A method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose

Abstract

The present invention belongs to the technical field of papermaking, and particularly relates to a method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose, which comprises the steps of: S1, crushing and drying bamboo slices to make bamboo powder; S2, obtaining holocellulose fibers after treating the bamboo powder with extraction of lignin, sodium chlorite acid solution and KOH solution; S3, neutralizing the alkali in the holocellulose fibers with hydrochloric acid and then washing with water; S4, diluting the holocellulose fibers with water to a suspension with a concentration of 0.5-1.5%, and then performing high-speed dispersion to obtain a pretreated cellulose fiber suspension; S5, performing homogenization treatment on the pretreated cellulose fiber suspension, and then concentrating to obtain a nanocellulose suspension; S6, compounding the nanocellulose suspension with cationic starch to obtain a coating solution, and coating the decorative base paper to obtain a decorative base paper coated with bamboo pulp nanocellulose. The method of the present invention can effectively improve the printing color fidelity of the decorative base paper and improve the quality and aesthetics of the decorative base paper.

Description

Technical Field

[0001] The present invention belongs to the technical field of papermaking, and particularly relates to a method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose. Background Art

[0002] Decorative base paper is a special industrial paper mainly made of high-quality wood pulp and titanium dioxide, and is processed by a special process. After printing and impregnating with melamine resin, it is mainly used as the facing paper layer, surface paper, and bottom paper of artificial boards such as fiberboard and particleboard. The decorative materials prepared from decorative base paper have many excellent properties such as heat insulation, flame retardancy, no warping, no cracking, and easy cleaning. Moreover, they have a wide variety of color patterns, rich and beautiful patterns, bright and vivid colors, and prominent layering, and are widely loved by users. After the decorative base paper is prepared, it also needs to be printed by inkjet or other methods, and the designed graphics and texts are formed on the surface before use.

[0003] Therefore, for decorative base paper, its most important function is to decorate and beautify the surface, and the printing color fidelity is the main index to measure the paper performance. Higher color fidelity can make the image colors brighter and more vivid, closer to the viewing effect of real scenes in nature, and greatly improve the quality and aesthetics of decorative base paper.

[0004] In view of this, providing a method that can effectively improve the printing color fidelity of decorative base paper is one of the technical problems that need to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose for the above-mentioned existing technical problems.

[0006] In view of this, the present invention provides a method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose, and the method includes the steps:

[0007] S1, pulverize and dry bamboo slices to make bamboo powder for standby;

[0008] S2, extract lignin from the bamboo powder in a suitable organic solvent for 3 - 5 h, then immerse the extracted bamboo powder in sodium chlorite acid solution, and stir at 70 - 80 °C to deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. Filter, place the obtained holocellulose powder in a KOH solution with a mass concentration of 1 - 3%, stir at 80 - 100 °C for 1 - 3 h, and then filter; then repeatedly treat with the sodium chlorite acid solution and KOH solution in sequence for 2 - 3 cycles to dissolve other components in the bamboo powder and obtain all-cellulose fibers;

[0009] S3. The holocellulose fibers obtained in step S2 are alkaline. Neutralize the alkali therein with a hydrochloric acid solution having a concentration of 0.5-2%, so that the holocellulose fiber suspension is neutral. Then, purify by centrifugal separation. After removing the supernatant, wash with water until the holocellulose fibers are neutral.

[0010] S4. Dilute the treated holocellulose fibers with water to obtain a suspension having a concentration of 0.5-1.5%. Then, place it in a high-speed disperser and perform pretreatment for 1-3 h at a rotation speed of 10,000-20,000 r / min to obtain a pretreated cellulose fiber suspension.

[0011] S5. Use a high-pressure homogenizer to perform homogenization treatment on the pretreated cellulose fiber suspension until the suspension becomes a fluorescent white. Then, concentrate the suspension into a nanocellulose suspension having a nanocellulose content of 3-7% for standby.

[0012] S6. Compound the nanocellulose suspension and cationic starch according to the following weight ratio by adding water: (0.5%-1.0%) NCC+(0-1.0%) cationic starch to obtain a coating solution. After the coating solution is ultrasonically dispersed evenly, coat it on the decorative base paper. After drying at a temperature above 100 °C, obtain the decorative base paper coated with bamboo pulp nanocellulose.

[0013] Further, in step S1, before crushing, perform debarking and node removal treatment on the bamboo chips. After crushing, screen and filter the obtained bamboo powder with a 200-mesh sieve. The material passing through the sieve is dried in an oven at 100-130 °C for standby.

