Cellulose-based superabsorbent hydrogel bead preparation method, hydrogel beads prepared thereby, and absorbent article comprising same

Abstract

The present invention relates to a cellulose-based hydrogel bead preparation method, hydrogel beads prepared thereby, and an absorbent article comprising same, the preparation method enabling hydrogel beads to be washed with water without a separate organic solvent in a post-treatment process and shortening a drying time of the hydrogel beads, thereby enabling excellent economic feasibility and safety. In addition, the hydrogel beads prepared by the preparation method and the absorbent article comprising same may have excellent water absorption capacity and atmospheric water capturing ability while also being biodegradable, thereby being environmentally friendly and easily recyclable.

Description

Method for producing cellulose-based superabsorbent hydrogel beads, hydrogel beads produced therefrom, and absorbent articles comprising the same

[0001] This specification claims the benefit of Korean Patent Application No. 10-2023-0097972, filed with the Korean Intellectual Property Office on July 27, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for producing a cellulose-based superabsorbent hydrogel bead, a hydrogel bead produced therefrom, and an absorbent article comprising the same.

[0003]

[0004] Super absorbent polymers (SAPs) are hydrophilic polymers capable of absorbing tens to hundreds of times their own weight in water-soluble liquids. They are functional materials that contain aqueous solutions but are insoluble in them, and can maintain their absorbency even when a load is applied after sufficiently absorbing the aqueous solution. They are widely used in a variety of fields, including disposable sanitary products such as infant / adult diapers and feminine hygiene pads, as well as absorbent pads and ice packs for food packaging, soil moisture regulators for agriculture / horticulture, medical absorbent patches, and moisture-capturing wildfire prevention gels.

[0005] However, commercially available superabsorbent resins are manufactured based on non-biodegradable petroleum-based polymers, and cause serious environmental pollution, such as the generation of hazardous substances such as dioxins during the incineration and landfill of superabsorbent resin waste. Therefore, it is necessary to develop an eco-friendly superabsorbent material that can replace petroleum-based superabsorbent resins.

[0006] Cellulose, a natural biomass resource, is an environmentally friendly material abundant in nature. Its high hydroxyl content allows it to be used as a superabsorbent polymer, such as a superabsorbent resin. However, cellulose that has not undergone chemical treatment, such as crosslinking, lacks a water-retaining structure and flows as a highly viscous aqueous solution upon absorption. This precludes its application in disposable hygiene products such as diapers and sanitary pads, absorbent pads for food packaging, medical absorbent patches, and forest fire prevention gels.

[0007] To address these issues, one example of a method for manufacturing a cellulose-based superabsorbent polymer having a structure capable of retaining moisture includes a method of manufacturing a modified cellulose in which the hydroxyl groups of the cellulose are replaced with carboxyl groups, by adding an acrylic resin such as acrylic acid. However, the acrylic resin is not only non-biodegradable but also toxic, which can be harmful to the environment and the human body. In addition, it has the disadvantage of having lower physical properties compared to 100% petrochemical-based superabsorbent polymers.

[0008] As another example of a method for producing a cellulose-based superabsorbent polymer, a three-dimensional network-like structure such as a hydrogel can be produced by adding epichlorohydrin compounds, aldehyde compounds, and glycidyl compounds to modified cellulose in which the hydroxyl groups of the cellulose are replaced with carboxyl groups. However, the cellulose-based hydrogel has the disadvantage of having inferior physical properties such as water absorption rate and atmospheric moisture capture rate compared to existing superabsorbent resin materials derived from fossil fuels. In addition, when washed with water during the post-treatment process to wash away residual compounds and unreacted samples immediately after gel formation, the hydrogel absorbs water, making dehydration difficult and taking a long time to dry. Therefore, in order to shorten the drying time, a method of replacing the solvent with an organic solvent such as ethanol, methanol, and acetone has been mainly used in the past. In this case, washing and replacing with organic solvents and drying not only requires a lot of money, but there is also a risk of fire and explosion during the process.

[0009] Therefore, there is a need for a technology that can manufacture an environmentally friendly, non-toxic, biodegradable superabsorbent material that has properties comparable to those of petroleum-based superabsorbent resins, is simple to manufacture, and is biodegradable for the protection of the environment and human body.

[0010]

[0011] The problem to be solved by the present invention is to provide a method for manufacturing hydrogel beads with excellent safety and economy by being able to wash hydrogel beads with water without a separate organic solvent and shortening the drying time of hydrogel beads.

[0012] In addition, the present invention provides a hydrogel bead manufactured by the above manufacturing method and having excellent moisture absorption capacity and atmospheric moisture capture capacity.

[0013] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0014]

[0015] According to one aspect of the present invention, a method for producing a cellulose-based hydrogel bead is provided, comprising: a step of preparing a mixture by stirring a cellulose raw material suspension containing a cellulose raw material, a crosslinking agent, and a catalyst; a step of dropping the mixture in a saline solution in the form of drops to encapsulate the mixture; and a step of crosslinking the encapsulated mixture to prepare a hydrogel bead.

[0016] In addition, according to another aspect of the present invention, a cellulose-based hydrogel bead is provided, which is manufactured by the method for manufacturing the cellulose-based hydrogel bead and absorbs atmospheric moisture of 1 to 10 times the dry weight of the cellulose-based hydrogel bead.

[0017] In addition, according to another aspect of the present invention, an absorbent article comprising the cellulose-based hydrogel beads is provided.

[0018]

[0019] A method for manufacturing cellulose-based hydrogel beads according to one embodiment of the present invention can wash hydrogel beads with water without a separate organic solvent in a post-processing step, and can shorten the drying time of hydrogel beads, thereby improving economic efficiency and safety.

