Superabsorbent resin film and absorbent articles containing the same

Abstract

The present invention relates to a superabsorbent resin film with excellent moisture absorption properties, and an absorbent article that contains the superabsorbent resin film, thereby improving external dampness and reducing skin rashes and other irritations that occur when warmed by the wearer's body, resulting in a superior user experience. [Solution] The thickness is 500 μm or less, and the moisture absorption capacity measured by the KS F 2611 standard is 10 to 100 g / m². 2 This is a superabsorbent polymer film.

Description

[Technical Field]

[0001] Mutual citation with related applications This application claims priority rights based on Korean Patent Application No. 10-2021-0039666 dated March 26, 2021, and Korean Patent Application No. 10-2022-0034232 dated March 18, 2022, and all content disclosed in the documents of said Korean patent applications is incorporated herein by reference.

[0002] The present invention relates to a superabsorbent resin film with excellent moisture absorption capacity and a water-absorbing article that contains the superabsorbent resin film, thereby improving the feeling of dampness on the outside and providing a superior user experience. [Background technology]

[0003] Absorbent items such as disposable diapers, sanitary napkins, and incontinence pads generally include a liquid-impermeable back sheet, an absorbent core, and a liquid-permeable top sheet that comes into contact with the wearer's skin. They may further include, if necessary, a breathable waterproof film to improve breathability, a decorative sheet to improve appearance, and leg elastics to improve comfort and prevent leakage.

[0004] In such absorbent articles, the liquid-permeable top sheet is made of a material that allows bodily fluids to pass rapidly through to the absorbent core, such as a synthetic polymer nonwoven fabric. The absorbent core is made of superabsorbent polymer, pulp, tissue, or nonwoven fabric, and rapidly absorbs and retains bodily fluids that have passed through the liquid-permeable top sheet. The liquid-impermeable back sheet prevents the bodily fluids absorbed by the absorbent core from leaking out, and is made of a woven or nonwoven fabric made of natural or synthetic fibers.

[0005] The aforementioned liquid-impermeable back sheet is designed to be waterproof for its intended purpose. However, if the waterproofing is excessively high, water vapor and air cannot pass through, leading to a decrease in wearing comfort. Therefore, liquid-impermeable back sheets typically use a breathable waterproof woven or nonwoven fabric with pores that are impermeable to water particles but permeable to smaller water vapor particles. However, due to the breathability of the back sheet, moisture released from the absorbent material is transmitted to the outside of the back sheet, resulting in a damp feeling even outside the absorbent material during prolonged wear, thus reducing the overall wearing comfort. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to solve the aforementioned problems and to provide a superabsorbent resin film that is thin and has excellent moisture absorption capacity, and a water-absorbing article that contains the superabsorbent resin film and has improved external dampness. [Means for solving the problem]

[0007] According to one embodiment of the present invention, the thickness is 500 μm or less, and the moisture absorption capacity measured by the KS F 2611 standard is 10 to 100 g / m². 2 A superabsorbent resin film is provided.

[0008] The superabsorbent resin film may have a thickness of 10 to 200 μm.

[0009] The superabsorbent resin film may have a water content of 1 to 15% and a tensile strength of 5 to 50 MPa.

[0010] According to another embodiment of the present invention, there is provided a water-absorbent article including a liquid-impermeable back sheet, a breathable waterproof film, an absorber containing a superabsorbent resin powder and pulp, and a liquid-permeable top sheet, wherein a superabsorbent resin film is included between the liquid-impermeable back sheet and the breathable waterproof film, and / or between the breathable waterproof film and the absorber, the superabsorbent resin film having a thickness of 500 μm or less and a moisture absorption capacity of 10 to 100 g / m 2 as measured by the KS F 2611 standard.

[0011] The superabsorbent resin film may have a thickness of 10 to 200 μm.

[0012] The superabsorbent resin film may be bonded to one side of the liquid-impermeable back sheet and / or one or both sides of the breathable waterproof film.

[0013] As an example, the superabsorbent resin film is bonded to one side of the breathable waterproof film, and the air permeability of the bonded superabsorbent resin film and the breathable waterproof film may be 3000 to 5000 g / m 2 ·24 h. <000009^{8}> The liquid-impermeable back sheet may be a non-woven fabric having pore sizes of 20 to 1000 μm. <0000^{101}><00001^{02}>The breathable waterproof film may have an air permeability of 2000 to 5000 g / m 2 ·24 h.

[0016] The absorber may contain 10 to 90% by weight of the superabsorbent resin powder.

[0017] The liquid-permeable top sheet may have a basis weight of 15 to 30 g / m 2 as well.

Advantages of the Invention

[0018] The superabsorbent polymer film of the present invention is extremely thin yet possesses excellent moisture absorption capabilities, making it suitable for use in articles requiring moisture absorption. Furthermore, by including the superabsorbent polymer film separately from the absorbent material in the absorbent article of the present invention, the feeling of dampness perceived from the outside is significantly reduced, thereby reducing skin rashes and other irritations that occur when the article is warmed by the wearer's body, resulting in a superior user experience. [Brief explanation of the drawing]

[0019] [Figure 1] This is a cross-sectional view showing the structure of an existing absorbent article. [Figure 2] This is a cross-sectional view showing the structure of an absorbent article according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view showing the structure of an absorbent article according to one embodiment of the present invention. [Figure 4] This is a cross-sectional view showing the structure of an absorbent article according to one embodiment of the present invention. [Modes for carrying out the invention]

[0020] The terms used herein are used solely to describe exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless they are clearly different in context. In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the existence of implemented features, stages, components, or combinations thereof, and should not be understood to preemptively exclude the existence or possibility of adding one or more other features, stages, components, or combinations thereof.

[0021] Because the present invention can be modified in various ways and take on many forms, specific embodiments are illustrated and described in detail below. However, this should be understood not as an attempt to limit the invention to any particular form of disclosure, but rather as including all modifications, equivalents, or substitutes that fall within the spirit and technical scope of the present invention.

[0022] Similarly, the drawings attached to this specification are for explaining the present invention and are one embodiment of the present invention. The present invention can be realized in various different forms and is not limited to this specification. At this time, in the drawings, parts unnecessary for explanation are omitted for clearly explaining the present invention, and similar drawing reference numerals are used for similar parts throughout the specification. Also, the size and relative size of the components shown in the drawings have no relation to the actual scale and may be reduced or exaggerated for the clarity of the explanation.

[0023] Hereinafter, the superabsorbent resin film of the present invention and the absorbent article containing the same will be described in detail.

[0024] Superabsorbent resin film The superabsorbent resin film according to one embodiment of the present invention has a thickness of 500 μm or less and a moisture absorption capacity measured according to the KS F 2611 standard of 10 to 100 g / m 2 satisfying.

[0025] The superabsorbent resin film is a film-shaped acrylic acid polymer in a film form that is distinguished from existing particulate superabsorbent resins, has a water content of 15% or less, is colorless and transparent, has elasticity, and exhibits an excellent flexible film form. The superabsorbent resin film does not scatter during handling or leak from the absorbent article and can be used without auxiliary agents such as pulp.

[0026] Also, the superabsorbent resin film has a thin thickness and excellent moisture absorption capacity, and can be used as a moisture absorbent for various articles without increasing the volume of the article or damaging the form.

[0027] Specifically, the moisture absorption capacity of the superabsorbent resin film is 10 g / m 2 or more, 13 g / m 2 or more, 15 g / m 2 or more, or 20 g / m 2 or more, and 100 g / m 2 or less, or 90 g / m 2The following may also apply. The moisture absorption capacity can be measured using the KS F 2611 standard, and the specific measurement method will be described later in the examples.

[0028] The moisture absorption capacity can be increased by increasing the thickness of the superabsorbent polymer film, but if it is excessively thick, exceeding 500 μm, it may affect the shape of the article to which it is applied. Conversely, if the superabsorbent polymer film is excessively thin, the moisture absorption effect cannot be sufficiently obtained.

[0029] Furthermore, while air permeability may decrease when the thickness of the superabsorbent polymer film exceeds 500 μm, thin-film superabsorbent polymer films with a thickness of 500 μm or less exhibit significantly increased flexibility and increased inter-polymer chain capacity when absorbing moisture, thus maintaining air permeability while exhibiting moisture absorption performance. Therefore, they can be more suitably used in articles that require both moisture absorption and air permeability, such as the water-absorbing articles described later.

[0030] From this viewpoint, the thickness (h) of the superabsorbent polymer film is preferably 5 μm or more, 10 μm or more, or 15 μm or more, but may also be 400 μm or less, 300 μm or less, 200 μm or less, or 150 μm or less.

