A low-odor flexographic ink for breathable films and its preparation method

Abstract

This invention discloses a low-odor flexographic ink for breathable membranes and its preparation method, belonging to the field of water-based flexographic ink technology. It aims to solve the technical problems of existing flexographic inks for breathable membranes, such as strong odor, high VOC emissions, severe damage to breathability, poor adhesion to PE substrates, insufficient abrasion resistance and storage stability, and the inability to synergistically improve multiple performance aspects. The ink of this invention uses a core-shell structured water-based acrylic composite emulsion as the core film-forming component, combined with optimized proportions of composite pigments, low-odor film-forming aids, and composite dispersants; and is equipped with a pre-dispersion, grinding, paint mixing, and filtration / degassing preparation process. The resulting ink can synergistically achieve low odor and low VOC, high breathability retention, strong adhesion, high abrasion resistance, and high storage stability, making it suitable for the flexographic printing needs of PE breathable membranes in hygiene products, medical protective equipment, food packaging, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of water-based flexographic ink technology, specifically relating to a low-odor flexographic ink for breathable films and its preparation method, which is particularly suitable for flexographic printing of polyethylene breathable films in the fields of hygiene products, medical protective equipment, and food packaging. Background Technology

[0002] With the rapid development of functional film materials, polyethylene (PE) breathable membranes, due to their excellent breathability and water resistance, good flexibility, safety and environmental friendliness, and low cost, have been widely used in disposable hygiene products such as baby diapers, feminine hygiene products, and adult incontinence products. Meanwhile, their application in high-end fields such as medical protective clothing, medical dressings, and food preservation packaging continues to expand. The core function of PE breathable membranes stems from their continuous nanoscale microporous structure formed through stretching and molding. Water vapor can freely permeate through the micropores, while liquid water cannot, thus achieving a balance between breathability and waterproofing.

[0003] Flexographic printing is a core process for surface decoration and information labeling of breathable membranes, characterized by high printing speed, adaptability to flexible substrates, and environmental friendliness and efficiency. Flexographic inks are the key materials determining the printing quality, performance, and environmental safety of breathable membranes. Currently, flexographic inks for breathable membranes are mainly divided into two categories: solvent-based inks and water-based inks. Solvent-based inks use organic solvents such as alcohols, esters, and benzenes as dispersion media. While they exhibit good adhesion and printability to PE substrates, they suffer from drawbacks such as high VOC emissions, strong odor, flammability, explosiveness, and poor environmental safety. Furthermore, they cannot meet the stringent requirements of low odor and no harmful residues in fields such as hygiene products, medical protective equipment, and food packaging, and their use is gradually being restricted.

[0004] Water-based flexographic inks, using water as the primary dispersion medium, are low in VOCs, environmentally friendly, safe, and pose no flammable or explosive risks, making them the mainstream development direction for breathable film printing inks. However, existing water-based flexographic inks still face a series of intractable technical bottlenecks in breathable film applications, preventing the synergistic improvement of multiple performance aspects. Specific shortcomings are as follows: First, the odor and VOC control effects are poor. To improve film-forming properties and printability, existing water-based inks often add large amounts of alcohol ether organic solvents, high-odor film-forming aids, and functional additives. At the same time, the acrylic emulsions used have a high residual monomer content, resulting in a strong odor in the finished ink. This fails to meet the core requirement of low odor in the medical and hygiene product fields, and long-term exposure can easily cause discomfort to users and even pose health risks.

[0005] Secondly, the breathability is severely compromised, resulting in the loss of core functions. The micropores of PE breathable membranes are mostly between 100 and 500 nm in diameter. Existing water-based inks have large pigment particle sizes and poor dispersibility, easily leading to agglomeration and directly clogging the micropores of the breathable membrane. Simultaneously, after ink film formation, a continuous and dense polymer film is created, completely covering the microporous structure on the surface of the breathable membrane. This results in a significant decrease in the water vapor permeability of the printed breathable membrane, causing it to lose its core function and fail to meet usage requirements. Current technologies often reduce the amount of ink coating and the content of film-forming materials to minimize the impact on breathability, but this directly leads to unclear printed patterns and a significant decrease in adhesion and abrasion resistance, creating a performance contradiction.

[0006] Third, the adhesion to PE breathable membranes is extremely poor. PE breathable membranes are non-polar, low surface energy materials with low surface tension, while existing water-based inks generally have a surface tension of over 35 mN / m, making it difficult to wet and spread on the surface of PE breathable membranes. Simultaneously, the polarity difference between existing water-based acrylic resins and PE substrates is significant, resulting in weak interfacial bonding and easy ink smudging and delamination after printing, failing to meet the abrasion resistance requirements of hygiene products during packaging, transportation, and use. To improve adhesion, existing technologies often add chlorinated polypropylene resin and high-content silane coupling agents, but chlorinated polypropylene resin has problems such as strong odor and poor weather resistance, while high-content coupling agents lead to decreased ink storage stability and further exacerbate the problem of pore blockage.

[0007] Fourth, the abrasion resistance and scratch resistance are insufficient. Existing breathable films use water-based inks with low levels of abrasion-resistant additives and poor compatibility. During the high-speed packaging, folding, and use of hygiene products, problems such as ink layer peeling and blurred patterns are very likely to occur, seriously affecting the appearance and safety of the product.

[0008] Fifth, poor storage stability. The pigment dispersion system of existing water-based inks is poorly designed, and pigments are prone to sedimentation, stratification, and flocculation, which cannot meet the storage and use requirements of industrial production. At the same time, the pH stability of the ink is poor, and acid value changes are prone to occur during storage, leading to emulsion demulsification and loss of performance.

[0009] Sixth, environmental and safety requirements are insufficient for high-end applications. Existing inks often contain harmful residues such as heavy metals, phthalates, and APEO, which do not meet the relevant national standards and regulations for food contact materials and medical materials, thus preventing them from entering the high-end application market.