[0020] In addition, the cellulose-based hydrogel beads manufactured by the above method are biodegradable and thus environmentally friendly, and can have excellent moisture absorption capacity and atmospheric moisture capture capacity.

[0021] Furthermore, the cellulose-based hydrogel beads only swell when they absorb water, but maintain their overall shape (structure), so they can be easily recycled after drying.

[0022] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the specification herein.

[0023]

[0024] When a part in this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0025] Throughout this specification, when it is said that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0026] Throughout this specification, the unit “parts by weight” means the weight ratio of each component.

[0027] Throughout this specification, concentration may be a percent concentration, which is the mass of solute dissolved in a unit mass of solution expressed as a percentage. Accordingly, the unit may be written as “%” or “wt%,” and for example, a 5 wt% calcium chloride solution means a concentration where 5 g of calcium chloride is dissolved in 100 g of calcium chloride solution.

[0028] Hereinafter, the present invention will be described in more detail.

[0029] One embodiment of the present invention provides a method for producing a cellulose-based hydrogel bead, comprising the steps of: preparing a mixture by stirring a cellulose raw material suspension containing a cellulose raw material, a crosslinking agent, and a catalyst; dropping the mixture in the form of drops into a saline solution to encapsulate the mixture; and crosslinking the encapsulated mixture to produce a hydrogel bead.

[0030] According to one embodiment of the present invention, the cellulose raw material may include at least one cellulose raw material among a cellulose derivative and a cellulose fiber.

[0031] The above cellulose derivative may include one or more selected from alkyl cellulose, carboxy cellulose, acetyl cellulose, nitro cellulose, and hydro cellulose.

[0032] Specifically, the alkyl cellulose may include at least one selected from methyl cellulose (MC), dimethyl cellulose, ethyl cellulose (EC), and methylethyl cellulose. The carboxy cellulose may include at least one selected from carboxymethyl cellulose (CMC), carboxymethylethyl cellulose, and carboxyethylmethyl cellulose. The acetyl cellulose may include at least one selected from cellulose acetate (CA), triacetyl cellulose (TAC), acetyl methyl cellulose, and acetyl ethyl cellulose. The nitrocellulose may be cellulose nitrate (CN). The hydrocellulose may include at least one selected from hydroxypropyl methylcellulose (HPMC), hydroxyethyl methylcellulose, hydroxyethyl cellulose, 2-hydroxyethyl cellulose, methyl 2-hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxybutyl methyl cellulose.When the above-mentioned cellulose raw material includes the above-mentioned cellulose derivative, the hydrogel beads produced may have excellent moisture absorption capacity and atmospheric moisture capture capacity, and the moisture absorption capacity may be the absorption capacity of distilled water or saline solution.

[0033] The above cellulose fiber may be a cellulose fiber manufactured from one or more selected from woody biomass and non-woody biomass. Specifically, the woody biomass may be one or more selected from coniferous wood chips and hardwood wood chips, and the non-woody biomass may be one or more selected from bamboo, kenaf, hemp, rice, bagasse, seaweed, corn stalks, corn cores, rice straw, rice husks, wheat straw, and sugarcane stalks, but the types of the woody biomass and non-woody biomass are not limited. By using the cellulose fiber manufactured from the woody biomass and non-woody biomass, an environmentally friendly hydrogel bead having high biodegradability can be manufactured.

[0034] According to one embodiment of the present invention, the cellulose raw material may be at least one selected from carboxymethyl cellulose, methyl cellulose, ethyl cellulose, methylethyl cellulose, cellulose acetate, triacetyl cellulose, acetylmethyl cellulose, acetylethyl cellulose, cellulose nitrate, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose, hydroxyethyl cellulose, 2-hydroxyethyl cellulose, methyl 2-hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxybutylmethyl cellulose.

[0035] The above cellulose raw material suspension can be prepared by mixing the cellulose raw material with a solvent. The solvent may be one or more selected from distilled water, water, salt water, acetone, ethanol, and methanol. By using the above-mentioned solvent, the cellulose raw material can be uniformly mixed, facilitating the production of hydrogel beads.

[0036] According to one embodiment of the present invention, the content of the cellulose raw material may be 1 part by weight to 10 parts by weight with respect to 100 parts by weight of the mixture. Specifically, the content of the cellulose raw material may be 1 part by weight to 10 parts by weight, 1 part by weight to 8 parts by weight, 1 part by weight to 6 parts by weight, 1 part by weight to 5 parts by weight, 2 parts by weight to 10 parts by weight, 2 parts by weight to 9 parts by weight, 2 parts by weight to 5 parts by weight, or 3 parts by weight to 5 parts by weight. When the content of the cellulose raw material is within the above-mentioned range, the water absorption capacity and atmospheric moisture capture capacity of the manufactured hydrogel beads may be excellent.

[0037] According to one embodiment of the present invention, the crosslinking agent may be at least one selected from an epoxy compound and an aldehyde compound.

[0038] Specifically, the crosslinking agent may be at least one selected from an epoxy compound and an aldehyde compound. Specifically, the epoxy compound may include at least one selected from epichlorohydrin, glycerol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polybutadiene diglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, or pentaerythritol polyglycidyl ether. More specifically, the epoxy compound may contain at least two glycidyl groups within its molecular structure.

