JP2023121005A - Molding and sound absorption material - Google Patents

Abstract

To provide a molding having adequate rigidity while holding sound absorption performance, and a sound absorption material using the molding.SOLUTION: A molding contains a pulp fiber and a synthetic resin, wherein density of the molding is 0.1 g/cm3 or more and 0.8 g/cm3 or less, and a bending elastic gradient of the molding is 0.5 N/cm or more.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a molded article and a sound absorbing material using the molded article.

Conventionally, in home electric appliances such as electric refrigerators, air conditioners, vacuum cleaners, etc., in order to absorb noise and vibration generated by motors, compressors, etc., for example, porous sound absorbing materials (porous sound absorbing materials) have been used. Are known.
In addition, sound absorbing materials are also used in interior materials for buildings and automobiles. are pasted together.
In Patent Document 1, the density is 0.04 to 0.20 g / cm for the purpose of providing a sound absorbing material that has a high sound absorbing effect even if it is thin with respect to sound in a wide frequency band from low frequency sound to high frequency sound. ³ , and an Asker FP ^hardness of 15 to 95; 100 to 800%, and an adhesive layer provided between the porous body and the film, a sound absorbing material provided with a slit penetrating the film and the adhesive layer. disclosed.
Further, in Patent Document 2, there is provided an easily formable sound absorbing material which has good moldability in deep drawing or shallow drawing, excellent soundproofing, and excellent safety, and furthermore, contains a flame retardant. In order to provide an easily moldable sound absorbing material having excellent flame retardancy and low shrinkage, a sound absorbing material comprising a skin material laminated on at least one side of an organic fiber nonwoven fabric, wherein the skin material has a depth of An easily formable sound absorbing material is disclosed which contains a resin binder having a glass transition temperature lower than the drawing or shallow drawing temperature and has a bulk density of 0.1 to 0.8 g/cm ³ .

Patent No. 6769423 JP-A-2005-335279

As disclosed in Patent Documents 1 and 2, nonwoven fabrics generally have a bulky and porous structure with a high porosity, so they have sound absorbing performance, and are used as sound absorbing materials based on the sound absorbing performance. .
Sound absorbing materials used in the field of automotive interiors and construction are required to have not only sound absorbing performance but also appropriate rigidity. was not done.

An object of the present invention is to provide a molded article having appropriate rigidity while maintaining sound absorbing performance, a method for producing the molded article, and a sound absorbing material using the molded article.

The inventors of the present invention have found that, in a molded body containing pulp fibers and a synthetic resin, by setting the density to a specific range and the flexural elastic gradient to a specific value or more, sound absorption performance is maintained while maintaining appropriate rigidity. was found to be exhibited, and the present invention was completed.

That is, the present invention relates to the following <1> to <9>.
<1> A molded article containing pulp fibers and a synthetic resin, wherein the molded article has a density of 0.1 g/cm ³ or more and 0.8 g/cm ³ or less, and a bending elastic gradient of 0.1 g/cm 3 or more and 0.8 g/cm 3 or less. A molded article having a strength of 5 N/cm or more.
<2> The molded article according to <1>, wherein the molded article has a thickness of 2 mm or more and 20 mm or less.
<3> The molded article according to <1> or <2>, wherein the molded article has a basis weight of 500 g/m ² or more and 4000 g/m ² or less.
<4> The molded body according to any one of <1> to <3>, wherein the molded body has a normal incident sound absorption coefficient of 5% or more at a frequency of 2 kHz.
<5> The molded article according to any one of <1> to <4>, wherein the synthetic resin is polyolefin.
<6> The molded article according to any one of <1> to <5>, wherein the synthetic resin contains synthetic fibers.
<7> Any one of <1> to <6>, wherein the mass ratio of the synthetic resin to the pulp fibers in the molded article (synthetic resin/pulp fiber) is 10/90 or more and 95/5 or less. molded body.
<8> A sound absorbing material comprising the molded article according to any one of <1> to <7>.
<9> A method for producing a molded article according to any one of <1> to <7>, comprising the following steps 1 and 2 in this order.
Step 1: Step of preparing a porous body containing pulp fibers and synthetic resin Step 2: Step of hot-pressing the porous body

ADVANTAGE OF THE INVENTION According to this invention, the sound-absorbing material which uses the molded object which has moderate rigidity, its manufacturing method, and the said molded object can be provided, maintaining sound absorption performance.

FIG. 1 is a schematic diagram showing a web forming apparatus used in the production method for producing the molded article of the present embodiment.

[Molded body]
The molded body of the present embodiment is a molded body containing pulp fibers and a synthetic resin, the density of the molded body is 0.1 g/cm ³ or more and 0.8 g/cm ³ or less, and the bending of the molded body is The elastic gradient is 0.5 N/cm or more.
The molded article of the present embodiment has appropriate rigidity while maintaining sound absorption performance.
Although the detailed reason why the above effect is obtained is unknown, part of it is considered as follows.
It is considered that the sound absorbing performance is maintained by setting the density of the compact to 0.1 g/cm ³ or more and 0.8 g/cm ³ or less. In addition, it is considered that appropriate rigidity is imparted by setting the bending elastic gradient of the molded body to 0.5 N/cm or more.
The present invention will be described in detail below.

[Pulp fiber]
The pulp fiber applicable to the molded article of the present embodiment is not particularly limited in its manufacturing method, type, and the like. For example, chemical pulps such as hardwood and/or softwood kraft pulps, mechanical pulps such as SGP, RGP, BCTMP and CTMP, waste paper pulps such as deinked pulps, and kenaf, jute, bagasse, bamboo, straw, hemp, etc. of non-wood pulp. Chlorine-free pulp such as ECF pulp and TCF pulp can also be used.

Among the above pulp fibers, kraft pulp fibers, particularly softwood kraft pulp fibers (NBKP) having a long fiber length are preferably used because they are superior in the rigidity of molded articles.

