JP6030381B2 - Sound-absorbing material including meltblown nonwoven fabric - Google Patents

Description

  The present invention relates to a sound absorbing material comprising a fiber assembly including a melt blown nonwoven fabric.

  Conventionally, single-layer organic and inorganic fiber aggregates are often used as sound-absorbing materials contained in automobile engine rooms and home appliances. These fiber aggregates have the function of absorbing and attenuating the generated noise, but the effect is not always sufficient and is often unsatisfactory. In addition, a sound absorbing material composed of two or more layers of fiber aggregates having an ultrafine fiber layer with a very small basis weight as a surface layer has been proposed (see, for example, Patent Document 1), but has a drawback that the sound absorbing characteristics are not necessarily good. was there.

JP 2002-161464 A

  The present invention is intended to solve the above-described problems, and an object of the present invention is to provide a novel sound-absorbing material that is excellent in heat resistance and that is remarkably excellent in noise-absorbing performance and surface wear resistance. Is.

  As a result of various studies on the above problems, the present inventor found that the meltblown nonwoven fabric having a specific apparent density and the constituent fibers accumulated in a planar shape and other fiber aggregates are in a flat state of the meltblown nonwoven fabric. It has been found that the sound-absorbing performance is dramatically improved and the above-mentioned problems can be solved by joining and integrating while maintaining. Melt blown non-woven fabrics have low surface wear resistance, so there are practical problems depending on the application, but as a solution, polyester spunbond non-woven fabric with excellent wear strength and heat resistance is coated on one or both sides. It has been found that the practical performance is further improved by making it disposed on the outermost surface, and the present invention has been completed.

That is, the present invention has an apparent density of 0. 20% by mass to 20% by mass of a copolymerized polyethylene terephthalate resin and 20% by mass to 80% by mass of polybutylene terephthalate, which are substantially flatly integrated. A melt-blown nonwoven fabric having a weight of 1 to 0.4 g / cm ³ and a basis weight of 5 to 300 g / m ^{2, and} a spunbond nonwoven fabric having a basis weight of 10 to 100 g / m ² made of polyester fibers having a single fiber fineness of 1 to 11 dtex on at least one surface of the nonwoven fabric; Is a sound-absorbing material characterized in that the spunbonded nonwoven fabric is disposed on the outermost surface, and preferably a copolymerized polyethylene terephthalate resin comprises a dicarboxylic acid component and a glycol component. The above sound-absorbing material, more preferably copolymer polyethylene terephthalate resin, Among dicarboxylic acids, 75 mol% or more is a terephthalic acid component, 1.0 mol% to 3.5 mol% is a component derived from a compound represented by the following formula (I), and 2.0 mol% to The above sound absorbing material, which is the melt blown nonwoven fabric, characterized in that 10.0 mol% is a cyclohexanedicarboxylic acid component and 2.0 mol% to 8.0 mol% is an aliphatic dicarboxylic acid component. .

  Further, the present invention is preferably a vehicle, an electric product or a wall layer material using the above sound absorbing material.

  Unlike the conventional sound absorbing material, the sound absorbing material of the present invention includes at least one melt-blown nonwoven fabric having a specific apparent density and basis weight, and therefore has excellent sound absorbing performance. Moreover, since the polyester spunbond nonwoven fabric excellent in abrasion resistance is arranged on the surface of the melt blown nonwoven fabric, it is excellent in practicality such as durability.

  The copolymerized polyethylene terephthalate (hereinafter referred to as PET) resin used for the melt blown nonwoven fabric of the present invention is a copolymerized polyester composed of a dicarboxylic acid component and a glycol component. The copolymerized PET resin is a polyester having an ethylene terephthalate unit as a main repeating unit, and among the dicarboxylic acid component, 75 mol% or more of the repeating unit is a terephthalic acid component. It is preferable to consist of the above copolymerization components.

  Further, in the present invention, the copolymerized PET comprises a dicarboxylic acid and a glycol component, and among the dicarboxylic acid component, 75 mol% or more is a terephthalic acid component, and 1.0 mol% to 3.5 mol% is the following. It is a component derived from the compound represented by formula (I), 2.0 mol% to 10.0 mol% is a cyclohexanedicarboxylic acid component, and 2.0 mol% to 8.0 mol% is an aliphatic dicarboxylic acid. It is preferably composed of a polyester fiber that is a component.