[0039] In addition, the aldehyde compound may include at least one of glutaraldehyde, formaldehyde, dialdehyde starch, succinic aldehyde, acrylaldehyde, oxalaldehyde, 2-methylacrylaldehyde, 2-oxopropanal, dextrin aldehyde, grioxal, succialdehyde, and adipaldehyde. By using the epoxy compound and the aldehyde compound as a crosslinking agent, crosslinking between the celluloses can be easily formed, and thereby a hydrogel and hydrogel bead having a three-dimensional network structure can be stably formed. Furthermore, the moisture absorption capacity and atmospheric moisture capture capacity of the manufactured hydrogel bead can be improved.

[0040] According to one embodiment of the present invention, the content of the crosslinking agent may be 0.7 to 17.5 parts by weight with respect to 100 parts by weight of the mixture. Specifically, the content of the crosslinking agent may be 0.7 parts by weight to 17.5 parts by weight, 0.7 parts by weight to 17 parts by weight, 0.7 parts by weight to 16.5 parts by weight, 0.7 parts by weight to 10 parts by weight, 0.7 parts by weight to 8 parts by weight, 1 part by weight to 17.5 parts by weight, 1 part by weight to 17 parts by weight, 1 part by weight to 16.5 parts by weight, 1 part by weight to 10 parts by weight, 1 part by weight to 7 parts by weight, 1.25 parts by weight to 17.5 parts by weight, 1.25 parts by weight to 17 parts by weight, 1.25 parts by weight to 16.5 parts by weight, 1.25 parts by weight to 10 parts by weight, or 1.25 parts by weight to 6 parts by weight. When the content of the cross-linking agent is within the above-mentioned range, cross-linking between the celluloses can be appropriately formed, and the moisture absorption capacity and atmospheric moisture capture capacity of the manufactured hydrogel beads can be improved.

[0041] According to one embodiment of the present invention, the content ratio of the cellulose raw material and the cross-linking agent may be 1:0.7 to 1:1.65. Specifically, the content ratio of the cellulose raw material and the cross-linking agent may be 1:0.7 to 1:1.65, 1:0.75 to 1:1.65, 1:0.85 to 1:1.65, 1:1 to 1:1.65, 1:1.1 to 1:1.65, 1:1.25 to 1:1.65, or 1:1.3 to 1:1.65. When the content ratio of the cellulose raw material and the cross-linking agent is within the above-mentioned range, cross-linking between the cellulose can be appropriately formed, and the moisture absorption capacity and atmospheric moisture capture capacity of the manufactured hydrogel beads can be improved.

[0042] According to one embodiment of the present invention, the catalyst may be at least one selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide. By using the above-described catalyst, the time for the cross-linking reaction between cellulose can be shortened, and the temperature at which the cross-linking reaction is performed can be lowered.

[0043] According to one embodiment of the present invention, the content of the catalyst may be 0.1 to 10 parts by weight with respect to 100 parts by weight of the mixture. Specifically, the content of the catalyst may be 0.1 to 10 parts by weight, 0.1 to 8 parts by weight, 0.1 to 6 parts by weight, 1 to 10 parts by weight, 1 to 7 parts by weight, 1 to 5 parts by weight, or 1 to 3 parts by weight. When the content of the catalyst is within the above-mentioned range, the cross-linking reaction between the celluloses is promoted, thereby reducing the manufacturing time of the cellulose-based hydrogel and improving the moisture absorption capacity and atmospheric moisture capture capacity of the manufactured hydrogel beads.

[0044] According to one embodiment of the present invention, the brine solution may be at least one selected from a calcium chloride (CaCl2) aqueous solution, a sodium chloride (NaCl2) aqueous solution, an ammonium chloride (NH4Cl) aqueous solution, a magnesium chloride (MgCl2) aqueous solution, a manganese chloride (MnCl2) aqueous solution, a barium chloride (BaCl2) aqueous solution, a zinc chloride (ZnCl2) aqueous solution, a calcium sulfate (CaSO4) aqueous solution, a sodium sulfate (Na2SO4) aqueous solution, an ammonium sulfate ((NH4)2SO4) aqueous solution, a magnesium sulfate (MgSO4) aqueous solution, a manganese sulfate (MnSO4) aqueous solution, a barium sulfate (BaSO4) aqueous solution, and a zinc sulfate (ZnSO4) aqueous solution. When using the aforementioned type of saline solution, the salt of the saline solution forms an ionic bond on the surface of the mixture in the form of droplets dropped into the saline solution, thereby easily maintaining the beads. Furthermore, the moisture absorption capacity and atmospheric moisture capture capacity of the hydrogel beads manufactured may vary depending on the type of saline solution, and preferably, the moisture absorption capacity and atmospheric moisture capture capacity of the hydrogel beads manufactured using a calcium chloride aqueous solution may be excellent.

[0045] According to one embodiment of the present invention, the concentration of the brine solution may be 1 wt% to 90 wt%. Specifically, the concentration of the brine solution may be 1 wt% to 90 wt%, 10 wt% to 90 wt%, 20 wt% to 90 wt%, 30 wt% to 90 wt%, 40 wt% to 90 wt%, 40 wt% to 80 wt%, 40 wt% to 70 wt%, 50 wt% to 90 wt%, 50 wt% to 80 wt%, 50 wt% to 70 wt%, 55 wt% to 85 wt%, 55 wt% to 75 wt%, 60 wt% to 90 wt%, 60 wt% to 80 wt%, or 60 wt% to 70 wt%. When the concentration of the above-mentioned saline solution is within the above-mentioned range, hydrogel beads can be easily manufactured, and the manufactured hydrogel beads can have excellent moisture absorption capacity and atmospheric moisture capture capacity.

