WO2017056413A1

WO2017056413A1 - Fiber assembly and sound absorbing material

Info

Publication number: WO2017056413A1
Application number: PCT/JP2016/004109
Authority: WO
Inventors: 伊藤　亨; 俊文名木野; 和史宮武; 航太中平; 徹藤澤; 悠中嶋
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2015-09-28
Filing date: 2016-09-09
Publication date: 2017-04-06
Also published as: JP6037322B1; JP2017066584A; JP6653476B2; JP2017066575A

Abstract

This fiber assembly is an assembly of fibers containing a thermoplastic resin. The fibers have a melt viscosity within the range of from 250 mPa·s to 7,000 mPa·s (inclusive). The number-based median diameter of the fibers is within the range of from 0.3 μm to 0.9 μm (inclusive). The ratio of the number of fibers having diameters of 8 μm or less relative to the total number of fibers is 99% or more.

Description

Fiber assembly and sound absorbing material

The present disclosure relates to a fiber assembly applicable to a sound absorbing material and a sound absorbing material including the fiber assembly.

Conventionally, sound absorbing materials have been used to suppress driving sound emitted from transport vehicles such as automobiles. The driving source of the conventional transportation vehicle is mainly an internal combustion engine such as a gasoline engine. Since the driving sound of the internal combustion engine includes a lot of high-frequency sounds, the sound-absorbing material is required to have high absorbability of high-frequency sounds, particularly sounds having a frequency of 2 kHz or higher.

As such a sound-absorbing material, Patent Document 1 discloses that the fiber is made of thermoplastic resin fiber, and the fiber diameter integration frequency of 1 μm or less is 5% or more and the fiber diameter integration frequency of 10 μm or more is 0.1 to 5%. Melt blown nonwoven fabrics in the range are disclosed.

In recent years, transportation vehicles including a drive source other than an internal combustion engine such as an electric vehicle and a hybrid vehicle have been put into practical use, and accordingly, a sound having a medium frequency range, for example, a sound having a frequency of 500 Hz or more and 1500 Hz or less, is applied to the sound absorbing material. Absorbability is now required.

JP 2013-147771 A

The present disclosure provides a fiber assembly having high mid-range sound absorbability and a sound absorbing material including the fiber assembly.

The fiber assembly according to one embodiment of the present disclosure is a fiber assembly including a thermoplastic resin, and the fiber has a melt viscosity in the range of 250 mPa · s to 7000 mPa · s. The median diameter of the fibers is in the range of 0.3 μm to 0.9 μm. The ratio of the number of fibers having a diameter of 8 μm or less to the total number of fibers is 99% or more.

A fiber assembly according to another embodiment of the present disclosure is a fiber assembly including a thermoplastic resin, and the fiber has a melt flow rate within a range of 1600 g / 10 min to 5000 g / 10 min. The median diameter of the fibers is in the range of 0.3 μm to 0.9 μm. The ratio of the number of fibers having a diameter of 8 μm or less to the total number of fibers is 99% or more.

A sound-absorbing material according to another aspect of the present disclosure includes a fiber assembly according to any one of the above-described fibers.

According to one aspect of the present disclosure, a fiber assembly and a sound absorbing material that can effectively absorb mid-range sound can be obtained.

FIG. 1 is a schematic diagram of a fiber assembly according to an embodiment. FIG. 2 is a diagram showing the relationship between the melt flow rate and the melt viscosity diagram. FIG. 3 is a schematic diagram of a sound absorbing material according to the embodiment.

Hereinafter, embodiments of the present disclosure will be described.

FIG. 1 is a schematic diagram of a fiber assembly according to an embodiment. The fiber assembly 1 is an assembly of fibers 2 containing a thermoplastic resin. In one aspect of the embodiment, the fiber 2 has a melt viscosity in the range of 250 mPa · s to 7000 mPa · s. The median diameter of the fibers 2 is in the range of 0.3 μm or more and 0.9 μm or less. The ratio of the quantity of the fibers 2 having a diameter of 8 μm or less to the total quantity of the fibers 2 is 99% or more.

In another aspect of the embodiment, the fiber 2 has a melt viscosity in the range of 1600 g / 10 min to 5000 g / 10 min. The median diameter of the fiber 2 is in the range of 0.3 μm to 0.9 μm. The ratio of the quantity of the fibers 2 having a diameter of 8 μm or less to the total quantity of the fibers 2 is 99% or more.

The fiber assembly 1 and the sound-absorbing material 11 (see FIG. 3 described later) including the fiber assembly 1 can effectively absorb mid-range sound, particularly sound having a frequency of 500 Hz to 1500 Hz.

The sound absorbing material 11 provided with the fiber assembly 1 is preferably for vehicle use. In particular, when the sound absorbing material 11 is applied for driving sound suppression in a transportation vehicle including a driving source other than the internal combustion engine such as an electric vehicle or a hybrid vehicle, the driving sound from the driving source can be effectively absorbed.

