Composite filament nonwoven fabric and soundproof material

Abstract

Provided is a composite filament nonwoven fabric that exhibits excellent vibration-damping property in a wide frequency range. The composite filament nonwoven fabric is formed from composite filaments each having, in a cross section orthogonal to the fiber axial direction, a portion formed from a component containing a first styrene-based elastomer and a portion formed from a component containing a second styrene-based elastomer. The first and the second styrene-based elastomers are each a hydrogenated product of a copolymer having a polystyrene-based hard segment and a vinyl-polydiene-based soft segment. The glass transition temperature Tg1 of the first styrene-based elastomer is lower than the glass transition temperature Tg2 of the second styrene-based elastomer. The composite filaments are fused to each other at a plurality of contact points, thereby forming a network structure of the composite filaments.

Description

Composite long fiber nonwoven fabric and soundproofing material Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2024-068328, filed on April 19, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a conjugated long-fiber nonwoven fabric formed of conjugated long fibers having a component containing a first styrene-based elastomer and a component containing a second styrene-based elastomer, and to a soundproofing material containing the conjugated long-fiber nonwoven fabric.

[0003] In recent years, hybrid electric vehicles (HEVs) and electric vehicles (EVs), which include electric motors as their driving sources, have become increasingly popular, replacing automobiles that are driven solely by engines. The electrification of automobiles has significantly improved quietness, as it eliminates engine noise, which is the main noise generated in conventional automobiles. As a result, there is a demand for reducing road noise, etc., generated between the ground and tires, which was not a problem in conventional automobiles.

[0004] Therefore, reducing noise using vibration-damping materials has been studied, and composite fibers containing elastomers as materials with excellent vibration damping properties have been proposed as vibration-damping fibers. For example, Patent Document 1 (WO 2022 / 080167) discloses a composite fiber composed of a core component A and a component B that at least partially covers the core component A, wherein the core component A contains a vibration-damping elastomer having a tan δ peak top strength of 0.5 or more, the core component B contains a thermoplastic elastomer having a tan δ peak top strength of less than 0.5, and the core component B covers 70% or more of the cross-sectional circumference of the core component A in the fiber cross section.

[0005] International Publication No. 2022 / 080167

[0006] Vibration damping properties are generally evaluated by the loss factor tan δ obtained by dynamic viscoelasticity measurement, and increasing tan δ in a frequency band of about 1 to 1000 Hz is effective in reducing road noise, etc. This frequency band corresponds to a temperature range of about 0 to 40°C according to the frequency-temperature conversion rule, and if the temperature range in which tan δ is high is wide, it can be said that the material has high vibration damping properties over a wide frequency band.

[0007] Patent Document 1 describes that high vibration-damping performance can be exhibited over a wide temperature range, and measures tan δ for composite fibers, but does not evaluate the temperature dependency of tan δ for the fiber structure.

[0008] Therefore, an object of the present invention is to provide a conjugated continuous fiber nonwoven fabric that has excellent vibration damping properties over a wide frequency range.

[0009] As a result of intensive investigations to solve the above problems, the present inventors have found that a conjugate long-fiber nonwoven fabric formed from conjugate long fibers containing two types of styrene-based elastomers having different glass transition temperatures, in which the conjugate long fibers are fused at multiple contact points to form a conjugate long-fiber network structure, can transmit vibrations to both components of the two types of styrene-based elastomers, and can efficiently utilize the vibration-damping properties of both components, thereby widening the temperature range (frequency band) in which tan δ is high, and have completed the present invention.