[0046] According to one embodiment of the present invention, the stirring may be performed at a temperature of 20°C to 50°C for 5 to 60 minutes. Specifically, the stirring may be performed to form a cellulose gel by mixing a mixture including a cellulose raw material suspension, a crosslinking agent, and a catalyst. More specifically, the stirring temperature may be 20°C to 50°C, 20°C to 40°C, 20°C to 30°C, or room temperature (25°C). In addition, the stirring time may be 5 to 60 minutes, 5 to 40 minutes, 5 to 20 minutes, 10 to 60 minutes, 10 to 50 minutes, 10 to 30 minutes, or 10 to 20 minutes. When the stirring temperature and stirring time are within the above-mentioned ranges, the cellulose raw material, the crosslinking agent, and the catalyst can be uniformly mixed, and thus, hydrogel beads can be stably manufactured.

[0047] According to one embodiment of the present invention, the step of encapsulating the mixture by dropping the mixture in the form of drops into a saline solution may be such that the surface of the drop-shaped mixture (bead-shaped) dropped into the saline solution is encapsulated by dropping the mixture in the form of drops into the saline solution, thereby maintaining the drop-shaped shape. Specifically, the surface of the drop-shaped mixture dropped into the saline solution may be hardened and translucent by ion bonding with the salt of the saline solution. Accordingly, the encapsulation may mean that the surface of the dropped mixture in the saline solution is hardened.

[0048] The salt ionically bonded to the surface of the drop-shaped mixture dropped into the above-mentioned saline solution may be a salt of the above-mentioned saline solution, and specifically, may be a cation of the saline solution. More specifically, a cation (sodium, etc.) that is ionically bonded or was ionically bonded to the cellulose raw material of the drop-shaped cellulose gel in the saline solution (cellulose derivative of hydrogel beads or cellulose fibers) may be replaced by a cation of the saline solution (calcium cation, sodium cation, ammonium cation, magnesium cation, manganese cation, barium cation or zinc cation). The cation that was ionically bonded to the above-mentioned cellulose raw material may be one that was ionically bonded during the process of manufacturing the cellulose raw material.

[0049] By encapsulating the droplet-shaped mixture dropped into the above-described saline solution, the hydrogel beads can be washed with water without a separate organic solvent during the post-processing process. Furthermore, by shortening the washing and drying time of the hydrogel beads, large quantities of hydrogel beads can be efficiently manufactured quickly and at low cost.

[0050] According to one embodiment of the present invention, the step of crosslinking the encapsulated mixture to produce hydrogel beads may be a step of reacting cellulose, a crosslinking agent, and a catalyst included in the encapsulated mixture to produce hydrogel beads.

[0051] According to one embodiment of the present invention, the cross-linking reaction may be performed at a temperature of 50°C to 100°C for 10 minutes to 6 hours. Specifically, the temperature of the cross-linking reaction may be 50°C to 100°C, 50°C to 90°C, 50°C to 80°C, 55°C to 100°C, 55°C to 85°C, 55°C to 75°C, 60°C to 100°C, 60°C to 90°C, or 60°C to 80°C, and the time of the cross-linking reaction may be 10 minutes to 6 hours, 10 minutes to 4 hours, 10 minutes to 3 hours, 30 minutes to 6 hours, 30 minutes to 5 hours, 30 minutes to 4 hours, 1 hour to 6 hours, 1 hour to 5 hours, or 1 hour to 3 hours. When the temperature and time of the cross-linking reaction are within the above-mentioned ranges, hydrogel beads can be stably manufactured.

[0052] According to one embodiment of the present invention, after the step of manufacturing the hydrogel beads, the method may further include a step of washing and drying the manufactured hydrogel beads.

[0053] According to one embodiment of the present invention, the washing may be performed with water. Specifically, impurities (unreacted residual compounds) of the manufactured hydrogel beads may be removed with water. The washing may be repeated several times, and for example, the washing may be performed 1 to 5 times with water. When washing under the above-described conditions, the hydrogel beads can be washed with water without a separate organic solvent, which is safe and reduces the drying time of the hydrogel beads, thereby improving cost-effectiveness.

[0054] After the washing and before drying, a step of dehydrating the hydrogel beads may be further included. Specifically, the washed hydrogel beads may be dehydrated using a compression filtration or vacuum filtration method. Through the dehydration, the solvent contained in the hydrogel beads can be effectively removed in the subsequent drying step, thereby improving drying efficiency and further reducing the time and cost of manufacturing the hydrogel beads.

[0055] According to one embodiment of the present invention, the drying may be performed using hot air drying, reduced pressure drying, natural drying, or microwave drying methods. By drying using the aforementioned drying methods, the hydrogel beads produced can be produced without re-agglomeration even after drying and can have excellent moisture absorption and atmospheric moisture capture capabilities.

[0056] The drying may be performed at a temperature of 20°C to 200°C. Specifically, the drying temperature may be 20°C to 200°C, 20°C to 150°C, 20°C to 80°C, 50°C to 180°C, 50°C to 130°C, or 50°C to 100°C. When the temperature range of the drying is within the above-described range, the manufactured hydrogel beads can be prevented from being damaged by heat, and the hydrogel beads can be easily dried.

[0057] The above hot air drying method can be performed at a temperature of 20°C or higher and 200°C or lower under conditions of atmospheric pressure (1±0.2 atm) for a time of 1 hour or longer and 24 hours or shorter.

[0058] The above-mentioned reduced pressure drying method can be performed at a pressure of 1 mTorr or more and 50 mTorr or less and a temperature of 20°C or more and 200°C or less for a time of 1 hour or more and 24 hours or less.

[0059] The above natural drying method can be performed at atmospheric pressure (1±0.2 atm) and room temperature (25±5 ℃) for a period of 1 hour or more and 24 hours or less.

