JP2019168476A - Porous body and sound insulation material - Google Patents

Abstract

To provide a porous body and a sound insulation material which are lightweight and have superior sound insulation properties.SOLUTION: There are provided: a porous body 10 which is made of xerogel having successive pores 12, and has a first surface A and a second surface B on the opposite side of the first surface A, wherein the total area of apertures open on the first surface A is 30% or less of the area of the first surface A; and a sound insulation material comprising the porous body 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a porous body and a sound insulating material provided with the porous body.

  When the sound insulating material is made of a dense and uniform material, it is said that the sound insulating property (transmission loss) of the sound insulating material follows a mass rule that is proportional to the logarithm of the sound frequency and the surface density of the sound insulating material. That is, there is a common sense that the heavier the sound insulation material, the better the sound insulation. Therefore, a plate made of a metal such as lead or iron is used as a normal sound insulating material.

  On the other hand, as a lightweight sound insulating material that does not follow the mass law, a sound insulating material in which a non-breathable layer is provided on the surface of a porous layer has been proposed (Patent Documents 1 to 3). The sound insulating material is expected to have sound insulating properties due to sound absorption by the porous layer and sound reflection by a highly rigid non-breathable layer.

Japanese Patent No. 425696 JP 2002-46203 A JP 2004-202915 A

However, since the porous layer in the conventional sound insulating material has a low porosity, the sound absorbing property is insufficient, and the sound insulating property as a sound insulating material is still insufficient.
Moreover, since the sound insulating material in which the porous layer contains fibers does not have flexibility, it is difficult to follow a complicated shape. The sound insulating material in which the porous layer includes fibers has fiber falling or powder falling when cut.

  The present invention provides a porous body and a sound insulating material that are lightweight and have excellent sound insulating properties.

The porous body of the present invention is a porous body made of xerogel having continuous pores; the porous body has a first surface and a second surface opposite to the first surface. The total area of the openings opened in the first surface is 30% or less of the area of the first surface.
The sound insulating material of the present invention includes the porous body.

  The porous body and the sound insulating material of the present invention are lightweight and excellent in sound insulating properties.

It is a cross-sectional schematic diagram which shows an example of the porous body of this invention. It is a cross-sectional schematic diagram which shows the other example of the porous body of this invention. 2 is an electron micrograph of the first surface of the cross section in the thickness direction of the porous body of Example 1 and the vicinity thereof. 4 is an electron micrograph of the vicinity of the center of the cross section in the thickness direction of the porous body of Example 1. FIG. 2 is an electron micrograph of the second surface of the cross section in the thickness direction of the porous body of Example 1 and the vicinity thereof. 2 is an electron micrograph of the first surface of the porous body of Example 1. FIG. 2 is an electron micrograph of the second surface of the porous body of Example 1. FIG. It is an electron micrograph of the 1st surface of the section of the thickness direction of the porous body of Example 4, and its neighborhood. 4 is an electron micrograph of the vicinity of the center of the cross section in the thickness direction of the porous body of Example 4. It is an electron micrograph of the 2nd surface of the cross section of the thickness direction of the porous body of Example 4, and its vicinity. 4 is an electron micrograph of the first surface of the porous body of Example 4. FIG. 4 is an electron micrograph of the second surface of the porous body of Example 4. FIG. It is a graph which shows normal incidence sound transmission loss with respect to the frequency of the sound-insulating material of Example 5, and the sound-absorbing material of the comparative example 3.

The following definitions of terms apply throughout this specification and the claims.
“Porosity” refers to pores formed by voids formed in a porous body.
“Continuous pores” refers to pores in which pores communicate with each other.
“Xerogel” is the definition of terminology related to the structure and process of sols, gels, stitches, and inorganic / organic composite materials (IUPAC) Inorganic Chemistry Subcommittee and Polymer Subcommittee Polymer Terminology Subcommittee ( "IUPAC Recommendation 2007)" means "a gel composed of an open network formed by removing a swelling agent from a gel." Classification of airgel with swelling agent (solvent) removed by supercritical drying, xerogel with swelling agent (solvent) removed by normal evaporation drying, and cryogel with swelling agent (solvent) removed by freeze drying Although there is a law, in the present specification and claims, these are collectively referred to as xerogel.
The “matrix” refers to a base material excluding particles among materials forming a skeleton (open network) of a porous body.
The “average pore diameter” is a value obtained by measuring the pore diameter of continuous pores by a mercury intrusion method using a mercury porosimeter and averaging the output pore diameters.
The “average porosity” is a value obtained by the following equation from the volume of the porous body before pressing and the volume of the porous body after pressing under the conditions of temperature: 100 ° C., pressure: 50 MPa, time: 10 minutes. It is.
Porosity = 1− (volume of porous body after pressing / volume of porous body before pressing)
The “ratio of the total area of the apertures to the area of the first surface” refers to the area of the apertures present in the 500 μm × 500 μm region of the first surface by observing the first surface of the porous body with an electron microscope. It was measured, calculated by the total area of the opening of the ([mu] m ²⁾ divided by 250000μm ^2.