The fiber assembly 1 and the sound absorbing material 11 according to this embodiment will be described in more detail.

As described above, the fiber 2 in the fiber assembly 1 includes a thermoplastic resin.

As described above, the fiber 2 has at least one of a melt flow rate in the range of 1600 g / 10 min to 5000 g / 10 min and a melt viscosity in the range of 250 mPa · s to 7000 mPa · s.

Here, the melt flow rate and the melt viscosity have a certain correlation, and the melt flow rate can be used as a substitute evaluation value of the melt viscosity. That is, the value of the common logarithm of the melt viscosity with respect to the value of the melt flow rate is correlated as shown in FIG. 2, and the range of the melt viscosity from 250 mPa · s to 7000 mPa · s is 1600 g / This corresponds to a range of 10 min to 5000 g / 10 min.

The significance of the melt flow rate and melt viscosity of the fiber 2 in this embodiment will be described in detail. The inventor found that the material of the fiber 2 has a great influence on the mid-range sound absorbability through many experiments, and as a result of examining the factors, the melt flow rate and melt viscosity of the fiber 2 are low. It was found that there is a large correlation with the absorbability of Based on this knowledge, the inventors tried to improve the mid-range sound absorbency by defining the melt flow rate or melt viscosity of the fiber 2. As a result, at least one of the melt flow rate within the range of 1600 g / 10 min or more and 5000 g / 10 min or less and the melt viscosity within the range of 250 mPa · s or more and 7000 mPa · s or less of the fiber 2 as described above. If there is, it has been found that the mid-range sound absorption is greatly improved.

In particular, since the melt flow rate of the fiber 2 is 5000 g / 10 min or less, the fiber assembly 1 also has high heat resistance.

Furthermore, if the fiber 2 has at least one of a melt flow rate in the range of 1600 g / 10 min to 5000 g / 10 min and a melt viscosity in the range of 250 mPa · s to 7000 mPa · s, the fiber High heat resistance can be imparted to the aggregate 1. In the present specification, the high heat resistance of the fiber assembly 1 means that even if the fiber assembly 1 is heated, it is difficult to reduce the sound absorbability of the midrange of the fiber assembly 1.

Furthermore, if the fiber 2 has at least one of a melt flow rate in the range of 1600 g / 10 min or more and 5000 g / 10 min and a melt viscosity in the range of 250 mPa · s or more and 7000 mPa · s, When a fiber 2 is produced by spinning a material (hereinafter referred to as a spinning material), the median diameter of the fiber 2 is a small value within a range of 0.3 μm or more and 0.9 μm or less. The fibers 2 can be manufactured stably, and the fiber assembly 1 can be easily reduced in density. That is, if the fiber 2 has at least one of a melt flow rate of 1600 g / 10 min or more and a melt viscosity of 7000 mPa · s or less, the spinning material flows when the fiber 2 is produced by spinning the spinning material. Therefore, it is easy to reduce the diameter of the fiber 2. In this case, when air current is blown during spinning as in the melt blown method, the diameter of the fiber 2 can be further reduced even in a weak air current, and the density of the fiber assembly 1 can be reduced. Is easy. Therefore, if the spinning conditions are the same, when the fiber 2 has at least one of a melt flow rate of 1600 g / 10 min or more and a melt viscosity of 7000 mPa · s or less, the fiber 2 has a higher viscosity than the other cases. The diameter can be reduced and the density of the fiber assembly 1 can be reduced. Further, when the fiber 2 has at least one of a melt flow rate of 5000 g / 10 min or less and a melt viscosity of 250 mPa · s or more, it is easy to form the fiber 2 having a sufficient length by spinning. Therefore, it is easy to collect the fiber 2 and produce the fiber assembly 1. For this reason, it becomes possible to manufacture the fiber 2 which has a small diameter, suppressing the amount of the airflow at the time of spinning the spinning material, and it becomes possible to manufacture the fiber assembly 1 having a low density.

The fiber 2 preferably has a melt flow rate in the range of 2000 g / 10 min to 5000 g / 10 min, and more preferably has a melt flow rate in the range of 3500 g / 10 min to 5000 g / 10 min. When the fiber 2 has a melt flow rate of 2000 g / 10 min or more, the diameter of the fiber 2 can be further reduced and the density of the fiber assembly 1 can be reduced. When the fiber 2 has a melt flow rate of 3500 g / 10 min or more, particularly the diameter of the fiber 2 can be reduced and the density of the fiber assembly 1 can be reduced.

Further, the fiber 2 preferably has a melt viscosity in the range of 250 mPa · s to 3000 mPa · s, more preferably in the range of 250 mPa · s to 800 mPa · s. When the fiber 2 has a melt viscosity of 3000 mPa · s or less, the fiber diameter can be further reduced and the density of the fiber assembly 1 can be reduced. When the fiber 2 has a melt viscosity of 800 mPa · s or less, the diameter of the fiber 2 can be particularly reduced and the density of the fiber assembly 1 can be reduced.