[0060] The above microwave drying method can dry 10% to 90% of the weight of the wet hydrogel beads using electric power energy of 250 W to 1000 W.

[0061] One embodiment of the present invention provides a cellulose-based hydrogel bead manufactured by the method for manufacturing the cellulose-based hydrogel bead, and absorbs atmospheric moisture of 1 to 10 times the dry weight of the cellulose-based hydrogel bead. The atmospheric moisture absorption amount of the hydrogel bead may vary depending on the relative humidity and absorption time, and specifically, when absorbed for 72 hours at 90% relative humidity, the hydrogel bead may have an atmospheric moisture absorption amount of 1 to 10 times, 1 to 7 times, 2 to 10 times, 2 to 8 times, 2 to 6 times, 4 to 10 times, 4 to 8 times, or 4 to 6 times the dry weight of the hydrogel bead.

[0062] One embodiment of the present invention provides an absorbent article comprising the cellulose-based hydrogel beads. The absorbent article may comprise at least one of a sanitary product, a soil moisture regulator, an absorbent pad, an ice pack, and a hydro patch. Specifically, the absorbent article may comprise at least one of sanitary products such as diapers for infants and adults, sanitary pads for women, soil moisture regulators for agriculture or gardening, absorbent pads for food packaging, ice packs, medical hydro patches, and gels for forest fire prevention. The absorbent article of the above type, because it comprises the hydrogel beads, has excellent moisture absorption and high atmospheric moisture capture rates, and is also biodegradable, thereby reducing environmental pollution caused by incineration and landfill processes, making it environmentally friendly. In addition, calcium chloride, which is commonly included in absorbent articles, is difficult to recycle due to its deliquescent nature, which causes it to dissolve when it absorbs water. However, the hydrogel beads retain their shape even after absorbing water, and can thus be easily recycled by drying.

[0063] The matters mentioned in the method for manufacturing cellulose-based hydrogel beads of the present invention, cellulose-based hydrogel beads and absorbent articles including cellulose-based hydrogel beads are equally applicable unless they are contradictory to each other.

[0064]

[0065] Hereinafter, the present invention will be described in detail with examples and experimental examples to specifically explain the present invention. However, the examples and experimental examples according to the present invention may be modified in various different forms, and the scope of the present invention is not construed as being limited to the examples and experimental examples described below. The examples and experimental examples in this specification are provided to more fully explain the present invention to those of average skill in the art.

[0066]

[0067] Example 1-1. Preparation of cellulose-based hydrogel beads

[0068] A carboxymethyl cellulose suspension was prepared by mixing 3 g of carboxymethyl cellulose having a degree of substitution of 0.8 as a cellulose raw material with distilled water. Thereafter, 3 g of sodium hydroxide (NaOH, Sodium hydroxide, DAEJUNG Chemicals & Metals co. Ltd., Korea) as a catalyst and 4 g of epichlorohydrin (Epi, Epichlorohydrin, Guaranteed, JUNCEI Chemicals co. Ltd., Japan) as a crosslinking agent were sequentially added to the carboxymethyl cellulose suspension, and the mixture was stirred at 600 rpm at room temperature for 10 minutes using a stirrer. At this time, with respect to 100 parts by weight of the mixture, the content of carboxymethyl cellulose was 3 parts by weight, the content of sodium hydroxide was 3 parts by weight, and the content of epichlorohydrin was 4 parts by weight.

[0069] Thereafter, the mixture was dropped into a 60 wt% calcium chloride aqueous solution in the form of droplets to produce a droplet-encapsulated mixture. Specifically, the mixture was dropped from a height of 25 cm at a rate of 0.2 mL / min using a syringe (needle inner diameter: 2 mm). Then, the droplet-encapsulated mixture was cross-linked in a constant-temperature water bath at 70°C for 2 hours to produce hydrogel beads.

[0070] The hydrogel beads after the reaction were filtered through a 200 mesh screen and washed five times with water. The repeatedly washed hydrogel beads were dried with hot air at 50°C to produce final dried cellulose-based hydrogel beads.

[0071]

[0072] Examples 1-2 to 1-4, Examples 2-1 to 2-10, Examples 3-1 and 3-2

[0073] Except that the content of carboxymethyl cellulose (CMC), the content of sodium hydroxide, the content of epichlorohydrin (Epi), and the concentration of the calcium chloride aqueous solution were adjusted as shown in Table 1 below, cellulose-based hydrogel beads of Examples 1-2 to 1-4, Examples 2-1 to 2-10, Example 3-1, and Example 3-2 were manufactured in the same manner as in Example 1-1. In Table 1 below, the content of CMC, the content of NaOH, and the content of Epi are based on 100 parts by weight of the mixture.

[0074] CMC content (parts by weight) NaOH content (parts by weight) Epi content (parts by weight) Concentration of calcium chloride aqueous solution (wt%) Example 1-133460 Example 1-23.515.860 Example 1-355360 Example 1-4558.560 Example 2-133470 Example 2-233480 Example 2-333490 Example 2-433450 Example 2-533440 Example 2-633430 Example 2-733420 Example 2-833410 Example 2-93345 Example 2-103341 Example 3-131460 Example 3-232460

[0075]

[0076] Examples 4-1 and 4-2

[0077] Cellulose-based hydrogel beads of Examples 4-1 and 4-2 were manufactured in the same manner as in Example 1-1, except that an ammonium chloride (NH4Cl) aqueous solution or a magnesium chloride (MgCl2) aqueous solution was used instead of a calcium chloride (CaCl2) aqueous solution as shown in Table 2 below.

