A method for preparing paper for colored yarn

Abstract

The application belongs to the technical field of papermaking and textile, and provides a preparation method of colored paper for yarns. Carboxylated nanocellulose, dopamine hydrochloride, a catalytic oxidation system and an alkaline buffer are mixed to perform a polymerization reaction to obtain a polydopamine composite nanocellulose system; the polydopamine composite nanocellulose system, paper pulp, a dye and a dyeing assistant are mixed to perform dyeing and wet forming in sequence to obtain the colored paper for yarns; and the catalytic oxidation system comprises silver nitrate and sodium iodate. The application provides a green, safe and convenient preparation method for preparing yarn paper with high color fastness, high dyeing uniformity and high strength.

Description

Technical Field

[0001] This invention relates to the fields of papermaking and textile technology, and in particular to a method for preparing colored yarn paper. Background Technology

[0002] In the paper and textile industries, colored yarn paper has always been a research hotspot. Traditional dyeing methods for colored yarn paper mainly involve directly adding dyes to the pulp. However, this method has many drawbacks. For example, the binding force between the dye and the pulp fibers is weak, resulting in low color fastness and easy fading during subsequent use, affecting the quality and lifespan of the colored yarn paper. Furthermore, it is difficult to guarantee dyeing uniformity, leading to uneven color distribution and reduced product quality. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a method for preparing colored yarn paper. The colored yarn paper prepared by the method provided by the present invention has high color fastness and uniform dyeing.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing colored yarn paper, comprising the following steps:

[0006] Carboxylated nanocellulose, dopamine hydrochloride, a catalytic oxidation system, and an alkaline buffer solution were mixed and polymerized to obtain a polydopamine composite nanocellulose system.

[0007] The polydopamine composite nanocellulose system, pulp, dye and dyeing aid are mixed and dyed and wet-formed sequentially to obtain the colored yarn paper.

[0008] The catalytic oxidation system includes silver nitrate and sodium iodate.

[0009] Preferably, the carboxyl group content in the carboxylated nanocellulose is 0.5–2 mmol / g, and the aspect ratio is 100–200.

[0010] Preferably, the mass ratio of dopamine hydrochloride to carboxylated nanocellulose is 1:1.25 to 20.

[0011] Preferably, the ratio of dopamine hydrochloride to silver nitrate is 1-4 g: 4-15 mmol, and the ratio of dopamine hydrochloride to sodium iodate is 1-4 g: 5-30 mmol.

[0012] Preferably, the polymerization reaction is carried out at a temperature of 20–40°C for a time of 30–120 min.

[0013] Preferably, the mass ratio of the polydopamine composite nanocellulose system to the pulp, based on oven-dry weight, is 10:90 to 0.5:99.5; and the freeness of the pulp is 35 to 65°SR.

[0014] Preferably, the amount of dye used is 2-10% owf.

[0015] Preferably, the dyeing agent includes sodium sulfate and sodium carbonate, wherein the amount of sodium sulfate is 20-60 g / L and the amount of sodium carbonate is 10-30 g / L.

[0016] Preferably, the staining temperature is 40–80°C and the time is 30–120 min.

[0017] Preferably, the basis weight of the colored yarn paper is 12-20 g / m². 2 .

[0018] This invention provides a method for preparing colored yarn paper.

[0019] In this invention, dopamine hydrochloride is used as a monomer, and polydopamine is formed by polymerization on the surface of carboxylated nanocellulose through an AgNO3 / NaIO3 catalytic oxidation system. Since carboxylated nanocellulose is homologous to pulp fibers and possesses ultra-high specific surface area, ultra-high aspect ratio, and uniform micro / nano size, the polydopamine-nanocellulose composite system can be uniformly dispersed in the pulp, meaning polydopamine can be uniformly dispersed in the pulp. Polydopamine is a polymer with strong adhesive properties, containing numerous active groups such as phenolic hydroxyl and amino groups in its molecular structure. These active groups promote covalent adsorption between polydopamine and dyes. This covalent adsorption stably and firmly fixes the dye onto the pulp fibers, ultimately improving the color fastness of colored yarn paper. Furthermore, by loading polydopamine onto carboxylated nanocellulose, its dispersibility in the pulp is improved, thereby enhancing dyeing uniformity. Adding a catalytic oxidation system to the polymerization reaction system promotes the formation of polydopamine into micro- and nano-sized particles, which are then uniformly distributed on the surface of the pulp fibers. This, in turn, ensures the uniform distribution of dyes bonded to the pulp fibers via polydopamine, ultimately improving the dyeing uniformity of colored yarn paper. Furthermore, carboxylated nanocellulose, being long and thin filaments and homologous to pulp fibers, promotes interweaving between pulp fibers, strengthens the hydrogen bond network between them, and thus improves the tensile strength of colored yarn paper.

