Preparation method of high-flexibility abrasive paper

Abstract

The invention relates to the field of abrasive paper, in particular to a preparation method of high-flexibility abrasive paper. The preparation method of the abrasive paper comprises the following steps: step 1, preparing a water-based binder; step 2, pretreating the base material; step 3, prime coating and sand planting; step 4, surface coating and curing treatment; and 5, post-treatment is conducted, specifically, after calendaring treatment is conducted, slitting and packaging are conducted, and the high-flexibility abrasive paper is obtained. The process for preparing the high-flexibility abrasive paper comprises the five stages of base material pretreatment, binder synthesis, coating compounding, heating curing and aftertreatment. Abrasive paper prepared by compounding the water-based adhesive prepared by the method and a sand grain matrix has excellent environmental protection property, flexibility, wear resistance and heat resistance.

Description

Technical Field

[0001] The invention relates to the field of sandpaper, and in particular to a method for preparing high-flexibility sandpaper. Background Art

[0002] Sandpaper is an abrasive product that can be divided into two main categories based on its usage: wet sandpaper and dry sandpaper. Dry sandpaper is manufactured using a unique process, using a synthetic resin as a binder to tightly bond the abrasive to latex. This is then coated with an antistatic coating, giving it anti-blocking and anti-static properties while maintaining its softness and abrasion resistance, making it ideal for dry sanding applications. Wet sandpaper, also known as water-resistant sandpaper, uses a base of water-resistant or specially treated paper, with paint or resin as a binder to securely bond the abrasive to the base. This type of sandpaper operates stably in water or oil and is used for polishing metal and non-metal surfaces.

[0003] Traditional sandpaper products typically consist of a base paper or plastic film coated with a binder, which is then bonded with suitable abrasive grains. Organic solvent-based epoxy resin adhesives are commonly used as binders. While these adhesives offer excellent adhesion and corrosion resistance, they suffer from poor flexibility and a short service life. Furthermore, the solvents used in these epoxy resin adhesives, such as toluene, are highly volatile, causing significant environmental pollution and impacting human health. These drawbacks make sandpaper difficult to apply to fine grinding applications such as automotive crankshafts, automotive paint jobs, electronics, and optical discs. Summary of the Invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a method for preparing high-flexibility sandpaper.

[0005] The purpose of the present invention is achieved by adopting the following technical solutions: A method for preparing highly flexible sandpaper comprises the following steps: Step 1, prepare water-based binder: Weigh the raw materials of the water-based adhesive according to the number of parts, mix the other raw materials except the curing agent, then add the curing agent, and mix again to obtain a water-based adhesive; Step 2, substrate pretreatment: Select polymer material as the base material layer, and plasma treat it to remove surface grease and increase the roughness; Step 3, Primer and Sand Planting: The water-based adhesive is applied to the substrate layer by roller coating, and then heated for the first pre-curing to form a semi-cured primer layer; the sand is planted by an electrostatic sand planting process, and then heated for the second pre-curing; Step 4, surface coating and curing: Take the water-based adhesive again and apply it evenly by spraying until it covers 1 / 4-1 / 3 of the height of the sand particles, then heat it up to dry and solidify it; Step 5, post-processing: After calendering, slitting and packaging, high-flexibility sandpaper is obtained.

[0006] Preferably, the aqueous binder, calculated in parts by weight, comprises: 100 parts of water-based modified epoxy resin emulsion, 0.5-1.5 parts of wetting agent, 0.3-0.8 parts of defoaming agent, 1-2 parts of coupling agent, 15-28 parts of curing agent and 20-30 parts of deionized water.

[0007] Preferably, the wetting agent is BYK-346 or BYK-310; the defoaming agent is BYK-024 or BYK-044; the coupling agent is KH-560 or KH-550; and the curing agent is 1,2-cyclohexanediamine, diethylenetriamine or triethylenetetramine.

[0008] Preferably, in step 2, the polymer material is a polyester material or a nylon material with a thickness of 0.2-0.8 mm.

