Particle-dispersed long fiber entangled aggregate

Abstract

To provide an entangled aggregate of polyolefin-based resin long fibers that are drawn by a melt blow method and include dispersed functional particles, and also to provide a manufacturing method thereof.SOLUTION: A resin long fiber is drawn into an average cross-sectional diameter d of 10 μm or less and has a dispersed part including functional particles dispersed on a surface along the resin long fiber and a non-dispersed part not including the functional particles. In a manufacturing method thereof, the functional particles are dispersed in a polyolefin-based resin fused by an extruder and the polyolefin-based resin is discharged from a resin discharge port; a high speed gas flow is horizontally ejected from a gas ejection port provided near the discharge port; and the resin is released in the air while being cooled and drawn by the high speed gas flow. When manufacturing an entangled aggregate formed of the resin long fiber drawn into an average cross-sectional diameter of 10 μm or less, the diameter of the resin discharge port is set to 500 μm or more and average particle diameter D50 of the functional particles is set to 1 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an entangled aggregate of polyolefin resin long fibers stretched by a melt-blowing method and having functional particles dispersed therein, and a method for producing the same. [Background technology]

[0002] Nonwoven fabrics made of polyolefin resins such as polyethylene (PE) and polypropylene (PP) are widely used. Here, a method is known in which such a thermoplastic resin is melted, extruded from an extruder, and stretched with a high-speed airflow to produce nonwoven fabrics and raw fabrics (e.g., Patent Document 1). Such a melt-blowing method can continuously produce nonwoven fabrics and the like at high speed, and can control the diameter of fine wires from micron diameters to nano-diameters of submicrons or less, so it is expected to be applied to the manufacture of products for various purposes such as agriculture, industry, and medicine.

[0003] By the way, as a method for dispersing functional particles in resin fibers obtained by the melt-blowing method and compounding them, there is a method in which pellets kneaded with functional particles are fed into an extruder and melt-blowing (melting and stretching) is performed. In this method, as the resin fibers are thinned, the diameter of the resin discharge nozzle attached to the extruder is narrowed, which makes it easy for the particle powder to clog. In addition, there is also a problem that the particles break the thin fibers, making it difficult to perform stretching well.

[0004] For example, Patent Document 2 discloses a method for obtaining an antibacterial nonwoven fabric made of ultrafine fibers containing nanosilver particles by the melt-blowing method. In this method, an inorganic or organic silver compound and PP resin are heated and melted in an extruder, and nanosilver particles with an average particle diameter of 10 to 100 nm are generated in the PP resin in the process to produce a nanosilver masterbatch. This is blended with highly fluid neat PP resin, and a nonwoven fabric with an average fiber diameter of 2 to 10 μm is obtained by the melt-blowing method. It is said that clogging of the resin discharge nozzle (circular hole with a diameter of 0.3 to 1.0 mm) during fiber spinning, thread breakage, fly, etc. can be prevented by nanoizing and dispersing the silver particles in the resin.

[0005] On the other hand, for example, Patent Document 3 discloses that in a method for producing a nonwoven fabric by the melt-blowing method, a resin discharge nozzle having a diameter relatively larger than the diameter of the obtained fiber can be used by controlling the arrangement of the resin discharge nozzle and the blow gas nozzle attached to the extruder, and the resin discharge amount and the gas amount, etc. For example, it discloses that a nano-diameter fiber can be obtained by using a resin discharge nozzle having a millimeter diameter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-139864 [Patent Document 2] JP 2013-142215 A [Patent Document 3] Patent No. 6171072 Summary of the Invention [Problem to be solved by the invention]

[0007] In the method for producing a nonwoven fabric by the melt-blowing method, by using a resin discharge nozzle with a diameter larger than the diameter of the resulting fiber, clogging of the resin discharge nozzle with particle powder can be prevented even when pellets containing functional particles are used. This makes it possible to obtain a functional nonwoven fabric made of an entangled aggregate of polyolefin resin fibers and functional particles, which has a function that cannot be obtained by polyolefin resin alone.

[0008] Here, when dispersing functional particles in polyolefin resin fibers obtained by the melt-blowing method to form a composite, if the ratio of particle powder to resin fibers is increased to enhance the function of the functional particles, the fibers cannot be stretched, and even if they can be stretched, they become stiff and lose their texture. Therefore, a method for efficiently exerting the function of the functional particles without increasing the ratio of particle powder has been desired.