The melting point or softening point of the fiber 2 is preferably 130 ° C. or higher. In this case, even if the fiber assembly 1 is heated, it is difficult to reduce the sound absorbability of the midrange of the fiber assembly 1. More preferably, the melting point or softening point is 140 ° C. or higher. More preferably, the melting point or softening point is 150 ° C. or higher.

In addition, the melt flow rate of the fiber 2 is measured under conditions of a temperature of 230 ° C. and a load of 2.16 kg in accordance with ASTM D1238. The melt viscosity of the fiber 2 is a melt viscosity at 230 ° C. Further, the melting point and softening point of the fiber 2 are determined from the peak of the heat of fusion peak obtained by a DSC (Differential Scanning Colorimetry) method at a temperature rising rate of 5 ° C./min.

The melt flow rate, melt viscosity, melting point, and softening point of the fiber 2 are values related to the fiber 2 in the fiber assembly 1, and are not related to the spinning material, but are related to the components contained in the spinning material. Not a value.

The median diameter of the fibers 2 is in the range of 0.3 μm to 0.9 μm, and the ratio of the number of fibers 2 having a diameter of 8 μm or less to the total number of fibers 2 is 99% or more. In the present embodiment, by defining the diameter of the fiber 2 in the fiber assembly 1 in this way, it is possible to improve the mid-range sound absorbability of the fiber assembly 1 and the sound absorbing material 11.

The improvement of the mid-range sound absorbency by defining the diameter of the fiber 2 will be described in detail. According to the well-known Biot model for the porous sound absorbing material 11, the peak of the sound absorbing characteristic of the sound absorbing material 11 shifts from 2 kHz to a lower frequency region as the diameter of the fiber 2 in the sound absorbing material 11 becomes smaller. However, in reality, simply including the fibers 2 having a small diameter does not sufficiently increase the mid-range sound absorbability. This is because if the small-diameter fiber 2 and the large-diameter fiber 2 are mixed in the sound-absorbing material 11, air flow in the sound-absorbing material 11 is likely to occur, and this impedes the sound absorption of the mid-range. The inventor speculated that this was the case. Based on this assumption, the inventor tried to improve the mid-range sound absorbability by defining the diameter of the fiber 2. As a result, not only the median diameter of the fibers 2 is in the range of 0.3 μm or more and 0.9 μm or less as described above, but also the fibers 2 having a diameter of 8 μm or less with respect to the total number of fibers 2. The inventor has found that when the ratio of the quantity is 99% or more, the mid-range sound absorbability is greatly improved.

It is particularly preferable that the ratio of the number of fibers having a diameter of 5 μm or less to the total number of fibers 2 is 99% or more. In this case, the mid-range sound absorbability can be further improved.

It is particularly preferable that the maximum diameter of the fiber 2 is smaller than 10 μm. That is, it is particularly preferable that the fiber assembly 1 does not include the fiber 2 having a diameter of 10 μm or more. In this case, the weight ratio of the fibers 2 having a small diameter per unit volume of the fiber assembly 1 increases, and therefore, the sound absorbability in the middle range is particularly high.

The length of the fiber 2 is preferably 5 mm or more, for example, but is not particularly limited as long as the fiber 2 has a length that allows the fibers 2 to sufficiently intertwine.

The value of the aspect ratio of each fiber 2 is preferably 1000 or more.

In addition, the diameter and length of the fiber 2 are measured by performing image processing on an image obtained by photographing the fiber 2 with an electron microscope. The median diameter of the fibers 2 is a quantity-based median value calculated from the measurement results of the diameters of the 200 fibers 2. In defining the diameter and length of the fibers 2 in the present embodiment, the portions where the fibers 2 are thermally fused together and the portions which are not formed into fibers and are agglomerated are not regarded as fibers.

The fiber assembly 1 preferably has a density of 0.03 g / cm ³ or less. In this case, the absorbability of the midrange sound of the fiber assembly 1 is further improved. It is also preferable that the fiber assembly 1 has a density of 0.003 g / cm ³ or more. In this case, the deformation and density change due to the weight of the fiber assembly 1 are suppressed, and therefore, good absorbability of the fiber assembly 1 can be maintained over a long period of time.

The fiber assembly 1 is, for example, a sheet or a layer. When the fiber assembly 1 is a sheet or a layer, the basis weight of the fiber assembly 1 (that is, the mass per unit plan view area) is preferably within a range of 100 g / m ² or more and 1000 g / m ² or less. Preferably, it is in the range of 100 g / m ² or more and 600 g / m ² or less, more preferably in the range of 100 g / m ² or more and 500 g / m ² or less. If the basis weight is 100 g / m ² or more, the fiber assembly 1 can have higher sound absorption. Further, if the basis weight is 1000 g / m ² or less, the fiber assembly 1 can be made compact and light, and therefore, the degree of freedom in vehicle design, particularly when the fiber assembly 1 is for vehicle use. Will increase.

