A method for preparing medical dialysis base paper

Abstract

This invention provides a method for preparing medical dialysis base paper. First, a certain amount of a softener of a specific composition is added to hardwood pulp, which is then mixed with softwood pulp to obtain dialysis paper. Next, the dialysis paper is surface-treated with a sizing solution of a specific composition, and the content and coating amount of each component in the sizing solution are controlled to ultimately obtain medical dialysis base paper with high strength, high air permeability, antibacterial properties, and high softness. In the above process, by adding an appropriate amount of ethylene glycol to the commonly used softener cationic quaternary ammonium salt resin, the synergistic effect between the two increases the number of hydroxyl groups on the surface of hardwood fibers in the hardwood pulp, thereby achieving the purpose of increasing softness without affecting the paper strength. By adding cellulose nanofibers to the sizing solution, their strength properties can be utilized to impart high strength to the paper, while simultaneously adjusting the air permeability of the paper to meet the air permeability requirements of medical dialysis base paper in practical applications.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a method for preparing medical dialysis base paper. Background Technology

[0002] Aseptic protective packaging is the part that comes into direct contact with medical devices (surgical instruments, disposable medical supplies, etc.) and forms a microbial barrier to ensure that the product remains sterile throughout its expected lifespan. Its main materials are medical dialysis paper and medical cover paper. Medical devices are generally packaged in boxes, sealed with medical dialysis paper, and then sterilized. Currently, the flexibility of medical dialysis paper is insufficient, making it easily damaged or punctured by the packaged medical devices when used as cover paper, leading to sterilization failure. Furthermore, in recent years, with the continuous development and progress of the medical industry and people's increasing emphasis on hygiene and health, the market has placed higher quality demands on medical dialysis paper.

[0003] In the prior art, patent application number 202011261818.0, publication date November 11, 2022, entitled "A medical dialysis paper and its production method", discloses a medical dialysis paper and its production method. In this technical solution, softwood pulp, chitosan fiber and bamboo fiber are used as raw materials to make medical dialysis paper with high antibacterial properties and strength. However, this technical solution only considers strength and antibacterial properties. Medical dialysis paper with these properties still cannot meet the application requirements.

[0004] In view of this, it is necessary to design an improved method for preparing medical dialysis paper to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing medical dialysis paper.

[0006] To achieve the above-mentioned objectives, this invention provides a method for preparing medical dialysis paper, comprising the following steps:

[0007] S1. The softwood pulp and hardwood pulp are refined separately. After refining, the freeness of the softwood pulp is 50-60°SR, and the freeness of the hardwood pulp is 30-35°SR. The refined hardwood pulp is mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets are formed, and after the paper is formed, it is peeled off and pressed under a pressure of 500-550 kPa for 2-4 minutes. After drying, dialysis paper is obtained.

[0008] S2. The dialysis paper obtained in step S1 is coated with a sizing solution and dried to obtain medical dialysis base paper. The sizing solution is obtained by dispersing cationic starch and polyvinyl alcohol in a cellulose nanofiber suspension.

[0009] As one embodiment of the present invention, the medical dialysis paper has the following properties: basis weight of 60±3g / m³. 2 Tightness ≤ 0.8g / cm 3 Transverse tear strength ≥ 500 mN, longitudinal tear strength ≥ 440 mN, longitudinal tensile strength ≥ 4.9 kN / m, longitudinal wet tensile strength ≥ 1.0 kN / m, transverse tensile strength ≥ 2.5 kN / m, bursting strength ≥ 1.5 kPa, water absorption ≤ 22 g / m 2 Air permeability ≥3.1µm / Pa·s.

[0010] In one embodiment of the present invention, in step S1, the softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium salt resin and water, wherein the weight ratio of cationic quaternary ammonium salt resin and ethylene glycol is (0.02-0.03):1, and the amount of softener added is 0.1-0.2% of the oven-dry weight of hardwood pulp.

[0011] In one embodiment of the present invention, in step S2, the sizing solution is composed of 0.5-1 parts cationic starch, 10-15 parts PVA, and 2-3 parts cellulose nanofiber suspension, and the coating amount of the surface sizing solution is 7-10 g / m². 2 .

[0012] In one embodiment of the present invention, the concentration of the cellulose nanofiber suspension is 1-3 g / L, and the average fiber diameter of the cellulose nanofibers is 2-20 nm.

