JP2015174398A - Complex nonwoven fabric for sound absorption material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight/thin complex nonwoven fabric for a sound absorption material excellent in sound absorption performance in a frequency region of 3,000-5,000 Hz, producible easily and inexpensively, and further excellent in flame resistance.SOLUTION: A complex nonwoven fabric for a sound absorption material includes a laminated structure formed by laminating a short fiber nonwoven fabric containing crimped hollow fibers and a sound absorption film layer comprising a synthetic resin film. The thickness of the short fiber nonwoven fabric is below 12 mm, and the thickness of the sound absorption film layer is 20-60 μm.

Description

  The present invention relates to a nonwoven fabric for sound absorbing materials mainly used in automobiles, and particularly to a composite nonwoven fabric for sound absorbing materials that is light weight and excellent in sound absorbing performance.

  Since automobiles generate noise as they travel, noise absorbing materials are placed around the noise source to reduce noise and measures are taken to prevent and reduce noise and noise. The main causes of noise are known as engine sound, tire sound caused by the tire coming into contact with the road surface, wind noise, etc. The frequency of these noises is mainly engine sound of 5000 Hz or less, tire sound. It is known that the frequency is 1000 Hz or less and the wind noise is about 500 to 5000 Hz.

  Thus, since the noise generated from the running automobile covers various frequency ranges, various materials have been developed to absorb the noises having a wide frequency range. There are roughly three types of sound absorbing materials: a porous type, a resonator type, and a plate / membrane vibration type. Porous sound absorbing materials have been widely used in the past for the purpose of absorbing sounds in a wide range of mid- and high-frequency ranges. For example, porous sound-absorbing materials have a low melting point as fibers constituting the sound-absorbing material. There are fiber-cotton nonwoven fabrics in which core-sheath composite fibers having a resin are used, the fabric is pressed and hardened to make the fibers dense, and continuous fine voids or holes are formed. However, in order to demonstrate higher sound absorption performance, it is necessary to add weight and thickness to the sound absorbing material itself, and in recent years, there has been a demand for "weight reduction" and "space saving" required for vehicle sound absorbing materials. It was not enough to respond.

  In order to meet the demands for "lightweight" and "space-saving", a method to combine resonance type and plate / membrane vibration type characteristics by combining materials other than non-woven fabric with porous type non-woven fabric for sound absorbing material Has been. For example, Patent Document 1 discloses a sound absorbing material in which holes are made in a synthetic resin film such as polyethylene and polypropylene, and the hole-processed synthetic resin film is spot-bonded to a sheet-like sound absorbing material such as a porous film, urethane foam, or felt. A sheet is disclosed. Further, Patent Document 2 uses a film in which a thermoplastic elastomer and a plastic are blended with a polymer, and the film thickness, the blending amount of the thermoplastic elastomer, and a film with a gradient in the blending amount are combined to 800 to 1300 Hz. A sound absorbing material having a sound absorbing peak is disclosed. Patent Document 3 discloses a composite sound-absorbing material that includes sound-absorbing layers on both sides of a resonance layer so that noise from the engine room is not propagated into the passenger compartment. Patent Document 4 discloses a sound absorbing material in which a film and a meltblown nonwoven fabric are bonded using an adhesive.

Japanese Patent Laid-Open No. 2000-20070 JP 2010-237418 A JP 2005-227747 A JP 2008-299073 A

  However, the sound-absorbing material of Patent Document 1 has a problem that it is necessary to produce a porous film or to perforate a synthetic resin film, and the process becomes complicated. In addition, in Patent Document 1, it is conceivable to make a hole in the film by needle punching. However, in order to ensure a desired thickness while performing needle punching, the sound-absorbing material needs a certain weight, There has been a problem that it is difficult to achieve the purpose of weight reduction. Further, the sound absorbing material of Patent Document 2 has a problem that it lacks versatility because the formation process of the compound film is complicated. Furthermore, the sound-absorbing material of Patent Document 3 has not been reduced in weight and space to the level required in recent years for the basis weight / thickness, which is not sufficient. In Patent Document 4, the sound that can be absorbed by the sound absorbing material is limited to a relatively low frequency range of 1000 to 2000 Hz, and cannot widely cover noise from automobiles.

  In addition, sound-absorbing materials installed in automobiles are required to have flame-retardant properties such as when a fire occurs, the flame spreads, toxic gases such as cyan are generated, and combustion drops do not form during combustion. It is necessary to overcome the problem of combustibility.

  Under such circumstances, the present invention provides a composite nonwoven fabric for sound-absorbing materials that is excellent in sound-absorbing performance in the frequency range of 3000 to 5000 Hz, is lightweight and thin, can be manufactured easily and inexpensively, and is excellent in flame retardancy. It was raised as an issue.

  As a result of intensive studies to solve the above problems, the present inventor laminated a short fiber nonwoven fabric containing crimped hollow fibers and a sound absorbing film layer made of a synthetic resin film, and the thickness of the short fiber nonwoven fabric. It is found that a composite nonwoven fabric for sound absorbing material having excellent sound absorbing performance and flame retardancy in a frequency range of 3000 to 5000 Hz can be obtained by adjusting the thickness to less than 12 mm and further setting the thickness of the sound absorbing film layer to 20 to 60 μm. The present invention has been completed.

That is, the composite nonwoven fabric for sound absorbing material according to the present invention includes a laminated structure in which a short fiber nonwoven fabric including crimped hollow fibers and a sound absorbing film layer made of a synthetic resin film are laminated, and the thickness of the short fiber nonwoven fabric is It is less than 12 mm, and the thickness of the sound absorbing film layer is 20 to 60 μm. The basis weight of the short fiber nonwoven fabric is preferably 50 g / m ² or more and less than 150 g / m ² , and the bulk density of the short fiber nonwoven fabric is more preferably 0.005 to 0.04 g / cm ³ . The short fiber nonwoven fabric includes low melting point fibers having a melting point lower by 50 ° C. than the melting point of the crimped hollow fibers, and the fineness of the low melting point fibers is 2.2 to 33 dtex, and the short fiber nonwoven fabric has a weight of 100 weight. The blending ratio of the low-melting fiber in% is preferably 20 to 95% by weight. Further, the total amount of crimped hollow fibers is preferably 5 to 80% by weight in 100% by weight of the short fiber nonwoven fabric, and the basis weight is 10 on the surface of the sound absorbing film layer opposite to the joint surface with the short fiber nonwoven fabric. It is a more desirable embodiment that a cover layer having a thickness of ˜30 g / m ² and a thickness of 0.1 to 0.3 mm is laminated. In addition, it is desirable that the composite nonwoven fabric for sound-absorbing material conforms to HF-1 in flame retardancy determined according to the UL94HF method (horizontal combustion test of foamed material in plastic material flammability test). Moreover, this invention also includes the sound-absorbing material containing the said composite nonwoven fabric for sound-absorbing materials.

  According to the present invention, the short-fiber nonwoven fabric and the sound-absorbing film layer are laminated, and the thickness of the short-fiber nonwoven fabric and the thickness of the sound-absorbing film layer are within the predetermined ranges, so that the noise in the frequency range of 3000 to 5000 Hz is effective. Can absorb sound. And since the whole can be finished bulky by mix | blending crimped hollow fiber with a short fiber nonwoven fabric, the composite nonwoven fabric for sound-absorbing materials which is excellent also in a flame retardance is obtained. Moreover, since the composite nonwoven fabric for sound absorbing material of the present invention uses crimped hollow fibers, it is very light and thin, so there is a strong demand for "light weight" and "space saving" for automobiles. Can be used particularly effectively.

FIG. 1 is a schematic cross-sectional view showing an example of a composite nonwoven fabric for sound absorbing material according to the present invention. FIG. 2 is a schematic sectional view showing another example of the composite nonwoven fabric for sound absorbing material according to the present invention.

