Mixed fiber nonwoven fabric

Abstract

To provide a nonwoven fabric with excellent sound absorption effect in a low frequency range.SOLUTION: In a mixed fiber nonwoven fabric made of two or more kinds of thermoplastic resin fibers, at least one or more kinds thereof are a thermoplastic resin fiber A (fiber A) with a tensile elastic modulus of less than 500 MPa, and at least one or more kinds thereof are a thermoplastic resin fiber B (fiber B) with a tensile elastic modulus of 500 MPa or more. A ratio B / A of a mass of the fiber B to a mass of the fiber A is 1.0 to 3.0 in a mass of the entire mixed fiber nonwoven fabric. The mixed fiber nonwoven fabric has a thickness of 5 mm or more and a basis weight of 100 g / m2 to 500 g / m2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a mixed fiber nonwoven fabric having excellent sound absorbing effect in the low frequency range. [Background technology]

[0002] Conventionally, nonwoven fabrics have been widely used for applications such as sound absorbing materials, heat insulating materials, filtering materials, and adsorbents. In particular, in recent years, sound absorbing materials using nonwoven fabrics have been used as noise countermeasures in rooms such as automobiles and buildings. In addition to the above-mentioned nonwoven fabrics, many porous materials such as urethane foam and felt are used as materials for these sound absorbing materials.

[0003] Generally, the sound absorbing mechanism of these porous sound absorbing materials is that when sound waves pass through the voids in the porous material, air vibrates, causing friction, and the sound energy is converted into heat energy, which is believed to absorb the sound. For this reason, methods of improving sound absorbing performance have been adopted, such as increasing the basis weight or narrowing the fiber diameter to form gaps and increase the resistance of air passage. However, increasing the basis weight leads to an increase in vehicle weight and an increase in costs, so the main method of improving the sound absorbing performance of porous materials is to form fine voids. In particular, among porous materials, the above-mentioned nonwoven fabrics can easily make the voids fine by narrowing the fiber diameter, so the development of sound absorbing materials made of nonwoven fabrics containing ultrafine fibers has been proposed. However, if the material used for the fiber is too soft, the voids are easily crushed and the sound absorbing effect is impaired, and if a hard material is used, the bulkiness increases but the weight increases. Methods proposed to solve these problems include laminating a nonwoven fabric made of ultrafine fibers with a nonwoven fabric made of relatively fine fibers, or laminating two or more types of nonwoven fabric made of different fiber materials to obtain a nonwoven fabric with high sound absorption properties (Patent Documents 1, 2, 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3613727 [Patent Document 2] Patent Publication No. 2022-40591 [Patent Document 3] Patent Publication No. 2010-203033 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even with the proposed method, while it is possible to improve the sound absorption effect in the high frequency range as with conventional sound-absorbing materials, it is difficult to obtain a sound absorption effect in the low frequency range below 1500 Hz. One measure to improve sound absorption performance in the low frequency range is to make the nonwoven fabric thicker, but the more ultra-fine the fibers are, the more easily the voids are crushed, making it difficult to increase the thickness, and measures such as stacking nonwoven fabrics have many issues with the interlayer processing method, and lead to increased weight and cost. For this reason, it has been considered difficult to apply this method to components with high sound insulation requirements in the low frequency range in automotive applications, especially to engine peripheral parts.

[0006] Therefore, the object of the present invention is to provide a mixed fiber nonwoven fabric that has excellent sound absorbing effect in the low frequency range, and can exhibit low frequency absorbing effect with a thinner thickness than conventional sound absorbing materials even when nonwoven fabrics are laminated. As a result of intensive research by the inventors to achieve the above object, it is possible to obtain a mixed fiber nonwoven fabric having a mixed fiber structure in which fibers made of two or more thermoplastic resins with different tensile moduli are entangled, and by controlling the mass ratio of the fibers made of two or more thermoplastic resins with different tensile moduli, the thickness and basis weight of the mixed nonwoven fabric, it is possible to obtain a mixed fiber nonwoven fabric having high sound absorbing effect in the low frequency range of 1500 Hz or less. [Means for solving the problem]