[0010] In summary, current technologies lack flexographic inks for breathable films that simultaneously achieve low odor and low VOC content, high breathability retention, strong adhesion, excellent abrasion resistance, high storage stability, and environmental safety. These limitations fail to meet the stringent requirements of high-end applications such as hygiene products, medical protective equipment, and food packaging, indicating a significant technological gap. Therefore, developing a low-odor flexographic ink for breathable films that can comprehensively address all the aforementioned technological deficiencies is of significant technological importance and market application value. Summary of the Invention

[0011] To address the shortcomings of existing flexographic inks for breathable membranes, such as strong odor, high VOC emissions, severely impaired breathability of the membrane, poor adhesion to PE substrates, insufficient abrasion resistance, poor storage stability, and failure to meet environmental and safety standards, and the inability to achieve synergistic improvement in multiple performance aspects, this invention provides a low-odor flexographic ink for breathable membranes and its preparation method. Through innovative formulation design and specialized preparation process, this invention overcomes the performance contradictions of existing technologies, achieving a synergistic improvement in low odor, high breathability, strong adhesion, high abrasion resistance, high stability, and high environmental friendliness, while ensuring excellent flexographic printing adaptability to meet the printing needs of high-end breathable membrane products.

[0012] The objective of this invention can be achieved through the following technical solutions: A low-odor flexographic ink for breathable films, comprising, by weight, the following raw material components: 35-55 parts of core-shell structured waterborne acrylic composite emulsion, 8-18 parts of composite pigment, 2-6 parts of low-odor film-forming aid, 1-3 parts of composite dispersant, 1-4 parts of waterborne abrasion-resistant aid, 0.5-2.5 parts of adhesion promoter, 0.3-1.2 parts of low-odor functional additive, and 20-40 parts of deionized water.

[0013] 1. Core-shell structured waterborne acrylic composite emulsion The core innovative component of this invention is the film-forming body of the ink, which determines the ink's adhesion, air permeability, film-forming properties, and basic mechanical properties. The amount added is 35-55 parts by weight, preferably 40-50 parts by weight.

[0014] The core-shell structured aqueous acrylic composite emulsion of this invention has a core-shell structure, wherein the core layer is obtained by copolymerizing methyl methacrylate and styrene at a mass ratio of 3:1, and the glass transition temperature (Tg) of the core layer is 80-100℃; the shell layer is obtained by copolymerizing butyl acrylate, isooctyl acrylate, and hydroxyethyl methacrylate at a mass ratio of 5:3:2, and the glass transition temperature (Tg) of the shell layer is -10 to -5℃; the ends of the shell layer molecular chains are grafted with polyolefin blocks accounting for 2%-5% of the total mass of the shell layer, and the polyolefin blocks are polyethylene-propylene block copolymers; the solid content of the core-shell structured aqueous acrylic composite emulsion is 45%-50%, and the particle size (D50) is 100-200 nm.

[0015] This invention, through the precise design of a core-shell structure, breaks through the core contradiction in existing technologies of "improving adhesion while maintaining breathability." Its working principle is as follows: First, the core layer is a high-Tg hard monomer copolymer structure with a Tg of 80-100℃, exhibiting extremely high hardness and structural rigidity. During the ink film formation process, it can serve as a rigid support skeleton, preventing the polymer from flowing and collapsing during film formation. This prevents the polymer from entering and clogging the nanopores of the breathable membrane, thus preserving complete water vapor permeation channels for the breathable membrane and fundamentally solving the problem of decreased breathability caused by ink film formation. At the same time, the high-Tg core layer can improve the scratch resistance and heat resistance of the ink layer, preventing plate sticking and clogging during printing.

[0016] Secondly, the shell layer is a low-Tg soft monomer copolymer structure with a Tg of -10 to -5℃, which has excellent flexibility and film-forming properties. It can achieve good film formation at room temperature without the need to add a large amount of film-forming aids. At the same time, the low-Tg shell layer can achieve good wetting and spreading on the surface of PE breathable membrane, forming a tight interfacial contact with the substrate, which greatly improves the adhesion between the ink layer and the substrate.

[0017] Third, the polyolefin blocks grafted to the ends of the shell molecular chains are highly similar to the chemical structure of the PE breathable membrane. According to the principle of similar compatibility, they can form a very strong interfacial bond with the PE substrate. Without the need to add high-odor adhesion promoters, the ink layer can achieve super strong adhesion on the surface of the PE breathable membrane, fundamentally solving the technical problem of poor adhesion of water-based inks on non-polar PE substrates. At the same time, the grafting of polyolefin blocks does not affect the water dispersibility of the emulsion, ensuring the storage stability of the ink.

[0018] Fourth, the emulsion particle size D50 is precisely controlled at 100-200nm, which is much smaller than the micropore size of the breathable membrane (100-500nm). This will not directly clog the micropores, while ensuring the dispersion stability of the emulsion in water and avoiding demulsification and stratification.

[0019] 2. Composite pigments Composite pigments are the color-developing components of inks, determining the ink's tinting strength, hiding power, and appearance properties. They also have a significant impact on air permeability and storage stability. The addition amount is 8-18 parts by weight, preferably 10-15 parts by weight.

[0020] The composite pigment of this invention is a nanoscale pigment modified with a silane coupling agent, which is composed of inorganic pigment and organic pigment in a mass ratio of 2:1. The inorganic pigment is at least one of rutile nano titanium dioxide, nano iron oxide red, and nano iron oxide yellow, and the organic pigment is at least one of phthalocyanine blue BGS, phthalocyanine green G, and permanent red F5RK. The particle size D50 of the composite pigment is 80-150nm, and the oil absorption is 18-25g / 100g.

[0021] This invention features a specialized design for composite pigments, addressing the problems of easy agglomeration, pore clogging, and poor dispersibility in existing pigments. First, an inorganic and organic pigment blend is used. Inorganic pigments have excellent hiding power, weather resistance and chemical stability, while organic pigments have bright colors and high tinting strength. The blend can balance the hiding power, tinting strength and color performance of the ink, while avoiding the performance defects caused by excessive addition of a single pigment.

[0022] Secondly, the surface of the pigment is modified by using a silane coupling agent, which introduces hydrophilic groups on the pigment surface, greatly improving the dispersibility and wettability of the pigment in the aqueous system, avoiding pigment agglomeration and sedimentation, and improving the storage stability of the ink. At the same time, the modified pigment surface can form chemical bonds with the acrylic emulsion, improving the density and abrasion resistance of the ink layer.

[0023] Third, the pigment particle size D50 is precisely controlled at 80~150nm, which is much smaller than the micropore size of the breathable membrane. It will not directly block the micropores, while ensuring excellent coloring power and hiding power. The printed pattern is delicate and clear, without any graininess.

