Environment-friendly waterproof abrasive paper and preparation method thereof

Abstract

The invention discloses environment-friendly waterproof abrasive paper and a preparation method thereof, and relates to the technical field of waterproof abrasive paper. The environment-friendly waterproof abrasive paper comprises a base material, a primer layer coated on the base material, and an abrasive material layer attached to the primer layer, the grinding material layer is composed of grinding materials; and the bottom adhesive layer is formed by an environment-friendly water-resistant adhesive. Compared with a traditional solvent type adhesive scheme, the environment-friendly adhesive has the advantages that VOCs emission can be effectively reduced, the environment-friendly policy requirement is met, and the influence on the environment is reduced.

Description

Technical Field

[0001] This invention relates to the field of water-resistant sandpaper technology, specifically to an environmentally friendly water-resistant sandpaper and its preparation method. Background Technology

[0002] Water-resistant sandpaper, as a key material for surface grinding and polishing, is widely used in various fields such as automotive repair, furniture manufacturing, metal processing, and building material grinding. Its core performance requirements not only include excellent water resistance, grinding efficiency, and adhesion, but also adaptability to complex usage scenarios such as outdoor storage and open-air operations. Therefore, resistance to ultraviolet aging has become one of the core indicators affecting the product's service life.

[0003] In existing technologies, the base adhesive layer of water-resistant sandpaper mostly uses traditional solvent-based adhesives. Although these adhesives can ensure the bonding strength between the abrasive and the substrate in the short term, the volatile organic compounds they contain can cause environmental pollution, which does not comply with current environmental protection policies. At the same time, under long-term ultraviolet radiation, the molecular chains of traditional adhesives are prone to breakage and the cross-linking density decreases, leading to problems such as yellowing, embrittlement, and cracking of the base adhesive layer.

[0004] The negative effects of UV aging are particularly prominent: on the one hand, UV rays will damage the chemical bond structure of the adhesive, reduce its bonding performance, and cause the abrasive to fall off easily during the grinding process, which will greatly shorten the service life of the sandpaper; on the other hand, the waterproof performance of the aged base layer will decrease, and it will be prone to delamination and blistering in humid environments, which will further affect the grinding accuracy and performance.

[0005] Although some products add UV absorbers to improve weather resistance, traditional absorbers have poor compatibility with adhesive systems, are prone to leaching and loss, and have limited long-term UV resistance. Meanwhile, while existing environmentally friendly water-based adhesives have solved the VOCs emission problem, they generally suffer from insufficient UV aging resistance, making it difficult to balance environmental friendliness and long-term weather resistance. Therefore, developing a water-resistant sandpaper that combines environmental friendliness, excellent water resistance, and strong UV aging resistance has become a pressing technical challenge for the industry. Summary of the Invention

[0006] This invention addresses the problems of severe pollution, poor UV aging resistance (the base adhesive is prone to yellowing and embrittlement, and the abrasive is prone to falling off) and insufficient weather resistance of existing water-based adhesives in water-resistant sandpaper. It provides an environmentally friendly water-resistant sandpaper and its preparation method. The base adhesive layer uses a specific ratio of environmentally friendly water-resistant adhesive, which can achieve low VOC emissions, while having excellent UV aging resistance and water resistance, improving abrasive adhesion, extending the service life of sandpaper, and meeting the needs of use in automotive repair, furniture manufacturing and other fields.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An environmentally friendly water-resistant sandpaper includes a substrate, a base coat coated on the substrate, and an abrasive layer attached to the base coat.

[0009] The abrasive layer is composed of abrasives;

[0010] The base layer is made of an environmentally friendly, water-resistant adhesive;

[0011] The environmentally friendly water-resistant adhesive comprises the following components by weight: 40-60 parts of waterborne polyurethane emulsion, 15-25 parts of modified phenolic resin, 5-10 parts of nano-silica sol, 2-5 parts of crosslinking agent, 0.5-2 parts of wetting and dispersing agent, 1.5-2 parts of ultraviolet absorber, 0.2-1 parts of defoamer, and 10-20 parts of deionized water;

[0012] The ultraviolet absorber is a compound represented by Formula 1;

[0013] Formula 1;

[0014] R1 in Formula 1 is any one of methyl, hydroxy, methoxy, and carboxyl groups.