[0031] On the other hand, the water content of the superabsorbent resin film may be 15% by weight or less, or 12% by weight or less, or 11% by weight or less, or 10% by weight or less, but may also be 1% by weight or more, or 2% by weight or more, or 4% by weight or more, or 6% by weight or more.

[0032] The aforementioned "moisture content" is expressed as a percentage of the amount of water contained in the sample relative to its weight before drying. Specifically, the moisture content can be calculated by subtracting the weight of the sample after drying from the weight of the sample before drying, dividing the result by the weight of the sample before drying, and then multiplying by 100. In this case, the drying conditions are set to raise the temperature to approximately 150°C at room temperature and then maintain it at 150°C, with a total drying time of 20 minutes, including a 5-minute temperature rise stage.

[0033] The superabsorbent polymer film satisfies the requirement of having a thickness of 500 μm or less, and exhibits high transparency with a total light transmittance of 89.5% for visible light within this thickness range. The total light transmittance of the superabsorbent polymer film according to one embodiment of the present invention may be 90% or more, 90.3% or more, 91% or more, 91.5% or more, or 92% or more. The total light transmittance may theoretically be 100%, or as an example, 99% or less.

[0034] Furthermore, the superabsorbent polymer film of the present invention may have a yellowness index (Yellow Index) of 2.6 or less, 2.5 or less, 2.4 or less, 2.3 or less, 1.9 or less, 1.5 or less, or 1.3 or less according to the ASTM D1925 standard in the thickness range of 1 to 500 μm.

[0035] On the other hand, the superabsorbent polymer film may have a water content of 1% to 15% and a tensile strength of 5 MPa or more. Preferably, when the water content is 5% to 15%, the tensile strength of the superabsorbent polymer film may be 10 MPa or more, 13 MPa or more, 14 MPa or more, 19 MPa or more, or 22 MPa or more, while also being 50 MPa or less, 47 MPa or less, 45 MPa or less, 40 MPa or less, or 35 MPa or less. A superabsorbent polymer film that satisfies the above tensile strength range is less likely to break, and when applied to absorbent articles such as diapers, it will not be easily damaged by the wearer's movements and can exhibit excellent moisture absorption.

[0036] On the other hand, in order to further improve the breathability of the superabsorbent polymer film, a pattern including a hole structure can be formed in the superabsorbent polymer film. The shape of the pattern is not particularly limited, and by adjusting the shape of the holes, the maximum diameter, the average diameter, the spacing between holes, the arrangement, etc., a superabsorbent polymer film with appropriate breathability and moisture absorption capacity can be manufactured.

[0037] Alternatively, the breathability of the superabsorbent polymer film can be further improved by using a foaming agent such as calcium carbonate to form a porous structure during the manufacturing process.

[0038] The aforementioned superabsorbent polymer film can be manufactured by a manufacturing method comprising the steps of: mixing an acrylic acid monomer having acidic groups in which at least a portion of the acidic groups are neutralized, a cellulose-based thickener, a humectant, an internal crosslinking agent, a polymerization initiator, and a solvent to produce a monomer composition; casting the monomer composition onto a substrate to form a monomer composition film; irradiating the monomer composition film with heat and / or light while stretching it to form a water-containing gel polymer film; and drying the water-containing gel polymer film.

[0039] According to the above manufacturing method, a monomer composition film can be produced from a monomer composition solution with adjusted viscosity through a solution casting method, and a superabsorbent resin in film form can be produced by polymerization and drying of this film. In particular, the tensile strength of the superabsorbent resin film produced can be adjusted by applying tension to the monomer composition film and stretching it during the polymerization stage.

[0040] The method for manufacturing the superabsorbent polymer film will be described in detail below.

[0041] The monomer composition comprises an acrylic acid monomer having an acidic group in which at least a portion of the acidic group is neutralized, a cellulose-based thickener, a humectant, a polymerization initiator, and a solvent.

[0042] First, the acrylic acid monomer is a compound represented by the following chemical formula 1:

[0043] [Chemical formula 1] R 1 -COOM 1

[0044] In the above chemical formula 1, R 1 This is an alkyl group with 2 to 5 carbon atoms that contains an unsaturated bond. M 1 This is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0045] Preferably, the acrylic acid monomer comprises one or more selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.

[0046] Here, the acrylic acid monomer may have an acidic group, and at least a portion of the acidic group may be neutralized. Preferably, the monomer may be partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide. In this case, the degree of neutralization of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted according to the final physical properties. If the degree of neutralization is excessively high, the neutralized monomer may precipitate, making it difficult for polymerization to proceed smoothly, and conversely, if the degree of neutralization is excessively low, the absorption capacity of the polymer may be greatly reduced.

[0047] In one preferred embodiment, the alkali substance can be sodium hydroxide (NaOH), potassium hydroxide (KOH), or a combination thereof. In particular, when potassium hydroxide is included as the alkali substance, a superabsorbent polymer film with better flexibility and dimensional stability can be produced.

[0048] The concentration of the acrylic acid monomer can be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, relative to the monomer composition containing the raw materials and solvent for the superabsorbent resin, and can be set to an appropriate concentration considering the polymerization time and reaction conditions. However, if the concentration of the monomer is too low, the yield of the superabsorbent resin will be low, which may cause economic problems, and conversely, if the concentration is too high, process problems may occur, such as the precipitation of some of the monomer, and the physical properties of the superabsorbent resin may deteriorate.

[0049] On the other hand, in the present invention, the monomer composition includes a thickener and a humectant so that the monomer composition can be applied to a film form by a solution casting method.

[0050] By simultaneously containing a thickening agent and a humectant, the monomer composition of the present invention exhibits a viscosity suitable for casting into a film form, can maintain an appropriate water content during the polymerization process after film casting, and the resulting superabsorbent polymer film can exhibit high flexibility.

[0051] In the present invention, a cellulose-based thickener is used as the thickener, and specifically, one or more selected from the group consisting of nanocellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, and hydroxypropylmethylcellulose can be used. Preferably, nanocellulose, hydroxyethylcellulose, or a combination thereof can be used.

[0052] The cellulose-based thickener may be present in an amount of 0.01 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.35 parts by weight or more, but not exceeding 5 parts by weight, 3 parts by weight or less, 1 part by weight or less, or 0.9 parts by weight or less, per 100 parts by weight of solids in the monomer composition.

[0053] In this context, the solid content within the monomer composition refers to all components of the composition excluding the solvent. Specifically, the solid content refers to the total content of acrylic acid monomers, alkaline substances for neutralizing the acrylic acid monomers, cellulose-based thickeners, humectants, crosslinking agents, thermal polymerization initiators, photopolymerization initiators, internal crosslinking agents, and other additives.

[0054] If the content of the cellulose-based thickener is less than 0.01 parts by weight per 100 parts by weight of solids in the monomer composition, it may be difficult to ensure a sufficient thickening effect, making it difficult to manufacture the monomer composition film. Conversely, if it exceeds 5 parts by weight, the viscosity of the monomer composition will increase excessively, resulting in a thicker film and making it difficult to control the film thickness uniformly.

[0055] The aforementioned humectant may be any substance commonly used as a moisturizing ingredient in pharmaceuticals, cosmetics, chemical products, etc., without limitation. Examples of such humectants include one or more substances selected from the group consisting of polyhydric alcohols containing two or more intramolecular hydroxyl groups, citric acid, and citrate salts.

[0056] Specifically, the polyhydric alcohol can be a polyhydric alcohol having 3 to 30 carbon atoms and containing 3 to 12 intramolecular hydroxyl groups. For example, the polyhydric alcohol may be one or more selected from the group consisting of glycerin; diglycerin; propylene glycol; butylene glycol; sorbitol; polyethylene glycol; polyglycerin-3; polyglycerin-6; polyglycerin-10; and polyglyceryl-10 distearate and its derivatives (having 3 to 18 carbon atoms). Of these, one or more selected from the group consisting of glycerin, diglycerin, ethylene glycol, and sorbitol can be preferably used.

[0057] Additionally, citric acid and / or citrates can be used as humectants. Examples of citrates include triethyl citrate, methyl citrate, sodium citrate, and trisodium 2-methyl citrate.

[0058] The humectant is preferably used in an amount of 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, while being 50 parts by weight or more, per 100 parts by weight of the acrylic acid monomer, in an amount of 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, or 30 parts by weight or more.

[0059] If the humectant content is less than 5 parts by weight per 100 parts by weight of acrylic acid monomer, the moisture content of the monomer composition film may be insufficient, causing the film to dry out or crumble during the subsequent polymerization and drying process, resulting in a problem where the flexibility of the superabsorbent polymer film produced cannot be ensured. Conversely, if the polyhydric alcohol content exceeds 70 parts by weight per 100 parts by weight of acrylic acid monomer, there is a problem that the absorption capacity of the superabsorbent polymer film will decrease. Therefore, it is preferable that the humectant content satisfies the above range.

