Tough and degradable bacteriostatic wet toilet paper based on natural plant fiber and preparation process thereof

Abstract

The present application relates to daily necessities technical field, specifically, it relates to tough degradable bacteriostatic wet toilet paper based on natural plant fiber and its preparation process, it includes the following raw materials: coniferous wood pulp fiber, viscose fiber, low boron dynamic association type polysaccharide composite reinforcing agent, butanediol, phenoxy ethanol, ethyl hexyl glycerol, sodium citrate, glycerol, aloe extract.The present application, the starch / chitosan composite network in low boron dynamic association type polysaccharide composite reinforcing agent provides basic reinforcing effect, and dynamic borate ester association structure further improves the stability of wet state structure, so as to improve the tensile strength under wet state condition, and because the reversibility of borate ester bond, it can gradually dissociate under the dilution of water and external shear effect, improve the poor dispersibility and slow degradation problem of traditional wet strength system.

Description

Technical Field

[0001] This invention relates to the field of daily necessities technology, and more specifically, to strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers and its preparation process. Background Technology

[0002] Wet toilet paper is a type of wet nonwoven product that combines cleaning, softness, and hygiene functions. It is widely used in personal care, baby care, and household cleaning. Most existing wet toilet paper uses plant-based fibers such as wood pulp fiber and viscose fiber as the main raw materials, and is made through processes such as wet web forming, hydroentangling reinforcement, and impregnation with wetting liquid. Because wet toilet paper is in a high moisture content state for a long time during use, the fibers absorb water and swell, causing the fiber network that was originally bound by hydrogen bonds to become loose, resulting in a significant decrease in wet strength. This makes it easy to cause problems such as tearing and linting when wiping. To address this, existing technologies often introduce wet strength systems such as polyamide epichlorohydrin resin (PAE), polyvinyl alcohol (PVA), or polyacrylamide (PAM) to improve wet strength through chemical cross-linking or polymer entanglement.

[0003] However, although the above-mentioned wet strength system can effectively improve wet strength, the cross-linking network is too stable and the bonding force between fibers is too strong, which makes it difficult for the fibers to disintegrate quickly during washing and easily forms large fiber clumps. This poses a risk of poor dispersibility and blockage of the pipes. In view of this, the present invention proposes a strong, tough, biodegradable, and antibacterial wet toilet paper based on natural plant fibers and its preparation process. Summary of the Invention

[0004] The purpose of this invention is to provide a strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers and its preparation process, in order to solve the problem that although the wet strength system proposed in the background art can effectively improve wet strength, the cross-linking network is too stable and the bonding force between fibers is too strong, which makes it difficult for the fibers to quickly disintegrate during flushing, easily forming large fiber clumps, and posing a risk of poor dispersibility and blockage of the pipes.

[0005] To achieve the above objectives, the present invention provides a strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, comprising the following raw materials: softwood pulp fiber, viscose fiber, low-boron dynamic associative polysaccharide composite reinforcing agent, butylene glycol, phenoxyethanol, ethylhexylglycerin, sodium citrate, glycerin, and aloe vera extract. The low-boron dynamic associative polysaccharide composite enhancer is prepared by starch gelatinization and chitosan forming a composite network mainly based on hydrogen bonds and molecular entanglement under weakly acidic conditions, and then forming a dynamic reversible borate ester association structure by borate ions and ortho-hydroxyl groups of starch chains under weakly alkaline conditions, followed by homogenization and degassing.

[0006] Preferably, the raw materials, by weight, are: 45-60 parts by weight of softwood pulp fiber, 30-45 parts by weight of viscose fiber, 2-6 parts by weight of low-boron dynamic associative polysaccharide composite reinforcing agent, 1-3 parts by weight of butylene glycol, 0.2-0.4 parts by weight of phenoxyethanol, 0.05-0.20 parts by weight of ethylhexylglycerin, 0.05-0.20 parts by weight of sodium citrate, 1-3 parts by weight of glycerin, and 0.1-0.5 parts by weight of aloe vera extract.

[0007] Preferably, the preparation method of the low-boron dynamically associated polysaccharide composite enhancer is as follows: S1.1 Mix corn starch and deionized water at a mass ratio of 1:8-12, stir at 200-400 rpm for 20-40 min at 20-30℃, then heat to 75-85℃ and stir continuously at 300-500 rpm for 30-60 min at this temperature, then cool to 50-65℃ to obtain gelatinized starch. S1.2 Add chitosan to an aqueous acetic acid solution with a mass concentration of 1.0%-2.0%, and stir at 300-500 rpm for 2-5 hours at 20-35℃ to fully dissolve the chitosan and obtain a chitosan solution. S1.3 Under conditions of 50-65℃, add chitosan solution to gelatinized starch at a rate of 5-15mL / min, maintain stirring speed of 200-400rpm, and continue stirring for 30-90min after the addition is completed; S1.4 At 35-50℃, add boric acid solution to the system in S1.3 and mix thoroughly with stirring at 1000-3000 rpm; then adjust the pH of the system to 6.8-7.2 with 0.1 mol / L sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and continue the reaction for 20-40 min at high speed dispersion at 3000-5000 rpm; use high-speed shearing to inhibit the aggregation tendency of chitosan-starch composite network under weakly alkaline conditions and maintain the uniform colloidal dispersion of the system; S1.5 After the reaction is complete, cool the system to below 25°C, homogenize it with a high-speed shear homogenizer at 3000-6000 rpm for 5-15 min, and degas it under a vacuum of -0.06~-0.09 MPa for 10-30 min to obtain a low-boron dynamic associative polysaccharide composite enhancer.

