments, and the silanol groups in the silica sol, constructing a three-dimensional interpenetrating network that combines rigidity and flexibility with organic and inorganic interweaving. This network structure is the core of the sisal polishing wheel shaping adhesive in this embodiment to obtain high hardness, high toughness, and high heat resistance.

[0044] In this embodiment, a thickener is used to precisely control the viscosity of the setting adhesive (typically a target of 5000-15000 mPa·s @25℃). A suitable viscosity ensures that the sisal fiber bundles can fully and uniformly absorb the adhesive during impregnation, preventing both insufficient absorption leading to insufficient adhesive and excessive dripping, waste, and contamination. For example, the thickener may be an alkali-swellable thickener based on polyacrylic acid or an associative thickener based on polyurethane, but is not limited to these.

[0045] In some embodiments, the raw materials of the vinyl acetate-acrylic emulsion include, by mass parts: 100 parts deionized water; 50-70 parts vinyl acetate; 1-6 parts butyl acrylate; 10-20 parts methyl methacrylate; 1-3 parts acrylic acid; 1-10 parts functional monomer; 0.5-2 parts anionic emulsifier; 0.1-2 parts nonionic emulsifier; 0.1-0.2 parts oxidant; and 0.1-0.2 parts reducing agent.

[0046] Pure polyvinyl acetate (PVAc) emulsion (white glue) has low cost and good adhesion, but poor water resistance, low Tg (about 28°C), and poor creep resistance. By introducing acrylate monomers for copolymerization, its performance can be significantly improved. In this embodiment, vinyl acetate (VAc), butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA), and functional monomers are selected for multi-component copolymerization.

[0047] Specifically, vinyl acetate (50-70 parts) is the main monomer in the vinyl acetate-acrylic emulsion of this embodiment, providing basic adhesive properties and cost advantages. Its content determines the flexibility and cost of the polymer. If the content is too low, the cost will increase and the initial tack will decrease. If the content is too high, the heat resistance will be insufficient.

[0048] Butyl acrylate (1-6 parts), as a soft monomer, has a homopolymer Tg of -54℃. A small amount can internally plasticize, improving the flexibility and impact resistance of the film and preventing the adhesive layer from becoming too hard and brittle. However, excessive amounts will significantly reduce the hardness, heat resistance, and abrasion resistance of the adhesive layer. Methyl methacrylate (10-20 parts), as a hard monomer, has a homopolymer Tg of 105℃. Its core functions are threefold: a) significantly improving heat resistance: copolymerization with VAc can effectively increase the Tg of the copolymer; b) significantly improving moisture resistance: VAc homopolymers have high moisture absorption, and the hydrophobic methyl side chains of MMA can effectively block water molecules from penetrating the polymer chain, reducing the equilibrium water absorption rate of the film from approximately 40% of pure PVAc to below 5%; c) improving surface hardness and gloss: beneficial for obtaining a bright surface on the workpiece after polishing.

[0049] Acrylic acid (1-3 parts) is a functional monomer, and its carboxyl group (-COOH) plays a significant role: a) it provides crosslinking sites, which can react with the hydroxyl groups on the surface of the subsequently added silica sol, the functional groups of functional monomers, etc.; b) it improves the stability of the emulsion (through steric hindrance and electrostatic repulsion); c) it enhances the hydrogen bonding with polar substrates (such as sisal fibers).

[0050] Functional monomers (1-10 parts), wherein the functional monomers are one or more of silane coupling agents, hydroxypropyl acrylate, and N-hydroxymethylacrylamide. Preferably, a silane coupling agent containing double bonds (such as γ-methacryloyloxypropyltrimethoxysilane) is used, which acts as a molecular bridge: the vinyl group at one end participates in emulsion copolymerization, becoming part of the polymer chain; the methoxy group (-OCH3) at the other end hydrolyzes into silanols (-Si-OH) during curing, which can condense with other silanols to form a Si-O-Si network, or react with the hydroxyl groups (-OH) on the surface of sisal fibers to form strong Si-OC covalent bonds. This is key to achieving high-strength interfacial chemical bonding.