[0060] The monomer composition comprises an internal crosslinking agent for crosslinking the polymer. The internal crosslinking agent may be one that is commonly used in the production of superabsorbent polymers. More specifically, the internal crosslinking agent may be a crosslinking agent having one or more functional groups that can react with the water-soluble substituents of the acrylic acid monomer, while also having one or more ethylenically unsaturated groups; or a crosslinking agent having two or more functional groups that can react with the water-soluble substituents of the monomer and / or water-soluble substituents formed by hydrolysis of the monomer.

[0061] Specific examples of the internal crosslinking agent include bisacrylamide, bismethacrylamide, poly(meth)acrylate of a polyol having 8 to 12 carbon atoms, or poly(meth)allyl ether of a polyol having 2 to 10 carbon atoms. More specifically, one or more selected from the group consisting of N,N'-methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate, polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin diacrylate, glycerin triacrylate, trimethylol triacrylate, polyethylene glycol diacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, and propylene glycol can be used. In one embodiment, polyethylene glycol diacrylate can be used as the internal crosslinking agent.

[0062] The internal crosslinking agent is included in the monomer composition at a concentration of 5000 ppm or less to crosslink the polymerized polymer. In one embodiment, the internal crosslinking agent may be included at a concentration of 100 ppm or more, 250 ppm or more, or 500 ppm or more, but at a concentration of 5000 ppm or less, 4500 ppm or less, or 4000 ppm or less. The content of the internal crosslinking agent can be adjusted to an appropriate level depending on the thickness of the superabsorbent polymer film to be manufactured and the desired tensile strength range.

[0063] In the method for producing a superabsorbent polymer film of the present invention, the polymerization initiator used during polymerization is not particularly limited as long as it is one that is commonly used in the production of superabsorbent polymers.

[0064] Specifically, the polymerization initiator can be either a thermal polymerization initiator or a photopolymerization initiator induced by UV irradiation, depending on the polymerization method. However, even with photopolymerization methods, a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and a certain amount of heat is also generated by the progress of the polymerization reaction, which is an exothermic reaction, so a thermal polymerization initiator may also be included. In one preferred embodiment, a photopolymerization initiator and a thermal polymerization initiator can be used simultaneously as polymerization initiators.

[0065] The aforementioned photopolymerization initiator can be used without any limitations on its composition, as long as it is a compound that can form radicals when exposed to light such as ultraviolet light.

[0066] As the aforementioned photopolymerization initiator, one or more selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone can be used. On the other hand, specific examples of acyl phosphine include the commercially available lucirin TPO (2,4,6-Trimethylbenzoyldiphenylphosphine oxide) and Irgacure 819 (Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide). A wider variety of photopolymerization initiators are clearly described in Reinhold Schwalm's "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)," p. 115, and are not limited to the examples mentioned above.

[0067] The photopolymerization initiator may be present in the monomer composition at a concentration of 10 ppm or more, 20 ppm or more, or 40 ppm or more, but may also be present at a concentration of 2000 ppm or less, 1000 ppm or less, 500 ppm or less, or 100 ppm or less. If the concentration of the photopolymerization initiator is excessively low, the polymerization rate may be slowed, and if the concentration is excessively high, the molecular weight of the superabsorbent resin may be small and the physical properties may become non-uniform.

[0068] Furthermore, one or more initiators selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid can be used as the thermal polymerization initiator. Specifically, examples of persulfate initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8), while examples of azo initiators include 2,2-azobis-(2-amidinopropane)dihydrochloride and 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride. Examples include dihydrochloride, 2-(carbamoylazo)isobutylonitrile, 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, and 4,4-azobis-(4-cyanovaleric acid). A wider variety of thermal polymerization initiators are clearly described in Odian's 'Principle of Polymerization' (Wiley, 1981), p. 203, and are not limited to the examples mentioned above.

[0069] The thermal polymerization initiator may be present in the monomer composition at a concentration of 10 ppm or more, 100 ppm or more, or 500 ppm or more, but at a concentration of 2000 ppm or less, 1500 ppm or less, or 1000 ppm or less. If the concentration of the thermal polymerization initiator is excessively low, almost no additional thermal polymerization may occur, and the effect of adding the thermal polymerization initiator may be minimal. If the concentration of the thermal polymerization initiator is excessively high, the molecular weight of the superabsorbent polymer may be small, resulting in non-uniform physical properties.

[0070] The monomer composition may further contain additives such as plasticizers, preservatives, and antioxidants, as needed.

[0071] Alternatively, the monomer composition may further contain a foaming agent as an additive. A superabsorbent polymer film produced from such a monomer composition will have a porous structure with numerous pores, thereby exhibiting higher breathability.

[0072] The aforementioned foaming agent is one that foams during polymerization and / or drying, and can be one or more selected from the group consisting of, for example, thermally expandable microspheres, expanded microspheres, azo compounds, and inorganic foaming agents. These foaming agents cause a large number of pores to form in the superabsorbent polymer film, thereby greatly improving the initial absorption capacity of the superabsorbent polymer film.

[0073] The thermally expandable microsphere may have a structure comprising a hydrocarbon-containing core and a thermoplastic resin shell surrounding the core.

[0074] The hydrocarbon constituting the core of the thermally expandable microsphere may be one or more selected from the group consisting of n-propane, n-butane, iso-butane, cyclobutane, n-pentane, iso-pentane, cyclopentane, n-hexane, iso-hexane, cyclohexane, n-heptane, iso-heptane, cycloheptane, n-octane, iso-octane, and cyclooctane. Among these, hydrocarbons having 3 to 5 carbon atoms (n-propane, n-butane, iso-butane, cyclobutane, n-pentane, iso-pentane, cyclopentane) are suitable.

[0075] Furthermore, the thermoplastic resin constituting the shell of the thermally expandable microsphere may be a polymer formed from one or more monomers selected from the group consisting of (meth)acrylate, (meth)acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide, and vinylidene halide. Among these, copolymers of (meth)acrylate and (meth)acrylonitrile, or (meth)acrylate homopolymers, are most suitable for achieving the initial absorption capacity within the aforementioned range.

[0076] The aforementioned heat-expandable microspheres are a foaming agent that expands upon heat supply, and can expand under high-temperature conditions during the polymerization and / or drying stages of monomers to form pores in the superabsorbent polymer film. The expansion characteristics of such heat-expandable microspheres vary depending on the core and shell components, the weight of each component, and the average particle size. By adjusting these, they can be expanded to a desired size, thus allowing for adjustment of the pore structure of the superabsorbent polymer film.

[0077] The thermally expandable microspheres have an average particle size (D50) before expansion of 2 μm or more, 5 μm or more, 7 μm or more, or 10 μm or more, and may be 50 μm or less, 40 μm or less, or 35 μm or less. When the thermally expandable microspheres exhibit the above-mentioned average particle size, they can be judged to be suitable for achieving appropriate porosity.

[0078] At this time, the average particle size (D50) of the thermally expandable microspheres can be measured by dispersing the powder to be measured in a dispersion medium, then introducing it into a commercially available laser diffraction particle size analyzer (e.g., Mastersizer 3000), measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam, and calculating the particle size distribution.

[0079] Whether the thermally expandable microspheres can form pores of an appropriate size in the superabsorbent resin film can be confirmed by expanding the capsules in air and checking the expansion ratio and size.

[0080] The superabsorbent polymer film produced by the present invention has a thickness of 0.8 mm or less, preferably in the range of 0.001 to 0.8 mm, so the pore size should be approximately 10 to 500 μm. Therefore, it is necessary to understand the expansion characteristics of thermally expandable microspheres in order to form pores of an appropriate size in the superabsorbent polymer film.

[0081] Specifically, after coating a glass petri dish with heat-expandable microspheres, heat is applied in air for 10 minutes to expand the microspheres. When the microspheres exhibit a maximum expansion ratio in air of 3 to 15 times, 2 to 12 times, or 1 to 7 times, it is suitable for producing a superabsorbent polymer film with appropriately sized pores.

[0082] Furthermore, when the thermally expandable microspheres exhibit a maximum expansion size in air of 150 μm or less, they can form pores of appropriate size. Specifically, when the thermally expandable microspheres exhibit a maximum expansion size in air of 10-500 μm, 50-300 μm, 70-150 μm, or 75-150 μm, they are suitable for manufacturing superabsorbent polymer films with appropriately sized pores.

[0083] The thermally expandable microsphere may begin to expand at a temperature of 60-200°C, 70-170°C, or 80-165°C, and may reach a temperature of 100-240°C, 120-200°C, or 130-190°C.

