JP7197773B2 - sound absorbing material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sound absorbing material, and more particularly to a sound absorbing material containing porous resin particles, fiber clumps, and short fibers.

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 porous 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 nonwoven fabric is laminated as in Patent Document 1 needs to be thickened in order to ensure sound absorbing performance in the low frequency range, so it is difficult to use in automobiles and the like where space is limited. had its limits.
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. It provides a sound absorbing material.

That is, the sound absorbing material according to the invention of claim 1 includes porous resin particles, fiber lumps composed of crimped fibers and elastic resin, and short fibers other than the fiber lumps having a fiber length of 1 to 80 mm. A sound absorbing material,
The short fibers are contained in a mass ratio of 15 to 70% with respect to the total mass of the porous resin particles, the fiber mass and the short fibers,
The porous resin particles are provided with a plurality of protrusions, are particles having a maximum Feret diameter A of 10 to 100 μm, and have pores with a minimum Feret diameter B of 1 to 10 μm on the _surface . _A hole having _a ratio of the maximum Feret diameter B1 to the Feret diameter B2 of 1.5 to 5.0 is included, and the hole is provided with a communication structure that communicates with another hole that is not opened on the surface. and

According to the sound absorbing material according to the invention of claim 1, since the porous resin particles have a communication structure that communicates with other pores that are not open on the surface, the When sound is incident into the formed opening, the sound is subjected to friction and viscous resistance with the inner wall of the opening, and part of the sound energy is converted into heat energy and absorbed.
At that time, a plurality of protrusions formed on each porous resin particle vibrate due to the incident sound, and part of the sound energy is converted into heat energy. It can absorb sound.

Enlarged photograph of the sound absorbing material according to the present embodiment Enlarged photo of porous resin particles Enlarged photo of fiber mass Configuration diagram of sampling device Enlarged photo of polyurethane sheet

FIG. 1 shows a magnified 100-fold photograph of a sound absorbing material 1 according to the present invention. It has a configuration in which fiber clumps 3 with fine elastic resin 3b between them and short fibers 4 with a fiber length of 1 to 80 mm are fixed with a binder.
As shown in the magnified photograph of 500 times shown in FIG. A plurality of protrusions 2a are formed on the outer surface.
As shown in the 100-fold enlarged photograph shown in FIG. 3, the fiber mass 3 is formed into particles having a diameter of about 50 to 150 μm, in which fine elastic resin 3b enters between fibers 3a that are tangled in a bead shape. there is
Short fibers such as cotton, rayon, polyester, acrylic, nylon, and polypropylene can be used for the short fibers 4, and among them, polyester-based fibers are preferable, and in particular, the materials are easy to obtain and have excellent strength and heat resistance. Polyethylene terephthalate (PET) fibers are preferred in that respect.
The fiber length of the short fibers 4 is preferably in the range of 1 to 80 mm, more preferably in the range of 1.5 to 50 mm, even more preferably in the range of 2 to 30 mm. The fineness is preferably in the range of 1 to 20 dtex, more preferably in the range of 1.5 to 10 dtex, even more preferably in the range of 2 to 5 dtex.
Furthermore, it is also possible to adopt a core-sheath composite thermally fused staple fiber as the structure of the staple fiber 4. For example, the core is polyester and the sheath is a low-melting copolymer polyester, or a core-sheath composite consisting of polyethylene. A heat-sealable short fiber is mentioned. By using the thermally fused short fibers, the fused portion functions as a skeleton when the sound absorbing material has a low density, and the rigidity of the sound absorbing material can be improved.
By including the fiber clumps 3 having higher rigidity than the porous resin particles 2 in the sound absorbing material 1, the fiber clumps 3 play a role as an aggregate, increasing the rigidity of the sound absorbing material 1 and increasing the rigidity of the sound absorbing material 1. Sound absorption in the frequency domain can be improved.