Examples of the metal salt (A) of sulfoisophthalic acid represented by the above formula (I) include 5-sodium sulfoisophthalic acid, or sulfonic acid alkali metal bases such as 5-potassium sulfoisophthalic acid and 5-lithium sulfoisophthalic acid. And dicarboxylic acid component having 5-tetraalkylphosphonium sulfoisophthalic acid such as 5-tetrabutylphosphonium sulfoisophthalic acid and 5-ethyltributylphosphonium sulfoisophthalic acid.
Only one type of the metal salt (A) of sulfoisophthalic acid represented by the above formula (I) may be copolymerized in the polyester, or two or more types may be copolymerized.
By copolymerizing the metal salt (A) of sulfoisophthalic acid represented by the above formula (I), the amorphous structure can be retained in the fiber internal structure as compared with the conventional polyester fiber, and as a result, the dispersion Normal pressure dyeing is possible for dyes and cationic dyes.

  When the copolymerization amount of the metal salt (A) of sulfoisophthalic acid represented by the above formula (I) is less than 1.0 mol%, a cationic dyeable dye which becomes clear and has a good color tone when dyed with a cationic dye. Can not be obtained. On the other hand, when the copolymerization amount of (A) exceeds 3.5 mol%, the viscosity of the polyester is remarkably increased and spinning becomes difficult. The amount becomes excessive and the clarity of the color tone is rather lost. From the viewpoint of the sharpness and spinnability of the dyed product, the copolymerization amount of (A) is preferably 1.2 to 3.0 mol%, more preferably 1.5 to 2.5 mol%. preferable.

  In the present invention, among dicarboxylic acid components, cyclohexanedicarboxylic acid and / or an ester-forming derivative thereof is 2.0 to 10.0 mol%, preferably 5.0 to 10.0 mol%, and aliphatic dicarboxylic acid. And / or its ester-forming derivative is preferably copolymerized in an amount of 2.0 to 8.0 mol%, preferably 3.0 to 6.0 mol%.

  When cyclohexanedicarboxylic acid or its ester-forming derivative (hereinafter also referred to as cyclohexanedicarboxylic acid component) is copolymerized with PET, it has a characteristic that the disorder of the crystal structure is small, so a high dyeing rate is secured. Meanwhile, a fiber excellent in light fastness can be obtained.

  By copolymerizing the cyclohexanedicarboxylic acid component, the crystal structure of the polyester fiber is disturbed, and the orientation of the amorphous part is lowered. Therefore, it is suitable for producing a nonwoven fabric by melt blown, and the penetration of the cationic dye and the disperse dye into the fiber is facilitated, and the atmospheric pressure dyeability of the cationic dye and the disperse dye can be improved. . Furthermore, since the cyclohexane dicarboxylic acid component is less disturbed in crystal structure than other aliphatic dicarboxylic acids, it is excellent in light fastness.

  If the amount of copolymerization of the cyclohexanedicarboxylic acid component is less than 2.0 mol% in the dicarboxylic acid component, the degree of orientation of the amorphous part inside the fiber will be high, so that the dyeability in a normal pressure environment will be insufficient and the target dyeing will be insufficient. It is not preferable because the dressing rate cannot be obtained. Moreover, when it exceeds 10.0 mol% in the dicarboxylic acid component, a stable meltblown nonwoven fabric cannot be obtained due to the low glass transition temperature of the resin and the low degree of orientation of the amorphous part inside the fiber.

  The cyclohexanedicarboxylic acid used in the present invention includes three positional isomers of 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. From the point obtained, any positional isomer may be copolymerized, or a plurality of positional isomers may be copolymerized. Further, although there are cis / trans isomers for each positional isomer, any stereoisomer may be copolymerized, or both cis / trans positional isomers may be copolymerized. The same applies to the cyclohexanedicarboxylic acid derivative.

  As for the fatty acid dicarboxylic acid and its ester-forming derivative component, similarly to the cyclohexyne dicarboxylic acid component, the crystal structure of the polyester fiber is disturbed and the orientation of the amorphous part is lowered. In addition to being suitable, the penetration of the cationic dye and the disperse dye into the fiber is facilitated, and the atmospheric dyeability can be improved.

