A reverse osmosis high-absorption type sanitary nursing pad and a preparation process thereof

Abstract

The application discloses a reverse osmosis high-absorption type sanitary nursing pad and a preparation process thereof, and relates to the technical field of nursing pads. Specifically, the application comprises the following steps: S1: wood pulp fibers and ES fibers are mixed by a wet laying process to form a paper, water-absorbing resin is sprayed, and dehydration and drying are performed to obtain an absorption core layer; and S2: a skin-friendly surface layer, the absorption core layer and a breathable bottom film layer are hot-pressed to obtain the reverse osmosis high-absorption type sanitary nursing pad. The application introduces a salt-resistant water-absorbing resin into the sanitary nursing pad by means of wet compounding, so that the prepared product has excellent absorption capacity and reverse osmosis prevention performance.

Description

Technical Field

[0001] This invention relates to the field of nursing pad technology, specifically a reverse osmosis high-absorbency sanitary pad and its preparation process. Background Technology

[0002] Sanitary pads, as essential disposable products in medical care and daily hygiene, are widely used in hospital surgeries, bed rest, and other scenarios. They are designed to quickly absorb and lock in bodily fluids, thereby isolating contaminants from direct contact with skin and bedding, reducing the risk of infection. Currently, these products generally use absorbent polymers (APPs) as the core water-locking material, but this has significant drawbacks in application: for example, when absorbing saline or high-salt bodily fluids, the presence of cations in the fluids can counteract the electrostatic repulsion of anionic groups in the PAPs, leading to a decrease in resin osmotic pressure and a reduction in absorbency. Simultaneously, the gel network weakens in an ionic environment, making it prone to structural collapse under pressure, causing liquid backflow and severely impacting comfort and safety.

[0003] In summary, in order to solve the above problems, it is of great significance to prepare a reverse osmosis high-absorbency sanitary pad and its preparation process. Summary of the Invention

[0004] The purpose of this invention is to provide a reverse osmosis high-absorbency sanitary pad and its preparation process to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A manufacturing process for a reverse osmosis super absorbent sanitary pad includes the following steps: S1: Wood pulp fiber and ES fiber are mixed and formed into paper using a wet-process papermaking method, then sprayed with absorbent resin, and dehydrated and dried to obtain the absorbent core layer. S2: A reverse osmosis, highly absorbent sanitary pad is obtained by hot-pressing the skin-friendly surface layer, absorbent core layer, and breathable bottom membrane layer together.

[0006] Preferably, the raw materials of the absorbent core layer include wood pulp fiber and ES fiber in a mass ratio of 40:15~20; the areal density of the absorbent core layer is 150~180 g / m²; and the spraying amount of the water-absorbing resin is 40~60 g / m². 2 .

[0007] Preferred method for preparing the water-absorbing resin includes the following steps: adding acrylic acid to deionized water and mixing evenly, adding sodium hydroxide solution to adjust the degree of neutralization, adding acrylamide, sulfonic acid-modified bentonite, cerium ammonium nitrate, crosslinking agent and dextrin in sequence, stirring and reacting at 95~100℃ for 30~40 min, filtering, washing, drying, grinding to obtain the water-absorbing resin.

[0008] Preferably, the crosslinking agent accounts for 0.5 to 1 wt% of acrylic acid; and the degree of neutralization is 65 to 75%.

[0009] Preferably, the raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonic acid-modified bentonite, and dextrin in a mass ratio of 10:6~10:2.5~3.2:2~2.2; and the cerium ammonium nitrate accounts for 0.1~0.2 wt% of the acrylic acid.

[0010] Preferably, the sulfonic acid-modified bentonite is prepared by clicking alkenyl-modified bentonite with mercaptoacetic acid and then coupling with taurine; the alkenyl-modified bentonite is modified by an alkenyl-containing silane coupling agent.

