JP7104695B2 - Fiber structure, molded body and sound absorbing material - Google Patents

Description

Related application

This application claims the priority of Japanese Patent Application No. 2017-113821, which was filed in Japan on June 8, 2017, and is cited as a part of this application by reference in its entirety.

The present invention relates to a fiber structure having heat resistance and moldability, the molded body thereof, and a sound absorbing material using the same.

Conventionally, sound absorbing materials have been used in many products such as electric appliances, building wall materials, and vehicles. In particular, in vehicles, especially automobiles, sound absorbing materials are widely used for the purpose of preventing external acceleration noise, idling noise, exhaust noise, etc., or for the purpose of preventing noise from entering the vehicle interior. In particular, since the temperature around the engine, which is required to have soundproofing, becomes high, an aluminum member has been conventionally used as a sound absorbing material in this part. This suppresses the passage of sound waves by reflecting sound by aluminum, but it is insufficient in terms of sound absorption performance, and a soundproof material having higher sound absorption performance is required.

A fiber structure is known as a sound absorbing material having excellent sound absorbing properties, and Patent Document 1 (Patent No. 5819650) describes a sound absorbing material skin in which a non-woven fabric composed of melt blown fibers is embossed.

Further, Patent Document 2 (Patent No. 5812786) describes a melt-blown non-woven fabric containing a molten liquid crystal-forming total aromatic polyester as a main component as a fiber structure having excellent heat resistance.

Patent No. 5819650 Patent No. 5812786

Since the fiber structure described in Patent Document 1 requires embossing, it is insufficient in terms of moldability.

Further, since the fiber structure described in Patent Document 2 is heat-treated for a long time on the melt-blown non-woven fabric to improve its strength, the fibers are firmly adhered to each other in the heat treatment, and the melt-blown non-woven fabric is also molded. There is room for improvement in terms of sex.

For example, a sound absorbing material used in a high temperature environment such as around an automobile engine is often required to have moldability in addition to heat resistance and sound absorbing property. In particular, as a structure of the sound absorbing material, a sound absorbing body composed of a bulky raw fabric made of fibers and a sound absorbing skin material covering the surface thereof are often used in combination, and such a structure further increases the structure. Although it is possible to improve the sound absorption property, since this sound absorption skin material needs to be molded according to the shape of the sound absorbing body, formability, that is, followability required at the time of molding is required.

An object of the present invention is to provide a fiber structure having excellent heat resistance and also having moldability, a molded product thereof, and a sound absorbing material using the same.

In order to solve the above problems, the present inventors first (1) spin a resin having a high glass transition temperature by a melt blown method or the like to produce a fiber structure having a small average fiber diameter, and to obtain a high glass transition temperature. At the same time, it is necessary to raise the temperature conditions of the spinning nozzle and the like. As a result, the fibers are firmly fused to each other in the fiber structure, and the obtained fiber structure has excellent strength, but the fiber structure has a higher temperature condition. Inferior formability to the required shape, (2) For fiber aggregates with a small average fiber diameter, a calendar for fusing the fibers after spinning in order to impart the required strength when passing through the subsequent steps. Post-treatment such as treatment or embossing treatment is usually performed, and this post-treatment for imparting strength strengthens the fusion between fibers and enhances the strength as a fiber structure, while allowing the fibers to move freely. It was found that the formability was rather reduced in order to take away the degree. Then, as a result of further research to solve these problems, (3) in a fiber structure containing thermoplastic resin fibers having a specific glass transition temperature, first, a non-woven preliminary fiber aggregate was obtained. The present invention was completed by finding that a fiber structure having a heat-resistant ultrafine fiber structure but also having moldability can be obtained by forming and entwining the preliminary fiber aggregate. It came to.

That is, the present invention may be configured in the following aspects.

[Aspect 1]
A fiber structure containing a thermoplastic resin fiber made of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher (preferably 100 ° C. or higher, more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, particularly preferably 180 ° C. or higher). The average fiber diameter of the thermoplastic resin fiber is 10 μm or less (for example, 0.1 to 10 μm, preferably 0.5 to 7 μm, more preferably 1 to 5 μm, still more preferably 1.5 to 4.5 μm, A fiber structure having a breaking elongation of 10% or more (preferably 20% or more, more preferably 30% or more) in at least one direction in the MD direction and the CD direction, particularly preferably 2 to 4 μm).
[Aspect 2]
The fiber structure according to aspect 1, wherein the total elongation at break in the MD direction and the CD direction is 30% or more (preferably 40% or more, more preferably 50% or more, still more preferably 60% or more).
[Aspect 3]
Breaking strength in at least one direction in the MD direction and the CD direction is 10 N / 5 cm or more (preferably 20 N / 5 cm or more, more preferably 30 N / 5 cm or more, still more preferably 50 N / 5 cm or more, particularly preferably 100 N / 5 cm or more. ). The fiber structure according to aspect 1 or 2.
[Aspect 4]
The air permeability at a differential pressure of 125 Pa measured according to the Frazier method described in JIS L1913 is 5 to 50 cm ³ / cm ² / s (preferably 30 cm ³ / cm ² / s or less, more preferably 20 cm ³ / cm ² / s). Hereinafter, the fiber structure according to any one of aspects 1 to 3, which is more preferably 15 cm ³ / cm ² / s or less).
[Aspect 5]
The fiber structure according to any one of aspects 1 to 4, wherein the basis weight is 10 to 100 g / m ² (preferably 20 to 90 g / m ² , more preferably 40 to 80 g / m ² ).
[Aspect 6]
The heat shrinkage rate in at least one of the MD direction and the CD direction after being left in an atmosphere of 250 ° C. for 3 hours is 60% or less (preferably 50% or less, more preferably 20% or less, still more preferably 10% or less. The fiber structure according to any one of aspects 1 to 5, which is particularly preferably 5% or less).
[Aspect 7]
The fiber structure according to any one of aspects 1 to 6, wherein the thermoplastic resin fiber is a liquid crystal polyester fiber.
[Aspect 8]
The fiber structure according to any one of aspects 1 to 7, wherein the fiber structure is an entangled melt-blown non-woven fabric.
[Aspect 9]
The method for producing a fiber structure according to any one of aspects 1 to 8.
The manufacturing method includes an entanglement step of performing an entanglement treatment on the non-woven fabric-like preliminary fiber aggregate.
The non-woven preliminary fiber aggregate has an average fiber diameter of 10 μm or less (for example, 0.1 to 10 μm, preferably 0.5 to 7 μm, more preferably 1 to 5 μm, still more preferably 1.5 to 4.5 μm, particularly. It contains a thermoplastic resin fiber of preferably 2 to 4 μm), and the thermoplastic resin fiber has a glass transition temperature of 80 ° C. or higher (preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 150 ° C. or higher). A production method comprising a thermoplastic resin (particularly preferably 180 ° C. or higher).
[Aspect 10]
The preliminary fiber aggregates are a constrained single fiber group that is constrained and cannot move in the preliminary fiber aggregate, and an unconstrained single fiber group that is substantially unconstrained and can move in the preliminary fiber aggregate. A manufacturing method in which an unconstrained single fiber group is moved to form an entangled portion and an unentangled portion by the entanglement step.
[Aspect 11]
A molded product containing at least the fiber structure according to any one of aspects 1 to 8.
[Aspect 12]
A molded product obtained by heat-molding the fiber structure according to any one of aspects 1 to 8.
[Aspect 13]
A molded product containing at least the fiber structure and support according to any one of aspects 1 to 8.
[Aspect 14]
The molded product according to the thirteenth aspect, wherein the support is a bulky raw fabric.
[Aspect 15]
A sound absorbing material containing at least the fiber structure according to any one of aspects 1 to 8 or the fiber structure or molded product according to any one of aspects 11 to 14.

In the present invention, the MD direction is the flow direction of the fiber structure at the time of manufacture, and the MD direction can be determined from the orientation direction of the fibers. The CD direction is a direction orthogonal to the MD direction. Hereinafter, the MD direction may be referred to as a vertical direction, and the CD direction may be referred to as a width direction.
It should be noted that any combination of claims and / or at least two components disclosed in the specification and / or drawings is included in the present invention. In particular, any combination of two or more of the claims described in the claims is included in the present invention.

According to one configuration of the present invention, heat resistant fibers having a specific average fiber diameter are heat-resistant even though they are composed of ultrafine fibers in order to perform an entanglement treatment on a non-woven fabric-like preliminary fiber aggregate. A fiber structure having both property and moldability can be obtained. Further, in the method for producing a fiber structure, a fiber structure having excellent performance as described above can be efficiently produced.

In another configuration of the present invention, it is possible to obtain a molded body utilizing the molding processability of the fiber structure.

