A kind of digital inkjet printing paper coating and preparation method thereof

Abstract

The invention relates to the field of digital inkjet, in particular to a printing paper coating for digital inkjet and a preparation method thereof. PVA resin and deionized water are mixed, acrylic resin, polyurethane resin, fumed silica, silicate and surfactant are added, mixed and ground, coated on the surface of base paper, and dried to obtain a printing paper coating for digital inkjet; fumed silica is selected as a pigment and the fumed silica is modified; polybutylene adipate glycol, dihydroxymethyl propionic acid and isophorone diisocyanate are used as raw materials to synthesize a prepolymer, hydroxyl-terminated polydimethylsiloxane is introduced, and an organosilicon prepolymer is synthesized under the action of a catalyst dibutyltin dilaurate; low molecular weight chitosan and hyperbranched polylysine are used as chain extenders to prepare an internally cross-linked, high molecular weight and antibacterial waterborne polyurethane resin.

Description

Technical Field

[0001] The invention relates to the field of digital inkjet, in particular to a printing paper coating for digital inkjet and a preparation method thereof. Background Art

[0002] With the development of digital imaging, the requirements for digital inkjet printing paper are becoming more and more diverse. Digital inkjet printing paper is made by coating ordinary printing paper, so that it can absorb ink and prevent ink droplets from spreading to the surrounding area. The quality of digital inkjet printing paper coating on the market is uneven, and with the promotion of environmental protection concepts, consumers are paying more and more attention to environmentally friendly and healthy printing paper coatings.

[0003] Currently, the coating of conventional digital inkjet printing paper has poor water resistance and adhesion, resulting in poor printing effects. At the same time, in order to improve the mildew and antibacterial properties of printing paper, mildew inhibitors or antibacterial agents are usually added to the coating. After long-term use, they are easily worn out and fall off, which shortens the service life of the printing paper. Summary of the invention

[0004] The object of the present invention is to provide a digital inkjet printing paper coating and a preparation method thereof, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A coating for digital inkjet printing paper, wherein the components of the coating are, by weight, 0.8-1.2 parts of acrylic resin, 4-5 parts of polyurethane resin, 2-3 parts of PVA resin, 0.5-3 parts of fumed silica, 10-15 parts of silicate, 0.3-1 parts of surfactant and 38-45 parts of deionized water.

[0007] Furthermore, the silicate is one or a combination of sodium silicate, potassium silicate, tetramethylammonium sodium silicate, aluminum silicate, magnesium silicate, and magnesium aluminum silicate.

[0008] Furthermore, the surfactant is one or a combination of anionic surfactants, cationic surfactants and neutral surfactants.

[0009] Furthermore, the acrylic resin is one or a combination of methacrylic resin, styrene acrylic resin, urethane acrylic resin, and epoxy acrylic resin.

[0010] Further, the fumed silica is modified to obtain modified fumed silica, and the preparation of the modified fumed silica includes the following steps:

[0011] Mix hyperbranched polylysine and deionized water, adjust the pH to 10.9-11.1, add γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a 0°C ice-water bath, raise the temperature to 58-60°C and keep warm for 3-4 hours, transfer to a 0°C ice-water bath, cool, add γ-(2,3-epoxypropoxy)propyltrimethoxysilane, raise the temperature to 58-60°C and keep warm for 3-4 hours, adjust the pH to 3, add deionized water, then add fumed silica, keep warm at 88-92°C for 2-3 hours, centrifuge, wash with water, and obtain modified fumed silica.

[0012] In order to solve the problem of uneven dispersion of existing fumed silica in coatings, hyperbranched polylysine is synthesized using L-lysine, and the amino group in the hyperbranched polylysine is reacted with γ-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain a lysine-derived silane coupling agent, which is then coupled with fumed silica to modify the surface of the fumed silica with the lysine-derived silane coupling agent. The fumed silica is modified to greatly improve the dispersion uniformity and antibacterial properties of the fumed silica.

