Methods for manufacturing easily recyclable absorbent articles, as well as recycled raw materials, fibers, and textile products.

Abstract

To provide an absorbent article that is easily recyclable as a whole, a method for producing recycled raw materials or fibers from the absorbent article, and a method for producing textile products from the fibers. [Solution] An absorbent article comprising an interior part including a surface sheet and an absorbent, and an exterior part comprising a back sheet and gathers that constitute the parts other than the interior part, characterized in that the back sheet includes a sheet material containing a thermoplastic resin, and the gathers include thermoplastic elastic yarn, an absorbent article that is easily recyclable, and a method for manufacturing pelletized recycled raw materials, fibers, and textile products using the absorbent article as a raw material.

Description

[Technical Field]

[0001] This invention relates to easily recyclable absorbent articles, as well as to methods for manufacturing recycled raw materials, fibers, and textile products. [Background technology]

[0002] Conventional technologies for recycling used absorbent materials are known.

[0003] Patent Document 1 discloses a method for efficiently producing recycled pulp from used sanitary products that has ash content and antibacterial properties that meet sanitary product standards and can be reused as sanitary products. This method includes an ozone treatment step in which used sanitary products or pulp fibers are immersed in an ozone-containing aqueous solution to decompose superabsorbent polymers in the used sanitary products or attached to the pulp fibers, and is characterized by treating the used sanitary products or pulp fibers with a cationic antibacterial agent before, simultaneously with, or after the ozone treatment step.

[0004] Furthermore, Patent Document 2 discloses a method for manufacturing recycled products from the components of used absorbent articles, which involves separating and recovering the components according to their characteristics and reusing them according to their characteristics to manufacture recycled products. This method comprises: a material separation step of separating a plurality of used absorbent articles into at least a plurality of films and absorbent materials; a film separation step of separating the plurality of separated films into a plurality of types of recyclable films according to their filler content; and a pellet forming step of using the separated plurality of types of recyclable films to form a plurality of types of recycled resin pellets according to their filler content. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-79525 [Patent Document 2] Japanese Patent Publication No. 2018-171780 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, there has been a growing desire to reduce carbon dioxide emissions and waste generated during the disposal of absorbent materials, and to add value to such waste through recycling. Absorbent materials generally consist of an interior material including a surface sheet and absorbent core, and an exterior material including a backing sheet and gathers. Since the mass of the exterior material accounts for a large proportion, approximately 30%, of the total mass of the absorbent material, it is desirable for the exterior material to be recycled.

[0007] However, Patent Document 1 only discloses a method of recovering heat by incinerating the exterior as solid fuel (RPF), and does not disclose any technology for recycling the exterior. Furthermore, while Patent Document 2 discloses a method for recycling only the film, which is part of the outer casing, among the constituent components of an absorbent material, it does not disclose a technology for recycling the entire outer casing without separation. As stated above, to date, no absorbent material that facilitates the recycling of the entire exterior, nor any method for recycling the entire exterior, is known.

[0008] In view of the problems of the prior art described above, the problem that the present invention aims to solve is to provide an absorbent article that is easy to recycle as a whole, a method for producing recycled raw materials or fibers from the absorbent article, and a method for producing textile products from the fibers. [Means for solving the problem]

[0009] The inventors unexpectedly discovered that the aforementioned problem could be solved by having all the main components included in the outer casing of the absorbent article contain thermoplastic resin, and thus completed the present invention.

[0010] In other words, the present invention is as follows: [1] Interior part including surface sheet and absorbent, The exterior part, which comprises the interior part and includes the back sheet and gathers, An absorbent article consisting of, The back sheet comprises a sheet material containing a thermoplastic resin, and A recyclable absorbent article characterized in that the gathers include thermoplastic elastic yarn. [2] The easily recyclable absorbent article according to [1], wherein the outflow start temperature of the thermoplastic elastic yarn is 160°C or higher and 220°C or lower. [3] The easily recyclable absorbent article according to [1] or [2], wherein the thermoplastic elastic yarn is a thermoplastic polyurethane yarn. [4] The recyclable absorbent article according to any one of [1] to [3], wherein the outer casing contains a hot melt adhesive. [5] The easily recyclable absorbent article according to any one of [1] to [4], wherein the outer casing includes a thermoplastic film. [6] The exterior part is brought into contact with the following procedure: The outer casing is melted and kneaded to obtain pellets; The pellet is placed in a capillary rheometer furnace set to 230°C for 30 minutes; The melt viscosity is measured at a shear rate of 1857 / second while the sample is maintained at 230°C; Calculate the coefficient of variation of the melt viscosity for any 3-minute period from 8 minutes after the start of measurement until the end of the measurement. A recyclable absorbent article according to any of [1] to [5], wherein the coefficient of variation of the melt viscosity obtained by the method is 0.5 or less. [7] The easily recyclable absorbent article according to any of [1] to [6] above, wherein the outer casing is such that the maximum value of the melt viscosity at 200 to 220°C when pellets obtained by melting and kneading the outer casing are measured by a flow tester under conditions of an extrusion load of 49N, a starting temperature of 120°C, and a heating rate of 3°C / min is 5.0 or less when the pellets obtained by melting and kneading only the back sheet of the outer casing are measured in the same manner. [8] The following steps: (1) At least, a step of melt-kneading an outer package part separated from the recyclable absorbent article according to any one of [1] to [7] above; and (2) A step of pelletizing the product of the step (1); A method for producing a recycled raw material, comprising the above. [9] The production method according to [8] above, wherein in the step (1), virgin raw material is further added.

[10] The production method according to [9] above, wherein in the step (1), virgin raw material is added to the recycled raw material at 1 to 95% by mass.

[11] The following steps: (i) A step of separating at least an outer package part from the recyclable absorbent article according to any one of [1] to [7] above; [[ID=I4]](ii) At least, a step of melt-kneading the outer package part separated in the step (i); and (iii) A step of pelletizing the product of the step (ii); A method for producing a recycled raw material, comprising the above.