[0015] Furthermore, the modified phenolic resin is a rosin-modified phenolic resin.

[0016] Furthermore, the silica content in the nano-silica solution is 25±2%, and the pH is 5-7.

[0017] Furthermore, the crosslinking agent is either methylene diisocyanate trimer or isophorone diisocyanate trimer.

[0018] Furthermore, the wetting and dispersing agent is sodium polycarboxylate or ammonium polycarboxylate.

[0019] Furthermore, the defoamer is polydimethylsiloxane.

[0020] Furthermore, the abrasive is one or more of alumina, silicon carbide, or zirconium corundum.

[0021] Furthermore, the substrate layer is one of waterproof kraft paper, polyester film, or non-woven fabric.

[0022] Furthermore, the ultraviolet absorber is any one of the compounds shown in the following structures:

[0023] ;

[0024] .

[0025] A method for preparing environmentally friendly water-resistant sandpaper includes the following steps:

[0026] S1. Mix the waterborne polyurethane emulsion, modified phenolic resin, nano silica sol, crosslinking agent, wetting and dispersing agent, ultraviolet absorber, defoamer and deionized water evenly to prepare an environmentally friendly water-resistant adhesive.

[0027] S2. Pre-treat the substrate, remove surface impurities and dry it to obtain the treated substrate;

[0028] S3. Apply the environmentally friendly water-resistant adhesive to the treated substrate to form a primer layer;

[0029] S4. Using electrostatic sanding or gravity sanding, the abrasive is evenly attached to the surface of the uncured base layer, and then fed into a drying device for low-temperature drying and high-temperature curing treatment in sequence. After curing, an environmentally friendly water-resistant sandpaper is obtained.

[0030] Furthermore, the coating thickness of the base adhesive layer is 5-15 μm.

[0031] Furthermore, in S4, the low-temperature drying temperature is 60-80℃ and the drying time is 15-30 min; the high-temperature curing temperature is 120-150℃ and the curing time is 30-60 min.

[0032] This invention solves the core technical problems of poor environmental performance, insufficient UV aging resistance, and lack of weather resistance of traditional water-resistant sandpaper and environmentally friendly water-based adhesives by synergistically proportioning specific mass parts of each component. It uses water-based polyurethane emulsion as the core film-forming substrate, combined with rosin-modified phenolic resin, to replace traditional solvent-based adhesives, achieving low VOC emissions from the source. Simultaneously, the two synergistically impart basic water resistance and adhesive strength to the base layer. A UV absorber with a specific structure exhibits excellent compatibility with the adhesive system, can retain its properties for a long time, and continuously absorbs ultraviolet light, preventing molecular chain breakage in the base layer. This is further enhanced by nano-sized silica with a content of 25±2% and a pH of 5-7. Silica sol further enhances the structural stability of the base coat, jointly inhibiting yellowing and embrittlement; specific crosslinking agents increase the crosslinking density of the adhesive, enhancing the compactness of the base coat; polycarboxylate wetting and dispersing agents ensure uniform mixing of all components without local performance deficiencies; polydimethylsiloxane defoamer eliminates air bubbles during the coating process, reducing water penetration channels; and deionized water is used to adjust viscosity to ensure coating effect. All components work synergistically according to the above-mentioned mass proportions, ultimately achieving simultaneous improvement in environmental friendliness, UV aging resistance, water resistance, and abrasive adhesion, effectively solving problems such as abrasive detachment and base coat delamination, and extending the service life of sandpaper.

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

[0034] 1. It is more environmentally friendly. Compared with traditional solvent-based adhesives, it can effectively reduce VOC emissions, meet environmental protection policy requirements, and reduce the impact on the environment.

[0035] 2. Significantly improved UV aging resistance: Through the synergistic effect of specific components, it can reduce the yellowing and embrittlement of the base layer caused by UV radiation, reduce the risk of abrasive detachment, and extend the service life of sandpaper.

