Nonwoven fabric for oil absorption material and laminate for oil absorption material

Abstract

To provide a nonwoven fabric for oil absorption material that suppresses dropout or scattering of fibers, and is excellent in oil absorbing performance and absorbed oil holding performance, and has less load on environment.SOLUTION: A nonwoven fabric contains kapok fibers, cotton fibers, and polylactic acid fibers. The kapok fibers, the cotton fibers, and the polylactic acid fibers are bonded by at least either one of polyolefin resin and low melting polyester resin in a nonwoven fabric for oil absorption material. A laminate for oil absorption material is preferably formed by laminating the nonwoven fabric on at least either one of a front face and a rear face of the nonwoven fabric for oil absorption material.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Nonwoven fabrics are known for absorbing oil that has escaped due to ship accidents at sea or oil leaks in factories, etc. In addition, in restaurant kitchens and commercial kitchens, the installation of grease traps to separate and remove oils and fats (grease) contained in wastewater is mandatory, 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 that although it is a natural fiber mainly composed of cellulose, it itself has water repellency, that kapok fiber itself is composed of a single cell, the cell wall is thin but the lumen is thick, and since it contains air bubbles, it has an extremely small specific gravity and has the property of floating on water up to 20 to 40 times its own weight, and that it has a high oil absorption capacity of about 50 times that of 1 g of fiber.

[0004] In addition, various mixtures of kapok fiber with cotton fiber, polyester fiber, polypropylene fiber, etc. have been studied. For example, Patent Document 2 describes that by using a composite nonwoven fabric in which kapok fiber and thermoplastic polymer fiber are mixed, it is possible to suppress the falling off and scattering of kapok fiber compared to the case where only kapok fiber is used, and a filter material for a flow separation filter excellent in shape stability and flow separation performance can be obtained. In addition, Patent Document 3 discloses a sheet-shaped oil adsorbent in which kapok fiber and cotton fiber are bonded and fixed by heat-sealed fibers made of polypropylene or polyester, and describes that the use of cotton fiber reduces raw material costs and improves entanglement between the fibers, and that the bonding and fixing by heat-sealed fibers made of polypropylene or polyester prevents the scattering of kapok fiber, and a sheet-shaped oil adsorbent excellent in oil absorption and processability can be obtained.

[0005] On the other hand, in recent years, marine pollution by microplastics has become a global social problem, and waste fiber of general-purpose non-biodegradable synthetic fibers is considered to be one of the sources of microplastics. Therefore, from the viewpoint of environmental conservation, an oil adsorbent that does not contain non-biodegradable synthetic fibers is desired. As such an oil adsorbent, Patent Document 4 describes a method in which cellulose fiber wool is needle-punched to form a nonwoven fabric of a predetermined thickness, and the nonwoven fabric is immersed in a water repellent solution of a predetermined concentration to form a sheet-shaped oil adsorbent. However, the sheet-shaped oil sorbent of Patent Document 3 was insufficient in terms of its ability to retain the adsorbed oil. In addition, the oil sorbent of Patent Document 4 is formed into a sheet by needle punching without using heat-sealing fibers, and in order to ensure strength and buoyancy, 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) are used, or when cotton fibers with short single filaments are used, it is necessary to needle punch the cotton fibers to obtain a sheet-shaped nonwoven fabric, and then further stack cellulose nonwoven fabrics on top and bottom by needle punching, which makes the manufacturing process complicated and cost-inefficient. In addition, since only kapok fibers and cellulose fibers are used, the oil adsorption and retention performance is insufficient. [Prior art documents] [Patent documents]

[0006] [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] JP 2022-74353 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention is devised to solve the above problems, and aims to provide a nonwoven fabric for oil adsorbents that suppresses the shedding and scattering of kapok fibers, and that in addition to having excellent oil absorption performance, has excellent performance for retaining adsorbed oil and imposes a low burden on the environment, and a laminate for oil adsorbents that uses the nonwoven fabric for oil adsorbents. [Means for solving the problem]

[0008] The present inventors conducted extensive research to solve the above problems and arrived at the present invention. That is, the present invention relates to the following (i) to (iii). (i) A nonwoven fabric for oil adsorbents comprising kapok fibers, cotton fibers and polylactic acid fibers, the kapok fibers, cotton fibers and polylactic acid fibers being bonded together with at least one of a polyolefin resin and a low melting point polyester resin. (ii) The nonwoven fabric for oil adsorbents according to (i), wherein the combined content of kapok fiber and cotton fiber is 30% by mass or more when the total mass of the nonwoven fabric is 100% by mass. (iii) A laminate for an oil adsorbent, comprising the nonwoven fabric according to (i) above, and a further nonwoven fabric laminated on at least one of the front and back surfaces of the nonwoven fabric for an oil adsorbent. Effect of the Invention