The average fiber length of the pulp fibers is preferably 0.1 mm or more, more preferably 0.5 mm or more, and still more preferably 1 mm or more, from the viewpoint of improving the rigidity of the molded product and from the viewpoint of ease of manufacturing the molded product. And it is preferably 50 mm or less, more preferably 10 mm or less, still more preferably 5 mm or less, still more preferably 2.5 mm or less.
The average fiber length of pulp fibers is measured by the method described in Examples.

The average fiber width of the pulp fibers is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and even more preferably 15 μm or more, from the viewpoint of improving the rigidity of the molded article and from the viewpoint of ease of manufacturing the molded article. and is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, and even more preferably 50 μm or less.
The average fiber width of pulp fibers is measured by the method described in Examples.

When the molded article of the present embodiment is produced by hot press molding of a porous body (preferably nonwoven fabric, more preferably dry nonwoven fabric), the porous body is preferably a dry nonwoven fabric produced by an airlaid method, In this case, the pulp fibers can be in the form of defibrated dry pulp, for example.

The pulp fibers are preferably unbeaten pulp fibers from the viewpoint of improving the rigidity of the molded article.
In addition, the fine fiber ratio of the pulp fibers is preferably 50% or less, more preferably 30% or less, and still more preferably 20% or less from the above-mentioned viewpoint, and the lower limit is not particularly limited.
The fine fiber ratio of pulp fibers is measured by the method described in Examples.

The content of pulp fibers in the molded article is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more, from the viewpoints of sound absorption, productivity and ease of production. From the viewpoint of the degree of biomass conversion, it is more preferably 50% by mass or more, and particularly preferably 55% by mass or more. Moreover, from the viewpoint of obtaining a molded article having appropriate rigidity, the content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 75% by mass or less.

[Synthetic resin]
The molded article of this embodiment contains a synthetic resin.
Examples of synthetic resins include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polylactic acid (PLA), polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, and modifications thereof. materials, nylon (registered trademark), and the like.
Among these, from the viewpoint of moldability, the synthetic resin is preferably a polyolefin or a modified product thereof, and more preferably a polyolefin. Synthetic resins may be used singly or in combination of two or more.

Examples of polyolefins include polyethylene, polypropylene, and ethylene-propylene copolymers, with polyethylene and polypropylene being preferred.
In the modified polyolefin, methods for modifying the polyolefin include acid modification, chlorination, and the like, and among these, acid modification is preferred from the viewpoint of improving affinity with pulp fibers.
The acid-modifying component used for acid-modifying the acid-modified polyolefin is preferably an unsaturated carboxylic acid component. The unsaturated carboxylic acid component is a component derived from an unsaturated carboxylic acid and its acid anhydride. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid and crotonic acid. Among them, the unsaturated carboxylic acid component is preferably at least one selected from acrylic acid, methacrylic acid, maleic acid and maleic anhydride, and at least one selected from maleic acid and maleic anhydride. is particularly preferred. Polyolefins modified with at least one of maleic acid and maleic anhydride are also referred to as maleic acid-modified polyolefins.
As the acid-modified polyolefin, maleic acid-modified polyolefin is preferable, and maleic acid-modified polyethylene and maleic acid-modified polypropylene are more preferable. At least a part of the acid-modified polyolefin should be acid-modified.
The polyolefin is particularly preferably at least one selected from the group consisting of polyethylene, polypropylene, polyethylene at least partially modified with maleic acid, and polypropylene at least partially modified with maleic acid.
Polyolefin fibers may be used singly or in combination of two or more.

When the molded body of the present embodiment is produced by hot press molding of a porous body (preferably nonwoven fabric, more preferably dry nonwoven fabric), the porous body is preferably a dry nonwoven fabric produced by an airlaid method. It is preferable that the synthetic resin is a porous body obtained in the form of synthetic fibers.
Therefore, the molded article preferably contains synthetic fibers as the synthetic resin.
It should be noted that due to the heat press molding, some or all of the synthetic fibers contained in the porous body are melted, and there is a possibility that there will be a portion that does not retain the fiber shape in the molded body, or the fiber shape will not be observed. there is a possibility.

It is also preferable that the synthetic fibers (fibers made of synthetic resin) used to obtain the porous body have at least one of a hollow tubular shape and a crimped shape. Although the details will be described later, when the porous body is a nonwoven fabric, particularly an air-laid nonwoven fabric, it is preferable that the synthetic resin fibers do not melt during the heat treatment during the production of the air-laid nonwoven fabric.
The melting point of the synthetic resin constituting the synthetic fiber is preferably 200° C. or less, more preferably 195° C. or less, still more preferably 180° C. or less, from the viewpoint of moldability and suppression of pulp fiber deterioration, and , preferably 80° C. or higher, more preferably 90° C. or higher, still more preferably 100° C. or higher.

The synthetic fibers may be composite fibers made of two or more synthetic resins, and examples thereof include split fibers, sea-island fibers, core-sheath fibers, and laminated fibers. Sheath fibers are preferred. In the case of core-sheath fibers, fibers with a concentric cross-sectional structure or eccentric cross-sectional structures are used, but fibers with a concentric cross-sectional structure are preferred. The use of fibers having a concentric cross-sectional structure is preferred because it provides more uniform porous bodies and compacts.

The fiber length of the synthetic fiber is preferably 0.1 mm or more, more preferably 0.1 mm or more, from the viewpoint of obtaining a uniform porous body (preferably nonwoven fabric, more preferably dry-laid nonwoven fabric) and molded body, and from the viewpoint of ease of manufacturing the porous body. is 1.0 mm or more, more preferably 2.0 mm or more, still more preferably 3.0 mm or more, and is preferably 50 mm or less, more preferably 20 mm or less, still more preferably 10 mm or less.
The fiber length of synthetic fibers is measured by the method described in Examples.

The fiber diameter of the synthetic fiber is preferably 0.1 μm or more, more preferably 1 μm or more, and still more preferably 10 μm, from the viewpoint of obtaining a uniform porous body and molded body, and from the viewpoint of ease of manufacturing the porous body and molded body. and preferably 100 μm or less, more preferably 80 μm or less, even more preferably 50 μm or less.
The fiber diameter of synthetic fibers is measured by the method described in Examples.

