Method for producing environment-friendly abrasive paper by adopting water-based binder

Abstract

The invention relates to the technical field of abrasive paper production, in particular to a method for producing environment-friendly abrasive paper by adopting a water-based binder, which overcomes the defects in the prior art and comprises the following steps: preparing a water-based binder composition, coating a layer of cationic primer on the surface of a base material to form a primer layer, and drying the primer layer to obtain the environment-friendly abrasive paper. The method comprises the following steps: coating an anionic water-based binder composition on a dried priming coat, combining interface charge matching design of a cationic priming coat and an anionic binder, realizing vertical embedding of an abrasive material through high-voltage electrostatic sand planting, and finally coating a water-based composite adhesive layer on the surface of a sand layer after sand planting. According to the method, an organic-inorganic interpenetrating network structure is constructed in situ, the water resistance, the high-temperature size stability and the abrasive holding force of an adhesive film are remarkably improved, and the problems of sand falling, softening and the like of water-based abrasive paper in high-load dry / wet grinding are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of sandpaper production technology, and in particular to an environmentally friendly sandpaper production method using a water-based binder. Background Technology

[0002] With increasingly stringent environmental regulations and the popularization of green manufacturing concepts, the application of water-based binders in sandpaper production is gradually becoming an industry trend. Compared with traditional solvent-based adhesives, water-based systems have advantages such as low VOC emissions, non-toxicity, and safe operation. However, existing water-based binders still face many challenges in practical applications, especially under high-load dry or wet grinding conditions. Their adhesive films are prone to softening, sand shedding, poor water resistance, and insufficient dimensional stability at high temperatures, which restricts the promotion and application of water-based sandpaper in high-end sanding fields.

[0003] A search revealed a patent with publication number CN109290971B (authorization announcement date: February 11, 2020) proposing a water-based environmentally friendly green sandpaper and its production method. This solution improves the overall performance of the sandpaper by setting a waterproof and anti-clogging treatment layer and using a water-based system as the bonding base. However, the adhesive used in this technology mainly relies on physical drying to form a film, without introducing chemical cross-linking structures or functional reinforcing components. This results in a low cross-linking density of the adhesive film, exhibiting a certain degree of plasticization tendency under wet or high-temperature conditions, affecting the anchoring strength of the abrasive particles, and thus limiting the stability and service life of the sandpaper during high-load sanding. Furthermore, while the solution explicitly uses a water-based system, it does not provide specific process optimization measures for issues such as insufficient initial adhesion, abrasive distribution uniformity control, and substrate-adhesive interface bonding faced by water-based adhesives during the sand-planting stage. Its production method still follows conventional coating and sand-planting processes, lacking targeted technical means in terms of abrasive embedding depth, perpendicularity, and adhesion firmness, which may affect the sanding performance and service life of the final product.

[0004] While existing technologies have adopted water-based adhesives to meet environmental protection requirements, they still lack systematic solutions in areas such as compatibility with sand-planting processes, strengthening interfacial bonding, and improving the efficiency of electrostatic sand-planting. Furthermore, current water-based sandpaper bonding technologies lack effective integration of organic-inorganic synergistic strengthening mechanisms in film structure design, particularly in improving the crosslinking density, water resistance, and high-temperature dimensional stability of the adhesive film.

[0005] To address these issues, we provide an environmentally friendly sandpaper production method using water-based binders. Summary of the Invention

[0006] The purpose of this invention is to provide an environmentally friendly sandpaper production method using a water-based binder to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an environmentally friendly sandpaper production method using a water-based binder, comprising the following steps: S10: Prepare an aqueous adhesive composition comprising an aqueous acrylic emulsion, nano silica sol, a bifunctional silane coupling agent, an aqueous cyclopropane, a pH adjuster, deionized water, a film-forming aid, and a stabilizer. Adjust the pH of the system to 7.5-9.0 using the pH adjuster to obtain an anionic aqueous adhesive composition. S20: Apply a layer of cationic primer to the surface of the substrate to form a base coating, with the coating amount controlled at 5-15g / m². S30: Place the substrate coated with the primer in a hot air drying tunnel at 60-70℃ and dry for 1-2 minutes; S40: Apply an anionic waterborne adhesive composition to a base coating that has been dried, controlling its viscosity to be 80-120 mPa·s, the coating amount to be 20-40 g / m², and the surface tension after coating to be 35-45 mN / m. S50: After the abrasive particles are preheated to 110-120℃, they are fed into a high-voltage electrostatic spray gun. A DC voltage of +30 to +50kV is applied at the nozzle of the spray gun to make the abrasive particles positively charged and sprayed vertically onto the surface of the grounded substrate. S60: The semi-finished product with sand planting completed will be subjected to pre-drying and high-temperature curing treatment in sequence. The pre-drying condition is 80℃ for 2 minutes, and the high-temperature curing condition is 120-140℃ for 5-8 minutes. S70: A water-based adhesive layer is coated on the surface of the sand layer after sand planting. The water-based adhesive layer is composed of modified water-based phenolic resin emulsion, nano alumina dispersion and crosslinking accelerator. The coating thickness is 15-25μm. After curing at 140℃-170℃ for 6-10 minutes, the finished environmentally friendly sandpaper is obtained.

