JP4344288B2 - Non-combustible sheet-like composition having electromagnetic wave absorption / sound absorption performance, electromagnetic wave absorption / sound absorption structure and sound insulation wall using the same - Google Patents

Description

  The present invention is a non-combustible sheet-like composition that is used as a sound insulation wall for noise prevention on roads and the like, and has an electromagnetic wave absorption performance that absorbs and shields unnecessary electromagnetic noise, and an electromagnetic wave absorption / sound absorption structure and sound insulation wall using the same About.

  In recent years, information and communication technologies centering on terminals such as mobile phones and personal computers have become higher performance and diversified. With the spread of information communication terminals, the problem of electronic devices malfunctioning due to unnecessary electromagnetic noise increases, which may lead to a major social problem.

  On the other hand, the automobile industry is no exception. For example, automatic toll collection systems that use narrow-area communication technology have already become widespread, and in the future, advanced road systems (ITS-Intelligent Transport Systems) have been developed, and mutual communication between in-vehicle devices installed in vehicles, or Communication between roadside devices installed on roads and in-vehicle devices mounted on vehicles tends to expand. Along with this, there is concern about deterioration of the electromagnetic environment due to unnecessary electromagnetic noise.

  In addition, when current highways, toll roads and other roads pass through the vicinity of urban areas or densely populated areas, sound insulation walls are constructed to prevent noise. However, most of the sound insulation walls are made of a metal decorative plate whose surface on the road side is an electromagnetic wave reflector, and the electromagnetic wave environment on the road may be further deteriorated by the reflected electromagnetic waves.

As a sound insulation wall having an electromagnetic wave absorption function to cope with this problem, for example, as shown in the following Patent Document 1 or the like, a laminate with an electromagnetic wave absorption layer and a sound absorption layer made of a decorative sheet on the surface is used. Are known.
JP 2003-301422 A

  However, the conventional sound insulation wall having electromagnetic wave absorbing performance uses a resin composition mainly as an electromagnetic wave absorbing layer and a glass wool molded body as a sound absorbing layer. Therefore, it is necessary to laminate a special electromagnetic wave absorbing sheet made of a resin composition on a conventional sound absorbing body such as a glass wool molded body, resulting in a problem that the manufacturing cost is increased. Moreover, since the heat-resistant temperature of the electromagnetic wave absorbing sheet made of the resin composition is low, there is a problem that it cannot be used in a tunnel where heat-resistant performance is required.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to use a non-combustible sheet-like composition having low cost, high heat resistance, and further having electromagnetic wave absorption / sound absorption performance. The object is to provide an electromagnetic wave absorption / sound absorption structure and a sound insulation wall.

  In order to achieve the above object, the present invention is a single layer or a multilayer structure of two or more layers, and the relative permittivity is gradually increased within the range of 1.2 to 5.0 from the electromagnetic wave incident side. The gist is that the composition is a non-combustible sheet-like composition.

Further, the non-combustible sheet-like composition comprises non-combustible fibers 92 to 98 wt%, solid content of fibrillated pulp 0.5 to 5 wt%, solid content of agglomerated material 0.01 to 5 wt%, and alumina sol 0.1 to 5 wt%. The compounding ratio is 0.01 to 0.06 vol% of conductive fibers having a fiber length of 1 to 10 mm, the thickness is 30 to 100 mm, and the density is 80 to 150 kg / m ³ .

  Further, the non-combustible sheet-like composition is accommodated in a housing made of a resin plate-like member having a measure for transmitting sound waves on at least one surface and a metal plate, and constitutes an electromagnetic wave absorption / sound absorption structure. A plurality of the electromagnetic wave absorbing / sound absorbing structures are arranged in a plane and constitute a sound insulating wall such as an expressway or a toll road.