Regarding the ratio of the porous resin particles 2, the fiber clumps 3, and the short fibers 4 in the sound absorbing material 1, the short fibers 4 are It is desirable that it be contained at a mass ratio of 15 to 70%.
If the short fibers 4 are 15% or more, the porosity is improved and a high sound absorbing effect can be obtained, and if it is 70% or less, high sound insulation can be obtained. The greater the amount of short fibers added, the higher the peak value of the sound absorption coefficient can be on the high frequency side, and the less the amount of short fibers added, the better the sound insulation (transmission loss). The amount of fiber should be adjusted.

FIG. 4 shows a collecting device 11 for collecting the porous resin particles 2 and the fiber clumps 3, which includes 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.
A sheet S made of porous polyurethane for collecting the porous resin particles 2 or a sheet S made of a resin-impregnated nonwoven fabric for collecting the fiber clumps 3 is wound around the supply roller 12 .
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 porous resin particles 2 and fiber clumps 3 are recovered in the recovery box 14 .

The polyurethane sheet S used for collecting the porous resin particles 2 has a diameter of 1.5 mm on the resin wall between the large pores, as shown in the photograph of the surface of the polyurethane sheet S magnified 500 times shown in FIG. It has a large number of small pores of 1 to 10 μm, and has a communication structure in which the large and small pores communicate with other pores that are not open on the surface. Such a polyurethane sheet S can be manufactured using a conventionally known wet film-forming method.
The porous resin particles 2 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 2, and the maximum Feret diameter _B1 and minimum Feret diameter B2 of the small pores present on the surface of the porous resin particles ₂ 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, was prepared by continuously applying the polyurethane resin solution to a film-forming substrate in a preparation step of preparing a polyurethane resin solution, followed by A sheet is produced through a coagulation regeneration step of coagulating and regenerating a polyurethane resin into a sheet in a coagulation liquid, and a washing/drying step of washing and drying the coagulated and regenerated polyurethane resin. 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 N,N-dimethylformamide (hereinafter abbreviated as DMF) and N,N-dimethylacetamide (DMAc), and 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. As the additive, a hydrophilic additive that promotes pore opening, a hydrophobic additive that stabilizes the regeneration of the polyurethane resin, and the like can be used in order to control the size and amount (number) of the pore.

The polyurethane resin preferably contains 0 to 30% by mass, more preferably 1 to 10% by mass, of carbon black as an inelastic filler.
When the non-elastic filler is within 30% by mass, the polyurethane resin sheet is easily stretched, and the elongated protrusions 2a are easily formed. If the non-elastic filler is 0% by mass or more, protrusions are likely to be formed. If the inelastic filler is 1% by mass or more, even if the type of polyurethane resin is likely to stretch and is difficult to break, the carbon black can act as a filler and suppress the stretch, which is preferable.

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 2 can be increased. The broken portion tends to remain as the protrusion 2a.
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.

Further, the polyurethane resin matrix component has a breaking strength (kg/mm ² )×breaking elongation (%) of preferably 25 to 1500, more preferably 35 to 1000, and more preferably 50 to 800. More preferred.
Here, the elongation at break is preferably 50 to 300%. The breaking elongation indicates the degree of elongation when the resin is stretched until it breaks, and the larger the value, the easier it is to stretch and deform.
Moreover, the breaking strength is preferably 0.5 to 5.0 kg/mm ² . The breaking strength indicates the stress when the resin is stretched until it breaks.
When the value of breaking strength (kg/mm ² )×breaking elongation (%) is in the range of 25 to 1500, the stretched and deformed resin is plastically deformed, and the protruding portion 2a remains stretched without returning to its original state. can be formed, and the sound absorption properties can be improved.
If the value of breaking strength (kg/mm ² )×breaking elongation (%) is less than 25, the resin is likely to break and is difficult to stretch, making it difficult to form projections 2a. On the other hand, if the value of breaking strength (kg/mm ² )×breaking elongation (%) exceeds 1500, the stretched resin will return to its original state, making it difficult to form the projections 2a.

