JP2011126217A - Plate-like sound absorbing material and soundproof panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing material capable of absorbing a wide range of sounds in a frequency region of high sensitivity in human ears or efficiently absorbing sounds from a specific sound source, and a soundproof panel using the sound absorbing material. <P>SOLUTION: This plate-like sound absorbing material 2 is made of a resin foam molding molded using closed cell beads and having a porosity of 15-50%, and manufactured by partially changing the thickness of the resin foam molding according to the frequency of a sound absorbing object utilizing the correlation between the thickness of the resin foam molding and sound absorbing frequency. At least one surface of the plate-like sound absorbing material is covered with a sound insulating sheet 3 to form the soundproof panel 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plate-shaped sound absorbing material and a soundproof panel using the same, and more particularly to a plate-shaped sound absorbing material used for preventing the propagation of sound and a soundproof panel using the same.

  Conventionally, a soundproof panel has been used to prevent noise generated at a building or construction site from propagating to the surrounding environment. This soundproof panel is produced by combining a sound insulation sheet and a foamed synthetic resin plate having sound absorption.

  For example, Patent Document 1 discloses a plate-like sound-absorbing material having a large number of communicating holes and the surface of a thermoplastic resin foam having a porosity of 20 to 50% covered with a porous sheet. A partition material in which a sound absorbing material is attached to the sound source side of the enclosure is also disclosed.

  Patent Document 2 discloses a plate-like sound absorbing material in which a large number of holes are formed in a closed cell foam molded product made of a synthetic resin, and Patent Document 3 discloses a closed cell foam molded product also made of a synthetic resin. A plate-like sound-absorbing material is disclosed in which a thin groove having a predetermined width is formed. In any case, a normal foamed molded product having an expansion ratio of several tens of times and a porosity of about 1 to 20% is used, and a needle-like member or a plate-like member heated above the melting point of the synthetic resin is pressed to form a hole or groove. Formed.

  Usually, the audible frequency of the human ear is 20 to 20000 Hz. In normal conversation, the frequency range of 200 to 8000 Hz is used, and the sensitivity is highest in the range of 1000 to 3500 Hz. Therefore, the plate-like sound absorbing material is also set so as to have a sound absorption characteristic peak in the frequency range of 1000 to 3500 Hz. However, the sound absorption characteristic of the foamed molded product itself has a pattern having a peak in a relatively narrow frequency region, and many frequencies of sound that cannot be absorbed remain. Therefore, the foam molded product has been devised to provide multiple types of holes or grooves with different depths, diameters, or widths to widen the frequency band of the sound to be absorbed. Since the porosity is small, it is impossible to dramatically change the sound absorption characteristics even if the shape of the hole or groove is devised.

  In addition, Patent Document 4 discloses a polypropylene resin foam molded body in which columnar beads are spot-bonded and the molded body has a porosity of 20 to 50%, and it can be used as a plate-like sound absorbing material. ing.

Utility Model Registration No. 3147955 JP 2005-119257 A JP-A-2005-212112 WO2006 / 016478

  The characteristics to be provided as the plate-like sound absorbing material are that the sound absorption coefficient is high in a wide range in the frequency region of 1000 to 3500 Hz, which is highly sensitive to human ears, and that the shape retention is good. When investigating the sound absorption characteristics of the polypropylene resin foam molded article described in Patent Document 4, the present inventors have found that the sound absorption characteristics change dramatically depending on the thickness of the resin foam molded article.

  Accordingly, in view of the above-described situation, the present invention intends to solve a board that can absorb a wide range of sound in a frequency range with high sensitivity in the human ear, or can efficiently absorb sound from a specific sound source. The present invention provides a sound absorbing panel and a soundproof panel using the plate sound absorbing material.

  In order to solve the above-mentioned problems, the present invention comprises a resin foam molded article having a porosity of 15% or more and 50% or less molded using closed cell beads. The correlation between the thickness of the resin foam molded article and the sound absorption frequency is obtained. A plate-like sound-absorbing material characterized in that the thickness of the resin foam molded article was partially changed according to the frequency of the sound-absorbing object.