  Since the nonflammable sheet-like composition of the present invention uses rock wool or the like as the base fiber, it is excellent in heat resistance and has a low relative dielectric constant on the electromagnetic wave incident side, and is excellent in electromagnetic wave absorption performance. Furthermore, since an electromagnetic wave absorbing function is added to the rock wool sound absorber used conventionally, a special electromagnetic wave absorbing sheet is not necessary and can be manufactured at low cost.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  1 (a) and 1 (b) are partial cross-sectional views showing a configuration example of the non-combustible sheet-like composition according to the present invention. In FIG. 1A, the nonflammable sheet-like composition 10 has a single-layer structure, and has a relative dielectric constant of 1.2 to 5.0 in the arrow A direction (thickness direction) in the figure. It has a configuration.

  On the other hand, in FIG.1 (b), the nonflammable sheet-like composition 10 is made into the multilayered structure, and laminates | stacks several layers from which a dielectric constant differs, and the dielectric constant is 1.2-5.0 in the arrow A direction. It has a sloped structure, and preferably has a two-layer structure. The first layer on which electromagnetic waves are incident has a relative dielectric constant of 1.2 to 1.4, and the second layer has a relative dielectric constant. It is desirable that it is 1.4-2.0.

The non-combustible sheet-like composition 10 has a total thickness L of 30 to 100 mm and a density of 80 to 150 Kg / m ³ , preferably a total thickness L of 50 to 60 mm and a density. Is preferably 100 to 120 Kg / m ³ . When the nonflammable sheet-like composition 10 is used as a sound insulation wall, the sound absorbing performance is evaluated at frequencies of 400 Hz and 1000 Hz, but when the density of the nonflammable sheet-like composition 10 is in the range of 80 to 150 Kg / m ^3. In addition, the sound absorption performance in the low frequency region near 400 Hz is the highest. Moreover, although the said sound-absorbing performance improves, so that the total thickness L of the nonflammable sheet-like composition 10 is thick, cost also increases in connection with it. For this reason, the thickness L is set to 30 to 100 mm to satisfy both the sound absorption performance and the cost.

  The non-combustible sheet-like composition 10 according to the present invention is prepared by adding and mixing an organic binder such as fibrillated pulp, an aggregating agent, and an alumina sol to a slurry composed of non-combustible fibers, conductive fibers, and water. Manufactured by papermaking.

  The non-combustible fiber is a base fiber, and for example, rock wool is used. The rock wool has an appropriate bulk density in water of 0.004 to 0.02 g / ml and a shot content of 45 μm or more of 40 wt.% Or less, preferably 0.004 to 0 in bulk density in water. 0.01 g / ml, shot content of 45 μm or more and 35 wt% or less.

  As such a nonflammable fiber, the same sound absorbing performance and electromagnetic wave absorbing performance can be obtained even when ceramic fiber, glass wool or the like is used in addition to rock wool. Further, the heat resistance can be further improved by using a part or all of ceramic fibers having a total content of aluminum oxide and silicon oxide of 90 wt% or more with respect to rock wool. The content of the non-combustible fiber varies depending on the relationship with the content of other components, but is preferably 92 to 98 wt% as the base fiber.

  In addition, metal fibers, silicon carbide fibers, carbon fibers, and the like are appropriate as the conductive fibers. In this embodiment, the dielectric property is expressed in the non-combustible fiber molded body by adding conductive fibers having a fiber length of 1 to 10 mm. In this case, in order to realize the above-described gradient of the relative dielectric constant of 1.2 to 5.0, for example, in the configuration of FIG. 1B, the first layer on the electromagnetic wave incident side to the noncombustible sheet-like composition 10 Is 0.01 to 0.03 vol (volume)% (0.04 to 0.12 wt%), and the second layer is 0.04 to 0.06 vol% (0.16 to 0.24 wt%) carbon fiber. Is preferably added.

  The fibrillated pulp selected as the organic binder in the present embodiment can obtain good shape retention with a small amount of addition. The same effect can be obtained even when acrylic, starch or the like is used as the organic binder. The addition amount of fibrillated pulp is suitably 0.5 to 5 wt%, preferably 0.5 to 1.5 wt%.