[0010] That is, the present invention can be configured in the following aspects. [Aspect 1] A conjugated long-fiber nonwoven fabric formed from conjugated long fibers having, in a cross section perpendicular to the fiber axis direction, a portion formed from a component containing a first styrene-based elastomer and a portion formed from a component containing a second styrene-based elastomer, wherein both the first and second styrene-based elastomers are hydrogenated copolymers having a polystyrene-based hard segment and a vinyl-polydiene-based soft segment, the glass transition temperature Tg1 of the first styrene-based elastomer is lower than the glass transition temperature Tg2 of the second styrene-based elastomer, and the conjugated long fibers are fused together at multiple contact points to form a conjugated long-fiber network structure. [Aspect 2] A conjugated long-fiber nonwoven fabric according to Aspect 1, wherein the conjugated long fibers are sheath-core conjugated long fibers, and the sheath portion is formed from a component containing the first styrene-based elastomer. [Aspect 3] The conjugated long-fiber nonwoven fabric according to Aspect 1 or 2, wherein the difference Tg2 - Tg1 between the glass transition temperature Tg2 of the second styrene-based elastomer and the glass transition temperature Tg1 of the first styrene-based elastomer is 50°C or less (preferably 5 to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 30°C). [Aspect 4] The conjugated long-fiber nonwoven fabric according to any one of Aspects 1 to 3, wherein the weight ratio of the first styrene-based elastomer to the second styrene-based elastomer (first:second) is 40:60 to 99:1 (preferably 45:55 to 97:3, more preferably 50:50 to 95:5, or preferably 60:40 to 99:1, more preferably 80:20 to 99:1, even more preferably 85:15 to 99:1, and even more preferably 90:10 to 99:1). [Aspect 5] The conjugate long fiber nonwoven fabric according to any one of Aspects 1 to 4, wherein the average fiber diameter of the conjugate long fiber is 25 μm or less (preferably 0.1 to 20 μm, more preferably 1 to 15 μm). [Aspect 6] The conjugate long fiber nonwoven fabric according to any one of Aspects 1 to 5, wherein the apparent density is 0.10 g / cm ３ or more (preferably 0.10 to 0.50 g / cm ３, more preferably 0.16 to 0.45 g / cm ３ , more preferably 0.18 to 0.40 g / cm ３ A conjugate continuous fiber nonwoven fabric according to any one of Aspects 1 to 6, having an air permeability of 800 cm ３ / cm ２ s or less (preferably 1 to 800 cm ３ / cm ２ s, more preferably 5 to 600 cm ３ / cm ２ s, more preferably 10 to 100 cm ３ / cm ２ s, even more preferably 10 to 50 cm ３ / cm ２ s, particularly preferably 12 to 45 cm ３ / cm ２ s, particularly preferably 15 to 40 cm ３ / cm ２ A conjugate long-fiber nonwoven fabric having a peak temperature of loss factor tan δ within a range of 0 to 40°C (preferably 2 to 37°C, more preferably 3 to 35°C, and even more preferably 4 to 33°C). [Aspect 9] A conjugate long-fiber nonwoven fabric having a temperature dependency curve of loss factor tan δ obtained by dynamic viscoelasticity measurement, wherein the integral value of the range of loss factor tan δ of 0.2 or more within a temperature range of 0 to 40°C is 20 or more (preferably 22 or more, more preferably 25 or more, and even more preferably 28 or more). [Aspect 10] A method for producing the conjugated long-fiber nonwoven fabric according to any one of Aspects 1 to 9, comprising the steps of melting a first styrene-based elastomer and a second styrene-based elastomer and extruding the melted elastomers from a conjugated spinning nozzle, and collecting the extrudates on a collecting surface while fusing the extrudates together. [Aspect 11] A soundproofing material comprising the conjugated long-fiber nonwoven fabric according to any one of Aspects 1 to 9. [Aspect 12] A soundproofing material according to Aspect 11, which is for vehicles, buildings, or acoustic equipment.

[0011] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms, including "at least one," unless the content clearly dictates otherwise. As used herein, the terms "and / or," "at least one," and "one or more" include any and all combinations of the associated listed items.

[0012] It should be noted that any combination of at least two elements disclosed in the claims and / or the specification and / or the drawings is included in the present invention, and in particular any combination of two or more of the claims set forth in the claims is included in the present invention.

[0013] The conjugated continuous fiber nonwoven fabric of the present invention has excellent vibration damping properties over a wide frequency range and can be used as various soundproofing materials for sounds corresponding to those frequency ranges.

[0014] 1 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Example 2. FIG. 2 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Example 4. FIG. 3 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Example 5. FIG. 4 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Example 8. FIG. 5 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Comparative Example 1. FIG. 6 is a graph showing the temperature dependency curve of loss factor tan δ in dynamic viscoelasticity measurement of the conjugate long-fiber nonwoven fabric obtained in Comparative Example 2.

[0015] The conjugated continuous fiber nonwoven fabric is formed from conjugated continuous fibers having, in a cross section perpendicular to the fiber axis direction, a portion formed from a component containing a first styrene-based elastomer and a portion formed from a component containing a second styrene-based elastomer.

[0016] Both the first and second styrene elastomers are hydrogenated copolymers having a polystyrene hard segment and a vinyl-polydiene soft segment. The hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment is a copolymer obtained by hydrogenating the unsaturated double bonds in the structural units derived from the conjugated diene in the vinyl-polydiene soft segment. Styrenic elastomers having such a structure tend to have excellent tan δ characteristics at temperatures around 0 to 40°C. Furthermore, because they are hydrogenated copolymers, they have excellent melt spinnability and are therefore easily formed into conjugated long fibers.

[0017] The polystyrene-based hard segment may have a structural unit derived from styrene or a derivative thereof. Examples of styrene derivatives include α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and 1,3-dimethylstyrene. Styrene and its derivatives may be used alone or in combination of two or more. When two or more structural units derived from styrene or its derivatives are used, the respective structural units in the polystyrene-based hard segment may be a random copolymer.

[0018] The vinyl-polydiene soft segment may have a structural unit derived from a conjugated diene such as butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, or 1,3-hexadiene. The conjugated dienes may be used alone or in combination of two or more. The structural unit derived from the conjugated diene may be a 1,2-bond unit and / or a 1,4-bond unit. When two or more structural units derived from the conjugated diene are used, the respective structural units in the vinyl-polydiene soft segment may be a random copolymer.

