Low-VOC emission special ink for children's picture books, preparation method and application thereof

Abstract

The present invention relates to the field of ink technology, specifically, to a special ink for children's picture books with low VOC emissions, a preparation method thereof, and an application thereof, comprising the following raw materials: 25-35 parts by weight of epoxy-acrylic acid copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan. In the design of the present invention, the epoxy-acrylic acid copolymer resin forms hydrogen bonds and chemical bonds with the substrate through the rigid skeleton and polar groups of bisphenol A epoxy resin, thereby improving the adhesion on non-absorbent substrates and reducing the risk of falling off; hydroxyethyl methacrylate is grafted to introduce flexible acrylic acid segments, avoiding the brittleness of pure epoxy resin, so that the ink film has both high hardness and toughness; in addition, the long-chain alkyl improves the hydrophobicity of the resin, enhances the wettability to low surface energy substrates, and maintains the environmental protection of the aqueous system.

Description

Technical Field

[0001] The present invention relates to the technical field of inks, and in particular to a special ink for children's picture books with low VOC emissions, a preparation method thereof, and applications thereof. Background Art

[0002] Traditional printing inks usually contain volatile organic compounds (VOCs), which are released into the air during use, negatively affecting indoor air quality and causing harm to human health. VOCs include benzene, toluene, xylene, etc., which can not only cause acute poisoning and paralysis of the central nervous system, but long-term exposure can also lead to more serious health problems such as leukemia. Children are particularly sensitive to harmful substances in the environment, especially those chemicals that enter the body through skin contact or breathing.

[0003] Patent number CN110054931A discloses an environmentally friendly printing ink for children's books and periodicals, and a preparation method thereof. The ink comprises 30-60 parts by weight of soybean oil, 8-20 parts by weight of linseed oil, 8-12 parts by weight of edible glycerin, 15-30 parts by weight of rosin-modified phenolic resin, 0.5-2 parts by weight of aluminum phosphate, 18-25 parts by weight of food coloring, 0.1-0.5 parts by weight of disodium ethylenediaminetetraacetic acid, and 0.2-1 parts by weight of ferric isooctanoate. The ink uses soybean oil as the primary solvent, as the raw material is readily available and its production is environmentally friendly. The ink, combined with the rosin-modified phenolic resin, exhibits good water resistance. Furthermore, the use of linseed oil and ferric isooctanoate facilitates rapid drying, and linseed oil, as an edible oil, does not harm children's health.

[0004] However, these new inks also have some limitations. On non-absorbent substrates (such as certain coated papers), water-based inks have insufficient adhesion and are prone to falling off or abrasion. In view of this, we propose low-VOC emission inks specifically for children's picture books, as well as their preparation method and application. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-VOC emission ink specifically for children's picture books, as well as a preparation method and application thereof, to solve the problem mentioned in the above background art that water-based inks have insufficient adhesion on non-absorbent substrates (such as certain coated papers) and are easily detached or worn.

[0006] In a first aspect, the present invention provides a low-VOC emission ink for children's picture books, comprising the following raw materials: 25-35 parts by weight of epoxy-acrylic copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan;

[0007] The epoxy-acrylic acid copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate.

[0008] Preferably, in the epoxy-acrylic copolymer resin, the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.1-0.3.

[0009] Preferably, the preparation method of the epoxy-acrylic acid copolymer resin is as follows:

[0010] Mixing bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid, adding 0.5-1% tetrabutylammonium bromide, and reacting at 80-90°C for 2-3 hours under nitrogen protection; after the reaction is completed, performing reduced pressure distillation at 80-90°C and 10-15 mmHg to remove unreacted monomers, adding propylene glycol methyl ether to adjust the solid content of the system, and obtaining a modified epoxy resin solution;

[0011] The modified epoxy resin solution is heated to 85-95°C, hydroxyethyl methacrylate is added dropwise, and 0.2-0.5% azobisisobutyronitrile is added, and the mixture is kept warm for 3-4 hours. After the reaction is completed, 0.05-0.1% tocopherol is added, and the mixture is cooled to room temperature and filtered to obtain an epoxy-acrylic copolymer resin.