[0013] In one embodiment of the present invention, the slurry sizing agent is composed of modified polyamide epichlorohydrin resin, cationic polyacrylamide and alkyl ketene dimer emulsion, with a mass ratio of (1-2):1:(4-5); the alkyl ketene dimer emulsion has a solid content of 20-25%, a pH value of 4-5 and a particle size of 1.5-2.0 μm.

[0014] In one embodiment of the present invention, in step S1, during the preparation of the mixed pulp, the mass percentage of softwood pulp is 10-25% and the mass percentage of hardwood pulp is 75-90%.

[0015] In one embodiment of the present invention, in step S1, the amount of sizing agent added is 200-250g per 1kg of slurry.

[0016] As one embodiment of the present invention, in step S1, the modified PAE is prepared by reacting adipic acid, thiourea and diethylenetriamine in a mass ratio of 5:4:8 at 160-200℃ for 3-4 hours.

[0017] In one embodiment of the present invention, in step S1, during the pulping process, the pulping time for softwood pulp is 3-4 hours and the rotation speed is 4000-5000 r / min; the pulping time for hardwood pulp is 3-4 hours and the rotation speed is 3000-3500 r / min.

[0018] The beneficial effects of this invention are:

[0019] 1. The method for preparing medical dialysis base paper provided by the present invention involves first adding a certain amount of softener of a specific composition to hardwood pulp, then mixing it with softwood pulp to obtain dialysis paper. Next, the dialysis paper is surface-treated with a sizing solution of a specific composition, and the content and coating amount of each component in the sizing solution are controlled to finally obtain medical dialysis base paper with high strength, high air permeability, antibacterial properties and high softness.

[0020] 2. The preparation method of medical dialysis base paper provided by the present invention involves adding an appropriate amount of ethylene glycol to a commonly used softener, cationic quaternary ammonium salt resin. This utilizes the synergistic effect between the two to increase the number of hydroxyl groups on the surface of hardwood fibers in the hardwood pulp, thereby achieving softening without affecting paper strength. Furthermore, the addition of ethylene glycol reduces the amount of cationic quaternary ammonium salt resin added to the softener and imparts excellent water absorption to the paper. By adding cellulose nanofibers to the sizing solution, their strength characteristics are utilized to impart high strength to the paper. Simultaneously, by controlling their concentration and fiber length, not only can the aggregation of cellulose nanofibers in the paper be avoided during the coating process, but the spacing between paper fibers can also be controlled using cellulose nanofibers, thereby adjusting the paper's air permeability to meet the air permeability requirements of medical dialysis base paper in practical applications. By first performing internal sizing to obtain dialysis paper with certain properties, and then performing surface sizing, the performance of the dialysis paper is further adjusted, facilitating the acquisition of medical dialysis base paper with excellent overall performance. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0022] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the text, while other details that are not closely related to the present invention are omitted.

[0023] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0024] The method for preparing medical dialysis paper provided by the present invention includes the following steps:

[0025] S1. The softwood pulp and hardwood pulp are refined separately. After refining, the freeness of the softwood pulp is 50-60°SR, and the freeness of the hardwood pulp is 30-35°SR. The refined hardwood pulp is mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets are formed, and after the paper is formed, it is peeled off and pressed under a pressure of 500-550 kPa for 2-4 minutes. After drying, dialysis paper is obtained.

[0026] The pulp sizing agent consists of modified PAE (polyamide epichlorohydrin resin), CPAM (cationic polyacrylamide), and AKD (alkyl ketene dimer) emulsion, with a mass ratio of (1-2):1:(4-5). The AKD emulsion has a solid content of 20-25%, a pH value of 4-5, and a particle size of 1.5-2.0 μm. The AKD emulsion is prepared according to conventional methods in this field and will not be discussed in detail here. In the preparation of mixed pulp, the mass percentage of softwood pulp is 10-25% (W / W), and the mass percentage of hardwood pulp is 75-90% (W / W).

[0027] S2. The dialysis paper obtained in step S1 is coated with a sizing solution and dried to obtain medical dialysis base paper. The sizing solution is obtained by dispersing cationic starch and polyvinyl alcohol (PVA) in a cellulose nanofiber suspension.

[0028] As one embodiment of the present invention, in step S1, the modified PAE is prepared by reacting adipic acid, thiourea and diethylenetriamine in a mass ratio of 5:4:8 at 160-200℃ for 3-4 hours.