[0084] Examples of such thermally expandable microspheres include Nouryon's Expansion DU series, such as Expansion 461 DU 40, Expansion 461 DU 20, Expansion 031 DU 40, Expansion 053 DU 40, and Expansion 551 DU 40; and / or Matsunomo's Microsphere F series, such as Microsphere F-AC170D, Microsphere F-36, Microsphere F-36LV, Microsphere F-48, Microsphere F-80GS, and Microsphere F-50. Preferably, Expansion 031 DU 40, which includes a hydrocarbon core and a shell of acrylate and acrylonitrile copolymer, and / or Microsphere F-AC170D, which includes a hydrocarbon core and a shell of acrylate copolymer, can be used, but are not limited to these.

[0085] The aforementioned expanded microspheres are a foaming agent that is already expanded before use, and may consist of hollow thermoplastic resin particles coated with an inorganic substance such as talc and / or calcium carbonate.

[0086] The thermoplastic resin may be a polymer formed from one or more monomers selected from the group consisting of (meth)acrylate, (meth)acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide, and vinylidene halide.

[0087] Preferably, the expanded microspheres may be hollow particles of (meth)acrylate and / or (meth)acrylonitrile copolymer coated with calcium carbonate on their surface.

[0088] The expanded microspherical hollow thermoplastic resin particles do not expand further and shrink when heated, but the inorganic material on the surface exhibits foaming properties. Therefore, pores of a similar size to the expanded microspherical particle size are formed, and the size of the pores formed in the superabsorbent polymer film can be adjusted by appropriately selecting the particle size of the expanded microspherical particles.

[0089] Therefore, the average particle size (D50) of the expanded microspheres being 10 μm or more, 20 μm or more, or 30 μm or more, and within the range of 150 μm or less, 130 μm or less, or 120 μm or less, is suitable for producing a superabsorbent polymer film with appropriately sized pores as described above. In this case, the average particle size can be measured using the particle size measurement method for thermally expandable microspheres described above.

[0090] On the other hand, the foaming temperature of the expanded microspheres may be 130°C or higher, 140°C or higher, or 150°C or higher, and may be 200°C or lower, or 180°C or higher.

[0091] Examples of the aforementioned expanded capsules include Matsunomo's Microsphere MFL series, such as MFL-110CAL, MFL-100MCA, MFA HD60CA, MFL HD30CA, and MFL-SEVEN. Preferably, MFL-110CAL, in which the surface of hollow particles of acrylate and acrylonitrile copolymer is coated with calcium carbonate powder, can be used, but the invention is not limited to this.

[0092] As the azo compound, azoamidine compounds such as 2,2'-azobis(2-methylpropionamidine)dihydrochloride and 2,2-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate can be used, and preferably 2,2'-azobis(2-methylpropionamidine)dihydrochloride can be used.

[0093] As the inorganic blowing agent, one or more selected from calcium carbonate (CaCO3), sodium bicarbonate (NaHCO3), ammonium bicarbonate (NH4HCO3), ammonium carbonate ((NH4)2CO3), ammonium nitrite (NH4NO2), sodium borohydride (NaBH4), and sodium carbonate (Na2CO3) can be used, and calcium carbonate can be used, preferably.

[0094] As the inorganic foaming agent, any micro-sized or nano-sized particles in the particle size range of 1 nm to 100 μm can be used, and the appropriate type can be selected depending on the physical properties of the target superabsorbent resin sheet. At this time, the particle size of the inorganic foaming agent can be measured by the laser diffraction method described above, or by scanning electron microscopy (SEM).

[0095] In the present invention, the thermally expandable microspheres, expanded microspheres, azo compounds, and inorganic blowing agents can each be used as blowing agents, or one or more blowing agents can be used in combination.

[0096] On the other hand, when one or more of thermally expandable microspheres and expanded microspheres are used as the first blowing agent, and one or more of azo compounds and inorganic blowing agents are used as the second blowing agent, the weight ratio of the first blowing agent to the second blowing agent may be in the range of 1:0.3 to 1:3, or in the range of 1:0.5 to 1:2. When such a weight ratio is satisfied, the improved initial absorption rate described above can be achieved.

[0097] On the other hand, the foaming agent is included in an amount of 0.1 to 10 parts by weight, more preferably 0.5 to 7 parts by weight, or 1 to 5 parts by weight, per 100 parts by weight of the monomer composition.

[0098] If the foaming agent content is less than 0.1 parts by weight per 100 parts by weight of the monomer composition, it will not be possible to secure the porous structure of the superabsorbent polymer film through foaming, and thus the effect of improving the initial absorption rate cannot be obtained.

[0099] Furthermore, if the content of the blowing agent exceeds 10 parts by weight per 100 parts by weight of the monomer composition, there is a problem that the degree of crosslinking of the polymer will decrease due to the blowing agent during polymerization. In addition, because the thermally expandable microspheres and the expanded microsphere blowing agent have low solubility in solvents (e.g., water) and low density, if their content exceeds 10 parts by weight per 100 parts by weight of the monomer composition, the blowing agent may precipitate from the monomer composition, which may result in poor foaming.

[0100] The aforementioned foaming agent is most actively foamed at temperatures above 80°C or 100°C. Therefore, the foaming of the foaming agent mainly occurs during the drying stage of the water-containing gel polymer film.

[0101] The raw materials, such as the aforementioned acrylic acid-based unsaturated monomers, cellulose-based thickeners, humectants, internal crosslinking agents, polymerization initiators, and additives, are prepared in the form of monomer composition solutions dissolved in a solvent.

[0102] The solvents that can be used are not limited in composition as long as they can dissolve the aforementioned components, and can be used in combination of one or more selected from, for example, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide. As an example, water can be used as the solvent.

[0103] In the present invention, the monomer composition exhibits a viscosity suitable for the solution casting method by containing a cellulose-based thickener and a humectant. Specifically, the viscosity of the monomer composition at 25°C is 100 mPa·s or more, 140 mPa·s or more, or 200 mPa·s or more, but may also be 5000 mPa·s or less, 2300 mPa·s or less, 2000 mPa·s or less, 1500 mPa·s or less, or 1400 mPa·s or less. The viscosity of the monomer composition can be measured with a viscometer (e.g., TOKI TV-22) under conditions of spindle #1 and rotation speed of 1 rpm.

[0104] If the viscosity of the monomer composition is less than 100 mPa·s, it may be difficult to cast the monomer composition film to a uniform thickness and polymerize it while stretching it. Conversely, if the viscosity of the monomer composition exceeds 5000 mPa·s, it is difficult to produce a uniform monomer composition, the monomer composition has low fluidity which reduces processability, and degassing is difficult, which is undesirable.

[0105] After producing the monomer composition, it is cast onto a substrate to produce a monomer composition film, which is then stretched and polymerized simultaneously to form a hydrated gel polymer film. This casting and polymerization process of the monomer composition can be carried out continuously through a roll-to-roll process.

[0106] First, a monomer composition is applied to a substrate to produce a monomer composition film.

[0107] Specifically, as the substrate, a polyethylene terephthalate (PET) film, which is normally used as a release film and has at least one surface hydrophobically treated with silicone or fluorine, can be used. For example, the substrate may be a PET film surface-treated with a siloxane polymer or polytetrafluoroethylene (Teflon®). However, the material of the substrate is not limited to this, and a suitable substrate can be selected depending on the composition and properties of the monomer composition.

[0108] For example, the PET film whose surface is hydrophobic may have a contact angle with water of 105° to 110°, and a surface energy in the range of 20 to 25 mN / m. Such a hydrophobic PET film not only facilitates the application of monomer composition films, but also facilitates the peeling of water-containing gel polymer films produced after polymerization, thereby improving the convenience of the manufacturing process. In particular, when the monomer composition contains the aforementioned polyether-modified siloxane surfactant, the affinity with the hydrophobic PET film having the aforementioned contact angle and surface energy characteristics is even higher, enabling casting with a uniform thickness. This allows for the formation of uniform and thin films even in a continuous roll-to-roll process, further improving productivity.

[0109] Unlike typical polymer solution casting methods, where the solvent is removed after polymer solution casting, the present invention involves applying the monomer composition to the substrate and immediately performing the stretching and polymerization processes to prevent a decrease in water content.

[0110] If the moisture content of the monomer composition film is excessively low, components of the pre-polymerization monomer composition may precipitate, which can cause the polymerized film to crumble. Therefore, it is preferable that the moisture content of the monomer composition film is in the range of 30% to 60% by weight, and more preferably in the range of 30% to 50% by weight, or 30% to 45% by weight.