  If the copolymerization amount of the fatty acid component in the dicarboxylic acid component is less than 2.0 mol%, the degree of orientation of the amorphous part inside the fiber is high, so that the dyeing property for the disperse dye under the normal pressure environment is insufficient. This is not preferable because a dyeing rate of 2 is not obtained. Moreover, when the copolymerization amount of the fatty acid component in the dicarboxylic acid component exceeds 8.0 mol%, the degree of orientation of the amorphous part in the fiber is lowered, and a stable meltblown nonwoven fabric cannot be obtained, which is not preferable.

  Preferred examples of the aliphatic dicarboxylic acid component of the present invention include aliphatic dicarboxylic acids such as adipic acid, sebacic acid and decanedicarboxylic acid. These can be used alone or in combination of two or more.

  As long as the atmospheric pressure dyeability and quality of the melt blown nonwoven fabric in the present invention are not deteriorated, other dicarboxylic acid components other than the terephthalic acid component, cyclohexane dicarboxylic acid component, and aliphatic dicarboxylic acid component may be copolymerized. Also good. Specifically, an aromatic dicarboxylic acid component such as isophthalic acid or naphthalenedicarboxylic acid or an ester-forming derivative thereof may be used alone or a plurality of types may be copolymerized within a range of 10.0 mol% or less.

  However, copolymerization of these components not only makes the transesterification reaction and polycondensation reaction complicated, but if the amount of copolymerization exceeds an appropriate range, washing fastness may be reduced. Specifically, when isophthalic acid and its ester-forming derivative are copolymerized in an amount exceeding 10 mol% with respect to the dicarboxylic acid component, the fastness to washing may be deteriorated even if the constituent requirements of the present invention are satisfied. It is desirable that the amount be 5 mol% or less, more desirably 0 mol% (not copolymerize).

  Furthermore, the copolymerized PET resin of the present invention includes a matting agent such as titanium oxide, barium sulfate and zinc sulfide, a heat stabilizer such as phosphoric acid and phosphorous acid, a light stabilizer, an antioxidant, an oxidation agent, respectively. A surface treatment agent such as silicon may be included as an additive. By using a heat stabilizer, thermal decomposition during heat melting or subsequent heat treatment can be suppressed. Moreover, the light resistance at the time of use of a fiber can be improved by using a light stabilizer, and it is also possible to improve dyeability by using a surface treating agent.

  These additives may be added in advance to the polymerization system when the copolymerized PET resin is obtained by polymerization. However, it is generally preferable to add an antioxidant or the like at the end of the polymerization, and this is preferable particularly when the polymerization system is adversely affected or when the additive is deactivated under the polymerization conditions. On the other hand, matting agents, heat stabilizers, and the like are preferably added at the time of polymerization because they are easily dispersed uniformly in the resin polymer.

  The copolymerized PET resin of the present invention has an intrinsic viscosity of 0.55 to 0.7, preferably 0.58 to 0.68, and more preferably 0.58 to 0.60. When the intrinsic viscosity exceeds 0.7, the crystallinity cannot be sufficiently increased at the time of meltblown, so that the thermal stability is low, that is, free under a temperature exceeding 70 to 80 ° C. above the glass transition point. If placed, the fiber contracts greatly, which causes a very large problem in practical use. On the other hand, when the intrinsic viscosity is less than 0.55, not only is the fiber easily broken during spinning, but the productivity is poor, and the strength of the obtained fiber is low.

  The melt blown nonwoven fabric used for the sound absorbing material of the present invention has an average fiber diameter of 10 μm produced by a melt blown method from a mixture of 80% by mass to 20% by mass of copolymerized PET resin and 20% by mass to 80% by mass of polybutylene terephthalate. It is important that the fibers are composed of the following fibers and that the constituent fibers are accumulated substantially in a planar shape. Although it is possible to obtain a nonwoven fabric having an average fiber diameter exceeding 10 μm by the melt blown method, a melt blown nonwoven fabric having an average fiber diameter exceeding 10 μm cannot achieve the object of the present invention. It is more preferable to use a melt blown nonwoven fabric made of fibers having an average fiber diameter of 2 μm to 8 μm.