[0051] Composite emulsifier systems (anionic + nonionic): These systems combine anionic emulsifiers (such as sodium dodecyl sulfate, providing electrostatic stability) with nonionic emulsifiers (such as OP-10, providing steric hindrance stability). This combination maintains the stability of the emulsion polymerization process and the final product over a wide range of pH, temperature, and electrolyte concentrations, and is particularly beneficial for withstanding the subsequent addition of silica sol (which is typically alkaline). For example, the anionic emulsifier may be one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate, and sodium dodecyl diphenyl ether disulfonate, but is not limited to these; the nonionic emulsifier may be one or two of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, but is not limited to these.

[0052] Redox initiation system: Free radicals can be generated at relatively low temperatures (75-80℃), achieving mild and uniform polymerization, avoiding explosive polymerization and monomer volatilization caused by high temperatures, and facilitating the formation of polymers with uniform molecular weight distribution; for example, the oxidant is one or more of sodium persulfate, ammonium persulfate and potassium persulfate; the reducing agent is one or a mixture of two of sodium formaldehyde sulfoxylate and sodium bisulfite, but is not limited thereto.

[0053] In some embodiments, a method for preparing the sisal polishing wheel shaping adhesive as described in this invention is also provided, such as... Figure 1 As shown, it includes the following steps:

[0054] Preparation of acrylic emulsion:

[0055] S10. Pre-emulsification: Add 60-80% of the total mass of deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomers, 60-80% of the total mass of anionic emulsifier and nonionic emulsifier to a pre-emulsification kettle according to the formula. Stir at 800-1500 rpm for 20-40 minutes at room temperature and pressure to obtain a uniform and stable pre-emulsion.

[0056] S20, Seed Polymerization: Add the remaining deionized water and remaining anionic emulsifier to the reactor, heat to 78-82℃, then add 5-15% of the total mass of the pre-emulsion as seed liquid, followed by 40-60% of the total mass of oxidant and 40-60% of the total mass of reducing agent, and react at 78-82℃ for 20-40 minutes;

[0057] S30, Droplet polymerization: Maintain the reaction temperature at 75-80℃, and simultaneously start adding the remaining pre-emulsion to the reactor, along with the remaining oxidant and reducing agent, controlling the dropping time to 240-300 minutes;

[0058] S40. Post-processing: After the addition is completed, keep warm at 75-80℃ for 40-60 minutes, then cool down to 45-55℃ and discharge to obtain the acetic acid-propylene emulsion.

[0059] S50, Formulation of the setting adhesive: The vinyl acetate emulsion, silica sol, ethylene-vinyl acetate copolymer emulsion and thickener are mixed evenly under stirring conditions according to the specified ratio to obtain the sisal polishing wheel setting.

[0060] Specifically, the preparation of the sisal polishing wheel shaping adhesive in this embodiment involves two steps: first, the synthesis of functionalized vinyl acetate-acrylic emulsion, and then the compounding of various components. The vinyl acetate-acrylic emulsion is prepared using a pre-emulsification + seed polymerization + semi-continuous dripping process. The advantages of this process are: Pre-emulsification: All monomers, emulsifiers, and deionized water are pre-mixed and emulsified to form a fine and uniform monomer droplet emulsion, ensuring the uniformity of subsequent polymerization reactions and facilitating the acquisition of polymers with narrow molecular weight distribution and stable performance; Seed polymerization: A small amount of pre-emulsified liquid is first polymerized to form latex seed particles, which helps control the nucleation process of latex particles and obtain emulsions with uniform particle size; Semi-continuous dripping: The remaining pre-emulsified liquid is added slowly and synchronously with the initiator, maintaining the monomer concentration in the reaction system at a consistently low level. This effectively inhibits chain termination reactions between free radicals, facilitating the generation of high molecular weight polymers, and better controlling the heat of polymerization to prevent explosive polymerization, which is crucial for the safe and stable implementation of industrial production. Combination of components: Add silica sol, VAE emulsion, and thickener to vinyl acetate emulsion at a low temperature of <55℃. Low temperature can prevent silica sol from accelerating gelation due to high temperature, and also prevent unnecessary side reactions of residual monomers or initiators during the compounding process.