[0020] Furthermore, the carboxyl content in the carboxylated nanocellulose is 0.5–2 mmol / g, and the aspect ratio is 100–200. The addition of carboxylated nanocellulose with a high aspect ratio can promote the interweaving between pulp fibers, enhance the hydrogen bond network between pulp fibers, and thus improve the tensile strength of colored yarn paper.

[0021] Data from the examples show that the colored yarn paper prepared by the present invention has high color fastness: wash fastness ≥ 4.5 grade, rubbing fastness ≥ 4 grade; color depth K / S value ≥ 15; green process: reduced amount of dyeing auxiliaries, low COD of wastewater, no need to use urea or high temperature color fixing; high strength of colored yarn paper: tensile strength increased by 20% to 30%; good antibacterial properties: antibacterial rate against common pathogenic bacteria such as Escherichia coli and Staphylococcus aureus ≥ 90%. Attached Figure Description

[0022] Figure 1 SEM image of the colored yarn paper obtained in Comparative Example 2;

[0023] Figure 2 This is a SEM image of the colored yarn paper obtained in Example 2. Detailed Implementation

[0024] This invention provides a method for preparing colored yarn paper, comprising the following steps:

[0025] Carboxylated nanocellulose, dopamine hydrochloride, a catalytic oxidation system, and an alkaline buffer solution were mixed and polymerized to obtain a polydopamine composite nanocellulose system.

[0026] The polydopamine composite nanocellulose system, pulp, dye and dyeing aid are mixed and dyed and wet-formed sequentially to obtain the colored yarn paper.

[0027] The catalytic oxidation system includes silver nitrate and sodium iodate.

[0028] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0029] This invention involves mixing carboxylated nanocellulose, dopamine hydrochloride, a catalytic oxidation system, and an alkaline buffer solution to perform a polymerization reaction, thereby obtaining a polydopamine composite nanocellulose system, denoted as the CNF@PDA system.

[0030] In this invention, the content of carboxyl groups in the carboxylated nanocellulose (carboxylated CNF) is preferably 0.5 to 2 mmol / g, specifically preferably 0.5 mmol / g, 1 mmol / g, 1.5 mmol / g, 1.8 mmol / g or 2 mmol / g; the aspect ratio is preferably 100 to 200, specifically preferably 100, 120, 140, 150, 160, 180 or 200.

[0031] In this invention, the mass ratio of dopamine hydrochloride to carboxylated nanocellulose is preferably 1:1.25 to 20, and more preferably 1:1.25, 1:2.5, 1:5, 1:7.5, 1:10, 1:12.5, 1:15, 1:17.5 or 1:20.

[0032] In this invention, the catalytic oxidation system comprises silver nitrate and sodium iodate. In this invention, the preferred ratio of dopamine hydrochloride to silver nitrate is 1–4 g:4–15 mmol, more preferably 1 g:4–15 mmol, and specifically preferably 1 g:2 mmol, 1 g:4 mmol, or 1 g:5 mmol; the preferred ratio of dopamine hydrochloride to sodium iodate is 1–4 g:5–30 mmol, more preferably 1 g:5–30 mmol, and specifically preferably 1 g:10 mmol or 1 g:15 mmol. In this invention, using AgNO3 and NaIO3 as the oxidation system significantly increases the polymerization rate of dopamine hydrochloride (DA) while effectively reducing the particle size of polydopamine (PDA). + Polydopamine forms complexes (such as Ag-O or Ag-N coordination bonds) with the phenolic hydroxyl and amino functional groups of dopamine quinone intermediates, creating a charged layer (increased zeta potential) on the surface of PDA particles. This electrostatic repulsion inhibits PDA particle aggregation, reducing the particle size from micrometers (1–5 μm) to micro-nano sizes (50–200 nm). These micro-nano-sized PDA particles can be more uniformly distributed on the pulp fiber surface, further improving the bonding effect between polydopamine and pulp fibers, as well as dyeing uniformity. On the other hand, reducing intermediates (such as semiquinone radicals) generated during dopamine oxidation can partially degrade Ag... + The Ag is reduced to nano-sized elemental Ag and uniformly adsorbed onto the surface of polydopamine composite nanocellulose. These elemental Ags impart long-lasting antibacterial properties to colored yarn paper by contact disruption of bacterial cell membranes and inhibition of enzyme activity.