  Hereinafter, the composite nonwoven fabric for sound-absorbing material according to the present invention will be specifically described with reference to the drawings showing examples, but the present invention is not limited to the illustrated examples, and conforms to the purpose described above and below. It is also possible to carry out the present invention with appropriate modifications within the possible range, and all of them are included in the technical scope of the present invention.

  In FIG. 1, the schematic sectional drawing which shows an example of the composite nonwoven fabric for sound-absorbing materials which concerns on this invention is shown. The composite nonwoven fabric 4 for sound absorbing material of the present invention has a configuration in which a short fiber nonwoven fabric 1 including crimped hollow fibers and a sound absorbing film layer 2 are laminated. In the composite nonwoven fabric 4 for sound absorbing material of the present invention, the short fiber nonwoven fabric 1 and the sound absorbing film layer 2 constitute a resonance system that uses the elasticity of the short fiber nonwoven fabric 1 as a spring. When sound enters the sound absorbing material composite nonwoven fabric 4, the transmitted sound vibrates the sound absorbing film layer 2, and vibration energy of the sound is converted into vibration energy and heat energy of the sound absorbing material composite nonwoven fabric 4. Further, some of the sounds are repeatedly absorbed with the fibers in the short fiber nonwoven fabric 1, and the energy is attenuated and absorbed. As a result, the vibration energy of the sound generated from the engine is reduced, so that the noise generated by the automobile is reduced. As a result of the study by the present inventors, such a sound absorbing performance is not sufficiently exhibited by the sound absorbing material composed of the short fiber nonwoven fabric 1 alone or the sound absorbing film layer 2 alone, and is a composite of the short fiber nonwoven fabric 1 and the sound absorbing film layer 2. It was found that this was brought about by

  The short fiber nonwoven fabric 1 is a nonwoven fabric laminated in order to finish the composite nonwoven fabric 4 for sound-absorbing materials high in bulk. By finishing the composite nonwoven fabric 4 for sound absorbing material to a predetermined density and a predetermined thickness, the peak of the frequency at which sound can be absorbed can be adjusted to 3000 to 5000 Hz. On the other hand, the sound absorbing film layer 2 is a layer that vibrates when a sound wave hits the composite nonwoven fabric 4 for sound absorbing material. That is, in the composite nonwoven fabric 4 for sound-absorbing material of the present invention, the sound-absorbing film layer 2 plays a role of absorbing sound, while the short fiber nonwoven fabric 1 has a predetermined density and a predetermined thickness so that the sound can be absorbed. It plays the role of adjusting the frequency.

  The sound absorbing film layer 2 is made of a synthetic resin. Therefore, it is important that the composite nonwoven fabric 4 for sound-absorbing material of the present invention has a property of being difficult to burn even when the flame approaches, since it is easily burnable and dangerous when in contact with a flame or heat source. . Although details will be described later, in the present invention, flame retardancy is imparted to the composite nonwoven fabric 4 for sound-absorbing material by using the short fiber nonwoven fabric 1 including crimped hollow fibers.

  In addition, in order to prevent the short fiber nonwoven fabric 1 and the sound absorbing film layer 2 from being damaged, and in order to prevent the molten resin in the sound absorbing film layer 2 from fouling the manufacturing apparatus at the time of manufacture, as shown in FIG. It is also possible to laminate the cover layer 3 on the surface of the sound absorbing film layer 2 opposite to the bonding surface of the sound absorbing film layer 2. Hereinafter, the present invention will be described in detail.

<Short fiber nonwoven fabric>
In the present invention, the “short fiber” is a fiber with respect to a long fiber (filament), and particularly refers to a fiber having a fiber length cut to 100 mm or less (more preferably 10 to 80 mm, still more preferably 40 to 70 mm). The short fiber nonwoven fabric used in the present invention is characterized in that the short fiber includes a fiber having a hollow inside and a crimped structure (hereinafter referred to as “crimped hollow fiber”). Have. By using crimped fibers, it is possible to finish a bulky nonwoven fabric even with the same weight as that of ordinary fibers. In addition, since the crimped hollow fiber is hollow, even if the nonwoven fabric is formed with the same basis weight as a normal crimped fiber, the nonwoven fabric using the crimped hollow fiber is not suitable for a sound absorbing material without increasing the bulk density. A composite nonwoven fabric can be finished thick. Furthermore, if it is a crimped hollow fiber, since the inside of a fiber is a cavity, it becomes possible to finish the bulk density of a short fiber nonwoven fabric low. If the bulk density is low, voids are present in the nonwoven fabric, so that even if a flame comes into contact with the short fiber nonwoven fabric, it is possible to prevent the fire from moving to adjacent fibers. In addition, because of the so-called bamboo effect, the nonwoven fabric containing crimped hollow fibers has bending rigidity, and therefore can be used for a long time without being deformed even when subjected to pressure such as wind pressure.

  The thickness of the short fiber nonwoven fabric is less than 12 mm, more preferably 11.5 mm or less, still more preferably 11 mm or less, and particularly preferably 10.5 mm or less. When the thickness of the short fiber nonwoven fabric exceeds the upper limit, there is a problem that the weight of the short fiber nonwoven fabric increases and it becomes difficult to finish the composite nonwoven fabric for sound absorbing material to be lightweight. On the other hand, if the upper limit is exceeded, there is a possibility that a sufficient flame retardant effect may not be exhibited. Furthermore, the sound absorption coefficient at 3000 to 5000 Hz is generally reduced, and particularly, the sound absorption coefficient in the vicinity of 3150 Hz is lowered, and the desired effect may not be exhibited. Although a minimum is not specifically limited, For example, 1 mm or more is preferable, More preferably, it is 3 mm or more, More preferably, it is 5 mm or more, Most preferably, it is 7.5 mm or more. If the thickness is below the lower limit, the sound absorption peak may shift to another frequency range.

The bulk density of the short fiber nonwoven fabric, for example, is preferably 0.005~0.04g / cm ^3, more preferably from 0.01~0.03g / cm ^3, more preferably 0.017 greater ( 0.017 g / cm ³ is not included) to 0.022 g / cm ³ . If the bulk density exceeds the upper limit value, a sufficient flame retardant effect may not be exhibited. In addition, the sound absorption coefficient at 3000 to 5000 Hz generally decreases, and particularly, the sound absorption coefficient near 3150 Hz becomes low, and the desired effect may not be exhibited. On the other hand, if the bulk density is lower than the lower limit value, it is not preferable because the short fiber nonwoven fabric tends to sag due to the use of the composite nonwoven fabric for sound absorbing material. The method for measuring the bulk density will be described in detail in the Examples section.

The basis weight of the short fiber nonwoven fabric is preferably, for example, less than 150 g / m ² , more preferably 120 g / m ² or less, and still more preferably 100 g / m ² . When the basis weight is equal to or higher than the upper limit value, the resulting composite nonwoven fabric for sound-absorbing material becomes heavier and it becomes difficult to finish it into a lightweight sound-absorbing material. The lower limit of the basis weight of the short fiber nonwoven fabric is, for example, preferably 50 g / m ² or more, more preferably 60 g / m ² or more, and further preferably 65 g / m ² or more. If the basis weight is below the lower limit, the resulting composite nonwoven fabric for sound absorbing material may not exhibit sufficient rigidity.