[0007] That is, the invention comprises [1] to [3]. [1] A mixed fiber nonwoven fabric made of two or more kinds of thermoplastic resin fibers, at least one of which is a thermoplastic resin fiber A (fiber A) having a tensile modulus of elasticity of less than 500 MPa, and at least one of which is a thermoplastic resin fiber B (fiber B) having a tensile modulus of elasticity of 500 MPa or more, the ratio B / A of the mass of the fiber B to the mass of the fiber A in the total mass of the mixed fiber nonwoven fabric is 1.0 to 3.0, the thickness is 5 mm or more, and the basis weight of the nonwoven fabric is 100 g / m 2 ~500g / m 2 A blended nonwoven fabric. [2] The mixed fiber nonwoven fabric according to [1], wherein the ratio B / A of the mass of fiber B to the mass of fiber A in the total mass of the mixed fiber nonwoven fabric is 1.2 to 3.0. [3] The mixed fiber nonwoven fabric according to [2], wherein the fiber A is a polyester elastomer fiber. Effect of the Invention

[0008] The mixed fiber nonwoven fabric of the present invention is capable of absorbing sound in the low frequency range of 1500 Hz or less, which could not be achieved with conventional sound absorbing materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described.

[0010] The mixed fiber nonwoven fabric of the present invention is a mixed fiber nonwoven fabric made of two or more kinds of thermoplastic resin fibers, at least one of which is a thermoplastic resin fiber A (fiber A) having a tensile modulus of elasticity of less than 500 MPa and at least one of which is a thermoplastic resin fiber B (fiber B) having a tensile modulus of elasticity of 500 MPa or more, the ratio B / A of the mass of fiber B to the mass of fiber A in the total mass of the mixed fiber nonwoven fabric is 1.0 to 3.0, the thickness is 5 mm or more, and the basis weight is 100 g / m 2 ~500g / m 2 It is a mixed fiber nonwoven fabric.

[0011] The thermoplastic resin fiber A having a tensile modulus of elasticity of less than 500 MPa used in the present invention is not particularly limited as long as it is less than 500 MPa, but is preferably a thermoplastic elastomer fiber, and particularly preferably a polyester elastomer fiber from the viewpoints of heat resistance and chemical resistance.

[0012] In a preferred embodiment of the polyester elastomer used in the present invention, the hard segment has, as a main constituent unit, an aromatic polyester unit formed mainly from an aromatic dicarboxylic acid or an ester-forming derivative thereof, and a diol or an ester-forming derivative thereof.

[0013] Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, and sodium 3-sulfoisophthalate.

[0014] In the present invention, the aromatic dicarboxylic acids are mainly used, but if necessary, a part of the aromatic dicarboxylic acids can be replaced with alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, and 4,4'-dicyclohexyldicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, succinic acid, oxalic acid, sebacic acid, dodecanedioic acid, and dimer acid. Furthermore, ester-forming derivatives of dicarboxylic acids, such as lower alkyl esters, aryl esters, carbonate esters, and acid halides, can of course be used equally well.

[0015] Specific examples of the diol include diols having a molecular weight of 400 or less, for example, aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, and decamethylene glycol, alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, and tricyclodecane dimethanol, and xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)diphenyl, and bis(p-hydroxyphenyl)diphenyl. Aromatic diols such as 4,4'-dihydroxydiphenylpropane, 2,2'-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4'-dihydroxy-p-terphenyl, and 4,4'-dihydroxy-p-quarterphenyl are preferably used, and such diols may also be used in the form of ester-forming derivatives, for example, acetylated forms or alkali metal salts.

[0016] These dicarboxylic acids, derivatives thereof, diol components and derivatives thereof can also be used in combination of two or more kinds.

