JP2015030218A - Nonwoven fabric excellent in absorbing property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated nonwoven fabric excellent in absorbing property.SOLUTION: A laminated nonwoven fabric has a surface layer part and a base part. The surface layer part has at least a nonwoven fabric layer ((1) layer) formed of a nanofiber which is formed from a thermoplastic resin having a number-average single fiber diameter of 1 to 500 nm, and a nonwoven fabric layer ((2) layer) formed of a fiber having a larger number-average single fiber diameter than that of the nanofiber, and is a nonwoven fabric layer A having a basis weight of 30-100 g/m. The base part is a nonwoven fabric B having a basis weight of 200-800 g/mand contains 10 mass% or more of a fiber having a number-average single fiber diameter of 15 μm or less. A sound absorbing rate at a frequency of 2,000 Hz is 85% or more.

Description

  The present invention relates to a laminated nonwoven fabric having excellent sound absorbing performance and heat insulation properties by laminating two or more layers of nonwoven fabrics having a specific fiber diameter.

  Nonwoven fabrics are used for the purpose of sound absorption and heat insulation in automobiles and electrical products. Especially for automobiles, there is a demand for non-woven fabrics made of materials that are light and thin to improve fuel efficiency and that are easy to recycle after use.

  Patent Document 1 discloses a needle punched nonwoven fabric having excellent sound absorption including polytrimethylene terephthalate short fibers. However, only using the nonwoven fabric described in the cited document 1 has a problem that the sound absorption of the nonwoven fabric is insufficient.

  Patent Document 2 discloses a sound absorbing material in which a nonwoven fabric and a perforated film are laminated. However, there is a problem that sound absorption is insufficient only by laminating the nonwoven fabric and the perforated film.

  Patent Document 3 discloses a sound absorbing structure in which a thin nonwoven fabric having a specific thickness and a fiber structure are laminated. However, this also has a problem that the sound absorbing property is insufficient.

  Patent Document 4 discloses a non-woven fabric for skin application containing nanofibers having a single fiber diameter of 1 to 500 nm based on the number average. However, the non-woven fabric is for skin application, and there is a problem that the sound absorbing property and the workability when used as the sound absorbing material are insufficient for use as a sound absorbing material.

JP 2009-209596 A JP2013-96014A JP 2009-186825 A JP 2007-70347 A

  An object of the present invention is to provide a laminated nonwoven fabric having excellent heat absorption performance while having excellent heat absorption performance and excellent workability.

A laminated nonwoven fabric having a surface layer portion and a base portion, wherein the surface layer portion is a nonwoven fabric layer ((1) layer) composed of nanofibers made of a thermoplastic resin having a number average single fiber diameter of 1 to 500 nm, and the number It is the nonwoven fabric A which has at least the nonwoven fabric layer ((2) layer) comprised by the fiber whose average single fiber diameter is larger than the said nanofiber, and a fabric weight is 30-100 g / m < ² >, The said base part is, A laminated nonwoven fabric having a basis weight of 200 to 800 g / m ² , a nonwoven fabric B containing 10 mass% or more of fibers having a single fiber diameter of 15 μm or less, and a sound absorption coefficient at 2000 Hz of 85% or more.

  The present invention can provide a laminated nonwoven fabric excellent not only in sound absorption properties but also in heat insulation and workability.

  Hereinafter, the actual form of the present invention will be described in detail.

The laminated nonwoven fabric of the present invention is a laminated nonwoven fabric having a surface layer portion and a base portion, and the surface layer portion has a basis weight of 30 to 100 g / m ² and is a thermoplastic resin having a number average single fiber diameter of 1 to 500 nm. A nonwoven fabric layer ((1) layer) composed of nanofibers, and a nonwoven fabric A having at least a nonwoven fabric layer ((2) layer) composed of fibers having a single-fiber diameter larger than that of the nanofibers. The base portion is a nonwoven fabric B having a basis weight of 200 to 800 g / m ² and containing 10% by mass or more of fibers having a single fiber diameter of 15 μm or less by number average.