The fineness of the synthetic fiber is preferably 0.01 dtex or more, more preferably 0.1 dtex or more, and still more preferably 0.1 dtex or more, more preferably It is 1 dtex or more, and preferably 100 dtex or less, more preferably 50 dtex or less, and even more preferably 10 dtex or less.

The molded article of the present embodiment may contain the following other synthetic resins as synthetic resins.
When other synthetic resin is contained, the content of the other synthetic resin is preferably 0.1% by mass or more and 45% by mass or less, more preferably 0.3% by mass or more and 30% by mass, based on the total mass of the molded product %, more preferably 0.4% by mass or more and 20% by mass or less, and even more preferably 0.5% by mass or more and 10% by mass or less. By setting the content of the other synthetic resin within the above range, it is possible to improve the handleability and the like when producing the molded article.
Other synthetic resins include sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, acrylic resin, styrene-(meth)acrylic acid ester copolymer resin, urethane resin, polyvinyl alcohol (PVA) resin, various starches, cellulose derivatives, polyacryl. Sodium Acid, Polyacrylamide, Polyvinylpyrrolidone, Acrylamide-Acrylic Ester-Methacrylic Ester Copolymer, Styrene-Maleic Anhydride Copolymer Alkaline Salt, Isobutylene-Maleic Anhydride Copolymer Alkaline Salt, Polyvinyl Acetate Resin, Styrene -Butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-(meth)acrylic acid ester copolymer and the like can be used.

The content of the synthetic resin in the molded article is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass, from the viewpoints of improving sound absorption and productivity and ease of manufacture. %, more preferably 50% by mass or less, particularly preferably 45% by mass or less, from the viewpoint of the degree of biomass conversion. Moreover, from the viewpoint of obtaining a molded article having appropriate rigidity, the content is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 25% by mass or more.
In addition, when using 2 or more types of synthetic resins, the above content means the total content of the synthetic resins.

The mass ratio of the synthetic resin to the pulp fibers in the molded article (synthetic resin/pulp fiber) is preferable from the viewpoint of obtaining a molded article having appropriate rigidity, the productivity and ease of production of the molded article, and the sound absorption. is 10/90 or more, more preferably 15/85 or more, still more preferably 25/75 or more, and preferably 95/5 or less, more preferably 90/10 or less, further preferably 85/15 or less. , From the viewpoint of the degree of biomass conversion, it is more preferably 50/50 or less, particularly preferably 45/55 or less.

The total amount of pulp fibers and synthetic resin in the molded article is preferably 55% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably is 95 mass % or more and 100 mass % or less.

[Other ingredients]
The molded article may contain other components in addition to the above-mentioned pulp fibers and synthetic resin. Other components include natural resins.
Examples of natural resins include various starches and caseins.

The molded article may further contain fillers and papermaking chemicals as other components.
Examples of fillers include kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite and smectite. Examples include mineral pigments and organic pigments such as polystyrene-based resins, urea-based resins, melamine-based resins, acrylic-based resins and vinylidene chloride-based resins.
Paper manufacturing chemicals include paper strength agents, retention aids, drainage improvers, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control agents, and the like. Paper strength agents include polyacrylamide and the like. A wet strength agent can also be used in combination, and examples thereof include polyamide resins, melamine-formaldehyde resins, urea-formaldehyde resins, polyamide-polyamine-epichlorohydrin resins and polyethyleneimine resins.
When other components are contained, the content of the other components excluding pulp fibers and synthetic resins is preferably 0.1% by mass or more and 45% by mass or less, more preferably 0.3% by mass, based on the total mass of the molded product. % by mass or more and 30% by mass or less, more preferably 0.4% by mass or more and 20% by mass or less, and even more preferably 0.5% by mass or more and 10% by mass or less.

As described above, the molded body of the present embodiment is preferably produced by hot-press molding a porous body (preferably nonwoven fabric, more preferably dry nonwoven fabric). That is, the molded article of the present embodiment is preferably manufactured by a manufacturing method including the following steps 1 and 2 in this order.
Step 1: Step of preparing a porous body containing pulp fibers and a synthetic resin Step 2: Step of hot-pressing the porous body A porous body suitable for producing a molded body will be described below.

[Characteristics of porous material]
When the tensile strength of the porous body in the first direction is T and the tensile strength in the second direction perpendicular to the first direction is Y, T/Y is preferably 0.5 or more and 1 .5 or less. By setting T/Y within the above range, excellent rigidity and strength are obtained, which is preferable.
T/Y is more preferably 0.60 or more, more preferably 0.70 or more, still more preferably 0.80 or more, particularly preferably 0.85 or more, and more preferably 1.45 or less, More preferably 1.40 or less, still more preferably 1.35 or less.
The first direction of the porous body is any one direction in the planar direction of the porous body. However, when the fibers and the like contained in the porous body are oriented in one of the planar directions, the oriented direction is defined as the first direction. In addition, when the flow direction in the manufacturing process of the porous body is known, the flow direction is defined as the first direction. When the flow direction in the manufacturing process of the porous body is known, the flow direction in the manufacturing process is called the first direction (MD direction), and the flow direction in the obtained porous body is sometimes called the T-th direction.
The second direction of the porous body is one direction in the planar direction of the porous body and is a direction orthogonal to the first direction. When the flow direction in the manufacturing process of the porous body is known, the direction orthogonal to the flow direction in the manufacturing process is called the second direction (CD direction), and the second direction in the obtained porous body is the Y line. Sometimes I say

Measurement of the tensile strength of the porous body in the first direction and the second direction is carried out according to JIS P 8113:2006. The tensile strength in each direction is a value obtained by measuring a strip of 15 ± 0.1 mm × 180 ± 1 mm at a speed of 20 ± 5 mm / min using a Tensilon manufactured by A&D Co., Ltd. as a tensile tester. be.

