Heat-resistant ink and preparation method thereof

Abstract

The present invention provides a heat-resistant ink and a preparation method thereof, belonging to the field of ink technology. Wherein, the preparation method of the heat-resistant ink includes: flax fiber is subjected to alkali treatment and then subjected to silanization modification, followed by grafting of fluorosilane-acrylic copolymer to obtain modified fiber B; nanocellulose crystals are subjected to oxidative modification to obtain modified nanocellulose crystals; modified nanocellulose crystals are loaded on modified fiber B to obtain modified fiber C; organic pigments are grafted onto modified fiber C to obtain modified pigments; after mixing the modified pigments with aqueous polyurethane resin, dispersant, zirconium phosphate nanosheets, and deionized water, heat-resistant ink is obtained. The heat-resistant ink prepared by the above-mentioned preparation method shows excellent heat resistance, and other mechanical properties of the ink are also improved, and has a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the technical field of inks, and in particular to a heat-resistant ink and a preparation method thereof. Background Art

[0002] Ink is a crucial material used in printing, creating designs and text on substrates through printing or inkjet printing. Ink consists of a primary and secondary component, which is uniformly mixed and repeatedly rolled to form a viscous, colloidal fluid. It is commonly used in a variety of printing applications, including books and periodicals, packaging and decoration, architectural decoration, and electronic circuit boards.

[0003] However, traditional inks often have poor heat resistance and cannot meet the diverse needs of the market. Therefore, how to improve the heat resistance of inks is of great significance. Summary of the Invention

[0004] In order to solve the problems mentioned in the background technology, the present invention provides a heat-resistant ink, which has heat resistance and excellent mechanical properties through a special composition combination.

[0005] Specifically:

[0006] A method for preparing heat-resistant ink comprises the following steps:

[0007] Step 1: treating flax fiber with alkali, and then performing silanization modification to obtain modified fiber A;

[0008] Step 2, oxidatively modifying the nanocellulose crystals to obtain modified nanocellulose crystals;

[0009] Step 3, immersing the modified fiber A in an ethanol solution containing acrylic acid, styrene, and heptafluorodecyltrimethoxysilane, adding an auxiliary agent, reacting at 40-50° C. under nitrogen protection, washing with water to remove unreacted monomers, and drying to obtain a modified fiber B;

[0010] Step 4: adding the modified nanocellulose crystals obtained in step 2 and PEG2000 to MES buffer, adding EDC and NHS, reacting at room temperature, centrifuging and separating the activated modified nanocellulose crystals, and then adding them to MES buffer for ultrasonic dispersion to obtain a dispersion containing the modified nanocellulose crystals;

[0011] Step 5: pre-treating the modified fiber B obtained in step 3 by immersing it in MES buffer, taking out the pre-treated modified fiber B and transferring it to the dispersion containing modified nanocellulose crystals obtained in step 4, evacuating to -0.08-0 MPa, maintaining the pressure for 0.5-1 h, and centrifuging to obtain modified fiber C;

[0012] Step 6: Immerse the amino organic pigment and the modified fiber C obtained in step 5 in a PBS buffer solution containing glutaraldehyde, react at 50-60° C., wash, and dry to obtain a modified pigment;

[0013] Step 7: Mix the modified pigment obtained in step 6 with water-based polyurethane resin, dispersant, zirconium phosphate nanosheets, and deionized water, first treat it with an ultrasonic cell disruptor, and then stir it with a high-speed shear machine to obtain a heat-resistant ink.

[0014] Furthermore, in step 1, the flax fiber alkali treatment method is to immerse the flax fiber in a 5%-5.5% NaOH solution at a solid-liquid ratio of 1g:20-25mL, stir at 80-85°C for 1 hour, wash with water until neutral, and dry;

[0015] The silanization modification method is to immerse the alkali-treated flax fiber in an ethanol aqueous solution containing a mass fraction of 3%-3.5% KH550 silane coupling agent at a solid-liquid ratio of 1g:10-20mL, react at 60-65℃ for 4-5h, wash with water and dry; the volume ratio of ethanol to water in the ethanol aqueous solution is 9:1, and acetic acid is used to adjust the pH to 4-4.5.