[0012] The C15 long-chain alkyl group in 2-hydroxy-6-pentadecylbenzoic acid has significant hydrophobicity, which can reduce the surface tension of the resin system and make it easier to wet non-absorbent substrates (such as the polyethylene / polypropylene coating of coated paper); the long-chain alkyl group is physically adsorbed to the hydrophobic surface of the substrate through van der Waals forces, forming an "anchoring effect" and thus enhancing the interfacial bonding force; in addition, the hydroxyl groups and ether bonds in bisphenol A epoxy resin can form hydrogen bonds or dipole effects with trace polar groups (such as carboxyl or amino groups) on the surface of the substrate, providing secondary chemical bonding force; the unreacted epoxy groups (from bisphenol A diglycidyl ether) undergo ring-opening reactions with active groups (such as -OH, -NH2) on the surface of the substrate during the film formation process to form covalent bonds (chemical bonding).

[0013] The hydroxyl groups in hydroxyethyl methacrylate (HEMA) can react with the remaining epoxy or carboxyl groups of the epoxy resin to form a cross-linked network, thereby increasing the cured density of the resin. The grafted acrylic acid segments introduce flexibility, reducing the risk of brittle shedding due to excessive rigidity. The rigid skeleton of the epoxy resin provides high hardness and wear resistance, while the flexibility of the acrylic acid segments enhances impact resistance and flexibility, preventing the ink film from cracking due to bending or friction.

[0014] Preferably, propylene glycol methyl ether is added to adjust the solid content of the system to 50-60%.

[0015] Preferably, the rate of adding hydroxyethyl methacrylate is 1-2 mL / min.

[0016] In a second aspect, the present invention provides a method for preparing a low-VOC emission ink for children's picture books, which is used to prepare any of the above-mentioned low-VOC emission inks for children's picture books, comprising the following steps:

[0017] S1.1. Weigh the following raw materials in parts by weight: 25-35 parts by weight of epoxy-acrylic copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan;

[0018] S1.2. Add epoxy-acrylic acid copolymer resin and 30-40°C deionized water into a reaction kettle and stir at 200-300 rpm for 10-15 minutes to obtain a resin base;

[0019] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 400-500 rpm and continue stirring for 15-20 minutes. Then, sprinkle in the crushed palm wax and continue stirring at 400-500 rpm for 20-30 minutes at 40-50°C. Then, add the pigment slurry and stir at 400-500 rpm for 10-15 minutes.

[0020] Rosin glycerol ester is a natural resin derivative with an amphiphilic structure consisting of a hydrophobic rosin acid backbone and hydrophilic glycerol ester groups. This structure can reduce the surface tension of ink systems, making them easier to spread on low-surface-energy coated paper (such as PE / PP coatings). Its hydrophobic portion is compatible with the hydrophobic coating of the substrate (such as polyethylene), while its hydrophilic portion is compatible with water-based resins (such as epoxy-acrylic copolymers), forming a "bridge" effect that reduces interfacial defects, thereby improving the adhesion and durability of the ink. In addition, the high viscosity of rosin glycerol ester can improve the initial adhesion of the ink, allowing the ink to better "grasp" the substrate surface before drying, reducing the risk of peeling due to printing pressure or drying shrinkage. As a natural tackifier, it can also prevent pigment sedimentation, ensure ink uniformity, and avoid localized adhesion loss due to pigment aggregation.

[0021] Palm wax is a natural plant wax that can partially migrate to the surface during the ink drying process, forming a microcrystalline protective layer, thereby improving the wear resistance and scratch resistance of the ink film. This wax film can effectively reduce the damage to the ink caused by external friction, such as friction from children's fingers or wear from stacked books. The addition of palm wax can also optimize the rheological properties of the ink, making it less likely to accumulate during printing, thereby improving printability. In addition, the hydrophobic properties of the wax can reduce the absorption of water by the ink film, preventing expansion and shedding due to changes in humidity.