[0111] The thickness of the monomer composition film can be appropriately adjusted according to the desired thickness of the superabsorbent polymer film. Although the thickness of the monomer composition film hardly changes during the polymerization stage, it may decrease by about 10-40% or 15-35% during the drying process of the water-containing gel polymer film after polymerization, as the water content decreases. Therefore, the monomer composition film is manufactured with an appropriate thickness, taking this into consideration.

[0112] For example, the thickness of the monomer composition film may be 800 μm or less, 600 μm or less, or 500 μm or less, but may also be 1 μm or more, 5 μm or more, or 10 μm or more. However, it is not limited to these, and can be appropriately adjusted depending on the composition of the monomer composition, the polymerization and drying conditions, and the desired thickness of the superabsorbent polymer film.

[0113] Next, the monomer composition film is stretched in the longitudinal direction (MD direction) while being irradiated with heat and / or light to carry out a polymerization reaction and form a water-containing gel polymer film. By stretching the film during polymerization in this way, the physical properties of the superabsorbent resin film produced, such as its tensile strength, can be adjusted.

[0114] At this time, the tension applied to the monomer composition film may be 40 N / m or more, 45 N / m or more, 50 N / m or more, or 60 N / m or more, but may also be 100 N / m or less, 90 N / m or less, or 70 N / m or less. If excessively high tension is applied and the film is stretched, problems may occur such as the monomer composition film tearing or becoming excessively thin, and if the tension is excessively low, it may not be possible to ensure the physical properties of the film, such as its tensile strength.

[0115] The polymerization temperature can be appropriately adjusted depending on the composition of the monomer composition, but it is preferable to have a temperature of 40°C or 50°C or higher for smooth reaction progress. Furthermore, if the temperature is excessively high, the solvent may evaporate and components constituting the monomer composition may precipitate, so it is preferable that the polymerization temperature be 90°C or lower, or 80°C or lower.

[0116] The water content of the water-containing gel polymer film produced through the polymerization step is approximately 20% by weight or more, preferably 25% by weight or more, but may be 40% by weight or less, or 35% by weight or less. Therefore, the water-containing gel polymer film is dried to produce the final superabsorbent resin film.

[0117] The temperature for the drying step is preferably in the range of 80 to 150°C or 90 to 100°C. By drying within this temperature range for about 5 to 30 minutes, a superabsorbent polymer film can be obtained that has a moisture content of 15% by weight or less, or 12% by weight or less, or 10% by weight or less, or 9% by weight or less, while having a water content of 1% by weight or more, or 2% by weight or more, or 4% by weight or more, or 6% by weight or more.

[0118] water absorbent articles An absorbent article according to one embodiment of the present invention is characterized by including the aforementioned superabsorbent resin film between a liquid-impermeable backing sheet and an absorbent material. As a result, the absorbent article can exhibit an improved feeling of dampness from the outside due to moisture released from the absorbent material that has absorbed the liquid, thereby providing a superior user experience.

[0119] Figure 1 is a cross-sectional view showing the configuration of an existing water-absorbing article 1. The existing water-absorbing article 1 includes a liquid-impermeable back sheet 11, a breathable waterproof film 12, an absorbent body 13, and a liquid-permeable top sheet 14.

[0120] In contrast, as shown in Figures 2-4, the water-absorbing articles 2, 3, and 4 of the present invention include a superabsorbent resin film 20 between the liquid-impermeable backing sheet 11 and the breathable waterproof film 12, and / or between the breathable waterproof film 12 and the absorbent body 13. The superabsorbent resin film has a thickness (h) of 500 μm or less and a moisture absorption capacity of 10-100 g / m² as measured by the KS F 2611 standard. 2 The absorbent material absorbs moisture released to the outside, thereby maintaining the dry feel of the absorbent material.

[0121] On the other hand, as shown in Figure 4, when superabsorbent polymer films are interposed between the liquid-impermeable backing sheet 11 and the breathable waterproof film 12, and between the breathable waterproof film 12 and the absorbent body 13, the thickness (h) and / or physical properties of each superabsorbent polymer film may be the same or different.

[0122] The water-absorbing articles of the present invention will be described in detail below, component by component.

[0123] Superabsorbent resin film In the water-absorbing article of the present invention, a superabsorbent resin film as described above is interposed between a liquid-impermeable backing sheet and a breathable waterproof film, and / or between the breathable waterproof film and the absorbent.

[0124] As described above, the superabsorbent resin film has excellent moisture absorption capacity and can absorb moisture released from the absorbent material, significantly improving the damp feeling felt from outside the back sheet. Furthermore, since the superabsorbent resin film is thin, with a thickness of 500 μm or less, it can exhibit the above-mentioned moisture absorption performance without significantly increasing the thickness of the absorbent article, thereby significantly improving the feel of the absorbent article.

[0125] Liquid-impermeable backing sheet As the liquid-impermeable backing sheet for the absorbent article, a nonwoven fabric manufactured by spinning olefin resins such as polyethylene and polypropylene can be used. The manufacturing method of the nonwoven fabric is not particularly limited, and fabrics manufactured by processing methods such as airlaid, thermal bond, spunlace, spunbond, meltblown, and stitchbond can be used without restriction.

[0126] The nonwoven fabric used in the liquid-impermeable back sheet can have pore sizes in the range of 20-1000 μm, 50-700 μm, or 10-300 μm. When the pores of the woven or nonwoven fabric satisfy the above range, liquid permeability is blocked, while water vapor and air permeability is possible, resulting in excellent wearability.

[0127] The basis weight of the liquid-impermeable backing sheet is not particularly limited, but is approximately 10-25 g / m². 2 Preferably about 12-20 g / m 2 In this case, the tactile sensation can be further improved while preventing the absorbed waste from leaking out of the absorbent core.

[0128] The aforementioned liquid-impermeable backing sheet and superabsorbent polymer film can be bonded together by methods such as heat bonding before manufacturing the absorbent article. Specifically, the superabsorbent polymer film can be bonded to one side of the liquid-impermeable backing sheet, and an absorbent article can be manufactured by laminating a breathable waterproof film, an absorbent material, and a liquid-permeable top sheet on the superabsorbent polymer film surface of the bonded assembly.

[0129] Breathable waterproof film On the other hand, the water-absorbing article of the present invention includes a breathable waterproof film on a liquid-impermeable backing sheet that provides waterproofing while facilitating smoother airflow.

[0130] The breathable waterproof film can be manufactured by blending a thermoplastic polymer and additives to produce a resin composition, and then molding it using casting, expanded film extrusion, or other suitable film-forming techniques. The resin composition may have, for example, a composition of 40-60% thermoplastic polymer and 40-60% additives. The additives may be a variety of components depending on the desired properties, such as antioxidants, filler particles, and dyes.

[0131] For example, a waterproof film with breathability can be manufactured by casting a resin composition made by blending a thermoplastic polymer and additives, and then stretching the film uniaxially or biaxially through a three-step process: preheating, stretching, and heat setting.

[0132] The thermoplastic polymers include, but are not limited to, ultra-low density polyethylene (VLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, copolymers of ethylene and C3-C12 alpha-olefins, copolymers of propylene and ethylene and / or C4-C12 alpha-olefins, and soluble polyolefins including propylene-base polymers containing both atactic and isotactic propylene units in the polypropylene main chain; elastomers, such as polyurethane, copolyether esters, polyamide polyether block copolymers, ethylene vinyl acetate copolymers, block copolymers such as copoly(styrene / ethylene-butylene), styrene-poly(ethylene-propylene)-styrene, styrene-poly(ethylene-butylene)-styrene, polystyrene / poly(ethylene-butylene) / polystyrene, and poly(styrene / ethylene-butylene / styrene).

[0133] As the aforementioned additive, fillers such as calcium carbonate (CaCO3) can be used. Calcium carbonate is a white solid substance produced by the reaction of carbonate ions and calcium ions, and can form numerous holes in the film while being bonded by a polymer resin. In the present invention, when manufacturing a breathable waterproof film, the size of the holes formed in the film can be adjusted by adjusting the calcium carbonate content to a range of 40 to 45% by weight based on the total weight of the breathable waterproof film forming composition, and by adjusting the stretch ratio of the film in the mechanical direction to a range of 2.5 to 3.5 times, taking into consideration the tensile strength and moisture permeability, thereby preventing the excrement absorbed by the absorbent from leaking to the outside, while allowing air and water vapor to pass more smoothly through the backing sheet.

[0134] Specifically, when the calcium carbonate content and the film stretching ratio are adjusted to the aforementioned ranges, holes with a size (diameter) of approximately 10 to 90 μm, preferably in the range of approximately 40 to 60 μm, can be formed in the film. The size of such holes is smaller than the size of water particles, which are 100 μm or larger, and larger than the size of vapor, which is approximately 0.001 to 0.01 μm. Therefore, excrement absorbed by the absorbent material is not leaked to the outside by the breathable waterproof film, but hot air and water vapor inside the diaper can be easily discharged to the outside through the breathable waterproof film.