  Examples of crimped hollow fibers contained in the short fiber nonwoven fabric include, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, and polyarylate; polyamide resins such as nylon 6 and nylon 66; polyacrylonitrile, polyacrylonitrile-vinyl chloride Acrylic resins such as copolymers; Synthetic fibers made from raw materials; Recycled fibers such as rayon and polynosic; Semi-synthetic fibers such as acetate fibers and triacetate fibers; Various chemical fibers such as cotton, pulp, kapok, hemp, And natural fibers such as hair and silk. These fibers may be used alone or in combination. Among them, it is desirable to use synthetic fibers so that the short fiber nonwoven fabric has a certain rigidity, more preferably polyester, and still more preferably polyethylene terephthalate. In addition, various types of composite fibers in which crimped hollow fibers are combined with thermoplastic resins having different heat shrinkage ratios and the fibers are crimped by utilizing the difference in heat shrinkability can also be used.

  As the crimped fiber, either an actual crimped fiber or a latent crimped fiber can be used. However, since the crimp can be sufficiently expressed at the raw material stage, the actual crimped fiber is used in the present invention. preferable. If it is an actual crimped fiber, the advantage that the fiber can be easily obtained and the heat setting step of the fiber can be omitted.

  The fineness of the crimped hollow fiber is, for example, preferably 1 to 25 dtex, more preferably 3 to 22 dtex, and still more preferably 5 to 17 dtex. If the fineness of the crimped hollow fiber is within the above range, the short fiber nonwoven fabric can be finished bulky.

  The above-described crimped hollow fibers can be used by appropriately combining two or more kinds of fibers different in at least one of material, thickness, length and the like. For example, a relatively thick first fiber may be used to impart moderate rigidity to the short fiber nonwoven fabric, and a second fiber may be further used to improve the cutting performance of the composite nonwoven fabric for sound absorbing material.

1. First fiber The crimped hollow fiber used as the first fiber is preferably a thick fiber of 8 dtex or more, for example. The fineness of the first fiber is more preferably 10 dtex or more, still more preferably 12 dtex or more, and the upper limit is, for example, preferably 25 dtex or less, more preferably 22 dtex or less, still more preferably 17 dtex or less. By using a thick fiber having a fineness of 8 dtex or more, it is possible to give an appropriate rigidity to the short fiber nonwoven fabric.

  The blending ratio of the first fibers in 100% by weight of the short fiber nonwoven fabric is preferably 20 to 80% by weight, more preferably 30 to 70% by weight, and further preferably 35 to 50% by weight. If the blending ratio of the first fibers is below the lower limit value, the short fiber nonwoven fabric is not sufficiently rigid, and the composite nonwoven fabric for sound absorbing material may be easily sag by use. On the other hand, if the blending ratio of the first fiber exceeds the upper limit value, processing problems such as difficulty in cutting the composite nonwoven fabric for sound absorbing material may occur when the composite nonwoven fabric for sound absorbing material is finished. It is not preferable.

2. Second fiber The crimped hollow fiber used as the first fiber has a large fineness and has a crimp. Therefore, when finished into a composite nonwoven fabric for sound absorbing material, the composite nonwoven fabric for sound absorbing material is cut. May be difficult. In order to prepare for such a situation, in order to easily cut the composite nonwoven fabric for sound absorbing material in advance in the short fiber nonwoven fabric, a fiber having a fineness smaller than that of the first fiber described above (hereinafter referred to as “second fiber”). ). The fineness of the second fiber is, for example, preferably 1 to 10 dtex, more preferably 3 to 8.5 dtex, and still more preferably 5 to 7 dtex. If the fineness of the second fiber is less than the lower limit, the resulting short fiber nonwoven fabric tends to sag, which is not preferable. On the other hand, if the fineness of the second fiber exceeds the upper limit, the fiber is too thick and the effect of assisting the cutting of the composite nonwoven fabric for sound-absorbing material may not be sufficiently exhibited.

  As the second fiber, it is particularly preferable to use a crimped hollow fiber. Since crimped hollow fibers have crimps, they can be finished into a non-woven fabric having a certain thickness even with the same weight as compared with ordinary short fibers, and because the fibers are hollow, It is also possible to suppress an increase in the weight of the short fiber nonwoven fabric.

  The blending ratio of the second fiber in 100% by weight of the short fiber nonwoven fabric is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, and further preferably 15 to 25% by weight. If the blending ratio of the second fiber is below the lower limit value, the effect of blending the second fiber may not be sufficiently exhibited. Moreover, since the average fineness of the fiber which forms a short fiber nonwoven fabric will fall when the mixture ratio of a 2nd fiber exceeds an upper limit, it becomes difficult to give sufficient rigidity to a short fiber nonwoven fabric.

  The blending ratio of the second fiber to the first fiber is preferably, for example, 1 to 150 parts by weight, more preferably 25 to 75 parts by weight with respect to 100 parts by weight of the first fiber. More preferably 35 to 60 parts by weight, particularly preferably 40 to 55 parts by weight. If the amount is less than 1 part by weight, the effect of adding the second fiber may not be sufficiently exhibited. Moreover, since a short fiber nonwoven fabric will be comprised from a comparatively thin fiber when it exceeds an upper limit, it will become difficult to finish to a rigid short fiber nonwoven fabric.

  In the present invention, in particular, the total amount of crimped hollow fibers contained in the short fiber nonwoven fabric is desirably 5% by weight or more, more preferably 30% by weight or more, and still more preferably 100% by weight of the short fiber nonwoven fabric. Is 40% by weight or more, desirably 100% by weight or less, more preferably 80% by weight or less, and still more preferably 70% by weight or less. If the blending ratio of the crimped hollow fibers is below the lower limit, it is difficult to increase the thickness of the short fiber nonwoven fabric without increasing the bulk density, which is not desirable.

  When the short fiber nonwoven fabric is manufactured by the thermal bond method, the short fiber nonwoven fabric contains a certain amount of low-melting fibers described later. For this reason, when manufacturing a short fiber nonwoven fabric by a thermal bond method, the total amount of crimped hollow fibers used in the short fiber nonwoven fabric is desirably 5 to 80% by weight, more preferably 100% by weight of the short fiber nonwoven fabric. Is 20 to 70% by weight, more preferably 45 to 65% by weight.

3. Although the manufacturing method of a low melting point fiber short fiber nonwoven fabric is not specifically limited, It is desirable to form by a dry method. That is, it is preferable that the fibers used in the short fiber nonwoven fabric are lightened and then mixed, then carded using a card machine, and then wrapped with a cross wrapper. Examples of the fiber bonding method include a thermal bond method, a chemical bond method, a needle punch method, and a water entanglement method. Among them, the thermal bond method is a particularly preferable method because it can be formed without breaking the crimp of the crimped fiber.

  When producing a short fiber nonwoven fabric by the thermal bond method, a fiber having a melting point lower by 50 ° C. or more than the crimped hollow fiber forming the skeleton of the short fiber nonwoven fabric (hereinafter also referred to as a low melting point fiber) is included in the short fiber nonwoven fabric. It is good to be. By blending the low melting point fibers, the bonds between the fibers can be strengthened, and the low melting point fibers after melting and solidification can increase the rigidity of the short fiber nonwoven fabric. If the melting point difference is less than 50 ° C., depending on the heating conditions, both the crimped hollow fiber and the low-melting fiber are melted or softened, and the entire nonwoven fabric is solidified, or both the crimped hollow fiber and the low-melting fiber are both solidified. Is not preferable because it does not melt or soften, and there is a possibility that the bonding strength of the fibers in the short fiber nonwoven fabric may be weakened. The melting point of the low-melting fiber is more preferably 60 ° C. or lower than the melting point of the crimped hollow fiber. The lower limit of the melting point of the low-melting fiber is not particularly limited. For example, it is preferably 150 ° C. or lower from the melting point of the crimped hollow fiber, and more preferably 100 ° C. or lower from the melting point of the crimped hollow fiber. The melting point of the low-melting fiber is, for example, preferably 80 to 160 ° C, more preferably 90 to 120 ° C.

