High-humidity base paper and quantifiable preparation process thereof

Abstract

The invention provides high-humidity base paper and a quantifiable preparation process thereof, and relates to the field of paper production and processing. Comprising the following raw materials in percentage by mass: 15%-25% of softwood pulp, 40%-55% of hardwood pulp, 10%-25% of soft fibers, 10%-20% of nanocellulose, 0.5%-1.5% of vegetable fat polymer composite microspheres and 1%-3% of functional aids, wherein the solid content of aqueous suspension of the softwood pulp and the hardwood pulp is 3%-8%; the nano cellulose is subjected to surface modification treatment. According to the paper, coniferous wood pulp long fibers, hardwood pulp short fibers and soft fibers are utilized to form a three-dimensional framework, nano-crystalline cellulose enhances wet load transmission through a nanoscale bridging network, vegetable fat microspheres construct a hydrophobic layer to inhibit moisture permeation, the three components have a synergistic effect, so that the wet tensile strength is improved, and meanwhile, high air permeability is kept; and the balance of water resistance and ventilation is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of paper production and processing, and particularly to high-moisture base paper and its quantifiable preparation process. BACKGROUND

[0002] In the field of household paper (such as facial tissue, toilet paper, kitchen paper towel, etc.), the paper needs to meet the core needs of high water absorption, wet strength, softness, environmental protection, and degradability. For example, facial tissue needs to remain intact and not break when wiping sweat or water stains, toilet paper needs to have sufficient flexibility in a wet environment, and kitchen paper towel needs to quickly absorb oil stains and maintain strength. However, traditional household paper relies on single wood pulp fiber structure, and the fiber swells when absorbing water in wet state, resulting in a sharp drop in strength (wet tensile strength <1.0 kN / m). Moreover, there is a common problem of "dry strength and wet weakness", which is prone to breakage and shedding when wiping. At the same time, in order to pursue softness and water absorption, waterproofness and structural stability are often sacrificed, which leads to problems such as mold growth and delamination in high-moisture environments (such as bathrooms and kitchens), and cannot meet the needs of modern families for high-quality household paper.

[0003] Existing household paper technology mainly optimizes performance through the following methods: fiber ratio adjustment: increasing the proportion of short fibers (such as broadleaf wood pulp, straw pulp) or adding chemical softening agents (such as cationic surfactants) to improve softness, but this will reduce the bonding force between fibers, resulting in further decrease in wet strength, and some softening agents have the risk of skin irritation. Surface sizing modification: temporary increase in wet strength by using starch, polyvinyl alcohol (PVA), etc. for surface sizing, but sizing agents can block fiber pores, reducing water absorption (water absorption <50 g / m²), and chemical residues can affect hygiene safety. Traditional papermaking process: relying on experience to control beating degree and drying temperature, resulting in excessive or insufficient fiber fanning, leading to imbalance between softness and strength, and without the introduction of functional nanomaterials, water absorption and wet strength cannot be improved simultaneously.

[0004] However, the above methods cannot solve the core problems of household paper, and technical breakthroughs are urgently needed. Firstly, softness and wet strength are negatively correlated, and the wet tensile strength is generally low in traditional processes, which is prone to breakage when wiping. Water absorption and waterproofness are contradictory, such as kitchen paper towel that is prone to penetration after absorbing oil, and toilet paper that is prone to breaking when wet, which cannot meet the needs of high-moisture scenarios. Secondly, there is a lack of multi-level structure design, which cannot simultaneously achieve the functions of "fast water absorption-wet strength-softness", such as ordinary facial tissue that is prone to sticking to the skin after absorbing water, and kitchen paper towel that cannot balance oil absorption and strength. SUMMARY

[0005] The present application aims to solve the problems in the background art and improve the difficulty of existing paper to simultaneously achieve water absorption and waterproofness, and improve the comfort of use.

[0006] To achieve the above object, the application provides the following technical scheme, a high-moisture base paper, comprising: raw materials including 15%-25% of coniferous pulp, 40%-55% of broadleaf pulp, wherein the water suspension solid content of the coniferous pulp and the broadleaf pulp is 3%-8%, 10%-25% of soft fiber, 10%-20% of nanocellulose, 0.5%-1.5% of plant oil high polymer composite microspheres, and 1%-3% of functional additives; the nanocellulose is subjected to surface modification treatment, the plant oil high polymer composite microspheres are prepared by Pickering emulsion polymerization, and the nanocellulose, the plant oil high polymer composite microspheres, the soft fiber, the coniferous pulp and the broadleaf pulp are mixed and then formed into a single-layer composite structure base paper by papermaking, the finished product has a wet tensile strength of ≥1.5 kN / m, a moisture content of 7.0±0.5%, and a softness of ≤0.03 cN·cm² / cm.