[0014] Further, in step S2, select a mixed solution of benzene and ethanol to extract lignin, and the volume ratio of benzene to ethanol is 2:1.

[0015] Further, in step S2, place the bamboo powder in a suitable organic solvent to extract lignin for 4 h. Then, immerse the extracted bamboo powder in an acidified sodium chlorite solution and perform deep removal of residual lignin under stirring at 75 °C until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. Filter, place the obtained holocellulose powder in a KOH solution having a mass concentration of 2%, and perform stirring treatment at 90 °C for 2 h, then filter. Then, repeatedly treat with the acidified sodium chlorite solution and the KOH solution in sequence for 2 cycles to dissolve other components in the bamboo powder and obtain holocellulose fibers.

[0016] Further, in step S3, neutralize the alkali in the holocellulose fibers obtained in step S2 with a hydrochloric acid solution having a concentration of 1% to make the holocellulose fiber suspension neutral. Then, purify by centrifugal separation. After removing the supernatant, wash with water until the holocellulose fibers are neutral.

[0017] Further, in the step S4, the treated holocellulose fibers are diluted with water to obtain a suspension with a concentration of 1%, and then placed in a high-speed disperser for pretreatment for 2 h at a rotation speed of 15,000 r / min to obtain a pretreated cellulose fiber suspension.

[0018] Further, in the step S6, the coating thickness of the obtained coating is 5-50 μm, and the temperature of the coating solution is 10-50 °C.

[0019] Further, in the step S6, nanocellulose and cationic starch are compounded with water according to the following weight ratios: 1.0% NCC, or 0.5% NCC + 0.5% cationic starch, or 1.0% NCC + 1.0% cationic starch to obtain a coating solution.

[0020] Further, the coating solution formulation is 0.5% NCC + 0.5% cationic starch, and the coating thickness is 25 μm.

[0021] The decorative base paper prepared by the method for improving the printing color fidelity of the decorative base paper as described above.

[0022] In the method for improving the printing color fidelity of the decorative base paper by using bamboo pulp nanocellulose according to the present invention, a coating solution containing nanocellulose and cationic starch is coated on the decorative base paper and then printed. Thus, a printed ink layer is printed on the paper substrate formed by the decorative base paper and the coating thereon. Since the paper surface is coated with a coating containing bamboo pulp nanocellulose and printing ink is provided on the coating, when sunlight shines on the paper surface, refraction will occur on the printed ink layer and the paper substrate respectively, and then the refracted light enters the human eye. Thus, the pattern seen by the human eye will be more three-dimensional, vivid, bright and colorful. Description of the Drawings

[0023] Figure 1 is a schematic diagram of the principle of the printing color fidelity of the decorative base paper described in the present invention;

[0024] Figure 2 is a schematic diagram of the influence of the coating amount and coating temperature on the smoothness of the paper;

[0025] Figure 3 is a schematic diagram of the influence of the coating amount and coating temperature on the glossiness of the paper;

[0026] Figure 4 is a photograph of the boundary of the printed pattern obtained during the ink diffusion test in Test Example 3;

[0027] Figure 5 is the Lab value of the IT8.7-4CMYK test chart during the color rendering effect test in Test Example 3;

[0028] Figure 6 It is a comparison diagram of the sample color gamut during the color rendering effect test in Test Example 3;

[0029] The markings in the figure are indicated as:

[0030] 1 - paper base, 2 - printing ink layer. Specific implementation manners

[0031] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0032] In the description of the present application, it should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. Technologies, methods, and devices known to those of ordinary skill in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / " generally represents an "or" relationship between the associated objects before and after.

[0034] It should be noted that in this application, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising such element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of this application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0035] Bamboo pulp nano microfibrillated cellulose is a fibrillar cellulose product with a diameter of 1 - 100 nm and a length of 500 - 2000 nm prepared from bamboo pulp fibers. It has excellent properties such as high crystallinity, strong adsorption capacity, good water solubility, and high mechanical strength, and the fiber as a whole contains a disordered amorphous region and a highly ordered crystalline region. At the same time, nanocellulose (NCC) has a one-dimensional rod-like morphology, and a certain amount of sulfonic acid groups will be carried on the crystalline nanocellulose, which makes the whole cellulose nanorod negatively charged. The electrostatic repulsion force makes the crystalline cellulose not easily precipitate in aqueous solution and can be evenly dispersed. In addition, the solution containing nanocellulose can be induced to self-assemble by evaporation, and when forming a self-supporting solid film, it has a chiral nematic helical structure. This special structure, combined with the right-handed chiral curly morphology of the crystalline nanocellulose itself, makes the self-supporting solid film have special optical properties, capable of causing Bragg diffraction and generating birefringence. Therefore, when light hits the nanocellulose, the color of the reflected light will be brighter, and if observed with a polarizing microscope, colorful and bright colors will be seen. In the prior art, materials or waveguides with optical anisotropy can be processed using the most characteristic birefringence property of crystalline nanocellulose, and various unique functions or performances can be realized, such as miniaturized polarized beam control, organic electroluminescent display, etc.