[0011] Preferredly, the preparation method of the crosslinking agent includes the following steps: (1) under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate, and hydroquinone are mixed evenly and stirred at 180~185℃ for 6~8h, purified, to obtain C21-diacid di(trimethylolpropane) ester; (2) under a nitrogen atmosphere, C21-diacid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate, and azobisisobutyronitrile are mixed evenly and stirred at 60℃ for 6~8h. Stirring at ~70℃ for 3~5h, purifying, to obtain sulfonic acid C21-diacarboxylic acid di(trimethylolpropane) ester; (3) Under a nitrogen atmosphere, sulfonic acid C21-diacarboxylic acid di(trimethylolpropane) ester, maleic anhydride, and 4-dimethylaminopyridine are mixed evenly, stirred at 70~75℃ for 8~12h, p-hydroxyanisole, glycidyl methacrylate and tetrabutylammonium bromide are added, stirred at 110~120℃ for 8~12h, purified, to obtain crosslinking agent.

[0012] The C21-diacarboxylic acid is prepared according to existing technology. The process involves: under a nitrogen atmosphere, linoleic acid and iodine are mixed evenly in a high-pressure reactor, stirred at 150-155°C for 20-40 minutes, then acrylic acid and hydroquinone are added, the temperature is raised to 240-250°C, and the mixture is stirred for 3-4 hours. After purification, the C21-diacarboxylic acid is obtained. The raw materials for the C21-diacarboxylic acid include linoleic acid, acrylic acid, iodine, and hydroquinone in a mass ratio of 20:5.5-6.5:0.01-0.05:0.7-0.8. Preferably, the raw materials for the C21-diacarboxylic acid di(trimethylolpropane) ester include C21-diacarboxylic acid, trimethylolpropane, anhydrous zinc acetate, and hydroquinone in a mass ratio of 20:16~16.4:0.03~0.04:1~1.1. The raw materials for the sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester include C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate, and azobisisobutyronitrile in a mass ratio of 20:5.5~5.7:0.01~0.05. The crosslinking agent comprises the following raw materials, in parts by weight: 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.5-10.7 parts of maleic anhydride, 0.1-0.2 parts of 4-dimethylaminopyridine, 0.05-0.1 parts of p-hydroxyanisole, 7.6-7.8 parts of glycidyl methacrylate, and 0.2-0.3 parts of tetrabutylammonium bromide.

[0013] The preparation method of the macromolecular crosslinking agent is as follows: C21-diacid has one double bond and two carboxyl groups. By using anhydrous zinc acetate as a catalyst and under the condition of hydroquinone as a polymerization inhibitor, two molecules of trimethylolpropane and the two carboxyl groups of C21-diacid react to obtain C21-diacid di(trimethylolpropane) ester containing four hydroxyl groups. Further, under the condition of azobisisobutyronitrile, the thiol group in sodium 3-mercapto-1-propanesulfonate is used to click with the double bond of the previous step to introduce a sulfonic acid group to obtain sulfonic acid C21-diacid di(trimethylolpropane) ester. Further, using 4-dimethylaminopyridine as a catalyst, maleic anhydride reacts with the four hydroxyl groups of the product to generate an anhydride half-ester intermediate containing carboxyl and alkenyl groups. Further, using tetrabutylammonium bromide as a catalyst, the carboxyl group on the intermediate undergoes an epoxy ring-opening esterification reaction with glycidyl methacrylate to introduce a methacrylate double bond and obtain the crosslinking agent.

[0014] The preparation method of modified bentonite includes the following steps: (1) adding bentonite and 3-(isobutyryloxy)propyltrimethoxysilane in a mass ratio of 1:0.05~0.1 to an 80~90% ethanol aqueous solution and dispersing them evenly, treating at 50~60℃ for 2~3h, washing, and drying to obtain alkenyl modified bentonite; (2) adding alkenyl modified bentonite in a mass ratio of 1:0.15~0.2:0.001~0.002. (2) Add mercaptoacetic acid and azobisisobutyronitrile to deionized water and mix evenly. Stir at 70-80℃ for 1-2 hours, wash and dry to obtain carboxyl-modified bentonite; (3) Mix carboxyl-modified bentonite, EDC, NHS and taurine in a mass ratio of 1:0.1-0.15:0.08-0.1:0.1-0.15 evenly, stir at 50-60℃ for 5-6 hours, wash and dry to obtain sulfonic acid-modified bentonite.