[0019] The glass transition temperature Tg1 of the first styrene-based elastomer is lower than the glass transition temperature Tg2 of the second styrene-based elastomer. Styrenic elastomers with different glass transition temperatures exhibit different behaviors in the temperature dependence of tan δ. Using these elastomers as components of the conjugate long fiber allows the tan δ characteristics of each styrene-based elastomer to be effectively combined and exhibited. That is, while the temperature range over which tan δ is high is not very wide for each styrene-based elastomer alone, by more homogeneously blending the temperature dependence curves of the tan δ of each elastomer, the temperature range over which tan δ is high can be broadened, thereby enabling vibration damping properties to be exhibited over a wide frequency range. The glass transition temperature of the styrene-based elastomer can be adjusted by adjusting the type of hard segment and soft segment, the ratio of the hard segment to the soft segment, and / or the molecular weight of the copolymer, etc.

[0020] From the viewpoint of effectively utilizing the tan δ characteristics of the first and second styrene-based elastomers, the difference Tg2 - Tg1 between the glass transition temperature Tg2 of the second styrene-based elastomer and the glass transition temperature Tg1 of the first styrene-based elastomer may be 50°C or less. Moreover, from the viewpoint of broadening the temperature range in which tan δ is high, Tg2 - Tg1 may be preferably 5 to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 30°C. In this specification, the glass transition temperature is the peak temperature in the temperature dependence curve of tan δ in dynamic viscoelasticity measurement, and is a value measured by the method described in the Examples below.

[0021] The glass transition temperatures Tg1 and Tg2 of the first and second styrene-based elastomers may both be within a range of −60 to 50° C., preferably −40 to 40° C., and more preferably −10 to 35° C. Furthermore, from the viewpoint of promoting fusion bonding between the first styrene-based elastomers at the contact points between the conjugated long fibers, the glass transition temperature Tg1 of the first styrene-based elastomer may be within a range of −60 to 20° C., preferably −50 to 15° C., and more preferably −40 to 10° C.

[0022] The weight ratio (first:second) of the first styrene-based elastomer to the second styrene-based elastomer may be 40:60 to 99:1, preferably 45:55 to 97:3, and more preferably 50:50 to 95:5, from the viewpoints of effectively utilizing the tan δ characteristics of each elastomer, promoting fusion between the conjugated long fibers, and facilitating the formation of a network structure. Alternatively, the weight ratio may be preferably 60:40 to 99:1, more preferably 80:20 to 99:1, even more preferably 85:15 to 99:1, and even more preferably 90:10 to 99:1.

[0023] The conjugated continuous fiber may contain components other than the first and second styrene-based elastomers, provided that the effects of the present invention are not impaired. Examples of such components include elastomeric resins and various additives. These components may be contained in a mixed state with the first styrene-based elastomer and / or the second styrene-based elastomer, or may be contained as components forming island portions or the like of the conjugated continuous fiber. The elastomeric resin is a copolymer composed of hard segments (polymer blocks) and soft segments (polymer blocks). Specific examples of the elastomeric resin include a styrene-based elastomer different from the first and second styrene-based elastomers, an olefin-based elastomer, a urethane-based elastomer, an ester-based elastomer, an amide-based elastomer, and a vinyl chloride-based elastomer, depending on the type of hard segment.

[0024] The total content of the first and second styrene-based elastomers in the conjugated long fiber may be 80% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more, even more preferably 98% by weight or more, and still more preferably 99.9% by weight or more, based on the weight of the conjugated long fiber.

[0025] A conjugated continuous fiber is a fiber having a conjugated shape in which multiple types of components exist in a cross section (fiber cross section) perpendicular to the fiber axis direction of a single fiber, and the components that form the conjugated shape include a first styrene-based elastomer and a second styrene-based elastomer. The conjugated shape of the cross section of the conjugated continuous fiber is not particularly limited as long as the conjugated continuous fibers are fused at their contact points, and examples of such cross-sectional structures include a core-sheath type and an islands-in-sea type, and modified composite cross-sectional structures thereof are also possible. For example, a modified composite cross-sectional structure may be a three-layer sheath-core type in which a core is surrounded by an intermediate section and a covering section is further surrounded by the intermediate section. Of these, the sheath-core type is preferred, and in the sheath-core type, the core and sheath may be concentrically or eccentrically arranged, and the cross-sectional shapes of the core and sheath may be the same shape but different in size, or may be different shapes.

[0026] From the viewpoint of increasing the number of fusion points between conjugated long fibers, it is preferable that the portion formed by the component containing the first styrene-based elastomer be exposed on the surface of the conjugated long fiber, because the first styrene-based elastomer has a lower glass transition temperature and is therefore more likely to fuse. For example, the first styrene-based elastomer may be contained in the sheath portion of a core-sheath type conjugated long fiber or the sea portion of an islands-in-sea type conjugated long fiber. For example, the coverage of the first styrene-based elastomer in the cross section of the conjugated long fiber may be 70% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 100%. In this specification, the coverage refers to the proportion of the circumferential length of the fiber cross section occupied by the portion formed by the component containing the first styrene-based elastomer (e.g., the sheath portion or the sea portion) to the total circumferential length of the fiber cross section.

