High-haze high-light-transmittance paper as well as preparation method and application thereof

Abstract

The invention discloses high-haze and high-light-transmittance paper as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) adding bamboo canes into a sulfate system for cooking, and bleaching with sodium chlorite to remove residual lignin so as to obtain bamboo pulp fibers which are not swollen; the sulfate system comprises sodium hydroxide, sodium sulfide and anthraquinone; (2) respectively adding the obtained bamboo pulp fibers into a chloroacetic acid system and a sodium hydroxide system for carboxymethylation modification to obtain non-uniformly swollen bubbling fibers; and (3) dispersing the obtained bubbling fibers in water, and performing suction filtration and drying to prepare the high-haze and high-light-transmittance paper. According to the invention, a sulfate method is used for carrying out primary regulation and control on a bamboo pulp fiber structure, then carboxymethylation modification is used for promoting fiber swelling, and the paper with the characteristic of high haze is prepared. Moreover, accurate regulation and control of the form of the bamboo pulp fibers are realized through a sulfate method / deep eutectic solvent method, and the bamboo pulp fiber paper with adjustable optical and mechanical properties is prepared.

Description

Technical Field

[0001] The present invention belongs to the field of advanced papermaking and paper-based materials, and particularly relates to a high-fog and high-light transmittance paper and a preparation method and application thereof. Background Art

[0002] Overexploitation and use of fossil fuels has exacerbated the global energy crisis and significantly increased greenhouse gas emissions. To this end, the United Nations has set a carbon neutrality goal and called for the establishment of a global carbon neutrality alliance. The utilization of biomass resources, particularly biodegradable, high-transmittance paper with high haze and excellent mechanical properties, provides a sustainable solution for reducing dependence on fossil fuels and supporting green development initiatives.

[0003] Among the many biomass resources, bamboo is an ideal raw material for producing high-haze cellulose paper due to its short growth cycle (3-5 years), abundant reserves, and unique multi-layered fiber structure. Currently, the main methods for producing high-haze, transparent bamboo pulp cellulose paper include micro-nano fiber composite, impregnation, and chemical modification. Among them, micro-nano fiber composite mainly mixes a certain proportion of micron fibers and nanofibers to produce high-haze cellulose paper. However, fiber nano-fiberization requires high-energy processing methods such as high-pressure homogenization and grinding. The equipment cost is high and the production efficiency is low, which seriously restricts the large-scale promotion of this technology. The impregnation method is to immerse the paper in a solution containing specific substances, and change the surface or internal structure of the paper through adsorption, deposition, etc., thereby producing high-haze, transparent cellulose paper. However, this method usually involves multiple steps such as multiple impregnation and drying and curing. The process flow is lengthy and complicated, which not only increases production costs, but is also prone to problems such as solution residue and unstable batch quality, limiting its industrial application. In contrast, the chemical modification method has become a very promising preparation technology due to its advantages of simple process and low energy consumption. For example, Fang et al. (Nano letters. 2014, 14(2): 765-773.) prepared highly transparent and high haze cellulose paper (transparency 96%, haze 60%) by chemical modification. However, it is difficult to prepare high haze paper directly using bamboo as the starting material by chemical modification, which hinders the direct application and promotion in the field of high haze and transparent cellulose paper. In addition, how to rationally regulate the optical and mechanical properties of cellulose paper according to specific application requirements still faces major challenges (for example: solar cells require high transparency and high haze, while display screens require high transparency and low haze, etc.). This not only restricts the ability to customize the performance of paper in specific application scenarios, but also becomes a key bottleneck restricting the large-scale commercial application of cellulose paper.

[0004] Fiber morphology is a key but underexplored factor that directly affects inter-fiber bonding, paper light scattering behavior, and stress transfer, thereby affecting the optical and mechanical properties of paper. Recent studies have shown that fiber morphology regulation has great potential in controlling paper properties. For example, Zhou et al. (Cellulose. 2018, 25(3), 2051–2061.) promoted fiber swelling by TEMPO oxidation treatment and successfully prepared paper with both high transparency and high haze. Lin et al. (Small. 2024, 20(33), 2400151.) prepared a uniformly swollen fiber. The uniformly swollen fiber morphology significantly enhanced the inter-fiber bonding force. The prepared paper had a tensile strength of up to 248 MPa, while the haze was reduced to 56%.