[0036] 3. It has better water resistance and bonding stability. While ensuring environmental protection and UV resistance, it can reduce the delamination and bubbling of the base adhesive in humid environments, and maintain the sanding accuracy and performance. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an environmentally friendly water-resistant sandpaper according to the present invention.

[0038] Figure 2 This is the NMR spectrum of the ultraviolet absorber 1 described in this invention. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Preparation Example 1

[0041] Preparation of UV absorber 1:

[0042] ;

[0043] Under a nitrogen atmosphere, 3g of compound 1 and 30ml of dichloromethane were added sequentially to the reaction system. After stirring until homogeneous, 12.53g of N,N-diisopropylethylamine was added and stirred until homogeneous. The air was then replaced twice with nitrogen, and the system temperature was lowered to 0°C with dry ice. A 10ml dichloromethane solution containing 4.32g of triphosgene was slowly added dropwise, and the system temperature was maintained at 0°C. The mixture was stirred for 2 hours. Then, a 15ml dichloromethane solution containing 3.16g of compound 2 was added to the reaction system, and the system was brought to room temperature and stirred for another 16 hours. After the reaction was complete, 1000ml of water was added for quenching. After stirring, shaking, and separation, the organic phase was retained. The organic phase was dried with anhydrous sodium sulfate, filtered to remove the desiccant, and evaporated to dryness to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: a mixture of petroleum ether and ethyl acetate). The eluent was evaporated to dryness to obtain 4.00g of the target compound 3. The mass spectrometry showed an MS+1 of 661.

[0044] ;

[0045] Under a nitrogen atmosphere, 4.00 g of compound 3, 0.79 g of compound 4, and 60 mL of a mixed solvent of dioxane and diisopropylamine (40 mL / 20 mL) were added sequentially to the reaction system. After stirring until homogeneous, 0.04 g of palladium acetate, 0.05 g of triphenylphosphine, and 0.03 g of CuI were added sequentially. The mixture was stirred until homogeneous, heated to 95 °C, and refluxed for 6 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The filtrate was used to remove the solvent using a rotary evaporator and purified by silica gel column chromatography (eluent: a mixture of petroleum ether and ethyl acetate). The eluent was evaporated to dryness to obtain UV absorber 1 with a concentration of 3.40. The mass spectrometry showed ms+1: 757, and the NMR results were as follows: Figure 2 .

[0046] Preparation Examples 2-4

[0047] In Preparation Examples 2-4, UV absorber 2-UV absorber 4 were prepared sequentially, following the preparation method of Preparation Example 1, except that compound 4 was replaced. The rest remained the same as in Preparation Example 1. See Table 1 for details.

[0048] Table 1

[0049]

[0050] Example 1

[0051] Preparation of an environmentally friendly water-resistant sandpaper:

[0052] 1. Raw material composition by weight:

[0053] 1.1 Waterborne polyurethane emulsion: 50 parts, solid content 39-41 wt%, pH value 7.0-9.0, purchased from Foshan Wode Polymer Materials Co., Ltd.;

[0054] 1.2 Modified phenolic resin: 20 parts (rosin-modified phenolic resin, specifically rosin-modified phenolic resin 221#, purchased from Foshan Baolin Chemical Industry Co., Ltd.);

[0055] 1.3 nm silica sol: 8 parts (silica content 25±2%, pH=6, model: HN-S01Z, purchased from: Hangzhou Hengge Technology Co., Ltd.);

[0056] 1.4 Crosslinking agent: 3 parts (methylene diisocyanate trimer);

[0057] 1.5 Wetting and dispersing agent: 1 part (sodium polycarboxylate);

[0058] 1.6 UV absorber: 1.8 parts (UV absorber 1 obtained from Preparation Example 1);

[0059] 1.7 Defoamer: 0.5 parts (polydimethylsiloxane);

[0060] 1.8 Deionized water: 15 parts;

[0061] 1.9 Abrasive: Alumina (80 mesh particle size); Substrate: Polyester film;

[0062] 2. Preparation method:

[0063] S1. According to the above mass parts, waterborne polyurethane emulsion, rosin-modified phenolic resin, nano silica sol, methylene diisocyanate trimer, sodium polycarboxylate, UV absorber obtained in Preparation Example 1, and polydimethylsiloxane are added to deionized water in sequence, and stirred at 25°C and 500 r / min for 30 min to ensure that each component is mixed evenly, so as to obtain a uniform and stable environmentally friendly water-resistant adhesive.