[0027] From the viewpoint of increasing the density of the nonwoven fabric and adjusting the air permeability, the conjugated continuous fiber may have an average fiber diameter of 25 μm or less, preferably 0.1 to 20 μm, and more preferably 1 to 15 μm. In this specification, when the cross section of the conjugated continuous fiber is not a perfect circle (for example, an irregular cross section such as an ellipse), its cross section is measured, and the diameter of the perfect circle when the fiber cross section is assumed to be a perfect circle having that cross section is converted to the fiber diameter.

[0028] In this specification, long fibers are fibers that are continuous to a certain length and can be distinguished from short fibers that are intentionally cut to a specified fiber length. For example, fibers that make up long-fiber nonwoven fabrics obtained by the melt-blowing method or the spunbonding method are considered to be long fibers.

[0029] In the conjugated long-fiber nonwoven fabric, the conjugated long fibers are fused together at multiple contact points to form a conjugated long-fiber network structure. In this specification, "fused" refers to a state in which the conjugated long fibers are bonded together at the contact points without the intervention of other components (e.g., binders). Examples of bonding between conjugated long fibers include a state in which at least a portion of the boundary between the fibers is no longer visible. Because the first styrene-based elastomer, which has a lower glass transition temperature, is more likely to fuse, it is preferable that the conjugated long fibers at least include portions where the first styrene-based elastomer is fused together at the multiple contact points. Furthermore, in this specification, "network structure" refers to a structure in which the conjugated long fibers are entangled and fused together at multiple contact points to form a three-dimensional connection. In the present invention, the conjugated long fibers are fused together at multiple contact points to form a network structure, which allows vibrations to be transmitted to both the first and second styrene-based elastomer components throughout the entire nonwoven fabric, making it possible to effectively combine the tan δ characteristics of both components and to exhibit vibration-damping properties over a wide frequency range.

[0030] Examples of long-fiber nonwoven fabrics include meltblown nonwoven fabrics and spunbonded nonwoven fabrics. Meltblown nonwoven fabrics are more preferred because they can reduce the fiber diameter and improve density. While spunbonded nonwoven fabrics are made of continuous filaments, meltblown nonwoven fabrics are made of filaments of a finite length, although they have a certain length, and can be distinguished from nonwoven fabrics made of short fibers that are intentionally cut as described above.

[0031] From the viewpoint of improving vibration damping properties in a frequency band of about 1 to 1000 Hz, the peak temperature of the loss factor tan δ calculated by dynamic viscoelasticity measurement of the conjugated long-fiber nonwoven fabric may be in the range of 0 to 40°C, preferably 2 to 37°C, more preferably 3 to 35°C, and even more preferably 4 to 33°C. In this specification, the peak of the temperature dependence curve of tan δ is considered to be the maximum value when tan δ increases, reaches a maximum value, and then decreases when viewed from the low-temperature side to the high-temperature side; minute fluctuations (noise, etc.) are not considered to be peaks. In this specification, the temperature dependence curve of loss factor tan δ is measured by the method described in the Examples below, and in the case of a multi-peak curve, the peak temperature of tan δ is the peak temperature of the peak at which tan δ reaches a maximum value.

[0032] In a temperature dependency curve of loss factor tan δ obtained by measuring the dynamic viscoelasticity of the conjugated long-fiber nonwoven fabric, tan δ may be 0.2 or more in a temperature range of at least 15 to 40° C., preferably at least 5 to 45° C., and more preferably at least 0 to 50° C. A tan δ of 0.2 or more can be regarded as an index of vibration damping properties.

[0033] Since the conjugate long-fiber nonwoven fabric has excellent vibration-damping properties over a wide frequency range, in a temperature dependency curve of loss factor tan δ obtained by measuring the dynamic viscoelasticity of the conjugate long-fiber nonwoven fabric, the integral value in the range of loss factor tan δ of 0.2 or more within a temperature range of 0 to 40°C may be 20 or more, preferably 22 or more, more preferably 25 or more, and even more preferably 28 or more.

[0034] From the viewpoint of improving sound absorption, improving appearance by making the base less visible, and improving strength and durability, for example, the air permeability of the composite long fiber nonwoven fabric is set to 800 cm ３ / cm ２ ・s or less (for example, 100 cm ３ / cm ２ From the viewpoint of improving comfort, it is preferably 1 to 800 cm ３ / cm ２ s, more preferably 5 to 600 cm ３ / cm２ s, more preferably 10 to 100 cm ３ / cm ２ s, even more preferably 10 to 50 cm ３ / cm ２ s, particularly preferably 12 to 45 cm ３ / cm ２ s, particularly preferably 15 to 40 cm ３ / cm ２ In this specification, the air permeability is a value measured by the method described in the Examples below.