[0005] In summary, although researchers have achieved high haze / high strength cellulose paper using chemical modification methods, they still face two key challenges: (1) it is still difficult to directly extract fibers from natural bamboo; and (2) the mapping relationship between fiber morphology (such as "bubbling" and "uniform swelling") and paper macroscopic properties has not yet been fully elucidated. Summary of the Invention

[0006] In order to solve the shortcomings and deficiencies of the prior art, the object of the present invention is to provide a high-haze and high-transmittance paper and a preparation method and application thereof.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A method for preparing high-haze and high-transmittance paper comprises the following steps:

[0009] (1) adding bamboo strips into a sulfate system for steaming, and bleaching with sodium chlorite to remove residual lignin, thereby obtaining unswollen bamboo pulp fibers; the sulfate system comprises sodium hydroxide, sodium sulfide, and anthraquinone;

[0010] (2) adding the bamboo pulp fiber obtained in step (1) into chloroacetic acid and sodium hydroxide systems respectively for carboxymethylation modification to obtain non-uniformly swollen "bubble" fibers;

[0011] (3) The "bubble" fibers obtained in step (2) are dispersed in water, and then filtered and dried to prepare high-haze and high-transmittance paper.

[0012] Preferably, in step (1), the process of adding bamboo strips into a sulfate system for steaming is as follows: the liquid-to-solid ratio is 10:1-15:1, the amount of alkali used is 12-20%, the degree of sulfidation is 10-40%, the holding time is 50-140 minutes, the maximum temperature is 140-170° C., and the amount of anthraquinone added is 0.08-0.15% relative to the mass of the bamboo.

[0013] Further preferably, in step (1), the process of adding bamboo strips into a sulfate system for steaming is as follows: liquid-solid ratio is 10:1, the amount of alkali used is 12%, the degree of sulfidation is 10%, the holding time is 50 minutes, the maximum temperature is 140°C, and the amount of anthraquinone added is 0.1% relative to the mass of the bamboo.

[0014] Preferably, the process for bleaching bamboo pulp fiber with sodium chlorite in step (1) is as follows: 0.6-1.8 g of sodium chlorite and 0.3-0.9 mL of glacial acetic acid are added per gram of bamboo pulp fiber (absolute dry basis), the liquid-to-solid ratio is 20:1-30:1, the temperature is 75-85°C, and the reaction time is 0.5-4 h.

[0015] Further preferably, the process of bleaching bamboo pulp fiber with sodium chlorite in step (1) is as follows: 0.6 g of sodium chlorite and 0.3 mL of glacial acetic acid are added per gram of bamboo pulp fiber (absolute dry basis), the liquid-solid ratio is 20:1, the temperature is 80°C, and the reaction time is 60 min.

[0016] Preferably, the carboxymethylation modification in step (2) is performed by first adding the bamboo pulp fiber to a chloroacetic acid ethanol solution, and then adding a sodium hydroxide ethanol-water solution for reaction when the temperature rises to 64-72° C.; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1-1:1.3, the liquid-solid ratio is 25:1-40:1, the reaction temperature is 85-95° C., and the reaction time is 50-70 min;

[0017] The "bubble" fibers of different lengths / widths obtained in step (2) are obtained by regulating the degree of sodium chlorite bleaching and the degree of carboxymethylation reaction.

[0018] Further preferably, the carboxymethylation modification in step (2) is to first add the bamboo pulp fiber to a chloroacetic acid ethanol solution, and when the temperature rises to 70°C, add a sodium hydroxide ethanol-water solution for reaction; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1.1, the liquid-solid ratio is 30:1, the reaction temperature is 90°C, and the reaction time is 60 min.

[0019] The high-haze and high-light-transmittance paper prepared by any of the above preparation methods has a haze of 80%-94% (at 550nm).

[0020] The above-mentioned high haze and high transmittance paper is used in transparent packaging, optoelectronic devices, and flexible sensors.

[0021] A method for regulating the optical and mechanical properties of transparent paper based on fiber morphology, comprising the following steps:

[0022] (1) steaming bamboo strips in a low eutectic solvent system or a sulfate system, and bleaching with sodium chlorite to remove residual lignin, thereby obtaining pre-swollen or unswollen bamboo pulp fibers; the low eutectic solvent system comprises choline chloride and lactic acid; and the sulfate system comprises sodium hydroxide, sodium sulfide, and anthraquinone;

[0023] (2) placing the two forms of bamboo pulp fibers obtained in step (1) in a chloroacetic acid and sodium hydroxide system in turn for carboxymethylation modification to obtain uniformly stretched fibers or non-uniformly swollen "bubble" fibers, and regulating the length / width of the bamboo pulp fibers by adjusting the degree of carboxymethylation reaction;

[0024] (3) The uniformly stretched fibers or the non-uniformly swollen "bubble" fibers are dispersed in water, and then filtered and dried to prepare paper, thereby obtaining transparent paper with high haze or high strength, respectively.

