Nonwoven fabrics, sound absorbing materials, and oil absorbents

Abstract

To provide a nonwoven fabric excellent in water repellency particularly under harsh conditions such as high temperature and high humidity, a sound absorption material excellent in water repellency and sound absorbency made of the nonwoven fabric, and an oil adsorption material excellent in oil absorbency made of the nonwoven fabric.SOLUTION: A nonwoven fabric comprises a water repellent pulp and a heat fusible adhesive. The water repellent pulp satisfies the following item (1). (1) In water absorption testing specified in JIS L1907:2010 standard, the starting time of sedimentation is 30 seconds or more.

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric, a sound absorbing material, and an oil sorbent material. [Background technology]

[0002] Currently, nonwoven fabrics are used in a wide range of fields, from consumer goods such as clothing, daily necessities, and medical supplies to industrial goods. In addition, their uses are also diverse, and they are used not only as fabrics, but also as filters, absorbents, sound absorbers, and heat insulators. Among these, sound absorbing materials are used in home appliances and the like to absorb noise and vibrations generated by motors, compressors, and the like.

[0003] The above-mentioned nonwoven fabric is required to be water-repellent. For example, when the nonwoven fabric is used as a sound-absorbing material in an environment where condensation occurs, the water-repellent property suppresses the deterioration of performance due to water absorption and also has the effect of suppressing the growth of microorganisms such as mold. Patent Document 1 describes a nonwoven fabric made of organic fibers and an air permeability measured according to JIS L1096 of 0.01 to 30 cc / cm 2 / sec, and describes a water-repellent sound-absorbing material that is characterized by having at least two layers of a skin material treated with a water-repellent agent laminated together. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-208599 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a nonwoven fabric that has excellent water repellency, particularly under harsh conditions such as high temperature and humidity. Another object of the present invention is to provide a sound absorbing material using the nonwoven fabric that has excellent water repellency and sound absorption properties. Another object of the present invention is to provide an oil adsorbent using the nonwoven fabric that has excellent oil absorbency. [Means for solving the problem]

[0006] The present inventors have discovered that the above problems can be solved by a nonwoven fabric containing a specific water-repellent pulp and a heat-fusible adhesive. That is, the present invention provides the following: <1> ~ <13> Regarding. <1> A nonwoven fabric containing a water-repellent pulp and a heat-fusible adhesive, wherein the water-repellent pulp satisfies the following (1): (1) In the water absorption test specified in the JIS L1907:2010 standard, the settling start time is 30 seconds or more. <2> The water-repellent pulp further satisfies at least one of the following (2) to (5): <1> The nonwoven fabric described in (2) The pulp has a water retention capacity of 15 g or less in a water retention test. (3) The amount of liquid flowing in the liquid flow test is 35 g or more. (4) When observed under a microscope, the swelling rate when water is dropped onto the product is 20% or less. (5) The water absorption amount in the tea bag test is 10 (g / g) or less. <3> The nonwoven fabric is a dry nonwoven fabric. <1> or <2> The nonwoven fabric described in <4> The Klemm water absorption measured in accordance with JIS P8141:2004 is less than 30 mm; <1> ~ <3> 13. The nonwoven fabric according to any one of claims 1 to 12. <5> After subjecting the nonwoven fabric to a water washing treatment in which the nonwoven fabric is washed with running water for 1 hour, the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm; <1> ~ <4> 13. The nonwoven fabric according to any one of claims 1 to 12. <6> After the nonwoven fabric is subjected to a heat resistance test in which it is exposed to an environment of 100°C for 1000 hours, the Klemm water absorption measured in accordance with JIS P8141:2004 is less than 30 mm. <1> ~ <5> 13. The nonwoven fabric according to any one of claims 1 to 12. <7> After subjecting the nonwoven fabric to a high temperature and high humidity test in which the nonwoven fabric is exposed to an environment of 85°C and 95% RH for 600 hours, the Klemm water absorption measured in accordance with JIS P8141:2004 is less than 30 mm. <1> ~ <6> 13. The nonwoven fabric according to any one of claims 1 to 12. <8> The nonwoven fabric is subjected to a heat cycle test in which one cycle is at -10°C for one hour and at 60°C for one hour, and this cycle is repeated 30 times. After that, the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm. <1> ~ <7> 13. The nonwoven fabric according to any one of claims 1 to 12. <9> <1> ~ <8> A sound-absorbing material comprising the nonwoven fabric according to any one of the preceding claims. <10> The content of the water-repellent pulp in the nonwoven fabric is 50% by mass or more. <9> The sound-absorbing material described in <11> A resin layer is provided on at least one surface of the nonwoven fabric. <9> or <10> The sound-absorbing material described in <12> <1> ~ <8> An oil adsorbent comprising the nonwoven fabric according to any one of the preceding claims. <13> The content of the water-repellent pulp in the nonwoven fabric is 50% by mass or more. <12> The oil adsorbent according to claim 1. Effect of the Invention

[0007] According to the present invention, it is possible to provide a nonwoven fabric having excellent water repellency, particularly excellent water repellency even under harsh conditions such as high temperature and humidity. Furthermore, according to the present invention, it is possible to provide a sound absorbing material having excellent water repellency and sound absorption properties using the nonwoven fabric. Furthermore, according to the present invention, it is possible to provide an oil adsorbent having excellent oil absorbency using the nonwoven fabric. [Brief description of the drawings]

[0008] [Figure 1] Figure 1 shows the measurement results of normal incidence sound absorption coefficient at each frequency. [Diagram 2]Figure 2 shows the results of the drop test in the oil and water absorption test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Nonwoven fabric] The nonwoven fabric of the present invention is a nonwoven fabric containing water-repellent pulp and a heat-fusible adhesive, and the water-repellent pulp satisfies the following (1). (1) In the water absorption test specified in the JIS L1907:2010 standard, the settling start time is 30 seconds or more. The water-repellent pulp preferably further satisfies at least one of the following (2) to (5). (2) The pulp has a water retention capacity of 15 g or less in a water retention test. (3) The amount of liquid flowing in the liquid flow test is 35 g or more. (4) When observed under a microscope, the swelling rate when water is dropped onto the product is 20% or less. (5) The water absorption amount in the tea bag test is 10 (g / g) or less. Conventionally, methods that have been adopted for imparting water repellency to nonwoven fabrics include making the nonwoven fabric itself from non-water-absorbent organic synthetic fibers, impregnating the nonwoven fabric with a liquid containing a water repellent as described in Patent Document 1, or spraying a liquid containing a water repellent onto the nonwoven fabric. However, the method of treating a nonwoven fabric with a water repellent agent has problems in that the coverage of the water repellent agent is insufficient, making it impossible to obtain sufficient water repellency, and the water repellency decreases over time or when the fabric is stored or used in a high-temperature, high-humidity environment. In addition, when the nonwoven fabric itself is made of organic synthetic fibers that do not have water absorption properties, the organic synthetic fibers have a smooth fiber surface, so there is a problem that the sound absorption properties are inferior to those of a sound absorbing material including a nonwoven fabric made of pulp fibers of the same thickness, density, and specific gravity. In addition, since pulp fibers have high sound absorption properties but also high water absorption properties, there is also a problem that the method of treating the nonwoven fabric with a water repellent agent cannot impart sufficient water repellency. Furthermore, there is a problem that the method of treating the nonwoven fabric with a water repellent agent impairs the sound absorption properties due to the water repellent agent covering the surface. When treating the nonwoven fabric with a water repellent agent, in the case of a porous sound absorbing material, the sound absorption properties may be impaired by the porous material being covered with the water repellent agent, and when treating the nonwoven fabric with a water repellent agent, the voids between the fibers may also be partially covered, so that the sound absorption properties may be impaired.