[0015] Preferably, the material of the skin-friendly surface layer includes one or more of PP nonwoven fabric, PE nonwoven fabric, and ES nonwoven fabric; the material of the breathable bottom film layer includes either polyolefin breathable film or polyurethane breathable film.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: Based on a macromolecular crosslinking agent containing sulfonic acid groups, the present invention uses dextrin as the water-absorbing skeleton, sulfonic acid-modified bentonite as the reinforcing filler, acrylic acid and acrylamide as grafting monomers, and cerium ammonium nitrate as a catalyst to successfully prepare a salt-resistant water-absorbing resin. The absorbent core layer is prepared by wet composite method and used to prepare sanitary care pads, so that the product has excellent absorption capacity and anti-backflow performance.

[0017] In the preparation of superabsorbent polymers, the traditional small-molecule crosslinking agent N,N-methylenebisacrylamide, due to its small molecular chain segment and high reactivity, participates in the reaction in large quantities in the early stage. This results in a large amount of non-uniform linear water-soluble polymer in the superabsorbent polymer, leading to reduced swelling performance and decreased water absorption performance. Trimethylolpropane triacrylate, with its hydrophobic ester structure and trifunctionality, can increase the crosslinking density and enhance the crosslinking network structure through hydrophobic association to resist the destructive effects of high salt. However, its low hydrophilicity makes it difficult to disperse evenly in aqueous graft polymerization, resulting in reduced water absorption and salt resistance. Therefore, this invention uses a C21-diacid prepared by the reaction of linoleic acid and acrylic acid as the crosslinking agent backbone. Its long-chain aliphatic hydrophobic structure helps to achieve a flexible spatial spacing effect, effectively avoiding the problem of excessive consumption of crosslinking agent due to the high activity of small molecules in the early stage, thus constructing a more uniform and elastic crosslinking network. The introduction of sulfonic acid groups by sodium 3-mercapto-1-propanesulfonate improves hydrophilicity and increases the diversity of hydrophilic groups in the superabsorbent resin. The introduction of four hydroxyl groups by trimethylolpropane and esterification with maleic anhydride introduces an anhydride half-ester intermediate containing carboxyl and alkenyl groups. This intermediate contains four double bonds that can participate in crosslinking and contains hydrophilic carboxyl groups, improving the swelling performance of the superabsorbent resin. However, due to the presence of maleic anhydride, the swelling performance of the superabsorbent resin is not improved. The double bonds introduced by the anhydride belong to electron-deficient olefins, which have relatively low reactivity. Therefore, this invention further introduces glycidyl methacrylate, using epoxy and carboxyl groups to introduce terminal double bonds and generate hydrophilic hydroxyl groups. Since the terminal double bonds have higher reactivity, the basic framework will be preferentially formed during the crosslinking process, solving the problem of low reactivity and slow crosslinking network formation in the early stage, and improving swelling performance. However, the amount of glycidyl methacrylate grafted needs to be limited. When too much grafting occurs, the hydrophilicity of the crosslinking agent decreases and the uniformity decreases due to the reaction of the carboxyl groups. In addition, too many crosslinking sites are formed, reducing the network that can accommodate water molecules and decreasing the water absorption performance. When the amount of grafting is too small, it is difficult to achieve the effect of activity gradient.

[0018] It should be noted that conventional salt-resistant absorbent resins typically incorporate sulfonic acid monomers to improve their resistance. However, due to their relatively large steric hindrance, this may hinder the efficiency of graft copolymerization. Therefore, this invention modifies the surface of bentonite by introducing hydrophilic sulfonic acid and amide bonds. This reduces bentonite agglomeration and improves dispersibility. At the same time, the introduction of polar amide bonds after bentonite modification allows reactants to be adsorbed onto the surface through hydrogen bonding, promoting grafting. Meanwhile, the sulfonic acid groups can further disperse the crosslinking agent through common ion repulsion, improving the uniformity of hydrogel network formation, thereby enhancing salt resistance and swelling performance, and improving the absorbency of the pad. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the following quantities are by weight. There are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: bentonite with a particle size of 1-10 μm; CAS number 2530-85-0 for 3-(isobutenoyloxy)propyltrimethoxysilane; CAS number 68-11-1 for mercaptoacetic acid; CAS number 107-35-7 for taurine; CAS number 60-33-3 for linoleic acid; CAS number 77-99-6 for trimethylolpropane; CAS number 17636-10-1 for sodium 3-mercapto-1-propanesulfonate; CAS number 108-31-6 for maleic anhydride; CAS number 106-91-2 for glycidyl methacrylate; CAS number 16774-21-3 for cerium ammonium nitrate; and dextrin, catalog number 10049.