[12] The production method according to [8] above, wherein in the step (ii), virgin raw material is further added.

[13] The production method according to

[12] above, wherein in the step (ii), virgin raw material is added to the recycled raw material at 1 to 95% by mass.

[14] A method for producing fibers, comprising a step of fiberizing the recycled raw material produced by the production method according to any one of [8] to

[13] above.

[15] A method for producing a fiber product, comprising a step of producing a fiber product using the fiber produced by the production method according to

[14] above.

[16] The following steps: (A) At least, a step of melt-kneading an outer package part separated from the recyclable absorbent article according to any one of [1] to [7] above; and (B) A step of melt-spinning the product of the step (A); A method for producing fibers, comprising the above.

[17] The production method according to

[16] above, wherein in the step (B), virgin raw material is further added.

[18] The manufacturing method according to

[17] , wherein in step (B), virgin raw material is added to recycled raw material in an amount of 1 to 95% by mass.

[19] The following steps: (a) A step of separating at least the outer casing from the easily recyclable absorbent article described in any of [1] to [7] above; (b) A step of melting and kneading the outer casing separated in step (a); and (c) A step of melt-spinning the product of step (b); A method for manufacturing fibers, including

[20] The manufacturing method according to

[19] , wherein virgin raw material is further added in step (b) above.

[21] The manufacturing method according to

[20] , wherein in step (b), virgin raw material is added to the recycled raw material in an amount of 1 to 95% by mass. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an absorbent article that is easily recyclable as a whole, a method for producing recycled raw materials or fibers from the absorbent article, and a method for producing textile products from the fibers. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example of the configuration of an easily recyclable absorbent article according to this embodiment. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and can be implemented with various modifications within the scope of its gist. In this specification, "thermoplastic" means a material that can be melted by heating below its decomposition temperature, exhibits plastic flow while in the molten state, and solidifies upon cooling, thus possessing reversible properties. In this specification, "recycling" refers to the reuse, collection, and regeneration of products that are no longer needed in daily life or items obtained as by-products of industrial activities, and refers to material recycling or chemical recycling. For example, it involves obtaining recycled raw materials from used sanitary materials or sanitary materials that did not meet quality standards during manufacturing.

[0014] One embodiment of the present invention is an absorbent article comprising an interior part including a surface sheet and an absorbent, and an exterior part comprising a back sheet and gathers, which constitute the parts other than the interior part, wherein the back sheet includes a sheet material including a thermoplastic resin, and the gathers include thermoplastic elastic yarn, making it an easily recyclable absorbent article (hereinafter also simply referred to as "absorbent article"). The absorbent articles of this embodiment are primarily used to absorb and retain bodily fluids excreted from the body, such as urine, menstrual blood, and vaginal discharge. Absorbent articles include, but are not limited to, disposable diapers, sanitary napkins, incontinence pads, and panty liners, and broadly encompass articles used to absorb fluids excreted from the human body.

[0015] The interior section is the part of the absorbent article that is on the wearer's side, and includes a surface sheet and an absorbent material. The interior section may also include three-dimensional gathers for purposes such as preventing leakage. The surface sheet is a liquid-permeable sheet that first receives excreted bodily fluids into the absorbent article, and conventionally known sheet materials such as spunbond nonwoven fabric are used. The absorbent material is the part that absorbs and retains bodily fluids excreted from the body, and is placed between the surface sheet and the back sheet. Conventional materials can be used for the absorbent material, but typically include pulp fibers, superabsorbent polymers (SAP), and absorbent paper.

[0016] The outer casing is the part that constitutes everything except the inner casing, and includes a backing sheet and gathers. The absorbent article of this embodiment is characterized in that the backing sheet includes a sheet material containing thermoplastic resin, and the gathers include thermoplastic elastic yarn. In other words, the absorbent article of this embodiment is characterized in that all the main components included in the outer casing contain thermoplastic resin, and because of this characteristic, the entire outer casing can be thermoformed into recycled raw materials or fibers, making it an easily recyclable absorbent article.

[0017] The backing sheet is a liquid-impermeable sheet that prevents leakage of bodily fluids held in the absorbent material, and includes a sheet material containing a thermoplastic resin. The backing sheet includes, for example, sheet materials such as nonwoven fabric, synthetic resin film, or a composite sheet of nonwoven fabric and synthetic resin film. The sheet material included in the backing sheet may include, for example, polyolefin resins such as polyethylene and polypropylene, polyamide resins such as 6-nylon and 6,6-nylon, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and it is preferable that it includes a polyolefin resin.

[0018] The backing sheet may contain inorganic fillers, pigments, etc. Examples of inorganic fillers included in the backing sheet include calcium carbonate, calcium oxide, zeolite, amorphous aluminosilicate, clay, synthetic silica, titanium dioxide, alumina, barium sulfate, aluminum sulfate, magnesium hydroxide, etc., with calcium carbonate, zeolite, amorphous aluminosilicate, barium sulfate, synthetic silica, and magnesium hydroxide being preferred, and calcium carbonate and barium sulfate being particularly preferred. From the viewpoint of discharge stability during melt mixing, the particle size of the inorganic filler is preferably 0.1 μm to 30 μm, more preferably 1 μm to 20 μm, and even more preferably 3 μm to 10 μm. From the viewpoint of discharge stability during molten polymer discharge after melt kneading, the inorganic filler content is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and most preferably 5% by mass or less, relative to the mass of the outer casing.

[0019] From the viewpoint of discharge stability during molten polymer discharge after melt kneading, the sheet material included in the backing sheet preferably contains a thermoplastic resin with an discharge start temperature of 230°C or higher, with a content of 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and most preferably 5% by mass or less, relative to the mass of the outer casing.