In another configuration of the present invention, the fiber structure can be used as a sound absorbing material. Since the fiber structure can be applied to a portion in a high temperature environment such as the vicinity of an automobile engine and can be molded into various shapes, it can be suitably used for, for example, a sound absorbing skin material. Therefore, the sound absorbing material using such a sound absorbing material has a much wider range of application than the conventional sound absorbing material, and can be a sound absorbing material having a high degree of freedom in molding.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, embodiments and drawings are for illustration and illustration purposes only and should not be used to define the scope of the invention. The scope of the invention is determined by the accompanying claims. In the attached drawings, the same part number in a plurality of drawings indicates the same part.
FIG. 1 is an SEM photograph showing a cross section of the fiber structure 1 according to the present invention in the thickness direction. FIG. 2 is a schematic cross-sectional view schematically showing a cross section of the molded body (sound absorbing material) 10 according to the present invention in the thickness direction. FIG. 3 is a diagram schematically showing a mold used for evaluating the moldability of the fiber structure in the examples.

The fiber structure of the present invention is a fiber structure containing a thermoplastic resin fiber made of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher.

<Thermoplastic resin fiber>
The thermoplastic resin fiber constituting the fiber structure is a fiber formed of a thermoplastic resin having a glass transition temperature Tg of 80 ° C. or higher.

In the present invention, the glass transition temperature (the temperature at which the polymer starts micromolecular movement) is an index of heat resistance, and the thermoplastic resin fiber is formed from a thermoplastic resin having a glass transition temperature of 80 ° C. or higher. A fiber structure having excellent heat resistance can be obtained.

For the glass transition temperature, the temperature dependence of the loss tangent (tan δ) was measured at a frequency of 10 Hz and a temperature rise rate of 10 ° C./min using a solid dynamic viscoelastic device “Leospectra DVE-V4” manufactured by Leologi. It may be obtained from the peak temperature. Here, the peak temperature of tan δ is the temperature at which the first derivative value of the amount of change of the value of tan δ with respect to the temperature becomes zero.

The glass transition temperature of the thermoplastic resin used for the thermoplastic resin fiber is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and further preferably 180 ° C. or higher from the viewpoint of enhancing the heat resistance of the fiber structure. Is particularly preferable. Further, from the viewpoint of spinnability, the glass transition temperature of the thermoplastic resin is preferably 250 ° C. or lower, more preferably 230 ° C. or lower.

The thermoplastic resin fiber is not particularly limited as long as it is a fiber formed of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher. Fibers, Polybenzothiazole Fibers, Acrylic Polyarilate Fibers, Polyethersulfone Fibers, Liquid Liquid Polyester Fibers, Polygonic Fibers, Polyetherimide Fibers, Polyether Ether Ketone Fibers, Polyether Ketone Fibers, Polyether Ketone Ketone Fibers, Polyamide Iimide fibers, semi-aromatic polyamide fibers (for example, polyamide fibers composed of aliphatic diamine units and aromatic dicarboxylic acid units), polyphenylene sulfide fibers and the like can be used. These fibers may be used alone or as a mixture of two or more.

Further, the thermoplastic resin fiber of the present invention may be substantially composed of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher, and may be contained in the thermoplastic resin as long as the effect of the present invention is not impaired. Another resin component may be blended. For example, examples of such resin components include polyethylene terephthalate, modified polyethylene terephthalate, polybutylene terephthalate, polycyclohexine dimethylene terephthalate, polyolefins, polycarbonates, polyamides, thermoplastic polymers such as fluororesins, and thermoplastic elastomers. The resin components of the above can be added alone or in combination of two or more as long as the functions of the present invention are not impaired.
Further, any additive may be added to the thermoplastic resin fiber as long as the effect of the present invention is not impaired. For example, as additives, carbon black, colorants such as dyes and pigments, inorganic fillers such as titanium oxide, kaolin, silica and barium oxide, antioxidants, ultraviolet absorbers, light stabilizers and the like are usually used. Additives and the like can be mentioned.

Among these fibers, from the viewpoint of melt spinnability and heat resistance, liquid crystal polyester fiber, polyetherimide fiber, polyphenylene sulfide fiber, semi-aromatic polyamide fiber (for example, the dicarboxylic acid unit contains a terephthalic acid unit and is a diamine. The unit is preferably a semi-aromatic polyamide fiber containing 1,9-nonanediamine unit and / or 2-methyl-1,8-octanediamine unit).

(Liquid crystal polyester fiber)
Liquid crystal polyester fibers (sometimes referred to as polyarylate-based liquid crystal resin fibers) can be obtained by melt-spinning liquid crystal polyester (LCP). The liquid crystal polyester is composed of a repeating structural unit derived from, for example, an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, etc., and the aromatic diol, the aromatic dicarboxylic acid, the aromatic, etc. The structural unit derived from the group hydroxycarboxylic acid is not particularly limited in terms of its chemical composition. Further, the liquid crystal polyester may contain a structural unit derived from an aromatic diamine, an aromatic hydroxyamine or an aromatic aminocarboxylic acid as long as the effect of the present invention is not impaired. For example, as a preferable structural unit, examples shown in Table 1 can be mentioned.

Y is an alkyl group (eg, methyl) such as a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.) independently in the range of 1 to the maximum number of substitutables in the aromatic ring. Group, ethyl group, isopropyl group, alkyl group having 1 to 4 carbon atoms such as t-butyl group), alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl group (eg, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.) For example, phenyl group, naphthyl group, etc.), aralkyl group [benzyl group (phenylmethyl group), phenethyl group (phenylethyl group), etc.], aryloxy group (eg, phenoxy group, etc.), aralkyloxy group (eg, benzyloxy group). (Group, etc.) and so on.

More preferable structural units include the structural units described in Examples (1) to (18) shown in Tables 2, 3 and 4 below. When the structural unit in the formula is a structural unit capable of exhibiting a plurality of structures, two or more such structural units may be combined and used as the structural unit constituting the polymer.

In the structural units of Tables 2, 3 and 4, n is an integer of 1 or 2, and the respective structural units n = 1, n = 2 may exist alone or in combination; Y1 and Y2. Independently, each has a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.) and the number of carbon atoms. Alkyl groups 1 to 4), alkoxy groups (eg, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), aralkyl group [benzyl group (benzyl group (eg, benzyl group) (Phenylmethyl group), phenethyl group (phenylethyl group), etc.], aryloxy group (for example, phenoxy group, etc.), aralkyloxy group (for example, benzyloxy group, etc.), etc. Among these, Y is preferable. Examples include a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group.

Further, as Z, a substituent represented by the following formula can be mentioned.

The preferable liquid crystal polyester may be a combination having a naphthalene skeleton as a constituent unit. Particularly preferably, it contains both the structural unit (A) derived from hydroxybenzoic acid and the structural unit (B) derived from hydroxynaphthoic acid. For example, the following formula (A) can be mentioned as the constituent unit (A), and the following formula (B) can be mentioned as the constituent unit (B). The ratio of the unit (B) may be preferably in the range of 9/1 to 1/1, more preferably 7/1 to 1/1, and even more preferably 5/1 to 1/1.

Further, the total of the constituent units of (A) and (B) may be, for example, 65 mol% or more, more preferably 70 mol% or more, and further preferably 80 mol% with respect to all the constituent units. It may be% or more. Among the polymers, liquid crystal polyester having a constituent unit (B) of 4 to 45 mol% is particularly preferable.

Further, as the composition of the liquid crystal polyester (polyarylate type liquid crystal resin) forming the liquid crystal polyester fiber, parahydroxybenzoic acid and 2-hydroxy-6-naphthoic acid are the main components, or parahydroxybenzoic acid. , 2-Hydroxy-6-naphthoic acid, terephthalic acid and biphenol are the main components.

The liquid crystal polyester preferably has a melt viscosity at 310 ° C. of 20 Pa · s or less from the viewpoint of less oligomer generation during polymerization and easy fineness. Further, from the viewpoint of easiness of fiberization, it is preferable that the melt viscosity at 310 ° C. is 5 Pa · s or more.

The melting point of the liquid crystal polyester preferably used in the present invention is preferably in the range of 250 to 360 ° C, more preferably 260 to 320 ° C. The melting point referred to here is the main absorption peak temperature measured and observed by a differential scanning calorimeter (DSC; "TA3000" manufactured by METTLER TEPCO) in accordance with the JIS K7121 test method. Specifically, after taking 10 to 20 mg of a sample in the DSC device and encapsulating it in an aluminum pan, 100 cc / fraction of nitrogen is flowed as a carrier gas, and the endothermic peak when the temperature is raised at 20 ° C./min is measured. .. Depending on the type of polymer, if a clear peak does not appear at 1st run in DSC measurement, the temperature is raised to a temperature 50 ° C higher than the expected flow temperature at a heating rate of 50 ° C / min, and that temperature is used for 3 minutes. After it is completely melted, it is advisable to cool it to 50 ° C. at a temperature lowering rate of −80 ° C./min, and then measure the heat absorption peak at a heating rate of 20 ° C./min.