In this embodiment, the porous body is preferably a dry-laid nonwoven fabric obtained by mixing at least pulp fibers and synthetic fibers and then dry-paper-making, and is preferably in the form of a sheet. It is preferably a nonwoven fabric obtained by pressing a cotton-like porous body after dry papermaking (hereinafter also referred to as a cotton-like porous body).
The density of the porous body is preferably 0.04 g/cm ³ or more, more preferably 0.05 g/cm ³ or more, still more preferably 0.06 g/cm ³ or more, and preferably 0.1 g/cm less than ³ , more preferably 0.08 g/cm ³ or less.
The density of the porous body is measured by the method described in Examples.

[Method for producing porous body]
In the present embodiment, the method for producing the porous body (preferably nonwoven fabric) is not particularly limited, and from the viewpoint of obtaining the desired T/Y and density, for example, an airlaid method, which is a dry production method, and a wet production method. A hydroentangling method is exemplified. Among these, from the viewpoint of suppressing fiber orientation in order to obtain a desired T/Y, the dry manufacturing method is preferable, and specifically, manufacturing by the airlaid method is preferable.
The manufacturing process of the porous body preferably includes a process of mixing pulp fibers and synthetic fibers in the air and depositing them. That is, the porous body of this embodiment is preferably a dry-laid nonwoven fabric.

When producing a porous body using a dry papermaking method, it is preferable to employ an airlaid method. In the air-laid method, an air-laid web is produced by blowing an air stream containing synthetic fibers and pulp fibers uniformly mixed in an air stream onto an endless mesh belt equipped with a suction box on the lower side. is a method of forming That is, the airlaid method is a method including a step of mixing pulp fibers and synthetic fibers in the air and depositing them. In the air-laid method, the above operation may be repeated multiple times as necessary.

The web formed by the above method is made into a sheet by a fiber bonding process as described below. As the fiber bonding step, for example, there is a method such as a needle punch method in which a needle is passed through the web surface in a vertical direction to entangle synthetic fibers or pulp fibers to form a sheet. Such a bonding step is preferably used in combination with a web forming method by a carding method. In addition, in the fiber bonding process, the heat-sealing adhesive blended in the dry method web is fused by heating to bond the raw material fibers (thermal bonding method), and the adhesive is applied to the obtained dry method web. A process (chemical bond method) in which the raw material fibers are bonded together using a thermal bond method or a method in which the thermal bond method and the chemical bond method are combined (multi-bond method) can be employed.

In the thermal bonding method, it is preferable to heat at a temperature 20° C. or more higher than the melting point of the heat-fusible adhesive. Examples of the heat treatment include hot air treatment and heat pressure treatment at low pressure after hot air treatment.

When a thermal bond method or a multi-bond method is employed, it is preferable to use a particulate or fibrous heat-fusible adhesive. The heat-sealable adhesive may be a synthetic fiber or binder component as described above.
As the particulate heat-fusible adhesive, heat-fusible resin particles such as polyethylene, polypropylene, polyester low-melting-point polyethylene terephthalate, low-melting-point polyamide, low-melting-point polylactic acid, and polybutylene succinate are used.
Fibrous heat-fusible adhesives include polyesters such as low-melting polyethylene terephthalate, low-melting polylactic acid, polybutylene succinate (PBS), and polyethylene terephthalate (PET), low-melting polyamides, acrylic resins, vinyl acetate ( PVAc) resins are used.
As the heat-fusible synthetic fiber, a heat-fusible composite synthetic fiber having a core-sheath structure obtained by combining two kinds of resins having different melting points and melting only on the surface of the fiber is also preferably used. can. A heat-fusible conjugate synthetic fiber having a core-sheath structure has a structure in which a sheath made of a resin with a low melting point is formed on the outer periphery of a core made of a resin with a high melting point. Specifically, there is a form in which two resins having different melting points are combined (PET/PET composite fiber, PE/PET composite fiber, PP/PET composite fiber, PE/PP composite fiber, PVAc/PET composite resin). .

Further, when a chemical bond method is used for bonding fibers, it is preferable to add a binder component to fix the fibers together. The binder component can be appropriately selected as necessary. For example, solution-type binders such as starch, casein, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose sodium salt, polyvinyl alcohol (PVA), and sodium polyacrylate, Polyacrylic acid ester, acrylic styrene copolymer, polyvinyl acetate, ethylene vinyl acetate copolymer, acrylonitrile butadiene copolymer, methyl methacrylate butadiene copolymer, urea-melamine resin, styrene-butadiene copolymer resin, etc. , an emulsion type binder, etc., can be used. It is also preferred to use the binder component described above. As the binder, various forms such as fibers, powder, granules, solutions, emulsions, etc. can be used, and two or more types can be used in combination.

When a porous body is produced using a dry papermaking method, a calendering treatment may be performed as necessary for the purpose of improving the smoothness and controlling the density after the heat treatment. In calendering, the density of the sheet can be arbitrarily controlled by pressing with a metal roll or a resin roll. Further, by setting the temperature of the rolls for calendering to an arbitrary temperature and heating and pressurizing the sheet, a highly smooth and high-density sheet can be obtained.

In the porous body manufactured by the dry papermaking method as described above, each fiber constituting the porous body is randomly three-dimensionally oriented in the longitudinal direction, the width direction and the thickness direction. Therefore, in the present embodiment, the tensile strength in the first direction and the tensile strength in the second direction of the porous body are approximately the same value. That is, in this embodiment, a porous body having excellent isotropy in the planar direction can be obtained.

In the manufacturing process of the porous body, a laminated sheet may be manufactured by laminating an arbitrary sheet that does not impede moldability on the porous body. For example, any sheet can be laminated on the surface of the porous body or between sheets when the porous bodies are laminated. Sheets such as tissues and nonwoven fabrics can be used as optional sheets to be laminated. These optional sheets are laminated for the purpose of improving surface properties, improving interlaminar strength, and imparting other functions.

The porous body can be obtained by heat-pressing molding using a roll press. In the roll press treatment, the density of the sheet can be arbitrarily controlled by pressing with metal rolls or resin rolls. Further, by setting the temperature and clearance of rolls for roll-pressing to an arbitrary temperature and pressing the sheet, a porous body having an arbitrary density can be obtained.