  The fineness of the low melting point fiber is, for example, preferably 2.2 to 33 dtex, more preferably 2.5 to 20 dtex, and further preferably 4 to 10 dtex. If the fineness of the low melting point fiber is within the above range, it is preferable because the low melting point fiber is easy to melt and the heat treatment time can be shortened.

  The form of the low-melting fiber is not particularly limited, but the low-melting fiber is a composite having a core-sheath structure, an eccentric structure, or a side-by-side structure composed of a plurality of resins having different melting points such as polyethylene-polypropylene and polyester-low-melting polyester. Fibers; modified polyester fibers; modified polyamide fibers; modified polyolefin fibers such as modified polypropylene fibers; Among these, a modified polyester fiber is preferable because the selection range of the melting point is wide.

  The blending ratio of the low melting point fiber in 100% by weight of the short fiber nonwoven fabric is preferably 20 to 95% by weight, more preferably 30 to 80% by weight, and further preferably 35 to 55% by weight. If the blending ratio of the low melting point fibers is below the lower limit value, the fibers cannot be firmly bonded, and the amount of the low melting point fibers after melting and solidification is small. Moreover, if the blending ratio of the low melting point fiber exceeds the upper limit value, the short fiber nonwoven fabric becomes thin, and it becomes difficult to obtain the required thickness, the form as the nonwoven fabric becomes unstable, and the manufacturing cost increases. It is not preferable.

  The production conditions of the short fiber nonwoven fabric may be appropriately selected according to the fibers to be blended. In the case of the thermal bond method, the heat treatment time is preferably 0.1 to 3 minutes, for example, more preferably 0.8. 5 to 2 minutes. If the heat treatment time is within the above range, the fibers can be thermally bonded without impairing the texture of the blended fibers, which is preferable. For the same reason, the heat treatment temperature is, for example, preferably 160 to 220 ° C, more preferably 170 to 210 ° C.

  In addition to the crimped hollow fiber and the low melting point fiber described above, the short fiber nonwoven fabric may include a third fiber as a fiber other than these. Examples of the third fiber include natural fibers such as cotton, hemp, hair, and silk; regenerated fibers such as rayon, polynosic, cupra, and reyocell; semisynthetic fibers such as acetate fiber and triacetate fiber; nylon 6, nylon 66, and the like Polyamide fiber: Polyethylene fiber such as polyethylene terephthalate fiber, polybutylene terephthalate fiber, polylactic acid fiber, polyarylate, etc .; Acrylic fiber such as polyacrylonitrile fiber, polyacrylonitrile-vinyl chloride copolymer fiber; Polyolefin such as polyethylene fiber and polypropylene fiber Fibers: polyvinyl alcohol fibers such as vinylon fibers and polyvinyl alcohol fibers; polyvinyl chloride fibers such as polyvinyl chloride fibers, vinylidene fibers and polyclar fibers; synthetic fibers such as polyurethane fibers; polyethylene oxide Polyether based fibers such as polypropylene oxide; and the like. The third fiber may be a non-crimped fiber or a crimped fiber. Furthermore, both solid fibers and hollow fibers can be used. However, it is preferable that the short fiber nonwoven fabric has a higher blending ratio of the crimped hollow fiber and the low melting point fiber. For example, the total amount of the crimped hollow fiber and the low melting point fiber is 70 to 100 in 100% by weight of the short fiber nonwoven fabric. % By weight is preferable, more preferably 80 to 100% by weight, still more preferably 90 to 100% by weight, particularly preferably 95 to 100% by weight, and most preferably 100% by weight.

<Sound absorbing film layer>
Next, the sound absorbing film layer will be described. The sound absorbing film layer is a layer that can exhibit sound absorbing performance with the whole layer, and is made of a synthetic resin film. The sound absorbing film layer is a layer that vibrates when a sound wave hits the composite nonwoven fabric for sound absorbing material, and the vibration energy possessed by the sound absorbing film layer vibrates to the vibration energy and thermal energy of the composite nonwoven fabric for sound absorbing material. Is converted to

  The thickness of the sound absorbing film layer is 20 to 60 μm, more preferably 25 to 50 μm, and still more preferably 27 to 40 μm. When the thickness is less than the lower limit, the sound absorbing film layer is thin, and the composite nonwoven fabric for sound absorbing material cannot be sufficiently vibrated when a sound wave hits, and the sound absorbing effect is reduced, which is not preferable. On the other hand, when the value is below the lower limit, the mechanical strength of the film is lowered, and the film is easily perforated or broken. On the other hand, if the thickness of the sound absorbing film layer exceeds the upper limit value, it is difficult to vibrate and absorb energy, or inside the sound absorbing material composite non-woven fabric, such as when the sound absorbing material composite non-woven fabric is in contact with flame. When heat is stored, the sound-absorbing film layer continuously ignites and burns (so-called candle core phenomenon), and the flame spreads over the short-fiber nonwoven fabric and the cover layer that constitute the composite nonwoven fabric for the sound-absorbing material, or combustion drops May occur.

Weight The sound absorbing film layer, for example, preferably 25~60g / m ^2, more preferably 27~45g / m ^2, more preferably from 30 to 40 g / m ^2. If the weight of the sound-absorbing film layer is within the above range, the resulting composite nonwoven fabric for sound-absorbing material can be finished light.

  As the synthetic resin constituting such a sound absorbing film layer, a thermoplastic resin is preferable, and specifically, polyolefin resins such as polyethylene (low density polyethylene, medium density polyethylene, high density polyethylene), polypropylene, and polyolefin copolymers. At least one selected from a resin, a polyester resin, and a polyamide resin is selected.

  The synthetic resin constituting the sound absorbing film layer may be, for example, a thermoplastic resin having a relatively low melting point (melting point of 70 ° C. or more and less than 200 ° C.), and a high melting point (melting point of 200 to 300 ° C.). It may be a thermoplastic resin.

  The form of the sound-absorbing film layer is not particularly limited, but the sound-absorbing film layer may be a single layer made of one film or a laminate in which two or more films are integrated. Good. As the sound absorbing film layer, for example, when the short fiber non-woven fabric and the sound absorbing film layer are integrated by heat fusion, the surface of the sound absorbing film layer exhibits heat fusion properties, or the heat treatment Occasionally, a non-heat-sealable film or the like in which the sound-absorbing film layer itself does not exhibit heat-sealability can be used.

  Moreover, it is preferable that both the sound absorption property and the adhesiveness are imparted to the sound absorbing film layer so that the sound absorbing film layer can be bonded to the above-described short fiber nonwoven fabric. As a method for imparting both sound absorption and adhesion to the sound absorption film layer, for example, (1) a single layer self-heat-bonding film that exhibits both sound absorption and adhesion is used as the sound absorption film layer. Method (2) A relatively low melting point having a melting point of 200 ° C. to 300 ° C. and a relatively low melting point having a melting point of 70 ° C. or more and less than 200 ° C. on at least one side of the non-thermal fusion film. A method of using a laminate obtained by integrating the self-heat-adhesive film of the above as a sound-absorbing film layer, (3) using a single-layer non-heat-adhesive film exhibiting only the sound-absorbing property as the A method of providing an adhesive means on at least one surface of the sound absorbing film layer is conceivable. Since the method (1) uses a single-layer self-heat-bonding film, the material cost can be kept low. The method (2) is preferable because it does not impair the elasticity of the composite nonwoven fabric for sound absorbing material. In (3), since the sound-absorbing film layer is not easily deformed by heat treatment, the composite nonwoven fabric for sound-absorbing material can be sufficiently vibrated when subjected to sound waves, which is preferable.

  As the self-heat-bondable film used in the method (1), a single-layer film made of a thermoplastic resin having a melting point of 70 ° C. or higher and lower than 200 ° C. may be used. The melting point of the thermoplastic resin is more preferably 85 to 190 ° C, still more preferably 85 to 170 ° C, and particularly preferably 85 to 150 ° C. When a film made of a low-melting resin is used, part or all of the film is melted by heat treatment to exhibit adhesiveness, and can exhibit sound absorption as a film after cooling and solidification. In (1), the thermoplastic resin is preferably a polyethylene resin.