As the liquid crystal polyester, for example, a molten liquid crystal forming total aromatic polyester (manufactured by Polyplastics Co., Ltd., Vectra-L type) composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Is used.

(Polyetherimide fiber)
Polyetherimide fibers can be obtained by melt-spinning polyetherimide (PEI). The polyetherimide is a repeating constituent unit of an aliphatic, alicyclic or aromatic ether unit and a cyclic imide, and the cyclic imide and the ether bond are bonded to the main chain of the polyetherimide as long as the effect of the present invention is not impaired. Structural units other than the above, for example, aliphatic, alicyclic or aromatic ester units, oxycarbonyl units and the like may be contained. The polyetherimide may be either crystalline or amorphous, but is preferably an amorphous resin.

As a specific polyetherimide, a polymer having a unit represented by the following general formula is preferably used. However, in the formula, R1 is a divalent aromatic residue having 6 to 30 carbon atoms; R2 is a divalent aromatic residue having 6 to 30 carbon atoms, and 2 to 20. 2 selected from the group consisting of a polydiorganosiloxane group chain-terminated with an alkylene group having 2 to 20 carbon atoms and an alkylene group having 2 to 8 carbon atoms. It is a valent organic group.

As the above R1 and R2, for example, those having an aromatic residue or an alkylene group (for example, m = 2 to 10) represented by the following formula group are preferably used.

In the present invention, 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-, which mainly have the structural unit represented by the following formula, from the viewpoint of melt spinnability and cost. A condensate with phenylenediamine is preferably used. Such polyetherimides are commercially available from Servic Innovative Plastics under the trademark "Ultem".

The resin constituting the polyetherimide fiber preferably contains at least 50% by mass or more, more preferably 80% by mass or more, and 90% by mass or more of the polymer having the unit represented by the above general formula in the resin. Is more preferable, and it is particularly preferable that the content is 95% by mass or more.

As the polyetherimide, it is preferable to use an amorphous polyetherimide having a melt viscosity of 900 Pa · s at a temperature of 330 ° C. and a shear rate of 1200 sec ^-1 using a Toyo Seiki Capillograph type 1B.

(Polyphenylene sulfide fiber)
Polyphenylene sulfide fibers can be obtained by melt spinning polyarylene sulfide. The polyarylene sulfide has an arylene sulfide represented by -Ar-S- (Ar is an arylene group) as a repeating constituent unit, and examples of the arylene group include p-phenylene, m-phenylene, and a naphthylene group. From the viewpoint of heat resistance, it is preferable that the repeating constituent unit is p-phenylene sulfide.

The resin constituting the polyphenylene sulfide fiber preferably contains at least 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more of the polymer having allylene sulfide as a repeating constituent unit in the resin. preferable.

The average fiber diameter of the thermoplastic resin fiber is preferably 10 μm or less from the viewpoint of sound absorption and moldability. Further, from the viewpoint of moldability, it is preferably 0.1 μm or more. It is more preferably 0.5 to 7 μm, still more preferably 1 to 5 μm, even more preferably 1.5 to 4.5 μm, and particularly preferably 2 to 4 μm.

In general, it is known that the sound absorption property of a fiber structure can be indexed by its air permeability, and the lower the air permeability, the better the sound absorption property. By setting the average fiber diameter to 10 μm or less, the air permeability of the fiber structure can be lowered, so that the sound absorption property can be improved, and further, the thickness of the fiber structure can be reduced, so that the formability is also improved. It is possible to have a good fiber structure. Further, by setting the average fiber diameter to 0.1 μm or more, it is possible to impart appropriate strength required at the time of molding the fiber structure, and it is possible to improve the moldability.

<Manufacturing method of fiber structure>
Next, the method for producing the fiber structure of the present invention will be described.

The method for producing a fiber structure of the present invention includes an entanglement step of performing an entanglement treatment on a non-woven fabric-like preliminary fiber aggregate containing thermoplastic resin fibers having an average fiber diameter of 10 μm or less. Here, the non-woven fabric-like preliminary fiber aggregate is a preliminary non-woven fabric-like fiber aggregate in which the adhesion between fibers is weak, or a preliminary fiber aggregate having a non-woven fabric shape in a state where the fibers are not adhered to each other and are entangled with each other. Means. The weak adhesion between the fibers can be confirmed, for example, by the weak breaking strength per unit weight and the occurrence of fluffing when the surface is rubbed with a finger.
In the method for producing a fiber structure of the present invention, the object of the entanglement treatment described later is formed of ultrafine fibers having an average fiber diameter of 10 μm or less. Therefore, since the fiber diameter is too small to perform the normal entanglement treatment, it is preferable to use a non-woven fabric-like preliminary fiber aggregate to which the fibers are preliminarily bonded to the extent that the entanglement treatment can be performed.

The term "adhesion" as used herein refers to a state in which fibers are softened by heating and the fibers are deformed and meshed by overlapping forces at their intersections, and / or a state in which the fibers are melted and integrated. To tell. It may be called "fusion" in the same meaning as "adhesion" here.

On the other hand, in the conventional fiber structure in which the fibers are firmly fused to each other, the elongation of the fiber structure may not be improved because the fibers do not move even if the entanglement treatment is performed.

The non-woven fabric-like preliminary fiber aggregate can be obtained, for example, as the above-mentioned direct-bonded spinning type non-woven fabric of the thermoplastic resin. The spinning means is not particularly limited as long as the non-woven fabric-like preliminary fiber aggregate can be formed, and for example, a melt blown method, a spunbond method, an electrostatic spinning method and the like can be used. The spinning method may be either melt spinning or solution spinning, but melt spinning is preferable from the viewpoint of controlling adhesiveness. Of these, the melt blown method is preferable from the viewpoint of excellent production efficiency and the ability to reduce the average fiber diameter. The device used for the melt blown method is not particularly limited.

In the present invention, it is preferable to suppress excessive fusion of fibers in the preliminary fiber assembly. For example, when spinning by direct-coupled spinning such as the melt blown method, the temperature near the spinning nozzle or on the fiber collecting surface is set low. In addition to increasing the degree of freedom of movement of fibers by intentionally suppressing the fusion of fibers, it is possible to impart appropriate breaking strength and breaking elongation by applying a specific entanglement treatment to such a preliminary fiber aggregate. It is possible to provide the followability required at the time of molding while ensuring the strength required when handling the fiber structure. Further, the fiber structure of the present invention is preferably not subjected to post-treatment such as calendar treatment, roll press, embossing treatment after spinning from the viewpoint of increasing the degree of freedom of movement between fibers and improving moldability.

In the case of the melt blown method, a conventionally known melt blown device can be used as the spinning device, but the spinning nozzle to be used has a nozzle hole diameter of 0.1 to 0.5 mmφ from the viewpoint of suppressing nozzle clogging and yarn breakage. It is preferably 0.12 to 0.35 mmφ, and more preferably 0.12 to 0.35 mmφ.

Further, regarding the spinning nozzle to be used, the ratio (L / D) of the nozzle hole length to the nozzle hole diameter is preferably 5 to 50, preferably 8 to 45, from the viewpoint of good productivity and suppression of yarn breakage. Is more preferable.

The distance between the nozzle holes (nozzle hole pitch) is preferably 0.2 to 1.0 mm, more preferably 0.25 to 0.75 mm. When the distance between the nozzle holes is within the above range, fusion of adjacent fibers directly under the spinning is suppressed, there are few yarn lumps, and the interfiber gaps are appropriate, which is preferable because the homogeneity is excellent. ..

The spinning conditions can be appropriately set according to the type of resin forming the fiber, but the spinning temperature is 300 to 450 ° C, the hot air temperature is 300 to 450 ° C, and the amount of air (per nozzle length 1 m) is 5 to 30 Nm. It is preferable to carry out under the condition of ³ / min.

Further, from the viewpoint of improving the degree of freedom of the fibers in the non-woven fabric-like preliminary fiber aggregate, the temperature in the vicinity of the spinning nozzle and the temperature of the collecting surface may be set to lower temperatures than usual, if necessary. For example, in the case of polyetherimide, the temperature near the spinning nozzle may be set to about 20 to 80 ° C. Further, the temperature of the collecting surface may be set to about 50 to 150 ° C. For other resins, if necessary, the temperature in the vicinity of the spinning nozzle may be set to be lower than the glass transition temperature in the range of 100 to 200 ° C. Further, the temperature of the collecting surface may be set to be lower than the glass transition temperature in the range of 100 to 200 ° C. The temperature may be as low as 50 to 150 ° C.

