Nonwoven fabric for oil absorber

Abstract

To provide a nonwoven fabric for oil absorber, which suppresses falling off or dispersion of fibers, is excellent in oil absorbing performance and absorbed oil holding performance, and imposes less load on environment.SOLUTION: A nonwoven fabric includes kapok fibers, cotton fibers, and polylactic acid fibers. The polylactic acid fiber has single fiber fineness of 3 to 20 dtex. When total mass of the nonwoven fabric is 100 mass%, total content of the kapok fibers and the cotton fibers is 15 to 30 mass%, and content of the polylactic acid fibers is 70 to 85 mass% in the nonwoven fabric for oil absorber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric for an oil sorbent, which comprises kapok fiber, cotton fiber, and polylactic acid fiber. [Background technology]

[0002] Nonwoven fabrics are known for absorbing oil spilled in marine accidents or oil leaks in factories. In addition, restaurant kitchens and commercial kitchens are required to install grease interceptors (grease traps) to separate and remove oils and fats (grease) contained in wastewater, and nonwoven fabrics are known for recovering oil in such grease traps.

[0003] Conventionally, the use of kapok fiber has been considered for the composition of these nonwoven fabrics. Here, Patent Document 1 describes kapok fiber as being the seed fiber of a plant belonging to the Bombaceae family, and as being a natural fiber primarily composed of cellulose, which is inherently water-repellent, and as being composed of a single cell, with a thin cell wall but a thick lumen, which contains air bubbles, giving it an extremely low specific gravity and allowing it to float in water up to 20 to 40 times its own weight, and as having a high oil absorption capacity of approximately 50 times that of 1 g of fiber.

[0004] Various blends of kapok fiber with cotton, polyester, or polypropylene fibers have also been investigated. For example, Patent Document 2 describes how using a composite nonwoven fabric containing kapok fiber and thermoplastic polymer fibers can reduce the shedding and scattering of kapok fiber compared to using kapok fiber alone, resulting in a filter material for a flowing water separation filter with excellent shape stability and flowing water separation performance. Patent Document 3 also describes a sheet-shaped oil adsorbent in which kapok fiber and cotton fiber are bonded and fixed with heat-sealed fibers made of polypropylene or polyester. It describes how using cotton fiber reduces raw material costs and improves entanglement between the fibers, and how bonding and fixing with heat-sealed fibers made of polypropylene or polyester prevents scattering of the kapok fiber, resulting in a sheet-shaped oil adsorbent with excellent oil absorption and processability.

[0005] Meanwhile, in recent years, marine pollution by microplastics has become a global social problem, and fiber waste from general-purpose non-biodegradable synthetic fibers has been identified as one of the sources of microplastics. Therefore, from the perspective of environmental conservation, oil sorbents that do not contain non-biodegradable synthetic fibers are desired. As such an oil sorbent, Patent Document 4 describes a method in which cellulose fiber waste is needle-punched to form a nonwoven fabric of a predetermined thickness, and this is then immersed in a water-repellent solution of a predetermined concentration to form a sheet-shaped oil sorbent.

[0006] However, the sheet-shaped oil sorbent of Patent Document 3 is inadequate from the perspective of environmental conservation because the heat-fusible fibers are made from fossil fuel-derived materials, and its ability to retain adsorbed oil is also insufficient. Furthermore, the oil sorbent of Patent Document 4 is formed into a sheet by needle punching, and in order to ensure strength and buoyancy, it uses special extra-long staple cotton fibers with long single filaments or cellulose fibers other than cotton fibers with long single filaments (e.g., rayon fibers). Furthermore, when using cotton fibers with short single filaments, it is necessary to needle punch the cotton fibers to obtain a sheet-shaped nonwoven fabric, and then further needle punch cellulose nonwoven fabrics to be laminated on top and bottom of it, resulting in a complex manufacturing process that is cost-inefficient. Furthermore, because it uses only kapok fiber and cellulose fiber, its oil adsorption and retention capabilities are insufficient. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 52-138081 [Patent Document 2] Korean Patent Publication No. 10-2015-0092506 [Patent Document 3] Japanese Patent Application Publication No. 4-161289 [Patent Document 4] Japanese Patent Publication No. 2022-74353 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention solves the above problems, and aims to provide a nonwoven fabric for oil adsorbents that suppresses the shedding and scattering of kapok fibers, and that not only has excellent oil absorption performance but also has excellent performance in retaining adsorbed oil, and that places a small burden on the environment. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention.