[0078] Content of CMC (parts by weight) Content of NaOH (parts by weight) Content of Epi (parts by weight) Type of salt solution Concentration of salt solution (wt%) Example 1-1334 Calcium chloride solution 60 Example 4-1334 Ammonium chloride solution 60 Example 4-2334 Magnesium chloride solution 60

[0079]

[0080] Experimental Example 1. Moisture Absorption Evaluation

[0081] The water absorption of the hydrogel beads manufactured in Examples 1-1 to 1-4, Examples 2-1 to 2-10, Examples 3-1, 3-2, 4-1, and 4-2 was measured as follows.

[0082] Specifically, the mass of the completely dried hydrogel beads was measured, and then immersed in distilled water or saline solution for 10 minutes. The hydrogel beads were then removed, left to stand for 5 minutes to remove any remaining moisture, and then the mass of the hydrogel beads was measured. Using the same method as above, the mass of the hydrogel beads was measured after immersion in distilled water or saline solution for 30 minutes, 1 hour, 3 hours, and 24 hours.

[0083] The mass of the completely dried hydrogel beads and the mass of the hydrogel beads after immersion were substituted into the following mathematical equation 1 to calculate the water absorption of the hydrogel beads, and the results are shown in Tables 3 and 4.

[0084] [Mathematical Formula 1]

[0085] W t = (M t - M0) / M0

[0086] In the above mathematical expression 1, W t is the water absorption (g / g) for saline or distilled water after t hours (or minutes), and M t is the mass (g) of the hydrogel beads after immersion for t hours and after t hours, and M0 is the mass (g) of the initially dried hydrogel beads.

[0087] Distilled water absorption W 10분 (g / g)W 0.5 (g / g)W1(g / g)W3(g / g)W 24(g / g) Example 1-17.95 8.10 9.36 12.99 38.46 Example 1-27.0 38.09 10.17 13.89 34.34 Example 1-37.8 19.42 12.40 18.37 35.72 Example 1-47.42 8.76 12.78 18.16 23.10 Example 2-17.25 7.78 8.33 12.90 38.14 Example 2-25.39 5.28 5.99 8.07 34.88 Example 2-36.1 36.0 16.40 8.25 34.15 Example 2-46.5 9.9 51 11.16 16.75 33.41 Example 2-59.749.5211.9019.5933.83 Example 2-69.1811.7516.7627.7533.54 Example 2-78.2311.7713.9722.6932.91 Example 2-89.0311.9114.0925.0732.90 Example 2-99.4612.5714.1520.1534.38 Example 2-1013.0919.7925.8830.7838.89 Example 3-18.8010.2012.0013.3034.20 Example 3-27.708.4010.2013.1035.20Example 4-17.6011.9015.8016.5018.80Example 4-22.803.304.206.8018.30

[0088]

[0089] Saline absorption W 10분 (g / g)W 0.5 (g / g)W1(g / g)W3(g / g)W 24(g / g) Example 1-16.7 28.18 9.42 13.56 26.39 Example 1-27.89 8.43 9.87 11.28 25.16 Example 1-38.86 10.39 11.81 20.5 120.47 Example 1-46.40 8.09 9.84 15.40 20.00 Example 2-16.56 7.69 7.98 10.24 24.76 Example 2-26.37 6.64 9.25 13.03 24.70 Example 2-35.80 6.06 6.55 8.39 24.70 Example 2-48.50 9.57 10.19 15.65 25.29 Example 2-59.7711.3413.2017.9125.18Example 2-69.0212.2714.8523.0424.54Example 2-79.7313.2717.3520.0324.51Example 2-89.4613.3812.4019.5525.17Example 2-910.0913.4114.7321.5828.35Example 2-1017.1920.8127.7729.0536.68Example 3-19.409.309.7010.2023.30Example 3-29.909.009.4010.3022.10 Example 4-15.207.108.909.3011.70 Example 4-22.302.403.403.806.70

[0090] Looking at Tables 3 and 4 above, it was confirmed that the hydrogel beads of Examples 1-1 to 1-4, Examples 2-1 to 2-10, Examples 3-1, 3-2, Example 4-1, and Example 4-2 all had excellent water absorption capacities of 10 g / g or more for saline solution or distilled water.

[0091] Experimental Example 2. Evaluation of atmospheric moisture capture capacity

[0092] The atmospheric moisture capture amount of the hydrogel beads manufactured in Examples 1-1 to 1-4, Examples 2-1 to 2-10, Examples 3-1, 3-2, 4-1, and 4-2 was measured.

[0093] Specifically, the mass of the completely dried hydrogel beads was measured, and then stored in a desiccator at relative humidity of 30%, 50%, 70%, and 90%, and the mass of the hydrogel beads was measured after 24 hours, 48 ​​hours, and 72 hours.

[0094] In addition, the mass of the completely dried hydrogel beads and the hydrogel beads after storage in a desiccator were substituted into the following mathematical equation 1 to calculate the moisture capture amount of the hydrogel beads, and the results are shown in Tables 5, 6, 7, and 8.

[0095] [Equation 2]

[0096] AW t = (AM t - AM0) / AM0

[0097] In the above mathematical expression 2, AW t is the atmospheric moisture capture amount (g / g) after t hours, and AM t is the mass (g) of the hydrogel beads stored in a desiccator at a constant relative humidity for t hours, and AM0 is the mass (g) of the initially dried hydrogel beads.