[0009] The nonwoven fabric for oil adsorbents of the present invention contains kapok fiber, cotton fiber, and polylactic acid fiber, and is bonded with at least one of a polyolefin resin and a low-melting polyester resin, so that it has excellent oil absorption performance and excellent oil retention performance. In addition, since it contains polylactic acid fiber, which is a biodegradable fiber, it puts less strain on the environment and is preferable from the viewpoint of environmental conservation. Furthermore, by laminating an additional nonwoven fabric on at least one of the front and back surfaces of the nonwoven fabric for oil adsorbents, the laminate for oil adsorbents of the present invention can have improved strength and shape stability, making it possible to use the laminate for various purposes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The nonwoven fabric for oil adsorbents of the present invention (hereinafter sometimes referred to as the nonwoven fabric of the present invention) is a nonwoven fabric containing kapok fibers, cotton fibers and polylactic acid fibers, which are the main fibers constituting the nonwoven fabric and are bonded by at least one of a polyolefin resin or a low-melting polyester resin. That is, it is preferable that the kapok fibers, cotton fibers and polylactic acid fibers, which are the main fibers, are bonded by softening or melting at least a part of the polyolefin resin or the low-melting polyester resin through a heat treatment process in the manufacturing process of the nonwoven fabric.

[0011] The kapok fiber used in the present invention is a seed hair that grows on the inner surface of the fruit of the kapok tree, and is a fiber mainly composed of cellulose with an average fiber length of about 15 mm. The morphological characteristics of kapok fiber are that it has a hollow structure (hollow ratio of about 70 to 80%), and the fiber surface is smooth and covered with a type of wax. In the present invention, the kapok fiber is preferably thin in diameter and long in length from the viewpoint of strength when made into a nonwoven fabric and suppression of falling off 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 has little contamination in the raw cotton, such as impurities such as seeds and fruit skins, and polypropylene, which is a material for forming packaging materials.

[0012] The nonwoven fabric of the present invention contains cotton fiber as the main fiber in addition to kapok fiber. The reason for including cotton fiber is that, as described above, kapok fiber is a very lightweight fiber with a hollow ratio of about 70 to 80%, and is prone to falling off and scattering during handling, making it difficult to form a nonwoven fabric using only kapok fiber. By using cotton fiber, which is a natural fiber like kapok fiber, it is possible to prevent the falling off and scattering of kapok fiber and improve operability. In addition, cotton fiber is also a plant fiber with plant-derived oil attached, like kapok fiber, so it can impart water repellency to the nonwoven fabric of the present invention. As for the cotton fiber used in the present invention, any type of raw cotton that has not been chemically treated from the viewpoint of water repellency can be used, but it is preferable to use spun cotton (combed cotton) with a short fiber length that has a lot of oil and wax on the surface and is suitable for retaining oil. The cotton fibers preferably have a fiber length of 20 to 40 mm in order to ensure good entanglement with the kapok fibers and polylactic acid fibers.

[0013] Furthermore, the nonwoven fabric of the present invention contains polylactic acid fiber as the main fiber. Polylactic acid fiber has a suitable oil adsorption performance, and is a biomass material made from plant resources and has biodegradability. Therefore, by using polylactic acid fiber in the present invention, the obtained nonwoven fabric of the present invention exhibits excellent oil adsorption performance and has a low environmental impact. The polylactic acid fiber preferably has a fiber length of 35 to 65 mm in order to improve the entanglement with the kapok fiber or cotton fiber. The single fiber fineness is preferably 1 to 25 dtex, more preferably 1.5 to 20 dtex, and even more preferably 5 to 15 dtex, in order to improve the oil adsorption and retention performance. Among them, if it is 5 to 15 dtex, the oil adsorption and retention performance will be further improved, and the heat shrinkage of the polylactic acid fiber during the thermal processing treatment can be suppressed, so that the obtained nonwoven fabric of the present invention has few defects such as holes.

[0014] The polylactic acid fiber contained in the nonwoven fabric of the present invention includes polylactic acid melt-spun into fibers of a predetermined thickness, and 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 the melting point is preferably 150°C or higher and 190°C or lower. The melting points of poly-D-lactic acid and poly-L-lactic acid are about 180°C, and when a copolymer is used, the copolymerization ratio of the monomer components may be determined so that the melting point of the copolymer is 150°C or higher. If the melting point of the polylactic acid falls within the above range, it has high crystallinity, so that heat shrinkage is unlikely to occur during heat treatment processing, and the obtained nonwoven fabric of the present invention has few defects such as holes.