[0033] In this invention, the pH value of the alkaline buffer solution is preferably 8-9, more preferably 8.5. Specifically, the alkaline buffer solution is preferably a Tris buffer solution. In one specific embodiment of this invention, the preparation method of the Tris buffer solution specifically includes the following steps: mixing tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) and a first portion of deionized water, then adjusting the pH to alkaline using concentrated hydrochloric acid, and adding deionized water quantitatively to obtain the Tris buffer solution. In this invention, the preferred ratio of tris(hydroxymethyl)aminomethane hydrochloride to the first portion of deionized water is 15.76 g: 800 mL; the preferred mass concentration of the concentrated hydrochloric acid is 36-38%; the preferred alkaline pH value is consistent with the above technical solution and will not be repeated here; the preferred quantitative volume is 1000 mL.

[0034] In this invention, the mixing of carboxylated nanocellulose, dopamine hydrochloride, catalytic oxidation system and alkaline buffer preferably includes the following steps: dispersing carboxylated nanocellulose in alkaline buffer to obtain a carboxylated nanocellulose dispersion; and sequentially adding dopamine hydrochloride and catalytic oxidation system to the carboxylated nanocellulose dispersion.

[0035] In this invention, the temperature of the polymerization reaction is preferably 20 to 40°C, specifically 20°C, 25°C, 30°C, 35°C or 40°C; the time is preferably 30 to 120 min, specifically 30 min, 60 min, 90 min or 120 min.

[0036] Following the polymerization reaction, the present invention preferably further includes ultrasonic dispersion to obtain a polydopamine composite nanocellulose system. In the present invention, the ultrasonic dispersion time is preferably 10–30 min, more preferably 20 min.

[0037] After obtaining the polydopamine composite nanocellulose system, the present invention mixes the polydopamine composite nanocellulose system, pulp, dye and dyeing agent, and performs dyeing and wet forming in sequence to obtain the colored yarn paper.

[0038] In this invention, the pulp is preferably bleached pulp. Specifically, the pulp is preferably softwood pulp. The freeness of the pulp is preferably 35–65°SR, specifically 35°SR, 40°SR, 45°SR, 50°SR, 55°SR, 60°SR, or 65°SR. This invention does not specify a particular method for preparing the pulp; any method well-known to those skilled in the art can be used.

[0039] In this invention, the mass ratio of the polydopamine composite nanocellulose system to the pulp, measured on an oven-dry basis, is preferably 10:90 to 0.5:99.5, and more preferably 10:90, 9:91, 8:92, 7:93, 6:94, 5:95, 4:96, 3:97, 2:98, 1:99 or 0.5:99.5.

[0040] In this invention, the amount of dye used is preferably 2-10% owf, specifically preferably 2% owf, 3% owf, 4% owf, 5% owf, 6% owf, 7% owf, 8% owf, 9% owf, or 10% owf. In this invention, the dye is preferably a dark-colored dye, specifically preferably a brown dye, a black dye, or a navy blue dye. In one specific embodiment of this invention, the dye is specifically preferably anthraquinone series dye, azo dye, or phthalocyanine dye; the anthraquinone series dye is specifically preferably Reactive Blue 19KN-R; the azo dye is specifically preferably Direct Fast Black G, Reactive Black 5, or sulfur black; and the phthalocyanine dye is specifically preferably copper phthalocyanine blue.

[0041] In this invention, the dyeing agent preferably includes sodium sulfate and sodium carbonate. The amount of sodium sulfate is preferably 20-60 g / L, specifically 20 g / L, 30 g / L, 40 g / L, 50 g / L or 60 g / L; the amount of sodium carbonate is preferably 10-30 g / L, specifically 10 g / L, 15 g / L, 20 g / L, 25 g / L or 30 g / L.