[0008] Preferably, in step S1.2, the mass ratio of chitosan to aqueous acetic acid solution is 1:20-30.

[0009] Preferably, in step S1.3, the mass ratio of gelatinized starch to chitosan is 4-10:1.

[0010] Preferably, in step S1.4, the amount of boric acid added is 1.0%-3.5% of the total mass of starch and chitosan.

[0011] Preferably, in step S1.4, the concentration of the boric acid solution is 0.03-0.10 mol / L.

[0012] On the other hand, the present invention provides a preparation process for strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, for preparing the above-mentioned strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, comprising the following steps: S2.1 Weigh the raw materials according to their weight proportions; S2.2 After dispersing and pulping softwood pulp fiber and viscose fiber separately, mix them together, add low boron dynamic associative polysaccharide composite reinforcing agent, add deionized water to dilute to a pulp mass concentration of 0.15%-0.25%, and stir at 80-120 rpm for 10-20 min; After slag removal, the slurry is conveyed to the headbox and evenly cast onto an 80-120 mesh polyester forming mesh through a lip plate to form a wet fiber mesh. S2.3 The wet fiber web enters the hydroentangling zone and undergoes a three-stage hydroentangling process, while vacuum dewatering is carried out simultaneously, so that the dryness of the fiber web reaches 35%-45% after dewatering. The hydroentangled fiber web enters a hot air penetration dryer and undergoes a two-stage low-temperature drying process: The first stage involves drying at 70-85℃ until the moisture content reaches 15%-25%. The second stage involves final drying at 85-95℃ until the moisture content reaches 5%-8%; After being cooled to 30-35℃ by cooling rollers, it is then wound into a master roll; S2.4. Heat 180-350 parts by weight of deionized water to 40-50℃, then add glycerin, butylene glycol and sodium citrate in sequence and stir until well mixed. After the system is cooled to below 30°C, aloe vera extract, phenoxyethanol and ethylhexylglycerin are added. After stirring, filtering and standing to remove bubbles, a wetting solution is obtained. S2.5 After the master roll is impregnated with the wetting solution, the impregnation rate is controlled to be 2.5-3.2 times by the rubber pressure roller; After impregnation, the wet substrate is slit, folded, and packaged to obtain strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers.

[0013] In the wet toilet paper of this invention, after hydroentangling, drying and impregnation with wetting solution, the residual amount of free boric acid is lower than the limit requirements for boric acid and its salts in the "Cosmetic Safety Technical Specifications".

[0014] Preferably, in step S2.2, the pulp concentration of softwood pulp fiber is 3%-5%; The viscose fiber pulp concentration is 0.8%-1.5%.

[0015] Preferably, in S2.3, the three-stage hydroentangling process includes: The first stage of hydroentanglement is at a pressure of 2-4 MPa, used for initial fiber entanglement. The second-stage hydroentanglement pressure is 4-6 MPa, used for fiber network reinforcement; The third-stage hydroentanglement pressure is 1-3 MPa, used for fabric finishing and reducing excessive fiber entanglement.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention relates to a strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers and its preparation process. In this process, the starch / chitosan composite network in the low-boron dynamically associated polysaccharide composite reinforcing agent provides basic reinforcement, while the dynamic borate ester association further improves the stability of the wet structure, thereby enhancing tensile strength under wet conditions. Furthermore, due to the reversibility of the borate ester bonds, they can gradually dissociate under water dilution and external shearing, improving the poor dispersibility and slow degradation problems of traditional wet-strength systems. Simultaneously, the cationic structure of chitosan can adsorb and disrupt bacterial cell membranes, and the dynamic borate ester association structure improves the fixation and stable distribution of chitosan on the fiber surface, reducing its loss in high-moisture environments, thus enhancing the antibacterial properties of the system. In conjunction with the aloe polysaccharide components in the aloe extract, the system's moisturizing properties are improved, enabling the system to achieve a balance between wet strength and moderate dispersibility and biodegradability after flushing. Attached Figure Description

[0017] Figure 1 The viscosity change curves for Example 6 and Comparative Example 2 are shown below; Figure 2 SEM images showing the wet fiber network structure comparison of Example 6, Comparative Example 1 (without reinforcing agent), and Comparative Example 3 (PAE); Figure 3 This is a comparison diagram of the wet tensile strength of Example 6 and Comparative Examples 1-4; Figure 4 The graphs show the 28-day biodegradation rates of Example 6, Comparative Example 3, and Comparative Example 4. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, comprising the following raw materials: softwood pulp fiber, viscose fiber, low-boron dynamic associative polysaccharide composite reinforcing agent, butylene glycol, phenoxyethanol, ethylhexylglycerin, sodium citrate, glycerin, and aloe vera extract. The low-boron dynamic associative polysaccharide composite enhancer is prepared by starch gelatinization and chitosan forming a composite network mainly based on hydrogen bonds and molecular entanglement under weakly acidic conditions, and then forming a dynamic reversible borate ester association structure by borate ions and ortho-hydroxyl groups of starch chains under weakly alkaline conditions, followed by homogenization and degassing.