[0015] The nonwoven fabric of the present invention is made by bonding the main fibers, kapok fiber, cotton fiber, and polylactic acid fiber, with at least one of a polyolefin resin and a low-melting polyester resin. That is, in the embodiment of the nonwoven fabric of the present invention, at least one of a polyolefin resin and a low-melting polyester resin, which has a melting point lower than that of the kapok fiber, cotton fiber, and polylactic acid fiber, as a binder component, is preferably at least partially softened or melted by heat treatment processing in the manufacturing process of the nonwoven fabric, bonding the kapok fiber, cotton fiber, and polylactic acid fiber. The melting point of the polyolefin resin or low-melting polyester resin as the binder component is preferably at least 20° C. lower than the melting point of the polylactic acid fiber, and more preferably at least 30° C. lower. If the melting point is at least 20° C. lower, the kapok fiber, cotton fiber, and polylactic acid fiber are not affected by heat during heat treatment processing and maintain their fiber form well, and the fibers are bonded together by at least one of the polyolefin resin and the low-melting polyester resin, which are at least partially softened or melted.

[0016] As the polyolefin resin, polyethylene, polypropylene, a mixture of polyethylene and polypropylene, etc. can be used, but polypropylene is preferably used from the viewpoint of oil adsorption performance and making the nonwoven fabric of the present invention lighter and easier to float on water. Also, as the polyolefin resin, polyethylene and polypropylene derived from biomass obtained by fermenting biomass such as sucrose, starch, cellulose, etc. through ethanol by fermentation technology can be used. If the polyolefin resin used in the present invention is made of biomass, the nonwoven fabric of the present invention can be made into a material with a smaller environmental load.

[0017] As the polyester resin having a low melting point, a copolymer polyester resin or a polylactic acid resin can be used. Specific examples of the copolymer polyester resin include copolymer polyester resins in which ethylene terephthalate is used as a main repeating unit, dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, sebacic acid, adipic acid, succinic acid, and ε-caprolactone are used as copolymer components, and diol components such as ethanediol, propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol are used as copolymer components. In addition, examples of the polylactic acid resin 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.

[0018] In the present invention, from the viewpoints of both oil adsorption performance and environmental consideration, it is preferable that a polylactic acid resin having a low melting point is contained as a binder component. Although there is no particular limitation on the polylactic acid resin, it is preferable that it is a copolymer of D-lactic acid and L-lactic acid, and that the melting point is preferably 110 to 140°C.

[0019] In the present invention, a method for incorporating at least one of a polyolefin resin and a low-melting polyester resin in a nonwoven fabric includes, as described below, a method of using fibers made of a polyolefin resin or fibers made of a low-melting polyester resin as a raw material in the manufacturing process of the nonwoven fabric. Specifically, it is preferable to use polypropylene fibers or low-melting polylactic acid fibers. The form of the fibers is preferably short fibers, and the fiber cross section may be a fiber made of a single component, or a composite fiber. The composite fiber may be one in which the polyolefin resin or the low-melting polyester resin occupies at least a part of the fiber surface, and may be a concentric or eccentric core-sheath type, a side-by-side type, an island-in-the-sea type, or the like.

[0020] One of the preferred embodiments of the composite fiber used in the present invention is a method using a core-sheath type polylactic acid composite fiber in which the sheath is made of a polylactic acid resin with a low melting point and the core is made of a polylactic acid resin with a melting point higher than that of the polylactic acid resin of the sheath. When the above-mentioned core-sheath type polylactic acid composite fiber is used as the fiber constituting the nonwoven fabric, the polylactic acid resin of the sheath only partially softens or melts during the heat treatment process during the production of the nonwoven fabric, bonding the kapok fiber, cotton fiber, and polylactic acid fiber, while the polylactic acid resin of the core does not soften or melt and remains in the form of fiber in the nonwoven fabric.

[0021] As for the core-sheath type polylactic acid composite fiber, the sheath is preferably a copolymer of D-lactic acid and L-lactic acid as described above, and preferably has a melting point of 110 to 140° C. The core is preferably a copolymer of D-lactic acid and L-lactic acid, and preferably has a melting point of 150° C. or more and 190° C. or less. The difference between the melting point of the polylactic acid resin of the core and the melting point of the polylactic acid resin of the sheath (melting point of the polylactic acid resin of the core minus the melting point of the polylactic acid resin of the sheath) is preferably 20°C or more, and more preferably 30°C or more. If the difference in melting points is 20°C or more, it is possible to suppress the thermal deformation and thermal shrinkage of the polylactic acid resin of the core due to the heat treatment process when obtaining the nonwoven fabric, and it is possible to increase the density of the nonwoven fabric. In the present invention, the melting point is measured using a DSC (differential scanning calorimeter) at a DSC heating rate of 20°C / min, and the temperature giving the extreme value in the obtained melting endothermic curve is taken as the melting point. The mass ratio of the core to the sheath of the core-sheath type polylactic acid composite fiber (core / sheath) is preferably 1 / 1 to 5 / 1, and more preferably 3 / 1 to 4 / 1. The cross-sectional shape of the core-sheath type polylactic acid composite fiber is not particularly limited, but a circular shape is preferable.