[Molded body]
The molded body of the present embodiment is preferably obtained by hot-press molding the porous body described above. The porous body can be hot-pressed at any pressure and temperature according to the desired density of the molded body. In addition, the porous body may be used singly, or may be laminated so that the molded body has a desired thickness, and the thickness of the molded body is adjusted by adjusting the number of layers. can do. In the molded article, pulp fibers are retained as pulp fibers, and the molded article is a pulp fiber-containing molded article.
Part or all of the synthetic resin contained in the porous body may be melted by controlling the heating temperature and heating time in the molding process.

<Hot press molding>
The molded body is preferably a hot-press molded body obtained by a step of hot-press molding a porous body. Part of the synthetic resin contained in the porous body may be melted by performing hot press molding, and it is preferable to perform hot press molding so as to obtain a desired density. In hot press molding, the pulp fibers and synthetic fibers in the porous body are maintained in a uniform mixed state in which the orientation is suppressed, and a molded body in which the pulp fibers are extremely uniformly dispersed can be obtained.

The step of hot press molding is a step of heating and pressurizing the porous body. It is preferable to heat the porous body to 100° C. or higher and pressurize it to 2 MPa or higher.
The heating temperature in the step of hot press molding is preferably 100° C. or higher, but is preferably adjusted appropriately according to the type of synthetic resin contained in the porous body. Specifically, it is preferable to perform heating within a range of ±20° C. of the melting point of the synthetic resin contained in the porous body. By heating within such a temperature range, it is possible to suppress the thermal decomposition of the pulp fibers contained in the porous body (decomposition of hemicellulose), and obtain a molded body having a more excellent bending elastic gradient and strength. be able to.
The pressure conditions in the step of hot press molding are preferably 2 MPa or more, more preferably 3 MPa or more, and preferably 25 MPa or less, from the viewpoint of obtaining a molded body excellent in bending elastic gradient and strength, and from the viewpoint of reducing the energy load. It is preferably 15 MPa or less, more preferably 10 MPa or less.
Further, the rate of temperature increase until the desired holding temperature is reached is preferably 3° C./min or more and 30° C./min or less, and the holding time under the desired heating and pressurizing conditions is preferably 1 minute or more and 30 minutes or less. After that, it is preferable to set the cooling rate to 3° C./min or more and 20° C./min or less while maintaining the pressure up to the temperature at which the compact is taken out.
In addition, before obtaining the above heating and pressurizing conditions, a preliminary pressing step may be performed, and after preliminary pressing is performed at a lower pressure under the desired heating conditions, the pressure is increased, and hot pressing is performed. It is also preferable to carry out a process.

As a method of hot press molding, among various hot press molding methods, autoclave method, which is often used when producing molded body members such as large aircraft, and mold press, which has a relatively simple process. method is preferred. The autoclave method is preferable from the viewpoint of obtaining a high-quality molded article with few voids.

In the step of hot press molding, hot press molding may be performed multiple times for the purpose of preventing defects such as breakage due to insufficient elongation of pulp fibers and synthetic fibers. As a result, it is possible to obtain a molded article having a more excellent bending elastic gradient and strength.

[Characteristics of molded body]
The density of the compact of this embodiment is 0.1 g/cm ³ or more and 0.8 g/cm ³ or less. By setting the density of the molded body within the above range, it is possible to obtain appropriate rigidity while maintaining the sound absorbing performance, which is preferable.
The density of the molded body is preferably 0.10 g/cm ³ or more, more preferably 0.13 g/cm ³ or more, still more preferably 0.15 g/cm ³ or more, and preferably 0.60 g/cm ³ . Below, more preferably 0.50 g/cm ³ or less, still more preferably 0.40 g/cm ³ or less.
The density of the molded body is measured by the method described in Examples.

The thickness of the molded body is not particularly limited, but is preferably 1 mm or more, more preferably 1.5 mm or more, still more preferably 2 mm or more, and preferably 50 mm or less, more preferably 50 mm or more, from the viewpoint of sound absorption performance and rigidity. 20 mm or less, more preferably 10 mm or less.
The thickness of the molded body is measured by the method described in Examples.

Although the basis weight of the molded article is not particularly limited, it is preferably 100 g/m ² or more, more preferably 300 g/m ² or more, and still more preferably 500 g/m ^{2 or} more from the viewpoint of sound absorption performance and rigidity, and It is preferably 6,000 g/m ² or less, more preferably 4,000 g/m ² or less, still more preferably 3,000 g/m ² or less, and even more preferably 1,500 g/m ² or less.
When the basis weight is within the above range, it is preferable because the molded article is lightweight, excellent in sound absorption, and has appropriate rigidity.
The basis weight of the molded article is measured by the method described in Examples.

The male compact of the present embodiment has a flexural elastic gradient of 0.5 N/cm or more from the viewpoint that it preferably has appropriate rigidity.
The bending elastic gradient is preferably 1.0 N/cm or more, more preferably 5.0 N/cm or more, still more preferably 20 N/cm or more, still more preferably 50 N/cm or more, particularly preferably 100 N/cm or more, and most preferably 1.0 N/cm or more. It is preferably 300 N/cm or more, and preferably 5000 N/cm or less, more preferably 3000 N/cm or less, still more preferably 1000 N/cm or less from the viewpoint of maintaining sound absorption performance.
When the flexural elastic gradient is within the above range, bending is suppressed when fixing or assembling the molded article, and handling and workability are improved.
The bending elastic gradient is measured by the method described in Examples.

The molded article of the present embodiment preferably has an appropriate flexural modulus. By having an appropriate flexural modulus, the molded article has excellent bending rigidity while maintaining sound absorption performance. preferable.
The flexural modulus of the molded article is preferably 0.001 GPa or more, more preferably 0.003 GPa or more, still more preferably 0.01 GPa or more, and even more preferably 0.1 GPa or more. Although the upper limit is not particularly limited, it is preferably 1.5 GPa or less, more preferably 1.0 GPa or less from the viewpoint of maintaining the sound absorbing performance.
The flexural modulus of the molded article is measured according to JIS K 7171:2016.

