JP7212246B2 - SOUND ABSORBING MATERIAL AND PRODUCTION METHOD THEREOF - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material and its manufacturing method, and more particularly to a sound absorbing material including a fiber mass composed of crimped fibers and an elastic resin and a binder, and a manufacturing method thereof.

Conventionally, sound absorbing materials have been used in various fields, and such sound absorbing materials have various modes according to their uses. For example, as a sound absorbing material used in automobiles and houses, a sound absorbing material made of a composite nonwoven fabric obtained by laminating and integrating an organic fiber nonwoven fabric and a melt blown nonwoven fabric made of organic fibers having a fineness of 0.5 dtex or less (Patent Document 1), A sound absorbing material is known in which a resin film is laminated on a substrate in which resin particles are bound by a binder (Patent Document 2).

JP 2009-184296 A JP-A-2008-32977

However, the sound absorbing material in which the nonwoven fabric is laminated as in Patent Document 1 has good sound absorbing performance in a high frequency range, for example, 2000 to 5000 Hz, but in order to ensure sound absorbing performance in a low frequency range, the sound absorbing material must be thick. Therefore, there was a limit to use in automobiles and the like with limited space.
In addition, the sound absorbing material of Patent Document 2 is composed only of a cell skeleton obtained by removing the cell membrane from the porous resin particles. There was a problem of hoarding.
As described above, sound absorbing materials are used in various places and are required to have various performances, and sound absorbing materials with various modes and performances are still in demand. A sound absorbing material and a manufacturing method thereof are provided.

That is, the sound absorbing material according to the invention of claim 1 is a sound absorbing material containing a fiber mass composed of crimped fibers and an elastic resin, wherein the fiber mass includes a plurality of fine particles inside the crimped fiber. It is characterized in that it is formed by entering and holding an elastic resin, the fineness of the fibers is 1 to 50 dtex, and the diameter of the fiber mass is 25 to 300 μm.
In a method for manufacturing a sound absorbing material according to the invention of claim 5, the fiber clumps constituting the sound absorbing material according to any one of claims 1 to 4 are moved at a speed of 0.5 to 15 m/min. The non-woven fabric sheet impregnated with polyurethane resin is recovered by contacting it with a grinding sheet having a coarseness of 50 to 300 and rotating at a rotation speed of 1000 to 3000 rpm and grinding it.

The fiber mass contained in the sound absorbing material according to the present invention is formed by a plurality of fine elastic resins entering and being held inside crimped fibers .
For this reason, the sound incident on the sound absorbing material penetrates into the gaps between the fibers and the elastic resin, and part of the sound energy is converted into heat energy by friction and viscous resistance and is absorbed. The elastic resin particles held by the crimped and entangled fibers vibrate, converting sound energy into vibrations. Thereby, good sound absorption performance can be obtained.
In addition, since the fiber clumps are excellent in compressive deformability due to the fibers tangled in a ball shape, when the sound absorbing material is compressed, only the compressed fiber clumps are compressed and deformed, and the continuous foam body absorbs sound. An effect is also obtained in that the effect of strain due to compression is less likely to spread over a wider area than in the case of creating a material.

Enlarged photograph of the sound absorbing material according to the present embodiment Enlarged photo of fiber mass Enlarged photo of porous resin particles Configuration diagram of sampling device Enlarged photo of polyurethane sheet Graph showing experimental results on sound absorption performance Graph showing experimental results on sound insulation performance

FIG. 1 shows a 100-fold enlarged photograph of a sound absorbing material 1 according to the present invention. It has a configuration bonded by a binder.
As shown in the 100-fold enlarged photograph shown in FIG. 2, the fiber mass 2 is in the form of a mass with a diameter of about 25 to 300 μm, in which fine elastic resin 2b enters between fibers 2a that are tangled in a ball shape. .
The porous resin particles 3, as shown in the 500-fold enlarged photograph shown in FIG. is formed with an aperture having a minimum Feret diameter of 1 to 10 μm, and a plurality of protrusions 3a are formed.
Regarding the ratio of the fiber clumps 2 and the porous resin particles 3, the fiber clumps 2 can be set at a ratio of 20 to 60% by mass with respect to the total mass of the fiber clumps 2 and the porous resin particles 3.
Here, since the fiber clumps 2 have a higher rigidity than the porous resin particles 3, and the fiber clumps 2 play a role as an aggregate, by increasing the ratio of the fiber clumps 2, the rigidity of the sound absorbing material 1 is increased. , the sound absorption coefficient can be improved.