[0013] Further, the preparation of the polyurethane resin comprises the following steps:

[0014] 1) mixing chitosan and hydrogen peroxide solution, keeping warm at 18-25° C. for 20-24 hours, washing with acetone, centrifuging, and freeze-drying to obtain low molecular weight chitosan;

[0015] 2) Under nitrogen protection, polybutylene adipate, hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate are mixed, heated to 88-92° C. and kept warm for 1-2 hours, cooled to 58-62° C., dimethylolpropionic acid, 1,4-butanediol, dibutyltin dilaurate and acetone are added, heated to 78-82° C. and kept warm for 1-2 hours to obtain an organosilicon prepolymer; low molecular weight chitosan and acetone are added, kept warm at 73-78° C. for 1-2 hours, cooled to 30-35° C., triethylamine is added and kept warm for 1-2 hours, cooled to 18-22° C., deionized water is added, emulsified at 2000 r / min for 8-10 minutes, a mixed solution of hyperbranched polylysine and deionized water is added, stirring is continued for 20-30 minutes, and reduced pressure distillation is performed to obtain a polyurethane resin.

[0016] Water-based polyurethane is used as the coating binder, prepolymer is synthesized with polybutylene adipate, dimethylol propionic acid and isophorone diisocyanate as raw materials, hydroxy-terminated polydimethylsiloxane is introduced to improve water resistance, silicone prepolymer is synthesized under the action of catalyst dibutyltin dilaurate, low molecular weight chitosan and hyperbranched polylysine are used as chain extenders to prepare internally cross-linked, high molecular weight, antibacterial water-based polyurethane resin, which effectively improves the water resistance, antibacterial property and adhesion of the coating.

[0017] Furthermore, the mass ratio of the pretreated fumed silica to 2,3-epoxypropyltrimethylammonium chloride is 2:1.

[0018] Furthermore, the mass ratio of low molecular weight chitosan to hyperbranched poly-lysine is 1.1:1.6.

[0019] Furthermore, the preparation of hyperbranched polylysine includes the following steps: under a nitrogen atmosphere, L-lysine and deionized water are mixed, bubbling for 20-30 minutes, heating to 178-182°C and keeping warm for 5-6 hours, cooling, adding ethanol, adding ethyl acetate for precipitation, adding deionized water, rotary evaporation, and freeze-drying to obtain hyperbranched polylysine.

[0020] Furthermore, a method for preparing a digital inkjet printing paper coating comprises the following steps: mixing PVA resin and deionized water, heating to 93-97°C, adding acrylic resin, polyurethane resin, fumed silica, silicate, and surfactant, mixing and grinding, coating on the surface of base paper, and drying to obtain a digital inkjet printing paper coating.

[0021] Beneficial effects of the present invention:

[0022] The invention provides a digital inkjet printing paper coating and a preparation method thereof, and prepares a green, environmentally friendly and antibacterial coating, which can be widely used in the field of digital inkjet.

[0023] In the present invention, non-toxic and environmentally friendly fumed silica with a large specific surface area is selected as a coating pigment. Aiming at the problem that the existing fumed silica is unevenly dispersed in the coating, the present invention performs a modification treatment on the fumed silica, uses the green raw material L-lysine to synthesize a multi-amino hyperbranched polylysine with excellent antibacterial property, uses the amino group in the hyperbranched polylysine to react with γ-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain a lysine-derived silane coupling agent, and then undergoes a coupling reaction with the fumed silica, and modifies the lysine-derived silane coupling agent on the surface of the fumed silica, thereby greatly improving the dispersion uniformity and antibacterial property of the fumed silica.

[0024] The invention uses waterborne polyurethane as a coating binder. In order to improve the defects of traditional waterborne polyurethane in water resistance, adhesion and the like, the invention uses polybutylene adipate glycol, dihydroxymethyl propionic acid and isophorone diisocyanate as raw materials to synthesize a prepolymer. In order to improve water resistance, hydroxyl-terminated polydimethylsiloxane is introduced. An organosilicon prepolymer is synthesized under the action of a catalyst, dibutyltin dilaurate. Low-molecular-weight chitosan and hyperbranched polylysine are used as chain extenders to prepare an internally cross-linked, high-molecular-weight, antibacterial waterborne polyurethane resin, thereby effectively improving the water resistance, antibacterial property and adhesion of the coating. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, and back, the directional indication is only used to explain a specific posture such as the relative position relationship between the components, the movement status, etc. If the specific posture changes, the directional indication will also change accordingly. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0027] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0028] Embodiment 1: A method for preparing a digital inkjet printing paper coating, comprising the following steps: mixing PVA resin and deionized water, heating to 93° C., adding acrylic resin, polyurethane resin, fumed silica, silicate, and surfactant, mixing and grinding, coating on the surface of base paper, and drying to obtain a digital inkjet printing paper coating;