[0035] From the viewpoint of increasing the loss factor tanδ, it is preferable that the conjugate long-fiber nonwoven fabric has excellent density. For example, the apparent density of the conjugate long-fiber nonwoven fabric is 0.10 g / cm ３ or more, preferably 0.16 g / cm ３ More preferably, 0.18 g / cm ３ In order to provide a certain degree of breathability, the apparent density of the composite long-fiber nonwoven fabric may be 0.50 g / cm or more. ３ or less, preferably 0.45 g / cm ３ or less, more preferably 0.40 g / cm ３ In this specification, the apparent density of the conjugated continuous fiber nonwoven fabric is calculated from the basis weight and thickness of the conjugated continuous fiber nonwoven fabric, and is a value measured by the method described in the examples below.

[0036] The weight of the composite long fiber nonwoven fabric is, for example, 10 to 100 g / m ２ and preferably 15 to 90 g / m ２ , more preferably 20 to 80 g / m ２ The thickness of the conjugated long-fiber nonwoven fabric may be, for example, 0.05 to 2 mm, preferably 0.1 to 1 mm, more preferably 0.15 to 0.8 mm, and even more preferably 0.2 to 0.5 mm. The basis weight and thickness of the conjugated long-fiber nonwoven fabric can be measured in accordance with JIS L 1913.

[0037] The method for producing a composite long-fiber nonwoven fabric may include a step of melting a first styrene-based elastomer and a second styrene-based elastomer and discharging the melted elastomers from a composite spinning nozzle, and a step of collecting the discharged composite long fibers on a collecting surface while fusing the resulting fibers together.

[0038] The composite long-fiber nonwoven fabric can be produced by a direct spinning method (melt-blowing method, spunbonding method, etc.) using a composite spinning nozzle. From the viewpoint of promoting fusion between the composite long fibers in the collection step, it is preferable to use a composite spinning nozzle having a configuration in which the first styrene-based elastomer is exposed on the surface of the composite long fibers. For example, a component containing the first styrene-based elastomer may be discharged from a sheath hole of a core-sheath type composite spinning nozzle or a sea hole of an islands-in-sea type composite spinning nozzle.

[0039] As described above, the composite long fiber may contain components other than the first and second styrene-based elastomers, as long as the effects of the present invention are not impaired. Such components may be mixed with the component containing the first styrene-based elastomer and / or the component containing the second styrene-based elastomer and extruded from each hole of the composite spinning nozzle, or may be extruded as a separate component from a hole in the composite spinning nozzle provided separately from the holes for extruding the components containing the first and second styrene-based elastomers.

[0040] From the viewpoint of being able to reduce the fiber diameter and improve the density, a production method using the melt-blowing method is preferred. In the melt-blowing method, the first styrene-based elastomer and the second styrene-based elastomer are each melted and extruded from each hole of a conjugate spinning nozzle, and a high-speed airflow is directly blown onto the extruded material from an air flow path built into the nozzle, and the fibrous extruded material is drawn out from the nozzle together with the high-speed airflow and collected on a collecting surface to form the conjugate fiber. The high-speed airflow can entangle the extruded multiple conjugate fibers and promote fusion bonding between the conjugate long fibers.

[0041] The composite long-fiber nonwoven fabric has excellent vibration-damping properties over a wide frequency range, and therefore can be used as a vibration-damping sheet and as various soundproofing materials for sounds corresponding to those frequency ranges. Since the composite long-fiber nonwoven fabric can convert vibration energy into thermal energy to damp vibrations, the soundproofing material may be, for example, a laminate containing the composite long-fiber nonwoven fabric as a sound-absorbing layer, and the laminate may also contain a known sound-insulating material as a sound-insulating layer.

[0042] The soundproofing material can be used for vehicles, building materials, audio equipment, electronic devices, etc. In particular, it is preferable to use it in insulators for automobiles, as quietness is required due to the electrification of automobiles. For example, it can be used as a soundproofing material for components near the undercarriage of the vehicle body, such as fender liners, floor undercovers, and engine undercovers, as well as a soundproofing material for inner tires.

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited by these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0044] [Glass Transition Temperature of Styrenic Elastomer] The glass transition temperature of a styrene-based elastomer was determined from the peak temperature of the curve obtained by measuring the temperature dependence of the loss factor tan δ using a solid dynamic viscoelasticity analyzer "Rheogel E-4000" manufactured by UBM Co., Ltd. in shear mode at a frequency of 1 Hz and a heating rate of 3°C / min. Here, the peak temperature of tan δ refers to the temperature at which the first derivative of the change in tan δ with respect to temperature becomes zero.

[0045] [Network Structure] The surface of the obtained conjugated long-fiber nonwoven fabric was observed using a scanning electron microscope (JEOL Ltd., "JCM6000PLUS"). At the contact points between conjugated long fibers, the points where the conjugated long fibers were bonded without any other component in between were regarded as fusion points. Conjugated long-fiber nonwoven fabrics confirmed to have multiple fusion points were judged to have formed a network structure.