[0009] Preferably, in step 2, the parameters of the plasma treatment include: air atmosphere, power 200-300W, and treatment speed 3-5m / min.

[0010] Preferably, in step 3, the coating thickness of the water-based adhesive is 100-200 μm.

[0011] Preferably, in step 3, the first pre-curing treatment method is: 80° C. hot air pre-curing for 3 minutes; the second pre-curing treatment method is: 100° C. hot air pre-curing for 3 minutes.

[0012] Preferably, in step 3, the sand particles are white corundum particles or brown corundum particles, with a Mohs hardness of 9 and a particle size of 80-150 μm.

[0013] Preferably, in step 3, the parameters of the electrostatic sand planting process include: voltage 35-45 kV, pole distance 6-12 cm, and sand particle falling speed 1-5 m / min.

[0014] Preferably, in step 4, drying is performed using hot air drying at 60°C for 3 minutes; the curing treatment is step curing, including three stages performed in sequence: the first stage is treated at 100°C for 20 minutes; the second stage is treated at 120°C for 40 minutes; and the third stage is treated at 160°C for 20 minutes.

[0015] Preferably, in step 5, the calendering is performed using a silicone roller at a temperature of 180° C. and a pressure of 0.5 MPa to eliminate burrs.

[0016] Preferably, the preparation method of the water-based modified epoxy resin emulsion comprises: S1. Add 3-formaldehyde benzofuran and 2-aminobenzenethiol to the solvent respectively, stir until uniform, then add the catalyst, stir and react at 100-110° C. for 1-2 hours, cool to room temperature, precipitate, wash and dry to obtain a modifier; S2. Weigh alicyclic epoxy resin and bisphenol A epoxy resin, mix them in a reactor, stir them evenly, add a modifier, heat them to 55-65° C., keep them warm and stir for 1-1.5 hours, then add an emulsifier, stir them until they are evenly mixed, cool them to room temperature, adjust the viscosity, and obtain a modified epoxy resin mixture; S3. Weigh polyvinyl alcohol and deionized water, mix them, heat them to 35-45°C, and stir them thoroughly to obtain an aqueous phase mixture; add the aqueous phase mixture dropwise to the modified epoxy resin mixture at 55-65°C. After the addition is complete, shear at high speed to obtain a water-based modified epoxy resin emulsion.

[0017] Preferably, in S1, the solvent is N,N-dimethylformamide and distilled water mixed in a volume ratio of 1:1-1.5, and the ratio of 3-formaldehyde benzofuran, 2-aminobenzenethiol and solvent is 0.99 g:(0.93-1.03) g:(10-20) mL.

[0018] Preferably, in S1, the catalyst is a phase transfer catalyst tetrabutylammonium bromide, and the added amount is 3%-6% of the mass of 3-formylbenzofuran.

[0019] Preferably, in S2, the brand of the alicyclic epoxy resin is CY179 or CY184, and the brand of the bisphenol A epoxy resin is E-51 or E-44. More preferably, the alicyclic epoxy resin is CY179, and the bisphenol A epoxy resin is E-51.

[0020] Preferably, in S2, the mass ratio of the alicyclic epoxy resin, the bisphenol A epoxy resin and the modifier is 2-4:6-8:0.5-1.5.

[0021] Preferably, in S2, the emulsifier is a mixture of emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.2-0.4. The amount of the emulsifier added is 2%-8% of the mass of the bisphenol A epoxy resin.

[0022] Preferably, in S2, propylene glycol methyl ether acetate is used to adjust the viscosity of the system to 300-500 mPa·s.

[0023] Preferably, in S3, the ratio of polyvinyl alcohol to deionized water is (1-3) g:100 mL.

[0024] Preferably, in S3, the volume ratio of the aqueous phase mixed liquid to the modified epoxy resin mixed liquid is 1.2-1.6:1.

[0025] Preferably, in S3, the high-speed shearing speed is 4000-6000 rpm, and the time is 0.2-0.6 h.