  As described above, the resin used in the present invention is a mixture of copolymerized PET resin and polybutylene terephthalate. A general-purpose PET-only melt blown nonwoven fabric shrinks by 40% when treated in a drying furnace at 120 ° C., for example, and does not have sufficient heat resistance. On the other hand, a meltblown nonwoven fabric containing only polybutylene terephthalate does not adhere to a polyester spunbond nonwoven fabric that is easily available in the city by thermal calendering or hot embossing. However, according to the present invention, 80% by mass to 20% by mass of the copolymerized PET resin and 20% by mass to 80% by mass of the polybutylene terephthalate are mixed and melt blown to provide excellent heat resistance and polyester spunbond. A meltblown nonwoven fabric that is easily bonded to the nonwoven fabric by thermocompression bonding is obtained. When the mixing ratio is outside this range, a melt blown nonwoven fabric that satisfies both heat resistance and adhesiveness at the same time cannot be obtained.

The apparent density of the melt blown nonwoven fabric used in the present invention needs to be in the range of 0.1 to 0.4 g / cm ³ . When the apparent density is less than 0.1 g / cm ³ , the sound absorption effect is significantly impaired. On the other hand, if the apparent density exceeds 0.4 g / cm ³ , the sound absorbing effect is reduced, which is not preferable.

Basis weight of the meltblown nonwoven fabric is preferably in the range of 5~300g / m ² is preferably in the 10 to 100 g / m ^2. When the basis weight is less than 5 g / m ² , a sufficient sound absorbing effect cannot be exhibited when the fiber aggregate on the inner surface is joined and integrated. On the other hand, if the basis weight exceeds 300 g / m ² , the cost increases and the utility is lacking.

  Furthermore, in the sound-absorbing material of the present invention, the meltblown nonwoven fabric is accumulated in a planar shape on a collection surface such as an accumulation net in the nonwoven fabric production process, and the fibers are hardly arranged in the three-dimensional direction. The resulting melt-blown nonwoven fabric made of ultrafine fibers generally has low surface wear strength, so when used as it is as a surface layer of a sound-absorbing material, the fibers are worn away by cutting or the like due to friction during handling or use. The role as a meltblown nonwoven is lost.

In order to compensate for such drawbacks, the present inventors have found that it is extremely effective to coat one or both sides of a melt blown nonwoven fabric using a polyester spunbond nonwoven fabric having excellent wear strength. That is, by disposing a spunbond nonwoven fabric made of polyester fiber having a basis weight of 10 to 100 g / m ² and a single fiber fineness of 1 to 11 dtex on the surface of the meltblown nonwoven fabric, the surface wear strength is remarkably improved and the sound absorbing performance of the sound absorbing material is improved. It is maintained for a long time. Furthermore, the polyester spunbonded nonwoven fabric has a melting point of 200 ° C. or higher, which is a desirable material from the viewpoint of heat resistance.

  It is desirable to bond the meltblown nonwoven fabric and the polyester spunbond nonwoven fabric by hot embossing or thermal calendaring. When bonding by a hot embossing calendar, the embossed area is desirably 50% or less, particularly 15% or less. This is because the embossed portion is usually easily formed into a film, and the film portion of such a melt-blown nonwoven fabric has a lower sound absorption effect than the fiber portion, so it is desirable that the amount is as small as possible.

  The sound-absorbing material of the present invention is obtained by laminating a polyester spunbonded nonwoven fabric on at least one surface of the meltblown nonwoven fabric, and is used as a sound-absorbing material so that the spunbonded nonwoven fabric side is on the outermost surface. May be laminated on the other surface of the meltblown nonwoven fabric as needed, if necessary.

In this case, organic or inorganic natural fibers or synthetic fibers can be appropriately used as the fiber aggregate of the base layer. This fiber web can be produced by a dry method such as a spunbond method or a card method, or a wet method using papermaking. The fiber web prepared by such a method can be applied to various means such as resin bonding by impregnation or spraying, heat melting bonding by fusing fiber, mechanical entanglement such as needle punching or water entanglement, and combinations thereof. Are combined into a fiber assembly. However, the preferred form is not one in which fibers are entangled three-dimensionally, such as needle punching or water entanglement, but a fiber assembly in which the fibers are accumulated as flat as possible is preferred. The apparent density of the fiber assembly is preferably 0.01 to 0.10 g / cm ³ and the basis weight is preferably 30 to 2000 g / m ² . If the apparent density is less than 0.01 g / cm ^3, the rigidity for supporting the meltblown nonwoven fabric may be insufficient, and the entire sound absorbing material may be deformed. On the other hand, if it is greater than 0.10 g / cm ^{3, the} sound absorption characteristics may deteriorate. Similarly, when the basis weight is less than 30 g / m ² , the result of the rigidity is insufficient, which is not preferable. On the other hand, if the basis weight exceeds 2000 g / m ² , the rigidity becomes too large, and it becomes difficult to process the laminate.