[0022] S1.4. Add the rosemary extract nanoemulsion dropwise to the reaction kettle and reduce the stirring speed to 200-300 rpm. Then add carboxymethyl chitosan and stir at 200-300 rpm for 5-10 minutes to obtain ink.

[0023] When children's picture books are stored for a long time or come into contact with hand sweat, microorganisms (such as mold and bacteria) will decompose the organic components in the ink (such as resins and plasticizers), causing the ink film to become brittle and its adhesion to decrease. The carnosic acid and rosmarinic acid in rosemary extract have natural antibacterial properties and can effectively extend the life of the ink. At the same time, its phenolic compounds can capture free radicals and delay aging. In addition, the uniform dispersion of nano-emulsion will not affect the transparency and printing effect of the ink.

[0024] Carboxymethyl chitosan (CMCS) is a water-soluble chitosan derivative. Its carboxylic acid group (-COOH) and hydroxyl group (-OH) can form hydrogen bonds with the polar groups of epoxy-acrylic resin, thereby improving the mechanical strength of the ink film and reducing film rupture caused by external forces. The amino group (-NH2) of carboxymethyl chitosan can form ionic bonds or hydrogen bonds with the carboxyl group (-COOH) on the surface of coated paper, enhancing chemical adsorption. Carboxymethyl chitosan itself has antibacterial properties and works synergistically with rosemary extract to further inhibit microbial growth, meeting the safety standards for children's products.

[0025] S1.5. Adjust the pH to 5.5-6.0 with 0.05-0.1 mol / L citric acid and adjust the ink viscosity by adding deionized water. Degas the ink at -0.09-0.1 MPa and 30-40°C for 15-20 minutes. After degassing, filter through a 3-5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0026] Preferably, in S1.3, the pigment slurry is prepared by mixing the pigment and deionized water in a ratio of 1:1, treating the mixture at a power of 100-200 W for 5-10 minutes, and then grinding the mixture 3-4 times in a grinding machine while controlling the grinding temperature to be 30-35°C.

[0027] Preferably, in S1.4, the rate at which the rosemary extract nanoemulsion is dripped into the reaction kettle is 2-3 mL / min.

[0028] Preferably, in S1.5, deionized water is added to adjust the ink viscosity to 500-800 mPa·s.

[0029] In a third aspect, the present invention provides applications of low-VOC emission inks specifically for children's picture books, including the above-mentioned low-VOC emission inks specifically for children's picture books, and applications of the inks in children's picture books.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. In this low-VOC emission ink specifically designed for children's picture books, as well as its preparation method and application, the epoxy-acrylic copolymer resin forms hydrogen bonds and chemical bonds with the substrate through the rigid skeleton and polar groups (such as hydroxyl groups and ether bonds) of the bisphenol A epoxy resin, thereby improving adhesion to non-absorbent substrates (such as coated paper) and reducing the risk of shedding; hydroxyethyl methacrylate grafting introduces flexible acrylic chain segments, avoiding the brittleness of pure epoxy resin and giving the ink film both high hardness and toughness; in addition, the long-chain alkyl group improves the hydrophobicity of the resin and enhances its wettability to low-surface-energy substrates, while maintaining the environmental friendliness of the water-based system.

[0032] 2. In this low-VOC emission ink specifically designed for children's picture books, as well as its preparation method and application, rosin glycerol ester serves as a highly efficient tackifier. Its unique esterified rosin structure significantly enhances the viscosity and cohesion of the ink system, allowing the printed pattern to adhere more firmly to the surface of non-absorbent substrates. Secondly, the amphiphilic molecular structure of rosin glycerol ester (hydrophobic rosin skeleton + hydrophilic glycerol group) effectively reduces the surface tension of the ink, significantly improving its wettability and spreadability on low-surface-energy substrates such as PE / PP coated paper. In addition, rosin glycerol ester can form intermolecular hydrogen bonds with epoxy-acrylic resins, enhancing the compatibility of the resin-pigment system and preventing localized adhesion loss caused by pigment sedimentation. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] The present invention provides a special ink for children's picture books with low VOC emissions, comprising the following raw materials: 25-35 parts by weight of epoxy-acrylic copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan;

[0035] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate, and the residual bisphenol A content in the epoxy-acrylic copolymer resin is ≤0.01ppm.