[0061] The sisal polishing wheel shaping adhesive provided by this invention, through the aforementioned ingenious formula design and preparation process, achieves the following significant technological advancements: Excellent high-temperature resistance: the glass transition temperature (Tg) can reach above 45℃, and the long-term operating temperature exceeds 130℃, far exceeding that of ordinary VAE or white latex (approximately 90℃), effectively solving the problems of adhesive layer softening and fiber shedding under high-speed, high-temperature operation; Excellent wear resistance and long lifespan: the wear amount of the composite adhesive layer is as low as below 0.03g, significantly increasing the polishing wheel's lifespan from the industry average of 45 hours to over 80 hours; Ultra-high adhesive strength and interface stability: the tensile shear strength reaches 8. With a strength exceeding 5 MPa and a high strength retention rate (>98%) after room temperature storage or humid heat aging, this is attributed to the dual effects of the chemical bonding bridge of the silane coupling agent and the physical interlocking of the silica sol; excellent environmental friendliness: the entire system uses deionized water as the dispersion medium, with no formaldehyde or organic solvent volatilization, complying with the strictest environmental regulations; good process adaptability: the viscosity is adjustable, it has a fast and deep wetting speed for sisal fibers, and is suitable for various sizing processes such as impregnation, roller coating, and spraying. The curing temperature requirement is low (100-120℃ is sufficient), saving energy and reducing consumption; good overall polishing effect: the sisal wheel polishing of the workpiece has a high surface finish and no blackening or contamination.

[0062] The present invention will be further described below with reference to the embodiments. However, the embodiments described below are only for illustrating the content of the present invention and are not intended to limit it. Therefore, any changes that are equivalent in meaning and scope to the claims of the present invention should be considered to be included within the scope of the claims.

[0063] Example 1

[0064] A sisal polishing wheel setting adhesive, the formulation of which, by weight, comprises: 100 parts of vinyl acetate-acrylic emulsion, 10 parts of silica sol (30% solid content, 20nm particle size), 15 parts of ethylene-vinyl acetate copolymer emulsion (70% vinyl acetate content, 50% solid content), and 1 part of thickener (ASE-60); wherein, the vinyl acetate-acrylic emulsion, by weight, comprises:

[0065] 100 parts deionized water; 60 parts vinyl acetate (VAc); 3 parts butyl acrylate (BA); 15 parts methyl methacrylate (MMA); 2 parts acrylic acid (AA); 2 parts γ-methacryloyloxypropyltrimethoxysilane (KH-570); 1 part anionic emulsifier sodium dodecyl sulfate (SDS); 0.5 parts nonionic emulsifier alkylphenol polyoxyethylene ether (OP-10); 0.15 parts oxidizing agent sodium persulfate (NaPS); 0.15 parts reducing agent sodium bisulfite (NaHSO3).

[0066] Its preparation method includes the following steps:

[0067] Preparation of acrylic emulsion:

[0068] a. Pre-emulsification: Add 80 parts of deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomer, 0.8 parts of SDS and OP-10 to a pre-emulsification tank according to the formula, and stir at 25℃ and 1200 rpm for 30 minutes to obtain a milky white and uniform pre-emulsion A;

[0069] b. Seed polymerization: Add 20 parts of deionized water and 0.2 parts of SDS to a four-necked reactor equipped with a stirrer, condenser, thermometer and dropping device. Turn on the stirrer and heat to 80°C. Add 10% of the total mass of pre-emulsion A, and then simultaneously add 50% of NaPS (dissolved in 5 parts of water) and 50% of NaHSO3 (dissolved in 5 parts of water). Maintain the reaction at 80°C for 30 minutes. The system will show blue light, indicating that seed latex particles have formed.

[0070] c. Droplet polymerization: Adjust the reaction temperature to 78℃, and start to drop the remaining 90% of pre-emulsion A, as well as the remaining 50% NaPS aqueous solution and 50% NaHSO3 aqueous solution simultaneously. Control the dropping rate so that the total dropping time is about 270 minutes, and maintain the temperature at 78±1℃ during the dropping process.

[0071] d. Post-processing: After the addition is complete, continue to maintain the temperature at 78℃ for 50 minutes. Then, cool the mixture with cooling water to 50℃, filter the material, and obtain functionalized vinyl acetate-acrylic emulsion B with a solid content of approximately 45%.