The breaking elongation is measured by punching out a polyurethane sheet into a dumbbell shape (sample preparation shape/size specified), sandwiching the measurement sample between the upper and lower air chucks of the measuring machine, starting the measurement at a tensile speed of 100 mm / min and an initial grip interval of 50 mm. The value at which the value reached the peak (cleavage) was taken as tenacity (maximum load). Conducted with n number 2, breaking strength (kgf / mm ² ) = strength (maximum load) kgf / (thickness (mm) × sample width (10 mm)) to calculate the breaking strength, and calculated the breaking strength from the average value do.
The elongation at break of the polyurethane sheet is the elongation at break in the tensile measurement. The tensile strength and elongation at break are measured using a Tensilon universal tester RTC manufactured by A&D Co., Ltd. according to Japanese Industrial Standards (JIS K6550).
When checking the breaking strength and breaking elongation of a 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 no foam. can be measured by forming a resin sheet of

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 serving as the film-forming base material, so replacement of DMF with water occurs on the skin layer side, and larger pores are formed on the film-forming base side than on the skin layer side. be.

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.
Desolvation of DMF from the polyurethane resin solution, that is, replacement of water with DMF, results in the formation of large cells, and the micropores of the skin layer and the large cells communicate with the small cells 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 2 are collected from the polyurethane sheet S, the feed speed of the sheet S by the supply roller 12 in the collecting device 11 is set within the range of 0.5 to 15 m/min, and the buff roller 13 preferably Sandpaper with a roughness of 100 to 350, more preferably 150 to 250, was attached, and the buff roller 13 was pressed against the sheet S while being rotated at a rotation speed of 1000 to 3000 rpm.
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 2a 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.

When the polyurethane resin formed in the shape of partitions defining large pores shown in FIG. 5 is stretched and broken, the pores of 1 to 10 μm formed on the surface extend in a certain direction, and the minimum Feret diameter is 1 to 10 μm. Thus, porous resin particles 2 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 2 separated from the polyurethane sheet S, the broken portions are stretched and plastically deformed to form a plurality of pointed geometric projections 2a, and each projection 2a is also stretched. Some have approximately elliptical openings extending in one direction.
Such a plurality of protrusions 2a vibrate when receiving sound energy, thereby converting the sound into vibration and generating a sound absorbing effect. Further, when sound enters the elongated opening of the projecting portion 2a, it receives collision or friction inside, and is converted into thermal energy and absorbed.

Next, the resin-impregnated nonwoven fabric used for collecting the fiber mass 3 has a structure in which a nonwoven fabric such as polyester fiber is impregnated with a polyurethane resin. Impregnated ones can be used.
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 punching method, the fibers are not fixed by an adhesive resin or fusible fibers but are mechanically entangled.
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 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 cp 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 out 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 resin-impregnated nonwoven fabric has a density within the above range, it has an appropriate porosity, so that the sound absorbing performance can be improved.

When collecting the fiber clumps 3 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 to m/s in the range of 0.5 to 15 m/min, and the buff roller 13 Preferably, sandpaper with a roughness of 50 to 300, more preferably 80 to 240 is attached, and the buff roller 13 is rotated at a rotation speed of 1000 to 3000 rpm while the buff roller 13 is pressed against the sheet S. and pressed against it.
When the buff roller 13 comes into contact with the surface of the resin-impregnated nonwoven fabric while rotating, the fibers 3a constituting the nonwoven fabric are pulled out from the surface of the resin-impregnated nonwoven fabric by friction with the buff roller 13, and the pulled out fibers 3a are crimped to form a ball of yarn. entangled in shape.
At that time, the porous resin impregnated in the nonwoven fabric is torn off from the surrounding resin as the fibers 3a are pulled out, and then taken into the interior of the fibers 3a as the fibers 3a are entangled. .
After that, the friction of the buff roller 13 further acts to break the root portion of the fiber 3a entangled in the ball shape, and the fiber 3a in which the fine elastic resin 3b is held in the fiber 3a entangled in the ball shape. It becomes a lump 3 and leaves. At this time, some of the elastic resin 3b adheres to the fibers 3a, and some does not adhere to the fibers 3a but is taken in and held in the fibers 3a that are tangled in a bead shape.