[0036] Furthermore, bamboo pulp nanocellulose is a cellulose material derived from bamboo, with high structural stability and strength. Bamboo is a common plant material with a high cellulose content, wide sources, and low costs.

[0037] Based on this, the present invention uses bamboo pulp nanocellulose as the main raw material and, by virtue of the special optical properties of nanocellulose, develops a method for improving the printing color fidelity of decorative base paper. Specifically, the method includes the following steps:

[0038] S1, crush and dry bamboo chips to make bamboo powder for standby;

[0039] S2, extract lignin from the bamboo powder in a suitable organic solvent for 3 - 5 h. Then immerse the extracted bamboo powder in sodium chlorite acidified solution, and under the condition of 70 - 80 °C, stir to deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. Filter, place the obtained holocellulose powder in a KOH solution with a mass concentration of 1 - 3%, and under the condition of 80 - 100 °C, stir and process for 1 - 3 h, then filter; then repeatedly process with the sodium chlorite acidified solution and KOH solution in sequence for 2 - 3 cycles to dissolve other components in the bamboo powder and obtain holocellulose fibers;

[0040] S3, the holocellulose fibers obtained in step S2 are alkaline. Neutralize the alkali in them with a hydrochloric acid solution with a concentration of 0.5 - 2% to make the holocellulose fiber suspension neutral; then purify by centrifugal separation, remove the supernatant, and wash with water until the holocellulose fibers are neutral;

[0041] S4, dilute the processed holocellulose fibers with water to obtain a suspension with a concentration of 0.5 - 1.5%, then place it in a high - speed disperser and perform pretreatment for 1 - 3 h at a rotation speed of 10,000 - 20,000 r / min to obtain a pretreated cellulose fiber suspension;

[0042] S5, use a high - pressure homogenizer to homogenize the pretreated cellulose fiber suspension until the suspension becomes a fluorescent white, and then concentrate the suspension into a nanocellulose suspension with a nanocellulose content of 3 - 7% for standby;

[0043] S6, compound the nanocellulose suspension and cationic starch according to the following weight ratio and add water: (0.5% - 1.0%) NCC+(0 - 1.0%) cationic starch to obtain a coating solution. After the coating solution is ultrasonically dispersed evenly, coat it on the decorative base paper. After drying at a temperature above 100 °C, obtain the decorative base paper coated with bamboo pulp nanocellulose.

[0044] As some examples of the present invention, in step S1, bamboo chips can be crushed by means of equipment such as ball mills, crushers, and cutters.

[0045] Preferably, in the step S1, the bamboo slices are peeled and knotted before crushing. After crushing, the obtained bamboo powder is sieved and filtered through a 200-mesh sieve, and the material passing through the sieve is dried in an oven at 100-130 °C for standby.

[0046] As some examples of the present invention, in the step S1, after the bamboo powder is sieved and filtered, it can be dried in an oven at 105 °C, 110 °C, or 120 °C.

[0047] Preferably, in the step S2, the extraction temperature is 70-90 °C.

[0048] As some examples of the present invention, in the step S2, a mixed solution of benzene and ethanol is used to extract lignin.

[0049] Preferably, in the mixed solution of benzene and ethanol, the volume ratio of benzene to ethanol is 1.5-2.5:1.

[0050] More preferably, in the mixed solution of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1.

[0051] As some examples of the present invention, in the step S2, the acidified sodium chlorite solution is obtained by adjusting the pH to 4-5 with glacial acetic acid, where the mass concentration of sodium chlorite is 1%-1.5%. The dosage of the acidified sodium chlorite solution and the weight ratio of bamboo powder is 30-150:1.

[0052] As some examples of the present invention, in the step S2, the dosage of the KOH solution and the weight ratio of bamboo powder is 30-150:1.