[0025] Preferably, the mass ratio of choline chloride to lactic acid in the deep eutectic solvent system of step (1) is 1:7-1:12, the liquid-solid ratio is 10:1-15:1, the reaction temperature is 140-160°C, the holding time is 50-70min, and the reaction is carried out in a microwave digestion apparatus.

[0026] Further preferably, the mass ratio of choline chloride to lactic acid in the low eutectic solvent system of step (1) is 1:9, and the mixture is stirred at 60°C until a clear transparent solution is obtained, the liquid-solid ratio is 10:1, the reaction temperature is 150°C, the holding time is 60min, and the reaction is carried out in a microwave digester with a digestion power of 1000W, the purpose of which is to obtain initially swollen bamboo pulp fibers.

[0027] Preferably, the liquid-to-solid ratio in the sulfate system described in step (1) is 10:1-15:1, the amount of alkali used is 12-20%, the degree of sulfidation is 10-40%, the holding time is 50-140 minutes, the maximum temperature is 140-170°C, the amount of anthraquinone added is 0.08-0.15% relative to the mass of the bamboo, and the reaction is carried out in a reactor, wherein the purpose is to obtain unswollen bamboo pulp fiber.

[0028] Further preferably, the liquid-to-solid ratio in the sulfate system in step (1) is 10:1, the amount of alkali used is 12%, the degree of sulfidation is 10%, the holding time is 50 minutes, the maximum temperature is 140°C, the amount of anthraquinone added is 0.1% relative to the mass of the bamboo, and the reaction is carried out in a reactor.

[0029] Preferably, the process for bleaching bamboo pulp fiber with sodium chlorite in step (1) is as follows: 0.6-1.8 g of sodium chlorite and 0.3-0.9 mL of glacial acetic acid are added per gram of bamboo pulp fiber, the liquid-solid ratio is 20:1-30:1, the temperature is 75-85°C, and the reaction time is 0.5-4 h.

[0030] Further preferably, in step (1), a sodium chlorite bleaching method is adopted, with an amount of 0.6 g of sodium chlorite and 0.3 mL of glacial acetic acid per gram of bamboo pulp fiber (absolute dry basis), a liquid-to-solid ratio of 20:1, a temperature of 80° C., and a reaction time of 60 min.

[0031] The purpose of step (1) is to preliminarily change the fiber morphology and obtain preliminarily swollen and unswollen bamboo pulp fibers, thereby laying the foundation for subsequently obtaining "bubbled" fibers and uniformly swollen bamboo pulp fibers.

[0032] Preferably, the carboxymethylation modification in step (2) is performed by first adding the bamboo pulp fiber to a chloroacetic acid ethanol solution, and then adding a sodium hydroxide ethanol-water solution for reaction when the temperature rises to 64-72°C; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1-1:1.3, the liquid-solid ratio is 25:1-40:1, the reaction temperature is 85-95°C, and the reaction time is 50-70min.

[0033] Further preferably, the carboxymethylation modification in step (2) is to first add the bamboo pulp fiber to a chloroacetic acid ethanol solution, and when the temperature rises to 70°C, add a sodium hydroxide ethanol-water solution for reaction; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1.1, the liquid-solid ratio is 30:1, the reaction temperature is 90°C, and the reaction time is 60 min.

[0034] Preferably, the fibers of different lengths / widths in step (2) are prepared by the following method: the fiber length / width is regulated by adjusting the amount of sodium hydroxide and chloroacetic acid; wherein the amount of sodium hydroxide is 12-30 g / L and the amount of chloroacetic acid is 13.2-33 g / L.

[0035] The purpose of step (2) is to obtain bamboo pulp fibers with a "bubble" morphology and a uniformly swollen morphology, and to achieve regulation of the fiber length / width of bamboo pulp fibers with different morphologies, laying the foundation for the subsequent regulation of paper properties.

[0036] Preferably, in step (3), the bamboo pulp fibers of different forms obtained in step (2) are prepared into wet filter cakes by vacuum filtration, and the wet filter cakes are successively subjected to cold pressing and hot pressing to obtain bamboo pulp fiber paper.

[0037] Preferably, the basis weight of the paper in step (3) is 40-50 g / m 2 .

[0038] Preferably, the concentration of the fiber aqueous dispersion used in the vacuum filtration in step (3) is 0.08-0.1 wt%.

[0039] Preferably, the weight applied for the cold-press drying of the paper in step (3) increases gradually from small to 2.5 kg, 5 kg, 10 kg, 15 kg, 20 kg, and 30 kg, respectively.

[0040] Preferably, the temperature of the hot pressing drying of the paper in step (3) is 90° C., and the hot pressing time is 120 seconds.