[0022] In the present invention, the content of kapok fiber is preferably 15 to 40% by mass, and more preferably 20 to 35% by mass, based on the total mass (100% by mass) of the nonwoven fabric. If the content of kapok fiber is 15 to 40% by mass, the oil absorption performance is unlikely to decrease due to too little kapok fiber, and the dimensional stability of the nonwoven fabric is unlikely to decrease due to too much kapok fiber. The content of cotton fiber is preferably 15 to 30% by mass, more preferably 20 to 30% by mass, based on the total mass of the nonwoven fabric. When the content of cotton fiber is 15 to 30% by mass, the scattering of kapok fiber can be suppressed by using the cotton fiber together with kapok fiber, and the nonwoven fabric can have excellent moldability.

[0023] Furthermore, the total content of kapok fiber and cotton fiber is preferably 30% by mass or more, more preferably 40-70% by mass, and particularly preferably 45-65% by mass, based on the total mass of the nonwoven fabric. If the total content of both fibers is 30% by mass or more, the nonwoven fabric of the present invention can have oil adsorption performance and less environmental load. If the total content is 70% by mass or less, the nonwoven fabric of the present invention can be easily bonded by polyolefin resin or low-melting polyester resin as a binder component, and can also have excellent oil retention performance. Furthermore, when a polylactic acid resin is used as the resin contained as the binder component, all of the fibers and resins constituting the nonwoven fabric of the present invention are derived from plants, which is most preferable from the standpoint of environmental consideration. In the present invention, the nonwoven fabric may contain fibers other than kapok fiber, cotton fiber and polylactic acid fiber, as long as the oil absorption performance of the nonwoven fabric is not impaired.

[0024] The basis weight of the nonwoven fabric of the present invention is 100 to 500 g / m 2 It is preferable that the thickness is 150 to 300 g / m 2 It is more preferable that the basis weight is 100 g / m 2 When the hardness is 500 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 absorbing oil is recovered, damage caused by the fabric becoming too heavy can be suppressed.

[0025] The thickness of the nonwoven fabric of the present invention is preferably 3.0 to 15.0 mm, more preferably 6.0 to 12.0 mm, from the viewpoint of achieving a good balance between strength and permeability to a mixture containing water and oil, and keeping the basis weight in an appropriate range. The size (surface area) of the nonwoven fabric is not particularly limited, and can be appropriately selected depending on the actual usage environment.

[0026] The nonwoven fabric of the present invention is formed by bonding kapok fibers, cotton fibers and polylactic acid fibers with at least one of a polyolefin resin and a low-melting point polyester resin, but in order to improve strength and dimensional stability, it can also be formed into a laminate (laminate for oil adsorbent) in which an additional nonwoven fabric is laminated on at least one of the front and back sides of the nonwoven fabric (hereinafter sometimes referred to as the laminate of the present invention). In the laminate of the present invention, examples of a method for laminating a nonwoven fabric to the front or back surface include a needle punch method, a spun lace method, a thermal bond method, and a chemical bond method. Among these, from the viewpoints of adhesiveness and ease of processing, it is preferable to use a nonwoven fabric containing heat-fusible fibers and laminate it to the front or back surface by thermal bonding. As will be described in detail later in the manufacturing process, when a nonwoven fabric is further laminated, the laminate of the present invention can have the following two forms. Form 1: A laminate in which a nonwoven fabric is laminated on at least one of the front and back surfaces of the nonwoven fabric of the present invention. Mode 2: A laminate obtained by laminating a nonwoven fabric containing heat-fusible fibers directly onto at least one of the front and back surfaces of a web obtained during the manufacturing process of the nonwoven fabric of the present invention, without going through a process of forming the web into a nonwoven fabric.

[0027] The nonwoven fabric containing heat-fusible fibers is preferably a nonwoven fabric containing the polyolefin fibers or low-melting point polyester fibers, more preferably one containing 80 mass% or more of polyolefin fibers or low-melting point polyester fibers, and from the viewpoint of adhesion to the nonwoven fabric of the present invention and the web, it is particularly preferable to use a nonwoven fabric composed of 100 mass% polyolefin fibers.

[0028] In the laminate of the present invention, the total mass of all the nonwoven fabrics to be laminated is preferably 2 to 20 parts by mass, and more preferably 5 to 15 parts by mass, when the nonwoven fabric web of the present invention is taken as 100 parts by mass. If the mass of the nonwoven fabrics to be laminated is within the above range, the laminate of the present invention can further suppress the scattering and detachment of kapok fibers, improve the strength, and have excellent handleability. In addition, if the mass is within the above range, when a nonwoven fabric made of polyolefin fibers is used, the proportion of fibers made of plant-derived resin in the entire laminate can be prevented from decreasing significantly, which is also preferable from the viewpoint of environmental consideration.