[0098] Relative humidity 30 %AW 24 (g / g)AW 48 (g / g)AW 72 (g / g) Example 1-11.581.781.79 Example 1-21.591.801.82 Example 1-31.191.201.22 Example 1-41.211.221.24 Example 2-11.541.771.78 Example 2-21.551.551.55 Example 2-31.501.461.46 Example 2-41.531.531.55 Example 2-51.531.531.54 Example 2-61.341.341.35 Example 2-71.251.251.27 Example 2-81.141.151.15 Example 2-91.051.061.07Example 2-101.031.031.04Example 3-11.091.101.10Example 3-21.011.031.04Example 4-11.531.551.59Example 4-21.571.611.65

[0099]

[0100] Relative humidity 50 %AW 24 (g / g)AW 48 (g / g)AW 72 (g / g) Example 1-12.0 3 2.1 4 2.17 Example 1-22.0 5 2.2 3 2.26 Example 1-31.4 9 1.6 1 1.63 Example 1-41.3 9 1.4 9 1.52 Example 2-12.0 2.1 4 2.15 Example 2-22.0 1 2.0 3 2.03 Example 2-31.9 7 1.9 8 2.02 Example 2-41.9 2 1.95 1.96 Example 2-5 1.8 4 1.8 7 1.89 Example 2-6 1.6 7 1.6 8 1.70 Example 2-7 1.5 8 1.6 0 1.61 Example 2-8 1.3 0 1.3 2 1.33 Example 2-91.151.181.19Example 2-101.121.131.14Example 3-11.101.101.10Example 3-21.031.041.05Example 4-11.942.012.01Example 4-22.032.112.11

[0101]

[0102] Relative humidity 70 %AW 24 (g / g)AW 48 (g / g)AW 72 (g / g) Example 1-12.47 2.61 2.61 Example 1-22.50 2.59 2.66 Example 1-31.58 1.65 1.67 Example 1-41.50 1.74 1.78 Example 2-12.42 2.60 2.60 Example 2-22.46 2.52 2.58 Example 2-32.49 2.50 2.56 Example 2-42.22 2.34 2.44 Example 2-52.10 2.23 2.30 Example 2-61.99 2.07 2.16 Example 2-71.96 2.06 2.13 Example 2-81.63 1.70 1.75 Example 2-91.271.291.31Embodiment 2-101.211.211.21Embodiment 3-12.152.372.39Embodiment 3-22.302.542.56Embodiment 4-11.061.071.09Embodiment 4-21.101.101.11

[0103]

[0104] Relative humidity 90 %AW 24(g / g)AW 48 (g / g)AW 72 (g / g) Example 1-13.95 4.12 4.46 Example 1-24.00 4.16 4.52 Example 1-32.97 3.07 3.30 Example 1-42.90 3.00 3.23 Example 2-13.91 4.10 4.45 Example 2-23.90 4.05 4.41 Example 2-33.89 4.09 4.43 Example 2-43.24 3.66 4.11 Example 2-53.22 3.65 4.05 Example 2-62.83 3.23 3.49 Example 2-72.66 3.04 3.25 Example 2-82.22 2.38 2.50 Example 2-91.601.681.74 Example 2-101.531.581.60 Example 3-13.323.914.11 Example 3-23.624.234.44 Example 4-12.923.183.36 Example 4-21.401.491.65

[0105] Looking at Examples 1-1, 1-2, 1-3 and 1-4 in Tables 5, 6, 7 and 8 above, it was confirmed that the atmospheric moisture capture amount (relative humidity 30%, 50%, 70% and 90%) of the hydrogel beads having a content ratio of carboxymethyl cellulose and epichlorohydrin of 1:1.33 (Example 1-1) and 1:1.64 (Example 1-2) was significantly superior to the atmospheric moisture capture amount of the hydrogel beads having a content ratio of carboxymethyl cellulose and epichlorohydrin of 1:0.6 (Example 1-3) and 1:1.7 (Example 1-4).

[0106] Looking at Examples 1-1, 2-1 to 2-10 in Tables 5, 6, 7 and 8 above, it was confirmed that the atmospheric moisture capture amount (relative humidity 30%, 50%, 70% and 90%) of the hydrogel beads having a calcium chloride aqueous solution concentration of 40 wt% to 90 wt% (Examples 1-1, 2-1 to 2-5) was significantly superior to the atmospheric moisture capture amount of the hydrogel beads having a calcium chloride aqueous solution concentration of 1 wt% to 30 wt% (Examples 2-6 to 2-10).

[0107] Looking at Examples 1-1, 3-1, and 3-2 in Tables 5, 6, 7, and 8 above, it was confirmed that the atmospheric moisture capture capacity (relative humidity 30%, 50%, 70%, and 90%) of the hydrogel beads having a sodium hydroxide content of 1 part by weight (Example 3-1), 2 parts by weight (Example 3-2), and 3 parts by weight (Example 1-1) were all excellent.

[0108] Looking at Examples 1-1, 4-1, and 4-2 in Tables 5, 6, 7, and 8 above, it was confirmed that the atmospheric moisture capture amount (relative humidity 30%, 50%, 70%, and 90%) of the hydrogel beads in which the saline solution was a calcium chloride solution (Example 1-1) was superior to the atmospheric moisture capture amounts of the hydrogel beads in which the saline solution was an ammonium chloride solution (Example 4-1) and a magnesium chloride solution (Example 4-2).

[0109]

[0110] Experimental Example 3. Inductively Coupled Plasma Analysis

[0111] The hydrogel beads manufactured in Examples 1-1, 2-1, and 2-4 to 2-9 were subjected to inductively coupled plasma (ICP) analysis.