[0016] Furthermore, the oxidative modification method of the nanocellulose crystals in step 2 is to disperse the nanocellulose crystals in a phosphate buffer solution with a pH of 6-6.3 at a solid-liquid ratio of 1 g: 20-25 mL, add 2-2.2 mmol TEMPO and 10-10.5 mmol NaBr for every 1 g of nanocellulose crystals added, add 5-5.2 mmol NaClO dropwise, react at room temperature for 6-7 hours, and centrifuge and wash until neutral.

[0017] Furthermore, in step 3, the solid-liquid ratio of the modified fiber A to the ethanol solution is 1 g: 15-20 mL; the ethanol solution contains 10%-12% by mass of acrylic acid, 1.5%-2% by mass of styrene, and 0.45%-0.5% by mass of heptadecafluorodecyltrimethoxysilane;

[0018] The auxiliary agents are APS and TEMED initiators; the ethanol solution contains 0.05%-0.1% APS and 0.04%-0.05% TEMED initiator.

[0019] Furthermore, in step 4, the mass ratio of modified nanocellulose crystals to PEG2000 is 1:3-3.5; the solid-liquid ratio of modified nanocellulose crystals to MES buffer is 1 g:40-45 mL; 4.5-5 mmol EDC and 2-2.5 mmol NHS are added for every 1 g of modified nanocellulose crystals added; the solid-liquid ratio of activated modified nanocellulose crystals to MES buffer is 1 g:10-15 mL; and the pH of MES buffer is 5-5.5.

[0020] Furthermore, in step 5, the solid-liquid ratio of the modified fiber B to the MES buffer is 1 g: 20-25 mL; the pretreatment time is 6-12 h at room temperature; the pH of the MES buffer is 5-5.5; and the solid-liquid ratio of the pretreated modified fiber B to the dispersion containing modified nanocellulose crystals is 1 g: 30-50 mL.

[0021] Furthermore, in step 6, the mass ratio of the amino organic pigment to the modified fiber C is 1:2; the solid-liquid ratio of the modified fiber C to the PBS buffer is 1 g:25-30 mL; the PBS buffer contains 1%-1.5% glutaraldehyde by mass and has a pH of 7.4-7.5.

[0022] Furthermore, in step 6, the organic pigment is selected from any one of azo pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments or isoindolinone pigments.

[0023] Furthermore, in step 7, the proportions are calculated by mass as follows: 12-15 parts of modified pigment, 22-25 parts of waterborne polyurethane resin, 0.8-1 part of dispersant, 0.5-0.7 parts of zirconium phosphate nanosheets, and 55-60 parts of deionized water.

[0024] On the other hand, the present invention also provides a heat-resistant ink, which is prepared using the above-mentioned preparation method of the heat-resistant ink.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The heat-resistant ink of the present invention improves its heat resistance by specially modifying the organic pigment, making the ink less likely to fade in a high temperature environment. The method is to use flax fiber for silanization modification so that it can react with components such as acrylic acid, styrene, and heptadecafluorodecyltrimethoxysilane, and then graft fluorosilane-acrylic acid copolymer on the surface of the flax fiber. The fluorosilane combines with the organic pigment through hydrophobic interaction, and the acrylic acid chain segment provides steric hindrance through electrostatic repulsion, thereby anchoring the organic fiber on the flax fiber. On the one hand, the pigment's resistance to thermal decomposition can be improved. On the other hand, the flax fiber is also grafted with a dispersant to prevent the organic pigment from agglomerating. Cross-linking with polyglutaraldehyde can also reduce the migration of pigment molecules and improve the dispersion stability and wetting properties of organic pigments; surface modification of organic pigments with amino groups can also enhance the binding with dispersants; in addition, flax fibers have natural grooves and cracks, and the grooves and silanized groups of the modified flax fibers capture nanocellulose crystals (NCC) through van der Waals forces and hydrogen bonds. Vacuum assists in forcing NCC into the porous structure inside the fiber to form a mechanical interlock. NCC is a natural spherical body, and when subjected to force, it can utilize the ball bearing effect to improve the wear resistance of the ink. The flexible spacer arm of the PEG chain allows NCC to slightly displace when subjected to force, maintaining the ball bearing effect while avoiding falling off.