[0026] The beneficial effects of the present invention are: The process for preparing highly flexible sandpaper according to the present invention includes five stages: substrate pretreatment, binder synthesis, coating and lamination, temperature curing, and post-processing. Sandpaper prepared using the aqueous binder prepared according to the present invention and a sand matrix exhibits excellent environmental performance, flexibility, wear resistance, and heat resistance.

[0027] 2. The water-based modified epoxy resin emulsion used in the water-based adhesive of the present invention uses a cycloaliphatic epoxy resin and a bisphenol A epoxy resin as the resin matrix. Through the enhancement treatment of the modifier, the adhesive exhibits excellent effects of high strength, high toughness, and high temperature resistance. The modifier is prepared from 3-formylbenzofuran and 2-aminobenzenethiol as raw materials through a condensation reaction between aldehyde groups, amino groups, and thiol groups. The resulting modifier contains a benzofuran-thiazole fused ring structure. This rigid skeleton not only provides good strength and toughness, but also improves heat resistance, solving the shortcomings of traditional water-based epoxy resins such as poor toughness and short service life. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be regarded as the scope of the present invention.

[0029] In order to better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0030] The present invention will be further described below with reference to the following examples.

[0031] Example 1 A method for preparing highly flexible sandpaper comprises the following steps: Step 1, prepare water-based binder: The water-based binder is calculated in parts by weight and includes: 100 parts of water-based modified epoxy resin emulsion, 1 part of wetting agent BYK-346, 0.6 parts of defoaming agent BYK-024, 1.5 parts of coupling agent KH-560, 21 parts of curing agent diethylenetriamine and 25 parts of deionized water; Weigh the raw materials of the water-based adhesive according to the number of parts, mix the other raw materials except the curing agent, stir at 800 rpm for 15 minutes, then add the curing agent, and stir at 300 rpm for 4 minutes to obtain a water-based adhesive; Step 2, substrate pretreatment: A polyester PET material with a thickness of 0.5 mm was selected as the substrate layer and plasma treatment was performed. The parameters of the plasma treatment included: air atmosphere, power of 200 W, and treatment speed of 4 m / min to remove surface grease and increase roughness. Step 3, Primer and Sand Planting: A water-based adhesive was applied to the substrate layer by roller coating to a thickness of 150 μm. The adhesive was then heated to 80°C and pre-cured with hot air for 3 minutes to form a semi-cured primer layer. The sand was then electrostatically implanted with white corundum particles with a Mohs hardness of 9 and a particle size of 120 μm. The parameters of the electrostatic implantation process included a voltage of 40 kV, an inter-electrode distance of 8 cm, and a sand drop speed of 3 m / min. After implantation, the adhesive was heated again to 100°C and pre-cured with hot air for 3 minutes. Step 4, surface coating and curing: Once again, the water-based adhesive was evenly applied to the sandpaper by spraying until it covered 1 / 3 of the sand grain height. The temperature was then raised to 60°C and hot air dried for 3 minutes. A stepwise curing process was then performed: the first stage was at 100°C for 20 minutes; the second stage was at 120°C for 40 minutes; and the third stage was at 160°C for 20 minutes. Step 5, post-processing: The paper is calendered using a silicone roller at a temperature of 180°C and a pressure of 0.5 MPa to eliminate burrs, and then cut and packaged to obtain highly flexible sandpaper.