[0042] In this invention, the mixing of the polydopamine composite nanocellulose system, pulp, dye, and dyeing auxiliaries preferably includes the following steps: after a first mixing of the polydopamine composite nanocellulose system and pulp, the dye and dyeing auxiliaries are added sequentially. In this invention, the first mixing method is preferably shear dispersion, with the shear dispersion rotation speed preferably between 200 and 600 rpm, specifically preferably 200 rpm, 300 rpm, 400 rpm, 500 rpm, or 600 rpm; the time is preferably 20 to 40 minutes, more preferably 30 minutes.

[0043] In this invention, the dyeing temperature is preferably 40-80℃, specifically 40℃, 50℃, 60℃, 70℃ or 80℃; the dyeing time is preferably 30-120min, specifically 30min, 60min, 90min or 120min.

[0044] After dyeing, the present invention preferably further includes washing. In the present invention, the washing agent is preferably water. The present invention does not specifically limit the number of washings or the amount of washing agent used, as long as the fibers are washed until they are neutral.

[0045] In this invention, the basis weight of the colored yarn paper is preferably 12-20 g / m³. 2 Specifically, the preferred value is 12g / m 2 13g / m 2 14g / m 2 15g / m 2 16g / m 2 17g / m 2 18g / m 2 19g / m 2 Or 20g / m 2 The present invention does not specifically limit the wet forming method, as long as a corresponding quantity of colored yarn paper can be obtained.

[0046] In this invention, the molecular structure of polydopamine contains a large number of active groups such as phenolic hydroxyl and amino groups. These active groups can form covalent bonds or hydrogen bonds with dyes, firmly fixing the dyes onto the wood pulp fibers, thereby improving the color fastness of colored yarn paper. Simultaneously, polydopamine is a polymer with strong adhesive properties, capable of forming stable adhesion on the surface of carboxylated nanocellulose. The introduction of carboxylated nanocellulose promotes the uniform dispersion of polydopamine in the pulp, thereby improving dyeing uniformity. Furthermore, the introduction of a catalytic oxidation system promotes the formation of micro / nano-sized polydopamine particles, which are uniformly distributed on the surface of the wood pulp fibers. This ensures that the dyes attached to the pulp fibers by polydopamine are also uniformly distributed, ultimately improving the dyeing uniformity of colored yarn paper.

[0047] The following detailed description of the preparation method of the colored yarn paper provided by the present invention, in conjunction with the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] (1) Preparation method of alkaline buffer solution: 15.76g of tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl, 157.6g / mol) was added to 800mL of deionized water, the pH was adjusted to 8.5 with concentrated hydrochloric acid (36-38%), and deionized water was added to make up to 1L. The alkaline buffer solution has a mass concentration of 1% and a pH value of 8.5.

[0050] (2) Carboxylated CNF (carboxyl content 1.5 mmol / g, aspect ratio 150) was dispersed in 1 L of alkaline buffer solution to obtain a 5 g / L carboxylated CNF dispersion; dopamine hydrochloride (DA) was added to the obtained carboxylated CNF dispersion at a mass ratio of 1:5, followed by AgNO3 (4 mmol) and NaIO3 (10 mmol), and the mixture was stirred at 30 °C for 60 min, followed by ultrasonic dispersion for 20 min to obtain the CNF@PDA system.

[0051] (3) Based on absolute dryness, the bleached softwood pulp (freezing degree 40°SR) and CNF@PDA system were mixed at a mass ratio of 90:10 and sheared and dispersed at 300 rpm for 30 min. Reactive Black 5 (2% owf), Na2SO4 20 g / L and Na2CO3 10 g / L were added, and the mixture was dyed at 60℃ for 120 min. Then, the fibers in the system were washed with water until neutral. Finally, wet forming was carried out to obtain colored yarn paper with a basis weight of 14 g / m2.

[0052] The tensile strength of the colored yarn paper was determined using the constant-speed tensile method (20 mm / min) of GB / T 12914-2018, "Determination of Tensile Strength of Paper and Paperboard". The absorbance at the maximum absorption wavelength (540 nm) was measured using a UV-Vis spectrophotometer, and the dye uptake rate of the colored yarn paper was calculated. The color fastness of the colored yarn paper was determined using GB / T 3922-2013, and the K / S value was measured using a Colori7 computer colorimeter. The antibacterial properties of the colored yarn paper were determined using GB / T20944.3—2008.