[0009] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an entangled aggregate of polyolefin resin long fibers, which is capable of dispersing functional particles in long fibers stretched by a melt-blowing method and satisfactorily exhibiting the functions of the functional particles, and a method for producing the same. [Means for solving the problem]

[0010] The present inventors have focused on the fact that functional particles dispersed on the surface of long resin fibers can better exhibit their functions without being hindered by the resin than in the core, and have intensively tried to develop a method for concentrating and dispersing functional particles on the surface of long fibers in an entangled aggregate of polyolefin-based resin long fibers stretched by a melt-blowing method and having functional particles dispersed therein. As a result, they have come up with the idea that although particles in the center of a fiber to be stretched move only in the stretching direction during stretching, if the fiber to be stretched is torn apart while being stretched, the particles can be concentrated on the surface by arranging the particles on the surface of the torn fiber and then stretching it. In other words, they have found that functional particles can be dispersed on the surface of each long resin fiber by splitting and stretching the resin discharged from a resin discharge port.

[0011] The particle-dispersed entangled long fiber aggregate according to the present invention is an entangled aggregate of polyolefin resin long fibers stretched by a melt-blowing method and having functional particles dispersed therein, characterized in that the resin long fibers are stretched to an average cross-sectional diameter d of 10 μm or less, and have a dispersed portion containing the functional particles dispersed along the surface of the resin long fibers, and a non-dispersed portion not containing the functional particles.

[0012] According to this feature, the functional particles can be dispersed on the surface of the long resin fibers, and the functional particles can be effectively expressed relative to the amount of the particles, thereby making it possible to obtain a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate. In addition, by providing a non-dispersed portion that does not contain functional particles, the texture of the entangled long fiber aggregate is not impaired.

[0013] In the above-mentioned invention, the long resin fibers may have branched parts, and the functional particles may be dispersed in the branched parts. According to this feature, the resin discharged from a resin discharge port by a melt-blowing method is split into a plurality of long resin fibers by the functional particles, and the long fibers are stretched from the branched parts, thereby making it possible to obtain a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate.

[0014] In the above-mentioned invention, the dispersed portion may be characterized in that the functional particles are exposed from the surface. With this feature, the function of the functional particles can be more satisfactorily expressed relative to the amount ratio, and a functional nonwoven fabric can be obtained that does not impair the texture of the entangled long-fiber aggregate.

[0015] In the above-mentioned invention, the functional particles may have an average particle diameter D50 of d to d / 10. This feature allows the function of the functional particles to be better expressed relative to the amount ratio, and provides a functional nonwoven fabric that does not impair the texture of the entangled long-fiber aggregate.

[0016] In the above-mentioned invention, the functional particles may be made of an inorganic oxide. According to this feature, the inorganic oxide is stable against molten resin and the usage environment, and the functional nonwoven fabric can maintain the function of the functional particles for a long period of time.

[0017] In addition, the present invention provides a method for producing an entangled aggregate of polyolefin resin long fibers stretched by a melt-blowing method and having functional particles dispersed therein, the method comprising dispersing the functional particles in a polyolefin resin molten in an extruder and discharging the resin from a resin outlet, ejecting a high-velocity gas stream horizontally from a gas outlet provided in the vicinity of the resin outlet, and cooling and stretching the resin discharged from the resin outlet with the high-velocity gas stream while discharging it into the air to obtain an entangled aggregate made of the resin long fibers stretched to an average cross-sectional diameter d of 10 μm or less, the diameter of the resin outlet being 500 μm or more and the average particle diameter D50 of the functional particles being 1 μm or more, thereby obtaining an entangled aggregate made of the resin long fibers having a dispersed portion containing the functional particles dispersed along the surface of the resin long fibers and a non-dispersed portion not containing the functional particles.

[0018] According to this feature, the surface tension of the polyolefin resin is reduced by the resin discharge port having a relatively large diameter, which makes it easier to branch the resin long fibers, and the functional particles are dispersed on the surfaces of the resin long fibers without causing fiber breakage during stretching, allowing the functional particles to be favorably expressed relative to the amount ratio, thereby obtaining a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate. Furthermore, by providing a non-dispersed portion that does not contain functional particles, breakage during stretching can be prevented and the texture of the entangled long fiber aggregate is not impaired.