[0024] 3. Low-odor film-forming aids The role of low-odor film-forming aids is to lower the minimum film-forming temperature of the emulsion, promote the fusion of emulsion particles to form a film, improve the density and flexibility of the ink layer, and at the same time ensure low odor and low VOC characteristics. The addition amount is 2-6 parts by weight, preferably 3-5 parts by weight.

[0025] The low-odor film-forming aid of this invention is a compound of refined grade 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and polypropylene glycol diglycidyl ether in a mass ratio of 3:1. The refined grade 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate has a VOC content ≤5g / L and an odor level ≤1. The refined grade 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate undergoes special distillation purification to remove residual aldehydes, alcohols, and other low-molecular-weight impurities, significantly reducing odor and VOC content. It also exhibits excellent film-forming aid effects, good compatibility with acrylic emulsions, and can effectively lower the minimum film-forming temperature. Polypropylene glycol diglycidyl ether is a reactive film-forming aid that can undergo cross-linking reactions with the hydroxyl and carboxyl groups in the acrylic emulsion. It integrates into the polymer network structure during film formation, does not volatilize and generate VOCs or odor, and can increase the cross-linking density of the ink layer, further enhancing adhesion and water resistance. The combination of the two ensures excellent film-forming effect while achieving extremely low odor and VOC emissions, thus solving the technical defects of existing film-forming aids, such as strong odor and high VOC.

[0026] 4. Composite dispersants The function of the composite dispersant is to wet the pigment surface, reduce the surface tension between pigment particles, prevent pigment agglomeration and sedimentation, and improve the dispersion stability of pigment and the storage stability of ink. The addition amount is 1-3 parts by weight, preferably 1.5-2.5 parts by weight.

[0027] The composite dispersant of this invention is a mixture of an aqueous ammonium polyacrylate dispersant and a polyether-modified siloxane dispersant in a mass ratio of 2:1. The aqueous ammonium polyacrylate dispersant has a weight-average molecular weight of 5000-8000 and an acid value of 120-150 mgKOH / g; the polyether-modified siloxane dispersant has an HLB value of 10-14. The aqueous ammonium polyacrylate dispersant is an anionic dispersant, which can form a stable adsorption layer on the pigment surface through charge repulsion, preventing pigment particle aggregation and exhibiting excellent dispersion effects on inorganic pigments. The polyether-modified siloxane dispersant is a nonionic dispersant, which can improve dispersion stability through steric hindrance, exhibiting excellent wetting and dispersion effects on organic pigments, while also reducing the surface tension of the ink and improving the wetting and spreading properties of the ink on a PE substrate. The combination of these two dispersants can simultaneously achieve efficient dispersion of both inorganic and organic pigments, significantly improving the dispersion stability of the pigments and the storage stability of the ink, while also improving the printability of the ink.

[0028] 5. Water-based abrasion-resistant additives The function of water-based abrasion-resistant additives is to improve the surface smoothness, abrasion resistance and scratch resistance of the ink layer, and to prevent ink loss and scratches after printing. The amount added is 1-4 parts by weight, preferably 2-3 parts by weight.

[0029] The water-based abrasion-resistant additive of this invention is a compound of high-density polyethylene wax emulsion and polytetrafluoroethylene-modified polyethylene wax micropowder at a mass ratio of 4:1. The high-density polyethylene wax emulsion has a solid content of 35%-40% and a particle size D50 ≤ 150 nm. The polytetrafluoroethylene-modified polyethylene wax micropowder has a melting point of 105-115℃ and a particle size D50 ≤ 200 nm. The high-density polyethylene wax emulsion can form a uniform, smooth film on the ink layer surface, reducing the coefficient of friction and improving dry and wet abrasion resistance. It also has good compatibility with acrylic emulsions and does not affect the adhesion and film-forming properties of the ink layer. The polytetrafluoroethylene-modified polyethylene wax micropowder has an extremely low coefficient of friction and excellent high-temperature resistance, which can further improve the scratch resistance and abrasion durability of the ink layer, while preventing plate sticking during high-speed printing. The compound of the two can synergistically improve the abrasion resistance of the ink layer while ensuring that the ink's breathability and printability are not affected.

[0030] 6. Adhesion promoters The role of adhesion promoters is to further enhance the interfacial bonding between the ink layer and the PE breathable membrane, thereby improving the adhesion performance of the ink on low surface energy PE substrates, without affecting the low odor characteristics of the ink. The addition amount is 0.5-2.5 parts by weight, preferably 1-2 parts by weight. When the addition amount is less than 0.5 parts, the adhesion improvement effect is not significant; when the addition amount is more than 2.5 parts, it will lead to softening of the ink layer, decreased abrasion resistance and heat resistance, and affect the storage stability of the ink.

[0031] The adhesion promoter of this invention is a water-based nonionic polyolefin modified resin with a solid content of 30%-35%, a softening point of 85-95℃, a viscosity of 500-1000 mPa·s at 25℃, no solvent residue, and specific adhesion properties to polyethylene substrates. This adhesion promoter has a similar polyolefin structure to the PE substrate, forming a very strong interfacial bond with the PE breathable membrane. It also exhibits excellent compatibility with core-shell structured acrylate emulsions, allowing it to integrate into the polymer film-forming network, further enhancing the anchoring effect between the ink layer and the substrate, thus significantly improving adhesion. Furthermore, this additive is a water-based, solvent-free system, odorless, and VOC-free, meeting environmental protection and low-odor requirements, thus overcoming the shortcomings of existing adhesion promoters that have a strong odor and affect storage stability.

[0032] 7. Low-odor functional additives The role of low-odor functional additives is to adjust the printability, defoaming, leveling and pH stability of inks, to ensure the printing effect and storage stability of inks, while maintaining low odor characteristics. The addition amount is 0.3-1.2 parts by weight, preferably 0.6-1.0 parts by weight.