[0029] In terms of weight, the components of the coating are: 0.8 parts of acrylic resin, 4 parts of polyurethane resin, 2 parts of PVA resin, 0.5 parts of fumed silica, 10 parts of silicate, 0.3 parts of surfactant, and 38 parts of deionized water;

[0030] The silicate is sodium silicate; the surfactant is a cationic surfactant; the acrylic resin is epoxy acrylic resin;

[0031] The fumed silica is modified to obtain modified fumed silica. The preparation of the modified fumed silica includes the following steps:

[0032] 2 g of hyperbranched polylysine and 25 mL of deionized water were mixed, the pH was adjusted to 10.9, 0.7 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added in a 0°C ice-water bath, the temperature was raised to 58°C and kept for 4 h, the mixture was transferred to a 0°C ice-water bath, cooled, 0.8 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was raised to 58°C and kept for 4 h, the pH was adjusted to 3, 20 mL of deionized water was added, and then 0.8 g of fumed silica was added, the mixture was kept at 88°C for 3 h, centrifuged, and washed with water to obtain modified fumed silica;

[0033] The preparation of the polyurethane resin comprises the following steps:

[0034] 1) 3 g of chitosan and 120 mL of 10% hydrogen peroxide solution were mixed, kept at 18° C. for 24 h, washed with acetone, centrifuged, and freeze-dried to obtain low molecular weight chitosan;

[0035] 2) Under nitrogen protection, 21g of polybutylene adipate, 3g of hydroxyl-terminated polydimethylsiloxane, and 10g of isophorone diisocyanate were mixed, heated to 88°C and kept warm for 2h, cooled to 58°C, 0.9g of dihydroxymethylpropionic acid, 1g of 1,4-butanediol, 2 drops of dibutyltin dilaurate, and 10mL of acetone were added, and the temperature was raised to 78°C and kept warm for 2h to obtain a silicone prepolymer; 1.1g of low molecular weight chitosan and 3mL of acetone were added, and the temperature was kept at 73°C for 2h, cooled to 30°C, 0.6g of triethylamine was added and kept warm for 1h, cooled to 18°C, 85mL of deionized water was added, and emulsified at 2000r / min for 8min, 1.6g of hyperbranched polylysine and 10mL of deionized water were added, and the mixture was stirred for 20min, and distilled under reduced pressure to obtain a polyurethane resin;

[0036] The preparation of the hyperbranched polylysine comprises the following steps: in a nitrogen atmosphere, 1 g of L-lysine and 2 mL of deionized water are mixed, bubbling for 20 minutes, heating to 178° C. and keeping the temperature for 6 hours, cooling, adding 4 mL of ethanol, adding 40 mL of ethyl acetate for precipitation, adding 2 mL of deionized water, rotary evaporation, and freeze-drying to obtain the hyperbranched polylysine.

[0037] Embodiment 2: A method for preparing a digital inkjet printing paper coating, comprising the following steps: mixing a PVA resin and deionized water, heating to 95° C., adding an acrylic resin, a polyurethane resin, fumed silica, a silicate, and a surfactant, mixing and grinding, coating the mixture on a base paper surface, and drying the mixture to obtain a digital inkjet printing paper coating;

[0038] In terms of weight, the components of the coating are: 1 part of acrylic resin, 4.5 parts of polyurethane resin, 2.4 parts of PVA resin, 2 parts of fumed silica, 13 parts of silicate, 0.6 parts of surfactant, and 40 parts of deionized water;

[0039] The silicate is potassium silicate; the surfactant is a cationic surfactant; the acrylic resin is epoxy acrylic resin;

[0040] The fumed silica is modified to obtain modified fumed silica. The preparation of the modified fumed silica includes the following steps:

[0041] 2 g of hyperbranched polylysine and 25 mL of deionized water were mixed, the pH was adjusted to 11, 0.7 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added in a 0°C ice-water bath, the temperature was raised to 59°C and kept for 3.5 h, the mixture was transferred to a 0°C ice-water bath, cooled, 0.8 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was raised to 59°C and kept for 3.5 h, the pH was adjusted to 3, 20 mL of deionized water was added, and then 0.8 g of fumed silica was added, the mixture was kept at 90°C for 2.5 h, centrifuged, and washed with water to obtain modified fumed silica;