[0020] The softwood pulp fiber (beating degree 30-40°SR) was purchased from Shandong Daoxin New Material Co., Ltd.

[0021] The viscose fiber (6-10mm in length, 1.2-1.8dtex in fineness) was purchased from Shandong Xuzheng Textile Co., Ltd.

[0022] Corn starch (CAS No.: 9005-25-8), chitosan (CAS No.: 9012-76-4, degree of deacetylation ≥85%), phenoxyethanol (CAS No.: 122-99-6, purity 98%), ethylhexylglycerin (CAS No.: 70445-33-9), sodium citrate (CAS No.: 68-04-2, purity 98%), and glycerin (CAS No.: 56-81-5) were all purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0023] Boric acid (CAS No.: 10043-35-3) was purchased from Changzhou Guxu Chemical Co., Ltd.

[0024] The aloe vera extract (solid content ≥10%, aloe vera polysaccharide content ≥5wt%) was purchased from Fufeng Sinote Biotechnology Co., Ltd.

[0025] Example 1: The preparation process of strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers includes the following steps: S2.1 Weigh the raw materials by weight: 45 parts by weight of softwood pulp fiber, 30 parts by weight of viscose fiber, 2 parts by weight of low-boron dynamic associative polysaccharide composite reinforcing agent, 1 part by weight of butylene glycol, 0.24 parts by weight of phenoxyethanol, 0.05 parts by weight of ethylhexylglycerin, 0.05 parts by weight of sodium citrate, 1 part by weight of glycerin, and 0.1 parts by weight of aloe vera extract; S2.2. After dispersing and pulping softwood pulp fiber and viscose fiber separately, they are mixed together, wherein the pulping concentration of softwood pulp fiber is 3% and the pulping concentration of viscose fiber is 0.8%; add low boron dynamic associative polysaccharide composite reinforcing agent, add deionized water to dilute to a pulp mass concentration of 0.15%, and stir at 80 rpm for 10 min; After slag removal, the slurry is conveyed to the headbox and evenly cast onto an 80-mesh polyester forming mesh through a lip plate to form a wet fiber mesh. S2.3, The wet fiber web enters the hydroentangled zone and undergoes a three-stage hydroentanglement process: The first stage of hydroentanglement pressure is 2MPa, used for initial fiber entanglement; The second-stage hydroentanglement pressure is 4MPa, used for fiber network reinforcement; The third-stage hydroentanglement pressure is 1MPa, used for fabric finishing and reducing excessive fiber entanglement; Simultaneously, vacuum dehydration is performed to achieve a fiber web dryness of 35% after dehydration; the hydroentangled fiber web then enters a hot air penetration dryer, employing a two-stage low-temperature drying process. The first stage involves drying at 70℃ until the moisture content reaches 15%. The second stage involves final drying at 85℃ until the moisture content reaches 5%. After being cooled to 30°C by cooling rollers, it is then wound into a master roll; S2.4. Heat 190 parts by weight of deionized water to 40°C, then add glycerin, butylene glycol and sodium citrate in sequence and stir until well mixed. After the system is cooled to below 30°C, aloe vera extract, phenoxyethanol and ethylhexylglycerin are added. After stirring, filtering and standing to remove bubbles, a wetting solution is obtained. S2.5 After the master roll is impregnated with wetting liquid, the impregnation rate is controlled to be 2.5 times by rubber pressure rollers; After impregnation, the wet substrate is slit, folded, and packaged to obtain strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers.

[0026] The preparation method of the low-boron dynamically associated polysaccharide complex enhancer is as follows: S1.1 Mix corn starch and deionized water at a mass ratio of 1:8, stir at 200 rpm for 20 min at 20℃, then heat to 75℃ and stir continuously at 300 rpm for 30 min at this temperature, then cool to 50℃ to obtain gelatinized starch. S1.2 Add chitosan to a 1.0% acetic acid aqueous solution at a mass ratio of 1:20, and stir at 300 rpm for 2 hours at 20°C to fully dissolve the chitosan and obtain a chitosan solution. S1.3 At 50℃, add the chitosan solution to the gelatinized starch at a rate of 5 mL / min, wherein the mass ratio of gelatinized starch to chitosan is 7:1, maintain the stirring speed at 200 rpm, and continue stirring for 30 min after the addition is completed; S1.4 At 35℃, add boric acid solution to the system in S1.3, wherein the amount of boric acid added is 2.0% of the total mass of starch and chitosan, and mix evenly under stirring at 1000 rpm; then adjust the pH of the system to 7.0 with 0.1 mol / L sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and continue to react for 20 min under high-speed dispersion at 3000 rpm; S1.5 After the reaction is complete, the system is cooled to below 25°C, homogenized at 3000 rpm for 5 min using a high-speed shear homogenizer, and degassed for 10 min under a vacuum of -0.09 MPa to obtain a low-boron dynamic associative polysaccharide composite enhancer.