[0020] The gathers are stretchable members having numerous pleats, stretching in at least one direction, and are positioned around the waist and legs of the absorbent article. The gathers may be formed by joining thermoplastic elastic yarn to a part of the backing sheet, or by joining thermoplastic elastic yarn to a sheet material separate from the backing sheet, and the separate sheet material may be a sheet material containing the same thermoplastic resin as the backing sheet. The thermoplastic elastic yarn included in the gathers is a yarn that is both thermoplastic and elastic. As thermoplastic elastic yarn, for example, elastic yarns containing styrene-based, olefin-based, polyester-based, and polyurethane-based thermoplastic elastomers can be used, but elastic yarns containing polyurethane-based thermoplastic elastomers (hereinafter also referred to as "thermoplastic polyurethane elastic yarn") are preferred.

[0021] The thermoplastic elastic yarn preferably has an outflow initiation temperature of 160°C or higher, 170°C or higher, or 180°C or higher, and also preferably 220°C or lower, 215°C or lower, or 210°C or lower. If the outflow initiation temperature is 160°C or higher, the heat resistance is sufficiently high, and yarn breakage due to heat, such as during hot melt adhesive coating, is less likely to occur during the manufacturing process of absorbent articles. On the other hand, if the outflow initiation temperature is 220°C or lower, excessive high-temperature melting is not required during recycling, so thermal decomposition of polyurethane is less likely to proceed. The outflow initiation temperature is determined using a Shimadzu flow tester CFT-500D (manufactured by Shimadzu Corporation), under the conditions of a sample amount of 1.5g, die (nozzle) diameter of 0.5mm, and thickness of 1.0mm, by applying an extrusion load of 49N, preheating at an initial temperature of 120°C for 240 seconds, and then heating at a constant rate of 3°C / min, and the flow temperature at which the polymer begins to flow is taken as the average of three measurements.

[0022] Thermoplastic polyurethane elastic yarn is not particularly limited as long as it is thermoplastic and contains polyurethane. Preferably, thermoplastic polyurethane elastic yarn contains polyurethane which is a polymer of a polymer polyol, diisocyanate, and an active hydrogen-containing compound that reacts with isocyanate groups. The polymer polyols used in the polymerization of polyurethane are preferably polyalkylene ether diols, polyester diols, and polycarbonate diols, which are commonly used in the polymerization of polyurethane, and are particularly preferably polyalkylene ether diols, with a number average molecular weight of 900 to 3,000. Examples of polyalkylene ether diols include those in which the alkylene group is a tetramethylene group, or a tetramethylene group and a linear or branched alkylene group having 1 to 8 carbon atoms. Specifically, polytetramethylene ether diol, copolymerized poly(tetramethylene-neopentylene) ether diol, and copolymerized poly(tetramethylene-2-methylbutylene) ether diol are preferred.

[0023] Diisocyanates used in the polymerization of polyurethanes can include, for example, all aliphatic, alicyclic, and aromatic diisocyanates that are soluble or liquid under reaction conditions. Specifically, these include methylene-bis(4-phenylisocyanate), methylene-bis(3-methyl-4-phenylisocyanate), 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, m- and p-xylylenediisocyanate, α,α,α',α'-tetramethyl-xylylenediisocyanate, m- and p-phenylenediisocyanate, 4,4'-dimethyl-1,3-xylylenediisocyanate, 1-alkylphenylene-2,4- and 2,6-diisocyanate, and 3-(α Examples include (-isocyanate ethyl)phenyl isocyanate, 2,6-diethylphenylene-1,4-diisocyanate, diphenyl-dimethylmethane-4,4-diisocyanate, diphenyl ether-4,4'-diisocyanate, naphthylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate, methylene-bis(4-cyclohexyl isocyanate), 1,3- and 1,4-cyclohexylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, etc., with methylene-bis(4-phenyl isocyanate) being particularly preferred.

[0024] Examples of active hydrogen-containing compounds used in the polymerization of polyurethane include low molecular weight glycols, specifically ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, hexamethylene glycol, diethylene glycol, 1,10-decanediol, 1,3-dimethylolcyclohexane, or 1,4-dimethylolcyclohexanehydrazine, with 1,4-butanediol being particularly preferred. Alkanolamines such as monoethanolamine can also be used as active hydrogen-containing compounds.

[0025] From the viewpoint of recyclability, thermoplastic polyurethane elastic yarn is preferably free from chemical crosslinking, and in particular, it is preferable that it is free from allophanate bonds formed by the reaction of isocyanate groups to crosslink urethane bonds. Thermoplastic polyurethane elastic yarn may contain additives such as stabilizers and plasticizers as needed. Examples of stabilizers include compounds commonly used in polyurethane resins, such as UV absorbers, antioxidants, light stabilizers, gas stabilizers, and antistatic agents.

[0026] The exterior may contain a hot-melt adhesive for purposes such as bonding the various components together. The hot-melt adhesive typically contains a base polymer, a tackifier, and a plasticizer. Examples of base polymers include acrylic, silicone, rubber, and olefin polymers. Examples of acrylic polymers include those consisting of a (co)polymer of vinyl monomers (such as ethylene vinyl acetate copolymer) whose main component is 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, cyanoacrylate, vinyl acetate, methyl methacrylate, etc. Examples of silicone polymers include polydimethylsiloxane polymer polymers. Examples of rubber polymers include natural rubber, polyisoprene, styrene-butadiene copolymer (SBR), styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butadiene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS).

[0027] From the viewpoint of suppressing the stickiness of the outer casing and other parts separated from sanitary materials in the recycling process and improving handling, the hot melt adhesive content is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and most preferably 5% by mass or less, relative to the mass of the outer casing.

[0028] The exterior may include components such as fastening tape and fasteners, and may also be decorated with prints or other designs, as long as it does not hinder recyclability.

[0029] The outer casing is processed using the following procedure to suppress viscosity fluctuations during the recycling process and improve the productivity (recyclability) of recycled materials: The outer casing is melted and kneaded to obtain pellets; The pellet is placed in a capillary rheometer furnace set to 230°C for 30 minutes; The melt viscosity is measured at a shear rate of 1857 / second while the sample is maintained at 230°C; The coefficient of variation of the melt viscosity (hereinafter also simply referred to as the "coefficient of variation of melt viscosity") is measured for any 3-minute period from 8 minutes after the start of measurement until the end of the measurement; The coefficient of variation of the melt viscosity obtained is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and most preferably 0.5% or less. The smaller the coefficient of variation of the melt viscosity, the smaller the rate of variation in the outer shape of the strand, the better the kneading state in the extruder, and the smaller the discharge fluctuation, resulting in a stable shape when pelletized and good recyclability. Furthermore, when using recycled raw materials for reshaping such as fiberization, the viscosity variation is small and the moldability is good, resulting in good recyclability.