[0053] Preferably, in the step S2, the bamboo powder is placed in a suitable organic solvent to extract lignin for 4 h. Then, the extracted bamboo powder is immersed in the acidified sodium chlorite solution, and under the condition of 75 °C and stirring, the residual lignin is deeply removed until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. After filtration, the obtained holocellulose powder is placed in a KOH solution with a mass concentration of 2%, and after stirring at 90 °C for 2 h, it is filtered; then, the acidified sodium chlorite solution and the KOH solution are repeatedly treated in sequence for 2 cycles to dissolve other components in the bamboo powder, and the cellulose fiber is obtained.

[0054] Preferably, in the step S3, the alkali in the cellulose fiber obtained in the step S2 is neutralized with a 1% hydrochloric acid solution to make the cellulose fiber suspension neutral; then, it is purified by centrifugal separation. After removing the supernatant, water is added for washing until the cellulose fiber is neutral.

[0055] Preferably, in the step S4, the treated holocellulose fibers are diluted with water to obtain a suspension with a concentration of 1%, and then placed in a high-speed disperser and pretreated at a rotation speed of 15,000 rpm for 2 h. While making the fibers disperse evenly, the high-speed shearing force of the water flow is used to separate the non-crystalline regions of the fibers, exposing the crystalline regions.

[0056] Preferably, in the step S5, a high-pressure homogenizer is used to homogenize the pretreated cellulose fiber suspension until the suspension becomes a fluorescent white, and then the suspension is concentrated into a nano-cellulose suspension with a nano-cellulose content of 5% for standby.

[0057] Preferably, in the step S6, the coating thickness of the obtained coating is 5 - 50 μm, and the temperature of the coating solution is 10 - 50 °C.

[0058] Preferably, in the step S6, after drying at 100 - 130 °C after coating, the decorative base paper coated with bamboo pulp nano-cellulose is obtained.

[0059] As some examples of the present invention, in the step S6, the nano-cellulose and cationic starch are compounded in the following ratios: 1.0% NCC, or 0.5% NCC + 0.5% cationic starch, or 1.0% NCC + 1.0% cationic starch. After ultrasonic dispersion, a coating solution is obtained, and then coating is carried out. The coating thicknesses are 6 μm, 25 μm, and 40 μm respectively; the temperatures of the coating solution are 25 °C, 35 °C, and 45 °C respectively; after coating, drying is carried out at 105 °C to obtain the bamboo pulp nano-cellulose coating.

[0060] In the method for improving the printing color fidelity of the decorative base paper by using bamboo pulp nano-cellulose according to the present invention, by coating a coating solution containing nano-cellulose and cationic starch on the decorative base paper and then printing, a structure as shown in Figure 1 can be formed on the paper surface. In Figure 1 , a printing ink layer 2 is printed on a paper base 1 formed by the decorative base paper and the coating thereon. Since the paper surface is coated with a coating containing bamboo pulp nano-cellulose and printing ink is provided on the coating, when sunlight shines on the paper surface, refraction will occur on the printing ink layer 2 and the paper base 1 respectively, and then the refracted light enters the human eye. In this way, the pattern seen by the human eye will be more three-dimensional, vivid, bright, and colorful.

[0061] The following is an example of the method for improving the printing color fidelity of the decorative base paper by using bamboo pulp nano-cellulose according to the present invention through specific examples:

[0062] Example 1

[0063] A method for improving the printing color fidelity of the decorative base paper by using bamboo pulp nano-cellulose:

[0064] S1. After removing the skin and nodes from the bamboo slices, pulverize them using a ball mill. After pulverization, sieve and filter the obtained bamboo powder through a 200-mesh sieve. The material passing through the sieve is dried in an oven at 100 °C for later use.

[0065] S2. Place the bamboo powder in a mixed solution of benzene and ethanol (the volume ratio of benzene to ethanol is 1.5:1), and extract lignin at 70 °C for 5 h. Then immerse the extracted bamboo powder in an acidified sodium chlorite solution, and under the condition of 70 °C, stir to deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. The obtained powder is holocellulose. Then filter it, place the obtained holocellulose powder in a KOH solution with a mass concentration of 1%, stir at 80 °C for 3 h and then filter; then repeatedly treat it with the acidified sodium chlorite solution and the KOH solution in sequence for 3 cycles to dissolve other components in the bamboo powder, and obtain a suspension of cellulose fibers. Among them, the mass concentration of sodium chlorite is 1%, the pH is 4, and the dosage ratio of the acidified sodium chlorite solution to the weight of the bamboo powder in each soaking process is 30:1, and the dosage ratio of the KOH solution to the weight of the bamboo powder is 30:1.