  That is, the laminated nonwoven fabric of the present invention is formed by laminating the (1) layer, the (2) layer, and the base portion, so that the sound absorption rate at 2000 Hz is 85% or more and excellent sound absorption and excellent heat insulation. In addition to being excellent in workability. The laminated nonwoven fabric of the present invention is preferably formed by laminating the (1) layer, the (2) layer, and the base portion in this order because more excellent sound absorption is obtained.

The surface layer portion is a nonwoven fabric A having a basis weight of 30 to 100 g / m ² . By setting the basis weight to 30 g / m ² or more, the shape stability of the laminated nonwoven fabric is good, and the handleability during use is improved. Further, by setting the basis weight to 100 g / m ² or less, good sound absorption can be obtained from low frequency to high frequency. It is preferably 50 to 90 g / m ² because good sound absorption is obtained from low frequency to high frequency.

  The surface layer part is a non-woven fabric layer (hereinafter referred to as (1) layer) composed of nanofibers made of a thermoplastic resin having a number average single fiber diameter of 1 to 500 nm, and the number average single fiber diameter is nano. It is the nonwoven fabric A which has at least the nonwoven fabric layer (henceforth (2) layer) comprised by the fiber larger than a fiber. The nonwoven fabric A layer is formed by laminating the (1) layer and the (2) layer.

  Examples of the thermoplastic resin include polyethylene terephthalate, polyamide, and polyolefin. Polyamide is preferred because it has a high melting point and excellent chemical resistance.

  The nanofiber used in the present invention has a number average single fiber diameter of 1 to 500 nm.

  By using nanofibers defined in this range and (1) making the voids formed in the layer very fine, good sound absorption and good heat insulation can be obtained from low frequency to high frequency.

  As the single fiber diameter based on the number average of the nanofibers, preferably better sound absorption is obtained from low frequency to high frequency, and better heat insulation is obtained, preferably 1 to 300 nm, more preferably 100 to 250 nm. It is.

  In addition, the nanofiber in the present invention is in the form of a single fiber dispersed separately, a single fiber partially bonded, an aggregate of a plurality of single fibers (for example, a bundle), etc. That is, what is necessary is just a so-called fibrous form, and it does not stick to its length or cross-sectional shape.

  Here, as a method for obtaining the nanofiber, for example, the following method can be employed.

  That is, from two or more types of polymers having different solubility in solvents, a polymer alloy melt is formed in which the easily soluble polymer is the sea (matrix) and the hardly soluble polymer is the island (domain). After spinning this, it is cooled and solidified. And fiberize. And after extending | stretching and heat processing as needed and obtaining a polymer alloy fiber, it is set as a fabric (nonwoven fabric) by a conventional method. Then, nanofibers can be obtained by removing the easily soluble polymer with a solvent.

  In this method, since the single fiber diameter of the nanofiber is almost determined by the size of the island (domain) in the polymer alloy fiber that is the precursor of the nanofiber, the size of the island (domain) in the polymer alloy fiber can be controlled. is important.

  The island (domain) size can be controlled by controlling the kneading of the polymer and is preferably highly kneaded by a kneading extruder, a stationary kneader or the like.

In addition, a combination of polymers is also important for ultra-fine dispersion of islands with a size of 1 to 500 nm. In order to make an island (domain) close to a circle, the island (domain) polymer and the sea (matrix) polymer are preferably incompatible with each other. However, it is difficult to sufficiently ultra-disperse the island (domain) polymer by a simple combination of incompatible polymers. Therefore, a combination of polymers may be selected using the solubility parameter (SP value) as an index. Here, the SP value is a parameter reflecting the cohesive strength of a substance defined by (evaporation energy / molar volume) ^1/2 , and the SP value of various polymers is, for example, “Plastic Data Book” Asahi Kasei Amidus Co., Ltd. / Plastic editorial co-editor, page 189, etc.

It is preferable that the difference in SP value between the two polymers is 1 to 9 (MJ / m ² ) ^{1/2 because} it is easy to achieve both circularization of islands (domains) due to incompatibility and ultrafine dispersion. For example, the difference in SP value between polyamide 6 (N6) and polylactic acid is about 8 (MJ / m ² ) ^1/2, which is a preferred example. N6 and polyethylene (PE) have a difference in SP value of 11 It is about (MJ / m ² ) ^1/2, which is an undesirable example.