[0010] That is, the present invention is summarized as follows (a) to (b). (i) A nonwoven fabric for oil adsorbents comprising kapok fiber, cotton fiber and polylactic acid fiber, wherein the polylactic acid fiber has a single yarn fineness of 3 to 20 dtex, and when the total mass of the nonwoven fabric is 100% by mass, the total content of the kapok fiber and cotton fiber is 15 to 30% by mass, and the content of the polylactic acid fiber is 70 to 85% by mass. (ii) The nonwoven fabric for oil adsorbents according to (i), having an oil adsorption capacity calculated by the following formula of 18 times or more and an oil retention rate of 84% or more. Oil adsorption rate = (w2-w1) / w1 Oil retention rate (%)=(w3 / w2)×100 (w1: weight of nonwoven fabric before oil absorption, w2: weight of nonwoven fabric after 5 minutes of oil absorption, w3: weight of nonwoven fabric after 65 minutes of oil absorption) [Effects of the Invention]

[0011] The nonwoven fabric for oil adsorbents of the present invention contains kapok fiber, cotton fiber, and polylactic acid fiber in specific proportions, with the polylactic acid fiber having a specific single filament fineness. Therefore, it has excellent oil absorption performance and also excellent oil retention performance. Furthermore, since it contains polylactic acid fiber, which is a biodegradable fiber, it places less strain on the environment, making it preferable from the perspective of environmental conservation. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] The nonwoven fabric for oil adsorbent of the present invention (hereinafter sometimes referred to as the nonwoven fabric of the present invention) is a nonwoven fabric containing kapok fiber, cotton fiber, and polylactic acid fiber.

[0014] The kapok fiber used in the present invention is the seed hair that grows on the inner surface of the fruit of the kapok tree, and is a fiber composed mainly of cellulose with an average fiber length of about 15 mm. Kapok fiber is characterized by its hollow structure (hollowness of about 70-80%) and a smooth fiber surface that is coated with a type of wax.

[0015] In the present invention, the kapok fiber preferably has a small fiber diameter and a long fiber length from the viewpoints of strength when made into a nonwoven fabric and prevention of shedding or scattering from the nonwoven fabric. Specifically, it is preferable to use kapok fiber with an average fiber length of 11 to 18 mm, an average fiber diameter of 20 to 28 μm, and a hollow ratio of 65 to 85%. It is preferable that the kapok fiber raw cotton contains as little impurities as possible, such as seeds and fruit peels, and contamination with polypropylene, a material used in packaging materials.

[0016] The nonwoven fabric of the present invention contains cotton fibers in addition to kapok fibers. The reason for including cotton fibers is that, as mentioned above, kapok fibers are very lightweight fibers with a hollowness of approximately 70-80% and are prone to shedding and scattering during handling, making it difficult to form a nonwoven fabric using only kapok fibers. By using cotton fibers, which are natural fibers like kapok fibers, it is possible to prevent the shedding and scattering of kapok fibers and improve operability. Furthermore, because cotton fibers, like kapok fibers, are plant fibers that contain plant-derived oils, they can impart water repellency to the nonwoven fabric of the present invention.

[0017] The cotton fiber used in the present invention can be any type of raw cotton that has not been chemically treated from the viewpoint of water repellency, but it is preferable to use combed cotton, which has a high content of oils and waxes on the surface and has a short fiber length suitable for retaining oil.The cotton fiber preferably has a fiber length of 20 to 40 mm from the viewpoint of ensuring good entanglement with kapok fiber or polylactic acid fiber.

[0018] Furthermore, the nonwoven fabric of the present invention contains polylactic acid fibers. Polylactic acid fibers have moderate oil adsorption properties and are biodegradable biomass materials derived from plant resources. Therefore, by using polylactic acid fibers in the present invention, the resulting nonwoven fabric of the present invention exhibits excellent oil adsorption properties and is environmentally friendly.