  Here, the density of the resin foam molded body is preferably 15 to 150 g / L, and the thickness of the resin foam molded body is preferably set in the range of 20 to 200 mm.

  The plate-like sound absorbing material of the present invention is formed by forming a concavo-convex structure on one or both sides of the plate-like resin foam molded article, and partially changing the thickness in the in-plane position with respect to the sound propagation direction. It is preferable to do. In this case, the concavo-convex structure of the resin foam molded body may be formed during molding of the resin foam molded body, or the concavo-convex structure of the resin foam molded body may be formed by post-processing after molding of the resin foam molded body. Is possible.

  Moreover, this invention can comprise a soundproof panel suitably by using the plate-shaped sound-absorbing material of the above-mentioned characteristic, and covering at least one surface of this plate-shaped sound-absorbing material with a sound insulation sheet. Here, it is preferable that the soundproof panel has a structure in which a concavo-convex structure is formed on one surface of the plate-like sound absorbing material, and the surface on which the concavo-convex structure is formed is covered with a sound insulating sheet.

  The plate-like sound-absorbing material of the present invention formed as described above uses a resin foam molded body having a porosity of 15% or more and 50% or less, which is foam-molded using closed-cell beads, and the resin foam molded body according to the frequency of the sound absorption target. Since the thickness is partially changed, a specific area or a wide range of sounds can be absorbed efficiently.

  And as the said resin foam molding, by using a material having a porosity of 15% to 50% and a density of 15 to 150 g / L with closed cells, a resonant absorption peak at a specific frequency with respect to a specific plate thickness Sound absorption characteristics with Here, the resin foam molded body tends to absorb the sound in the high frequency range if the thickness is reduced, and absorbs the sound in the low frequency range if the thickness is increased. By changing the thickness partially, it is possible to form a portion that can efficiently absorb a sound of a specific frequency in a wide frequency range, thereby efficiently absorbing a sound of a wide frequency range, or The target can be effectively absorbed by focusing on the sound of a specific frequency of a specific sound source.

  Then, if the plate-like sound absorbing material having the above-mentioned sound absorbing characteristics is used and a soundproof panel is formed by covering at least one surface of the plate-like sound absorbing material with a sound insulating sheet, the sound is absorbed by the plate-like sound absorbing material, and the sound insulating sheet absorbs the sound. Since transmission is prevented, it is possible to prevent noise generated at a construction site or construction site from propagating to the surrounding environment. In addition, the soundproof panel has a concavo-convex structure on one side of the recording plate-like sound-absorbing material, and has a structure in which the surface on which the concavo-convex structure is formed is covered with a sound insulation sheet. This is practical because dust does not collect and damage to the projections can be prevented.

It is sectional drawing of the soundproof panel which concerns on this invention. The plate-like sound-absorbing material used in this embodiment is shown, (a) is a simple plate-like sound-absorbing material, (b) is a plate-like sound-absorbing material having a corrugated uneven structure on one side, and (c) is a cross-section on one side. A plate-like sound-absorbing material having a quadrangular concavo-convex structure is shown, and (d) shows a plate-shaped sound-absorbing material having a concavo-convex structure having a trapezoidal cross section on one side. It is a graph which shows the sound absorption rate with respect to the frequency when the plate | board thickness of the plate-shaped sound absorption material used by this invention is 10 mm, 20 mm, 30 mm, and 40 mm. The test piece (Example 1) of the plate-shaped sound-absorbing material which formed the step-shaped uneven structure in which thickness changes discontinuously with 20 mm and 40 mm is shown, (a) is a front view, (b) is a side view. . The test piece (Example 2) of the plate-shaped sound-absorbing material in which the corrugated uneven structure whose thickness changes continuously between 20 mm and 40 mm is shown, (a) is a front view, (b) is a side view. It is. 4 is a graph showing the sound absorption coefficient with respect to the frequency of a normal EPP 30-fold foam (thickness: 40 mm) as Comparative Example 1. FIG. It is a graph which shows the sound absorption rate with respect to the frequency at the time of making the plate-shaped sound-absorbing material used by this embodiment into the simple plate shape of thickness 40mm as the comparative example 2. 6 is a graph showing a sound absorption coefficient with respect to a frequency when the plate-like sound absorbing material used in the present embodiment is set as a simple plate having a thickness of 20 mm as Comparative Example 3. It is a graph which shows the sound absorption rate with respect to the frequency of the plate-shaped sound-absorbing material of Example 1. It is a graph which shows the sound absorption rate with respect to the frequency of the plate-shaped sound-absorbing material of Example 2.

  Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. FIG. 1 shows a soundproof panel according to the present invention, and FIG. 2 shows a plate-like sound absorbing material.

  The soundproof panel 1 of the present invention comprises a resin foam molded article having a porosity of 15% or more and 50% or less molded using closed cell beads, utilizing the correlation between the thickness of the resin foam molded article and the sound absorption frequency, The plate-like sound absorbing material 2 in which the thickness of the resin foam molded body was partially changed according to the frequency of the sound absorbing object was used, and at least one surface of the plate-like sound absorbing material 2 was covered with the sound insulating sheet 3. Here, it is preferable that the soundproof panel 1 has a structure in which the concavo-convex structure 4 is formed on one surface of the plate-like sound absorbing material 2 and the surface on which the concavo-convex structure 4 is formed is covered with the sound insulating sheet 3.

  The plate-like sound absorbing material 2 of the present invention forms the concavo-convex structure 4 on one side or both sides of the plate-like resin foam molded article, and partially changes the thickness with respect to the sound propagation direction at the in-plane position. Is configured.

  FIG. 2 shows an example of the uneven structure 4 of the plate-like sound absorbing material 2. FIG. 2A shows a simple plate-shaped sound absorbing material 2 that does not have the uneven structure described for reference. In the present invention, the plate-shaped sound absorbing material 2 having this shape alone is not used. It is possible to partially change the thickness by partially stacking and bonding a plurality of plate-shaped sound absorbing materials 2. FIG. 2B shows a plate-like sound absorbing material 2 having a corrugated uneven structure 4 formed on one side. In the case of the corrugated concavo-convex structure 4, the wave bottom 5 is the thinnest, the wave top 6 is the thickest, and the thickness is continuously changing in the middle. . FIG. 2C shows a plate-like sound absorbing material 2 in which a concavo-convex structure 4 having a square cross section is formed on one side. In the case of the concavo-convex structure 4, when the concave portion 7 and the convex portion 8 are repeated in the same pattern, the thickness only changes in two steps. However, if the depth of the concave portion 7 is changed, the thickness is changed in multiple steps. be able to. FIG. 2D shows a plate-like sound absorbing material 2 in which a concavo-convex structure 4 having a trapezoidal cross section is formed on one side. The concave-convex structure 4 is also formed by repeatedly forming the concave portion 9 and the convex portion 10 in the same manner as described above. However, even if the concave / convex structure 4 is repeated in the same pattern, the portion of the slope 11 between the concave portion 9 and the convex portion 10 has a continuous thickness. It is characteristic that it changes.

  The concavo-convex structure 4 described above can also be formed on both surfaces of the plate-like sound absorbing material 2. Moreover, the above-mentioned concavo-convex structure 4 can repeat a pattern in one direction along the wide surface of the plate-like sound absorbing material 2 or can have a two-dimensional structure by repeating the pattern in two directions. Further, when the uneven structure 4 having a partially different thickness is formed on the surface of the plate-like sound absorbing material 2, the area of each thickness range is set to absorb the sound of a specific frequency particularly effectively. It is also possible to do so. For example, it is also preferable to set the area of the 40 mm thick region to 50%, the area of the 30 mm thick region to 20%, and the area of the 20 mm thick region to 30%.