[0027] 2. The heat-resistant ink of the present invention further comprises zirconium phosphate nanosheets. The layered structure of the zirconium phosphate nanosheets physically blocks the diffusion of heat and oxygen, which not only improves the overall heat resistance of the ink but also reduces the oxidation rate of the pigment. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] In order to facilitate those skilled in the art to implement the present invention, some of the reagents used in the examples and comparative examples are now described:

[0030] Flax fiber: Lanzhou Waterless Biotechnology;

[0031] Nanocellulose crystals: Hubei Kemaidi Chemical;

[0032] Acrylic acid: Jinan Juyang Chemical;

[0033] Styrene: Jinan Zhengkang Chemical;

[0034] Heptadecafluorodecyltrimethoxysilane: Wuhan Lanabai Chemical;

[0035] PEG2000 (polyethylene glycol 2000): Jining Fangyu Chemical;

[0036] MES buffer (2-(N-morpholino)ethanesulfonic acid buffer): Shanghai Shangbao Biotechnology;

[0037] EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride): Wuhan Lanabai Chemical;

[0038] NHS (N-hydroxysuccinimide): Wuhan Lanabai Chemical;

[0039] Glutaraldehyde: Jinan Juyang Chemical;

[0040] PBS buffer (phosphate buffered saline): Shanghai Shangbao Biotechnology;

[0041] KH550 silane coupling agent: Shandong Qiyun Chemical;

[0042] TEMPO (2,2,6,6-tetramethylpiperidinyl oxide): Wuhan Lanabai Chemical;

[0043] NaBr: Jinan Zi'an Chemical;

[0044] NaClO: Jinan Zi'an Chemical;

[0045] APS (ammonium persulfate): Yunsheng Chemical;

[0046] TEMED (Tetramethylethylenediamine): Shandong Haoshun Chemical

[0047] Waterborne polyurethane resin: polyurethane emulsion, Jining Fangyu Chemical;

[0048] Dispersant: BYK-190, Shandong Polychemical;

[0049] Zirconium phosphate nanosheets: Wuhan Kemik Biomedical Technology;

[0050] Organic pigment: Phthalocyanine blue, Shandong Polychemical;

[0051] Phthalocyanine blue amination treatment process: Phthalocyanine blue is placed in a reaction container, concentrated sulfuric acid 5 times the mass of phthalocyanine blue is added, and fuming sulfuric acid of the same amount as phthalocyanine blue is added, the temperature is raised to 90°C, the mixture is stirred and reacted for 4 hours, and after cooling, an ice-water mixture is introduced to precipitate, and the sulfonated phthalocyanine blue is obtained after filtration, washing, and drying; the sulfonated phthalocyanine blue is dispersed in a borate buffer solution of pH=8, ultrasonically dispersed, the solid-liquid ratio of sulfonated phthalocyanine blue to borate buffer solution is 1g:10mL, and ethylenediamine 3 times the mass of sulfonated phthalocyanine blue is added, the mixture is heated to 60°C in a water bath, the pH is adjusted to 8, the mixture is stirred and reacted for 12 hours, centrifuged, washed, and dried to obtain the amination phthalocyanine blue.

[0052] Example 1

[0053] A heat-resistant ink, the preparation steps comprising:

[0054] Step 1: Immerse the flax fiber in a 5% by mass NaOH solution at a solid-liquid ratio of 1 g:20 mL, stir at 80°C for 1 hour, wash with water until neutral, and dry; then immerse the alkali-treated flax fiber in an ethanol aqueous solution containing a 3% by mass KH550 silane coupling agent at a solid-liquid ratio of 1 g:10 mL, wherein the volume ratio of ethanol to water in the ethanol aqueous solution is 9:1, adjust the pH to 4 with acetic acid, react at 60°C for 4 hours, wash with water, and dry to obtain modified fiber A;