Further, from the viewpoint of improving the degree of freedom of fibers in the nonwoven fabric-like preliminary fiber aggregate and enhancing the effect of the entanglement treatment described later, the nonwoven fabric-like preliminary fiber aggregate may have a fiber fusion rate of 90% or less. , 70% or less, more preferably 30% or less, further preferably 10% or less, and particularly preferably 5% or less. Here, the fiber fusion rate (%) can be obtained by the same method as the fiber fusion rate of the fiber structure of the present invention described later.

The entanglement treatment method is not particularly limited as long as the fibers can be pushed in the thickness direction of the preformed body to improve the formability of the fiber structure, but a spunlace method, a needle punching method, or the like can be used. In particular, the spunlace method is preferable from the viewpoint of imparting excellent moldability to the fiber structure.

In the case of the spunlace method, for example, by performing the entanglement treatment using nozzles in which orifices are provided at specific intervals, a portion of the fiber structure that is particularly exposed to water flow and a portion that is relatively unaffected by water flow are generated, and entanglement occurs. An entangled portion and an unentangled portion are formed.

Further, as the support of the fiber structure at the time of the entanglement treatment, a punching drum and / or a net support may be used. For example, a punching drum is preferable because it is easy to partially apply a water stream to the fiber structure. The net support is preferable because it is easy to adjust the entanglement rate.

For example, when the entanglement treatment is performed by the spunlace method, the pre-spun preliminary fiber aggregate is placed on a punching drum support having a specific aperture ratio and hole diameter and continuously in the longitudinal direction (MD direction). At the same time as the transfer, a high-pressure water stream is injected from above by a nozzle provided with orifices at specific intervals to perform an entanglement treatment, and a fiber structure can be manufactured.

In this case, the entanglement ratio of the fiber structure can be adjusted by adjusting the distance between the orifices of the nozzles, the opening ratio of a support such as a punching drum or a net support, and the hole diameter. For example, the net support may have a plain weave shape, for example, a mesh having a fiber diameter of about 0.10 to 1.50 mm (lines / inch), preferably about 7 to 50 (lines / inch). There may be.

Further, the entanglement process may be performed in a plurality of times. For example, in the first half, a preliminary entanglement treatment (preliminary entanglement treatment) is performed to unravel the fibers constituting the preliminary fiber aggregate to increase the degree of freedom of the fibers, and in the second half, the fibers are moved to be predetermined. Elongation may be given to the fiber structure. In that case, the water pressure of the last entanglement treatment (main entanglement treatment) is higher than the water pressure of the first entanglement treatment, for example, the final water pressure is about 2 to 8 times the initial water pressure. It may be present, preferably about 2.5 to 5 times. In this case, different supports may be used in each entanglement process. For example, it is preferable to perform the entanglement treatment using a punching drum as a support and then perform the entanglement treatment using a net support. By performing the entanglement treatment in a plurality of portions, the fiber structure is subjected to a good entanglement treatment, and a fiber structure having improved moldability can be obtained.

FIG. 1 is an SEM (scanning electron microscope) photograph showing a cross section of the fiber structure 1 according to the second embodiment of the present invention cut in the CD direction and in the thickness direction thereof. In FIG. 1, a region 2 having a width indicated by a white arrow is an entangled portion, and the other region 3 is a non-entangled portion.

In the present invention, the "entangled portion" means a portion where the fiber is pushed in the thickness direction of the fiber structure by performing the above entanglement treatment, and the cross section of the fiber structure is observed by SEM or the like. At this time, the region where the fibers are pushed in the thickness direction is observed as the entangled portion in distinction from the non-entangled portion.
Further, in the entangled portion, the fibers tend to be oriented more in the thickness direction than in the non-entangled portion, and such a feature is used as a secondary judgment material to distinguish between the entangled portion and the non-entangled portion. May be good.

For example, in the case of spunlace, the part of the fiber structure through which the water flow passes most strongly is observed as an entangled part by pushing the fiber in the thickness direction. Further, in the case of a needle punch, a portion where the fiber is pushed in the thickness direction by the passage of the needle is observed as an entangled portion.

The non-entangled portion is a portion where the entanglement treatment is not applied and the fibers are hardly pushed in the thickness direction. If the entanglement treatment is not performed, the entire fiber structure becomes a non-woven fabric, and when the entanglement treatment is performed, the water stream is partially passed through, for example, by using a nozzle provided with an orifice at a specific interval. The non-woven fabric is the portion where the water flow does not pass and the state of the fiber does not substantially change from the time of spinning.

Further, in the fiber structure in which the fibers are firmly fused to each other, the fibers are not pushed in the thickness direction even in the region subjected to the entanglement treatment, so such a region is also regarded as a non-entangled portion.

In the present invention, it is preferable that the entangled portion and the unentangled portion are mixed in the fiber structure by partially entwining the fiber structure. In such a case, the fiber structure is visually observed. At that time, the entangled portion may be observed as a state in which holes are scattered on at least one surface.

In the present invention, the "entanglement rate" is the ratio of the entangled portion in the entire fiber structure, and specifically, is a value obtained by the method described in Examples. The entanglement rate can be appropriately set as long as a predetermined elongation at break is imparted to the fiber structure, but the entanglement rate of the fiber structure is preferably 5% or more. If the entanglement rate is less than 5%, the elongation at break required at the time of molding is not exhibited, so that good moldability may not be obtained. The entanglement rate is more preferably 10% or more, further preferably 20% or more, and even more preferably 40% or more. Further, from the viewpoint of moldability, the entanglement rate is preferably 90% or less, more preferably 80% or less, still more preferably 70% or less. When the fiber structure has an appropriate entanglement ratio by performing the entanglement treatment, the fiber structure can have a sufficient elongation at break for handleability. In addition, the entanglement treatment can increase the entanglement between the fibers to improve the breaking strength of the fiber structure. By the entanglement treatment, the followability required at the time of molding is exhibited, and a fiber structure having improved moldability can be obtained. The entanglement rate given to the fiber structure in the entanglement treatment is not particularly limited, but for example, when the entanglement rate is 90% or less, the entangled portion and the non-entangled portion, that is, expansion and contraction on the fiber structure. A portion that is difficult to stretch and a portion that easily expands and contracts are mixed, and appropriate strength and elongation required at the time of molding are imparted, and the moldability can be further improved.

<Fiber structure>
The fiber structure contains the above-mentioned thermoplastic resin fibers, the average fiber diameter of the thermoplastic resin fibers is 10 μm or less, and the breaking elongation in at least one direction in the MD direction and the CD direction is 10% or more. The shape can be selected depending on the application, but is usually sheet-shaped or plate-shaped.

Further, regarding the breaking elongation of the fiber structure, from the viewpoint of moldability, the breaking elongation of the fiber structure in at least one direction in the MD direction and the CD direction is 10% or more. The elongation at break is more preferably 20% or more, further preferably 30% or more. Further, the elongation at break in both the MD direction and the CD direction is preferably 5% or more, and more preferably 10% or more. Further, the total breaking elongation in the MD direction and the CD direction is preferably 30% or more, preferably 40% or more, more preferably 50% or more, and further preferably 60% or more. Further, the total breaking elongation in the MD direction and the CD direction may be 100% or more.

Further, the breaking strength of the fiber structure is preferably 10 N / 5 cm or more, preferably 20 N / 5 cm or more, in at least one direction of the fiber structure in the MD direction and the CD direction from the viewpoint of moldability and handleability. It is more preferably 30 N / 5 cm or more, further preferably 55 N / 5 cm or more, and particularly preferably 100 N / 5 cm or more. From the viewpoint of improving the degree of freedom of molding, the breaking strength of the fiber structure in both the MD direction and the CD direction is 10 N / 5 cm or more, preferably 20 N / 5 cm or more, and more preferably 30 N / 5 cm or more. May be good.

The air permeability of the fiber structure can be treated as an index of sound absorption performance, and the lower the air permeability, the better the sound absorption performance. Therefore, the air permeability at a differential pressure of 125 Pa measured in accordance with the Frazier method described in JIS L1913 is 50 cm. ³ / cm ² / s or less is preferable, more preferably 40 cm ³ / cm ² / s or less, still more preferably 30 cm ³ / cm ² / s or less, still more preferably 20 cm ³ / cm ² / s or less, particularly preferably. It may be 15 cm ³ / cm ² / s or less. Further, from the viewpoint of suppressing sound reflection and enhancing sound absorption performance, the air permeability is preferably 5 cm ³ / cm ² / s or more . If the air permeability is too low, the sound will be reflected, which may be disadvantageous in sound absorption.