[0135] The aforementioned breathable waterproof film has an air permeability of 2000 to 5000 g / m². 2 24hr, preferably 3500-4500 g / m² 2 • The range may be 24 hours. If the aforementioned breathability range is satisfied, it can more effectively prevent skin side effects caused by humid air.

[0136] The basis weight of the aforementioned breathable waterproof film is not particularly limited, but is approximately 15-22 g / m². 2 In this case, the strength of the film is further improved, and the air permeability of the film is approximately 3500-4500 g / m². 2 Because it is regulated within a 24-hour range, it blocks the leakage of waste absorbed by the absorbent core while allowing air and water vapor to pass smoothly through the back sheet, further improving the wearer's comfort.

[0137] The aforementioned breathable waterproof film and superabsorbent resin film can be bonded together by methods such as heat bonding before the manufacture of the absorbent article. For example, the superabsorbent resin film is bonded to one side of the breathable waterproof film, and the air permeability of the bonded superabsorbent resin film and breathable waterproof film is 3000 g / m². 2 • 24 hours or more, or 3200 g / m² 2 • Despite being over 24 hours old, it weighs 5000g / m². 2 ·24hr or less, 4500g / m 2 • Less than 24 hours, or 4200 g / m²2 • It may be less than 24 hours. As mentioned above, the superabsorbent resin film has excellent moisture absorption capacity and high breathability, so it can impart moisture absorption performance to absorbent articles without reducing their breathability.

[0138] absorbent material The absorbent material used in the absorbent article of the present invention comprises superabsorbent resin powder, which is an aggregate of superabsorbent resin particles, and pulp.

[0139] The superabsorbent polymer powder can be any substance commonly used to impart absorbent properties to absorbent articles, without limitation. The superabsorbent polymer may be one or more selected from the group consisting of, for example, acrylate polymer crosslinks, vinyl alcohol-acrylate copolymer crosslinks, maleic anhydride grafted polyvinyl alcohol crosslinks, acrylate-methacrylate copolymer crosslinks, methyl acrylate-vinyl acetate copolymer crosslinks, starch-acrylate graft copolymer crosslinks, starch-acrylonitrile graft copolymer crosslinks, carboxymethylcellulose crosslinks, isobutylene-maleic anhydride copolymer crosslinks, and methylene oxide polymer crosslinks, and preferably an acrylate polymer crosslink.

[0140] The size of the superabsorbent resin particles constituting the superabsorbent resin powder may be 100 to 1,000 μm, 150 to 800 μm, or 300 to 600 μm. If the size of the superabsorbent resin particles is less than 100 μm, the superabsorbent resin gel that has absorbed bodily fluids and swollen may be discharged to the outside of the absorbent article, or a gel blocking phenomenon may occur, impairing the physical properties. If the particle size exceeds 1,000 μm, there is a problem in that it is difficult to slim down the absorbent article.

[0141] The superabsorbent polymer powder may be included in an amount of 10 to 90% by weight of the total weight of the absorbent material, preferably 20% or more by weight, 30% or more by weight, or 40% or more by weight, but may also be included in an amount of 80% or less by weight, or 60% or less by weight.

[0142] The pulp used in the absorbent may be cellulose cotton pulp formed by crushing wood pulp. The pulp can rapidly absorb liquid and separate the superabsorbent resin particles from each other, thereby reducing gel adhesion.

[0143] To ensure such effects, the pulp may be included in an amount of 10 to 90% by weight of the total weight of the absorbent, preferably 20% or more by weight, or 40% or more by weight, but may also be included in an amount of 80% or less by weight, 70% or less by weight, or 50% or less by weight.

[0144] Specifically, the superabsorbent resin may be about 10 to 90% by weight, preferably about 30 to 60% by weight, based on the total weight of the absorbent core, and the pulp content may be about 10 to 90% by weight, preferably about 40 to 70% by weight, based on the total weight of the absorbent material.

[0145] In addition to the superabsorbent polymer powder and pulp, the absorbent material may further contain, selectively, synthetic fibers such as polyethylene fibers, polypropylene fibers, polyester fibers, polyamide fibers, rayon fibers, and polyurethane fibers. In this case, the binding strength of the superabsorbent polymer powder and pulp can be further improved. Such synthetic fibers can be used in an amount of 20% by weight or less, or 10% by weight or less, of the total weight of the absorbent material.

[0146] The method for manufacturing the absorbent material is not particularly limited. For example, it can be manufactured by uniformly mixing superabsorbent polymer powder, pulp, and selectively synthetic fibers, compressing the mixture to form it, and then packaging the compressed material with packaging material such as tissue.

[0147] Liquid permeable top sheet As the liquid-permeable upper sheet, a material that is hydrophilic to allow liquid to pass through quickly, while being soft to the touch and not irritating the user's skin, can be suitably used.

[0148] The liquid-permeable upper sheet may be, for example, a hydrophilic nonwoven fabric, an open film such as an open polyethylene film, or a foamed film such as urethane foam, and one or more of these can be laminated together for use.

[0149] Preferably, the liquid-permeable upper sheet may be a hydrophilic nonwoven fabric made using synthetic or natural fibers such as polypropylene, polyethylene, polyester, polyethylene terephthalate, rayon, cotton, or cotton. The method of manufacturing the nonwoven fabric is not particularly limited, and those manufactured by processing methods such as air-laid, thermal bond, spunlace, spunbond, meltblown, and stitch bond can be used without limitation.

[0150] The fiber thickness (fineness) of the liquid-permeable nonwoven fabric is not particularly limited, but when the fiber thickness is in the range of about 1.5 to 6 denier (d), preferably about 1.5 to 2 denier (d), skin irritation can be minimized when wearing the absorbent product, the occurrence of skin side effects can be minimized, and the instantaneous absorption function can be improved.

[0151] Furthermore, while the length of the fibers is not particularly limited, if it is approximately 36 to 39 mm, the workability of the carding process during nonwoven fabric manufacturing can be improved, the uniformity of the nonwoven fabric surface can be improved, and friction on the wearer's skin can be minimized.

[0152] The basis weight of nonwoven fabrics formed from such fibers is not particularly limited, but is approximately 15-30 g / m². 2 Preferably about 15-20 g / m 2 In this case, it is possible to improve absorption while making the surface texture softer, thereby minimizing the occurrence of skin side effects.

[0153] Method for manufacturing absorbent articles The method for manufacturing the water-absorbing article of the present invention is not particularly limited, and the article can be manufactured by laminating each component, namely the liquid-impermeable back sheet, the superabsorbent resin film, the breathable waterproof film, the absorbent, and the liquid-permeable top sheet, in an appropriate order, and then fixing them using embossing, or by fixing the spaces between each component using an adhesive such as a hot-melt adhesive.

[0154] For example, when a superabsorbent polymer film is interposed between a breathable waterproof film and an absorbent material, an absorbent article can be manufactured by laminating a liquid-impermeable back sheet, a breathable waterproof film, a superabsorbent polymer film, an absorbent material, and a liquid-permeable top sheet in that order, and then fixing them with an adhesive or embossing.

[0155] Alternatively, an absorbent article can be manufactured by first heat-bonding a superabsorbent polymer film to a liquid-impermeable backing sheet or a breathable waterproof film, and then laminating and fixing it with other components.

[0156] On the other hand, when a superabsorbent polymer film is interposed between a liquid-impermeable backing sheet and a breathable waterproof film, the superabsorbent polymer film can be first bonded to one side of the liquid-impermeable backing sheet, then the breathable film can be laminated onto the upper surface of the superabsorbent polymer film (the side not in contact with the liquid-impermeable backing sheet), and finally the absorbent material and liquid-permeable upper sheet can be laminated and fixed in place to manufacture an absorbent article.

[0157] Alternatively, a superabsorbent polymer film can be laminated to one or both sides of a breathable waterproof film, placed on a liquid-impermeable backing sheet, and then an absorbent material and a liquid-permeable top sheet can be laminated and fixed to produce an absorbent article.

[0158] The bonding of the superabsorbent resin film to the liquid-impermeable backing sheet, and the bonding of the superabsorbent resin film to the breathable waterproof film, can be performed by heat bonding. The temperature and pressure during heat bonding can be appropriately adjusted according to the properties of the liquid-impermeable backing sheet, breathable waterproof film, and superabsorbent resin film used.

[0159] The absorbent article may be a disposable diaper, a sanitary napkin, or an incontinence pad.