As the binder, an acrylic resin emulsion-based adhesive can be used, and in addition, a vinyl acetate resin emulsion-based adhesive, an ethylene-vinyl acetate resin emulsion-based adhesive, and a urethane resin emulsion-based adhesive can be used. In this example, the adhesive was diluted with water to 5.5% and used.
When the sound absorbing material 1 is prepared by binding the porous resin particles 2, the fiber clumps 3, and the short fibers 4 using the binder, the porous resin particles 2, the fiber clumps 3, and the short fibers are mixed at a predetermined ratio. The fibers 4 are put into a mixer, and a binder is sprayed with a spray gun or the like while stirring them, or while stirring the porous resin particles 2, fiber lumps 3, and short fibers 4 with a ball mill.
As a result, the surfaces of the porous resin particles 2, the fiber clumps 3, and the short fibers 4 are coated with the binder. After that, the sound absorbing material 1 can be obtained by drying at a predetermined temperature for a predetermined time.
Here, the amount of the binder used is preferably 0.5 to 50%, more preferably 1 to 15%, based on the weight of the porous resin particles 2, fiber lumps 3, and short fibers 4. is desirable. If the binder content is 50% or less, a sound absorbing effect can be obtained by spaces formed between the porous resin particles 2, the fiber clumps 3, and the short fibers 4, which will be described later, and the binder content is 0.5% or less. , the shape of the sound absorbing material 1 can be maintained.

(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 this embodiment has a structure in which porous resin particles 2, fiber clumps 3, and short fibers 4 are fixed with a binder, and a complicated space is formed between them. The surface area of the sound absorbing material per hit can be increased.
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, the space formed by the porous resin particles 2, the fiber clumps 3, and the short fibers 4 can complicate the paths of sound waves that have entered, making it more efficient. Acoustic energy can be attenuated.
In other words, by dispersing linear short fibers in multiple directions in particulate or clump-like porous resin particles and fiber clumps, the short fibers form a skeleton, and the voids can be widened. Sound energy can be attenuated more efficiently than a sound absorbing material consisting only of fibers, and the sound absorption coefficient can be improved.
In addition, the sound absorbing material 1 can be made to have a low density, and can be lighter in weight than a sound absorbing material made only of particles. Therefore, it is possible to achieve both weight reduction and sound absorption performance.
Further, by setting the fiber length of the short fibers 4 of the sound absorbing material 1 to 1 to 80 mm, it is possible to obtain the sound absorbing material 1 with high flexibility and elasticity, and the place where the sound absorbing material 1 is installed has a complicated shape. can be installed following this.

The first porous resin particle 2 has a plurality of projections 2a on the surface, and the porous resin particle 2 has a communication structure in which large and small pores communicate with other pores that are not open on the surface. It has pores with a minimum Feret diameter of 1 to 10 μm on the surface.
Therefore, when sound enters the sound absorbing material 1, the sound penetrates inside the pores through the pores on the surface of the porous resin particles 2, and the resin walls formed between the pores Sound energy is converted into heat energy by friction and vibration of the body, and sound energy is absorbed.
At this time, the smaller the openings, the greater the friction and vibration with the resin wall, and the easier the conversion of sound energy into heat energy, the higher the sound absorption performance. By setting the minimum Feret diameter of the pores contained in the porous resin particles 2 to preferably 1 to 10 μm, more preferably 1 to 8 μm, a high sound absorbing effect can be obtained.
Furthermore, it includes an elliptical opening having a maximum Feret diameter B ₁ of 1.5 to 5.0 with respect to the minimum Feret diameter B ₂ of the opening, and the opening is different from another hole not opened on the surface. By providing a communicating structure for ventilation, it is easy to allow the intrusion of sound, and a high sound absorbing effect can be obtained.
Moreover, a plurality of protrusions 2a are formed on the surface of the porous resin particles 2 of the present embodiment, and some protrusions 2a are not fixed by the binder. Such protrusions 2a vibrate sensitively to sound, and the vibration of the protrusions 2a can also absorb sound energy.