[0021] In the following examples, parts refer to parts by weight, and all raw materials mentioned above and others not mentioned are commercially available.

[0022] In each embodiment and comparative example, the skin-friendly surface layer is a hydrophilic PP nonwoven fabric with a surface density of 22 g / m²; the absorbent core layer has a surface density of 160 g / m²; and the breathable bottom film layer has a surface density of 25 g / m². 2 The polyolefin breathable membrane base film; the water-absorbing resin spraying rate is 50g / m². 2 .

[0023] Pre-preparation: The preparation method of modified bentonite includes the following steps: (1) Bentonite and 3-(isobutyryloxy)propyltrimethoxysilane with a mass ratio of 1:0.1 are added to 80% ethanol aqueous solution and dispersed evenly. The mixture is treated at 60℃ for 2h, washed, and dried to obtain alkenyl modified bentonite; (2) Alkenyl modified bentonite, mercaptoacetic acid, and azobisisobutyronitrile with a mass ratio of 1:0.15:0.001 are added to deionized water and mixed evenly. The mixture is stirred at 75℃ for 2h, washed, and dried to obtain carboxyl modified bentonite; (3) Carboxyl modified bentonite, EDC, NHS, and taurine with a mass ratio of 1:0.12:0.08:0.1 are mixed evenly. The mixture is stirred at 50℃ for 5h, washed, and dried to obtain sulfonic acid modified bentonite.

[0024] Preparation of C21-diacarboxylic acid: Under a nitrogen atmosphere, linoleic acid and iodine were mixed evenly in a high-pressure reactor and stirred at 150°C for 30 min. Acrylic acid and hydroquinone were added, and the mixture was heated to 240°C and stirred for 3 h. After purification, C21-diacarboxylic acid was obtained. The raw materials for C21-diacarboxylic acid included linoleic acid, acrylic acid, iodine, and hydroquinone in a mass ratio of 20:6:0.01:0.7.