[0019] In the above-mentioned invention, the resin discharged from the resin discharge port may be split into a plurality of the long resin fibers by the functional particles and then stretched. According to this feature, the functional particles are dispersed on the surfaces of the long resin fibers, and the functions thereof can be satisfactorily exhibited relative to the amount ratio, thereby obtaining a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate.

[0020] In the above-mentioned invention, the long resin fibers may have branched parts, and the functional particles may be dispersed in the branched parts. According to this feature, the long fibers can be stretched from the branched parts, which split the resin discharged from a resin discharge port by a melt-blowing method into a plurality of long resin fibers with the functional particles, thereby obtaining a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate.

[0021] In the above-mentioned invention, the dispersed portion may be characterized in that the functional particles are exposed from the surface. With this feature, the function of the functional particles can be more satisfactorily expressed relative to the amount ratio, and a functional nonwoven fabric that does not impair the texture of the entangled long-fiber aggregate can be obtained.

[0022] In the above-mentioned invention, the stretching may be performed so that the average particle diameter D50 of the functional particles is d to d / 10. According to this feature, the function of the functional particles can be more satisfactorily expressed relative to the amount ratio, and a functional nonwoven fabric that does not impair the texture of the entangled long-fiber aggregate can be obtained. [Brief description of the drawings]

[0023] [Figure 1] 1A is a photograph showing the appearance of an entangled aggregate of long resin fibers in one example according to the present invention, and FIG. 1B is a magnified photograph thereof. [Diagram 2] FIG. 2 is a schematic diagram of a resin long fiber. [Diagram 3] FIG. 2 is a side cross-sectional view of an apparatus for producing an entangled mass. [Figure 4] FIG. 2 is a front view of a nozzle head of the manufacturing apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an entangled aggregate of polyolefin resin long fibers as a typical example of the present invention will be described with reference to Figs.

[0025] As shown in Fig. 1(a), the entangled resin long fiber aggregate 10 is a particle-dispersed entangled long fiber aggregate in which a polyolefin resin such as polypropylene is stretched by a melt-blowing method and functional particles (black ceramic particles are used here for the purpose of observation) are dispersed. The average cross-sectional diameter d of the resin long fibers is 10 µm or less.

[0026] As shown in FIG. 1(b), the entangled aggregate 10 has a biased dispersion of the functional particles, and has a dispersion portion 2 containing the functional particles dispersed on the surface along the resin long fiber 1, and a non-dispersion portion 3 in which the functional particles are not dispersed on the surface. In the dispersion portion 2, the functional particles are concentrated and dispersed on the surface, which can facilitate the expression of their functions. In addition, in the dispersion portion 2, the functional particles are preferably exposed from the surface of the resin long fiber 1, which can facilitate the expression of the desired function. In addition, the resin long fiber may have branch portions 4 that branch the fiber into multiple parts, and the functional particles are dispersed inside the branch portions 4.

[0027] Such entangled aggregates 10 are believed to be formed by the following mechanism during the production by melt-blowing.

[0028] First, as shown in FIG. 2(a), in melt-blowing, functional particles 5 are dispersed in resin 9 discharged from a resin discharge port. Then, the resin 9 is easily torn from the vicinity of the interface between the functional particles 5 and the resin 9 by stretching due to melt-blowing. This is because the functional particles 5 are not deformed and are not stretched with respect to the stretched resin 9. A crack 4a is formed that selectively passes through the vicinity of the interface with a plurality of such functional particles 5. In such a crack 4a, each of the functional particles 5 is located in one of the avoided sides or the other side. In other words, the distribution of the functional particles 5 is locally biased between one side of the crack and the other side of the crack 4a.

[0029] As shown in FIG. 2(b), the resin 9 branches from the crack 4a to generate a branch 4 or splits into a plurality of resin fibers. At this time, the resin 9 is stretched, but due to the localized bias described above, the area where the functional particles 5 are low in distribution density is preferentially stretched. This is because the functional particles 5 do not deform even under melt-blowing conditions and therefore hinder the stretching of the resin 9. For this reason, the functional particles 5 are dispersed in the area that remains as the branch 4 without being stretched. Furthermore, such branch 4 also becomes a fiber in which a relatively large amount of the functional particles 5 is dispersed by further stretching. The area where the functional particles 5 are highly distributed is difficult to stretch and the decrease in distribution density is small, while the area where the functional particles 5 are low in distribution density is easy to stretch and the distribution density is further decreased. As a result, the bias in the distribution density of the functional particles 5 is promoted.