  In addition, the melt viscosity is also important. If the melt viscosity of the polymer forming the island component is set lower than that of the sea component, the island component polymer is likely to be deformed by shearing force, so that the island component polymer can be finely dispersed. It is preferable from the viewpoint of easy formation of nanofibers. However, if the island component polymer is excessively low in viscosity, it tends to be seamed and the blend ratio with respect to the entire fiber cannot be increased. Therefore, the viscosity of the island component polymer is preferably 1/10 or more of the viscosity of the sea component polymer.

  In order to remove the sea (matrix) polymer from the polymer alloy fiber to obtain the island (domain) polymer, a solvent that dissolves the sea (matrix) polymer and hardly dissolves the island (domain) polymer is used. Here, examples of the solvent that dissolves the sea (matrix) polymer and hardly dissolves the island (domain) polymer include an alkaline solution, an acidic solution, an organic solvent, and a supercritical fluid. For example, in a combination of polyamide and polylactic acid, polyamide exhibits poor solubility and polylactic acid exhibits easy solubility in an alkaline solution.

  (2) By laminating the layers, effects that cannot be obtained with nanofibers alone can be expressed. For example, when the (1) layer is used alone, the strength of the (1) layer is so weak that it cannot withstand actual use. While being utilized, the mechanical strength as the fiber structure can be improved, and a reinforcing effect can be obtained.

  In addition, when the (1) layer is used alone, the (1) layer may undergo dimensional change due to water absorption swelling or the like when subjected to high-order processing, but the (2) layer is laminated. Thus, dimensional stability can be imparted.

  Note that mixing the nanofibers with other fibers having a large single fiber diameter by number average results in a loss of sound absorption because there is no uniform nanofiber layer. However, by adopting a laminated structure of the (1) layer and the (2) layer, the above-described effects can be obtained without impairing sound absorption.

  (2) Examples of the fibers constituting the layer include polyethylene terephthalate fibers, polyamide 6 fibers, and polypropylene fibers. (1) When the polyamide is used for the thermoplastic resin constituting the nanofibers of the layer (1) because the layer having a melting point closer to the layer is preferable for maintaining the nonwoven fabric form of the sound absorbing layer at the time of bonding, (2) The fibers constituting the layer are preferably polyamide fibers.

  (2) The single fiber diameter by the number average of the fibers constituting the layer is larger than the single fiber diameter by the number average of the nanofibers in order to obtain the above-described effect. In order to make the above effects more prominent, the single fiber diameter based on the number average of the fibers constituting the layer (2) is preferably 1 to 100 μm. (2) Since the voids formed in the layer can be made fine and the sound absorption and heat insulation properties of the laminated nonwoven fabric can be further improved, the single fiber diameter by the number average of the fibers constituting the layer (2) is 15 to 50 μm. Is more preferable.

  In addition, the fibers constituting the (2) layer may be mixed with one or more kinds of fibers having different single fiber diameters by number average. In that case, it is preferable that the single fiber diameter by each number average of the 2 or more types of fiber which comprises a (2) layer is larger than the single fiber diameter by each number average of a nanofiber.

  Further, the fibers constituting the (2) layer may be a blend of two or more kinds of fibers made of different materials.

  The method for forming the (1) layer and the (2) layer may be a dry method or a wet method.

  In addition, as a method of forming a laminated nonwoven fabric, (1) a method in which a binder is applied between the layer and (2) layer and bonding, a method in which the layer is entangled with a needle punch or high-pressure water flow, and (2) the layer is heated. A method in which fusible fibers are mixed and heat-sealed with a heating roll, and a fiber constituting the other layer (or a fiber of its precursor) is directly laminated on one layer by a melt blow method or a spun bond method. A method or the like can be adopted.

  Moreover, about (2) layers, a surface layer part or a lamination nonwoven fabric may be formed in the state of the polymer alloy fiber which is a precursor of a nanofiber, and nanofiber may be formed by sea removal treatment after that.