  In the present invention, using the correlation between the thickness of the resin foam molded body and the sound absorption frequency, the “thickness” in the case where the thickness of the resin foam molded body is partially changed in accordance with the frequency of the sound absorption target. , Shows the thickness along the sound propagation direction. That is, when sound is incident on the surface of the plate-like sound absorbing material 2 perpendicularly, the plate thickness itself is thick, and when sound is incident on the surface of the plate-like sound absorbing material 2 obliquely, the incident direction It is the length that crosses.

  Here, the density of the resin foam molded body used as the plate-like sound absorbing material 2 is preferably 15 to 150 g / L. The density and porosity of the resin foam molding are closely related and are not independent parameters, but in the present invention, the resin foam molding with a porosity of 15% to 50% molded using closed cell beads When the thickness of the resin foam molded body is set in a range of 20 to 200 mm, sound having a frequency of 1000 to 3500 Hz, which is highly sensitive to human ears, can be absorbed.

The density of the resin foam molding is a value obtained by dividing the weight of the resin foam molding by the apparent volume X. Here, the porosity (%) of the resin foam molded article is expressed by the following equation when the apparent volume of the resin foam molded article is X (cm ³ ) and the true volume of the resin foam molded article is Y (cm ³ ). Calculated.
Porosity of resin foam molding (%) = {(XY) / X} × 100
The apparent volume X of the resin foam molded body can be calculated from the outer dimensions of the resin foam molded body. Moreover, the true volume Y of the resin foam molded article is an increased volume when the resin foam molded article is submerged in alcohol.

  Further, the uneven structure 4 of the resin foam molded body used as the plate-like sound absorbing material 2 is formed at the time of molding the resin foam molded body, or formed by post-processing after molding of the resin foam molded body. May be formed. However, the fine structure of the surface differs depending on the method of forming the uneven structure 4. That is, when the uneven structure 4 is formed during foam molding, a bead surface layer is present on the surface of the uneven structure 4. In addition, when the concavo-convex structure 4 is formed by cutting after foam molding, closed cells are exposed on the surface of the recess, and when the concavo-convex structure 4 is formed by thermal fusing with a heating wire, a melted part is formed on the surface of the recess. The As described above, the fine structure of the surface differs depending on the method of forming the concavo-convex structure 4, and the degree of reflection and intrusion of the sound wave on the surface is different. Therefore, a manufacturing method optimum for the purpose of use should be selected.

  The sound insulation sheet 3 is a flexible sheet material having a large surface density, such as a vibration damping sheet formed of an asphalt sheet, a vinyl chloride sheet, a synthetic rubber, or the like, and further mixed with a metal powder or an inorganic material. Some have improved the sound insulation effect.

  In this embodiment, it is preferable to use a polypropylene resin foam molded body as the resin foam molded body. This polypropylene resin is a polymer comprising propylene monomer units of 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and polymerized with a Ziegler type titanium chloride catalyst or a metallocene catalyst. Those having high stereoregularity are preferred. Specific examples include, for example, propylene homopolymer, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene-butene random copolymer, ethylene-propylene block copolymer, maleic anhydride -Propylene random copolymer, maleic anhydride-propylene block copolymer, propylene-maleic anhydride graft copolymer, etc. are mentioned, and each is used alone or in combination. In particular, an ethylene-propylene random copolymer, a propylene-butene random copolymer, and an ethylene-propylene-butene random copolymer can be suitably used. Further, these polypropylene resins are preferably non-crosslinked, but crosslinked resins can also be used.