[0029] In the laminate of the present invention, from the viewpoint of the amount of oil adhesion and buoyancy, the thickness of the nonwoven fabric laminated on the nonwoven fabric of the present invention is preferably 0.2 to 3.0 mm, more preferably 0.5 to 1.5 mm. 2 It is preferable that:

[0030] The nonwoven fabric and laminate of the present invention have excellent oil absorption performance, and when the oil absorption amount is measured by the method described below, it is preferable that the nonwoven fabric and laminate of the present invention can absorb oil at least 20 times their own weight. In other words, the oil absorption performance by the method described below indicates that the nonwoven fabric and laminate of the present invention can absorb a large amount of oil in a short period of time. Here, if the oil absorption amount is 20 times or more than its own weight, the amount of oil recovered in one oil absorption operation is sufficiently large, and the workability is excellent. The oil absorption amount is preferably 20 times or more than its own weight, and more preferably 25 times or more. (Oil adsorption capacity, ratio of oil adsorption capacity to nonwoven fabric for oil adsorbent (or laminate for oil adsorbent)) The nonwoven fabric of the present invention (or the laminate of the present invention) is cut into a size of 10 cm x 10 cm to prepare a test piece, and its mass (w1) (g) is measured. Next, 1 liter of salad oil (Ajinomoto Co., Inc.'s "Soybean Oil Plenty Salad Oil", a mixture of edible soybean oil and edible rapeseed oil) kept at 25°C is poured into a stainless steel tray (width 220 mm x depth 275 mm x height 45 mm) to a depth of about 18 mm, and the test piece is gently floated on it, and then the test piece is gently moved for 3 minutes to adsorb the oil. Next, the test piece is gently removed and left for 5 minutes with the oil dripping onto a stainless steel sieve (size: 23 cm x 30 cm), and the mass (w2) (g) is measured again. Then, the oil adsorption amount (g) and the oil adsorption ratio to the weight of the test piece are calculated by the following formula. The above is repeated twice (N = 2). Oil adsorption amount (g)=w2-w1 Oil adsorption rate of nonwoven fabric for oil adsorbent (or laminate for oil adsorbent) = (w2-w1) / w1

[0031] Furthermore, the nonwoven fabric and laminate of the present invention have excellent performance in retaining adsorbed oil for a long time, and the retention rate, as measured by the method described below, is preferably 45% or more, and more preferably 50% or more. If the oil retention rate is 45% or more, oil once adsorbed is unlikely to be released from the nonwoven fabric even after a certain period of time has passed. (Oil retention measurement) After measuring the mass (w2) (g) in the above oil adsorption measurement test, place the test piece back on the stainless steel sieve (size: 23 cm x 30 cm) and leave it for 1 hour with the oil dripping off, after which measure the mass (w3) (g). Next, calculate the oil retention rate using the following formula. Repeat the above twice (N=2). Oil retention rate (%) = (w3 / w2) x 100

[0032] The reason why the nonwoven fabric and the laminate of the present invention are excellent not only in oil absorption performance but also in the retention of absorbed oil is believed to be due to the use of polylactic acid fibers. Conventionally used nonwoven fabrics that use a mixture of kapok fibers and cotton fibers have a certain level of oil absorption performance because the cotton fibers are fibers with plant-derived oil (lipophilic) attached to the surface, but the cotton fibers themselves are cellulose fibers that have many hydrophilic -OH groups in the molecules, so the oil is easily released from the fibers after adsorbing oil over time. In addition, when the nonwoven fabric for oil adsorbent comes into contact with the surfactant component contained in the detergent, if it contains a large amount of kapok fibers and cotton fibers, the oil in the surface of the kapok fibers and cotton fibers is lost, making it more hydrophilic and less absorbent. On the other hand, polylactic acid fibers have a moderate oil absorption performance, and the fibers themselves are lipophilic, so that the adsorbed oil is not easily released from the fibers. Similarly, the polyolefin resin and low-melting polyester resin as binder components are also lipophilic, so that the adsorbed oil is not easily released from the fibers. Therefore, the nonwoven fabric and the laminate of the present invention are excellent not only in oil absorption performance but also in oil retention performance, and it is considered that the deterioration of the oil absorption performance and oil retention performance can be suppressed even when they come into contact with a surfactant component. Therefore, even when the nonwoven fabric and the laminate of the present invention are installed in, for example, a grease trap, more oil can be collected, so that the number of replacements can be reduced, and further, since the oil is appropriately retained in the nonwoven fabric or the laminate, it is easy to handle when replacing it.

[0033] In order to improve the oil absorption performance of the nonwoven fabric or laminate of the present invention, a water repellent may be attached to the surface of the nonwoven fabric or laminate of the present invention. The method for attaching the water repellent will be described in the manufacturing process described below.