[0041] The method described above can adjust the haze of the transparent paper to 36%-94% (at 550nm) and the tensile strength to 41-137MPa.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] (1) The present invention uses the sulfate method and the sodium chlorite method to initially regulate the structure of bamboo pulp fibers, and then promotes fiber swelling through carboxymethylation modification to prepare paper with high haze characteristics.

[0044] (2) The present invention achieves precise control of bamboo pulp fiber morphology, producing bamboo pulp fiber paper with adjustable optical and mechanical properties. Paper made from bamboo pulp fibers with a "bubble" morphology has a high haze characteristic, while paper made from bamboo pulp fibers with uniform swelling has a high strength characteristic. Furthermore, by rationally controlling the length and width of bamboo pulp fibers with different morphologies, the optical and mechanical properties of the paper can be controlled.

[0045] (3) The bamboo pulp fiber paper of the present invention avoids mechanical processing during its preparation, requiring less equipment and being more suitable for large-scale industrial production. The resulting paper has broad application prospects in optoelectronic devices, flexible sensors, and other fields. Furthermore, my country has abundant reserves of bamboo raw materials and their availability, which has promoted the high-value-added utilization of bamboo resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 These are microscope images of preliminarily stretched bamboo pulp fibers obtained by pulping with a deep eutectic solvent in Examples 1, 3, 5, and 7 of the present invention.

[0047] Figure 2 These are microscope images of unswollen bamboo pulp fibers obtained by sulfate pulping in Examples 2, 4, 6, and 8 of the present invention.

[0048] Figure 3 This is a microscope image of the uniformly swollen bamboo pulp fibers in Example 1 of the present invention.

[0049] Figure 4 1 is a stress-strain curve of paper made from the uniformly swollen bamboo pulp fibers in Example 1 of the present invention.

[0050] Figure 5 Graphs showing the light transmittance and haze of paper prepared from the uniformly swollen bamboo pulp fibers in Example 1 of the present invention.

[0051] Figure 6 This is a microscope image of the bamboo pulp fiber in the "bubble" form in Example 4 of the present invention.

[0052] Figure 7 1 is a stress-strain curve of the “bubble” bamboo pulp fiber paper in Example 4 of the present invention.

[0053] Figure 8 This is a graph of light transmittance and haze of the “bubble” bamboo pulp fiber paper in Example 4 of the present invention. DETAILED DESCRIPTION

[0054] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0055] In the following examples, the tensile strength is tested using the national standard GB / T1040-2006; the light transmittance and haze of paper are measured according to the national standard GB / T 2410-2008.

[0056] In the examples of the present invention, if the specific conditions are not specified, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. All raw materials and reagents used without specifying the manufacturer are conventional products that can be purchased from the market.

[0057] Example 1

[0058] Choline chloride and lactic acid were weighed in a beaker at a mass ratio of 1:9 and then stirred in a 60°C waterbath until the choline chloride was completely dissolved, yielding a transparent deep eutectic solvent. Bamboo was peeled and cut into strips approximately 4 cm × 0.5 mm × 0.5 mm. The strips were placed in a microwave reactor, and the deep eutectic solvent was added at a solid-to-liquid ratio of 1:10. The reaction was then carried out in a microwave digester under the following conditions: temperature 150°C, heating time 20 minutes, reaction time 1 hour, and power 1000W. After the reaction, the fibers were thoroughly washed with deionized water and then sieved using a pulp flatbed sieving machine to obtain lignin-containing bamboo fibers. The bamboo fibers were bleached using the sodium chlorite method (bleaching process: 0.6 g sodium chlorite and 0.3 mL glacial acetic acid per gram of bamboo fiber, bleaching temperature 80°C, bleaching time 60 minutes), yielding pre-stretched bamboo fibers.

[0059] Take 10g (absolute dry weight) of the above-mentioned preliminarily swollen bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10 minutes, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 5.4g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 5.94g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain uniformly swollen bamboo pulp fiber.

[0060] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0061] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 137 MPa, a haze of 53%, and a light transmittance of 86% (550 nm).

[0062] Example 2

[0063] The bamboo was peeled and cut into strips approximately 4cm x 0.5mm x 0.5mm. The strips were placed in a high-pressure reactor, and sodium hydroxide solution and sodium sulfide solution were added, followed by a reaction. The reaction process was as follows: solid-liquid ratio of 1:10, anthraquinone 0.1% (relative to the mass of the bamboo), alkali dosage of 12%, maximum temperature of 140°C, degree of sulfidation of 10%, and holding time of 50 minutes. After the reaction, the bamboo pulp was thoroughly washed with deionized water, and then the extracted bamboo pulp fiber was screened using a pulp flat plate sieving instrument to obtain bamboo pulp containing lignin. The bamboo pulp fiber was bleached using the sodium chlorite method (bleaching process: 0.6g sodium chlorite and 0.3mL glacial acetic acid were added per gram of bamboo pulp fiber, bleaching temperature was 80°C, and bleaching time was 60 minutes) to obtain unstretched bamboo pulp fiber.