[0010] As a result of intensive research, the present inventors have found that the above problems can be solved by a nonwoven fabric containing a water-repellent pulp having specific water repellency and a heat-fusible adhesive, and that a nonwoven fabric having high water repellency and excellent durability of the water repellency as well as excellent sound absorption can be provided, and have completed the present invention. Furthermore, they have found that the above nonwoven fabric is useful as an oil adsorbent having selectivity for oil and excellent adsorption properties. That is, in the nonwoven fabric containing the water-repellent pulp and the heat-fusible adhesive, the pulp itself is given water repellency, and therefore it is believed that a nonwoven fabric having high sound absorption and excellent durability has been obtained compared to a case where the nonwoven fabric is treated with a water repellent agent. In the present invention, since the nonwoven fabric itself is made using water-repellent pulp, it is believed that the bond between the water repellent agent and the pulp is stronger than in a post-processing step in which the nonwoven fabric is treated with a water repellent agent after it has been made, and therefore a nonwoven fabric having excellent water repellency and durability has been obtained. Thus, a sound-absorbing material that has sound-absorbing properties equivalent to those of pulp sound-absorbing materials and also has water-repellent properties has been discovered for the first time. Furthermore, as described above, the nonwoven fabric of the present invention has excellent water repellency and therefore does not adsorb water, but has selective adsorption properties for oil, and is therefore considered to also function as an oil adsorbent having excellent oil adsorption properties. The present invention will now be described in further detail.

[0011] <Water-repellent pulp> The nonwoven fabric of the present invention contains a water-repellent pulp, and the water-repellent pulp satisfies the following (1), and preferably also satisfies at least one of the following (2) to (5). The nonwoven fabric of the present invention is characterized in that it is produced using water-repellent pulp, rather than by treating the nonwoven fabric with a water repellent agent. (1) In the water absorption test specified in the JIS L1907:2010 standard, the settling start time is 30 seconds or more. (2) The pulp has a water retention capacity of 15 g or less in a water retention test. (3) The amount of liquid flowing in the liquid flow test is 35 g or more. (4) When observed under a microscope, the swelling rate when water is dropped onto the product is 20% or less. (5) The water absorption amount in the tea bag test is 10 (g / g) or less. The above items (1) to (5) will be described in detail below.

[0012] (1) In the water absorption test specified in the JIS L1907:2010 standard, the settling start time is 30 seconds or more. More specifically, the measurement is performed according to the water absorption test (sedimentation method) specified in the JIS L1907: 2010 standard. After floating the sample in a water tank containing water at 20°C ± 2°C, the time until the sample becomes wet and starts to sink in the water (sedimentation start time) is measured. In the present invention, the water-repellent pulp has a settling start time of 30 seconds or more, and preferably 60 seconds or more.

[0013] (2) The pulp has a water retention capacity of 15 g or less in a water retention test. This test measures how much water the pulp can retain out of 40cc (40g) of water, and the more water the pulp can retain, the higher its water absorption. Specifically, the measurement is performed using the following method. An acrylic base is placed on an acrylic frame (hollow rectangular prism) 10cm long and 10cm high, with the inside diameter fitting snugly to the frame. The fit should be such that when water is poured into the frame with the base placed, a small amount of water seeps out. Separately, weighed filter paper (enough filter paper to absorb 40cc of water) is placed under the frame with the bottom installed. 2g of pulp fiber is placed evenly inside this frame, and 40cc of water is poured over the entire frame. After one minute, a 700gf acrylic weight with approximately the same dimensions as the inner diameter of the frame is placed on top to gently apply a load to the pulp fiber. After one minute, the mass of the filter paper below the frame is measured, and the amount of water that has seeped out from the frame is measured. The difference between this and the 40g of water poured in is taken as the pulp water retention capacity (g). In other words, the pulp water retention capacity is expressed by the following formula (a). Water retention capacity of pulp (g) = 40 (g) - amount of water leaked out (g) Formula (a) The amount of water that has seeped out is measured by taking the difference between the mass of the filter paper measured before the test and the mass of the filter paper that has absorbed water after the test. The water retention capacity of the water-repellent pulp is preferably 12.5 g or less, more preferably 10 g or less, even more preferably 7.5 g or less, and even more preferably 5 g or less.

[0014] (3) The amount of liquid flowing in the liquid flow test is 35 g or more. An acrylic cylinder with an inner diameter of 3 cm and five drainage holes with a diameter of 3 mm in a cross shape on the bottom was placed on the wire mesh, and 1 g of pulp fiber was placed at a height of 4 cm (density 0.035 g / cm 3 ), then 50cc of water is poured in all at once and the amount of water discharged is measured to obtain the liquid flow rate. The greater the amount of liquid flow, the lower the water absorbency and the better the water repellency. The liquid flow rate of the water-repellent pulp is preferably 37.5 g or more, more preferably 40 g or more, even more preferably 42.5 g or more, and still more preferably 45 g or more.

[0015] (4) When observed under a microscope, the swelling rate when water is dropped onto the product is 20% or less. When water is dropped onto the water-repellent pulp under a microscope, the swelling ratio is 20% or less, preferably 15% or less, more preferably 10% or less, even more preferably 5% or less, still more preferably 3% or less, and even more preferably 0%. The swelling ratio is measured by the following method. Specifically, 3 to 5 mg of pulp fibers are placed on a slide, and about 0.1 ml of water is dripped onto it using a dropper. After leaving it for about 5 minutes, the slide is tilted, and the water not absorbed by the pulp fibers is removed using a Kimwipe or the like. The fiber diameter of the pulp fibers is measured from micrographs taken before and after the dripping of water, and the swelling ratio is calculated using the following formula. Swelling ratio = {fiber diameter (width dimension) of pulp fiber after water dripping - fiber diameter (width dimension) of pulp fiber before water dripping} ÷ fiber diameter (width dimension) of pulp fiber before water dripping × 100 (%) Here, a swelling rate of 0% means that the water and pulp fibers do not mix, the water remains spherical due to surface tension, and the fibers sit on top of the water droplets, or that spherical water droplets are attached to the fibers.