The components contained in the fiber 2 will be described in detail.

Examples of the thermoplastic resin include polypropylene, polyethylene, polyolefin-based thermoplastic elastomer, 1-butene polymer, 1-hexene polymer, 1-octene polymer, 1-decene polymer, 1-hexadecene polymer, and 1-heptadecene polymer. Polymer, 1-octadecene polymer, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyurethane, polybutene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, liquid crystal polymer, ethylene vinyl acetate copolymer, polyacrylonitrile, cyclic It contains at least one component selected from the group consisting of polyolefin and polyoxymethylene. The thermoplastic resin may contain a wax-like component such as polyethylene wax, polypropylene wax, and paraffin wax. In particular, the thermoplastic resin preferably contains at least one component selected from the group consisting of polypropylene, polyethylene, polyolefin-based thermoplastic elastomer and paraffin. In this case, the mid-range sound absorbability of the fiber assembly 1 is particularly high.

The thermoplastic resin can contain two or more kinds of resins. In this case, these resins can have at least one of different melt flow rates and different melt viscosities. In this case, at least one of the melt flow rate and the melt viscosity of the fibers 2 can be easily adjusted by adjusting the amount of each resin in the thermoplastic resin. Further, as a component of the thermoplastic resin, a component whose physical properties do not match those of the fiber 2, that is, its melt flow rate is not in the range of 1600 g / 10 min to 5000 g / 10 min and its melt viscosity is 250 mPa · s to 7000 mPa. It is possible to apply ingredients that are not within the range of s or less. For this reason, the freedom degree of selection of the component of a thermoplastic resin increases.

At least a part of the components in the thermoplastic resin (hereinafter referred to as a specific component) may be manufactured through a thermal decomposition step. The thermal decomposition step is a step of obtaining a specific component having a molecular weight adjusted by thermally decomposing a raw material of a specific component (hereinafter referred to as a specific raw material). In this case, at least one of the melt flow rate and the melt viscosity of the fiber can be easily adjusted by adjusting the molecular weight of the specific component. Moreover, as the specific raw material, it is possible to apply a component having a melt flow rate lower than 1600 g / 10 min and a melt viscosity higher than 7000 mPa · s. For this reason, the freedom degree of selection of the raw material of a thermoplastic resin increases. For example, when a thermoplastic resin contains 2 or more types of resin, at least 1 type of resin may be manufactured through a thermal decomposition process. Further, all of the thermoplastic resin may be manufactured through a thermal decomposition process.

Also, in order not to melt when the fiber assembly 1 is heat-sealed to a support or the like, it is preferable that the thermoplastic resin has high crystallinity. It is also preferable that the surface tension of the thermoplastic resin is as low as possible. In this case, when the fiber 2 is produced by spinning a spinning material containing the thermoplastic resin, stable spinning is possible.

The fiber 2 may contain a plasticizer having at least one of a melt flow rate lower than that of the thermoplastic resin and a melt viscosity lower than that of the thermoplastic resin. In this case, at least one of the melt flow rate and the melt viscosity of the fiber 2 can be easily adjusted by adjusting the amount of the plasticizer. Moreover, as a thermoplastic resin, it is possible to apply a component having a melt flow rate lower than 1600 g / 10 min and a melt viscosity higher than 7000 mPa · s. For this reason, the freedom degree of selection of a thermoplastic resin increases.

The plasticizer preferably has compatibility with the thermoplastic resin. In this case, bleeding of the plasticizer from the fiber 2 is suppressed. However, a material that is not compatible with the thermoplastic resin may be contained in the fiber 2 as long as the material does not cause bleeding out.

The plasticizer may contain a liquid material such as oil. Specifically, the plasticizer can contain, for example, one or more materials selected from the group consisting of liquid paraffin, petroleum lubricant, naphtha lubricant, synthetic oil such as silicone oil, fluorine oil, and grease.

The plasticizer is within the range of 0.1% by mass or more and 50% by mass or less with respect to the total of the thermoplastic resin and the plasticizer, but is not limited thereto.

The melt viscosity of the resin and the plasticizer is measured using a viscoelasticity measuring device MCR302 manufactured by Anton Paar Japan Co., Ltd. under a nitrogen atmosphere at 230 ° C. under a shear rate of 10 [1 / s]. Viscosity. Moreover, the melt viscosity of resin and a plasticizer is a melt viscosity in 230 degreeC.

The fiber 2 in the fiber assembly 1 can contain an antioxidant. In this case, the heat resistance of the fiber assembly 1 is improved. Further, when the fiber 2 is produced by spinning a spinning material containing a base resin, when the spinning material contains an antioxidant, the base resin at the time of material kneading, spinning, and the like after spinning Oxidative deterioration of the sound absorbing material 11 is suppressed.