[0008] Among them, the aqueous acrylic emulsion is a core-shell structured acrylic copolymer emulsion with a glass transition temperature of 35-65℃, a solid content of 40%-55%, and an average particle size of 80-150 nanometers. Nano-silica sol is an alkaline or acidic colloidal silica dispersion, wherein the average particle size of the silica particles is 5-30 nanometers and the solid content is 10%-30%. The bifunctional silane coupling agent is composed of any two selected from KH-570 (γ-methacryloyloxypropyltrimethoxysilane), KH-560 (γ-glycidyl etheroxypropyltrimethoxysilane) or KH-791 (N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane) in a volume ratio of 1:1. The pH adjuster is one or more of ammonia, triethanolamine, or sodium bicarbonate, used to adjust the pH value of the aqueous adhesive composition to 7.5-9.0; the film-forming aid is dodecyl alcohol ester; and the stabilizer is propylene glycol.

[0009] In some embodiments, in step S10, the aqueous adhesive composition comprises the following components by weight: 65-75 parts of aqueous acrylic emulsion, 8-12 parts of nano silica sol, 0.4-0.8 parts of bifunctional silane coupling agent, an appropriate amount of pH adjuster, 0.8-2.0 parts of aqueous cyclopropane, 0.8-1.5 parts of film-forming aid, 1.5-2.5 parts of stabilizer, and the balance being deionized water, to a total of 100 parts.

[0010] In some embodiments, the preparation process of the aqueous adhesive composition includes: Q1. First, add deionized water to the mixing container and stir at 300 rpm for 5 minutes. Then, slowly add the stabilizer and continue stirring for 8-10 minutes until completely dissolved. Keep the stirring speed constant. Add nano-silica sol dropwise to the container at a rate of 1-2 mL / min. After the addition is complete, increase the stirring speed to 350 rpm and continue stirring for 15 minutes. Then, add some pH adjuster to adjust the pH of the system to 7.5-8.5 and stir for 10 minutes until the pH is stable. Q2. Slowly add the bifunctional silane coupling agent dropwise into the container, with the dropping rate controlled at 0.5-1 mL / min. After the addition is complete, increase the stirring speed to 400 rpm and continue stirring for 20-25 minutes to allow it to fully hydrolyze and form a stable inorganic-organic transition layer. Q3. Reduce the stirring speed to 350 rpm and slowly add the water-based acrylic emulsion in 3-4 batches, stirring for 5 minutes after each addition. After all the emulsion has been added, keep stirring for 15 minutes until the system is completely homogeneous. Then, add pH adjuster to adjust the pH to 7.5-9.0 and stir for 10 minutes to keep the pH stable. Q4. Keep the stirring speed at 350 rpm and slowly add water-based cyclopropane dropwise at a rate of 0.3-0.5 mL / min. After the addition is complete, increase the stirring speed to 450 rpm and continue stirring for 25-30 minutes to ensure that the water-based cyclopropane is fully dispersed in the system. Q5. Reduce the stirring speed to 400 rpm, add the film-forming aid to the container, stir for 8-10 minutes to evenly disperse the film-forming aid, then stop stirring and let the system stand for 5-6 minutes to remove surface air bubbles. Then sieve through a 100-200 mesh screen to obtain the anionic water-based adhesive composition.

[0011] In some embodiments, in step S20, the cationic primer is applied by roller coating, blade coating, or spray coating, and the coating amount is controlled at 5-15 g / m².

[0012] In some embodiments, in step S30, the air velocity in the hot air drying duct is controlled at 2-5 m / s to ensure that the moisture in the primer evaporates quickly without thermal degradation, forming a continuous, dense cationic interface layer with a permanent positive charge.

[0013] In some embodiments, in step S40, the anionic aqueous adhesive composition is applied by roller coating or blade coating, the coating amount is controlled at 20-40 g / m², and the surface tension after coating is controlled at 35-45 mN / m.

[0014] In some embodiments, in step S50, the abrasive particles are one or more of alumina, silicon carbide, zirconium corundum, or ceramic abrasive; the abrasive particles are preheated at 100-120°C for 10-30 minutes before entering the high-pressure electrostatic spray gun to reduce the surface adsorbed moisture content to below 0.1%.

[0015] In some embodiments, in step S50, the nozzle diameter of the high-voltage electrostatic spray gun is 1.0 to 2.5 mm, the spray distance is 150 to 300 mm, the spray pressure is 0.3 to 0.6 MPa, and the abrasive delivery rate is 50-150 g / min.

[0016] In some embodiments, in step S60, pre-drying is performed using infrared heating or hot air convection with a heating rate of 5-10°C / min; high-temperature curing is performed using a hot air circulating oven with a heating rate of 3-8°C / min, and the oxygen concentration is controlled below 5% during curing to inhibit the oxidative degradation of the adhesive.

[0017] In some embodiments, in step S70, the water-based adhesive composition used for the topcoat layer can be the same as that for the base coat layer, or a formulation with a higher crosslinking density can be used, that is, the amount of bifunctional silane coupling agent is increased to 1%-5% on the basis of the original formulation, and 0.1%-0.5% of water-based blocked isocyanate crosslinking agent is added.

[0018] In some embodiments, in step S70, the coating amount of the adhesive layer is 15-30 g / m², and after coating, it is heat-cured at 120-150℃ for 5-10 minutes to form a dense coating structure that wraps the root of the abrasive particles and fills the gaps between the particles.

[0019] Among them, the interface layer formed by the cationic primer after drying contains a large number of quaternary ammonium salt cations or protonated amino groups, and its surface zeta potential is +20 to +50mV; the anionic waterborne adhesive composition has a zeta potential of -30 to -60mV because the acrylic emulsion contains carboxyl or sulfonic acid groups. When the two come into contact, they generate a strong electrostatic attraction, which makes the adhesive spread more evenly on the substrate surface, and the contact angle is reduced from 70°-85° in the untreated case to 30°-45°.