[0036] The rosemary extract nanoemulsion was prepared by mixing the rosemary extract and Tween-80 in a mass ratio of 1:2 and then subjecting the mixture to high-pressure homogenization (50-100 MPa, 3 cycles).

[0037] The main active ingredients in rosemary extract include phenolic compounds (carnosic acid, carnosol, rosmarinic acid), flavonoids (apigenin, luteolin), terpenoids (α-pinene, β-pinene) and organic acids.

[0038] The preparation method of epoxy-acrylic acid copolymer resin is as follows:

[0039] Mixing bisphenol A diglycidyl ether with 2-hydroxy-6-pentadecylbenzoic acid, adding 0.5-1% tetrabutylammonium bromide, and reacting at 80-90°C for 2-3 hours under nitrogen protection; after the reaction is completed, performing reduced pressure distillation at 80-90°C and 10-15 mmHg to remove unreacted monomers, and adding propylene glycol methyl ether to adjust the solid content of the system to 50-60%, thereby obtaining a modified epoxy resin solution;

[0040] The modified epoxy resin solution was heated to 85-95°C, hydroxyethyl methacrylate was added dropwise at a rate of 1-2 mL / min, and 0.2-0.5% azobisisobutyronitrile was added, and the mixture was kept warm for 3-4 hours. After the reaction was completed, 0.05-0.1% tocopherol was added, and the mixture was cooled to room temperature and filtered to obtain an epoxy-acrylic copolymer resin.

[0041] Example 1: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0042] S1.1. Weigh the following raw materials in parts by weight: 25 parts by weight of epoxy-acrylic copolymer resin, 6 parts by weight of pigment, 2 parts by weight of rosin glycerol ester, 1 part by weight of palm wax, 0.1 part by weight of rosemary extract nanoemulsion, and 0.2 part by weight of carboxymethyl chitosan;

[0043] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0044] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0045] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0046] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0047] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0048] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.2.

[0049] Example 2: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0050] S1.1. Weigh the following raw materials in parts by weight: 30 parts by weight of epoxy-acrylic copolymer resin, 6 parts by weight of pigment, 2 parts by weight of rosin glycerol ester, 1 part by weight of palm wax, 0.1 part by weight of rosemary extract nanoemulsion, and 0.2 part by weight of carboxymethyl chitosan;

[0051] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0052] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0053] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0054] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0055] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0056] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.2.

[0057] Example 3: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0058] S1.1. Weigh the following raw materials in parts by weight: 35 parts by weight of epoxy-acrylic copolymer resin, 6 parts by weight of pigment, 2 parts by weight of rosin glycerol ester, 1 part by weight of palm wax, 0.1 part by weight of rosemary extract nanoemulsion, and 0.2 part by weight of carboxymethyl chitosan;

[0059] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0060] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0061] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0062] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0063] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0064] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.2.

[0065] Example 4: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0066] S1.1. Weigh the following raw materials in parts by weight: 30 parts by weight of epoxy-acrylic copolymer resin, 8 parts by weight of pigment, 3 parts by weight of rosin glycerol ester, 1.5 parts by weight of palm wax, 0.15 parts by weight of rosemary extract nanoemulsion, and 0.3 parts by weight of carboxymethyl chitosan;

[0067] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0068] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0069] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0070] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0071] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0072] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.2.

[0073] Example 5: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0074] S1.1. Weigh the following raw materials in parts by weight: 30 parts by weight of epoxy-acrylic copolymer resin, 8 parts by weight of pigment, 3 parts by weight of rosin glycerol ester, 1.5 parts by weight of palm wax, 0.15 parts by weight of rosemary extract nanoemulsion, and 0.3 parts by weight of carboxymethyl chitosan;

[0075] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0076] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0077] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0078] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0079] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0080] Among them, the epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.3.