  (1) The proportion of the layer in the laminated nonwoven fabric is preferably 15% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. By setting it as 15 mass% or more, while being able to improve the sound absorption property and heat insulation of a laminated nonwoven fabric, it can prevent that another fiber is exposed to the surface of a nanofiber layer from between the fibers of a nanofiber. . Moreover, as an upper limit, it is preferable that it is 50 mass% or less. By setting it to 50% by mass or less, the strength of the laminated nonwoven fabric can be made sufficient.

  The surface layer portion may have a plurality of (1) layers or (2) layers, or may have a layer different from the (1) layers or (2) layers. Here, the layer different from the (1) layer or the (2) layer is, for example, a non-woven fabric layer (hereinafter referred to as (2) -1) layers) and (2) non-woven fabric layers (hereinafter referred to as (2-2) layers) composed of fibers different from the fibers constituting the layers, and perforated films.

  As a laminated structure in the surface layer portion, at least one surface only needs to be composed of (1) layers. (1) layer / (2) layer / (1) layer, (1) layer / (2-1) layer / (2-2) layer, (1) layer / (2-1) layer / (2-2) layer / (1) layer, etc. can be employed.

Next, about a base part, a fabric weight is 200-800 g / m < ² >. By setting the basis weight to 200 g / m ² or more, a laminated nonwoven fabric having sufficient air permeability can be obtained. Moreover, a light-weight laminated nonwoven fabric is obtained by setting it as 800 g / m < ² > or less, As a result, workability, such as when a laminated nonwoven fabric is stuck as a sound-absorbing material, improves.

For the reason that the above effect is more remarkable, a preferable range of the basis weight of the base portion is 200 to 600 g / m ² , more preferably 300 to 500 g / m ² .

  The base portion includes 10% by mass or more of fibers having a single fiber diameter of 15 μm or less.

  By including 10% by mass or more of fibers having a single fiber diameter of 15 μm or less, the sound absorption can be improved also for the nonwoven fabric of the base portion. By setting the single fiber diameter based on the number average of the above fibers to 15 μm or less, the voids formed in the nonwoven fabric can be made fine, and sound absorption and heat insulation are improved. Although there is no restriction | limiting in particular about a minimum, It is preferable that it is 4 micrometers or more from a viewpoint of the card | curd permeability at the time of nonwoven fabric preparation. The fiber content of 15 μm or less is preferably 15% by mass or more for the reason that sound absorption and heat insulation can be improved. Moreover, although there is no restriction | limiting in particular about an upper limit, It is preferable that it is 40 mass% or less from a viewpoint of the card | curd permeability at the time of nonwoven fabric preparation, and cost.

  In the base part, it is preferable to use one or more types of fibers having a single fiber diameter exceeding 15 μm, other than fibers having a single fiber diameter of 15 μm or less. By using one or more kinds of fibers having a single fiber diameter exceeding 15 μm, the thickness of the nonwoven fabric can be easily controlled. More preferably, two or more kinds of fibers having a single fiber diameter exceeding 15 μm are used in combination.

  In order to maintain the form of the base part, it is preferable to use a binder fiber.

  Since the binder fiber is melted and used as an adhesive component, it is preferable to use a fiber having a melting point lower than that of a fiber having a number average single fiber diameter of 15 μm or less.

  Moreover, as a preferable range of content of a binder fiber, it is 10-30 mass%. By setting it as 10 mass% or more, the shape retention characteristic of a base part improves, and the laminated nonwoven fabric which is further excellent in sound-absorbing property can be obtained by setting it as 30 mass% or less.

  The cross-sectional shape of the fiber is not particularly limited, but other than the round cross-section, a different cross-section yarn such as a hollow cross-section or a Y-type cross-section may be used.

  Examples of the fiber constituting the base part include polyethylene terephthalate fiber, polyamide fiber, and polyolefin fiber. In view of productivity and cost, polyethylene terephthalate fibers are preferable. Moreover, in order to improve the flame retardance of a laminated nonwoven fabric, you may use the flame retardant polyester which is a flame retardant material.

  In addition, as a method of forming the base portion on the laminated nonwoven fabric, a nonwoven fabric B containing binder fibers is prepared in advance by a needle punch method, an airlay method, etc., and then heated with a far infrared heater, or a nonwoven fabric B with a heating roll. It is possible to employ a method in which the material is thermally fused to the nonwoven fabric A.