The antioxidant may be mixed with the raw material of the base resin when synthesizing the material such as the base resin. Further, the antioxidant may be mixed with a base resin or the like when the spinning material is prepared.

Antioxidants include, for example, phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, amine antioxidants, hydrazine antioxidants, amide antioxidants, and light stabilizers (HALS). At least one material selected from the group consisting of:

Especially when the antioxidant contains a phenolic antioxidant, the long-term heat resistance of the fiber assembly can be improved. The phenolic antioxidant may be any of a hindered type, a semi-hindered type, and a less hindered type. Further, when the antioxidant contains at least one of a phosphorus-based antioxidant and a sulfur-based antioxidant in addition to the phenol-based antioxidant, oxidative deterioration of the base resin and the like during spinning is further suppressed.

It is particularly preferred that the antioxidant contains both a phenolic antioxidant and a phosphorus antioxidant. By combining such two kinds of antioxidants, the heat resistance of the fiber assembly is improved and high heat resistance is maintained over a long period of time. That is, even at high temperatures, the mid-range high sound absorptivity is maintained for a long time.

When the fiber 2 contains a phenol-based antioxidant and a phosphorus-based antioxidant, the total percentage of the phenol-based antioxidant and the phosphorus-based antioxidant with respect to the thermoplastic resin is 0.1% by mass or more; It is preferably within the range of 0% by mass or less. If this percentage is 0.1% by mass or more, oxidative degradation of the fiber can be particularly suppressed. Moreover, when this percentage is more than 2.0 mass%, the inhibitory action of the oxidative degradation of the fiber assembly 1 will be saturated, and the amount of phenolic antioxidant and phosphorus antioxidant will increase unnecessarily. At the same time, an economical disadvantage is also caused, so that the percentage is preferably 2.0% by mass or less. The mass ratio of the phenolic antioxidant to the phosphorus antioxidant is preferably within the range of 1.0 / 3.0 to 3.0 / 1.0. When this mass ratio is 1.0 / 3.0 or more, high heat resistance is maintained particularly for a long period of time. Moreover, when this mass ratio is 3.0 / 1.0 or less, the heat resistance of the fiber assembly is particularly high. Furthermore, consumption of the phenolic antioxidant in obtaining the fiber by spinning can be suppressed.

The fiber 2 may contain additives such as a weather resistance stabilizer, a light resistance stabilizer, an anti-blocking agent, a lubricant, a nucleating agent, a pigment, a softening agent, a hydrophilic material, an auxiliary agent, a water repellent, a filler, and an antibacterial agent. .

The fiber 2 can be produced by spinning a spinning material containing, for example, a thermoplastic resin as described above.

The composition of the spinning material is determined so as to match the composition of the fiber 2. That is, the spinning material can include a plasticizer. The spinning material can also contain an antioxidant. The spinning material may contain a phenolic antioxidant and a phosphorus antioxidant. The spinning material contains additives such as weathering stabilizer, light stabilizer, anti-blocking agent, lubricant, nucleating agent, pigment, softener, hydrophilic material, auxiliary agent, water repellent, filler, antibacterial agent. May be.

In order to prepare the spinning material, for example, the components of the spinning material may be dry blended, or the components of the spinning material may be mixed while being heated and melted. In the case where the components of the spinning material are mixed while being heated and melted, the components may be mixed batchwise in a heating vessel or may be mixed with a continuous spinning extruder. When mixing with a continuous spinning extruder, the spinning extruder may be any of a single screw type, a twin screw type, and a multi-screw type.

As a method for spinning a spinning material, a melt spinning method such as a melt blown method or an electrospinning method can be applied. In this case, the fiber can be manufactured stably.

When producing fibers by the melt spinning method, for example, the spinning material is first melted by heating. When the spinning material is prepared with a continuous spinning extruder, the spinning material is prepared in a molten state. The melted spinning material is discharged from a nozzle. The spinning material may be stretched by blowing a heated air current onto the spinning material discharged from the nozzle. The direction of the airflow may be a direction along the discharge direction of the spinning material from the nozzle, or may be a direction different from the discharge direction. The fiber may be drawn by applying a voltage to the spinning material discharged from the nozzle. Thereby, the fiber 2 can be manufactured.

The diameter of the fiber 2 depends on the composition of the spinning material, for example, the heating conditions when melting the spinning material, the hole diameter of the nozzle, the discharge amount of the spinning material from the nozzle, the temperature of the airflow when blowing the airflow In addition, the voltage can be controlled by adjusting the flow rate and the voltage application condition when applying the voltage.