The molded article of the present embodiment preferably has sound absorption properties, and the normal incident sound absorption coefficient at a frequency of 2 kHz is preferably 5% or more, more preferably 10% or more, still more preferably 20% or more, and even more preferably 30%. % or more, and the upper limit is not particularly limited, but is preferably 80% or less, more preferably 70% or less, and still more preferably 65% or less from the viewpoint of imparting appropriate rigidity to the molded article.

(Application)
The molded article of this embodiment is suitably used as a sound absorbing material. That is, the sound absorbing material of this embodiment uses the molded article of this embodiment.
The sound absorbing material can be used in various applications in which conventional sound absorbing materials have been used. is suitable for

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

(Example 1)
<Preparation of nonwoven fabric>
NBKP was defibrated using a swirl-type jet stream defibrator to obtain defibrated dry pulp. The processing wind speed in the defibrator was 45 m/min, and the flow was turbulent with a baffle provided in the apparatus. The obtained defibrated dry pulp (pulp fiber) had an average fiber length of 2.38 mm, an average fiber width of 34.3 μm, and a fine fiber ratio of 11.4%.

Next, the obtained defibrated dry pulp, polypropylene fiber (melting point 160 ° C., fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm), polyethylene / polypropylene composite core-sheath fiber (core melting point 160 ° C., sheath melting point 110° C., fineness of 1.7 dtex, fiber length of 5 mm, fiber diameter of 15 μm) were uniformly mixed with an air stream at a ratio (mass ratio) of 70/15/15 to obtain a fiber mixture.

Next, using the web forming apparatus 1 shown in FIG. 1, an airlaid web was formed from the fiber mixture. Specifically, the first carrier sheet 41 was let out by the first carrier sheet supplying means 40 onto the air-permeable endless belt 20 mounted on the conveyor 10 and running. In Example 1, a tissue (basis weight: 14 g/m ² ) was used as the first carrier sheet 41 . The “basis weight” was measured in accordance with “Paper and paperboard—Method for measuring basis weight” described in JIS P8124:2011.

While sucking the air-permeable endless belt 20 with the suction box 60, the fiber mixture was dropped and accumulated on the first carrier sheet 41 from the fiber mixture supplying means 30 together with an air flow to obtain a cotton-like nonwoven fabric. At that time, the fiber mixture was supplied so that the basis weight of the airlaid web portion was 600 g/m ² .

Next, a second carrier sheet 51 was laminated on the cotton-like fiber assembly on the first carrier sheet 41 by a second carrier sheet supplying means 50 to obtain an airlaid web-containing laminated sheet. In Example 1, a tissue (basis weight: 14 g/m ² ) was used as the second carrier sheet 51 . That is, in Example 1, the same sheet was used for the first carrier sheet 41 and the second carrier sheet 51 .

The air-laid web-containing laminated sheet thus obtained was passed through a box-type drier of a hot air circulation conveyor oven system and subjected to hot air treatment at a temperature of 140°C. Thereafter, the density was adjusted to 0.06 g/cm ³ by roll pressing, and the first carrier sheet and the second carrier sheet were separated to obtain a nonwoven fabric having a basis weight of 600 g/m ² . . The nonwoven fabric had a T/Y of 1.18, a density of 0.062 g/cm ³ and a thickness of 10 mm.

<Preparation of compact>
The nonwoven fabric was cut into pieces of 20 cm×20 cm to obtain two cut pieces. The obtained cut pieces were piled up to produce a two-layer laminated structure. Next, the laminated structure was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 2.5 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 1130 g/m ² and a density of 0.45 g/cm ³ . It should be noted that the heat press molding may cause the non-woven fabric to slightly expand and contract in the vertical and horizontal directions, and the basis weight of the molded product may vary from the basis weight of the non-woven fabric.

(Example 2)
In the <preparation of molded article> of Example 1, four cut pieces were obtained, and the obtained cut pieces were stacked to prepare a four-layer laminated structure. Next, the laminated structure was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 5.0 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 2200 g/m ² and a density of 0.44 g/cm ³ .

(Example 3)
In <Preparation of compact> in Example 1, 6 cut pieces were obtained, and the obtained cut pieces were stacked to prepare a 6-layer laminated structure. Next, the laminated structure was placed in a stainless steel mold having an opening of 20 cm×20 cm and 8 mm in depth. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 3600 g/m ² and a density of 0.44 g/cm ³ .

(Example 4)
In <Preparation of Molded Body> in Example 1, one cut piece was obtained and a molded body was prepared with a single layer. The nonwoven fabric was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 2.5 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 660 g/m ² and a density of 0.26 g/cm ³ .

(Example 5)
In <preparation of compact> of Example 1, the laminated structure was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 5.0 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 1200 g/m ² and a density of 0.25 g/cm ³ .

(Example 6)
In <Preparation of compact> in Example 1, three cut pieces were obtained, and a compact was prepared with a three-layer laminated structure. The nonwoven fabric was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 8.0 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 2000 g/m ² and a density of 0.25 g/cm ³ .

(Example 7)
In <Preparation of nonwoven fabric> in Example 1, defibrated dry pulp, polypropylene fiber (melting point 160 ° C., fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm), and polyethylene / polypropylene composite core-sheath fiber (core melting point 160° C., sheath melting point 110° C., fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm) were uniformly mixed by an air flow at a ratio (mass ratio) of 60/20/20 to obtain a fiber mixture. Except for that, a nonwoven fabric was obtained in the same manner.
After that, in <Preparation of Molded Body>, 6 cut pieces were obtained, and the obtained cut pieces were stacked to prepare a 6-layer laminate structure. Next, the laminated structure was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 8.0 mm. Next, the mold was set in a hot press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 3400 g/m ² and a density of 0.42 g/cm ³ .