[0072] Formulation of the setting adhesive: Place 100 parts of vinyl acetate-acrylic emulsion B in a mixing tank, and slowly add 10 parts of silica sol and 15 parts of VAE emulsion while stirring at 300 rpm. After the addition is complete, increase the speed to 600 rpm and stir for 20 minutes to mix evenly. Finally, while continuing to stir, slowly add 1 part of thickener ASE-60 pre-diluted with an appropriate amount of water to adjust the viscosity of the system to approximately 10000 mPa·s (25℃), thus obtaining the sisal polishing wheel setting adhesive C1.

[0073] Example 2

[0074] A sisal polishing wheel shaping adhesive, the formulation of which differs from that of Example 1 in that the amount of VAc is adjusted to 70 parts and the amount of MMA is adjusted to 10 parts, in order to examine the effect of the reduced proportion of hard monomers. The remaining components and preparation process are the same as those of Example 1, and sisal polishing wheel shaping adhesive C2 is obtained.

[0075] Example 3

[0076] A sisal polishing wheel shaping adhesive, the formulation of which differs from that of Example 1, is that only the amount of silica sol is increased to 20 parts in order to examine the effect of increased inorganic reinforcing phase content. The other components and preparation process are the same as those of Example 1, and sisal polishing wheel shaping adhesive C3 is obtained.

[0077] Comparative Example 1 (Commercially available white glue type I (RF601))

[0078] Commercially available polyvinyl acetate emulsion (solid content approximately 45%, Tg approximately 28°C) is used as the setting agent, labeled D1. This product does not contain modified components such as MMA, functional monomers, silica sol, and VAE, and represents the most basic existing technology.

[0079] Comparative Example 2 (without silane coupling agent KH-570)

[0080] A sisal polishing wheel setting adhesive, the formulation of which differs from that of Example 1, is that KH-570 functional monomer is not added during the preparation of the vinyl acetate emulsion, thus producing setting adhesive D2.

[0081] Comparative Example 3 (without silica sol)

[0082] A sisal polishing wheel shaping adhesive, the formulation of which differs from that of Example 1 in that no silica sol is added during the compounding of the shaping adhesive, thus producing shaping adhesive D3.

[0083] Comparative Example 4 (VAE-free emulsion)

[0084] A sisal polishing wheel setting adhesive, the formulation of which differs from that of Example 1 in that VAE emulsion is not added during the compounding of the setting adhesive, thus producing setting adhesive D4.

[0085] Comparative Example 5 (MMA dosage too low)

[0086] A sisal polishing wheel setting adhesive, the formulation of which differs from that of Example 1, is that the amount of MMA is changed from 15 parts to 2 parts, and the reduced mass of 13 parts is made up with an equal amount of VAc (i.e., VAc becomes 73 parts), thus obtaining setting adhesive D5.

[0087] Comparative Example 6 (simple physical mixing of silica sol and vinyl acetate emulsion)

[0088] This comparative example aims to verify the importance of the synergistic effect of introducing functional monomers through in-situ polymerization and the subsequent addition of silica sol. The specific method is as follows: First, an acrylic emulsion was prepared according to the formulation and process of Comparative Example 2 (without KH-570). Then, during the compounding stage, in addition to adding silica sol, VAE, and thickener, 2% (by weight of KH-570) of the total emulsion mass was added (directly added, without participating in polymerization). After thorough mixing, sizing agent D6 was obtained. The final content of each component in this formulation was exactly the same as in Example 1, but KH-570 did not participate in copolymerization; it was only physically incorporated.

[0089] The film properties and simulated sisal wheel properties of the sizing adhesives prepared in Examples 1-3 and Comparative Examples 1-6 were tested. The film properties were as follows: each sizing adhesive was cast into a film, dried at room temperature for 7 days, and then cured in an oven at 100°C for 2 hours to obtain a film with a thickness of about 0.5 mm.

[0090] Wear amount: According to GB / T 1768-2006 standard, the wear was tested using a Taber abrasion tester (CS-10 grinding wheel, 1000g load, 1000 rpm), and the mass loss was calculated.

[0091] Application performance (simulated sisal wheel): Prepare samples by impregnating sisal fiber felt of the same specification in various shaping adhesives, controlling the amount of adhesive to be consistent (dry adhesive content accounts for 30% of the fiber mass), take it out and mold it into a standard round sample at 100℃, and then cure it at 120℃ for 2 hours.