[0030] Incidentally, the functional particles 5 present in large quantities at the starting points of the cracks 4a are located near the surface of the cracked resin 9 because the cracks 4a are formed near the interface with the resin 9. That is, when the functional particles 5 are stretched in a state where the distribution density is relatively high, they tend to be concentrated and distributed on the surface of the resin 9 and are also likely to be aligned in the stretching direction. On the other hand, as described above, in a portion where the distribution density of the functional particles 5 is low and the resin is stretched further, thin fibers are likely to be formed as a result of being stretched longer. That is, as described above, a dispersion portion 2 containing the functional particles 5 dispersed on the surface and a non-dispersion portion 3 not containing the functional particles 5 are formed. In addition, the functional particles 5 dispersed near the surface of the resin 9 due to the formation of the cracks 4a, etc. tend to relatively move to the surface side and be exposed from the surface due to the diameter reduction caused by the stretching of the resin 9.

[0031] In contrast, in the portion where the crack 4a is not formed, the functional particles 5a in the core of the resin 9 tend to remain inside the resin 9 even after stretching. This is because, except for the relative movement such as the movement toward the surface side described above, the movement of the functional particles 5 occurs only due to the movement of the resin 9, and even if stretched, only movement in the stretching direction can occur in the core of the resin 9. In other words, it is important to generate the crack 4a near the functional particle 5 so that the functional particle 5 is located on the surface during stretching by melt blowing as described above, in order to make it easier for the obtained entangled aggregate 10 to exhibit the function of the functional particle 5 well. In addition, it can be presumed that the crack 4a is selectively generated near the interface between the functional particle 5 and the resin 9 by forming the branch portion 4 in which the functional particle 5 is dispersed inside.

[0032] The mechanism by which the functional particles 5 are dispersed in the long resin fibers 1 is presumed as described above. As described above, the entangled aggregate 10 contains the dispersed portions 2 and the non-dispersed portions 3, and thus can satisfactorily express the function of the functional particles 5 in relation to the quantitative ratio, and becomes a functional nonwoven fabric that does not impair the texture of the entangled long fiber aggregate.

[0033] It is also useful to make the average particle size of the functional particles 5 relatively large in order to obtain such an entangled aggregate 10 made of the long resin fibers 1. For example, it is also preferable to set the average particle size D50 of the functional particles to be within the range of d to d / 10, where d is the average cross-sectional diameter of the stretched long resin fibers 1.

[0034] As the functional particles 5, various known materials can be used, but in order to form the cracks 4a as described above, it is preferable that the material has a stable shape and other properties even in the molten resin during melt blowing. In addition, in order to enable long-term use, it is preferable that the material is stable in the environment in which the entangled aggregate 10 is used. For example, a hard material such as an inorganic oxide can be preferably used as the functional material. If a powder obtained by crushing sintered apatite is used as the inorganic oxide as the functional particles 5, biocompatibility can be imparted to the entangled aggregate 10 using a polyolefin resin. In addition, a function of generating far infrared rays, a function of increasing hydrophilicity, etc. can be imparted by using other known ceramics.

[0035] Next, a method for producing the entangled mass 10 will be described with reference to FIGS.

[0036] 3, a manufacturing apparatus 20 can be used to manufacture the entangled mass 10. The manufacturing apparatus 20 is a known apparatus for manufacturing resin fibers by melt-blowing, and will be briefly described below.

[0037] The manufacturing apparatus 20 includes an extruder 21 that extrudes a molten resin from a nozzle 22a, and a nozzle head 30 attached to the tip of the nozzle 22a. The extruder 21 further includes a gas supply unit 26 and a gas heating unit 27 for supplying a heated gas to the nozzle head 30. As a result, the manufacturing apparatus 20 heats and melts the pellets fed from the hopper 24 in the extruder 21 with the heater 25, kneads and conveys the pellets with the screw 23 in the barrel 22, supplies the molten resin to the nozzle head 30, and further supplies the heated gas to be ejected as a high-speed gas flow to the nozzle head 30. The pellets are obtained by blending the polyolefin resin 9 and the functional particles 5 described above, and the functional particles 5 are dispersed in the resin 9 melted in the extruder 21.