<Porous body>
The porous body of the present invention is a porous body made of xerogel having continuous pores, and has a first surface and a second surface opposite to the first surface.
The porous body of the present invention may contain a plurality of particles.

FIG. 1 is a schematic cross-sectional view showing an example of the porous body of the present invention.
The porous body 10 has continuous pores 12.
The continuous pores 12 are hardly opened on the first surface A side and are opened on the second surface B side. Therefore, the porous body 10 has a so-called skin layer 20 in which the continuous pores 12 are hardly open on the first surface.
The partition walls and the skin layer 20 of the continuous pores 12 are formed by the skeleton 16 of the porous body 10.

FIG. 2 is a schematic cross-sectional view showing another example of the porous body of the present invention.
The porous body 10 has continuous pores 12. The porous body 10 includes a plurality of particles 14.
The continuous pores 12 are hardly opened on the first surface A side and are opened on the second surface B side. Therefore, the porous body 10 has a so-called skin layer 20 in which the continuous pores 12 are hardly open on the first surface.
The partition walls and the skin layer 20 of the continuous pores 12 are formed by the skeleton 16 of the porous body 10.
A part of the particles 14 is completely buried in the skeleton 16, and the remaining part of the particles 14 is movably present in the continuous pores 12 or is partially buried in the skeleton 16 to be continuous pores. 12 is present.

(Continuous pores)
In a porous body, when sound waves pass through pores existing in the porous body, sound is absorbed by the viscous resistance of air. Since the porous body has continuous pores, the distance that the sound wave passes through the porous body through the pores is longer than the independent pores where the pores do not communicate with each other. The friction occurs efficiently. Therefore, the porous body and sound insulation material having continuous pores are excellent in sound insulation.

  The average pore diameter of the continuous pores is preferably 10 to 150 μm, more preferably 30 to 120 μm, further preferably 50 to 100 μm, and particularly preferably 55 to 60 μm. If the average pore diameter of the continuous pores is equal to or greater than the lower limit of the above range, the viscosity resistance of the air in the pores does not become too high and the air easily moves, so that the sound insulation of the porous body and the sound insulation material is further improved. If the average pore diameter of the continuous pores is less than or equal to the upper limit of the above range, the surface area of the partition walls of the continuous pores in contact with the air is sufficiently increased, so that friction between the air (sound) and the partition occurs efficiently. Therefore, the sound insulation of the porous body and the sound insulation material is further improved.

  The average porosity of the porous body is preferably 50 to 98%, more preferably 55 to 90%, and still more preferably 60 to 85%. If the average porosity of the porous body is equal to or greater than the lower limit of the above range, the surface area of the partition walls of the continuous pores in contact with air will be sufficiently large, so that friction between the air (sound) and the partition occurs efficiently. Therefore, the sound insulation of the porous body and the sound insulation material is further improved. Further, the specific gravity of the porous body is reduced, and the porous body and the sound insulating material are further reduced in weight. If the average pore diameter of the porous body is less than or equal to the upper limit of the above range, the mechanical strength becomes sufficiently large, and therefore handling can be performed without crushing or breaking the porous body in production and use. Moreover, it is excellent in mass productivity.

(particle)
When the porous body contains particles, the sound insulating properties of the porous body and the sound insulating material are further improved.
Examples of the particles include fillers.
The filler may be an inorganic filler or an organic filler. They may be used alone or in combination with several kinds of fillers.

  Examples of the inorganic filler include inorganic particles, flaky clay, and inorganic fiber materials. Examples of inorganic particles include silica particles, zirconia particles, titania particles, alumina particles, and zinc oxide particles. As the inorganic particles, silica particles are preferable from the viewpoints of a wide variety of particle sizes, structures, and shapes.

Examples of the type of silica particles include silica gel particles, non-porous silica particles, porous silica particles, scaly silica particles, hollow silica particles, fumed silica particles, and the like. The shape of the silica particles is preferably spherical from the viewpoint of dispersibility.
Examples of flaky clay include mica, montmorillonite, and mica.
Glass fiber etc. are mentioned as an inorganic fiber material.