[0017] A preferred example of such a hard segment is a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol. Also preferably used is a hard segment consisting of a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate and a polybutylene isophthalate unit derived from isophthalic acid and / or dimethyl isophthalate and 1,4-butanediol.

[0018] The soft segment of the polyester elastomer used in the present invention is mainly composed of aliphatic polyether units and / or aliphatic polyester units. Examples of aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide addition polymers of poly(propylene oxide) glycol, and copolymer glycols of ethylene oxide and tetrahydrofuran.

[0019] Examples of aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate. Among these aliphatic polyethers and / or aliphatic polyesters, in view of the elastic properties of the resulting polyester elastomer, it is preferable to use poly(tetramethylene oxide) glycol, an ethylene oxide adduct of poly(propylene oxide) glycol, a copolymer glycol of ethylene oxide and tetrahydrofuran, poly(ε-caprolactone), polybutylene adipate, and polyethylene adipate, and among these, it is particularly preferable that poly(tetramethylene oxide) glycol is used as a constituent unit. It is also preferable that the number average molecular weight of these soft segments is about 300 to 6000 in a copolymerized state.

[0020] The ratio of the hard segment to the soft segment in the polyester elastomer used in the present invention is preferably from 20 / 80 to 95 / 5, more preferably from 45 / 55 to 85 / 15, and even more preferably from 55 / 45 to 85 / 15.

[0021] The polyester elastomer of the present invention may optionally contain or remove, within the scope of not impairing the performance, known antioxidants such as hindered phenols, phosphites, thioethers, and aromatic amines, light fasteners such as benzophenones, benzotriazoles, and hindered amines, thickeners such as epoxy compounds and isocyanate compounds, colorants such as dyes and pigments, ultraviolet blocking agents such as titanium oxide and carbon black, reinforcing agents such as glass fibers, carbon fibers, and potassium titanate fibers, fillers such as silica, clay, calcium carbonate, zinc oxide, magnesium oxide, calcium sulfate, and glass beads, plasticizers such as liquid polyisobutene, liquid polybutene, liquid (hydrogenated) polyisoprene, liquid (hydrogenated) polybutadiene, paraffinic oil, naphthenic oil, epoxy plasticizers, phosphates, phthalates, aliphatic dibasic acid esters, and glycol esters, nucleating agents such as talc, tackifiers, flame retardants, fluorescent agents, crosslinking agents, and surfactants.

[0022] Furthermore, the thermoplastic resin fiber B having a tensile modulus of elasticity of 500 MPa or more is not particularly limited as long as it is 500 MPa or more, but examples of the thermoplastic resin fiber B include fibers made of polyolefin resins such as polypropylene, polyethylene, copolymerized polyethylene, and copolymerized polypropylene, polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, polyamide resins, and acrylic resins.

[0023] The mixed fiber nonwoven fabric obtained from two or more kinds of fibers of the present invention is a mixed fiber nonwoven fabric composed of at least two or more kinds of the above-mentioned fiber A and fiber B, and in the mass of the entire mixed fiber nonwoven fabric, the ratio B / A of the mass of fiber B to the mass of fiber A is 1.0 to 3.0, preferably 1.2 to 3.0. When the ratio B / A of the mass of fiber B to the mass of fiber A is less than 1.0, that is, when the mass of fiber A exceeds the mass of fiber B, the basis weight of the nonwoven fabric increases, and the voids are crushed due to the weight increase, which is a factor in reducing the sound absorption performance. In addition, when the mass of fiber A is small, the fiber diameter is not stable, which may impair the productivity of the nonwoven fabric.

[0024] The mixed fiber nonwoven fabric of the present invention is not limited in thickness whether it is a single layer or a laminate, but from the viewpoint of improving the sound absorption effect and adjusting the sound absorption frequency peak, the thickness is 5 mm or more, as with conventional nonwoven fabrics. From the viewpoint of the increase in weight due to the increase in thickness and the installation space of the members, the thickness is preferably 15 mm or less.