[0016] (5) The water absorption amount in the tea bag test is 10 (g / g) or less. When the water-repellent pulp is subjected to a tea bag test, the water absorption is 10 (g / g) or less, preferably 7.5 (g / g) or less, more preferably 5 (g / g) or less, and even more preferably 3 (g / g) or less. The water absorption is measured by the following tea bag test. Specifically, about 5 g of pulp fiber is placed in a tea bag (9.5 cm x 7 cm, nonwoven fabric with polyester as the main fiber material, Tokiwa Tea Bag M, manufactured by Tokiwa Kogyo Co., Ltd.), and a weight (500 g) is tied to the tip of the tea bag with a string. The tea bag with the weight is placed in a beaker containing water. The water is added to a height where the entire tea bag is completely submerged under the water surface. After soaking the tea bag for 5 minutes, it is removed from the water and hung in the air for 5 minutes to drain the water. The mass of the tea bag (containing pulp fiber) after draining is measured, and the water absorption is calculated by the following formula. Here, the amount of water absorbed by the tea bag itself is very small and does not need to be taken into consideration. Water absorption (g / g) = (mass of tea bag containing pulp fiber after draining - mass of tea bag containing pulp fiber before immersion in water) ÷ mass of pulp fiber before test Here, a state where the water absorption is 1x means that the water and the pulp fibers do not mix, the water remains spherical due to surface tension, and the fibers sit on top of the water droplets, or that spherical water droplets are attached to the fibers.

[0017] In the present invention, the water-repellent pulp satisfies the above requirement (1) and preferably also satisfies at least one of requirements (2) to (5). The water-repellent pulp preferably satisfies at least (1), more preferably satisfies at least (1) and (2), even more preferably satisfies at least (1), (2), and (3), and even more preferably satisfies all of (1) to (5).

[0018] The water-repellent pulp contains pulp fibers and may be directly or indirectly treated with a water-repellent agent, and may have water-repellency by selecting the raw material of the pulp fibers. Pulp fibers are fibers having an irregularly bent shape and a crimped form, and also have a hollow tubular form having pores (lumens) that were occupied by the protoplasm of plant cells. The use of water-repellent pulp is preferable from the viewpoint of obtaining excellent sound absorption properties and further reducing the environmental load. Pulp fibers include pulps such as wood pulp (coniferous pulp, hardwood pulp), rag pulp, linter pulp, linen pulp, non-wood pulps such as paper mulberry, mitsumata and gampi pulp, and waste paper pulp; and fluff pulp, which is made by using these pulps as raw material pulp and defibrating the raw material pulp into fibers by mechanical processing. From the viewpoint of sound absorption, fine fiber pulp is preferable as the raw material pulp, but if the density is high, the sound absorption may be poor. In addition, from the viewpoint of easily obtaining a nonwoven fabric with excellent water repellency, it is also preferable to use wood with a high alkane content, such as eucalyptus, or wood with a high paraffin content as the raw material pulp. Furthermore, fluff pulp is preferred because of its excellent sound absorbing properties. The method for pulping the raw pulp is not particularly limited, and the raw pulp may be pulped by a conventionally known method.

[0019] In the present invention, the water-repellent pulp may be the above-mentioned fiber pulp treated with a water-repellent agent. The water-repellent agent is not particularly limited, and may be, for example, various waxes; higher fatty acid derivatives; synthetic resins such as polyolefin resins, polyamide resins, and polyamine resins; fluororesins such as polytetrafluoroethylene and polychlorotrifluoroethylene; silicone resins such as polymethylhydrogensiloxane and polydimethylsiloxane; chromates; zirconium salts; etc. In addition, rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, styrene sizing agents, neutral rosin sizing agents, alkenyl succinic anhydrides, alkyl ketene dimers, etc. may also be used as water-repellent agents in the present invention. Specific examples of water repellents include vegetable waxes such as carnauba wax, cotton wax, wood wax, and rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as montan wax, ozokerite, ceresin, and wax extracted from oil shells, and petroleum waxes such as paraffin, microcrystalline, and petrolatum. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as higher fatty acid amides, esters, ketones, and ethers such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride, and chlorinated hydrocarbons can also be used. Furthermore, crystalline polymers having long alkyl groups in the side chains can also be used.

[0020] In the nonwoven fabric of the present invention, the content of the water-repellent pulp is not particularly limited, but from the viewpoint of imparting water repellency to the nonwoven fabric, it is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 70% by mass or more. The upper limit is not particularly limited, but from the viewpoint of fixing the water-repellent pulp with a hot-melt adhesive described later, it is preferably 95% by mass or less, more preferably 90% by mass or less. The content of the water-repellent pulp relative to the total of the water-repellent pulp and the heat-fusible adhesive is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of imparting water repellency to the nonwoven fabric. The upper limit is not particularly limited, but is preferably 95% by mass or less, more preferably 90% by mass or less, from the viewpoint of maintaining the content of the heat-fusible adhesive described later.

[0021] <Heat-fusible adhesive> The nonwoven fabric of the present invention contains a heat-fusible adhesive. The heat-fusible adhesive may be supplied in particulate form as a heat-fusible powder, or may be supplied by spraying in a state dissolved or dispersed in a solvent, or may be supplied in fibrous form as a heat-fusible fiber, but it is preferable that the heat-fusible adhesive is supplied to the nonwoven fabric in fibrous form. In other words, it is more preferable that the heat-fusible adhesive is a heat-fusible fiber. Examples of components of the heat-sealing adhesive include, but are not limited to, polyethylene (PE), polypropylene (PP), polyethylene-vinyl acetate copolymer, polyamide, polyesters such as polyethylene terephthalate (PET), etc.

[0022] The heat-fusible fibers are not particularly limited as long as they are at least partially melted by heat treatment after the web is formed and function as a binder. The heat-fusible fiber may be a core-sheath structure obtained by combining two types of resins with different melting points, in which the fiber is partially melted. The heat-fusible fiber with the core-sheath structure has a structure in which a sheath made of a resin with a low melting point is formed on the outer periphery of a core made of a resin with a high melting point, and specific examples thereof include a form in which two types of resins with different melting points are combined (PET / PET composite fiber, PE / PE composite fiber, PP / PP composite fiber, PE / PET composite fiber, PP / PET composite fiber, PE / PP composite fiber).

[0023] In the nonwoven fabric of the present invention, the content of the heat-fusible adhesive is not particularly limited, but from the viewpoint of imparting strength to the nonwoven fabric, it is preferably 5% by mass or more, more preferably 10% by mass or more, and from the viewpoint of maintaining the content of the water-repellent pulp, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 70% by mass or less, still more preferably 50% by mass or less, and even more preferably 30% by mass or less. The content of the heat-fusible adhesive relative to the total amount of the water-repellent pulp and the heat-fusible adhesive is preferably 5% by mass or more, more preferably 10% by mass or more, from the viewpoint of imparting strength to the nonwoven fabric, and is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 70% by mass or less, still more preferably 50% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of maintaining the content of the water-repellent pulp.

[0024] <Other ingredients> The nonwoven fabric of the present invention may contain other components in addition to the water-repellent pulp and the heat-fusible adhesive described above. Specific examples of such functional powders, fibers, and liquids include functional powders, fibers, and liquids. The functional powders, fibers, and liquids preferably have at least one of deodorizing, antibacterial, antiviral, antiallergen, antifungal, aromatic, and flame-retardant components, and examples thereof include flame-retardant particles such as zeolite, activated carbon, chitin, chitosan, scallop shells, titanium oxide, titanium dioxide, magnesium oxide, plant extracts, mushroom extracts, catechin, flavonol, cyclodextrin, collagen fibers, iron oxide, citric acid, zinc pyrithione, copper pyrithione, hinokitiol, eucalyptus extract, halogen bromine, hydrated metal, antimony oxide, phosphorus, and phosphorus-nitrogen condensates.