  Examples of the organic filler include resin particles and organic fiber materials.

  When the porous body contains particles, the content of the particles in the entire porous body is preferably 1 to 300 parts by weight, and 30 to 200 parts by weight with respect to 100 parts by weight of the matrix forming the skeleton of the porous body. Part is more preferable, and 50 to 100 parts by mass is further preferable. When the particle content is at least the lower limit of the above range, the sound insulating properties of the porous body and the sound insulating material are further improved. If the content of the particles is not more than the upper limit of the above range, the porous body and the sound insulating material are further lightened. Moreover, the porous body is excellent in flexibility, and the porous body can easily follow a complicated shape.

  It is preferable that at least a part of the particles are movably present in the continuous pores, or are partially buried in the skeleton and exist in the continuous pores. The presence of at least a part of the particles in the continuous pores makes the pores in the porous body have a complicated shape compared to the case without particles, and the friction between the air (sound) and the particles occurs more efficiently. . Therefore, the sound insulation of the porous body and the sound insulation material is further improved.

  Moreover, it is preferable that at least a part of the particles present in the continuous pores are movably present in the continuous pores. When at least a part of the particles are movably present in the continuous pores, the kinetic energy of the sound is converted into thermal energy and absorbed by the friction caused by the movement of the particles in the continuous pores. Therefore, the sound insulation of the porous body and the sound insulation material is further improved.

(Porous body skeleton)
The skeleton of the porous body is a portion that becomes a partition wall of continuous pores. Further, the skeleton of the porous body forms a so-called skin layer in which the continuous pores are hardly or not open on the first surface.
The skeleton of the porous body includes a matrix that is a base material. When the porous body includes particles, the skeleton of the porous body further includes particles embedded in a state dispersed in the matrix.

  The matrix may be an organic matrix or an inorganic matrix. As the matrix, an organic matrix is preferable because it is lightweight, the porous body is excellent in flexibility, and the porous body can easily follow a complicated shape.

  Examples of the organic matrix include a cured product of a curable resin and nano organic fibers. As the organic matrix, a cured product of a curable resin is preferable from the viewpoint of easily producing a porous body having a skin layer.

  As a cured product of the curable resin, a cured product of a photocurable resin containing at least one selected from the group consisting of a photocurable monomer, a photocurable oligomer, and a photocurable polymer; a thermosetting monomer, a heat Cured thermosetting resin containing at least one selected from the group consisting of curable oligomers and thermosetting polymers; and those obtained by polycondensing monomers such as melamine resin, phenol resin, polyimide, etc. It is done.

  Examples of nano organic fibers include celluloses, bio-based nano fibers, and synthetic resin-based nano fibers. Examples of celluloses include cellulose obtained from wood, bacterial cellulose synthesized by bacteria, and the like. Examples of bio-based nanofibers include xanthan and chitosan. Examples of the synthetic resin-based nanofiber include a nanofiber obtained by electrospinning a synthetic resin.

  Examples of the inorganic matrix include metal oxides. Examples of the metal oxide include silica, alumina, titania, zirconia and the like.

  The total area of the openings opened on the first surface, that is, the surface of the skin layer, is 30% or less, preferably 20% or less, more preferably 10% or less of the area of the first surface. The lower limit value of the ratio of the total area of the openings to the area of the first surface is 0%. When the ratio of the total area of the apertures to the area of the first surface is equal to or less than the upper limit value of the above range, the first surface side becomes rigid and the rigidity of the entire porous body is increased. Since sound is reflected due to the rigidity of the entire porous body, the sound insulation of the porous body and the sound insulating material is excellent.

(Thickness of porous body)
The thickness of the porous body is preferably 0.5 to 50 mm, more preferably 1 to 30 mm, and still more preferably 5 to 20 mm. If the thickness of the porous body is not less than the lower limit of the above range, the sound insulation properties of the porous body and the sound insulation material are further improved. When the thickness of the porous body is equal to or less than the upper limit of the above range, the porous body and the sound insulating material are further reduced in weight. Moreover, the porous body is excellent in flexibility, and the porous body can easily follow a complicated shape.

(Xerogel)
The porous body of the present invention is made of xerogel.
Xerogel has the advantages that the average pore diameter of the continuous pores is sufficiently small, the average porosity of the porous body is sufficiently high, and is lightweight.