[0025] The weight of the mixed fiber nonwoven fabric of the present invention is 100 g / m 2 ~500g / m 2 100g / m 2 If it is less than 500 g / m, the production stability of the nonwoven fabric will be poor. 2 If the thickness exceeds this value, it may result in an increase in weight and may impair the sound absorbing effect in the high frequency range, which is an inherent characteristic of nonwoven fabric.

[0026] The mixed fiber nonwoven fabric of the present invention is not particularly limited as long as two or more types of fibers are entangled, but the smaller the average fiber diameter of fiber A is, the easier it is to control the thickness of the nonwoven fabric, and the more suitable the nonwoven fabric is for obtaining a sound absorbing effect in the low frequency range. The average fiber diameter of fiber A is preferably 10 μm or less, and more preferably 5 μm or less. If the average fiber diameter is too small, the fibers will break, the fibers will be less entangled, the voids will be crushed, and the sound absorbing performance will rapidly decrease.

[0027] The normal incidence sound absorption coefficient (hereinafter referred to as "sound absorption coefficient") of the mixed fiber nonwoven fabric of the present invention, measured by a method in accordance with JIS A1405 (2007) in the frequency range of 500 to 1500 Hz, which is the main frequency range where road noise is generally a problem, is preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and particularly preferably 60% or more. The sound absorption coefficient can be measured, for example, using a normal incidence sound absorption coefficient measuring system WinZacMTX manufactured by Nihon Onkyo Engineering Co., Ltd.

[0028] The method for producing the mixed fiber nonwoven fabric of the present invention is not particularly limited as long as it can extrude two or more types of fibers, but the general production methods of spunbonding, meltblowing, thermal bonding, and needle punching are preferred. The meltblowing method is preferred for producing ultrafine fibers. The thermal bonding method is preferred for producing a nonwoven fabric with a thickness of 10 mm or more.

[0029] The mixed fiber nonwoven fabric of the present invention may be used alone, or may be laminated with other sound absorbing nonwoven fabrics, felt, aluminum die casting, iron, or other materials. EXAMPLES

[0030] The effects of the present invention will be described below with reference to examples, but the present disclosure is not limited to these examples. The physical properties shown in the examples were measured as follows.

[0031] [Thickness of nonwoven fabric] Each nonwoven fabric was cut with scissors into a square measuring 1 m lengthwise and widthwise, and the thickness at the center of each of the four sides was measured with a constant pressure caliper (measuring force: 0.5 to 1 N) to obtain the average value, which was used as the average thickness of the nonwoven fabric.

[0032] [Nonwoven fabric basis weight] Each nonwoven fabric was cut with scissors into a square measuring 50 cm in length and width, and the weight was measured using a precision electronic balance manufactured by Shimadzu Corporation. The weight was then divided by the area of ​​the nonwoven fabric to obtain the basis weight of the nonwoven fabric.

[0033] [Average fiber diameter] Observation was performed using a scanning electron microscope (FE-SEM) manufactured by JEOL Ltd. Ten thin and ten thick fibers were randomly selected, and the average fiber diameters of the ten fibers were calculated, which was taken as the average fiber diameter for each fiber.

[0034] [Tensile modulus] Pellets of each thermoplastic resin were processed into a JIS K7113 No. 2 dumbbell test piece shape using an injection molding machine, and the tensile modulus was measured according to JIS K7113 (1995 edition).

[0035] [Sound absorption coefficient] The mixed fiber nonwoven fabric obtained was cut into a circular shape of Φ39.5 mm using a punching blade, and the normal incidence sound absorption coefficient in the frequency range of 400 Hz to 5000 Hz was measured using a normal incidence sound absorption coefficient measuring system WinZacMTX manufactured by Nippon Engineering Co., Ltd. in accordance with a method of JIS A1405 (2007). From the obtained results, the sound absorption coefficients at 800, 1000, and 1500 Hz were read, and the average value was calculated as the sound absorption coefficient of the mixed fiber nonwoven fabric of the present invention.