[0033] The low-odor functional additives of this invention, by weight, include 0.1-0.4 parts of a low-odor defoamer, 0.1-0.4 parts of a low-odor leveling agent, and 0.1-0.4 parts of a pH adjuster. The low-odor defoamer is a mineral oil-free and silicone-free polyether-based defoamer, which effectively eliminates foam generated during ink production and printing, while preventing silicone oil precipitation, pinhole risk, odor, and VOC emissions. The low-odor leveling agent is a non-ionic acrylate leveling agent, which effectively reduces the surface tension of the ink, improves the wetting and spreading properties of the ink on the PE breathable membrane surface, and improves the smoothness and clarity of the printed pattern, without affecting the adhesion of the ink layer, and is odorless and leaves no harmful residues. The pH adjuster is a low-odor N-methyldiethanolamine, which can stabilize the pH value of the ink within the range of 8.0-9.0, ensuring the storage stability of the acrylate emulsion and preventing demulsification and stratification. It also has extremely low odor and no VOC emissions, solving the problem of strong odor in existing pH adjusters such as AMP-95.

[0034] 8. Deionized water Deionized water is the main dispersion medium for inks. It is environmentally friendly, safe, odorless, and has no VOC emissions. The addition amount is 20-40 parts by weight, preferably 25-35 parts by weight. It is used to adjust the solid content and viscosity of the ink to make it suitable for the process requirements of flexographic printing.

[0035] Furthermore, the present invention also provides a method for preparing the above-mentioned low-odor flexographic ink for breathable films, comprising the following steps: S1 Pre-dispersion: According to the mass ratio, add deionized water and composite dispersant to the dispersion tank, stir evenly at a speed of 300-500 r / min, then add composite pigment, increase the speed to 1200-1500 r / min, stir and disperse for 20-30 min to obtain pigment pre-dispersion slurry; the purpose of this step is to make the dispersant fully wet the pigment surface through high-speed stirring, initially break up the pigment agglomerates, and prepare for subsequent grinding.

[0036] S2 Grinding: The pigment pre-dispersion slurry obtained in step S1 is fed into a horizontal sand mill, using 0.6~0.8mm zirconia beads as the grinding medium, and ground until the pigment fineness is ≤15μm to obtain nano pigment paste; this step controls the pigment particle size within the design range through fine grinding, ensuring the dispersibility and coloring power of the pigment, and avoiding large pigment particles from clogging the micropores of the breathable membrane.

[0037] S3 Paint Mixing: Transfer the nano-pigment paste obtained in step S2 into a paint mixing tank. At a medium-low speed of 400-600 r / min, add the core-shell structured waterborne acrylic composite emulsion, adhesion promoter, low-odor film-forming aid, and waterborne abrasion-resistant aid in sequence. After stirring evenly, add the low-odor functional aid and continue stirring for 15-25 min to obtain a mixed slurry. This step uses medium-low speed stirring to avoid emulsion breakage caused by high-speed stirring, while ensuring that all components are fully mixed evenly to avoid generating a large amount of foam.

[0038] S4 Filtration and Degassing: The mixed slurry obtained in step S3 is filtered through a 200-300 mesh filter to remove a small amount of large particulate impurities and agglomerates. Then, it is vacuum degassed for 10-20 minutes under a vacuum of -0.06-0.08 MPa to remove air bubbles from the slurry, thus obtaining the low-odor flexographic ink for the breathable membrane. This step can ensure the fineness and printability of the ink and avoid defects such as pinholes and ink breaks caused by air bubbles.

[0039] The beneficial effects of this invention are: (1) The entire system of this invention uses low-odor, low-VOC raw materials, with deionized water as the only dispersion medium, and no organic solvents such as benzene, ketones, alcohols and ethers are added; by selecting refined low-odor film-forming aids, solvent-free functional aids, and low-residue monomer core-shell structure emulsions, the source of odor and VOC is controlled from the source.

[0040] (2) This invention uses an innovative core-shell structure waterborne acrylic composite emulsion design. The high Tg rigid core layer serves as a supporting skeleton to prevent polymer collapse and blockage of breathable micropores during film formation. The low Tg flexible shell layer achieves good wetting and spreading. The polyolefin blocks grafted onto the shell layer achieve a super strong bond with the PE substrate, fundamentally breaking through the performance bottleneck of the existing technology that "improving adhesion inevitably leads to a decrease in breathability".

[0041] (3) This invention significantly improves the smoothness and wear resistance of the ink layer by combining high-density polyethylene wax emulsion with polytetrafluoroethylene modified polyethylene wax micro powder; through the precise design of composite dispersant and the application of surface-modified nano-composite pigments, the pigments are stable in the water system for a long time; at the same time, the pH value of the ink is stabilized in the optimal range of 8.0~9.0 by using a low-odor pH adjuster, which ensures the long-term stability of the acrylic emulsion. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following detailed description, in conjunction with embodiments, provides a detailed explanation of the specific implementation methods, structures, features, and effects of the present invention. Experimental methods in this embodiment, unless otherwise specified, were conducted according to conventional methods and conditions in the art. All raw materials used were commercially available industrial-grade products that meet the relevant standards for food contact materials. Specific raw material specifications are as follows: 1. Core-shell structured waterborne acrylic composite emulsion: self-made, solid content 48%, core layer Tg 90℃, shell layer Tg -8℃, shell layer grafted with 3% polyethylene-propylene block copolymer, particle size D50 150nm; 2. Common water-based acrylic emulsion: commercially available, solid content 48%, Tg 10℃, particle size D50 150nm, used for comparative examples; 3. Composite pigment: self-made, rutile nano titanium dioxide and phthalocyanine blue BGS are compounded at a mass ratio of 2:1, and surface modified by γ-aminopropyltriethoxysilane, with a particle size D50 of 120nm and an oil absorption of 22g / 100g. 4. Ordinary unmodified pigment: Rutile titanium dioxide and Phthalocyanine Blue BGS are compounded at a mass ratio of 2:1, without surface modification, with a particle size of D50 500nm and an oil absorption of 35g / 100g, used as a comparative example; 5. Low-odor film-forming aid: Refined grade 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and polypropylene glycol diglycidyl ether are compounded at a mass ratio of 3:1; 6. Common film-forming aid: Commercially available industrial-grade dodecyl alcohol ester, used for comparative examples; 7. Composite dispersant: Aqueous polyacrylate ammonium salt dispersant (weight average molecular weight 6000, acid value 135mgKOH / g) and polyether modified siloxane dispersant (HLB value 12) are compounded at a mass ratio of 2:1; 8. Single dispersant: Water-based ammonium polyacrylate dispersant (weight average molecular weight 6000, acid value 135 mg KOH / g), used for comparative examples; 9. Water-based wear-resistant additive: High-density polyethylene wax emulsion (solid content 38%, particle size D50 120nm) and polytetrafluoroethylene modified polyethylene wax micro powder (melting point 110℃, particle size D50 180nm) are compounded at a mass ratio of 4:1. 10. Adhesion promoter: Water-based nonionic polyolefin modified resin, solid content 32%, softening point 90℃, viscosity at 25℃ 800mPa·s; 11. Low-odor functional additives: mineral oil-free, organosilicon polyether defoamer, nonionic acrylate leveling agent, N-methyldiethanolamine, compounded in a mass ratio of 1:1:1; 12. Deionized water: conductivity ≤ 5 μS / cm.