[0032] Wherein, in step 1, the preparation method of the water-based modified epoxy resin emulsion includes: S1. Preparation of modifier: Weigh N,N-dimethylformamide and distilled water in a volume ratio of 1:1.3 as a solvent, add 0.99 g of 3-formylbenzofuran and 0.97 g of 2-aminobenzenethiol to 15 mL of the prepared solvent, stir until uniform, then add 4% catalyst tetrabutylammonium bromide based on the mass of 3-formylbenzofuran, and carry out condensation reflux reaction at 110°C. After reacting for 2 hours, cool to room temperature, pour into 3 times the volume of ice water, collect the precipitate, wash and dry it in sequence to obtain a modifier; S2. Preparation of modified epoxy resin: 30 g of alicyclic epoxy resin CY179 and 70 g of bisphenol A epoxy resin E-51 were weighed and mixed in a reactor. After stirring, 10 g of a modifier was added, and the temperature was raised to 60°C. The mixture was stirred at this temperature for 1.2 h. Then, an emulsifier (5% by weight of the bisphenol A epoxy resin) was added, wherein the emulsifier was a mixture of TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3. After stirring, the mixture was cooled to room temperature, and propylene glycol methyl ether acetate was added dropwise to adjust the viscosity of the system to 300-500 mPa·s to obtain a modified epoxy resin mixture. S3, emulsification preparation: Weigh 2 g of polyvinyl alcohol (PVA-1788) and 100 mL of deionized water, mix them, heat to 40°C, and stir thoroughly to obtain an aqueous phase mixture; at 60°C, add the aqueous phase mixture dropwise to the modified epoxy resin mixture, with a volume ratio of the aqueous phase mixture to the modified epoxy resin mixture of 1.4:1. After the addition is complete, high-speed shearing is performed at a speed of 5000 rpm for 0.4 h to obtain a water-based modified epoxy resin emulsion.

[0033] Example 2 A method for preparing highly flexible sandpaper comprises the following steps: Step 1, prepare water-based binder: The water-based binder is calculated in parts by weight and includes: 100 parts of water-based modified epoxy resin emulsion, 0.5 parts of wetting agent BYK-310, 0.3 parts of defoaming agent BYK-044, 1 part of coupling agent KH-550, 15 parts of curing agent 1,2-cyclohexanediamine and 20 parts of deionized water; wherein the preparation of the water-based modified epoxy resin emulsion is the same as that of Example 1; Weigh the raw materials of the water-based adhesive according to the number of parts, mix the other raw materials except the curing agent, stir at a speed of 500 rpm for 10 minutes, then add the curing agent, and stir at a speed of 200 rpm for 3 minutes to obtain a water-based adhesive; Step 2, substrate pretreatment: A polyester PBT material with a thickness of 0.2 mm was selected as the substrate layer and subjected to plasma treatment. The plasma treatment parameters included: air atmosphere, power 200 W, and treatment speed 3 m / min to remove surface grease and increase roughness. Step 3, Primer and Sand Planting: A water-based adhesive was applied to the substrate layer by roller coating to a thickness of 100 μm, and then heated to 80°C for hot air pre-curing for 3 minutes to form a semi-cured primer layer. The sand was then electrostatically implanted using white corundum particles with a Mohs hardness of 9 and a particle size of 80 μm. The parameters of the electrostatic implantation process included a voltage of 35 kV, an inter-electrode distance of 6 cm, and a sand drop speed of 2 m / min. The substrate was then heated again to 100°C for hot air pre-curing for 3 minutes. Step 4, surface coating and curing: The water-based adhesive was sprayed evenly again until it covered 1 / 4 of the sand height, then heated to 60°C and dried with hot air for 3 minutes, followed by a step-by-step curing process: the first stage was 20 minutes at 100°C; the second stage was 40 minutes at 120°C; and the third stage was 20 minutes at 160°C. Step 5, post-processing: After calendering using a silicone roller at a temperature of 180°C and a pressure of 0.5 MPa, burrs are removed, the sandpaper is cut and packaged to obtain highly flexible sandpaper.