[0025] When the nonwoven fabric of the present invention contains other components, the total amount of the other components in the nonwoven fabric may be appropriately selected within a range that does not affect the water repellency of the nonwoven fabric, and is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, still more preferably 50% by mass or less, still more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less, and still more preferably 10% by mass or less. The lower limit of the content of the other components is not particularly limited.

[0026] In the present invention, the average fiber diameter of all fibers (raw fibers) constituting the nonwoven fabric is preferably 5 to 80 μm, more preferably 10 to 60 μm. If the average fiber diameter of the fibers constituting the nonwoven fabric is within the above range, it is preferable because the sound absorption is excellent. In the case of synthetic fibers, the average fiber diameter can be measured by observation with a microscope, and in the case of pulp fibers, the average fiber diameter can be measured from the results of image analysis using a fiber length measuring device (e.g., KAANI Fiber Lab.).

[0027] In the present invention, the average fiber length of all fibers (raw fibers) constituting the nonwoven fabric is preferably 0.5 to 150 mm, and when the nonwoven fabric is an airlaid nonwoven fabric, the average fiber length of all fibers (raw fibers) constituting the nonwoven fabric is preferably 0.5 to 10 mm, more preferably 0.5 to 6 mm. If the average fiber length of all fibers constituting the nonwoven fabric is within the above range, the bulk density of the nonwoven fabric is low and the sound absorption properties are excellent, which is preferable. In the case of synthetic fibers, the average fiber length can be measured by observation with a microscope, and in the case of pulp fibers, the fiber length can be measured with a fiber length measuring device (e.g., KAJAANI Fiber Lab.).

[0028] <Nonwoven fabric manufacturing method> In the present invention, the method for producing a nonwoven fabric preferably includes a web formation step in which a sheet-like web is formed from raw fibers containing at least water-repellent pulp, and a fiber bonding step in which the raw fibers in the obtained web are bonded.

[0029] In the present invention, the nonwoven fabric may be either a wet-laid nonwoven fabric or a dry-laid nonwoven fabric, and specific examples thereof include air-laid nonwoven fabric, air-through nonwoven fabric, spunlace nonwoven fabric, needle-punched nonwoven fabric, resin-bonded nonwoven fabric, etc. From the viewpoint that it is difficult to disperse water-repellent pulp in water, the nonwoven fabric is preferably a dry-laid nonwoven fabric, i.e., a nonwoven fabric obtained by a dry manufacturing method, and more preferably an air-laid nonwoven fabric. When the nonwoven fabric is an airlaid nonwoven fabric, there is no need to disperse water-repellent pulp in water. In addition, in airlaid nonwoven fabric, the raw fibers are randomly oriented in three dimensions, which creates many voids and results in a nonwoven fabric with high sound-absorbing properties.

[0030] An air-laid nonwoven fabric is a nonwoven fabric in which a web is formed by an air-laid method, in which fibers constituting the nonwoven fabric are randomly laminated in a three-dimensional manner using an air flow. For example, air-laid nonwoven fabrics are produced as follows: First, an air-permeable carrier sheet is placed on a mesh-like endless belt, and the fibers constituting the nonwoven fabric are deposited on the air-permeable carrier sheet while being dispersed in the air using an air-laid web forming device to form a web. Next, the web is thermally bonded by the heat-fusible adhesive contained in it through heating (thermal bonding method). The heat treatment of the formed air-laid web may be carried out by a general thermal bonding method, for example, a method of introducing the air-laid web into a heating furnace, a method of subjecting the air-laid web to hot air treatment, or the like. Furthermore, a sheet may be placed on the surface of the nonwoven fabric before or after heat fusion. When the surface on which the breathable carrier sheet is placed is considered the back surface, the sheet is placed on the other surface (front surface). Here, the sheet placed on the front surface is not limited to a breathable sheet, and various sheets can be placed. The sheet on the front surface may be the same as the breathable carrier sheet on the back surface.

[0031] Examples of hot air treatment include a method in which the web is heat-treated by passing it through a through-air dryer equipped with a rotating drum with air permeability on its peripheral surface (hot air circulating rotary drum method), and a method in which the web is heat-treated by passing it through a box-type dryer that can pass hot air through the web (hot air circulating conveyor oven method). The heat treatment temperature should be equal to or higher than the melting point of the heat-fusible adhesive. When the heat-fusible adhesive is made of two or more resins, the heat treatment temperature should be equal to or higher than the melting point of the resin with the lowest melting point. When heated to a temperature equal to or higher than the melting point of the heat-fusible adhesive, the heat-fusible adhesive melts, and the fibrous raw materials including the water-repellent pulp are bonded to each other via the molten heat-fusible adhesive.

[0032] After the fiber bonding step, a heat press treatment may be performed for the purpose of finely adjusting the density of the formed nonwoven fabric, etc. In this case, the pressing pressure is preferably 44 kg / cm or less, more preferably 10 kg / cm or less, in terms of linear pressure, which is lower than the pressure in the heat press step generally performed as a fiber bonding step for bonding fibers together.

[0033] The nonwoven fabric is obtained by peeling off the gas-permeable carrier sheet from the nonwoven fabric obtained as described above. The gas-permeable carrier sheet may be left as it is without being peeled off. In the case where the gas-permeable carrier sheet is left as it is without being peeled off, it is preferable to use a carrier sheet having water repellency as the gas-permeable carrier sheet.

[0034] In the present invention, the basis weight, density and thickness of the nonwoven fabric are not particularly limited, and may be appropriately selected depending on the required performance. When the nonwoven fabric of the present invention is used as a sound absorbing material, the basis weight, density, and thickness can be set in consideration of, for example, the frequency band to be absorbed, the installation space of the sound absorbing material, etc. When the nonwoven fabric of the present invention is used as a sound absorbing material with a thickness of 3.0 to 6.0 mm, the basis weight is 400 to 500 g / m 2 , Density: 0.05~0.1g / cm 3 is preferred.

[0035] The nonwoven fabric of the present invention preferably has a Klemm water absorbency of less than 30 mm as measured in accordance with JIS P8141: 2004. Here, the Klemm water absorbency means the height (mm) to which water rises due to capillary action in 10 minutes when a nonwoven fabric (sample) is vertically immersed in water. The nonwoven fabric of the present invention has a Klemm water absorbency of more preferably 20 mm or less, further preferably 10 mm or less, even more preferably 5 mm or less, further more preferably 1 mm or less, and further more preferably 0 mm. According to the findings of the present inventors, when a nonwoven fabric is made of hydrophobic organic synthetic fibers, the Klemm water absorbency is 30 mm or more due to capillary action. Since the Klemm water absorbency depends on density, nonwoven fabrics with low density tend to have low Klemm water absorbency. However, in order to obtain a certain sound absorption effect in a porous sound absorbing material, a total amount of porous material itself is required for sound to be converted into energy, and a certain density is required under conditions where thickness is restricted. Therefore, when comparing Klemm water absorbency, if there is a thickness that can produce a sound absorption effect, the density of the nonwoven fabric should be 0.03 g / cm. 3 It is preferable that the concentration is 0.05 g / cm or more. 3 More preferably, it is 0.07 g / cm or more. 3 More preferably, it is equal to or greater than this.