[0030] From the viewpoint of suppressing viscosity fluctuations in the recycling process and improving the productivity of recycled raw materials, the value obtained by dividing the maximum melt viscosity at 200-220°C of pellets obtained by melting and kneading the outer casing, measured using a flow tester under conditions of an extrusion load of 49N, a starting temperature of 120°C, and a heating rate of 3°C / min, by the maximum melt viscosity at 200-220°C of pellets obtained by melting and kneading only the back sheet of the outer casing in the same manner (hereinafter also referred to as the "value of the melt viscosity ratio") is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. The smaller the value of the melt viscosity ratio, the smaller the fluctuation rate of the strand, the better the kneading state in the extruder, and the smaller the discharge fluctuation, resulting in a stable shape when pelletized and good recyclability. Furthermore, when reshaping such as fiberization using recycled raw materials, the viscosity variation is small and the moldability is good, resulting in good recyclability.

[0031] Another embodiment of the present invention involves the following steps: (1) At least the step of melting and kneading the outer casing separated from the above-mentioned easily recyclable absorbent article; and (2) A step of pelletizing the product of step (1); This is a method for producing recycled raw materials, which includes [the specified element].

[0032] The outer casing used in this embodiment only needs to be separated from the absorbent article by some means, and there are no particular limitations on the separation method; conventionally known methods can be used. The absorbent article may be either a pre-consumer product or a post-consumer product. Furthermore, the outer casing may be washed, dried, sterilized, cut, and / or pulverized before or after separation. The outer casing is preferably washed, dried, sterilized, cut, and / or crushed before being melt-kneaded. There are no particular limitations on the method of melt-kneading, but one example is a method using a screw. During melt-kneading, virgin raw materials may be added for purposes such as stabilizing the quality of the final recycled raw material. In addition, during melt-kneading, components of the absorbent article other than the outer casing, including thermoplastic resin, may be added to the extent that they do not impede recyclability; for example, all components of the absorbent article other than the absorbent body may be added. The product generated by melt kneading is pelletized using conventionally known methods such as the strand cut method, die face cut method, flat die method, ring die method, hot cut method, and screw method, thereby providing recycled raw material.

[0033] Another embodiment of the present invention involves the following steps: (i) A step of separating at least the outer casing from the above-mentioned easily recyclable absorbent material; (ii) A step of melting and kneading the outer casing separated in step (i); and (iii) A step of pelletizing the product of step (ii); This is a method for producing recycled raw materials, which includes [the specified element]. In this embodiment, there are no particular limitations on the method for separating the outer packaging from the absorbent article, and conventionally known methods can be used. The absorbent article may be either a pre-consumer product or a post-consumer product. The outer packaging may be washed, dried, sterilized, cut, and / or crushed before or after separation. The outer casing is preferably washed, dried, sterilized, cut, and / or crushed before being melt-kneaded. There are no particular limitations on the method of melt-kneading, but one example is a method using a screw. During melt-kneading, virgin raw materials may be added for purposes such as stabilizing the quality of the final recycled raw material. In addition, during melt-kneading, components of the absorbent article other than the outer casing, including thermoplastic resin, may be added to the extent that they do not impede recyclability; for example, all components of the absorbent article other than the absorbent body may be added. The product generated by melt kneading is pelletized using conventionally known methods such as the strand cut method, die face cut method, flat die method, ring die method, hot cut method, and screw method, thereby providing recycled raw material.

[0034] The above-described method for producing recycled raw materials may also involve passing through strands in the pelletizing process. When passing through strands, from the viewpoint of preventing fusion and adhesion between strands due to fluctuations and irregularities in the strands, the distance between strand discharge holes is preferably 5 mm or more, more preferably 7 mm or more, even more preferably 10 mm or more, and most preferably 15 mm or more. Furthermore, the lower limit of the outer diameter of the strands is preferably 2 mm or more, more preferably 4 mm or more, even more preferably 6 mm or more, and most preferably 8 mm or more. The upper limit of the outer diameter is preferably 20 mm or less, more preferably 15 mm or less, even more preferably 12 mm or less, and most preferably 10 mm or less.

[0035] In the above-described method for producing recycled raw materials, water cooling may be performed during the pelletizing process. When water cooling is performed, the water temperature is preferably kept below 50°C, more preferably below 40°C, even more preferably below 30°C, and most preferably below 20°C, from the viewpoint of reducing the stickiness of the polymer discharged after melting and kneading and improving the cutability during pelletizing.

[0036] When water cooling is performed, a water cooling tank may be provided after melting and kneading. When a water cooling tank is provided, from the viewpoint of preventing fusion and adhesion between strands due to fluctuations and disturbances of the strands, it is preferable to keep the water level fluctuation to 100 mm or less, more preferably 80 mm or less, even more preferably 50 mm or less, and most preferably 30 mm or less. Furthermore, when a water cooling tank is provided, from the viewpoint of preventing fusion and adhesion between strands due to fluctuations and disturbances of the strands, it is preferable to keep the height from the strand discharge hole to the water level of the water cooling tank to 500 mm or less, more preferably 300 mm or less, even more preferably 100 mm or less, and most preferably 50 mm or less.

[0037] In the above-described method for producing recycled raw materials, from the viewpoint of reducing the stickiness of the strands in the pelletizing process, the moisture content of the strands immediately before cutting is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and most preferably 3% by mass or less. Furthermore, the moisture content is measured using the following procedure. Approximately 100g of the strand is taken just before it enters the pelletizer, and its mass is precisely weighed. The collected strands are placed in a vacuum dryer set to a furnace temperature of 100°C and maintained under vacuum for 12 hours using a vacuum pump to obtain dried strands. Measure the mass of the dry strand and use the following formula: Moisture content (mass%) = {(mass before drying (g) - mass after drying (g)) / mass after drying (g)} × 100 The moisture content is then calculated.