The heating temperature for melting the spinning material depends on the composition of the spinning material, but it is at least 10 ° C higher than the melting point or softening point of the thermoplastic resin in the spinning material and below the thermal decomposition temperature of the thermoplastic resin. It is preferable to be within the range. The discharge amount of the spinning material from the nozzle is preferably in the range of 0.05 g / min or more and 0.5 g / min or less per hole of the nozzle. In the case where an air stream is blown onto the fiber during spinning, the temperature of the air stream is preferably in the range of 200 ° C. or higher and 450 ° C. or lower. The flow rate of air flow, 50 Nm ³ / h · m or more, is preferably in the range of 500 Nm ³ / h · m.

When manufacturing the fiber 2, as described above, the specific raw material may be manufactured by pyrolyzing the specific raw material to obtain the specific component whose molecular weight is adjusted.

In the thermal decomposition of the specific raw material, for example, before preparing the spinning material, the specific raw material is preferably brought to a temperature at which thermal decomposition of the specific raw material occurs in an inert atmosphere (for example, under a nitrogen atmosphere) or a reduced pressure atmosphere. By arranging, the specific raw material is thermally decomposed. This temperature depends on the type of the specific raw material. For example, when the specific raw material is a polypropylene resin, the temperature is 300 ° C. or higher. The thermal decomposition of the specific raw material may be performed batchwise in a heating vessel, or may be performed continuously in a closed continuous reactor. A spinning material can be prepared by mixing the specific component thus obtained and a component other than the specific component of the fiber. A fiber containing a specific component can be produced by spinning this spinning material.

A specific raw material and a component other than the specific component of the fiber are mixed to prepare a spinning material containing the specific raw material, and when the spinning material is spun to produce a fiber, the specific raw material in the spinning material is heated. You may produce the fiber containing a specific component by making it decompose. For example, when a fiber is produced by melt spinning the spinning material as described above, the temperature at which the spinning material is melted is set to a temperature at which the thermal decomposition of the particular raw material is performed. May be thermally decomposed. However, in order to produce the fiber assembly more stably, it is preferable to thermally decompose the specific raw material before preparing the spinning material.

The temperature at which thermal decomposition occurs is, for example, the temperature at which the weight loss of the specific raw material occurs under an inert atmosphere, or the temperature at which the melt viscosity of the specific raw material decreases under an inert atmosphere.

In this embodiment, the fiber 2 has at least one of a melt flow rate within a range of 1600 g / 10 min to 5000 g / 10 min and a melt viscosity within a range of 250 mPa · s to 7000 mPa · s. Therefore, such a fiber 2 can be stably produced by the melt spinning method described above, whereby the ratio of the quantity of the fibers 2 having a diameter of 8 μm or less to the total quantity of the fibers 2 is 99% or more. The fiber 2 can be stably produced.

The fiber assembly 1 is obtained by assembling the fibers 2. In the fiber assembly 1, it is preferable that the fibers 2 are intertwined. The fiber assembly 1 is, for example, a nonwoven fabric, but is not limited thereto.

It is preferable to anneal the fiber assembly 1. For example, it is preferable to treat the fiber assembly 1 at a heating temperature of 100 ° C. for 2 hours. The annealing process promotes crystallization of the fibers 2 and increases the shape stability of the fiber assembly 1.

FIG. 3 is a schematic diagram of a sound absorbing material according to the embodiment. The sound absorbing material 11 may be composed of only the fiber assembly 1 or may include the fiber assembly 1 and the support 3 that supports the fiber assembly 1. The support 3 is, for example, a microfiber nonwoven fabric. The sound absorbing material 11 may include a fiber assembly 1 and a bag containing the fiber assembly 1. The bag is made of, for example, a microfiber nonwoven fabric. In order to support the fiber assembly 1 on the support 3, the fiber assembly 1 may be thermally fused to the support 3 by hot pressing or blowing hot air.

The fiber assembly 1 preferably has a heat resistance of 120 ° C. This heat resistance is evaluated based on the vertical sound absorption coefficient of the fiber assembly 1 after the fiber assembly 1 is subjected to a treatment of exposure to a high-temperature air atmosphere at 120 ° C. for 500 hours. When the sound absorption coefficient of 600 Hz sound of the fiber assembly 1 after this treatment is 20% or more and the sound absorption coefficient of sound of 1000 Hz is 50% or more, it is evaluated as having heat resistance of 120 ° C.

Such high heat resistance can be achieved by appropriately adjusting the composition of the fibers 2 constituting the fiber assembly 1 within the range described above.

(1) Production of fiber assemblies of Examples and Comparative Examples Except in the case of Example 10, the components shown in the column of “Composition” in Tables 1 and 2 below are 200 ° C. under inert conditions. After mixing for 10 minutes in the molten state, the mixture was solidified by cooling to room temperature, and further pulverized to obtain a spinning material.

In the case of Example 10, components other than the antioxidants shown in the “Composition” column of Tables 1 and 2 below were placed in a reaction vessel under a nitrogen atmosphere to obtain a mixture. The temperature of the mixture was raised to 350 ° C. while stirring in the reaction vessel and then held for 10 minutes, whereby the PP (polypropylene) resin (f) in the mixture was thermally decomposed. Subsequently, the mixture was cooled to 200 ° C. Subsequently, an antioxidant was added to the mixture, mixed for 5 minutes, solidified by cooling to room temperature, and further pulverized to obtain a spinning material.