[0034] Next, a method for producing the nonwoven fabric of the present invention will be described below. Kapok fibers, cotton fibers, polylactic acid fibers, and fibers made of polyolefin resin or fibers made of low-melting point polyester resin are mixed together, then carded into a sheet (web) and subjected to a heat treatment process at 100 to 140°C to soften or melt at least a portion of the fibers made of polyolefin resin or low-melting point polyester resin, thereby obtaining the nonwoven fabric of the present invention in which the kapok fibers, cotton fibers, and polylactic acid fibers are bonded together by the resinified polyolefin fibers or low-melting point polyester fibers.

[0035] First, kapok fiber, cotton fiber, polylactic acid fiber, and at least one of fibers made of polyolefin resin or fibers made of low-melting polyester resin as a binder component are prepared. Either one of the fibers made of polyolefin resin and the fibers made of low-melting polyester resin (hereinafter, collectively referred to as heat-sealing fibers) may be used alone or in combination.

[0036] The single filament fineness of the heat-fusible fiber is preferably 1 to 20 dtex, more preferably 3 to 15 dtex, and the average fiber length is preferably 10 to 100 mm, more preferably 30 to 70 mm. If the fineness of the heat-fusible fiber is within the above range, the contact points between the fibers are sufficiently secured when the fibers are thermally bonded after being mixed with other fibers (here, kapok fiber, cotton fiber, and polylactic acid fiber), so that the nonwoven fabric has excellent strength and shape stability. Also, if the average fiber length of the heat-fusible fiber is within the above range, it is possible to prevent the fibers from falling off the card during carding, and it is possible to form a uniform web.

[0037] Next, the kapok fiber, cotton fiber, polylactic acid fiber and heat-sealing fiber are mixed while being stirred, and carded to form a thin web. When the entire web is taken as 100% by mass, the mixing ratios of the kapok fiber, cotton fiber, polylactic acid fiber and heat-sealing fiber are preferably 15-40% by mass, 15-30% by mass, 10-40% by mass and 10-35% by mass, respectively. In addition, the total content of the polylactic acid fiber and the heat-sealing fiber is preferably 30% by mass or more.

[0038] If the kapok fiber content in the entire web is 15 to 40% by mass, the oil absorption performance is unlikely to decrease due to too little kapok fiber, and the shape stability of the nonwoven fabric is unlikely to decrease due to too much kapok fiber. Also, if the contents of cotton fiber and polylactic acid fiber satisfy the above ranges, the scattering of kapok fiber can be suppressed by blending with kapok fiber, and the nonwoven fabric can be stably formed. Furthermore, if the total content of the polylactic acid fibers and the heat-fusible fibers falls within the above range, the web will contain an appropriate amount of lipophilic fibers, resulting in excellent oil retention properties. Furthermore, if the content of the heat-fusible fibers is 10 to 35% by mass, the oil absorption performance of the kapok fibers and cotton fibers is maintained while excellent adhesiveness is also achieved, so that the nonwoven fabric can be stably formed. Furthermore, when the thermal adhesive fibers are at least partially made of polylactic acid, the ratio of plant-derived fibers to the fibers and resins constituting the nonwoven fabric of the present invention is increased, which is preferable from the standpoint of environmental consideration.

[0039] The web is then bonded between the fibers to form a nonwoven fabric. As a method for bonding the fibers, it is preferable to use a method of fusing them by heating (thermal bonding), in which the heat-fusible fibers at least partially soften or melt, bonding the kapok fibers, cotton fibers, and polylactic acid fibers in the web, thereby obtaining the nonwoven fabric of the present invention.

[0040] The heat treatment is preferably carried out at 90 to 140°C, more preferably 100 to 130°C. By carrying out the heat treatment at a temperature within the above range, at least a part of the heat-sealed fiber is softened or melted, and the kapok fiber, cotton fiber, and polylactic acid fiber are bonded. The heat treatment temperature may be set to a temperature at which the heat-sealed fiber (here, fiber made of polyolefin resin or fiber made of low-melting point polyester resin) melts or softens, and is appropriately selected in detail according to the treatment time, line pressure, etc. Specifically, it is preferable to set the temperature in the range from 20°C lower to 20°C higher than the melting point of the heat-sealed fiber. However, when polylactic acid fiber or the core-sheath type polylactic acid composite fiber is used, the heat treatment temperature is preferably 30°C or more lower than the melting point of the polylactic acid fiber or the polylactic acid constituting the core, and more preferably 40°C or more lower than the melting point of the polylactic acid fiber or the polylactic acid constituting the core, so that the polylactic acid constituting the core is not melted or softened by the heat treatment.