[0019] To improve oil adsorption and retention, the polylactic acid fiber has a single fiber fineness of 3 to 20 dtex, preferably 3 to 16 dtex, and more preferably 4 to 12 dtex. If the single fiber fineness is less than 3 dtex, the voids formed between the fibers when made into a nonwoven fabric are too small, resulting in a low oil adsorption capacity and poor entanglement with the kapok fiber or cotton fiber, resulting in poor oil retention. On the other hand, if the single fiber fineness exceeds 20 dtex, the voids formed between the fibers when made into a nonwoven fabric are too large, which may cause the absorbed oil to easily leak out and reduce retention. Furthermore, the average fiber length is preferably 35 to 76 mm, more preferably 45 to 55 mm, from the viewpoint of good entanglement with the kapok fiber or cotton fiber.

[0020] The polylactic acid fibers contained in the nonwoven fabric of the present invention include those obtained by melt-spinning polylactic acid to a predetermined diameter. Examples of polylactic acid include poly-D-lactic acid or poly-L-lactic acid, which are homopolymers of polylactic acid, as well as copolymers of D-lactic acid and L-lactic acid, copolymers of D-lactic acid and hydroxycarboxylic acid, copolymers of L-lactic acid and hydroxycarboxylic acid, and copolymers of D-lactic acid, L-lactic acid and hydroxycarboxylic acid. In the present invention, among the polylactic acids, poly-D-lactic acid or poly-L-lactic acid, or copolymers of D-lactic acid and L-lactic acid, are preferred, and their melting points are preferably 150°C or higher and 190°C or lower. The melting points of poly-D-lactic acid and poly-L-lactic acid are approximately 180°C, and when using a copolymer, the copolymerization ratio of the monomer components can be determined so that the melting point of the copolymer is 150°C or higher. If the melting point of polylactic acid satisfies the above range, it has high crystallinity, so that heat shrinkage is unlikely to occur even when heat treatment processing is performed, and the nonwoven fabric has few defects such as holes.

[0021] The kapok fiber content is preferably 8 to 25% by mass, and more preferably 10 to 20% by mass, when the total mass of the nonwoven fabric is 100% by mass. If the kapok fiber content is 8 to 25% by mass, the kapok fiber content is not too small, resulting in excellent oil absorption performance, and is not too large, resulting in little scattering during the manufacturing process and less deterioration in the shape stability of the nonwoven fabric.

[0022] The content of cotton fiber is preferably 5 to 20% by mass, and more preferably 8 to 18% by mass, when the total mass of the nonwoven fabric is 100% by mass. When the content of cotton fiber is 5 to 20% by mass, by using it together with kapok fiber, scattering of kapok fiber can be suppressed, and the nonwoven fabric can have excellent formability.

[0023] Furthermore, when the total mass of the nonwoven fabric is taken as 100% by mass, the total content of kapok fiber and cotton fiber is 15 to 30% by mass, preferably 15 to 25% by mass. When the total content of these fibers is 15% by mass or more, the nonwoven fabric of the present invention can have oil adsorption properties and a reduced environmental impact. Furthermore, when the total content is 30% by mass or less, even when the fibers are combined by needle punching during the manufacturing process of the nonwoven fabric of the present invention, as described below, scattering of kapok fiber during the process can be suppressed, and the nonwoven fabric can have excellent moldability.

[0024] The content of polylactic acid fiber is 70 to 85% by mass, preferably 75 to 85% by mass, when the total mass of the nonwoven fabric is 100% by mass. A polylactic acid fiber content of 70% by mass or more can further suppress scattering and detachment of kapok fiber, improving strength and providing excellent handleability. Furthermore, the nonwoven fabric of the present invention can be made to have excellent oil retention. On the other hand, a content of 85% by mass or less can ensure that the kapok fiber and cotton fiber are contained in an appropriate amount in the nonwoven fabric, resulting in a well-balanced oil adsorption and oil retention. Furthermore, the biodegradability of polylactic acid fiber reduces fiber embrittlement, thereby preventing deterioration in the overall strength of the nonwoven fabric of the present invention even during long-term storage.