[0036] The nonwoven fabric of the present invention is resistant to deterioration in water repellency even by washing, and after subjecting the nonwoven fabric to a water washing treatment in which the nonwoven fabric is washed with running water for 1 hour, it is preferable that the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm. Here, the washing is preferably performed using tap water at a water temperature of 30° C.±2° C. Under the above conditions, when the nonwoven fabric is post-treated with a water repellent, the water repellent is reduced by the washing treatment, and the Klemm water absorbency tends to be higher. On the other hand, the nonwoven fabric of the present invention is formed using a water-repellent pulp having water repellency, and the above-mentioned decrease in water repellency is unlikely to occur. The Klemm's water absorbency after the above-mentioned water washing treatment is more preferably 20 mm or less, even more preferably 10 mm or less, even more preferably 5 mm or less, even more preferably 1 mm or less, and even more preferably 0 mm.

[0037] Furthermore, the nonwoven fabric of the present invention is resistant to deterioration in water repellency even in a heat resistance test, and after subjecting the nonwoven fabric to a heat resistance test in which it is exposed to an environment of 100°C for 1,000 hours, it is preferable that the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm. The heat resistance test is performed by exposing the nonwoven fabric to an environment of 100°C for 1000 hours. When the nonwoven fabric is post-treated with a water repellent agent or when a water repellent sheet is attached to the nonwoven fabric to impart water repellency, the water repellency is likely to decrease due to the heat resistance test. In particular, when a water repellent sheet is attached, the water repellent sheet and the nonwoven fabric may peel off, resulting in a decrease in water repellency. On the other hand, the nonwoven fabric of the present invention is formed using a water repellent pulp having water repellency, and the above-mentioned decrease in water repellency is unlikely to occur. The Klemm water absorbency of the nonwoven fabric after the above-mentioned heat resistance test is more preferably 20 mm or less, even more preferably 10 mm or less, even more preferably 5 mm or less, even more preferably 1 mm or less, and even more preferably 0 mm.

[0038] Furthermore, the nonwoven fabric of the present invention is resistant to deterioration in water repellency even when subjected to a high temperature and high humidity test, and it is preferable that the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm after being subjected to a high temperature and high humidity test in which the fabric is exposed to an environment of 85°C and 95% RH for 600 hours. The high temperature and high humidity test is performed by exposing the nonwoven fabric to an environment of 85°C and 95% RH for 600 hours. When the nonwoven fabric is post-treated with a water repellent agent or when a water repellent sheet is attached to the nonwoven fabric to impart water repellency, the water repellency is likely to decrease due to the high temperature and high humidity test. In particular, when a water repellent sheet is attached, the water repellent sheet and the nonwoven fabric may peel off, resulting in a decrease in water repellency. On the other hand, the nonwoven fabric of the present invention is formed using a water repellent pulp having water repellency, and the above-mentioned decrease in water repellency is unlikely to occur. The Klemm water absorbency of the nonwoven fabric after the above-mentioned high temperature and high humidity test is more preferably 20 mm or less, even more preferably 10 mm or less, even more preferably 5 mm or less, even more preferably 1 mm or less, and even more preferably 0 mm.

[0039] Furthermore, the nonwoven fabric of the present invention is resistant to deterioration in water repellency even when subjected to a heat cycle test, and after subjecting the nonwoven fabric to a heat cycle test in which one cycle is at -10°C for one hour and at 60°C for one hour, and this cycle is repeated 30 times, it is preferable that the Klemm water absorbency measured in accordance with JIS P8141:2004 is less than 30 mm. The heat cycle test is performed by repeating 30 cycles of one hour at -10°C and one hour at 60°C. When the nonwoven fabric is post-treated with a water repellent agent or when a water repellent sheet is attached to the nonwoven fabric to impart water repellency, the water repellency is likely to decrease due to the heat cycle test. In particular, when a water repellent sheet is attached, the water repellency may decrease due to peeling between the water repellent sheet and the nonwoven fabric. On the other hand, the nonwoven fabric of the present invention is formed using a water repellent pulp having water repellency, and the above-mentioned decrease in water repellency is unlikely to occur. The Klemm water absorbency of the nonwoven fabric after the above-mentioned heat cycle test is more preferably 20 mm or less, even more preferably 10 mm or less, even more preferably 5 mm or less, even more preferably 1 mm or less, and even more preferably 0 mm.

[0040] [Sound absorbing material] In the present invention, the nonwoven fabric is preferably used as a sound absorbing material. In addition, the nonwoven fabric of the present invention uses pulp fibers, and the surface of pulp fibers has a more complex shape than organic synthetic fibers. When sound waves pass through the nonwoven fabric, the degree of pathology becomes high, and sound energy is converted into thermal energy more efficiently, resulting in high sound absorption properties. The sound-absorbing material of the present invention comprises at least the nonwoven fabric of the present invention, and may further comprise another layer on at least one surface of the nonwoven fabric. The sound-absorbing material of the present invention comprises the nonwoven fabric of the present invention and has excellent water repellency. As described above, the water repellency and sound absorption properties are maintained even after heat resistance tests, high temperature and high humidity tests, and heat cycle tests, and therefore the sound-absorbing material can withstand use in a variety of environments.

[0041] When the nonwoven fabric of the present invention is used as a sound-absorbing material, the content of water-repellent pulp in the nonwoven fabric is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of obtaining high sound absorption properties, and is preferably 95% by mass or less, more preferably 90% by mass or less, from the viewpoint of keeping the content of the heat-fusible adhesive in an appropriate range.

[0042] Although the sound absorbing material may be a nonwoven fabric as it is, it is preferable that the nonwoven fabric has a resin layer on at least one side thereof. Examples of the resin layer include a surface layer and a rubber layer as described in JP 2016-71376 A, and may also be a film layer. In the present invention, from the viewpoint that it is preferable that the sound absorbing material also has water repellency, it is preferable that layers other than the nonwoven fabric of the present invention also have water repellency.

[0043] In a preferred embodiment, the water-repellent sound-absorbing material of the present invention has a long-term water-repellent durability under harsh conditions such as high temperature and humidity. In addition, the sound-absorbing material of the present invention has excellent sound-absorbing properties, so it can be used in small devices. Therefore, it is more preferable to use it as a sound-absorbing material for electrical products that cannot be easily replaced, and more preferably as a sound-absorbing member for devices that generate drainage or condensation due to temperature changes, such as compressors and heat exchangers, and devices that are always used under high humidity conditions.

[0044] [Oil adsorbent] The nonwoven fabric of the present invention is also preferably used as an oil adsorbent. An oil adsorbent is also called an oil sorbent. Here, it is preferable that the oil adsorbent has a higher oil adsorption ability than the water adsorption ability, and selectively adsorbs oil. Oil adsorbents are used in the treatment of kitchen wastewater in restaurants, oil-water separation tanks, oil spill accidents, construction sites, etc., and are required to have oil adsorption selectivity, absorption speed, ease of disposal, etc. Conventionally, adsorbent mats made of polypropylene or the like have been used as oil adsorbents, but such oil adsorbents do not provide sufficient oil adsorption. The nonwoven fabric of the present invention has high water repellency, and has high oil adsorption ability compared to water adsorption ability, and can selectively adsorb oil. In addition, since it is manufactured using water repellent pulp, it has high oil adsorption ability and can obtain a fast absorption rate. Furthermore, since it uses pulp, it can be incinerated after use and does not become industrial waste.