  The non-heat-adhesive film used in the method (2) has, for example, preferably a thickness of 7 to 20 μm, more preferably 9 to 18 μm, and still more preferably 10 to 16 μm. If the thickness of the non-heat-bondable film is lower than the lower limit, the sound absorbing film is thin, and the composite nonwoven fabric for sound absorbing material cannot be sufficiently vibrated when struck with sound waves, which is not preferable. On the other hand, if the thickness of the non-heat-fusible film is lower than the lower limit value, the mechanical strength of the film is lowered, and the film is likely to be pierced or torn. On the other hand, if the thickness of the non-heat-adhesive film exceeds the upper limit value, the sound-absorbing film layer is continuous when heat is stored inside the sound-absorbing material composite nonwoven fabric, such as when a flame contacts the sound-absorbing material composite nonwoven fabric. In particular, ignition and combustion continue, and the flame spreads over the short fiber nonwoven fabric and the cover layer constituting the composite nonwoven fabric for sound absorbing material, and combustion drops may be generated.

  As the non-heat-bondable film, for example, a film made of a nylon resin or a polyester resin may be used. Especially, since it has moderate rigidity, in this invention, use of nylon is preferable. Moreover, it is preferable that melting | fusing point is 200-300 degreeC as resin which comprises a non-heat-fusion film. If the melting point of the resin constituting the non-heat-bondable film is below the lower limit, the heat resistance is low, and the non-heat-bondable film may be melted in the heat treatment in the joining step, and there is a possibility that holes may be formed in the film. Absent.

  The weight ratio of the non-heat-sealable film in the sound-absorbing film layer (laminate) is not particularly limited. For example, the weight of the non-heat-sealable film is 20% in 100% by weight of the sound-absorbing film layer. It is preferable that it is -45 weight%, More preferably, it is 30-40 weight%. If the weight of the non-heat-fusible film is within the above range, the sound absorption effect by laminating the non-heat-fusible film is sufficiently exhibited.

  On the other hand, the melting point of the heat-fusible film used in (2) is, for example, preferably 180 ° C. or lower, more preferably 170 ° C. or lower, still more preferably 160 ° C. or lower, and preferably 70 ° C. or higher, more Preferably it is 80 degreeC or more, More preferably, it is 90 degreeC or more. When the melting point exceeds the upper limit value, the melting point approaches the melting point of the non-heat-fusible film, so that the non-heat-fusible film is deformed and the non-heat-fusible film may not vibrate sufficiently. On the other hand, if the value is below the lower limit, the heat-fusible film after melting is not sufficiently solidified, and the adhesive strength of each layer is weakened.

  As the heat-sealable film, for example, a heat-sealable film made of polyethylene, polypropylene, or polyethylene-vinyl acetate copolymer is preferable. Among these, it is desirable to select polyethylene because it is easily available.

  As for the thickness of the heat-fusible film, for example, a thin layer of about 0.1 μm is acceptable, but it is desirable that the thickness of the heat-fusible film is 7 to 20 μm because moderate rigidity can be imparted. More preferably, it is 9-18 micrometers, More preferably, it is 10-16 micrometers. When the thickness of the heat-fusible film exceeds the upper limit, heat is accumulated in the heat-fusible film when storing heat inside the sound-absorbing material composite nonwoven fabric, such as when a flame contacts the sound-absorbing material composite nonwoven fabric. This remains as a combustion source and ignites and burns continuously, and there is a risk that the flame spreads over the short fiber nonwoven fabric and the cover layer, or combustion drops are formed. In addition, when the heat-fusible film thickness exceeds the upper limit, the heat-fusible film is thick, and when the heat-fusible film is solidified, the non-heat-fusible film may not sufficiently vibrate. Moreover, when the thickness of the heat-fusible film becomes thinner than the lower limit, it is not preferable because the bonding force between the non-heat-fusible film and the short fiber nonwoven fabric or the cover layer may be weakened. In particular, when a heat-fusible film is used, the mechanical strength of the film is lowered, and the film is easily perforated or broken.

  In the laminate (2), it is more preferable that the thickness and the heat shrinkage rate of the non-heat-fusible film and the heat-fusible film are the same. For this reason, it is desirable to strictly control the thickness and heat shrinkage rate of the heat-fusible film as much as possible.

  The heat-fusible film is preferably provided on at least a surface on which the non-heat-fusible film can be bonded to the short fiber nonwoven fabric, or both surfaces of the non-heat-fusible film. In addition, since the heat-fusible film is easily melted by heat treatment, when the heat-fusible film is disposed on both sides of the non-heat-fusible film, it is bonded to the short fiber nonwoven fabric during the production. The surface opposite to the surface is easily soiled with a molten heat-fusible film. Therefore, from the viewpoint of preventing contamination of the heating device, a cover layer described later is preferably laminated on the surface opposite to the joint surface with the short fiber nonwoven fabric.

  A method for producing a laminate by laminating a non-heat-fusible film and a heat-fusible film is not particularly limited, but has been preliminarily molded in order to ensure a flexible movement of the film. Sand lamination method in which raw resin of non-heat-sealable film is melt-extruded between two heat-sealable films, laminated and pressure-bonded. It is preferable to adopt an inflation method that swells and folds it in two and winds it up.

  In addition, as the non-heat-bondable film used in the method (3), a film made of a thermoplastic resin having a melting point of 200 to 300 ° C. may be used. The melting point of the thermoplastic resin is more preferably 210 to 290 ° C, still more preferably 220 to 270 ° C. As the thermoplastic resin, polyolefin resins such as polyethylene (low density polyethylene, medium density polyethylene, high density polyethylene) and polypropylene are preferable.

  In addition, as an adhesive means, a method using a heat-fusible non-woven fabric represented by “DYNAC (registered trademark)” manufactured by Kureha Tech; an adhesive by a dry laminating method, sintering (resin point bonding), or the like Method; and the like.

Basis weight of the heat-fusible non-woven fabric is 5~45g / m ^2, preferably 8~30g / m ^2, more preferably from 9~20g / m ^2. Moreover, as a fiber which comprises a heat-fusible nonwoven fabric, the fiber which uses a thermoplastic resin whose melting | fusing point is 70-250 degreeC as a raw material is preferable, More preferably, melting | fusing point is 90-150 degreeC.

  Examples of the heat-fusible nonwoven fabric include one or more thermoplastic resins selected from modified nylon resins, modified polyester resins, modified polyolefin resins (modified polyethylene resins, modified polypropylene resins, etc.), polyethylene-vinyl acetate resins, and polyurethane resins. It is preferable that it is comprised with the fiber of this.

  The melt index of the thermoplastic resin used as the raw material for the heat-fusible nonwoven fabric is, for example, about 8 to 20 g / 10 min (2.16 kgf, 160 ° C.). The melt viscosity of the thermoplastic resin is, for example, about 500 to 1500 Pa · s (160 ° C.).

  As the heat-fusible nonwoven fabric, either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric can be used. In the present invention, it is particularly desirable to use a long-fiber nonwoven fabric (spunbond nonwoven fabric). The heat-fusible nonwoven fabric is preferably entangled in a web shape.

<Cover layer>
In the composite nonwoven fabric for sound-absorbing material of the present invention, a cover layer is optionally laminated on the surface of the sound-absorbing film layer opposite to the joint surface with the short-fiber nonwoven fabric in order to prevent the short-fiber nonwoven fabric and the sound-absorbing film layer from being damaged. Is also possible. The cover layer is not essential, and the cover layer does not have to be laminated when a high-density polyethylene film or a polypropylene film that is difficult to be damaged is used as the sound-absorbing film layer.