[0055] Step 2: Disperse the nanocellulose crystals in a PBS buffer solution at a solid-liquid ratio of 1 g:20 mL, add 2 mmol TEMPO and 10 mmol NaBr per 1 g of nanocellulose crystals, add 5 mmol NaClO dropwise, react at room temperature for 6 h, and centrifuge and wash until neutral to obtain modified nanocellulose crystals;

[0056] Step 3, the modified fiber A was immersed in an ethanol solution containing 10% acrylic acid, 1.5% styrene, and 0.45% heptafluorodecyltrimethoxysilane at a solid-liquid ratio of 1 g:15 mL, 0.05% APS and 0.04% TEMED initiators were added, and the reaction was carried out at 40°C under nitrogen protection. The unreacted monomers were removed by washing with water, and the modified fiber B was obtained after drying;

[0057] Step 4: Add the modified nanocellulose crystals obtained in step 2 and PEG2000 at a mass ratio of 1:3 to MES buffer, and the solid-liquid ratio of the modified nanocellulose crystals to the MES buffer is 1 g:40 mL. Subsequently, 4.5 mmol EDC and 2 mmol NHS are added for every 1 g of modified nanocellulose crystals added. After reaction at room temperature, the activated modified nanocellulose crystals are separated by centrifugation and then added to pH = 5 MES buffer at a solid-liquid ratio of 1 g:10 mL for ultrasonic dispersion to obtain a dispersion containing modified nanocellulose crystals.

[0058] Step 5, immersing the modified fiber B obtained in step 3 in a MES buffer solution with a solid-liquid ratio of 1 g: 20 mL at pH = 5, pretreating at room temperature for 6 h, taking out the pretreated modified fiber B and transferring it to the dispersion containing modified nanocellulose crystals obtained in step 4 at a solid-liquid ratio of 1 g: 30 mL, evacuating to -0.08 MPa, maintaining the pressure for 0.5 h, and centrifuging to obtain modified fiber C;

[0059] Step 6: Immerse the amino organic pigment and the modified fiber C obtained in step 5 in a PBS buffer solution containing 1% glutaraldehyde at a mass ratio of 1:2, the pH of the PBS buffer solution is 7.4, and the solid-liquid ratio of the modified fiber C to the PBS buffer solution is 1 g:25 mL. The mixture is reacted at 50-60° C., washed, and dried to obtain a modified pigment.

[0060] Step 7: Mix 12 parts of the modified pigment obtained in step 6, 22 parts of waterborne polyurethane resin, 0.8 parts of dispersant, 0.5 parts of zirconium phosphate nanosheets, and 55 parts of deionized water in parts by mass, first treat with an ultrasonic cell disruptor and then stir with a high-speed shear machine to obtain a heat-resistant ink.

[0061] Example 2

[0062] A heat-resistant ink, the preparation steps comprising:

[0063] Step 1: Immerse the flax fiber in a 5.5% by mass NaOH solution at a solid-liquid ratio of 1 g:25 mL, stir at 85°C for 1 hour, wash with water until neutral, and dry; then immerse the alkali-treated flax fiber in an ethanol aqueous solution containing a 3.5% by mass KH550 silane coupling agent at a solid-liquid ratio of 1 g:20 mL, wherein the volume ratio of ethanol to water in the ethanol aqueous solution is 9:1, adjust the pH to 4.5 with acetic acid, react at 65°C for 5 hours, wash with water, and dry to obtain modified fiber A;

[0064] Step 2: Disperse the nanocellulose crystals in PBS buffer at a solid-liquid ratio of 1 g:25 mL at pH 6.3. Add 2.2 mmol TEMPO and 10.5 mmol NaBr per 1 g of nanocellulose crystals, and dropwise add 5.2 mmol NaClO. React at room temperature for 7 h, and centrifuge and wash until neutral to obtain modified nanocellulose crystals.