[0029] In one embodiment of the present invention, in step S1, the softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium resin, and a small amount of water, wherein the weight ratio of cationic quaternary ammonium resin to ethylene glycol is (0.02-0.03):1, and the amount of softener added is 0.1-0.2% of the oven-dry weight of the hardwood pulp. It should be noted that the water added in the above process is used to disperse the ethylene glycol and cationic quaternary ammonium resin, and its amount can be adjusted according to the amount of raw materials added in the compounding process, as long as the dispersion requirements are met; this is not a limitation. In particular, in some other embodiments, ethylene glycol can be replaced with alcohols such as ethanol and propanol.

[0030] In one embodiment of the present invention, in step S1, during the pulping process, the pulping time for softwood pulp is 3-4 hours and the rotation speed is 4000-5000 r / min; the pulping time for hardwood pulp is 3-4 hours and the rotation speed is 3000-3500 r / min.

[0031] In one embodiment of the present invention, in step S1, the amount of sizing agent added is 200-250g per 1kg of slurry.

[0032] In one embodiment of the present invention, in step S2, the sizing solution is composed of 0.5-1 parts cationic starch, 10-15 parts PVA, and 2-3 parts cellulose nanofiber suspension, wherein the concentration of the cellulose nanofiber suspension is 1-3 g / L, and the average fiber diameter of the cellulose nanofibers is 2-20 nm; the coating amount of the surface sizing solution is 7-10 g / m². 2 It should be noted that the cationic starch in this invention is prepared using conventional methods, therefore the specific preparation process is not given here.

[0033] In the above process, the surface of the initially prepared dialysis paper is modified using a suspension of cationic starch, polyvinyl alcohol, and cellulose nanofibers as a surface coating liquid. The strength and antibacterial properties of polyvinyl alcohol can be utilized to improve the paper's performance. Introducing cellulose nanofibers not only utilizes their fiber morphology to minimize the impact of the coating process on the paper's softness, but also enhances the paper's strength by leveraging the strength properties of the nanofibers during coating. Furthermore, the small size of the cellulose nanofibers effectively reduces the clogging of the gaps between fibers during coating, ensuring the paper's air permeability. However, if the concentration of the cellulose nanofiber suspension is too high or the fiber length is too long, the nanofibers are prone to aggregation during coating, leading to uneven surface properties and clogging of the paper's pore structure, thus affecting its air permeability.

[0034] In one embodiment of the present invention, in step S2, the drying temperature is 50-60°C and the time is 12-24 hours.

[0035] Furthermore, the medical dialysis base paper prepared using the method proposed in this invention has the following properties: basis weight of 60±3 g / m³. 2 Tightness ≤ 0.8g / cm 3 Transverse tear strength ≥ 500 mN, longitudinal tear strength ≥ 440 mN, longitudinal tensile strength ≥ 4.9 kN / m, longitudinal wet tensile strength ≥ 1.0 kN / m, transverse tensile strength ≥ 2.5 kN / m, bursting strength ≥ 1.5 kPa, water absorption ≤ 22 g / m 2 Air permeability ≥3.1µm / Pa·s.

[0036] The preparation method of the medical dialysis base paper of the present invention will be further explained below with reference to specific embodiments:

[0037] Example 1

[0038] This embodiment prepares a medical dialysis base paper. The specific preparation method includes the following steps:

[0039] S1. The softwood pulp and hardwood pulp were refined separately. After refining, the freeness of the softwood pulp was 50°SR and the freeness of the hardwood pulp was 35°SR. The refined hardwood pulp was mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets were formed, and after the paper was formed, it was peeled off and pressed under 500 kPa pressure for 4 minutes. After drying, dialysis paper was obtained.

[0040] The amount of sizing agent added is 200g per 1kg of pulp. It consists of modified PAE, CPAM, and AKD emulsion in a mass ratio of 1:1:4. The AKD emulsion has a solid content of 25%, a pH of 4-5, and a particle size of 1.5-2.0μm. In the preparation of mixed pulp, the mass percentage of softwood pulp is 25% (w / w), and the mass percentage of hardwood pulp is 75% (w / w). In the refining process, the refining time for softwood pulp is 3 hours, and the refining speed is 5000r / min. The refining time for hardwood pulp is 4 hours, and the refining speed is 3500r / min.