[0081] Example 6: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0082] S1.1. Weigh the following raw materials in parts by weight: 30 parts by weight of epoxy-acrylic copolymer resin, 8 parts by weight of pigment, 3 parts by weight of rosin glycerol ester, 1.5 parts by weight of palm wax, 0.15 parts by weight of rosemary extract nanoemulsion, and 0.3 parts by weight of carboxymethyl chitosan;

[0083] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0084] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0085] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0086] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0087] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0088] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.1.

[0089] Example 7: Low VOC emission ink for children's picture books and its preparation method and application, comprising the following steps:

[0090] S1.1. Weigh the following raw materials in parts by weight: 30 parts by weight of epoxy-acrylic copolymer resin, 10 parts by weight of pigment, 5 parts by weight of rosin glycerol ester, 2 parts by weight of palm wax, 0.2 parts by weight of rosemary extract nanoemulsion, and 0.5 parts by weight of carboxymethyl chitosan;

[0091] S1.2. Add epoxy-acrylic acid copolymer resin and 40°C deionized water into a reaction kettle and stir at 300 rpm for 15 minutes to obtain a resin base;

[0092] S1.3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 500 rpm and continue stirring for 20 minutes. Then sprinkle in the crushed palm wax and continue stirring at 500 rpm for 30 minutes at 50°C. Then add the pigment slurry and stir at 400 rpm for 15 minutes.

[0093] The pigment slurry was prepared by mixing the pigment with deionized water in a ratio of 1:1, treating the mixture at a power of 200 W for 10 minutes, and then grinding the mixture four times using a grinding machine while controlling the grinding temperature at 35°C.

[0094] S1.4. Add the rosemary extract nanoemulsion dropwise to the reactor at a rate of 3 mL / min and reduce the stirring speed to 300 rpm. Then, add carboxymethyl chitosan and stir at 300 rpm for 10 min to obtain ink.

[0095] S1.5. Adjust the pH to 6.0 with 0.05 mol / L citric acid and adjust the ink viscosity to 500-800 mPa·s by adding deionized water. Degassing is performed at -0.09 MPa and 40°C for 20 min. After degassing, filter through a 5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

[0096] The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid is 1:0.2.

[0097] Comparative Example 1: Using the method of Example 4, in the preparation method of the special ink for children's picture books with low VOC emissions, bisphenol A diglycidyl ether is directly used as the resin base material.

[0098] Comparative Example 2: The method of Example 4 was adopted, but rosin glycerol ester was not added in the preparation method of the special ink for children's picture books with low VOC emissions.

[0099] Comparative Example 3: The method of Example 4 was adopted, but carboxymethyl chitosan was not added in the preparation method of the special ink for children's picture books with low VOC emissions.

[0100] The present invention is a low-VOC emission special ink for children's picture books prepared by epoxy-acrylic copolymer resin. The performance index inspection items and inspection standards of the low-VOC emission special ink for children's picture books are as follows:

[0101] According to the national standard GB / T13217.7-2023, use a grid cutter to create a 1mm x 1mm or 2mm x 2mm grid on the ink layer, ensuring that the cuts penetrate the ink layer to the substrate. Apply 3M600 tape tightly to the grid and quickly remove it at a 90° angle. Assess the adhesion level based on the amount of ink remaining on the tape (the area of ​​detachment). The smaller the detachment area, the stronger the adhesion between the ink and the substrate.

[0102] The printed coated paper was fixed to the turntable of the Taber Abraser and abraded at 500-1000 revolutions at 60 rpm using a CS-10 rubber abrasive wheel (load 500g or 1000g) to simulate long-term friction. The abrasion resistance of the ink was evaluated based on the color difference ΔE of the coating after friction. A smaller ΔE value means that the coating color does not change much, indicating that the ink has good abrasion resistance.

[0103] According to the national standard GB / T23986-2020, the ink is coated on a simulated substrate (such as coated paper) and dried, and then placed in a closed environmental chamber with a temperature of 23±2°C, a humidity of 50±5%RH, and an air exchange rate of 0.5 times / h; activated carbon adsorption tubes are used to collect volatile organic compounds (VOCs) in the air, and the specific VOC types and concentrations are analyzed by thermal desorption-gas chromatography-mass spectrometry (TD-GC / MS). The total VOC emissions are calculated based on the released concentration and exposure time; for water-based inks, low VOC emissions require that the total VOC content must be ≤30%.