FIG. 4 shows a collecting device 11 for collecting the fiber clumps 2 and the porous resin particles 3, comprising a supply roller 12 for supplying the sheet S, a buff roller 13 for grinding the surface of the sheet S, and It is composed of a recovery box 14 for recovering generated particles and a recovery roller 15 for recovering the sheet S after grinding.
Around the supply roller 12 is wound a sheet S made of resin-impregnated nonwoven fabric for collecting the fiber lumps 2 or a sheet S made of porous polyurethane for collecting the porous resin particles 3 .
The sheet S is moved at a predetermined speed by winding the sheet S by the collection roller 15 while feeding the sheet S from the supply roller 12 .
Between the supply roller 12 and the recovery roller 15, a holding roller 16 is provided at a position opposed to the buff roller 13, and the sheet S passes between the buff roller 13 and the holding roller 16, It is ground by the buff roller 13 .
Sandpaper having a required roughness is attached to the outer periphery of the buff roller 13, and the surface of the sheet S is ground by pressing the buff roller 13 against the sheet S while rotating. The fiber clumps 2 and the porous resin particles 3 are recovered in the recovery box 14 .

The resin-impregnated nonwoven fabric used for collecting the fiber mass 2 has a structure in which a nonwoven fabric such as polyester fiber is impregnated with a polyurethane resin, and the nonwoven fabric is impregnated with a polyurethane resin using a conventionally known method. can use things.
The fibers used for the nonwoven fabric are not particularly limited, and may be nonwoven fabrics produced from natural fibers (including modified fibers), synthetic fibers, and the like. For example, resin fibers such as polyester fibers, polyamide fibers, and acrylic fibers, and natural fibers such as cotton and hemp may be used. Considering the prevention of swelling of the raw material fibers due to the absorption of washing liquids such as organic solvents and water, and the mass productivity of the raw material fibers, use resin fibers such as polyester fibers that do not have water absorption (liquid) properties. is preferred. It is preferable to use fibers having a fineness of 1 to 50 dtex and a fiber length of 20 to 100 mm as raw material fibers.

Methods for producing nonwoven fabrics include needle punching, thermal bonding, chemical bonding, water entanglement, melt blowing, and combinations thereof.
Among these, in the present invention, the needle punch method is preferably used to produce the fiber substrate. When a fiber substrate is produced using the needle punch method, the fibers are not fixed by an adhesive resin or fusion fiber but are mechanically entangled, so the fibers are easily pulled out and the fiber mass 2 is easily formed.
If the thickness of the non-woven fabric substrate is less than 1.5 mm, movement of the polyurethane resin in the thickness direction (resin migration) occurs during drying after impregnation with the polyurethane resin solution, and the coating thickness of the polyurethane resin tends to be uneven. , the polyurethane resin solution cannot permeate into the interior of the nonwoven fabric substrate, so the range is preferably 1.5 to 5.0 mm.
If the density of the non-woven fabric substrate is less than 0.1 g/cm ^{3 ,} the polyurethane resin flows out through the interstices of the fibers and hardly adheres to the fibers even when impregnated with the polyurethane resin solution. Since the adhesion amount increases and closes the gaps between the fibers, the range of 0.1 to 0.2 g/cm ³ is preferable.
In this example, polyester fibers having a fineness of 2 to 3 dtex and a fiber length of 51 mm are used. The resin layer is formed by cross-linking a polyurethane resin formed by a wet coagulation method with a polyvalent isocyanate compound (cross-linking agent) having two or more isocyanate groups in the molecule.

As the polyurethane resin, a polyester-based, polyether-based, polycarbonate-based resin or the like having a 100% modulus (tension when pulled to double length) of 1 to 50 MPa or less is used.
The polyurethane resin used in the resin impregnation step is mixed with the polyvalent isocyanate compound and dissolved in the organic solvent DMF. At this time, if the solid content concentration of the polyurethane resin in the polyurethane resin solution is less than 10% by weight, it becomes difficult to adjust the density of the nonwoven fabric to the target value, and if it exceeds 40% by weight, the polyurethane resin becomes difficult to dissolve.
The viscosity of the polyurethane resin solution measured at 20° C. using a B-type rotational viscometer is preferably 8000 cp or less, more preferably 100 cp to 5000 cp, and even more preferably 400 cp to 3000 cp.
Therefore, the polyurethane resin solution in the impregnation step preferably has a concentration in the range of 10 to 40% by weight and a viscosity in the range of 100 to 5000 cp. Moreover, the solid content concentration of the polyvalent isocyanate compound is used within the range of 1 to 4% by weight.