[0020] Furthermore, the alkoxy groups in the bifunctional silane coupling agent undergo hydrolysis in an aqueous system to generate silanol groups. These silanol groups condense with the hydroxyl groups on the surface of the nano-silica sol to form Si-O-Si bonds. Simultaneously, the organic functional groups (such as methacryloyloxy, epoxy, or amino groups) at the other end undergo free radical copolymerization or ring-opening addition reactions with the polymer chains in the acrylic emulsion. During the thermosetting process at 60-140℃, a three-dimensional organic-inorganic interpenetrating network structure is constructed in situ. In this structure, the inorganic phase uses nano-silica as nodes, and the organic phase uses acrylate copolymers as the skeleton. The two phases interpenetrate to form a composite adhesive film with high crosslinking density, high modulus, and low water absorption.

[0021] In some embodiments, in step S70, the modified waterborne phenolic resin emulsion is prepared by emulsifying linear phenolic resin with polyvinyl alcohol formaldehyde under alkaline conditions, and has a solid content of 35%-45%; the nano-alumina dispersion has a particle size of 20-60 nm, a solid content of 5%-15%, and a mass fraction of 2%-6% in the composite layer; the crosslinking accelerator is hexamethylenetetramine, and the amount used is 3%-7% of the solid content of the modified phenolic resin.

[0022] In some embodiments, the preparation process and raw materials of the modified waterborne phenolic resin emulsion are as follows: Raw materials for preparation (based on 1000g of finished emulsion): 320-340 parts of linear phenolic resin (number average molecular weight 800-1500g / mol, softening point 80-100℃, free phenol content <0.1%), 85-95 parts of polyvinyl alcohol formaldehyde (degree of polymerization 1700-2000, degree of acetalization 30%-40%), 520-540 parts of deionized water, 16-18 parts of 10% sodium hydroxide aqueous solution (alkalinity regulator) (based on pure product), 6-7 parts of co-emulsifier (AEO-9), 1.5 parts of defoamer (organosilicon), and 9 parts of stabilizer (ethylene glycol).

[0023] Preparation process: Linear phenolic resin is preheated and melted at 85-90℃, and polyvinyl alcohol formal is dissolved in 1 / 3 deionized water at 65-70℃ until transparent; the molten phenolic resin is mixed with the polyvinyl alcohol formal aqueous solution, a co-emulsifier is added, and the mixture is stirred at 250r / min for 60min; 10% sodium hydroxide aqueous solution is slowly added dropwise to adjust the pH to 9.0-10.0, and the mixture is stirred at 70-75℃ and 250r / min for 100-110min to emulsify; the temperature is lowered to 45-50℃, a defoamer and a stabilizer are added, and the mixture is stirred at 150r / min for 60min to mature; the mixture is cooled to room temperature and filtered to obtain a modified waterborne phenolic resin emulsion with a solid content of 35%-45%.

[0024] When nano-silica sol is acidic colloidal silica, its pH value is 2-4, and its surface is rich in silanol groups, resulting in high condensation reaction activity with silane coupling agents. When it is alkaline colloidal silica, its pH value is 8-10, and the particle surface is negatively charged, resulting in good compatibility with anionic emulsions. The condensation reaction can be promoted by adjusting the pH of the system to neutral.

[0025] The core layer of the core-shell structured acrylate copolymer emulsion has a glass transition temperature of 10-30℃, while the shell layer has a glass transition temperature of 60-90℃. During film formation, the shell layer preferentially aggregates on the particle surface, enhancing initial adhesion, while the core layer provides flexibility to prevent film brittleness.

[0026] During the high-voltage electrostatic sand planting process, the potential of the grounded substrate is 0V, and the interface potential gradient formed by the primer and water-based adhesive is -100 to -300V / mm. This negative potential field has a directional guiding effect on the positively charged abrasive particles, making their movement trajectory perpendicular to the substrate surface, with an embedding angle deviation of less than 5°.

[0027] The charge-to-mass ratio of abrasive particles in an electrostatic field is controlled at 0.5-2.0 μC / g. By adjusting the spray gun voltage and air pressure, a balance between charging efficiency and flight speed is achieved, avoiding particle repulsion due to excessive charge or rebound due to excessive speed.

[0028] In some embodiments, the substrate is one of kraft paper, polyester film, nonwoven fabric or composite paper, and its surface is treated with corona or plasma to increase the surface energy to 45-60 mN / m to enhance the physical anchoring effect with the cationic primer.

[0029] The water-based adhesive composition exhibits storage stability of more than 30 days at 80°C and a viscosity change rate of less than 10%; the water absorption rate of the cured adhesive film is less than 5%, and the tensile strength retention rate is greater than 85% after immersion in water at 90°C for 24 hours; and the dimensional change rate is less than 0.5% after heat aging at 120°C for 72 hours.

[0030] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. This invention utilizes a functionally synergistic charge-matching design between a cationic interface layer and an anionic aqueous binder. This not only enhances the interfacial wetting and bonding between the substrate and the binder, but more importantly, it leverages the interfacial electrostatic field to induce the enrichment and orderly arrangement of functional components (silane coupling agent, nano-silica) in the binder at the interface. This results in the in-situ construction of a three-dimensional organic-inorganic interpenetrating network structure that grows gradient from the interface to the bulk layer during subsequent curing. This structure significantly improves the overall crosslinking density, water resistance, and high-temperature dimensional stability of the adhesive film. Combined with a high-voltage electrostatic abrasive embedding process, it ensures that the abrasive particles are vertically, uniformly, and firmly embedded, thereby maintaining high grinding efficiency, low abrasive shedding rate, and long service life under high-load dry or wet grinding conditions.