[0043] Preparation Example Preparation method of core-shell structured aqueous acrylic composite emulsion This self-made core-shell structured waterborne acrylic composite emulsion was prepared using a semi-continuous seeded emulsion polymerization method. The entire process was free of APEO emulsifiers and high-residue monomers. The final product has a solid content of 48%, a core layer Tg of 90℃, a shell layer Tg of -8℃, and 3% (by total shell mass) of polyethylene-propylene block copolymer grafted to the ends of the shell molecular chains. The particle size D50 is 150nm. The specific preparation steps are as follows: 1. Raw material proportioning preparation Core layer monomer composition: 30 parts methyl methacrylate, 10 parts styrene; Shell monomer composition: 30 parts butyl acrylate, 18 parts isooctyl acrylate, and 12 parts hydroxyethyl methacrylate; Polymerizable polyolefin macromonomer: 1.8 parts of methacrylate-terminated polyethylene-propylene block copolymer (3% of the total mass of the shell monomer, used for grafting at the shell end); Composite emulsifier: 1.2 parts sodium dodecyl diphenyl ether disulfonate, 0.8 parts isotridecyl alcohol polyoxyethylene ether 1000 (anionic-nonionic compound, without APEO); Initiation system: Prepare a 5% (w / w) initiator aqueous solution by mixing 0.4 parts ammonium persulfate with deionized water; pH buffer: 0.15 parts sodium bicarbonate; Deionized water: 108 parts in total, including 60 parts bottom water and 48 parts water for pre-emulsion; Post-treatment reducing agents: 0.05 parts tert-butyl hydroperoxide and 0.05 parts sodium formaldehyde sulfoxylate, used to reduce residual monomers.

[0044] 2. Preparation of pre-emulsion Preparation of core layer pre-emulsion: Add 24 parts of deionized water and 0.8 parts of composite emulsifier to the pre-emulsion tank, stir evenly at 300 r / min, and slowly add the core layer monomer composition dropwise. After the dropwise addition is completed, increase the rotation speed to 800 r / min and emulsify at high speed for 20 min to obtain a uniform and stable core layer pre-emulsion for later use. Preparation of shell pre-emulsion: Add 24 parts of deionized water and 1.2 parts of composite emulsifier to another pre-emulsion tank, stir evenly at 300 r / min, then add shell monomer composition and polymerizable polyolefin macromonomer in sequence. After the addition is completed, increase the speed to 800 r / min and emulsify at high speed for 30 min to obtain a uniform and stable shell pre-emulsion for later use.

[0045] 3. Core layer seed emulsion polymerization Add 60 parts of bottom water and 0.15 parts of pH buffer to a stainless steel reactor equipped with a reflux condenser, temperature control device, and constant pressure dripping device. Turn on the stirring and set the speed to 400 r / min. Heat the reactor to 78°C and keep it at that temperature for 10 min. Add 1 / 3 of the total initiator aqueous solution to the reactor at once, keep it warm for 5 minutes, and then add the core layer pre-emulsion at a constant pressure dropping device at a uniform rate. The dropping time is controlled at 90 minutes, and the reaction temperature is kept stable at 78~80℃ during the dropping process. After the core layer pre-emulsion was added, the reaction was kept at a constant temperature for 60 minutes to obtain the core layer seed emulsion. The monomer conversion rate was ≥98%, confirming that the core layer polymerization was complete.

[0046] 4. Shell grafting polymerization Maintain the reactor temperature at 78~80℃, and add the remaining 2 / 3 of the initiator aqueous solution to the reactor at a uniform rate. At the same time, add the shell pre-emulsion at a uniform rate. The addition time of both is controlled at 120 min. During the addition process, strictly control the matching of the addition rate to ensure that the shell monomer is uniformly polymerized on the surface of the core seed and that the polyolefin macromonomer is simultaneously grafted to the end of the shell molecular chain. After the shell pre-emulsion and initiator aqueous solution were added dropwise, the temperature was raised to 85℃ and kept warm for 90 minutes. The monomer conversion rate was measured to be ≥99%.

[0047] 5. Post-processing and finished product preparation Cool the material in the reactor to 45°C, add post-treatment reducing agent tert-butyl hydrogen peroxide and sodium formaldehyde sulfoxylate, keep the reaction at the temperature for 30 minutes to further eliminate residual monomers and control the total amount of residual monomers to ≤100ppm. Cool to 30°C, add low-odor N-methyldiethanolamine, adjust the pH of the system to 8.0~8.5, filter through a 200-mesh filter to obtain the core-shell structured waterborne acrylic composite emulsion.

[0048] Preparation method of silane coupling agent surface modified composite pigment This self-made composite pigment is a nanoscale pigment modified with γ-aminopropyltriethoxysilane. The inorganic to organic pigment mass ratio is 2:1, the particle size D50 is 120nm, and the oil absorption is 22g / 100g. The specific preparation steps are as follows: 1. Raw material pretreatment Accurately weigh rutile nano titanium dioxide (inorganic pigment) and phthalocyanine blue BGS (organic pigment) at a mass ratio of 2:1, put them into a high-speed mixer, and premix them at 1500 r / min for 15 min to obtain a pigment mixture. The pigment mixture was placed in a vacuum drying oven and dried at 105°C for 2 hours to remove the free moisture adsorbed on the pigment surface. After cooling to room temperature, it was ready for use, and the moisture content of the pigment was controlled to be ≤0.2%.