After the nonwoven fabric base material is immersed in the polyurethane resin solution, a pair of pressurizable mangle rollers are used to squeeze off excess polyurethane resin solution, and the nonwoven fabric base material is impregnated substantially uniformly. In the impregnated nonwoven fabric substrate, the surfaces of the polyester fibers are covered with the polyurethane resin and the polyvalent isocyanate compound.
At this time, the temperature of the polyurethane resin solution is preferably adjusted in the range of 5 to 40.degree. C., more preferably in the range of 20 to 30.degree. By performing the impregnation step within this temperature range, the progress of the cross-linking reaction by the polyvalent isocyanate compound is suppressed.

In the coagulation regeneration step, the non-woven fabric impregnated with the resin is coagulated and regenerated with the polyurethane resin in an aqueous coagulation liquid containing water, which is a poor solvent for the polyurethane resin, as a main component. In the water-based coagulating liquid, replacement of the DMF with the coagulating liquid progresses from the surface of the polyurethane resin solution adhering to the polyester fibers, whereby the polyurethane resin is coagulated and regenerated on the surfaces of the polyester fibers.
As long as the fibers constituting the fiber substrate are not eluted, the temperature of the coagulation liquid and the immersion time are not particularly limited. ) should be immersed.

In the washing/drying step, the nonwoven fabric obtained by coagulating and regenerating the polyurethane resin on the surface of the polyester fiber is immersed in a washing liquid such as water to remove DMF and the like remaining in the nonwoven fabric. After washing, the nonwoven fabric is pulled up from the washing solution, and excess washing solution is squeezed off with a mangle roller. After that, for example, the nonwoven fabric is dried in a dryer at 60 to 120° C. for about 10 to 500 minutes.

The density of the obtained resin-impregnated nonwoven fabric is preferably in the range of 0.20 to 1.00 g/cm ³ and more preferably in the range of 0.25 to 0.65 g/cm ³ . When the density of the resin-impregnated nonwoven fabric is within the above range, the sound absorption performance can be improved because the resin-impregnated nonwoven fabric has an appropriate porosity.

When collecting the fiber mass 2 from the resin-impregnated nonwoven fabric sheet S by the collection device 11, the feeding speed of the sheet S by the supply roller 12 is set in the range of 0.5 to 15 m/min, and the buff roller 13 is preferably Sandpaper with a roughness of 50 to 300, more preferably 80 to 240 is attached, and the buff roller 13 is pressed against the sheet S while rotating the buff roller 13 at a rotation speed of 1000 to 3000 rpm. rice field.
When the buff roller 13 comes into contact with the surface of the resin-impregnated nonwoven fabric sheet S while rotating, the fibers 2a constituting the nonwoven fabric are pulled out from the surface of the resin-impregnated nonwoven fabric due to friction with the buff roller 13, and the pulled out fibers 2a are crimped into threads. Tangle into balls.
At that time, the elastic resin impregnated in the resin-impregnated nonwoven fabric sheet S is torn off from the surrounding resin as the fibers 2a are pulled out, and then the fibers 2a are crimped and entangled, causing the fibers 2a to become entangled. It will be taken inside.
After that, the friction of the buff roller 13 further acts to break the root portion of the fibers 2a that are crimped and entangled in a ball-like shape, and the fine elastic resin 2b is incorporated into the ball-like entangled fibers 2a. The fiber clumps 2 are separated from each other. At this time, some of the elastic resin 2b adheres to the fibers 2a, and some does not adhere to the fibers 2a but is taken in and held in the fibers 2a that are tangled in a bead shape.

The fiber clumps 2 separated from the resin-impregnated nonwoven fabric sheet S in this manner have a diameter of 25 to 300 μm, more preferably 50 to 250 μm. The diameter of the fiber clump 2 is determined by detecting particles present in an arbitrary region of an image taken at 50x magnification with a scanning electron microscope (SEM) or a microscope, and averaging the equivalent circle diameters of the particles. Calculated. At this time, the single fibers extending from the fiber clump 2 are excluded from the measurement targets.