[0104] The low VOC emission inks for children's picture books prepared in Examples 1-7 and Comparative Examples 1-3 were tested using the above standards, and the obtained data are shown in Table 1:

[0105] Table 1 Performance data of inks for picture books of Examples 1-7 and Comparative Examples 1-3

[0106]

[0107] Examples 1-3 demonstrate that, with other components remaining unchanged in a low-VOC children's picture book ink, an epoxy-acrylic copolymer resin in an amount ranging from 25 to 35 parts by weight can achieve excellent adhesion and abrasion resistance. As shown in Examples 1-3, these performances are significantly superior to those of the comparative examples.

[0108] The hydroxyl groups, ether bonds of the epoxy components and the carboxyl groups of the acrylic acid segments in the copolymer resin can form hydrogen bonds or covalent bonds with the polar groups on the surface of the substrate (such as -OH and -COOH of coated paper), thereby enhancing the interfacial chemical bonding and reducing the shedding area. As the resin content increases, the density of active groups per unit area increases, the interface bonding becomes tighter, and at the same time, the hydrophobic segments are tightly bonded to the low surface energy substrate (such as PE / PP coating) through van der Waals forces, forming a stronger physical anchoring effect. In addition, as the main film-forming substance, the copolymer resin can fill the gaps between the pigment and the additive with an increased content, reduce interfacial defects, form a denser and continuous ink film, and reduce the risk of local shedding caused by stress concentration.

[0109] The epoxy groups in the resin react with the hydroxyl groups of hydroxyethyl methacrylate (HEMA) to form a three-dimensional cross-linked network; as the resin proportion increases, the cross-linking point density rises, and the film hardness (Shore D hardness) and shear strength are significantly improved, thereby improving wear resistance and scratch resistance; the rigid skeleton of the epoxy resin provides high hardness, reducing plastic deformation during friction; while the flexibility of the acrylic chain segments disperses mechanical stress and avoids brittle cracking; the copolymer resin and palm wax work synergistically, and when the resin content increases, the wax migrates to the surface to form a more uniform and dense microcrystalline protective layer, which directly reduces the friction contact area and reduces the wear rate.

[0110] Furthermore, by comparing Examples 4-7, it can be seen that as the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecylbenzoic acid increases, the adhesion and abrasion resistance of the low VOC emission children's picture book ink continue to improve.

[0111] As the proportion of C15 long-chain alkyl groups in 2-hydroxy-6-pentadecylbenzoic acid increases, the hydrophobicity of the resin system is significantly improved, and its compatibility with low-surface-energy substrates (such as PE / PP-coated paper) is better. The long-chain alkyl groups are tightly bonded to the hydrophobic surface of the substrate through van der Waals forces, forming a physical anchoring layer that effectively reduces the risk of interfacial debonding. In addition, after the hydroxyl groups (-OH) of 2-hydroxy-6-pentadecylbenzoic acid react with the epoxy groups of bisphenol A diglycidyl ether, the remaining hydroxyl groups can form hydrogen bonds with trace polar groups (such as carboxyl groups) in the non-absorbent substrate, ensuring wettability while providing chemical bonding sites.

[0112] 2-Hydroxy-6-pentadecylbenzoic acid modifies epoxy resin through an esterification reaction, and its long-chain alkyl group can suppress the brittleness caused by excessive cross-linking; when the proportion of 2-hydroxy-6-pentadecylbenzoic acid is high, the long-chain alkyl group increases the molecular chain spacing, giving the cross-linked network moderate flexibility, thereby more evenly dispersing stress during friction; when the proportion is low, the cross-linking density is high but the brittleness increases, which is prone to wear due to local stress concentration (ΔE is high); in addition, the long-chain alkyl group of 2-hydroxy-6-pentadecylbenzoic acid migrates to the ink surface and synergizes with palm wax to form a protective layer with a low friction coefficient; as the proportion of 2-hydroxy-6-pentadecylbenzoic acid increases, the surface alkyl chains are arranged more densely, the friction contact area is reduced, and the wear rate is reduced.