[0092] Tensile shear strength: Two specimens are bonded together with the corresponding sizing adhesive, and after curing, they are tested according to GB / T 7124-2008 standard.

[0093] Temperature resistance: The cured sisal wheel sample was placed in a 130℃ oven and left to stand for 24 hours. After cooling, the surface condition (whether it is sticky or powdery) was observed and the residual tensile and shear strength was tested. The strength retention rate was calculated.

[0094] Actual polishing life: Standard sisal polishing wheels made of various shaped adhesives are installed on a fixed polishing machine and polished with constant pressure and speed on 304 stainless steel plates. The time until the diameter of the polishing wheel wears more than 15% or serious burrs or blackening of the workpiece is recorded as the service life.

[0095] The performance test results are shown in Table 1.

[0096] Table 1 Performance Test Results

[0097]

[0098] Table 1's performance test data strongly demonstrates the significant effects of the technical solution of this invention (Examples 1-3). Compared with all comparative examples, the product of this invention achieves a comprehensive and significant improvement in core indicators such as high temperature resistance, bonding strength, wear resistance, and service life. Comparative Example 1 (commercially available ordinary white glue), representing traditional technology, has the lowest performance in all aspects. In contrast, the product of this invention increases the tensile shear strength from 5.0 MPa to 8.6-8.9 MPa (an increase of over 70%), increases the strength retention rate after 130℃ heat aging from 58% to 97-99%, significantly extends the polishing wheel service life from 30 hours to 78-85 hours (an increase of over 160%), and reduces the adhesive film wear by approximately 65-75%. This signifies that this invention has successfully broken through the performance bottleneck of traditional water-based adhesives in high-end industrial applications. The above data also demonstrates that this invention does not rely on the enhancement of a single component, but rather achieves a synergistic effect through the precise formulation and process combination of vinyl acetate emulsion matrix, silica sol, VAE emulsion, and functional monomers. The absence of any key component (e.g., Comparative Examples 2-4), improper formulation (e.g., Comparative Example 5), or changes in key processes (e.g., Comparative Example 6) will lead to a significant decrease in overall performance to varying degrees. This, in turn, confirms the necessity and innovation of the complete technical solution of this invention. This invention successfully solves the traditional contradiction of adhesives being either too hard and brittle or too soft and sticky. The embodiments achieve high hardness (manifested as low wear and high tensile shear strength) while maintaining excellent toughness (through VAE toughening) and interfacial stability, thereby achieving long lifespan and high-quality surface treatment effects (bright and non-blackening devices) under harsh polishing conditions.

[0099] Specifically, as can be seen from the data in Table 1, the performance of Comparative Example 1 (Type I white glue (RF601)) is as follows: all test indicators are poor, the strength retention rate after heat aging is only 58%, the service life is only 30 hours, and the wear amount is as high as 0.095g.

[0100] Mechanism Analysis: The comparative example is a homopolymer of pure polyvinyl acetate (PVAc), which has a highly polar molecular chain containing a large number of ester groups. It readily forms hydrogen bonds with water molecules, resulting in an extremely high equilibrium water absorption rate (typically >30%). This high water absorption rate causes a sharp decrease in mechanical strength in humid environments or under heat (where water acts as a plasticizer). Its glass transition temperature (Tg) is low (approximately 28°C). Under the high temperatures generated during polishing (>120°C), the polymer chain segments move violently, causing severe softening and stickiness of the adhesive film, resulting in loss of binding force on the fibers, leading to fraying and blackening of the workpiece. Simultaneously, the bond between PVAc and sisal fibers relies solely on weak physical adsorption and limited hydrogen bonding, resulting in weak interfacial adhesion. Furthermore, PVAc itself has low hardness and is not wear-resistant. Therefore, it embodies the inherent defects of traditional water-based adhesives in terms of temperature resistance, water resistance, wear resistance, and interfacial adhesion, which is the target of this invention for improvement and replacement.