In the fiber clump 2, the elastic resin 2b is attached to the surface of the fiber 2a, or is not attached, but is wound around and held by the tangled fibers. The presence of the elastic resin 2b complicates the gaps between the fibers 2a and the fibers 2a, and when sound enters the gaps of the fiber mass 2, it is converted into heat energy by collision and friction. In addition, the elastic resin 2b held without adhering to the fibers 2a vibrates, converting sound energy into vibration. This makes it possible to obtain good sound absorption performance.
Furthermore, since the crimped fibers 2a constituting the fiber mass 2 are entangled in a ball shape and the fiber masses 2 are independent from each other, when a part of the sound absorbing material 1 is compressed, the compressed portion Only the fiber mass 2 is compressed and deformed, and the other fiber masses 2 are not affected.

Next, the polyurethane sheet S used for collecting the porous resin particles 3 has resin particles between the large pores, as shown in the photograph of the surface of the polyurethane sheet S enlarged 500 times shown in FIG. It has a large number of small pores of 1 to 10 μm in the wall, and has a communication structure in which the large and small pores communicate with other pores that are not open on the surface inside, and has a continuous foam structure that communicates like a mesh. are doing. Such a polyurethane sheet S can be manufactured using a conventionally known wet film-forming method.
The porous resin particles 3 obtained by grinding the polyurethane sheet S have pores with a minimum Feret diameter of 1 to 10 μm based on the small pores of the polyurethane sheet S, and the maximum Feret diameter of the pores is 1 to 10 μm. It has an elliptical pore with a diameter/minimum Feret diameter value of 1.5 to 5.0.

The maximum Feret diameter A of the porous resin particles 3 and the maximum Feret diameter _B1 and minimum Feret diameter B2 of the small pores present on the surface of the porous resin particles ₃ are obtained from scanning electron microscope (SEM) photographs. be able to.
As for the method of measuring the Feret diameter, an image file of the sound absorbing material observed with the SEM can be obtained using, for example, image analysis software ImageJ (registered trademark). The maximum Feret diameter is the diameter at which the distance between the parallel lines becomes the largest when the object is sandwiched between parallel lines. The Feret diameter was set to A.
On the other hand, the minimum Feret diameter is the diameter at which the distance between the parallel lines is the smallest when the object is sandwiched between parallel lines, and the maximum Feret diameter and the minimum Feret diameter of the pores of the porous resin particles at 30 points are measured. and their average values _were defined as the maximum Feret diameter _B1 and the minimum Feret diameter B2.

The polyurethane sheet S used in this example, which is manufactured using a conventionally known wet film-forming method, includes a preparatory step of preparing a polyurethane resin solution, continuous application of the polyurethane resin solution to a film-forming base material, and water-based coagulation. A sheet is produced through a coagulation and regeneration process in which the polyurethane resin is coagulated and regenerated in a liquid into a sheet, and a washing and drying process in which the coagulated and regenerated polyurethane resin is washed and dried. The order of steps will be described below.

In the preparation step, a polyurethane resin, a water-miscible organic solvent capable of dissolving the polyurethane resin, and additives are mixed to dissolve the polyurethane resin. Examples of the organic solvent include DMF and N,N-dimethylacetamide (DMAc). DMF is used in this example.
The polyurethane resin can be selected from among polyester, polyether, and polycarbonate resins. , a product name of Dainichiseika Kogyo Co., Ltd., ``Lesamine'', or the like, or a resin having desired properties may be produced by oneself.
This polyurethane resin is dissolved in DMF in a range of 20 to 40% by weight. In addition, as additives, in order to control the size and amount (number) of foaming and small foaming, pigments such as carbon black, hydrophilic additives that promote foaming, and hydrophobic additives that stabilize the regeneration of polyurethane resin. etc. can be used. In this example, carbon black is added at a rate of 0 to 30% by weight.

The polyurethane resin preferably has a 100% modulus of 1-40 MPa, more preferably a 100% modulus of 2-25 MPa. When the 100% modulus is within the above range, the polyurethane resin stretches when the surface of the sheet S is ground, and the pores are easily enlarged, and the voids in the porous resin particles 3 can be increased. The portion that is torn and broken tends to remain as the protrusion 3a.
The modulus is an index representing the hardness of the resin, and is the value obtained by dividing the load applied when a non-foamed resin sheet is stretched 100% (when stretched to twice its original length) by the cross-sectional area. (hereinafter sometimes referred to as 100% modulus). A higher value means that the resin is harder. When confirming the resin modulus from the sound absorbing material, the sound absorbing material is dissolved in DMF to obtain a low-concentration polyurethane resin DMF solution, and then the fibers, etc. are filtered through a filter, and the DMF is vaporized by a casting method to form a non-foamed resin sheet. It can be measured by forming.