[0160] The following examples illustrate the present invention, but these examples are merely illustrative, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications naturally fall within the scope of the attached claims. [Examples]

[0161] [Examples] <Manufacturing of superabsorbent polymer film> Example 1-1 A neutralized solution was prepared by mixing 55 g of acrylic acid, 66.6 g of a 45 wt% potassium hydroxide (KOH) solution, and 55 g of water, resulting in the neutralization of 70 mol% of the acrylic acid.

[0162] Hydroxyethylcellulose (HEC, Ashland Natrosol 250HR), glycerin, sodium persulfate as a thermal polymerization initiator, and Irgacure 819 as a photopolymerization initiator were added to the neutralization solution to produce a monomer composition with a solids content (TSC) of 54% by weight.

[0163] At this time, HEC was added at a rate of 0.45 parts by weight per 100 parts by weight of solids in the monomer composition, glycerin at a rate of 40 parts by weight per 100 parts by weight of acrylic acid, a thermal polymerization initiator at a rate of 1000 ppm relative to the total weight of the monomer composition, and a photopolymerization initiator at a rate of 80 ppm.

[0164] The viscosity of the manufactured monomer composition at 25°C was measured using a TOKI TV-22 viscometer with spindle #1 and a rotation speed of 1 rpm. The viscosity of the monomer composition was confirmed to be 201 mPa·s.

[0165] Next, the monomer composition was coated onto one surface of a polyethylene terephthalate (PET) film to form a monomer composition film with a thickness of 20 μm (water content of 30%). A comma coater was used for the coating, and the applicator roll movement speed was set to 0.5 m / min.

[0166] Subsequently, 370 mJ / cm³ was added to the monomer composition film. 2 Polymerization was carried out by irradiation with ultraviolet light to form a hydrated gel polymer film. During this process, the monomer composition film was stretched by applying a tension of 60 N / m in the MD direction while the polymerization reaction was performed. The thickness of the produced hydrated gel polymer film was 20 μm, and it was confirmed that there was no significant change compared to the monomer composition, and the water content was 15% by weight.

[0167] Next, the manufactured water-containing gel polymer film was dried at 80°C for 5 minutes to produce a superabsorbent polymer film (SAP film) with a water content of 10% by weight and a thickness of 17 μm.

[0168] The moisture content was calculated from the weight of the superabsorbent polymer film before drying (a) and after drying (b) using the following formula. In this case, the superabsorbent polymer film was dried by raising the temperature from room temperature (25°C) to 150°C over 5 minutes, and then maintaining it at 150°C for 15 minutes.

[0169] Moisture content (%)=(ab) / a×100

[0170] Examples 1-2 A superabsorbent polymer film with a water content of 10% by weight and a thickness of 45 μm was produced in the same manner as in Example 1-1, except that the thickness of the monomer composition film was 50 μm, and the drying temperature of the water-containing gel polymer was 80°C and the drying time was 10 minutes.

[0171] Examples 1-3 A superabsorbent polymer film with a water content of 10% by weight and a thickness of 149 μm was produced in the same manner as in Example 1-1, except that the thickness of the monomer composition film was 160 μm, and the drying temperature of the water-containing gel polymer was 90°C and the drying time was 10 minutes.

[0172] Examples 1-4 A neutralized solution was prepared by mixing 55 g of acrylic acid, 66.6 g of a 45 wt% potassium hydroxide (KOH) solution, and 55 g of water, resulting in the neutralization of 70 mol% of the acrylic acid.

[0173] An internal crosslinking agent (polyethylene glycol diacrylate (PEGDA), MW=400, Aldrich), expanded microspheres MFL110CAL (Matsumoto Yushi-Seiyaku, average particle size 90-120 μm, foaming temperature 160-170°C), hydroxyethylcellulose (HEC, Ashland Natrosol 250HR), glycerin, sodium persulfate as a thermal polymerization initiator, and Irgacure 819 as a photopolymerization initiator were added to the neutralization solution to produce a monomer composition with a solids content (TSC) of 40% by weight.

[0174] At this time, the foaming agent was added at a rate of 1 part by weight per 100 parts by weight of the monomer composition, HEC at a rate of 0.45 parts by weight per 100 parts by weight of the solids content of the monomer composition, and glycerin at a rate of 40 parts by weight per 100 parts by weight of acrylic acid. The thermal polymerization initiator was added at a rate of 1000 ppm relative to the total weight of the monomer composition, and the photopolymerization initiator at a rate of 80 ppm.

[0175] The viscosity of the manufactured monomer composition at 25°C was measured using a TOKI TV-22 viscometer with spindle #1 and a rotation speed of 1 rpm. The viscosity of the monomer composition was confirmed to be 211 mPa·s.

[0176] Next, the monomer composition was coated onto one surface of a polyethylene terephthalate (PET) film to form a monomer composition film with a thickness of 160 μm (water content of 30%). A comma coater was used for the coating, and the applicator roll movement speed was set to 0.5 m / min.

[0177] Subsequently, 370 mJ / cm³ was added to the monomer composition film. 2 Polymerization was carried out by irradiation with ultraviolet light to form a hydrated gel-like polymer film. During this process, the monomer composition film was stretched by applying a tension of 60 N / m in the MD direction while the polymerization reaction was performed.

[0178] Next, the water-containing gel polymer produced was dried at 90°C for 10 minutes to produce a superabsorbent polymer film (SAP film) with a water content of 10% by weight and a thickness of 153 μm.

[0179] <Manufacturing of absorbent materials> Comparative Example 1 (1) Manufacturing of liquid-impermeable backing sheets A liquid-impermeable backing sheet (nonwoven fabric, pore size approximately 40-60 μm, basis weight 12 g / m²) is formed by spinning polypropylene at high temperature to form a web of laminated polypropylene fibers, and then joining the web through a calendar roll with a specific pattern of embossed protrusions, thereby creating a specific pattern of embossing on the surface. 2 They manufactured ).

[0180] (2) Manufacturing of breathable waterproof film A waterproof film-forming composition was obtained by mixing 50-55% by weight of polyethylene, 40-45% by weight of calcium carbonate, 1-1.5% by weight of a dispersant, 1-1.5% by weight of an antioxidant, and 2-3% by weight of a coloring agent.

[0181] The waterproof film-forming composition was fed into an extruder through a feed hopper and melted. After the molten composition was kneaded in the extruder, it was extruded into a film form through a T-die, cooled, and then heated to a stretchable temperature to stretch the film so that the stretch ratio in the mechanical direction was 2.5 to 3.5 times. After gradually cooling, it was cut into pieces of a certain width and length, weighing 17 g / m². 2 Basis weight breathable waterproof film (air permeability 4400g / m²) 2 (24 hours)

[0182] (3) Manufacturing of absorbent material A deodorizing composition was prepared by mixing 8% by weight salicylic acid, 61% by weight polyethylene glycol, and 31% by weight cetyl alcohol. Subsequently, the deodorizing composition was coated using a gravure coating apparatus at a base weight of 30 g / m². 2 The surface of a breathable bonded nonwoven fabric sheet made from cotton spunlace was coated with the deodorizing composition. Subsequently, the breathable bonded nonwoven fabric sheet coated with the deodorizing composition was passed through a hot air drying chamber to evaporate the moisture and produce a core wrap sheet surface-treated with the deodorizing composition.

[0183] Basis weight 50g / m 2 40% by weight of fluff pulp was mixed with 60% by weight of polyacrylate-based superabsorbent polymer powder (average particle size 400 μm, CRC: 34 g / g, 0.3 psi AUP: 28 g / g) with a particle size of 250-600 μm. This mixture was then surrounded by the aforementioned core wrap sheet to produce an absorbent body with a thickness of 3.0 mm.

[0184] (4) Manufacturing of liquid permeable upper sheet For the liquid-permeable top sheet, 15 g / m² 2 A 0.1 mm thick spunbond nonwoven fabric was used. The liquid-permeable upper sheet was manufactured in a shape that could completely cover the body-facing surface of the upper absorbent layer so that liquids such as urine could diffuse into the upper absorbent layer without leakage.

[0185] (5) Manufacturing of absorbent articles A breathable waterproof film was laminated to one side of the liquid-impermeable back sheet manufactured as described above. Then, the absorbent material and the liquid-permeable top sheet were sequentially laminated on the breathable waterproof film, and these were bonded together to manufacture an absorbent article (disposable diaper).

[0186] Example 2-1 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that the superabsorbent polymer film manufactured in Example 1-1 was additionally laminated between the liquid-impermeable backing sheet and the breathable waterproof film.

[0187] Example 2-2 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that the superabsorbent polymer film manufactured in Example 1-2 was additionally laminated between the liquid-impermeable backing sheet and the breathable waterproof film.