Further, the fiber clumps 3 contained in the sound absorbing material 1 have a configuration in which fine elastic resins 3b are held in fibers 3a that are crimped and tangled in a bead shape, and gaps between the fiber clumps 3 and the fiber clumps 3 and the porous fibers are formed. The voids between the resin particles 2 form a complicated space, and when sound is incident on the sound absorbing material 1, the sound energy is absorbed by giving friction to the sound.
In particular, since the fiber mass 3 has a structure in which the fine elastic resin 3b is held in the fibers 3a that are crimped and tangled in a bead shape, fine gaps are formed between the fibers 3a and the elastic resin 3b. is formed.
For this reason, when the sound incident on the sound absorbing material 1 further enters the fiber mass 3, it enters the complex gaps formed by the fibers 3a and the elastic resin 3b, receives friction and viscous resistance, and is held without adhering to the fibers 3a. It collides with the elastic resin 3b which is fine and can vibrate, and part of the sound energy is converted into heat energy and absorbed, so that good sound absorption performance can be obtained.

The following experiments were performed on the sound absorbing material 1 of Examples 1 to 8 according to the present invention produced 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.

Further, the maximum Feret diameter A, the maximum Feret diameter B ₁ , and the minimum Feret diameter B ₂ of the porous resin particles 2 contained in the sound absorbing materials 1 according to Examples 1 to 3 were measured as follows.
The Feret diameter was determined by observing the sound absorbing material with an electron microscope (JMS-5500LV, manufactured by JEOL Ltd.) at a magnification of 100, and extracting arbitrary 30 points of porous resin particles 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 is composed of polyethylene terephthalate (PET) fibers having a fiber length of 5 mm and a fineness of 1.6 dtex as short fibers 4, the porous resin particles 2, and the fiber lumps 3, and is porous. 48 g of resin particles 2, 12 g of fiber lumps 3, and 40 g of short fibers 4 were blended, 100 g of acrylic emulsion having a concentration of 10% was sprayed with a spray gun, and these were mixed with a mixer.
Subsequently, the mixture is filled into a molded container having a size of 23 cm long × 23 cm wide × 1.6 cm deep, dried in a dryer at 80 ° C. for 4 hours, dried at 140 ° C. for 1 hour, and then cooled. A sound absorbing material 1 having a thickness of 14.98 mm and a density of 0.255 g/cm ³ was obtained.

Example 2
The sound absorbing material 1 according to Example 2 is different from the sound absorbing material 1 of Example 1 except that the weight of each material is 32 g of the porous resin particles 2, 8 g of the fiber lumps 3, and 60 g of the short fibers 4. A sound absorbing material 1 having a thickness of 14.89 mm and a density of 0.257 g/cm ³ was obtained as a result of the same operation as in Example 1 above.

Example 3
The sound absorbing material 1 according to Example 3 uses polyethylene terephthalate (PET) fibers with a fiber length of 10 mm and a fineness of 3.3 dtex as the short fibers 4 in contrast to the sound absorbing materials 1 of Examples 1 and 2, and the weight of each material is Except that 64 g of the porous resin particles 2, 16 g of the fiber lumps 3 and 20 g of the short fibers 4 were blended, the same operation as in Example 1 was performed, resulting in a thickness of 15.57 mm and a density of 0.245 g/ A sound absorbing material 1 of cm ³ was obtained.

Example 4
The sound absorbing material 1 according to Example 4 contains 48 g of the porous resin particles 2, 12 g of the fiber lumps 3, and 40 g of the short fibers 4 as compared with the sound absorbing material 1 of Example 3 (Example 1 A sound absorbing material 1 having a thickness of 14.7 mm and a density of 0.260 g/cm ³ was obtained in the same manner as in Example 1 except that the same mass ratio was used.

Example 5
The sound absorbing material 1 according to Example 5 contains 32 g of porous resin particles 2, 8 g of fiber clumps 3, and 60 g of short fibers 4 in weight of each material compared to the sound absorbing materials 1 of Examples 3 and 4 (implemented). A sound absorbing material 1 having a thickness of 14.95 mm and a density of 0.256 g/cm ³ was obtained in the same manner as in Example 1, except that the mass ratio was the same as in Example 2).