  The aggregating material is added for the purpose of agglomerating non-combustible fibers, conductive fibers and other additives in the slurry. In this embodiment, modified polyacrylamide is selected and added as the aggregating material. The addition amount is suitably 0.01-5 wt%, preferably 0.01-0.1 wt%.

  Further, the alumina sol is added as an inorganic binder. In addition to this, aluminum sulfate can also be used as the inorganic binder. The addition amount of the inorganic binder is suitably 0.1 to 5 wt%.

  In the manufacturing method of the nonflammable sheet-like composition 10 according to the present embodiment, the manufacturing process is configured in the order of defibration of nonflammable fibers, addition of conductive fibers, mixing, addition of other members, mixing, dehydration molding, and drying. Has been. In addition, when the density of the nonflammable sheet-like composition 10 reaches the target value mentioned above, you may employ | adopt wet papermaking instead of the said dehydration molding.

  In addition, the nonflammable sheet-like composition 10 according to the present embodiment is coated with a fluororesin, polyethylene, epoxy, vinyl chloride, nylon or the like to prevent moisture absorption, or is a film of fluororesin, polyethylene, polypropylene, nylon or the like. It is preferable to use a fluororesin coating or a fluororesin film that is suitably covered, preferably excellent in weather resistance and excellent in electromagnetic wave transmission performance.

  FIG. 2 shows a partial cross-sectional view of an embodiment of an electromagnetic wave absorption / sound absorption structure using the nonflammable sheet-like composition 10 according to the present invention. In FIG. 2, the electromagnetic wave absorption / sound absorbing structure has a configuration in which a nonflammable sheet-like composition 10 is accommodated in a casing 16 composed of a resin plate 12 and a metal plate 14. An air layer 18 is formed between the noncombustible sheet-like composition 10 and the metal plate 14.

  The metal plate 14 constituting the housing 16 is selected from iron, aluminum, or zinc-iron alloy, and is coated with a fluororesin or vinyl chloride. The resin plate 12 is selected from polycarbonate, acrylic, polypropylene, or vinyl chloride, and is preferably a polycarbonate plate that has been subjected to hole processing for sound wave transmission and excellent in weather resistance. This resin plate 12 corresponds to the resin plate member of the present invention.

  The electromagnetic wave absorption / sound absorption structure shown in FIG. 2 can constitute a sound insulation wall by arranging a plurality of planar structures.

  EXAMPLES The present invention will be described in detail below by examples, but the present invention is not limited to these examples.

  The electromagnetic wave absorption performance in the present invention is evaluated by a vector network analyzer. The reflection coefficient S11 is measured by irradiating the surface of the measurement sample with circularly polarized light in the range of 4.9 to 7.05 GHz at an incident angle of 15 °. did. A metal plate having the same area as the sample was placed behind the sample in the same manner as the actual machine.

  The reverberation chamber method sound absorption coefficient was measured according to JIS A 1409: 1998 “Method for measuring reverberation room method sound absorption coefficient”. As the measurement sample, 20 samples of 605 mm × 910 mm were used and 3025 mm × 3640 mm walls were used.