(Example 8)
In <Preparation of nonwoven fabric> in Example 7, defibrated dry pulp, polypropylene fiber (melting point 160 ° C., fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm), and polyethylene / polypropylene composite core-sheath fiber (core melting point 160° C., sheath melting point 110° C., fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm) were uniformly mixed by an air flow at a ratio (mass ratio) of 50/25/25 to obtain a fiber mixture. Except for that, a nonwoven fabric was obtained in the same manner.
Thereafter, in the same manner as in Example 7, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 3600 g/m ² and a density of 0.44 g/cm ³ .

(Example 9)
In <Preparation of nonwoven fabric> in Example 8, defibrated dry pulp, polypropylene fiber (melting point 160 ° C., fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm), and polyethylene / polypropylene composite core-sheath fiber (core melting point 160° C., sheath melting point 110° C., fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm) were uniformly mixed by an air flow at a ratio (mass ratio) of 30/35/35 to obtain a fiber mixture. Except for that, a nonwoven fabric was obtained in the same manner.
Thereafter, in the same manner as in Example 8, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 4100 g/m ² and a density of 0.51 g/cm ³ .

(Example 10)
A nonwoven fabric was obtained in the same manner as in Example 9.
Thereafter, in the same manner as in Example 1, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 1320 g/m ² and a density of 0.53 g/cm ³ .

(Example 11)
A nonwoven fabric was obtained in the same manner as in Example 9.
Thereafter, in the same manner as in Example 5, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 1630 g/m ² and a density of 0.33 g/cm ³ .

(Example 12)
A nonwoven fabric was obtained in the same manner as in Example 9.
Then, in <Preparation of Molded Body>, two cut pieces were obtained, and a molded body was prepared with a two-layer laminated structure. The nonwoven fabric was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 8.0 mm. Next, the mold was set in a heat press, preliminarily pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 5 MPa for 15 minutes. After that, it was cooled while maintaining 5 MPa to obtain a molded article containing pulp fibers. The pulp fiber-containing compact had a basis weight of 1900 g/m ² and a density of 0.24 g/cm ³ .

(Example 13)
A nonwoven fabric was obtained in the same manner as in Example 9.
Thereafter, in the same manner as in Example 4, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 550 g/m ² and a density of 0.21 g/cm ³ .

(Example 14)
A nonwoven fabric was obtained in the same manner as in Example 8.
Then, in the same manner as in Example 11, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 1250 g/m ² and a density of 0.25 g/cm ³ .

(Example 15)
A nonwoven fabric was obtained in the same manner as in Example 8.
Thereafter, in the same manner as in Example 12, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 1360 g/m ² and a density of 0.17 g/cm ³ .

(Example 16)
In <Preparation of nonwoven fabric> in Example 8, defibrated dry pulp, polypropylene fiber (melting point 160 ° C., fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm), and polyethylene / polypropylene composite core-sheath fiber (core melting point 160° C., sheath melting point 110° C., fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm) were uniformly mixed by an air flow at a ratio (mass ratio) of 20/40/40 to obtain a fiber mixture. Except for that, a nonwoven fabric was obtained in the same manner.
Thereafter, in the same manner as in Example 14, a molded body containing pulp fibers was obtained. The pulp fiber-containing compact had a basis weight of 1600 g/m ² and a density of 0.32 g/cm ³ .

(Comparative example 1)
A nonwoven fabric was obtained in the same manner as in Example 1.
After that, in <Preparation of Molded Body>, 5 cut pieces were obtained, and the obtained cut pieces were stacked to prepare a 6-layer laminated structure. Next, the laminated structure was placed in a stainless steel mold having an opening of 20 cm x 20 cm and a depth of 3.0 mm. Next, the mold was set in a hot press, pre-pressed at a temperature of 180° C. and a pressure of 1.5 MPa for 5 minutes, and further pressurized to 10 MPa for 15 minutes. After that, it was cooled while maintaining 10 MPa to obtain a molded body containing pulp fibers. The pulp fiber-containing compact had a basis weight of 3600 g/m ² and a density of 1.2 g/cm ³ .

(Comparative example 2)
In <Preparation of Nonwoven Fabric> of Example 1, the air-laid web-containing laminated sheet obtained was passed through a box-type dryer of a hot air circulation conveyor oven system, subjected to hot air treatment at a temperature of 140° C., and then roll-pressed to a density of 0.0. The density was adjusted to 06 g/cm ³ and the first carrier sheet and the second carrier sheet were separated to obtain a nonwoven fabric with a basis weight of 600 g/m ² . The nonwoven fabric had a T/Y of 1.18, a density of 0.06 g/cm ³ and a thickness of 10.0 mm.

(Comparative Example 3)
<Production of porous body>
A porous body comprising a middle layer using pulp fibers as raw material fibers and surface layers on both sides of the middle layer was produced as follows.
A spunbonded nonwoven fabric (basis weight: 40 g/m ² ) is fed out as a surface layer A onto a mesh conveyor having a suction box, and 5 g/m ² of polyethylene powder (powder adhesive) is applied onto the surface layer A with a spray device. Then, NBKP and polyethylene / polypropylene composite core-sheath fiber (core melting point 160 ° C., sheath melting point 110 ° C., fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm) were mixed at a ratio of 70/30 ( (mass ratio)), and an air-laid web (intermediate layer, basis weight: 910 g/m ² ) was formed on the surface layer A using a dry air-laid web forming apparatus.
Next, on the airlaid web, the same powder adhesive as that used previously was sprayed with a layered spraying device at 5 g/m ² , and further a rayon PET spunlace (basis weight 40 g / m ² ) were fed out in a layered manner, led to a hot air dryer, and heated to a temperature higher than the melting point of the sheath so as to melt the sheath of the heat-fusible fiber. As a result, the laminate S was formed by adhering the surface layers to both surfaces of the airlaid web. After that, the laminate S was further passed through press rolls to obtain a porous body.