[0049] 2. Preparation of silane coupling agent hydrolysate Weigh out γ-aminopropyltriethoxysilane (KH550), the amount of which is 1.5% of the total mass of the above pigment mixture; Prepare a mixed solvent with anhydrous ethanol and deionized water in a mass ratio of 9:1, using 10 times the mass of the silane coupling agent. Adjust the pH of the mixed solvent to 4.0-4.5 with glacial acetic acid. The silane coupling agent was slowly added dropwise to the pH-adjusted mixed solvent. After stirring at 300 rpm until homogeneous, the mixture was hydrolyzed at room temperature for 30 minutes to obtain a transparent and homogeneous silane coupling agent hydrolysate for later use.

[0050] 3. Wet surface modification reaction Add anhydrous ethanol (8 times the total mass of the pigment mixture) to a reactor equipped with a temperature control, stirring, and reflux condenser. Turn on the stirring and set the speed to 500 r / min. Slowly add the pretreated pigment mixture. After the addition is complete, increase the speed to 1200 r / min and disperse at high speed for 30 min to obtain a uniform pigment suspension. Heat the pigment suspension to 60°C, maintain the stirring speed at 800 r / min, and add the above-mentioned silane coupling agent hydrolysate dropwise at a constant pressure dropwise device at a uniform rate, with the dropwise time controlled at 40 min. After the addition is complete, keep the temperature at 60℃ and continue stirring for 2 hours to allow the active silanol groups generated by the hydrolysis of the silane coupling agent to fully undergo dehydration condensation reaction with the hydroxyl groups on the pigment surface, forming a stable chemically bonded graft layer on the pigment surface.

[0051] 4. Post-processing and particle size control After the modification reaction is completed, the material is cooled to room temperature and filtered through a plate and frame filter press to obtain a modified pigment filter cake. The filter cake is washed three times with anhydrous ethanol to completely remove unreacted silane coupling agent and free impurities. The washed filter cake was placed in a vacuum drying oven and dried under vacuum at 105°C for 6 hours to obtain dried modified pigment powder. The dried powder was fed into a supersonic airflow pulverizer for pulverization and classification. The rotation speed of the classifier was controlled to obtain modified powder with a particle size D50 of 120 nm, which is the silane coupling agent surface modified composite pigment. Example 1

[0052] This embodiment provides a low-odor flexographic ink for breathable films, comprising the following raw material components by weight: The composition consists of 45 parts of a core-shell structured waterborne acrylic composite emulsion, 12 parts of a composite pigment, 4 parts of a low-odor film-forming aid, 2 parts of a composite dispersant, 2.5 parts of a waterborne abrasion-resistant aid, 1.5 parts of an adhesion promoter, 0.8 parts of a low-odor functional aid, and 32.2 parts of deionized water.

[0053] The method for preparing low-odor flexographic ink for breathable films in this embodiment includes the following steps: S1 Pre-dispersion: According to the above mass proportions, add deionized water and composite dispersant to a clean dispersion tank, stir at 400 r / min for 5 min, and mix evenly; then slowly add composite pigment. After the addition is complete, increase the speed to 1300 r / min and stir at high speed for 25 min to fully wet the pigment surface with dispersant, break up pigment agglomerates, and obtain a uniform pigment pre-dispersion slurry. S2 Grinding: The pigment pre-dispersed slurry obtained in step S1 is fed into a horizontal sand mill. Zirconia beads of 0.6~0.8mm are used as the grinding medium. The speed of the sand mill is controlled at 2000r / min. The mill is circulated and ground 4 times. The pigment fineness is tested to be ≤10μm to obtain nano pigment paste. S3 Paint Mixing: Transfer the nano-pigment paste obtained in step S2 into a clean paint mixing tank. At a medium-low speed of 500 r / min, slowly add the core-shell structured waterborne acrylic composite emulsion, adhesion promoter, low-odor film-forming aid, and waterborne abrasion-resistant aid in sequence. Stir for 5 minutes after each addition to ensure uniform mixing. After all components have been added, add the low-odor functional aid and continue stirring for 20 minutes to obtain a uniform mixed slurry. S4 Filtration and Degassing: The mixed slurry obtained in step S3 is filtered through a 250-mesh filter to remove a small amount of large particulate impurities and agglomerates; then the filtered slurry is transferred to a vacuum degassing tank and vacuum degassed for 15 minutes at a vacuum degree of -0.07MPa to completely remove air bubbles from the slurry, thus obtaining the low-odor flexographic ink for the breathable membrane. Example 2

[0054] This embodiment provides a low-odor flexographic ink for breathable films, comprising the following raw material components by weight: The composition includes 35 parts of a core-shell structured waterborne acrylic composite emulsion, 8 parts of a composite pigment, 2 parts of a low-odor film-forming aid, 1 part of a composite dispersant, 1 part of a waterborne abrasion-resistant aid, 0.5 parts of an adhesion promoter, 0.3 parts of a low-odor functional aid, and 52.2 parts of deionized water.

[0055] The preparation method in this embodiment is exactly the same as that in Example 1. Example 3

[0056] This embodiment provides a low-odor flexographic ink for breathable films, comprising the following raw material components by weight: The composition includes 55 parts of a core-shell structured waterborne acrylic composite emulsion, 18 parts of a composite pigment, 6 parts of a low-odor film-forming aid, 3 parts of a composite dispersant, 4 parts of a waterborne abrasion-resistant aid, 2.5 parts of an adhesion promoter, 1.2 parts of a low-odor functional aid, and 10.3 parts of deionized water.

[0057] The preparation method in this embodiment is exactly the same as that in Example 1.

[0058] Comparative Example 1 The only difference from Example 1 is that the core-shell structured waterborne acrylic composite emulsion is replaced by an equal mass of commercially available ordinary waterborne acrylic emulsion, while the other components, proportions and preparation methods are exactly the same.

[0059] Comparative Example 2 The only difference from Example 1 is that the composite pigment is replaced with an ordinary unmodified pigment, while the other components, proportions and preparation methods are exactly the same.

[0060] Comparative Example 3 The only difference from Example 1 is that no low-odor film-forming aid is added, and the reduced mass fraction is made up by deionized water. The other components, proportions and preparation methods are exactly the same.

[0061] Comparative Example 4 The only difference from Example 1 is that the composite dispersant is replaced by a single water-based ammonium polyacrylate dispersant, while the other components, proportions and preparation methods are exactly the same.