[0038] When packaging recycled raw materials produced by the above manufacturing method, from the viewpoint of preventing the recycled raw materials from sticking together, the pellet temperature at the time of packaging is preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, and most preferably 30°C or lower.

[0039] The recycled raw materials produced by the above manufacturing method are suitable for use in products such as automobile parts, home appliance parts, packaging films, food containers, caps, trays, containers, pallets, clothing boxes, textiles, medical devices, daily necessities, and waste containers.

[0040] Another embodiment of the present invention is a method for producing fibers, comprising the step of fiberizing the recycled raw material produced by the above-described manufacturing method. The fiberization method can be any of the conventionally known techniques and may be wet spinning, dry spinning, or melt spinning.

[0041] Another embodiment of the present invention is a method for manufacturing textile products using fibers produced by the above manufacturing method. Here, "textile products" refers to products containing fibers, and specifically, examples include woven fabrics, knitted fabrics, nonwoven fabrics, clothing, bedding, interior furnishings, household goods, fishing nets, ropes, outdoor equipment, industrial materials, reinforcing materials such as plastics and concrete, and absorbent articles. When absorbent articles are manufactured by the manufacturing method of this embodiment, so-called horizontal recycling is achieved.

[0042] Another embodiment of the present invention involves the following steps: (A) At least the step of melting and kneading the outer casing separated from the above-mentioned easily recyclable absorbent article; and (B) A step of melt-spinning the product of step (A); This is a method for manufacturing fibers, which includes [the specified element]. The outer casing used in this embodiment only needs to be separated from the absorbent article by some means, and there are no particular limitations on the separation method; conventionally known methods can be used. The absorbent article may be either a pre-consumer product or a post-consumer product. Furthermore, the outer casing may be washed, dried, sterilized, cut, and / or pulverized before or after separation. The outer casing is preferably washed, dried, sterilized, cut, and / or crushed before being melt-kneaded. There are no particular limitations on the method of melt-kneading, but one example is a method using a screw. During melt-kneading, virgin raw materials may be added for purposes such as stabilizing spinning in the next spinning process or stabilizing the quality of the final fiber. In addition, during melt-kneading, components of the absorbent article other than the outer casing, including thermoplastic resin, may be added to the extent that it does not impede recyclability; for example, all components of the absorbent article other than the absorbent material may be added. The product produced by melt kneading is directly melt-spun to yield fibers without undergoing pelletization. Conventional known methods can be used for melt spinning. The fibers produced in this manner are suitable for use in clothing, bedding, interior furnishings, household goods, fishing nets, ropes, outdoor equipment, industrial materials, and reinforcing materials for plastics, concrete, etc.

[0043] Another embodiment of the present invention involves the following steps: (a) A step of separating at least the outer casing from the above-mentioned easily recyclable absorbent article; (b) A step of melting and kneading the outer casing separated in step (a); and (c) A step of melt-spinning the product of step (b); This is a method for manufacturing fibers, which includes [the specified element]. In this embodiment, there are no particular limitations on the method for separating the outer casing from the absorbent article, and conventionally known methods can be used. The absorbent article may be either a pre-consumer product or a post-consumer product. The outer casing may also be washed, dried, sterilized, cut, and / or pulverized before or after separation, and may include, for example, all components of the absorbent article other than the absorbent body. The outer casing is preferably washed, dried, sterilized, cut, and / or crushed before being melt-kneaded. There are no particular limitations on the method of melt-kneading, but one example is a method using a screw. During melt-kneading, virgin raw materials may be added for purposes such as stabilizing spinning in the subsequent spinning process or stabilizing the quality of the final fiber obtained. In addition, during melt-kneading, components of absorbent articles other than the outer casing, including thermoplastic resin, may be added to the extent that they do not impede recyclability. The product produced by melt kneading is directly melt-spun to yield fibers without undergoing pelletization. Conventional known methods can be used for melt spinning. The fibers produced in this manner are suitable for use in clothing, bedding, interior furnishings, household goods, fishing nets, ropes, outdoor equipment, industrial materials, and reinforcing materials for plastics, concrete, etc.

[0044] In the melt-kneading step of the above-described method for producing recycled raw materials or fibers, when virgin raw materials are added, the addition rate is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 30% by mass, most preferably 40% by mass, and also preferably 95% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less, and most preferably 50% by mass or less. If the addition rate of virgin raw materials is 1% by mass or more, even if the shape of the separated outer casing is uneven or the bulk density is low, the weight of the virgin raw materials will push the material in the raw material input section of the melt-kneading step, making it less likely for snagging or clogging to occur and resulting in good penetration. Furthermore, if the addition rate of virgin raw materials is 95% by mass or less, the difference in melt viscosity between the outer casing and the virgin raw materials will be small, so torque fluctuations during melt-kneading will be suppressed, the kneading state and discharge will be stable, and recycled raw materials or fibers of a uniform shape will be obtained.

[0045] In the above-described method for producing recycled raw materials or fibers, it is preferable that the raw materials, such as the separated outer casings, subjected to the melt-kneading process are cooled, specifically, 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, and most preferably 30°C or lower. Furthermore, it is preferable that the raw material input section (such as an extruder) is also cooled, specifically, the surface temperature of the chute section is preferably 100°C or lower, more preferably 80°C or lower, even more preferably 60°C or lower, and most preferably 40°C or lower. Cooling the raw materials and / or the raw material input section (such as an extruder) helps to suppress manufacturing problems caused by the hot-melt adhesive contained in the separated outer casings, such as the outer casings sticking to the equipment or the outer casings sticking to each other and hardening, preventing them from being properly bonded.