  In addition to the method described above, the nonwoven fabric A and the nonwoven fabric B may be bonded together by spraying a resin powder for adhesion to the nonwoven fabric A and the nonwoven fabric B, followed by heat treatment and bonding, or heating with a far infrared heater or heating roll. And heat fusing.

  The laminated nonwoven fabric of the present invention thus obtained has a sound absorption rate of 85% or more at 2000 Hz and has good sound absorption.

  If the sound absorption rate at 2000 Hz is 85% or more, the sound absorption is excellent and suitable for use in automobiles and the like.

  Moreover, the laminated nonwoven fabric of the present invention thus obtained has a thermal conductivity of 0.030 W / mK or less, and has good heat insulating properties.

  When a laminated nonwoven fabric is practically used as a sound-absorbing material, there are many cases where thermal insulation is required as well as sound-absorbing properties, and the laminated nonwoven fabric of the present invention is suitable for use as a sound-absorbing material for automobiles, electrical equipment, houses, etc. It is.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, this invention is not limited to these Examples.

[Measuring method]
(1) Domain size in sea-island structure A synthetic fiber is sliced so that a cross section appears, and the cross section is observed with a transmission electron microscope (TEM). When the number of in-plane islands exceeds 50, the number n is 50. Were extracted at random, the cross-sectional area of each island was measured with image analysis software, and the domain size corresponding to the diameter in terms of a true circle was calculated from the area as an average value.

(2) Non-woven fabric surface observation by SEM An ultra-thin section was cut out in the cross-sectional direction of the non-woven fabric of the surface layer portion, and the non-woven fabric surface was observed with a scanning electron microscope at a magnification of 1200 times (SEM) (S-3500N type manufactured by Hitachi, Ltd.). .

(3) Single fiber diameter based on the number average of nanofibers When observing the nonwoven fabric surface with the SEM, a photograph of the nonwoven fabric surface is taken, a nanofiber layer is extracted from the photograph, and image processing software (WINROOF) is used. Then, a group of 30 nanofibers adjacent to each other in the same photograph at a magnification of 10 was randomly extracted at 10 locations, the diameter of a total of 300 single fibers was measured, and the simple average value was obtained. It was set as the single fiber diameter by the number average of a fiber.

(4) (2) Single fiber diameter based on the number average of the fibers of the layer and the base part The fineness is measured based on JIS L 1015 (1999), and the fineness and “Fiber Handbook (Edited by Japan Chemical Fiber Association)” etc. are published. The single fiber diameter of the fiber was determined from the specific gravity of the material. When the fiber was a modified cross-section fiber, the cross section of the modified cross-section fiber was calculated by converting it into a circle having the same area.

(5) Weight per unit area Measured based on JIS L 1913 (1998) 6.2. Three 300 mm × 300 mm test pieces were collected from the sample using a steel ruler and a razor blade. The mass of the test piece in the standard state was measured, the mass per unit area was determined by the following formula, and the average value was calculated.
ms = m / S
ms: Mass per unit area (g / m ² )
m: average weight of the test piece (g)
S: Area (m ² ) of the test piece.

(6) Mass ratio of (1) layer in surface layer part The mass ratio of (1) layer in the surface layer part is the above (5) for each of the (1) layer before lamination and the (2) layer before lamination. The basis weight was measured by the following formula, and calculated by the following formula.
Mass ratio (%) of (1) layer in the surface layer portion = (m (1-1) + m (1-2) +... + M (1-n)) / (m (1-1) + m (1-2) + ... + m (1-n) + m (2-1) + m (2-2) ... + m (2-o)) × 100
n: number of (1) layers o: (2) number of layers m (1-n): basis weight of the (1) layer of the nth layer before lamination (g / m ² )
m (2-o): Weight of the (2) layer of the o-th layer before lamination (g / m ² )
m (1-1) + m (1-2) + ... + m (1-n): total value m (1-1) + m (1-2) + ... + m (1) of each of the plurality of (1) layers -N) + m (2-1) + m (2-2) ... + m (2-o): total value of the basis weights of the plurality of (1) layers and the plurality of (2) layers.