<Adhesion of film layer to porous body>
A hot-melt adhesive is applied to one side of a polyethylene film (basis weight 20 g/m ² , tensile elongation in the MD direction: 250%, air permeability: 440 sec/100 cc, thickness: 20 μm, density: 1 g/cm ³ ). It was applied in an amount of 5 g/m ² to form an adhesive layer. The film and the porous body were pasted together so that the adhesive layer and the porous body were in contact with each other, and the film and the porous body were bonded together by a hot-melt method. Next, on the film surface, slits each having a length of 100 mm and a width of 0.5 mm were made so as to penetrate to the adhesive layer, and the ratio of the total slit area to the area of the film surface, that is, the area of the film surface The opening area ratio (hereinafter, also referred to as “slit ratio”) of 0.8% and all the slits were formed in the same direction to obtain a molded body.

[Measurement/evaluation method]
(Method for measuring fiber length and fiber diameter of synthetic fiber)
Twenty randomly selected synthetic fibers were observed with an optical microscope to measure the fiber length and fiber diameter.

(Measuring method of average fiber length, average fiber diameter, and fine fiber ratio of pulp fiber)
According to ISO16065-2, the average fiber length and average fiber diameter of the pulp fibers were measured using a fiber image analyzer (Valmet FS5, manufactured by Valmet Co., Ltd.). Also, the proportion of fine fibers of 0.1 mm or less in the measured length-weighted average fiber length distribution was defined as the fine fiber ratio.

(Method for measuring the melting point of synthetic fibers)
5 mg of the synthetic fiber is cut out, and the melting point of the synthetic fiber is measured with a differential scanning calorimeter (DSC). The melting point is measured by increasing the temperature from 30° C. to 280° C. at a rate of 20° C./min under a nitrogen atmosphere using a Diamond DSC manufactured by Perkin-Elmer.
If there are catalog values for synthetic fibers, etc., the catalog values may be adopted.

(Basis weight of non-woven fabric, and method for measuring thickness, basis weight and density of molded body)
The basis weight of the non-woven fabric was measured according to "Paper and paperboard - Method for measuring basis weight" described in JIS P8124:2011.
The density of the molded article was calculated by measuring the thickness and mass after conditioning the humidity of the 50 mm square molded article under conditions of 23° C. and 50% RH for 24 hours. The thickness of the molded body was measured with a digital thickness gauge (DG-127 manufactured by Ozaki Seisakusho Co., Ltd.).

(T/Y measurement method)
The flow direction (running direction of the conveyor 10) in the manufacturing process of the obtained nonwoven fabric is the first direction, the direction perpendicular to the first direction is the second direction, and the tensile strength ( The unit is N/m). The tensile strength in each direction was calculated by dividing this tensile strength by the thickness of the test piece (unit: MPa). As a tensile tester, Tensilon manufactured by A&D Co., Ltd. was used to measure a strip of 15 mm×180 mm at a speed of 20 mm/min.
Assuming that the tensile strength in the first direction is T and the tensile strength in the second direction perpendicular to the first direction is Y, T/Y was calculated.

<Evaluation>
The flexural modulus, flexural elastic gradient, and sound absorption coefficient of the obtained molded article were measured by the following methods. Table 1 shows the results.

(Method for measuring flexural modulus and flexural elastic gradient of molded product)
The resulting molded product was cut into a strip-shaped test piece of 80 mm length×10 mm width, and subjected to a three-point bending test according to JIS K 7171:2016. For the obtained flexural modulus and flexural elastic gradient, the larger the values, the better the rigidity against bending.

(Method for measuring vertical incident sound absorption coefficient of compact)
The obtained compact was cut into a circular test piece with a diameter of 29 mm, and the normal incident sound absorption coefficient in the high frequency range (500 to 6300 Hz) was measured according to JIS A 1405-2:2007. Table 1 shows normal incident sound absorption coefficients at 2000 Hz. It was evaluated that the higher the normal incident sound absorption coefficient obtained, the better the sound absorption performance.

As shown in Examples 1 to 16, the molded articles of the present invention had appropriate rigidity while maintaining sound absorbing performance.
On the other hand, the molded article of Comparative Example 1, in which the density of the molded article exceeded 0.8 g/cm ³ , did not provide sufficient sound absorbing performance. The molded article of Comparative Example 2, which had a density of less than 0.1 g/cm ³ and a gradient of flexural elasticity of less than 0.5 N/cm, did not have sufficient rigidity. Furthermore, the molded article of Comparative Example 3, which had a density of less than 0.1 g/m ² , did not have sufficient rigidity.

1 Web Forming Device 10 Conveyor 20 Permeable Endless Belt 30 Fiber Mixture Feeding Means 40 First Carrier Sheet Feeding Means 41 First Carrier Sheet 50 Second Carrier Sheet Feeding Means 51 Second Carrier Sheet A Airlaid Web

Claims (9)

A molded body containing pulp fibers and a synthetic resin,
The molded body has a density of 0.1 g/cm ³ or more and 0.8 g/cm ³ or less,
The molded article has a bending elastic gradient of 0.5 N/cm or more.
molding. The molded article according to claim 1, wherein the molded article has a thickness of 2 mm or more and 20 mm or less. The molded article according to claim 1 or 2, wherein the molded article has a basis weight of 500 g/m ² or more and 4000 g/m ² or less. The molded article according to any one of claims 1 to 3, wherein the molded article has a normal incident sound absorption coefficient of 5% or more at a frequency of 2 kHz. The molded article according to any one of claims 1 to 4, wherein the synthetic resin is polyolefin. The molded article according to any one of claims 1 to 5, wherein the synthetic resin contains synthetic fibers. The molded article according to any one of claims 1 to 6, wherein the mass ratio of the synthetic resin to the pulp fibers in the molded article (synthetic resin/pulp fiber) is 10/90 or more and 95/5 or less. A sound absorbing material comprising the molded article according to any one of claims 1 to 7. A method for producing a molded article according to any one of claims 1 to 7, comprising the following steps 1 and 2 in this order.
Step 1: Step of preparing a porous body containing pulp fibers and synthetic resin Step 2: Step of hot-pressing the porous body