  The base layer, the meltblown nonwoven fabric and the polyester spunbond nonwoven fabric are preferably integrated by bonding. For the joining, a resin adhesive such as hot melt, an adhesive net or powder, a fusion fiber, or the like is mainly used, but the number of superposed layers in this case is not particularly limited. As long as the melt blown nonwoven fabric, the base fiber aggregate, and the polyester spunbonded nonwoven fabric are in a range that satisfies the conditions of the basis weight and the thickness of the sound absorbing material specified in the present invention, specific usage modes such as the required level of sound absorbing performance Depending on the situation, not only one layer but also two or more layers may be laminated as required.

  It should be noted that mechanical entanglement means such as a needle punch should be avoided as much as possible in the interlayer bonding between the melt blown nonwoven fabric and the fiber assembly. With such a means, the opening of the dense meltblown nonwoven fabric is caused by the action of the needles penetrating each other. Further, the constituent fibers of the meltblown nonwoven fabric accumulated in a planar shape are rearranged three-dimensionally by the action of the above means. These two points both have a very bad influence on the sound absorption and insulation performance. Therefore, it is necessary to join the layers so as not to damage the two-dimensional fiber arrangement of the meltblown nonwoven fabric as much as possible.

  The overall thickness of the sound absorbing material of the present invention is 5 to 50 mm. When the thickness is less than 5 mm, a sufficient effect on the sound absorbing performance cannot be obtained, which is not preferable. Further, when the thickness exceeds 50 mm, it is preferable in terms of sound absorbing performance, but when used as a sound absorbing material, the installation space becomes excessive, which is not desirable for product design, and further, it is not preferable because it is difficult to handle in terms of processing such as cutting and molding. Providing excessive performance is also uneconomical.

  The sound absorbing material of the present invention obtained in this way is excellent in heat resistance and sound absorbing performance such as noise, and as a sound absorbing material included in an engine room of a vehicle such as an automobile or a home appliance, It can be used for building wall coverings, house wraps, etc.

  Next, in order to describe the present invention more specifically, examples of the present invention will be shown below, but the present invention is not limited to these examples.

[Example 1 and Comparative Example 1]
Of the dicarboxylic acid component, 88.3 mol% is terephthalic acid, 1.7 mol% of 5-sodium sulfoisophthalic acid, 5.0 mol% of 1,4-cyclohexanedicarboxylic acid, and 5.0 of adipic acid. A transesterification reaction and a polycondensation reaction were carried out with the total carboxylic acid component, ethylene glycol, and predetermined additives contained in mol% to obtain a copolymerized polyethylene terephthalate resin polymer.
A melt blown nonwoven fabric having a weight per unit area of 35 g / m ^{2 made} of a polymer blend having a blending ratio of the copolymer polyethylene terephthalate resin / polybutylene terephthalate of 40/60 was prepared. This nonwoven fabric had an average fiber diameter of 4.2 ηm and an apparent density of 0.25 g / cm ³ . Next, a spunbonded nonwoven fabric having a basis weight of 20 g / m ² made of polyester fiber having a single fiber fineness of 6.2 dtex was prepared, laminated on the surface of the meltblown nonwoven fabric, and both were partially bonded using an embossed calendar. The embossed area in the hot embossed calendar adhesion by this dot-like pattern was 4.1%.