[0064] S2. Place the polyester film substrate in a constant temperature oven and dry it at 80°C for 20 minutes to remove surface dust, oil and other impurities. After cooling to room temperature, the treated substrate is obtained.

[0065] S3. Using a scraper coating method, the prepared environmentally friendly water-resistant adhesive is evenly coated onto the surface of the substrate, and the coating thickness is controlled to be 10μm to form a base layer;

[0066] S4. Using electrostatic sanding, alumina abrasive is evenly attached to the surface of the uncured base layer. The substrate is then sent to a drying and curing device. It is first dried at a low temperature of 70℃ for 20 minutes, and then heated to 135℃ for high-temperature curing for 45 minutes. After curing, it is naturally cooled to room temperature to obtain an environmentally friendly water-resistant sandpaper.

[0067] Example 2

[0068] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the ultraviolet absorber 1 was replaced with ultraviolet absorber 2, and the rest remained the same as in Example 1.

[0069] Example 3

[0070] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the ultraviolet absorber 1 was replaced with ultraviolet absorber 3, and the rest remained the same as in Example 1.

[0071] Example 4

[0072] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the ultraviolet absorber 1 was replaced with ultraviolet absorber 4, and the rest remained the same as in Example 1.

[0073] Comparative Example 1

[0074] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the ultraviolet absorber 1 was replaced with ultraviolet absorber 234 (70321-86-7), and the rest remained the same as in Example 1.

[0075] Comparative Example 2

[0076] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the ultraviolet absorber 1 was replaced with ultraviolet absorber 1600 (204583-39-1), and the rest remained the same as in Example 1.

[0077] Comparative Example 3

[0078] An environmentally friendly water-resistant sandpaper was prepared according to the preparation method of Example 1, except that no ultraviolet absorber was added, and the rest remained the same as in Example 1.

[0079] Comparative Example 4

[0080] An environmentally friendly water-resistant sandpaper was prepared according to the preparation method of Example 1, but without the addition of nano-silica sol, and otherwise remained the same as in Example 1.

[0081] Comparative Example 5

[0082] An environmentally friendly water-resistant sandpaper was prepared by referring to the preparation method of Example 1, except that the mass fraction of the modified phenolic resin was replaced with 10 parts, and the rest remained the same as in Example 1.

[0083] Performance testing:

[0084] 1. Environmental protection test (VOCs emission test): The test was conducted in accordance with GB / T 23985-2009, and the data is shown in Table 2.

[0085] 2. Tensile strength: The test was conducted in accordance with JB / T 7424-2007, and the data are shown in Table 2.

[0086] 3. UV aging resistance test: A QUV UV aging test chamber was used, with a light wavelength of 340nm and an irradiance of 0.68W / (m²). 2 The temperature of the blackboard was 60℃, the spraying cycle was 18h light exposure / 2h condensation, and the cumulative test was 2400h. The tensile strength was retested and the tensile strength retention rate was calculated. The data are shown in Table 2.

[0087] 4. Water resistance test: The sample was completely immersed in deionized water at 25℃ for 480 hours. After drying, the tensile strength was retested and the tensile strength retention rate was calculated. The data are shown in Table 2.