[0062] Comparative Example 5 The only difference from Example 1 is that no water-based wear-resistant additives are added, and the reduced mass is made up by deionized water. The other components, proportions and preparation methods are exactly the same.

[0063] Comparative Example 6 The only difference from Example 1 is that no adhesion promoter is added, and the reduced mass is made up by deionized water. The other components, proportions and preparation methods are exactly the same.

[0064] Comparative Example 7 The only difference from Example 1 is that the low-odor film-forming aid is replaced by commercially available industrial-grade alcohol ester twelve, while the other components, proportions and preparation methods are exactly the same.

[0065] Comparative Example 8 The only difference from Example 1 is that the core layer Tg of the core-shell structured aqueous acrylate composite emulsion used is 60°C (lower than the 80~100°C range specified in this invention), while the other components, proportions and preparation methods are exactly the same.

[0066] Comparative Example 9 The only difference from Example 1 is that the shell Tg of the core-shell structured aqueous acrylate composite emulsion used is 0°C (higher than the -10~-5°C range specified in this invention), while the other components, proportions and preparation methods are exactly the same.

[0067] Comparative Example 10 The only difference from Example 1 is that the particle size D50 of the composite pigment used is 600 nm (higher than the 80~150 nm range defined in this invention), while the other components, proportions and preparation methods are exactly the same.

[0068] Performance testing 1. Test samples: Ink samples prepared in Examples 1-3 and Comparative Examples 1-10.

[0069] 2. Printing substrate: Commercially available PE breathable film for diapers, 20μm thick, water vapor permeability 3000g / (m²). 2 •24h), micropore diameter 100~500nm.

[0070] 3. Printing method: Flexographic proofing machine is used, with an anilox roller line count of 180 lines / inch, printing speed of 100m / min, dry film thickness of 2μm, and hot air drying at 80℃ for 30s after printing. Performance testing is carried out after 24h.

[0071] 4. Testing standards and methods: (1) VOC content: Tested in accordance with GB 38507-2020 "Limits for the content of volatile organic compounds (VOCs) in inks"; (2) Odor rating: 100cm 2 After printing, the breathable membrane sample was placed in a 500mL sealed wide-mouth bottle and placed in a 40℃ constant temperature box for 24 hours. After being taken out, it was evaluated by 10 professional evaluators, and the average value was taken. The odor level was divided into 1 to 5 levels: Level 1 no odor, Level 2 slight odor, Level 3 obvious odor, Level 4 strong odor, and Level 5 irritating odor. (3) Air permeability retention rate: According to GB / T 1037-2021 "Determination of water vapor transmission performance of plastic films and sheets - cup method", the water vapor transmission rate of blank PE breathable film and printed breathable film were tested respectively, and the air permeability retention rate was calculated according to the following formula: Air permeability retention rate = (Water vapor transmission rate of the printed breathable membrane / Water vapor transmission rate of the blank breathable membrane) × 100% (4) Adhesion: The adhesion was tested according to GB / T 9286-2021 "Paints and Varnishes Cross-cut Test". A cross-cut tester with a 1mm spacing was used. After the cross-cut test, 3M 600 tape was used to peel off the film. The film was divided into 0 to 5 grades according to the degree of peeling. Grade 0 is no peeling and Grade 5 is severe peeling. (5) Friction resistance: The test shall be conducted in accordance with GB / T 7706-2008 "Relief Printing of Decorative Products". The friction tester shall be used with a load of 500g. The number of dry friction and wet friction shall be tested respectively. The end point shall be that the ink layer does not fall off obviously and the ink layer is exposed. (6) Storage stability: In accordance with GB / T 6753.3-1986 "Test Method for Storage Stability of Coatings", the ink samples were sealed and stored in a constant temperature chamber at 25℃ for 12 months. The presence of stratification, precipitation, or flocculation was observed. Simultaneously, the viscosity before and after storage was tested according to GB / T 13217.4-2008, and the viscosity change rate was calculated. Viscosity change rate = |Viscosity after storage - Viscosity before storage| / Viscosity before storage × 100% (7) Fineness: Tested in accordance with GB / T 6753.1-2007 "Determination of grinding fineness of paints, varnishes and printing inks"; (8) Environmental safety: Heavy metals and specific migrations were tested according to GB 4806.1-2016, and all sample samples in the examples met the standard requirements.

[0072] 5. Test Results The performance test results of all embodiments and comparative examples are shown in Table 1 below: Table 1. Performance test results of the examples and comparative examples. As can be clearly seen from the test results in Table 1, the low-odor flexographic inks for breathable films prepared in Examples 1-3 of this invention have all achieved the expected performance targets, realizing a synergistic improvement in low odor, high breathability, strong adhesion, high abrasion resistance, and high stability. The specific analysis is as follows: (1) The VOC content of Examples 1 to 3 is ≤10g / L and the odor level is 1, which is far superior to the existing technology level and fully meets the requirements of low odor and low VOC in the high-end field. Among them, Comparative Example 7 uses ordinary industrial grade alcohol ester twelve as film-forming aid, and the VOC content rises to 28.6g / L and the odor level reaches 3, which proves the key role of the selection of low odor film-forming aid in the control of odor and VOC.

[0073] (2) The air permeability retention rate of Examples 1 to 3 is ≥95%, which hardly affects the core air permeability function of the PE breathable membrane; while Comparative Example 1 uses ordinary water-based acrylic emulsion, and the air permeability retention rate is only 72.5%; Comparative Example 8 has a core layer Tg lower than the limit range of this invention, and the air permeability retention rate is only 78.6%; Comparative Example 10 has a pigment particle size that exceeds the range, and the air permeability retention rate is only 68.2%. This fully demonstrates that the core-shell structure emulsion design, core layer Tg parameter control, and selection of nanoscale composite pigments of this invention are the core keys to ensuring high air permeability retention rate, and solve the technical defects of existing ink film formation blocking micropores.

[0074] (3) The adhesion of Examples 1 to 3 all reached level 0, with no ink loss. However, Comparative Example 1 used ordinary emulsion and the adhesion was only level 3. Comparative Example 3 did not add film-forming aid and the adhesion was level 2. Comparative Example 6 did not add adhesion promoter and the adhesion was only level 4. Comparative Example 9 had a shell Tg that exceeded the range and the adhesion was level 2. This fully demonstrates that the polyolefin block grafting design, the addition of adhesion promoter, and the control of shell Tg parameters of the core-shell structure emulsion of the present invention are the core to achieve super strong adhesion and solve the technical problem of poor adhesion of water-based inks on PE substrates.