[0045] When the nonwoven fabric of the present invention is used as an oil sorbent, the content of water-repellent pulp in the nonwoven fabric is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more from the viewpoint of obtaining high oil adsorption, and is preferably 95% by mass or less, more preferably 90% by mass or less from the viewpoint of keeping the content of the heat-fusible adhesive in an appropriate range. An oil sorbent using a nonwoven fabric containing a large amount of pulp is preferred from the viewpoint of ease of disposal after absorbing oil.

[0046] When the nonwoven fabric of the present invention is used as an oil adsorbent, it is preferable to further provide another layer on at least one surface of the nonwoven fabric from the viewpoint of obtaining a powder removal prevention effect. The other layer is also called a skin layer, and is not particularly limited as long as it does not have water absorbency, and preferable examples thereof include PP spunbond, PET spunlace, and meltblown.

[0047] The oil that can be adsorbed by the oil adsorbent of the present invention is preferably oil with a viscosity of 10 to 500 cps, specifically, edible oil such as salad oil or sesame oil, heavy oil, industrial lubricating oil, gear oil, etc.

[0048] The oil sorbent of the present invention has a structure that does not fall apart when absorbing oil, and has the advantage of being easy to recover. The oil sorbent of the present invention is also preferable in that it does not easily sink in water after absorbing oil. The water-repellent pulp used in the nonwoven fabric constituting the oil adsorbent of the present invention may be used alone as the oil adsorbent, or the water-repellent pulp may be processed into a sheet, tube, or other shape for use. Furthermore, the water-repellent pulp may be packed into a bag and used as the oil adsorbent.

[0049] [Other uses] The nonwoven fabric of the present invention is not limited to applications as a sound absorbing material and an oil adsorbent, and can be used as a nonwoven fabric for various products such as breathable covers, breathable separators, automobile interiors, air conditioning equipment, and vacuum cleaners in the medical, pharmaceutical, beauty, hygiene, food and cooking, automotive, electrical and electronic equipment, electronics, and agricultural fields. EXAMPLES

[0050] The features of the present invention will be described in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0051] <Method of measuring average fiber diameter and average fiber length> The average fiber diameter and average fiber length of the fibers described below were measured by the following method. For synthetic fibers, the average fiber diameter was measured by referring to the manufacturer's standard value (test value) or by observation with a microscope. For pulp fibers, the average fiber diameter was measured based on the results of image analysis using a fiber length measuring device (e.g., KAANI Fiber Lab.). The average fiber length of synthetic fibers was measured by observation under a microscope, and that of pulp fibers was measured by a fiber length measuring device (e.g., KAANI Fiber Lab.) and observation under a microscope.

[0052] <Preparation of water-repellent pulp> A pulp sheet made from hardwood was defibrated to prepare defibrated pulp. The defibrated pulp obtained was impregnated with a water repellent (water repellent mainly composed of maleic petroleum resin alkali salt and liquid paraffin) to impart water repellency, and then dried to obtain water repellent pulp with strengthened bonds between the pulp and the water repellent. The average fiber diameter of the obtained water repellent pulp was 20 μm, and the average fiber length was 1.5 mm.

[0053] As comparative examples, the following pulp fibers were used: - Bleached softwood kraft pulp (NBKP): average fiber diameter 50μm, average fiber length 4mm

[0054] [Water repellency test] <Start time of subsidence> The settling time was measured according to the water absorption test (sedimentation method) specified in the JIS L1907: 2010 standard. Specifically, 1,000 mg of water-repellent pulp and NBKP were floated in a water tank (20 x 20 cm) containing water at 20°C ± 2°C, and the time until the samples became wet and started to settle (sedimentation time) was measured.

[0055] <Water retention capacity of pulp in water retention test> An acrylic base was placed on an acrylic frame (hollow rectangular prism) measuring 10 cm in length, width, and height, 6 cm, so that the inside diameter of the frame was tightly fitted to the acrylic base. The degree of fit of the base was such that even if water was poured into the frame with the base placed on it, a small amount of water would seep out. Separately, weighed filter paper (enough filter paper to absorb 40cc of water) was placed under the frame with the bottom installed, 2g of pulp fiber was evenly placed in this frame, 40cc of water was poured in, and after one minute, an acrylic weight of 700gf with approximately the same dimensions as the inner diameter of the frame was placed on it to gently apply a load to the pulp fiber. After one minute, the mass of the filter paper under the frame was measured, and the amount of water that had seeped out from the frame was measured. The difference between this and the 40g of water that had been poured in was taken as the pulp water retention capacity (g). In other words, the pulp water retention capacity is expressed by the following formula (a). Water retention capacity of pulp (g) = 40 (g) - amount of water leaked out (g) The amount of water that leaked out was measured from the difference between the mass of the filter paper measured before the test and the mass of the filter paper that had absorbed water after the test. The water retention capacity (blank) without pulp fiber was 0.6 g.

[0056] <Liquid flow test> An acrylic cylinder with an inner diameter of 3 cm and five drainage holes with a diameter of 3 mm in a cross shape on the bottom was placed on the wire mesh, and 1 g of pulp fiber was placed at a height of 4 cm (density 0.035 g / cm 3 ), 50 cc of water was poured in all at once, and the amount of water (g) that was discharged was measured and used as the liquid flow amount (g).

[0057] <Swelling ratio when water is dropped under microscope observation> 3-5 mg of pulp fiber was placed on a slide, and about 0.1 ml of water was dripped onto it using a dropper. After leaving it for about 5 minutes, the slide was tilted, and the water not absorbed by the pulp fiber was removed using a Kimwipe or similar. The fiber diameter of the pulp fiber was measured from micrographs taken before and after the dripping of water, and the swelling ratio was calculated using the following formula. Swelling ratio = {fiber diameter (width dimension) of pulp fiber after water dripping - fiber diameter (width dimension) of pulp fiber before water dripping} ÷ fiber diameter (width dimension) of pulp fiber before water dripping × 100 (%)

[0058] <Water absorption in tea bag test> The pulp fibers were placed in a tea bag (9.5 cm x 7 cm, nonwoven fabric with polyester as the main fiber material) (Tokiwa Tea Bag M, manufactured by Tokiwa Kogyo Co., Ltd.) so that the total mass was approximately 5 g, and a weight (500 g) was tied to the tip of the tea bag with a string. The mass of the pulp fibers before the test was calculated by subtracting the mass of the empty tea bag from the total mass. The tea bag with the weight attached was placed in a beaker containing water. The water was added to a height where the entire tea bag was completely submerged under the water surface. After soaking for 5 minutes, the tea bag was removed from the water and hung in the air for 5 minutes to drain the water. The mass of the tea bag (containing pulp fibers) after draining was measured, and the water absorption was calculated using the following formula. Water absorption (g / g) = (mass of tea bag containing pulp fiber after draining - mass of tea bag containing pulp fiber before immersion in water) ÷ mass of pulp fiber before test The mass of the empty tea bag was 0.42 g. The results of the water repellency test of the fibers used in the examples and comparative examples are shown in the table below.