[0046] In the above-described method for producing recycled raw materials or fibers, a lubricant may be added during the melt-kneading step. The lubricant may be, for example, a metal salt of a fatty acid. When the lubricant is a fatty acid, the number of carbon atoms in the fatty acid is preferably 8 to 30, more preferably 11 to 28, and even more preferably 12 to 22. Specific examples of the fatty acid include metal salts of stearic acid, palmitic acid, lauric acid, behenic acid, and 12-hydroxystearic acid. Examples of metals that form salts with fatty acids include alkali metals such as lithium, potassium, and sodium, and alkaline earth metals such as magnesium, calcium, and barium. A particularly suitable metal salt of a fatty acid as a lubricant is calcium stearate. The lubricant may be added in an amount of preferably more than 0% by mass, preferably 1% by mass or less, more preferably 0.7% by mass or less, even more preferably 0.5% by mass, and most preferably 0.3% by mass or less, relative to the mass of the outer casing.

[0047] In the above-mentioned method for producing recycled raw materials or fibers, from the viewpoint of how well the raw materials are incorporated into the raw material input section during the melt-kneading process, the bulk density of the raw materials when they are introduced into the raw material input section is 0.1 g / cm³. 3 More than 1.0g / cm 3 The following is preferable: 0.2 g / cm³ 3 More than 0.9g / cm 3 The following is more preferable: 0.3 g / cm³ 3 More than 0.8g / cm 3 The following is even more preferable: 0.4 g / cm³ 3 More than 0.7g / cm 3 The following is the most preferable. [Examples]

[0048] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. First, we will explain the evaluation method used in the following examples.

[0049] <Coefficient of variation of melt viscosity> The exterior part was melt-kneaded and pelletized to prepare a sample for measurement. Using a capillary rheometer Rheograf20 (manufactured by Goettfert), a capillary die of 0.5 mm×5.0 mm was attached to a barrel with a barrel diameter of 9.55 mm, and the temperature inside the furnace was heated to 230 °C. From the upper part of the barrel, about 5 g of the sample was pushed in and introduced little by little so that no bubbles entered. After the sample was introduced, it was left for 30 minutes with a load applied and maintained at 230 °C. The measurement of the melt viscosity at a shear rate of 1857 / second was started, and the coefficient of variation of the melt viscosity in any arbitrary continuous 3 minutes from 8 minutes after the start of the measurement until the end of the measurement (the state where the sample is discharged and there is no residue in the barrel, or the piston is pushed to the lower limit of the barrel and the equipment is in a stopped state) was calculated. Note that the arbitrary 3 minutes are selected within a range that does not include a sudden decrease in pressure caused when bubbles are bitten in, a sudden increase in pressure caused by a foreign object getting caught in the capillary, etc. When the above sudden pressure fluctuation occurs and an arbitrary continuous 3 minutes cannot be ensured, re-measurement is performed. The melt viscosity η is obtained by solving the following simultaneous equations (1) to (4). The coefficient of variation (%) is calculated as the value obtained by dividing the standard deviation of the melt viscosity in any arbitrary continuous 3 minutes by the average value, where the standard deviation and the average value are calculated. Q = Aν …(1) γ = 32Q / πD 3 …(2) τ = PD / 4L …(3) η = τ / γ …(4) {In the formula, Q is the flow rate of the molten resin (mm 3 / s), A is the piston cross-sectional area (mm 2 ), ν is the piston speed (mm / s), γ is the apparent shear rate (s -1 ), D is the capillary inner diameter (mm), τ is the apparent shear stress (Pa), P is the barrel lower pressure (Pa), L is the capillary length (mm), and η is the melt viscosity (Pa·sec).}

[0050] <Outflow start temperature> Elastic yarn was cut to an appropriate length to prepare a sample for measurement. Using a Shimadzu CFT-500D flow tester (manufactured by Shimadzu Corporation), under the conditions of a sample amount of 1.5 g, a die (nozzle) diameter of 0.5 mm, and a thickness of 1.0 mm, an extrusion load of 49 N was applied, preheated for 240 seconds at an initial temperature of 120 °C, and then heated at a constant rate of 3 °C / min. The plunger stroke-temperature curve drawn during this process was determined. As the temperature increased at a constant rate, the sample gradually heated up and the polymer began to flow out. The temperature at which the polymer began to flow out was defined as the flow start temperature. The measurement was performed three times, and the average temperature was adopted as the flow start temperature.

[0051] <Ratio of melt viscosity> Samples for measurement were prepared by melting and kneading the outer casing and only the back sheet of the outer casing to form pellets, and each was subjected to the following measurements. Using a Shimadzu flow tester CFT-500D (manufactured by Shimadzu Corporation), under the conditions of a sample amount of 1.5 g, a die (nozzle) diameter of 0.5 mm, and a thickness of 1.0 mm, an extrusion load of 49 N was applied, preheated to an initial temperature of 120 °C for 240 seconds, and then heated at a constant rate of 3 °C / min. The amount of piston descent (flow rate) when the molten pellet was pushed out from the pores of the die at the bottom of the cylinder was recorded at intervals, and a flow curve was drawn with the descent amount on the horizontal axis and time on the vertical axis, and the melt viscosity at 200-220 °C was detected. The maximum melt viscosity of the pellet obtained by melting and kneading the outer casing was divided by the maximum melt viscosity of the pellet obtained by melting and kneading only the back sheet of the outer casing to obtain the value of the melt viscosity ratio.

[0052] <Variation rate of strand outer diameter> In the strand fabrication process of the following embodiment, a KEYENCE LS-9030D twin-axis outer diameter measuring instrument is installed 35 mm below the discharge hole to measure the outer diameter of the strand, and the outer diameter of the strand is measured for 1 minute using the following formula: Outer diameter variation rate (%) = {(Maximum outer diameter - Minimum outer diameter) / Average outer diameter} × 100 The variation rate of the strand's outer diameter was calculated using the following method. In this evaluation, a smaller variation in the outer shape of the strand indicates better mixing conditions within the extruder, resulting in smaller discharge fluctuations, more stable pellet shapes, and better recyclability—in other words, "easy to recycle." A variation rate of less than 100% can be considered sufficiently good for recyclability.