[0025] In the present invention, by setting the contents of kapok fiber, cotton fiber, and polylactic acid fiber within specific ranges as described above, and by setting the single filament fineness of the polylactic acid fiber within specific ranges, it is possible to obtain a nonwoven fabric that has a good balance of oil absorption and oil retention properties and is excellent in both.

[0026] In addition to kapok fiber, cotton fiber, and polylactic acid fiber, the nonwoven fabric of the present invention may contain other fibers as long as the oil adsorption performance is not impaired. Examples of other fibers include cellulose fibers other than kapok fiber and cotton fiber, wool fibers, polyester fibers, polyurethane fibers, and polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.). In particular, the use of polyolefin fibers can further improve the oil adsorption performance of the nonwoven fabric. From the perspectives of oil retention performance and environmental conservation, it is preferable that the content of other fibers be 10% by mass or less of the total mass of the nonwoven fabric.

[0027] Furthermore, from the viewpoint of supplementing strength and improving dimensional stability, a nonwoven fabric or woven fabric may be laminated on at least one of the front and back surfaces of the nonwoven fabric of the present invention as a base fabric. The nonwoven fabric or woven fabric that serves as the base fabric is not limited as long as it does not impair the oil adsorption and oil retention properties, and preferred examples include nonwoven fabrics or woven fabrics made of cotton fibers, polylactic acid fibers, polyester fibers, polyurethane fibers, polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), etc.

[0028] The basis weight of the nonwoven fabric of the present invention is 150 to 220 g / m 2 It is preferable that the thickness is 160 to 200 g / m 2 It is more preferable that the basis weight is 150 g / m 2 When the density is 220 g / m or more, the strength is excellent, the oil absorption amount is sufficiently improved, and the oil retention property is also excellent. 2 If the amount is less than this, the amount of oil adsorbed will not be too large, and when the nonwoven fabric after oil absorption is recovered, breakage due to the fabric becoming too heavy can be suppressed.

[0029] The thickness of the nonwoven fabric of the present invention is preferably 1.0 to 6.0 mm, more preferably 1.5 to 5.0 mm, and even more preferably 1.5 to 4.0 mm, from the viewpoint of achieving an excellent balance between strength and liquid permeability for mixtures containing water and oil, and keeping the basis weight within an appropriate range. The size (surface area) of the nonwoven fabric is not particularly limited and can be selected appropriately depending on the actual usage environment.

[0030] The nonwoven fabric of the present invention has excellent oil absorption performance, and when the oil adsorption capacity is measured by the method described below as an index of oil absorption capacity, it is preferably able to adsorb 18 times or more of its own weight of oil. That is, the oil adsorption multiplier measured by the method described below indicates that the nonwoven fabric of the present invention can adsorb a large amount of oil in a short period of time. Here, if the oil adsorption multiplier is 18 times or more of its own weight, the amount of oil recovered in one oil absorption operation is sufficiently large, resulting in excellent workability. The oil adsorption multiplier is preferably 18 times or more of its own weight, more preferably 20 times or more, and even more preferably 22 times or more. In the present invention, the oil adsorption capacity can be adjusted to a suitable range by adjusting the content and fineness of various fibers, the basis weight and thickness of the nonwoven fabric, etc.

[0031] (Oil absorption capacity, oil absorption capacity ratio compared to nonwoven fabric for oil absorbent) The nonwoven fabric of the present invention was cut into a 10 cm x 10 cm test piece and its mass (w1) (g) was measured. Next, 1 liter of salad oil (Ajinomoto Co., Inc.'s "Soybean Oil Salad Oil," a mixture of edible soybean oil and edible rapeseed oil) maintained at 25°C was poured into a stainless steel tray (220 mm wide x 275 mm deep x 45 mm high) to a depth of approximately 18 mm. The test piece was gently floated on top of the oil and then gently moved for 3 minutes to absorb the oil. The test piece was then gently removed and left on a stainless steel sieve (23 cm x 30 cm) for 5 minutes with the oil dripping down. The mass (w2) (g) was then measured again (i.e., the weight of the nonwoven fabric after being left for 5 minutes after oil absorption). The oil adsorption amount (g) and the oil adsorption ratio relative to the test piece's own weight were calculated using the following formula. This procedure was repeated twice (N = 2) and the average value was calculated. Oil adsorption amount (g)=w2-w1 Oil absorption rate for nonwoven fabric for oil absorbent = (w2-w1) / w1