Next, 40% by mass of a polyester fiber having a cut length of 51 mm at 13 dtex, 45% by mass of a polyester fiber having a cut length of 40 mm by 3.3 dtex, and a copolymer polyester having a polyethylene terephthalate as a core component and a softening point of about 170 ° C. as a sheath component We were prepared two kinds of card web having a mass per unit area of 200 g / m ² and basis weight 265 g / m ² of composite polyester fibers 15% by weight of 2.2dtex to. Next, a card web having a basis weight of 200 g / m ² was subjected to heat fusion processing through a dryer at 180 ° C. The apparent density was 0.017 g / cm ³ . Subsequently, the surface of this nonwoven fabric is laminated with a polyamide melt-bonded net having a basis weight of 10 g / m ² , the melt blown nonwoven fabric, and the polyester spunbond nonwoven fabric in this order, and is passed through a heating roll as it is to be fused and joined to form a unit weight of 265 g. A fiber laminate of / m ² was obtained.

The obtained basis weight 265 g / m ² of fiber laminate (Example 1, thickness 13 mm) nonwoven (Comparative Example 1, thickness 15 mm) was obtained by heat-treating and the card web aforementioned basis weight 265 g / m ² When the sound absorption performance was examined by the reverberation chamber method sound absorption rate measurement method of JIS A1409, the former shows about 30% in the latter 1000 Hz region, and about 50% or more good in 3000 Hz, and is an excellent sound absorbing material. It turned out to be. Moreover, this sound-absorbing material was also excellent in surface wear strength, and it was found that there was no problem in practical durability.

[Example 2]
Copolymer polyethylene having a single fiber fineness of 13 dtex and a cut length of 51 mm of polyester fiber of 38% by mass, a single fiber fineness of 3.3 dtex and a cut length of 51 mm of polyvinyl alcohol fiber of 50% by mass, and the single fiber fineness of 2.2 dtex used in Example 1 A card web composed of 12% by mass of terephthalate fibers was prepared, and the web was treated with hot air to obtain a felt having a weight of 15 mm and a basis weight of 250 g / m ² . On the other hand, the laminate nonwoven fabric of the melt blown nonwoven fabric and the polyester spunbond nonwoven fabric used in Example 1 was used, and an ethylene-vinyl acetate hot melt adhesive was applied to the melt blown nonwoven fabric surface at a rate of 30 g / m ² by a sintering method. Next, the felt and the meltblown nonwoven fabric were laminated so that the hot melt adhesive application surface was in the middle, and both were adhered by a thermal calendar. The obtained laminate had a thickness of 14 mm and excellent sound absorption performance and surface wear strength similar to Example 1.

  The sound-absorbing material of the present invention is excellent in heat resistance and sound-absorbing performance such as noise, and is used as a sound-absorbing material included in an engine room of a vehicle such as an automobile or a household appliance, and a wall material for a building. Can be used for house wrap etc.

Claims (5)

Apparent density of 0.1 to 0.00 in which fine fibers made of a mixture of 80% by mass to 20% by mass of a copolymerized polyethylene terephthalate resin and 20% by mass to 80% by mass of polybutylene terephthalate are accumulated substantially in a plane. 4g / cm ^3, and melt-blown nonwoven fabric having a basis weight 5~300g / ^{m 2,} at least consisting of polyester fibers of single fiber fineness 1~11dtex on one basis weight 10 to 100 g / ^{m 2} spunbond nonwoven of the nonwoven fabric are laminated A sound-absorbing material comprising a laminate having a thickness of 5 to 50 mm, wherein the spunbond nonwoven fabric is disposed on the outermost surface, wherein the copolymerized polyethylene terephthalate resin comprises a dicarboxylic acid component and a glycol component, The dicarboxylic acid component is a component derived from a compound represented by formula (I) A sound absorbing material comprising a sundicarboxylic acid component and an aliphatic dicarboxylic acid component .

[In the above formula, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or an ester-forming functional group, and X represents an alkali metal salt. ] In the copolymerized polyethylene terephthalate resin, 75 mol% or more of the dicarboxylic acid is a terephthalic acid component, and 1.0 mol% to 3.5 mol% is a component derived from the compound represented by the following formula (I). The sound absorbing material according to claim 1, wherein 2.0 mol% to 10.0 mol% is a cyclohexanedicarboxylic acid component and 2.0 mol% to 8.0 mol% is an aliphatic dicarboxylic acid component. Wood.

[In the above formula, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or an ester-forming functional group, and X represents an alkali metal salt . ]   A vehicle using the sound absorbing material according to claim 1.   An electrical product using the sound absorbing material according to claim 1.   A wall covering made of the sound absorbing material according to claim 1.