The basis weight of the fiber structure may be, for example, 10 to 100 g / m ² , preferably 20 to 90 g / m ² , and more preferably 20 to 90 g / m 2, from the viewpoint of improving handleability while contributing to weight reduction. It may be 30 to 80 g / m ² .

Further, from the viewpoint of heat resistance, the fiber structure may have a heat shrinkage rate of 60% or less in at least one direction of the fiber structure in the MD direction and the CD direction when heat-treated at 250 ° C. for 3 hours. % Or less is preferable, 50% or less is more preferable, 20% or less is further preferable, 10% or less is even more preferable, and 5% or less is particularly preferable. Further, it is preferable that both the heat shrinkage rate in the MD direction and the heat shrinkage rate in the CD direction are within the above ranges.

In the fiber structure of the present invention, in order to have high followability, the fibers are not bonded to each other, are bonded to each other with low adhesive strength, or are bonded to each other with a small adhesive area. preferable. As a result, the bonding force due to the adhesion between the fibers is weak, the fibers can adopt a flexible positional relationship, and the fiber structure can exhibit high followability.

The fiber structure of the present invention may have a fiber fusion rate of 90% or less, preferably 70% or less, more preferably 30% or less, further preferably 10% or less, and particularly preferably 5% or less. Here, for the fiber fusion rate (%), a scanning electron microscope is used to take a photograph in which the cross section of the fiber structure in the thickness direction is magnified 1000 times, and the fiber cut surface (fiber cross section) is visually observed from this photograph. ) To the number of cut surfaces to which the fibers are fused. The ratio of the number of cross sections in which two or more fibers are fused to the total number of fiber cross sections found in each region is calculated by the formula:
Fiber fusion rate (%) = (number of cross sections of two or more fibers fused) / (total number of fiber cross sections) x 100
Expressed as a percentage based on.
However, for each photograph, all the fibers whose cross sections are visible are counted, and when the number of fiber cross sections is 100 or less, an observation photograph is added so that the total number of fiber cross sections exceeds 100. If it is difficult to determine the cross section of each fiber because the fibers are partially densely bonded to each other, the number of fiber cross sections can be calculated by dividing the approximate area of the bonded surface by the average fiber diameter. You may ask.

The thickness of the fiber structure is not particularly limited, but from the viewpoint of moldability, it may be, for example, 5 mm or less, preferably 1.0 mm or less, more preferably 0.80 mm or less, still more preferably 0.60 mm or less. .. Further, from the viewpoint of sound absorption and strength, 0.01 mm or more is preferable, 0.05 mm or more is more preferable, and 0.10 mm or more is further preferable.

Further, a plurality of fiber structures of the present invention may be used in combination. In that case, the total thickness of the plurality of fiber structures may be, for example, 100 mm or less, 50 mm or less, or 10 mm or less.

<Molded body>
The molded product of the present invention may contain at least a fiber structure. For example, the molded body may be a molded body in which a plurality of fiber structures are integrated by adhesion or the like, or may be a molded body including at least a fiber structure and a support. Although the fiber structure of the present invention is made of ultrafine fibers, it has a predetermined elongation, so that the handleability of the fiber structure can be improved at the time of molding. As a result, it is possible to form the fiber structure into a desired shape while preventing wrinkles from being generated.
The molded body of the present invention is useful for covering a coated surface having a non-planar surface (curved surface or stepped surface) by utilizing the formability of the fiber structure.

In the molded body, the fiber structure may be integrated with an adhesive, or may be a molded body obtained by thermally molding the fiber structure by utilizing the thermoplasticity of the fiber structure. In the case of a molded body obtained by thermoforming, the fiber structure of the present invention has improved moldability and can be deformed into a desired shape. By thermoforming, the fiber structure is given a molded shape. At the same time, the fibers are fused to each other by heating, so that the molded body can be formed into a molded body in which the molded shape is fixed and the strength is added.

Further, in the case of thermoforming using the fiber structure of the present invention, it is possible to fuse the fibers together while maintaining the shape of the molding by heating in the molding process, and as a result, the molding shape. It is possible to obtain a molded product having the same strength as that of a conventional fiber structure.

Further, in the molded body including at least the fiber structure and the support, the fiber structure and the support may be integrated with an adhesive, or the fiber structure and the support may be thermally pressure-bonded to each other. It may be integrated.

FIG. 2 is a schematic cross-sectional view of the molded body 10 including at least the fiber structure 12 and the support 11. Since the fiber structure 12 is made of ultrafine fibers, it is adhered or fused to the support 11 in order to improve handleability. In FIG. 2, the fiber structure 12 is arranged on one surface of the support 11, but the fiber structure 12 may be arranged on both surfaces of the support 11. Further, it may have a structure in which a large number of supports and fiber structures are alternately combined.

The support 11 can be appropriately selected depending on the intended use as long as it supports the fiber structure 12, but may be, for example, a film-like support, a porous support, or the like, and is particularly bulky made of fibers. It may be a raw fabric (bulky fiber aggregate) or the like.
The molded body 10 can cover the covering surface of the covering target 13. Since the molded body 10 is excellent in molding processability, for example, even when the covering surface has a non-planar shape (for example, a curved surface shape or a stepped shape), it is possible to satisfactorily cover the molded body 10.

Since the fiber structure of the present invention has both heat resistance and moldability, the molded body provided with the fiber structure can be molded into a desired shape, for example, in the fields of industrial materials and medical / sanitary materials. , Electrical and electronic fields, construction / civil engineering fields, agricultural materials fields, aircraft / automobiles / ships fields, etc. (for example, interior materials, packaging materials, sanitary materials, especially covering materials).

<Sound absorbing material>
Next, a sound absorbing material using a fiber structure will be described. An example of the sound absorbing material of the present invention will be described with reference to FIG. In FIG. 2, the above-mentioned molded body 10 corresponds to the sound absorbing material 10, the support 11 corresponds to the sound absorbing body 11, the fiber structure 12 corresponds to the sound absorbing skin material 12, and the covering target 13 corresponds to the object 13. do.

The sound absorbing material 10 in FIG. 2 includes a sound absorbing body 11 and a sound absorbing skin material 12. In the case of the example of FIG. 2, the sound absorbing body 11 is, for example, a bulky raw fabric made of fibers, and the sound absorbing skin material 12 is the fiber structure 1 of the present invention. As described above, the sound absorbing skin material 12 covers the surface of the sound absorbing body 11 to improve the sound absorbing property and durability of the sound absorbing material 10.

The sound absorbing material 10 is used, for example, by being attached to an object 13 to be sound absorbed. Therefore, it is necessary to form the shape of the sound absorbing material 10 according to the surface shape of the object 13, and in particular, the sound absorbing skin material 12 (fiber structure 1) needs to be able to follow the shape of the object to be sound-absorbed and the shape of the sound absorbing body. It becomes.

Further, since the fiber structure of the present invention is excellent in heat resistance and sound absorption and also has moldability, it is suitable as a sound absorbing material for vehicles such as automobiles, trains, airplanes, ships, motorcycles, helicopters, and submarines. In particular, as a sound absorbing material for automobiles, it can be suitably used for automobile interior materials such as ceiling materials, dashboards, and carpets, and also as an undercover, bulkhead, engine head cover, etc. in the vicinity of an engine. Used for. Further, the sound absorbing material of the present invention includes a vacuum cleaner, a dishwasher, a washing machine, a dryer, a refrigerator, a microwave oven, an oven range, an air conditioner, a heater, an audio system, a television, a sewing machine, a copy machine, a telephone, a facsimile, a personal computer, and a word processor. Electrical appliances such as wallpaper, flooring, tatami mats, ceiling materials, roofing materials, house wraps, heat insulating materials, etc. It can be suitably used for civil engineering materials and the like.

Further, the fiber structure of the present invention can be used for any part of the sound absorbing material. For example, when the sound absorbing material is composed of a sound absorbing body and a sound absorbing skin material, the fiber structure of the present invention is a sound absorbing body. However, it can also be used as a sound-absorbing skin material, and in particular, it is preferably used even if it is a sound-absorbing skin material that is required to have heat resistance and sound-absorbing property while being thin and needs to be molded according to the shape of the sound-absorbing body. can do.

In the sound absorbing material composed of the sound absorbing body and the sound absorbing skin material, when the fiber structure of the present invention is used as the sound absorbing skin material, the material of the sound absorbing body is not particularly limited, and any bulky raw fabric or the like is used to absorb sound. For example, glass wool or felt can be used as the body. By laminating the fiber structure of the present invention on the bulky raw fabric, it is possible to improve the sound absorption property and heat resistance of the sound absorbing material.