In the coagulation regeneration step, the polyurethane resin solution obtained in the preparation step is coated substantially uniformly in a sheet form on the belt-shaped film-forming base material at room temperature using an applicator such as a knife coater.
At this time, the coating thickness (coating amount) of the polyurethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater or the like and the film-forming substrate. In this example, the coating thickness is adjusted so that the thickness of the urethane sheet after drying (thickness of the film) is in the range of 200 to 3000 μm.
Resin films, fabrics, non-woven fabrics, and the like can be used as the film-forming base material. In this example, a film made of polyethylene terephthalate (hereinafter abbreviated as PET) is used.

The polyurethane resin solution applied to the film-forming substrate is continuously guided into a coagulating liquid (aqueous coagulating liquid) containing water as a poor solvent for the polyurethane resin as a main component. Although an organic solvent such as DMF or a polar solvent other than DMF may be added to the coagulating liquid in order to adjust the regeneration rate of the polyurethane resin, water is used in this example.
In the coagulating liquid, a film is first formed on the interface between the polyurethane resin solution and the coagulating liquid, and countless micropores forming a skin layer are formed in the polyurethane resin in the immediate vicinity of the film. Thereafter, the diffusion of DMF in the polyurethane resin solution into the coagulating liquid and the infiltration of water into the polyurethane resin proceed in concert with the regeneration of the polyurethane resin having an open-cell structure.
At this time, water (coagulating liquid) does not permeate the PET film that serves as the film forming substrate, so replacement of DMF with water occurs on the skin layer side, and larger bubbles are formed on the film forming substrate side than on the skin layer side. .

Here, the formation of foam accompanying the regeneration of polyurethane resin will be described. After the film is formed in the coagulating liquid, the polyurethane resin has a large cohesive force, so regeneration proceeds rapidly in the polyurethane resin in the immediate vicinity of the film, forming a skin layer.
Therefore, after the skin layer is formed, the polyurethane resin in the polyurethane resin solution before solidification moves to the skin layer side and aggregates. As a result, the amount of polyurethane resin on the film-forming substrate side decreases, so that foams are formed that are larger on the film-forming substrate side than on the skin layer side.
By desolvating the DMF from the polyurethane resin solution, that is, by replacing the DMF with water, large bubbles are formed, and the micropores of the skin layer and the large and small bubbles communicate in a network.

In the washing/drying step, the polyurethane sheet S regenerated in the coagulating and regenerating step is washed in a washing liquid such as water to remove DMF remaining in the polyurethane resin, and then dried.
For drying the polyurethane resin, in this example, a cylinder dryer having a cylinder with a heat source inside is used. The polyurethane resin dries as it passes along the circumference of the cylinder. The dried polyurethane sheet S is wound into a roll.

When the porous resin particles 3 are collected from the polyurethane sheet S by the collecting device 11, the feeding speed of the sheet S by the supply roller 12 in the collecting device 11 is in the range of 0.5 to 15 m/min, The buff roller 13 is preferably equipped with sandpaper having a roughness of 100 to 350, more preferably 150 to 250, and the buff roller 13 is rotated at a rotation speed of 1000 to 3000 rpm. pressed against.
In this embodiment, sandpaper is used for the buff roller 13, but any one such as a diamond buff roller can be used as long as it can be uniformly processed (removed by grinding). The plurality of protrusions 3a can be obtained by adjusting the buff number, the feeding speed of the supply roller and the sheet, the number of revolutions of the buff roller, etc. according to the polyurethane resin modulus used for the polyurethane sheet.
When the buff roller 13 comes into contact with the surface of the polyurethane sheet S while rotating, a part of the polyurethane resin on the surface of the polyurethane sheet S is stretched by being pulled by friction with the buff roller 13, and the stretched portion becomes thinner and then breaks. do.
On the outer surface of the porous resin particles 3 separated from the polyurethane sheet S in this way, pores of 1 to 10 μm formed in the polyurethane resin are extended in a certain direction, and have a minimum Feret diameter of 1 to 10 μm. Porous resin particles 3 having substantially elliptical pores with a maximum Feret diameter of 1.5 to 5.0 relative to the minimum Feret diameter are formed.
Furthermore, in the porous resin particles 3 separated from the polyurethane sheet S, the broken portions are stretched and plastically deformed to form a plurality of pointed geometric projections 3a, and each projection 3a is also stretched. Some have approximately elliptical openings extending in one direction.
The projecting portion 3a vibrates when receiving sound energy, thereby converting the sound into vibration and generating a sound absorbing effect. Also, when sound enters the stretched openings, it receives collisions and friction inside, is converted into heat energy, and is absorbed.