[0027] Example 2: The difference between this example and Example 1 is that the mass ratio of gelatinized starch to chitosan is 4:1.

[0028] Example 3: The difference between this example and Example 1 is that the mass ratio of gelatinized starch to chitosan is 10:1.

[0029] Example 4: The difference between this example and Example 1 is that the amount of boric acid added is 1.0% of the total mass of starch and chitosan.

[0030] Example 5: The difference between this example and Example 1 is that the amount of boric acid added is 3.5% of the total mass of starch and chitosan.

[0031] The specific steps for determining the thixotropic recovery rate are as follows: Take the reinforcing agent sample and let it stand at 25℃ for 12 hours to eliminate residual stress inside the sample; use a rotational rheometer for testing, select a flat plate fixture with a diameter of 40mm and a test gap of 1mm; place the sample evenly in the center of the test platform, remove excess sample from the edges, and equilibrate at 25℃ for 5 minutes; first, at a low shear rate of 1s... -1 The system was tested under the specified conditions for 60 seconds, and the initial viscosity η0 after stabilization was recorded. Then, the system was switched to a high shear rate of 1000 s. -1 The high shear rate is maintained for 60 seconds to disrupt the dynamic associative network within the system; immediately after the high shear rate ends, the system returns to a low shear rate of 1 second. -1 The system was tested for 300 seconds, and the viscosity η1 after the system stabilized was recorded. The thixotropic recovery rate (%) was calculated as follows: (η1 / η0)×100%. The higher the thixotropic recovery rate, the stronger the reversible recovery ability of the dynamic association structure of the system.

[0032] The specific steps for determining the swelling-dissociation index are as follows: The prepared composite reinforcing agent is uniformly coated on a polytetrafluoroethylene plate and vacuum dried at 40℃ to constant weight; the dried sample is cut into small pieces of about 20mm×20mm and its initial mass m0 is accurately weighed; the sample is placed in a beaker containing 100mL of deionized water and slowly stirred at 100rpm at 25℃; after 4h, the sample is taken out and the remaining undissociated part is filtered through a 100-mesh sieve; the surface moisture of the residue on the sieve is gently absorbed with filter paper and weighed, and the wet mass m1 is recorded; the residue is then placed in a vacuum drying oven at 50℃ and dried to constant weight, and the mass m2 after drying is recorded; the swelling ratio (g / g) of the sample is calculated by the following formula = (m1-m2) / m2; the mass loss rate (%) is calculated by the following formula = (m0-m2) / m0×100%; the higher the mass loss rate, the stronger the water dispersion loss ability of the system in the water environment.

[0033] Table 1 Performance data of low-boron dynamically associated polysaccharide composite enhancers in Examples 1-5

[0034] Data from Examples 1-3 show that in Example 2, the mass ratio of gelatinized starch to chitosan was reduced to 4:1, increasing the chitosan proportion in the system. This enhanced hydrogen bonding between chitosan molecular chains, molecular entanglement, and complex association with starch, resulting in a more dense and stable dynamic network structure. Consequently, the thixotropic recovery rate increased from 86.2% in Example 1 to 90.3%, indicating a stronger structural recovery capability after high shear failure. Simultaneously, the increased network association density restricted water molecule entry into the system, leading to a decrease in the swelling ratio after 4 hours. The mass ratio of starch to chitosan was increased to 14.2 g / g, and the mass loss rate over 4 hours decreased to 58.7%. In Example 3, the mass ratio of gelatinized starch to chitosan was increased to 10:1, and the proportion of starch in the system increased. Although the number of flexible segments increased, the density of effective association sites decreased, and the dynamic network stability weakened. Therefore, the thixotropic recovery rate decreased to 79.1%. At the same time, the looser network structure was more conducive to water penetration and system expansion, which increased the swelling ratio over 4 hours to 23.6 g / g and the mass loss rate over 4 hours to 82.5%, indicating that the system's ability to disperse water loss in water was enhanced.

[0035] Data from Examples 1, 4, and 5 show that in Example 4, the amount of boric acid added was reduced to 1.0%. Due to the decrease in the number of dynamic borate ester bonds formed in the system, the association density decreased significantly, resulting in insufficient network structure stability. Consequently, the thixotropic recovery rate decreased to 71.8%. At the same time, the lower degree of association made it easier for water to enter the network and promote structural dissociation, thereby increasing the 4-hour swelling ratio to 26.4 g / g and the 4-hour mass loss rate to 88.3%. In Example 5, the amount of boric acid added was increased to 3.5%. With the increase in the amount of boric acid added, the number of dynamic association sites in the system increased, and the network stability improved, thus increasing the thixotropic recovery rate. However, the excessively high association density also limited water diffusion and network breakage, resulting in a decrease in the swelling capacity of the system. The 4-hour swelling ratio decreased to 11.8 g / g, and the 4-hour mass loss rate decreased to 49.6%.