[0025] Example 1: A preparation process for a reverse osmosis high-absorbency sanitary pad includes the following steps: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 7.7 parts of glycidyl methacrylate, and 0.2 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0026] Example 2: A preparation process for a reverse osmosis high-absorbency sanitary pad includes the following steps: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 7.7 parts of glycidyl methacrylate, and 0.2 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonic acid-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonic acid-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 1 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0027] Example 3: A preparation process for a reverse osmosis high-absorbency sanitary pad includes the following steps: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 7.7 parts of glycidyl methacrylate, and 0.2 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100°C for 30 minutes. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of the acrylic acid; and the crosslinking agent accounts for 0.5 wt% of the acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0028] Comparative Example 1: Based on Example 1, the crosslinking agent used was trimethylolpropane triacrylate, and the remaining processes remained unchanged, as follows: Step 1: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent (trimethylolpropane triacrylate), and dextrin are added sequentially. The mixture is stirred and reacted at 100°C for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step Two: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0029] Comparative Example 2: Based on Example 1, the amount of glycidyl methacrylate introduced during the preparation of the crosslinking agent was increased, while the other processes remained unchanged, as follows: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 15.4 parts of glycidyl methacrylate, and 0.4 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0030] Comparative Example 3: Based on Example 1, glycidyl methacrylate was not introduced during the preparation of the crosslinking agent, and the rest of the process remained unchanged, as follows: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0031] Comparative Example 4: Based on Example 1, 2-acrylamido-2-methylpropanesulfonic acid was introduced into the preparation process of the water-absorbing resin at an addition amount of 30 wt% of acrylic acid, while the rest of the process remained unchanged, as follows: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 7.7 parts of glycidyl methacrylate, and 0.2 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, sulfonate-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, sulfonate-modified bentonite, and dextrin in a mass ratio of 10:8:3:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0032] Comparative Example 5: Based on Example 1, alkenyl-modified bentonite was used instead of sulfonic acid-modified bentonite, with the remaining processes unchanged, as follows: Step 1: Preparation of crosslinking agent: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone were mixed evenly and stirred at 180°C for 7 h. After purification, C21-diacid di(trimethylolpropane) ester was obtained. The raw materials of C21-diacid di(trimethylolpropane) ester included C21-diacid, trimethylolpropane, anhydrous zinc acetate and hydroquinone in a mass ratio of 20:16.2:0.03:1. (2) Under a nitrogen atmosphere, C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile were mixed evenly and stirred at 70°C for 4 h. After purification, sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester was obtained. The raw materials of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester included C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate and azobisisobutyronitrile in a mass ratio of 20:5.6:0.01. (3) Under a nitrogen atmosphere, 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.6 parts of maleic anhydride, and 0.1 parts of 4-dimethylaminopyridine were mixed evenly and stirred at 70°C for 8 hours. Then, 0.05 parts of p-hydroxyanisole, 7.7 parts of glycidyl methacrylate, and 0.2 parts of tetrabutylammonium bromide were added and stirred at 110°C for 8 hours. After purification, the crosslinking agent was obtained. Step 2: Preparation of the water-absorbing resin: Acrylic acid is added to deionized water and mixed evenly. Sodium hydroxide solution is added to adjust the neutralization degree to 70%. Acrylamide, alkenyl-modified bentonite, cerium ammonium nitrate, crosslinking agent, and dextrin are added sequentially. The mixture is stirred and reacted at 100℃ for 30 min. After filtration, washing, drying, and grinding, the water-absorbing resin is obtained. The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonic acid-modified bentonite, and dextrin in a mass ratio of 10:8:2.8:2.1; cerium ammonium nitrate accounts for 0.1 wt% of acrylic acid; and the crosslinking agent accounts for 0.6 wt% of acrylic acid. Step 3: Preparation of Reverse Osmosis High Absorbency Sanitary Pads: S1: Weigh wood pulp fiber and ES fiber at a mass ratio of 40:15, process them into pulp by pulping and refining, add wet strength agent, mix evenly, form paper by inclined wire paper machine, and form paper with a concentration of 0.8wt% on the wire to obtain wet layer paper with a moisture content of 50%. Spray water-absorbing resin on one side of the wet layer paper, and laminate another layer of wet layer paper, press to dehydrate, and dry to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are hot-pressed together, cooled and shaped by cooling rollers, divided and rolled up to obtain a reverse osmosis high absorbency sanitary pad.

[0033] The preparation method of alkenyl modified bentonite includes the following steps: adding bentonite and 3-(isobutenoyloxy)propyltrimethoxysilane in a mass ratio of 1:0.1 into an 80% ethanol aqueous solution and dispersing them evenly, treating at 60℃ for 2h, washing, and drying to obtain alkenyl modified bentonite.

[0034] Performance Test 1: (1) After drying the water-absorbing resins prepared in each example and comparative example, add them to a 0.9% sodium chloride solution, remove them, weigh them after controlling the water content, and calculate the water absorption ratio; (2) After the water-absorbing resins prepared in each example and comparative example are adsorbed to equilibrium in a 0.9% sodium chloride solution, place them in a 200-mesh sieve funnel, apply a 200g weight for 1 minute, measure the outflow of water, and calculate the water retention rate; (3) After the water-absorbing resins prepared in each example and comparative example are adsorbed to equilibrium in a 0.9% sodium chloride solution, dry them at 60°C, place them in a 0.9% sodium chloride solution, remove them after adsorption equilibrium, weigh them, repeat 5 times, and calculate the water absorption ratio retention rate.