  The cover layer is preferably excellent in wear resistance in order to prevent the short fiber nonwoven fabric and the sound absorbing film layer from being damaged. Since it is excellent in abrasion resistance, it is good to use a fabric as a cover layer, for example. As the fabric used for the cover layer, a nonwoven fabric, a woven fabric, a knitted fabric, a braid, a lace, a net, or the like can be used, and among these, it is desirable to use a nonwoven fabric.

  Nonwoven fabrics used for the cover layer include spunbonded nonwoven fabrics; dry-type nonwoven fabrics obtained by various bonding methods such as thermal bond method, chemical bond method, needle punch method, hydroentanglement method, stitch bond method; thermal bond method, chemical bond method And wet nonwoven fabrics obtained by various bonding methods such as a spunlace method. In the present invention, it is desirable to use a spunbonded nonwoven fabric or a thermalbonded nonwoven fabric because there are few fibers coming out and the wear resistance is excellent.

  Further, it is desirable that the cover layer is subjected to consolidation processing such as calendering and / or embossing as necessary. This is because the wear resistance as the cover material is improved by performing the consolidation process, whereby the cover layer can be made of a material having good durability. That is, the cover layer is preferably at least one selected from embossed spunbond nonwoven fabric, embossed or calendered hydroentangled nonwoven fabric, and calendered thermal bond nonwoven fabric.

  Although the fiber which comprises a cover layer is not specifically limited, Polyester fiber, such as a polyethylene terephthalate fiber, a polybutylene terephthalate fiber, a polylactic acid fiber, a polyarylate fiber; Polyamide fiber, such as nylon 6, nylon 66; Polyacrylonitrile Examples thereof include acrylic fibers such as fibers and polyacrylonitrile-vinyl chloride copolymer fibers; regenerated fibers such as rayon and polynosic; semi-synthetic fibers such as acetate fibers and triacetate fibers; and natural fibers such as cotton, hemp and wool. Among them, it is desirable to use polyester fibers (more preferably polyethylene terephthalate fibers) and polyamide fibers (more preferably nylon fibers) having heat resistance and wear resistance.

The basis weight of the cover layer is not particularly limited, but is preferably, for example, 10 to 30 g / m ² , and more preferably 10 to 20 g / m ² . If the basis weight of the cover layer is below the lower limit, the cover layer is thin, and when the cover layer is laminated, the sound absorbing film layer itself or the resin melted by the heat-fusible film may ooze out to the back surface of the cover layer. is there. Moreover, since the expense required for manufacture of a cover layer will increase when the fabric weight of a cover layer exceeds an upper limit, it is not economical. Furthermore, since the cover layer becomes thick, the resin melted therein easily penetrates into the cover layer. Thus, if the molten resin penetrates into the cover layer, the adhesiveness is not sufficiently exhibited, the adhesive strength is weakened, and there is a possibility that the adhesion with the sound absorbing film layer may be hindered.

  Although the thickness of a cover layer is not specifically limited, For example, 0.1-0.3 mm is preferable. If the thickness of the cover layer is within the above range, the short fiber nonwoven fabric and the sound absorbing film layer can be prevented from being damaged by external force such as friction.

  The method for producing the cover layer is not particularly limited, and a method capable of producing a nonwoven fabric, a woven fabric, a knitted fabric, a braid, a lace, and a net may be appropriately employed.

<Composite non-woven fabric for sound absorbing material>
The composite nonwoven fabric for sound-absorbing material of the present invention is formed by laminating a short-fiber nonwoven fabric, a sound-absorbing film layer, and, if necessary, a cover layer formed by the method described above. When the composite nonwoven fabric for sound absorbing material is a three-layer laminate of a short fiber nonwoven fabric, a sound absorbing film layer, and a cover layer, the order in which the materials are laminated is preferably the order of the short fiber nonwoven fabric, the sound absorbing film layer, and the cover layer. As shown in FIG. 2, by arranging the sound absorbing film layer in the middle of the composite nonwoven fabric for sound absorbing material, even if the flame approaches the composite nonwoven fabric for sound absorbing material, the flame burns on the short fiber nonwoven fabric. It is possible to prevent the flame from moving to the sound-absorbing film layer having relatively high combustibility. Further, it is preferable to dispose the cover layer on the front side of the sound absorbing film layer because the sound absorbing film layer can be reliably protected.

  Although the thickness of the composite nonwoven fabric for sound absorbing material is not particularly limited, it is preferably less than 13 mm, more preferably 10 mm or less, still more preferably 7 mm or less, and particularly preferably 5 mm or less. The lower limit of the thickness of the composite nonwoven fabric for sound absorbing material is, for example, preferably 1 mm or more, more preferably 2 mm or more, and further preferably 3 mm or more. If the thickness of the composite nonwoven fabric for sound absorbing material is within the above range, it is preferable because noise with a frequency of 3000 to 5000 Hz can be efficiently absorbed.

The composite nonwoven fabric for sound absorbing material is preferably lightweight. Therefore, the basis weight of the composite nonwoven fabric for sound absorbing material is, for example, preferably 150 g / m ² or less, more preferably 145 g / m ² or less, and further preferably 140 g / m ² or less. For example, the lower limit is preferably 50 g / m ² or more, more preferably 65 g / m ² or more, and still more preferably 85 g / m ² or more. If the basis weight exceeds the upper limit value, there is a possibility that a sufficient flame retardant effect may not be exhibited, which is not preferable, and the sound absorption rate at 3000 to 5000 Hz is lowered overall, particularly the sound absorption rate near 3150 Hz is lowered, which is desirable. May not be effective.

  The thus obtained composite nonwoven fabric for sound-absorbing material has a flame-retardant performance determined according to the UL94HF method (foamed material horizontal combustion test in the plastic material flammability test) even before the flame-retardant treatment. Conforms to -1. Therefore, the flame-retardant treatment for the composite nonwoven fabric for sound-absorbing material of the present invention is not essential, and may be performed as necessary. As the flame retardant treatment, for example, (I) a method of applying a flame retardant to the entire composite nonwoven fabric for sound absorbing material or a part of the composite nonwoven fabric for sound absorbing material, (II) Examples include a method of blending a fiber having a property of burning and then extinguishing when the flame moves away (hereinafter also referred to as a flame retardant fiber).

  The flame retardant is not particularly limited, and examples thereof include bromine compounds such as pentabromodiphenyl ether, octabromodiphenyl ether, decabromodiphenyl ether, and hexabromocyclododecane; phosphorus compounds such as triphenyl phosphate; chlorinated paraffins, and the like. Various flame retardants such as chlorine compounds; antimony compounds such as antimony trioxide and antimony pentoxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide;

  In addition, flame retardant fibers that can be blended into the short fiber nonwoven fabric include polyvinyl chloride fibers, polyvinylidene chloride fibers, polyclar fibers, modacrylic fibers, acrylic fibers, meta aramid fibers, novoloid fibers, and polybenzimidazole (PBI) fibers. Examples thereof include synthetic fibers having flame retardancy such as: flame retardant rayon, flame retardant polynosic, flame retardant acrylic, flame retardant polyester and other modified fibers imparted with a flame retardant effect.

  However, in the present invention, it is desirable not to mix the above-mentioned flame retardant fiber with the short fiber nonwoven fabric as much as possible. The flame retardant fiber is usually used in a mixture with other fibers. On the other hand, the flame retardant fiber has a property of extinguishing naturally (self-extinguishing property) when the flame in contact with the flame retardant fiber is removed. The extinguished fiber has heat, and this heat becomes a heat source, and other mixed fibers (for example, polyester and the like) are ignited, which may cause the composite nonwoven fabric for sound absorbing material to burn. Therefore, in the present invention, it is desirable that the amount of flame retardant fiber in the short fiber nonwoven fabric is as small as possible. The blending amount of the flame retardant fiber is preferably 0 to 10% by weight and more preferably 0% by weight in 100% by weight of the short fiber nonwoven fabric.