[0034] Example 3 A method for preparing highly flexible sandpaper comprises the following steps: Step 1, prepare water-based binder: The water-based binder is calculated in parts by weight and includes: 100 parts of water-based modified epoxy resin emulsion, 1.5 parts of wetting agent BYK-346, 0.8 parts of defoaming agent BYK-044, 2 parts of coupling agent KH-560, 28 parts of curing agent triethylenetetramine and 30 parts of deionized water; wherein the preparation of the water-based modified epoxy resin emulsion is the same as that of Example 1; Weigh the raw materials of the water-based adhesive according to the number of parts, mix the other raw materials except the curing agent, stir at a speed of 1000 rpm for 20 minutes, then add the curing agent, and stir at a speed of 400 rpm for 6 minutes to obtain a water-based adhesive; Step 2, substrate pretreatment: Nylon 66 material with a thickness of 0.8 mm was selected as the substrate layer and subjected to plasma treatment. The plasma treatment parameters included: air atmosphere, power of 300 W, and treatment speed of 5 m / min to remove surface grease and increase roughness. Step 3, Primer and Sand Planting: A water-based adhesive was applied to the substrate layer by roller coating to a thickness of 200 μm, and then heated to 80°C for hot air pre-curing for 3 minutes to form a semi-cured primer layer. The sand was electrostatically implanted using brown corundum particles with a Mohs hardness of 9 and a particle size of 150 μm. The parameters of the electrostatic implantation process included a voltage of 45 kV, an inter-electrode distance of 12 cm, and a sand drop speed of 5 m / min. The temperature was then raised again to 100°C for hot air pre-curing for 3 minutes. Step 4, surface coating and curing: The water-based adhesive was sprayed evenly again until it covered 1 / 3 of the sand grain height, and then heated to 60°C for hot air drying for 3 minutes, followed by a step-by-step curing process: the first stage was 20 minutes at 100°C; the second stage was 40 minutes at 120°C; and the third stage was 20 minutes at 160°C. Step 5, post-processing: After calendering using a silicone roller at a temperature of 180°C and a pressure of 0.5 MPa, burrs are removed, the sandpaper is cut and packaged to obtain highly flexible sandpaper.

[0035] Example 4 A method for preparing highly flexible sandpaper is provided, which differs from Example 1 in that the preparation parameters of the water-based modified epoxy resin emulsion in step 1 are slightly different.

[0036] The preparation method of the water-based modified epoxy resin emulsion comprises: S1. Preparation of modifier: Weigh N,N-dimethylformamide and distilled water in a volume ratio of 1:1.5 and mix them evenly as a solvent. Add 0.99 g of 3-formaldehyde benzofuran and 1.03 g of 2-aminobenzenethiol to 20 mL of the solvent respectively, stir until uniform, then add 6% catalyst tetrabutylammonium bromide based on the mass of 3-formaldehyde benzofuran, and carry out condensation reflux reaction at 110°C. After reacting for 2 hours, cool to room temperature, pour into 3 times the volume of ice water, collect the precipitate, wash and dry it in sequence to obtain a modifier; S2. Preparation of modified epoxy resin: 20 g of alicyclic epoxy resin CY184 and 80 g of bisphenol A epoxy resin E-44 were weighed and mixed in a reactor. After stirring, 5 g of a modifier was added, and the temperature was raised to 55°C. The mixture was stirred at this temperature for 1 hour. Then, an emulsifier (2% by weight of the bisphenol A epoxy resin) was added. The emulsifier was a mixture of emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.2. The mixture was stirred until uniform, cooled to room temperature, and propylene glycol methyl ether acetate was added dropwise to adjust the viscosity of the system to 300-500 mPa·s to obtain a modified epoxy resin mixture. S3, emulsification preparation: Weigh 1 g of polyvinyl alcohol (PVA-1799) and 100 mL of deionized water, mix them, heat to 35°C, and stir thoroughly to obtain an aqueous phase mixture. At 55°C, add the aqueous phase mixture dropwise into the modified epoxy resin mixture. The volume ratio of the aqueous phase mixture to the modified epoxy resin mixture is 1.2:1. After the addition is complete, high-speed shearing is performed at 4000 rpm for 0.6 h to obtain a water-based modified epoxy resin emulsion.

[0037] Example 5 A method for preparing highly flexible sandpaper is different from that of Example 1 in that the preparation parameters of the water-based modified epoxy resin emulsion in step 1 are slightly different.