  The polypropylene resin preferably has a melt index (hereinafter referred to as MI) measured at a temperature of 230 ° C. and a load of 2.16 kg in a range of 0.1 g / 10 min to 9 g / 10 min in accordance with JIS K7210. Preferably they are 2g / 10min or more and 8g / 10min or less. When MI is less than 0.1 g / 10 min, the foaming power when producing closed cell beads is low, and it becomes difficult to obtain closed cell beads having a high expansion ratio. Moreover, it becomes difficult to ensure the fusion strength between the closed-cell beads when the foam-molded body is formed. If MI exceeds 9 g / 10 min, it may be difficult to control the porosity of the foamed molded product with a stable value.

  The polypropylene resin has a melting point of preferably 130 ° C. or higher and 168 ° C. or lower, more preferably 135 ° C. or higher and 160 ° C. or lower, particularly preferably, in order to obtain a foamed molded article having excellent mechanical strength and heat resistance. 140 ° C. or higher and 155 ° C. or lower. When the melting point is within this range, there is a strong tendency to easily balance moldability, mechanical strength, and heat resistance. Here, the melting point is a temperature of 10 to 10 ° C./min from 40 ° C. to 220 ° C., and then cooled to 40 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter. The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is increased again to 220 ° C. at a rate of 10 ° C./min.

  The closed cell beads for producing the resin foam molded article preferably have a cell diameter of 150 μm or less using the above polypropylene resin as a base resin, and two DSC curves obtained by differential scanning calorimetry. It has a melting peak, β / (α + β) is 0.35 or more and 0.75 or less when the heat of fusion α (J / g) of the low temperature side peak and the heat of fusion β (J / g) of the high temperature side peak Preferably there is. By satisfying these requirements, it is possible to stably and economically produce a resin foam molded article made of a polypropylene-based resin having a small variation in magnification and a porosity of 15% to 50%. Tend.

  Here, the DSC curve obtained by differential scanning calorimetry of closed cell beads means that 1 to 10 mg of closed cell beads is heated from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min by a differential scanning calorimeter. It is a DSC curve obtained in (1). Further, the melting heat quantity α (J / g) of the low temperature side peak is calculated from the contact point on the low temperature side between the straight line passing through the maximum point of the obtained DSC curve and the DSC curve and the area surrounded by the DSC curve. From the contact point on the high temperature side of the straight line passing through the maximum point and the DSC curve and the area surrounded by the DSC curve, the heat of fusion β (J / g) of the high temperature side peak is calculated.

  Next, a method for producing closed cell beads using a polypropylene resin will be described. The polypropylene resin is melted using a known method, for example, using an extruder, a kneader, a Banbury mixer (trademark), a roll or the like, and the weight of one particle is 0.2 to 10 mg, preferably 0.8. Processed into 5-6 mg resin particles. Generally, it melts using an extruder and is manufactured by a strand cut method or an underwater cut method. For example, when the strand cutting method is used, a polypropylene resin extruded in a strand form from a circular die is cooled and solidified with water, air, or the like to obtain resin particles having a desired shape.

Furthermore, during the production of the resin particles, various additives can be added as necessary within a range that does not impair the properties of the polypropylene resin.
For example, it is preferable to add a modified polyolefin resin and / or a modified styrene resin. Oxidized polyethylene wax, oxidized polypropylene wax, maleic anhydride-modified polyethylene, and maleic anhydride-modified polypropylene are more preferably used.
When using an oxidized polyethylene wax, the viscosity measured at 150 ° C. in accordance with ASTM D3236 is preferably 5 mPa · s or more and 800 mPa · s or less, more preferably 10 mPa · s or more and 500 mPa · s or less. .

  Further, the acid value measured in accordance with ASTM D1386 is preferably 5 mgKOH / g or more and 50 mgKOH / g or less, and preferably 10 mgKOH / g or more and 30 mgKOH / g or less in order to obtain higher affinity. . The number average molecular weight varies depending on the branched structure and the like, but in many cases is in the range of 500 or more and 5000 or less.