[0053] The results were as follows: tensile strength: 117 N·m / g; dye uptake: 70.5%; color fastness: wash fastness grade 4.5, rubbing fastness grade 4.3; K / S value: 19.7 (integral of visible light across the entire spectrum); inhibition rate against Staphylococcus aureus: 94.5%, inhibition rate against Escherichia coli: 95.2%.

[0054] Example 2

[0055] (1) The preparation of alkaline buffer solution is the same as in Example 1.

[0056] (2) The difference from (2) in Example 1 is that the carboxyl content of the carboxylated CNF is 1.8 mmol / g, the aspect ratio is 200, the amount of AgNO3 added is 5 mmol, and the amount of NaIO3 added is 15 mmol.

[0057] (3) The difference from (3) in Example 1 is that the dye is sulfur black, the amount is 7% owf, and the dyeing is carried out at 70°C for 60 min.

[0058] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 124 N·m / g; dye uptake: 76.4%; color depth K / S value: 22.5 (better than reactive black); wash fastness: 4.7; rubbing fastness: 4.5; inhibition rate against Staphylococcus aureus: 95.8%; inhibition rate against Escherichia coli: 96.4%.

[0059] Example 3

[0060] (1) The preparation of alkaline buffer solution is the same as in Example 1.

[0061] (2) The difference from (2) in Example 1 is that the amount of AgNO3 added is 2 mmol, the amount of NaIO3 added is 10 mmol, and the polymerization reaction is carried out at 25°C for 120 min.

[0062] (3) The difference from (3) in Example 1 is that, based on absolute dryness, the mass ratio of CNF@PDA system to bleached softwood pulp is 5:95, and the amount of dye used is 3% owf.

[0063] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 104.4 N·m / g; dye uptake: 71.5%; K / S value: 16.3; color fastness to rubbing: 4.0; color fastness to washing: 4.5; inhibition rate against Staphylococcus aureus: 94%; inhibition rate against Escherichia coli: 95.2%.

[0064] Comparative Example 1

[0065] (1) The preparation of alkaline buffer solution is the same as in Example 1.

[0066] (2) The difference from (2) in Example 2 is that silver nitrate is replaced with copper sulfate and sodium iodate is replaced with hydrogen peroxide. The rest is the same as in Example 1.

[0067] (3) Same as Example 2.

[0068] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 110.8 N·m / g; dye uptake: 69.5%; color depth K / S value: 16.1; color fastness to washing: grade 3.5; rubbing resistance: grade 4; inhibition rate against Staphylococcus aureus: 90.2%; inhibition rate against Escherichia coli: 91.3%.

[0069] Comparative Example 2

[0070] Similar to Example 2, the difference is that the CNF@PDA system is not used, and the bleached softwood pulp is directly dyed according to (3) to obtain colored yarn paper.

[0071] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 88.4 N·m / g; dye uptake: 20.8%; K / S value: 5.4; color fastness to rubbing: 1.0; color fastness to washing: 1.5; inhibition rate against Staphylococcus aureus: 0%; inhibition rate against Escherichia coli: 0%.

[0072] Comparative Example 3

[0073] Similar to Example 2, except that silver nitrate and sodium iodate are not added.

[0074] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 106.6 N·m / g; dye uptake: 65.2%; K / S value: 15.5; color fastness to rubbing: 4.0; color fastness to washing: 3.5; inhibition rate against Staphylococcus aureus: 0%; inhibition rate against Escherichia coli: 0%.

[0075] Comparative Example 4

[0076] Carboxylated CNF (carboxyl content 1.8 mmol / g, aspect ratio 200) was dispersed in 1 L of alkaline buffer solution to obtain a 5 g / L carboxylated CNF dispersion; dopamine hydrochloride (DA) was added to the obtained carboxylated CNF dispersion at a mass ratio of 1:5 to dopamine hydrochloride to obtain a mixed system.

[0077] Based on oven-dry weight, bleached softwood pulp (40°SR) and the mixed system were mixed at a mass ratio of 90:10 and sheared at 300 rpm for 30 min. Sulfur black (7% owf), 20 g / L Na₂SO₄, and 10 g / L Na₂CO₃ were added, and the mixture was dyed at 70°C for 60 min. The fibers in the system were then washed with water until neutral. Finally, wet forming was performed to obtain a basis weight of 14 g / m³. 2 Paper for colored yarn.