[0038] The preparation method of the water-based modified epoxy resin emulsion comprises: S1. Preparation of modifier: Weigh N,N-dimethylformamide and distilled water in a volume ratio of 1:1.5 and mix them evenly as a solvent. Add 0.99 g of 3-formaldehyde benzofuran and 1.03 g of 2-aminobenzenethiol to 20 mL of the solvent respectively, stir until uniform, then add 6% catalyst tetrabutylammonium bromide based on the mass of 3-formaldehyde benzofuran, and carry out condensation reflux reaction at 110°C. After reacting for 2 hours, cool to room temperature, pour into 3 times the volume of ice water, collect the precipitate, wash and dry in sequence to obtain a modifier; S2. Preparation of modified epoxy resin: 40 g of alicyclic epoxy resin CY184 and 60 g of bisphenol A epoxy resin E-44 were weighed and mixed in a reactor. After stirring, 15 g of a modifier was added, and the temperature was raised to 65°C. The mixture was stirred at this temperature for 1.5 h. Then, an emulsifier (8% by weight of the bisphenol A epoxy resin) was added. The emulsifier was a mixture of emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.4. The mixture was stirred until uniform, cooled to room temperature, and propylene glycol methyl ether acetate was added dropwise to adjust the viscosity of the system to 300-500 mPa·s to obtain a modified epoxy resin mixture. S3, emulsification preparation: Weigh 3 g of polyvinyl alcohol (PVA-2099) and 100 mL of deionized water, mix them, heat to 45°C, and stir thoroughly to obtain an aqueous phase mixture; at 65°C, add the aqueous phase mixture dropwise to the modified epoxy resin mixture, with a volume ratio of the aqueous phase mixture to the modified epoxy resin mixture of 1.6:1. After the addition is complete, high-speed shearing is performed at a speed of 6000 rpm for 0.2 h to obtain a water-based modified epoxy resin emulsion.

[0039] Comparative Example 1 A method for preparing sandpaper, which differs from Example 1 in that no modifier is added to the water-based modified epoxy resin emulsion in step 1, but is replaced by a water-based epoxy resin emulsion. The preparation method comprises: S1. Preparation of epoxy resin mixture: 30 g of alicyclic epoxy resin CY179 and 70 g of bisphenol A epoxy resin E-51 were weighed and mixed in a reactor. After stirring, the mixture was heated to 60° C. and stirred for 1.2 h. An emulsifier (5% by weight of the bisphenol A epoxy resin) was added, wherein the emulsifier was a mixture of emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3. The mixture was stirred until uniform, cooled to room temperature, and propylene glycol methyl ether acetate was added dropwise to adjust the viscosity of the system to 300–500 mPa·s to obtain an epoxy resin mixture. S2. Emulsification preparation: Weigh 2 g of polyvinyl alcohol (PVA-1788) and 100 mL of deionized water, mix them, heat to 40°C, and stir thoroughly to obtain an aqueous phase mixture; at 60°C, add the aqueous phase mixture dropwise to the modified epoxy resin mixture, with a volume ratio of the aqueous phase mixture to the modified epoxy resin mixture of 1.4:1. After the addition is complete, high-speed shearing is performed at a speed of 5000 rpm for 0.4 h to obtain a water-based modified epoxy resin emulsion.

[0040] Comparative Example 2 A method for preparing sandpaper, which differs from Example 1 in that the preparation process of the modifier of the water-based modified epoxy resin emulsion in step 1 is different. The preparation method of the water-based modified epoxy resin emulsion comprises: S1. Preparation of modified epoxy resin: 30 g of alicyclic epoxy resin CY179 and 70 g of bisphenol A epoxy resin E-51 were weighed and mixed in a reactor. After stirring, 10 g of 3-formaldehyde benzofuran was added as a modifier. The temperature was raised to 60° C. and stirred for 1.2 h. Then, an emulsifier (5% by weight of the bisphenol A epoxy resin) was added, wherein the emulsifier was a mixture of emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3. The mixture was stirred until uniform, cooled to room temperature, and propylene glycol methyl ether acetate was added dropwise to adjust the viscosity of the system to 300-500 mPa·s to obtain a modified epoxy resin mixture. S3, emulsification preparation: Weigh 2 g of polyvinyl alcohol (PVA-1788) and 100 mL of deionized water, mix them, heat to 40°C, and stir thoroughly to obtain an aqueous phase mixture; at 60°C, add the aqueous phase mixture dropwise to the modified epoxy resin mixture, with a volume ratio of the aqueous phase mixture to the modified epoxy resin mixture of 1.4:1. After the addition is complete, high-speed shearing is performed at a speed of 5000 rpm for 0.4 h to obtain a water-based modified epoxy resin emulsion.