[0032] Furthermore, the nonwoven fabric of the present invention has excellent ability to retain absorbed oil for a long period of time. As an index of oil retention, the oil retention rate, measured by the following method, is preferably 84% or more, more preferably 86% or more, and even more preferably 88% or more. Here, an oil retention rate of 84% or more means that oil once absorbed is unlikely to be released from the nonwoven fabric even after a certain period of time has passed. In the present invention, the oil retention rate can be adjusted to a suitable range by adjusting the content and fineness of various fibers, the basis weight and thickness of the nonwoven fabric, etc.

[0033] (Oil retention rate measurement) After measuring the mass (w2) (g) in the oil adsorption measurement test, the test piece is placed back on the stainless steel sieve (size: 23 cm x 30 cm) and left for 1 hour with the oil dripping off, after which the mass (w3) (g) is measured (i.e., the weight of the nonwoven fabric after being left for a total of 65 minutes after oil adsorption). The oil retention rate is then calculated using the following formula. The above procedure is repeated twice (N=2) and the average value is calculated. Oil retention rate (%)=(w3 / w2)×100

[0034] The reason why the nonwoven fabric of the present invention is excellent not only in oil absorption but also in the ability to retain absorbed oil is thought to be due to the use of polylactic acid fibers. Conventionally used nonwoven fabrics that blend kapok and cotton fibers have excellent oil absorption performance above a certain level because the cotton fibers have plant-derived oil (lipophilic) attached to their surface. However, because the cotton fibers themselves are cellulose fibers with many hydrophilic -OH groups in their molecules, the oil is easily released from the fibers over time after adsorption. Furthermore, when an oil adsorbent nonwoven fabric containing a large amount of kapok and cotton fibers comes into contact with the surfactant components contained in detergents, the oil in the surface of the kapok and cotton fibers is lost, resulting in a fabric that is less hydrophilic and has poorer oil absorption performance.

[0035] On the other hand, polylactic acid fibers have moderate oil absorption capacity, and the fibers themselves are lipophilic, so absorbed oil is less likely to be released from the fibers. Therefore, the nonwoven fabric of the present invention is excellent not only in oil absorption capacity but also in oil retention capacity, and is thought to be able to suppress a decrease in oil absorption capacity and oil retention capacity even when it comes into contact with surfactant components. Therefore, even when the nonwoven fabric of the present invention is installed in, for example, a grease trap, it can collect more oil, reducing the number of replacements, and further, because the oil is properly retained in the nonwoven fabric, it is easy to handle when replacing it.

[0036] As described above, the nonwoven fabric of the present invention has specific ranges of contents of kapok fiber, cotton fiber, and polylactic acid fiber, and also has specific ranges of single filament fineness of the polylactic acid fiber, so that the nonwoven fabric can have an oil absorption capacity and retention rate equal to or greater than specific levels, and is excellent in both oil absorption and oil retention. Therefore, the nonwoven fabric can have performance equivalent to that of a nonwoven fabric made only of polypropylene fiber, which is generally considered to have excellent oil absorption and oil retention.

[0037] Furthermore, in order to improve the oil absorption capacity of the nonwoven fabric of the present invention, a water repellent agent may be attached to the surface of the nonwoven fabric. The method for attaching the water repellent agent will be explained later in the manufacturing process.

[0038] Next, the method for producing the nonwoven fabric of the present invention will be described below.