Among those skilled in the art, the part between the driver's seat and the passenger's seat is called a "tunnel", especially in automobiles. In the technique, no suitable sound absorbing material having better sound absorbing property than the aluminum material was found, but in the fiber structure of the present invention, since it has sound absorbing property and heat resistance and also has moldability, it can be used for "tunnels" and the like. It is possible to provide a sound absorbing material which can be preferably used and whose shape, formability, strength and the like can be flexibly designed as compared with an aluminum material or the like. Therefore, the fiber structure of the present invention has a much wider range of application than the conventional sound absorbing material in terms of temperature environment and shape, and also has high strength comparable to that of the conventional fiber structure depending on the conditions at the time of molding. It is possible to grant it, and its technical significance is extremely high.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples, and these examples can be modified or modified based on the gist of the present invention, and these examples are excluded from the scope of the present invention. is not.

Each physical property value in Examples and Comparative Examples was measured by the method shown below.

<Metsuke measurement>
Measured by cutting the fiber structure into a size of 2.5 cm in width x 25 cm in length in accordance with "6 Test method 6.2 Mass per unit area (ISO method)" of JIS L1913 "General non-woven fabric test method". Then, the scale (g / m ² ) was calculated from this value.

<Measurement of thickness>
In accordance with "6 Test Method 6.1 Thickness (ISO Method)" of JIS L1913 "General Nonwoven Fabric Test Method", the fiber structure is suppressed and the thickness is 12 g / cm ² and the presser plate is 1 inch Φ measuring instrument. (Mm) was measured.

<Measurement of apparent density>
The apparent density (g / cm ³ ) was calculated using the equation (1) from the measured basis weight and thickness values.
Apparent density (g / cm ³ ) = basis weight / thickness (1)

<Measurement of breaking strength and breaking elongation>
The breaking strength (tensile strength) and breaking elongation (elongation rate) were measured according to "6 Measurement method 6.3 Tensile strength and elongation" of JIS L1913 "General non-woven fabric test method". The breaking strength was measured in the MD direction (flow direction of the fiber structure; hereinafter also referred to as the vertical direction) and the CD direction (direction orthogonal to the MD direction; hereinafter also referred to as the horizontal direction or the width direction).

<Measurement of air permeability>
The air permeability (breathability) at a differential pressure of 125 Pa was measured in accordance with "6 Measurement method 6.8 Breathability (JIS method) 6.8.1 Frazier type method" of JIS L1913 "General non-woven fabric test method".

<Measurement of heat shrinkage rate>
A total of four points were set at positions 50 mm apart in both the MD direction and the CD direction, centered on the intersection of the diagonal lines of the fiber structure cut 150 mm in the MD direction and 150 mm in the CD direction, and at 250 ° C., 3 in the atmosphere. After leaving for a long time, the distance xmm of the point in the MD direction and the distance ymm of the point in the CD direction were measured, and the MD heat shrinkage rate a (%) and the CD heat shrinkage rate b (%) were calculated from the following formulas, respectively. ..
MD heat shrinkage rate a (%) = x / 100 × 100,
CD heat shrinkage b (%) = y / 100 × 100

In a fiber structure having a width (length in the CD direction) of 10 mm, the fiber structure was cut in the CD direction, and the cross section was observed with a scanning electron microscope at a magnification of 50. The width (length in the CD direction) zmm of the entangled portion observed in the fiber structure having a width of 10 mm was measured, and the entanglement rate c (%) was calculated by the following formula. In the observation region, when the entangled portion had a tapered shape, the length of the longest portion in the CD direction was defined as z.
Entanglement rate c (%) = z (mm) / 10 (mm) x 100

<Measurement of average fiber diameter>
A test piece (length x width = 5 cm x 5 cm) is taken from the fiber structure, and the central part (the part centered on the intersection of the diagonal lines) on the surface of the test piece is 1000 using a scanning electron microscope (SEM). I took a picture at double magnification. A circle with a radius of 30 cm is drawn on the photograph centering on the central part (intersection of diagonal lines) of the obtained photograph, and 100 fibers are randomly selected from within the circle, and the central part in the length direction or a portion close to it. The fibers in the above were measured with a nogis, and the average value was taken to obtain the average fiber diameter (number average fiber diameter). In the measurement, the fibers shown in the SEM photograph are shown without distinguishing whether the fibers photographed in the photograph are the fibers located on the outermost surface of the fiber structure or the fibers located inside. The average fiber diameter (μm) was determined for all of the above.

<Evaluation of moldability>
A fiber structure is molded using a mold (mold frame 21 and mold top lid 22) as schematically shown in FIG. 3, and the appearance of the molded fiber structure is observed to observe the fiber structure. Was evaluated according to the following criteria.

Good: No wrinkles on the appearance.
Defective: Wrinkles and holes are seen on the appearance.

(Example 1)
<Manufacturing of fiber structure>
It is composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and has a glass transition temperature of 193 ° C, a melting point of 300 ° C, and a melt viscosity of 15 Pa · s at 310 ° C. Aromatic polyester (Polyplastics Co., Ltd., Vector L type) is extruded by a twin-screw extruder, and the nozzle hole diameter is 0.15 mmφ, L / D (ratio of nozzle hole length to nozzle hole diameter) = 30, per width 1 m. It is supplied to a melt blown non-woven fabric manufacturing apparatus having a nozzle with 4000 holes (distance between nozzle holes 0.25 mm), and has a single hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ / min. By spraying, a non-woven fabric (preliminary fiber aggregate) having a texture of 60 g / m ² was obtained. The value obtained by dividing the breaking strength (N) in the CD direction per 5 cm width of this non-woven fabric by the basis weight (g / m ² ) is 0.4 N · m ² / g, and the adhesive force between the fibers is very weak. there were.

This non-woven fabric is placed on a punching drum support having an aperture ratio of 25% and a hole diameter of 0.3 mm and continuously transferred in the longitudinal direction (MD direction) at a speed of 30 m / min, and at the same time, a high-pressure water stream is jetted from above. Preliminary entanglement treatment was performed to produce a fiber web (nonwoven fabric). In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction (CD direction) of the web are used (distance between adjacent nozzles is 20 cm). The water pressure of the high-pressure water stream jetted from the nozzles in the first row was 3.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 5.0 MPa.

On the other surface, the fiber diameter is 0.90 mm, the mesh is 10 (books / inch), and the plain weave is placed on a flat net support and continuously transferred, and a high-pressure water stream is sprayed to perform the main entanglement process. Was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement process uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction (CD direction) of the web, and the water pressure of the high-pressure water stream is 10. It was carried out under the condition of 0 MPa. Further, it was dried at 135 ° C. to obtain a fiber structure.

(Example 2)
<Manufacturing of fiber structure>
A molten liquid crystal forming total aromatic polyester (polyplastics) composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting viscosity of 15 Pa · s at a melting point of 300 ° C. and 310 ° C. A vector L type manufactured by Co., Ltd.) is extruded by a twin-screw extruder, and has a nozzle with a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a number of holes of 4000 per 1 m of width (distance between nozzle holes 0.25 mm). A non-woven fabric (preliminary fiber aggregate) with a grain size of 60 g / m ² supplied to a melt blown non-woven fabric manufacturing apparatus and sprayed at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ / min. Got

This non-woven fabric is placed on a punching drum support having an aperture ratio of 25% and a hole diameter of 0.3 mm and continuously transferred in the longitudinal direction (MD direction) at a speed of 30 m / min, and at the same time, a high-pressure water stream is jetted from above. Preliminary entanglement treatment was performed to produce a fiber web (nonwoven fabric). In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction (CD direction) of the web are used (distance between adjacent nozzles is 20 cm). The water pressure of the high-pressure water stream jetted from the nozzles in the first row was 2.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 4.0 MPa.

On the other surface, the fiber diameter is 0.90 mm, the mesh is 10 (books / inch), and the plain weave is placed on a flat net support and continuously transferred, and a high-pressure water stream is sprayed to perform the main entanglement process. Was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement process uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction (CD direction) of the web, and the water pressure of the high-pressure water stream is 6. It was carried out under the condition of 0 MPa. Further, it was dried at 135 ° C. to obtain a fiber structure.

(Example 3)
<Manufacturing of fiber structure>
Using an amorphous polyetherimide having a melt viscosity at 330 ° C. of 900 Pa · s, it is extruded by an extruder, and the nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole. It was supplied to a melt blown apparatus having a nozzle with a pitch of 0.75 mm, and sprayed at a single hole discharge rate of 0.09 g / min, a spinning temperature of 420 ° C., a hot air temperature of 420 ° C., and a nozzle width of 10 Nm ³ / min. At this time, the linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and is located on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by the thermometer (AD-5601A (manufactured by A & D Co., Ltd.)) provided as described above was 41 ° C. Further, a thermometer (AD-5601A) provided so as to be located 1 cm from the collection surface on the straight line with respect to the linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. The temperature measured by And Day )) was 110 ° C. In this way, a non-woven fabric (preliminary fiber aggregate) having a basis weight of 50 g / m ² was obtained. The breaking strength (N) in the CD direction per 5 cm width of this non-woven fabric was very weak and could not be measured.