[0041] Furthermore, the modified PAE is prepared as follows: Adipic acid, thiourea, and diethylenetriamine in a mass ratio of 5:4:8 are reacted at 160℃ for 4 hours; the softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium resin, and a small amount of water, wherein the weight ratio of cationic quaternary ammonium resin to ethylene glycol is 0.02:1, and the amount of softener added is 0.1% of the oven-dry weight of the hardwood pulp;

[0042] S2. Coat the surface of the dialysis paper obtained in step S1 with a sizing solution, with a coating amount of 7.5 g / m. 2 After coating, the paper is dried at 60°C for 12 hours to obtain medical dialysis base paper. The sizing solution consists of 0.5 parts cationic starch, 12 parts PVA, and 2 parts cellulose nanofiber suspension. The concentration of the cellulose nanofiber suspension is 1 g / L, and the average fiber diameter of the cellulose nanofibers is 2-20 nm. It should be noted that, unless otherwise specified, the reagents and raw materials used in the embodiments mentioned in this invention can be obtained commercially.

[0043] Example 2

[0044] This embodiment prepares a medical dialysis base paper. The specific preparation method includes the following steps:

[0045] S1. The softwood pulp and hardwood pulp were refined separately. After refining, the freeness of the softwood pulp was 55°SR and the freeness of the hardwood pulp was 30°SR. The refined hardwood pulp was mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets were formed, and after the paper was formed, it was peeled off and pressed under 500 kPa pressure for 2 minutes. After drying, dialysis paper was obtained.

[0046] The amount of sizing agent added is 220g per 1kg of pulp. It consists of modified PAE, CPAM, and AKD emulsion in a mass ratio of 1:1:4. The AKD emulsion has a solid content of 25%, a pH of 4-5, and a particle size of 1.5-2.0μm. In the preparation of mixed pulp, the mass percentage of softwood pulp is 20% (w / w), and the mass percentage of hardwood pulp is 80% (w / w). In the pulping process, the pulping time for softwood pulp is 3 hours, and the pulping speed is 4500r / min. The pulping time for hardwood pulp is 3 hours, and the pulping speed is 3000r / min.

[0047] Furthermore, the modified PAE is prepared as follows: Adipic acid, thiourea, and diethylenetriamine in a mass ratio of 5:4:8 are reacted at 160℃ for 4 hours; the softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium resin, and a small amount of water, wherein the weight ratio of cationic quaternary ammonium resin to ethylene glycol is 0.02:1, and the amount of softener added is 0.2% of the oven-dry weight of the hardwood pulp;

[0048] S2. Coat the surface of the dialysis paper obtained in step S1 with a sizing solution, with a coating amount of 8 g / m. 2After coating, the paper is dried at 60℃ for 12 hours to obtain medical dialysis base paper. The sizing solution consists of 0.7 parts cationic starch, 13 parts PVA, and 3 parts cellulose nanofiber suspension. The concentration of the cellulose nanofiber suspension is 2.5 g / L, and the average fiber diameter of the cellulose nanofiber is 2-20 nm.

[0049] Example 3

[0050] This embodiment prepares a medical dialysis base paper. The specific preparation method includes the following steps:

[0051] S1. The softwood pulp and hardwood pulp were refined separately. After refining, the freeness of the softwood pulp was 60°SR and the freeness of the hardwood pulp was 35°SR. The refined hardwood pulp was mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets were formed, and after the paper was formed, it was peeled off and pressed under 550 kPa pressure for 2 minutes. After drying, dialysis paper was obtained.

[0052] The amount of sizing agent added is 250g per 1kg of pulp. It consists of modified PAE, CPAM, and AKD emulsion in a mass ratio of 1:1:4. The AKD emulsion has a solid content of 25%, a pH of 4-5, and a particle size of 1.5-2.0μm. In the preparation of mixed pulp, the mass percentage of softwood pulp is 25% (w / w), and the mass percentage of hardwood pulp is 75% (w / w). In the pulping process, the pulping time for softwood pulp is 4 hours, and the pulping speed is 5000r / min. The pulping time for hardwood pulp is 4 hours, and the pulping speed is 3500r / min.