[0031] 2. The present invention uses a high-voltage electrostatic sand-planting process to ensure that the abrasive particles are vertically, uniformly and firmly embedded, thereby maintaining high grinding efficiency, low sand shedding rate and long service life under high-load dry grinding or wet grinding conditions.

[0032] 3. This invention adds waterborne cyclopropane to the raw materials of the waterborne adhesive composition. At room temperature, it can undergo a cross-linking reaction with the carboxyl and hydroxyl groups in the acrylic emulsion to form a dense cross-linking network, which significantly improves the water resistance, wet adhesion and wet grinding strength of the product, solving the problem of sand removal in traditional waterborne adhesives during wet grinding. Moreover, it can take effect with a low addition amount, does not affect the stability of the system, and is suitable for anionic environments. Detailed Implementation

[0033] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0034] This application provides a method for producing environmentally friendly sandpaper using a water-based binder. The structure of this environmentally friendly sandpaper, from bottom to top, includes: a substrate layer, a cationic interface layer, a primer layer, a vertically oriented abrasive layer, and a top-coating layer. The substrate layer is one of kraft paper, polyester film, non-woven fabric, or composite paper. The cationic interface layer is formed by drying a cationic primer. Both the primer layer and the top-coating layer are composed of a water-based binder containing an organic-inorganic interpenetrating network structure. The abrasive particles in the abrasive layer are vertically embedded in the primer layer, with an embedding depth of 40%-70% of their particle size, a verticality deviation of less than 5°, and a distribution density deviation of less than 8%.

[0035] Experiment 1: Determination of abrasive orientation, water resistance, thermal stability, and service life of sandpaper Example 1:

[0036] An environmentally friendly sandpaper production method using a water-based binder includes the following steps: S10: Prepare an aqueous adhesive composition, wherein the aqueous adhesive composition comprises, by weight, 65 parts of aqueous acrylic emulsion (i.e., core-shell structured acrylic ester copolymer emulsion, glass transition temperature of 50℃, solid content of 50%, average particle size of 120 nm, core layer Tg of 20℃, and shell layer Tg of 80℃), 8 parts of nano silica sol (pH value of 3.0 (acidic), average particle size of 15 nm, solid content of 20%), 0.4 parts of bifunctional silane coupling agent (selected from KH-570 and KH-560 in a volume ratio of 1:1), appropriate amount of pH adjuster (selected from sodium bicarbonate), 0.8 parts of aqueous cyclopropane, 0.8 parts of film-forming aid (i.e., alcohol ester dodecyl), 1.5 parts of stabilizer (i.e., propylene glycol), and the balance being deionized water.

[0037] S20: 60g / m² corona-treated kraft paper is selected as the substrate, with a surface energy of 52mN / m. A polyethyleneimine aqueous solution (solid content of 8wt%) is coated on its surface using a roller coating method, with the coating amount controlled at 10g / m², to form a cationic base coating.

[0038] S30: Place the substrate coated with the primer in a hot air drying tunnel and dry it for 1.5 minutes at 65°C and a wind speed of 3.5m / s to allow the moisture to evaporate and form a dense cationic interface layer with a surface zeta potential of +35mV.

[0039] S40: The above-mentioned anionic aqueous adhesive composition is applied to the cationic interface layer by a scraping method, with the coating amount controlled at 30g / m² and the surface tension after coating at 40mN / m, to form a primer layer.

[0040] In steps S20 and S40, the cationic undercoat and the anionic binder together constitute a microscopic "charge-induced assembly" system. The functional synergy of this system is reflected in the following two aspects: ① Induced interfacial enrichment and orientation: Polymer micelles, negatively charged nano-silica sols, and hydrolyzed silanediol groups in anionic binders overcome Brownian motion under the influence of a strong positive electric field at the interface (generated by the cationic layer), and migrate directionally to the substrate surface and arrange themselves tightly. This enrichment effect significantly increases the local concentration of reactive functional groups (such as silanol and carboxyl groups) at the interface.

[0041] ② Promoting In-situ Network Construction: In the subsequent drying and curing steps (S60), the pre-enriched and orderly arranged silane coupling agent and nano-silica undergo a condensation reaction at the interface, forming inorganic nanonodes anchored to the substrate surface. These nodes act as "initiation points," extending outward and cross-linking with the polymer chains in the acrylic emulsion, ultimately growing into a three-dimensional interpenetrating network structure that spans the interface layer and the bulk layer. This gradient-structured adhesive film exhibits a gradient change in cross-linking density from the substrate interface to the abrasive layer, ensuring both extremely high adhesion strength to the substrate and providing the toughness and holding power required to encapsulate the abrasive. This synergistic effect cannot be achieved through simple physical mixing or electrostatic attraction.

[0042] S50: Calcined alumina abrasive particles with a particle size of P120 are selected and preheated at 110℃ for 20 minutes to reduce the surface adsorbed moisture content to 0.08%. The preheated abrasive is fed into a high-voltage electrostatic spray gun with a nozzle diameter of 1.8mm, a spray distance of 220mm, a spray pressure of 0.45MPa, and an abrasive feed rate of 100g / min. A +40kV DC voltage is applied at the spray gun outlet to give the abrasive particles a positive charge with a charge-to-mass ratio of 1.2μC / g. The particles are then sprayed vertically onto a grounded substrate surface (potential of 0V). Under the influence of an electrostatic field with an interfacial potential gradient of -200V / mm, the abrasive particles are oriented and vertically embedded to form an abrasive layer.