[0041] In order to more clearly illustrate the contents of the present invention, the water-based adhesives and sandpaper materials prepared in Example 1 of the present invention and Comparative Examples 1-2 were tested and compared. The tests included: bond strength (refer to ASTM D903, metal substrate pull-out test), elongation at break (refer to ASTM D638), flexural modulus (refer to ASTM D790), water resistance (immersion in water for 168 hours, refer to ISO 62), and solvent resistance (acetone rub 100 times, refer to ASTM D4752).

[0042] The test results are shown in Table 1: Table 1 Comparison of performance tests of different water-based binders Example 1 Comparative Example 1 Comparative Example 2 Bond strength (MPa) 23.5 14.1 16.7 Elongation at break (%) 16.1 7.2 9.8 Flexural modulus (GPa) 2.2 1.3 1.6 Water resistance (168h) No blistering, no shedding No blistering and no shedding There is blistering and shedding Solvent resistance (acetone wipe 100 times) No blistering, no shedding No blistering and no shedding There is blistering and shedding As can be seen from Table 1, the water-based adhesive prepared in Example 1 of the present invention has better performance in strength and toughness than the traditional water-based epoxy adhesive (Comparative Example 1) and the traditional modified water-based epoxy adhesive (Comparative Example 2), and can also maintain excellent water resistance and solvent resistance.

[0043] The sandpaper materials prepared in Example 1 of the present invention and Comparative Examples 1-2 were tested and compared with respect to sand grain shedding rate (referring to ISO 6344, grinding at a linear speed of 10 m / s), peel strength (referring to ASTM D903), 50 mm curling, bending fatigue life (referring to ASTM D2176, curvature radius of 10 mm), and heat distortion temperature (referring to ASTM D648).

[0044] The test results are shown in Table 2: Table 2 Performance comparison of different sandpapers Example 1 Comparative Example 1 Comparative Example 2 Sand falling rate ＜3% ＞15% 6%-8% Peel strength (N / cm) 9.7 5.2 7.8 Degree of curl 50mm without cracking 80mm fracture 80mm without cracking Bending fatigue life (times) >50,000 ＜2000 10,000-20,000 Thermal distortion temperature (℃) 220 160 185 It can be seen from Table 2 that the sandpaper prepared by the method of Example 1 of the present invention has a lower sand particle shedding rate and a higher peel strength. In addition, the sandpaper of Example 1 can be curled at 50 mm without cracking, has a bending fatigue life of more than 50,000 times, and a thermal distortion temperature of 220°C, indicating that it not only has high strength and adhesion, but also has better flexibility, wear resistance and heat resistance.

[0045] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0046] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing highly flexible sandpaper, characterized in that: The following steps are involved: Step 1, prepare water-based binder: Weigh the raw materials of the water-based adhesive according to the number of parts, mix the other raw materials except the curing agent, then add the curing agent, and mix again to obtain a water-based adhesive; The aqueous binder is calculated in parts by weight and includes: 100 parts of water-based modified epoxy resin emulsion, 0.5-1.5 parts of wetting agent, 0.3-0.8 parts of defoaming agent, 1-2 parts of coupling agent, 15-28 parts of curing agent and 20-30 parts of deionized water; Step 2, substrate pretreatment: Select polymer material as the base material layer, and plasma treat it to remove surface grease and increase the roughness; Step 3, Primer and Sand Planting: The water-based adhesive is applied to the substrate layer by roller coating, and the temperature is increased for the first pre-curing; the sand is planted by an electrostatic sand planting process, and the temperature is increased again to complete the second pre-curing; Step 4, surface coating and curing: Take the water-based adhesive and spray it again until it covers 1 / 4-1 / 3 of the height of the sand particles, heat and dry it, and then solidify it; Step 5, post-processing: After calendering, slitting and packaging, high-flexibility sandpaper is obtained.