[0053] Furthermore, the modified PAE is prepared as follows: Adipic acid, thiourea, and diethylenetriamine in a mass ratio of 5:4:8 are reacted at 160℃ for 4 hours; the softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium resin, and a small amount of water, wherein the weight ratio of cationic quaternary ammonium resin to ethylene glycol is 0.02:1, and the amount of softener added is 0.15% of the oven-dry weight of the hardwood pulp;

[0054] S2. Coat the surface of the dialysis paper obtained in step S1 with a sizing solution, with a coating amount of 10 g / m. 2 After coating, the paper is dried at 60℃ for 12 hours to obtain medical dialysis base paper. The sizing solution consists of 0.9 parts cationic starch, 10 parts PVA, and 3 parts cellulose nanofiber suspension. The concentration of the cellulose nanofiber suspension is 3 g / L, and the average fiber diameter of the cellulose nanofiber is 2-20 nm.

[0055] The properties of the medical dialysis paper prepared in Examples 1 to 3 are shown in Table 1. As can be seen from the data in the table, the properties of the medical dialysis paper are affected by multiple process parameters in the preparation process, but medical dialysis paper with excellent performance can be obtained under the given range of process parameters.

[0056] Table 1. Performance comparison of medical dialysis base paper prepared in Examples 1 to 3

[0057]

[0058] Examples 4 to 7

[0059] The only difference between Examples 4 to 7 and Example 1 is that the composition of the softener and sizing solution differs from that of Example 1; the remaining steps are the same as in Example 1 and will not be repeated here. The composition of the softener and sizing solution in Examples 1 and 4 to 7 is shown in Table 2. The properties of the medical dialysis base paper prepared under different conditions are shown in Table 3. From the data in the table, it can be seen that the medical dialysis base paper prepared using the given process parameters of this invention has the following properties: basis weight 60 ± 3 g / m³. 2 Tightness ≤ 0.8g / cm 3 Transverse tear strength ≥ 500 mN, longitudinal tear strength ≥ 460 mN, longitudinal tensile strength ≥ 4.9 kN / m, longitudinal wet tensile strength ≥ 1.0 kN / m, transverse tensile strength ≥ 2.5 kN / m, bursting strength ≥ 1.5 kPa, water absorption ≤ 22 g / m 2 First, the air permeability is ≥3.1µm / Pa·s. Second, the performance of medical dialysis base paper is affected by the composition of the softener and sizing solution, and the medical dialysis base paper prepared under the conditions of Example 7 has the best performance.

[0060] Table 2. Composition of softener and sizing agent in Examples 1 and 4 to 7

[0061]

[0062] Table 3. Performance comparison of medical dialysis base paper prepared in Examples 1 and 4 to 7

[0063]

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that the mass ratio of cationic quaternary ammonium salt resin to ethylene glycol in the softener is 0.05:1. The other experimental parameters and preparation process are the same as in Example 1, and will not be repeated here.

[0066] Comparative Example 2

[0067] The only difference between Comparative Example 2 and Example 1 is that in step S1, the softener is first mixed evenly with softwood pulp, and then mixed with hardwood pulp. The remaining experimental parameters and preparation process are the same as in Example 1, and will not be repeated here.

[0068] Comparative Example 3

[0069] The only difference between Comparative Example 3 and Example 1 is that in step S1, softwood pulp and hardwood pulp are mixed first, and then mixed with softener. The remaining experimental parameters and preparation process are the same as in Example 1, and will not be repeated here.

[0070] Comparative Example 4

[0071] The only difference between Comparative Example 4 and Example 1 is that the amount of softener added is 0.4% of the oven-dry weight of the hardwood pulp. The other experimental parameters and preparation process are the same as those in Example 1, and will not be repeated here.

[0072] Comparative Example 5

[0073] The only difference between Comparative Example 5 and Example 1 is that the softener does not contain ethylene glycol in step S1, that is, the softener in Comparative Example 5 contains only cationic quaternary ammonium salt resin. However, the amount of softener added in Comparative Example 5 and Example 1 is the same. The other experimental parameters and preparation process are the same as those in Example 1, and will not be repeated here.

[0074] Comparative Example 6

[0075] The only difference between Comparative Example 6 and Example 1 is that in step S2, the sizing solution does not contain cellulose nanofibers, but is a mixture of 0.5 parts cationic starch and 12 parts PVA dissolved in water, and the concentrations of cationic starch and PVA in the mixture are the same as in Example 1.