[0064] Take 10g (absolute dry basis) of the above-mentioned un-swelled bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 5.4g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 5.94g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain bamboo pulp fiber in a "bubble" form.

[0065] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0066] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 41 MPa, a haze of 93%, and a light transmittance of 55% (550 nm).

[0067] Example 3

[0068] Choline chloride and lactic acid were weighed in a beaker at a mass ratio of 1:9 and then stirred in a 60°C waterbath until the choline chloride was completely dissolved, yielding a transparent deep eutectic solvent. Bamboo was peeled and cut into strips approximately 4 cm × 0.5 mm × 0.5 mm. The strips were placed in a microwave reactor, and the deep eutectic solvent was added at a solid-to-liquid ratio of 1:10. The reaction was then carried out in a microwave digester under the following conditions: temperature 150°C, heating time 20 minutes, reaction time 1 hour, and power 1000W. After the reaction, the fibers were thoroughly washed with deionized water and then sieved using a pulp flatbed sieving machine to obtain lignin-containing bamboo fibers. The bamboo fibers were bleached using the sodium chlorite method (bleaching process: 0.6 g sodium chlorite and 0.3 mL glacial acetic acid per gram of bamboo fiber, bleaching temperature 80°C, bleaching time 60 minutes), yielding pre-stretched bamboo fibers.

[0069] Take 10g (absolute dry basis) of the above-mentioned preliminarily swollen bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10 minutes, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 7.2g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 7.92g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain uniformly swollen bamboo pulp fiber.

[0070] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0071] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 119 MPa, a haze of 36%, and a light transmittance of 88% (550 nm).

[0072] Example 4

[0073] The bamboo was peeled and cut into strips approximately 4cm x 0.5mm x 0.5mm. The strips were placed in a high-pressure reactor, and sodium hydroxide solution and sodium sulfide solution were added, followed by a reaction. The reaction process was as follows: solid-liquid ratio of 1:10, anthraquinone 0.1% (relative to the mass of the bamboo), alkali dosage of 12%, maximum temperature of 140°C, degree of sulfidation of 10%, and holding time of 50 minutes. After the reaction, the bamboo pulp was thoroughly washed with deionized water, and then the extracted bamboo pulp fiber was screened using a pulp flat plate sieving instrument to obtain bamboo pulp containing lignin. The bamboo pulp fiber was bleached using the sodium chlorite method (bleaching process: 0.6g sodium chlorite and 0.3mL glacial acetic acid were added per gram of bamboo pulp fiber, bleaching temperature was 80°C, and bleaching time was 60 minutes) to obtain unstretched bamboo pulp fiber.

[0074] Take 10g (absolute dry basis) of the above-mentioned un-swelled bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 7.2g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 7.92g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain bamboo pulp fiber in a "bubble" form.

[0075] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0076] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 46 MPa, a haze of 92%, and a light transmittance of 66% (550 nm).

[0077] Example 5

[0078] Choline chloride and lactic acid were weighed in a beaker at a mass ratio of 1:9 and then stirred in a 60°C waterbath until the choline chloride was completely dissolved, yielding a transparent deep eutectic solvent. Bamboo was peeled and cut into strips approximately 4 cm × 0.5 mm × 0.5 mm. The strips were placed in a microwave reactor, and the deep eutectic solvent was added at a solid-to-liquid ratio of 1:10. The reaction was then carried out in a microwave digester under the following conditions: temperature 150°C, heating time 20 minutes, reaction time 1 hour, and power 1000W. After the reaction, the fibers were thoroughly washed with deionized water and then sieved using a pulp flatbed sieving machine to obtain lignin-containing bamboo fibers. The bamboo fibers were bleached using the sodium chlorite method (bleaching process: 0.6 g sodium chlorite and 0.3 mL glacial acetic acid per gram of bamboo fiber, bleaching temperature 80°C, bleaching time 60 minutes), yielding pre-stretched bamboo fibers.

[0079] Take 10g (absolute dry basis) of the above-mentioned preliminary swollen bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 9g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 9.9g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (set up a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90℃. When the water bath is heated to 70℃, start adding sodium hydroxide solution. When the temperature rises to 90℃, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain uniformly swollen bamboo pulp fiber.