(7) Fineness Based on JIS L 1015 (1999) 8.5.1 A method, pull the sample in parallel with a hammer and place it on Rasha paper placed on a cutting table. The gauge plate is crimped as it is, cut to a length of 30 mm with a blade such as a safety razor, and 300 fibers are counted as a set, and the mass is measured to determine the apparent fineness. From the apparent fineness and the equilibrium moisture content measured separately, the positive fineness (dtex) was calculated by the following formula, and the average value of 5 times was obtained.
F0 = D ′ × {(100 + R0) / (100 + Re)}
F0: Positive fineness (dtex)
D ': Apparent fineness (dtex)
R0: Official moisture content (0.4)
Re: equilibrium moisture content.

(8) Fiber length Based on JIS L 1015 (1999) 8.4.1 A method, a sample is drawn in parallel with a hammer and a staple diagram is made to be about 25 cm wide with a pair type sorter. At the time of preparation, the number of times the fibers are grasped and pulled out to arrange all the fibers on the velvet plate is about 70 times. Place a celluloid plate with ticks on it and draw it on graph paper. The staple diagram illustrated in this way is equally divided into 50 fiber length groups, the boundaries of each segment and the fiber lengths at both ends are measured, 49 boundary fiber lengths are added to the average of the fiber lengths at both ends, and the result is divided by 50. The average fiber length (mm) was calculated.

(9) Strength and elongation Based on JIS L 1015 (1999) 8.7.1, the distance is 20 mm and the fibers are loosely stretched one by one on the dividing line. One sample per category. Attach the sample to the grip of the tensile tester, cut the piece of paper near the upper grip, pull at a grip interval of 20 mm, and a tensile speed of 20 mm / min, and load (N) and elongation (mm) when the sample is cut. The tensile strength (cN / dtex) and the elongation (%) were calculated by measurement and the following formula.
Tb = SD / F0
Tb: Tensile strength (cN / dtex)
SD: Load at break (cN)
F0: Positive fineness of sample (dtex)
S = {(E2-E1) / (L + E1)} × 100
S: Elongation rate (%)
E1: Looseness (mm)
E2: Elongation at cutting (mm) or Elongation at maximum load (mm)
L: Grasp interval (mm).

(10) Sound absorption at 2000 Hz Three circular test pieces having a diameter of 90 mm and a thickness of 20 ± 2 mm (no problem) were taken from the sample, and the normal incident sound absorption coefficient was measured according to JIS A 1405 (1998).

(11) Thermal conductivity Measured according to JIS A 1412-2 (1999) 6.2. The thermal conductivity was measured using a thermal conductivity measuring device HC-074 manufactured by Eihiro Seiki Co., Ltd. A sample having a width of 300 mm, a length of 300 mm, and a thickness of 20 ± 5 mm was prepared, and the sample was compressed in the thickness direction to obtain a measurement sample having a thickness of 20 mm. As the standard sample, expanded polystyrene was used. The sample is left in a standard condition of a temperature of 20 ° C. and a humidity of 65% RH for 24 hours, and then the sample is put into a measuring machine, the temperature difference of the plate is 25 ° C., the average temperature is 20 ° C. The plate temperature was 7.5 ° C.), and the thermal conductivity (W / m · K) was calculated from the average value of the number of tests three times.

[Example 1]
(Polymer alloy fiber)
Melt viscosity 212 Pa · s (262 ° C., shear rate 121.6 sec ⁻¹ ), melting point 220 ° C. polyamide 6 (N6) (40 mass%), weight average molecular weight 120,000, melt viscosity 30 Pa · s (240 ° C., shear Poly L-lactic acid (60 mass%) having a speed of 2432 sec ⁻¹ ) and a melting point of 170 ° C. and an optical purity of 99.5% or higher is separately weighed and separately supplied to a biaxial extrusion kneader having the following details. The polymer alloy chip was obtained by kneading.
Screw shape: Fully meshed in the same direction Double thread screw: Diameter 37 mm, effective length 1670 mm, L / D = 45.1
Kneading section length is 28% of screw effectiveness
The kneading part has three back flow parts located on the discharge side from 1/3 of the effective screw length. Vent: 2 parts.