A fiber 2 was obtained by spinning the spinning material by the melt spinning method. Specifically, after the spinning material was melted, the fiber 2 was obtained by blowing an air current onto the spinning material while discharging the spinning material from the nozzle. The conditions for the heating temperature for melting the spinning material, the discharge amount of the spinning material per hole in the nozzle, the nozzle hole diameter, the air temperature and the air velocity are shown in Tables 1 and 2. As shown in the column “Condition”. In the case of Comparative Example 3, a nozzle having a 0.25 mm diameter hole and a 1.0 mm diameter hole in a quantity ratio of 15: 1 was used. The discharge amount of the spinning material was adjusted by extruding a specified amount of the spinning material from an independent extruder for each nozzle hole diameter value.

Furthermore, the fiber assembly 1 was obtained by collecting the fibers 2 formed by cooling the spinning material discharged from the nozzles on a conveyor. The feed rate of the conveyor was adjusted so that the basis weight of the fiber assembly 1 was 400 g / m ² . In the case of Example 11, after producing the fiber assembly 1 on a spunbonded nonwoven fabric having a basis weight of 20 g / m ² , the spunbonded nonwoven fabric and the fiber assembly 1 were bonded by a hot roll press.

Details of the components in Tables 1 and 2 below are as follows.
PP resin (a): Polypropylene resin manufactured by Sun Allomer, product number PWH00N, weight average molecular weight 87,000, melt flow rate 1700 g / 10 min, 230 ° C. melt viscosity 6000 mPa · s, melting point 166 ° C.
PP resin (b): crystalline polypropylene resin (homopolymer) manufactured by Mitsui Chemicals, product number NP805, weight average molecular weight 35,000, melt flow rate 3500 g / 10 min, 230 ° C. melt viscosity 800 mPa · s, melting point 155 ° C. .
PP resin (c): crystalline polypropylene resin (homopolymer) manufactured by Mitsui Chemicals, product number NP500, weight average molecular weight 35,000, melt flow rate 5000 g / 10 min, 230 ° C. melt viscosity 270 mPa · s, melting point 164 ° C. .
PP resin (d): crystalline polypropylene resin (homopolymer) manufactured by Mitsui Chemicals, product number NP055, weight average molecular weight 10,000, melt flow rate 6000 g / 10 min, 230 ° C. melt viscosity 25 mPa · s, melting point 145 ° C. .
PP resin (e): polypropylene resin manufactured by Total Petrochemical, product number 3962, weight average molecular weight 145,000, melt flow rate 1300 g / 10 min, 230 ° C. melt viscosity 7500 mPa · s, melting point 165 ° C.
PP resin (f): Polymylay polypropylene resin, product number HP461X, weight average molecular weight 150,000, melt flow rate 1100 g / 10 min, 230 ° C. melt viscosity 8600 mPa · s, melting point 168 ° C.
PE resin: polyethylene wax manufactured by Mitsui Chemicals, product number 40800, 230 ° C. melt viscosity 135 mPa · s, melting point 130 ° C.
Paraffin: Paraffin wax manufactured by Nippon Seiki Co., Ltd., product number FT115, 230 ° C. melt viscosity 5 mPa · s, melting point 113 ° C.
-Thermoplastic elastomer: Product name VISTAMAXX manufactured by ExxonMobil, product number 6202, melt flow rate 20 g / 10 min, 230 ° C melt viscosity 196000 mPa · s, softening point 94 ° C.
Phenol antioxidant: phenolic antioxidant manufactured by BASF, product name IRGANOX 1010.
Phosphorous antioxidant: Phosphoric antioxidant manufactured by ADEKA Corporation, product name ADK STAB PEP-36.

(2) Evaluation test The following evaluation tests were conducted for each of the examples and comparative examples. The results are shown in the column “Evaluation Test” in Tables 1 and 2 below.

In the case of Comparative Example 4, although it was difficult to form into a fiber shape even when the spinning material was spun, only the molded body that can be regarded as a fiber was collected to produce the fiber assembly 1. Evaluation was performed.

(2-1) Melt flow rate evaluation test The melt flow rate of the fibers 2 in the fiber assembly 1 was measured in accordance with ASTM D-1238. The measurement conditions of the melt flow rate are determined according to the type of the thermoplastic resin in the spinning material used for producing the fiber 2, and the thermoplastic resin in the spinning material contains two or more types of resins. When it contained, it determined according to the kind of resin with the largest mass ratio among them.

(2-2) Melt Viscosity Evaluation Test Using a viscoelasticity measuring device (model number MCR302) manufactured by Anton Paar Japan Co., Ltd., the melt viscosity at 230 ° C. of the fibers 2 in the fiber assembly 1 was measured under a nitrogen atmosphere. The measurement was performed under the condition of a shear rate of 10 [1 / s].