[0065] Step 3, the modified fiber A was immersed in an ethanol solution containing 12% acrylic acid, 2% styrene, and 0.5% heptafluorodecyltrimethoxysilane at a solid-liquid ratio of 1 g:20 mL, 0.1% APS and 0.05% TEMED initiator were added, and the reaction was carried out at 50°C under nitrogen protection. The unreacted monomers were removed by washing with water, and the modified fiber B was obtained after drying;

[0066] Step 4: Add the modified nanocellulose crystals obtained in step 2 and PEG2000 at a mass ratio of 1:3.5 to MES buffer, and the solid-liquid ratio of the modified nanocellulose crystals to the MES buffer is 1 g:45 mL. Subsequently, 5 mmol EDC and 2.5 mmol NHS are added for every 1 g of modified nanocellulose crystals added. After reaction at room temperature, the activated modified nanocellulose crystals are separated by centrifugation and then added to pH = 5.5 MES buffer at a solid-liquid ratio of 1 g:15 mL for ultrasonic dispersion to obtain a dispersion containing modified nanocellulose crystals.

[0067] Step 5: The modified fiber B obtained in step 3 was immersed in a MES buffer solution with a solid-liquid ratio of 1 g: 25 mL, and pretreated at room temperature for 12 h. The pretreated modified fiber B was taken out and transferred to the dispersion containing modified nanocellulose crystals obtained in step 4 at a solid-liquid ratio of 1 g: 50 mL. The mixture was vacuumed to 0 MPa, maintained at pressure for 1 h, and centrifuged to obtain modified fiber C.

[0068] Step 6: Immerse the amino organic pigment and the modified fiber C obtained in step 5 in a PBS buffer solution containing 1.5% glutaraldehyde at a mass ratio of 1:2, the pH of the PBS buffer solution is 7.5, and the solid-liquid ratio of the modified fiber C to the PBS buffer solution is 1 g:30 mL. The mixture is reacted at 60° C., washed, and dried to obtain a modified pigment.

[0069] Step 7: Mix 15 parts of the modified pigment obtained in step 6, 25 parts of waterborne polyurethane resin, 1 part of dispersant, 0.7 parts of zirconium phosphate nanosheets, and 60 parts of deionized water in parts by mass, first treat with an ultrasonic cell disruptor and then stir with a high-speed shear machine to obtain a heat-resistant ink.

[0070] Example 3

[0071] A heat-resistant ink, the preparation steps comprising:

[0072] Step 1: Immerse the flax fiber in a 5% by mass NaOH solution at a solid-liquid ratio of 1 g:25 mL, stir at 85°C for 1 hour, wash with water until neutral, and dry; then immerse the alkali-treated flax fiber in an ethanol aqueous solution containing a 3% by mass KH550 silane coupling agent at a solid-liquid ratio of 1 g:20 mL, wherein the volume ratio of ethanol to water in the ethanol aqueous solution is 9:1, adjust the pH to 4 with acetic acid, react at 65°C for 4 hours, wash with water, and dry to obtain modified fiber A;

[0073] Step 2: Disperse the nanocellulose crystals in PBS buffer at a solid-liquid ratio of 1 g:25 mL, add 2 mmol TEMPO and 10 mmol NaBr per 1 g of nanocellulose crystals, add 5 mmol NaClO dropwise, react at room temperature for 7 h, and centrifuge and wash until neutral to obtain modified nanocellulose crystals;

[0074] Step 3, immersing the modified fiber A in an ethanol solution containing 10% acrylic acid, 2% styrene, and 0.45% heptafluorodecyltrimethoxysilane at a solid-liquid ratio of 1 g:15 mL, adding 0.1% APS and 0.04% TEMED initiator, reacting at 40-50° C. under nitrogen protection, washing with water to remove unreacted monomers, and drying to obtain modified fiber B;

[0075] Step 4: Add the modified nanocellulose crystals obtained in step 2 and PEG2000 at a mass ratio of 1:3 to MES buffer, and the solid-liquid ratio of the modified nanocellulose crystals to the MES buffer is 1 g:45 mL. Subsequently, 5 mmol EDC and 2 mmol NHS are added for every 1 g of modified nanocellulose crystals added. After reaction at room temperature, the activated modified nanocellulose crystals are separated by centrifugation and then added to pH = 5 MES buffer at a solid-liquid ratio of 1 g:15 mL for ultrasonic dispersion to obtain a dispersion containing modified nanocellulose crystals.