[0080] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0081] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 136 MPa, a haze of 37%, and a light transmittance of 89% (550 nm).

[0082] Example 6

[0083] The bamboo was peeled and cut into strips approximately 4cm x 0.5mm x 0.5mm. The strips were placed in a high-pressure reactor, and sodium hydroxide solution and sodium sulfide solution were added, followed by a reaction. The reaction process was as follows: solid-liquid ratio of 1:10, anthraquinone 0.1% (relative to the mass of the bamboo), alkali dosage of 12%, maximum temperature of 140°C, degree of sulfidation of 10%, and holding time of 50 minutes. After the reaction, the bamboo pulp was thoroughly washed with deionized water, and then the extracted bamboo pulp fiber was screened using a pulp flat plate sieving instrument to obtain bamboo pulp containing lignin. The bamboo pulp fiber was bleached using the sodium chlorite method (bleaching process: 0.6g sodium chlorite and 0.3mL glacial acetic acid were added per gram of bamboo pulp fiber, bleaching temperature was 80°C, and bleaching time was 60 minutes) to obtain unstretched bamboo pulp fiber.

[0084] Take 10g (absolute dry basis) of the above-mentioned unswelled bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 9g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 9.9g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain bamboo pulp fiber in a "bubble" form.

[0085] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2 . Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0086] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 73 MPa, a haze of 80%, and a light transmittance of 85% (550 nm).

[0087] Example 7

[0088] Choline chloride and lactic acid were weighed in a beaker at a mass ratio of 1:9 and then stirred in a 60°C waterbath until the choline chloride was completely dissolved, yielding a transparent deep eutectic solvent. Bamboo was peeled and cut into strips approximately 4 cm × 0.5 mm × 0.5 mm. The strips were placed in a microwave reactor, and the deep eutectic solvent was added at a solid-to-liquid ratio of 1:10. The reaction was then carried out in a microwave digester under the following conditions: temperature 150°C, heating time 20 minutes, reaction time 1 hour, and power 1000W. After the reaction, the fibers were thoroughly washed with deionized water and then sieved using a pulp flatbed sieving machine to obtain lignin-containing bamboo fibers. The bamboo fibers were bleached using the sodium chlorite method (bleaching process: 0.6 g sodium chlorite and 0.3 mL glacial acetic acid per gram of bamboo fiber, bleaching temperature 80°C, bleaching time 60 minutes), yielding pre-stretched bamboo fibers.

[0089] Take 10g (absolute dry basis) of the above-mentioned preliminarily swollen bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 3.6g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 3.96g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain uniformly swollen bamboo pulp fiber.

[0090] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2. Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0091] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 123 MPa, a haze of 69%, and a light transmittance of 86% (550 nm).

[0092] Example 8

[0093] The bamboo was peeled and cut into strips approximately 4cm x 0.5mm x 0.5mm. The strips were placed in a high-pressure reactor, and sodium hydroxide solution and sodium sulfide solution were added, followed by a reaction. The reaction process was as follows: solid-liquid ratio of 1:10, anthraquinone 0.1% (relative to the mass of the bamboo), alkali dosage of 12%, maximum temperature of 140°C, degree of sulfidation of 10%, and holding time of 50 minutes. After the reaction, the bamboo pulp was thoroughly washed with deionized water, and then the extracted bamboo pulp fiber was screened using a pulp flat plate sieving instrument to obtain bamboo pulp containing lignin. The bamboo pulp fiber was bleached using the sodium chlorite method (bleaching process: 0.6g sodium chlorite and 0.3mL glacial acetic acid were added per gram of bamboo pulp fiber, bleaching temperature was 80°C, and bleaching time was 60 minutes) to obtain unstretched bamboo pulp fiber.

[0094] Take 10g (absolute dry basis) of the above-mentioned un-swelled bamboo pulp fiber and mix it with 100mL of ethanol and stir for 10min, then use 800 mesh filter cloth to squeeze out the ethanol. Weigh 3.6g of NaOH and dissolve it in a mixed solution of 75mL of ethanol and 30mL of water. Weigh 3.96g of chloroacetic acid and dissolve it in 195mL of ethanol. Add the bamboo pulp fiber and chloroacetic acid solution to a three-hole flask (with a condensation reflux device) and place the flask in a water bath. Set the reaction temperature to 90°C. When the water bath is heated to 70°C, start adding sodium hydroxide solution. When the temperature rises to 90°C, start timing the reaction for 1 hour. After the reaction is completed, wash it twice with ethanol, and then wash it with a large amount of deionized water until neutral to obtain bamboo pulp fiber in a "bubble" form.