[0112] Specifically, calcium cations (Ca 2+ ) and sodium cations (Na + ) to measure the concentration of hydrogel beads. 0.3 g of the hydrogel beads manufactured in Examples 1-1, 2-1, and 2-4 to 2-9 in the dried state was added with 6 ml of nitric acid, stirred at 90°C until the solution became transparent, and then filtered using a membrane filter. The filtrate was diluted 100 times with deionized distilled water and analyzed using an inductively coupled plasma optical spectrometer (ICP-OES, OPTIMA 7300DV), and the results are shown in Table 9.

[0113] Concentration of calcium chloride solution (wt%) Concentration of ions (ppm [mg / L])Ca 2+ Na + Example 1 - 160 wt% 872.96 17.90 Example 2 - 170 wt% 964.24 18.02 Example 2 - 450 wt% 854.42 18.94 Example 2 - 540 wt% 754.13 20.97 Example 2 - 630 wt% 708.24 20.11 Example 2 - 720 wt% 668.35 22.85 Example 2 - 810 wt% 633.30 25.49 Example 2 - 95 wt% 516.45 38.47

[0114] Looking at Table 9 above, it can be seen that as the concentration of the calcium chloride aqueous solution increases, the content of calcium cations included in the hydrogel beads increases, but the content of sodium cations tends to decrease.

[0115] Although the present invention has been described above through limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0116]

[0117]

[0118] The present invention relates to a method for manufacturing cellulose-based hydrogel beads, hydrogel beads manufactured thereby, and absorbent articles comprising the same. The method enables washing of hydrogel beads with water without a separate organic solvent in a post-processing step, and shortens the drying time of the hydrogel beads, thereby improving economic efficiency and safety. In addition, the hydrogel beads manufactured by the method and absorbent articles comprising the same have excellent moisture absorption and atmospheric moisture capture capabilities, are biodegradable, and are thus environmentally friendly and easily recyclable.

Claims

1. A step of preparing a mixture by stirring a cellulose raw material suspension containing a cellulose raw material, a crosslinking agent, and a catalyst; A step of encapsulating the mixture by dropping the mixture in the form of drops into a saline solution; and A method for producing cellulose-based hydrogel beads, comprising the step of cross-linking the encapsulated mixture to produce hydrogel beads.

2. In paragraph 1, A method for producing a cellulose-based hydrogel bead, wherein the cellulose raw material is at least one selected from carboxymethyl cellulose, methyl cellulose, ethyl cellulose, methylethyl cellulose, cellulose acetate, triacetyl cellulose, acetylmethyl cellulose, acetylethyl cellulose, cellulose nitrate, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose, hydroxyethyl cellulose, 2-hydroxyethyl cellulose, methyl 2-hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxybutylmethyl cellulose.

3. In paragraph 1, For 100 parts by weight of the above mixture, A method for producing cellulose-based hydrogel beads, wherein the content of the cellulose raw material is 1 to 10 parts by weight.

4. In paragraph 1, A method for producing a cellulose-based hydrogel bead, wherein the crosslinking agent is at least one selected from an epoxy-based compound and an aldehyde-based compound.

5. In paragraph 1, For 100 parts by weight of the above mixture, A method for producing a cellulose-based hydrogel bead, wherein the content of the cross-linking agent is 0.7 to 17.5 parts by weight.

6. In paragraph 1, A method for manufacturing a cellulose-based hydrogel bead, wherein the content ratio of the cellulose raw material and the crosslinking agent is 1:0.7 to 1:1.

65.

7. In paragraph 1, A method for producing a cellulose-based hydrogel bead, wherein the catalyst is at least one selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide.

8. In paragraph 1, For 100 parts by weight of the above mixture, A method for producing cellulose-based hydrogel beads, wherein the content of the catalyst is 0.1 to 10 parts by weight.

9. In paragraph 1, A method for producing a cellulose-based hydrogel bead, wherein the saline solution is at least one selected from a calcium chloride aqueous solution, a sodium chloride aqueous solution, an ammonium chloride aqueous solution, a magnesium chloride aqueous solution, a manganese chloride aqueous solution, a barium chloride aqueous solution, a zinc chloride aqueous solution, a calcium sulfate aqueous solution, a sodium sulfate aqueous solution, an ammonium sulfate aqueous solution, a magnesium sulfate aqueous solution, a manganese sulfate aqueous solution, a barium sulfate aqueous solution, and a zinc sulfate aqueous solution.

10. In paragraph 1, A method for producing cellulose-based hydrogel beads, wherein the concentration of the above saline solution is 1 wt% to 90 wt%.

11. In paragraph 1, A method for producing cellulose-based hydrogel beads, wherein the above stirring is performed at a temperature of 20°C to 50°C for 5 to 60 minutes.

12. In paragraph 1, A method for producing cellulose-based hydrogel beads, wherein the cross-linking reaction is performed at a temperature of 50°C to 100°C for 10 minutes to 6 hours.

13. In paragraph 1, After the step of manufacturing the above hydrogel beads, A method for producing cellulose-based hydrogel beads, further comprising the step of washing and drying the manufactured hydrogel beads.

14. In paragraph 13, A method for producing cellulose-based hydrogel beads, wherein the above washing is performed with water.

15. In paragraph 13, A method for manufacturing cellulose-based hydrogel beads, wherein the above drying is performed by hot air drying, reduced pressure drying, natural drying or microwave drying.

16. Manufactured by the method for manufacturing cellulose-based hydrogel beads of Article 1, A cellulose-based hydrogel bead that absorbs atmospheric moisture in an amount of 1 to 10 times its dry weight.

17. An absorbent article comprising the cellulose-based hydrogel beads of paragraph 16.