[0101] As shown in Table 1, the performance of Comparative Example 2 (without silane coupling agent KH-570) is as follows: the tensile shear strength (7.2 MPa) is significantly lower than that of Example 1 (8.8 MPa), a decrease of approximately 18%; the polishing wheel life (65 h) is also significantly shortened; and its aging resistance retention rate (92%) is still acceptable. This indicates that KH-570 plays a crucial role as a "molecular bridge" in this invention. The vinyl group at one end of its molecule participates in copolymerization, chemically bonding the siloxane structural unit to the polymer backbone; the methoxy group at the other end hydrolyzes into silanol groups during curing, which can condense with the silanol groups in the silica sol and also undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of sisal fibers, forming a strong Si-OC covalent bond. The absence of KH-570 means that this high-strength, water- and heat-resistant chemical bond connection between the adhesive and the fiber is lost, relying mainly on physical-mechanical interlocking and hydrogen bonds, resulting in a significant reduction in interfacial bonding strength. Furthermore, the siloxane structures bonded to the polymer chains can also improve the hydrophobicity of the polymer and reduce water absorption. Therefore, the decrease in strength and durability in Comparative Example 2 directly demonstrates the core role of functional monomers in strengthening the interface through chemical bonding.

[0102] As can be seen from the data in Table 1, the performance of Comparative Example 3 (without silica sol) is as follows: significantly worse heat resistance (strength retention rate 72%), deteriorated wear resistance (wear loss 0.055g), lower tensile shear strength (6.5 MPa), and significantly shortened lifespan (48h). This indicates that silica sol provides three key roles in this invention: an inorganic heat-resistant skeleton, a hard wear-resistant filler, and an interfacial physical reinforcing agent. Temperature resistance: The abundant silanol groups on the surface of nano-SiO2 particles form a dense hydrogen bond network with the carboxyl and hydroxyl groups on the polymer chains. The thermal stability of this inorganic network is much higher than that of organic polymer chains. When heated, it can effectively "pin" and inhibit the movement of polymer chains, thereby significantly improving the heat distortion temperature and high-temperature modulus of the adhesive film. This is the main reason for the improved heat aging resistance. Abrasion resistance: The high-hardness nano-SiO2 particles are uniformly dispersed in the polymer matrix, directly bearing the friction load, which greatly improves the surface hardness and scratch resistance of the adhesive film. Interface and strength: The nanoparticles can penetrate into the micropores of sisal fibers, producing an anchoring effect and enhancing physical interlocking. At the same time, the silanol groups on their surface form strong hydrogen bonds with the hydroxyl groups of the fibers, enhancing interfacial interactions. Without silica sol, the inorganic reinforcing phase is lost, and the adhesive system reverts to a common organic polymer blend. Its heat resistance, hardness, and physical anchoring ability to fibers naturally return to a lower level.

[0103] As shown in Table 1, Comparative Example 4 (without VAE emulsion) exhibits the following performance characteristics: acceptable tensile shear strength (8.0 MPa), excellent heat retention rate (98%), and very low wear (0.027 g). However, its polishing wheel life (70 h) is significantly lower than that of Example 1 (82 h). This indicates that the VAE emulsion primarily functions as a toughening agent and wetting agent in this invention. The ethylene segments in the VAE molecular chain endow it with excellent flexibility and elasticity. In the continuous phase composed of relatively hard vinyl acetate-silica sol, VAE can form dispersed "islands" or jointly construct an interpenetrating network (IPN). When the adhesive layer is subjected to repeated impacts and shear stresses during polishing, the flexible VAE phase can absorb and disperse energy through deformation, preventing the initiation and propagation of microcracks, thereby improving the fracture toughness and fatigue resistance of the adhesive layer. Due to the lack of this toughening mechanism, the adhesive layer in Comparative Example 4 is brittle and more prone to internal damage and accumulation under long-term dynamic load, leading to premature failure and thus shortened lifespan. VAE emulsion has excellent wettability on porous and rough surfaces, which can promote the rapid and deep penetration of the adhesive into the sisal fiber bundles, ensuring a more uniform and stronger bonding foundation.