Vinyl acetate resin emulsion adhesives can be used as the binder, and acrylic resin emulsion adhesives, ethylene-vinyl acetate resin emulsion adhesives, and urethane resin emulsion adhesives can also be used. In this example, the adhesive was diluted with water to 5.5% and used.
When the sound absorbing material 1 is produced by binding the fiber lumps 2 and the porous resin particles 3 using the binder, the fiber lumps 2 and the porous resin particles 3 are put into a mixer at a predetermined ratio, A binder is sprayed with a spray gun or the like while stirring these or while stirring the fiber lumps 2 and the porous resin particles 3 with a ball mill.
As a result, the surfaces of the fiber clumps 2 and the porous resin particles 3 are coated with the binder. After that, the fiber clumps 2 and the porous resin particles 3 to which the binder is attached are put into a mold, and then dried at a predetermined temperature for a predetermined time. Thus, the sound absorbing material 1 can be obtained.
Here, the amount of the binder used is preferably 0.5 to 50%, more preferably 1 to 15%, based on the weight of the fiber mass 2 and the porous resin particles 3. If the binder content is 50% or less, the gap between the fibers 2a and the elastic resin 2b in the fiber mass 2 is prevented from being blocked, and a sufficient sound absorbing effect can be obtained. The shape of the sound absorbing material 1 can be maintained due to the presence of this. Further, by setting the binder to the above range, only the compressed portion of the fiber lumps 2 is compressed and deformed, and the other fiber lumps 2 are not affected.

(action, etc.)
Next, the operation and the like of the sound absorbing material 1 of this embodiment will be described.

The sound absorbing material 1 of the present embodiment comprises fiber masses 2 in which fine elastic resin 2b is held in fibers 2a that are crimped and tangled in a bead shape, and porous resin particles 3 having a plurality of protrusions 3a on their surfaces. It is composed of
Therefore, the gaps between the fiber clumps 2 and the gaps between the fiber clumps 2 and the porous resin particles 3 form complex spaces, and when sound is incident on the sound absorbing material 1, friction is applied to the sound. designed to absorb energy.
In particular, since the fiber mass 2 has a structure in which the fine elastic resin 2b is held in the fibers 2a that are crimped and tangled in a bead shape, fine gaps are formed between the fibers 2a and the elastic resin 2b. is formed.
Therefore, when the sound incident on the sound absorbing material 1 is further incident on the fiber mass 2, it enters the complex voids formed by the fibers 2a and the elastic resin 2b, receives friction and viscous resistance, and is held without adhering to the fibers 2a. A part of the sound energy is converted into heat energy and absorbed by the fine elastic resin 2b that can vibrate.
In addition, the fiber lumps 2 are excellent in compressive deformability due to the fibers 2a entangled in a bead shape, and when the sound absorbing material 1 is compressed, only the compressed fiber lumps 2 are compressed and deformed to form a continuous foam body. Compared to the case where the sound absorbing material is prepared in , the effect of strain due to compression is less likely to spread over a wide area.
In other words, in a continuous foam body or a continuous fibrous body, the porosity is lowered to the vicinity of the compressed part and the sound absorption coefficient is lowered. Since the vicinity of the compressed portion is hardly affected by compression, the reduction in sound absorption coefficient is suppressed only in the compressed portion, and a high sound absorbing effect can be obtained according to the space in which the sound absorbing material 1 is arranged.