[0076] Table 4 shows a comparison of the properties of the medical dialysis base paper prepared in Example 1 and Comparative Examples 1 to 6. The data in the table shows that the properties of the medical dialysis base paper prepared in Comparative Examples 1 to 6 are all inferior to those in Example 1. This indicates that the composition (Comparative Example 5), the amount added (Comparative Example 4), and the timing of addition (Comparative Examples 2-3) of the softener have a significant impact on the strength of the medical dialysis base paper. The addition of cellulose nanofibers in the sizing solution can effectively enhance the strength of the medical dialysis base paper, thereby improving its air permeability. The main reasons for the above differences include the following aspects: First, by adding an appropriate amount of ethylene glycol to the softener, it is possible to... By utilizing the synergistic effect between the two, the softness of the paper can be improved without affecting its strength. By mixing the softener with hardwood pulp first and then with softwood pulp, the number of hydroxyl groups on the surface of hardwood pulp can be effectively increased. This is because there are more hydroxyl groups on softwood pulp than on hardwood pulp. Using the above mixing method, only a small amount of softener needs to be added to achieve the softening effect. Secondly, by adding cellulose nanofibers to the sizing solution, the strength properties of the paper can be utilized to improve its strength. At the same time, cellulose nanofibers of a specific size can regulate the spacing between paper fibers, thereby adjusting the paper's air permeability.

[0077] Table 4. Performance comparison of medical dialysis paper prepared in Example 1 and Comparative Examples 1 to 6

[0078]

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing medical dialysis base paper, characterized in that, Includes the following steps: S1. The softwood pulp and hardwood pulp are refined separately. After refining, the freeness of the softwood pulp is 50-60°SR, and the freeness of the hardwood pulp is 30-35°SR. The refined hardwood pulp is mixed evenly with a softener, and then mixed with softwood pulp and sizing agent to obtain mixed pulp. Then, hand-made sheets are formed, and after the paper is formed, it is peeled off and pressed under a pressure of 500-550 kPa for 2-4 minutes. After drying, dialysis paper is obtained. The softener is an emulsion obtained by compounding ethylene glycol, cationic quaternary ammonium salt resin and water, wherein the weight ratio of cationic quaternary ammonium salt resin to ethylene glycol is (0.02-0.03):1, and the amount of softener added is 0.1-0.2% of the oven-dry weight of hardwood pulp; the pulp sizing agent is composed of modified polyamide epichlorohydrin resin, cationic polyacrylamide and alkyl ketene dimer emulsion, wherein the mass ratio of the three is (1-2):1:(4-5); the solid content of the alkyl ketene dimer emulsion is 20-25%, the pH value is 4-5, and the particle size is 1.5-2.0μm; the modified polyamide epichlorohydrin resin is prepared by reacting adipic acid, thiourea and diethylenetriamine in a mass ratio of 5:4:8 at 160-200℃ for 3-4h. S2. The dialysis paper obtained in step S1 is coated with a sizing solution and dried to obtain medical dialysis base paper. The sizing solution is obtained by dispersing cationic starch and polyvinyl alcohol in a cellulose nanofiber suspension. The sizing solution consists of 0.5-1 parts cationic starch, 10-15 parts PVA, and 2-3 parts cellulose nanofiber suspension. The coating amount of the surface sizing solution is 7-10 g / m². 2 The concentration of the cellulose nanofiber suspension is 1-3 g / L, and the average fiber diameter of the cellulose nanofibers is 2-20 nm. The medical dialysis paper has the following properties: basis weight of 60±3 g / m³. 2 Tightness ≤ 0.8g / cm 3 Transverse tear strength ≥ 500 mN, longitudinal tear strength ≥ 440 mN, longitudinal tensile strength ≥ 4.9 kN / m, longitudinal wet tensile strength ≥ 1.0 kN / m, transverse tensile strength ≥ 2.5 kN / m, bursting strength ≥ 1.5 kPa, water absorption ≤ 22 g / m 2 Air permeability ≥3.1µm / Pa·s.

2. The method for preparing medical dialysis paper according to claim 1, characterized in that, In step S1, during the preparation of the mixed pulp, the mass percentage of softwood pulp is 10-25%, and the mass percentage of hardwood pulp is 75-90%.

3. The method for preparing medical dialysis paper according to claim 1, characterized in that, In step S1, the amount of sizing agent added is 200-250g per 1kg of slurry.

4. The method for preparing medical dialysis paper according to claim 1, characterized in that, In step S1, during the pulping process, the pulping time for softwood pulp is 3-4 hours and the rotation speed is 4000-5000 r / min; the pulping time for hardwood pulp is 3-4 hours and the rotation speed is 3000-3500 r / min.

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