  The obtained polymer alloy chip is supplied to a uniaxial extrusion-type melting apparatus for a staple spinning machine, and melt spinning is performed at a melting temperature of 235 ° C., a spinning temperature of 235 ° C. (a base surface temperature of 220 ° C.), and a spinning speed of 1200 m / min. A polymer alloy fiber was obtained. After the yarns were combined, steam drawing was performed to obtain a tow composed of polymer alloy fibers having a single yarn fineness of 3.6 dtex.

(Crimping and cutting process)
The tow made of the polymer alloy fiber was crimped (12 peaks / 25 mm) and then cut into 51 mm short fibers. The strength of the obtained polymer alloy fiber showed excellent properties of 3.0 cN / dtex and elongation of 40%. When the cross section of the fiber was observed with a TEM in accordance with the method for measuring the single fiber diameter based on the number average of the nanofibers described above, the islands (domains) were uniformly dispersed with a number average diameter of 200 nm. That is, the single fiber diameter based on the number average of the nanofibers was 200 nm.

(Surface layer part) (1) layer After opening the said short fiber with a card | curd, it was set as the web with the cross wrap weber. This web was needle punched at a punch density of 80 / cm ² to obtain a nonwoven fabric having a basis weight of 30 g / m ² and a thickness of 0.3 mm.

(Surface Layer) (2) Layer A staple fiber having a single yarn fineness of 2.2 dtex (single fiber diameter: 20 μm) and a fiber length of 51 mm made of polyamide 6 (N6) was opened with a card, and then a web was formed with a cross wrap weber. This web was needle punched at a punch density of 80 / cm ² to obtain a nonwoven fabric having a basis weight of 60 g / m ² and a thickness of 0.4 mm.

The two types of nonwoven fabrics obtained above were laminated, and needle punching was performed at a punch density of 40 / cm ² to obtain nonwoven fabric A having a basis weight of 90 g / m ² and a thickness of 0.5 mm.

By treating the non-woven fabric A with a 1% aqueous sodium hydroxide solution at a temperature of 95 ° C. and a bath ratio of 1:40, the polylactic acid is removed from the sea, and the basis weight composed of N6 nanofibers and N6 yarns is 72 g / A non-woven fabric A having m ² and a thickness of 0.4 mm was obtained.

(Base part)
Single fiber fineness 2.2 dtex (single fiber diameter 20 μm) made of polyethylene terephthalate (PET), 50% by mass of staple fiber having a fiber length of 51 mm, hollow cross section (single fiber diameter 38 μm) made of PET and having a single yarn fineness 6.6 dtex, 15% staple fiber with a fiber length of 51 mm, made of PET, single yarn fineness of 0.8 dtex (single fiber diameter 12 μm), 20% by weight of staple fiber with a fiber length of 35 mm, and single yarn fineness of copolymerized polyester as binder fiber 4 A staple fiber having a diameter of 4 dtex (single fiber diameter: 32 μm) and a fiber length of 51 mm was mixed at a ratio of 15 wt%, opened with a card, and then a web was obtained with a cross-wrap weber. Next, a nonwoven fabric B having a basis weight of 400 g / m ² and a thickness of 20 mm was obtained by heat treatment at 120 ° C. for 3 minutes using a hot air circulation dryer.

In order to paste the surface layer and the base part together, heat treatment is performed by spraying a polyethylene resin powder between them. A laminated nonwoven fabric having a basis weight of 485 g / m ² and a thickness of 21 mm was obtained.

  The laminated nonwoven fabric obtained had a sound absorbing property at 2000 Hz of 92% and a thermal conductivity of 0.029 (W / m · K), and a laminated nonwoven fabric having a good sound absorbing property could be obtained.

[Example 2]
(Surface part)
The same laminated nonwoven fabric for surface layer as in Example 1 was used.