[0046] [Coverage of the first styrene-based elastomer] The conjugated continuous fiber was cut as it was, and gold was sputtered onto the cross section of the fiber using an ion sputtering device ("JFC-1500" manufactured by JEOL Ltd.) to prepare a sample. For the cross sections of 100 single fibers randomly selected from an electron microscope photograph, the ratio of the circumferential length occupied by the component containing the first styrene-based elastomer to the total circumferential length was measured, and the average value was taken as the coverage (%).

[0047] [Average Fiber Diameter of Conjugated Continuous Fiber] The fiber diameters of 100 single fibers randomly selected from an electron microscope photograph were measured from the side to determine the number average fiber diameter, which was taken as the average fiber diameter (µm) of the conjugated continuous fiber.

[0048] [Basis Weight of Composite Long-Fiber Nonwoven Fabric] The basis weight (g / m) of the composite long-fiber nonwoven fabric was measured in accordance with 6.2 of JIS L 1913 "General Nonwoven Fabric Testing Method." ２ ) was measured.

[0049] [Thickness of Composite Continuous Fiber Nonwoven Fabric] The thickness (mm) of the composite continuous fiber nonwoven fabric was measured in accordance with 6.1 of JIS L 1913 "Testing Methods for General Nonwoven Fabrics."

[0050] [Apparent density of composite long-fiber nonwoven fabric] The apparent density (g / cm ３ ) was calculated by dividing the basis weight measured above by the thickness.

[0051] [Air permeability] Air permeability (cm) was measured by the Frazier method in accordance with 6.8 of JIS L 1913 "General nonwoven fabric testing method." ３ / cm ２ s) was measured.

[0052] [Temperature Dependence of Loss Factor tan δ of Composite Long-Fiber Nonwoven Fabric] Test specimens were prepared by cutting the composite long-fiber nonwoven fabrics obtained in the Examples and Comparative Examples into pieces measuring 30 mm lengthwise and 5 mm widthwise. Using a solid-state dynamic viscoelasticity analyzer "Rheogel E-4000" manufactured by UBM Corporation, the temperature dependence of the loss factor tan δ of the test specimens was measured in tension mode at a frequency of 1 Hz, a heating rate of 3°C / min, and in a temperature range from -50°C to 50°C. From the obtained temperature dependence curve of loss factor tan δ, tan δ at 0°C, 20°C, and 40°C, the peak temperature of tan δ, the temperature range in which tan δ was 0.2 or greater, and the integral value in the temperature range from 0 to 40°C in which tan δ was 0.2 or greater were calculated.

[0053] Example 1: A hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 6°C was used as the first styrene elastomer, and a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 33°C was used as the second styrene elastomer. They were melted in separate extruders to a weight ratio of 50 / 50, and extruded from a multi-component spinning nozzle to form a core-sheath cross-sectional structure with the first styrene elastomer as the sheath and the second styrene elastomer as the core. The extruder temperature was 220°C, the piping temperature was 280°C, the die temperature was 320°C, and the single-hole throughput rate was 0.2 g / min H. Immediately afterwards, hot air at 280°C was blown at a rate of 9.5 Nm per 1 m width. ３ The meltblown nonwoven fabric was produced by spraying the mixture at a rate of 1 / min to thin the fibers, and the die-to-collection distance (DCD) was set to 380 mm. The resulting meltblown nonwoven fabric had a basis weight of 61.8 g / m ２ , thickness 0.336 mm, breathability 156.4 cm ３ / cm ２ ・It was s.

[0054] [Example 2] A meltblown nonwoven fabric was produced under the same conditions as in Example 1, except that the temperature of the hot air during spinning was 310°C and the distance between the die and the collecting surface (DCD) was 300 mm. The obtained meltblown nonwoven fabric had a basis weight of 65.6 g / m２ , thickness 0.364 mm, breathability 69.2 cm ３ / cm ２ The obtained meltblown nonwoven fabric was subjected to dynamic viscoelasticity measurement, and a graph showing the temperature dependency of loss factor tan δ was obtained as shown in FIG.

[0055] [Example 3] A meltblown nonwoven fabric was produced under the same conditions as in Example 2, except that the weight ratio of the first styrene-based elastomer to the second styrene-based elastomer was set to 75 / 25. The obtained meltblown nonwoven fabric had a basis weight of 62.0 g / m ２ , thickness 0.332 mm, breathability 46.6 cm ３ / cm ２ ・It was s.

[0056] [Example 4] A meltblown nonwoven fabric was produced under the same conditions as in Example 2, except that the weight ratio of the first styrene-based elastomer to the second styrene-based elastomer was 90 / 10. The obtained meltblown nonwoven fabric had a basis weight of 67.2 g / m ２ , thickness 0.345 mm, breathability 32.4 cm ３ / cm ２ The dynamic viscoelasticity of the obtained meltblown nonwoven fabric was measured, and a graph showing the temperature dependency of the loss factor tan δ was obtained as shown in FIG.