[0113] According to the above test experiments, embodiment 4 is regarded as the optimal embodiment;

[0114] By comparing Example 4 with Comparative Example 1, it can be seen that in the preparation method of low-VOC emission children's picture book special ink, when bisphenol A diglycidyl ether is directly used as the resin base material, the adhesion and wear resistance of the ink are significantly reduced; the unmodified bisphenol A diglycidyl ether molecule contains only epoxy and hydroxyl groups and lacks a long-chain alkyl hydrophobic structure, and cannot form effective van der Waals force adsorption with the low surface energy surface of non-absorbent substrates (such as PE / PP coated paper), resulting in easy peeling of the ink and increased shedding area; in addition, the polar epoxy group of bisphenol A diglycidyl ether makes the resin surface energy higher, making it difficult to It spreads evenly on the hydrophobic substrate, resulting in local defects in the ink film (such as pinholes), further reducing the adhesion; the epoxy cross-linked network of unmodified bisphenol A diglycidyl ether has high hardness but is brittle, and is prone to microcracks and expansion during friction, resulting in local peeling of the ink film; in contrast, the long-chain alkyl and palm wax in the modified resin can synergistically form a low-friction surface, while pure bisphenol A diglycidyl ether lacks this function, has a high friction coefficient, and accelerates wear; due to the excessive polarity of bisphenol A diglycidyl ether, it has poor compatibility with hydrophobic pigments (such as organic pigments), uneven grinding and dispersion, and the pigment is more likely to fall off during wear.

[0115] A comparison of Example 4 with Comparative Example 2 shows that, in the method for preparing a low-VOC emission ink specifically for children's picture books, the adhesion of the ink is significantly reduced when rosin glycerol ester is not added. The molecular structure of rosin glycerol ester contains a hydrophobic rosin skeleton and a hydrophilic glycerol ester group, which enables it to significantly reduce the surface tension of the ink and improve the wettability of low-surface-energy substrates (such as PE / PP coatings). When not added, the ink easily forms shrinkage or micropores on the substrate, resulting in insufficient interfacial contact and reduced adhesion. In addition, the high viscosity of rosin glycerol ester can enhance the initial adhesion of the ink, allowing the ink to quickly "anchor" to the substrate surface after printing, reducing shrinkage and delamination during the drying process. Its absence can weaken the mechanical interlocking effect between the ink film and the substrate, thereby reducing adhesion.

[0116] By comparing Example 4 with Comparative Example 3, it can be seen that: in the preparation method of special ink for children's picture books with low VOC emissions, when carboxymethyl chitosan is not added, the adhesion of the ink is significantly reduced; the carboxyl group (-COOH) and amino group (-NH2) in the carboxymethyl chitosan molecule can form hydrogen bonds or ionic bonds with polar groups on the surface of the substrate (such as coated paper) and hydroxyl groups in the resin, thereby enhancing the interfacial bonding strength of the ink film and reducing peeling; when carboxymethyl chitosan is not added, the ink and the substrate rely solely on physical adsorption, the interfacial bonding strength is weak, and peeling is prone to occur; the chain structure of carboxymethyl chitosan is cross-linked with the resin through hydrogen bonds, which significantly enhances the cohesion of the ink film, enhances the intermolecular force, and thus improves the mechanical strength of the film; in addition, the amphiphilicity of carboxymethyl chitosan helps to stabilize the pigment dispersion system, prevent pigment agglomeration or sedimentation, avoid the formation of stress concentration points, and further slow down interfacial shedding.