(Base part)
Hollow cross section (single average by single average) with a single yarn fineness of 2.2 dtex made of polyethylene terephthalate (PET) (single fiber diameter of 20 μm by number average), 60 wt% staple fiber with a fiber length of 51 mm, single yarn fineness of 6.6 dtex made of PET 15% staple fiber with a fiber diameter of 38 μm), a fiber length of 51 mm, a PET single fiber fineness of 0.8 dtex (number average single fiber diameter of 12 μm), a staple fiber with a fiber length of 35 mm is 10% by mass, and a binder fiber. After blending 15% by mass of staple fiber with a single yarn fineness of 4.4dtex (number average single fiber diameter of 32μm) and fiber length of 51mm made of polymerized polyester, and opening with a card, the web with a cross wrap weber Obtained. Next, a nonwoven fabric B having a basis weight of 400 g / m ² and a thickness of 20 mm was obtained by heat treatment at 120 ° C. for 3 minutes using a hot air circulation dryer.

In order to paste the surface layer and the base part together, heat treatment is performed by spraying a polyethylene resin powder between them. A laminated nonwoven fabric having a basis weight of 485 g / m ² and a thickness of 20 mm was obtained.

  The laminated nonwoven fabric obtained had a sound absorbing property at 2000 Hz of 88% and a thermal conductivity of 0.030 (W / m · K), and a laminated nonwoven fabric having a good sound absorbing property could be obtained.

[Comparative Example 1]
(Surface part)
The same laminated nonwoven fabric for surface layer as in Example 1 was used.

(Base part)
Hollow section of single yarn fineness 2.2 dtex made of polyethylene terephthalate (PET) (single fiber diameter 20 μm by number average), staple fiber of fiber length 51 mm, single fiber fineness 6.6 dtex made of PET (by number average) 15% staple fiber having a single fiber diameter of 38 μm), a fiber length of 51 mm, 15 mass% of staple fiber having a single fiber fineness of 4.4 dtex (number average single fiber diameter of 32 μm) made of a copolyester as a binder fiber, and 15 mass of staple fiber. %, And after opening with a card, a web was obtained with a cross-wrap weber. Next, a nonwoven fabric B having a basis weight of 400 g / m ² and a thickness of 20 mm was obtained by heat treatment at 120 ° C. for 3 minutes using a hot air circulation dryer.

In order to paste the surface layer and the base part together, heat treatment is performed by spraying a polyethylene resin powder between them. A laminated nonwoven fabric having a basis weight of 485 g / m ² and a thickness of 20 mm was obtained.

  The obtained laminated nonwoven fabric had a sound absorbing property at 2000 Hz of 82% and a thermal conductivity of 0.030 (W / m · K).

[Comparative Example 2]
(Surface part)
None.

(Base part)
The same nonwoven fabric as in Example 1 was used.

  The obtained laminated nonwoven fabric had a sound absorption of 72% at 2000 Hz and a thermal conductivity of 0.033 (W / m · K), resulting in a laminated nonwoven fabric inferior in sound absorption.

  Table 1 shows the configurations, sound absorption coefficient (%), and thermal conductivity of Examples 1-2 and Comparative Examples 1-2.

Claims (5)

It is a laminated nonwoven fabric having a surface layer part and a base part,
The surface layer part is a nonwoven fabric layer ((1) layer) composed of nanofibers made of a thermoplastic resin having a number average single fiber diameter of 1 to 500 nm, and the number average single fiber diameter is larger than that of the nanofibers. It is a nonwoven fabric A having at least a nonwoven fabric layer ((2) layer) composed of fibers and having a basis weight of 30 to 100 g / m ² .
The base portion is a nonwoven fabric B having a basis weight of 200 to 800 g / m ² and containing 10% by mass or more of fibers having a single fiber diameter of 15 μm or less,
A laminated nonwoven fabric having a sound absorption coefficient of 85% or more at 2000 Hz. The laminated nonwoven fabric according to claim 1, which has a thermal conductivity of 0.030 W / mK or less. The laminated nonwoven fabric according to claim 1 or 2, wherein the fibers contained in the base portion include polyethylene terephthalate fibers. The laminated nonwoven fabric according to any one of claims 1 to 3, wherein the thermoplastic resin constituting the nanofiber is polyamide. The sound-absorbing material which has the laminated nonwoven fabric in any one of Claims 1-4.