[0053] [Comparative Example 1] A commercially available diaper was used as the absorbent material. The outer casing of the diaper used a thermoplastic polypropylene nonwoven fabric laminated with a thermoplastic polyethylene film as the backing sheet, and the gathers were formed by bonding dry-spun spandex to the backing sheet with a styrene-based hot-melt adhesive. The outer casing was composed of 75% by mass of polypropylene nonwoven fabric, 16% by mass of polyethylene film, 4% by mass of dry-spun spandex, and 5% by mass of hot-melt adhesive, relative to the mass of the outer casing. The dry-spun spandex had a melting start temperature of 235°C and was not thermoplastic. The outer casings were separated by hand from several of the diapers to obtain approximately 1.3 kg of outer casing. The separated outer casing was heat-pressed at 150°C for 20 seconds via heat-resistant paper, cooled to room temperature, and cut into pieces of approximately 5-10 mm square with a cutter to obtain the outer casing fragments. The aforementioned outer casing fragments were melted and kneaded at 160°C to 180°C using a twin-screw extruder, and extruded in strand form towards a water-cooling tank through three discharge holes with a hole spacing of 5 mm. After water cooling, the material was cut with a pelletizer to produce pellets.

[0054] [Example 1] 2400 g of polytetramethylene ether diol with a number-average molecular weight of 1800 and 750.75 g of 4,4'-diphenylmethane diisocyanate were reacted under a dry nitrogen atmosphere at 60°C for 3 hours with stirring to obtain a polyurethane prepolymer capped with terminal isocyanates. To this reaction solution, 9 g of ADEKA AO-60 as an antioxidant and 9 g of ADEKA LA-36 as an ultraviolet absorber were mixed, and then 150.95 g of 1,4-butanediol was added and stirred for 15 minutes to obtain a polyurethane with a viscosity of 200 Pa·s (30°C). The polyurethane was then dispensed into a Teflon® tray, and while still in the tray, it was annealed in a 110°C hot air oven for 19 hours to obtain polyurethane resin. The polyurethane resin thus obtained was pulverized to a powder of approximately 3 mm in size using a Horai UG-280 pulverizer. 0.35 parts by mass of dried ethylenebisstearamide was added to the polyurethane resin powder, and the mixture was fed from the hopper and melted in the extruder. The mixture was weighed and pressurized using a gear pump installed in the head, filtered, and then extruded at a die temperature of 210°C from a nozzle with a diameter of 0.23 mm and 60 holes at a discharge rate of 31 g / min. Cold air with a cold air velocity of 0.6 m / s and a cold air temperature of 16°C was blown from a cold air chamber with a cold air length of 900 mm and applied perpendicularly to the yarn. Using a ring-type false twisting machine installed 5m below, the twist was propagated to a convergence point of 1400mm, which is the distance from the spinneret to the twist propagation point. Then, while applying a treatment agent mainly composed of polydimethylsiloxane and mineral oil, the yarn was wound at a speed of 500m / min to obtain a thermoplastic polyurethane elastic yarn with a single yarn fineness of 10dtex, a total fineness of 620dtex, and an outflow start temperature of 182°C. The application rate of the treatment agent to the polyurethane elastic yarn was 2 parts by mass. The pellets, which are recycled raw materials, were prepared in the same manner as in Comparative Example 1, except that the dry-spun spandex used in the diaper in Comparative Example 1 was replaced with the thermoplastic polyurethane elastic yarn prepared as described above.

[0055] [Example 2] Except for using 1134.47 g of 4,4'-diphenylmethane diisocyanate, 292.47 g of 1,4-butanediol, and a die temperature of 230°C, a polyurethane elastic yarn with an outflow start temperature of 220°C was obtained in the same manner as in Example 1. Pellet material, which is a recycled raw material, was prepared in the same manner as in Comparative Example 1, except that the dry-spun spandex from the diaper used in Comparative Example 1 was replaced with the thermoplastic polyurethane elastic yarn prepared as described above.

[0056] [Example 3] Recycled pellets were prepared in the same manner as in Example 1, except that 10 parts by mass of polypropylene pellets were added as virgin raw material to 90 parts by mass of the outer packaging fragments before melt-kneading.

[0057] [Example 4] Recycled pellets were prepared in the same manner as in Example 3, except that 50 parts by mass of virgin raw material were added to 50 parts by mass of the outer packaging fragments.

[0058] [Example 5] Recycled pellets were prepared in the same manner as in Example 3, except that 80 parts by mass of virgin raw material were added to 20 parts by mass of the outer packaging fragments.

[0059] [Example 6] Recycled pellets were prepared in the same manner as in Example 3, except that the distance between the discharge holes in the strand was set to 10 mm.

[0060] [Example 7] The recycled raw material pellets were prepared in the same manner as in Example 6, except that the temperature inside the water-cooling tank was maintained at 20-22°C by continuously circulating cooling water through the tank.

[0061] [Example 8] Except for controlling fluctuations in water level to a maximum of 15 mm by installing a partition inside the water cooling tank and adjusting the positions of water inlet and outlet, pellets, which are recycled raw materials, were produced in the same manner as in Example 7.

[0062] [Example 9] Except for the fact that the moisture content of the strand immediately before cutting was reduced to 5% by mass by blowing off any moisture adhering to the strand with compressed air between the time it left the water cooling tank and when it entered the pelletizer, the recycled raw material pellets were prepared in the same manner as in Example 8.

[0063] [Example 10] The outer casing is cut without pressing, and the bulk density of the cut outer casing fragments is 0.3 g / cm³. 3 Except for the above, pellets, which are recycled raw materials, were prepared in the same manner as in Example 8.

[0064] The measurement results for Comparative Example 1 and Examples 1-10 are summarized in Table 1 below.

[0065] [Table 1]

[0066] Table 1 shows that in the absorbent articles of Examples 1 to 10, where all the main components of the exterior are made of thermoplastic resin, recycling is easy because the variation in the outer diameter of the strands is small when producing pellets, which are recycled raw materials.