  A conventionally known method can be used for producing the closed cell beads in the present invention. For example, an aqueous dispersion medium containing the resin particles, the foaming agent, the dispersant, and the dispersion aid is charged into a sealed container, and the temperature is raised while stirring to increase the temperature of the resin particles as a constant temperature (hereinafter sometimes referred to as the foaming temperature). After impregnating with a foaming agent, add additional foaming agent as necessary to maintain the inside of the sealed container at a constant pressure (hereinafter sometimes referred to as foaming pressure), and then remove the contents from the bottom of the sealed container. Closed-cell beads are produced by a method of discharging under a lower pressure atmosphere.

Examples of the blowing agent include aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane, and mixtures thereof; inorganic gases such as air, nitrogen, and carbon dioxide; and water. In order to obtain closed cell beads having a higher expansion ratio, it is preferable to use isobutane, normal butane and a mixture thereof as a foaming agent. In order to obtain closed-cell beads with low expansion ratio and small expansion ratio variation, it is preferable to use water as a foaming agent.
When water is used as a foaming agent, it is preferable to add a water absorbing agent such as sodium ionomer, potassium ionomer, melamine, or isocyanuric acid when the resin particles are produced.

The aqueous dispersion of polypropylene resin particles thus adjusted in a sealed container is heated to a predetermined foaming temperature with stirring, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. At the same time, the pressure in the sealed container rises and the foaming agent is impregnated into the resin particles. Thereafter, the foaming agent is additionally supplied until a predetermined foaming pressure is reached, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. Thus, an aqueous dispersion of polypropylene resin particles held at the foaming temperature and foaming pressure is released by opening the valve provided at the bottom of the sealed container and releasing it in a low-pressure atmosphere (usually atmospheric pressure). Beads can be produced.
When the aqueous dispersion of resin particles is discharged into a low-pressure atmosphere, it can be discharged through an opening orifice of 2 to 10 mmφ for the purpose of adjusting the flow rate and reducing the variation in magnification. In some cases, the low-pressure atmosphere is filled with saturated steam for the purpose of increasing the expansion ratio.

  The shape of the closed-cell beads obtained as described above is not particularly limited, and is a general spherical shape or a column shape as disclosed in, for example, WO2006 / 16478, for example, JP-A-7-137063. Examples include irregular shapes such as a cylindrical shape disclosed in the gazette. However, since the void ratio of the resin foam molded body is easily set to 15% or more and 50% or less, a columnar shape or an irregular shape is preferable. .

In the case of a columnar shape, the ratio of the average value D of Dmax and Dmin (L / D) when the length of the longest part of the closed cell beads is L and the maximum diameter Dmax and the minimum diameter Dmin in the cross section perpendicular to the L direction Is preferably a columnar shape of 1.5 or more and 3 or less.
The cross-sectional shape perpendicular to the L direction is a closed curve without a concave portion such as a circle or an ellipse, and Dmax and Dmin take substantially constant values along the L direction. Specific examples of the columnar closed cell beads include a columnar shape and an elliptical columnar shape.
When L / D is 1.5 or more and 3 or less, when filling the mold for molding, an appropriate contact area between the closed cell beads is maintained, and a high porosity tends to be formed. When L / D is less than 1.5, it may be difficult to obtain a resin foam molded article having a sufficient porosity when filled in a mold. When L / D exceeds 3, clogging at the filling port when filling the mold is likely to occur, and the cause of filling failure or the void ratio between the local portions of the resin foam molded product tends to vary. Tend.

  In the case of an irregular shape, the closed cell beads as described in JP-A-7-137063 are each at least one point on each of the above-mentioned closed cell beads in each of the xy, yz, and zx planes on the three-dimensional coordinates. When arranged on a three-dimensional coordinate so that the flat surfaces do not cut the closed cell beads, any one of the maximum absolute values of the x, y, and z coordinates on the closed cell bead surface can be taken. Let a be the minimum coordinate value absolute value, b be the smallest possible value of the two coordinate value absolute values in the direction orthogonal to the coordinate axis that indicated the coordinate value absolute value a, and the remaining coordinate value absolute When the value is c, a ≦ b ≦ c, 1 ≦ b / a <2, and a shape satisfying 1 ≦ c / a <2 is preferable.