[0066] S3. The suspension of cellulose fibers obtained in step S2 is alkaline. Neutralize the alkali in it with a hydrochloric acid solution with a concentration of 0.5% to make the suspension neutral; then purify it by centrifugal separation, remove the supernatant, and wash it with water until the cellulose fibers are neutral.

[0067] S4. Dilute the treated cellulose fibers with water to obtain a suspension with a concentration of 0.5%, and then place it in a high-speed disperser and perform pretreatment at a rotation speed of 20,000 r / min for 1 h. While making the fibers disperse evenly, use the high-speed shearing force of the water flow to separate the non-crystalline regions of the fibers and expose the crystalline regions to obtain a pretreated suspension of cellulose fibers.

[0068] S5. Use a high-pressure homogenizer to homogenize the pretreated suspension of cellulose fibers until the suspension becomes a fluorescent white, and then concentrate the suspension into a suspension of nanocellulose with a nanocellulose content between 3% for later use.

[0069] S6. Dilute the nanocellulose suspension with water to obtain a coating solution with an NCC content of 1.0%. After the coating solution is ultrasonically dispersed evenly, coat it on the decorative base paper. After coating, dry it at 110 °C to obtain the decorative base paper coated with bamboo pulp nanocellulose.

[0070] Example 2

[0071] A method for improving the printing color fidelity of decorative base paper using bamboo pulp nanocellulose:

[0072] S1. After peeling and knotting removal of bamboo slices, pulverize them using a ball mill. After pulverization, sieve and filter the obtained bamboo powder through a 200-mesh sieve. The material passing through the sieve is dried in an oven at 105 °C for later use.

[0073] S2. Place the bamboo powder in a mixed solution of benzene and ethanol (the volume ratio of benzene to ethanol is 2:1), and extract lignin at 80 °C for 4 h. Then immerse the extracted bamboo powder in an acidified sodium chlorite solution, and under the condition of 75 °C, stir to deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. The obtained powder is holocellulose. Then filter it, place the obtained holocellulose powder in a KOH solution with a mass concentration of 2%, stir at 90 °C for 2 h and then filter; then repeatedly treat it with the acidified sodium chlorite solution and the KOH solution in sequence for 2 cycles to dissolve other components in the bamboo powder and obtain a suspension of holocellulose fibers; among them, the mass concentration of sodium chlorite is 1.2% and the pH is 4.3. The dosage ratio of the acidified sodium chlorite solution to the weight of the bamboo powder in each soaking process is 100:1, and the dosage ratio of the KOH solution to the weight of the bamboo powder is 100:1.

[0074] S3. The suspension of holocellulose fibers obtained in step S2 is alkaline. Neutralize the alkali in it with a 1% hydrochloric acid solution to make the suspension neutral; then purify it by centrifugal separation, remove the supernatant, and wash it with water until the holocellulose fibers are neutral.

[0075] S4. Dilute the treated holocellulose fibers with water to obtain a 1% suspension, and then place it in a high-speed disperser and perform pretreatment at a rotation speed of 15,000 r / min for 2 h. While making the fibers disperse evenly, use the high-speed shearing force of the water flow to separate the non-crystalline regions of the fibers and expose the crystalline regions to obtain a pretreated suspension of cellulose fibers.

[0076] S5. Use a high-pressure homogenizer to homogenize the pretreated suspension of cellulose fibers until the suspension becomes a fluorescent white, and then concentrate the suspension into a suspension of nanocellulose with a nanocellulose content of between 5% for later use.

[0077] S6. Recompound the nanocellulose suspension and cationic starch according to the following weight ratio by adding water: 0.5% NCC + 0.5% cationic starch to obtain a coating solution. After the coating solution is ultrasonically dispersed evenly, coat it on the decorative base paper. After coating, dry it at 105 °C to obtain a decorative base paper coated with bamboo pulp nanocellulose.

[0078] Example 3

[0079] A method for improving the printing color fidelity of decorative base paper using bamboo pulp nanocellulose:

[0080] S1. After removing the skin and joints of the bamboo slices, pulverize them using a ball mill. After pulverization, sieve and filter the obtained bamboo powder through a 200-mesh sieve. The material passing through the sieve is dried in an oven at 130 °C for later use.