[0041] If the temperature is set 20°C lower than the melting point of the heat-fusible fiber, the heat-fusible fiber, which is the binder component, does not melt or soften sufficiently, resulting in insufficient adhesion and a decrease in strength. On the other hand, if the temperature is set 20°C higher than the melting point of the heat-fusible fiber, the polylactic acid fiber and the polylactic acid that constitutes the core become susceptible to the effects of heat, resulting in thermal shrinkage or a nonwoven fabric with poor mechanical strength. The nonwoven fabric obtained after the heat treatment is cooled and then cut to a predetermined size, and can be used as a nonwoven fabric for an oil adsorbent.

[0042] Next, a method for producing the laminate of the present invention will be described. The laminate of the present invention can be obtained by laminating a nonwoven fabric on at least one of the front and back surfaces of the nonwoven fabric (or web) of the present invention. Three embodiment examples of the method for producing the laminate of the present invention are given below.

[0043] The first method for obtaining the laminate of the present invention is to laminate a nonwoven fabric on at least one of the front and back surfaces of the nonwoven fabric of the present invention. The method for laminating the nonwoven fabric is preferably performed by thermal bonding or needle punching.

[0044] The second method for obtaining the laminate of the present invention is to form a nonwoven fabric by a method other than thermal bonding using a web obtained in the middle of the manufacturing process of the nonwoven fabric of the present invention, and then further laminate a nonwoven fabric containing heat-sealing fibers on at least one of the front and back surfaces of the nonwoven fabric. Methods for forming a nonwoven fabric using the web by a method other than thermal bonding include chemical bonding using an adhesive resin (chemical bonding, resin bonding), fusion by heating (thermal bonding), mechanical entanglement using a hooked needle (needle punch), hydroentanglement or spunlace by jetting a high-pressure water stream to entangle, and stitch bonding to sew the web, but it is preferable to bond the fibers by needle punching. Next, a nonwoven fabric containing heat-sealing fibers is further laminated on the obtained nonwoven fabric, and the heat-sealing fibers are melted by thermal bonding, and the nonwoven fabric of the present invention and the nonwoven fabric containing heat-sealing fibers are bonded to each other to obtain the laminate of the present invention.

[0045] The third method for obtaining the laminate of the present invention is to use a web obtained in the middle of the manufacturing process of the nonwoven fabric of the present invention, and directly laminate a nonwoven fabric containing heat-sealing fibers on at least one of the front and back sides of the web without going through a process of forming the web into a nonwoven fabric, and then perform a heat treatment process while applying pressure (thermal bonding) to bond the web and the nonwoven fabric containing heat-sealing fibers to obtain the laminate of the present invention. That is, the heat treatment process at least partially softens or melts both the heat-sealing fibers contained in the web and the heat-sealing fibers in the laminated nonwoven fabric, and the kapok fibers, cotton fibers, and polylactic acid fibers in the web are bonded together. In the present invention, it is preferable to obtain the laminate of the present invention by this method from the viewpoint of improving strength and dimensional stability.

[0046] In addition, when a water repellent is applied to the surface of a nonwoven fabric or a laminate for the purpose of improving the oil absorption performance of the nonwoven fabric or the laminate of the present invention, the water repellent may be applied to the cotton (wadding) state when kapok fiber, cotton fiber, polylactic acid fiber, and fiber made of polyolefin resin or fiber made of low melting point polyester resin are mixed in the web formation process, or the water repellent may be applied to the surface of the nonwoven fabric or laminate by a known method after the nonwoven fabric or laminate is made. However, from the viewpoint of facilitating oil capture and improving oil adsorption, it is preferable to apply the water repellent to the cotton state when mixed and to adhere the water repellent to the entire fiber surface. It is preferable to use a non-fluorine-based water repellent. If the water repellent is a non-fluorine-based water repellent, it can achieve both oil adsorption and water repellency at the same time because the surface tension is higher than oil and lower than water. In addition, when short fibers are carded to create a web, polylactic acid fibers are easily charged when opened, so it is common to use an antistatic agent together with the water repellent. However, the use of an antistatic agent may improve hydrophilicity and thus may actually reduce water repellency. Even in such a case, the use of a non-fluorinated water repellent agent can simultaneously achieve oil adsorption and water repellency.

[0047] The nonwoven fabric of the present invention and the laminate of the present invention can be used in various forms by processing them into a predetermined shape. For example, they can be used by folding them or fixing them with heat fusion or adhesives. When the nonwoven fabric of the present invention is used in a mixture containing water and oil (e.g., wastewater), it can efficiently separate the water and oil and sufficiently adsorb only the oil. Therefore, it can significantly reduce the burden of the work of treating wastewater in a grease trap or oil spilled in an accident at sea. EXAMPLES

[0048] The present invention will now be described in more detail with reference to examples. The methods for measuring and evaluating various property values ​​are as follows.