[0036] Example 6: The preparation process of strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers includes the following steps: S2.1 Weigh the raw materials by weight: 52 parts by weight of softwood pulp fiber, 38 parts by weight of viscose fiber, 4 parts by weight of low-boron dynamic associative polysaccharide composite reinforcing agent, 2 parts by weight of butylene glycol, 0.3 parts by weight of phenoxyethanol, 0.12 parts by weight of ethylhexylglycerin, 0.12 parts by weight of sodium citrate, 2 parts by weight of glycerin, and 0.3 parts by weight of aloe vera extract; S2.2. After dispersing and pulping softwood pulp fiber and viscose fiber separately, they are mixed together, wherein the pulping concentration of softwood pulp fiber is 4% and the pulping concentration of viscose fiber is 1.1%; add low boron dynamic associative polysaccharide composite reinforcing agent, add deionized water to dilute to a pulp mass concentration of 0.20%, and stir at 120 rpm for 20 min; After slag removal, the slurry is conveyed to the headbox and evenly cast onto a 120-mesh polyester forming mesh through a lip plate to form a wet fiber mesh. S2.3, The wet fiber web enters the hydroentangled zone and undergoes a three-stage hydroentanglement process: The first stage of hydroentanglement pressure is 3MPa, used for initial fiber entanglement; The second-stage hydroentanglement pressure is 5MPa, used for fiber network reinforcement; The third-stage hydroentanglement pressure is 2MPa, used for fabric finishing and reducing excessive fiber entanglement; Simultaneously, vacuum dehydration is performed to achieve a fiber web dryness of 40%; the hydroentangled fiber web then enters a hot air penetration dryer, employing a two-stage low-temperature drying process. The first stage involves drying at 75℃ until the moisture content reaches 20%. The second stage involves final drying at 90℃ until the moisture content reaches 6%. After being cooled to 35°C by cooling rollers, it is then wound into a master roll; S2.4. Heat 260 parts by weight of deionized water to 45°C, then add glycerin, butylene glycol and sodium citrate in sequence and stir until well mixed. After the system is cooled to below 30°C, aloe vera extract, phenoxyethanol and ethylhexylglycerin are added. After stirring, filtering and standing to remove bubbles, a wetting solution is obtained. S2.5 After the master roll is impregnated with wetting liquid, the impregnation rate is controlled to be 2.8 times by rubber pressure rollers; After impregnation, the wet substrate is slit, folded, and packaged to obtain strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers.

[0037] The preparation method of the low-boron dynamically associated polysaccharide complex enhancer is as follows: S1.1 Mix corn starch and deionized water at a mass ratio of 1:10, stir at 400 rpm for 40 min at 30℃, then heat to 80℃ and stir continuously at 500 rpm for 60 min at this temperature, then cool to 65℃ to obtain gelatinized starch. S1.2 Add chitosan to a 1.5% acetic acid aqueous solution at a mass ratio of 1:25, and stir at 500 rpm for 4 hours at 25°C to fully dissolve the chitosan and obtain a chitosan solution. S1.3 At 55℃, chitosan solution is added to gelatinized starch at a rate of 10 mL / min, wherein the mass ratio of gelatinized starch to chitosan is 7:1. The stirring speed is maintained at 400 rpm, and stirring is continued for 90 min after the addition is completed. S1.4 At 40℃, add boric acid solution to the system in S1.3, wherein the amount of boric acid added is 2.0% of the total mass of starch and chitosan, and mix evenly under stirring at 2000 rpm; then adjust the pH of the system to 7.0 with 0.1 mol / L sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and continue to react for 30 min under high-speed dispersion at 4000 rpm; S1.5 After the reaction is complete, the system is cooled to below 25°C, homogenized at 4000 rpm for 15 min using a high-speed shear homogenizer, and degassed under a vacuum of -0.06 MPa for 30 min to obtain a low-boron dynamic associative polysaccharide composite enhancer.

[0038] Example 7: The difference between this example and Example 6 is that 2 parts by weight of low boron dynamic associative polysaccharide composite enhancer are added.

[0039] Example 8: The difference between this example and Example 6 is that 6 parts by weight of low boron dynamic associative polysaccharide composite enhancer are used.

[0040] Example 9: The difference between this example and Example 6 is that the second-stage hydroentanglement pressure is 4 MPa.

[0041] Example 10: The difference between this example and Example 6 is that the second-stage hydroentanglement pressure is 6 MPa.

[0042] Wet tensile strength test procedure: Cut the wet toilet paper sample into specimens 15mm wide and 150mm long; equilibrate for 4 hours at 23℃ and 50% relative humidity; test using an electronic tensile testing machine; clamp distance set to 100mm; tensile speed set to 300mm / min; record the maximum tensile force value when the sample breaks; the result is expressed as N / 15mm; the higher the wet tensile strength, the better the integrity of the product during wet use.