[0057] [Example 5] A meltblown nonwoven fabric was produced under the same conditions as in Example 2, except that the weight ratio of the first styrene-based elastomer to the second styrene-based elastomer was 95 / 5. The obtained meltblown nonwoven fabric had a basis weight of 69.9 g / m ２ , thickness 0.288 mm, breathability 30.0 cm ３ / cm ２ The obtained meltblown nonwoven fabric was subjected to dynamic viscoelasticity measurement, and a graph showing the temperature dependency of loss factor tan δ was obtained as shown in FIG.

[0058] [Example 6] A meltblown nonwoven fabric was produced under the same conditions as in Example 1, except that the weight ratio of the first styrene-based elastomer to the second styrene-based elastomer was 90 / 10. The obtained meltblown nonwoven fabric had a basis weight of 61.6 g / m２ , thickness 0.301 mm, breathability 224.8 cm ３ / cm ２ ・It was s.

[0059] [Example 7] A meltblown nonwoven fabric was produced under the same conditions as in Example 2, except that the first styrene-based elastomer was extruded from the conjugate spinning nozzle so as to have an islands-in-sea cross-sectional structure in which the first styrene-based elastomer constituted the sea portion and the second styrene-based elastomer constituted the island portion. When the fiber cross section was examined, it was found that the island portion was partially exposed on the surface, and the exposure rate of the first styrene-based elastomer was 90%. The obtained meltblown nonwoven fabric had a basis weight of 60.3 g / m ２ , thickness 0.371 mm, breathability 92.3 cm ３ / cm ２ ・It was s.

[0060] [Example 8] A meltblown nonwoven fabric was produced under the same conditions as in Example 2, except that the first styrene-based elastomer was a hydrogenated copolymer having a Tg of 14°C and a polystyrene-based hard segment and a vinyl-polydiene-based soft segment, and the second styrene-based elastomer was the same as in Example 1. They were melted in separate extruders to a weight ratio of 95 / 5, and extruded from a multi-component spinning nozzle so as to have a core-sheath cross-sectional structure with the first styrene-based elastomer as the sheath and the second styrene-based elastomer as the core. The resulting meltblown nonwoven fabric had a basis weight of 70.5 g / m. ２ , thickness 0.295 mm, breathability 44.8 cm ３ / cm ２ The obtained meltblown nonwoven fabric was subjected to dynamic viscoelasticity measurement, and a graph showing the temperature dependency of loss factor tan δ was obtained as shown in FIG.

[0061] Example 9: The first styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 6°C, and the second styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 33°C. These elastomers were melted in separate extruders at a weight ratio of 50 / 50, and extruded through a multi-component spinning nozzle to form a core-sheath cross-sectional structure with the first styrene elastomer as the sheath and the second styrene elastomer as the core. The extruder temperature was 220°C, the piping temperature was 280°C, the die temperature was 320°C, and the single-hole throughput rate was 0.2 g / min H. The extruder temperature was set at 220°C, the piping temperature was set at 280°C, the die temperature was set at 320°C, and the nozzle orifice diameter was 0.3 mm. The extruder temperature was set at 220°C, the piping temperature was set at 280°C, the die temperature was set at 320°C, and the single-hole throughput rate was set at 0.2 g / min H. The extruder temperature was set at 280°C, the die temperature was set at 320°C, and the nozzle orifice diameter was set at 0.3 mm. The extruder temperature was set at 280°C, the die temperature was set at 320°C, and the single-hole throughput rate was set at 0.2 g / min H. The extruder temperature was set at 280°C, the piping temperature was set at 280°C, the die temperature was set at 320°C, and the single-hole orifice diameter was set at 0.3 mm. The extruder temperature was set at 280°C, the die temperature was set at 2 ２ , thickness 0.181 mm, air permeability 580.0 cm ３ / cm ２ ・It was s.

[0062] Comparative Example 1: The first styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 6°C, and the second styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 33°C. They were melted in separate extruders to a weight ratio of 50 / 50, and extruded from a multi-component spinning nozzle to have a core-sheath cross-sectional structure with the first styrene elastomer as the core and the second styrene elastomer as the sheath. The extruder temperature was 220°C, the piping temperature was 280°C, the die temperature was 320°C, and the single-hole throughput rate was 0.2 g / min H. Immediately afterwards, hot air at 310°C was blown at a rate of 9.5 Nm per 1 m width. ３ The meltblown nonwoven fabric was produced by spraying the mixture at a rate of 1000 kJ / min to thin the fibers, and the die-to-collection distance (DCD) was set to 300 mm. The resulting meltblown nonwoven fabric had a basis weight of 71.0 g / m ２ , thickness 0.373 mm, breathability 50.7 cm ３ / cm２ The obtained meltblown nonwoven fabric was subjected to dynamic viscoelasticity measurement, and a graph showing the temperature dependency of loss factor tan δ was obtained as shown in FIG.