  A xerogel is a porous body formed by replacing a solvent contained in a gel with a gas, and has a three-dimensional fine porous structure in which continuous pores exist between network skeletons. Xerogel includes aerogels and cryogels.

  Specific examples of the xerogel include a polymer xerogel whose matrix is a cured product of a curable resin; a cellulose xerogel whose matrix is celluloses; a silica xerogel whose matrix is silica, and the like. As the xerogel, polymer xerogel or cellulose xerogel is preferable, and polymer xerogel is more preferable because it is lightweight and excellent in flexibility and easily follows a complicated shape of the porous body.

(Method for producing xerogel)
Examples of the method for producing xerogel include the following steps (I) to (IV).
Step (I): A step of pouring a solution containing a matrix or its precursor and a solvent, or a dispersion further containing particles into a mold.
Step (II): A step of obtaining a hydrogel or an organogel by gelling a solution or a dispersion after the step (I).
Step (III): A step of obtaining an organogel from the hydrogel when a hydrogel is obtained in the step (II).
Step (IV): A step of obtaining a xerogel by drying the organogel after the step (II) or the step (III).

  In step (II), gelation may be performed by a known method according to the type of matrix or its precursor. When the precursor of the matrix is a photocurable resin, a skin layer is easily formed on the light irradiation surface when the solution or dispersion is irradiated with light to gel the dispersion. Therefore, when the skin layer is formed on the first surface, light may be irradiated from the first surface side when the solution or dispersion is gelled, and the skin layer is applied to the first surface and the second surface. In the case of forming the film, light may be irradiated from the first surface side and the second surface side when the solution or dispersion is gelled.

  In step (III), water in the hydrogel may be replaced with an organic solvent by a known method.

  Examples of the method for drying the organogel in the step (IV) include a normal pressure drying method, a freeze drying method (freeze drying), a subcritical drying method, and a supercritical drying method. As a drying method, a freeze-drying method is preferable because it causes less gel breakage and pore collapse during drying and is suitable for mass production.

The freeze-drying method is a method in which after the organogel is frozen, the frozen gel is vacuum-dried.
When lyophilization is performed, t-butanol, cyclohexane, a fluorinated solvent, and the like are preferable as an organic solvent contained in the organogel in terms of mass production because a special apparatus is not required.

The supercritical drying method is a method of drying an organogel in a supercritical atmosphere. In supercritical drying, a supercritical state such as carbon dioxide, methanol, or ethanol is used. Supercritical drying is preferably performed, for example, by bringing supercritical carbon dioxide into contact with the organogel under conditions of a temperature of 35 to 60 ° C. and a pressure of 7.4 to 30 MPa.
In the case of performing supercritical drying, the organic solvent contained in the organogel is preferably an alcohol (methanol, ethanol, isopropanol, etc.).

(Production method of polymer xerogel)
As a specific method for producing the polymer xerogel, for example, a method having the following steps may be mentioned.
Step (α-I): A step of pouring a solution containing a photocurable resin, a photoinitiator and an organic solvent or a dispersion further containing particles into a mold.
Step (α-II): A step of obtaining a polymer organogel by irradiating the solution or dispersion with light after the step (α-I) to gel the solution or dispersion.
Step (α-IV): A step of lyophilizing the polymer organogel after the step (α-II) to obtain a polymer xerogel.

(Method for producing cellulose xerogel)
A specific method for producing cellulose xerogel includes, for example, a method having the following steps.
Step (β-I): A step of pouring a dispersion containing cellulose nanofibers and water or a dispersion further containing particles into a mold.
Step (β-II): A step of obtaining a cellulose hydrogel by adding an acid to the dispersion after the step (β-I) to gel the dispersion.
Step (β-III): A step of substituting alcohol in the cellulose hydrogel with alcohol after the step (β-II) to obtain a cellulose organogel.
Step (β-IV): A step of freeze-drying the cellulose organogel after the step (β-III) to obtain a cellulose xerogel.

(Method for producing silica xerogel)
As a specific method for producing silica xerogel, for example, a method having the following steps may be mentioned.
Step (γ-I): A step of pouring a solution containing tetraalkoxysilane and water or a dispersion further containing particles into a mold.
Step (γ-II): A step of obtaining a silica hydrogel by hydrolyzing and polycondensing tetraalkoxysilane in the solution or dispersion after the step (γ-I) to gel the solution or dispersion.
Step (γ-III): A step of replacing the water in the silica hydrogel with alcohol after the step (γ-II) to obtain a silica organogel.
Step (γ-IV): A step of obtaining silica xerogel by supercritical drying of the silica organogel after the step (γ-III).