[0088] Table 2

[0089] VOC emissions (g / L) Tensile strength (MPa) Tensile strength retention rate after UV aging (%) Tensile strength retention rate after water immersion (%) Example 1 1.2 18.5 95.2 91.3 Example 2 1.3 18.3 97.5 90.8 Example 3 1.2 18.6 96.5 91.5 Example 4 1.3 18.4 96.8 90.5 Comparative Example 1 1.4 18.2 65.3 90.4 Comparative Example 2 1.3 18.1 68.7 89.6 Comparative Example 3 1.2 18.0 42.6 89.2 Comparative Example 4 1.2 16.8 89.4 78.5 Comparative Example 5 1.3 14.5 90.3 75.8

[0090] In embodiments using the specific UV absorber of this invention, the retention rate of tensile strength after UV aging is significantly better than that of the comparative examples using traditional UV absorbers or without adding UV absorbers, while maintaining low VOC emissions. In the comparative examples without adding nano-silica sol or reducing the amount of modified phenolic resin, the retention rate of tensile strength related to water resistance is significantly reduced. The initial tensile strength of each scheme is less affected by component adjustments, but the type of UV absorber, the presence or absence of nano-silica sol and the amount of modified phenolic resin have a more significant impact on UV aging resistance and water resistance.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly water-resistant sandpaper, characterized by, The base material, the primer layer coated on the base material, and the abrasive layer attached to the primer layer; The abrasive layer is composed of abrasives; The primer layer is composed of an environmentally friendly water-resistant adhesive; The environmentally friendly water-resistant adhesive contains the following components by mass fraction: water-based polyurethane emulsion 40-60 parts, modified phenolic resin 15-25 parts, nano-silica sol 5-10 parts, crosslinking agent 2-5 parts, wet dispersing agent 0.5-2 parts, ultraviolet absorber 1.5-2 parts, defoaming agent 0.2-1 part, and deionized water 10-20 parts; The ultraviolet absorber is a compound represented by Formula 1. Formula 1; R1 in Formula 1 is any one of methyl, hydroxyl, methoxy, and carboxyl.

2. The environment-friendly water-resistant sandpaper according to claim 1, characterized in that, The modified phenolic resin is a rosin-modified phenolic resin.

3. The environment-friendly water-resistant sandpaper according to claim 1, characterized in that, The nano-silica sol has a silica content of 25±2% and a pH of 5-7.

4. The environment-friendly water-resistant sandpaper according to claim 1, characterized in that, The crosslinking agent is any one of methylene diisocyanate trimer or isophorone diisocyanate trimer.

5. The environment-friendly water-resistant sandpaper according to claim 1, characterized in that, The wet dispersing agent is a sodium or ammonium polycarboxylate salt.

6. The environment-friendly water-resistant sandpaper according to claim 1, wherein The defoaming agent is polydimethylsiloxane.

7. The environment-friendly water-resistant sandpaper according to claim 1, wherein the binder is a mixture of the polyurethane resin and the acrylic resin. The abrasive is one or more of alumina, silicon carbide, or zirconia alumina.

8. The environment-friendly water-resistant sandpaper according to claim 1, wherein, The base material layer is one of waterproof cowhide paper, polyester film, or non-woven fabric.

9. The method for preparing the environment-friendly water-resistant sandpaper according to any one of claims 1-8, characterized in that, The method comprises the following steps: S1. Mix and stir the water-based polyurethane emulsion, modified phenolic resin, nano-silica sol, crosslinking agent, wet dispersing agent, ultraviolet absorber, defoaming agent, and deionized water to prepare an environmentally friendly water-resistant adhesive; S2. Pretreat the base material to remove surface impurities and dry to obtain a treated base material; S3. Apply the environmentally friendly water-resistant adhesive to the treated base material to form a primer layer; S4. Use electrostatic sanding or gravity sanding to uniformly attach the abrasives to the surface of the uncured primer layer, and then send it to a drying device for low-temperature drying and high-temperature curing in sequence. After curing, the environmentally friendly water-resistant sandpaper is obtained.

10. The method for preparing the environment-friendly water-resistant sandpaper according to claim 9, characterized in that, The primer layer has a coating thickness of 5-15 μm; In S4, the low-temperature drying temperature is 60-80°C, and the drying time is 15-30 min; the high-temperature curing temperature is 120-150°C, and the curing time is 30-60 min.

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