[0104] As can be seen from the data in Table 1, the performance of Comparative Example 5 (with too low MMA content) is as follows: all properties are deteriorated: strength retention (75%), tensile shear strength (6.0 MPa), abrasion resistance (0.070 g), and lifespan (40 h) are all far inferior to those of the Example. This indicates that methyl methacrylate (MMA), as a "hard monomer," is the core component for improving the rigidity, heat resistance, and water resistance of the product of this invention; the Tg of MMA homopolymer is as high as 105℃, and copolymerizing it with VAc can effectively increase the overall Tg of the copolymer, which is the basis for heat resistance; the side chain of MMA is a hydrophobic methyl group, and when it reaches a certain proportion in the polymer chain, it can form an effective hydrophobic shielding layer around the molecular chain, which greatly hinders the diffusion and penetration of water molecules into the polymer interior, thereby reducing the equilibrium water absorption rate of the film from 40% of pure PVAc to below 5%. Low water absorption rate is the key to maintaining strength stability and aging resistance at high temperatures; MMA contributes to the rigidity of the chain segments, improving the hardness and compressive modulus of the film. In Comparative Example 5, the amount of MMA was only 2 parts (far below the optimized range of 10-20 parts), which made the copolymer properties closer to PVAc. As a result, its heat resistance, moisture resistance and hardness were lost, and its performance was closer to that of Comparative Example 1, but slightly better than pure PVAc (because there were still a small amount of BA and AA).

[0105] As can be seen from the data in Table 1, the performance of Comparative Example 6 (KH-570 physically incorporated, non-copolymerized) is as follows: its performance (strength 7.5 MPa, retention rate 85%, wear 0.040 g, lifespan 60 h) is between that of Example 1 and Comparative Example 2, but significantly inferior to Example 1. The design of this comparative example is highly convincing, revealing the essential difference and importance between in-situ chemical copolymerization and simple physical blending. In Example 1, KH-570 participates in polymerization through double bonds, and its silanoxy groups are uniformly and firmly chemically bonded to specific positions on the polymer chain, becoming an inherent part of the polymer. During curing, these "pre-defined" reaction sites can react efficiently and directionally with the fiber surface; in Comparative Example 6, KH-570 is physically dispersed in the system as a small molecule, which may lead to uneven distribution and easy migration to the surface or phase interface. Although it can also react with fibers and silica sol, it cannot "anchor" the large polymer chain to the fiber because it is not chemically linked to the polymer backbone. It exists more like a separate "small molecule glue" in the interfacial region, with a connection efficiency and load-bearing capacity far lower than that of an "anchor point" connected to the entire polymer network through chemical bonds. Therefore, Comparative Example 6 outperforms Comparative Example 2, which has no KH-570 at all (proving that physical addition also has some effect), but is significantly inferior to Example 1, which involves KH-570 in copolymerization. This strongly demonstrates the inventiveness and necessity of the claim to introduce functional monomers into the polymer chain through copolymerization, and is the optimal process route to achieve a high-strength, high-durability interface.

[0106] Figure 2 This is a comparison of the wear levels of the sisal polishing wheels prepared with the shaped adhesive in Example 1 and Comparative Example 1 after polishing for 1 hour. Results: The sisal wheel on the left (marked in white or corresponding to Example 1) retains a relatively intact shape after polishing, with uniform wear, and the surface of the metal workpiece polished by it is bright without any blackening. The sisal wheel on the right (corresponding to Comparative Example 1) shows obvious fiber shedding, loose structure, and may even be accompanied by charred adhesive adhesion; the surface of the workpiece polished by it shows dark streaks or is generally dark (blackened).

[0107] This comparative diagram intuitively and vividly demonstrates the core advantages of the sizing adhesive of this invention in terms of high-temperature resistance and wear resistance. High-temperature resistance: Under the high temperatures generated by high-speed polishing, the adhesive film of Comparative Example 1 (ordinary white glue) undergoes severe softening, stickiness, and even thermal degradation. The softened adhesive cannot effectively bind the sisal fibers, resulting in "flying fibers"; at the same time, the viscous, degraded adhesive and detached fibers contaminate the high-temperature metal surface, forming a visible "blackening" phenomenon under frictional oxidation. In contrast, the adhesive film of Example 1, due to the heat-resistant network constructed from MMA and silica sol, can maintain sufficient hardness and morphological stability at the same high temperature, thereby avoiding adhesive softening and contamination and abnormal fiber shedding, ensuring the smoothness of the workpiece surface. Wear resistance and structural integrity: The adhesive film of Comparative Example 1 has poor hardness and wear resistance, resulting in not only rapid wear itself but also a rapid decrease in the holding force of the fibers during friction, causing the wheel structure to collapse (fibers falling off in pieces). The adhesive film of Example 1 has high hardness and good wear resistance, and is firmly bonded to the fiber (chemical bonds + physical interlocking). Therefore, the wear mode is uniform and progressive, and the wheel structure remains intact during the test, showing a longer service life and stable polishing effect. Figure 2 This is a visual demonstration of the performance data (such as wear, life, and workpiece effect) in Table 1, vividly illustrating how the sizing adhesive of this invention solves the two major pain points of traditional adhesives—thermal softening and poor wear resistance—ultimately achieving the dual goals of improving polishing wheel life and ensuring polishing quality.