  The closed cell beads made of the polypropylene resin obtained as described above can be made into a polypropylene resin foam molded article having a porosity of 15% or more and 50% or less by a conventionally known molding method. For example, a) a method in which closed cell beads are pressurized with an inorganic gas, impregnated with the inorganic gas in the closed cell beads, given a predetermined internal cell bead internal pressure, filled into a mold, and heated and fused with water vapor. B) A method in which closed cell beads are compressed by gas pressure and filled into a mold, and the recovery force of the closed cell beads is used to heat and melt with water vapor. C) Closed cell beads are not subjected to any pretreatment. A method such as a method of filling a mold and heat-sealing with water vapor can be used.

Among the above molding methods, the closed cell beads are pressurized with an inorganic gas, impregnated with the inorganic gas in the closed cell beads to give a predetermined closed cell bead internal pressure, filled into a mold, and heated and melted with steam. more preferably a method of wearing, even more preferably to the closed cell beads pressure than 0.2kgf / cm ² · G or 0.7kgf / cm ² · G. By the closed cell beads pressure than 0.2kgf / cm ² · G or 0.7kgf / cm ² · G, control of the porosity becomes easier, porosity 15% to 50% of a resin foam molded article Can be manufactured more stably.

As the inorganic gas, air, nitrogen, oxygen, helium, neon, argon, carbon dioxide, or the like can be used. These may be used alone or in combination of two or more. Among these, highly versatile air and nitrogen are preferable.
In addition to the molding method described above, a resin foam molded article having a porosity of 15% or more and 50% or less is obtained by applying an adhesive to closed cell beads, pouring the closed cell beads into a mold having a desired shape, and solidifying. Also good.

  The porosity of the resin foam molding is strongly related to the sound absorption characteristics, and the porosity is 15% to 50%, more preferably 20% to 45%. When the porosity is less than 15%, the sound absorption rate at the peak frequency is lowered, and sufficient sound absorption characteristics cannot be obtained. When the porosity exceeds 50%, the contact area between the closed cell beads is reduced, and the foamed molded body is liable to crack, and the mechanical strength is lowered to be unusable for practical use.

  The above-described cylindrical polypropylene-based resin closed cell beads are commercially available as dB (Dockbone: manufactured by Kaneka Corporation). FIG. 3 shows the sound absorption characteristics of a 33-fold foamed resin foam molded article produced using these closed cell beads. FIG. 3 is a graph of the sound absorption coefficient with respect to the frequency when the thickness of the resin foam molded article is 10 mm, 20 mm, 30 mm, and 40 mm. It can be seen that there is a resonance absorption peak depending on the thickness. As the thickness of the resin foam molding increases, the sound absorption peak moves to a lower frequency. Here, in the case of a resin foam molded body having a thickness of 10 mm, since it has a sound absorption peak at a frequency around 4500 Hz, it is not suitable for the soundproofing purpose of the present invention. The absorption peak is about 2400 Hz at a thickness of 20 mm, about 1600 Hz at 30 mm, and about 1250 Hz at 400 mm. The sound absorption characteristics of any thickness have a long tail in the treble region. On the other hand, if the thickness of the resin foam molding is less than 20 mm, the shape retainability is deteriorated and the mechanical strength is excessively lowered, so that it may not be suitable for use as a soundproof panel. Therefore, in the present invention, the lower limit of the thickness of the plate-like sound absorbing material 2 is set to 20 mm. Moreover, when the thickness of the plate-like sound absorbing material 2 exceeds 200 mm, it tends to be too thick as a soundproof panel and difficult to handle.