[0035] Table 1

[0036] As shown in Table 1, in Comparative Example 1, the crosslinking agent used was trimethylolpropane triacrylate. Because it lacks hydrophilic groups, it was difficult to disperse evenly during the reaction. Furthermore, as a small molecule crosslinking agent, its activity was high in the initial stage of the reaction, resulting in high local crosslinking density, uneven crosslinking network, decreased water absorption and swelling performance, and significantly poor pressure-bearing water retention rate and repeated water absorption tests. In Comparative Example 2, the amount of glycidyl methacrylate introduced during the preparation of the crosslinking agent increased, excessively consuming the hydrophilic carboxyl groups of the intermediate. Due to the large molecular structure of the crosslinking agent, its dispersibility decreased significantly, and the molecule contained too many crosslinkable points, resulting in excessively high crosslinking density and a significant decrease in liquid absorption and swelling performance. In Comparative Example 3, glycidyl methacrylate was not introduced during the preparation of the crosslinking agent. The electron-deficient double bond introduced by maleic anhydride... The relatively lower activity and slower crosslinking network formation speed result in a predominantly long-chain structure and a looser crosslinking network in the system, leading to a significant decrease in pressure-bearing water retention and performance in multiple water absorption tests. In Comparative Example 4, the introduction of 2-acrylamido-2-methylpropanesulfonic acid during the preparation of the water-absorbing resin hindered the graft copolymerization reaction due to its large steric hindrance, resulting in a decrease in grafting efficiency. Although the water absorption ratio did not decrease significantly due to the hydrophilicity of the sulfonic acid group, the performance was significantly reduced in multiple water absorption tests due to poor network uniformity and stability. In Comparative Example 5, alkenyl-modified bentonite was used instead of sulfonic acid-modified bentonite. Although it participated in the graft copolymerization process of the water-absorbing resin, it could not promote the dispersion of the crosslinking agent and the grafting process due to the absence of sulfonic acid groups and amide bonds, thus reducing the liquid absorption and swelling performance.

[0037] Performance Test 2: The reverse osmosis high-absorbency sanitary pad prepared in Example 1 was subjected to performance testing. The sample size was 600*900mm. In the liquid absorption rate test, the absorbent liquid was 0.9% sodium chloride solution. In the reverse osmosis performance test, the reabsorption volume was measured according to the standard GB / T28004.2. The absorption rate and diffusion length were tested using 150mL of 0.9% sodium chloride solution. The time for complete liquid absorption was measured, and the liquid absorption diffusion length was measured after five minutes.

[0038] Table 2

[0039] Conclusion: Based on a macromolecular crosslinking agent containing sulfonic acid groups, this invention successfully prepared a salt-resistant absorbent resin using dextrin as the absorbent skeleton, sulfonic acid-modified bentonite as the reinforcing filler, acrylic acid and acrylamide as grafting monomers, and cerium ammonium nitrate as a catalyst. The absorbent core layer was prepared by wet compounding and used to prepare sanitary pads, giving the product excellent absorbency and anti-backflow performance.

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A manufacturing process for a reverse osmosis high-absorbency sanitary pad, characterized in that: Includes the following steps: S1: Wood pulp fiber and ES fiber are mixed and formed into paper using a wet-process papermaking method, then sprayed with absorbent resin, and dehydrated and dried to obtain the absorbent core layer. S2: The skin-friendly surface layer, absorbent core layer and breathable bottom film layer are combined by hot pressing to obtain a reverse osmosis high absorbency sanitary pad; The raw materials of the absorbent core layer include wood pulp fiber and ES fiber in a mass ratio of 40:15~20; the areal density of the absorbent core layer is 150~180 g / m²; and the spraying amount of the water-absorbing resin is 40~60 g / m². 2 ; The preparation method of the water-absorbing resin includes the following steps: adding acrylic acid to deionized water and mixing evenly, adding sodium hydroxide solution to adjust the degree of neutralization, adding acrylamide, sulfonic acid-modified bentonite, cerium ammonium nitrate, crosslinking agent and dextrin in sequence, stirring and reacting at 95~100℃ for 30~40min, filtering, washing, drying, grinding to obtain water-absorbing resin. The preparation method of the sulfonic acid modified bentonite includes the following steps: (1) Bentonite and 3-(isobutyryloxy)propyltrimethoxysilane with a mass ratio of 1:0.1 are added to 80% ethanol aqueous solution and dispersed evenly, treated at 60℃ for 2h, washed and dried to obtain alkenyl modified bentonite; (2) Alkenyl modified bentonite, mercaptoacetic acid and azobisisobutyronitrile with a mass ratio of 1:0.15:0.001 are added to deionized water and mixed evenly, stirred at 75℃ for 2h, washed and dried to obtain carboxyl modified bentonite; (3) Carboxyl modified bentonite, EDC, NHS and taurine with a mass ratio of 1:0.12:0.08:0.1 are mixed evenly, stirred at 50℃ for 5h, washed and dried to obtain sulfonic acid modified bentonite.