(Other embodiments)
The porous body of the present invention is a porous body made of xerogel having continuous pores; has a first surface and a second surface opposite to the first surface; It is only necessary that the total area of the opened holes is 30% or less of the area of the first surface, and is not limited to the illustrated example.

For example, the porous body of the present invention may have a total area of openings opened to the second surface of 30% or less of the area of the second surface. That is, the skeleton of the porous body may form a so-called skin layer having few or no continuous pores on the second surface.
In addition, the porous body of the present invention may have only particles completely or partially embedded in the skeleton of the porous body, and may not have particles that are movably present in the continuous pores; It may have only particles that are movably present in the continuous pores, and may not have particles that are completely or partially embedded in the skeleton of the porous body.

(Normal incidence sound transmission loss)
The porous body of the present invention preferably has a normal incident sound transmission loss at 100 Hz in accordance with ASTM E2611 of 25 dB or more in the sound perpendicularly incident from the first surface side. When the normal incident sound transmission loss at 100 Hz is 25 dB or more, for example, transmission of engine sound of a bus or truck can be suppressed. The normal incident sound transmission loss at 100 Hz is more preferably 30 dB or more, further preferably 35 dB or more, and particularly preferably 40 dB or more.

  The porous body of the present invention preferably has a normal incident sound transmission loss of 500 Hz or more in accordance with ASTM E2611 in a sound incident perpendicularly from the first surface side of 30 dB or more. If the normal incident sound transmission loss at 500 Hz is 30 dB or more, for example, transmission of road noise of an automobile can be suppressed. The normal incident sound transmission loss at 500 Hz is more preferably 35 dB or more, further preferably 40 dB or more, and particularly preferably 45 dB or more.

  The porous body of the present invention preferably has a normal incident sound transmission loss at 1000 Hz in accordance with ASTM E2611 of 30 dB or more in the sound perpendicularly incident from the first surface side. If the normal incident sound transmission loss of 1000 Hz is 30 dB or more, for example, the transmission of wind noise of an automobile can be suppressed. The normal incident sound transmission loss at 1000 Hz is more preferably 35 dB or more, further preferably 40 dB or more, and particularly preferably 45 dB or more.

(Mechanism of action)
Since the porous body of the present invention described above is made of xerogel having continuous pores, it is lightweight.
Moreover, since it consists of xerogel which has a continuous pore, the friction with air (sound) and the partition of a continuous pore arises efficiently. In addition, since the total area of the openings opened in the first surface is 30% or less of the area of the first surface, the first surface side becomes rigid, and the rigidity of the entire porous body is increased. Due to the synergistic effect of sound absorption due to efficient friction between the air and the partition walls of the continuous pores and sound reflection due to the rigidity of the entire porous body, the sound insulation of the porous body is reduced. improves.
Further, when the porous body is made of xerogel and the matrix forming the skeleton of the porous body is an organic matrix, the porous body is flexible and easy to process.

<Sound insulation>
The sound insulating material of the present invention includes the porous body of the present invention.
The sound insulating material of the present invention may be composed only of the porous body of the present invention; it may be a laminate composed of the porous body of the present invention and other layers; A frame-like frame that supports the body may be provided on the periphery.

  Examples of the other layer include a non-porous film layer, a layer made of a known sound absorbing material, and a layer made of a known sound insulating material. As the other layer, a non-porous film layer is preferable because the sound insulation of the sound insulation material is further excellent. As the non-porous film, a flexible film such as a polyvinyl butyral film or a soft polyvinyl chloride film is preferable because the sound insulating property of the sound insulating material is further improved.

  As a sound insulating material having a non-porous film layer, a non-porous film layer is adjacent to either the first surface or the second surface of the porous body because the sound insulating property of the sound insulating material is further improved. Preferably provided; a non-porous film layer provided adjacent to both the first surface and the second surface of the porous body is more preferable.

  Since the sound insulating material of the present invention described above is light and has the porous body of the present invention having excellent sound insulating properties, it is lightweight and has excellent sound insulating properties.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Average pore diameter of continuous pores)
The average pore size of the continuous pores in the porous body is determined by measuring the pore size of the continuous pores by the mercury intrusion method using a mercury porosimeter (manufactured by Kantachrome Instruments, Poremster), and averaging the output pore sizes. Asked.