[0007] Further, the nanocellulose is modified by esterification of succinic anhydride or allyl glycidyl ether grafting, the surface carboxyl content of the modified nanocellulose is 0.2-1.5 mmol / g, the average particle size is 20-50 nm, and the length is 100-500 nm, so that the nanocellulose is uniformly dispersed on the fiber surface and the intersection points at an interval of 0.1-0.3 μm to form a flexible bridging network.

[0008] Further, the plant oil high polymer composite microspheres are prepared by Pickering emulsion polymerization with carboxylated nanocellulose as a stabilizer and plant oil and epoxy monomers as reaction monomers, the particle size is 1-5 μm, and the solid content is 5-10%, so that the epoxy groups are connected to the fiber hydroxyl groups by covalent bonds to form a hydrophobic micro barrier on the fiber surface.

[0009] Further, the functional additives include natural fatty acid ester softening agent (1%-2.5%), glycerol moisturizing agent (0.5%-1.5%), or fluorine-containing propylene acrylate oil-proof agent (1%-2%), which are uniformly dispersed in the fiber network to improve the touch feeling or functionality.

[0010] Further, the coniferous pulp and the broadleaf pulp are subjected to two-stage grading refining treatment, the first-stage refining power is 60-70 kW / t, the second-stage parallel refining power is 30-40 kW / t, the coniferous pulp has a freeness of 400-450 CSF after refining, the broadleaf pulp has a freeness of 300-350 CSF, and the soft fiber has a freeness of 350-400 CSF.

[0011] Further, the pore size distribution of the base paper is determined by mercury injection method, the proportion of pores with a size of 0.1-10 μm is ≥90%, the proportion of pores with a size of 0.5-5 μm is ≥70%, the water absorption rate is ≥60 g / m², the biodegradation rate is ≥90%, and no fluorescent whitening agent or formaldehyde-releasing wet strength agent is used, so that the base paper meets the GB 15979 sanitary standard for household paper.

[0012] A quantifiable preparation process of high-moisture base paper, comprising the following steps: Step S1: mixing soft fibers with coniferous wood pulp and broadleaf wood pulp in a certain proportion, and then performing two-stage fractionation to prepare a surface-modified nanocellulose water dispersion, a vegetable oil microsphere dispersion, and a functional additive solution; Step S2: mixing water, modified nanocellulose, vegetable oil microspheres, and functional additives with the milled pulp, dispersing the mixture through high-speed shearing (1500-1800 r / min) and high-pressure homogenization (50-100 MPa), and then forming a wet paper web through a cylinder paper machine, with the linear pressure of the press section being controlled to be 60-70 kN / m, and the water content after the press being controlled to be 55%-58%; Step S3: adopting a three-stage drying process, adjusting the drying cylinder temperature (preheating section: 80-85℃, constant-speed section: 125-130℃, and falling-speed section: 70-75℃) and the steam amount through linkage of a humidity sensor, an infrared moisture meter, and a PLC system, and controlling the water content of the finished product to be 7.0±0.3%, and online detecting the softness and wet tensile strength.

[0013] Further, the surface modification method of the nanocellulose in step S1 is as follows: mixing nanocellulose with succinic anhydride at a mass ratio of 1:0.5-1.0, and reacting at 50-60℃ and pH 8-9 for 2-3h to obtain carboxylated nanocellulose.

[0014] Further, the preparation method of the vegetable oil high-molecular composite microspheres in step S1 is as follows: using carboxylated nanocellulose accounting for 5-10% of the mass of monomers as a stabilizer, and performing Pickering emulsion polymerization with vegetable oil epoxy monomers at 40-50℃ for 3-4h to obtain a dispersion with a solid content of 5-10%.

[0015] Further, the functional additive adding step in step S2 is as follows: preparing a natural fatty acid ester softener into a 10%-15% aqueous solution, and mixing the solution with the pulp during pulp preparation, or uniformly applying the solution to the surface of the wet paper web through a surface application device before papermaking.