[0043] S60: The semi-finished product with sand planting completed is first pre-dried using hot air convection at 80℃ for 2 minutes with a heating rate of 7℃ / min; then it enters the high-temperature curing stage, at 130℃ for 6 minutes with a heating rate of 5℃ / min. During the curing process, the oxygen concentration in the oven is controlled at 4% to form a cross-linked and cured base layer.

[0044] S70: A water-based adhesive layer is coated on the surface of the sand layer after sand planting. The water-based adhesive layer is composed of modified water-based phenolic resin emulsion, nano alumina dispersion and crosslinking accelerator. The coating amount is 22g / m². Then, it is heat-cured at 140℃ for 8 minutes to form an adhesive layer that wraps the root of the abrasive particles and fills the gaps between the particles. Example 2:

[0045] S10: Prepare an aqueous adhesive composition, wherein the aqueous adhesive composition comprises, by weight, 70 parts of aqueous acrylic emulsion (i.e., core-shell structured acrylic copolymer emulsion, glass transition temperature of 50°C, solid content of 50%, average particle size of 120 nm, core layer Tg of 20°C, and shell layer Tg of 80°C), 10 parts of nano silica sol (pH value of 9.0 (alkaline), average particle size of 25 nm, solid content of 25%), 0.6 parts of bifunctional silane coupling agent (selected from KH-570 and KH-791 in a volume ratio of 1:1), an appropriate amount of pH adjuster (selected from triethanolamine), 1.4 parts of aqueous cyclopropane, 1.2 parts of film-forming aid (i.e., alcohol ester dodecyl), 2 parts of stabilizer (i.e., propylene glycol), and the balance being deionized water.

[0046] S20: A 50μm thick polyester film treated with plasma is selected as the substrate with a surface energy of 58mN / m. Quaternized acrylic emulsion (solid content of 7wt%) is applied by spraying with a coating amount of 12g / m².

[0047] S30: The substrate coated with the primer is placed in a hot air drying tunnel and dried for 1.2 minutes at 68°C and 4 m / s to allow the moisture to evaporate and form a dense cationic interface layer with a surface zeta potential of +42 mV.

[0048] S40: The above-mentioned anionic aqueous adhesive composition is applied to the cationic interface layer by roller coating, with the coating amount controlled at 35g / m² and the surface tension after coating at 42mN / m, to form a primer layer.

[0049] S50: Select silicon carbide abrasive with a particle size of P80. Preheat it at 115℃ for 25 minutes to reduce the surface adsorbed moisture content to 0.07%. Feed the preheated abrasive into a high-voltage electrostatic spray gun with a nozzle diameter of 2.0 mm, a spray distance of 250 mm, a spray pressure of 0.5 MPa, and an abrasive feed rate of 120 g / min. Apply a +45 kV DC voltage at the spray gun outlet to give the abrasive particles a positive charge with a charge-to-mass ratio of 1.5 μC / g. Spray it vertically onto the grounded substrate surface (potential of 0 V). Under the action of an electrostatic field with an interfacial potential gradient of -250 V / mm, the abrasive particles are oriented and vertically embedded to form an abrasive layer.

[0050] S60: The semi-finished product with sand planting completed is first pre-dried using hot air convection at 80℃ for 2 minutes with a heating rate of 6℃ / min; then it enters the high-temperature curing stage, at 135℃ for 7 minutes with a heating rate of 4℃ / min. During the curing process, the oxygen concentration in the oven is controlled at 3.5% to form a cross-linked cured base layer.

[0051] S70: A water-based adhesive layer is coated on the surface of the sand layer after sand planting. The water-based adhesive layer is composed of modified water-based phenolic resin emulsion, nano alumina dispersion and crosslinking accelerator. The coating thickness is 15-25μm. After curing at 145℃ for 9 minutes, the finished environmentally friendly sandpaper is obtained. Example 3:

[0052] S10: Prepare an aqueous adhesive composition, wherein the aqueous adhesive composition comprises, by weight, 75 parts of aqueous acrylic emulsion (i.e., core-shell structured acrylic copolymer emulsion, glass transition temperature of 50°C, solid content of 50%, average particle size of 120 nm, core layer Tg of 20°C, and shell layer Tg of 80°C), 12 parts of nano silica sol (pH value of 2.5 (acidic), average particle size of 10 nm, solid content of 15%), 0.8 parts of bifunctional silane coupling agent (selected from KH-560 and KH-791 in a volume ratio of 1:1), an appropriate amount of pH adjuster (selected from ammonia), 2.0 parts of aqueous cyclopropane, 1.5 parts of film-forming aid (i.e., alcohol ester dodecyl), 2.5 parts of stabilizer (i.e., propylene glycol), and the balance being deionized water.

[0053] S20: Non-woven fabric is selected as the substrate, with a surface energy of 50 mN / m. Polyethyleneimine aqueous solution (solid content of 6 wt%) is coated on its surface by a blade coating method, with the coating amount controlled at 8 g / m², to form a cationic primer coating.

[0054] S30: The substrate coated with the primer is placed in a hot air drying tunnel and dried for 1 minute at 70°C and a wind speed of 5m / s to evaporate the moisture and form a dense cationic interface layer with a surface zeta potential of +30mV.