[0076] Step 5, immersing the modified fiber B obtained in step 3 in a MES buffer solution with a solid-liquid ratio of 1 g: 25 mL, pretreating at room temperature for 12 h, taking out the pretreated modified fiber B and transferring it to the dispersion containing modified nanocellulose crystals obtained in step 4 at a solid-liquid ratio of 1 g: 30 mL, evacuating to -0.05 MPa, maintaining the pressure for 1 h, and centrifuging to obtain modified fiber C;

[0077] Step 6: Immerse the amino organic pigment and the modified fiber C obtained in step 5 in a PBS buffer solution containing 1% glutaraldehyde at a mass ratio of 1:2, the pH of the PBS buffer solution is 7.5, and the solid-liquid ratio of the modified fiber C to the PBS buffer solution is 1 g:25 mL. The mixture is reacted at 60° C., washed, and dried to obtain a modified pigment.

[0078] Step 7: Mix 14 parts of the modified pigment obtained in step 6, 24 parts of waterborne polyurethane resin, 0.8 parts of dispersant, 0.6 parts of zirconium phosphate nanosheets, and 58 parts of deionized water in parts by mass, first treat with an ultrasonic cell disruptor and then stir with a high-speed shear machine to obtain a heat-resistant ink.

[0079] Comparative Example 1

[0080] An ink, the preparation steps comprising: mixing 12 parts of phthalocyanine blue, 22 parts of waterborne polyurethane resin, 0.8 parts of dispersant, 0.5 parts of zirconium phosphate nanosheets, and 55 parts of deionized water in parts by mass, treating the mixture with an ultrasonic cell disruptor, and then stirring the mixture with a high-speed shearing machine to obtain the ink.

[0081] The inks obtained in Examples 1-3 and Comparative Example 1 were tested as follows:

[0082] 1. Thermogravimetric analysis: The thermogravimetric properties of the cured ink film were tested using a thermogravimetric analyzer. Nitrogen was used as the test atmosphere and the heating rate was 10°C / min.

[0083] 2. Thermal environment chromaticity test: Place an aluminum plate with an ink film (thickness 1μm) in an environment with a temperature of 250℃ for 120 hours and observe its color change degree.

[0084] 3. Abrasion resistance test: The ink is evenly scraped onto an A4 paper as a sample. Using an ink abrasion resistance tester, the sample is cut into 25cm×6cm and fixed on the test device. A blank A4 paper is cut into 20cm×5cm and fixed on the friction slider. Weights are added to increase the pressure to 4 pounds. The number of frictions is set to 100. After the test, the floating color on the blank A4 paper surface and the discoloration on the sample surface are observed.

[0085] 4. Pigment dispersion test: Use screen printing equipment to apply ink on ABS board (thickness 10μm). After the paint film is dry, observe its color uniformity and check whether there are spots or areas with uneven color. Make 10 samples for each group. If there is uneven color, it is unqualified.

[0086] The test results are as follows:

[0087]

[0088] It can be seen from the above test results that the test results of Examples 1-4 are better than those of Comparative Example 1.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heat-resistant ink, characterized in that: The steps include: Step 1: treating flax fiber with alkali, and then performing silanization modification to obtain modified fiber A; Step 2, oxidatively modifying the nanocellulose crystals to obtain modified nanocellulose crystals; Step 3, immersing the modified fiber A in an ethanol solution containing acrylic acid, styrene, and heptafluorodecyltrimethoxysilane, adding an auxiliary agent, reacting at 40-50° C. under nitrogen protection, washing with water to remove unreacted monomers, and drying to obtain a modified fiber B; Step 4: adding the modified nanocellulose crystals obtained in step 2 and PEG2000 to MES buffer, adding EDC and NHS, reacting at room temperature, centrifuging and separating the activated modified nanocellulose crystals, and then adding them to MES buffer for ultrasonic dispersion to obtain a dispersion containing the modified nanocellulose crystals; Step 5: pre-treating the modified fiber B obtained in step 3 by immersing it in MES buffer, taking out the pre-treated modified fiber B and transferring it to the dispersion containing modified nanocellulose crystals obtained in step 4, evacuating to -0.08-0 MPa, maintaining the pressure for 0.5-1 h, and centrifuging to obtain modified fiber C; Step 6: Immerse the amino organic pigment and the modified fiber C obtained in step 5 in a PBS buffer solution containing glutaraldehyde, react at 50-60° C., wash, and dry to obtain a modified pigment; Step 7: Mix 12-15 parts of the modified pigment obtained in step 6 with 22-25 parts of an aqueous polyurethane resin, 0.8-1 part of a dispersant, 0.5-0.7 parts of zirconium phosphate nanosheets, and 55-60 parts of deionized water, by mass, and then treat with an ultrasonic cell disruptor and then stir with a high-speed shearing machine to obtain a heat-resistant ink.