(Average porosity of porous material)
The average porosity of the porous body is obtained by the following formula from the volume of the porous body before pressing and the volume of the porous body after pressing under the conditions of temperature: 100 ° C., pressure: 50 MPa, time: 10 minutes. It was.
Porosity = 1− (volume of porous body after pressing / volume of porous body before pressing)

(Ratio of the total area of the opening to the area of the first surface)
The first surface of the porous body is observed with an electron microscope, the area of the holes present in the 500 μm × 500 μm region of the first surface is measured, and the total area of the holes (μm ² ) Area: Divided by 250,000 μm ² , the ratio (%) of the total area of the openings to the area of the first surface was determined.

(Ratio of the total area of the opening to the area of the second surface)
The second surface of the porous body is observed with an electron microscope, the area of the holes present in the 500 μm × 500 μm region of the second surface is measured, and the total area of the holes (μm ² ) Area: Dividing by 250,000 μm ² , the ratio (%) of the total area of the apertures to the area of the second surface was determined.

(Normal incidence sound transmission loss)
A disk-shaped sample was cut out from the porous body. Samples were measured using a normal incidence sound transmission loss measurement system (Bruel Care Co., acoustic tube: 4206T, PULSE analyzer, hardware: 3560 B, software: PULSE Labshop Type 7700, 7758, MS1021) in accordance with ASTM E2611, The normal incident sound transmission loss of 100 to 6400 Hz was measured for the sound incident perpendicularly from the surface of 1.

Example 1
10 g of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., UA-160TM), 10 g of polyethylene glycol # 400 diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-400) and 5 g of dipentaerythritol hexaacrylate as a photocurable resin. (Shin-Nakamura Chemical Co., Ltd., A-DPH) and 1.3 g of α-ketoglutaric acid as a photoinitiator were dissolved in 225 g of t-butanol.

Step (I):
The solution was poured into a circular container made of polypropylene.
Step (II):
The solution in the circular container is irradiated from the high pressure mercury lamp with an illuminance of 150 mW / cm ² for 15 minutes, that is, with an integrated light amount of 135 J / cm ^{2 from} the surface (first surface) side of the solution to gel the solution. To obtain a polymer organogel.

Step (IV):
The polymer organogel was placed in a freezer at −30 ° C. together with the container and cooled for 16 hours to freeze. Remove the frozen gel from the container, vacuum dry it with a freeze dryer at 40 ° C. for 24 hours, and have a skin layer on the first side and no skin layer on the second side, a polymer with a thickness of 10 mm A xerogel was obtained.

  For the polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Transmission loss was measured. The results are shown in Table 1. Further, FIG. 3 shows an electron micrograph of the first surface of the cross section in the thickness direction and the vicinity thereof, FIG. 4 shows an electron micrograph of the center of the cross section in the thickness direction, and FIG. FIG. 5 shows an electron micrograph of the surface 2 and the vicinity thereof, FIG. 6 shows an electron micrograph of the first surface, and FIG. 7 shows an electron micrograph of the second surface.

(Example 2)
10 g of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., UA-160TM), 10 g of polyethylene glycol # 400 diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-400) and 5 g of trimethylolpropane triacrylate as a photocurable resin (Shin-Nakamura Chemical Co., Ltd., A-TMPT) and 1.3 g of 1-hydroxycyclohexyl phenyl ketone (BASF, Irgacure (registered trademark) 184) as a photoinitiator were dissolved in 225 g of t-butanol. It was.

Except that the solution of Example 2 was used instead of the solution of Example 1, a skin layer was formed on the first surface and a skin layer was not formed on the second surface in the same manner as in Example 1. Sa: 10 mm polymer xerogel was obtained.
For this polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Sound transmission loss was measured. The results are shown in Table 1.

Example 3
5 g of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., UA-160TM) and 20 g of dipentaerythritol hexaacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-DPH) as a photocurable resin, and 2.0 g as a photoinitiator 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (manufactured by BASF, Irgacure (registered trademark) 907) was dissolved in 225 g of t-butanol.

Step (I):
The solution was poured into a circular container made of polypropylene. A polyethylene film was placed on the surface of the solution.
Step (II):
The solution is gelated by irradiating the solution in the circular container with ultraviolet light at an illuminance of 300 mW / cm ² for 5 minutes from the high pressure mercury lamp, that is, the integrated light amount: 90 J / cm ^{2 from} the surface (first surface) side of the solution To obtain a polymer organogel.

Step (IV):
After removing the polyethylene film on the first side of the polymer organogel, freeze drying is performed in the same manner as in Example 1, having a skin layer on the first side and no skin layer on the second side, A polymer xerogel having a thickness of 10 mm was obtained.
For the polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Transmission loss was measured. The results are shown in Table 1.