(2-3) Measurement of fiber diameter After attaching the fiber 2 in the fiber assembly 1 to a 3 mm × 3 mm region of the carbon tape, the fiber 2 is made of Au by vapor-depositing Au on the fiber 2 for about 2 minutes. Coated. Subsequently, a 3000 times image of the fiber 2 was obtained using a scanning electron microscope (manufactured by Keyence Corporation, model number VE-7800). By processing this image, the diameters of arbitrary 200 fibers 2 were measured, and the median value of the diameters of the fibers 2 was calculated from the measurement results.

Further, from this measurement result, the ratio of the number of fibers 2 having a diameter of 10 μm or more, the ratio of the number of fibers 2 having a diameter of 8 μm or less, and the fibers 2 having a diameter of 5 μm or less among the 200 fibers 2. The percentage of the quantity was calculated.

(2-4) Weight per unit area and density The fiber assembly 1 was cut to prepare ten samples having dimensions of 50 mm × 50 mm in plan view. The mass of the sample was measured, and the average value of the mass was calculated from the result. The basis weight of the fiber assembly 1 was calculated by dividing the average value of the mass of the sample by the area of the sample in plan view.

Also, the thickness of the central part of each of the four sides of the sample was measured with a caliper, and the average value of the sample thickness was calculated from the measurement result. The value obtained by multiplying the planar view area of the sample by the average value of the thickness of the sample was taken as the average value of the volume of the sample. The density of the fiber assembly 1 was calculated by dividing the average value of the mass of the sample by the average value of the volume of the sample.

(2-5) Sound absorption characteristic test A test piece having a diameter of 29 mm in plan view was cut out from the fiber assembly 1. Based on JIS A1405-2, a vertical sound absorption system (manufactured by Ono Sokki Co., Ltd., model number DS-200) is used to calculate the normal incident sound absorption coefficient of sound of each frequency of 600 Hz, 1000 Hz, and 1500 Hz. ).

(2-6) Heat resistance test The fiber assembly 1 after the above sound absorption characteristic test was heated at 120 ° C. for 500 hours, and then each frequency of 600 Hz, 1000 Hz and 1500 Hz was used in the same manner as in the above sound absorption characteristic test. The normal incident sound absorption coefficient of the sound was measured.

The fiber assembly of the present disclosure and the sound absorbing material including the fiber assembly are useful in a transportation vehicle including a drive source other than an internal combustion engine such as an electric vehicle and a hybrid vehicle.

DESCRIPTION OF SYMBOLS 1 Fiber assembly 2 Fiber 3 Support body 11 Sound absorbing material

Claims

An aggregate of fibers containing a thermoplastic resin;
The fiber has a melt viscosity within a range of 250 mPa · s to 7000 mPa · s,
The median value of the fiber diameter is in the range of 0.3 μm or more and 0.9 μm or less,
The ratio of the number of fibers having a diameter of 8 μm or less to the total number of fibers is 99% or more.
Fiber assembly.
An aggregate of fibers containing a thermoplastic resin;
The fiber has a melt flow rate within a range of 1600 g / 10 min to 5000 g / 10 min,
The median value of the fiber diameter is in the range of 0.3 μm or more and 0.9 μm or less,
The ratio of the number of fibers having a diameter of 8 μm or less to the total number of fibers is 99% or more.
Fiber assembly.
The fiber has a melt flow rate within a range of 1600 g / 10 min to 5000 g / 10 min.
The fiber assembly according to claim 1.
The fiber has a melt flow rate within a range of 2000 g / 10 min to 5000 g / 10 min.
The fiber assembly according to claim 1 or 3.
The fiber has a melt viscosity within a range of 250 mPa · s to 3000 mPa · s.
The fiber assembly according to claim 2 or 3.
Having a density of 0.03 g / cm 3 or less,
The fiber assembly according to claim 1 or 2.
The thermoplastic resin contains two or more kinds of resins,
The resins have different melt flow rates, or have different melt viscosities,
The fiber assembly according to claim 1 or 2.
The thermoplastic resin contains at least one component selected from the group consisting of polypropylene, polyethylene, polyolefin-based thermoplastic elastomer and paraffin.
The fiber assembly according to claim 1 or 2.
The fiber contains a plasticizer,
The plasticizer has a higher melt flow rate than the thermoplastic resin, or a lower melt viscosity than the thermoplastic resin,
The fiber assembly according to claim 1 or 2.
At least some of the components in the thermoplastic resin are manufactured through a thermal decomposition step.
The fiber assembly according to claim 1 or 2.
Having heat resistance of 120 ° C,
The fiber assembly according to claim 1 or 2.
Sound absorbing material comprising the fiber assembly according to any one of claims 1 to 11.
The sound-absorbing material according to claim 12, which is used for in-vehicle use.