[0067] [Evaluation of the spinnability of the prepared pellets] Using the pellets prepared in Comparative Example 1 and Examples 1-10, melt spinning was performed under the same conditions using a known method. Specifically, the prepared pellets were melted in an extruder at 200-230°C, weighed using a gear pump attached to the head, pressurized, filtered through a filter consisting of one layer each of 50-mesh, 200-mesh, and 400-mesh wire mesh, and then extruded at a die temperature of 220°C from a 0.4 mm diameter, 12-hole nozzle at a discharge rate of 15 g / min. Cold air with a cold air velocity of 0.6 m / s and a cold air temperature of 16°C was blown from a cold air chamber with a cold air length of 900 mm and applied perpendicularly to the yarn. Subsequently, the yarn was wound at a speed of 1000 m / min and spun under conditions that yielded yarn with a single filament fineness of 1.3 dtex and a total fineness of 16 dtex. When pellets prepared in Comparative Example 1 were used, the spinning pack pressure increased rapidly to 0.3 MPa / min, and yarn breakage occurred frequently, once every 3 minutes, making stable spinning impossible. On the other hand, when pellets prepared in Examples 1 to 10 were used, the spinning pack pressure was 0.1 MPa / hour or less, there was no rapid pressure increase, and stable spinning was possible without yarn breakage during 5 hours of spinning. From this, it can be seen that the absorbent articles of Examples 1 to 10, in which the main components of the outer casing all contain thermoplastic resin, are easily recyclable. [Industrial applicability]

[0068] Because the absorbent articles of the present invention are easily recycled after disposal, they are suitable for use as environmentally friendly absorbent articles. Furthermore, the methods for producing recycled raw materials and fibers of the present invention are suitable for use as methods for obtaining recycled raw materials and fibers from waste absorbent articles. [Explanation of Symbols]

[0069] 1. Absorbent articles 2. Surface sheet 3 Absorbent 4. Backing sheet 5 Gathers 6 Thermoplastic elastic yarn 7 Fastening material

Claims

1. Interior part including surface sheet and absorbent, The exterior part, which comprises the interior part and includes the back sheet and gathers, An absorbent article consisting of, The back sheet comprises a sheet material containing a thermoplastic resin, and A recyclable absorbent article characterized in that the gathers include thermoplastic elastic yarn.

2. The absorbent article according to claim 1, wherein the outflow initiation temperature of the thermoplastic elastic yarn is 160°C or higher and 220°C or lower.

3. The easily recyclable absorbent article according to claim 1 or 2, wherein the thermoplastic elastic yarn is a thermoplastic polyurethane yarn.

4. The easily recyclable absorbent article according to claim 1 or 2, wherein the exterior portion contains a hot melt adhesive.

5. The easily recyclable absorbent article according to claim 1 or 2, wherein the outer casing includes a thermoplastic film.

6. The exterior part is subjected to the following procedure: The outer casing is melted and kneaded to obtain pellets; The pellet is placed in a capillary rheometer furnace set to 230°C for 30 minutes; The melt viscosity is measured at a shear rate of 1857 / second while the sample is maintained at 230°C; Calculate the coefficient of variation of the melt viscosity for any 3-minute period from 8 minutes after the start of measurement until the end of measurement; The easily recyclable absorbent article according to claim 1 or 2, wherein the coefficient of variation of the melt viscosity obtained is 0.5 or less.

7. The easily recyclable absorbent article according to claim 1 or 2, wherein the value obtained by dividing the maximum melt viscosity at 200-220°C when pellets obtained by melting and kneading the outer casing are measured by a flow tester under conditions of an extrusion load of 49 N, a starting temperature of 120°C, and a heating rate of 3°C / min, by the maximum melt viscosity at 200-220°C when pellets obtained by melting and kneading only the back sheet of the outer casing are measured in the same manner, is 5.0 or less.

8. The following steps: (1) A step of melting and kneading an outer casing separated from an easily recyclable absorbent article as described in claim 1 or 2; and (2) A step of pelletizing the product of step (1); A method for producing recycled raw materials, including

9. The manufacturing method according to claim 8, wherein virgin raw materials are further added in step (1) above.

10. The manufacturing method according to claim 9, wherein in step (1) above, virgin raw material is added to recycled raw material in an amount of 1 to 95% by mass.

11. The following steps: (i) A step of separating at least the outer casing from the easily recyclable absorbent article described in claim 1 or 2; (ii) A step of melting and kneading the outer casing separated in step (i); and (iii) A step of pelletizing the product of step (ii); A method for producing recycled raw materials, including

12. The manufacturing method according to claim 11, wherein virgin raw materials are further added in step (ii) above.

13. The manufacturing method according to claim 12, wherein in step (ii) above, virgin raw material is added to recycled raw material in an amount of 1 to 95% by mass.

14. A method for producing fibers, comprising the step of fiberizing a recycled raw material produced by the manufacturing method described in claim 8.

15. A method for manufacturing a textile product, comprising manufacturing a textile product using fibers produced by the manufacturing method described in claim 14.

16. The following steps: (A) At least the step of melting and kneading the outer casing separated from the easily recyclable absorbent article described in claim 1 or 2; and (B) A step of melt-spinning the product of step (A); A method for manufacturing fibers, including

17. The manufacturing method according to claim 16, wherein virgin raw materials are further added in step (A) above.

18. The manufacturing method according to claim 17, wherein in step (A), virgin raw material is added to recycled raw material in an amount of 1 to 95% by mass.

19. The following steps: (a) A step of separating at least the outer casing from the easily recyclable absorbent article described in claim 1 or 2; (b) A step of melting and kneading the outer casing separated in step (a); and (c) A step of melt-spinning the product of step (b); A method for manufacturing fibers, including

20. The manufacturing method according to claim 19, wherein virgin raw materials are further added in step (b) above.

21. The manufacturing method according to claim 20, wherein in step (b), virgin raw material is added to recycled raw material in an amount of 1 to 95% by mass.

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