Furthermore, the sound absorbing material 1 of the present embodiment contains porous resin particles 3, and the porous resin particles 3 have a plurality of protrusions 3a on their surfaces, and are substantially elliptical with pores having a minimum Feret diameter of 1 to 10 μm. are formed. Pores are also formed inside the porous resin particles 3 and communicate with each other inside.
Therefore, the sound incident on the sound absorbing material 1 enters the inside of the pores of the porous resin particles 3 through the pores, and the energy of the sound is converted into heat energy by friction and vibration with the resin wall. Sound energy is absorbed.
At this time, the smaller the pores formed in the porous resin particles 3, the greater the friction and vibration with the resin walls, so that the sound energy is easily converted into heat energy, and the sound absorption performance is improved. In addition, the minimum Feret diameter of the pores contained in the porous resin particles 3 is 1 to 10 μm or less, and the pores have a communication structure that communicates with other pores that are not opened on the surface. Sound is easily absorbed.
The porous resin particles 3 have a plurality of protrusions 3a on the surface, and the protrusions 3a that are not fixed by the binder vibrate sensitively to sound, thereby absorbing sound energy. can.

The following experiments were performed on the sound absorbing material 1 of Examples 1 to 3 according to the present invention, which were prepared based on the above-described examples, and a conventionally known comparative sound absorbing material for comparison.
In the experiment, the normal incidence sound absorption coefficient was measured based on JIS A 1405-2 to confirm the sound absorption performance, and the normal incidence transmission loss was measured to confirm the sound insulation performance. A 4206S acoustic tester manufactured by Brüel & Kjær was used to measure the normal incidence sound absorption coefficient and normal incidence transmission loss.

The diameters of the fiber clumps 2 contained in the sound absorbing materials 1 according to Examples 1 to 3 were measured as follows.
Detect any 30 points of particles present in any area of an image taken at 50x with a scanning electron microscope (manufactured by JEOL Ltd., JMS-5500LV), determine their equivalent circle diameters, and take the average. to obtain the diameter of the fiber clump 2. At this time, single fibers extending from the fiber mass were excluded from the measurement targets.

The maximum Feret diameter A, the maximum Feret diameter B ₁ , and the minimum Feret diameter B ₂ of the porous resin particles 3 contained in the sound absorbing materials 1 according to Examples 1 to 3 were measured as follows.
For the Feret diameter, the sound absorbing material was observed with a scanning electron microscope (JMS-5500LV, manufactured by JEOL Ltd.) at a magnification of 100, and 30 arbitrary points of porous resin particles were extracted as samples for measurement.
After that, the extracted image is analyzed by image processing software ImageJ, the image is binarized, and the maximum Feret diameter A of the porous resin particles, the maximum Feret diameter B ₁ of pores existing on the surface of the porous resin particles, _The minimum Feret diameter B2 was measured.
The maximum Feret diameter A, the maximum Feret diameter B ₁ , and the minimum Feret diameter B ₂ are determined as average values of the maximum Feret diameter and the minimum Feret diameter at arbitrary 30 points. Also, the ratio of the maximum Feret diameter _B1 to the minimum Feret diameter B2 is obtained as the _average value of the values of maximum Feret diameter/minimum Feret diameter at arbitrary 30 points.

Example 1
The sound absorbing material 1 according to Example 1 contains 60 parts by mass of fiber lumps 2 and 40 parts by mass of porous resin particles 3, to which a vinyl acetate resin-based emulsion adhesive is diluted to a concentration of 11%. 50 parts by mass of binder was sprayed with a spray gun and mixed with a mixer.
Subsequently, the mixture is filled into a molded container of length 23 x width 23 x depth 2.0 cm, dried in a dryer at 80 ° C. for 4 hours, dried at 140 ° C. for 1 hour, and then cooled. A sound absorbing material having a thickness of 17.4 mm and a density of 0.182 g/cm ³ was obtained. At this time, the fineness of the fibers 2a of the fiber mass 2 was 2 to 3 dtex, and the diameter of the fiber mass 2 was 103 μm.

Example 2
The sound absorbing material 1 according to Example 2 contains 40 parts by mass of fiber clumps 2 and 60 parts by mass of porous resin particles 3 in contrast to the sound absorbing material 1 of Example 1, and the other components are the same as those of Example 1. A sound absorbing material having a thickness of 18.5 mm and a density of 0.172 g/cm ³ was obtained using the same operation. At this time, the fineness of the fibers 2a of the fiber mass 2 was 2 to 3 dtex, and the diameter of the fiber mass 2 was 95 μm.