[0078] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 108.6 N·m / g; dye uptake: 68.7%; K / S value: 17.8; color fastness to rubbing: 3.0; color fastness to washing: 3.0; inhibition rate against Staphylococcus aureus: 0%; inhibition rate against Escherichia coli: 0%.

[0079] Comparative Example 5

[0080] The difference from Example 2 is that carboxylated CNF, dopamine hydrochloride, AgNO3, and NaIO3 are directly added to the mixed softwood pulp (freezing degree 40°SR). Specifically:

[0081] Carboxylated CNF (carboxyl content 1.8 mmol / g, aspect ratio 200) was dispersed in 1 L of alkaline buffer solution to obtain a 5 g / L carboxylated CNF dispersion. Dopamine hydrochloride (DA) was added to the obtained carboxylated CNF dispersion at a mass ratio of 1:5 to dopamine hydrochloride, followed by AgNO3 (5 mmol) and NaIO3 (15 mmol) to obtain a mixed system.

[0082] Based on oven-dry weight, bleached softwood pulp (40°SR) and the mixed system were mixed at a mass ratio of 90:10 and sheared at 300 rpm for 30 min. Sulfur black (7% owf), 20 g / L Na₂SO₄, and 10 g / L Na₂CO₃ were added, and the mixture was dyed at 70°C for 60 min. The fibers in the system were then washed with water until neutral. Finally, wet forming was performed to obtain a basis weight of 14 g / m³. 2 Paper for colored yarn.

[0083] The properties of the obtained colored yarn paper were tested using the method of Example 1. The results were as follows: tensile strength: 115.7 N·m / g; dye uptake: 70%; K / S value: 18.8; color fastness to rubbing: 3.0; color fastness to washing: 3.5; inhibition rate against Staphylococcus aureus: 87%; inhibition rate against Escherichia coli: 90%.

[0084] Figure 1 SEM image of the colored yarn paper obtained in Comparative Example 2; Figure 2 This is a SEM image of the colored yarn paper obtained in Example 2.

[0085] contrast Figure 1 and Figure 2 It can be seen that after the yarn paper is treated with the CNF@PDA system and dyed, PDA particles and intertwined CNF networks can be seen growing uniformly inside and on the surface of the yarn paper.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing colored yarn paper, characterized in that, Includes the following steps: Carboxylated nanocellulose, dopamine hydrochloride, a catalytic oxidation system, and an alkaline buffer solution were mixed and polymerized to obtain a polydopamine composite nanocellulose system. The polydopamine composite nanocellulose system, pulp, dye and dyeing aid are mixed and dyed and wet-formed sequentially to obtain the colored yarn paper. The catalytic oxidation system includes silver nitrate and sodium iodate; The carboxylated nanocellulose contains 0.5-2 mmol / g of carboxyl groups and has an aspect ratio of 100-200. The mass ratio of dopamine hydrochloride to carboxylated nanocellulose is 1:1.25~20; The ratio of dopamine hydrochloride to silver nitrate is 1~4g:4~15mmol, and the ratio of dopamine hydrochloride to sodium iodate is 1~4g:5~30mmol. The polymerization reaction is carried out at a temperature of 20~40℃ for a time of 30~120 min; The alkaline buffer solution is a Tris buffer solution.

2. The preparation method according to claim 1, characterized in that, On an oven-dry basis, the mass ratio of the polydopamine composite nanocellulose system to the pulp is 10:90~0.5:99.5; the freeness of the pulp is 35~65°SR.

3. The preparation method according to claim 1, characterized in that, The amount of dye used is 2~10% owf; the dye is a dark-colored dye.

4. The preparation method according to claim 1, characterized in that, The dyeing aid includes sodium sulfate and sodium carbonate, wherein the amount of sodium sulfate used is 20~60 g / L and the amount of sodium carbonate used is 10~30 g / L.

5. The preparation method according to claim 1, 2, 3, or 4, characterized in that, The staining temperature is 40~80℃ and the time is 30~120min.

6. The preparation method according to claim 1, characterized in that, The basis weight of the colored yarn paper is 12~20 g / m². 2 .

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