(Examples 1 and 2)
Next, using a closed cell bead of dB (Docbone, a trade name of Kaneka Corporation's closed cell bead), the foam was expanded 33 times in a mold, and a test piece (porosity) having the shape shown in FIGS. 25%), and the sound absorption characteristics were examined. The test piece (Example 1) shown in FIG. 4 has a diameter of 40 mm, and a concavo-convex structure in which the thickness is changed to a step shape (step type) from 40 mm and 20 mm with the diameter portion as a boundary on one side. is there. The test piece (Example 2) shown in FIG. 5 has a diameter of 40 mm, and a corrugated concavo-convex structure having a bottom thickness of 20 mm and a top thickness of 40 mm formed on one surface thereof.

(Comparative Examples 1-3)
As Comparative Example 1, a normal EPP 30-fold foam (thickness 40 mm) was produced. In addition, resin foam molded products having thicknesses of 40 mm (Comparative Example 2) and 20 mm (Comparative Example 3), which were foamed 33 times in a mold using closed cell beads of dB (Dockbone), were produced.

  6 shows the sound absorption characteristics of the resin foam molded article of Comparative Example 1, FIG. 7 shows the sound absorption characteristics of Comparative Example 2, and FIG. 8 shows the sound absorption characteristics of Comparative Example 3. The horizontal axis of each sound absorption characteristic graph indicates the frequency of sound waves, the vertical axis indicates the sound absorption rate, and the maximum value of the sound absorption rate is normalized to 1. From FIG. 6, it was found that the normal EPP 30-fold foam has almost no sound absorbing effect. 7 and 8, according to the thickness of the resin foam molded article, it absorbs sound in a specific frequency range, but absorbs less sound than other frequencies, and allows many sounds to pass through. You can see that

  On the other hand, in the case of Example 1 (dB33 20 mm + 40 mm step type), it has a sound absorption characteristic that combines the sound absorption characteristics of FIG. 7 and FIG. 8 and is effective in a wide frequency range (1000 to 3500 Hz). It can be seen that it absorbs. Similarly, in the case of Example 2 (dB33 20 mm to 40 mm wave type), as a sound absorption characteristic, a mountain that spreads widely in a wide frequency region (1000 to 3500 Hz) is formed, and sound is effectively absorbed in a wide frequency region. I understand that.

DESCRIPTION OF SYMBOLS 1 Soundproof panel 2 Plate-shaped sound-absorbing material 3 Sound insulation sheet 4 Uneven structure 5 Bottom part 6 Top part 7 Concave part 8 Convex part 9 Concave part 10 Convex part 11 Slope

Claims (8)

  It consists of a resin foam molding with a porosity of 15% or more and 50% or less molded using closed cell beads. The thickness of the resin foam molding is determined by utilizing the correlation between the thickness of the resin foam molding and the sound absorption frequency. A plate-like sound-absorbing material that is partially changed according to the frequency of the sound-absorbing target.   The plate-like sound-absorbing material according to claim 1, wherein the resin foam molded body has a density of 15 to 150 g / L.   The plate-like sound-absorbing material according to claim 1 or 2, wherein a thickness of the resin foam molded body is set in a range of 20 to 200 mm.   The plate shape according to any one of claims 1 to 3, wherein a concavo-convex structure is formed on one side or both sides of the plate-like resin foam molded body, and the thickness with respect to the sound propagation direction is partially changed at an in-plane position. Sound absorbing material.   The plate-like sound-absorbing material according to claim 4, wherein the concavo-convex structure of the resin foam molded body is formed when the resin foam molded body is molded.   The plate-like sound-absorbing material according to claim 4, wherein the uneven structure of the resin foam molded body is formed by post-processing after the resin foam molded body is molded.   A soundproof panel in which at least one surface of the plate-like sound absorbing material according to claim 1 is covered with a sound insulating sheet. The soundproof panel according to claim 7, wherein a concavo-convex structure is formed on one surface of the plate-like sound absorbing material, and the surface on which the concavo-convex structure is formed is covered with a sound insulating sheet.

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