[0042] The preparation of the polyurethane resin comprises the following steps:

[0043] 1) 3 g of chitosan and 120 mL of 10% hydrogen peroxide solution were mixed, kept at 20° C. for 22 h, washed with acetone, centrifuged, and freeze-dried to obtain low molecular weight chitosan;

[0044] 2) Under nitrogen protection, 21g of polybutylene adipate, 3g of hydroxyl-terminated polydimethylsiloxane, and 10g of isophorone diisocyanate were mixed, heated to 90°C and kept warm for 1.5h, cooled to 60°C, 0.9g of dihydroxymethylpropionic acid, 1g of 1,4-butanediol, 2 drops of dibutyltin dilaurate, and 10mL of acetone were added, and the temperature was raised to 80°C and kept warm for 1.5h to obtain a silicone prepolymer; 1.1g of low molecular weight chitosan and 3mL of acetone were added, and the temperature was kept at 75°C for 1.5h, cooled to 32°C, 0.6g of triethylamine was added and kept warm for 1.5h, cooled to 20°C, 85mL of deionized water was added, and emulsified at 2000r / min for 9min, 1.6g of hyperbranched polylysine and 10mL of deionized water were added, and the mixture was stirred for 25min, and distilled under reduced pressure to obtain a polyurethane resin;

[0045] The preparation of the hyperbranched polylysine comprises the following steps: in a nitrogen atmosphere, 1 g of L-lysine and 2 mL of deionized water are mixed, bubbling for 25 minutes, heating to 180° C. and keeping the temperature for 5.5 hours, cooling, adding 4 mL of ethanol, adding 40 mL of ethyl acetate for precipitation, adding 2 mL of deionized water, rotary evaporation, and freeze-drying to obtain the hyperbranched polylysine.

[0046] Embodiment 3: A method for preparing a coating of digital inkjet printing paper, comprising the following steps: mixing PVA resin and deionized water, heating to 97° C., adding acrylic resin, polyurethane resin, fumed silica, silicate, and surfactant, mixing and grinding, coating on the surface of base paper, and drying to obtain a coating of digital inkjet printing paper;

[0047] In terms of weight, the components of the coating are: 1.2 parts of acrylic resin, 5 parts of polyurethane resin, 3 parts of PVA resin, 3 parts of fumed silica, 15 parts of silicate, 1 part of surfactant, and 45 parts of deionized water;

[0048] The silicate is tetramethylammonium silicate; the surfactant is a cationic surfactant; the acrylic resin is epoxy acrylic resin;

[0049] The fumed silica is modified to obtain modified fumed silica. The preparation of the modified fumed silica includes the following steps:

[0050] 2 g of hyperbranched polylysine and 25 mL of deionized water were mixed, the pH was adjusted to 11.1, 0.7 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added in a 0°C ice-water bath, the temperature was raised to 60°C and kept for 3 h, the mixture was transferred to a 0°C ice-water bath, cooled, 0.8 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, the temperature was raised to 60°C and kept for 3 h, the pH was adjusted to 3, 20 mL of deionized water was added, and then 0.8 g of fumed silica was added, the mixture was kept at 92°C for 2 h, centrifuged, and washed with water to obtain modified fumed silica;

[0051] The preparation of the polyurethane resin comprises the following steps:

[0052] 1) 3 g of chitosan and 120 mL of 10% hydrogen peroxide solution were mixed, kept at 25° C. for 20 h, washed with acetone, centrifuged, and freeze-dried to obtain low molecular weight chitosan;

[0053] 2) Under nitrogen protection, 21g of polybutylene adipate, 3g of hydroxyl-terminated polydimethylsiloxane, and 10g of isophorone diisocyanate were mixed, heated to 92°C and kept warm for 1h, cooled to 62°C, 0.9g of dihydroxymethylpropionic acid, 1g of 1,4-butanediol, 2 drops of dibutyltin dilaurate, and 10mL of acetone were added, and the temperature was raised to 82°C and kept warm for 1h to obtain a silicone prepolymer; 1.1g of low molecular weight chitosan and 3mL of acetone were added, and the temperature was kept at 78°C for 1h, cooled to 35°C, 0.6g of triethylamine was added and kept warm for 2h, cooled to 22°C, 85mL of deionized water was added, and emulsified at 2000r / min for 10min, 1.6g of hyperbranched polylysine and 10mL of deionized water were added, and the mixture was stirred for 30min, and the mixture was distilled under reduced pressure to obtain a polyurethane resin;