This non-woven fabric is placed on a punching drum support having an aperture ratio of 25% and a hole diameter of 0.3 mm and continuously transferred in the longitudinal direction (MD direction) at a speed of 30 m / min, and at the same time, a high-pressure water stream is jetted from above. Preliminary entanglement treatment was performed to produce a fiber web (nonwoven fabric). In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction (CD direction) of the web are used (distance between adjacent nozzles is 20 cm). The water pressure of the high-pressure water stream jetted from the nozzles in the first row was 3.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 5.0 MPa.

On the other surface, the fiber diameter is 0.90 mm, the mesh is 10 (books / inch), and the plain weave is placed on a flat net support and continuously transferred, and a high-pressure water stream is sprayed to perform the main entanglement process. Was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement process uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction (CD direction) of the web, and the water pressure of the high-pressure water stream is 10. It was carried out under the condition of 0 MPa. Further, it was dried at 135 ° C. to obtain a fiber structure.

(Example 4)
<Manufacturing of fiber structure>
Using an amorphous polyetherimide having a melt viscosity at 330 ° C. of 900 Pa · s, it is extruded by an extruder, and the nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole. It was supplied to a melt blown apparatus having a nozzle with a pitch of 0.75 mm, and sprayed at a single hole discharge rate of 0.09 g / min, a spinning temperature of 420 ° C., a hot air temperature of 420 ° C., and a nozzle width of 10 Nm ³ / min. At this time, the linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and is located on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by the thermometer (AD-5601A (manufactured by A & D Co., Ltd.)) provided as described above was 41 ° C. Further, a thermometer (AD-5601A) provided so as to be located 1 cm from the collection surface on the straight line with respect to the linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. The temperature measured by And Day )) was 110 ° C. In this way, a non-woven fabric (preliminary fiber aggregate) having a basis weight of 50 g / m ² was obtained.

This non-woven fabric is placed on a punching drum support having an aperture ratio of 25% and a hole diameter of 0.3 mm and continuously transferred in the longitudinal direction (MD direction) at a speed of 30 m / min, and at the same time, a high-pressure water stream is jetted from above. Preliminary entanglement treatment was performed to produce a fiber web (nonwoven fabric). In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction (CD direction) of the web are used (distance between adjacent nozzles is 20 cm). The water pressure of the high-pressure water stream jetted from the nozzles in the first row was 2.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 4.0 MPa.

On the other surface, the fiber diameter is 0.90 mm, the mesh is 10 (books / inch), and the plain weave is placed on a flat net support and continuously transferred, and a high-pressure water stream is sprayed to perform the main entanglement process. Was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement process uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction (CD direction) of the web, and the water pressure of the high-pressure water stream is 6. It was carried out under the condition of 0 MPa. Further, it was dried at 135 ° C. to obtain a fiber structure.

(Comparative Example 1)
<Manufacturing of fiber structure>
A molten liquid crystal forming total aromatic polyester (polyplastics) composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting viscosity of 15 Pa · s at a melting point of 300 ° C. and 310 ° C. A vector L type manufactured by Co., Ltd.) is extruded by a twin-screw extruder, and has a nozzle with a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a number of holes of 4000 per 1 m of width (distance between nozzle holes 0.25 mm). A fiber structure having a grain size of 30 g / m ² by supplying it to a melt blown non-woven fabric manufacturing apparatus and spraying it at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ / min to produce a non-woven fabric. Got

(Comparative Example 2)
<Manufacturing of fiber structure>
A molten liquid crystal forming total aromatic polyester (polyplastics) composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting viscosity of 15 Pa · s at a melting point of 300 ° C. and 310 ° C. A vector L type manufactured by Co., Ltd.) is extruded by a twin-screw extruder, and has a nozzle with a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a number of holes of 4000 per 1 m of width (distance between nozzle holes 0.25 mm). It is supplied to a melt blown non-woven fabric manufacturing apparatus and sprayed at a single hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ / min to obtain a non-woven fabric, and then in air at 300 ° C. for 6 hours. The treatment gave a fiber structure having a grain size of 10 g / m ² .

(Comparative Example 3)
<Manufacturing of fiber structure>
A fused liquid crystal forming total aromatic polyester (polyplastics) composed of a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting point of 300 ° C. and a melt viscosity of 15 Pa · s at 310 ° C. A vector L type manufactured by Co., Ltd.) is extruded by a biaxial extruder, and has a nozzle with a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a number of holes of 4000 per 1 m of width (distance between nozzle holes 0.25 mm). It is supplied to a melt blown non-woven fabric manufacturing apparatus and sprayed at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ / min to obtain a non-woven fabric, and then in air at 300 ° C. for 6 hours. Treatment was performed to obtain a non-woven fabric. A non-woven fabric having a basis weight of 10 g / m ² was obtained. The value obtained by dividing the breaking strength (N) in the CD direction per 5 cm width of this non-woven fabric by the basis weight (g / m ² ) was 1.9 N · m ² / g, and the adhesive strength between the fibers was strong. ..

This non-woven fabric is placed on a punching drum support having an aperture ratio of 25% and a hole diameter of 0.3 mm and continuously transferred in the longitudinal direction (MD direction) at a speed of 30 m / min, and at the same time, a high-pressure water stream is jetted from above. Preliminary entanglement treatment was performed to produce a fiber web (nonwoven fabric). In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction (CD direction) of the web are used (distance between adjacent nozzles is 20 cm). The water pressure of the high-pressure water stream jetted from the nozzles in the first row was 3.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 5.0 MPa.

On the other surface, the fiber diameter is 0.90 mm, the mesh is 10 (books / inch), and the plain weave is placed on a flat net support and continuously transferred, and a high-pressure water stream is sprayed to perform the main entanglement process. Was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement process uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction (CD direction) of the web, and the water pressure of the high-pressure water stream is 10. It was carried out under the condition of 0 MPa. Further, it was dried at 135 ° C. to obtain a fiber structure.

(Comparative Example 4)
<Manufacturing of fiber structure>
Using an amorphous polyetherimide having a melt viscosity at 330 ° C. of 900 Pa · s, it is extruded by an extruder, and the nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole. It is supplied to a melt blown device having a nozzle with a pitch of 0.75 mm, and is sprayed at a single hole discharge rate of 0.09 g / min, a spinning temperature of 390 ° C, a hot air (primary air) temperature of 420 ° C, and a nozzle width of 10 Nm ³ / min. Manufactured. At this time, a hot air ejection device is provided so that hot air (secondary air) is blown into the tip of the spinning nozzle of the melt blown device, and hot air (secondary air) having a temperature of 260 ° C. is provided at a flow rate of 2 Nm ³ / min. I sprayed it toward the tip. The linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and it is provided so as to be located on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by a thermometer (AD- 5601A (manufactured by A & D)) was 253 ° C. Further, a thermometer (AD-5601A) provided so as to be located 1 cm from the collection surface on the straight line with respect to the linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. The temperature measured by And Day )) was 261 ° C. In this way, a fiber structure having a basis weight of 25 g / m ² was obtained.

(Comparative Example 5)
<Manufacturing of fiber structure>
Using an amorphous polyetherimide having a melt viscosity at 330 ° C. of 900 Pa · s, it is extruded by an extruder, and the nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole. It is supplied to a melt blown device having a nozzle with a pitch of 0.75 mm, and is sprayed at a single hole discharge rate of 0.09 g / min, a spinning temperature of 390 ° C, a hot air (primary air) temperature of 420 ° C, and a nozzle width of 10 Nm ³ / min. Manufactured. At this time, a hot air ejection device is provided so that hot air (secondary air) is blown into the tip of the spinning nozzle of the melt blown device, and hot air (secondary air) having a temperature of 260 ° C. is provided at a flow rate of 2 Nm ³ / min. I sprayed it toward the tip. The linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and it is provided so as to be located on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by a thermometer (AD- 5601A (manufactured by A & D)) was 253 ° C. Further, a thermometer (AD-5601A) provided so as to be located 1 cm from the collection surface on the straight line with respect to the linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. The temperature measured by And Day )) was 261 ° C. In this way, a non-woven fabric having a basis weight of 25 g / m ² was obtained. The value obtained by dividing the breaking strength (N) in the CD direction per 5 cm width of this non-woven fabric by the basis weight (g / m ² ) was 10 N · m ² / g, and the adhesive strength between the fibers was strong.
The non-woven fabric was subjected to an entanglement treatment (preliminary entanglement treatment and main entanglement treatment) in the same manner as in Example 1 to obtain a fiber structure.