[0016] The present application provides a high-moisture base paper and a quantifiable preparation process thereof, which have the following beneficial effects: The present application has the advantages that the long fibers of coniferous wood pulp, the short fibers of broadleaf wood pulp, and the soft fibers form a three-dimensional skeleton, the nanocellulose forms a nanoscale bridging network to enhance wet-state load transmission, and the vegetable oil microspheres construct a hydrophobic layer to inhibit water penetration, so that the wet tensile strength is improved, the high air permeability is maintained, and the balance between waterproofness and air permeability is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a structural schematic diagram of the high-moisture base paper of the present application.

[0018] Figure 2 A schematic diagram of the processing technology of the present application.

[0019] Figure 3 A schematic diagram of the high-moisture base paper product of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only 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 a person skilled in the art without creative work fall within the scope of protection of the present application.

[0021] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplifying the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but a person skilled in the art can realize the application of other processes and / or the use of other materials.

[0022] The embodiments of the present application provide a high-moisture base paper and a quantifiable preparation process thereof. The high-moisture base paper and the quantifiable preparation process thereof can realize the formation of a three-dimensional skeleton by using long fiber of conifer pulp, short fiber of broadleaf pulp and soft fiber, the enhancement of wet state load transfer by nano-cellulose bridging network at the nanoscale, and the inhibition of water penetration by hydrophobic layer constructed by vegetable oil microspheres. The three work together to improve the wet tensile strength while maintaining high air permeability, achieving the balance between waterproof and air permeability. The high-moisture base paper and the quantifiable preparation process thereof will be described in detail below. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments.

[0023] The present application will be described in detail below with reference to the drawings and specific embodiments.

[0024] A high-moisture base paper, comprising: raw materials including 15-25% of coniferous wood pulp, 40-55% of broadleaf wood pulp, wherein the water suspension solid content of the coniferous wood pulp and the broadleaf wood pulp is 3-8%, 10-25% of soft fibers, 10-20% of nanocellulose, 0.5-1.5% of plant oil polymer composite microspheres, and 1-3% of functional additives; the nanocellulose is surface modified, the plant oil polymer composite microspheres are prepared by Pickering emulsion polymerization, and the nanocellulose, the plant oil polymer composite microspheres, the soft fibers, the coniferous wood pulp and the broadleaf wood pulp are mixed and then formed into a single-layer composite structure base paper by papermaking, the finished product has a wet tensile strength of greater than or equal to 1.5 kN / m, a moisture content of 7.0±0.5%, and a softness of less than or equal to 0.03 cN·cm2 / cm.

[0025] During the processing, the raw materials are proportioned to form a multi-level reinforcing network. The long fibers of the coniferous wood pulp and the short fibers of the broadleaf wood pulp cooperate with each other to provide basic mechanical support; the nanocellulose and the plant oil polymer composite microspheres act as functional additives and respectively play the roles of enhancing the wet strength and constructing a hydrophobic network, so that the base paper has excellent mechanical properties and waterproof properties in a high-moisture environment. Compared with the traditional base paper raw material formula, the scheme realizes comprehensive improvement of performance and meets the strict requirements of life use, kitchen paper and other fields on the performance of paper in a high-moisture environment.

[0026] The nanocellulose is esterified by succinic anhydride or grafted by allyl glycidyl ether, and after modification, the surface carboxyl content is 0.2-1.5 mmol / g, the average particle size is 20-50 nm, and the length is 100-500 nm. The nanocellulose is uniformly dispersed on the fiber surface and the intersection point at an interval of 0.1-0.3 μm to form a flexible bridging network.

[0027] The surface modification enables the nanocellulose to have special chemical properties and structure, and the increased active groups such as carboxyl groups enable the nanocellulose to be better combined with the fiber network, so that the nanocellulose is uniformly dispersed in the form of a nanoscale bridging network between the fibers, greatly improves the wet load transmission capacity, and effectively enhances the strength of the base paper in a high-moisture environment. Compared with the unmodified nanocellulose, the modified nanocellulose can more stably play the role of reinforcement, and improve the stability and reliability of the performance of the base paper.