  Next, a method for producing the composite nonwoven fabric for sound absorbing material by integrating the materials will be described. The composite nonwoven fabric for sound-absorbing material of the present invention is manufactured in advance by manufacturing the short fiber nonwoven fabric, the sound-absorbing film layer, and, if necessary, the cover layer by the above-described method, and laminating these in order to integrate the materials. It is manufactured by. As a method for integrating each material, for example, by passing a laminated body in which each material is stacked through a heated laminating machine having a belt type continuous plate heater, the heat-fusible component is melted, Thereafter, a method of solidifying the heat-fusible component by cooling or the like is preferable.

  The clearance of the laminating machine may be set to be equal to or less than the thickness of the short fiber nonwoven fabric. If the clearance becomes too wide, the adhesive strength of each material becomes insufficient, and there is a possibility of causing a problem if it is peeled off during use. On the other hand, if the clearance is too narrow, the desired thickness and bulk density cannot be obtained, and the sound absorbing performance and flame retardancy are affected. From such a viewpoint, the clearance of the laminating machine is preferably, for example, less than 12 mm, more preferably 10 mm or less, still more preferably 8 mm or less, and particularly preferably 6 mm or less. Further, the lower limit is preferably 1 mm or more, more preferably 2 mm or more, still more preferably 2.5 mm or more, and particularly preferably 3.5 mm or more.

  The conditions for passing through the laminating machine are important factors that determine the thickness and bulk density of the composite nonwoven fabric for sound-absorbing material of the present invention. The heating temperature of the heater is desirably equal to or lower than the melting point temperature of the sound absorbing film layer, and is preferably 160 to 200 ° C, and more preferably 170 to 195 ° C, for example. If the heating temperature exceeds the upper limit value, the sound-absorbing film layer may be melted, which is not preferable. If the heating temperature is lower than the lower limit value, the heat-fusible film is not sufficiently melted, and the bonding strength of each layer is weakened. It is not preferable.

  The heating time in the heater is preferably 30 seconds to 3 minutes, more preferably 1 minute to 2 and a half minutes. When the heating time is shorter than 30 seconds, the heat-fusible film cannot be sufficiently melted, and the bonding force of each material is weakened, which is not preferable. When the heating time exceeds 3 minutes, the melted heat-fusible film penetrates into the cover layer and the short fiber nonwoven fabric, and after the heat fusible film is solidified, the cover layer and the short fiber nonwoven fabric are soft. This is not preferable because the properties may be impaired and the elasticity of the composite nonwoven fabric for sound absorbing material may be impaired.

  When the sound-absorbing film layer itself does not have heat-fusibility, when laminating the cover layer between the short-fiber nonwoven fabric and the sound-absorbing film layer, between the short-fiber nonwoven fabric and the sound-absorbing film layer, and An adhering means may be provided between the sound absorbing film layer and the cover layer.

<Sound absorbing material>
The composite nonwoven fabric for sound-absorbing material of the present invention is installed such that the sound-absorbing film layer surface or the cover layer surface faces the sound source direction. The composite nonwoven fabric for sound-absorbing material of the present invention exhibits an extremely high sound absorption rate for sound having a frequency of 3000 to 5000 Hz, and is therefore preferably used as a sound-absorbing material for noise reduction of 3000 to 5000 Hz. Examples of the sound absorbing material for noise reduction of 3000 to 5000 Hz include an automobile sound absorbing material mounted on an automobile.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

The characteristic evaluation method of the composite nonwoven fabric for sound absorbing material obtained from the following examples and comparative examples is as follows.
(1) Thickness; Apparent thickness was measured using a JIS Class 1 steel ruler, and less than 13 mm was determined as “thin”.
(2) Weight per unit area: According to JIS L1913 method 6.2, 150 g / m ² or less was determined to be “lightweight”.
(3) Flammability: Conforms to UL94HF method (horizontal combustion test of foamed material in plastic material flammability test). Evaluation was performed using a composite nonwoven fabric for sound absorbing material instead of the foamed material.
(4) Sound absorption performance: Measured according to JIS A1405.2 (normal incidence sound absorption coefficient), sound absorption coefficient of frequency 3150 Hz is 0.5 or more, sound absorption coefficient of 4000 Hz is 0.6 or more, and sound absorption coefficient of 5000 Hz is 0.00. Seven or more were judged to be acceptable. The sample was placed so that the sound incident side was the sound absorbing film layer surface or the cover layer surface.
(5) Bulk density of the short fiber nonwoven fabric after the composite; the bulk density of the short fiber nonwoven fabric after the thermocompression bonding step is the thickness after the composite of the short fiber nonwoven fabric measured by the method described above after combining the layers. And obtained by converting the unit to g / cm ³ .

Example 1
20% by weight of hollow apparently crimped polyester fiber (melting point 260 ° C.) having a fineness of 6.6 dtex and a fiber length of 51 mm, and 40% by weight of hollow apparently crimped polyester fiber (melting point 260 ° C.) having a fineness of 14.4 dtex and a fiber length of 64 mm; Weigh 40% by weight of low melting polyester fiber with a melting point of 110 ° C and a fineness of 4.4dtex and a fiber length of 51mm. After passing through blending, carding and wrapping steps, heat treatment for 1 minute is performed in a heat treatment machine heated to 190 ° C. Then, a short fiber nonwoven fabric having a basis weight of 80 g / m ² and a thickness of 10 mm was formed, and the obtained short fiber nonwoven fabric was rolled up.
A polyester resin (PET resin) was melt-spun and then pulled and thinned with an air jet to obtain a spunbond nonwoven fabric of 15 g / m ² . By embossing the obtained nonwoven fabric, a spunbond nonwoven fabric (SB) used as a cover layer was obtained.
A belt-type continuous plate heater in which a wound short fiber nonwoven fabric, a low-melting polyethylene film (30 μm, melting point 90 to 130 ° C.) as a sound absorbing film layer, and a spunbond nonwoven fabric that has been compacted are sequentially laminated and the clearance is set to 4 mm The composite nonwoven fabric for sound-absorbing material was obtained by thermocompression bonding at a temperature of 190 ° C. for 2 minutes using a laminating machine having The bulk density of the composite short fiber nonwoven fabric was 0.019 g / cm ³ .

Example 2
A composite nonwoven fabric for sound absorbing material was obtained in the same manner as in Example 1 except that the clearance of the laminating machine was changed to 3 mm.

Examples 3-5
In Example 3, a three-layer laminated film made of polyethylene-nylon-polyethylene (thickness of each layer: 10 μm) was used in Example 3, and in Example 4, a three-layer laminated film made of polyethylene-nylon-polyethylene (thickness of each layer). In Example 5, a three-layer laminated film made of polyethylene-nylon-polyethylene (thickness of each layer: about 16 μm, total thickness: 50 μm) was used, and the laminating machine was set to the conditions shown in the table. Thus, a composite nonwoven fabric for sound absorbing material was obtained in the same manner as in Example 1.

Example 6
A low-melting polyethylene film (50 μm, melting point 90-130 ° C.) was used as the sound-absorbing film layer, and the laminating machine was set to the conditions shown in the table to obtain a composite nonwoven fabric for sound-absorbing material in the same manner as in Example 1.

Example 7
A high-density polyethylene film (30 μm) was used as the sound absorbing film layer, and a polyester-based heat-meltable nonwoven fabric (melting point: 110 ° C.) was laminated between the short fiber nonwoven fabric and the sound absorbing film layer. In this example, the cover layer was not laminated. A laminating machine was set to the conditions shown in the table, and the rest was obtained in the same manner as in Example 1 to obtain a composite nonwoven fabric for sound absorbing material.