[0059] [Table 1]

[0060] [Example 1] <Preparation of nonwoven fabric> While PET spunbond was being fed onto the mesh-like endless belt that was attached to the conveyor and running, the water-repellent pulp and heat-fusible fiber (polyethylene terephthalate composite fiber) were fed into an airlaid web forming machine in a mass ratio (water-repellent pulp:heat-fusible fiber=1:1 to 3:1) to a basis weight of 450 g / m 2 The mixture was fed so that the content became equal to or greater than 100%, and while being uniformly mixed in the air, it was allowed to fall and accumulate on a mesh-like endless belt together with the intake air flow, thereby forming a web on the PET spunbond to obtain an airlaid web. Next, a PET spunbond was further laminated on the airlaid web, and the web was passed through a box-type dryer (hot air circulating conveyor oven) capable of passing hot air through the web to perform hot air treatment to obtain a nonwoven fabric. The hot air treatment temperature (hot air circulating conveyor oven temperature) was set to 160°C, and a nonwoven fabric was obtained. The total basis weight, thickness and density of the resulting nonwoven fabric were measured, and the results are shown in Table 2.

[0061] [Comparative Examples 1 to 3] Comparative Example 1: A nonwoven fabric (felt) made only from synthetic fibers (type: PET) that was sprayed with a water repellent (fluorine-based). Comparative Example 2: Nonwoven fabric made using NBKP instead of water-repellent pulp (no post-processing). Comparative Example 3: The nonwoven fabric of Comparative Example 2 was sprayed with a water repellent (fluorine-based).

[0062] <Klemm water absorption> The Klemm water absorbency of the obtained nonwoven fabric was measured in accordance with JIS P8141:2004. The results are shown in Table 2. The Klemm water absorbency was evaluated according to the following evaluation criteria. -Evaluation criteria- 3: A sheet that barely absorbs water. Specifically, the Klemm water absorbency is 0 mm or more and less than 15 mm. 2: A sheet that absorbs water by capillary force. Specifically, the Klemm water absorbency is 15 mm or more and less than 50 mm. 1: Water-absorbent sheet. Specifically, the Klemm water absorbency is 50 mm or more.

[0063] <Klemm water absorbency after washing treatment> The resulting nonwoven fabric was washed with running tap water at 30° C. for 1 hour, and then the Klemm water absorbency was measured in the same manner.

[0064] <Klemm water absorption after heat resistance test> The nonwoven fabric thus obtained was subjected to a heat resistance test in which it was exposed to an environment of 100° C. for 1000 hours, and then the Klemm water absorbency was measured in the same manner.

[0065] <Klemm water absorption after high temperature and humidity test> The obtained nonwoven fabric was subjected to a high temperature and high humidity test in which it was exposed to an environment of 85° C. and 95% RH for 600 hours, and then the Klemm water absorbency was measured in the same manner.

[0066] <Klemm water absorption after heat cycle test> The obtained nonwoven fabric was subjected to a heat cycle test in which one cycle was -10°C for 1 hour and 60°C for 1 hour, and this cycle was repeated 30 times, and then the Klemm water absorbency was measured in the same manner.

[0067] [Table 2]

[0068] The nonwoven fabric of Example 1 was subjected to a heat resistance test, a high temperature and high humidity test, and a heat cycle test, and the Klemm water absorbency of the nonwoven fabric after each test was similarly measured. As a result, the Klemm water absorbency of the nonwoven fabric after each test was 0 mm, and the evaluation was 3. Thus, it was demonstrated that the nonwoven fabric of the present invention has high water repellency, and furthermore, it is possible to provide a nonwoven fabric having excellent water repellency even under severe conditions such as high temperature and high humidity.

[0069] <Measurement of normal incidence sound absorption coefficient> Using sound absorption measurement samples made from each nonwoven fabric, normal incidence sound absorption was measured in accordance with JIS A 1405-2:2007 (ISO 10534-2, ASTM E1050). Note that the sound absorption rate of a material varies depending on the angle at which the sound is incident, so the value of the sound absorption rate differs depending on the measurement method. The sound absorption rate measured using an acoustic tube under conditions where sound is perpendicularly incident on the material is called the "normal incidence sound absorption rate." The "normal incidence sound absorption rate" is used to develop sound absorbing materials and understand their characteristics. The normal incidence sound absorption coefficient was measured for the following frequencies: 1,000Hz, 1,250Hz, 1,600Hz, 2,000Hz, 2,500Hz, 3,150Hz, 4,000Hz, 5,000Hz, and 6,300Hz. The normal incidence sound absorption coefficients at each frequency are shown in Figure 1. In addition, the evaluation was performed according to the following criteria. 3: 1,000-6,300 Hz average value is 35% or more, 2,500-6,300 Hz average value is 60% or more, and 6,300 Hz average value is 70% or more 2: Among nonwoven fabrics that do not satisfy the above evaluation 3, the average value of 1,000 to 6,300 Hz is 25% or more, the average value of 2,500 to 6,300 Hz is 35% or more, and the average value of 6,300 Hz is 50% or more 1: Does not fall under the above criteria of 3 or 2

[0070] [Table 3]

[0071] Comparative Example 3 exhibited the same sound absorbing properties as Comparative Example 2.

[0072] <Sound absorption rate after durability test> The obtained nonwoven fabrics were subjected to a heat resistance test, a high temperature and high humidity test, and a heat cycle test, and the sound absorption coefficients of the nonwoven fabrics after the tests were measured in the same manner as described above. For each nonwoven fabric, an excellent sound absorption coefficient similar to that before the tests was obtained.

[0073] [Oil and water absorption test] 1. Drop test The nonwoven fabric obtained in Example 1 (thickness: 5 mm) and the softwood pulp nonwoven fabric obtained in Comparative Example 2 above (thickness: 5 mm) were used as samples, each 3 cm square. These were placed on a petri dish (Fig. 2(A)), and 1.5 ml of water (Fig. 2(B)) and salad oil (Nissin salad oil (edible blended oil: edible soybean oil, edible rapeseed oil), manufactured by Nisshin Oillio Group, Ltd., viscosity 65 mpa s at 23.5°C) (Fig. 2(C)) were dropped onto the surface. The results are shown in Fig. 2.

[0074] In FIG. 2, (a) is the softwood pulp nonwoven fabric obtained in Comparative Example 2, and (b) is the nonwoven fabric obtained in Example 1. As shown in Fig. 2(A), each nonwoven fabric (3 cm square) was placed on a petri dish. As shown in Fig. 2(B), 1.5 ml of water was dropped onto each nonwoven fabric using a dropper, and water absorption was observed in the softwood pulp nonwoven fabric obtained in Comparative Example 2 (Fig. 2(B)(a)). On the other hand, the nonwoven fabric produced using the water-repellent pulp obtained in Example 1 (Fig. 2(B)(b)) exhibited water repellency, with water forming beads on the surface of the nonwoven fabric. Similarly, when 1.5 ml of oil was dropped onto each nonwoven fabric using a dropper, both samples showed oil absorption (Figure 2(C) (a) and (b)). As shown in the results, the nonwoven fabric of the present invention did not absorb water, but instead formed beads on the surface. On the other hand, the nonwoven fabric made using NBKP instead of water-repellent pulp (comparative example) absorbed water. Both the nonwoven fabric of the present invention and the nonwoven fabric made using NBKP absorbed edible oil.