[0081] S2. Place the bamboo powder in a mixed solution of benzene and ethanol (the volume ratio of benzene to ethanol is 2.5:1), and extract lignin at 90 °C for 3 h. Then immerse the extracted bamboo powder in an acidified sodium chlorite solution, and under the condition of 80 °C, stir to deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. The obtained powder is holocellulose. Then filter it, place the obtained holocellulose powder in a KOH solution with a mass concentration of 3%, stir at 100 °C for 1 h and then filter; then repeatedly treat it with the acidified sodium chlorite solution and the KOH solution in sequence for 2 cycles to dissolve other components in the bamboo powder, and obtain a suspension of holocellulose fibers; among them, the mass concentration of sodium chlorite is 1.5%, the pH is 5, and the dosage ratio of the acidified sodium chlorite solution to the weight of the bamboo powder in each soaking process is 150:1, and the dosage ratio of the KOH solution to the weight of the bamboo powder is 150:1.

[0082] S3. The suspension of holocellulose fibers obtained in step S2 is alkaline. Neutralize the alkali in it with a 2% hydrochloric acid solution to make the suspension neutral; then purify it by centrifugal separation, remove the supernatant, and wash it with water until the holocellulose fibers are neutral.

[0083] S4. Dilute the treated holocellulose fibers with water to obtain a suspension with a concentration of 1.5%, and then place it in a high-speed disperser and perform pretreatment at a rotation speed of 10,000 r / min for 3 h. While making the fibers disperse evenly, use the high-speed shearing force of the water flow to separate the non-crystalline regions of the fibers and expose the crystalline regions to obtain a pretreated suspension of cellulose fibers.

[0084] S5. Use a high-pressure homogenizer to homogenize the pretreated suspension of cellulose fibers until the suspension becomes a fluorescent white, and then concentrate the suspension into a nanocellulose suspension with a nanocellulose content of 7% for later use.

[0085] S6. Compound the nanocellulose suspension and cationic starch according to the following weight ratio and add water: (1.0%) NCC+(1.0%) cationic starch to obtain a coating solution. After the coating solution is ultrasonically dispersed evenly, coat it on the decorative base paper. After coating, dry it at a temperature above 100 °C to obtain a decorative base paper coated with bamboo pulp nanocellulose.

[0086] Experimental Example 1

[0087] Take the nanocellulose suspension prepared under the same conditions, and prepare coating liquids by compounding them in the proportions of 1.0% NCC, 0.5% NCC + 0.5% cationic starch, and 1.0% NCC + 1.0% cationic starch respectively. Then coat the decorative base paper at 25°C, 35°C, and 45°C respectively to obtain coatings with thicknesses of 6 μm, 25 μm, and 40 μm. At the same time, use the uncoated decorative base paper as a blank sample to test the effects of the temperature and coating amount of the coating liquid on the smoothness of the paper, and obtain the results as Figure 2 shown in the detection results.

[0088] It can be seen from Figure 2 that:

[0089] (1) The temperature of the coating liquid has little effect on the smoothness of the coated paper;

[0090] (2) After coating and finishing the surface of the base paper, its smoothness is improved. Among them, the coating formula of 25 μm coating amount and 0.5% NCC + 0.5% cationic starch has the best finishing effect on the paper surface.

[0091] Experimental Example 2

[0092] Take the coating liquids prepared by compounding 1.0% NCC, 0.5% NCC + 0.5% cationic starch, and 1.0% NCC + 1.0% cationic starch respectively, and coat the decorative base paper at 25°C, 35°C, and 45°C respectively to obtain coatings with thicknesses of 6 μm, 25 μm, and 40 μm. At the same time, use the uncoated decorative base paper as a blank sample to test the effects of the temperature and coating amount of the coating liquid on the glossiness of the paper, and obtain the results as Figure 3 shown in the detection results.

[0093] It can be seen from Figure 3 that:

[0094] (1) The temperature of the coating liquid has a greater impact on the glossiness after coating. When the temperature is 35°C, the glossiness of the paper generally increases;

[0095] (2) From the perspective of the coating amount, the improvement of the glossiness is greatly related to the coating liquid formula. Among them, the coating formula of 0.5% NCC + 0.5% cationic starch shows better glossiness at a coating amount of 25 μm.

[0096] Based on the above experiments, it is obtained that the coating liquid formula with better finishing effect on the paper surface is 0.5% NCC + 0.5% cationic starch, and the coating thickness is 25 μm.