[0063] Comparative Example 2: The first styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 6°C, and the second styrene elastomer was a hydrogenated copolymer having a polystyrene hard segment and a vinyl-polydiene soft segment with a Tg of 33°C. They were melted in separate extruders to a weight ratio of 50 / 50, and the first and second styrene elastomers were extruded from a multi-component spinning nozzle so as to have a side-by-side cross-sectional structure. The coverage of the first styrene elastomer was 50%. The extruder temperature was 220°C, the piping temperature was 280°C, the die temperature was 320°C, and the single-hole output rate was 0.2 g / min H. Immediately afterwards, hot air at 310°C was blown at a rate of 9.5 Nm per 1 m width. ３ The meltblown nonwoven fabric was produced by spraying the mixture at a rate of 1 / min to thin the fibers, and the die-to-collection distance (DCD) was set to 300 mm. The resulting meltblown nonwoven fabric had a basis weight of 62.7 g / m ２ , thickness 0.350 mm, breathability 75.6 cm ３ / cm ２ The obtained meltblown nonwoven fabric was subjected to dynamic viscoelasticity measurement, and a graph showing the temperature dependency of the loss factor tan δ was obtained as shown in FIG.

[0064]

[0065] As shown in Table 1, the conjugate long-fiber nonwoven fabrics of Examples 1 to 9 were formed from conjugate long fibers containing first and second styrene-based elastomers, and the conjugate long fibers were fused at multiple contact points to form a network structure, so that they had a high integrated value in the range where tan δ was 0.2 or more in the temperature range of 0 to 40° C., and exhibited excellent vibration-damping properties over a wide frequency range. Furthermore, the temperature dependence curves of tan δ for the conjugate long-fiber nonwoven fabrics of Examples 1 to 9 showed a wide temperature range where tan δ was 0.2 or more.

[0066] On the other hand, in the conjugated continuous fiber nonwoven fabrics of Comparative Examples 1 and 2, the conjugated continuous fibers were not fused to each other and did not form a network structure, and therefore, the integrated value in the range where tan δ was 0.2 or more in the temperature range of 0 to 40°C was lower than that of Examples 1 to 9.

[0067] Because the composite long-fiber nonwoven fabric has excellent vibration-damping properties over a wide frequency range, it can be used as a vibration-damping sheet and as a soundproofing material for various types of sound that correspond to the frequency range. The soundproofing material can be used for vehicles, building materials, audio equipment, electronic equipment, etc.

[0068] As described above, the preferred embodiments of the present invention have been described, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and such additions, modifications, or deletions are also included within the scope of the present invention.

Claims

1. A conjugated long-fiber nonwoven fabric formed of conjugated long fibers having, in a cross section perpendicular to the fiber axis, a portion formed from a component containing a first styrene-based elastomer and a portion formed from a component containing a second styrene-based elastomer, wherein the first and second styrene-based elastomers are both hydrogenated copolymers having a polystyrene-based hard segment and a vinyl-polydiene-based soft segment, the glass transition temperature Tg1 of the first styrene-based elastomer is lower than the glass transition temperature Tg2 of the second styrene-based elastomer, and the conjugated long fibers are fused together at multiple contact points to form a conjugated long-fiber network structure.

2. A conjugate continuous fiber nonwoven fabric according to claim 1, wherein the conjugate continuous fiber is a core-sheath type conjugate continuous fiber, and the sheath portion is formed from a component containing the first styrene-based elastomer.

3. A conjugated long-fiber nonwoven fabric according to claim 1 or 2, in which the difference Tg2 - Tg1 between the glass transition temperature Tg2 of the second styrene-based elastomer and the glass transition temperature Tg1 of the first styrene-based elastomer is 50°C or less.

4. A composite long-fiber nonwoven fabric according to claim 1 or 2, wherein the weight ratio (first:second) of the first styrene-based elastomer to the second styrene-based elastomer is 40:60 to 99:

1.

5. A composite continuous fiber nonwoven fabric according to claim 1 or 2, wherein the average fiber diameter of the composite continuous fiber is 25 μm or less.

6. The composite continuous fiber nonwoven fabric according to claim 1 or 2, having an apparent density of 0.10 g / cm ３ This is the composite long-fiber nonwoven fabric.

7. The composite continuous fiber nonwoven fabric according to claim 1 or 2, having an air permeability of 800 cm ３ / cm ２ - A composite long fiber nonwoven fabric having a thickness of s or less.

8. The conjugate continuous fiber nonwoven fabric according to claim 1 or 2, wherein the peak temperature of the loss factor tan δ is within the range of 0 to 40°C.

9. The conjugate long-fiber nonwoven fabric according to claim 1 or 2, wherein in a temperature dependency curve of loss factor tanδ obtained by dynamic viscoelasticity measurement, the integral value of the range of loss factor tanδ of 0.2 or more in the temperature range of 0 to 40°C is 20 or more.

10. A method for producing a composite long-fiber nonwoven fabric according to claim 1 or 2, comprising the steps of: melting a first styrene-based elastomer and a second styrene-based elastomer, respectively, and extruding them from a composite spinning nozzle; and collecting the extruding composite long fibers on a collecting surface while fusing them together.

11. A soundproofing material comprising the composite long-fiber nonwoven fabric according to claim 1 or 2.

12. The soundproofing material according to claim 11, which is for vehicles, buildings, or acoustic equipment.

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