Example 8
A polypropylene film (30 μm) was used as the sound absorbing film layer, and a polyester-based heat-meltable nonwoven fabric (melting point 110 ° C.) was laminated between the short fiber nonwoven fabric and the sound absorbing film layer. In this example, the cover layer was not laminated. A laminating machine was set to the conditions shown in the table, and the rest was obtained in the same manner as in Example 1 to obtain a composite nonwoven fabric for sound absorbing material.

Example 9
A thermal bond nonwoven fabric (TB) used as a cover layer is formed by mixing a polyester fiber with a low melting point polyester fiber having a melting point lower than that of the polyester fiber to form a thermal bond nonwoven fabric, and then calendering the nonwoven fabric. Obtained. This compacted thermal bond (TB) nonwoven fabric was used as a cover layer, the laminating machine was set to the conditions shown in the table, and the rest was obtained in the same manner as in Example 1 to obtain a composite nonwoven fabric for sound absorbing material.

Comparative Example 1
The sound-absorbing film layer was replaced with a meltblown nonwoven fabric made of polypropylene fibers (25 g / m ² per unit area), and a polyester-based heat-meltable nonwoven fabric (melting point 110 ° C.) was laminated between the short fiber nonwoven fabric and the meltblown nonwoven fabric. In this production example, the cover layer was not laminated. A laminating machine was set to the conditions shown in the table, and the rest was obtained in the same manner as in Example 1 to obtain a composite nonwoven fabric for sound absorbing material.

Comparative Example 2
Using a three-layer laminated film (thickness of each layer: 30 μm) made of polyethylene-nylon-polyethylene as the sound-absorbing film layer, setting the laminating machine to the conditions shown in the table, and using the same method as in Example 1, the composite for sound-absorbing material A nonwoven fabric was obtained.

Comparative Example 3
The sound-absorbing film layer was replaced with an aluminum metal thin film (11 μm), and a polyester-based hot-melt nonwoven fabric (melting point 110 ° C.) was laminated between the short fiber nonwoven fabric and the metal thin film. In this production example, the cover layer was not laminated. A laminating machine was set to the conditions shown in the table, and the rest was obtained in the same manner as in Example 1 to obtain a composite nonwoven fabric for sound absorbing material.

Comparative Example 4
20% by weight of hollow apparently crimped polyester fiber having a fineness of 6.6 dtex and a fiber length of 51 mm, 40% by weight of hollow apparently crimped polyester fiber having a fineness of 14.4 dtex and a fiber length of 64 mm, and a fineness of 4.4 dtex and fiber having a melting point of 110 ° C. 40% by weight of low-melting polyester fiber with a length of 51 mm was weighed and subjected to blending, carding, and lapping processes, followed by heat treatment for 1 minute with a heat treatment machine heated to 190 ° C., with a basis weight of 210 g / m ² , thickness A 20 mm short fiber nonwoven fabric was formed, and the obtained short fiber nonwoven fabric was rolled up.
The short fiber nonwoven fabric having a basis weight of 210 g / m ² obtained in this way was used as the short fiber nonwoven fabric, and the other was obtained as a composite nonwoven fabric for sound absorbing material under the conditions shown in the table.

Comparative Example 5
20% by weight of hollow apparently crimped polyester fiber having a fineness of 6.6 dtex and a fiber length of 51 mm, 40% by weight of hollow apparently crimped polyester fiber having a fineness of 14.4 dtex and a fiber length of 64 mm, and a fineness of 4.4 dtex and fiber having a melting point of 110 ° C. 40% by weight of low-melting polyester fiber with a length of 51 mm was weighed and subjected to blending, carding and wrapping processes, followed by heat treatment for 1 minute in a heat treatment machine heated to 190 ° C., with a basis weight of 350 g / m ² , thickness A 30 mm short fiber nonwoven fabric was formed, and the obtained short fiber nonwoven fabric was rolled up.
The short fiber nonwoven fabric having a basis weight of 350 g / m ² thus obtained was used as the short fiber nonwoven fabric, and the other was obtained as a composite nonwoven fabric for sound absorbing material under the conditions shown in the table.

Comparative Example 6
20% by weight of hollow apparently crimped polyester fiber having a fineness of 6.6 dtex and a fiber length of 51 mm, 40% by weight of hollow apparently crimped polyester fiber having a fineness of 14.4 dtex and a fiber length of 64 mm, and a fineness of 4.4 dtex and fiber having a melting point of 110 ° C. 40% by weight of low-melting polyester fiber with a length of 51mm was weighed and subjected to blending, carding, and lapping processes, followed by heat treatment for 1 minute with a heat treatment machine heated to 190 ° C, with a basis weight of 80g / m ² , thickness A 10 mm short fiber nonwoven fabric was formed, and the obtained short fiber nonwoven fabric was rolled up.
The rolled-up short fiber nonwoven fabric was heat-pressed for 2 minutes at a temperature of 190 ° C. with a laminator having a belt-type continuous plate heater set to a clearance of 4 mm to obtain a composite nonwoven fabric for sound absorbing material.

Comparative Example 7
The short fiber nonwoven fabric obtained by the method of Example 1, the polyester-based heat-meltable nonwoven fabric (melting point: 110 ° C.), and the spunbond nonwoven fabric that has been consolidated are laminated in this order without laminating the sound-absorbing film layer, and the clearance is 4 mm. A composite nonwoven fabric for sound absorbing material was obtained by thermocompression bonding at a temperature of 190 ° C. for 2 minutes in a laminating machine having a belt type continuous plate heater set.

  1: Short fiber nonwoven fabric, 2: Sound absorbing film layer, 3: Cover layer, 4: Composite nonwoven fabric for sound absorbing material

Claims (8)

Including a laminated structure in which a short fiber nonwoven fabric including crimped hollow fibers and a sound absorbing film layer made of a synthetic resin film are laminated,
A composite nonwoven fabric for sound absorbing material, wherein the short fiber nonwoven fabric has a thickness of less than 12 mm, and the sound absorbing film layer has a thickness of 20 to 60 µm. The short fiber nonwoven fabric having a basis weight sound absorbing material for a composite nonwoven fabric according to claim 1 is less than 50 g / m ² or more 150 g / m ^{2. 3. The} composite nonwoven fabric for sound-absorbing material according to claim 1, wherein a bulk density of the short fiber nonwoven fabric is 0.005 to 0.04 g / cm ³ .   The short fiber nonwoven fabric includes low melting point fibers having a melting point lower by 50 ° C. or more than the melting point of the crimped hollow fibers, the fineness of the low melting point fibers is 2.2 to 33 dtex, and the short fiber nonwoven fabric is 100% by weight. The composite nonwoven fabric for sound-absorbing material according to any one of claims 1 to 3, wherein a blending ratio of the low melting point fiber is 20 to 95% by weight.   The composite nonwoven fabric for sound-absorbing material according to any one of claims 1 to 4, wherein the total amount of crimped hollow fibers is 5 to 80% by weight in 100% by weight of the short fiber nonwoven fabric. The cover layer having a basis weight of 10 to 30 g / m ² and a thickness of 0.1 to 0.3 mm is laminated on the surface of the sound absorbing film layer opposite to the joint surface with the short fiber nonwoven fabric. The composite nonwoven fabric for sound-absorbing materials according to any one of the above.   The composite nonwoven fabric for sound-absorbing material according to any one of claims 1 to 6, wherein flame retardancy determined in accordance with UL94HF method (horizontal combustion test of foamed material in a plastic material flammability test) conforms to HF-1. .   A sound absorbing material comprising the composite nonwoven fabric for sound absorbing material according to claim 1.