[0188] Examples 2-3 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that the superabsorbent polymer film manufactured in Examples 1-3 was additionally laminated between the liquid-impermeable backing sheet and the breathable waterproof film.

[0189] Examples 2-4 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that a superabsorbent polymer film manufactured in Examples 1-4 was additionally laminated between the breathable waterproof film and the absorbent material.

[0190] Examples 2-5 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that a superabsorbent polymer film manufactured in Example 1-1 was additionally laminated between the breathable waterproof film and the absorbent material.

[0191] Examples 2-6 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that a superabsorbent polymer film manufactured in Example 1-2 was additionally laminated between the breathable waterproof film and the absorbent material.

[0192] Example 2-7 An absorbent article was manufactured in the same manner as in Comparative Example 1, except that a superabsorbent polymer film manufactured in Examples 1-3 was additionally laminated between the breathable waterproof film and the absorbent material.

[0193] Comparative Example 2 An absorbent article was manufactured in the same manner as in Example 2, except that a 52 μm thick superabsorbent fiber (SAP fiber, Luquafleece® SAF-52, Basf) was laminated between the liquid-impermeable backing sheet and the breathable waterproof film instead of a superabsorbent polymer film.

[0194] Comparative Example 3 An absorbent article was manufactured in the same manner as in Example 2, except that a 112 μm thick superabsorbent fiber (SAP fiber, Luquafleece® SAF-112, Basf) was laminated between the liquid-impermeable backing sheet and the breathable waterproof film instead of a superabsorbent polymer film.

[0195] Comparative Example 4 An absorbent article was manufactured in the same manner as in Example 2, except that a 1.0 mm thick absorbent material (40% cotton pulp, 60% superabsorbent resin) was laminated between the liquid-impermeable backing sheet and the breathable waterproof film instead of a superabsorbent resin film.

[0196] <Experimental Example 1: Evaluation of Physical Properties of Superabsorbent Polymer Film> (1) Moisture absorption A superabsorbent polymer film was cut to 15 cm x 24 cm, and aluminum tape was attached to one side to prevent moisture absorption, thereby producing a specimen for analyzing its moisture absorption performance. Using this specimen, the moisture absorption amount of the superabsorbent polymer was measured according to the KS F 2611:2019 standard using the following method.

[0197] 1) The initial mass (W1) is measured after curing for 12 hours in a constant temperature and humidity chamber maintained at 25°C and 50% relative humidity. 2) Maintain the temperature inside a constant temperature and humidity chamber at 25°C and relative humidity at 75% for 12 hours to allow moisture absorption, then measure the mass (W2). 3) Calculate the amount of moisture absorbed using the following formula. Moisture absorption (g / m 2 ) = (W2 - W1) / 0.036

[0198] (2) Tensile strength A superabsorbent polymer film was cut into a rectangular shape measuring 20 mm x 60 mm, ensuring a smooth cut edge, to prepare a test specimen. The initial grip spacing of the tensile strength measuring instrument (TAXTplus, Stable Micro Systems) was set to 20 mm, and the test specimen was mounted. The test specimen was pulled at a speed of 0.5 mm per second, and the force (N) at the point of fracture was measured. This value was then measured against the cross-sectional area (mm²) of the test specimen. 2 The tensile strength (MPa) was calculated by dividing by ).

[0199] <Experimental Example 2: Evaluation of the physical properties of absorbent materials> (1) Evaluation of external dampness In a chamber with a humidity of 50% and a temperature of 38.7°C, the absorbent articles produced in each of the above examples and comparative examples were placed on a glass plate, and 350 ml of physiological saline (0.9% NaCl aqueous solution) at 37°C was poured onto the liquid-permeable upper sheet of the absorbent article.

[0200] After 30 minutes, we checked whether steam had accumulated on the glass plate. If steam had accumulated, we evaluated it as "external dampness present" (O), and if no steam had accumulated, we evaluated it as "external dampness absent" (X).

[0201] (2) Water vapor barrier permeability 1000 ml of distilled water was injected into each of the 25 cm x 10 cm absorbent articles prepared in the above examples and comparative examples, and allowed to absorb the water. The absorbent articles that had absorbed the distilled water were then placed in a constant temperature and humidity chamber (humidity: 50%, temperature: 38.7°C) for 12 hours. The water vapor barrier permeability (g / m²) was then measured based on the increase in weight relative to the surface area of ​​the absorbent article. 2 The calculation for 12 hours was done using the following formula.

[0202] Water vapor barrier permeability (g / m³) 2 (12hr) = (W2 - W1) / T

[0203] (In the above calculation formula, W1 is the weight per square meter (g / m²) of the absorbent article that has absorbed distilled water before constant temperature and humidity treatment. 2 ) and W2 is the weight per unit area (g / m²) of the absorbent material after constant temperature and humidity treatment. 2 ) and T is the constant temperature and humidity treatment time, which is 12 hours.

[0204] (3) Air permeability The test specimen for measuring air permeability is a breathable waterproof film (basis weight 17 g / m²). 2 Air permeability 4400g / m² 2 The superabsorbent polymer film, SAP fiber, or absorbent material applied between the liquid-impermeable backing sheet and the breathable waterproof film, or between the breathable waterproof film and the absorbent material in each example and comparative example was heat-bonded to one surface of a 24hr (25 μm thick) sheet at 130°C and 20 kgf / cm².

[0205] Test samples measuring 150 mm (MD) x 150 mm (CD) were taken and tested using a Frazir Type Air Permeability Tester in accordance with JIS L 1096. The average value of n=5 was used as the measured value.

[0206] [Table 1]

[0207] The experimental results confirmed that Examples 1-1 to 1-4 exhibited excellent moisture absorption capacity and tensile strength. Furthermore, it was confirmed that the absorbent articles of Examples 2-1 to 2-7, when interposed between the liquid-impermeable backing sheet and the breathable waterproof film, or between the breathable waterproof film and the absorbent, showed a significant improvement in external dampness compared to Comparative Example 1, while not hindering breathability.

[0208] Furthermore, in order to evaluate the feel of using the diapers in actual use, a simulated wearing test was conducted (37°C saline solution was poured onto the liquid-permeable upper sheet of the diaper, left at 36.5°C for 5 minutes, and then the feel of the back sheet was checked). The results showed that the diapers of Examples 2-1 to 2-7 felt even warmer and drier than the diaper of Comparative Example 1.

[0209] However, when superabsorbent fibers were used instead of superabsorbent polymer film, while breathability was maintained at a good level, moisture permeability was inferior, and the effect of improving external dampness could not be ensured. Furthermore, when an absorbent material was applied instead of superabsorbent polymer film, external dampness improved, but it was confirmed that breathability decreased significantly. [Explanation of Symbols]

[0210] 1, 2, 3, 4: Water absorbent articles 11: Liquid-impermeable backing sheet 12: Breathable waterproof film 13: Absorbent material 14: Liquid permeable top sheet 20: Superabsorbent polymer film

Claims

1. The thickness is 500 μm or less. The moisture absorption capacity measured according to the KS F 2611 standard is 10-100 g / m². ２ This is a superabsorbent polymer film.

2. The superabsorbent resin film according to claim 1, having a thickness of 10 to 200 μm.

3. A superabsorbent polymer film according to claim 1 or 2, having a water content of 1 to 15% and a tensile strength of 5 to 50 MPa.

4. An absorbent article comprising a liquid-impermeable back sheet; a breathable waterproof film; an absorbent body containing superabsorbent resin powder and pulp; and a liquid-permeable top sheet, An absorbent article comprising a superabsorbent resin film according to any one of claims 1 to 3 between the liquid-impermeable backing sheet and the breathable waterproof film, and / or between the breathable waterproof film and the absorbent.

5. The superabsorbent resin film is laminated to one side of the liquid-impermeable backing sheet; and / or to one or both sides of the breathable waterproof film, as described in claim 4.

6. The superabsorbent resin film is laminated to one surface of the breathable waterproof film. The air permeability of the laminated superabsorbent resin film and breathable waterproof film is 3000 to 5000 g / m². ２ - The absorbent article according to claim 4, wherein the absorbency is 24 hours.

7. The water-absorbent article according to any one of claims 4 to 6, wherein the liquid-impermeable backing sheet is a nonwoven fabric having a pore size of 20 to 1000 μm.

8. The aforementioned breathable waterproof film has an air permeability of 2000 to 5000 g / m². ２ - An absorbent article according to any one of claims 4 to 7, wherein the absorbency is 24 hours.

9. The absorbent article according to any one of claims 4 to 8, wherein the absorbent material contains 10 to 90% by weight of superabsorbent polymer powder.

10. The aforementioned liquid-permeable upper sheet has a basis weight of 15 to 30 g / m². ２ The absorbent article according to any one of claims 4 to 9.

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