Example 1.
First, the preparation method of a nonflammable sheet-like composition is demonstrated. The amount of each additive was determined according to Table 1 described later. A predetermined amount of rock wool is sufficiently agitated and defibrated in 20 times the weight of water. Carbon fiber is added here and further stirred using a stirrer. Here, rock wool manufactured by NICHIAS CORPORATION, used was a fiber diameter of 3.3 μm, an underwater bulk density of 0.00465 g / ml, and a shot content of 35% of 45 μm or more. Moreover, the carbon fiber used Toho Tenax Co., Ltd. beth fight chopped fiber HTA-C6-GSX. A predetermined amount of fibrillated pulp as an organic binder, an agglomerated material, and an alumina sol as an inorganic binder were added to the obtained rock wool and carbon fiber dispersion and further stirred. The fibrillated pulp is obtained by adding water to SERISH KY100G manufactured by Daicel Industries, Ltd. to make the solid content 2 wt%, and the agglomerated material is made by dissolving Sanflock N0P manufactured by Sanyo Chemical Co., Ltd. As the alumina sol, AS520 manufactured by Nissan Chemical Industries, Ltd. was used. The obtained mixed slurry was put into a 250 × 250 mm dehydration mold and dehydrated and molded. The operations up to this point were repeated, and two types of molded articles using rock wool having a relative dielectric constant of 1.4 and 1.7 shown in Table 1 were produced. The obtained molded body was dried at 110 ° C. for 20 hours, and then cut into a predetermined size to obtain a sample of a noncombustible sheet composition having a relative dielectric constant of 1.4 and 1.7 and a thickness of 25 mm.

  Subsequently, as shown in Table 2, each incombustible sheet-like composition having a relative dielectric constant of 1.4 and 1.7 from the electromagnetic wave incident direction and a metal plate are arranged in this order, and the electromagnetic wave absorption / absorption structure is obtained. Configured. The electromagnetic wave absorption performance of the electromagnetic wave absorption / sound absorption structure was measured by the method described above. The reverberation chamber method sound absorption coefficient was also measured by the method described above. The measurement results are shown in FIGS. 3 and 4, respectively.

Example 2
A sample was prepared in the same manner as in Example 1 except that the rock wool of Example 1 was changed to glass wool (see Table 1). Moreover, the electromagnetic wave absorption and sound absorption structure was comprised similarly to Example 1 (refer Table 2). The electromagnetic wave absorption performance of this electromagnetic wave absorption / sound absorption structure was measured by the method described above. The measurement results are shown in FIG. Since the sample weight and density were the same as in Example 1, there was no change in the reverberation chamber method sound absorption rate, and the measurement results of the reverberation chamber method sound absorption rate were omitted.

Example 3
A polycarbonate plate having a thickness of 1.5 mm is disposed as the resin plate 12 on the electromagnetic wave incident side, that is, the side opposite to the metal plate with respect to the non-combustible sheet-like composition. An incombustible sheet-like composition having a relative dielectric constant of 1.4 and 1.7 and a metal plate were arranged in this order to constitute an electromagnetic wave absorption / sound absorption structure (see Table 2). The electromagnetic wave absorption performance of this electromagnetic wave absorption / sound absorption structure was measured by the method described above. The measurement results are shown in FIG. Since the sample weight and density were the same as in Example 1, there was no change in the reverberation chamber method sound absorption rate, and the measurement results of the reverberation chamber method sound absorption rate were omitted.

Comparative Example 1
An incombustible sheet-like composition having a relative dielectric constant of 1.7 and 1.4 and a metal plate were arranged in this order from the electromagnetic wave incident direction to constitute an electromagnetic wave absorption / sound absorption structure (see Table 2). The electromagnetic wave absorption performance of this electromagnetic wave absorption / sound absorption structure was measured by the method described above. The measurement results are shown in FIG. Since the sample weight and density were the same as in Example 1, there was no change in the reverberation chamber method sound absorption rate, and the measurement results of the reverberation chamber method sound absorption rate were omitted.

Comparative Example 2
An electromagnetic wave absorbing / sound absorbing structure was constructed in the same manner as in Example 1 except that the thickness was 50 mm with only a non-combustible sheet-like composition having a relative dielectric constant of 1.7 (see Table 2). The electromagnetic wave absorption performance of this electromagnetic wave absorption / sound absorption structure was measured by the method described above. The measurement results are shown in FIG. Since the weight and density of the sample are the same as in Example 1, there is no change in the reverberation chamber method sound absorption rate, so the measurement results of the reverberation chamber method sound absorption rate are omitted.