[0095] Bamboo pulp fiber paper is prepared by vacuum filtration, and the paper weight is 40g / m 2. Weigh 0.25g (absolute dry basis) of the above-mentioned uniformly swollen bamboo pulp fiber in a beaker, add water to 300mL, and then stir magnetically for 5 minutes to evenly disperse it in the water. Use a Buchner funnel with a diameter of 9cm for suction filtration, place 10 filter papers at the bottom of the Buchner funnel, place a mixed cellulose filter membrane on the filter paper, then add the evenly stirred fiber water dispersion, and place a filter membrane on the top. Place about 10 filter papers on each side of the filtered wet filter cake, then place it between two glass plates, and gradually place heavy objects on the glass plates, with the applied weight gradually increasing from small to large, namely 2.5kg, 5kg, 10kg, 15kg, 20kg, and 30kg. Press dry the filter cake at room temperature for 24 hours, and change the filter paper regularly to remove moisture from the film. Finally, hot press the paper at 90℃ for 2min.

[0096] The bamboo pulp fiber paper prepared through the above steps has a tensile strength of 36 MPa, a haze of 94%, and a light transmittance of 49% (550 nm).

[0097] Figure 1 These are micrographs of the initially swollen bamboo pulp fibers obtained by pulping with a deep eutectic solvent in Examples 1, 3, 5, and 7 of the present invention. As can be seen from the figures, the bamboo pulp fibers undergo initial swelling and surface fibrillation, which facilitates the subsequent acquisition of uniformly swollen bamboo pulp fibers.

[0098] Figure 2 These are microscopic images of unswollen bamboo pulp fibers obtained by kraft pulping in Examples 2, 4, 6, and 8 of the present invention. As can be seen from the images, the bamboo pulp fiber structure remains intact, with no significant swelling, which is beneficial for the subsequent acquisition of "bubbled" bamboo pulp fibers.

[0099] Figure 3 This is a microscope image of the uniformly swollen bamboo pulp fibers in Example 1 of the present invention. As can be seen from the image, the fibers have undergone significant and uniform swelling.

[0100] Figure 4 This is the stress-strain curve of the paper made from the uniformly swollen bamboo pulp fibers in Example 1 of the present invention. Due to the full and uniform swelling of the fibers, the bonding between the fibers is promoted, and the strength of the bamboo pulp fiber paper reaches 137 MPa.

[0101] Figure 5 The light transmittance and haze of paper made from the uniformly swollen bamboo pulp fibers in Example 1 of the present invention are shown below. The haze of the uniform bamboo pulp fiber paper was 53%, and the light transmittance was 86% (550nm). The uniform fiber morphology improves the uniformity of the paper's refractive index distribution, thereby reducing light scattering.

[0102] Figure 6This is a microscope image of the "bubble" morphology of bamboo pulp fiber in Example 6 of the present invention. As can be seen from the figure, there are a large number of "bubbles" in the bamboo pulp fiber.

[0103] Figure 7 This is the stress-strain curve of the "bubble" bamboo pulp fiber paper in Example 6 of the present invention. Due to the "bubble" fiber morphology, the inter-fiber bonding force is relatively weak and uneven, and the strength of the paper is 41 MPa, which is lower than that of the uniform bamboo pulp fiber.

[0104] Figure 8 The light transmittance and haze of the "bubbled" bamboo pulp fiber paper in Example 6 of the present invention are shown. The "bubbled" bamboo pulp fiber increases the non-uniformity of the paper's refractive index distribution, thereby improving the haze. The paper has a haze of 93% and a light transmittance of 55% (550nm).

[0105] By regulating the degree of carboxymethylation reaction of the two forms of bamboo pulp fibers, the optical and mechanical properties of bamboo pulp fiber paper can be regulated to obtain bamboo pulp fiber paper with high haze or high strength.

[0106] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing high haze and high transmittance paper, characterized in that: The following steps are involved: (1) adding bamboo strips into a sulfate system for steaming, and bleaching with sodium chlorite to remove residual lignin, thereby obtaining unswollen bamboo pulp fibers; the sulfate system comprises sodium hydroxide, sodium sulfide, and anthraquinone; (2) adding the bamboo pulp fiber obtained in step (1) into chloroacetic acid and sodium hydroxide systems respectively for carboxymethylation modification to obtain non-uniformly swollen "bubble" fibers; (3) The "bubble" fibers obtained in step (2) are dispersed in water, and then filtered and dried to prepare high-haze and high-transmittance paper.