[0028] The plant oil polymer composite microspheres are prepared by Pickering emulsion polymerization with carboxylated nanocellulose as a stabilizer and plant oil epoxy monomers as reaction monomers, the particle size is 1-5 μm, and the solid content is 5-10%. The plant oil polymer composite microspheres are connected to the fiber surface by forming covalent bonds between the epoxy groups and the hydroxyl groups of the fibers to form a hydrophobic micro barrier on the fiber surface.

[0029] The microspheres prepared by Pickering emulsion polymerization can form a hydrophobic layer with a coverage of 20%-30% on the surface of the fibers, and the spacing between the microspheres is 0.5-2μm, which effectively inhibits water penetration while maintaining the air permeability of the base paper. The use of plant oil and fat-based raw materials gives the microspheres environmental protection characteristics, in line with the trend of green manufacturing. Compared with traditional hydrophobic materials, the microspheres not only improve the water resistance of the base paper, but also do not pollute the environment, and are more firmly present in the base paper structure through covalent bonding, improving the stability of the base paper for long-term use.

[0030] The functional additives include natural fatty acid ester softening agent (1%-2.5%), glycerol moisturizing agent (0.5%-1.5%), or fluorine-containing propylene acrylate oil repellent (1%-2%), which are uniformly dispersed in the fiber network to improve the touch or functionality.

[0031] The softwood pulp and hardwood pulp are treated by two-stage grading refining, the first stage refining power is 60-70kW / t, and the second stage refining power is 30-40kW / t in parallel, the softwood pulp freeness is 400-450CSF after refining, the hardwood pulp freeness is 300-350CSF, and the soft fiber freeness is 350-400CSF.

[0032] The grading refining method optimizes the fiber structure. The first stage high-power refining retains long fibers to provide longitudinal strength for the base paper; the second stage low-power refining increases the specific surface area of the fibers, and the split fibers can better absorb nanocellulose and microspheres, improving the bonding force between the raw materials. Compared with the traditional single refining method, the grading refining method makes the fiber performance more fully utilized, improves the overall quality and physical properties of the base paper, and lays a good foundation for the subsequent improvement of the performance of the base paper The pore size distribution of the base paper is determined by mercury injection method, the pore size of 0.1-10μm accounts for ≥90%, the pore size of 0.5-5μm accounts for ≥70%, the water absorption is ≥60g / m², the biodegradation rate is ≥90%, and no fluorescent whitening agent or formaldehyde-releasing wet strength agent is used, which meets the GB15979 sanitary standard for household paper.

[0033] The unique structure design comprehensively improves the performance of the base paper. The fiber network structure provides basic strength and pore structure; the nano-enhanced structure enhances the wet strength; the hydrophobic network structure is waterproof and breathable; and the specific pore size distribution balances the air permeability and water resistance. The uncoated layer design avoids the increase in cost, energy consumption and environmental problems caused by the coating process, while maintaining the surface flatness, so that the base paper has excellent performance, cost advantage and environmental advantage, meeting the needs of modern industrial production.

[0034] A quantifiable preparation process of high-wet base paper, comprising the following steps: Step S1: Mix softwood pulp and hardwood pulp in proportion, then perform two-stage fractionation to form a post-milling pulp, and prepare a surface-modified nanocellulose and plant oil microsphere dispersion to form a raw material; Step S2: Mix the surface-modified nanocellulose, plant oil microsphere dispersion, and post-milling pulp, disperse by high-speed shearing (1500-2000 r / min) and high-pressure homogenization (50-200 MPa), and then form a wet paper web by a long net paper machine; Step S3: Adopt a three-stage drying process, adjust the drying cylinder temperature (preheating section 80-100℃, constant speed section 120-150℃, and falling speed section 60-80℃) and water spraying amount by the linkage of tension sensor, near-infrared moisture meter, and PLC system, and control the product moisture content to be 6±0.5%.

[0035] In step S1, the surface modification method of nanocellulose is as follows: mix nanocellulose and succinic anhydride in a mass ratio of 1:0.5-1.0, react at 50-60℃ and pH 8-9 for 2-3h, and obtain surface-modified nanocellulose.

[0036] In step S1, the preparation method of the plant oil microsphere dispersion is as follows: use carboxylated nanocellulose accounting for 5-10% of the monomer mass as a stabilizer, and perform Pickering emulsion polymerization with plant oil epoxy monomers at 40-50℃ for 3-4h to obtain a dispersion with a solid content of 5-10%.