2. The preparation process of a reverse osmosis high-absorbency sanitary pad according to claim 1, characterized in that: The crosslinking agent accounts for 0.5-1 wt% of acrylic acid; the degree of neutralization is 65-75%.

3. The preparation process of a reverse osmosis high-absorbency sanitary pad according to claim 1, characterized in that: The raw materials of the water-absorbing resin include acrylic acid, acrylamide, sulfonic acid-modified bentonite, and dextrin in a mass ratio of 10:6~10:2.5~3.2:2~2.2; and the cerium ammonium nitrate accounts for 0.1~0.2 wt% of the acrylic acid.

4. The preparation process of a reverse osmosis high-absorbency sanitary pad according to claim 1, characterized in that: The preparation method of the crosslinking agent includes the following steps: (1) Under a nitrogen atmosphere, C21-diacid, trimethylolpropane, anhydrous zinc acetate, and hydroquinone are mixed evenly and stirred at 180~185℃ for 6~8h, purified, and C21-diacid di(trimethylolpropane) ester is obtained; (2) Under a nitrogen atmosphere, C21-diacid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate, and azobisisobutyronitrile are mixed evenly and stirred at 60~70℃ for 6~8h. Stir the reaction at ℃ for 3-5 h, purify, and obtain sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester; (3) Under a nitrogen atmosphere, mix sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, maleic anhydride, and 4-dimethylaminopyridine evenly, stir the reaction at 70-75℃ for 8-12 h, add p-hydroxyanisole, glycidyl methacrylate and tetrabutylammonium bromide, stir the reaction at 110-120℃ for 8-12 h, purify, and obtain crosslinking agent.

5. The preparation process of a reverse osmosis high-absorption sanitary pad according to claim 4, characterized in that: The raw materials for the C21-diacarboxylic acid di(trimethylolpropane) ester include C21-diacarboxylic acid, trimethylolpropane, anhydrous zinc acetate, and hydroquinone in a mass ratio of 20:16~16.4:0.03~0.04:1~1.

1. The raw materials for the sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester include C21-dicarboxylic acid di(trimethylolpropane) ester, sodium 3-mercapto-1-propanesulfonate, and azobisisobutyronitrile in a mass ratio of 20:5.5~5.7:0.01~0.

05. The crosslinking agent comprises the following raw materials, in parts by weight: 20 parts of sulfonic acid C21-dicarboxylic acid di(trimethylolpropane) ester, 10.5-10.7 parts of maleic anhydride, 0.1-0.2 parts of 4-dimethylaminopyridine, 0.05-0.1 parts of p-hydroxyanisole, 7.6-7.8 parts of glycidyl methacrylate, and 0.2-0.3 parts of tetrabutylammonium bromide.

6. The preparation process of a reverse osmosis high-absorbency sanitary pad according to claim 1, characterized in that: The raw materials of the skin-friendly surface layer include one or more of PP nonwoven fabric, PE nonwoven fabric, and ES nonwoven fabric; the raw materials of the breathable bottom film layer include either polyolefin breathable film or polyurethane breathable film.

7. A reverse osmosis high absorbency sanitary pad prepared according to any one of claims 1 to 6.

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