[0039] The method for producing the nonwoven fabric of the present invention is not limited. The nonwoven fabric may be formed by bonding the fibers together using a web containing kapok fiber, cotton fiber, and polylactic acid fiber, using methods such as chemical bonding with an adhesive resin (chemical bonding, resin bonding), thermal fusion bonding, mechanical entanglement using hooked needles (needle punching), or hydroentanglement using a high-pressure water jet. In the present invention, a method of bonding the fibers together using needle punching is preferred. Specifically, the kapok fiber, cotton fiber, and polylactic acid fiber are first mixed and opened, and then a web is formed using a carding machine or air laying using an air flow. In the present invention, air laying is more preferred from the perspective of obtaining a nonwoven fabric with an appropriate thickness. Next, the fibers are bonded together using needle punching. By needle punching, the mixed fibers are intricately entangled in the thickness direction, mainly strengthening the entanglement of the nonwoven fabric in the thickness direction.

[0040] The needle-punching process may be performed on a single web, or multiple webs may be stacked as needed. When multiple webs are stacked, for example, by changing the layer direction angle each time a web is stacked (for example, by stacking the webs orthogonally), the nonwoven fabric of the present invention can be made to have superior strength and more uniform oil adsorption. In addition, from the viewpoint of further increasing the strength of the nonwoven fabric of the present invention, the web may be punched together with the nonwoven fabric or woven fabric that serves as the base fabric.

[0041] Furthermore, when a water repellent agent is applied to the surface of the nonwoven fabric of the present invention to improve the oil absorption performance, the water repellent agent can be applied to the cotton (wadding) state when kapok fiber, cotton fiber, and polylactic acid fiber are blended during the web formation process, or it can be applied to the surface of the nonwoven fabric using a known method after the nonwoven fabric is formed. However, from the perspective of facilitating oil capture and improving oil adsorption, it is preferable to apply the water repellent agent to the cotton state during blending so that the water repellent agent is applied to the entire fiber surface. A non-fluorinated water repellent agent is preferably used as the water repellent agent. Non-fluorinated water repellents have a surface tension higher than oil but lower than water, allowing for simultaneous oil adsorption and water repellency. Furthermore, when short fibers are air-laid or carded to form a web, polylactic acid fibers tend to become electrostatically charged when opened, so an antistatic agent is typically used in combination with the water repellent agent. However, the use of an antistatic agent can sometimes improve hydrophilicity, which can actually reduce water repellency. Even in such a case, if a non-fluorine-based water repellent agent is used, oil adsorption and water repellency can be achieved simultaneously.

[0042] The nonwoven fabric of the present invention can be used in various ways by processing it into a predetermined shape. For example, it can be used by folding it or fixing it with heat fusion or adhesive. When used in a mixture containing water and oil (e.g., wastewater), the nonwoven fabric of the present invention can efficiently separate the water and oil and sufficiently adsorb only the oil. This significantly reduces the burden of work involved in treating wastewater in grease traps or oil spills at sea due to accidents. [Example]

[0043] The present invention will be described in more detail below with reference to examples. The methods for measuring and evaluating various characteristic values ​​are as follows. (a) Single yarn fineness of polylactic acid fiber Measurement was carried out in accordance with JIS L1015 8.5.1 Method A. (b) Fiber length of polylactic acid fiber The measurements were carried out in accordance with JIS L1015 8.4.1 direct method (method C), except that the number of measurements was set to 25. (c) Weight The obtained nonwoven fabric was cut into a size of 10 cm x 10 cm, and the mass was measured. 2 Converted to mass per unit, basis weight (g / m 2 ) was sought. (d) Thickness The thickness of the obtained nonwoven fabric was measured at 10 points using a thickness measuring device (manufactured by Ozaki Seisakusho Co., Ltd.: product name Peacock H), and the average value was taken as the thickness (mm) of the nonwoven fabric. (e) Oil adsorption amount, ratio of oil adsorption amount to sheet The obtained nonwoven fabric was measured by the above-mentioned method. (f) Oil retention rate The obtained nonwoven fabric was measured by the above-mentioned method.

[0044] The kapok fiber, cotton fiber, polylactic acid fiber, and polypropylene fiber used in the examples are as follows.