[0043] Water dispersibility test procedure: Place a single wet toilet paper sample in 1000 mL of deionized water; mechanically stir at 100 rpm at 25℃; continue stirring for 30 min; filter the system through a 16-mesh standard sieve; collect the undissociated residue on the sieve; dry at 60℃ to constant weight; calculate the residue rate (%) = (m1 / m0) × 100%, where: m0 is the initial dry weight of the sample; m1 is the dry weight of the residue on the sieve; the lower the residue rate, the better the water dispersibility.

[0044] Antibacterial rate determination procedure: Select Escherichia coli and Staphylococcus aureus as test bacteria; adjust the bacterial concentration to 1×10⁻⁶. 5 -1×10 6 CFU / mL; Take a sample of wet toilet paper of a certain size and place it in a sterile petri dish; Inoculate the sample surface with a quantitative bacterial solution; Incubate at 37℃ for 24h; After washing away the bacteria, perform plate counting; Calculate the inhibition rate (%) according to the following formula = (BA) / B×100%, where: B is the number of colonies in the blank control; A is the number of colonies in the sample group; The higher the inhibition rate, the better the antibacterial performance.

[0045] Biodegradation rate determination procedure: Dry the wet toilet paper sample to constant weight and record the initial mass m0; bury the sample in a degradation system containing activated sludge or composted soil; control the temperature at 58±2℃ and the humidity at 50%-60%; take samples at 0d, 3d, 7d, 10d, 14d, 21d and 28d respectively; wash off the attached substances and dry to constant weight; record the remaining mass m1; calculate the 28d biodegradation rate (%) using the following formula: (m0-m1) / m0×100%; the higher the degradation rate, the better the environmental friendliness of the material.

[0046] Table 2 Performance data of wet toilet paper in Examples 6-10

[0047] As can be seen from the data of Examples 6-8, in Example 7, the amount of reinforcing agent added was reduced to 2 parts by weight, which reduced the dynamic association reinforcing network formed between fibers, resulting in a decrease in the interfiber bonding force. Therefore, the wet tensile strength decreased from 3.48 N / 15 mm in Example 6 to 2.61 N / 15 mm. At the same time, due to the decrease in dynamic association density, wet toilet paper is more prone to fiber dispersion and network dissociation in the water environment, resulting in a decrease in the residual rate to 24.8%, indicating that its water dispersibility is significantly improved. Meanwhile, the 28-day biodegradability rate increased to 93.6%. However, due to the simultaneous decrease in the content of chitosan and dynamic polysaccharide network in the system, its inhibitory effect on bacterial cell membranes weakened, thus the antibacterial rate against Escherichia coli and Staphylococcus aureus decreased.

[0048] In Example 8, increasing the amount of reinforcing agent to 6 parts by weight resulted in the formation of a more stable and dense dynamic association network between the fibers, which increased the wet tensile strength to 4.26 N / 15 mm. At the same time, the increased content of chitosan cationic structure enhanced the adsorption and destruction effect on bacterial cell membranes, thus further improving the antibacterial rate. However, the excessively high dynamic network density limited the rapid dissociation of fibers during flushing, increasing the residual rate to 45.6%. It also reduced the degradation rate of the material in the microbial environment, resulting in a decrease in the 28-day biodegradation rate to 79.5%.

[0049] Data from Examples 6, 9, and 10 show that in Example 9, after the second-stage hydroentanglement pressure was reduced to 4 MPa, the mechanical entanglement between fibers weakened, making the fiber network looser. As a result, the wet tensile strength decreased to 3.02 N / 15 mm. However, the looser structure was more conducive to water flow entering the fiber interior and promoting fiber dissociation. Therefore, the residual rate decreased to 28.5%, and the 28-day biodegradation rate increased to 89.1%.

[0050] In Example 10, after the second-stage hydroentanglement pressure was increased to 6 MPa, the entanglement between fibers became tighter, enhancing the overall stability of the network. As a result, the wet tensile strength increased to 3.86 N / 15 mm. However, excessive mechanical entanglement hindered the rapid disintegration of the fiber network during rinsing, causing the residual rate to rise to 41.2%. At the same time, the denser fiber structure also reduced the ability of microorganisms and moisture to penetrate the material, resulting in a decrease in the biodegradation rate to 83.8%. Since the antibacterial system mainly comes from chitosan and the anti-corrosion and antibacterial components in the wetting solution, the change in hydroentanglement pressure has little effect on the antibacterial rate.

[0051] Based on the above tests of wet strength, water dispersibility, antibacterial properties and biodegradability, Example 6 achieved a better match among the various properties, maintaining both high wet strength and excellent antibacterial properties, while also taking into account good water dispersibility and biodegradability. Therefore, Example 6 is the optimal example.

[0052] Comparative Example 1: The difference between this comparative example and Example 6 is that no low-boron dynamic associative polysaccharide complex enhancer was added.

[0053] Comparative Example 2: This comparative example differs from Example 6 in that boric acid is not added in S1.4.

[0054] Comparative Example 3: This comparative example differs from Example 6 in that it uses polyamide epichlorohydrin resin (PAE) instead of the low-boron dynamic associative polysaccharide composite reinforcing agent.