[0037] In step S2, the intelligent headbox of the long net paper machine realizes quantitative fluctuation control with a pressure pulsation of ≤±2%, the linear pressure of the press section is 80-120kN / m, and the water content after pressing is controlled at 48-52%.

[0038] In step S3, the drying section uses an adjustable steam nozzle for humidity compensation, and by real-time monitoring of the paper web tension (50-60N / m) and moisture distribution, the standard deviation of the product moisture content is ensured to be ≤±0.3%, and the standard deviation of the wet strength of the continuous production batch is ≤3.5N / m.

[0039] Example 1: Application of high-moisture base paper in the field of facial tissue paper Application scenario: used for daily facial cleaning and wiping, the base paper is required to have the characteristics of softness, skin-friendliness, high water absorption, and wet strength, and meet the hygiene and safety standards. Raw material ratio: Softwood pulp: 20% Hardwood pulp: 50% Cotton pulp: 15% Nanocellulose: 12% Plant oil high polymer composite microspheres: 0.8% Softener: 2.2% (natural fatty acid esters) Preparation process: Raw material preparation: The softwood pulp, hardwood pulp and cotton pulp were two-stage fractionally refined, the first stage refining power was 65 kW / t, and the second stage parallel refining power was 35 kW / t. After refining, the softwood pulp freeness was 420 CSF, the hardwood pulp freeness was 320 CSF, and the cotton pulp freeness was 380 CSF. The nanocellulose was mixed with succinic anhydride at a mass ratio of 1:0.7, and reacted at 55℃ and pH 8.5 for 2.3h to obtain surface-modified nanocellulose. The Pickering emulsion polymerization was carried out at 43℃ for 3.2h using 7% of carboxylated nanocellulose by mass of monomer as stabilizer and vegetable oil and fat epoxy monomer to obtain a vegetable oil and fat microsphere dispersion liquid with a solid content of 8%. The softener was uniformly mixed into water to prepare a softener solution with a mass fraction of 10% for standby. Slurry preparation and papermaking: The modified nanocellulose, vegetable oil and fat microsphere dispersion liquid, and softener solution were mixed with the refined pulp, treated by high-speed shearing at 1600r / min for 13min, then treated by high-pressure homogenization at 80MPa for 2 times, and then papermaking was carried out by a cylinder paper machine, the wire pressure of the press section was controlled at 60kN / m, and the water content after the press section was 55%.

[0040] Intelligent drying: A three-stage drying process was adopted, the preheating section temperature was 85℃, the constant speed section was 130℃, and the speed reduction section was 75℃. The oven temperature and steam quantity were adjusted through the linkage of humidity sensor, infrared moisture meter and PLC system to control the finished product moisture content at 7.0±0.3%. Performance test: The dry tensile strength reached 3.5kN / m, and the wet tensile strength was 1.8kN / m, which ensured that the paper would not be easily broken during use. The water absorption rate was 65g / m², which was much higher than that of ordinary facial tissue paper, and the water could be quickly absorbed. The softness was tested by KES-FB2 system, the bending stiffness was ≤0.02cN・cm² / cm, and the touch was soft and skin-friendly. After detection, the total number of colonies was <20CFU / g, and no coliform group or pathogenic pyogenic bacteria was detected, which met the sanitary standard GB15979 for living paper. Application effect: When wiping sweat or cleaning the face, the high-moisture base paper facial tissue paper can quickly absorb water and is not easy to break in wet state. After use, it can be quickly degraded in the natural environment, and has good environmental performance.