[0049] (a) Weight The obtained laminate was cut into a size of 10 cm x 10 cm, and the mass was measured.2 Converted to mass per unit, and the weight per unit (g / m 2 ) was sought. (b) Oil adsorption amount, ratio of oil adsorption amount to sheet The obtained laminate was measured by the above-mentioned method. (c) Oil retention The obtained laminate was measured by the above-mentioned method.

[0050] The kapok fibers, cotton fibers, polylactic acid fibers, core-sheath type polylactic acid composite fibers, and polypropylene fibers used in the examples are as follows.

[0051] [Kapok fiber (G1)] Made by PT Randu Indo Prima, produced in East Java, Indonesia, average fiber diameter 21.5 μm, average fiber length 14.6 mm. The average fiber diameter was calculated by measuring the average long diameter of kapok fibers using a microscope width measurement method in accordance with JIS L 1030 at the Boken Quality Evaluation Organization, a general incorporated foundation. The average fiber length was calculated by the Boken Quality Evaluation Organization, a general incorporated foundation, using the average fiber length of kapok fiber according to JIS L 1015, the test method for staple chemical fibers. [Cotton fiber (G2)] Indian organic cotton, BUNNY BRAHMA medium-length cotton class (fiber length 1.1 / 8 to 1.5 / 16 inches (28.6 mm to 33.3 mm), cotton thickness 3.5 to 4.9 micronaires, fiber strength 28 GPT (g / tex) or more) [Polylactic acid fiber] Made by Nippon Ester, Terramac, fiber length: 51 mm, fineness: 1.7 dtex, melting point 170°C, heat shrinkage rate 11.0% (measured according to JIS L1015 8.15 b method; 120°C x 30 minutes exposure condition) [Sheath-core polylactic acid composite fiber] A core-sheath type polylactic acid composite fiber in which the core component is polylactic acid (a copolymer of D-lactic acid and L-lactic acid (D-lactic acid content 1.4 mol%), melting point 170°C) and the sheath component is low-melting point polylactic acid (a copolymer of D-lactic acid and L-lactic acid (D-lactic acid content 10 mol%), melting point 130°C). The mass ratio of the core to the sheath (core / sheath) is 5 / 5, the fineness is 2.2 dtex, the fiber length is 51 mm, and the heat shrinkage rate is 22.5% (measured according to the method of JIS L1015 8.15 b; left at 120°C for 30 minutes). [Polypropylene fiber] Daiwabo, fiber length: 51mm, fineness: 2.2dtex, melting point 120℃

[0052] Example 1 The above kapok fiber, cotton fiber, polylactic acid fiber, core-sheath type polylactic acid composite fiber, and polypropylene fiber were mixed and carded to form a web. Next, a needle-punched nonwoven fabric (basis weight: 5 g / m) consisting of only polypropylene fiber was used as a nonwoven fabric to be laminated on the web. 2 ) was prepared. Nonwoven fabric was laminated on the front and back surfaces of the web, and bonded by heat treatment at 130°C while applying pressure, to obtain a laminate for an oil adsorbent. The fibers in the web and the nonwoven fabric for lamination are contained in the mass ratios shown in Table 1 when the entire laminate for an oil adsorbent is taken as 100 parts by mass.

[0053] Examples 2-3, Comparative Examples 1-2 A laminate for an oil adsorbent was obtained in the same manner as in Example 1, except that the mass ratio of each fiber mixed in the web was changed to the value shown in Table 1.

[0054] The results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

[0055] [Table 1]

[0056] As is clear from Table 1, the oil adsorbent laminates obtained in Examples 1 to 3 contained kapok fiber, cotton fiber and polylactic acid fiber, and the fibers were appropriately bonded by polyethylene resin, low-melting point polylactic acid resin, and nonwoven fabric laminated on the front and back, and therefore had excellent oil adsorption and oil retention properties. On the other hand, in Comparative Example 1, since it did not contain polylactic acid and contained too much kapok fiber, the laminate for the oil adsorbent had poor moldability and poor oil retention performance. Comparative Example 2 did not contain kapok fiber and therefore had poor oil adsorption performance.

Claims

1. A nonwoven fabric comprising kapok fiber, cotton fiber and polylactic acid fiber, The kapok fibers, cotton fibers and polylactic acid fibers are bonded together with at least one of a polyolefin resin and a low-melting point polyester resin to form a nonwoven fabric for oil adsorbents.

2. 2. The nonwoven fabric for oil adsorbents according to claim 1, wherein the total content of the kapok fiber and the cotton fiber is 30% by mass or more when the total mass of the nonwoven fabric is 100% by mass.

3. A laminate for an oil adsorbent, comprising the nonwoven fabric according to claim 1 and a further nonwoven fabric laminated on at least one of the front and back surfaces of the nonwoven fabric for an oil adsorbent.

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