[0054] The preparation of the hyperbranched polylysine comprises the following steps: in a nitrogen atmosphere, 1 g of L-lysine and 2 mL of deionized water are mixed, bubbling for 30 minutes, heating to 182° C. and keeping warm for 5 hours, cooling, adding 4 mL of ethanol, adding 40 mL of ethyl acetate for precipitation, adding 2 mL of deionized water, rotary evaporation, and freeze-drying to obtain the hyperbranched polylysine.

[0055] Comparative Example 1: Example 2 was used as a control group, in which the fumed silica was not modified, and other processes were normal.

[0056] Comparative Example 2: Example 2 was used as the control group, in which no hyperbranched polylysine was prepared, and other processes were normal.

[0057] Comparative Example 3: Example 2 was used as the control group, the polyurethane resin was an aqueous polyurethane resin (99%, Pandex (Shanghai) International Trading Co., Ltd.), and the other processes were normal.

[0058] Source of raw materials (for demonstration only):

[0059] PVA resin 2021: Xi'an Jinxiang Pharmaceutical Excipients Co., Ltd.; fumed silica S5130: Sigma-Aldrich (Shanghai) Trading Co., Ltd.; cationic surfactant as antistatic agent SN: Linyi Guoli Chemical Co., Ltd.; epoxy acrylic resin L-6135: Dongguan Sanqi Chemical Raw Materials Co., Ltd.; polybutylene adipate 32472-85-8: Hubei Chengfeng Chemical Co., Ltd.; tetramethylammonium silicate T466371, γ-(2,3-epoxypropoxy)propyl trimethoxy Silane G107576, chitosan C105802, hydroxy-terminated polydimethylsiloxane P304442, isophorone diisocyanate I109582, dihydroxymethylpropionic acid B104539, 1,4-butanediol B110391, dibutyltin dilaurate D100274, triethylamine T103285, L-lysine L103479: Aladdin reagent; sodium silicate, potassium silicate, acetone, anhydrous ethanol, hydrogen peroxide, ethyl acetate, analytical grade: Sinopharm Group reagent.

[0060] Performance Test:

[0061] Adhesion: Tested with reference to GB / T13217.7-2023, coated 50μm of the prepared coating raw material on PP synthetic paper (FW-XP02: Longgang Fuwei Paper and Plastic Products Factory), dried, and tested by disc peeling method at a speed of 0.7m / s; Antibacterial property: coated 50μm of the prepared coating raw material on PP synthetic paper (FW-XP02: Longgang Fuwei Paper and Plastic Products Factory), dried, and tested the antibacterial effect with reference to GB / T21866-2008. The bacteria were evenly contacted with the sample by the film sticking method, cultured for 24h, the number of live bacteria on the sample was detected, and the antibacterial rate was calculated. The experimental bacteria were Staphylococcus aureus AS1.89; the results are shown in Table 1;

[0062] Table 1

[0063]

[0064] Comparative Example 1 and Comparative Example 2 are compared with Example 2. In the present invention, non-toxic and environmentally friendly fumed silica with a large specific surface area is selected as the pigment of the coating. In view of the problem that the existing fumed silica is easy to agglomerate in solvent water, the present invention modifies the fumed silica, uses the green raw material L-lysine to synthesize a multi-amino hyperbranched polylysine with excellent antibacterial property, and uses the amino group in the hyperbranched polylysine to react with γ-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain a lysine-derived silane coupling agent, which is then coupled with the fumed silica to modify the lysine-derived silane coupling agent on the surface of the fumed silica, thereby greatly improving the dispersion uniformity and antibacterial property of the fumed silica.