[0036] [Method 1 for producing mixed fiber nonwoven fabric used in the examples] The nonwoven fabrics of Examples 1 to 3 and Comparative Examples 1 to 3 were produced by the manufacturing method described below.

[0037] Toray Celanese Corporation's Hytrel 5501 (hereinafter referred to as HY 5501), Hytrel 7247 (hereinafter referred to as HY 7247), or polyethylene terephthalate (hereinafter referred to as PET) was discharged using a 134-hole discharge nozzle for fiber A, and Prime Polymer Corporation's polypropylene S119 (hereinafter referred to as PP S119) was discharged using a 67-hole discharge nozzle for fiber B. The discharge rates were set to give the fiber B / fiber A mass ratios shown in the table below, and the resulting mixed fiber web in which fibers A and B were entangled was manufactured into a mixed fiber nonwoven fabric with the thickness shown in the table below by adjusting the line speed of the collector positioned under the nozzle.

[0038] [Method 2 for producing mixed fiber nonwoven fabric used in the examples] The nonwoven fabrics of Examples 4 to 6 and Comparative Example 4 were produced by the manufacturing methods described below.

[0039] Toray Celanese's HY 7247 was melted and extruded to produce yarn, which was then cut to produce cotton-like short fibers (staple fibers). In a similar manner, staple fibers were also produced using Prime Polymer's PP S119. The prepared staple fibers A and B were mixed in the ratios shown in the table below to form a sheet-like mixed fiber web. The formed webs were layered, and the fibers were entangled by moving needles back and forth to produce a nonwoven fabric. The webs were layered to produce a mixed fiber nonwoven fabric of the thickness shown in the table below.

[0040] Table 1 below shows examples used in the present invention, and Table 2 below shows comparative examples used in the present invention.

[0041] [Table 1]

[0042] [Table 2]

[0043] From the above results, it was confirmed that the average sound absorption coefficient of all of Examples 1 to 6 was 30% or more. Comparative Example 1, in which both fiber A and fiber B had a tensile modulus of 500 MPa or more (3000 MPa and 1400 MPa), Comparative Example 2, in which the ratio B / A of the mass of fiber B to the mass of fiber A was outside the range of 1.0 to 3.0 (0.67), Comparative Example 3, in which the thickness of the nonwoven fabric was 2.5 mm instead of 5 mm or more, and Comparative Example 4, in which the nonwoven fabric was not a mixed fiber but was made only of fiber PP S119, all had a low average sound absorption coefficient of 25% or less. Comparative Examples 1, 2, and 4, in which the stiffness of the fibers was high, had a low attenuation effect on sound waves in the low frequency range, and the resulting sound absorption effect was also low. In addition, it is generally the case that the attenuation of sound waves is greatly affected by the distance from when the sound waves are emitted to when they reach the target, but in Comparative Example 3, the thickness of the nonwoven fabric was thin, so the attenuation effect was low and the resulting sound absorption effect was low.

Claims

1. A mixed fiber nonwoven fabric made of two or more kinds of thermoplastic resin fibers, at least one of which is a thermoplastic resin fiber A (fiber A) having a tensile modulus of elasticity of less than 500 MPa, and at least one of which is a thermoplastic resin fiber B (fiber B) having a tensile modulus of elasticity of 500 MPa or more, the ratio B / A of the mass of the fiber B to the mass of the fiber A in the total mass of the mixed fiber nonwoven fabric is 1.0 to 3.0, the thickness is 5 mm or more, and the basis weight is 100 g / m ２ Up to 500 g / m ２ A blended nonwoven fabric.

2. 2. The mixed fiber nonwoven fabric according to claim 1, wherein the ratio B / A of the mass of said fiber B to the mass of said fiber A in the total mass of the mixed fiber nonwoven fabric is 1.2 to 3.

0.

3. 3. The mixed fiber nonwoven fabric according to claim 2, wherein said fiber A is a polyester elastomer fiber.

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