[0038] As shown in FIG. 4, the nozzle head 30 is provided with a discharge port 32 for discharging a resin and a gas discharge port 33 for discharging a high-speed gas flow, and is attached to the tip of the extruder 21 so that the high-speed gas flow can be horizontally discharged from the gas discharge port 33. For example, the nozzle head 30 is provided with a pair of discharge ports 32 and gas discharge ports 33 arranged in close proximity to each other. In this embodiment, a plurality of pairs of discharge ports 32 and gas discharge ports 33 are provided, which is preferable because it can improve the production amount of the entangled aggregate 10 per unit time. Here, the inner diameter of the outlet portion of the discharge port 32 is set to 500 μm or more. Details will be described later.

[0039] Other details of the manufacturing apparatus 20 are known and will not be described here, but other types of nozzle heads, such as those with different numbers of discharge ports and ejection ports, may be used. The manufacturing apparatus 20 also includes a collection unit that collects the discharged resin fibers, and collects the resin fibers to form the entangled aggregate 10.

[0040] The entangled aggregate 10 is produced by using the above-mentioned production apparatus 20, and the production method is as follows. That is, the polyolefin resin 9, which has been melted in the extruder 21 and has the functional particles 5 dispersed therein, is discharged from the discharge port 32, and a high-velocity gas flow is horizontally ejected from the gas ejection port 33 disposed in the vicinity of the discharge port 32. Then, the resin 9 ejected from the discharge port 32 is stretched by the high-velocity gas flow and released into the air, where it is cooled. Here, the production conditions are adjusted so that the average cross-sectional diameter d of the long resin fibers obtained from the resin 9 is 10 μm or less.

[0041] In particular, the inner diameter of the outlet of the discharge port 32 is set to 500 μm or more, and the average particle diameter D50 of the functional particles 5 is set to 1 μm or more. In this way, the average particle diameter D of the functional particles 5 is relatively large, and the discharge port 32 is also large, thereby obtaining the above-mentioned entangled aggregate 10. That is, by increasing the inner diameter of the outlet of the discharge port 32, the surface tension of the molten resin 9 is reduced, and the above-mentioned cracks 4a are formed, making it easier to branch and split, and the functional particles 5 can be easily concentrated and dispersed on the surface. In addition, the ease of branching is also related to the size of the functional particles 5 as described above, but by increasing the inner diameter of the discharge port 32, clogging is less likely to occur even when such relatively large functional particles 5 are used.

[0042] According to the above-mentioned production method, the above-mentioned entangled aggregate 10 can be obtained. That is, the dispersed portion 2 can satisfactorily express the function in relation to the amount of the functional particles 5, and the non-dispersed portion 3 can suppress breakage due to stretching during production by melt-blowing, and the obtained entangled aggregate 10 of long fibers can provide a functional nonwoven fabric without impairing the texture.

[0043] Although the embodiments of the present invention and modifications based thereon have been described above, the present invention is not necessarily limited to these examples. In addition, a person skilled in the art will be able to find various alternative embodiments and modifications without departing from the spirit of the present invention or the scope of the appended claims. [Explanation of symbols]

[0044] 1. Long resin fibers 2 Dispersion part 3 Non-dispersed part 4 Branches 5 Functional particles 10 Intertwined Aggregates

Claims

1. An entangled aggregate of polyolefin-based resin long fibers stretched by a melt-blowing method and having inorganic oxide particles dispersed therein, The long resin fibers are stretched to an average cross-sectional diameter d of 10 μm or less, and are stretched while being split into a plurality of the long resin fibers starting from the particles having an average particle diameter D50 of 1 μm or more, and the long resin fibers are stretched, the long resin fibers comprising branched portions containing a plurality of the particles, and fiber portions containing the particles exposed from the surface along the long resin fibers.

2. 2. The entangled long fiber aggregate with dispersed particles according to claim 1, wherein the fiber portion has a biased distribution density of the particles along the long resin fibers, and the diameter of the portion with low distribution density is small.

3. 3. The particle-dispersed entangled long fiber aggregate according to claim 2, wherein the particles have an average particle size D50 of d to d / 10.

4. 4. The particle-dispersed entangled long fiber aggregate according to claim 1, wherein the particles are made of powder obtained by pulverizing sintered apatite.

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