[0055] Comparative Example 4: This comparative example differs from Example 6 in that the amount of boric acid added in S1.4 is increased to 6% of the total mass of starch and chitosan.

[0056] Table 3 Performance data of wet toilet paper in Example 6 and Comparative Examples 1-3

[0057] As shown in Table 3, compared with Example 6, Comparative Example 1 did not introduce a low-boron dynamic associative polysaccharide composite reinforcing agent, and the fibers mainly relied on natural hydrogen bonding to maintain their structure. Therefore, the wet tensile strength was reduced to 1.82 N / 15 mm. However, due to the lack of chemically associated structure, the fibers were easily and rapidly dissociated in water, with a residual rate of only 15.8%. At the same time, the biodegradation rate was the highest (96.8%), indicating that the natural fiber system itself has excellent environmental friendliness, but it cannot meet the strength requirements for wet use.

[0058] In Comparative Example 2, starch and chitosan can still form a certain reinforcing network through hydrogen bonding, molecular entanglement, and film formation, thus its wet tensile strength is higher than that of Comparative Example 1. However, due to the lack of boric acid to form a dynamic association structure, the network is less stable in a high water content state, and the interfiber bonding force is more likely to decrease. Therefore, its wet tensile strength is still significantly lower than that of Example 6. At the same time, the network structure is relatively loose, which reduces the residual rate to 21.3% and the water dispersibility is better. However, due to the lack of the binding of the dynamic association structure, chitosan molecules are more likely to dissolve and be lost. Although its 28-day biodegradation rate is as high as 94.1%, its wet strength can no longer meet the product requirements, showing an imbalance of high degradation and low strength. In Comparative Example 2, since the chitosan and starch mainly rely on hydrogen bonding and electrostatic interaction to maintain the composite network, the system stability is weak in a high water content environment. Some chitosan is more likely to migrate and be lost, resulting in a reduction of effective cationic active sites on the fiber surface. Therefore, its antibacterial ability is lower than that of Example 6.

[0059] like Figure 1As shown, in Example 6, although the viscosity of the system decreased rapidly after high shear, it was able to recover to a relatively high level of the initial viscosity in the recovery phase, indicating that there is a reversible dynamic association structure inside the system; while in Comparative Example 2, the network structure has a significantly weaker recovery ability after high shear failure.

[0060] Compared with Example 6, Comparative Example 3 uses polyamide epichlorohydrin resin to form an irreversible covalent cross-linked network, which increases the wet tensile strength to 4.85 N / 15 mm. However, this permanent cross-linked structure makes the fiber network extremely difficult to dissociate in water, with a residual rate as high as 71.5% and poor water dispersibility. At the same time, due to the irreversible covalent cross-linked structure formed by PAE, the accessibility of the fiber material in the microbial environment is reduced, and the fiber water absorption swelling and structural disintegration are inhibited. Therefore, its 28-day biodegradation rate is only 28.6%, which is significantly lower than that of Example 6.

[0061] like Figure 2 As shown, in Example 6, a uniform and continuous three-dimensional entangled network structure was formed between the fibers, and the bonding between the fibers was relatively stable. In Comparative Example 1, due to the lack of a reinforcement system, the fiber network was relatively loose, and there were obvious fracture areas in some places. In contrast, Comparative Example 3 formed a relatively dense blocky structure, with excessive cross-linking between fibers, which was not conducive to rapid dissociation in the subsequent aquatic environment.

[0062] Compared with Example 6, when the amount of boric acid added was too high, the system formed an excessive borate ester cross-linking structure, which enhanced the network rigidity and increased the wet tensile strength to 3.76 N / 15 mm. However, due to the excessive cross-linking density, water could not easily enter the fiber network, resulting in a residual rate of 51.3% and a significant decrease in water dispersibility. At the same time, the highly cross-linked network restricted the structural loosening and disintegration of the fiber in the early stage of degradation, causing the 28-day biodegradation rate to decrease to 66.2%. Furthermore, it inhibited the migration of chitosan cationic groups to the fiber surface and their contact with bacterial cell membranes, thus its antibacterial rate was lower than that of Example 6.

[0063] like Figure 4 As shown, Example 6 exhibited a faster biodegradation rate within 28 days, while Comparative Example 3 showed a significantly slower degradation rate due to the permanent cross-linking structure formed by PAE. Although Comparative Example 4 used a boric acid cross-linking system, the excessive amount of boric acid added led to an increased cross-linking density, which also reduced the material degradation rate. This indicates that the low-boron dynamic association structure of the present invention is more conducive to the later degradation of the material.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, characterized in that: The ingredients include: softwood pulp fiber, viscose fiber, low-boron dynamic associative polysaccharide composite reinforcing agent, butylene glycol, phenoxyethanol, ethylhexylglycerin, sodium citrate, glycerin, and aloe vera extract; The low-boron dynamic associative polysaccharide composite enhancer is prepared by starch gelatinization and chitosan forming a composite network mainly based on hydrogen bonds and molecular entanglement under weakly acidic conditions, and then forming a dynamic reversible borate ester association structure by borate ions and ortho-hydroxyl groups of starch chains under weakly alkaline conditions, followed by homogenization and degassing.

2. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 1, characterized in that, The raw materials, by weight, are: 45-60 parts by weight of softwood pulp fiber, 30-45 parts by weight of viscose fiber, 2-6 parts by weight of low-boron dynamic associative polysaccharide composite reinforcing agent, 1-3 parts by weight of butylene glycol, 0.2-0.4 parts by weight of phenoxyethanol, 0.05-0.20 parts by weight of ethylhexylglycerin, 0.05-0.20 parts by weight of sodium citrate, 1-3 parts by weight of glycerin, and 0.1-0.5 parts by weight of aloe vera extract.

3. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 2, characterized in that, The preparation method of the low-boron dynamically associated polysaccharide composite enhancer is as follows: S1.1 Mix corn starch and deionized water at a mass ratio of 1:8-12, stir at 200-400 rpm for 20-40 min at 20-30℃, then heat to 75-85℃ and stir continuously at 300-500 rpm for 30-60 min at this temperature, then cool to 50-65℃ to obtain gelatinized starch. S1.2 Add chitosan to an aqueous acetic acid solution with a mass concentration of 1.0%-2.0%, and stir at 300-500 rpm for 2-5 hours at 20-35℃ to fully dissolve the chitosan and obtain a chitosan solution. S1.3 Under conditions of 50-65℃, add chitosan solution to gelatinized starch at a rate of 5-15mL / min, maintain stirring speed of 200-400rpm, and continue stirring for 30-90min after the addition is completed; S1.4 At 35-50℃, add boric acid solution to the system in S1.3 and mix thoroughly with stirring at 1000-3000 rpm; then adjust the pH of the system to 6.8-7.2 with 0.1 mol / L sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and continue the reaction for 20-40 min at high speed dispersion at 3000-5000 rpm; S1.5 After the reaction is complete, cool the system to below 25°C, homogenize it with a high-speed shear homogenizer at 3000-6000 rpm for 5-15 min, and degas it under a vacuum of -0.06~-0.09 MPa for 10-30 min to obtain a low-boron dynamic associative polysaccharide composite enhancer.

4. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 3, characterized in that, In step S1.2, the mass ratio of chitosan to aqueous acetic acid solution is 1:20-30.

5. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 3, characterized in that, In S1.3, the mass ratio of gelatinized starch to chitosan is 4-10:

1.

6. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 3, characterized in that, In step S1.4, the amount of boric acid added is 1.0%-3.5% of the total mass of starch and chitosan.

7. The strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 3, characterized in that, In step S1.4, the concentration of the boric acid solution is 0.03-0.10 mol / L.

8. A preparation process for strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers, used to prepare the strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers as described in any one of claims 1-7, characterized in that, The preparation process is as follows: S2.1 Weigh the raw materials according to their weight proportions; S2.2 After dispersing and pulping softwood pulp fiber and viscose fiber separately, mix them together, add low boron dynamic associative polysaccharide composite reinforcing agent, add deionized water to dilute to a pulp mass concentration of 0.15%-0.25%, and stir at 80-120 rpm for 10-20 min; After slag removal, the slurry is conveyed to the headbox and evenly cast onto an 80-120 mesh polyester forming mesh through a lip plate to form a wet fiber mesh. S2.3 The wet fiber web enters the hydroentangling zone and undergoes a three-stage hydroentangling process, while vacuum dewatering is carried out simultaneously, so that the dryness of the fiber web reaches 35%-45% after dewatering. The hydroentangled fiber web enters a hot air penetration dryer and undergoes a two-stage low-temperature drying process: The first stage involves drying at 70-85℃ until the moisture content reaches 15%-25%. The second stage involves final drying at 85-95℃ until the moisture content reaches 5%-8%; After being cooled to 30-35℃ by cooling rollers, it is then wound into a master roll; S2.

4. Heat 180-350 parts by weight of deionized water to 40-50℃, then add glycerin, butylene glycol and sodium citrate in sequence and stir until well mixed. After the system is cooled to below 30°C, aloe vera extract, phenoxyethanol and ethylhexylglycerin are added. After stirring, filtering and standing to remove bubbles, a wetting solution is obtained. S2.5 After the master roll is impregnated with the wetting solution, the impregnation rate is controlled to be 2.5-3.2 times by the rubber pressure roller; After impregnation, the wet substrate is slit, folded, and packaged to obtain strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers.

9. The preparation process of the strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 8, characterized in that, In step S2.2, the pulp concentration of softwood pulp fiber is 3%-5%; The viscose fiber pulp concentration is 0.8%-1.5%.

10. The preparation process of the strong, biodegradable, and antibacterial wet toilet paper based on natural plant fibers according to claim 8, characterized in that, In S2.3, the three-stage hydroentangling process includes: The first stage of hydroentanglement is at a pressure of 2-4 MPa, used for initial fiber entanglement. The second-stage hydroentanglement pressure is 4-6 MPa, used for fiber network reinforcement; The third-stage hydroentanglement pressure is 1-3 MPa, used for fabric finishing and reducing excessive fiber entanglement.

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