[0041] Example 2: Application of high-moisture base paper in the field of toilet paper Application scenario: used for toilet cleaning, requiring the base paper to have good flexibility, high water absorption and certain wet strength, and pay attention to environmental degradability. Raw material ratio: Softwood pulp: 15% Hardwood pulp: 49% Bamboo pulp: 20% Nano-cellulose: 13% Plant oil polymer composite microspheres: 0.7% Moisturizing agent: 2.3% (glycerol) Preparation process: Raw material preparation: Two-stage fractionation grinding, first stage 60 kW / t, second stage 30 kW / t, after grinding, softwood pulp freeness 450 CSF, hardwood pulp freeness 350 CSF, bamboo pulp freeness 360 CSF. Nano-cellulose and succinic anhydride were mixed at a mass ratio of 1:0.6, and the modification was completed at 52°C, pH 8.2 for 2.2h. Pickering emulsion polymerization was carried out at 42°C for 3h using 6% carboxylated nano-cellulose as stabilizer to prepare plant oil microsphere dispersion. Mix the moisturizing agent with water to make a 15% solution. Pulp preparation and papermaking: After mixing the raw materials, high-speed shearing at 1500r / min for 12min, high-pressure homogenization at 70MPa for 2 times, papermaking on a cylinder paper machine, the press section was discharged with a moisture content of 58%. Intelligent drying: preheating section 80°C, constant speed section 125°C, speed reduction section 72°C, finished product moisture 7.5±0.4%. Performance test: Lateral liquid absorption height 18mm / 100s, can quickly absorb moisture. Wet burst strength reaches 80kPa, ensuring the strength during use. Good dispersibility, can disperse quickly in water, avoiding blockage of sewer. Biodegradation rate 92%, meeting environmental protection requirements. Application effect: The high-moisture raw paper toilet paper has good flexibility, strong water absorption performance, and can disperse well after flushing into the sewer, reducing the risk of pipe blockage, and its environmentally friendly and degradable characteristics are more friendly to the environment.

[0042] Example 3: Application of high-moisture raw paper in kitchen paper towel field Application scenario: used for kitchen oil stain wiping, food material water absorption, etc., requiring the raw paper to have super water absorption, certain strength and good oil stain resistance. Raw material ratio: Softwood pulp: 25% Hardwood pulp: 47% Hemp pulp: 15% Nano-cellulose: 10% Plant oil polymer composite microspheres: 1.2% Oil repellent: 1.8% (fluorine-containing acrylic ester) Preparation process: Raw material preparation: The first stage of pulp refining power was 70 kW / t, and the second stage was 38 kW / t. After refining, the freeness of the softwood pulp was 400 CSF, the freeness of the hardwood pulp was 300 CSF, and the freeness of the hemp pulp was 340 CSF. The nanocellulose modification was carried out at a mass ratio of 1:0.8, at 58°C and pH 8.6 for 2.6 hours.

[0043] The microsphere dispersion was prepared by using 9% carboxylated nanocellulose as a stabilizer, polymerizing at 46°C for 3.4 hours. The oil repellent was prepared into an 8% solution. Slurry preparation and papermaking: high-speed shearing at 1700 r / min for 14 minutes, high-pressure homogenization at 100 MPa for 2 times, long net paper machine, double roller linear pressure at the press section was 70 kN / m, and the water content after the press was 53%. Intelligent drying: preheating section 90°C, constant speed section 140°C, and falling speed section 78°C, finished product moisture 6.8±0.3%. Performance test: The oil absorption rate reached 8 times the weight of itself, and it could effectively absorb kitchen oil stains. Dry tensile strength 4.2 kN / m, wet tensile strength 2.0 kN / m, and could withstand the pulling force during wiping. After the oil-proof test, the paper surface did not penetrate after contacting with edible oil, and remained dry. Application effect: The high-wet base paper kitchen towel performed well in wiping the stove oil stains and absorbing the surface moisture of food materials, had strong oil and water absorption capacity, high strength, was not easy to break, and was convenient and efficient to use.

[0044] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0045] The above provides a detailed introduction to a high-wet base paper and its quantifiable preparation process. This document applies specific examples to explain the principles and implementation methods of the present application. The above embodiment description is only used to help understand the technical solutions and core ideas of the present application; those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent substitutions for some technical features; and these modifications or substitutions do not change the essence of the corresponding technical solutions beyond the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-humidity base paper, characterized in that: include: The raw materials include 15%-25% by weight of coniferous pulp, 40%-55% by weight of hardwood pulp, an aqueous suspension of coniferous pulp and hardwood pulp having a solid content of 3%-8%, 10%-25% of soft fiber, 10%-20% of nanocellulose, 0.5%-1.5% of plant oil polymer composite microspheres, and 1%-3% of functional additives; the nanocellulose is surface-modified, the plant oil polymer composite microspheres are prepared by Pickering emulsion polymerization, the nanocellulose, plant oil polymer composite microspheres, soft fiber, coniferous pulp and hardwood pulp are mixed and papered to form a single-layer composite structure base paper, the finished product has a wet tensile strength of ≥1.5kN / m, a moisture content of 7.0±0.5%, and a softness of ≤0.03cN・cm² / cm.