[0075] (4) The dry friction resistance times of Examples 1 to 3 are all ≥500 times and the wet friction resistance times are all ≥300 times, which shows excellent friction resistance performance; while Comparative Example 5, without the addition of water-based wear-resistant additives, has only 180 dry friction resistance times and only 90 wet friction resistance times, which fully demonstrates the key role of the compound design of the water-based wear-resistant additives in improving the friction resistance performance.

[0076] (5) Examples 1-3 showed no stratification, precipitation, or flocculation after 12 months of storage at room temperature, with viscosity change rates ≤10%, demonstrating excellent storage stability. In contrast, Comparative Example 2, using ordinary unmodified pigments, showed significant precipitation after 6 months, with a viscosity change rate of 28.5%. Comparative Example 4, using a single dispersant, showed stratification and precipitation after 8 months, with a viscosity change rate of 22.3%. Comparative Example 10, with excessively large pigment particle size, showed severe precipitation after 3 months, with a viscosity change rate of 35.7%. This fully demonstrates that the design of the surface-modified nanocomposite pigments and composite dispersants in this invention is the core key to achieving long-term storage stability of inks.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A low-odor flexographic ink for breathable films, characterized in that, By weight, it includes the following raw material components: 35-55 parts of core-shell structured waterborne acrylic composite emulsion, 8-18 parts of composite pigment, 2-6 parts of low-odor film-forming aid, 1-3 parts of composite dispersant, 1-4 parts of waterborne abrasion-resistant aid, 0.5-2.5 parts of adhesion promoter, 0.3-1.2 parts of low-odor functional aid, and 20-40 parts of deionized water; The core-shell structured aqueous acrylic composite emulsion has a core-shell structure, wherein the core layer is obtained by copolymerizing methyl methacrylate and styrene at a mass ratio of 3:1, and the glass transition temperature Tg of the core layer is 80-100℃. The shell is made by copolymerizing butyl acrylate, isooctyl acrylate and hydroxyethyl methacrylate in a mass ratio of 5:3:2, and the glass transition temperature Tg of the shell is -10 to -5℃. The shell molecular chain ends are grafted with polyolefin blocks accounting for 2%-5% of the total mass of the shell, and the polyolefin blocks are polyethylene-propylene block copolymers; The core-shell structured aqueous acrylic composite emulsion has a solid content of 45%-50% and a particle size D50 of 100-200 nm.

2. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The composite pigment is a nanoscale pigment modified with a silane coupling agent, which is composed of inorganic pigment and organic pigment in a mass ratio of 2:

1. The inorganic pigment is at least one of rutile nano titanium dioxide, nano iron oxide red, and nano iron oxide yellow; the organic pigment is at least one of phthalocyanine blue BGS, phthalocyanine green G, and permanent red F5RK. The composite pigment has a particle size D50 of 80-150nm and an oil absorption of 18-25g / 100g.

3. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The low-odor film-forming aid is a compound of refined grade 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and polypropylene glycol diglycidyl ether in a mass ratio of 3:

1.

4. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The composite dispersant is a mixture of water-based ammonium polyacrylate dispersant and polyether-modified siloxane dispersant in a mass ratio of 2:

1. The water-based ammonium polyacrylate dispersant has a weight-average molecular weight of 5000-8000 and an acid value of 120-150 mgKOH / g. The HLB value of the polyether-modified siloxane dispersant is 10-14.

5. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The water-based wear-resistant additive is a compound of high-density polyethylene wax emulsion and polytetrafluoroethylene modified polyethylene wax micro powder in a mass ratio of 4:

1. The high-density polyethylene wax emulsion has a solid content of 35%-40% and a particle size D50≤150nm; The polytetrafluoroethylene modified polyethylene wax micropowder has a melting point of 105-115℃ and a particle size D50≤200nm.

6. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The adhesion promoter is a water-based nonionic polyolefin modified resin with a solid content of 30%-35%, a softening point of 85-95℃, a viscosity of 500~1000mPa·s at 25℃, and no solvent residue.

7. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, The low-odor functional additives, by weight, include 0.1-0.4 parts of low-odor defoamer, 0.1-0.4 parts of low-odor leveling agent, and 0.1-0.4 parts of pH adjuster; the low-odor defoamer is a mineral oil-free and organosilicon-free polyether defoamer, the low-odor leveling agent is a nonionic acrylate leveling agent, and the pH adjuster is low-odor N-methyldiethanolamine.

8. The low-odor flexographic ink for breathable membranes according to claim 1, characterized in that, By weight, it includes the following raw material components: 40-50 parts of core-shell structured waterborne acrylic composite emulsion, 10-15 parts of composite pigment, 3-5 parts of low-odor film-forming aid, 1.5-2.5 parts of composite dispersant, 2-3 parts of waterborne abrasion-resistant aid, 1-2 parts of adhesion promoter, 0.6-1.0 parts of low-odor functional aid, and 25-35 parts of deionized water.

9. A method for preparing a low-odor flexographic ink for a breathable film according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. According to the mass fraction, add deionized water and composite dispersant to the dispersion tank, stir evenly at a speed of 300-500 r / min, then add composite pigment, increase the speed to 1200-1500 r / min, stir and disperse for 20-30 min to obtain pigment pre-dispersion slurry; S2. The pigment pre-dispersion slurry obtained in step S1 is fed into a horizontal sand mill and ground with zirconium bead grinding media until the pigment fineness is ≤15μm to obtain nano pigment slurry; S3. Transfer the nano pigment paste obtained in step S2 into a paint mixing tank. At a speed of 400-600 r / min, add the core-shell structure waterborne acrylic composite emulsion, adhesion promoter, low-odor film-forming aid, and waterborne wear-resistant aid in sequence. After stirring evenly, add the low-odor functional aid and continue stirring for 15-25 min to obtain a mixed slurry. S4. Filter the mixed slurry obtained in step S3 through a 200-300 mesh filter, and then degas it under vacuum at a vacuum degree of -0.06--0.08MPa for 10-20 minutes to obtain the low-odor flexographic ink for the breathable membrane.

Images