[0075] 2. Absorption test with water-oil mixture The sample from 1 above was used. 40 ml of water was placed in a petri dish with an inner diameter of 90 mm, and 4 ml of edible oil was added to it to prepare a mixed liquid. Each sample was placed on the surface of the mixed liquid and allowed to absorb for about 10 seconds. With the nonwoven fabric of the present invention, most of the oil was absorbed, and only water remained. With the softwood pulp nonwoven fabric, both water and oil were absorbed, and a lot of oil remained.

[0076] 3. Oil and water absorption test In the same manner as in Example 1, air-laid nonwoven fabrics A to C were produced using water-repellent pulp. The obtained nonwoven fabrics A to C were subjected to oil absorption and water absorption tests by the following method. 2 ) was immersed for 5 minutes in an aluminum bath filled with salad oil (Nissin salad oil (edible blended oil: edible soybean oil, edible rapeseed oil), manufactured by Nisshin Oillio Group, Ltd., viscosity 65 mPa s at 23.5°C) or water. The nonwoven fabric was then removed onto a wire mesh, left to drain off the oil or water for 1 minute, and the mass of each was measured. The results are shown in Tables 4 and 5.

[0077] [Table 4]

[0078] [Table 5]

[0079] As shown in the results of Tables 4 and 5, in the oil absorption test, 10 to 13 g of oil was absorbed. The oil began to be rapidly absorbed into the nonwoven fabric immediately after immersion, and was absorbed into the entire nonwoven fabric within about 1 minute of immersion. In the water absorption test, the amount of water absorbed was 0.3 to 0.4 g, but this was attached to the surface of the nonwoven fabric and did not penetrate into the nonwoven fabric.

[0080] Next, a 5 cm square (0.0025 m 2) was floated in an aluminum tray containing water in which salad oil had been suspended to a concentration of 5% by mass, and the liquid and tray were shaken to thoroughly contact the floating oil on the surface of the water, after which the nonwoven fabric was removed and its mass was measured. Additional nonwoven fabric was added until the floating oil on the surface of the water disappeared. The thickness and mass of the second piece of nonwoven fabric added are as shown in Table 6. The results are shown in Table 6.

[0081] [Table 6]

[0082] As shown in the results in Table 6, in this test, the two sheets of nonwoven fabric were able to adsorb the floating oil added. In addition, it was confirmed that when the nonwoven fabric was allowed to float, the oil was adsorbed on the edge surface of the nonwoven fabric sheet, and then only the oil was selectively sucked into the inside of the sheet. The total amount of liquid absorbed by the two sheets of nonwoven fabric was 14.4 g, which was almost the same as the amount of oil put into the pad. In other words, it was confirmed that the nonwoven fabric of the present invention selectively absorbs oil. The amount of adsorption was also high. Here, the amount of adsorption is an index of oil adsorption test data, and normally, an adsorption amount of 6 g / g or more or 0.8 / cm is required for an oil adsorbent. 3 If the above is met, it can be said that the product is sufficiently effective (see Oil Adsorbent (Mat-like) Performance Test Standards: Type Approval Standards, Notice No. 52 from the Director-General of the Ship Bureau, Ministry of Transport). The nonwoven fabric of the present invention used in the oil absorption test did not lose paper powder from the sample and had a fast absorption rate; oil absorption began immediately after immersion and was completed within approximately one minute. [Industrial Applicability]

[0083] The nonwoven fabric of the present invention has high water repellency, and maintains high water repellency even under harsh conditions such as high temperature and humidity. Furthermore, the nonwoven fabric of the present invention is suitable for use as a sound absorbing material, and has high sound absorption, and also maintained high sound absorption even after durability testing. Furthermore, the nonwoven fabric of the present invention is suitable for use as an oil adsorbent, and has been shown to have high selectivity for oil. As a water repellent nonwoven fabric, the nonwoven fabric of the present invention is expected to be used in various applications, and is particularly useful as a sound absorbing material that absorbs noise and vibration, and an oil adsorbent.

Claims

1. A sound-absorbing material comprising a nonwoven fabric containing water-repellent pulp and a heat-fusible adhesive, The water-repellent pulp satisfies the following (1), The nonwoven fabric has a water absorption of 0.3 g / g or less. Sound absorbing material. (1) In the water absorption test specified in the JIS L1907:2010 standard, the settling start time is 30 seconds or more.

2. The sound-absorbing material according to claim 1, wherein the water-repellent pulp further satisfies at least one of the following (2) to (5). (2) The pulp water retention capacity in the water retention test is 15 g or less. (3) The amount of liquid flowing in the liquid flow test is 35 g or more. (4) When water is dropped onto the product under a microscope, the swelling rate is 20% or less. (5) The water absorption amount in the tea bag test is 10 (g / g) or less.

3. The sound-absorbing material according to claim 1 or 2, wherein the nonwoven fabric is a dry-laid nonwoven fabric.

4. The sound-absorbing material according to claim 1, wherein the density of the nonwoven fabric is 0.05 g / cm 3 or more and 0.1 g / cm 3 or less.

5. An acoustic material described in any one of claims 1 to 4, wherein the thickness of the nonwoven fabric is 3.0 mm or more and 6.0 mm or less.

6. A sound-absorbing material as described in any one of claims 1 to 5, wherein the average normal incidence sound absorption coefficient at 1,000 to 6,300 Hz is 35% or more, the average normal incidence sound absorption coefficient at 2,500 to 6,300 Hz is 60% or more, and the normal incidence sound absorption coefficient at 6,300 Hz is 70% or more.

7. An acoustic material as described in any one of claims 1 to 6, wherein the Klemm water absorbency of the nonwoven fabric measured in accordance with JIS P8141:2004 is less than 30 mm.

8. The sound-absorbing material according to any one of claims 1 to 7, wherein the nonwoven fabric has a Klemm water absorbency of less than 30 mm as measured in accordance with JIS P8141:2004 after being subjected to a water washing treatment in which the nonwoven fabric is washed with running water for 1 hour.

9. The sound-absorbing material according to any one of claims 1 to 8, wherein the nonwoven fabric has a Klemm water absorption of less than 30 mm as measured in accordance with JIS P8141:2004 after being subjected to a heat resistance test in which the nonwoven fabric is exposed to an environment of 100°C for 1000 hours.

10. The sound-absorbing material according to any one of claims 1 to 9, wherein the nonwoven fabric is subjected to a high temperature and high humidity test in which the nonwoven fabric is exposed to an environment of 85°C and 95% RH for 600 hours, and then has a Klemm water absorption of less than 30 mm as measured in accordance with JIS P8141:2004.

11. The sound-absorbing material according to any one of claims 1 to 10, wherein the nonwoven fabric is subjected to a heat cycle test in which one cycle is at -10°C for 1 hour and at 60°C for 1 hour, and this cycle is repeated 30 times. After this, the Klemm water absorption measured in accordance with JIS P8141:2004 is less than 30 mm.

12. The sound-absorbing material according to any one of claims 1 to 11, wherein the content of the water-repellent pulp in the nonwoven fabric is 50% by mass or more and 95% by mass or less.

13. The sound-absorbing material according to any one of claims 1 to 12, comprising a resin layer on at least one surface of the nonwoven fabric.

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