2. The method for preparing high haze and high transmittance paper according to claim 1, wherein: The process of adding bamboo strips into a sulfate system for steaming in step (1) is as follows: the liquid-to-solid ratio is 10:1-15:1, the amount of alkali used is 12-20%, the degree of sulfidation is 10-40%, the holding time is 50-140 minutes, the maximum temperature is 140-170° C., and the amount of anthraquinone added is 0.08-0.15% of the mass of the bamboo.

3. The method for preparing high haze and high transmittance paper according to claim 1, wherein: The process for bleaching bamboo pulp fiber with sodium chlorite in step (1) is as follows: 0.6-1.8 g of sodium chlorite and 0.3-0.9 mL of glacial acetic acid are added per gram of bamboo pulp fiber, the liquid-solid ratio is 20:1-30:1, the temperature is 75-85° C., and the reaction time is 0.5-4 h.

4. The method for preparing high haze and high transmittance paper according to claim 1, wherein: The carboxymethylation modification in step (2) is performed by first adding the bamboo pulp fiber to a chloroacetic acid ethanol solution, and then adding a sodium hydroxide ethanol-water solution for reaction when the temperature rises to 64-72° C.; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1-1:1.3, the liquid-solid ratio is 25:1-40:1, the reaction temperature is 85-95° C., and the reaction time is 50-70 min; The "bubble" fibers of different lengths / widths obtained in step (2) are obtained by regulating the degree of sodium chlorite bleaching and the degree of carboxymethylation reaction.

5. A high haze and high light transmittance paper prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the high haze and high transmittance paper according to claim 5 in transparent packaging, optoelectronic devices, and flexible sensors.

7. A method for regulating the optical and mechanical properties of transparent paper based on fiber morphology, characterized in that: The following steps are involved: (1) steaming bamboo strips in a low eutectic solvent system or a sulfate system, and bleaching with sodium chlorite to remove residual lignin, thereby obtaining pre-swollen or unswollen bamboo pulp fibers; the low eutectic solvent system comprises choline chloride and lactic acid; and the sulfate system comprises sodium hydroxide, sodium sulfide, and anthraquinone; (2) placing the two forms of bamboo pulp fibers obtained in step (1) in a chloroacetic acid and sodium hydroxide system in turn for carboxymethylation modification to obtain uniformly stretched fibers or non-uniformly swollen "bubble" fibers, and regulating the length / width of the bamboo pulp fibers by adjusting the degree of carboxymethylation reaction; (3) The uniformly stretched fibers or the non-uniformly swollen "bubble" fibers are dispersed in water, and then filtered and dried to prepare paper, thereby obtaining transparent paper with high haze or high strength, respectively.

8. The method for regulating the optical and mechanical properties of transparent paper based on fiber morphology according to claim 7, characterized in that: The mass ratio of choline chloride to lactic acid in the deep eutectic solvent system of step (1) is 1:7-1:12, the liquid-solid ratio is 10:1-15:1, the reaction temperature is 140-160° C., the holding time is 50-70 min, and the reaction is carried out in a microwave digestion apparatus; In the sulfate system described in step (1), the liquid-to-solid ratio is 10:1-15:1, the amount of alkali used is 12-20%, the degree of sulfidation is 10-40%, the holding time is 50-140 minutes, the maximum temperature is 140-170° C., the amount of anthraquinone added is 0.08-0.15% of the mass of the bamboo, and the reaction is carried out in a reactor.

9. The method for regulating the optical and mechanical properties of transparent paper based on fiber morphology according to claim 7, characterized in that: The process for bleaching bamboo pulp fiber with sodium chlorite in step (1) is as follows: 0.6-1.8 g of sodium chlorite and 0.3-0.9 mL of glacial acetic acid are added per gram of bamboo pulp fiber, the liquid-solid ratio is 20:1-30:1, the temperature is 75-85° C., and the reaction time is 0.5-4 h.

10. The method for regulating the optical and mechanical properties of transparent paper based on fiber morphology according to claim 7, characterized in that: The carboxymethylation modification in step (2) is performed by first adding the bamboo pulp fiber to a chloroacetic acid ethanol solution, and then adding a sodium hydroxide ethanol-water solution for reaction when the temperature rises to 64-72° C.; wherein the weight ratio of sodium hydroxide to chloroacetic acid is 1:1-1:1.3, the liquid-solid ratio is 25:1-40:1, the reaction temperature is 85-95° C., and the reaction time is 50-70 min; The fibers of different lengths and widths in step (2) are prepared by the following method: the fiber length and width are regulated by adjusting the amount of sodium hydroxide and chloroacetic acid; wherein the amount of sodium hydroxide is 12-30 g / L and the amount of chloroacetic acid is 13.2-33 g / L.

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