Example 3
The sound absorbing material 1 according to Example 3 contains 20 parts by mass of fiber lumps 2 and 80 parts by mass of porous resin particles 3. Other than that, the same operation as in Examples 1 and 2 was performed to reduce the thickness. A sound absorbing material having a thickness of 18.9 mm and a density of 0.195 g/cm ³ was obtained. At this time, the fineness of the fibers 2a of the fiber clump 2 was 2 to 3 dtex, and the diameter of the fiber clump 2 was 120 μm.

Comparative Example In a comparative example, a sound absorbing material made of non-woven fabric with a thickness of 25 mm and a density of 0.014 g/cm ³ is used, which uses polyethylene terephthalate fibers (fineness of 2 to 3 dtex, fiber length of 10 to 20 μm) and is made into a non-woven fabric by needle punching. bottom.

FIG. 6 shows the measurement results of the normal incident sound absorption coefficient, which indicates sound absorption performance, for Examples 1 to 3 and Comparative Example.
According to the experimental results, in the high frequency range of 4000 to 5000 Hz, the sound absorbing material 1 of Examples 1 to 3 has slightly better sound absorbing performance than the sound absorbing material of the comparative example. rice field.
On the other hand, in the low frequency range of 1000 to 2000 Hz, the sound absorbing materials 1 of Examples 1 to 3 exhibited better sound absorbing performance than the sound absorbing material of the comparative example.

On the other hand, FIG. 7 shows measurement results of normal incidence transmission loss, which indicates sound insulation performance, for Examples 1 to 3 and Comparative Example.
According to the experimental results, the sound absorbing material 1 of Examples 1 to 3 exhibited better sound insulation performance than the sound absorbing material of the comparative example from the high frequency range to the low frequency range.

In general, the mechanism of sound absorption by the sound absorbing material 1 is that when a sound wave is incident on the sound absorbing material 1, the vibrating air receives viscous resistance due to collision and friction inside the sound absorbing material 1, and is converted into heat energy and dissipated. It is said that sound is absorbed by attenuation of acoustic energy.
According to the sound absorbing material 1 according to the present embodiment, voids formed by entangling the crimped fibers 2a of the fiber lumps 2, and voids formed between the fiber lumps 2 and between the fiber lumps 2 and the elastic resin 2b. In addition to complicating the path of the incident sound wave, the elastic resin that can vibrate with respect to the sound is attached to the crimped fibers, so that the acoustic energy can be efficiently attenuated.
The sound absorbing material 1 of this embodiment has porous resin particles 3, and the projections 3a formed on the porous resin particles 3 are formed by projections that are easily vibrated by sound waves incident on the sound absorbing material 1. Therefore, it is presumed that the protrusions 3a efficiently convert acoustic energy into vibrations and cause further sound absorption effects, and it is thought that high sound absorption performance in the low frequency range can be obtained by this. be done.

REFERENCE SIGNS LIST 1 sound absorbing material 2 fiber mass 2a fiber 2b elastic resin 3 porous resin particles 3a protrusion 11 sampling device

Claims (5)

A sound absorbing material containing a fiber mass composed of crimped fibers and an elastic resin, wherein the fiber mass is formed by entrapping and holding a plurality of fine elastic resins inside the crimped fiber, A sound absorbing material characterized in that said fiber has a fineness of 1 to 50 dtex and said fiber mass has a diameter of 25 to 300 μm. 2. The sound absorbing material according to claim 1, wherein the fiber mass is formed into a bead shape by crimping fibers having a fiber length of 10 to 100 mm. 3. The sound absorbing material according to claim 1, wherein said fiber lumps are fixed together by a binder. Porous resin particles to which a binder is fixed, wherein the porous resin particles are particles having a plurality of protrusions, a maximum Feret diameter A of 10 to 100 μm, and a minimum Feret diameter B2 of ₁ to 1 on the surface. It has an opening of ₁₀ μm and _a ratio of the maximum Feret diameter B1 to the minimum Feret diameter B2 of the opening is 1.5 to 5.0, and the opening is not open on the surface 4. The sound absorbing material according to any one of claims 1 to 3, further comprising porous resin particles having a communication structure for communicating with another hole. A non-woven fabric sheet impregnated with a polyurethane resin that moves the fiber lumps constituting the sound absorbing material according to any one of claims 1 to 4 at a speed of 0.5 to 15 m/min is rotated at 1000 to 3000 rpm. 1. A method for producing a sound absorbing material, characterized in that the sound absorbing material is recovered by being brought into contact with a rotating grinding sheet having a roughness of 50 to 300 and grinding the material.

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