[0108] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A sisal buffing wheel sizing gum, characterized by, According to mass parts, it comprises: 100 parts of vinyl acetate-acrylic emulsion, 5-20 parts of silica sol, 10-20 parts of ethylene-vinyl acetate copolymer emulsion, and 0.5-2 parts of thickening agent; the raw materials of the vinyl acetate-acrylic emulsion comprise: 100 parts of deionized water; 50-70 parts of vinyl acetate; 1-6 parts of butyl acrylate; 10-20 parts of methyl methacrylate; 1-3 parts of acrylic acid; 1-10 parts of functional monomer; 0.5-2 parts of anionic emulsifier; 0.1-2 parts of nonionic emulsifier; 0.1-0.2 parts of oxidant; 0.1-0.2 parts of reducing agent; the functional monomer is gamma-methacryloyloxypropyl trimethoxysilane, the vinyl group at one end of the gamma-methacryloyloxypropyl trimethoxysilane participates in emulsion copolymerization; the particle size of the silica sol is 10-30 nm, and the solid content is 20-40%; the vinyl acetate content of the ethylene-vinyl acetate copolymer emulsion is 65-75%, and the solid content is 45-55%.

2. The sisal buffing wheel sizing gum according to claim 1, characterized by, The anionic emulsifier is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, fatty alcohol polyoxyethylene ether sulfosuccinic acid monoester disodium, and sodium dodecyl diphenyl ether disulfonate.

3. The sisal buffing wheel sizing gum according to claim 1, characterized by, The nonionic emulsifier is one or both of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

4. The sisal buffing wheel sizing gum according to claim 1, characterized by, The oxidant is one or more of sodium persulfate, ammonium persulfate, and potassium persulfate; the reducing agent is a mixture of one or both of formaldehyde sodium sulfoxylate and sodium bisulfite.

5. The sisal buffing wheel sizing gum according to claim 1, wherein The thickening agent is a polyacrylic alkali-swellable thickening agent or a polyurethane associative thickening agent.

6. A process for the preparation of a sisal buffing wheel sizing gum as claimed in any one of claims 1 to 5, characterized in that, The method comprises the steps of: Preparation of vinyl acetate-acrylic emulsion: Pre-emulsification: according to the proportion, 60-80% of the total mass of deionized water, vinyl acetate, butyl acrylate, methyl methacrylate, acrylic acid, functional monomer, 60-80% of the total mass of anionic emulsifier, and nonionic emulsifier are added to a pre-emulsification kettle, stirred at a speed of 800-1500 rpm at normal temperature and pressure for 20-40 minutes to obtain a uniform and stable pre-emulsion; Seed polymerization: the remaining deionized water and the remaining anionic emulsifier are added to the reaction kettle, heated to 78-82°C, then 5-15% of the total mass of the pre-emulsion is added as a seed solution, followed by the addition of 40-60% of the total mass of the oxidant and 40-60% of the total mass of the reducing agent, and the reaction is carried out at 78-82°C for 20-40 minutes; Drop polymerization: the reaction temperature is maintained at 75-80°C, while the remaining pre-emulsion is added dropwise to the reaction kettle, and the remaining oxidant and reducing agent are added dropwise simultaneously, and the dropwise addition time is controlled to be 240-300 minutes; Post-treatment: after the dropwise addition is completed, the temperature is maintained at 75-80°C for 40-60 minutes, then cooled to 45-55°C, discharged, and the vinyl acetate-acrylic emulsion is obtained; Compound of sizing adhesive: the vinyl acetate-acrylic emulsion, silica sol, ethylene-vinyl acetate copolymer emulsion, and thickening agent are mixed uniformly under stirring according to the proportion, and the sisal polishing wheel sizing adhesive is obtained.

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