Example 4
5 g of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., UA-160TM), 10 g of polyethylene glycol # 400 diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-400) and 10 g of trimethylolpropane triacrylate as photocurable resins (Shin-Nakamura Chemical Co., Ltd., A-TMPT) and 1.3 g of α-ketoglutaric acid as a photoinitiator were dissolved in 225 g of t-butanol. 25 g of spherical non-porous silica particles (manufactured by AGC S-Tech, Sunsphere NP-200, average particle size: 20 μm) are added to this solution so that the amount is 100 parts by mass with respect to 100 parts by mass of the matrix. Evenly dispersed.

Except for using the dispersion liquid of Example 4 instead of the solution of Example 1, it has a skin layer on the first surface and no skin layer on the second surface in the same manner as in Example 1. A polymer xerogel having a thickness of 10 mm was obtained.
For the polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Transmission loss was measured. The results are shown in Table 1. FIG. 8 shows an electron micrograph of the first surface of the cross section in the thickness direction and the vicinity thereof, and FIG. 9 shows an electron micrograph of the center of the cross section in the thickness direction. FIG. 10 shows an electron micrograph of the second surface and the vicinity thereof, FIG. 11 shows an electron micrograph of the first surface, and FIG. 12 shows an electron micrograph of the second surface.

(Example 5)
A dry weight equivalent of 6 g of undried sulfite bleached softwood pulp, 0.075 g 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), and 0.75 g sodium bromide in 450 mL water After the dispersion, 13% by mass of sodium hypochlorite aqueous solution was added with sodium hypochlorite so that the amount of sodium hypochlorite was 2.5 mmol with respect to 1 g of pulp to initiate the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10. When the pH no longer changes, the reaction is considered to be complete, the reaction product is filtered through a glass filter, washed with a sufficient amount of water and filtered 10 times to impregnate water with a solid content of 25% by mass. Oxidized pulp was obtained.

  Next, water was added to the oxidized pulp to form a 2% by mass slurry, which was then treated with a rotary blade homogenizer for 10 minutes. Since the viscosity of the slurry significantly increased with the treatment, water was gradually added, and the dispersion treatment with the mixer was continued until the solid content concentration became 0.5 mass%. Next, after treating for 5 minutes with an ultrasonic homogenizer, undissolved pulp and the like were removed by centrifugation to obtain a TEMPO-oxidized cellulose nanofiber dispersion. This dispersion was concentrated with an evaporator to obtain a dispersion having a solid content of 1% by mass. 4 g of spherical non-porous silica particles (manufactured by AGC S-Tech, Sunsphere NP-200, average particle size: 20 μm) are added to 200 g of this dispersion so as to be 200 parts by mass with respect to 100 parts by mass of the matrix. And uniformly dispersed.

  The dispersion was poured into a polypropylene circular container and allowed to stand for 1 hour. Thereafter, 1 mol / L hydrochloric acid is added to the surface (first surface) of the dispersion so that the liquid surface of the dispersion is not disturbed, and the dispersion is gelled by leaving it to stand for 20 hours. A hydrogel was obtained. About hydrogel, the solvent substitution was performed using ion-exchange water. Next, solvent substitution was performed using a mixed solvent of 25% by mass of t-butanol and 75% by mass of water. Furthermore, the same solvent substitution was performed by gradually increasing the fraction of t-butanol to 50 mass%, 75 mass%, and 100 mass%. The solvent replacement was performed by immersing the hydrogel in a sufficient amount of the replacement solvent and rotating the entire container at a speed of 20 rpm. Solvent replacement was performed over 24 hours for ion-exchanged water and a mixed solvent of each t-butanol fraction, and over 50 hours for 100 mass% t-butanol. Organogel was obtained by the above solvent substitution.

The organogel was placed in a freezer at −30 ° C. together with the container, cooled for 16 hours, and frozen. The frozen gel is taken out from the container, vacuum-dried at 40 ° C. for 24 hours with a freeze dryer, has a skin layer on the first surface side, has no skin layer on the second surface side, and has a thickness of 10 mm. A xerogel was obtained.
For this polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Sound transmission loss was measured. The results are shown in Table 1.

(Example 6)
In the same manner as in Example 1, a polymer xerogel having a thickness of 46 mm and having a skin layer on the first surface and no skin layer on the second surface was obtained.
For the polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. The results are shown in Table 1.