2. The method for preparing the heat-resistant ink according to claim 1, wherein: In step 1, the flax fiber alkali treatment method is to immerse the flax fiber in a 5%-5.5% NaOH solution at a solid-liquid ratio of 1g:20-25mL, stir at 80-85°C for 1 hour, wash with water until neutral, and dry; The silanization modification method is to immerse the alkali-treated flax fiber in an ethanol aqueous solution containing a mass fraction of 3%-3.5% KH550 silane coupling agent at a solid-liquid ratio of 1g:10-20mL, react at 60-65℃ for 4-5h, wash with water and dry; the volume ratio of ethanol to water in the ethanol aqueous solution is 9:1, and acetic acid is used to adjust the pH to 4-4.

5.

3. The method for preparing the heat-resistant ink according to claim 1, wherein: The oxidative modification method of the nanocellulose crystals in step 2 is to disperse the nanocellulose crystals in PBS buffer with a pH of 6-6.3 at a solid-liquid ratio of 1g:20-25mL, add 2-2.2mmol TEMPO and 10-10.5mmol NaBr for every 1g of nanocellulose crystals, add 5-5.2mmol NaClO dropwise, react at room temperature for 6-7h, and centrifuge and wash until neutral.

4. The method for preparing the heat-resistant ink according to claim 1, wherein: In step 3, the solid-liquid ratio of the modified fiber A to the ethanol solution is 1 g: 15-20 mL; the ethanol solution contains 10%-12% by mass of acrylic acid, 1.5%-2% by mass of styrene, and 0.45%-0.5% by mass of heptadecafluorodecyltrimethoxysilane; The auxiliary agents are APS and TEMED initiators; the ethanol solution contains 0.05%-0.1% APS and 0.04%-0.05% TEMED initiator.

5. The method for preparing the heat-resistant ink according to claim 1, wherein: In step 4, the mass ratio of modified nanocellulose crystals to PEG2000 is 1:3-3.5; the solid-liquid ratio of modified nanocellulose crystals to MES buffer is 1 g:40-45 mL; 4.5-5 mmol EDC and 2-2.5 mmol NHS are added for every 1 g of modified nanocellulose crystals added; the solid-liquid ratio of activated modified nanocellulose crystals to MES buffer is 1 g:10-15 mL; the pH of MES buffer is 5-5.

5.

6. The method for preparing heat-resistant ink according to claim 1, wherein: In step 5, the solid-liquid ratio of the modified fiber B to the MES buffer is 1 g: 20-25 mL; the pretreatment time is 6-12 h at room temperature; the pH of the MES buffer is 5-5.5; and the solid-liquid ratio of the pretreated modified fiber B to the dispersion containing modified nanocellulose crystals is 1 g: 30-50 mL.

7. The method for preparing the heat-resistant ink according to claim 1, wherein: In step 6, the mass ratio of the amino organic pigment to the modified fiber C is 1:2; the solid-liquid ratio of the modified fiber C to the PBS buffer is 1 g:25-30 mL; the PBS buffer contains 1%-1.5% glutaraldehyde by mass and has a pH of 7.4-7.

5.

8. The method for preparing heat-resistant ink according to claim 1, wherein: In step 6, the organic pigment is selected from any one of azo pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments or isoindolinone pigments.

9. A heat-resistant ink, characterized in that: The heat-resistant ink is prepared by the method for preparing the heat-resistant ink according to any one of claims 1 to 8.

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