[Comparative Example 6]
A semi-random web was prepared using a liquid crystal polyester fiber (“Vectran” manufactured by Kuraray Co., Ltd.) having a fineness of 2.8 dtex and a fiber length of 51 mm by using the card method. The semi-random web was entangled in the same manner as in Example 1 to obtain a fiber structure.

[Comparative Example 7]
A semi-random web was prepared using a liquid crystal polyester fiber (manufactured by Kuraray Co., Ltd., "Vectran") having a fineness of 2.8 dtex and a fiber length of 51 mm by the card method. The semi-random web was entangled in the same manner as in Example 1 to obtain a fiber structure.

[Comparative Example 8]
Polyetherimide fibers (manufactured by Kuraray Co., Ltd., "KURAKISSS") having a fineness of 2.2 dtex and a fiber length of 51 mm were produced on a semi-random web using the card method. The semi-random web was entangled in the same manner as in Example 1 to obtain a fiber structure.

[Comparative Example 9]
A semi-random web was prepared using a polyetherimide fiber (manufactured by Kuraray Co., Ltd., "KURAKISSS") having a fineness of 2.2 dtex and a fiber length of 51 mm by the card method. The semi-random web was entangled in the same manner as in Example 1 to obtain a fiber structure.

[Comparative Example 10]
Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., 200FP),
Extruded by a biaxial extruder, supplied to a melt blown non-woven fabric manufacturing apparatus having a nozzle with a nozzle hole diameter of 0.3 mmφ, L / D = 10, and a nozzle with a number of holes of 3000 per 1 m of width (distance between nozzle holes 0.75 mm), and ejected with a single hole. A fiber structure was obtained by spraying at an amount of 0.3 g / min, a resin temperature of 290 ° C., a hot air temperature of 290 ° C., and 32 Nm ³ / min.

For the obtained fiber structure, grain size measurement, thickness measurement, and apparent density measurement, average fiber diameter measurement, breaking strength and breaking elongation measurement, air permeability measurement, heat shrinkage measurement, and entanglement. The total rate was measured. The results obtained are shown in Table 5.

As shown in Table 5, the fiber structures of Examples 1 to 4 contain a thermoplastic resin having a glass transition temperature of 80 ° C. or higher, have a high elongation at break, and have good moldability. Further, the fiber structures of Examples 1 to 4 have good breaking strength even though they have a small basis weight.

On the other hand, since the fiber structure of Comparative Example 1 was not entangled, the entanglement rate was 0%, the elongation at break was low, and the moldability was poor. In addition, the breaking strength was extremely low as compared with the examples, and the handleability was also inferior. Further, since the air permeability is higher than that of the examples, it is considered that the sound absorption is inferior.

The fiber structure of Comparative Example 2 had excellent breaking strength because the fibers were firmly fused to each other by heat treatment, but the entanglement rate was 0%, the breaking elongation was low, and the formability was inferior. .. Further, since the air permeability is higher than that of the examples, it is considered that the sound absorption is inferior.

In Comparative Example 3, the fiber structure of Comparative Example 2 was entangled, but since the fibers were firmly fused to each other, no entangled portion was generated even after the entanglement treatment, and the fibers were entangled. The rate was 0%, and although the breaking strength was excellent as in Comparative Example 2, the breaking elongation was low and the moldability was inferior. Further, since the air permeability is higher than that of the examples, it is considered that the sound absorption is inferior.

In the fiber structure of Comparative Example 4, the fibers were firmly fused to each other at the time of spinning, and although the breaking strength was excellent, the breaking elongation was low and the moldability was inferior.

In Comparative Example 5, the fiber structure of Comparative Example 4 was entangled, but since the fibers were firmly fused to each other, no entangled portion was generated even after the entanglement treatment, and the fibers were entangled. The ratio was 0%, and although the breaking strength was excellent as in Comparative Example 3, the breaking elongation was low and the formability was inferior.

In Comparative Example 6, water flow entanglement treatment was performed using a liquid crystal polyester fiber web by the card method, but since the average fiber diameter was large, the denseness of the fiber structure could not be improved, and Example 6 It was more breathable.

The purpose of Comparative Example 7 was to increase the basis weight and increase the denseness of the fiber structure as compared with Comparative Example 6, but the density of the fiber structure could not be increased and the air permeability was sufficiently lowered. I couldn't.

Comparative Examples 8 and 9 were subjected to water flow entanglement treatment using a polyetherimide fiber web by the curd method. However, as in Comparative Examples 6 and 7 , since the average fiber diameter was large, the fiber structure had a large average fiber diameter. Denseness could not be increased, and the air permeability was higher than in the examples.

Comparative Example 10 is a melt-blown non-woven fabric of polybutylene terephthalate fiber, but this non-woven fabric is not sufficient in terms of heat resistance because the glass transition temperature of the resin constituting the fiber is low, and the elongation at break is higher than that of the examples. Since it was low, it was inferior in moldability.

Further, the fiber structures of Examples 1 and 3 subjected to the entanglement treatment at a higher pressure can increase the total elongation at break in the MD direction and the CD direction as compared with the fiber structures of Examples 2 and 4. Further, the fiber structures of Examples 1 and 3 show a higher value of the highest breaking strength among the breaking strengths in the MD direction and the CD direction than the fiber structures of Examples 2 and 4. Further, the fiber structures of Examples 1 and 3 can have a lower air permeability than the fiber structures of Examples 2 and 4.

Further, in Examples 3 and 4, heat shrinkage occurs when heated at 250 ° C. exceeding the glass transition temperature for 3 hours, but heat shrinkage occurs in a range not exceeding the glass transition temperature, for example, 215 ° C. or lower. It is predicted that it will not occur.

Since the fiber structure of the present invention has heat resistance and good moldability, it is subjected to high temperature (for example, 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher). , Particularly preferably 200 ° C. or higher, particularly more preferably 230 ° C. or higher), and the like can be usefully used as a coating material or the like. In particular, a fiber structure having low air permeability can be effectively used as a constituent material such as a sound absorbing material.

As described above, a preferred embodiment of the present invention has been described with reference to the drawings, but those skilled in the art can easily assume various changes and modifications within a self-evident range by looking at the present specification. There will be. Therefore, such changes and amendments are construed as being within the scope of the invention as defined by the claims.

1,12 Fiber structure (sound absorbing skin material)
10 Mold (sound absorbing material)
11 Bulky original fabric (sound absorber)

Claims (15)

A fiber structure containing a thermoplastic resin fiber made of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher.
The average fiber diameter of the thermoplastic resin fiber is 10 μm or less.
The breaking elongation in at least one direction in the MD direction and the CD direction is 10% or more .
A fiber structure having an entangled portion in which the thermoplastic resin fiber is pushed in the thickness direction of the fiber structure. The fiber structure according to claim 1, wherein the total elongation at break in the MD direction and the CD direction is 30% or more. The fiber structure according to claim 1 or 2, wherein the breaking strength in at least one direction in the MD direction and the CD direction is 10 N / 5 cm or more. The fiber structure according to any one of claims 1 to 3, wherein the air permeability at a differential pressure of 125 Pa measured according to the Frazier method described in JIS L1913 is 5 to 50 cm ³ / cm ² / s. The fiber structure according to any one of claims 1 to 4, which has a basis weight of 10 to 100 g / m ² . The fiber structure according to any one of claims 1 to 5, wherein the heat shrinkage rate in at least one of the MD direction and the CD direction after being left in an atmosphere of 250 ° C. for 3 hours is 60% or less. The fiber structure according to any one of claims 1 to 6, wherein the thermoplastic resin fiber is a liquid crystal polyester fiber. The fiber structure according to any one of claims 1 to 7, wherein the fiber structure is an entangled melt-blown non-woven fabric. The method for producing a fiber structure according to any one of claims 1 to 8.
The manufacturing method includes an entanglement step of performing an entanglement treatment on the non-woven fabric-like preliminary fiber aggregate.
A production method, wherein the non-woven preliminary fiber aggregate contains a thermoplastic resin fiber having an average fiber diameter of 10 μm or less, and the thermoplastic resin fiber is made of a thermoplastic resin having a glass transition temperature of 80 ° C. or higher. The production method according to claim 9, wherein the non-woven fabric-like preliminary fiber assembly is produced by a melt blown method, a spunbond method, or an electrostatic spinning method. A molded product containing at least the fiber structure according to any one of claims 1 to 8. A molded product obtained by heat-molding the fiber structure according to any one of claims 1 to 8. A molded product containing at least the fiber structure and the support according to any one of claims 1 to 8. The molded product according to claim 13, wherein the support is a bulky raw fabric. A sound absorbing material containing at least the fiber structure according to any one of claims 1 to 8 or the molded product according to any one of claims 11 to 14.

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