[0097] Experimental Example 3

[0098] Adopt coating liquid formula: 0.5% NCC + 0.5% cationic starch. The coating thickness is 25μm. The paper sample is prepared at the coating liquid temperature of 35°C. Then, the following tests are carried out on the paper sample:

[0099] (1) Ink transfer amount analysis

[0100] Analyze the ink transfer situation of the paper sample by using an IGT instrument, and obtain the test results shown in Table 1 below:

[0101] Table 1 Test results of ink transfer amount

[0102] Sample Name <![CDATA[Ink transfer amount (g / m 2 )]]> Uncoated Base Paper 7.641508 Coated Sample 8.309703

[0103] The test results show that: the ink transfer amount of the coated sample is improved compared with that of the uncoated original paper, indicating that the coating enhances the ability of the ink to transfer from the printing plate to the substrate, which is beneficial to improving the printing color rendering effect.

[0104] (2) Analysis of the solid color printing effect of the three primary colors

[0105] Analyze the solid color printing effect of the three primary colors of the paper sample by using an IGT instrument, and obtain the test results shown in Tables 2 - 4 below:

[0106] Table 2 Color analysis results of cyan ink

[0107] Name C M Y Color Strength Hue Error Gray Scale Color Efficiency Uncoated Base Paper 2.31 0.84 0.37 2.31 0.2452 0.1599 0.7370 Coated Sample 2.34 0.77 0.33 2.34 0.2222 0.1410 0.7635

[0108] Table 3 Color analysis results of yellow ink

[0109] Name C M Y Color Strength Hue Error Gray Scale Color Efficiency Uncoated Base Paper 0.09 0.34 1.70 1.70 0.1559 0.0568 0.8696 Coated Sample 0.08 0.36 1.70 1.70 0.1721 0.0468 0.8710

[0110] Table 4 Color analysis results of magenta ink

[0111]

[0112]

[0113] It can be seen from Tables 2 - 4 above that: the finished sample has good color reproducibility for the three primary colors, the color strength and color efficiency are higher than those of the original paper, and the hue error is relatively small.

[0114] (3) Ink abrasion resistance test

[0115] Print the coated sample by inkjet printing and test the abrasion resistance of the printed matter, and obtain the test results shown in Table 5 below:

[0116] Table 5 Test results of ink abrasion resistance

[0117] Test Paper Initial Mass (g) Mass after Wear (g) Wear Index Uncoated Base Paper 1.592 1.582 0.02 Coated Sample 1.615 1.609 0.012

[0118] It can be seen from Table 5 above that: compared with the uncoated base paper, the wear index of the ink shows a downward trend for the decorated samples, and this change indirectly proves that the nano-crystalline cellulose can enhance the adhesion ability of the ink on the paper substrate.

[0119] (4) Ink diffusion test

[0120] The coated samples were printed by inkjet printing, and the boundaries of the printed patterns on the prints were photographed and observed to obtain the Figure 4 photos as shown Figure 4 in. Among them, a is the photo of the uncoated decorative base paper, b is the photo of the coated sample, and the boundary lengths were calculated to investigate the ink diffusion situation, and the test results shown in Table 6 below were obtained:

[0121] Table 6 Ink diffusion test results

[0122] Test Paper Boundary Length (μm) Uncoated Base Paper 8.93 Coated Sample 7.70

[0123] From Figure 4 it can be seen that: the coated samples can effectively control the ink diffusion, and their boundary lengths are shorter than those of the uncoated base paper. Therefore, the nano-crystalline cellulose is beneficial to the printing effect after sample finishing.

[0124] (5) Color rendering effect test

[0125] The X-Rite 2011 IT8.7-4CMYK test chart was selected to print the samples, and the Lab values of each color block were measured. The measured data were fitted in MathLab, and the fitting results are as Figure 5 shown:

[0126] It can be Figure 5 seen from that: the fitting surface of the coated samples is smooth and flat, and can cover the entire test data, indicating that the coated samples have a better color rendering effect.

[0127] After that, the IT8.7-3 standard color target was selected to print the samples, and their color gamuts were measured, and the color gamut comparison chart of the samples as shown Figure 6 was obtained. Among them, the white contour line is the measurement result of the uncoated base paper, and the red contour line is the measurement result of the coated sample:

[0128] It can be Figure 6 seen from that: the color gamut of the coated samples is 3.64% larger than that of the uncoated base paper, indicating that the coated samples have a better color rendering effect.