[0055] S40: The above-mentioned anionic aqueous adhesive composition is applied to the cationic interface layer by a scraping method, with the coating amount controlled at 25g / m² and the surface tension after coating at 38mN / m, to form a primer layer.

[0056] S50: Zirconia-corundum abrasive with a particle size of P220 was selected and preheated at 120℃ for 30 minutes to reduce the surface adsorbed moisture content to 0.06%. The preheated abrasive was fed into a high-voltage electrostatic spray gun with a nozzle diameter of 1.5mm, a spray distance of 200mm, a spray pressure of 0.4MPa, and an abrasive feed rate of 80g / min. A +35kV DC voltage was applied at the spray gun outlet to give the abrasive particles a positive charge with a charge-to-mass ratio of 1.0μC / g. The abrasive particles were then sprayed vertically onto a grounded substrate surface (potential of 0V). Under the influence of an electrostatic field with an interfacial potential gradient of -180V / mm, the abrasive particles were oriented and vertically embedded to form an abrasive layer.

[0057] S60: The semi-finished product with sand planting completed is first pre-dried by infrared method at 80℃ for 2 minutes with a heating rate of 8℃ / min; then it enters the high temperature curing stage, at 125℃ for 5 minutes with a heating rate of 3℃ / min. During the curing process, the oxygen concentration in the oven is controlled at 4.5% to form a cross-linked cured base layer.

[0058] S70: A water-based adhesive layer is coated on the surface of the sand layer after sand planting. The water-based adhesive layer is composed of modified water-based phenolic resin emulsion, nano alumina dispersion and crosslinking accelerator. The coating amount is 20g / m². Then, it is heat-cured at 130℃ for 6 minutes to form an adhesive layer that wraps the root of the abrasive particles and fills the gaps between the particles.

[0059] It should be noted that the preparation process of the aqueous adhesive composition in the above embodiments is as follows: Q1. First, add deionized water to the mixing container and stir at 300 rpm for 5 minutes. Then, slowly add the stabilizer and continue stirring for 10 minutes until it is completely dissolved. Keep the stirring speed constant. Add nano-silica sol dropwise to the container at a rate of 1.2 mL / min. After the addition is complete, increase the stirring speed to 350 rpm and continue stirring for 15 minutes. Then, add some pH adjuster to adjust the pH of the system to 7.5-8.5 and stir for 10 minutes until the pH is stable. Q2. Slowly add the bifunctional silane coupling agent dropwise into the container at a rate of 0.7 mL / min. After the addition is complete, increase the stirring speed to 400 rpm and continue stirring for 20 minutes to allow it to fully hydrolyze and form a stable inorganic-organic transition layer. Q3. Reduce the stirring speed to 350 rpm and slowly add the water-based acrylic emulsion in 3 parts, stirring for 5 minutes after each addition. After all the emulsion has been added, keep stirring for 15 minutes until the system is completely homogeneous. Add pH adjuster to 7.5-9.0 dropwise and stir for 10 minutes to keep the pH stable. Q4. Keep the stirring speed at 350 rpm and slowly add water-based cyclopropane dropwise at a rate of 0.4 mL / min. After the addition is complete, increase the stirring speed to 450 rpm and continue stirring for 30 minutes to ensure that the water-based cyclopropane is fully dispersed in the system. Q5. Reduce the stirring speed to 400 rpm, add the film-forming aid to the container, stir for 10 minutes to evenly disperse the film-forming aid, then stop stirring and let the system stand for 5 minutes to remove surface air bubbles. Then sieve through a 180-mesh filter to obtain the anionic water-based adhesive composition.

[0060] Comparative Example 1: Except for the absence of a cationic primer, the remaining steps are the same as in Example 1. That is, the water-based adhesive composition is directly coated onto the corona-treated kraft paper for sand application.

[0061] Comparative Example 2: Except for the absence of nano-silica sol and silane coupling agent, the remaining steps are the same as in Example 1. The aqueous binder composition contains only acrylic emulsion, pH adjuster, and water.

[0062] Comparative Example 3: The sand planting process does not apply high voltage static electricity; the abrasive is simply spread onto the surface of the wet adhesive layer by gravity settling. The remaining steps are the same as in Example 1.

[0063] The sandpaper samples prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in the table below: project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Abrasive perpendicularity deviation / ° 3.2 2.8 4.1 12.5 3.5 18.7 Abrasive distribution density deviation / % 5.3 4.9 6.8 15.2 5.7 22.4 Tensile strength retention rate after immersion in 90℃ water for 24 hours / % 88.5 90.2 86.7 72.3 65.8 87.9 Dimensional change rate after 72 hours of heat aging at 120℃ / % 0.32 0.28 0.41 0.85 1.23 0.35 Dry grinding life / min 42 45 38 28 22 30 Wet grinding sand removal rate / % 1.8 1.5 2.3 5.7 8.2 6.9 As can be seen from the data in the table, the sandpaper prepared in Examples 1-3 is significantly better than the comparative examples in terms of abrasive orientation, water resistance, thermal stability and service life.

[0064] Comparative Example 1, due to the lack of a cationic interface layer, resulted in uneven adhesive spreading, weak interfacial bonding, and decreased water resistance and dimensional stability. Comparative Example 2, due to the lack of an organic-inorganic IPN structure, had a low crosslinking density in its adhesive film, resulting in severe performance degradation under high temperature and high humidity conditions. Comparative Example 3, due to the lack of electrostatic sand planting, resulted in disordered abrasive arrangement, reduced effective grinding area, and shortened lifespan.