Example 6
In the sound absorbing material 1 according to Example 6, in contrast to the sound absorbing material 1 of Examples 1 to 5, the staple fiber 4 is a core-sheath composite heat-fusible fiber having a fiber length of 5 mm and a fineness of 2.2 dtex (core: polyester fiber, sheath: Low melting point copolyester) was used, and the weight of each material was 64 g of porous resin particles 2, 16 g of fiber lumps 3, and 20 g of short fibers 4 (same mass ratio as in Example 3). A sound absorbing material 1 having a thickness of 17.29 mm and a density of 0.220 g/cm ³ was obtained.

Example 7
The sound absorbing material 1 according to Example 7 contains 48 g of the porous resin particles 2, 12 g of the fiber lumps 3, and 40 g of the short fibers 4 as compared with the sound absorbing material 1 of Example 6 (Example 1 , 4), and as a result, a sound absorbing material 1 having a thickness of 17.1 mm and a density of 0.211 g/cm ³ was obtained.

Example 8
The sound absorbing material 1 according to Example 8 contains 48 g of the porous resin particles 2, 12 g of the fiber mass 3, and 40 g of the short fibers 4, compared with the sound absorbing materials 1 of Examples 6 and 7. A sound absorbing material 1 having a thickness of 16.81 mm and a density of 0.223 g/cm ³ was obtained in the same manner as in Example 1, except that the mass ratio was the same as in Examples 2 and 5).

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. did.

Experimental Results Table 1 shows the experimental results for the sound absorbing material 1 of Examples 1 to 8 and the sound absorbing material of the comparative example. It shows the measurement results of incident transmission loss.
According to the experimental results, it was found that the sound absorbing materials 1 of Examples 1 to 8 according to the present invention had better sound absorbing performance and sound insulating performance than the comparative materials at all measured wavelengths.
Especially near 2000 Hz, which is a low frequency range, the sound absorbing materials 1 of Examples 1 to 8 show excellent sound absorption performance compared to the comparative examples, and show excellent sound insulation performance near 5000 Hz, which is a high frequency range. there is

Also, looking at Examples 3 to 5, which were made using the same material with different mass ratios, Example 4 in which the mass ratio of the short fibers 4 was 40% showed relatively good sound absorption performance, but the sound insulation performance was poor. Example 3 with a mass ratio of 20% was better.
On the other hand, among Examples 6 to 8 in which the short fibers were core-sheath composite fibers, Example 8 in which the mass ratio of the short fibers 4 was 40% showed the most excellent sound insulation performance in the low frequency range.
In addition, when comparing Examples 1, 4, and 7, which were made with the same mass ratio, the sound absorbing materials of Examples 1 and 4 had slightly better sound absorption than Example 7 using core-sheath composite fibers. showed performance.
Similarly, when comparing Examples 2, 5, and 8, which were created with the same mass ratio, the sound absorbing materials of Examples 1 and 4 are slightly better than Example 7 using core-sheath composite fibers. showed good sound absorption performance.

REFERENCE SIGNS LIST 1 sound absorbing material 2 porous resin particles 3 fiber mass 4 short fibers 11 sampling device

Claims (3)

A sound absorbing material comprising porous resin particles, fiber clumps composed of crimped fibers and elastic resin, and short fibers other than the fiber clumps having a fiber length of 1 to 80 mm,
The short fibers are contained in a mass ratio of 15 to 70% with respect to the total mass of the porous resin particles, the fiber mass and the short fibers,
The porous resin particles are provided with a plurality of protrusions, are particles having a maximum Feret diameter A of 10 to 100 μm, and have pores with a minimum Feret diameter B of 1 to 10 μm on the _surface . _A hole having _a ratio of the maximum Feret diameter B1 to the Feret diameter B2 of 1.5 to 5.0 is included, and the hole is provided with a communication structure that communicates with another hole that is not opened on the surface. sound absorbing material. 2. The sound absorbing material according to claim 1, wherein the short fibers have a fineness of 1 to 20 dtex. 1 or claim 2, wherein said fiber clumps are held by said fibers crimped with said elastic resin, said fibers have a fineness of 1 to 50 dtex, and said fiber clumps have a diameter of 25 to 300 μm. 2. The sound absorbing material according to 2.

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