2. The method for preparing a highly flexible sandpaper according to claim 1, wherein: The wetting agent is BYK-346 or BYK-310; the defoaming agent is BYK-024 or BYK-044; the coupling agent is KH-560 or KH-550; and the curing agent is 1,2-cyclohexanediamine, diethylenetriamine or triethylenetetramine.

3. The method for preparing a highly flexible sandpaper according to claim 1, wherein: In step 2, the polymer material is a polyester material or a nylon material with a thickness of 0.2-0.8 mm; the parameters of the plasma treatment include: air atmosphere, power of 200-300 W, and treatment speed of 3-5 m / min.

4. The method for preparing a highly flexible sandpaper according to claim 1, wherein: In step 3, the coating thickness of the water-based adhesive is 100-200 μm; the first pre-curing treatment method is: 80° C. hot air pre-curing for 3 minutes; the second pre-curing treatment method is: 100° C. hot air pre-curing for 3 minutes.

5. The method for preparing a highly flexible sandpaper according to claim 1, wherein: In step 3, the sand particles are white corundum particles or brown corundum particles, with a Mohs hardness of 9 and a particle size of 80-150 μm; The parameters of the electrostatic sand planting process include: voltage 35-45kV, pole distance 6-12cm, and sand falling speed 1-5m / min.

6. The method for preparing a highly flexible sandpaper according to claim 1, wherein: In step 4, drying is performed using hot air drying at 60°C for 3 minutes; the curing treatment is step curing, including three stages performed in sequence: the first stage is treated at 100°C for 20 minutes; the second stage is treated at 120°C for 40 minutes; and the third stage is treated at 160°C for 20 minutes.

7. The method for preparing a highly flexible sandpaper according to claim 1, characterized in that: The preparation method of the water-based modified epoxy resin emulsion comprises: S1. Add 3-formaldehyde benzofuran and 2-aminobenzenethiol to the solvent respectively, stir until uniform, then add the catalyst, stir and react at 100-110° C. for 1-2 hours, cool to room temperature, precipitate, wash and dry to obtain a modifier; S2. Weigh alicyclic epoxy resin and bisphenol A epoxy resin, mix them in a reactor, stir them evenly, add a modifier, heat them to 55-65° C., keep them warm and stir for 1-1.5 hours, then add an emulsifier, stir them evenly, cool them to room temperature, adjust the viscosity, and obtain a modified epoxy resin mixture; S3. Weigh polyvinyl alcohol and deionized water, mix them, heat them to 35-45°C, and stir them thoroughly to obtain an aqueous phase mixture; add the aqueous phase mixture dropwise to the modified epoxy resin mixture at 55-65°C. After the addition is complete, shear at high speed to obtain a water-based modified epoxy resin emulsion.

8. The method for preparing high-flexibility sandpaper according to claim 7, characterized in that: In S1, the solvent is a mixture of N,N-dimethylformamide and distilled water in a volume ratio of 1:1-1.5, the ratio of 3-formaldehyde benzofuran, 2-aminobenzenethiol, and solvent is 0.99 g:(0.93-1.03) g:(10-20) mL; the catalyst is a phase transfer catalyst tetrabutylammonium bromide, and the added amount is 3%-6% of the mass of 3-formaldehyde benzofuran.

9. The method for preparing highly flexible sandpaper according to claim 7, wherein: In S2, the mass ratio of the alicyclic epoxy resin, bisphenol A epoxy resin and modifier is 2-4:6-8:0.5-1.5; the emulsifier is obtained by mixing emulsifier TX-10 and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.2-0.4; and the amount of the emulsifier added is 2%-8% of the mass of the bisphenol A epoxy resin.

10. The method for preparing highly flexible sandpaper according to claim 7, characterized in that: In the S3, the ratio of polyvinyl alcohol to deionized water is (1-3) g:100 mL; and the volume ratio of the aqueous phase mixture to the modified epoxy resin mixture is 1.2-1.6:1.