[0065] Comparative Example 2 and Comparative Example 3 are compared with Example 2. In the present invention, water-based polyurethane is used as a coating binder. In order to improve the defects of traditional water-based polyurethane in water resistance, adhesion, etc., polybutylene adipate, dihydroxymethylpropionic acid, and isophorone diisocyanate are used as raw materials to synthesize a prepolymer. In order to improve water resistance, hydroxyl-terminated polydimethylsiloxane is introduced, and a silicone prepolymer is synthesized under the action of a catalyst, dibutyltin dilaurate. Low molecular weight chitosan and hyperbranched polylysine are used as chain extenders to prepare an internally cross-linked, high molecular weight, antibacterial water-based polyurethane resin, which effectively improves the water resistance, antibacterial property and adhesion of the coating.

[0066] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the present invention specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A coating for digital inkjet printing paper, characterized in that: In terms of weight, the components of the coating are: 0.8-1.2 parts of acrylic resin, 4-5 parts of polyurethane resin, 2-3 parts of PVA resin, 0.5-3 parts of fumed silica, 10-15 parts of silicate, 0.3-1 parts of surfactant, and 38-45 parts of deionized water; The fumed silica is modified to obtain modified fumed silica. The preparation of the modified fumed silica includes the following steps: Mix hyperbranched polylysine and deionized water, adjust the pH to 10.9-11.1, add γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a 0°C ice-water bath, raise the temperature to 58-60°C and keep it for 3-4 hours, transfer to a 0°C ice-water bath, cool, add γ-(2,3-epoxypropoxy)propyltrimethoxysilane, raise the temperature to 58-60°C and keep it for 3-4 hours, adjust the pH to 3, add deionized water, then add fumed silica, keep it at 88-92°C for 2-3 hours, centrifuge, wash with water, and obtain modified fumed silica; The preparation of the polyurethane resin comprises the following steps: 1) mixing chitosan and hydrogen peroxide solution, keeping warm at 18-25° C. for 20-24 hours, washing with acetone, centrifuging, and freeze-drying to obtain low molecular weight chitosan; 2) under nitrogen protection, polybutylene adipate glycol, hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate are mixed, heated to 88-92° C. and kept warm for 1-2 hours, cooled to 58-62° C., dimethylolpropionic acid, 1,4-butanediol, dibutyltin dilaurate and acetone are added, heated to 78-82° C. and kept warm for 1-2 hours to obtain an organosilicon prepolymer; low molecular weight chitosan and acetone are added, kept warm at 73-78° C. for 1-2 hours, cooled to 30-35° C., triethylamine is added and kept warm for 1-2 hours, cooled to 18-22° C., deionized water is added and emulsified at 2000 r / min for 8-10 minutes, a mixed solution of hyperbranched polylysine and deionized water is added, stirring is continued for 20-30 minutes, and reduced pressure distillation is performed to obtain a polyurethane resin; The preparation of the hyperbranched polylysine comprises the following steps: In a nitrogen atmosphere, L-lysine and deionized water were mixed, bubbled for 20-30 minutes, heated to 178-182°C and kept warm for 5-6 hours, cooled, ethanol was added, ethyl acetate was added for precipitation, deionized water was added, rotary evaporated, and freeze-dried to obtain hyperbranched polylysine.

2. The digital inkjet printing paper coating according to claim 1, characterized in that: The silicate is one or a combination of sodium silicate, potassium silicate, tetramethylammonium sodium silicate, aluminum silicate, magnesium silicate, and aluminum magnesium silicate.

3. The digital inkjet printing paper coating according to claim 1, characterized in that: The surfactant is one or a combination of anionic surfactant, cationic surfactant and neutral surfactant.

4. The digital inkjet printing paper coating according to claim 1, characterized in that: The acrylic resin is one or a combination of methacrylic resin, styrene acrylic resin, urethane acrylic resin and epoxy acrylic resin.

5. The digital inkjet printing paper coating according to claim 1, characterized in that: In the preparation of modified fumed silica, the mass ratio of hyperbranched polylysine to fumed silica is 2:0.

8.

6. The digital inkjet printing paper coating according to claim 1, characterized in that: In the preparation of polyurethane resin, the mass ratio of low molecular weight chitosan to hyperbranched polylysine is 1.1:1.

6.

7. A method for preparing a coating layer for digital inkjet printing paper according to any one of claims 1 to 6, characterized in that: The following steps are involved: PVA resin and deionized water are mixed, heated to 93-97°C, acrylic resin, polyurethane resin, fumed silica, silicate and surfactant are added, mixed and ground, coated on the surface of base paper, and dried to obtain a digital inkjet printing paper coating.

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