[0117] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. Low VOC emission children's picture book special ink, characterized by: The invention comprises the following raw materials: 25-35 parts by weight of epoxy-acrylic copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan; The epoxy-acrylic copolymer resin is prepared by modifying bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecyl benzoic acid through an esterification reaction and then grafting with hydroxyethyl methacrylate; wherein the mass ratio of bisphenol A diglycidyl ether to 2-hydroxy-6-pentadecyl benzoic acid is 1:0.1-0.3; The preparation method of the epoxy-acrylic acid copolymer resin is as follows: Mixing bisphenol A diglycidyl ether and 2-hydroxy-6-pentadecylbenzoic acid, adding 0.5-1% tetrabutylammonium bromide, and reacting at 80-90°C for 2-3 hours under nitrogen protection; after the reaction is completed, performing reduced pressure distillation at 80-90°C and 10-15 mmHg to remove unreacted monomers, adding propylene glycol methyl ether to adjust the solid content of the system, and obtaining a modified epoxy resin solution; The modified epoxy resin solution is heated to 85-95°C, hydroxyethyl methacrylate is added dropwise, and 0.2-0.5% azobisisobutyronitrile is added, and the mixture is kept warm for 3-4 hours. After the reaction is completed, 0.05-0.1% tocopherol is added, and the mixture is cooled to room temperature and filtered to obtain an epoxy-acrylic copolymer resin.

2. The low VOC emission special ink for children's picture books according to claim 1, characterized in that: The propylene glycol methyl ether is added to adjust the solid content of the system to 50-60%.

3. The low VOC emission special ink for children's picture books according to claim 1, characterized in that: The rate of adding hydroxyethyl methacrylate dropwise is 1-2 mL / min.

4. A method for preparing a low-VOC emission ink for children's picture books, which is used to prepare the low-VOC emission ink for children's picture books according to any one of claims 1 to 3, characterized in that: The preparation method of the low VOC emission special ink for children's picture books is as follows: S1.

1. Weigh the following raw materials in parts by weight: 25-35 parts by weight of epoxy-acrylic copolymer resin, 6-10 parts by weight of pigment, 2-5 parts by weight of rosin glycerol ester, 1-2 parts by weight of palm wax, 0.1-0.2 parts by weight of rosemary extract nanoemulsion, and 0.2-0.5 parts by weight of carboxymethyl chitosan; S1.

2. Add epoxy-acrylic acid copolymer resin and 30-40°C deionized water into a reaction kettle and stir at 200-300 rpm for 10-15 minutes to obtain a resin base; S1.

3. Pre-emulsify rosin glycerol ester and deionized water in a ratio of 1:2 and add to the resin base. Increase the stirring speed to 400-500 rpm and continue stirring for 15-20 minutes. Then, sprinkle in the crushed palm wax and continue stirring at 400-500 rpm for 20-30 minutes at 40-50°C. Then, add the pigment slurry and stir at 400-500 rpm for 10-15 minutes. S1.

4. Add the rosemary extract nanoemulsion dropwise to the reaction kettle and reduce the stirring speed to 200-300 rpm. Then add carboxymethyl chitosan and stir at 200-300 rpm for 5-10 minutes to obtain ink. S1.

5. Adjust the pH to 5.5-6.0 with 0.05-0.1 mol / L citric acid and adjust the ink viscosity by adding deionized water. Degas the ink at -0.09-0.1 MPa and 30-40°C for 15-20 minutes. After degassing, filter through a 3-5 μm nylon filter bag to obtain a low-VOC emission ink for children's picture books.

5. The method for preparing a special ink for children's picture books with low VOC emissions according to claim 4, characterized in that: In S1.3, the pigment slurry is prepared by mixing the pigment and deionized water in a ratio of 1:1, treating the mixture at a power of 100-200 W for 5-10 minutes, and then grinding the mixture 3-4 times in a grinding machine at a grinding temperature of 30-35°C.

6. The method for preparing a special ink for children's picture books with low VOC emissions according to claim 4, characterized in that: In S1.4, the rate of dripping the rosemary extract nanoemulsion into the reactor is 2-3 mL / min.

7. The method for preparing a special ink for children's picture books with low VOC emissions according to claim 4, characterized in that: In the above-mentioned S1.5, deionized water is added to adjust the ink viscosity to 500-800 mPa·s.

8. Application of a low-VOC emission ink for children's picture books, comprising the low-VOC emission ink for children's picture books according to any one of claims 1 to 3, characterized in that: Including the use of this ink in children's picture books.

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