A disc was cut from the polymer xerogel. Thickness: Two circular films having the same size as the polymer xerogel were cut out from a 2 mm polyvinyl butyral film. A sound insulation board having a thickness of 50 mm and an area density of 5.6 kg / m ² was obtained by sandwiching the top and bottom of the polymer xerogel disk with a circular polyvinyl butyral film.
With respect to the sound insulation plate, normal incidence sound transmission loss was measured. The results are shown in Table 1 and FIG.

(Comparative Example 1)
In the same manner as in Example 1, a polymer xerogel having a thickness of 12 mm and having a skin layer on the first surface and no skin layer on the second surface was obtained.
The first surface side of the polymer xerogel was excised by about 2 mm with an ultrasonic cutter to obtain a polymer xerogel having a thickness of 10 mm without a skin layer.
For this polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Sound transmission loss was measured. The results are shown in Table 1.

(Comparative Example 2)
In the same manner as in Example 2, a polymer xerogel having a thickness of 12 mm and having a skin layer on the first surface and no skin layer on the second surface was obtained.
The first surface side of the polymer xerogel was excised by about 2 mm with an ultrasonic cutter to obtain a polymer xerogel having a thickness of 10 mm without a skin layer.
For the polymer xerogel, the average pore diameter and the average porosity were measured, and the ratio of the total area of the opening to the area of the first surface and the ratio of the total area of the opening to the area of the second surface were determined. Transmission loss was measured. The results are shown in Table 1.

(Comparative Example 3)
A commercially available sound-absorbing material (manufactured by 3M, Synsalate (registered trademark)) was superposed to obtain a sound-absorbing material having a thickness of 50 mm and an area density of 3.2 kg / m ² . The normal incident sound transmission loss was measured for the sound absorbing material. The results are shown in Table 1 and FIG.

The porous bodies of Examples 1 to 6 are made of xerogel having continuous pores, and the total area of the openings opened to the first surface is 30% or less of the area of the first surface. It was excellent. As shown in FIG. 13, the sound insulating material in which the porous body of Example 6 is sandwiched between non-porous films has a mass of 1/70 with respect to an iron plate having the same thickness (surface density: 408 kg / m ² ). Despite being present, the sound insulation equivalent to that of the iron plate was exhibited.
In the porous bodies of Comparative Examples 1 and 2, since the total area of the openings opened to the first surface is more than 30% of the area of the first surface, the sound insulation is inferior to those of Examples 1 to 6. It was.
As shown in Comparative Example 3 in FIG. 13, when the commercially available sound absorbing material had the same thickness as the sound insulating material of Example 6, the sound insulating property was considerably inferior to that of Example 6.

  The porous body of the present invention is useful as a lightweight and thin sound insulating material that does not follow the mass law.

10 porous body,
12 continuous pores,
14 particles,
16 skeleton,
20 Skin layer A First side,
B Second side.

Claims (12)

It is a porous body made of xerogel having continuous pores,
The porous body has a first surface and a second surface opposite to the first surface;
The porous body in which the total area of the openings opened to the first surface is 30% or less of the area of the first surface.   The porous body according to claim 1, wherein an average pore diameter of the continuous pores is 10 to 150 µm.   The porous body according to claim 1 or 2, wherein the porous body has an average porosity of 50 to 98%.   The porous body according to any one of claims 1 to 3, wherein the matrix forming the skeleton of the porous body is an organic matrix.   The porous body according to claim 4, wherein the organic matrix is a cured product of a curable resin. The porous body includes a plurality of particles;
The content of the particles in the entire porous body is 1 to 300 parts by mass with respect to 100 parts by mass of the matrix forming the skeleton of the porous body. The porous body according to 1. The porous body includes a plurality of particles;
The porous body according to any one of claims 1 to 6, wherein at least a part of the particles are present in the continuous pores.   The porous body according to any one of claims 1 to 7, wherein a sound incident perpendicularly from the first surface side has a normal incident sound transmission loss of 100 Hz conforming to ASTM E2611 of 25 dB or more.   The porous body according to any one of claims 1 to 8, wherein a normal incident sound transmission loss at 500 Hz in conformity with ASTM E2611 is 30 dB or more in sound vertically incident from the first surface side.   The porous body according to any one of claims 1 to 9, wherein a sound incident vertically from the first surface side has a normal incident sound transmission loss of 1000 Hz conforming to ASTM E2611 of 30 dB or more.   A sound insulating material comprising the porous body according to any one of claims 1 to 10.   The sound insulating material according to claim 11, further comprising a non-porous film layer.