[0129] The embodiments of the present application have been described above in conjunction with the accompanying drawings. Without conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all of them fall within the protection scope of the present application.

Claims

1. A method for improving the printing color fidelity of decorative base paper by using bamboo pulp nanocellulose, characterized in that, The method includes the following steps: S1. Crush and dry bamboo slices to obtain bamboo powder for standby. S2. Extract lignin from the bamboo powder in a suitable organic solvent for 3 - 5 hours. Then immerse the extracted bamboo powder into sodium chlorite acidified solution, and under the condition of 70 - 80 °C with stirring, deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. Filter it, place the obtained holocellulose powder into a KOH solution with a mass concentration of 1 - 3%, and under the condition of 80 - 100 °C with stirring for 1 - 3 hours, then filter. Then repeatedly treat it with the sodium chlorite acidified solution and the KOH solution in sequence for 2 - 3 cycles to dissolve other components in the bamboo powder and obtain holocellulose fibers. S3. The holocellulose fibers obtained in step S2 are alkaline. Neutralize the alkali in them with a hydrochloric acid solution with a concentration of 0.5 - 2% to make the holocellulose fiber suspension neutral. Then purify it by centrifugal separation. After removing the supernatant, wash it with water until the holocellulose fibers are neutral. S4. Dilute the treated holocellulose fibers with water to obtain a suspension with a concentration of 0.5 - 1.5%. Then place it in a high - speed disperser and perform pretreatment for 1 - 3 hours at a rotational speed of 10,000 - 20,000 revolutions per minute to obtain a pretreated cellulose fiber suspension. S5. Use a high - pressure homogenizer to homogenize the pretreated cellulose fiber suspension until the suspension becomes a fluorescent white. Then concentrate the suspension into a nano - cellulose suspension with a nano - cellulose content between 3 - 7% for standby. S6. Compound the nano - cellulose suspension and cationic starch with water to obtain a coating solution. After the coating solution is uniformly dispersed by ultrasonic waves, coat it on the decorative base paper. After drying at a temperature above 100 °C, obtain the decorative base paper coated with bamboo pulp nano - cellulose. Among them, the coating solution includes 0.5% NCC and 0.5% cationic starch, and the coating thickness is 25 μm.

2. The method for improving the color fidelity of the printed decorative base paper according to claim 1, characterized in that, In step S1, before crushing, the bamboo slices are peeled and knotted. After crushing, the obtained bamboo powder is screened and filtered with a 200 - mesh sieve, and the undersize is dried in an oven at 100 - 130 °C for standby.

3. The method for improving the color fidelity of the printed decorative base paper according to claim 1, wherein, In step S2, a mixed solution of benzene and ethanol is selected to extract lignin, and the volume ratio of benzene to ethanol is 2:

1.

4. The method for improving the color fidelity of the printed decorative base paper according to claim 1 or 3, characterized in that In step S2, extract lignin from the bamboo powder in a suitable organic solvent for 4 hours. Then immerse the extracted bamboo powder into sodium chlorite acidified solution, and under the condition of 75 °C with stirring, deeply remove the residual lignin until the color of the bamboo powder changes from yellow to white. At this time, the obtained powder is holocellulose. Filter it, place the obtained holocellulose powder into a KOH solution with a mass concentration of 2%, and under the condition of 90 °C with stirring for 2 hours, then filter. Then repeatedly treat it with the sodium chlorite acidified solution and the KOH solution in sequence for 2 cycles to dissolve other components in the bamboo powder and obtain holocellulose fibers.

5. The method for improving the color fidelity of the printed decorative base paper according to claim 1, characterized in that, In the step S3, the alkali in the holocellulose fibers obtained in the step S2 is neutralized with a hydrochloric acid solution with a concentration of 1% to make the holocellulose fiber suspension neutral; then, it is purified by centrifugal separation, and after removing the supernatant, it is washed with water until the holocellulose fibers are neutral.

6. The method for improving the color fidelity of the printed decorative base paper according to claim 1, characterized in that, In the step S4, the treated holocellulose fibers are diluted with water to obtain a suspension with a concentration of 1%, and then placed in a high-speed disperser and pretreated at a rotation speed of 15,000 r / min for 2 h to obtain a pretreated cellulose fiber suspension.

7. The method for improving the color fidelity of printed decorative base paper according to claim 1, wherein In the step S6, the temperature of the coating solution is 10~50 °C.

8. A decorative base paper prepared by the method for improving the printing color fidelity of the decorative base paper according to any one of claims 1 to 7 above.

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