2. The high-humidity base paper according to claim 1, characterized in that The nanocellulose is modified by esterification with succinic anhydride or grafting with allyl glycidyl ether. After modification, the surface carboxyl content is 0.2-1.5 mmol / g, the average particle size is 20-50 nm, the length is 100-500 nm, and the nanocellulose is evenly dispersed on the fiber surface and intersections with a spacing of 0.1-0.3 μm to form a flexible bridging network.

3. The high-humidity base paper according to claim 1, characterized in that The plant oil polymer composite microspheres are prepared by Pickering emulsion polymerization using carboxylated nanocellulose as a stabilizer and plant oil epoxy monomer as a reaction monomer. They have a particle size of 1-5 μm and a solid content of 5-10%. They are connected to the fiber hydroxyl groups through covalent bonds formed by epoxy groups, forming a hydrophobic micro-barrier on the fiber surface.

4. The high-humidity base paper according to claim 1, characterized in that The functional additives include natural fatty acid ester softeners accounting for 1%-2.5%, glycerin moisturizers accounting for 0.5%-1.5% or fluorinated acrylic ester oil repellents accounting for 1%-2%, which are uniformly dispersed in the fiber network to improve the touch or functionality.

5. The high-humidity base paper according to claim 1, characterized in that The softwood pulp and hardwood pulp are processed by two-stage graded refining, with the first stage refining power of 60-70kW / t and the second stage parallel refining power of 30-40kW / t. After refining, the freeness of the softwood pulp is 400-450CSF, the freeness of the hardwood pulp is 300-350CSF, and the freeness of the soft fiber is 350-400CSF.

6. The high-humidity base paper according to claim 1, characterized in that The pore size distribution of the base paper is measured by mercury intrusion porosimetry, with the proportion of pores of 0.1-10 μm being ≥90%, of which the proportion of pores of 0.5-5 μm being ≥70%, the water absorption rate being ≥60 g / m², the biodegradation rate being ≥90%, and no fluorescent brightener or formaldehyde-releasing wet strength agent being used, thereby complying with the GB15979 hygiene standard for household paper.

7. A scalable preparation process for high-humidity base paper according to claims 1-6, characterized in that: The steps include: Step S1: softwood pulp, hardwood pulp and soft fiber are mixed in proportion and then subjected to two-stage graded refining to prepare a surface-modified nanocellulose aqueous dispersion, a plant oil microsphere dispersion and a functional additive solution; Step S2: mixing water, modified nanocellulose, plant oil microspheres, and functional additives with the milled slurry, dispersing the slurry through high-speed shearing at 1500-1800 r / min and high-pressure homogenization at 50-100 MPa, and then forming a wet paper web on a rotary paper machine. The linear pressure of the twin rollers in the press section is controlled at 60-70 kN / m, and the moisture content at the press outlet is 55%-58%. Step S3: A three-stage drying process is adopted. The humidity sensor, infrared moisture meter and PLC system are linked to adjust the drying cylinder temperature to 80-85°C in the preheating stage, 125-130°C in the constant speed stage, 70-75°C in the speed reduction stage and the steam volume. The moisture content of the finished product is controlled at 7.0±0.3%, and the softness and wet tensile strength are tested online.

8. The scalable preparation process according to claim 7, characterized in that: The surface modification method of the nanocellulose in step S1 is as follows: mixing the nanocellulose and succinic anhydride at a mass ratio of 1:0.5-1.0, reacting at 50-60° C. and pH 8-9 for 2-3 hours to obtain carboxylated nanocellulose.

9. The scalable preparation process according to claim 7, characterized in that: The preparation method of the plant oil polymer composite microspheres in S1 is as follows: using carboxylated nanocellulose accounting for 5-10% of the monomer mass as a stabilizer, and performing Pickering emulsion polymerization with plant oil epoxy monomer at 40-50° C. for 3-4 hours to obtain a dispersion with a solid content of 5-10%.

10. The scalable preparation process according to claim 7, characterized in that: The step of adding the functional additive in step S2 is as follows: preparing the natural fatty acid ester softener into a 10%-15% aqueous solution, mixing it with the slurry during slurry preparation, or evenly applying it to the surface of the wet paper web through a surface coating device before papermaking.

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