Summary of Results by Examples and Comparative Examples In Comparative Examples 1 and 2 in which a layer having a high relative dielectric constant is formed on the electromagnetic wave incident surface, the amount of electromagnetic waves absorbed is -8 dB or less in the entire measurement frequency range. Both measurement charts show almost the same tendency, indicating that the incident electromagnetic wave is reflected near the surface. On the other hand, Example 1 and Example 2 can suppress reflection of the electromagnetic wave of the surface vicinity by reducing the dielectric constant of an electromagnetic wave incident surface, and it turns out that the absorption factor of electromagnetic waves is improving significantly.

  In Example 3 where a polycarbonate plate is disposed on the electromagnetic wave incident side, which is closer to the actual situation, the amount of electromagnetic wave absorption is further improved, and the electromagnetic wave absorption rate at a frequency of 5.8 GHz is −20 dB or less. It was confirmed that the product had sufficient electromagnetic wave absorption performance.

  As shown in FIG. 4, the reverberation room method sound absorption coefficient is 0.7 or more at a frequency of 400 Hz and 0.8 or more at a frequency of 1000 Hz, and has a reverberation room method sound absorption coefficient sufficient for practical use. It could be confirmed.

  As described above, the electromagnetic wave absorbing / absorbing structure using the non-combustible sheet-like composition according to the present invention is used to suppress noise near roads such as expressways or toll roads and to improve the electromagnetic environment. Can do.

It is a fragmentary sectional view of the structural example of the nonflammable sheet-like composition concerning this invention. 1 is a partial cross-sectional view of an embodiment of an electromagnetic wave absorption and sound absorption structure using a noncombustible sheet-like composition. It is a figure which shows the electromagnetic wave absorption performance measurement chart of the electromagnetic wave absorption and sound absorption structure concerning Example 1. FIG. It is a figure which shows the reverberation chamber method sound absorption rate measurement chart of the electromagnetic wave absorption and sound absorption structure concerning Example 1. FIG. It is a figure which shows the electromagnetic wave absorption performance measurement chart of the electromagnetic wave absorption and sound absorption structure concerning Example 2. FIG. It is a figure which shows the electromagnetic wave absorption performance measurement chart of the electromagnetic wave absorption and sound absorption structure concerning Example 3. FIG. It is a figure which shows the electromagnetic wave absorption performance measurement chart of the electromagnetic wave absorption and sound absorption structure concerning the comparative example 1. It is a figure which shows the electromagnetic wave absorption performance measurement chart of the electromagnetic wave absorption and sound absorption structure concerning the comparative example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Nonflammable sheet-like composition, 12 Resin board, 14 Metal board, 16 Housing | casing, 18 Air layer.

Claims (5)

Incombustible fiber 92-98 wt% consisting of one or two kinds selected from ceramic fiber, rock wool, glass wool, solid content of fibrillated pulp 0.5-5 wt%, solid content of agglomerated material 0.01-5 wt%, It includes conductive fibers 0.01～0.06Vol% of alumina sol or aluminum sulfate 0.1-5 wt% and a fiber length of 1 to 10 mm, a thickness of 50 to 60 mm, a density of 100~120kg / ^{m 3,} the electromagnetic waves incident A noncombustible sheet-like composition characterized by having a relative dielectric constant gradually increasing from the side within a range of 1.2 to 5.0. The nonflammable sheet-like composition according to claim 1 is housed in a casing made of a resin plate-like member disposed on at least one surface and subjected to sound wave transmission measures and a metal plate. Electromagnetic wave absorbing / absorbing structure. 3. The electromagnetic wave absorption / sound absorption structure according to claim 2, wherein the noncombustible sheet-like composition is arranged so that a relative dielectric constant increases stepwise from an electromagnetic wave incident side. 4. The electromagnetic wave absorption / sound absorption structure according to claim 3, wherein moisture absorption prevention measures are taken on the non-combustible sheet-like composition. A sound insulation wall comprising a plurality of electromagnetic wave absorption / sound absorption structures according to any one of claims 2 to 4 arranged in a plane.

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