[0065] Experiment 2: Determination of peel strength, water resistance, and sand shedding resistance of water-based adhesives on sandpaper The following examples and comparative examples were prepared according to the "complete preparation process" of Example 1 above, except that the formulation components and dosage of the water-based adhesive were changed, and all other raw material specifications were the same. Example 4:

[0066] Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 0.6 parts bifunctional silane coupling agent, 1.2 parts water-based cyclopropane, 2.5 parts pH adjuster, 12.7 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0067] Example 5 (Lower limit of aqueous cyclopropane usage): Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 0.6 parts bifunctional silane coupling agent, 0.8 parts water-based cyclopropane, 2.5 parts pH adjuster, 13.1 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0068] Example 6 (Upper Limit of Aqueous Cyclopropane): Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 0.6 parts bifunctional silane coupling agent, 2.0 parts water-based cyclopropane, 2.5 parts pH adjuster, 11.9 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0069] Comparative Example 4 (Anhydrous cyclopropane): Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 0.6 parts bifunctional silane coupling agent, 2.5 parts pH adjuster, 12.7 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0070] Comparative Example 5 (Silane Coupling Agent without Bifunctional Groups): Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 1.2 parts water-based cyclopropane, 2.5 parts pH adjuster, 12.7 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0071] Comparative Example 6 (excess aqueous cyclopropane): Formula (parts by weight): 70 parts water-based acrylic emulsion, 10 parts nano silica sol, 0.6 parts bifunctional silane coupling agent, 3.0 parts water-based cyclopropane, 2.5 parts pH adjuster, 12.7 parts deionized water, 1.0 part film-forming aid, and 2.0 parts stabilizer.

[0072] The sandpaper samples prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in the table below: Peel strength (N / mm) Dry grinding sand removal rate (%) Wet grinding sand removal rate (%) Water resistance (24h immersion) Example 4 1.8 0.3 0.8 No whitening or peeling; wet abrasion strength retention rate of 92%. Example 5 1.6 0.5 1.5 Slight whitening, no peeling, wet abrasion strength retention rate of 88%. Example 6 1.9 0.2 0.6 No whitening or peeling; wet abrasion strength retention rate of 93%. Comparative Example 4 1.0 1.2 5.8 Noticeably whitened, with localized peeling; wet abrasion strength retention rate of 65%. Comparative Example 5 1.1 1.5 4.2 Slight whitening, no peeling, wet abrasion strength retention rate of 78%. Comparative Example 6 2.0 0.2 0.5 No whitening or peeling; wet abrasion strength retention rate of 94%. Experimental results: Examples 4-6 (containing aqueous cycloazinon, dosage 0.8-2.0 parts) showed significantly better peel strength, water resistance, and anti-sand shedding performance than Comparative Example 4 (anhydrous cycloazinon), proving that aqueous cycloazinon can effectively improve the crosslinking degree of the adhesive, enhance water resistance and adhesion, and solve the problem of sand shedding when sandpaper is wet-ground. Example 4 (1.2 parts of water-based cyclopropane) has the best overall performance, with a peel strength of 1.8 N / mm, a wet abrasion rate of only 0.8%, excellent water resistance, and good flexibility and storage stability, making it suitable for the industrial production needs of sandpaper. The adhesion and anti-sand-shedding performance of Comparative Example 5 (without bifunctional silane coupling agent) decreased, and slight delamination occurred, proving that the bifunctional silane coupling agent can effectively improve the interfacial bonding force and stabilize the system. Although Comparative Example 6 (excessive aqueous cyclopropane) exhibits excellent water resistance and adhesion, the system is prone to thickening and clumping, resulting in decreased flexibility and easy breakage of sandpaper. This demonstrates that the amount of aqueous cyclopropane used needs to be controlled within the range of 0.8-2.0 parts.

[0073] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection, the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the meaning of the above terms in this application according to the specific circumstances.

[0074] The above provides a detailed description of an environmentally friendly sandpaper production method using a water-based binder, as provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for producing environmentally friendly sandpaper using a water-based binder, characterized in that, Includes the following steps: S10: Prepare an aqueous adhesive composition comprising an aqueous acrylic emulsion, nano silica sol, a bifunctional silane coupling agent, an aqueous cyclopropane, a pH adjuster, deionized water, a film-forming aid, and a stabilizer. Adjust the pH of the system to 7.5-9.0 using the pH adjuster to obtain an anionic aqueous adhesive composition. S20: Apply a layer of cationic primer to the surface of the substrate to form a base coating, with the coating amount controlled at 5-15g / m². S30: Place the substrate coated with the primer in a hot air drying tunnel at 60-70℃ and dry for 1-2 minutes; S40: Apply an anionic waterborne adhesive composition to a base coating that has been dried, controlling its viscosity to be 80-120 mPa·s, the coating amount to be 20-40 g / m², and the surface tension after coating to be 35-45 mN / m. S50: After the abrasive particles are preheated to 110-120℃, they are fed into a high-voltage electrostatic spray gun. A DC voltage of +30 to +50kV is applied at the nozzle of the spray gun, and the interface potential gradient is set to -100 to -300V / mm, so that the abrasive particles are positively charged and sprayed vertically onto the grounded substrate surface. S60: The semi-finished product with sand planting completed will be subjected to pre-drying and high-temperature curing treatment in sequence. The pre-drying condition is 80℃ for 2 minutes, and the high-temperature curing condition is 120-140℃ for 5-8 minutes. S70: A water-based adhesive layer is coated on the surface of the sand layer after sand planting. The water-based adhesive layer is composed of modified water-based phenolic resin emulsion, nano alumina dispersion and crosslinking accelerator. The coating thickness is 15-25μm. After curing at 140℃-170℃ for 6-10 minutes, the finished environmentally friendly sandpaper is obtained.

2. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 1, characterized in that, In step S10, the aqueous adhesive composition comprises the following components by weight: 65-75 parts of aqueous acrylic emulsion, 8-12 parts of nano silica sol, 0.4-0.8 parts of bifunctional silane coupling agent, an appropriate amount of pH adjuster, 0.8-2.0 parts of aqueous cyclopropane, 0.8-1.5 parts of film-forming aid, 1.5-2.5 parts of stabilizer, and the balance being deionized water, to a total of 100 parts.

3. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 2, characterized in that, The aqueous acrylic emulsion is a core-shell structured acrylic ester copolymer emulsion; the nano-silica sol is an alkaline or acidic colloidal silica dispersion; the bifunctional silane coupling agent is a compound composed of any two selected from KH-570, KH-560, or KH-791 in a volume ratio of 1:1; the pH adjuster is one or more of ammonia, triethanolamine, or sodium bicarbonate; the film-forming aid is dodecyl alcohol ester; and the stabilizer is propylene glycol.

4. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 3, characterized in that, The preparation process of the aqueous adhesive composition includes: Q1. First, add deionized water to the mixing container and stir at 300 rpm for 5 minutes. Then, slowly add the stabilizer and continue stirring for 8-10 minutes until completely dissolved. Keep the stirring speed constant. Add nano-silica sol dropwise to the container at a rate of 1-2 mL / min. After the addition is complete, increase the stirring speed to 350 rpm and continue stirring for 15 minutes. Then, add some pH adjuster to adjust the pH of the system to 7.5-8.5 and stir for 10 minutes until the pH is stable. Q2. Slowly add the bifunctional silane coupling agent dropwise into the container, with the dropping rate controlled at 0.5-1 mL / min. After the addition is complete, increase the stirring speed to 400 rpm and continue stirring for 20-25 minutes to allow it to fully hydrolyze and form a stable inorganic-organic transition layer. Q3. Reduce the stirring speed to 350 rpm and slowly add the water-based acrylic emulsion in 3-4 batches, stirring for 5 minutes after each addition. After all the emulsion has been added, keep stirring for 15 minutes until the system is completely homogeneous. Then, add pH adjuster to adjust the pH to 7.5-9.0 and stir for 10 minutes to keep the pH stable. Q4. Keep the stirring speed at 350 rpm and slowly add water-based cyclopropane dropwise at a rate of 0.3-0.5 mL / min. After the addition is complete, increase the stirring speed to 450 rpm and continue stirring for 25-30 minutes to ensure that the water-based cyclopropane is fully dispersed in the system. Q5. Reduce the stirring speed to 400 rpm, add the film-forming aid to the container, stir for 8-10 minutes to evenly disperse the film-forming aid, then stop stirring and let the system stand for 5-6 minutes to remove surface air bubbles. Then sieve through a 100-200 mesh screen to obtain the anionic water-based adhesive composition.

5. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 1, characterized in that, In step S20, the cationic primer is an aqueous solution of polyethyleneimine or a quaternized acrylic emulsion. The coating method of the cationic primer in step S20 is roller coating, blade coating or spray coating. The coating method of the anionic aqueous adhesive composition in step S40 is roller coating or blade coating.

6. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 1, characterized in that, In step S50, the abrasive particles are one or more of alumina, silicon carbide, zirconium corundum, or ceramic abrasives, and the abrasive particles are preheated at 100-120°C for 10-30 minutes before entering the high-pressure electrostatic spray gun.

7. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 1, characterized in that, In step S60, pre-drying is performed using infrared heating or hot air convection, with a heating rate of 5-10℃ / min; high-temperature curing is performed using a hot air circulating oven, with a heating rate of 3-8℃ / min, and the oxygen concentration is controlled below 5% during the curing process.

8. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 1, characterized in that, In step S70, the modified waterborne phenolic resin emulsion is prepared by emulsifying linear phenolic resin with polyvinyl alcohol formaldehyde under alkaline conditions, with a solid content of 35%-45%; the nano-alumina dispersion has a particle size of 20-60 nm, a solid content of 5%-15%, and a mass fraction of 2%-6% in the composite layer; the crosslinking accelerator is hexamethylenetetramine, and the amount used is 3%-7% of the solid content of the modified phenolic resin.

9. The method for producing environmentally friendly sandpaper using a water-based binder according to claim 8, characterized in that, The preparation process of the modified waterborne phenolic resin emulsion is as follows: M1. Preheat and melt the linear phenolic resin at 85-90℃, and dissolve the polyvinyl alcohol formaldehyde in 1 / 3 deionized water at 65-70℃ until it is transparent. M2 mixes molten phenolic resin with a polyvinyl alcohol formal aqueous solution, adds a co-emulsifier, and stirs at 250 r / min for 60 min; M3. Slowly add 10% sodium hydroxide aqueous solution, adjust the pH to 9.0-10.0, and emulsify by stirring at 70-75℃ and 250r / min for 100-110min. M4, cool to 45-50℃, add defoamer and stabilizer, stir at 150r / min for 60min to mature, cool to room temperature and filter to obtain modified waterborne phenolic resin emulsion.