[0045] [Kapok fiber] Produced by PT Randu Indo Prima, produced in East Java, Indonesia, with an average fiber diameter of 21.5 μm and an average fiber length of 14.6 mm.

[0046] The average fiber diameter was calculated by the Boken Quality Evaluation Organization, a general incorporated foundation, by measuring the width using a microscope in accordance with JIS L 1030 to determine the average long diameter of the kapok fiber. The average fiber length was calculated by the Boken Quality Evaluation Organization, a general incorporated foundation, by determining the average fiber length of kapok fiber according to JIS L 1015, chemical fiber staple test method.

[0047] [Cotton fiber] Indian organic cotton, BUNNY BRAHMA medium-length staple (staple length 1.1 / 8 to 1.5 / 16 inches (28.6 mm to 33.3 mm), thickness 3.5 to 4.9 micronaires, fiber strength 28 GPT (g / tex) or more)

[0048] [Polylactic acid fiber] P1: Fiber length: 51 mm, single yarn fineness: 15 dtex, melting point: 170°C, heat shrinkage rate: 11.0% (measured according to JIS L1015 8.15 b; left at 120°C for 30 minutes) P2: Fiber length: 51 mm, single fiber fineness: 5.8 dtex, melting point: 170°C, heat shrinkage rate: 11.0% (measured according to JIS L1015 8.15 b method; left at 120°C for 30 minutes) P3: Fiber length: 51 mm, single yarn fineness: 1.7 dtex, melting point: 170°C, heat shrinkage rate: 11.0% (measured according to JIS L1015 8.15 b; left at 120°C for 30 minutes)

[0049] [Polypropylene fiber] Daiwabo, fiber length: 51mm, fineness: 2.2dtex, melting point: 120℃

[0050] Example 1 The kapok fiber, cotton fiber, and polylactic acid fiber P1 described above were mixed in the mass ratios shown in Table 1, and a web was formed using air laying. The web was then needle-punched to obtain a nonwoven fabric for an oil adsorbent.

[0051] Example 2, Comparative Examples 1 and 2, Reference Example 1 A nonwoven fabric for oil adsorbent was obtained in the same manner as in Example 1, except that the type of polylactic acid fiber mixed in the web and the mass ratio of each fiber were changed to the values ​​shown in Table 1.

[0052] The results of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1 are shown in Table 1.

[0053] [Table 1]

[0054] As is clear from Table 1, the nonwoven fabrics for oil adsorbents obtained in Examples 1 and 2 contained specific amounts of kapok fiber, cotton fiber, and polylactic acid fiber, and the single yarn fineness of the polylactic acid fiber was also within a specific range, so they were excellent in both oil adsorption capacity multiplier and oil retention rate. Compared to Reference Example 1, each performance was equivalent and they were suitable for practical use as oil adsorbents.

[0055] On the other hand, the nonwoven fabric for oil adsorbents obtained in Comparative Example 1 had a poor oil retention rate because the amount of polylactic acid fiber was small. Also, the nonwoven fabric for oil adsorbents obtained in Comparative Example 2 had a polylactic acid fiber single filament fineness that was too fine, so the oil adsorption rate was low and the entanglement of the fibers was insufficient, so the oil retention rate was also poor.

Claims

1. A nonwoven fabric comprising kapok fiber, cotton fiber and polylactic acid fiber, The polylactic acid fiber has a single yarn fineness of 3 to 20 dtex, A nonwoven fabric for oil adsorbents, in which the total content of kapok fiber and cotton fiber is 15 to 30 mass % and the content of polylactic acid fiber is 70 to 85 mass % when the total mass of the nonwoven fabric is 100 mass %.

2. 2. The nonwoven fabric for oil adsorbents according to claim 1, wherein the oil adsorption capacity multiplier calculated by the following formula is 18 times or more and the oil retention rate is 84% ​​or more. Oil adsorption rate = (w2 - w1) / w1 Oil retention rate (%) = (w3 / w2) x 100 (w1: weight of nonwoven fabric before oil absorption, w2: weight of nonwoven fabric after being left for 5 minutes after oil absorption, w3: weight of nonwoven fabric after being left for 65 minutes after oil absorption)

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